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Species and Varieties 

Their Origin by 
Mutation 

Lectures Delivered at the University of 
California 

by 

H ugo DeVries 

of b/tan> in the ( nivc;sit> of Atntiterdam 


Tdfied by 

Daniel rrembly MacDougal 

Ih I irtiittnt of Kt itrwh iL&tuutioc 

of VV 


Tliird Kdiiion, 
Ce*rrecltd and Revised 


CHICAiX) 

Thi l,)pen t'oiut rultlishing Company 



Copyright 1904 

BY 

The Open Court Pub. Co. 
Chicago 



THE ORIGIN OF SPECIES 


The origin of species is a natural phenomenon. 

Lamarck. 

The origin of species is an object of inquiry. 

Darwin. 


The origin of species is an object of experi- 
mental investigation. DeVries, 




PREFACE BY THE AUTHOR 


The purpose of these lectures is to point out the means 
and methods by which the origin of species and varieties 
may become an object for experimental inquiry, in the 
interest of agricultural and horticultural practice as well 
as in that of general biologic science. Comparative 
studies have contributed all the evidence hitherto adduced 
for the support of the Darwinian theory of descent and 
given us some general ideas about the main lines of the 
pedigree of the vegetable kingdom, but the way in which 
one species originates from another has not been ade- 
quately explained. The current belief assumes that spe- 
cies are slowly changed into new types. In contradiction 
to this conception the theory of mutation assumes that 
new species and varieties are produced from existing 
forms by sudden leaps. The parent-type itself remains 
unchanged throughout this process, and may repeatedly 
give birth to new forms. These may arise simultaneously 
and in groups or separately at more or less widely dis- 
tant periods. 

The principal features of the theory of mutation have 
been dealt with at length in my book “Die Mutations- 
theorie” (Vol- I., 1901, Vol. II., 1903. Leipsic, Veit 
& Co.), in which I have endeavored to present as com- 
pletely as possible the detailed evidence obtained from 
trustworthy historical records, and from my own experi- 
mental researches, upon which the theory is based. 

The University of California invited me to deliver a 
series of lectures on this subject, at Berkeley, during the 



viii Preface by the Author 

summer of 1904, and these lectures are offered in this 
form to a public now thoroughly interested in the pro- 
gress of modern ideas on evolution. Some of my experi- 
ments and pedigree-cultures are described here in a man- 
ner similar to that used in the “ Mutationstheoric,’^ but 
partly abridged and partly elaborated, in order to give a 
clear conception of their extent and scope. New experi- 
ments and observations have been added, and a wider 
choice of the material afforded by the more recent cur- 
rent literature has been made in the interest of a clear 
representation of the leading ideas, leaving the exact and 
detailed proofs thereof to the students of the larger book. 

Scientific demonstration is often long and encumbered 
with diflicult points of minor importance. In these lec- 
tures I have tried to devote attention to the more im- 
portant phases of the subject and have avoided the de- 
tails of lesser interest to the general reader. 

Considerable care has been bestowed upon the indica- 
tion of the lacunae in our knowledge of the subject and 
the methods by which they may be filled. ' Many inter- 
esting observations bearing upon the little known parts 
of the subject may be made with limited facilities, either 
in the garden or upon the wild flora. Accuracy and per- 
severance, and a warm love for Nature’s children are 
here the chief requirements in such investigations. 

In his admirable treatise on Evolution and Adaptation 
(New York, Macmillan & Co., 1903), Thomas Hunt Mor- 
gan has dealt in a critical manner with many of the 
speculations upon problems subsidiary to the theory of 
descent, in so convincing and complete a manner, that I 
think myself justified in neglecting these questions here. 
His book gives an accurate survey of them all, and is 
easily understood by the general reader. 

In concluding I have to offer my thanks to Dr. D. T. 
MacDougal and Miss A. M. Vail of the New York Botan- 
ical Garden for their painstaking work in the prepara- 
tion of the manuscript for the press. Dr. MacDougal, by 



Preface hy the Author 


ix 


his publications, has introduced my results to his Ameri- 
can colleagues, and moreover by his cultures of the muta- 
tive species of the great evening-primrose has con- 
tributed additional proof of the validity of my views, 
which will go far to obviate the difficulties, which are 
still in the way of a more universal acceptation of the 
theory of mutation. My work claims to bo in full ac- 
cord with the principles laid down by Darwin, and to give 
a thorough and sharp analysis of some of the ideas of 
variability, inheritance, selection, and mutation, which 
were necessarily vague at his time. It is only just to 
state, that Darwin established so broad a basis for scien- 
tific research upon these subjects, that after half a century 
many problems of major interest remain to be taken up. 
The work now demanding our attention is manifestly that 
of the experimental observation and control of the origin 
of species. The principal object of these lectures is to 
secure a more general appreciation of this kind of work. 

Hugo de Vries. 


Amsterdam, October, IBOJf, 




PEEFACE BY THE EDITOR 


Professor de Vries has rendered an additional service 
to all naturalists by the preparation of the lectures on 
mutation published in the present volume. A perusal of 
the lectures will show that the subject-matter of Die 
Mutationstheorie ” has been presented in a somewhat 
condensed form, and that the time which has elapsed 
since the original was prepared has given opportunity for 
the acquisition of additional facts, and a re-examination 
of some of the more important conclusions with the re- 
sult that a notable gain has been made in the treatment 
of some complicated problems. 

It is hoped that the appearance of this English version 
of the theory of mutation will do much to stimulate in- 
vestigation of the various phases of the subject. This 
volume, however, is by no means intended to replace, as a 
work of reference, the larger book with its detailed recital 
of facts and its comprehensive records, but it may prove 
a substitute for the use of the general reader. 

The revision of the lectures has been a task attended 
with no little pleasure, especially since it has given the 
editor the opportunity for an advance consideration of 
some of the more recent results, thus materially facilitat- 
ing investigations which have been in progress at the 
New York Botanical Garden for some time. So far as 
the ground has been covered the researches in question 
corroborate the conclusions of de Vries in all important 
particulars. The preparation of the manuscript for the 
printer has consisted chiefly in the adaptation of oral 



xii Preface by the Editor 

discussions and demonstrations to a form suitable for 
permanent record, together with certain other alterations 
which have been duly submitted to the author. The 
original phraseology has been preserved as far as pos- 
sible. The editor wishes to acknowledge material as- 
sistance in this work from Miss A. M. Vail, Librarian of 
the New York Botanical Garden. 

D. T. MacDougal. 

New York Botanical Garden, Octoher, IdOJh 


PREFACE TO THE SECOND EDITION. 

The constantly increasing interest in all phases of evo- 
lution has made necessary the preparation of a second 
edition of this book within a few months after the first 
appeared. The opportunity has been used to eliminate 
typographical errors, and to make alterations in the form 
of a few sentences for the sake of cleamess and smooth- 
ness. The subject matter remains practically unchanged. 
An explanatory note has been added on page 575 in order 
to avoid confusion as to the identity of some of the plants 
which figure prominently in the experimental investiga- 
tions in Amsterdam and New York. 

The portrait which forms the frontispiece is a repro- 
duction of a photograph taken by Professor F. E. Lloyd 
and Dr. W. A. Cannon during the visit of Professor de 
Vries at the Desert Botanical Laboratory of the Carnegie 
Institution, at Tucson, Arizona, in June, 1004. 

D. T. MacDougal. 


December 15, 1905. 



CONTENTS 

A. Introduction. 

Lecture Page 

I. Descent : theories of evolution and methods 

of investigation 1 

The theory of descent and of natural se- 
lection. Evolution and adaptation. 
Elementary species and varieties. Meth- 
ods of scientific i>edigree-culture. 

B. Elementary Species. 

IL Elementary species in nature ... 32 

Viola tricolor, Draba verna. Primula 
acaulis, and other examples. Euphorbia 
Ipecacuanha. Prunus maritima. Taraxa- 
cum and Ilieracium. 

III. Elementary species of cultivated plants. 63 
Beets, apples, pears, clover, flax and coco- 
nut. 

IV. Selection of elementary species ... 92 

Cereals. Le Couteur. Runiimg out of 
varieties. Rinijiau and Rislcr, Avena fa- 
tua. Meadows. Old Egyptian cereals. 
Selection by the Romans. Shirreff. Hays. 

C. Retrograde Varieties. 

V. Characters of retrograde varieties . . 121 

Seed varieties of pure, not hybrid origin. 
Differences from elementary si>ecies. 
Latent characters. Ray-florets of com- 
xiii 



XIV 


Contents 


Lecture Pace 

poeites. Progressive red varieties. Ap- 
parent losses. Xanthium can a dense. 
Correlative variability. Laciniate leaves 
and petals. Compound characters. 

VI. Stability and real atavism .... 154 

Constancy of retrograde varieties. Atav- 
ism in Eibes sanguincum albidum, in 
conifers, in Iris pallida. Seedlings of 
Acacia. Keversion by buds. 

VII. Ordinary or false atavism .... 185 

Vicinism or variation under the influence 
of pollination by neighboring individ- 
uals. Vicinism in nurseries. Purify- 
ing new and old varieties. A case of 
running out of com in Germany. 

VIII. Latent characters 216 

Leaves of seedlings, adventitious buds, sys- 
tematic latency and retrogressive c\olu- 
tion. Degressive evolution. Latency 
of specific and varietal characters in 
wheat-ear carnation, in the green <lahlias, 
in white campanulas and others. System- 
atic latency of flower colors. 

IX. Crossing of species and varieties . . 247 

Balanced and unbalanced, or species and 
variety crosses. Constant hybrids of 
Oenothera muricata and O, biennis. 
Aegilops, Medicago, brambles and other 
instances. 

X. Menders law of balanced crosses . . 276 
Pairs of antagonistic characters, one ac- 
tive and one latent. Papaver somnif- 



Contents 


XV 


Lecture Page 

emm Mephlsto Danebrop^, MendePa laws. 
Unit-characters. 

D. Eversportino Varieties. 

XI. Striped flowers 309 


Antirrhinum majus luteum rubro-striatum 
with pedigree. Striped flowers, fruits 
and radishes. Double stocks. 

XTT. Five leaved clover 340 

Origin of tliis variety. Periodicity of the 
anomaly. Pedigree-cultures. Ascidia. 


XIII. Pclycephalic poppies 369 

Permanency and high variability. Sensi- 
tive pericxl of the anomaly. Depend- 
ency on external conditions. 

XIV. Monstrosities 400 


Inheritance ul inonstrosiiies. Half races 
and middle races. Hereditary value of 
atavists. Twisted stems and fascia- 
tions. Middle races of tricotyls and 
syncotyls. Selection by tlie hereditary 
IKircentage among the offspring. 

XV. Double adaptations 430 

Analogy between double adaptations and 
anomalous middle races. Polygonum 
amphibium. Alpine plants. Othonna 
crassifolia. Ix?aves in sunshine and 
shadow. Giants and dwarfs. Figs and 
ivy. Li^aves of seedlings. 

E. Mutations. 

XVT. Origin of the pelorle toad-flax . . . 459 

Sudden and frequent origin in the wild 
state. Origin in the experiment-gardt^n. 
I>aw of repeated mutations. Probable 
origin of other pelories. 



XVI 


Contents 


Lecture Page 

XVII. The production of double flowers . . 488 

Sudden appearance of double flowers in 
horticulture. Historical evidence. Ex- 

perimental origin of Chrysanthemum 
segetum plenum. Dependency upon 
nourishment. Petalody of stamens. 

XVTII. New species of Oenothera .... 61C 

Mutations of Oenothera lamarckiana in 
the wild state near Hilversum, New 
varieties of O. laevifolia, O. brevistylis, 
and O. nanella. New elementary species, 

O. gigas, O. rubrinervis, albida, and ob- 
longa. O. lata a pistillate form. In- 
constancy of O. scintillans. 

XIX. Experimental pedigree-cultures . . . 547 

Pedigree of the mutative products c f 
Oenothera lamarckiana in the Botai^ 
ical Garden at Amsterdam. Laws of 
mutability. Sudden and repeated leaps 
from an unchanging main strain. Con- 
stancy of the new forms. Mutations in 
all directions. 

XX. Origin of wild species and varieties . . 57G 

Problems to solve. Capsella heegeri. 
Oenothera biennis cruciata. Epilobium 
hirsutum cruciatum. Ilibi^scus Mos- 
cheutos. Purple beech. Monophyllous 
strawberries. Chances of success with 
new mutations. 

XXI. Mutations in horticulture .... 604 

Chelidonium majus lacinatum. Dwarf and 
spineless varieties. Laciniate leaves, 
Monophyllous and broom-like varieties. 



Contents 


xvii 


Legtubb 


XXII. 


XXIIL 


XXIV. 


XXV. 


XXVI. 


Pau£ 

Purple leaves. Celosia. Italian poplar. 
Cactus dahlia. Mutative origin of Dah- 
lia fistulosa, and Geranium pratense in 
the experiment-garden. 

Systematic atavism # 630 

Reappearance of ancestral characters. 
Primula acaulis umbellata. Bracts 
crucifers. Zea Mays cryptosperma. 
Equisetum, Dipsacus sylvestris torsus. 
Tomatoes. 

Taxonomic anomalies 653 

Specific characters occurring in other cases 
as casual anomalies. Papaver brac- 
teatum monopetalum. Desmodlum 
gyrans and monophyllous varieties. Pel- 
tate leaves and ascidia. Flowers on 
leaves. Leaves. Hordeum trifurcatum. 

Hypothesis of periodical mutations * • 686 

Discovering mutable strains. Periods of 
mutability and constancy. Periods of 
mutations. Genealogical trees. Limited 
life-time of the organic kingdom* 

F. Fluctuations. 

General laws of fluctuations .... 715 

Fluctuating variability. Quetelet^s law. 
Individual and partial fluctuations. 
Linear variability. Influence of nutri- 
tion. Periodicity-curves. 

Asexual multiplication of extremes . . 742 

Selection between species and intra-spe- 
cifio selection. Excluding individual 



• •• 

zvm 

Lectukb 


ConterUs 


Paob 

and embryonic variability. Su^r-canes. 
Flowering cannas. Double lilacs. Other 
instances. Burbank’s method of eelee- 
tion. 

XXVIL Inconstancy of improved races . . . 770 

Larger variability in the case of propaga* 
lion by seed. Progression and regres- 
sion after a single selection, and after 
repeated selections. Selection experi- 
ments with com. Advantages and effect 
of repeated selection. 

ZXVHL Artificial and natural selection . . , 798 

Conclusions. Specific and intra-qpecific 
selection. Natural selection in the field. 
Acclimatization. Improvement-selection 
of sugar-beets by various methods. Rye. 
Hereditary percentage and centgener 
power as marks by which intra-specific 
selection may be guided. 

TnA« 827 



A. INTRODUCTION 


Lecture I 

DESCENT : THEORIES OF EVOLUTION, AND METHODS 
OF INVESTIGATION 

Newton convinced liis contemporaries that 
natural laws rule the wlK)]e universe. Lyell 
showed, hy his ])riii('i]»lo of slow and gradual 
evolution, that natural laws have reigned since 
the beginning of time. To Darwin we owe the 
almost universal acceptance of the theory of 
descent. 

This doctrine is one of the most noted land- 
marks in the advance of science. It teaches the 
validity of natural laws of life in its broadest 
sense, and (*rowns the jihilosophy founded by 
Newton and Lyell. 

Lamarck ])roposed the hypothesis of a com- 
mon origin of all living beings and this ingenious 
and thoroughly philosoidiieal eonee})tiou was 
warmly welcomed by his partisans, but was not 
widely accepted owing to lack of supporting eW- 
denee. To Darwin was reserved the task of 



2 


Descent 


bringing the theory of common descent to its 
present high rank in scientific and social phi- 
losophy. 

Two main features in his work have contrib- 
uted to this early and unexpected victory. One 
of them is the almost unlimited amount of com- 
parative evidence, tlie other is his demonstration 
of the possibility of a physiological exi)lanation 
of the process of descent itself. 

The universal belief in the independent crea- 
tion of living organisms was revised by 
Linnaeus and was put upon a new foundation. 
Before him the genera were supposed to be 
created, the species and minor forms having 
arisen from them through the agency of ex- 
ternal conditions. In his first book Linnaeus 
adhered to this belief, but later changed his 
mind and maintained the principle of the sej)- 
arate creation of species. The weight of his 
authority soon brought this conception to uni- 
versal acceptance, and up to the i>resent time 
the prevailing concejjtion of a species has been 
chiefly based on the definition given by Linnaeus. 
His s})eeies comprised sub8|)ecies an<l varieties, 
which were in their turn, suj)posed to have 
evolved from .species by the common method. 

Darwin tried to show that tlie links which 
bind species to genera are of tin? same natur<; 
as those which detenniue the relationship of 



Theories of Evolution 


3 


subspecies and varieties. If an origin by nat- 
ural laws is conceded for the latter, it must, on 
this ground be granted for the first also. In 
this discussion he simply returned to the pre- 
Linnean attitude. But his material was such 
as to allow him to go one step further, and this 
stop was an important and decisive one. He 
showed that the relation between the various 
gi'iiera of a family does not exhibit any fea- 
tures of a nature other than tliat between the 
si)ecios of a genus. AVhat has been conceded 
for the one must needs be accepted for the 
ether. The same holds good for the large 
groups. The conviction of the common origin 
of closely allied forms necessarily leads to the 
conception of a similar descent even in remote 
relationships. 

The origin of subspecies and varieties as 
found in nature was not proved, but only gen- 
erally recognized as evident. A broader 
knowledge has brought about the same state of 
o])inion for greaUw groups of relationships. 
{Systematic aninities find their one possible ex- 
])lanation by the aid of this principle; without 
it, all similarity is only ai>i)arent and aceidentid. 
(leograi)liie and j)aleontologie facts, brought to- 
gether by Darwin and others on a previously 
unecpialled scale, point clearly in the same di- 
rection. The vast amount of evidenct* of all 



4 


Descent 


comparative sciences compels ns to accept the 
idea. To deny it, is to give up all oppor- 
tunity of conceiving Nature in her true form. 

The general features of the theory of descent 
are now accepted as the basis of all biological 
science. Half a century of discussion and in- 
vestigation has cleared up the minor points and 
brought out an abundance of facts; but they 
have not changed the principle. Descent with 
modification is now universally accepted as the 
chief law of nature in the organic world. In 
honor of him, who with unsurpassed genius, and 
by unlimited labor has made it the basis of 
modem thought, this law is called the “ Dar- 
winian theory of descent.” 

Darwin’s second contribution to this attain- 
ment was his proof of the possibility of a phys- 
iological explanation of the process of descent 
itself. Of this possibility he fully convinced his 
contemporaries, but in indicating the particular 
means by which the change of species has been 
brought about, he has not succeeded in securing 
universal acceptation. Quite on the contrary, 
objections have been raised from the very out- 
set, and with such force as to compel Darwin 
himself to change his views in his later writings. 
This however, was of no avail, and objections 
and criticisms have since steadily accumulated. 

Physiologic facts concerning the origin of 



Theories of Evolution 


5 


species in nature were unknown in the time of 
Darwin. It was a happy idea to choose the ex- 
perience of the breeders in the production of 
new varieties, as a basis on which to build an 
explanation of the processes of nature. In my 
opinion Darwin was quite right, and he has suc- 
ceeded in giving the desired proof. But the 
basis was a frail one, and would not stand too 
close an examination. Of this Darwin was al- 
ways well aware. He has been prudent to the 
utmost, leaving many points undecided, and 
among them especially the range of validity of 
his several arguments. Unfortunately this 
prudence has not been adopted by his followers. 
Without suflSeient warrant they have laid stress 
on one phase of the jiroblem, tjuite overlooking 
the others. Wallace has even gone so far in his 
zeal and ardent veneration for Darwin, us to 
describe as Darwinism some things, which in my 
opinion, had never been a part of Darwin’s con- 
ceptions. 

The experience of the breeders was quite in- 
adequate to the use which Darwin made of it. 
It was neither scientific, nor critically accurate. 
Laws of variation were barely conjectured; the 
different types of variability were only imper- 
fectly distinguished. The breeders’ conception 
was fairly sufficient for practical purimses, 
but science needed a clear understanding of the 



6 


Descent 


factors in the general process of variation. Re- 
peatedly Darwin tried to formulate these causes, 
but the evidence available did not meet his re- 
quirements. 

Quetelet*s law of variation had not yet been 
published. Mendel’s claim of hereditary units 
for the explanation of certain laws of hybrids 
discovered by him, was not yet made. The 
clear distinction between spontaneous and sod- 
den changes, as compared with the ever-present 
fluctuating variations, is only of late coming into 
recognition by agriculturists. Innumerable 
minor points which go to elucidate the breeders’ 
experience, and with which we are now quite 
familiar, were unknown in Darwin’s time. No 
wonder that he made mistakes, and laid stress 
on modes of descent, which have since been 
proved to be of minor importance or even of 
doubtful validity. 

Notwithstanding all these apparently unsur- 
mountable difficulties, Darwin discovered the 
great principle which rules the evolution of or- 
ganisms. It is the principle of natural selec- 
tion. It is the sifting out of all organisms of 
minor worth through the struggle for life. It 
is only a sieve, and not a force of nature, not a 
direct cause of improvement, as many of Dar- 
win’s adversaries, and unfortunately many of 
his followers also, have so often asserted. It is 



Theories of Evolution 


7 


only a sieve, which decides what is to live, and 
what is to die. But evolutionary lines are of 
great length, and the evolution of a flower, or of 
an insectivorous plant is a way with many side- 
paths. It is the sieve that keeps evolution on 
the main line, killing all, or nearly all that try 
to go in other directions. By this means nat- 
ural selection is the one directing cause of the 
broad lines of evolution. 

Of course, with the single steps of evolution 
it has nothing to do. Only after the step has 
been taken, the sieve acts, eliminating the unfit. 
The problem, as to the manner in which the in- 
dividual steps arc brought about, is quite an- 
otlier side of the question. 

On this point Darwin has recognized two pos- 
sibilities. One means of change lies in the sud- 
den and spontaneous production of new forms 
from the old stock. The other meth(^Ts the 
gradual accumulation of those always present 
and ever fluctuating variations which are in- 
dicated by the common assertion that no two 
individuals of a given race are exactly alike. 
The first changes are what we now call “ muta- 
tions,” the second are designated as ” indiiviS^ 
ual variations,” or as this term is often used in 
another sense, as ” fluctuations.” Darwin rec- 
ognized both lines of evolution; Wallace disre> 
garded the sudden changes and propc^ed fluctu- 



8 


Descent 


ations as tlie exclusive factor. Of late, however, 
this point of view has been abandoned by many 
investigators, especially in America. 

The actual occurrence of mutations is now 
recognized, and the battle rages about the ques- 
tion, as to whether they are be regarded as the 
principal means of evolution, or, whether slow 
and gradual changes have not also played a 
large and important part. 

The defenders of the theory of evolution by 
slow accumulation of slight fluctuations are di- 
vided into two camps. One group is called the 
Neo-Lamarckians ; they assume a direct modi- 
fying agency of the environment, producing a 
corresponding and useful change in the organ- 
ization. The other group call themselves Dar- 
winians or selectionists, but to my mind with 
no other right beyond the arbitrary restriction 
of the Darwinian principles by Wallace. They 
assume fluctuating variations in all directions 
and leave the choice between them to the sieve 
of natural selection. 

Of course we are far from a decision between 
these views, on the sole ground of the facts as 
known at present. Mutations under observa- 
tion are as yet very rare; enough to indicate 
the possible and most probable ways, but no 
more. On the other hand the accumulation of 
fluctuations does not transgress relatively nar- 



Theories of Evolution 


9 


row limits as far as the present methods of 
selection go. But the question remains to be 
solved, whether our methods are truly the right 
ones, and whether by the use of new princi- 
ples, new results might not cause the balance of 
opinion to favor the opposite side. 

Of late, a thorough and detailed discussion of 
the opposing views has been given by Morgan 
in his valuable book on evolution and adapta- 
tion. He has subjected all the proposed theo- 
ries to a severe criticism both on the ground of 
facts and on that of their innate possibility and 
logical value. He decides in favor of the mu- 
tation-theory. His arguments are incisive and 
complete and wholly adapted to the compre- 
hension of all intelligent readers, so that his 
book relieves me entirely of the necessity of 
discussing these general questions, as it could 
not be done in a better or in a clearer way. 

I intend to give a review of the facts obtained 
from plants which go to prove the assertion, 
that species and varieties have originated by 
mutation, and are, at present, not known to orig- 
inate in any other way. This review consists 
of two parts. One is a critical survey of the 
facts of agricultural and horticultural breed- 
ing, as they have accumulated since the time of 
Darwin. This body of evidence is to be com- 
bined with some corresponding experiments 



10 


Descent 


concernmg the real nature of species in the wild 
state. The other part rests on my own obser- 
vations and experiments, made in the botanical 
garden of the University of Amsterdam. 

For many years past I have tried to elucidate 
the hereditary conditions of species and varie- 
ties, and the occasional occurrence of mutations, 
that suddenly produce new forms. 

The present discussion has a double purpose. 
On one side it will give the justification of the 
theory of mutations, as derived from the facts 
now at hand. On the other hand it will point 
out the deficiencies of available evidence, and 
indicate the ways by which the lacunae may 
gradually be filled. Experimental work on 
heredity does not require vast installments or 
a costly laboratory equipment. It demands 
chiefly assiduity and exactitude. Any one who 
has these two qualities, and who has a small 
garden at his disposal is requested to take part 
in this line of investigation. 

In order to observe directly the birth of new 
forms it is necessary, in the first place, to be 
fully dear concerning the question as to what 
forms are to be expected to arise from others, 
and before proceeding to a demonstration of the 
origin of spedes, it is pertinent to raise the 
question as to what constitutes a species. 

Species is a word, which always has had a 



Theories of Evolution 


11 


double meaning. One is the systematic species, 
which is the unit of our system. But these 
units are by no means indivisible. Long ago 
Linnaeus knew them to be compound in a great 
number of instances, and increasing knowledge 
has shown that the same rule prevails in other 
instances. Today the vast majority of the old 
systematic species are known to consist of minor 
units. These minor entities are called varieties 
in systematic works. However, there are many 
objections to this usage. First, the term vari- 
ety is applied in horticulture and agriculture 
to things so widely divergent as to convey no 
clear idea at all. Secondly, the subdivisions 
of species are by no means all of the same 
nature, and the systematic varieties include 
units the real value of which is widely differ- 
ent in different cases. Some of these vari- 
eties are in reality as good as species, and 
have been “ elevated,” as it is called, by some 
writers, to this rank. This conception of the 
elementary species would be quite justifiable, 
and would at once get rid of all difficulties, were 
it not for one practical obstacle. The number 
of the species in all genera would be doubled 
and tripled, and as these numbers are already 
cumbersome in many cases, the distinction of 
the native species of any given country would 
lose most of its charm and interest. 



12 


Descent 


In order to meet this diflSculty we must recog- 
nize two sorts of species. The systematic spe- 
cies are the practical units of the systematists 
and florists, and all friends of wild nature 
should do their utmost to preserve them as 
Linnaeus has proposed them. These units how- 
ever, are not really existing entities; they 
have as little claim to be regarded as such 
as genera and families. The real units are 
the elementary species; their limits often ap- 
parently overlap and can only in rare eases be 
determined on the sole ground of field-obser- 
vations. Pedigree-culture is the method re- 
quired and any form which remains constant 
and distinct from its allies in the garden is to 
be considered as an elementary species. 

In the following lectures we shall con- 
. sider this point at length, to show the compound 
nature of systematic species in wild and in culti- 
vated plants. In both cases, the principle is 
becoming of great importance, and many pa- 
pers published recently indicate its almost uni- 
versal acceptation. 

Among the systematic subdivisions of species, 
not all have the same claim to the title of ele- 
mentary species. In the first place the cases 
in which the differences may occur between 
parts of the same individual are to be excluded. 
Dividing an alpine plant into two halves and 



Theories of Evolution 


13 


planting one in a garden, varietal differences 
at once arise and are often designated in sys- 
tematic works under different varietal names. 
Secondly all individual differences which are of 
a fluctuating nature are to be combined into a 
group. But with these we shall deal later. 

Apart from these minor points the subdi- 
visions of the systematic species exhibit two 
widely different features. I will now try to 
make this clear in a few words, but will return 
in another lecture to a fuller discussion of this 
most interesting contrast. 

Linnaeus himself knew that in some cases all 
subdivisions of a species are of equal rank, to- 
gether constituting the group called species. 
No one of them outranks the others; it is not 
a species with varieties, but a group consisting 
only of varieties. A closer inquiry into the 
cases treated in this manner by the great master 
of systematic science, shows that here his varie- 
ties were exactly what we now call elementary 
species. 

In other cases the varieties are of a deriva- 
tive nature. The species constitutes a type that 
is pure in a race which ordinarily is still grow- 
ing somewhere, though in some cases it may 
have died out. From this type the varieties are 
derived, and the way of this derivation is usual- 
ly quite manifest to the botanist. It is ordina- 



14 


Descent 


rily by the disappearance of some superficial 
character that a variety is distinguished from 
its species, as by the lack of color in the flowers, 
of hairs on stems and foliage, of the spines and 
thorns, &c. Such varieties are, strictly speak- 
ing, not to be treated in the same way as elemen- 
tary species, though they often are. We shall 
designate them by the term of retrograde 
varieties,*' which clearly indicates the nature of 
their relationship to the species from which they 
are assumed to have sprung. In order to lay 
more stress on the contrast between elementary 
species and retrograde varieties, it should be 
stated at once, that the first are considered to 
have orig^ated from their parent-form in a 
progressive way. They have succeeded in at- 
taining something quite new for themselves, 
while retrograde varieties have only thrown 
off some peculiarity, previously acquired by 
their ancestors. 

The whole vegetable kingdom exhibits a coq 
stant struggle between progression and retro- 
gression. Of course, the great lines of the gen- 
eral pedigree are due to progression, many 
dngle steps in this direction leading together to 
the great superiority of the flowering plants 
over their cryptogamous ancestors. But pro- 
gression is nearly always accompanied by re- 
trogression in the prindpal lines of evolution, 



Theories of Evolution 


15 


as well as in the collateral branches of the gen- 
ealogical tree. Sometimes it prevails, and 
the monocotyledons are obviously a reduced 
branch of the primitive dicotyledons. In or- 
chids and aroids, in grasses and sedges, reduc- 
tion plays a most important part, leaving its 
traces on the flowers as well as on the embryo of 
the seed. Many instances could be given to prove 
that progression and retrogression are the two 
main principles of evolution at large. Hence 
the conclusion that our analysis must dissect the 
complicated phenomena of evolution so far as 
to show the separate functions of these two con- 
trasting principles. Hundreds of steps were 
needed to evolve the family of the orchids, but 
the experimenter must take the single steps 
for the object of his inquiry. He finds that 
some are progressive and others retrogressive 
and so his investigation falls under two heads, 
the origin of progressive characters, and the 
subsequent loss of the same. Progressive steps 
are the marks of elementary species, while re- 
trograde varieties are distinguished by ap- 
parent losses. They have equal claim to our 
interest and our study. 

As already stated I propose to deal first with 
the elementary spedes and afterwards with the 
retrograde varieties. I shall try to depict them 
to you in the first place as they are seen in 



16 


Descent 


nature and in culture, leaving tlie question of 
their origin to a subsequent experimental treat- 
ment 

The question of the experimental origin of 
new species and varieties has to be taken up 
from two widely separated starting points. This 
may be inferred from what we have already 
seen concerning the two opposing theories, de- 
rived and isolated from Darwin’s original 
broad conception. One of them considers 
mutations as the origin of new forms, while the 
other assumes fluctuations to be the source of 
all evolution. 

As mentioned above, my own experience has 
led me to accept the first view. Therefore I 
shall have to show that mutations do yield new 
and constant forms, while fluctuations are not 
adequate to do so. Retrograde varieties and 
elementary species may both be seen to be 
produced by sudden mutations. Varieties have 
often been observed to appear at once and quite 
unexpectedly in horticulture and agriculture, 
and a survey of these historical facts will be the 
subject of one of my lectures. In some in- 
stances I have succeeded in repeating these 
observations in my garden under the strict con- 
ditions of a scientific experiment, and these in- 
stances teach us the real nature of the process 
of mutation in all its visible features. New ele- 



Theories of Evolution 


17 


mentary species are far more rare, but I have 
discovered in the great evening-primrose, or 
Oenothera lamarckiana a strain which is pro- 
ducing them yearly in the wild state as well as 
in my garden. These observations and pedi- 
gree-experiments will be dealt with at due 
length in subsequent lectures. 

Having proved the existence and importance 
of mutations, it remains to inquire how far the 
improvements may go which are due only to 
fluctuating variability. As the term indicates, 
this variability is fluctuating to and fro, oscil- 
lating around an average type. It never fails 
nor does it, under ordinary circumstances, de- 
part far from the fixed average. 

But the deviation may be enlarged by a choice 
of extremes. In sowing their seed, the aver- 
age of the strain is seen to be changed, and in 
repeating the experiment the change may be 
considerable. It is not clear, whether theo- 
retically by such an accumulation, deviations 
might be reached which could not be attained at 
once in a single sowing. This question is hard- 
ly susceptible of an experimental answer, as it 
would require such an enormous amount of seed 
from a few mother plants as can scarcely ever 
be produced. 

The whole character of the fluctuations shows 
them to be of an opposite nature, contrasting 



18 


Descent 


manifestly 'with specific and varietal diaracters. 
By this method they may be proved to be in- 
adequate ever to make a single step along the 
great lines of evolution, in regard to progressive 
as well as to retrograde development. 

First of all fluctuations are linear, amplify- 
ing or lessening the existing qualities, but not 
really changing their nature. They are not 
observed to produce anything quite new, and 
evolution of course, is not restricted to the in- 
crease of the already existing peculiarities, but 
depends diiefly on the continuous addition of 
new characters to the stock. Fluctuations al- 
ways oscillate around an average, and if re- 
moved from this for some time, they show a 
tendency to return to it. This tendency, called 
retrogression, has never been observed to fail, 
as it should, in order to free the new strain from 
the links with the average, while new species 
and new varieties are seen to be quite free from 
their ancestors and not linked to them by 
intermediates. 

The last few lectures will be devoted to ques- 
tions concerning the great problem of the anal- 
ogy between natural and artificial selection. 
As already stated, Darwin made this analogy 
the foundation stone of his theory of descent, 
and he met 'with the severest objections and crit- 
icisms precisely on this point But I hope to 



Theories of Evolution 


19 


show that he was quite right, and that the 
cause of the divergence of opinions is due 
simply to the very incomplete state of knowl- 
edge concerning both processes. If both are 
critically analyzed they may be seen to comprise 
the same factors and further discussion may be 
limited to the appreciation of the part, which 
each of them has played in nature and among 
cultivated plants. 

Both natural and artificial selection are part- 
ly specific, and partly intra-specific or individ- 
ual. Nature of course, and intelligent men first 
chose the best elementary species from among 
the swarms. In cultivation this is the process of 
variety-testing. In nature it is the survival of 
the fittest species, or, as Morgan designates it, 
the survival of species in the struggle for ex- 
istence. The species are not changed by this 
struggle, they are only weighed against each 
other, the weak being thrown aside. 

Within the chosen elementary species there 
is also a struggle. It is obvious, that the fluc- 
tuating variability adapts some to the given 
circumstances, while it lessens the chances of 
others. A choice results, and this choice is 
what is often exclusively called selection, either 
natural or artificial. In cultivation it produces 
the improved and the local races ; in nature little 
is known about improvement in this way, but 



20 


Descent 


local adaptations with slight changes of the 
average character in separate localities, seem 
to be of quite normal occurrence. 

A new method of individual selection has 
been used in recent years in America, especially 
by W. M. Hays. It consists in judging the 
hereditary worth of a plant by the average con- 
dition of its offspring, instead of by its own 
visible characters. If this determination of the 
“ centgener power,” as Hays calls it, should 
prove to be the true principle of selection, then 
indeed the analogy between natural and artifi- 
cial selection would lose a large part of its im- 
portance. We will reserve this question for the 
last lecture, as it pertains more to the future, 
than to our present stock of knowledge. 

Something should be said here concerning 
hybrids and hybridism. This problem has of 
late reached such large proportions that it can- 
not be dealt with adequately in a short survey 
of the phenomena of heredity in general. It 
requires a separate treatment. For this reason 
I shall limit myself to a single phase of the prob- 
lem, which seems to be indispensable for a true 
and at the same time easy distinction between 
elementary species and retrograde varieties. Ac- 
cording to accepted terminology, some crosses 
are to be considered as unsymmetrical, while 
others are symmetrical. The first are one-sided, 



Theories of Evolution 


21 


some peculiarity being found in one of the 
parents and lacking in the other. The second 
are balanced, as all the characters are present 
in both parents, but are found in a different con- 
dition. Active in one of them, they are con- 
cealed or inactive in the other. Hence pairs of 
contrasting units result, while in unbalanced 
crosses no pairing of the particular character 
under consideration is possible. This leads to 
the principal difference between species and va- 
rieties, and to an experimental method of decid- 
ing between them in difficult and doubtful cases. 

Having thus indicated the general outlines of 
the subjects I shall deal with, something now 
may be said as to methods of investigation. 

There are two points in which scientific in- 
vestigation differs from ordinary pedigree-cul- 
ture in practice. First the isolation of the 
individuals and the study of individual inheri- 
tance, instead of averages. Next comes the task 
of keeping records. Every indi\'idual must be 
entered, its ancestry must be known as com- 
pletely as possible, and all its relations must be 
noted in such a form, that the most complete 
reference is always possible. Mutations may 
come unexpectedly, and when once arisen, their 
parents and grand-parents should be known. 
Records must be available which will allow of 
a most complete knowledge of the whole ancea 



22 


Descent 


tral line. This, and approximately this only, is 
the essential difference between experimental 
and accidental observation. 

Mutations are occorring from time to time in 
the wild state as well as in horticulture and 
agriculture. A selection of the most interest- 
ing instances will be given later. But in all 
such cases the experimental proof is wanting. 
The observations as a rule, only began when the 
mutation had made its appearance. A more or 
less vague remembrance about the previous 
state of the plants in question might be avail- 
able, though even this is generally absent. But 
on doubtful points, concerning possible crosses 
or possible introduction of foreign strains, mere 
recollection is insufficient. The fact of the mu- 
tation may be very probable, but the full proof 
is, of course, wanting. Such is the case with 
the mutative origin of Xanthium commune 
Wootoni from New Mexico and of Oenothera 
biennis cruciata from Holland. The same 
doubt exists as to the origin of the Capsella 
heegeri of Solms-Laubach, and of the oldest 
recorded mutation, that of Chelidonium ladnia- 
tum ia Heidelberg about 1600. 

First, we have doubts about the fact itself. 
These, however, gradually lose their impor- 
tance in the increasing accumulation of evi- 
dence. Secondly, the impossibility of a closer 



Theories of Evolution 


23 


inquiry into the real nature of the change. For 
experimental purposes a single mutation does 
not sulBSce; it must be studied repeatedly, and 
be produced more or less arbitrarily, according 
to the nature of the problems to be solved. And 
in order to do this, it is evidently not enough 
to have in hand the mutated individual, but it is 
indispensable to have also the mutable parents, 
or the mutable strain from which it sprang. 

All conditions previous to the mutation are to 
be considered as of far higher importance than 
all those subsequent to it. 

Now mutations come unexpectedly, and if the 
ancestry of an accidental mutation is to be 
known, it is of course necessary to keep ac- 
counts of all the strains cultivated. It is evi- 
dent that the required knowledge concerning the 
ancestry of a supposed mutation, must neces- 
sarily nearly all be acquired from the plants in 
the experimental garden. 

Obviously this rule is as simple in theory, as 
it is difficult to carry out in practice. First of 
all comes the book-keeping. The parents, 
grandparents and previous ancestors must be 
known individually. Accounts of them must be 
kept under two headings. A full description of 
their individual character and peculiarities 
must always be available on the one hand, and 
on the other, all facts concerning their heredi- 



24 


Descent 


tary qualities. These are to be deduced from 
the composition of the progeny, and in order 
to obtain complete evidence on this point, two 
successive generations are often required. The 
investigation must ascertain the average condi- 
tion of this offspring and the occurrence of any 
deviating specimens, and for both purposes it 
is necessary to cultivate them in relatively large 
numbers. It is obvious that, properly speak- 
ing, the whole family of a mutated individual, 
including all its nearer and more remote rela- 
tives, should be known and recorded. 

Hence pedigree-book-keeping must become 
the general rtile. Subordinate to this are two 
further points, which should likewise be stated 
here. One pertains to the pure or hybrid 
nature of the original strain, and the other to 
the life-conditions and all other external in- 
fluences. It is manifest that a complete under- 
standing of a mutation depends upon full infor- 
mation upon these points. 

All exi)eriment8 must have a beginning. The 
starting-point may be a single individual, or a 
small group of plants, or a lot of seeds. In 
many cases the whole previous history is ob- 
scure, but sometimes a little historical evidence 
is at hand. Often it is evident that the initial 
material belongs to a pure species, but with re- 
spect to the question of elementary species it is 



Theories of Evolution 


25 


not rarely open to doubt. Large numbers of 
hybrid plants and hybrid races are in existence, 
concerning the origin of which it is impossible 
to decide. It is impossible in many in- 
stances to ascertain whether they are of 
hybrid or of pure origin. Often there is only 
one way of determining the matter; it is to 
guess at the probable parents in case of a cross 
and to repeat the cross. This is a point which 
always requires great care in the interpretation 
of unusual facts. 

Three cases are to be distinguished as to 
heredity. Many plants are so constituted as to 
be fertilized with their own pollen. In this 
case the visits of insects have simply to be ex- 
cluded, which may be done by covering plants 
with iron gauze or with bags of prepared paper. 
Sometimes they fertilize themselves without 
any aid, as for instance, the common evening- 
primrose; in other cases the pollen has to be 
placed on the stigma artificially, as with La- 
marck’s evening-primrose and its derivatives. 
Other plants need cross-fertilization in order to 
produce a normal yield of seeds. Here two 
individuals have always to be combined, and 
the pedigree becomes a more complicated one. 
Such is the case with the toad-flax, which is 
nearly sterile with its own pollen. But even in 
these cases the visits of insects bringing pollen 



26 


Descent 


from other plants, must be carefully excluded. 
A special lecture will be devoted to this very in- 
teresting source of impurity and of imcertainty 
in ordinary cultures. 

Of course, crosses may lie in the proposed 
line of work, and this is the third point to be 
alluded to. They must be surrounded with the 
same careful isolation and protection against 
bees, as any other fertilizations. And not only 
the seed-parent, but also the pollen must be 
kept pure from all possible foreign admixtures. 

A pure and accurately recorded ancestry is 
thus to be considered as the most important 
condition of success in experimental plant- 
breeding. Next to this comes the gathering of 
the seeds of each individual separately. Fifty 
or sixty, and often more, bags of seeds are by no 
means uncommon for a single experiment, and 
in ordinary years the harvest of my garden is 
preserved in over a thousand separate lots. 

Complying with these conditions, the origin 
of species may be seen as easily as any other 
phenomenon. It is only necessary to have a 
plant in a mutable condition. Not all species 
are in such a state at present, and therefore I 
have begun by ascertaining which were stable 
and which were not These attempts, of course, 
had to be made in the experimental garden, and 
large quantities of seed had to be procured and 



Theories of Evolution 


27 


sown. Cultivated plants of course, had only 
a small chance to exhibit new qualities, as they 
have been so strictly controlled during so many 
years. Moreover their purity of origin is in 
many cases doubtful. Among wild plants only 
those could be expected to reward the investi- 
gator which were of easy cultivation. For this 
reason I have limited myself to the trial of wild 
plants of Holland, and have had the good for- 
tune to find among them at least one species in a 
state of mutability. It was not really a native 
plant, but one that had been introduced from 
America and belongs to an American genus. I 
refer to the great evening-primrose or the even- 
ing-primrose of Lamarck. A strain of this 
beautiful species is growing in an abandoned 
field in the vicinity of Hilversum, at a short dis- 
tance from Amsterdam. Here it has escaped 
from a park and multiplied. In doing so it has 
produced and is still producing quite a number 
of new types, some of which may be considered 
as retrograde varieties, while others evidently 
are of the nature of progressive elementary 
species. 

This interesting plant has afforded me the 
means of observing directly how new species 
originate, and of studying the laws of these 
changes. My researches have followed a double 
line of inquiry. On one side, I have limited 



28 


Descent 


myself to direct field observations, and to tests 
of seed, collected from the wild plants in their 
native locality. Obviously the mutations are 
decided within the seed, and the culture of 
young plants from them had no other aim than 
that of ascertaining what had occurred in the 
field. And then the many chances of destruc- 
tion that threaten young plants in a wild state, 
could be avoided in the garden, where enviro- 
mental factors can be controlled. 

My second line of inquiry was an experi- 
mental repetition of the phenomena which were 
only partly discerned at the native locality. It 
was not my aim to intrude into the process, nor 
to try to bring out new features. My only ob- 
ject was to submit to the precepts just given 
concerning pure treatment, individual seed- 
gathering, exclusion of crosses and accurate 
recording of all the facts. The result has been 
a pedigree which now permits of stating the re- 
lation between all the descendants of my orig- 
inal introduced plant. This pedigree at once 
exhibits the laws followed by the mutating spe- 
cies. The main fact is, that it does not change 
itself gradually, but remains unaffected during 
all succeeding generations. It only throws off 
new forms, which are sharply contrasted with 
the parent, and which are from the very begin- 
ning as perfect and as constant, as narrowly 



Theories of Evolution 


29 


defined and ae pure of type as might be ex- 
pected of any species. 

These new species are not produced once or 
in single individuals, but yearly and in large 
numbers. The whole phenomenon conveys the 
idea of a close group of mutations, all belonging 
to one single condition of mutability. Of course 
this mutable state must have had a beginning, 
as it must sometime come to an end. It is to 
be considered as a period within the life-time of 
the species and probably it is only a small part 
of it. 

The detailed description of this experiment, 
however, I must delay to a subsequent lecture, 
but I may be allowed to state, that the discov- 
ery of this period of mutability is of a definite 
theoretical importance. One of the greatest ob- 
jections to tlie Darwinian theory of descent 
arose from the length of time it would require, 
if all evolution was to be explained on the 
theory of slow and nearly invisible changes. 
This difficulty is at once met and fully sur- 
mounted by the hypothesis of periodical but 
sudden and quite noticeable steps. This as- 
sumption requires only a limited number of 
mutative periods, which might well occur within 
the time allowed by physicists and geologists 
for the existence of animal and vegetable life 
on the earth. 



Descent 


Smnmixig up the main points of these intro- 
ductory remarks, I propose to deal with the sub- 
jects mentioned above at some length, devoting 
to each of them, if possible at least an entire 
lecture. The decisive facts and discussions 
upon which the conclusions are based will be 
given in every case. Likewise I hope to point 
out the weak pla^s and the lacunae in our pres- 
ent knowledge, and to show the way in which 
each of you may try to contribute his part to- 
wards the advancement of science in this sub- 
ject Lastly I shall try to prove that sudden 
mutation is the normal way in which nature 
produces new species and new varieties. These 
mutations are more readily accessible to ob- 
servation and experiment than the slow and 
gradual changes surmised by Wallace and his 
followers, which are entirely beyond our pres- 
ent and future experience. 

The theory of mutations is a starting-point 
for direct investigation, while the general belief 
in slow changes has held back science from such 
investigations during half a century. 

Coming now to the subdivisions and headings 
under which my material is to be presented, I 
propose describing first the real nature of the 
elementary species and retrograde varieties, 
both in normal form and in hybridizations. A 
discussion of other types of varieties, includ- 



Theories of Evolution 


31 


ing monstrosities will complete the general plan. 
The second subdivision will deal with the origin 
of species and varieties as taught by esperiment 
and observation, treating separately the sud- 
den variations which to my mind do produce 
new forms, and subsequently the fluctuations 
which I hold to be not adequate to this purpose. 



B. ELEMENTARY SPECIES 
Lecttjbe II 

EliEMEKTABY SPECIES IN NATUBE 

What are species? Species are considered 
as the true units of nature by the vast majority 
of biologists. They have gained this high 
rank in our estimation principally through the 
influence of Linnaeus., They have supplanted 
the genera which were the accepted units before 
Linnaeus. They are now to be replaced in their 
turn, by smaller types, for reasons which do not 
rest upon comparative studies but upon direct 
experimental evidence. 

Biological studies and practical interests 
alike make new demands upon systematic bot- 
any. Species are not only the subject-material 
of herbaria and collections, but they are living 
entities, and their life-history and life-condi- 
tions command a gradually increasing interest. 
One phase of the question is to determine the 
easiest manner to deal with the collected forms 
of a country, and another feature is the problem 


32 



Elementary Species in Nature 33 

as to what groups are real units and will remain 
constant and unchanged through all the years 
of our observations. 

Before Linnaeus, the genera were the real 
units of the system. De Candolle pointed out 
that the old common names of plants, such as 
roses and clover, poplars and oaks, nearly all 
refer to genera. The type of the clovers is 
rich in color, and the shape of the flower-heads 
and the single flowers escape ordinary obser- 
vation; but notwithstanding this, clovers are 
easily recognized, even if new types come to 
hand. White and red clovers and many other 
species are distinguished simply by adjectives, 
the generic name remaining the same for all. 

Toumefort, who lived in the second half of 
the 17th century (1656-1708), is generally con- 
sidered as the author of genera in systematic 
botany. He adopted, what was at that time 
the general conception and applied it through- 
out the vegetable kingdom. He grouped the 
new and the rare and the previously over- 
looked forms in the same manner in which the 
more conspicuous plants were already ar- 
ranged by universal consent. Species were dis- 
tinguished by minor marks and often indicated 
by short descriptions, but they were consid- 
ered of secondary importance. 

Based on the idea of a direct creation of all 



34 


Elementary Species 


living beings, the genera were then accepted as 
the created forms. They were therefore re- 
garded as the real existing types, and it was 
generally surmised that species and varieties 
owed their origin to subsequent changes under 
the influence of external conditions. Even Lin- 
naeus agreed with this view in his first treatises 
and in his Philosophical Botany” he still kept 
to the idea that all genera had been created at 
once with the beginning of life. 

Afterwards Linnaeus changed his opinion on 
this important point, and adopted species as the 
units of the system. He declared them to be 
the created forms, and by this decree, at once re- 
duced the genera to the rank of artificial groups. 
Linnaeus was well aware that this conception 
was wholly arbitrary, and that even the species 
are not real indivisible entities. But he sim- 
ply forbade the study of lesser subdivisions. 
At his time he was quite justified in doing so, 
because the first task of the systematic botanists 
was the clearing up of the chaos of forms and 
the bringing of them into connection with their 
real allies. 

Linnaeus himself designated the subdivisions 
of the species as varieties, but in doing so he 
followed two clearly distinct principles. In 
some cases his species were real plants, and the 
varieties seemed to be derived from them by 



Elementary Species in Nature 35 

some simple changes. They were subordinated 
to the parent-species. In other cases his spe- 
cies were groups of lesser forms of equal value, 
and it was not possible to discern which was 
the primary and which were the derivatives. 

These two methods of subdivision seem in the 
main, and notwithstanding their relatively im- 
perfect application in many single examples, to 
correspond with two really distinct cases. The 
derivative varieties are distinguished from the 
parent-species by some single, but striking mark, 
and often this attribute manifests itself as the 
loss of some apparent quality. The loss of 
spines and of hairs and the loss of blue and red 
flower-colors are the most notorious, but in 
rarer cases many single peculiarities may dis- 
appear, thereby constituting a variety. This 
relation of varieties to the parentrspecies is 
gradually increasing in importance in the esti- 
mation of botanists, sharply contrasting with 
those cases, in which such dependency is not to 
be met with. 

If among the subdivisions of a species, no 
single one can be pointed out as playing a pri- 
mary part, and the others can not be traced 
back to it, the relation between these lesser 
units is of course of another character. They 
are to be considered of equal importance. They 
are distinguished from each other by more than 



36 


Elementary Species 


one character, often by slight differences in 
nearly all their organs and qualities. Such 
forms have come to he designated as “ elemen- 
tary species.” They are only varieties in a 
broad and vague systematic significance of the 
word, not in the sense accorded to this term in 
horticultural usage, nor in a sharper and more 
scientific conception. 

Genera and species are, at the present time, 
for a large part artificial, or stated more cor- 
rectly, conventional groups. Every systematist 
is free to delimit them in a wider or in a nar- 
rower sense, according to his judgment The 
greater authorities have as a rule preferred 
larger genera, others of late have elevated in- 
numerable subgenera to the rank of genera. 
This would work no real harm, if unfortu- 
nately, the names of the plants had not to be 
changed each time, according to current ideas 
concerning genera. Quite the same inconstancy 
is observed with species. In the Handbook 
of the British Flora, Bentham and Hooker de- 
scribe the forms of brambles under 5 species, 
while Babington in his Manual of British 
Botany makes 45 species out of the same mate- 
rial. So also in other cases. For instance, the 
willows which have 13 species in one and 31 
species in the other of these manuals, and the 
hawkweeds for which the figures are 7 and 32 



Elementary Species in Nature 37 

respectively. Other authors have made still 
greater numbers of species in the same groups. 

It is very difficult to estimate systematic dif- 
ferences on the ground of comparative studies 
alone. All sorts of variability occur, and no 
individual or small group of specimens can 
really be considered as a reliable representa- 
tive of the supposed type. Many original diag- 
noses of new species have been founded on di- 
vergent specimens and of course, the type can 
afterwards neither be derived from this indi- 
vidual, nor from the diagnosis given. 

This chaotic state of things has brought some 
botanists to the conviction that even in syste- 
matic studies only direct experimental evidence 
can be relied upon. This conception has in- 
duced them to test the constancy of species and 
varieties, and to admit as real units only such 
groups of individuals as prove to be uniform 
and constant throughout succeeding gener- 
ations. The late Alexis Jordan, of Lyons in 
France, made extensive cultures in this direc- 
tion. In doing so, he discovered that syste- 
matic species, as a rule, comprise some lesser 
forms, which often cannot easily be distin- 
guished when grown in different regions, or by 
comparing dried material. This fact was, of 
course, most distasteful to the systematists of 
his time and even for a long period afterwards 



38 


Elementary Species 


they attempted to discredit it Milde and many 
others have opposed these new ideas with some 
temporary success. Only of late has the school 
of Jordan received due recognition, after 
Thuret, de Bary, Rosen and others tested 
its practices and openly pronounced for them. 
Of late Wittrock of Sweden has joined them, 
making extensive experimental studies concern- 
ing the real units of some of the larger species 
of his country. 

From the evidence given by these eminent 
authorities, we may conclude that systematic 
species, as they are accepted nowadays, are as 
a rule compound groups. Sometimes they con- 
sist of two or three, or a few elementary types, 
but in other cases they comprise twenty, or fifty, 
or even hundreds of constant and weU differen- 
tiated forms. 

The inner constitution of these groups is 
however, not at all the same in all cases. This 
will be seen by the description of some of the 
more interesting of them. The European 
heartsease, from which our garden-pansies have 
been diiefly derived, will serve as an example. 
The garden-pansies are a hybrid race, won by 
crossing the Viola tricolor with the large flow- 
ered and bright yellow V. lutea. They com- 
bine, as everyone knows, in their wide range of 



Elementary Species in Nature 39 

varieties, the attributes of the latter with the 
peculiarities of the former species. 

Besides the lutea, there are some other spe- 
cies, nearly allied to tricolor, as for instance, 
cornuta, calcarata, and altaica, which are com- 
bined with it under the head of Melanium as a 
subgenus, and which together constitute a syste- 
matic unity of undoubted value, but ranging be- 
tween the common conceptions of genus and 
species. These forms are so nearly allied to 
the heartsease that they have of late been made 
use of in crosses, in order to widen the range 
of variability of garden-pansies. 

Viola tricolor is a common European weed. 
It is widely dispersed and very abundant, grow- 
ing in many localities in large numbers. It is 
an annual and ripens its seeds freely, and if op- 
portunity is afforded, it multiplies rapidly. 

Viola tricolor has three subspecies, which 
have been elevated to the rank of species by 
some authors, and which may here be called, for 
brevity’s sake, by their binary names. One is 
the typical V. tricolor, with broad flowers, vari- 
ously colored and veined with yellow, purple 
and white. It occurs in waste places on sandy 
soil. The second is called V. arvensis or the 
field-pansy; it has Ismail inconspicuous flowers, 
with pale yellowish petals which are shorter 
than the sepals. It pollinates itself without the 



40 


Elementary Species 


aid of insects, and is widely dispersed in culti- 
vated fields. The third form, F. alpestris, 
grows in the Alps, but is of lesser importance 
for our present discussion. 

Anywhere throughout the central part of 
Europe F. tricolor and F. arvensis may be seen, 
each occupying its own locality. They may be 
considered as ranging among the most common 
native plants of the particular regions they in- 
habit. They vary in the color of the flowers, 
branching of the stems, in the foliage and other 
parts, but not to such an extent as to consti- 
tute distinct strains. They have been brought 
into cultivation by Jordan, Wittrock and others, 
but throughout Europe each of them constitutes 
a single type. 

These types must be very old and constant, 
fluctuating always within the same distinct and 
narrow limits. No slow, gradual changes can 
have taken place. In different countries their 
various habitats are as old as the historical 
records, and probably many centuries older. 
They are quite independent of one another, the 
distance being in numerous cases far too great 
for the exchange of pollen or of seeds. If slow 
and gradual changes were the rule, the types 
could not have remained so uniform throughout 
the whole range of these two species. They 
would necessarily have split up into thousands 



Elementary Species in Nature 41 

and thousands of minor races, which would 
show their peculiar characteristics if tested by 
cultures in adjacent beds. This however, is not 
what happens. As a matter of fact V. tricolor 
and F. arvensis are widely distributed but 
wholly constant types. 

Besides these, there occur distinct types in 
numerous localities. Some of them evidently 
have had time and opportunity to spread more 
or less widely and now occupy larger regions or 
even whole countries. Others are narrowly lim- 
ited, being restricted to a single locality. Witt- 
rock collected seeds or plants from as many 
localities as possible in different parts of 
Sweden and neighboring states and sowed them 
in his garden near Stockholm. He secured 
seeds from his plants, and grew from them a 
second, and in many cases a third generation in 
order to estimate the amount of variability. As 
a rule the forms introduced into his garden 
proved constant, notwithstanding the new and 
abnormal conditions under which they were 
propagated. 

First of all we may mention three perennial 
forms called by him Viola tricolor ammotropha, 
V. tricolor coniophila and V. stenochUa. The 
typical F. tricolor is an annual plant* sowing 
itself in summer and germinating soon after- 
wards. The young plants thrive throughout 



42 Elementary Species 

the latter part of the summer and during the 
fall, reaching an advanced stage of development 
of the branched stems before winter. Early in 
the spring the flowers begin to open, but after 
the ripening of the seeds the whole plant dies. 

The three perennial species just mentioned 
develop in the same manner in the first year. 
During their flowering period, however, and 
afterwards, they produce new shoots from the 
lower parts of the stem. They prefer dry and 
sandy soils, often becoming covered with the 
sand that is blown on them by the winds. They 
are prepared for such seemingly adverse cir- 
cumstances by the accumulation of food in the 
older stems and by the capacity of the new 
shoots to thrive on this food till they have 
become long enough to reach the light. V. 
tricolor ammotropha is native near Ystad 
in Sweden, and the other two forms on Got- 
land. All three have narrowly limited habi- 
tats. 

The typical tricolored heartsease has re- 
mained annual in all its other subspecies. It 
may be divided into two types in the first place : 
V. tricolor genuina and F. tricolor versicolor. 
Both of them have a wide distribution and seem 
to be the prototypes from which the rarer forms 
must have been derived. Among these latter 
Wittrock describes seven local types, which 



Elementary Species in Nature 43 

proved to be constant in his pedigree-cultures. 
Some of them have produced other forms, re- 
lated to them in the way of varieties, ^hey all 
have nearly the same general habit and do not 
exhibit any marked differences in their growth, 
in the structure and branching of the stems, or 
in the character of their foliage. Differentiat- 
ing points are to be found mainly in the colors 
and patterns of the flowers. The veins, which 
radiate from the centre of the corolla are 
branched in some and undivided in others; in 
one elementary species they are wholly lack- 
ing. The purple color may be absent, leav- 
ing the flowers of a pale or a deep yellow. Or 
the purple may be reddish or bluish. Of 
the petals all five may have the purple hue 
on their tips, or this attribute may be limited to 
the two upper ones. Contrasting with this wide 
variability is the stability of the yellow spot in 
the centre, which is always present and becomes 
inconspicuous only, when the whole petals are 
of the same hue. It is a general conception 
that colors and color-markings are liable to 
great variability and do not constitute reliable 
standards. But the cultures of Wittrock have 
proved the contrary, at least in the case of the 
violets. No pattern, however quaint, appears 
changeable, if one elementary species only is 
considered. Hundreds of plants from seeds 



44 


Elementary Species 


from one locality may be grown, and all will ex- 
hibit exactly the same markings. Most of these 
forms are of very local occurrence. The most 
beautiful of all, the ornatissima, is found only in 
Jemtland, the aurobadia only in Sodermanland, 
the anopetala in other localities in the same 
country, the roseola near Stockholm, and the 
yellow lutescens in Finmarken. 

The researches of Wittrock included only a 
small number of elementary species, but every 
one who has observed the violets in the central 
parts of Europe must be convinced that many 
dozens of constant forms of the typical Viola 
tricolor might easily be found and isolated. 

We now come to the field pansy, the Viola ar- 
vensis, a very common weed in the grain-fields 
of central Europe. I have already mentioned 
its small corolla, surpassed by the lobes of the 
calyx and its capacity of self-fertilization. It 
has still other curious differentiating charac- 
ters; the pollen grains, which are square in 
F. tricolor, are five-sided in F. arvensis. 
Some transgressive fluctuating variability may 
occur in both cases through the admixture 
of pollen-grains. Even three-angled pollen- 
grains are seen sometimes. Other marks are 
observed in the form of the anthers and the 
spur. 

There seem to be very many local subspecies 



Elementary Species in Nature 45 

of the field-pansy. Jordan has described some 
from the vicinity of Lyons, and Wittrock others 
from the northern parts of Europe. They 
diverge from their common prototype in nearly 
all attributes, the flowers not showing the 
essential differentiating characters as in the 
V. tricolor. Some have their flower-stalks 
erect, and in others the flowers are held nearly 
at right angles to the stem. V. pallescens is a 
small, almost unbranched species with small 
pale flowers. V. segetalis is a stouter species 
with two dark blue spots on the tips of the upper 
petals. V. agrestis is a tall and branched, 
hairy form. F. nemausensis attains a height of 
only 10 cm., has rounded leaves and long 
flower-stalks. Even the seeds afford charac- 
ters which may be made use of in isolating the 
various species. 

The above-mentioned elementary forms be- 
long to the flora of southern France, and Witt- 
rock has isolated and cultivated a number of 
others from the fields of Sweden. A species 
from Stockholm is called Viola patens; F. arven- 
sis curtisepala occurs in Gotland, and F. arven- 
sis striolata is a distinct form, which has ap- 
peared in his cultures without its true origin 
being ascertained. 

The alpine violets comprise a more wide- 
spread type with some local elementary species 



46 


Elementary Species 


derived exactly in the same way as the trieol- 
ored field-pansies. 

Summarizing the general resnlt of this de- 
scription we see that the original species Viola 
tricolor may he split up into larger and lesser 
groups of separate forms. These last prove to 
be constant in pedigree-cultures, and therefore 
are to be considered as really existent units. 
They are very numerous, comprising many 
dozens in each of the two larger subdivisions. 

All systematic grouping of these forms, and 
their combination into subspecies and species 
rests on the comparative study of their charac- 
ters. The result of such studies mu^ neces- 
sarily depend on principles which underlie 
them. According to the choice of these 
principles, the construction of the groups 
will be found to be different. Wittrock trusts 
in the first place to morphologic charac- 
ters, and considers the development as passing 
from the more simple to the more complex 
types. On the other hand the geographic dis- 
tribution may be considered as an indication of 
the direction of evolution, the wide-spread 
forms being regarded as the common parents of 
the minor local species. 

However, such considerations are only of sec- 
ondary importance. It must be borne in mind 
that an ordinary systematic species may include 



Elementary Species in Nature 47 

many dozens of elementary forms, each of which 
remains constant and imchanged in successive 
generations, even if cultivated in the same gar- 
den and under similar external conditions. 

Leaving the violets, we may take the vernal 
whitlow-grass or Draba verna for a second illus- 
tration. This little annual cruciferous plant is 
common in the fields of many parts of the 
United States, though originally introduced 
from Europe. It has small basal rosettes which 
develop during summer and winter, and pro- 
duce numerous leafless flowering stems early in 
the spring. It is a native of central Europe 
and western Asia, and may be considered as one 
of the most common plants, occurring anywhere 
in immense numbers on sandy soils. Jordan 
was the first to point out that it is not the same 
throughout its entire range. Although a hasty 
survey does not reveal differences, they show 
themselves on closer inspection. De Bary, 
Thuret, Bosen and many others confirmed this 
result, and repeated the pedigree-cultures of 
Jordan. Every type is constant and remains 
unchanged in successive generations. The an- 
thers open in the flower-buds and pollinate the 
stigmas before the expansion of the flowers, 
thus assuring self-fertilization. Moreover, 
these inconspicuous little flowers are only spar- 
ingly visited by insects. Dozens of subspecies 



48 


Elementary Species 


may be cultivated in the same garden without 
any real danger of their intercrossing. They 
remain as pure as under perfect isolation. 

It is very interesting to observe the aspect of 
such- types, when growing near each other. 
Hundreds of rosettes exhibit one type, and are 
undoubtedly similar. The alternative group is 
distinguishable at first sight, though the differ- 
entiating marks are often so slight as to be 
traceable with difficulty. Two elementary spe- 
cies occur in Holland, one with narrow leaves in 
the western provinces and one with broader 
foliage in the northern parts. I have cultivated 
them side by side, and was as much sti ack with 
the uniformity within each group, as with the 
contrast between the two sets. 

Nearly all organs show differences. The 
most marked are those of the leaves, which may 
be small or large, linear or elliptic or oblong and 
even rhomboidal in shape, more or less hairy 
with simple or with stellate branched hairs, and 
finally of a pure green or of a glaucous color. 
The petals are as a rule obcordate, but this type 
may be combined with others having more or 
less broad emarginations at the summit, and 
with differences in breadth which vary from al- 
most linear types to others which touch along 
their margins. The pods are short and broad, 
or long and narrow, or varying in sundry other 



Elementary Species in Nature 49 

ways. All in all there are constant differences 
which are so great that it has been possible to 
distinguish and to describe large numbers of 
types. 

Many of them have been tested as to their 
constancy from seed. Jordan made numerous 
cultures, some of which lasted ten or twelve 
years; Thuret has verified the assertion con- 
cerning their constancy by cultures extending 
over seven years in some instances ; Villars and 
de Bary made numerous trials of shorter dura- 
tion. All agree as to the main points. The local 
races are uniform and come true from seed ; the 
variability of the species is not of a fiuctuating, 
but of a polymorphous nature. A given ele- 
mentary species keeps within its limits and can- 
not vary beyond them, but the whole group 
gives the impression of variability by its wide 
range of distinct, but nearly allied forms. 

The geographic distribution of these ele- 
mentary species of the whitlow-grass is quite 
distinct from that of the violets. Here predom- 
inant species are limited to restricted locali- 
ties. Most of them occupy one or more depart- 
ments of France, and in Holland two of them 
are spread over several provinces. An import- 
ant number are native in the centre of Europe, 
and from the vicinity of Lyons, Jordan suc- 
ceeded in establishing about fifty elementary 



50 


Elementary Species 


species in his garden. In this region they are 
crowded together and not rarely two or even 
more quite distinct forms are observed to grow 
side by side on the same spot. Farther away 
from this center they are more widely dispersed, 
each holding its own in its habitat. In all, Jor- 
dan has distinguished about two hundred spe- 
cies of Draha verna from Europe and western 
Asia. Subsequent authors have added new 
types to the already existing number from time 
to time. 

The constancy of these elementary species is 
directly proven by the experiments quoted 
above, and moreover it may be deduced from the 
uniformity of each type within its own domain. 
These are so large that most of the localities are 
practically isolated from one another, and must 
have been so for centuries. If the types were 
slowly changing such localities would often, 
though of course not always, exhibit slighter 
differences, and on the geographic limits of 
neighboring species intermediates would be 
found. Such however, are not on record. 
Hence the elementary species must be regarded 
as old and constant types. 

The question naturally arises how these 
groups of nearly allied forms may originally 
have been produced. Granting a common ori- 
gin for all of them, the changes may have been 



Elementary Species in Nature 51 

simultaneous or successive. According to the 
geographic distribution, the place of common 
origin must probably be sought in the southern 
part of central Europe, perhaps even in the 
vicinity of Lyons. Here we may assume that 
the old Draba verna has produced a host or a 
swarm of new types. Thence they must have 
spread over Europe, but whether in doing so 
they have remained constant, or whether some 
or many of them have repeatedly undergone 
specific mutations, is of course unknown. 

The main fact is, that such a small species as 
Draba verna is not at all a uniform type, but 
comprises over two hundred well distinguished 
and constant forms. 

It is readily granted that violets and whitlow- 
grasses are extreme instances of systematic 
variability. Such great numbers of elementary 
species are not often included in single species 
of the system. But the numbers are of second- 
ary importance, and the fact that systematic 
si)ecies consist, as a rule, of more than one inde- 
pendent and constant subspecies, retains its al- 
most universal validity. 

In some cases the systematic species are man- 
ifest groups, sharply differentiated from one 
another. In other instances the groups of ele- 
mentary forms as they are shown by direct ob- 
servation, have been adjudged by many authors 



52 


Elementary Species 


to be too large to constitute species. Hence the 
polymorphous genera, concerning the syste- 
matic subdivisions of which hardly two authors 
agree. Brambles and roses are widely known 
instances, but oaks, elms, apples, and pears, 
Mentha, Prunus, Vitis, Lactuca, Cucumis, Cu- 
curbita and numerous others are in the same 
condition. 

In some instances the existence of elementary 
species is so obvious, that they have been de- 
scribed by taxonomists as systematic varieties 
or even as good species. The primroses afford 
a widely known example. Linnaeus called them 
Primula veris, and recognized three types as 
pertaining to this species, but Jacquin and 
others have elevated these subspecies to the full 
rank of species. They now bear the names of 
Primula elatior with larger, P. officinalis with 
smaller flowers, and P. acaulis. In the last 
named the common flower-stalk is lacking and 
the flowers of the umbel seem to be borne in 
the axils of the basal leaves. 

In other genera such nearly allied species are 
more or less universally recognized. Galium 
Mollugo has been divided into G, datum with a 
long and weak stem, and G. erectum with 
shorter and erect stems; Cochlearia da/nica, cm- 
glica and officvncdis are so nearly allied as to be 
hardly distinguishable. Sagina apetala and pat- 



Elementary Species in Nature 53 

ula, Spergula media and salina and many other 
pairs of allied species have differentiating char- 
acters of the same value as those of the element- 
ary species of Draba verna. Filago, Plantago, 
Carex, Ficaria and a long series of other genera 
afford proofs of the same close relation be- 
tween smaller and larger groups of species. The 
European frost-weeds or Eelianthemum in- 
clude a group of species which are so closely al- 
lied, that ordinary botanical descriptions are 
not adequate to give any idea of their differen- 
tiating features. It is almost impossible to 
determine them by means of the common ana- 
lytical keys. They have to be gathered from 
their various native localities and cultivated 
side by side in the garden to bring out their 
differences. Among the species of France, ac- 
cording to Jordan, Eelianthemum polifolium, 
E. apenninum, E. pilosum and E, pulverulen- 
tum are of this character. 

A species of cinquefoil, Potentilla Tormen- 
tilla, which is distinguished by its quatemate 
flowers, occurs in Holland in two distinct types, 
which have proved constant in my cultural exper- 
iments. One of them has broad petals, meeting 
together at the edges, and constituting a round- 
ed saucer without breaks. The other has nar- 
row petals, which are strikingly separated from 
one another and show the sepals between them. 



54 


Elementary Species 


In the same manner bluebells vary in the size 
and shape of the corolla, which may be wide or 
narrow, bell-shaped or conical, with the tips 
turned downwards, sidewards or backwards. 

As a rule all of the more striking elementary 
types have been described by local botanists 
under distinct specific names, while they are 
thrown together into the larger systematic spe- 
cies by other authors, who study the distribu- 
tion of plants over larger portions of the 
world. Everything depends on the point of 
view taken. Large floras require large species. 
But the study of local floras yields the best re- 
sults if the many forms of the region are distin- 
guished and described as completely as possible. 
And the easiest way is to give to each of them a 
specific name. If two or more elementary spe- 
cies are united in the same district, they are 
often treated in this way, but if each region had 
its own type of some given species, commonly 
the part is taken for the whole, and the sundry 
forms are described under the same name, with- 
out further distinctions. 

Of course these questions are all of a practical 
and conventional nature, but involve the differ- 
ent methods in which different authors deal 
with the same general fact. The fact is that 
systematic species are compound groups, ex- 
actly like the genera and that their real units 



Elementary Species in Nature 55 

can only be recognized by comparative experi- 
mental studies. 

Though the evidence already given might be 
esteemed to be sufficient for our purpose, I 
should like to introduce a few more examples ; 
two of them pertain to American plants. 

The Ipecac spurge or Euphorbia Ipecacu- 
anha occurs from Connecticut to Florida, 
mainly near the coast, preferring dry and sandy 
soil. It is often found by the roadsides. Ac- 
cording to Britton and Brown’s “Illustrated 
Flora” it is glabrous or pubescent, with several 
or many stems, ascending or nearly erect ; with 
green or red leaves, which are wonderfully 
variable in outline, from linear to orbicular, 
mostly opposite, the upper sometimes whorled, 
the lower often alternate. The glands of the 
involucres are elliptic or oblong, and even the 
seeds vary in shape. 

Such a wide range of variability evidently 
points to the existence of some minor types. 
Dr. John Harshberger has made a study of 
those which occur in the vicinity of Whitings in 
New Jersey. His types agree with the descrip- 
tion given above. Others were gathered by 
him at Brown’s Mills in the pinelands. New 
Jersey, where they grew in almost pure sand in 
the bright sunlight. He observed still other 
differentiating characters. The amount of seed 



56 


Elementary Species 


produced and the time of flowering were vari- 
able to a remarkable degree. 

Dr. Harshberger had the kindness to send me 
some dried specimens of the most interesting of 
these types. They show that the peculiarities 
are individual, and that each specimen has its 
own characters. It is very probable that a 
comparative experimental study will prove the 
existence of a large number of elementary spe- 
cies, differing in many points; they will prob- 
ably also show differences in the amount of 
the active chemical substances, especially of 
emetine, which is usually recorded as present in 
about liy but which will undoubtedly be 
found in larger quantities in some, and in 
smaller quantities in other elementary species. 
In this way the close and careful distinction of 
the really existing units might perhaps prove 
of practical importance. 

Macfarlane has studied the beach-plum or 
Prunus maritima, which is abundant along the 
coast regions of the Eastern States from Vir- 
ginia to New Brunswick. It often covers areas 
from two to two hundred acres in extent, some- 
times to the exclusion of other plants. It is most 
prolific on soft drifting sand near the sea or 
along the shore, where it may at times be washed 
with ocean-spray. The fruit usually become 
ripe about the middle of August, and show ex- 



Elementary Species in Nature 57 

treme variations in size, shape, color, taste, con- 
sistency and maturation period, indicating the 
existence of separate races or elementary spe- 
cies, with widely differing qualities. The earlier 
varieties begin to ripen from August 10 to 20, 
and a continuous supply can be had till Septem- 
ber 10, while a few good varieties continue to 
ripen till September 20. But even late in Octo- 
ber some other types are still found maturing 
their fruits. 

Exact studies were made of fruit and stone 
variations, and their characteristics as to color, 
weight, size, shape and consistency were fully 
described. Similar variations have been ob- 
served, as is well known, in the cultivated 
plums. Fine blue-black fruits were seen on 
some shrubs and purplish or yellow fruits on 
others. Some exhibit a firmer texture and 
others a more watery pulp. Even the stones 
show differences which are suggestive of dis- 
tinct races. 

Recently Mr. Luther Burbank of Santa Rosa, 
California, has made use of the beach-plum to 
produce useful new varieties. He observed 
that it is a very hardy species, and never fails 
to bear, growing under the most trying condi- 
tions of dry and sandy, or of rocky and even of 
heavy soil. The fruits of the wild shrubs are 
utterly worthless for anything but preserving. 



58 


Elementary Species 


But by means of crossing with other species 
and especially with the Japanese plums, the 
hardy qualities of the beach-plum have been 
united with the size, flavor and other valuable 
qualities of the fruit, and a group of new plums 
have been produced with bright colors, ovoid and 
globular forms which are never flattened and 
have no suture. The experiments were not fin- 
ished, when I visited Mr. Burbank in July, 1904, 
and still more startling improvements were said 
to have been secured. 

I may perhaps be allowed to avail myself of 
this opportunity to point out a practical side of 
the study of elementary species. This always 
appears whenever wild plants are subjected to 
cultivation, either in order to reproduce them as 
pure strains, or to cross them with other al- 
ready cultivated species. The latter practice 
is as a rule made use of whenever a wild spe- 
cies is found to be in possession of some quality 
which is considered as desirable for the culti- 
vated forms. In the case of the beach-plum 
it is the hardiness and the great abundance of 
fruits of the wild species which might profit- 
ably be combined with the recognized qualities 
of the ordinary plums. Now it is manifest, that 
in order to make crosses, distinct individual 
plants are to be chosen, and that the variability 
of the wild species may be of very great im- 



Elementary Species in Nature 59 

portance. Among the range of elementary spe- 
cies those should he used which not only pos- 
sess the desired advantages in the highest de- 
gree, but which promise the best results in other 
respects or their earliest attainment. The 
fuller our knowledge of the elementary species 
constituting the systematic groups, the easier 
and the more reliable will be the choice for the 
breeder. Many Californian wild flowers with 
bright colors seem to consist of large numbers 
of constant elementary forms, as for instance, 
the lilies, godetias, eschscholtias and others. 
They have been brought into cultivation many 
times, but the minutest distinction of their ele- 
mentary forms is required to attain the highest 
success. 

In concluding, I will point out a very interest- 
ing difficulty, which in some cases impedes the 
clear understanding of elementary species. It 
is the lack of self-fertilization. It occurs in 
widely distant families, but has a special inter- 
est for us in two genera, which are generally 
known as very polymorphous groups. 

One of them is the hawkweed or Hieracium, 
and the other is the dandelion or Taraxacum 
officinale. Hawkweeds are known as a genus 
in which the delimitation of the species is al- 
most impossible. Thousands of forms may be 
cultivated side by side in botanical gardens, ex- 



60 


Elementary Species 


hibiting slight but undoubted differentiating 
features, and reproduce themselves truly by 
seed. Descriptions were formerly difficult and 
so complicated that the ablest writers on this 
genus, Fries and Nageli are said not to have 
been able to recognize the separate species by 
the descriptions given by each other. Are these 
types to be considered as elementary species, 
or only as individual differences? The decis- 
ion of course, would depend upon their behav- 
ior in cultures. Such tests have been made by 
various experimenters. In the dandelion the 
bracts of the involucre give the best characters. 
The inner ones may be linear or linear-lance- 
olate, with or without appendages below the tip ; 
the outer ones may be similar and only shorter, 
or noticeably larger, erect, spreading or even 
reflexed, and the color of the involucre may be 
a pure green or glaucous; the leaves may be 
nearly entire or pinnatifid, or sinuate-dentate, 
or very deeply runcinate>pinnatifid, or even 
pinnately divided, the whole plant being more 
or less glabrous. 

BaunMaer, who has studied experimentally a 
dozen types from Denmark, found them con- 
stant, but observed that some of them have no 
pollen at all, whUe in others the pollen, though 
present, is impotent. It does not germinate on 
the stigma, cannot produce the ordinary tube, 



Elementary Species in Nature 61 

and hence has no fertilizing power. But the 
young ovaries do not need such fertilization. 
They are sufficient unto themselves. One may 
cut off all the flowers of a head before the open- 
ing of the anthers, and leave the ovaries 
untouched, and the head will ripen its seeds 
quite as well. The same thing occurs in the 
hawkweeds. Here, therefore, we have no ferti- 
lization and the extensive widening of the varia- 
bility, which generally accompanies this pro- 
cess is, of course, wanting. Only partial or 
vegetative variability is present. Unfertilized 
eggs when developing into embryos are equiva- 
lent to buds, separated from the parent-plant 
and planted for themselves. They repeat both 
the specific and the individual characters of 
the parent. In the case of the hawkweed and 
the dandelion there is at present no means of' 
distinguishing between these two contrasting 
causes of variability. But like the garden- 
varieties which are always propagated in the 
vegetative way, their constancy and uniformity 
are only apparent and afford no real indication 
of hereditary qualities. 

In addition to these and other exceptional 
cases, seed-cultures are henceforth to be con- 
sidered as the sole means of recognizing the 
really existing systematic units of nature. All 
other groups, including systematic species and 



62 Elementary Species 

genera, are equally artificial or conventional. 

Tn other words we may state “ that current 
misconceptions as to the extreme range of fluc- 
tuating variability of many native species have 
generally arisen from a failure to recognize the 
composite nature of the forms in question,” as 
has been demonstrated by MacDougal in the 
case of the common evening-primrose, Oeno- 
thera biennis. “ It is evident that to study the 
behavior of the characters of plants we must 
have them in their simplest combinations; to 
investigate the origin and movements of species 
we must deal with them singly and uncompli- 
cated.” 



Lectuke in 


ELiEMENTABY SPECIES OF CULTIVATED PLANTS 

Becalling the results .of the last lecture, we 
see that the species of the systematists are not 
in reality units, though in the ordinary course 
of floristic studies they may, as a rule, seem to 
be so. In some eases representatives of the 
same species from different countries or re- 
gions, when compared with one another do not 
exactly agree. Many species of ferns afford 
instances of this rule, and Lindley and other 
great systematists have frequently been puz- 
zled by the wide range of differences between 
the individuals of a single species. 

In other cases the differing forms are ob- 
served to gi’ow near each other, sometimes in 
neighboring provinces, sometimes in the same 
locality, growing and flowering in mixtures of 
two or three or even more elementary types. 
The violets exhibit widespread ancient types, 
from which the local species may be taken to 
have arisen. The common ancestors of the 
whitlow-grasses are probably not to be found 



64 


Elementary Species 


among existing forms, but numerous types are 
crowded together in the southern part of central 
Europe and more thinly scattered elsewhere, 
even as far as western Asia. There can be lit- 
tle doubt that their common origin is to be 
sought in the center of their geographic dis- 
tribution. 

Numerous other cases exhibit smaller num- 
bers of elementary units within a systematic 
species; in fact purely uniform species seem 
to be relatively rare. But with small num- 
bers . there are of course no indications to 
be expected concerning their common origin or 
the starting point of their distribution. 

It is manifest that these experiences with wild 
species must find a parallel among cultivated 
plants. Of course cultivated plants were origi- 
nally wild and must have come under the gen- 
eral law. Hence we may conclude that when 
first observed and taken up by man, they must 
already have consisted of sundry elementary 
subspecies. And we may confidently assert 
that some must have been rich and others poor 
in such types. 

Granting this state of things as the only prob- 
able one, we can easily imagine what must have 
been the consequences. If a wild species had 
been taken into cultivation only once, the culti- 
vated form would have been a single element- 



Cultivated Elementary Species 65 

ary type. But it is not very likely that such 
partiality would occur often. The conception 
that different tribes at different times and in 
distant countries would have used the wild 
plants of their native regions seems far more 
natural than that all should have obtained 
plants for cultivation from the same source or 
locality. If this theory may be relied upon, 
the origin of many of the more widely cultivated 
agricultural plants must have been multiple, 
and the number of the original elementary spe- 
cies of the cultivated types must have been so 
much the larger, the more widely distributed 
and variable the plants under consideration 
were before the first period of cultivation. 

Further it would seem only natural to explain 
the wide variability of many of our larger agri- 
cultural and horticultural stocks by such an in- 
cipient multiformity of the species themselves. 
Through commercial intercourse the various 
types might have become mixed so as to make it 
quite impossible to point out the native locali- 
ties for each of them. 

Unfortunately historical evidence on this 
point is almost wholly lacking. The differences 
in question could not have been appreciated at 
that remote period, and interest the common ob- 
server but little even today. The history of 
most of the cultivated plants is very obscure, 



66 


Elementary Species 


and even the most skillful historians, by sifting 
the evidence afforded by the older writers, and 
that obtained by comparative linguistic investi- 
gations have been able to do little more than 
frame the most general outline of the cultural 
history of the most common and most widely 
used plants. 

Some authors assume that cultivation itself 
might have been the principal cause of variabil- 
ity, but it is not proved, nor even probable, that 
cultivated plants are intrinsically more variable 
than their wild prototypes. Appearances in 
this case are very deceptive. Of course widely 
distributed plants are as a rule richer in subspe- 
cies than forms with limited distribution, and 
the former must have had a better chance to be 
taken into cultivation than the latter. In many 
cases, especially with the more recent cultivated 
species, man has deliberately chosen variable 
forms, because of their greater promise. 
Thirdly, wide variability is the most efficient 
means of acclimatization, and only species with 
many elementary units would have offered 
tile adequate material for introduction into new 
countries. 

From this discussion it would seem that it is 
more reasonable to assert that variability is one 
of the causes of the success of cultivation, than 
to assume that cultivation is a cause of variabil- 



Cultivated Elementary Species 67 

ity at large. And this assumption would be 
equally sufficient to explain the existing condi- 
tions among cultivated plants. 

Of course I do not pretend to say that culti- 
vated plants should be expected to be less vari- 
able than in the wild state, or that swarms of 
elementary species might not be produced dur- 
ing cultivation quite as well as before. How- 
ever the chance of such an event, as is easily 
seen, cannot be very great, and we shall have to 
be content with a few examples of which the 
coconut is a notable one. 

Leaving this general discussion of the sub- 
ject, we may take up the example of the beets. 
The sugar-beet is only one type from among a 
horde of others, and though the origin of all the 
single types is not historically known, the plant 
is frequently found in the wild state even at the 
present time, and the native types may be com- 
pared with the corresponding cultivated varie- 
ties. 

The cultivation of beets for sugar is not of 
very ancient date. The Homans knew the beets 
and used them as vegetables, both the roots and 
the leaves. They distinguished a variety with 
white and one with red flesh, but whether they 
cultivated them, or only collected them from 
where they grew spontaneously, appears to be 
unknown. 



68 


Elementary Species 


Beets are even now fonnd in large quantities 
along the shores of Italy. They prefer the 
vicinity of the sea, as do so many other mem- 
bers of the beet-family, and are not limited to 
Italy, but are found growing elsewhere on the 
littoral of the Mediterranean, in the Canary 
Islands and through Persia and Babylonia to 
India. In most of their native localities they 
occur in great abundance. 

The color of the foliage and the size of the 
roots are extremely variable. Some have red 
leafstalks and veins, others a uniform red or 
green foliage, some have red or white or yellow 
roots, or exhibit alternating rings of a red and 
of a white tinge on cut surfaces. It seems only 
natural to consider the white and the red, and 
even the variegated types as distinct varieties, 
which in nature do not transgress their limits 
nor change into one another. In a subsequent 
lecture I will show that this at least is the rule 
with the corresponding color-varieties in other 
genera. 

The fleshiness or pulpiness of the roots is still 
more variable. Some are as thick as the arm 
and edible, others are not thicker than a Anger 
and of a woody composition, and the structure 
of this woody variety is very interesting. The 
sugar-beet consists, as is generally known, of 
concentric layers of sugar-tissue and of vascu- 



Cultivated Elementary Species 69 

lar strands ; the larger the first and tJie 
smaUer the latter, the greater is, as a rule, the 
average amount of sugar of the race. Through 
the kindness of the late Mr. Bimpau, a well- 
known German breeder of sugar-beet varieties, 
I obtained specimens from seed of a native wild 
locality near Bukharest. The plants produced 
quite woody roots, showing almost no sugar- 
tissue at all. Woody layers of strongly de- 
veloped fibrovascular strands were seen to be 
separated one from another only by very thin 
layers of parenchymatous cells. Even the 
number of layers is variable ; it was observed to 
be five in my plants ; but in larger roots double 
this number and even more may easily be met 
with. 

Some authors have distinguished specific 
types among these wild forms. While the 
cultivated beets are collected under the head of 
Beta vulgaris, separate tj^pes with more or less 
woody roots have been described as Beta mari- 
tima and Beta patula. These show differences 
in the habit of the stems and the foliage. Some 
have a strong tendency to become annual, 
others to become biennial. The first of course 
do not store a large quantity of food in their 
roots, and remain thin, even at the time of flow- 
ering. The biennial types occur in all sizes of 
roots. In the annuals the stems may vary from 



70 


Elementary Species 


erect to ascending, and the name patula indi- 
cates stems which arc densely branching from 
the base with widely spreading branches 
throughout. Mr. Em. von Proskowetz of Kwas- 
sitz, Austria, kindly sent me seeds of this Beta 
patvla, the variability of which was so great in 
my cultures as to range from nearly typical 
sugar-beets to the thin woody type of Buk- 
harest. 

Broad and narrow leaves are considered to be 
differentiating marks between Beta vulgaris 
and Beta patula, but even here a wide range of 
forms seem to occur. 

Bimpau, Proskowetz, Schindler and others 
have made cultures of beets from wild localities 
in order to discover a hypothetical common an- 
cestor of all the present cultivated types. 
These researches point to the B. patula as the 
probable ancestor, but of course they were not 
made to decide the question as to whether the 
origination of the several now existing types 
had taken place before or during culture. 
From a general point of view the variability of 
the wild species is parallel to that of the 
cultivated forms to such a degree as to suggest 
the multiple origin of the former. But a close 
investigation of this highly important prob- 
lem has still to be made. 

The varieties of the cultivated beets are com- 



Cultivated Elementary Species 71 

monly included in four subspecies. The two 
smallest are the salad-beets and the ornamental 
forms, the first being used as food, and ordinar- 
ily cultivated in red varieties, the second be- 
ing used as ornamental plants during the fall, 
when they fill the beds left empty by summer 
flowers, with a bright foliage that is exceedingly 
rich in form and color. Of the remaining sub- 
species, one comprises the numerous sorts culti- 
vated as forage-crops and the other the true 
sugar-beets. Both of them vary widely as to 
the shape and the size of the roots, the quality 
of the tissue, the foliage and other characteris- 
tics. 

Some of these forms, no doubt, have origi- 
nated during culture. Most of them have been 
improved by selection, and no beet found in the 
wild state ever rivals any cultivated variety. 
But the improvement chiefly affects the size, the 
amount of sugar and nutrient substances and 
some other qualities which recur in most of the 
varieties. The varietal attributes themselves 
however, are more or less of a specific nature, 
and have no relation to the real industrial 
value of the race. The short-rooted and the 
horn-shaped varieties might best be cited as 
examples. 

The assertion that the sundry varieties of 
forage-beets are not the result of artificial selec- 



72 Elementary Species 

tion, is supported in a large measure by the his- 
toric fact that the most of them are far older 
than the method of conscious selection of plants 
itself. This method is due to Louis Yilmorin 
and dates from the middle of the last century. 
But in the sixteenth century most of our present 
varieties of beets were already in cultivation. 
Caspar Bauhin gives a list of the beets of his 
time and it is not difficult to recognize in it a 
large series of subspecies and varieties and 
even of special forms, which are still cul- 
tivated. A more complete list was published 
towards the close of the same century by Olivier 
de Serres in his world-renowned “ Theatre 
d’Agriculture ” (Paris, 1600). 

The red forage-beets which are now cultivated 
on so large a scale, had been introduced from 
Italy into France only a short time before. 

From this historic evidence, the period during 
which the beets were cultivated from the time 
of the Romans or perhaps much later, up to the 
time of Bauhin and De Serres, would seem far 
too short for the production by the unguided se- 
lection of man of all the now existing types. On 
the other hand, the parallelism between the 
characters of some wild and some cultivated 
varieties goes to make it very probable that 
other varieties have been found in the same 
way, some in this country and others in that^ 



Cultivated Elementary Species 73 

and have been taken into cultivation separately. 
Afterwards of course all must have been im- 
proved in the direction required by the needs 
of man. 

Quite the same conclusion is afforded by ap- 
ples. The facts are to some extent of another 
character, and the rule of the derivation of the 
present cultivated varieties from original 
wild forms can be illustrated in this case in a 
more direct way. Of course we must limit our- 
selves to the varieties of pure ancestry and 
leave aside all those which are of hybrid or pre- 
sumably hybrid origin. 

Before considering their present state of cul- 
ture, something must be said about the earlier 
history and the wild state of the apples. 

The apple-tree is a common shrub in woods 
throughout all parts of Europe, with the only 
exception of the extreme north. Its distribu- 
tion extends to Anatolia, the Caucasus and 
Ghilan in Persia. It is found in nearly all 
forests of any extent and often in relatively 
large numbers of individuals. It exhibits vari- 
etal characters, which have led to the recog- 
nition of several spontaneous forms, especially 
in France and in Germany. 

The differentiating qualities relate to the 
shape and indumentum of the leaves. Nothing 
is known botanically as to differences between 



74 


Elementary Species 


the fruits of these varieties, but as a matter of 
fact the wild apples of different countries are 
not at all the same. 

Alphonse De Candolle, who made a profound 
study of the probable origin of most of our cul- 
tivated plants, comes to the conclusion that the 
apple-tree must have had this wide distribution 
in prehistoric times, and that its cultivation be- 
gan in ancient times everywhere. 

This very important conclusion by so high an 
authority throws considerable light on the rela- 
tion between cultivated and wild varieties at 
large. If the historic facts go to prove a mul- 
tiple origin for the cultivation of some of the 
more important useful plants, the probability 
that different varieties or elementary species 
have been the starting points for different lines 
of culture, evidently becomes stronger. 

Unfortunately, this historic evidence is 
scanty. The most interesting facts are those 
concerning the use of apples by the Romans 
and by their contemporaries of the Swiss and 
middle European lake-dwellings. Oswald Heer 
has collected large numbers of the relics of this 
prehistoric period. Apples were found in 
large quantities, ordinarily cut into halves and 
with the signs of having been dried. Heer dis- 
tinguished two varieties, one with large and 
one with small fruits. The first about 3 and 



Cultivated Elementary Species 75 

the other about 1.5-2 cm. in diameter. Both are 
therefore very small compared with our present 
ordinary varieties, but of the same general size 
as the wild forms of the present day. Like these, 
they must have been of a more woody and less 
fleshy tissue. They would scarcely have been 
tasteful to us, but in ancient times no better 
varieties were known and therefore no compari- 
son was possible. 

There is no evidence concerning the question, 
as to whether during the periods mentioned ap- 
ples were cultivated or only collected in the wild 
state. The very large numbers which are 
found, have induced some writers to believe in 
their culture, but then there is no reason why 
they should not have been collected in quantity 
from wild shrubs. The main fact is that the 
apple was not a uniform species in prehistoric 
times but showed even then at least some 
amount of variability. 

At the present day the wild apples are very 
rich in elementary species. Those of Ver- 
sailles are not the same as those of Belgium, 
and still others are growing in England and in 
Germany. The botanical differences derived 
from the blossoms and the leaves are slight, but 
the flavor, size and shape of the fruits diverge 
widely. Two opinions have been advanced to 
explain this high degree of variability, but 



76 


Elementary Species 


neither of them conveys a real explanation; 
their aim is chiefly to support different views as 
to the causes of variability, and the origin of 
elementary species at large. 

One opinion, advocated by De Candolle, Dar- 
win and others, claims that the varieties owe 
their origin to the direct influence of cultiva- 
tion, and that the corresponding forms found 
m the wild state, are not at all original, but have 
escaped from cultivation and apparently be- 
come wild. Of course this possibility cannot 
be denied, at least in any single instance, but it 
seems too sweeping an assertion to make for 
the whole range of observed forms. 

The alternative theory is that of van Mons, 
the Belgian originator of commercial varieties 
of apples, who has published his experiments in 
a large work called “ Arbres fruitiers ou Pomo- 
nomie beige.” Most of the more remarkable ap- 
ples of the flrst half of the last century were pro- 
duced by van Mons, but his greatest merit is 
not the direct production of a number of good 
varieties, but the foundation of the method, by 
which new varieties may be obtained and im- 
proved. 

According to van Mons, the production of a 
new variety consists chiefly of two parts. The 
first is the discovery of a subspecies with new 
desirable qualities. The second is the trans- 



Cultivated Elementary Species 77 

formation of the original small and woody ap- 
ple into a large, fleshy and palatable variety. 
Subspecies, or what we now call elementary 
species were not produced by man ; nature alone 
creates new forms, as van Mons has it. He ex- 
amined with great care the wild apples of his 
country, and especially those of the Ardennes, 
and found among them a number of species 
with different flavors. For the flavor is the 
one great point, which must be found ready in 
nature and which may be improved, but can 
never be created by artificial selection. The 
numerous differences in flavor are quite orig- 
inal; all of them may be found in the wild 
state and most of them even in so limited a 
region as the Ardennes Mountains. Of course 
van Mons preferred not to start from the 
wild types themselves, when the same flavor 
could be met with in some cultivated variety. 
His general method was, to search for a new 
flavor and to try to bring the bearer of it up 
to the desired standard of size and edibility. 

The latter improvement, though it always 
makes the impression of an achievement, is only 
the last stone to be added to the building up of 
the commercial value of the variety. Without 
it, the best flavored apple remains a crab ; with 
it, it becomes a conquest. According to the 
method of van Mons it may be reached within 



78 


Elementary Species 


two or three generations, and a man’s life is 
wholly snfficient to produce in this way many 
new types of the very best sorts, as van Mons 
himself has done. It is done in the usual way, 
sowing on .a large scale and selecting the best, 
which are in their turn brought to an early 
maturation of their fruit by grafting, because 
thereby the life from seed to seed may be re- 
duced to a few years. 

Form, taste, color, flavor and other valuable 
marks of new varieties are the products of 
nature, says van Mons, only texture, fleshiness 
and size are added by man. And this is done in 
each new variety by the same method and ac- 
cording to the same laws. The richness of the 
cultivated apples of the present day was al- 
ready present in the large range of original 
wUd elementary species, though unobserved 
and requiring improvement 

An interesting proof of this principle is af- 
forded by the experience of Mr. Peter M. 
Gideon, as related by Bailey. Gideon sowed 
large quantities of apple-seeds, and one seed 
produced a new and valuable variety called by 
him the Wealthy ” apple. He first planted a 
bushel of apple-seeds, and then every year, for 
nine years, planted enough seeds to produce 
a thousand trees. At the end of ten years all 
seedlings had perished except one hardy seed- 



Cultivated Elementary Species 79 

ling crab. This experiment was made in Min- 
nesota, and failed wholly. Then he bought a 
small lot of seeds of apples and crab-apples in 
Maine and from these the “ Wealthy ” came. 
There were only about fifty seeds in the lot of 
crab-apple seed which produced the “Wealthy,” 
but before this variety was obtained, more than 
a bushel of seed had been sown. Chance af- 
forded a species with an unknown taste ; but the 
growing of many thousands of seedlings of 
known varieties was not the best means to get 
something really new. 

Pears are more difiScult to improve than ap- 
ples. They often require six or more genera- 
tions to be brought from the wild woody state 
to the ordinary edible condition. But the va- 
rieties each seem to have a separate origin, as 
with apples, and the wide range of form and of 
taste must have been present in the wild state, 
long before cultivation. Only recently has the 
improvement of cherries, plums, currants and 
gooseberries been undertaken with success by 
Mr. Burbank, and the difference between the 
wild and cultivated forms has hitherto been 
very small. All indications point to the exist- 
ence, before the era of cultivation, of larger or 
smaller numbers of elementary species. 

The same holds good with many of the larger 
forage crops and other plants of great Indus- 



80 


Elementary Species 


trial value. Clover exhibits many varieties, 
which have been cultivated indiscriminately, 
and often in motley mixtures. The flower- 
heads may be red or white, large or small, cylin- 
drie or rounded, the leaves are broader or nar- 
rower, with or without white spots of a curious 
pattern. They may be more or less, hairy and 
so forth. Even the seeds exhibit differences in 
size, shape or color, and of late Martinet has 
shown, that by the simple means of picking out 
seeds of the same pattern, pure strains of clover 
may be obtained, which are of varying cultural 
value. In this way the best subspecies or va- 
rieties may be sought out for separate cultiva- 
tion. Even the white spots on the leaflets have 
proved to be constant characters corresponding 
with noticeable differences in yield. 

Flax is another instance. It was already cul- 
tivated, or at least made use of during the 
period of the lake-dwellers, but at that time it 
was a species referred to as Linum angusti- 
folium, and not the Linum usitatissimum, which 
is our present day flax. There are now many 
8ubsi>ecies, elementary species, and varieties 
under cultivation. The oldest of them is known 
as the “ springing flax,” in opposition to the 
ordinary “ threshing flax,” It has capsules 
which open of themselves, in order to dissemin- 
ate the seeds, while the ordinary heads of the 



Cultivated Elementary Species 81 

flax remain closed until the seeds are liberated 
by threshing. It seems probable that the first 
form or Linum crepitans might thrive in the 
wild state as well as any other plant, while in 
the common species those qualities are lacking 
which are required for a normal dissemination 
of the seeds. White or blue flowers, high or 
dwarf stems, more or less branching at the base 
and sundry other qualities distinguish the va- 
rieties, aside from the special industrial differ- 
ence of the fibres. Even the life-history varies 
from annual and biennial, to perennial. 

It would take us too long to consider other in- 
stances. It is well known that corn, though 
considered as a single botanical species, is rep- 
resented by different subspecies and varieties 
in nearly every region in which it is grown. Of 
course its history is unknown and it is impossi- 
ble to decide whether all the tall and dwarf 
forms, or starchy and sweet varieties, dented 
or rounded kernels, and hundreds of others are 
older than culture or have come into existence 
during historic times, or as some assume, 
through the agency of man. But our main 
point now is not the origin, but only the 
existence of constant and sharply differentiated 
forms within botanical species. Nearly every 
cultivated plant affords instances of such di- 
versity. Some include a few types only, while 



82 


Elementary Species 


others show a large number of forms clearly 
separated to a greater or lesser degree. 

In some few instances it is obvious that this 
variability is of later date than culture. The 
most conspicuous case is that of the coconut. 
This valuable palm is found on nearly all tropi- 
cal coasts, in America, as well as in Asia, but in 
Africa and Australia there are many hun- 
dreds of miles of shore line, where it is not 
found. Its importance is not at all the same 
everywhere. On the shores and islands of the 
Indian Ocean and the Malay Archipelago, man 
is chiefly dependent upon it, but in America it is 
only of subordinate usefulness. 

In connection with these facts, it abounds in 
subspecies and varieties in the East Indian re- 
gions, but on the continent of America little at- 
tention has as yet been given to its diverging 
qualities. In the Malayan region it affords near- 
ly all that is required by the inhabitants. The 
value of its fruit as food, and the delicious 
beverage which it yields, are well known. 
The fibrous rind is not less useful ; it is 
manufactured into a kind of cordage, mats 
and floor-cloths. An excellent oil is obtained 
from the kernel by compression. The hard 
covering of the stem is converted into drums 
and used in the construction of huts ; the lower 
part is so hard as to take on a beautiful polish 



Cultivated Elementary Species 83 

when it resembles agate. Finally the un- 
expanded terminal bud is a delicate article of 
food. Many other uses could be mentioned, but 
these may suffice to indicate how closely the life 
of the inhabitants is bound up with the culture 
of tliis palm, and how sharply, in consequence, 
its qualities must have been watched by early 
man. Any divergence from the ordinary tyjje 
must have been noted; those which were in- 
jurious must have been rejected, but the useful 
ones must have been appreciated and propa- 
gated. In a word any degree of variability 
afforded by nature must have been noticed and 
cultivated. 

More than fifty different sorts of tlie coco- 
nut are described from the Indian shores and 
islands, with distinct local and botanical names. 
Miquol, who was one of the best systematists of 
tropical plants, of the last century, described a 
largo number of them, and since, more have 
been added. Nearly all useful qualities vary in 
a higher or lesser degree in the different varie- 
ties. The fibrous strands of the rind of the 
nut are developed in some forms to such a 
length and strength as to yield the industrial 
product known ns the coir-fibre. Only three of 
them are mentioned by ^fiquel that have 
this quality, the Cocos micifera rutila, cupuU- 
formis and stupposa. Among them the rutila 



84 


Elementary Species 


yields the best and most supple fibres, while 
those of the stupposa are stiff and almost un- 
bending. 

The varieties also differ greatly in size, color, 
shape and quality, and the trees have also pe- 
culiar characteristics. One variety exhibits 
leaves which are nearly entire, the divisions be- 
ing only imperfectly separated, as often occurs 
in the very first leaves of the seedlings of other 
varieties. The flavor of the flesh, oil and milk 
likewise yield many good varietal marks. 

In short, the coconut-palm comes under the 
general rule, that botanical species are built up 
of a number of sharply distinguishable types, 
which prove their constancy and relative inde- 
I>endence by their wide distribution in culture. 
In systematic works all these forms are called 
varieties, and a closer investigation of their 
real systematic value has not yet been made. 
But the question as to the origin of the varieties 
and of the coconut itself has engrossed the at- 
tention of many botanists, among whom are De 
Candolle in the middle of the last century, and 
Cook at its close. 

Both questions are closely connected. Dc 
Candolle claimed an Asiatic origin for the whole 
species, while Cook’s studies go to prove that 
its original habitat is to be sought in the north- 
ern countries of South America. Numerous 



Cidtivated Elementary Species 85 

varieties are growing in Asia and have as yet 
not been observed to occur in America, where 
the coconut is only of subordinate importance, 
being one of many useful plants, and not the 
only one relied upon by the natives for their sub- 
sistence. If therefore, De Candolle’s opinion 
is the right one, the question as to whether the 
varieties are older or younger than the culti- 
vated forms of the species, must always remain 
obscure. But if the proofs of an American 
origin should be forthcoming, the possibility, 
and even the probability that the varieties are 
of later date than the begining of their culture, 
and have originated while in this condition must 
at once be granted. An important point in the 
controversy is the manner in which the coco- 
nuts were disseminated from shore to shore, 
from island to island. De Candolle, Darwin 
and most of the European writers claim that the 
dispersal was by natural agencies, such as 
ocean-currents. They point out that the fibrous 
rind or husk would keep the fruits afloat, and 
uninjured, for many days or even many weeks, 
while being carried from one country to another 
in a manner that would explain their geographic 
distribution. But the probability of the nuts be- 
ing thrown upon the strand, and far enough 
from the shore to find suitable conditions for 
their germination, is a very small one. To in- 



86 


Elementary Species 


sure healthy and vigorous seedlings the nuts 
must be fully ripe, after which planting cannot 
be safely delayed for more than a few weeks. If 
kept too moist the nuts rot. If once on the 
shore, and allowed to lie in the sun, they become 
overheated and are thereby destroyed ; if 
thrown in the shade of other shrubs and trees, 
the seedlings do not find the required conditions 
for a vigorous growth. 

Some authors have taken the fibrous rind to 
be especially adapted to transport by sea, but if 
this were so, this would argue that water is 
the normal or at least the verj' frequent medium 
of dissemination, which of course it is not. We 
may claim with quite as much right that the 
thick husk is necessary to enable the heavy 
fruit to drop from tall trees with safety. But 
even for this purpose the protection is not suffi- 
cient, as the nuts often suffer from falling 
to such a degree as to be badly injured as to 
their germinating qualities. It is well known 
that nuts, which are destined for propagation, 
are as a rule not allowed to fall off, but are 
taken from the trees with great care. 

Summing up his arguments. Cook concludes 
that there is little in the way of known facts 
to support the poetic theory of the coconut- 
palm dropping its fruits into the sea to float 
away to barren islands and prepare them for 



Cultivated Elementary Species 87 

human habitation. Shipwrecks might famish 
a successful method of launching viable coco- 
nuts, and such have no doubt sometimes con- 
tributed to their distribution. But this as- 
sumption implies a dissemination of the nuts by 
man, and if this principal fact is granted, it is 
far more natural to believe in a conscious in- 
telligent dissemination. 

The coconut is a cultivated tree. It may be 
met with in some spots distant from human 
dwellings, but whenever such cases have been 
subjected to a closer scrutiny, it appears that 
evidently, or at least probably, huts had for- 
merly existed in their neighborhood, but having 
been destroyed by some accident, had left the 
palm trees uninjured. Even in South America, 
where it may be found in forests at great dis- 
tances from the sea-shore, it is not at all certain 
that true native localities occur, and it seems to 
be quite lost in its natural condition. 

Granting the cultivated state of the palms as 
the only really important one, and considering 
the impossibility or at least great improbability 
of its dissemination by natural means, the dis- 
tribution by man himself, according to his 
wants, assumes the rank of an hypothesis fully 
adequate to the explanation of all the facts con- 
cerning the life-history of the tree. 

We now have to inquire into the main ques- 



88 


Elementary Species 


tion, whether it is probable that the coconut is 
of American or of Asiatic origin, leaving aside 
the historic evidence which goes to prove that 
nothing is known about the period in which its 
dissemination from one hemisphere to another 
took place, we will now consider only the bo- 
tanic and geographic evidence, brought forward 
by Cook. He states that the whole family of 
coconut-palms, consisting of about 20 genera 
and 200 species, are all strictly American with 
the exception of the rather aberrant African oil- 
palm, which has, however, an American relative 
referred to the same genus. The coconut is 
the sole representative of this group which is 
connected with Asia and the Malayan region, but 
there is no manifest reason why other members 
of the same group could not have established 
themselves there, and maintained an existence 
under conditions, which are not at all unfavor- 
able to them. The only obvious reason is the 
assumption already made, that the distribution 
was brought about by man, and thus only af- 
fected the sx)ecies, chosen by him for cultiva- 
tion. That the coconut cannot have been im- 
ported from Asia into America seems to be the 
most obvious conclusion from the arguments 
given. It should be briefly noted, that it was 
known and widely distributed in tropical Amer- 
ica at the time of the discovery of that continent 



Cultivated Elementary Species 89 


by Columbus, according to accounts of Oviedo 
and other contemporary Spanish writers. 

Concluding we may state that according to 
the whole evidence as it has been discussed by 
De Candolle and especially by Cook, the coco- 
nut-palm is of American origin and hasbeendis- 
tributed as a cultivated tree by man through the 
whole of its wide range. This must have hap- 
pened in a prehistoric era, thus affording time 
enough for the subsequent development of the 
fifty and more known varieties. But the pos- 
sibility that at least some of them have origin- 
ated before culture and have been deliberately 
chosen by man for distribution, of course re- 
mains unsettled. 

Coconuts are not very well adapted for 
natural dispersal on land, and this would rather 
induce us to suppose an origin within the period 
of cultivation for the whole group. There are 
a large number of cultivated varieties of differ- 
ent species which by some peculiarity do not 
seem adapted for the conditions of life in the 
wild state. These last have often been used to 
prove the origin of varietal forms during cul- 
ture. One of the oldest instances is the variety 
or rather subspecies of the opium-poppy, which 
lacks the ability to burst open its capsules. The 
seeds, which are thrown out by the wind, in the 
common forms, through the apertures under- 



90 


Elementary Species 


neath the stigma, remain enclosed. This is 
manifestly a very useful adaption for a culti- 
vated plant, as by this means no seeds are lost. 
It would be quite a disadvantage for a wild 
species, and is therefore claimed to have been 
connected from the beginning with the culti- 
vated form. 

The large kernels of com and grain, of beans 
and peas, and even of the lupines were consid- 
ered by Darwin and others to be unable to cope 
with natural conditions of life. Many valuable 
fruits are quite sterile, or produce extremely 
few seeds. This is notoriously the case with 
some of the best pears and grapes, with the 
pine-apples, bananas, bread-fruits, pomegran- 
ate and some members of the orange tribe. It 
is open to discussion as to what may be the im- 
mediate cause of this sterility, but it is quite 
evident, that all such sterile varieties must have 
originated in a cultivated condition. Otherwise 
they would surely have been lost. 

In horticulture and agriculture the fact that 
new varieties arise from time to time is beyond 
all doubt, and it is not this question with which 
we are now concerned. Our arguments were 
only intended to prove that cultivated species, 
as a rule, are derived from wild species, which 
obey the laws discussed in a previous lecture. 
The botanic units are compound entities, and 



Cultivated Elementary Species 91 

the real systematic units in elementary species 
play the same part as in ordinary wild species. 
The inference that the origin of the cultivated 
plants is multiple, in most cases, and that more 
than one, often many separate elementary 
forms of the same species must originally have 
been taken into cultivation, throws much light 
upon many highly important problems of culti- 
vation and selection. This aspect of the ques- 
tion will therefore be the subject of the next 
lecture. 



Lecture IV 

SELECTION OP ELEMENTARY SPECIES 

The improvement of cultivated plants must 
obviously begin with already existing forms. 
This is true of old cultivated sorts as well as for 
recent introductions. In either case the start- 
ing-point is as important as the improvement, 
or rather the results depend in a far higher de- 
gree on the adequate choice of the initial ma- 
terial than on the methodical and careful treat- 
ment of the chosen varieties. This however, 
has not always been appreciated as it deserves, 
nor is its importance at present universally 
recognized. The method of selecting plants for 
the improvement of the race was discovered by 
Louis Vilmorin about the middle of the last 
century. Before his time selection was ap- 
plied to domestic animals, but Vilmorin was the 
first to apply this principle to plants. As is 
well known, he used this method to increase 
the amount of sugar in beets and thus to raise 
their value as forage-crops, with such success, 
that his plants have since been used for the pro- 

92 



Selection of Elementary Species 93 

duction of sugar. He must have made some 
choice among the numerous available sorts of 
beets, or chance must have placed in his hands 
one of the most appropriate forms. On this 
point however, no evidence is at hand. 

Since the work of Vilmorin the selection-prin- 
ciple has increased enormously in importance, 
for practical purposes as well as for the the- 
oretical aspect of the subject. It is now being 
applied on a large scale to nearly all ornamental 
])lants. It is the one great principle now in 
universal practice as well as one of preeminent 
scientific value. Of course, the main argu- 
ments of the evolution theory rest upon mor- 
phologic, systematic, geographic and pale- 
ontologic evidence. But the question as to how 
we can co<>rdinate the relation between 
existing species and their supposed ancestors 
is of course one of a physiologic nature. Di- 
rect observation or experiments were not avail- 
able for Dam’in and so he found himself con- 
strained to make use of the experience of breed- 
ers. This he did on a broad scale, and with 
such success that it was precisely this side of 
his arguments that played the major part in 
convincing his contemporaries. 

The work of the breeders previous to Dar- 
win’s time had not been very critically per- 
formed. Recent analyses of the evidence ob- 



94 


Elementary Species 


tained from them show that numerous types 
of variability were usually thrown together. 
What type in each case afforded the material, 
which the breeder in reality made use of, has 
only been inquired into in the last few decades. 
Among those who have opened the way for 
thorough and more scientific treatment are to 
be mentioned Eimpau and Von Biimker of Ger- 
many and W. M. Hays of America. 

Von Eiimker is to be considered as the first 
writer, who sharply distinguished between two 
phases of methodical breeding-selection. One 
side he calls the production of new forms, the 
other the improvement of the breed. He dealt 
with both methods extensively. New forms are 
considered as spontaneous variations occurring 
or originating without human aid. They have 
only to be selected and isolated, and their 
progeny at once yields a constant and pure race. 
This race retains its character as long as it is 
protected against the admixture of other minor 
varieties, either by cross-pollination, or by ac- 
cidental seeds. 

Improvement, on the other hand, is the work 
of man. New varieties of course can only be 
isolated if chance offers them; the improve- 
ment is not incumbent on chance. It does not 
create really anything new, but develops char- 
acters, which were already existing. It brings 



Selection of Elementary Species 95 


the race above its average, and must guard 
constantly against the regression towards this 
average which usually takes place. 

Hays has repeatedly insisted upon the prin- 
ciple of the choice of the most favorable varie- 
ties as the foundation for all experiments in 
improving races. He asserts that half the bat- 
tle is won by choosing the variety which is to 
serve as a foundation stock, while the other half 
depends upon the selection of parent-plants 
within the chosen variety. Thus the choice of 
the variety is the first principle to be applied in 
every single case; the so-called artificial selec- 
tion takes only a secondary place. Calling all 
minor units within the botanic species by the 
common name of varieties, without regard to 
the distinction between elementary species and 
retrograde varieties, the principle is designated 
by the tenn of “ variety-testing.” This test- 
ing of varieties is now, as is universally known, 
one of the most important lines of work of the 
agricultural experiment stations. Every state 
and every region, in some instances even the 
larger farms, require a separate variety of 
com, or wheat, or other crops. They must be 
segregated from among the hundreds of gen- 
erally cultivated forms, within each single bo- 
tanic species. Once found, the type may be 
ameliorated according to the local conditions 



96 Elementary Species 

and needs, and this is a question of improve- 
ment. 

The fact that our cultivated plants are com- 
monly mixtures of different sorts, has not al- 
ways been known. The first to recognize it sems 
to have been the Spanish professor of botany, 
Mariano Lagasca, who published a number of 
Spanish papers dealing with useful plants and 
botanical subjects between 1810 and 1830, 
among them a catalogue of plants cultivated in 
the Madrid Botanical Garden. Once when he 
was on a visit to Colonel Le Couteur on his farm 
in Jersey, one of the Channel Islands off the 
coast of France, in discussing the value of the 
fields of wheat, he pointed out to his host, that 
they were not really pure and uniform, as was 
thought at that time, and suggested the idea 
that some of the constituents might form a 
larger part in the harvest than others. In a 
single field he succeeded in distinguishing no 
less than 23 varieties, all growing together. 
Colonel Le Couteur took the bint, and saved the 
seeds of a single plant of each supposed va- 
riety separately. These he cultivated and mul- 
tiplied till he got large lots of each and could 
compare their value. From among them he 
then chose the variety producing the greatest 
amount of the finest, whitest and most nu- 
tritious flour. This he eventually placed in the 



Selection of Elementary Species 97 

market under the name of “ Talavera de 
Bellevue.” It is a tall, white variety, with long 
and slender white heads, almost without awns, 
and with fine white pointed kernels. It was in- 
troduced into commerce about 1830, and is still 
one of the most generally cultivated French 
wheats. It was highly prized in the magnifi- 
cent collection of drawings and descriptions of 
wheats, published by Vilmorin under the title 
” Les meilleurs bles ” and is said to have quite 
a number of valuable qualities, branching freely 
and producing an abundance of good grain and 
straw. It is however, sensitive to cold win- 
ters in some degree and thereby limited in its 
distribution. Ilallett, the celebrated English 
wheat-breeder, tried in vain to improve the 
peculiar qualities of this valuable production 
of Le Couteur’s. 

Le Couteur worked during many years along 
this line, long before the time when Vilmorin 
conceived the idea of improvement by race- 
selections, and ho used only the simple 
principle of distinguishing and isolating the 
members of his different fields. Later he pub- 
lished his results in a work on the varieties, 
peculiarities and classification of wheat (1843), 
which though now very rare, has been the basis 
and origin of the principle of variety-testing. 

The discoverv of Lagasca and Le Couteur was 



98 Elementary Species 

of course not applicable to the wheat of Jersey 
alone. The common cultivated sorts of wheat 
and other grains were mixtures then as they 
are evmi now. Improved varieties are, or at 
least should be, in most cases pure and uniform, 
but ordinary sorts, as a rule, are mixtures. 
Wheat, barley and oats are self-fertile and do 
not mix in the field through cross-pollination. 
Every member of the assemblage propagates it- 
self, and is only checked by its own greater or 
less adaptation to the given conditions of life. 
Bimpau has dealt at large with the phenomenon 
as it occurs in the northern and middle parts of 
Germany. Even Rivett’s “ Bearded wheat,” 
which was introduced from England as a fine 
improved variety, and has become widely dis- 
tributed throughout Germany, cannot keep it- 
self pure. It is found mingled almost any- 
where with the old local varieties, which it was 
destined to supplant. Any lot of seed ex- 
hibits such impurities, as I have had the op- 
portunity of observing myself in sowings in 
the experimental-garden. But the impurities 
are only mixtures, and all the plants of 
Rivett^s ** Bearded wheat,” which of course 
constitute the large majority, are of pure blood. 
This may be confirmed when the seeds are col- 
lected and sown separately in cultures that 
be carefully guarded. 



Selection of Elementary Species 99 

In order to get a closer insight into the 
causes of this confused condition of ordinary 
races, Bimpau made some observations on 
Bivett’s wheat. He foimd that it suffers from 
frost during winter more than the local Ger- 
man varieties, and that from various causes, 
alien seeds may accidentally, and not rarely, 
become mixed with it. The threshing-machines 
are not always as clean as they should be and 
may be the cause of an accidental mixture. 
The manure comes from stables, where straw 
and the dust from many varieties are thrown 
together, and consequently living kernels 
may become mixed with the dung. Such stray 
grains will easily germinate in the fields, where 
they find more congenial conditions than does 
the improved variety. If winter arrives and 
kills quantities of this latter, the accidental local 
races will find ample space to develop. Once 
started, they will be able to multiply so rapidly, 
that in one or two following generations they 
will constitute a very considerable portion of 
the whole harvest. In this way the awnless 
German wheat often prevails over the intro- 
duced English variety, if the latter is not kept 
pure by continuous selection. 

The Swiss wheat-breeder Bislcr made an ex- 
periment which goes to prove the certainty of 
the explanation given by Bimpau. He ob- 



100 


Elementary Species 


served on his farm at Saleves near the lake of 
Geneva that after a lapse of time the “ Galland- 
wheat ” deteriorated and assumed, as was gen- 
erally believed, the characters of the local sorts. 
In order to ascertain the real cause of this ap- 
parent change, he sowed in alternate rows in a 
field, the “ Galland ’* and one of the local va- 
rieties. The “ Galland is a race with ob- 
vious characters and was easily distinguished 
from the other at the time when the heads were 
ripe. They are bearded when flowering, but 
afterwards throw off the awns. The kernels 
are very large and yield an extraordinarily 
good, white flour. 

During the first summer all the heads of the 
“ Galland ” rows had the deciduous awns but 
the following year these were only seen on half 
of the plants, the remainder having smooth 
heads, and the third year the “ Galland ” had 
nearly disappeared, being supplanted by the 
competing local race. The cause of this rapid 
change was found to be twofold. First the 
“ Galland,’* as an improved variety, suffers 
from the winter in a far higher degree than the 
native Swiss sorts, and secondly it ripens its 
kernels one or two weeks later. At the time of 
harvest it may not have become fully ripe, while 
the varieties mixed with it had reached maturity. 

The wild oat, Avena fatua, is very common in 



Selection of Elementary Species 101 

Europe from whence it has been introduced in 
the United States. In summers which are un- 
favorable to the development of the cultivated 
oats it may be observed to multiply with an al- 
most incredible rapidity. It does not contrib- 
ute to the harvest, and is quite useless. If no 
selection were made, or if selection were dis- 
continued, it would readily supplant the culti- 
vated varieties. 

From these several observations and experi- 
ments it may be seen, that it is not at all easy 
to keep the common varieties of cereals pure 
and that even the best are subject to the en- 
croachment of impurities. Hence it is only 
natural that races of cereals, when cultivated 
without the utmost care, or even when selected 
without an exact knowledge of their single con- 
stituents, are always observed to be more or 
less in a mixed condition. Here, as everywhere 
with cultivated and wild plants, the systematic 
species consist of a number of minor types, 
which pertain to different countries and cli- 
mates, and are growing together in the same 
climate and under the same external conditions. 
They do not mingle, nor are their differentiat- 
ing characters destroyed by intercrossing. 
They each remain pure, and may be isolated 
whenever and wherever the desirability for 
such a proceeding should arise. The purity of 



102 


Elementary Species 


the races is a condition implanted in them by 
man, and nature always strives against this 
arbitrary and one-sided improvement. Numer- 
ous slight differences in characters and numer- 
ous external influences benefit the minor types 
and bring them into competition with the better 
ones. Sometimes they tend to supplant the 
latter wholly, but ordinarily sooner or later a 
state of equilibrium is reached, in which hence- 
forth the different sorts may live together. 
Some are favored by warm and others by cool 
summers, some are injured by hard winters, 
while others thrive then and are therefore rela- 
tively at an advantage. The mixed condition 
is the rule, purity is the exception. 

Different sorts of cereals are not always 
easily distinguishable by the layman and there- 
fore I will draw your attention to conditions in 
meadows, where a corresponding phenomenon 
can be observed in a much simpler way. 

Only artificial pasture-grounds are seen to 
consist of a single species of grass or clover. 
The natural condition in meadows is the occur- 
rence of clumps of grasses and some clovers, 
mired up with perhaps twenty or more species 
of other genera and families. The numerical 
proportion of these constituents is of great in- 
terest, and has been studied at Bothamstead in 
En^and and on a number of other farms. It is 



Selection of Elementary Species 103 

always changing. No two successive years show 
exactly the same proportions. At one time one 
species prevails, at another time one or two or 
more other species. The weather during the 
spring and summer benefits some and hurts 
others, the winter may be too cold for some, but 
again harmless for others, the rainfall may 
partly drown some species, while others re- 
main uninjured. Some weeds may be seen flow- 
ering profusely during some years, while in 
other summers they are scarcely to be found in 
the same meadow. The whole population is in a 
fluctuating state, some thriving and others de- 
teriorating. It is a continuous response to the 
ever changing conditions of the weather. Bare- 
ly a species is wholly annihilated, though it 
may apparently be so for years ; but either from 
seeds or from rootstocks, or even from neigh- 
boring lands, it may sooner or later regain its 
foothold in the general struggle for life. 

This phenomenon is a very curious and in- 
teresting one. The struggle for life, which 
plays so considerable a part in the modem 
theories of evolution, may be seen directly at 
work. It does not alter the species themselves, 
as is commonly supposed, but it is always 
changing their numerical proportion. Any 
lasting change in the external conditions will of 
course alter the average oscillation and the in- 



104 


Elementary Species 


fluence of such alterations will manifest itself 
in most cases simply in new numerical propor- 
tions. Only extremes have extreme effects, and 
the chance for the weaker sorts to be complete- 
ly overthrown is therefore very small. 

Any one, who has the opportunity of observ- 
ing a waste held during a series of years, should 
make notes concerning the numerical propor- 
tions of its inhabitants. Exact figures are not 
at all required; approximate estimates will or- 
dinarily prove to be sufficient, if only the stand- 
ard remains the same during the succeeding 
years. 

The entire mass of historic evidence goes to 
prove that the same conditions have always 
prevailed, from the very beginning of cultiva- 
tion up to the present time. The origin of 
the cultivation of cereals is to be sought in cen- 
tral Asia. The recent researches of Sohns- 
Laubach show it to be highly probable that the 
historic origin of the wheat cultivated in China, 
is the same as that of the wheat of Egypt and 
Europe. Bemains of cereals are found in the 
graves of Egyptian mummies, in the mounds 
of waste material of the lake-dwellings of Cen- 
tral Europe, and figures of cereals are to be 
seen on old Roman coins. In the sepulchre of 
King Ba-n-Woser of the Fifth Djmasty of 
Egypt, who lived about 2000 years B. C., two 



Selection of Elementary Species 105 

tombs have recently been opened by the Ger- 
man Oriental Society. In them were found 
quantities of the tares of the Triticum dicoccum, 
one of the more primitive forms of wheat. In 
other temples and pyramids and among the 
stones of the walls of Dashur and El Kab 
studied by Unger, different species and varie- 
ties of cereals were discovered in large quan- 
tities, that showed their identity with the pres- 
ent prevailing cultivated races of Egypt. 

The inhabitants of the lake-dwellings in 
Switzerland possessed some varieties of cereals, 
which have entirely disappeared. They are 
distinguished by Heer under special names. 
The small barley and the small wheat of the 
lake-dwellers are among them. All in all there 
were ten well distinguished varieties of cereals, 
the Panicum and the Setaria or millet being of 
the number. Oats were evidently introduced 
only toward the very last of the lake-dwelling 
period, and rj'e is of far later introduction into 
westeni Europe. Similar results are attained 
by the examination of the cereals figured by the 
Romans of the same period. 

All these are archaeologic facts, and give but 
slight indications concerning the methods of 
cultivation or the real condition of the culti- 
vated races of that time. Vir^l has left us 
some knowledge of the requirements of method- 



106 


Elementary Species 


ical culture of cereals of his time. In his poem 
deorgics (1. 197) the following lines are found: 

Vidi lecta din, et multo spectata labore 

Degenerare tamen, ni vis humana quotannis 

Maxima quaeque manu legeret. 

(The chosen seed, through years and labor 
improved, 

Was seen to run back, unless yearly 

Man selected by hand the largest and fullest 
of ears.) 

Elsewhere Virgil and also some lines of 
Columella and Varro go to prove in the same 
way that selection was applied by the Romans 
to their cereals, and that it was absolutely 
necessary to keep their races pure. There is 
little doubt, but that it was the same principle 
as that which has led, after many centuries, to 
the complete isolation and improvement of the 
very best races of the mixed varieties. It fur- 
ther proves that the mixed conditions of the 
cereals was known to man at that time, al- 
though distinct ideas of specific marks and dif- 
ferences were of course still wholly lacking. It 
is proof also that cultivated cereals from the 
earliest times must have been built up of num- 
erous elementary forms. Moreover it is very 
probable, that in the lapse of centuries a good- 
ly number of such types must have disap- 



Selection of Elementary Species 107 

peared. Among the vanished forms are the 
special barley and wheat of the lake-dwellings, 
the remains of which have been accidentally 
preserved, but most of the forms must have dis- 
appeared without leaving any trace. 

This inference is supported by the researches 
of Solms-Laubach, who found that in Abyssinia 
numerous primitive types of cereals are still in 
culture. They are not adequate to compete 
with our present varieties, and would no doubt 
also have disappeared, had they not been pre- 
served by such quite accidental and almost 
primitive isolation. 

Closing this somewhat long digression into 
history we will now resume our discussion con- 
cerning the origin of the method of selecting 
cereals for isolation and segregate-cultivation. 
Some decades after Le Couteur, this method 
was taken up by the celebrated breeder Patrick 
Sheriff of Haddington in Scotland. His be- 
lief, which was general at that time, was “ That 
cultivation has not been found to change well 
defined kinds, and that improvement can be best 
attained by selecting new and superior varie- 
ties, which nature occasionally produces, as if 
inviting the husbandman to stretch forth his 
hand and cultivate them.’* • 

Before going into the details of Sheriff’s 
work it is as well to say something concerning 



108 


Elementary Species 


the use of the word “ selection.” This word 
was used by Sheriff as seen in the quotation 
given, and it was obviously designed to convey 
the same idea as the word “ lecta ” in the quo- 
tation from Virgil. It was a choice of the best 
plants from among known mixed fields, but the 
chosen individuals were considered to be repre- 
sentatives of pure and constant races, which 
could only be isolated, but not ameliorated. 
Selection therefore, in the primitive sense of 
the word, is the choice of elementary species 
and varieties, with no other purpose than that 
of keeping them as pure as possible from the 
admixture of minor sorts. The Romans at- 
tained this end only imperfectly, simply be- 
cause the laws governing the struggle for life 
and the competition of numerous sorts in the 
fields were unsuspected by them. 

Le Couteur and Sheriff succeeded in the solu- 
tion of the problem, because they had discovered 
the importance of isolation. The combination 
of a careful choice with subsequent isolation 
was all they knew about it, and it was one of 
the great achievements to which modem agri- 
culture owes its success. 

The other great principle was that of Vil- 
morin. It was the improvement within the 
race, or the ** amelioration of the race ” as it 
was termed by him. It was introduced into 



Selection of Elementary Species 109 

England by F. F. Hallett of Brighton in Sussex, 
who at once called it “ pedigree-culture,” and 
produced his first new variety under the very 
name of “ Pedigree- wheat. ” This principle, 
which yields improved strains, that are not con- 
stant but dependent on the continued and care- 
ful choice of the best plants in each succeeding 
generation, is now generally called “ selec- 
tion.” But it should always be remembered 
that according to the historic evolution of the 
idea, the word has the double significance of the 
distinction and isolation of constant races from 
mixtures, and that of the choice of the best rep- 
resentatives of a race during all the years of its, 
existence. Even sugar-beets, the oldest ” se- 
lected ” agricultural plants are far from having 
freed themselves from the necessity of contin- 
uous improvement. Without this they would 
not remain constant, but would retrograde with 
great rapidity. 

The double meaning of the word selection 
still prevailed when Darwin published his 
“ Origin of Species.” This was in the year 
1859, and at that time Shirrelf was the highest 
authority and the most successful breeder of 
cereals. Vilmorin’s method had been applied 
only to beets, and Hallett had commenced his 
pedigree-cultures only a few years before and 
his first publication of the ” Pedigree- wheat ” 



110 


Elementary Species 


appeared some years later at the International 
Exhibition of London in 1862. Hence, when- 
ever Darwin speaks of selection, Shirreff’s use 
of the word may as well be meant as that of 
Vilmorin. 

However, before going deeper into such the- 
oretical questions, we will first consider the 
facts, as given by Shirreff himself. 

During the best part of his life, in fact during 
the largest part of the first half of the nine- 
teenth century, Shirreff worked according to a 
very simple principle. When quite young he 
had noticed that sometimes single plants having 
better qualities than the average were seen 
in the fields. He saved the grains, or some- 
times the whole heads of such plants separate- 
ly, and tried to multiply them in such man- 
ner as to avoid intermixtures. 

His first result was the Mungoswell’s 
wheat.” In the spring of 1819 he observed 
quite accidentally in a field of the farm of that 
name, a single plant which attracted his atten- 
tion by a deeper green and by being more heav- 
ily headed out. Without going into further de- 
tails, he at once chose this specimen as the start- 
ing point of a new race. He destroyed the sur- 
rounding plants so as to give it more space, ap- 
plied manure to its roots, and tended it with 
special care. It yielded 63 heads and nearly 



Selection of Elementary Species 111 

2500 grains. All of these were sown the fol- 
lowing fall, and likewise in the succeeding years 
the whole harvest was sown in separate lots. 
After two years of rapid multiplication it 
proved to be a good new variety and was 
brought into commerce. It has become one of 
the prominent varieties of wheat in East 
Lothian, that county of Scotland of which Had- 
dington is the principal borough. 

The grains of “ Mungoswell’s wheat ” are 
whiter than those of the allied “ Hunter’s 
wheat,” more rounded but otherwise of the 
same size and weight. The straw is taller and 
stronger, and each plant produces more culms 
and more heads. 

Shirrefif assumed, that the original plant of 
this variety was a sport from the race in which 
he had foimd it, and that it was the only in- 
stance of this sport. He gives no details 
about this most interesting side of the question, 
omitting even to tell the name of the parent- 
variety. He only asserts that it was seen to be 
better, and afterwards proved so by the appre- 
ciation of other breeders and its success in 
trade. He observed it to be quite constant 
from the beginning, no subsequent selection be- 
ing needed. This important feature was simp- 
ly assumed by him to be true as a matter of 
course. 



112 


Elementary Species 


Some years afterwards, in the summer of 
1824, he observed a large specimen of oats 
in one of the fields of the same farm. Being 
at that time occupied in making a standard col- 
lection of oats for a closer comparison of the 
varieties, he saved the seeds of that plant and 
sowed them in a row in his experiment-field. 
It yielded the largest culms of the whole collec- 
tion and bore long and heavy kernels with a red 
streak on the concave side and it excelled all 
other sorts by the fine qualities of its very white 
meal. In the unequal length of its stalks it has 
however a drawback, as the field appears thin- 
ner and more meager than it is in reality. 
“ Hopetown oats,” as it is called, has found its 
way into culture extensively in Scotland and 
has even been introduced with success into Eng- 
land, Denmark and the United States. It has 
been one of the best Scottish oats for more 
than half a century. 

The next eight years no single plant judged 
worthy of selection on his own farm attracted 
Shirreff ’s attention. But in tlie fall of 1832 he 
saw a beautiful plant of wheat on a neighboring 
farm and he secured a head of it with about 100 
grains. From this he produced the “ Hope- 
town wheat.” After careful separation from 
kernels this original ear was preserved, and 
afterwards exhibited at the Stirling Agri- 



Selection of Elementary Species 113 

cultural Museum. The “ Hopetown wheat ” 
has proved to be a constant variety, excelling 
the ordinary “ Hunter’s wheat ” by larger 
grains and longer heads; it yields likewise a 
straw of superior quality and has become quite 
popular in large districts of England and Scot- 
land, where it is known by the name of “ White 
Hunter’s ” from its origin and the brilliant 
whiteness of its heads. 

In the same way Shirreff ’s oats were discov- 
ered in a single plant in a field where it was 
isolated in order to be brought into commerce 
after multiplication. It has won the surname 
of “ Make-him-rich.” Nothing is on record 
about the details of its origio. 

Four valuable new varieties of wheat and 
oats were obtained in this way in less than forty 
years. Then Shirreff changed his ideas and his 
method of working. Striking specimens ap- 
peared to be too rare, and the expectation of a 
profitable result too small. Therefore he be- 
gan work on a larger scale. He sought and 
selected during the summer of 1857 seventy 
heads of wheat, each from a single plant show- 
ing some marked and presumably favorable pe- 
culiarity. These were not gathered on one 
field, but were brought together from all the 
fields to which he had access in his vicinity. 
The grains of each of these selected heads were 



114 Elementary Spedes 

sown separately, and the lots compared during 
their whole life-period and chiefly at harvest 
time. Three of the lots were judged of high 
excellence, and they alone were propagated, and 
proving to be constant new varieties from the 
outset were given to the trade under the names 
of “ Shirreff’s bearded white,” “ Shirreff’s 
bearded red,” and “ Pringle’s wheat.” 
They have found wide acceptance, and the first 
two of them are still considered by Vilmorin as 
belonging to the best wheats of France. 

This second method of ShirrefF evidently is 
quite analogous to the principle of Lagasca and 
Le Couteur. The previous assumption that 
new varieties with striking features were being 
produced by nature from time to time, was 
abandoned, and a systematic inquiry into the 
worth of all the divergent constituents of the 
fields was begun. Every single ear at once 
proved to belong to a constant and pure race, 
but most of these were only of average value. 
Some few however, excelled to a degree, which 
made them worth multiplying, and to be intro- 
duced into trade as separate varieties. 

Once started, this new method of comparison, 
selection and isolated multiplication was of 
course capable of many improvements. The 
culture in the experiment-field was improved, so 
as to insure a fuller and more rapid growth. 



Selection of Elementary Species 115 

The ripe heads had to be measured and counted 
and compared with respect to their size and the 
number of their kernels. Qualities of grain 
and of meal had to be considered, and the in- 
fluence of climate and soil could not be over- 
looked. 

Concerning the real origin of his new types 
Shirreff seems never to have been very inquisi- 
tive. He remarks that only the best cultivated 
varieties have a chance to yield still better 
types, and that it is useless to select and sow 
the best heads of minor sorts. He further re- 
marks that it is not probable that he 
found a new sport every time; on the con- 
trary he assumes that his selections bad been 
present in the field before, and during a series 
of succeeding generations. How many years 
old they were, was of course impossible to de- 
termine. But there is no reason to believe that 
the conditions in the fields of Scotland were 
different from those observed on the Isle of 
Jersey by Le Couteur. 

In the year 1862 Shirreff devoted himself to 
the selection of oats, searching for the best 
panicles from the whole country, and compar- 
ing their offspring in his experimental-garden. 
“ Early Fellow,*’ “ Fine Fellow,” ” Longfel- 
low ” and ” Early Angus ” are very notable 
varieties introduced into trade in this way. 



116 


Elementary Species 


Some years later Patrick SMrreff described his 
experiments and results in a paper entitled, 

On the improvement of cereals,” but the de- 
scriptions are very short, and give few details 
of systematic value. The leading principle, 
however, is clearly indicated, and anyone who 
studies with care his method of working, may 
confidently attempt to improve the varieties of 
his own locality in the same way. 

This great principle of “ variety-testing,” as 
it has been founded by I<e Couteur and Patrick 
Shirreff, has increased in importance ever since. 
Two main features are to be considered here. 
One is the production of local races, the other 
the choice of the best starting-point for hybrid- 
izing experiments, as is shown in California 
by the work of Luther Burbank in crossing dif- 
ferent elementary species of Lilium pardali- 
num and others. 

Every region and locality has its own condi- 
tions of climate and soil. Any ordinary mixed 
race will contain some elementary forms which 
are better adapted to a given district, while 
others are more suitable to divergent condi- 
tions. Hence it can readily be inferred that 
the choice cannot be the same for different re- 
gions. Every region should select its own type 
from among the various forms, and variety- 
testing therefore becomes a task which every 



Selection of Elementary Species 117 

one must undertake under his own conditions. 
Some varieties will prove, after isolation, to 
be profitable for large districts and perhaps 
for whole states. Others will he found to be 
of more local value, but in such localities to excel 
all others. 

As an example we may take one of the varie- 
ties of wheat originated by the Minnesota Ex- 
periment Station. Hays described it as fol- 
lows. It was originated from a single plant 
From among 400 plants of “ Blue stem ” sev- 
eral of the best were chosen, each growing sep- 
arately, a foot apart in every direction. Each of 
the selected plants yielded 500 or more grains of 
wheat, weighing 10 or more grams. The seeds 
from these selected plants were raised for a few 
years until sufScient was obtained to sow a 
plot. Then for several years the new strains 
were grown in a field beside the parent-variety. 
One of them was so much superior that all 
others were discarded. It was the one named 
“ Minnesota No. 169.” For a large area of 
Minnesota this wheat seems capable of yielding 
at least 1 or 2 bushels more grain per acre than 
its parent variety, which is the best kind com- 
monly and almost universally found on the 
farms in southern and central Minnesota. 

It would be quite superfluous for our present 
purpose to give more instances. The fact of 



118 Elementary Species 

the oomponnd nature of so-called species of 
cultivated plants seems to be beyond all doubt, 
and its practical importance is quite obvious. 

Acclimatization is another process, which is 
largely dependent on the choice of adequate 
varieties. This is shown on a large scale by 
the slow and gradual dispersion of the varieties 
of com in this country. The largest types are 
limited to temperate and subtropical regions, 
while the varieties capable of cultivation in 
more northern latitudes are smaller in size and 
stature and require a smaller number of days 
to reach their full development from seed to 
seed. Northern varieties are small and short 
lived, but the “ Forty-day-cora ” or “ Quaran- 
tino maize is recorded to have existed in 
tropical America at the time of Columbus. In 
preference, or rather to the entire exclu- 
sion of taller varieties, it has thriven on the 
northern boundaries of the corn-growing states 
of Europe since the very beginning of its culti- 
vation. 

According to Naudin, the same mle prevails 
with melons, cucumbers and gherkins, and other 
instances could easily be given. 

Beferring now to the inferences that may be 
drawn from the experience of the breeders in 
order to elucidate the natural processes, we will 
return to the whitlow-grasses and pansies. 



Selection of Elementary Species 119 


Nature has constituted them as groups of 
slightly different constant forms, quite in the 
same way as wheat and oats and com. Assum- 
ing that this happened ages ago somewhere in 
central Europe, it is of course probable that 
the same differences in respect to the influence 
of climatic conditions will have prevailed as 
with cereals. Subsequent to the period wMch 
has produced the numerous elementary spe- 
cies of the whitlow-grass came a period of wide- 
spread distribution. The process must have 
been wholly comparable with that of acclimati- 
zation. Some species must have been more 
adapted to northern climates, others to the soils 
of western or eastern regions and so on. These 
qualities must have decided the general lines of 
the distribution, and the species must have 
been segregated according to their respective 
climatic qualities, and their adaptability to soil 
and weather. A stmggle for life and a natural 
selection must have accompanied and guided 
the distribution, but there is no reason to as- 
sume that the various forms were changed 
by this process, and that we see them now en- 
dowed with other qualities than they had at the 
outset. 

Natural selection must have played, in this 
and in a large number of other cases, quite the 
same part as the artificial method of variety- 



120 Elementary Species 

testing. Indeed it may be surmised that this 
has been its chief and prominent function. 
Taking up again our metaphor of the sieve we 
can assert that in such cases climate and soil 
exercise sifting action and in this way the ap- 
plication of the metaphor becomes more defi- 
nite. Of course, next to the climate and soil in 
importance, come ecological conditions, the veg- 
etable and animal enemies of the plants and 
other influences of the same nature. 

In conclusion it is to be pointed out that this 
side of the problem of natural selection and the 
struggle for life appears to offer the best pros- 
pects for experimental, or for continued statis- 
tical inquiry. Direct observations are possible 
and any comparison of numerical proportions 
of species in succeeding years affords clear 
proof of the part it plays. And above all, such 
observations can be made quite independently 
of doubtful theoretical considerations about 
presumed changes of character. 

The fact of natural selection is plain and 
it should be studied in its most simple condi- 
tions. 



C. RETBOGBADE VARIETIES 
Lectube V 

OHABAuGXEBS OF BETBOORADE VABIETIES 

Every one admires the luxuriance of gar- 
den-flowers, and their diversity of color and 
form. All parts of the world have contributed 
to their number and every taste can find its 
preference among them. New forms produced 
by the skill of the breeder are introduced every 
year. This has been done mostly by crossing 
and intermingling the characters of introduced 
species of the same genus. In some of the 
cases the history of our flowers is so old that 
their hybrid origin is forgotten, as in the case 
of the pansies. Hybridizations are still going 
on in other groups on a large scale, and new 
forms are openly claimed to be of hybrid origin. 

Breeders and amateurs generally have more 
interest in the results than in the way in 
which they have been brought about. Excel- 
lent flowers and fruit recommend them- 
selves and there eeems to be no reason for in- 

121 



122 


Retrograde Varieties 


quiring about their origin. In some cases the 
name of the originator may be so widely known 
that it adds weight to the value of the new form, 
and therefore may advantageously be coupled 
with it. The origin and history of the greater 
part of our garden-flowers, fruits and vege- 
tables are obscure; we see them as they are, 
and do not know from whence they came. The 
original habitat for a whole genus or for a 
species at large, may be known, but questions as 
to the origin of the single forms, of which it is 
built up, ordinarily remain unanswered. 

For these reasons we are restricted in most 
cases to the comparison of the forms before us. 
This comparison has led to the general use 
of the term “ variety ” in opposition to 
“ species.” The larger groups of forms, 
which are known to have been introduced as 
such are called species. All forms which by 
their characters belong to such a species are 
designated as varieties, irrespective of their 
systematic relation to the form, considered as 
the ancestor of the group. 

Hence, we distinguish between “ hybrid va- 
rieties ” and “ pure varieties ” according to 
their origin from different parents or from a 
single line of ancestors. Moreover, in both 
groups the forms may be propagated by seeds, 
or in the vegetative way by buds, by grafting or 



Retrograde VaHeties 


123 


by cutting, and this leads to the distinction of 
“ seed- varieties ” and “ vegetative varieties.” 
In the first case the inheritance of the special 
characters through the seeds decides the status 
of the variety, in the latter case this point is left 
wholly out of consideration. 

Leaving aside all these different t3rpe8, we 
are concerned here only with the ” seed- varie- 
ties ” of pure origin, or at least with those, that 
are supposed to be so. Hybridization and 
vegetative multiplication of the hybrids no 
doubt occur in nature, but they are very rare, 
when compared with the ordinary method of 
propagation by seed. Seed-varieties ” may 
further be divided into constant and inconstant 
ones. The difference is very essential, but the 
test is not always easy to apply. Constant 
varieties are as sharply defined and as narrowly 
limited as are the best wild species, while in- 
constant types are cultivated chiefly on account 
of their wide range of form and color. This 
diversity is repeated yearly, even from the 
purest seed. We wUl now discuss the constant 
seed-varieties, leaving the inconstant and ever- 
sporting types to a subsequent lecture. 

In this way we may make an exact inquiry 
into the departures from the species which are 
ordinarily considered to constitute the essential 
character of such a constant and pure seed- 



124 


Retrograde Varieties 


variety and need only compare these differ- 
ences with those that distinguish the elementary 
species of one and the same group from each 
other. 

Two points are very striking. By far the 
greatest part of the ordinary garden-varieties 
differ from their species by a single sharp char- 
acter only. In derivative cases two, three or 
even more such characters may be combined in 
one variety, for instance, a dwarfed variety of 
the larkspur may at the same time bear white 
flowers, or even double white flowers, but the 
individuality of the single characters is not in 
the least obscured by such combinations. 

The second point is the almost general oc- 
currence of the same variety in extended series 
of species. White and double flowers, varie- 
gated leaves, dwarfs and many other instances 
may be cited. It is precisely this universal 
repetition of the same character that strikes us 
as the essential feature of a variety. 

And again these two characteristics may now 
be considered separately. Let us beg^n with 
the sharpness of the varietal characters. In 
this respect varieties differ most obviously 
from elementary species. These are distin- 
guished from their nearest allies in almost all 
organs. There is no prominent distinctive 
feature between the single forms of Draba 



Retrograde Varieties 


125 


verna, Helianthemum or of Taraxacum; all 
characters are almost equally concerned. The 
elementary species of Draba are characterized, 
as we have seen, by the forms and the hairiness 
of the leaves, the number and height of the 
flower-stalks, the breadth and incision of the 
petals, the forms of the fruits, and so on. 
Every one of the two hundred forms included 
in this collective species has its own type, which 
it is impossible to express by a single term. 
Their names are chosen arbitrarily. Quite the 
contrary is the case with most of the varieties, 
for which one word ordinarily suffices to ex- 
press the whole difference. 

White varieties of species with red or blue 
flowers are the most common instances. If the 
species has a compound color and if only one 
of the constituents is lost, partially colored 
types arise as in AgrostemmaCoronaria bicolor. 
Or the spots may disappear and the color be- 
come uniform as in Gcntiana punctata concolor 
and the spotless Arum or Arum maculatum im- 
maculatum. Absence of hairs produces forms 
as Biscutella Icevigata glabra; lack of prickles 
gives the varieties known as inermis, as for in- 
stance, Ranunculus arvensis inermis. Cytisus 
prostratus has a variety ciliata, and Solanum 
Dulcamara, or the bitter-sweet, has a va- 
riety called tomentosum. The curious mon- 



126 Retrograde Varieties 

ophyllous variety of the strawberry and many 
other forms will be discussed later. 

To enlarge this list it would only be necessary 
to extract from a flora, or from a catalogue of 
horticultural plants, the names of the varieties 
enumerated therein. In nearly every instance, 
where true varieties and not elementary species 
are concerned, a single term expresses the 
whole character. 

Such a list would also serve to illustrate the 
second point since the same names would recur 
frequently. Long lists of varieties are called 
alha, or inermis, or canescens or lutea, and 
many genera contain the same appellations. In 
some instances the systematists use a diversity 
of names to convey exactly the same idea, as if 
to conceal the monotony of the character, as 
for instance in the case of the lack of hairs, 
which is expressed by the varietal names of 
Papaver dubium glabrum, Arabis cUiata gla- 
brata, Arabis hirsuta glaberrima, Veronica 
spicata nitens, Amygdalus persica laevis, 
Paeonia coraUina leiocarpa, &c. 

On the contrary we And elementary species in 
different genera based on the greatest possible 
diversity of features. The forms of Taraxacum 
or Helianthemum do not repeat those of Draha 
or Viola. In roses and brambles the distinguish- 
ing features are characteristic of the type, as 



Retrograde Varieties 


127 


they are evidently derived from it and limited 
to it. And this is so true that nobody claims 
the grade of elementary species for white roses 
or white brambles, but everyone recognizes that 
forms diverging from the nearest species by 
a single character only, are to be regarded as 
varieties. 

This general conviction is the basis on which 
we may build up a more sharply defined distinc- 
tion between elementary species and varieties. 
It is an old rule in systematic botany, that no 
form is to be constituted a species upon the 
basis of a single character. All authors agree 
on this point; specific differences are derived 
from the totality of the attributes, not from one 
organ or one quality. This rule is intimately 
connected with the idea that varieties are de- 
rived from species. The species is the typical, 
really existing form from which the variety has 
originated by a definite change. In enumer- 
ating the different forms the species is distin- 
guished by the term of genuine or typical, often 
only indicated as a or the first; then fol- 
low the varieties sometimes in order of their 
degree of difference, sometimes simply in alpha- 
betical order. In the case of elementary species 
there is no real type; no one of them predom- 
inates because all are considered to be equal in 
rank, and the systematic species to which they 



128 


Retrograde Varieties 


are referred is not a really existing form, but is 
the abstraction of the common type of all, just 
as it is in the case of a genus or of a family. 

Summarizing the main points of this discus- 
sion, we find that elementary species are of 
equal rank and together build up the collective 
or systematic ideal species. Varieties on the 
other hand are derived from a real and com- 
monly, still existing type. 

I hope that I have succeeded in showing that 
the difference between elementary species, or, as 
they are often called, smaller or subspecies, on 
the one hand and varieties on the other, is quite 
a marked one. However, in order to recognize 
this principle it is necessary to limit the term 
variety, to those propagating themselves by 
seed and are of pure and not of hybrid origin. 

But the principle as stated here, does not in- 
volve an absolute contrast between two groups 
of characters. It is more a difference in our 
knowledge and appreciation of them than a dif- 
ference in the things themselves. The characters 
of elementary species are, as a rule, new to us, 
while those of varieties are old and familiar. 
It seems to me that this is the essential point. 

And what is it that makes us familiar with 
them? Obviously the continuous recurrence of 
the same changes, because by a constant repeti- 
tion they must of course lose their novelty. 



Retrograde Varieties 


129 


Presently we shall look into these characters 
more in detail and then we shall find that they 
are not so simple as might be supposed at first 
sight; but precisely because we are so familiar 
with them, we readily see that their different 
features really belong to a single character; 
while in elementary species everything is so 
new that it is impossible for us to discern the 
unities of the new attributes. 

If we bear in mind all these difficulties we 
cannot wonder at the confusion on this ques- 
tion that seems to prevp,il everywhere. Some 
authors following Linnaeus simply call all the 
subdivisions of species, varieties; others fol- 
low Jordan and avoid the difficulty by desig- 
nating all smaller forms directly as species. 
The ablest systematists prefer to consider the 
ordinary species as collective groups, calling 
their constituents “ The elements of the spe- 
cies,” as was done by A. P. De Candolle, Alph. 
De Candolle and Lindley. 

By this method they clearly point out the dif- 
ference between the subdivisions of wild spe- 
des as they ordinarily occur, and the varieties 
in our gardens, which would be very rare, were 
they not singled out and preserved. 

Our familiarity with a character and our 
grounds for calling it an old acquaintance may 
result from two causes, which in judging a new 



130 


Retrograde Varieties 


variety are essentially different. The charac- 
ter in question may be present in the given spe- 
cies or it may be lacking, but present in the other 
group. In the first case a variety can only be 
formed by the loss of the character, in the sec- 
ond case it arises by the addition of a new one. 

The first mode may be called a negative pro- 
cess, while the second is then to be designated 
as positive. And as it is more easy to lose what 
one has than to obtain something new, negative 
varieties are much more common than are posi- 
tive ones. 

Let us now take an instance of a character 
that is apt to vary in both ways, for this is ob- 
viously the best way of making clear what is 
meant by a negative and a positive change. 

In the family of the composites we find a 
group of genera with two forms of florets on 
each flower-head. The hermaphrodite ones are 
tubular with 5, or rarely 4, equal teeth, and oc- 
cupy the center of the head. These are often 
called the flosculous florets or disk-florets. 
Those of the circumference are ligulate and 
ordinarily unisexual, without stamens. In many 
cases they are sterile, having only an imperfect 
ovary. They are large and brightly colored and 
are gmierally designated as ray-florets. As in- 
stances we may cite the camomile (Anthemis 
nobiUs), the wild camomile {Matricaria Cham- 



Retrograde Varieties 


131 


omiUa)^ the yarrow {Achillea Millefolium), 
the daisies, the Dahlia and many others. 
Species occur in this group of plants from time 
to time that lack the ray-florets, as in the tansy 
{Tanacetum vulgare) and some artemisias. 
And the genus of the marigolds or Bidens is 
noted for containing both of these types. The 
smaller and the three-toothed marigold {B. 
cernua and B. tripartita) are very common 
plants of wet soil and swamps, ordinarily lack- 
ing the ray-florets, and in some countries they 
are very abundant and wholly constant in this 
respect, never forming radiate flower-heads. 
On the other hand the white-flowered and the 
purple marigold {B. leucantha and B. atropur- 
purea) are cultivated species of our gardens, 
prized for their showy flower-heads with large 
white or deeply colored, nearly black-purple 
florets. 

Here we have opportunity to observe positive 
and negative varieties of the same character. 
The smaller, and the three-toothed marigold 
occur from time to time, provided with ray- 
florets, showing a positive variation. And the 
white marigold has produced in our gardens a 
variety without rays. Such varieties are quite 
constant, never returning to the old species. 

Positive and negative varieties of this kind 
are by no means rare among the compositae. 



132 


Retrograde Varieties 


In systematic works the positive ones are as a 
rule called “ radiate,” and the negative ones 
” discoid.” Discoid forms of the ordinary 
camomile, of the daisy, of some asters {Aster 
Tripolium), and of some centauries have been 
described. Radiate forms have been observed 
in the tansy {Tanacetum vtUgare)^ the common 
horse-weed or Canada fleabane {Erigeron cana- 
densis) and the common groundsel {Senedo 
vulgaris). Taken broadly the negative varie- 
ties seem to be somewhat more numerous than 
the positive ones, but it is very difficult to oome 
to a definite conclusion on this point. 

Quite the contrary is the case with regard to 
the color-varieties of red and blue flowers. 
Here the loss of color is so common that every 
one could give long lists of examples of it. Lin- 
naeus himself supposed that no blue or red-col- 
ored wild species would be without a white va- 
riety. It is well known that he founded his 
often criticized prescript never to trust to color 
in recognizing or describing a species, on this 
belief. 

On the other hand there are some red varie- 
ties of white-flowered species. But they are 
very rare, and little is known about their charac- 
ters or constancy. Blue varieties of white spe- 
cies are not found. The yarrow {Achillea Mil- 
lefolium) has a red-flowered form, which occurs 



Retrograde Varieties 


133 


from time to time in sunny and sandy localities. 
I have isolated it and cultivated it during a 
series of years and during many generations. 
It is quite true to its character, but the degree 
of its coloring fluctuates between pink and white 
and is extremely variable. Perhaps it can be 
considered as an inconstant variety. A red- 
flowered form of the common Begonia semper- 
florens is cultivated under the name of “ Ver- 
non,” the white hawthorn {Crataegus Oxya- 
cantha) is often seen with red flowers, and a 
pink-flowered variety of the “ Silverchain ” or 
“ Bastard acacia” {Robinia Pseud- Acacia) is 
not rarely cultivated. The “ Crown ” variety 
of the yellow wall-flower and the black varieties, 
are also to be considered as positive color- 
variations, the black being due in the latter 
cases to a very great amount of the red pigment. 

Among fruits there are also some positive 
red varieties of greenish or yellowish species, as 
for instance the red gooseberry {Ribes Grossu- 
laria) and the red oranges. The red hue is far 
more common in leaves, as seen among herbs, in 
cultivated varieties of Coleus and in the brown- 
leaved form of the ordinary white clover, among 
trees and shrubs in the hazelnut {Corylus), the 
beach {Fagus), the birch {Betula), the barberry 
(Berheris) and many others. But though most 
of these forms are very ornamental and abun- 



134 


Retrograde Varieties 


dant in parks and gardens, little is as yet known 
concerning the origin of their varietal attributes 
and their constancy, when propagated by seeds. 
Besides the ray-florets and the colors, there are 
of course a great many other characters in 
which varieties may differ from their species. 
In most of the cases it is easy to discern 
whether the new character is a positive or a 
negative one. And it is not at all necessary to 
scrutinize very narroyrly the list of forms to be- 
come convinced that the negative form is the 
one which prevails nearly everywhere, and that 
positive aberrations are in a general sense so 
rare that they might even be taken for excep- 
tions to the rule. 

Many organs and many qualities may be lost 
in the origination of a variety. In some in- 
stances the petals may disappear, as in Nigella, 
or the stamens, as in the Guelder-rose (Vibur- 
num Opulus) and the Hortensia and in some 
bulbs even the whole flowers may be wanting, 
as in the beautiful “ Plumosa ” form of the 
cultivated grape-hyacinth or Muscari comosum. 
Fruits of the pineapples and bananas without 
seeds are on record as well as some varieties of 
apples and pears, of raisins and oranges. And 
some years ago Mr. Biviere of Algeria de- 
scribed a date growing in his garden that forms 
fruit without pits. The stoneless plum of Mr. 



Retrograde Varieties 


135 


Burbank of Santa Bosa, California, is also a 
very curious variety, the kernel of which is fully 
developed but naked, no hard substance inter- 
vening between it and the pulp. 

More curious still are the unbranched varie- 
ties consisting of a single stem, as may be seen 
sometimes in the corn or maize and in the fir. 
Fir-trees of some three or four meters in height 
without a single branch, wholly naked and bear- 
ing leaves only on the shoots of the last yearns 
growth at the apex of the tree, may be seen. Of 
course they cannot bear seed, and so it is with 
the sterile maize, which never produces any 
seed-spikes or staminate flowers. Other seed- 
less varieties can be propagated by buds ; their 
origin is in most cases unknown, and we are not 
sure as to whether they should be classified with 
the constant or with the inconstant varieties. 

A very curious loss is that of starch in the 
grains of the sugar-corn and the sugar-peas. 
It is replaced by sugar or some allied substance 
(dextrine). Equally remarkable is the loss of 
the runners in the so-called “ Gaillon ” straw- 
berries. 

Among trees the pendulous or weeping, and 
the broomlike or fastigiate forms are very 
marked varieties, which occur in species belong- 
ing to quite different orders. The ash, the 
beach, some willows, many other trees and some 



136 Retrograde Varieties 

finer species of garden-plants, as Sophora jap- 
onica, have given rise to weeping varieties, and 
the yew-tree or Taxus has a fastigiate form 
which is much valued because of its ascending 
branches and pyramidal habit. So it is with 
the pyramidal varieties of oaks, elms, the bas- 
tard-acacia and some others. 

It is generally acknowledged that these forms 
are to be considered as varieties on the ground 
of their occurrence in so wide a range of species, 
and because they always bear the same attrib- 
utes. The pendulous forms owe their peculiar- 
ity to a lengthening of the branches and a loss 
of their habit of growing upwards ; they are too 
weak to retain a vertical position and the re- 
sponse to gravity, which is ordinarily the cause 
of the upright growth, is lacking in them. As 
far as we know, the cause of this weeping habit 
is the same in all instances. The fastigiate 
trees and shrubs are a counterpart of the weep- 
ing forms. Here the tendency to grow in a 
horizontal direction is lacking, and with it the 
bilateral and symmetric structure of the 
branches has disappeared. In the ordinary 
yew-tree the upright stem bears its needles 
equally distributed around its circumference, 
but on the branches the needles are inserted in 
two rows, one to the left and one to the right. 
All the needles turn their upper surfaces up- 



Retrograde Varieties 


137 


wards, and their lower surfaces downwards, and 
all of them are by this means placed in a single 
horizontal plane, and branching takes place in 
the same plane. Evidently this general ar- 
rangement is another response to gravity, and 
it is the failure of this reaction which induces 
the branches to grow upwards and to behave 
like stems. 

Both weeping and fastigiate characters are 
therefore to be regarded as steps in a negative 
direction, and it is highly important that even 
such marked departures occur without transi- 
tions or intermediate forms. If these should 
occur, though ever so rarely, they would proba- 
bly have been brought to notice, on account of 
the great prospect the numerous instances 
would offer. The fact that they are lacking, 
proves that the steps, though apparently great, 
are in reality to be considered as covering single 
units, that cannot be divided into smaller parts. 
Unfortunately we are still in the dark as to the 
question of the inheritance of these forms, 
since in most cases it is difficult to obtain pure 
seed. 

We now consider the cases of the loss of su- 
perficial organs, of which the nectarines are 
example. These are smooth peaches, lacking 
the soft hairy down, that is a marked pecul- 
iarity of the true peaches. They occur in differ- 



138 Retrograde Varieties 

ent races of the peach. As early as the begin- 
ning of the past century, Gallesio described no 
less than eight subvarieties of nectarines, each 
related to a definite race of peach. Most of 
them reproduce themselves truly from seed, as 
is well known in this country concerning the 
clingstones, freestones and some other types. 
Nectarines have often varied, giving rise to new 
sorts, as in the case of the white nectarine and 
many others differing greatly in appearance 
and flavor. On the other hand it is to be re- 
marked, that the trees do not differ in other re- 
spects and cannot be distinguished while young, 
the varietal mark being limited to the loss of 
the down on the fruit. Peaches have been 
known to produce nectarines, and nectarines to 
yield true peaches. Here we have another in- 
stance of positive and negative steps with refer- 
ence to the same character, but I cannot with- 
hold an expression of some doubt as to the possi- 
bility of crossing and subsequently splitting up 
of the hybrids as a more probable explanation 
of at least some of the cases quoted by various 
writers. 

Smooth or glabrous varieties often occur, and 
some of them have already been cited as in- 
stances of the multiplication of varietal names. 
Positive aberrations are rather rare, and are 
mostly restricted to a greater density of the 



Retrograde Varieties 


139 


pubescence in some hairy species, as in Galeop- 
sis Ladanum canescens, Lotus corniculatus 
hirsutus and so on. But Veronica scuteUata is 
smooth and has a pubescent variety, and Cyti- 
sus prostratus and C. spinescens are each re- 
corded to have a ciliate form. 

Comparable with the occurrence and the lack 
of hairs, is the existence or deficiency of the 
glaucous effect in leaves, as is well known in the 
common Ricinus. Here the glaucous appear- 
ance is due to wax distributed in fine particles 
over the surface of the leaves, and in the green 
variety this wax is lacking. Other instances 
could be given as in the green varieties of Pap- 
aver alpinum and Rumex scutatus. No positive 
instances are recorded in this case. 

Spines and prickles may often disappear and 
give rise to unarmed and defenceless types. 
Of the thorn-apples both species, the white- 
flowered Datura Stramonium and the purple 
D. Tatula have such varieties. Spinach has 
a variety called the “ Dutch,” which lacks 
the prickles of the fruit; it is a very old 
form and absolutely constant, as are also 
the thornless thorn-apples. Last year a very 
curious instance of a partial loss of prickles was 
discovered by Mr. Cockerell of East Las Vegas 
in New Mexico. It is a variety of the American 
cocklebur, often called sea-burdock, or the 



140 Retrograde Varieties 

hedgehog-bnrweed, a stout and conunon weed 
of the western States. Its latin name is Xan- 
thium camdense or X commune and the form 
referred to is named by Mr. Cockerell X. Woo- 
toni, in honor of Professor E. 0. Wooton who 
described the first collected specimens. 

The burs of the common species are densely 
covered with long prickles, which are slightly 
hooked at the apex. In the new form, which is 
similar in all other respects to the common 
cocklebur, the burs are more slender and the 
prickles much less numerous, about 25 to the 
bur and mostly stouter at the base. It occurs 
abimdantly in New Mexico, always growing 
with the common species, and seems to be quite 
constant from seed. Mr. Cockerell kindly sent 
me some burs of both forms, and from these I 
raised in my garden last year a nice lot of the 
common, as well as of the Wootoni plants. 

Spineless varieties are recorded for the bas- 
tard-acacia, the holly and the garden goose- 
berry (Ribes Grossularia, or R. Uva-crispa). A 
spineless sport of the prickly Broom {Ulex evr 
ropmis) has been seen from time to time, but it 
has not been propagated. 

Summarizing the foregoing facts, we have ex- 
cellent evidence of varieties being produced 
either by the loss of some marked peculiarity or 
by the acquisition of others that are already 



Retrograde Varieties 141 

/ 

present in allied species. There are a great 
many cases however, in which the morpho- 
logic cause of the dissimilarity is not so easily 
discerned. But there is no reason to doubt that 
most of them will be found to conform to the 
rule on closer investigation. Therefore we can 
consider the following as the principal differ- 
ence between elementary species and varieties ; 
that the first arise by the acquisition of entirely 
new characters, and the latter by the loss of 
existing qualities or by the gain of such pecul- 
iarities as may already be seen in other allied 
species. 

If we suppose elementary species and varie- 
ties originated by sudden leaps or mutations, 
then the elementary species have mutated in the 
line of progression, some varieties have 
mutated in the line of retrogression, while others 
have diverged from their parental types in a 
line of degression, or in the way of repetition. 
This conception agrees quite well with the cur- 
rent idea that in the building up of the vegeta- 
ble kingdom according to the theory of descent, 
it is species that form the links of the chain 
from the lower forms to the more highly organ- 
ized later derivatives. Otherwise expressed, 
the system is built up of species, and varieties 
are only local and lateral, but never of real 
importance for the whole structure. 



142 


Retrograde Varieties 


Heretofore we have generally assumed, that 
varieties differ from the parent-species in a sin- 
gle character only, or at least that only one need 
be considered. We now come to the study of 
those varieties, which differ in more than one 
character. Of these there are two types. In 
the first the points of dissimilarity are inti- 
mately connected with one another, in the 
second they are more or less independent. 

The mutually related peculiarities may be 
termed correlative, and we therefore speak, in 
such cases, of correlative variability. This 
phenomenon is of the highest importance and 
is of general occurrence. But before describing 
some examples, it is as well to note that in the 
lecture on fluctuating variability, cases of a 
totally different nature will be dealt with, which 
unfortunately are designated by the same 
term. Such merely fluctuating variations are 
therefore to be left out of the present dis- 
cussion. 

The purple thorn-apple, which is considered 
by some writers as a variety of the white-flow- 
ered species or Datura Stramonium, and by 
others as a separate species, Z>. Tatula, will 
serve as an illustration. But as its distinguish- 
ing attributes, as far as we are concerned with 
them here, are of the nature described above as 
characteristic of varietal peculiarities no ob- 



Retrograde Varieties 


143 


jection can be made to our using them as a case 
of correlative variability. 

The essential character of the purple thorn- 
apple lies in the color of the flowers, which are 
of a very beautiful pale blue. But this color 
is not limited to the corolla. It is also to be 
seen in the stems and in the stalks and veins of 
the leaves, which are stained with a deep purple, 
the blue color being added to the original green. 
Even on the surface of the leaves it may spread 
into a purplish hue. On the stems it is to be 
met with everywhere, and even the young seed- 
lings show it. This is of some importance, as 
the young plants when unfolding their cotyle- 
dons and primary leaves, may be distinguished 
by this means from the seedlings of the white- 
flowered species. In crossing experiments it is 
therefore possible to distinguish the whites and 
the blues, even in young seedlings, and ex- 
perience shows that the correlation is quite 
constant. The color can always be relied upon ; 
if lacking in the seedlings, it will be lacking in 
the stems and flowers also; but if the axis of 
the young plant is ever so slightly tinged, the 
color will show itself in its beauty in the later 
stages of the life of the plant. 

This is what we term correlation. The colors 
of the different organs are always in agreement. 
It is true that they require the concurrence of 



144 


Retrograde Varieties 


light for development, and that in the dark or in 
a faint light the seedlings are apt to remain 
green when they should become purple, but 
aside from such consideration all organs always 
come true to their color, whether pure green and 
white, or whether these are combined with the 
blue tinge. TMs constancy is so absolute that 
the colors of the different organs convey the 
suggestion, that they are only separate marks 
of a single character. 

It is on this suggestion that we must work, as 
it indicates the cause of the correlation. Once 
present, the faculty of producing the anthocyan, 
the color in question, will come into activity 
wherever and whenever opportunity presents 
itself. It is the cell-sap of the ordinary cell- 
tissue or parenchyma, which is colored by the 
anthocyan, and for this reason all organs pos- 
sessing this tissue, may exhibit the color in ques- 
tion. 

Thus the color is not a character belonging to 
any single organ or cell, nor is it bound to a 
morphologic unit ; it is a free, physiologic qual- 
ity. It is not localized, but belongs to the en- 
tire plant. If we wish to assume for its basis 
material representative particles, these parti- 
cles must be supposed to be diffused throughout 
the whole body of the plant. 

This conception of a physiologic unit as the 



Retrograde Varieties 


145 


cause of colors and other qualities is evidently 
opposed to the current idea of the cells and tis- 
sues as the morphologic units of the plants. 
But I do not doubt, that in the long run it will 
recommend itself as much to the scientist as to 
the breeder. For the breeder, when desiring to 
keep his varieties up to their standard, or when 
breeding to a definite idea, obviously keeps his 
standard and his ideal for the whole plant, even 
if he breeds only for flowers or for fruit. 

I have chosen the color of the purple thorn- 
apple as a first example, but the colors of other 
plants show so many diverging aspects, all 
pointing so clearly to the same conclusion, that 
it would be well to take a more extensive view 
of this interesting subject. 

First we must consider the correlation in the 
colors of flowers and fruits. If both are colored 
in the species, whether red or brown or purple 
or nearly black, and a variety lacking this hue 
is known, it will be lacking in both organs. If 
the color is pure, the flowers and berries will be- 
come white, but such cases are rare. Ordinar- 
ily a yellowish or greenish tinge underlies the 
ornamental color, and if this latter disappears, 
the yellowish groimd will become manifest. So 
for instance in the Belladonna, a beautiful per- 
ennial herb with great shiny black, but very 
poisonous, fruits. Its flowers are brown, but in 



146 


Retrograde Varieties 


some woods a variety with greenish flowers and 
bright yellow berries occurs, which is also fre- 
quently seen in botanic gardens. The anthocyan 
dye is lacking in both organs, and the same is 
the case with the stems and >the leaves. The 
lady’s laurel or Daphne Mezereum has red co- 
rollas, purple leaves and red fruits; its white- 
flowered variety may be distinguished by lack of 
the red hue in the stems and leaves, and by their 
beautiful yellow berries. Many other instances 
could be given, since the loss of color in berries 
is a very common occurrence, so common that 
for instance, in the heath-family or Ericaceae, 
with only a few exceptions, all berry-bearing 
species have white-fruited varieties. 

The same correlation is observed in the seeds. 
The white-flowered flax may be seen to yield 
yellow and not brown seeds as in the blue spe- 
cies. Many varieties of flowers may be recog- 
nized by the color of their seeds, as in the pop- 
pies, stocks and others. Other white-flowered 
varieties may be distinguished when germinat- 
ing, their young axes being of a pure instead of 
a purplish green. It is a test ordinarily used 
by gardeners, to purify their flower beds long 
before the blooming time, when thinning or 
weeding them. Even in wild plants, as in 
Erodium, Calluna, Brunella and others, a bot- 
anist may recognize the rare white-flowered 



Retrograde Varieties 


147 


variety by the pure green color of the leaves, 
at times when it is not in flower. Some sorts 
of peas bear colored flowers and a red mark on 
the stipules of their leaves. Among bulbous 
plants many varieties may be recognized even 
in the dry bulbs by the different tinges of the 
outer scales. 

Leaving the colors, we come now to another 
instance of correlation, which is still more as- 
tonishing. For it is as rare, as color-varieties 
are common. It is afforded by some plants the 
leaves of which, instead of being entire or 
only divided into large parts, are cleft to a 
greater extent by repeated fissures of the mar- 
ginal lobes. Such foliar variations are often 
seen in gardens, where they are cultivated for 
their beauty or singularity, as the laciniated 
alders, fern-leaved beeches and limes, oak- 
leaved laburnums, etc. Many of them are de- 
scribed under the varietal name of laciniata. 
In some cases this fissure extends to the petals 
of the flowers, and changes them in a way quite 
analogous to the aberrancy of the leaves. This 
is known to occur with a variety of brambles, 
and is often seen in botanic gardens in one of 
the oldest and most interesting of all anomalies, 
the laciniated variety of the greater celandine 
or Chelidonium majus. Many other instances 
could be given. Most of them belong to the 



148 Retrograde Varieties 

group of negative variations, as we have delBned 
them. But the same thing occurs also with 
positive varieties, though of course, such cases 
are very rare. The best fcuown instance is that 
of the ever-flowering begonia. Begonia semper- 
florens, which has green leaves and white flow- 
ers, but which has produced garden varieties 
with a brown foliage and pink flowers. Here 
also the new quality manifests itself in different 
organs. 

Enough has now been said on correlative 
changes, to convince us that they are as a rule 
to be considered as the expression of some gen- 
eral internal or physiologic quality, which is not 
limited to a single organ, but affects all parts 
of the organism, provided they are capable of 
undergoing the change. Such characters are 
therefore to he considered as units, and should 
be referred to the group of single characters. 

Opposed to these are the true compound char- 
acters, which consist of different units. These 
may he segregated by the production of varie- 
ties, and thereby betray the separate factors of 
the complex group. 

The most beautiful instances of such complex 
characters are offered by the colors of some of 
the most prized garden-flowers. Barely these 
are of a single hue, often two or three shades 
contribute to the effect, and in some cases spe- 



Retrograde Varieties 


149 


cial spots or lines or tracings are to be seen on a 
white or on a colored background. That such 
spots and lines are separate units is obvious 
and is demonstrated by the fact that some- 
times spotless varieties occur, which in all other 
respects have kept the colors of the species. 
The complexity of the color is equally evident, 
whenever it is built up of constituents of the 
anthocyan and of the yellow group. The an- 
thocyan dye is limited to the sap-cavity of the 
cells, while the yellow and pure orange colors 
are fixed in special organs of the protoplasm. 
The observation under the microscope shows at 
once the different units, which though lying in 
the same cell and in almost immediate vicinity 
of each other are always wholly separated from 
one another by the wall of the vacuole or sap- 
fiUed cell-cavity. 

The combination of red and yellow gives a 
brown tinge, as in the cultivated wall-flower, or 
those bright hues of a dark orange-red, which 
are so much sought in tulips. By putting such 
flowers for a short time in boiling water, the 
cells die and release the red pigment, which be- 
comes diffused in the surrounding fluids and the 
petals are left behind with their yellow tinge. 
In this way it is easy to separate the constitu- 
ents, and demonstrate the compound nature of 
the original colors. 



150 


Retrograde Varieties 


But the diversity of the color patterns is far 
from being exhausted with these simple in- 
stances. Apart from them, or joined to them, 
other complications are frequently seen, which 
it is impossible to analyze in such an artificial 
way. Here we have to return to our former 
principle, the comparison of different varieties. 
Assuming that single units may be lost, ir- 
respective of the others, we may expect to find 
them segregated by variation, wherever a suffi- 
ciently wide range of color-varieties is in culti- 
vation. In fact, in most cases a high degree of 
dissimilarity may be reached in the simplest 
way by such a separation of the components, 
and by their combination into most diverse 
smaller groups. A very nice instance of such 
an analysis of flower-colors is afforded by the 
ordinary snapdragon. The beautiful brown- 
red color of tins common garden-plant is com- 
posed on one side of yellow elements, on the 
other of red units. Of the yellow there are 
two, one staining the whole corolla with a light 
hue, as is to be seen in the pure yellow variety 
called hiteum. This form has been produced 
by the loss of the whole group of the red con- 
stituents. If the yellow tinge is also lost, there 
arises a white variety, but this is not absolutely 
colorless, but shows the other yellow constit- 
uent. This last stains only some small parts 



Retrograde Varieties 


151 


of the lips of the flower around the throat, 
brightening, as it seems, the entrance for the 
visiting insects. In many of the red or reddish 
varieties this one yellow patch remains, while 
the general yellow hue fails. In the variety 
called “ Brilliant ” the yellow ground makes 
the red color more shiny, and if it is absent the 
pure carmine tinge predominates. 

It is readily seen, that in the ordinary form 
the lips are of a darker red than the tube. This 
evident dissimilarity indicates some complexity. 
And in fact we have two varieties which exhibit 
the two causes of this attribute separately. One 
of them is called “ Delila,” and has the red 
color limited to the lips, whilst the tube is pure 
white. The other is called “ Fleshy,’^ and is of 
a pale pink throughout the whole corolla. Ad- 
ding these two units to one another, we get the 
original dark red of the wild type, and it may be 
briefly stated here, that the way of effecting 
such an addition is given us in the crossing of 
the “ Fleshy ” and the “ Delila ” variety, 
the hybrid showing the two colors and return- 
ing thereby to the old prototype. 

Other cases of compound flower colors or of 
color patterns might be given as in the Mimulus 
and the poppy, and in most of these cases some 
varieties are to be seen in our gardens which 
show only the single constituents of the group. 



152 Retrograde Varieties 

Many dark flowers have an intermediate bright 
hned form besides the white variety, as in the 
case of roses, asters, Nicandra and so on. 

Intermediate forms with respect to stature 
may also be seen. The opium-poppy, the snap- 
dragon, peas, the Nicandra, and many other 
garden-plants have not only dwarf varieties, 
but also some of intermediate height. These, 
though they are intermediate between the tall 
and dwarf types, cannot be considered as transi- 
tions, as between them and the extremes, inter- 
mediates are, as a rule wholly lacking. In- 
stances of the same occurrence of three types 
may be seen in the seeds of maize (“ Cuzco,” 
“ Horse-dent ” and “Gracillima”) of beans and 
some other plants. The Xanthium Wootoni, 
above referred to, with only part of the prickles 
of Xanthium commune is also a very curious in- 
stance of the demonstration of the compound 
nature of a character. 

Summarizing the conclusions that may be 
drawn from the evidence given in this lecture, 
we have seen that varieties ditfer from elemen- 
tary species in that they do not possess anything 
really new. They originate for the greater part 
in a negative way, by the apparent loss of some 
quality, and rarely in a positive manner by ac- 
quiring a character, already seen in allied spe- 
cies. These characters are not of the nature of 



Retrograde Va/rieties 


153 


morphologic entities, but are to be considered 
as physiologic units, present in all parts of the 
organisms, and manifesting themselves where- 
ever occasion is afforded. They are units in 
the sense that they may appear and disappear 
singly. But very often they are combined to 
yield compound characters, which are capable 
of analysis. Opportunities for such an analysis 
are afforded by these groups of cultivated va- 
rieties, of which some members show a single 
distinguishing quality, or a number of them. 



Lbctube VI 

STABILITY AKD BEAL ATAVISM 

It is generally believed that varieties are 
principally distinguished from species by their 
inconstancy. This conception is derived from 
some special cases and transferred to others, 
and in its common form this belief must have 
originated from the confusion which exists as 
to the meaning of the term variety. It is 
true that vegetative varieties as a rule run back, 
when propagated by seeds ; they are an obvious 
instance of inconstancy. In the second place 
we have considered the group of inconstant or 
sporting varieties, which of course we must ex- 
clude when studying the stability of other types. 
However, even these sporting varieties are un- 
stable only to a certain degree, and in a broader 
sense will prove to be as true to their character 
as the most constant types. 

Having separated these two groups, which 
include also the wide range of hybrid forms, we 
may next consider only those varieties of pure 
origin, and ordinarily propagated by seeds, 

154 



stability and Beal Atavism 155 

which have been discussed in former chapters. 
Their general character lies in their fidelity to 
type, and in the fact that this is single, and not 
double, as in the sporting varieties. 

But the current belief is, that they are only 
true to their peculiarities to a certain degree, 
and that from time to time, and not rarely, 
they revert to the type from which they have 
arisen. Such reversion is supposed to prove 
that they are mere varieties, and at the same 
time to indicate empirically the species from 
which they have sprung. 

In the next lecture we shall examine critically 
the evidence on which this assumption rests. 
Before doing so however, it will be necessary 
to collate the cases in which there is no re- 
version at all, or in which the reversion is ab- 
sent at least in experimental and pure sowings. 

In the present state of our knowledge it is 
very difficult to decide, whether or not true re- 
version occurs in constant varieties. If it does 
occur, it surely does so very rarely and only 
under unusual circumstances, or in particular 
individuals. However when such individuals 
are multiplied by buds and especially when they 
are the only representatives of their type, the 
reversion, though theoretically rare, will be 
shown by nearly every specimen of the va- 
riety. Examples of this will be given below. 



156 Retrograde Varieties 

They are generally called atavists or rever- 
sionists, but even these terms are sometimes 
used in a different sense. 

Lastly it is to be said that the empirical and 
experimental evidence as to the question of con- 
stancy is not as extensive as it should be. The 
experimental conditions are seldom described, 
and it is only recently that an interest in the 
matter has been awakened. 3d!uch remains to 
be done. Among other things the innumerable 
varieties of trees, shrubs and perennial herbs 
should be tested as to their constancy when 
grown from purely fertilized seeds. Many of 
them may be included among the number that 
sport constantly. 

Leaving aside the doubtful or insuflSciently 
studied cases, we may now turn our attention to 
the facts that prove the absolute stability of 
a large number of varieties, at least as far as 
such completeness can be attained by experi- 
ment or observation. 

The best proof is afforded by the varieties 
which grow wild in localities where they are 
quite isolated from the species, and where for 
this reason, no possibility of crossing disturbs 
the significance of the proof. As one instance 
the rayless form of the wild camomile, or the 
Matricaria Chamomilla discoidea may be men- 
tioned. Many systematists have been so strong- 



stability and Real Atavism 157 

ly impressed with its absolute constancy and its 
behavior as an ordinary species, that they have 
elevated it, as it is called, to the rank of a spe- 
cies. As such it is described under the name of 
Matricaria discoidea DC. It is remarkable 
for its rapid and widespread distribution, as of 
late years it has become naturalized in different 
parts of America and of Europe, where it is to 
be seen especially in France and in Norway. 
Experimentally I raised in succeeding years be- 
tween 1000 and 2000 seedlings, but observed no 
trace of reversion, either in the strongest or in 
the numerous very small and weak individuals 
which appeared in the cultures. 

The tansy-ragwort or Senecio Jacobaea may 
be chosen as a second instance. It is a per- 
ennial herb with short rootstocks and stout 
stems bearing numerous short-peduncled heads 
in a large compact corymb; it multiplies itself 
abundantly by seeds and is very common on 
the sand dunes of Holland. It has two forms, 
differing only in the occurrence or the lack of 
the ray florets. But these two varieties occupy 
different localities and are even limited to dif- 
ferent provinces. As far as I have been able to 
ascertain on numerous excursions during a 
series of years, they never sport, and are only 
intermingled on the outskirts of their habitats. 
The rayless form is generally considered as the 



158 Retrograde Varieties 

variety but it is quite as stable as the radiate 
species. 

The radiate varieties of marigold, quoted in a 
former lecture, seem to be equally constant, 
when growing far away from their prototypes. 
I sowed the seeds of a single plant of the radiate 
form of Bidens cernua, and found all of the 
seedlings came true, and in the next year I had 
from their seed between 2000 and 3000 flower- 
ing individuals, all equally radiate. Many 
species of composites have been tried, and they 
are all constant. On the other hand rare sports 
of this kind have been observed by Murr and 
other authors. 

Many kinds of vegetables and of fruits give 
instances of stability. White strawberries, 
green grapes, white currants, crisped lettuce, 
crisped parsley and some other crisped forms 
may be cited. The spinage without prickles is 
a widely known instance. White-flowered flax 
never reverts to the blue prototype, if kept pure. 
Sugar-peas and sugar-corn afford further in- 
stances. Strawberries without runners have 
come true from seed ever since their first ap- 
pearance, over a hundred years ago. 

Many garden-varieties, the stability of which 
under ordinary circumstances is doubtful, be- 
cause of their being sown too close to other va- 
rieties of the same species, have been tested in 



stability <md Real Atavism 159 

respect to their stability by different writers 
and at different times. In doing this it is plain 
that it is very essential to be sure of the purity 
of the seed. Specimens must be grown in posi- 
tions isolated from their allies, and if possible 
be pollinated artificially with the exclusion of 
the visits of insects. This may be done in differ- 
ent ways. If it is a rare species, not cultivated 
in the neighborhood, it is often sufficient to make 
sure of this fact. Pollen may be conveyed by 
bees from distances of some ten or twenty 
meters, or in rare cases from some hundred 
meters and more, but a greater distance is or- 
dinarily sufficient for isolation. If the flowers 
fertilize themselves, as is more often the case 
than is generally supposed, or if it is easy to 
pollinate them artificially, with their own pollen 
or in small groups of similar individuals, the 
best way is to isolate them by means of close 
coverings. When flowering, the plants are as a 
rule too large to be put under bell-glasses, and 
moreover such coverings would keep the air 
moist, and cause the flower-buds to be thrown 
off. The best coverings are of netting, or of 
canvas of sufficiently wide mesh, although after 
a long experience I greatly prefer cages of 
fine iron-wire, which are put around and over 
the whole plant or group of plants, and fastened 
securely and tightly to the ground. 



160 


Retrograde Varieties 


Paper bags also may be made use of. They 
are slipped over the flowering branches, and 
bound together around the twigs, thus enclosing 
the flowers. It is necessary to use prepared 
papers, in order that they may resist rain 
and wind. The best sort, and the one that I 
use almost exclusively in my fertilization-ex- 
periments, is made of parchment-paper. This 
is a wood-pulp preparation, freed artificially 
from the so-called wood-substance or lignin. 
Having covered the flowers with care, and 
having gathered the seeds free from inter- 
mixtures and if possible separately for each 
single individual, it only remains to sow them 
in quantities that will yield the greatest pos- 
sible number of individuals. Eeversions are 
supposed to be rare and small groups of seed- 
lings of course would not suffice to bring them 
to light. Only sowings of many hundreds or 
thousands of individuals are decisive. Such 
sowings can be made in one year, or can 
be extended over a series of years and of gen- 
erations. Hildebrand and Hoffman have pre- 
ferred the last method, and so did Hof- 
meister and many others. Hildebrand sowed 
the white hyacinth, and the white varieties of 
the larkspur, the stock and the sweet pea. Hoff- 
man cultivated the white flax and many other 
varieties and Hofmeister extended his sowings 



sterility and Beal Atavism 161 

over thirty years with the white variety of the 
yellow foxglove {Digitalis parviflora). 

White-flowered varieties of perennial garden- 
plants were used in my own experiments. I 
bought the plants, flowered them under isolation 
in the way described above, gathered the seeds 
from each individual separately and sowed them 
in isolated groups, keeping many hundreds and 
in some cases above a thousand plants up to 
the time of flowering. Among them I found 
only one inconstant variety, the white form of 
the yellow columbine, Aquilegia chrysantha. It 
evidently belonged to the group of sporting va- 
rieties already referred to. All others came ab- 
solutely true to type without any exception. The 
species experimented with, were Campanula 
persicifolia,Hyssopus officinalis, Lobelia syphil- 
itica, Lychnis chalcedonica, Polemonium dissec- 
tum, Salvia sylvestris and some others. Tested 
in the same way I found the white varieties of 
the following annual plants also quite true; 
Chrysanthemum coronarium, Godetia amoena, 
Linum usitatissimum. Phlox drummondi, and 
Silene Armeria. To these may be added the 
white hemlock stork’s-bill {Erodium cicutarium 
album) which grows very abundantly in some 
parts of my fatherland, and is easily recogniz- 
able by its pure green leaves and stems, even 
when not flowering. I cultivated it in large num- 



162 


Retrograde Varieties 


bers daring five succeeding generations, but was 
never able to find even the slightest indication 
of a reversion to the red prototype. The scar- 
let pimpernel or Anagallis arvensis has a blue 
variety which is absolutely constant. Even in 
Britton and Brown’s Flora,” which rarely 
enumerates varieties, it is mentioned as being 
probably a distinct species. Eight hundred 
blooming seedlings were obtained from isolated 
parents, all of the same blue color. The New 
Zealand spinage {Tetragonia expansa) has a 
greenish and a brownish variety, the red color 
extending over the whole foliage, including the 
stems and the branches. 1 have tried both of 
them during several years, and they never 
sported into each other. I raised more than 
5000 seedlings, from the different seeds of one 
lot of the green variety in succeeding years, but 
neither those germinating in the first year, nor 
the others coming into activity after two, three 
or four years of repose gave any sign of the 
red color of the original species. 

It is an old custom to designate intermediate 
forms as hybrids, especially when both the 
types are widely known and the intermediates 
rare. Many persons believe that in doing so, 
they are giving an explanation of the rarer 
forms. But since the laws of hybridism are 
coming to be known we shall have to break with 



stability and Real Atavism 163 

all such usages. So for instance there are num- 
erous flowers which are of a dark red or a dark 
blue color, and which, besides a white variety, 
have a pink or a pale blue form. Such pale 
varieties are of exactly the same value as others, 
and on testing they are found to be equally 
stable. So for instance the pink variety of the 
Sweet William (Silene Armeria rosea), the 
Glarkia pulchella carnea and the pale variety 
of the corn-cockle, called usually 
Githago nicaeensis or even simply A. nicaeensis. 
The latter variety I found pure during ten suc- 
ceeding generations. Another notable stable 
intermediate form is the poppy bearing the 
Danish flag (Papaver somniferum Danehrog). 
It is an old variety, and absolutely pure when 
cultivated separately. A long list of other in- 
stances might easily be given. 

Many garden-varieties, that are still univer- 
sally prized and cultivated are very old. It is 
curious to note how often such forms have been 
introduced as novelties. The common fox- 
glove is one of the best examples. It has a mon- 
strous variety, which is very showy because it 
bears on the summit of its raceme and branches, 
large erect cup-shaped flowers, which have quite 
a different aspect from the normal thimble- 
shaped side-blossoms. These flowers are or- 
dinarily described as belonging to the anomaly 



178 Retrograde Varieties 

descent is a requisite. By so doing, we exclude 
most of the facts which were until now gener- 
ally relied upon. For the roses, the hyacinths, 
the tulips, the chrysanthemums always have 
furnished the largest contributions to the dem- 
onstrations of bud-variation. But they have 
been crossed so often, that doubt as to the purity 
of the descent of any single form may recur, 
and may destroy the usefulness of their many 
recorded cases of bud-variation for the demon- 
stration of real atavism. The same assertion 
holds good in many other cases, as with Azalea 
and Camellia. And the striped varieties of 
these genera belong to the group of ever-sport- 
ing forms, and therefore will be considered 
later on. So it is with carnations and 
pinks, which occasionally vary by layering, and 
of which some kinds are so uncertain in char- 
acter that they are called by floriculturists 
catch-flowers.” On the other hand there is 
a larger group of cases of reversion by buds, 
which is probably not of hybrid nature, nor due 
to innate inconstancy of the variety, but must 
be considered as pure atavism. I refer to the 
bud-variations of so many of our cultivated 
varieties of shrubs and trees. Many of them 
are cultivated because of their foliage. They 
are propagated by grafting, and in most cases 
it is probable that all the numerous specimens 



sterility and Beal Atavism 179 

of the same variety have been derived in this 
way from one primitive, aberrant individual. 
We may disregard variegated leaves, spotted or 
marked with white or yellow, because they are 
too inconstant types. 

We may next turn our attention to the va- 
rieties of trees with cut leaves, as the oak- 
leaved Laburnum, the parsley-leaved vine and 
the fem-leaved birch. Here the margin of the 
leaves is deeply cut and divided by many 
incisions, which sometimes change only the 
outer parts of the blade, but in other cases may 
go farther and reach, or nearly reach, the mid- 
vein, and change the simple leaf into a seem- 
ingly compound structure. The anomaly may 
even lead to the almost complete loss of all the 
chorophyll-tissue and the greater part of the 
lateral veins, as in the case of the cut-leaved 
beech or Fagus sylvatica pectinata. 

Such varieties are often apt to revert by buds 
to the common forms. The cut-leaved beech 
sometimes reverts partially only, and the 
branches often display the different forms of 
cut-leaved, fern-like, oak-leaved and other vari- 
ously shaped leaves on the same twigs. But 
this is merely due to the wide variability of the 
degree of fissure and is to be considered only as 
a fluctuation between somewhat widely distant 
extremes, which may even apparently include 



180 


Retrograde Varieties 


the form of the commoii beech-leaves. It is not 
a bud-variation at all, and it is to be met with 
quite commonly while the true reversions by 
buds are very rare and are of the nature of 
sports appearing suddenly and remaining con- 
stant on the same twig. Analogous phenomena 
of wide variability with true reversion may be 
seen in the variety of the European hornbeam 
called Carpinus Betulus heterophylla. The 
leaves of this tree generally show the greatest 
diversity in form. Some other cases have been 
brought together by Darwin. In the first place 
a subvariety of the weeping-willow with leaves 
rolled up into a spiral coil. A tree of this kind 
kept true for twenty-five years and then threw 
out a single upright shoot bearing flat leaves. 
The barberry {Berheris) offers another case; 
it has a well known variety with seedless fruit, 
which can be propagated by cuttings or layers, 
but its runners are said klways to revert to the 
common form, and to produce ordinary berries 
with seeds. Most of the cases referred to by 
Darwin, however, seem to be doubtful and can- 
not be considered as true proofs of atavism until 
more is known about the circumstances under 
which they were produced. 

Red or brown-leaved varieties of trees and 
shrubs also occasionally produce green-leaved 
branches, and in this way revert to the type 



181 


Stability and Real Atavism 

from which they must evidently have arisen. 
Instances are on record of the hazel, Corylus 
Avellana, of the allied Corylus tubulosa, of 
the red beech, the brown birch and of some other 
purple varieties. Even the red bananas, which 
bear fruits without seeds and therefore have no 
other way of being propagated than by buds, 
have produced a green variety with yellow 
fruits. The Hortensia of our gardens is an- 
other instance of a sterile form which has been 
observed to throw out a branch with cymes 
bearing in their center the usual small stam- 
inate and pistillate flowers instead of the large 
radiate and neutral corollas of the variety, 
thereby returning to the original wild type. 
Crisped weeping-willows, crisped parsley and 
others have reverted in a similar manner. 

All such cases are badly in need of a 
closer investigation. And as they occur only 
occasionally, or as it is commonly stated, by ac- 
cident, the student of nature should be prepared 
to examine carefully any case which might pre- 
sent itself to him. Many phases of this difficult 
problem could no doubt be solved in this way. 
First of all the question arises as to whether the 
case is one of real atavism, or is only seemingly 
so, being due to hybrid or otherwise impure de- 
scent of the varying individual, and secondly 
whether it may be only an instance of the regu- 



182 Retrograde Varieties 

larly occurring so-called atavism of the sporting 
varieties with which we shall deal in a later 
lecture. If it proves to be real atavism 
and rare, the case should be accurately 
described and figured, or photographed if pos- 
sible; and the exact position of the reverting 
bud should be ascertained. Very likely the so- 
called dormant or resting buds are more liable 
to reversions than the primary ones in the axils 
of the leaves of young twigs. Then the char- 
acters of the atavistic branches should be mi- 
nutely compared with those of the presumed an- 
cestor ; they may be quite identical with them or 
slightly divergent, as has been asserted in some 
instances. The atavism may be complete in one 
case, but more or less incomplete in others. 

By far the most interesting point is the ques- 
tion, as to what is to he expected from the seeds 
of such an atavistic branch. Will they keep 
true to the reverted character, or return to the 
characters of the plant which bears the retro- 
grade branch? Will all of them do so, or only 
part of them, and how large a part? It is very 
astonishing that this question should still be 
unsolved where so many individual trees bear 
atavistic branches that remain on them through 
long series of years. But then many such 
branches do not flower at all, or if they flower 
and bear seed, no care is taken to prevent 



183 


Sterility and Real Atavism 

cross-fertilization with the other flowers of the 
same plant, and the results have no scientific 
value. For anyone who cares to work with 
the precautions prescribed by science, a wide 
field is here open for investigation, because old 
reverted branches may be met with much less 
rarely than new ones. 

Finally the possibility is always to he con- 
sidered that the tendency to bud-reversions may 
be a special feature of some individuals, and 
may not be met with in others of the same 
variety. I have spoken of this before. For the 
practical student it indicates that a specimen, 
once observed to produce atavistic buds, may be 
expected to do the same thing again. And then 
there is a very good chance that by combining 
this view with the idea that donnant buds are 
more apt to revert than young ones, we may get 
at a method for further investigation, if we re- 
cur to the practice of pruning. By cutting 
away the young twigs in the vicinity of dormant 
buds, we may incite these to action. Evidently 
we are not to expect that in so doing they will 
all become atavistic. For this result is not at 
all assured ; on the contrary, all that we might 
hope to attain would be the possibility of some 
of them being induced to sport in the desired 
direction. 

Many questions in scientific research can only 



184 


Retrograde Varieties 


be answered by long and arduous work in well- 
equipped laboratories; they are not to be at- 
tempted by every one. But there are other 
problems which the most complete of institu- 
tions are not able to study if opportunity is not 
offered them, and such opportunities are apt to 
occur more often in fields, gardens, parks, 
woods and plains, than in the relatively small 
experimental gardens of even the largest in- 
stitution. Therefore, whosoever has the good 
fortune to find such sports, should never allow 
the occasion to pass without making an investi- 
gation that may bring results of very great im- 
portance to science. 



Lectube vn 


FALSE ATAVISM OE VICINISM 

About the middle of the last century Louis 
de Vilmorin showed that it was possible to 
subject plants to the methods of ameliora- 
tion of races then in use for domestic animals, 
and since that time atavism has played a large 
part in all breeding-processes. It was consid- 
ered to be the greatest enemy of the breeder, 
and was generally spoken of as a definite force, 
working against and protracting the endeav- 
ors of the horticulturist. 

No clear conception as to its true nature had 
been formulated, and even the propriety of 
designating the observed phenomena by the 
term atavism seemed doubtful. Duchesne 
used this word some decades ago to designate 
those cases in which species or varieties revert 
spontaneously, or from unknown internal 
causes, to some long-lost characters of their an- 
cestors. Duchesne’s definition was evidently a 
sharp and useful one, since it developed for the 
first time the idea of latent or dormant qualities, 

185 



186 


Retrograde Varieties 


formerly active, and awaiting probably through 
centuries an occasion to awaken, and to dis- 
play the lost characters. 

Cases of apparent reversion were often seen 
in nurseries, especially in flower culture, which 
under ordinary circmnstances are rarely 
wholly pure, but always sport more or less into 
the colors and forms of allied varieties. Such 
sporting individuals have to be extirpated 
regularly, otherwise the whole variety would 
soon lose its type and its uniformity and run 
over to some other form in cultivation in the 
vicinity. For this reason atavism in nurseries 
causes much care and labor, and consequently 
is to be dealt with as a very important factor. 

From time to time the idea has suggested 
itself to some of the best authorities on the 
amelioration of plants, that this atavism was 
not due to an innate tendency, but, in many 
cases at least, was produced by crosses between 
neighboring varieties. It is especially owing 
to Verlot that this side of the question was 
brought forward. But breeders as a rule have 
not attached much importance to this supposi- 
tion, chiefly because of the great practical diffi- 
culties attending any attempt to guard the spe- 
cies of the larger cultures against intermixture 
with other varieties. Bees and humble-bees fly 
from bud to bud, and carry the pollen from one 



Fa^se Atavism 


187 


sort to another, and separation by great dis- 
tances would be required to avoid this source of 
impurity. Unfortunately the arrangements 
and necessities of large cultures make it impos- 
sible to isolate the allied varieties from each 
other. 

From a theoretical point of view the origin 
of these impurities is a highly important ques- 
tion. If the breeders’ atavism is due to crosses, 
and only to this cause, it has no bearing at all 
on the question of the constancy of varieties. 
And the general belief, that varieties are dis- 
tinguished from true species by their repeated 
reversion and that even such reversibility is the 
real distinction of a variety, would not hold. 

For this reason I have taken much trouble 
in ascertaining the circumstances which attend 
this form of atavism. I have visited a number 
of the leading nurseries of Europe, tested their 
products in various ways, and made some ex- 
periments on the unavoidable conditions of 
hybridizing and on their effect on the ensuing 
generations. These investigations have led me 
to the conclusion, that atavism, as it is gener- 
ally described, always or nearly always is due 
to hybridization, and therefore it is to be con- 
sidered as untrue or false atavism. 

True atavism, or reversion caused by an in- 
nate latent tendency, seems to be very rare. 



188 


Retrograde Varieties 


and limited to such cases as we have spoken of 
under our last heading. And since the defi- 
nition, given to this term by its author, Du- 
chesne, is generally accepted in scientific works, 
it seems better not to use it in another sense, 
but rather to replace it in such cases by another 
term. For this purpose I propose the word 
vicinism, derived from the Latin vicinus or 
neighbor, as indicating the sporting of a variety 
under the infiuence of others in its vicinity. 
Used in this way, this term has the same bear- 
ing as the word atavism of the breeders, but 
it has the advantage of indicating the true cause 
thereof. 

It is well known that the term variability is 
commonly employed in the broadest possible 
sense. No single phenomenon can be desig- 
nated by this name, unless some primary re- 
striction be given. Atavism and vicinism are 
both cases of variability, but in wholly different 
sense. For this reason it may be as well, to 
insert here a short survey of the general mean- 
ings to be conveyed by the term variation. It 
implies in the first place the occurrence of a 
wide range of forms and types, irrespective of 
their origin, and in the second place the process 
of the change in such forms. In the first signifi- 
cation it is nearly identical with polymorphy, 
or richness of tj^es, especially so when these 



False Atavism 


189 


types are themselves quite stable, or when it is 
not at all intended to raise the question of their 
stability. In scientific works it is commonly 
used to designate the occurrence of subspecies 
or varieties, and the same is the case in the 
ordinary use of the term when dealing with 
cultivated plants. A species may consist of 
larger or smaller groups of such units, and 
they may be absolutely constant, never sport- 
ing if hybridization is precluded, and neverthe- 
less it may be called highly variable. The 
opium-poppy affords a good instance. It 
“ varies ” in height, in color of foliage and 
flowers ; the last are often double or laciniated ; 
it may have white or bluish seeds, the capsules 
may open themselves or remain closed and so 
on. But every single variety is absolutely con- 
stant, and never runs into another, when the 
flowers are artificially pollinated and the visits 
of insects excluded. So it is with many other 
species. They are at the same time wholly 
stable and very variable. 

The terms variation and variety are used 
frequently when speaking of hybrids. By cross- 
ing forms, which are already variable in the 
sense just mentioned, it is easy to multiply the 
number of the types, and even in crossing pure 
forms the different characters may be combined 
in different ways, the resulting combinations 



190 


Retrograde Varieties 


yielding new, and very often, valuable varieties. 
But it is manifest that this form of variation 
is of quite another nature from the variations 
of pure races. Many hybrid varieties are quite 
constant, and remain true to their type if no 
further crosses are made ; many others are arti- 
ficially propagated only in a vegetative way, 
and for this reason are always found true. 
Hybrid varieties as a rule were formerly con- 
fused with pure varieties, and in many in- 
stances our knowledge as to their origin is quite 
insufficient for sharp distinctions. To .every 
student of nature it is obvious, that crossing 
and pure variability are wholly distinct groups 
of phenomena, which should never be treated 
under the same head, or under the same name. 

Leaving aside polymorphy, we may now dis- 
cuss those cases of variability, in which the 
changes themselves, and not only their final 
results play a part. Of such changes two types 
exist. First, the ever-recurring variability, 
never absent in any large group of individuals, 
and determining the differences which are al- 
ways to be seen between parents and their 
children, or between the children themselves. 
This type is commonly called “ individual 
variability ” and since this term also has still 
other meanings, it has of late become customary 
to use instead the term fluctuating varia- 



False Atavism 


191 


bility.” And to avoid the repetition of the lat- 
ter word it is called “ fluctuation.” In con- 
trast to these fluctuations are the so-called 
sports or single varieties, not rarely denomi- 
nated spontaneous variations, and for which I 
propose to use the term “ mutations.” They 
are of very rare occurrence and are to be con- 
sidered as sudden and definite steps. 

Lastly, we have to consider those varieties, 
which vary in a much wider range than the 
ordinary ones, and seem to fluctuate between 
two opposite extremes, as for instance varie- 
gated leaves, cultivated varieties with va- 
riegated or striped flowers, double flowers 
and some other anomalies. They are ever- 
sporting and ever-returning from one type to 
the other. If however, we take the group of 
these extremes and their intermediates as a 
whole, this group remains constant during the 
succeeding generations. Here we And once 
more an instance of the seemingly contradictory 
combination of high variability and absolute 
constancy. It means that the range of varia- 
bility has quite definite limits, which in the com- 
mon course of things, are never transgressed. 

We may infer therefore that the word varia- 
bility has such a wide range of meanings that 
it ought never be used without explanation. 



X92 


Retrograde Varieties 


Nothing indeed, is more variable than the sig- 
nification of the term variable itself. 

For this reason, we will furthermore desig- 
nate all variations under the influence of neigh- 
bors with the new and special term “ vicinism.” 
It always indicates the result of crossing. 

Leaving this somewhat lengthy terminolog- 
ical discussion, we now come to the description 
of the phenomenon itself. In visiting the plan- 
tations of the seedsmen in summer and exam- 
ining the large fields of garden-flowers from 
which seed is to be gathered, it is very rare to 
And a plot quite pure. On the contrary, occa- 
sional impurities are the rule. Every plot 
shows anomalous individuals, red or white 
flowers among a field of blue, normal among 
laciniated, single among double and so on. The 
most curious instance is afforded by dwarf 
varieties, where in the midst of hundreds and 
thousands of small individuals of the same 
height, some specimens show twice their size. 
So for instance, among the dwarfs of the lark- 
spur, Delphinium Ajacis, 

Everywhere gardeners are occupied in de- 
stroying these “ atavists,” as they call them. 
When in full bloom the plants are pulled up 
and thrown aside. Sometimes the degree of 
impurity is so high, that great piles of dis- 
carded plants of the same species lie about the 



FcAse Atavism 


193 


paths, as 1 have seen at Erfurt in the case of 
numerous varieties of the Indian cress or Tro- 
paeolum. 

Each variety is purified at the time when it 
shows its characters most clearly. With vege- 
tables, this is done long before flowering, but 
with flowers only when in full bloom, and with 
fruits, usually after fertilization has been ac- 
complished. It needs no demonstration to show 
that this difference in method must result in 
very diverging degrees of purity. 

We will confine ourselves to a consideration 
of the flowers, and ask what degree of purity 
may be expected as the result of the elimination 
of the anomalous plants during the period of 
blooming. 

Now it is evident that the colors and forms 
of the flowers can only be clearly distin- 
guished, when they are fuUy displayed. Fur- 
thermore it is impossible to destroy every 
single aberrant specimen as soon as it is seen. 
On the contrary, the gardener must wait until 
all or nearly all the individuals of the same va- 
riety have displayed their characters, as 
only in this way can all diverging specimens 
be eliminated by a single inspection. Un- 
fortunately the insects do not wait for this 
selection. They fertilize the flowers from the 
beginning, and the damage will have been done 



194 


Retrograde Varieties 


long before the day of inspection comes around. 
Crosses are unavoidable and hybrid seeds will 
unavoidably come into the harvest. Their 
number may be limited by an early eradication 
of the vicinists, or by the elimination of the 
first ripe seeds before the beginning of the regu- 
lar harvest, or by other devices. But some 
degree of impurity will remain under ordinary 
circumstances. 

It seems quite superfluous to give more de- 
tails. In any case in which the selection is not 
done before the blooming period, some impuri- 
ties must result. Even if it is done before that 
time, errors may occur, and among hundreds 
and thousands of individuals a single anomalous 
one may escape observation. 

The conclusion is, that flower seeds as they 
are offered in commerce, are seldom found 
absolutely pure. Every gardener knows that 
he will have to weed out aberrant plants in 
order to be sure of the purity of his beds. I 
tested a large number of samples of seeds for 
purity, bought directly from the best seed- 
growers. Most of them were found to contain 
admixtures and wholly pure samples were very 
rare. 

I will now give some illustrative examples. 
From seeds of a yellow snapdragon, I got one 
red-flowered specimen among half a hundred 



False Atavism 


195 


yellow ones, and from the variety “ Delila ” 
of the same species two red ones, a single white 
and two belonging to another variety called 
“ Firefly.’* CalUopsis tinctoria has 'three va- 
rieties, the ordinary type, a brown-flowered 
one and one with tubular rays. Seeds of each 
of these three sorts ordinarily contain a few 
belonging to the others. Iberis umbellata rosea 
often gives some white and violet examples. 
The “ Swan ” variety of the opium-poppy, a 
dwarfish double-flowered form of a pure white, 
contained some single-flowered and some red- 
flowered plants, when sown from commercial seed 
are said to be pure. But these were only occa- 
sional admixtures, since after artificial fertilizar 
tion of the typical specimens the strain at once 
became absolutely pure, and remained so for a 
series of generations, as long as the experiment 
was continued. Seeds of trees often contain 
large quantities of impurities, and the laciniated 
varieties of birch, elder and walnut have often 
been observed to come true only in a small 
number of seedlings. 

In the case of new or young varieties, seed- 
merchants often warn their customers as to the 
probable degree of purity of the seeds offered, 
in order to avoid complaints. For example the 
snow-white variety of the double daisy, Beilis 
perennis plena, was offered at the start as con- 



196 Retrograde Varieties 

taining as mncli as 20i( of red-flowered speci- 
mens. 

Many fine varieties are recorded to come true 
from seed, as in the case of the holly with 
yellow fruits, tested by Darwin. Others have 
been found untrue to a relatively high degree, 
as is notorious in the case of the purple beech. 
Seeds of the laciniated beech gave only 10^ 
of laciniated plants in experiments made by 
Strasburger; seeds of the monophyllous aca- 
cia, Rohinia Pseud-Acacia monophglla, were 
found to be true in only of the seedlings. 
Weeping ashes often revert to the upright type, 
red May-thoms {Crataegus) sometimes revert 
nearly entirely to the white species and the 
yellow cornel berry is recorded to have reverted 
in the same way to the red berries of the Cor- 
nus Mas. 

Varieties have to be freed by selection from 
all such impurities, since isolation is a means 
which is quite impracticable under ordinary 
circumstances. Isolation is a scientific require- 
ment that should never be neglected in ex- 
periments, indeed it may be said to be the first 
and most important requisite for all exact re- 
search in questions of variability and inherit- 
ance. But in cultivating large fields of allied va- 
rieties for commercial purposes, it is impossible 
to grow them at such distances from each other 



False Atavism 


197 


as to prevent cross-pollination by the visits of 
bees. 

This purification must be done in nearly every 
generation. The oldest varieties are to be sub- 
jected to it as well as the latest. There is no 
regular amelioration, no slow progression in the 
direction of becoming free from these admix- 
tures. Continuous selection is indispensable to 
maintain the races in the degree of purity which 
is required in commerce, but it does not lead to 
any improvement. Nor does it go so far as to 
become unnecessary in the future. This shows 
that there must be a continuous source of im- 
purities, which in itself is not neutralized by 
selection, but of which selection can only elim- 
inate the deteriorating elements. 

The same selection is usually applied to new 
varieties, when they occasionally arise. In this 
case it is called “ fixing,” as gardeners gener- 
ally believe that through selection the varieties 
are brought to the required degree of purity. 
This belief seems to rest mainly on obser- 
vations made in practice, where, as we have seen, 
isolation is of very rare application. Most va- 
rieties would no doubt be absolutely pure from 
the first moment of their existence, if it were 
only possible to have them purely fertilized. 
But in practice this is seldom to be obtained. 
Ordinarily the breeder is content with such slow 



198 


Retrograde Varieties 


improvement as may be obtained with a mini- 
mum of cost, and this mostly implies a culture in 
the same part of the nursery with older varie- 
ties of the same species. Three, four or five 
years are required to purify the novelty, and 
as this same length of time is also required to 
produce sufficient quantities of seed for 
commercial purposes, there is no strong 
desire to shorten the period of selection and 
fixation. I had occasion to see this process go- 
ing on with sundry novelties at Erfurt in 
Germany. Among them a chamois-colored va- 
riety of the common stock, a bluish Clarkia 
elegans and a curiously colored opium-poppy 
may be mentioned. In some cases the cross- 
fertilization is so overwhelming, that in the 
next generation the novelty seems entirely to 
have disappeared. 

The examples given may suffice to convey a 
general idea of the phenomenon, ordinarily 
called atavism by gardeners, and considered 
mostly to be the effect of some innate tendency 
to revert to the ancestral form. It is on this 
conception that the almost universal belief 
rests, that varieties are distinguished, as such, 
from species by their inconstancy. Now I do 
not deny the phenomenon itself. The impurity 
of seeds and cultures is so general and so mani- 
fest, and may so easily be tested by every one 



False Atavism 


199 


that it cannot reasonably be subjected to any 
doubt. It must be conceded to be a fact, that 
varieties as a rule revert to their species under 
the ordinary circumstances of commercial cul- 
ture. And I cannot see any reason why this 
fact should not be considered as stating a prin- 
cipal difference between varieties and species, 
since true species never sport into one another. 

My objection only refers to the explanation 
of the observed facts. According to my view 
nearly all these ordinary reversions are due to 
crosses, and it is for this reason that I proposed 
to call them by a separate name, that of “ vicin- 
ists.” Varieties then, by means of such spon- 
taneous intercrossing sport into one another, 
while species either do not cross, or when cross- 
ing produce hybrids that are otherwise consti- 
tuted and do not give the impression of atavis- 
tic reversion. 

I must not be content with proposing this 
new conception, but must give the facts on 
which this assumption rests. These facts are 
the results of simple experiments, which never- 
theless are by no means easy to carry out, as 
they require the utmost care to secure the 
absolute purity of the seeds that are employed. 
This can only be guaranteed by previous cul- 
tures of isolated plants or groups of plants, or 
by artificial pollination. 



200 


Retrograde Varieties 


Once sure of this preliminary condition, the 
experiment simply consists in growing a variety 
at a given distance from its species and allow- 
ing the insects to transfer the pollen. After 
harvesting the seed thus subjected to the pre- 
sumed cause of the impurities, it must he 
sown in quantities, large enough to bring to 
light any slight anomaly, and to be examined 
during the period of blooming. 

The wild seashore aster. Aster Tripolium, 
will serve as an example. It has pale violet or 
bluish rays, but has given rise to a white va- 
riety, which on testing, I have found pure from 
seed. Four specimens of this white variety 
were cultivated at a distance of nearly 100 
meters from a large lot of plants of the bluish 
species. I left fertilization to the bees, har- 
vested the seeds of the four whites separately 
and had from them the following year more than 
a thousand flowering plants. All of them were 
of the purest white, with only one exception, 
which was a plant with the bluish rays of the 
species, wholly reverting to its general type. As 
the variety does not give such reversions when 
cultivated in isolation, this sport was obviously 
due to some cross in the former year. In the 
same way I tried the white Jacob’s ladder, 
Polemonium coeruleum album in the neighbor- 
hood of the blue-flowered species, the distance 



False Atavism 


201 


in this case being only 40 meters. Of two hun- 
dred seeds one became a blue atavist, or rather 
vicinist, while all others remained true to the 
white type. The same was observed in the 
white creeping thyme, or Thymus Serpyllum 
album, and the white self-heal, Brunella vul- 
garis alba, gave even so much as 28^ seed- 
lings with purple corollas out of some 400 
specimens, after being cultivated in close prox- 
imity to its parent-species. I have tried many 
other species, but always with the same result. 
Such atavists only arise by cultivation in the 
proximity of allied varieties, never in isolation. 
They are not real atavists, but only vicinists. 

In order to show this yet more clearly, I 
made another experiment with the white self- 
heal. I had a lot of the pinnate-leaved variety 
with purple flowers and somewhat stouter 
stems, and cultivated single plants of the white- 
flowering sort at distances that varied from 
2-16 meters. The seeds of each plant were 
collected and sown separately, those of the 
nearest gave up to 5 or 6 hybrids from the seeds 
of one parent, while those of the farthest gave 
only one purple-flowered plant for each parent. 
Evidently the chance of the pollen being carried 
by bees is much greater on short than on longer 
distances. 

True hybrids between species may arise in 



202 


Retrograde Varieties 


quite the same way, and since it is obviously 
impossible to attribute them to an innate ten- 
dency to reversion, they afford an absolutely 
irrefutable proof of the assertion that pollen 
is often brought by insects from one lot of 
plants to another. In this way I obtained a 
hybrid between the common Jacob’s ladder and 
the allied species Polemonium dissectum. With 
a distance of 100 meters between them I had 
two hybrid seeds among a hundred of pure 
ones. At a similar distance pollen was carried 
over from the wild radish, Raphanus Raphanis- 
trum, to the allied Raphanus caudatus, and I 
observed the following year some very nice hy- 
brids among my seedlings. A hybrid-bean be- 
tween Phaseolus nanus and P. muUiflorus, and 
some hybrids between the yellow daisy, 
Chrysanthemum segetum and the allied Chrys- 
anthemum coronarium or ox-eye daisy which 
also arose spontaneously in my garden between 
parents cultivated at recorded distances, might 
further be noted. Further details of these ex- 
periments need not be given. Suffice to say, 
that occasional crosses between species do 
occur, and not even rarely, that they are easily 
recognized as such and cannot be confused with 
cases of atavism, and that therefore they give 
proof to the assumption that in the same way 
crosses ordinarily occur also between varieties 



False Atavism 


203 


of the same species, if cultivated at small dis- 
tances apart, say 40 - 50 meters or even more. 

Vicinism therefore, may play a part in all 
such cultures, enough to account for all the 
impurities observed in the nurseries or in com- 
mercial seed-samples. 

Of course this whole discussion is limited to 
such species as are not only as a rule visited by 
insects, but are dependent on these visits for 
their fertilization. Most of our garden-flowers 
are included in this category. If not then we 
may expect to find the cultures and seeds pure, 
irrespective of the distances between allied va- 
rieties, as for instance with peas, which are 
known to be self-fertilizing. Another instance 
is given by the barley. One of the most curious 
anomalous varieties of this cereal, is the 
“ Nepaul-barley,” with its small adventitious 
flowers on the palets or inner scales. It is a 
very old, widely cultivated sort, which always 
comes true from seed, and which has been 
tested in repeated experiments in my garden. 
The spikelets of this curious plant are one- 
flowered and provided with two linear glumes 
or outer scales. Of the inner scales or palets, 
the outer one is three-lobed at the summit, hence 
the varietal name of Hordeum vulgare trifur- 
catum. The central lobe is oblong and hollow, 
covering a small supernumerary floret inserted 



204 


Retrograde Varieties 


at its base. The two lateral lobes are narrower, 
sometimes linear, and are often prolonged into 
an awn, which is generally turned away from 
the center of the spike. The central lobe some- 
times bears two florets at its base, although but 
one is usually present and it may be incomplete. 

I might give one more instance from my own 
experience. A variety of the evening -primrose 
with small linear petals was once found by one 
of my sons growing wild near Amsterdam. It 
was represented by only one individual, flower- 
ing among a great many of the ordinary type 
with broad petals. But the evening-primroses 
open their anthers in the morning, fertilize 
themselves during the day, and only display 
their beautiful flowers in the evening, after the 
pollination has been accomplished. They then 
allure evening moths, such as Agrotis and 
Phisia, by their bright color, their sweet honey- 
smell and their nectar. Since the fertiliza- 
tion is accomplished many hours before opening, 
crosses are effected only in rare instances, and 
the seeds commonly remain true to the parent- 
type. The seeds of this one plant, when sown 
separately in my garden, produced exclusively 
flowers with the small linear petals of their 
parent. Although I had a hundred individuals 
bearing many thousands of flowers, there was 
not an instance of reversion. And such would 



False Atavism 


205 


immediately have been observed, had it oc- 
curred, because the hybrids between the cruci- 
ate and the normal flowers are not intermediate, 
but bear the broad petals of the 0. biennis. 

We may now take up another phase of the 
question, that of the running out of new varie- 
ties, shortly after their introduction into a new 
country, or later. 

The most widely known instance of this is 
that of the American corn in Baden, recorded 
by Metzger and quoted by Darwin as a remark- 
able instance of the direct and prompt action 
of climate on a plant. It has since been, con- 
sidered as a reversion to the old type. Such 
reversions invariably occur, according to Wal- 
lace, in cases of new varieties, which have 
been produced quickly. But as we now know, 
such reversions are due to spontaneous crosses 
with the old form, and to the rule, that the 
hybrids of such origin are not intermediate, 
but assume the features of the older of the 
two parents. In the light of this experience, 
Metzger’s observation becomes a typical in- 
stance of vicinism. It relates to the ** Tusca- 
rora ” com of St. Louis, a variety with broad 
and flat white seeds. 

About the year 1840, this corn was introduced 
into Baden in Germany, and cultivated by Metz- 
ger. In the first year it came true to type, and 



206 


Retrograde Varieties 


attained a height of 12 feet, but the season did 
not allow its seeds to ripen normally. Only 
a few kernels were developed before the winter. 
From this seed plants of a wholly different 
type came the next year, of smaller stature, and 
with more brownish and rounded kernels. They 
also flowered earlier and ripened a large num- 
ber of seeds. The depression on the outer side 
of the seed had almost disappeared, and the 
original white had become darker. Some of the 
seeds had even become yellow and in their 
rounded form they approached the common 
European maize. Obviously they were hybrids, 
assuming the character of their pollen-parent, 
which evidently was the ordinary com, culti- 
vated all around. The observation of the next 
year showed this clearly, for in the third gener- 
ation nearly all resemblance to the original and 
very distinct American species was lost. If 
we assume that only those seeds ripened which 
reverted to the early-ripening European type, 
and that those that remained true to the very 
late American variety could not reach maturity, 
the case seems to be wholly comprehensible, 
without supposing any other factors to have 
been at work than those of vicinism, which 
though unknown at the period of Metzger’s and 
Darwin’s writings, seems now to be fully un- 
derstood. No innate tendency to ran out and 



False Atavism 


207 


no changing influence of the climate are re- 
quired for an adequate explanation of the 
facts. 

In the observation quoted, what astonishes us 
most, is the great rapidity of the change, and the 
short time necessary for the offspring of the 
accidental crosses to completely supplant the in- 
troduced type. In the lecture on the selection 
of elementary species, closely analogous cases 
were described. One of them was the wild oat 
or Avena fatua which rapidly supplants the 
cultivated oats in bad years in parts of the 
fields. Other instances were the experiments of 
Risler with the “ Galland ” wheat and the ob- 
servation of Rimpau on “ Rivett’s bearded ” 
wheat. 

Before leaving the question of vicinism and 
its bearing on the general belief of the insta- 
bility of varieties, which when tested with due 
care, prove to be quite stable, it may be 
as well to consider the phenomena from 
another point of view. Our present knowledge 
of the effects of crosses between varieties ena- 
bles us to formulate some general rules, which 
may be used to calculate, and in some way to 
predict, the nature of the impurities which nec- 
essarily attend the cultivation of allied species 
in close vicinity. And this mode of cultivation 
being in almost universal use in the larger nur- 



208 


Retrograde Varieties 


series, we may, by this discussion, arrive at a 
more scientific estimation of the phenomena of 
vicinism, hitherto described. 

The simplest case that may be given, is when 
an ordinary retrograde variety is cultivated 
with the species to which it belongs. For in- 
stance, if dwarfs are cultivated next to the taller 
type, or a white variety next to the red or 
blue-flowering species, or thornless forms in 
neighboring beds with the armed species. 
Bees and humble-bees, butterflies and moths are 
seen flying from flower to flower, collecting the 
honey and carrying pollen. I frequently saw 
them cross the limits of the neighboring beds. 
Loaded with the pollen of the variety they visit 
the flowers of the different species and impreg- 
nate the stigma with it. And returning to the 
variety they bring about similar crosses in the 
flowers of the latter. Hybrid seeds will devel- 
op in both cases and become mixed with the 
crop. We now have to ask the question, what 
sort of plants will arise from these hybrid 
seeds. As a general rule we may state, first, 
that the hybrids of either form of cross are 
practically the same, secondly that they are not 
intermediate, but that the character of one par- 
ent prevails to the almost absolute exclusion 
of the other and in the third place that the older 
character dominates the younger. 



False Atavism 


209 


The hybrid offspring will therefore, in the 
main, have the character of the species and be 
indistinguishable from it, or show only such 
differences as escape ordinary observation. 
When occurring in the seeds of the variety 
they betray themselves as soon as the dif- 
ferential characters are displayed. Between 
the thousands of flowering plants of a white 
variety the hybrids will instantly catch the eye 
by their red or blue corollas. Quite the con- 
trary effect results from the admixture of hy- 
brids with the seeds of the species itself. Here 
no difference will show itself, even in the full- 
est bloom. The effect of the spontaneous 
crosses will pass unobserved. The strain, if 
pure in the first year, will seem to be still in the 
same condition. Or in other terms, the una- 
voidable spontaneous crosses will disturb the 
purity of the variety in the second year, while 
they do not seem to interfere at all with the uni- 
formity of the species. The direct effect of the 
visits of the insects is evident in the first case, 
but passes imobserved in the latter. 

From this it would seem, that spontaneous 
crosses are hurtful to varieties, but are in- 
nocuous to true species. Certainly this would 
be so, were there no selection. But it is easily 
seen, that through this operation the effect be- 
comes quite the opposite. For when the fields 



210 Retrograde Varieties 

are inspected at the time of the fullest display 
of the varietal characters, the obvious hybrids 
will be eliminated, but the hidden ones will of ne- 
cessity be spared, as they are concealed among 
the species by the similarity of their type. 
Hence, the harvest of the variety may be ren- 
dered pure or nearly so, while the harvest of 
the species will retain the seeds of the hybrids. 
Moreover it will contain seeds originated by the 
spontaneous but numerous crosses of the true 
plants with the sparsely intermingled hybrids. 

This brings us to the question, as to what will 
be the visible consequences of the occurrence of 
such invisible hybrids in the following gener- 
ation. In opposition to the direct effects just 
described, we may call them indirect. To judge 
of their influence, we must know how hybrid 
seeds of the first generation behave. 

In one of our lectures we will deal with the 
laws that show the numerical relations known 
as the laws of Mendel. But for our present 
purpose, these numerical relations are only of 
subordinate importance. What interests us here 
is the fact that hybrids of varieties do not re- 
main constant in the second generation but usu- 
ally split as it is said, remaining hybrid 
only in part of their oflFspring, the other por- 
tion returning to the parental types. This how- 
ever, will show itself only in those individuals 



False Atavism 


211 


which reassume the character of the varietal 
parent, all the others apparently remaining true 
to the type of the species. Now it is easy to 
foresee what must happen in the second gen- 
eration if the first generation after the cross 
is supposed to he kept free from new vicinistic 
infiuences, or from crosses with neighboring 
varieties. 

We may limit ourselves in the first place to 
the seeds of the unobserved hybrids. For the 
greater part they will repeat the character of 
their parents and still remain concealed. But a 
small number will display the varietal marks, 
as for example showing white flowers in a 
field of blue ones. Hence, the indirect conse- 
quence of the spontaneous crosses will be the 
same in the species, as was the direct effect 
in the variety, only, that it appears a year later. 
It will then be eliminated in the process of 
selection. 

Obviously, this elimination conduces only to 
a partial purification. The conspicuous plants 
will be destroyed, but a greater nmnber of hy- 
brids will remain, still concealed by their re- 
semblance to the general type and will be 
spared to repeat the same process next year. 
So while the variety may be freed every year 
from the impurities brought into it in the pro- 
ceeding summer, the admixtures of the spe- 



212 


Retrograde Varieties 


cies will contiime during a number of years, 
and it may not be possible to get rid of them 
at all. 

It is an often recurring assertion that white 
varieties of colored species are the most stable 
of all horticultural races. They are often said 
to be at least as constant as the species itself, 
and even to surpass it in this quality. With our 
present state of knowledge, the explanation of 
this general experience is easily given. For se- 
lection removes the effect of spontaneous cross- 
es from the variety in each year, and renders it 
practically pure, while it is wholly inadequate 
to produce the same effects on the species, be- 
cause of the concealed hybrids. 

The explanation given in this simple instance 
may be applied to the case of different varieties 
of the same species, when growing together 
and crossed naturally by insects. 

It would take too long to go into all the de- 
tails that present themselves here to the stu- 
dent of nature and of gardens. I will 
only state, that since varieties differ princi- 
pally from their species by the lack of some 
sharp character, one variety may be character- 
ized by the lack of color of the flowers, another 
by the lack of pubescence, a third by being 
dwarfed, and so on. Every character must be 
studied separately in its effects on the offspring 



False Atavism 


213 


of the crosses. And it is therefore easily seen, 
that the hybrids of two varieties may resemble 
neither of them, but revert to the species itself. 
This is necessarily and commonly the case, 
since it is always the older or positive charac- 
ters that prevail in the hybrids and the 
younger or negative that lie hidden. So for in- 
stance, a blue dwarf larkspur, crossed with a 
tall white variety, must ^ve a tall blue hybrid, 
reassuming in both characters the essentials 
of the species. 

Keeping this rule in view, it will be easy to 
calculate what may be expected from sponta- 
neous crosses for a wide range of occurrences, 
and thus to find an explanation of innumerable 
cases of apparent variability and reversion in 
the principle of vicinism. Students have only 
to recollect that specific characters prevail over 
varietal ones, and that every character com- 
petes only with its own antagonist. Or to give 
a sharper distinction : whiteness of fiowers can- 
not be expected to be interchanged with 
pubescence of leaves. 

In concluding I will point out another danger 
which in the principle of vicinism may be 
avoided. If you see a plant in a garden with all 
the characteristics of its species, how can you 
be sure that it is truly a representative of the 
species, and not a hybrid? The prevailing 



214 Retrograde Varieties 

characters are in either case the same. Perhaps 
on close inspection you may find in some oases 
a slight difference, some character being not 
as fully developed in the hybrid as in the spe- 
cies. But when such is not the case, or where 
the opportunity for such a closer examination 
is wanting, a hybrid may easily be taken for a 
specimen of the pure race. Now take the seeds 
of your plant and sow them. If you had not 
supposed it to be hybrid you will be astonished 
at finding among its progeny some of a wholly 
different type. You will be led to conclude 
that you are observing a sudden change in 
structure such as is usually called a sport. 

Or in other words you may think that you are 
assisting at the origination of a new variety. 
If you are familiar with the principle of vicin- 
ism, you will refrain from such an inference and 
consider the supposition of a hybrid origin. 
But in former times, when this principle 
was still unknown and not even guessed 
at, it is evident that many mistakes must have 
been made, and that many an instance, which 
until now has been considered reliable proof 
of a so-called single variation, is in fact only a 
case of vicinism. In reading the sparse litera- 
ture on sports, numerous cases will be found, 
which cannot stand this test. In many instances 
crossing must be looked to as an explanation, 



False Atavism 


215 


and in other cases the evidence relied upon does 
not suffice to exclude this assumption. Many 
an old argument has of late lost its force by 
this test. 

Eeturning to our starting point we may now 
state that regular reversions to a specific type 
characterize a form as a variety of that species. 
These reversions, however, are not due to an 
innate tendency, but to unobserved spontaneous 
crosses. 



Lecture VTII 


liATENT CHARACTERS 

No organism exhibits all of its qualities at 
any one time. Many of them are generally 
dormant and await a period of activity. For 
some of them this period comes regularly, while 
in others the awakening depends upon external 
influences, and consequently occurs very irreg- 
ularly. Those of the first group correspond to 
the differences in age ; the second constitute the 
responses of the plant to stimuli including 
wound-injuries. 

Some illustrative examples may be quoted in 
order to give a precise idea of this general con- 
ception of dormant or latent characters. Seed- 
leaves are only developed in the seed and the 
seedling; afterwards, during the entire life- 
time of the plant, the faculty of producing them 
is not made use of. Every new generation of 
seeds however, bears the same kind of seed- 
leaves, and hence it is manifest that it is 
the same quality, which shows itself from time 
to time. 


216 



Latent Characters 


217 


The primary leaves, following the seed-leaves, 
are different in many species from the later 
ones, and the difference is extremely pro- 
nounced in some cases of reduction. Often, 
when leaves are lacking in the adult plant, be- 
ing replaced by flattened stalks as in the case 
of the acacias, or by thorns, or green stems and 
twigs as in the prickly broom or Ulex europaeus, 
the first leaves of the young plant may be more 
highly differentiated, being pinnate in the first 
case and bearing three leaflets in the second in- 
stance. This curious behavior which is very 
common, brings the plants, when young, nearer 
to their allies than in the adult state, and mani- 
festly implies that the more perfect state of 
the leaves is latent throughout the life of the 
plant, with the exception of the early juvenile 
period. 

Eucalyptus Globulus, the Australian gum- 
tree, has opposite and broadly sessile leaves 
during the first years of its life. Later these 
disappear and are replaced by long sickle- 
shaped foliage organs, which seem to be scat- 
tered irregularly along the branches. The juve- 
nile characters manifestly lie dormant during 
the adult period, and that this is so, may be 
shown artificially by cutting off the whole crown 
of the tree, when the stem responds by produc- 
ing numerous new branches, which assume the 



218 


Retrograde Varieties 


shape proper to the young trees, bearing sessile 
and opposite leaves. 

It seems quite unnecessary to give further 
instances. They are familiar to every student. 
It is almost safe to say that every character has 
its periods of activity and of inactivity, and 
numbers of flowers and fruits can be mentioned 
as illustrations. One fact may be added to 
show that nearly every part of the plant must 
have the power of producing all or nearly all 
the characters of the individual to which it 
belongs. This proof is given by the formation 
of adventitious buds. These, when once 
formed, may grow out into twigs, with leaves 
and flowers and roots. They may even be sep- 
arated from the plants and used as cuttings 
to reproduce the whole. Hence we may 
conclude that all tissues, which possess the 
power of producing adventitious buds, must 
conceal in a latent state, all the numerous char- 
acters required for the full development of the 
whole individual. 

Adventitious buds may proceed from spe- 
cialized cells, as on the margin of the leaves of 
Bryophyllum calycinum; or from the cells of 
special tissues, as in the epidermis of the be- 
gonias; or they may be provoked by wounds 
in nearly every part of the plant, provided it 
be able to heal the wound by swelling tissues or 



Latent Characters 


219 


callus. The best instance is afforded by elms 
and by the horse-chestnut. If the whole tree is 
hewn down the trunk tries to repair the injury 
by producing small granulations of tissue be- 
tween the wood and the bark, which gradually 
coalesce while becoming larger. From this new 
ring of living matter innumerable buds arise, 
that expand into leafy branches, showing 
clearly that the old trunk possesses, in a latent 
state, all the qualities of the whole crown. In- 
deed, such injured stumps may be used for the 
production of copses and hedges. 

All the hitherto recorded cases of latency 
have this in common, that they may become ac- 
tive during the life-time of any given individual 
once, or oftener. This may be called the ordi- 
nary type of latency. 

Besides this there is another form of latent 
characters, in which this awakening power is 
extremely limited, or wholly absent. It is the 
systematic latency, which may be said to be- 
long to species and varieties in the same way as 
the ordinary latency belongs to individuals. 
As this individual latency may show itself from 
time to time during the life of a given plant, the 
first may only become active from time to time 
during the whole existence of the variety or the 
species. It has no regular period of activity, 
nor may it be incited by artificial stimulation. 



220 


Retrograde Varieties 


It emerges from concealment only very rarely 
and only on its own initiative. Such instances 
of atavism have been described in previous lec- 
tures, and their existence has been proved be- 
yond doubt. 

Systematic latency explains the innumerable 
instances in which species are seen to lack def- 
inite characteristics which ordinarily do not 
fail, either in plants at large, or in the group 
or family to which the plant belongs. If we 
take for instance the broom-rape or Orohanche, 
or some other pale parasite, we explain their 
occurrence in families of plants with green 
leaves, by the loss of the leaves and of the green 
color. But evidently this loss is not a true one, 
but only the latency of those characters. 
And even this latency is not a complete one, as 
little scales remind us of the leaves, and traces 
of chlorophyll still exist in the tissues. Nu- 
merous other cases will present themselves to 
every practical botanist. 

Taking for granted that characters, having 
once been acquired, may become latent, and that 
this process is of universal occurrence through- 
out the whole vegetable and animal kingdom, we 
may now come to a more precise and clear con- 
ception of the existing differences between spe- 
cies and varieties. 

For this purpose we must take a somewhat 



Latent Characters 


221 


broader view of the whole evolution of the 
vegetable kingdom. It is manifest that highly 
developed plants have a larger number of 
characters than the lower groups. These 
must have been acquired in some way, during 
preceding times. Such evolution must evident- 
ly be called a process of improvement, or a 
progressive evolution. Contrasted to this is the 
loss, or the latency of characters, and this may 
be designated retrogressive or retrograde evo- 
lution. But there is still a third possibility. 
For a latent character may reassume its ac- 
tivity, return to the active state, and become 
once more an important part of the whole or- 
ganization. This process may be designated 
as degressive evolution; it obviously completes 
the series of the general types of evolution. 

Advancement in general in living nature de- 
pends on progressive evolution. In different 
parts of the vegetable kingdom, and even in 
different families this progression takes place 
on different lines. By this means it results in 
an ever increasing divergency between the sev- 
eral groups. Every step is an advance, and 
many a step must have been taken to produce 
flowering plants from the simplest unicellular 
algae. 

But related to, and very intimately con- 
nected with this advancement is the retrogres- 



222 Retrograde Varieties 

sive evolution. It is equally universal, per- 
haps never failing. No great changes have 
been attained, without acquiring new qualities 
on one side, and reducing others to latency. 
Everywhere such retrogressions may be seen. 
The polypetalous genera Pyrola, Ledum, and 
Monotropa among the sympetalous heaths, are 
a remarkable instance of this. The whole evo- 
lution of the monocotyledons from the lowest 
orders of dicotyledons implies the seeming 
loss of cambial growth and many other quali- 
ties. In the order of aroids, from the cala- 
mus-root or sweet flag, with its small but com- 
plete flowers, up to the reduced duckweeds 
(Lemna), almost an unbroken line of interme- 
diate steps may be traced showing everywhere 
the concurrence of progressive and retrogres- 
sive evolution. 

Degressive evolution is not so common by far, 
and is not so easy to recognize, but no doubt it 
occurs very frequently. It is generally called 
atavism, or better, systematic atavism, and the 
clearest cases are those in which a quality which 
is latent in the greater part of a family or 
group, becomes manifest in one of its members. 
Bracts in the inflorescence of crucifers are or- 
dinarily wanting, but may be seen in some 
genera, Erucastrum polUchii being perhaps the 



Latent Chara>cter$ 223 

most widely known instance, although other 
cases might easily be cited. 

For our special purpose we may take up 
only the more simple cases that may be avail- 
able for experimental work. The great lines of 
evolution of whole families and even of genera 
and of many larger species obviously lie outside 
the limits of experimental observation. They 
are the outcome of the history of the ancestors 
of the present types, and a repetition of their 
history is far beyond human powers. We must 
limit ourselves to the most recent steps, to the 
consideration of the smallest ditferences. But 
it is obvious that these may be included under 
the same heads as the larger and older ones. 
For the larger movements are manifestly to be 
considered only as groups of smaller steps, 
going in the same direction. 

Hence we conclude, that even the smallest 
steps in the evolution of plants which we are 
able to observe, may be divided into progres- 
sive, retrogressive and degressive ones. The 
acquisition of a single new quality is the most 
simple step in the progressive line, the becom- 
ing latent and the reactivating of this same 
quality are the prototypes of the two other 
classes. 

Having taken this theoretical point of view, 
it remains to inquire, how it concurs with the 



224 


Retrograde Varieties 


various facts, given in former lectures and how 
it may be of use in our further discussions. 

It is obvious that the differences between ele- 
mentary species and varieties on the one hand, 
and between the positive and negative varieties 
as distinguished above, are quite comparable 
with our theoretical views. For we have seen 
that varieties can always be considered as hav- 
ing originated by an apparent loss of some 
quality of the species, or by the resumption of 
a quality which in allied species is present and 
visible. In our exposition of the facts we have 
of course limited ourselves to the observable 
features of the phenomena without searching 
for a further explanation. For a more com- 
petent inquiry however, and for an understand- 
ing of wider ranges of facts, it is necessary to 
penetrate deeper into the true nature of the im- 
plied causes. 

Therefore we must try to show that elemen- 
tary species are distinguished from each other 
by the acquisition of new qualities, and that 
varieties are derived from their species either 
by the reduction of one or more characteristics 

I 

to the laten^ state, or by the energizing of dor- 
mant characters. 

Here we meet with a great difficulty. Hither- 
to varieties and subspecies have never been 
clearly defined, or when they have been, it was 



Latent Characters 


225 


not by physiological, but only by morphological 
research. And the claims of these two great 
lines of inquiry are obviously very diverging. 
Morphological or comparative studies need 
a material standard, by which it may be readily 
decided whether certain groups of ani- 
mals and plants are to be described or de- 
nominated as species, as subspecies or as varie- 
ties. To get at the inner nature of the dif- 
ferences is in most cases impossible, but a de- 
cision must be made. The physiological line 
of inquiry has more time at its disposal ; it calls 
for no haste. Its experiments ordinarily cover 
years, and a conclusion is only to be reached 
after long and often weary trials. There is no 
making a decision on any matter imtil all 
doubtful points have been cleared up. Of 
course, large groups of facts remain uncertain, 
awaiting a closer inquiry, and the teacher is 
constrained to rely on the few known instances 
of thoroughly investigated cases. These alone 
are safe guides, and it seems far better to trust 
to them and to make use of them for the con- 
struction of sharp conceptions, which may help 
us to point out the lines of inquiry which are 
still open. 

Leaving aside aU such divisions and defini- 
tions, as were stamped with the name of pro- 
visional species and varieties by the great sys- 



226 


Retrograde Varieties 


tematist, Alphonse De Candolle, we may now 
try to give the proofs of our assertion, by using 
only those instances that have been thoroughly 
tested in every way. 

We may at once proceed to the retrogressive 
or negative varieties. The arguments for the 
assumption that elementary species owe their 
origin to the acquisition of new qualities may 
well be left for later lectures when we shall 
deal with the experimental proofs in this mat- 
ter. 

There are three larger groups of facts, on 
which the assumption of latent characters in 
ordinary varieties rests. These are true ata- 
vism, incomplete loss of characters, and system- 
atic affinity. Before dealing with each of these 
separately, it may be as well to recall once more 
that in former lectures we have treated the 
apparent losses only as modifications in a 
negative way, without contemplating the under- 
lying causes. 

Let us recall the cases of bud-atavism given 
by the whitish variety of the scarlet Ribes-, by 
peaches and nectarines, and by conifers, includ- 
ing Cephalotaams and Cryptomeria. These and 
many other analogous facts go to prove the re- 
lation of the variety to the species. Two as- 
sumptions are allowable. In one the variety 
differs from the species by the total loss of the 



Latent Characters 


227 


distinctive character. In the other this charac- 
ter is simply reduced to an inactive or dormant 
state. The fact of its recurrence from time to 
time, accompanied by secondary characters 
previously exhibited, is a manifest proof of the 
existence of some relation between the lost and 
the resumed peculiarity. Evidently this rela- 
tion cannot be accounted for on the assump- 
tion of an absolute disappearance; something 
must remain from which the old features may 
be restored. 

This lengthy discussion may be closed by the 
citation of the cases, in which plants not only 
show developmental features of a former state, 
but also reproduce the special features they 
formerly had, but seemingly have lost. Two 
good illustrative examples may be given. One 
is afforded by the wheat-ear carnation, the 
other by the green dahlias, and both have oc- 
curred of late in my own cultures. 

A very curious anomaly may from time to 
time be observed in large beds of carnations. 
It bears no flowers, but instead of them small 
green ears, which recall the ears of wheat. 
Thence the name of Wheat-ear ” carnation. 
On closer inspection it is easily seen how they 
originate. The normal flowers of the carna- 
tions are preceded by a small group of bracts. 



228 


Retrograde Varieties 


which are arranged in opposite pairs and there> 
fore constitute four rows. 

In this variety the flower is suppressed and 
this loss is attended by a corresponding in- 
crease of the number of the pairs of bracts. 
This malformation results in square spikes or 
somewhat elongated heads consisting only of 
the greenish bracts. As there are no flowers, 
the variety is quite sterile, and as it is not re- 
garded by horticulturists as an improvement on 
the ordinary bright carnations, it is seldom mul- 
tiplied by layering. Notwithstanding this, it 
appears from time to time and has been seen in 
different countries and at different periods, 
and, what is of great importance for us, in dif- 
ferent strains of carnations. Though sterile, 
and obviously dying out as often as it springs 
into existence, it is nearly two centuries old. 
It was described in the begining of the 18th cen- 
tury by Volckamer, and afterwards by Jaeger, 
De Candolle, Weber, Masters, Magnus and 
many other botanists. I have had it twice, at 
different times and from different growers. 

So far as I have been able to ascertain re- 
versions of this curious carnation to normal 
flowers have not yet been recorded. Such a 
modification occurred last summer in my gar- 
den on a plant which had not been divided or 
layered, but on which the slender branches had 



Latent Characters 


229 


been left on the stem. Some of them remained 
true to the varietal t3rpe and bore only green 
spikes. Others reverted wholly or partially to 
the production of normal flowers. Some 
branches bore these only, others had spikes and 
flowers on neighboring twigs, and in still other 
instances little spikes had been modified in such 
manner that a more or less well developed flow- 
er was preceded by some part of an ear. 

The proof that this retrograde modification 
was due to the existence of a character in the 
latent state was given by the color of the flow- 
ers. If the reverted bud had only lost the 
power of producing spikes, they would evident- 
ly simply have returned to the characteristics 
of the ordinary species, and their color would 
have been a pale pink. Instead of this, all 
flowers displayed corollas of a deep brown. 
They obviously reverted to their special prog- 
enitor, the chance variety from which they had 
sprung, and not to the common prototype of the 
species. Of course it was not possible to as- 
certain from which variety the plant had really 
originated, but the reproduction of any one 
clearly defined varietal mark is in itself proof 
enough of their origin, and of the latency of the 
dark brown flower-color in this special case. 

A still better proof is afforded by a new type 
of green dahlia. The ordinary green dahlia 



230 


Retrograde Varieties 


has large tufts of green bracts instead of flow- 
ering heads, the scales of the receptacle having 
assumed the texture and venation of leaves, and 
being in some measure as fleshy. But the 
green heads retain the form of the ordinary 
flower-heads, and as they have no real florets 
that may fade away, they remain unchanged on 
the plants, and increase in number through the 
whole summer. The new types of green dahlia 
however, with which I have now to deal, are 
distinguished by the elongation of the axis of the 
head, which is thereby changed into a long leafy 
stalk, attaining a length of several inches. 
These stalks continue growing for a very long 
time, and for the most part die without produc- 
ing anything else than green fleshy scales. 

This long-headed green dahlia originated at 
Haarlem some years ago, in the nursery of 
Messrs. Zocher & Co. It was seen to arise 
twice, from dilferent varieties. Both of these 
were double-flowered, one a deep carmine with 
white tips on the rays, the other of a pale orange 
tint, known by the name of “ Surprise.” As 
they did not bear any florets or seeds, they were 
qnite sterile. The strain arising from the car- 
mine variety was kindly given to me by Messrs. 
Zocher & Co., and was propagated in my gar- 
den, while the other was kept in the nursery. 
In the earlier cultures both remained true to 



Latent Characters 


231 


their types, never producing true florets. No 
mark of the original difference was to be seen 
between them. But last summer (1903) both 
reverted to their prototypes, bearing rela- 
tively large numbers of ordinary double flower- 
heads among the great mass of green stalks. 
Some intermediate forms also occurred consist- 
ing of green-scaled stalks ending in small heads 
with colored florets. 

Thus far we have an ordinary case of rever- 
sion. But the important side of the phenome- 
non was, that each plant exactly “ recollected ” 
from which parent it had sprung. All of those 
in my garden reverted to the carmine florets 
with white tips, and all of those in the nursery 
to the pale orange color and the other character- 
istics of the “ Surprise ” variety. 

It seems absolutely evident, that no simple 
loss can account for this difference. Something 
of the character of the parent-varieties must 
have remained in the plant. And whatever 
conception we may formulate of these vestigial 
characters it is clear that the simplest and most 
obvious idea is their preservation in a dormant 
or latent state. Assuming that the distinguish- 
ing marks have only become inactive by vires- 
cence, it is manifest that on returning each will 
show its own peculiarities, as recorded above. 

Our second point was the incomplete loss of 



232 Retrograde Varieties 

the distingnishing quality in some varieties. It 
is of general occurrence, though often over- 
looked. Many white varieties of colored flow- 
ers give striking instances, among them many 
of the most stable and most prized garden-flow- 
ers. If you look at them separately or in lit- 
tle bouquets they seem to be of irreproachable 
purity. But if you examine large beds a pale 
hue will become visible. In many cases this 
tinge is so slight as to be only noticeable in a 
certain illumination, or by looking in an oblique 
direction across the bed; in others it is at once 
evident as soon as it has been pointed out. It 
always reminds the observer of the color of 
the species to which the variety belongs, being 
bluish in violets and harebells, reddish in 
godetias and phloxes, in Silene Armeria and 
many others. It proves that the original color- 
quality of the species has not wholly, but only 
partly disappeared. It is dormant, but not en- 
tirely obliterated; latent, but not totally con- 
cealed; inactive, but only partially so. Our 
terminology is an awkward one; it practically 
assumes, as it so often does in other cases, a 
conventional understanding, not exactly cor- 
responding to the simple meaning of the words. 
But it would be cumbrous to speak always of 
partial inactivity, incomplete latency or half 
awakening qualities. Even such words as sub- 



Latent Characters 


233 


latent, which would about express the real state 
of things, would have little chance of coming 
into general use. 

Such sub-latent colors are often seen on spe- 
cial parts in white varieties of flowers. In 
many cases it is the outer side of the petals 
which recalls the specific color, as in some white 
roses. In violets it is often on the spur that 
the remains of the original pigment are to he 
seen. In many instances it is on the tips of 
the petals or of the segments of the corolla, and 
a large number of white or yellow flowers be- 
tray their affinity to colored species by becom- 
ing red or bluish at the edges or on the outer 
side. 

The reality of such very slight hues, and their 
relation to the original pigment of the species 
may in some cases be proved by direct experi- 
ment If it is granted that latency is not an ab- 
solute quality, then it will be readily accepted, 
that even latency must be subjected to the laws 
of gradual variation or fluctuating variability. 
We will deal with these laws in a later 
lecture but every one knows that greater de- 
viations than the ordinary may be attained by 
sowing very large numbers and by selecting 
from among them the extreme individuals and 
sowing anew from their seed. In this way the 
slightest tinge of any latent color may be 



234 Retrograde Varieties 

strengthened, not indeed to the restoration of 
the tinge of the species, but at least so far as 
to leave no doubt as to the identity of the visi- 
ble color of the species and the latent or sub- 
latent one of the variety. 

I made such an experiment with the peach- 
leaved harebell or Campanula persicifolia. The 
white variety of this species, which is often met 
with in our gardens, shows a very pale bluish 
hue when cultivated in large quantities, which 
however is subject to individual variations. I 
selected some plants with a decided tinge, 
flowered them separately, sowed their seeds, 
and repeated this during two generations. The 
result was an increase of the color on the tips 
of the segments of the corolla in a few in- 
dividuals, most of them remaining as purely 
white as the original strain. But in those few 
plants the color was very manifest, individually 
variable in degree, but always of the same blue 
as in the species itself. 

Many other instances could be given. 
Smooth varieties are seldom absolutely so, and 
if scattering hairs are found on the leaves or 
only on some more or less concealed parts, they 
correspond in their character to those of the 
species. So it is with prickles, and even the 
thornless thorn-apple has fruits with surfaces 
far from smooth. The thornless horse-chest- 



Latent Characters 


235 


nut has in some instances such evident protu- 
berances on the valves of its fruits, that it may 
seem doubtful whether it is a pure and stable 
variety. 

Systematic latency may betray itself in dif- 
ferent ways, either by normal systematic 
marks, or by atavism. With the latter I shall 
deal at length on another occasion, and there- 
fore I will give here only one very clear and 
beautiful example. It is afforded by the com- 
mon red clover. Obviously the clovers, with 
their three leaflets in each leaf, stand in the 
midst of the great family of papilionaceous 
plants, the leaves of which are generally pinnate. 
Systematic affinity suggests that the “ three- 
leaved ” forms must have been derived from 
pinnate ancestors, evidently by the reduction of 
the number of the leaflets. In some species of 
clover the middle of the three is more or less 
stalked, as is ordinarily the case in pinnate 
leaves ; in others it is as sessile as are its neigh- 
bors. In a subsequent chapter I will describe a 
very fine variety, which sometimes occurs in the 
wild state and may easily be isolated and culti- 
vated. It is an ordinary red clover with five 
leaflets instead of three, and with this number 
varying between three and seven, instead of be- 
ing nearly wholly stable as in the common form. 
It produces from time to time pinnate leaves. 



236 


Retrograde Varieties 


very few indeed, and only rarely, but then often 
two or three or even more on the same in- 
dividnaL Intermediate stages are not want- 
ing, but are of no consequence here. The pin- 
nate leaves obviously constitute a reversion to 
some prototype, to some ancestor with ordinary 
papilionaceous leaves. They give proof of the 
presence of the common character of the fam- 
ily, concealed here in a latent state. Any 
other explanation of this curious anomaly 
would evidently be artificial. On the other 
hand nothing is really known about the ances- 
tors of clover, and the whole conception rests 
only on the prevailing views of the systematic 
relationships in this family. But, as I have al- 
ready said, further proof must be left for a sub- 
sequent occasion. 

Many instances, noted in our former lectures, 
could be quoted here. The systematic distri- 
bution of rayed and rayless species and varie- 
ties among the daisy-group of the composites 
affords a long series of examples. Accidental 
variations in both directions occur. The Can- 
ada fleabane or Erigeron canadensis, the tansy 
or Tanacehm vulgare and some others may at 
times be seen with ray-fiorets, and according 
to Murr, they may sometimes be wanting in 
Aster Tripolium, Beilis perennis, some species 
of Anthemis, Arnica montana and in a number 



Latent Characters 


237 


of other well-known rayed species. Another in- 
stance may be quoted; it has been pointed out 
by Grant Allen, and refers to the dead-nettle or 
Lamium album. Systematically placed in a 
genus with red-flowering species, we may re- 
gard its white color as due to the latency of the 
general red pigment. But if the flower of this 
plant is carefully examined, it will be foimd in 
most cases not to be purely white, but to have 
some dusky lines and markings on its lower lip. 
Similar devices are observed on the lip of the 
allied Lamium maculatum, and in a less de- 
gree on the somewhat distant Lamium pur- 
pureum. With Lamium maculatum or spotted 
dead-nettle, the affinity is so close that even 
Bentham united the two in a single species, con- 
sidering the ordinary dead-nettle only as a va- 
riety of the dappled purple type. For the sup- 
port of this conception of a specific or varietal 
retrograde change many other facts are af- 
forded by the distribution of the characteristic 
color and of the several patterns of the lips of 
other labiates, and our general understanding of 
the relationships of the species and genera in 
this family may in a broad sense be based on the 
comparison of these seemingly subordinate 
characteristics. 

The same holds good in many other cases, 
and systematists have often become uncertain 



238 


Retrograde Varieties 


as to the true value of some form, by its rela- 
tionship to the allied types in the way of retro- 
gressive modification. Color-differences are so 
showy, that they easily* overshadow other char- 
acters. The white and the bine thorn-apple, 
the white and the red campion {Lychnis ves- 
pertina and diurna) and many other illustrative 
cases could be given, in which two forms are 
specifically separated by some authors, but 
combined by others on the ground of the retro- 
grade nature of some differentiating mark. 

Hitherto we have dealt with negative charac- 
ters and tried to prove that the conception of 
latency of the opposite positive characteristics 
is a more natural explanation of the phenome- 
non than the idea of a complete loss. We have 
now to consider the positive varieties, and to 
show that it is quite improbable that here the 
species have struck out for themselves a wholly 
new character. In some instances such may 
have been the case, but then I should prefer to 
treat these rather as elementary species. But 
in the mam we will have to assume the latency 
of the character in the species and its reassump- 
tion by the variety when originating, as the most 
probable explanation. 

Great stress is laid upon this conception by 
the fact, that positive varieties are so exces- 
sively rare when compared with the common oc- 



Latent Characters 


239 


currence of negative ones. Indeed, if we pnt 
aside the radiate and the color-varieties of 
flowers and foliage, hardly any cases can be 
cited. We have dealt with this question in a 
former lecture, and may now limit ourselves to 
the positive color-varieties. 

The latency of the faculty of producing the 
red pigment in leaves must obviously be ac- 
cepted for nearly the whole vegetable kingdom. 
Oaks and elms, the beautiful climbing species 
of Ampelopsis, many conifers, as for instance 
Cryptomeria japonica, some brambles, the 
Guelder-rose (Viburnum Opulus) and many 
other trees and shrubs assume a more or less 
bright red color in the fall. During summer 
this tendency must have been dormant, and that 
this is so, is shown by the young leaves of oaks 
and others, which, when unfolding in the spring 
show a similar but paler hue. Moreover, there 
is a way of awakening the concealed powers at 
any time. We have only to inflict small wounds 
on the leaves, or to cut through the nerves or to 
injure them by a slight bruising, and the leaves 
frequently respond with an intense reddening of 
the living tissues around and especially above 
the wounds. Azolla caroliniana, a minute moss- 
like floating plant allied to the ferns, responds 
to light and cold with a reddish tinge, and to 
shade or warmth with a pure green. The foli- 



240 


Retrograde Varieties 


age of many other plants behaves likewise, as 
also do apples and peaches on the insolated 
sides of the fruits. It is quite impossible to 
state these groups of facts in a more simple way 
than by the statement that the tendency to be- 
come red is almost generally present, though 
latent in leaves and stems, and that it comes 
into activity whenever a stimulus provokes it. 

Now it must be granted that the energizing 
of such a propensity under ordinary circum- 
stances is quite another thing from the orig- 
ination of a positive variety by the evolution 
of the same character. In the variety the ac- 
tivity has become independent of outer in- 
fluences or dependent upon them in a far lesser 
degree. The power of producing the red pig- 
ments is shown to be latent by the facts given 
above, and we see that in the variety it is no 
longer latent but is in perfect and lasting ac- 
tivity throughout the whole life of the plant. 

Bed varieties of white flowers are much more 
rare. Here the latency of the red pigment may 
be deduced partly from general arguments like 
those just given, partly from the special syste- 
matic relations in the given cases. Hildebrand 
has clearly worked out this mode of proof. He 
showed by the critical examination of a large 
number of instances that the occurrence of the 
red-flowered varieties is contingent upon the 



Latent Characters 


241 


existence of red species in the same genus, or 
in some rare cases, in nearly allied genera. 
Colors that are not systematically present in 
the group to which a white species belongs are 
only produced in its varieties in extremely rare 
cases. 

We may quote some special rules, indicated 
by Hildebrand. Blue species are in the main 
very rare, and so are blue varieties of white 
species also. Carnations, Asiatic or cultivated 
buttercups {Ranunculus asiaticus), Mirabilis, 
poppies, Gladiolus, Dahlia, and some other 
highly cultivated or very old garden-plants have 
not been able to produce true blue flowers. But 
the garden-anemone {Anemone coronaria) has 
allies with very fine blue flowers. The common 
stock has bluish varieties and is allied to Auhre-^ 
tia and Hesperis, and gooseberries have a red 
form, recalling the ordinary currant. In nearly 
all other instances of blue or red varieties every 
botanist will be able to point out some allied red 
or blue species, as an indication of the probable 
source of the varietal character. 

Dark spots on the lower parts of the petals 
of some plants afford another instance, as in 
poppies and in the allied Glaucium, where they 
sometimes occur as varietal and in other cases 
as specific marks. 

The yellow fails in many highly developed 



242 


Retrograde Varieties 


flowers, which are not liable to produce yellow 
variations, as in Salvia, Aster, Centaur ea. 
Vinca, Polygala and many others. Even the 
rare pale yellowish species of some of these 
genera have no tendency in this direction. The 
hyacinths are the most remarkable, if not the 
sole known instance of a species having red and 
blue and white and yellow varieties, but here the 
yellow is not the bright golden color of the but- 
tercups. 

The existence of varietal colors in allied spe- 
cies obviously points to a common cause, and 
this cause can he no other than the latency of 
the pigment in the species that do not show it. 

The conception of latency of characters as the 
common source of the origination of varieties, 
either in the positive or in the negative way, 
leads to some rules on variability, which are 
known under the names given to them by Dar- 
win. They are the rules of repeated, homolog- 
ous, parallel and analogous variability. Each 
of them is quite general, and may be recog- 
nized in instances from the most widely dis- 
tant families. Each of them is quite evident 
and easily understood on the principle of 
latency. 

By the term of repeated variability is meant 
the well-known phenomenon, that the same va- 
riety has sprung at different times and in dif- 



Latent Characters 


243 


ferent countries from the same species. The 
repetition obviously indicates a common inter- 
nal cause. The white varieties of blue- and red- 
flowered plants occur in the wild state so often, 
and in most of the instances in so few in- 
dividuals that a common pedigree is absolutely 
improbable. In horticulture this tendency is 
widely and vexatiously known, since the repeti- 
tion of an old variety does not bring any ad- 
vantage to the breeder. The old name of 

conquests,” given by the breeders of hya- 
cinths, tulips and other flower-bulbs to any 
novelty, in disregard of the common occurrence 
of repetitions, is an indication of the same ex- 
perience in the repeated appearance of certain 
varieties. 

The rule of parallel variations demands that 
the same character occasionally makes its ap- 
pearance in the several varieties or races, de- 
scended from the same species, and even in 
widely distinct species. This is a rule, which 
is very important for the general conception of 
the meaning of the term variety as contrasted 
with elementary species. For the recurrence 
of the same deviation always impresses us as a 
varietal mark. Laciniated leaves are perhaps 
the most beautiful instance, since they occur in 
so many trees and shrubs, as the walnut tree, 
the beech, the birch, the hazelnut, and even in 



244 


Retrograde Varieties 


brambles and some garden-varieties of the tur- 
nip {Brassica). 

In such cases of parallel variations the single 
instances obviously follow the same rules and 
are therefore to be designated as analogous. 
Pitchers or ascidia, formed by the union of the 
margins of a leaf, are perhaps the best proof. 
They were classified by Morren under two heads, 
according to their formation from one or more 
leaves. Monophyllous pitchers obey the same 
law, viz. : that the upper side of the leaf has be- 
come the inner side of the pitcher. Only one 
exception to this rule is known to me. It is af- 
forded by the pitchers of the banyan or holy 
fig-tree, Ficus religiosus, but it does not seem to 
belong to the same class as other pitchers, 
since as far as it has been possible to ascertain 
the facts, these pitchers are not formed by a 
few leaves as in all other cases, but by all the 
leaves of the tree. 

In some cases pitchers are only built up of 
part of the leaf-blade. Such partial malforma- 
tions obey a rule, that is common to them and to 
other foliar enations, viz. : that the side of the 
leaf from which they emerge, is always their 
outer side. The inner surface of these ena- 
tions corresponds to the opposite side of the 
leaf, both in color and in anatomical structure. 

The last of the four rules above mentioned is 



Latent Characters 


245 


that of the homologous variability. It asserts 
that the same deviation may occur in different, 
but homologous parts of the same plant. We 
have already dealt with some instances, as the 
occurrence of the same pigment in the flowers 
and foliage, in the fruits and seeds of the same 
plant, as also illustrated by the loss of the red 
or blue tinge by flowers and berries. Other in- 
stances are afforded by the curious fact that 
the division of the leaves into numerous and 
small segments is repeated by the petals, as 
in the common celandine and some sorts of 
brambles. 

It would take too long to make a closer exam- 
ination of the numerous cases which afford 
proof of these statements. Suffice it to say that 
ever3rwhere the results of close inspection point 
to the general rule, that the failure of definite 
qualities both in species and in varieties must, 
in a great number of cases, be considered as only 
apparent. Hidden from view, occasionally re- 
appearing, or only imperfectly concealed, the 
same character must be assumed to be present 
though latent. 

In the case of negative or retrogressive varie- 
ties it is the transition from the active into a 
dormant state to which is due the origin of the 
variety. Positive varieties on the contrary owe 
their origin to the presence of some character 



246 


Retrograde Varieties 


in the species in the latent state, and to the oc- 
casional re-energizing thereof. 

Specific or varietal latency is not the same 
thing as the ordinary latency of characters that 
only await their period of activity, or the ex- 
ternal influence which will awake them. They 
are permanently latent, and could well be des- 
ignated by the word perlatent. They spring 
into activity only by some sudden leap, and then 
at once become independent of ordinary exter- 
nal stimulation. 



Lectube IX 


CB0S6ES OE SPECIES AND VABIETIES 

In the foregoing lectures I have tried to show 
that there is a real difference between element- 
ary species and varieties. The first are of 
equal rank, and together constitute the col- 
lective or systematic species. The latter are 
usually derived from real and still existing 
types. Elementary species are in a sense inde- 
pendent of each other, while varieties are of a 
derivative nature. 

Furthermore I have tried to show that the 
ways in which elementary or minor species must 
have originated from their common ancestor 
must be quite different from the mode of origin 
of the varieties. We have assumed that the 
first come into existence by the production of 
something new, by the acquirement of a char- 
acter hitherto unnoticed in the line of their an- 
cestors. On the contrary, varieties, in most 
cases, evidently owe their origin to the loss of 
an already existing character, or in other less 

frequent cases, to the re-assumption of a quality 

247 



248 


Retrograde Varieties 


formerly lost. Some may originate in a 
negative, others in a positive manner, but in 
both cases nothing really new is acquired. 

This distinction holds good for all cases in 
which the relationship between the forms in 
question is well known. It seems entirely justi- 
fiable therefore to apply it also to cases in 
which the systematic affinity is doubtful, as well 
as to instances in which it is impossible to ar- 
rive at any taxonomic conclusions. The ex- 
treme application of the principle would no 
doubt disturb the limits between many species 
and varieties as now recognized. It is not to be 
forgotten however that all taxonomic distinc- 
tions, which have not been confirmed by physi- 
ologic tests are only provisional, a view ac- 
knowledged by the best sy stematists. Of course 
the description of newly discovered forms can 
not await the results of physiologic inquiries, 
but it is absolutely impossible to reach definite 
conclusions on purely morphologic evidence. 
This is well illustrated by the numerous dis- 
cords of opinion of different authors on the sys- 
tematic worth of many forms. 

Assuming the above mentioned principle as 
established, and disregarding doubtful cases as 
indicated, the term progressive evolution is 
used to designate the method in which element- 
ary species must have originated. It is the 



Unbalanced Crosses 


249 


maimer in which all advance in the animal and 
vegetable kingdoms must have taken place; con- 
tinuously adding new characters to the already 
existing number. Contrasted with this method 
of growing differentiation, are the retrogres- 
sive modifications, which simply retrace a 
step, and the degressive changes in which 
a backward step is retraced and old characters 
revived. No doubt both of these methods have 
been operative on a large scale, but they are evi- 
dently not in the line of general advancement. 

In all of these directions we see that the dif- 
ferentiating marks show more or less clearly 
that they are built up of units. Allied forms 
are separated from each other without interme- 
diates. Transitions are wholly wanting, al- 
though fallaciously apparent in some instances 
owing to the wide range of fluctuating variabil- 
ity of the forms concerned, or to the occurrence 
of hybrids and subvarieties. 

These physiologic units, which in the end 
must be the basis for the distinction of the sys- 
tematic units, may best be designated by the 
term of “ unit-characters.” Their internal na- 
ture is as yet unknown to us, and we will not 
now look into the theories, which have been pro- 
pounded as to the probable material basis un- 
derlying them. For our present purpose the 
empirical evidence of the general occurrence of 



250 


Retrograde Varieties 


sharp limits between nearly related characters 
must suffice. As Bateson has put it, species are 
discontinuous, and we must assume that their 
characters are discontinuous also. 

Moreover there is as yet no reason for trying 
to make a complete analysis of all the charac- 
ters of a plant. No doubt, if attained, such an 
analysis would give us a deep insight into the 
real internal construction of the intricate prop- 
erties of organisms in general. But taxonomic 
studies in this direction are only in their in- 
fancy and do not give us the material required 
for such an analysis. Quite on the contrary, 
they compel us to confine our study to the most 
recently acquired, or youngest characters, 
which constitute the differentiating marks be- 
tween nearly allied forms. 

Obviously this is especially the case in the 
realm of the hybrids, since only nearly related 
forms are able to give hybrid offspring. In 
dealing with this subject we must leave aside 
all questions concerning more remote relation- 
ships. 

It is not my purpose to treat of the doctrine 
of hybridization at any length. Experience is 
so rapidly increasing both in a practical 
and in a purely scientific direction that it would 
take an entire volume to give only a brief sur- 
vey of the facts and of all the proposed theories. 



Unbalanced Crosses 


251 


For our present purposes we are to deal with 
hybrids only in so far as they afford the means 
of a still better distinction between elementary 
species and varieties. I will try to show that 
these two contrasting groups behave in quite a 
different manner, when subjected to crossing 
experiments, and that the hope is justified 
that some day crosses may become the means of 
deciding in any given instance, what is to be 
called a species, and what a variety, on physio- 
logic grounds. It is readily granted that the 
labor required for such experiments, is perhaps 
too great for the results to be attained, but then 
it may be possible to deduce rules from a small 
series of experiments, which may lead us to a 
decision in wider ranges of cases. 

To reach such a point of view it is necessary 
to compare the evidence given by hybrids, with 
the conclusions already attained by the com- 
parison of the differentiating characteristics of 
allied forms. 

On this ground we first have to inquire what 
may be expected respecting the internal nature 
and the outcome of the process of crossing in 
the various cases cited in our former discussion. 

We must always distinguish the qualities, 
which are the same in both parents, from those 
that constitute the differentiating marks in 
every single cross. In respect to the first 



252 


Retrograde Varieties 


group the cross is not at all distinguished from 
a normal fertilization, and ordinarily these 
characters are simply left out of consideration. 
But it should never be forgotten that they con- 
stitute the enormous majority, amounting to 
hundreds and thousands, whereas the differen- 
tiating marks in each case are only one or two 
or a few at most. The whole discussion is to 
be limited to these last-named exceptions. We 
must consider first what would be the nature of 
a cross when species are symmetrically com- 
bined, and what must be the case when varieties 
are subjected to the same treatment In so do- 
ing, I intend to limit the discussion to the most 
typical cases. We may take the crosses between 
elementary species of the same or of very nar- 
rowly allied systematic species on the one side, 
and on the other, limit treatment to the crossing 
of varieties with the species, from which they 
are supposed to have sprung by a retrograde 
modification. Crosses of different varieties of 
the same species with one another obviously 
constitute a derivative case, and should only be 
discussed secondarily. And crosses of varie- 
ties with positive or degressive characters have 
as yet so rarely been made that we may well 
disregard them. 

Elementary species differ from their nearest 
allies by progressive changes, that is by the ac- 



Ufihalanced Crosses 


253 


quirement of some new character. The deriva- 
tive species has one unit more than the parent. 
All other qualities are the same as in the par- 
ent. Whenever such a derivative is combined 
with its parent the result for these qualities 
will be exactly as in a normal fertilization. In 
such ordinary cases it is obvious that each char- 
acter of the pollen-parent is combined with the 
same character of the pistil-parent. There may 
be slight individual differences, but each unit- 
character will become opposed to, and united 
with, the same unit-character in the other par- 
ent. In the offspring the units will thus 
be paired, each pair consisting of two equivalent 
units. As to their character the units of each 
single pair are the same, only they may exhibit 
slight differences as to the degree of develop- 
ment of this character. 

Now we may apply this conception to the sex- 
ual combination of two different elementary 
species, assuming one to be the derivative of 
the other. The differentiating mark is only 
present in one of the parents and wanting in the 
other. While all other units are paired in the 
hybrid, this one is not. It meets with no mate, 
and must therefore remain unpaired. The 
hybrid of two such elementary species is in 
some way incomplete and unnatural. In the 
ordinary course of things all individuals derive 



254 


Retrograde Varieties 


their qualities from both parents ; for each sin- 
gle mark they possess at least two units. Prac- 
tically but not absolutely equal, these two op- 
ponents always work together and give to the 
offspring a likeness to both parents. No un- 
paired qualities occur in normal offspring; these 
constitute the essential features of the hybrids 
of species and are at the same time the cause of 
their wide deviations from the ordinary rules. 

Turning now to the varieties, we likewise 
need discuss their differentiating marks only. 
In the negative types, these consist of the ap- 
parent loss of some quality which was active in 
the species. But it was pointed out in our last 
lecture that such a change is an apparent loss. 
On a closer inquiry we are led to the assumption 
of a latent or dormant state. The presumably 
lost characters have not absolutely, or at least 
not permanently disappeared. They show 
their presence by some slight indication of the 
quality they represent, or by occasional revers- 
ions. They are not wanting, but only latent. 

Basing our discussion concerning the process 
of crossing on this conception, and still limiting 
the discussion to one differentiating mark, we 
come to the inference, that this mark is present 
and active in the species, and present but dor- 
mant in the variety. Thus it is present in both, 
and as all other characters not differentiating 



Unbalanced Crosses 


255 


find their mates in the cross, so these two will 
also meet one another. They will unite just as 
well as though they were both active or both 
dormant. For essentially they are the same, 
only differing in their degree of activity. From 
this we can infer, that in the crossing of varie- 
ties, no unpaired remainder is left, all units 
combining in pairs exactly as in ordinary fertil- 
ization. 

Setting aside the contrast between activity 
and latency in this single pair, the procedure in 
the inter-crossing of varieties is the same as in 
ordinary normal fertilization. 

Summarizing this discussion we may con- 
clude that in normal fertilization and in the 
inter-crossing of varieties all characters are 
paired, while in crosses between elementary 
species the differentiating marks are not mated. 

In order to distinguish these two great types 
of fertilization we .will use the term bisexual for 
the one and unisexual for the other. The term 
balanced crosses theu conveys the idea of com- 
plete bisexuality, all unit>characters combining 
in pairs. Unbalanced crosses are those in which 
one or more units do not find their mates and 
therefore remain unpaired. This distinction 
was proposed by Macfarlane when studying 
the minute structure of plant-hybrids in com- 
parison with that of their parents (1892). 



256 


Retrograde Varieties 


In the first place it shows that a species- 
hybrid may inherit the distinguishing marks 
of both parents. In this way it may become in- 
termediate between them, having some charac- 
ters in common with the pollen-parent and others 
with the pistil-parent. As far as these charac- 
ters do not interfere with each other, they may 
be fully developed side by side, and in the main 
this is the way in which hybrid characters are 
evolved. But in most cases our existing knowl- 
edge of the units is far too slender to give a 
complete analysis, even of these distinguishing 
marks alone. We recognize the parental marks 
more or less clearly, but are not prepared for 
exact delimitations. Leaving these theoretical 
considerations, we will pass to the description 
of some illustrative examples. 

In the first place I will describe a hybrid 
between two species of Oenothera, which I 
made some years ago. The parents were the 
common evening-primrose or Oenothera bien- 
nis and of its small-flowered congener, Oeno- 
thera muricata. These two forms were distin- 
guished by Linnaeus as different species, but 
have been considered by subsequent writers as 
elementary species or so-called systematic va- 
rieties of one species designated with the name 
of the presumably older type, the 0. biennis. 
Varietal differences in a physiologic sense they 



Unbalanced Crosses 


257 


do not possess, and for this reason afford a 
pure instance of unbalanced union, though dif- 
fering in more than one point. 

I have made reciprocal crosses, taking at one 
time the small-flowered and at the other the 
common species as pistillate parent. These 
crosses do not lead to the same hybrid as is 
ordinarily observed in analogous cases ; quite on 
the contrary, the two types are different in most 
features, both resembling the pollen-parent 
far more than the pistil-parent. The same 
curious result was reached in sundry other re- 
ciprocal crosses between species of this genus. 
But I will limit myself here to one of the two 
hybrids. 

In the summer of 1895 I castrated some flow- 
ers of 0. muricata, and pollinated them with 0. 
biennis, surrounding the flowers with paper 
bags so as to exclude the visits of insects. I 
sowed the seeds in 1896 and the hybrids were 
biennial and flowered abundantly the next year 
and were artificially fertilized with their own 
pollen, but gave only a very small harvest. 
Many capsules failed, and the remaining con- 
tained only some few ripe seeds. 

From these I had in the following year the 
second hybrid generation, and in the same way 
I cultivated also the third and fourth. These 
were as imperfectly fertile as the first, and in 



258 


Retrograde Varieties 


some years did not give any seed at all, so that 
the operation had to be repeated in order to 
continue the experiment. Last summer (1903) 
I had a nice lot of some 25 biennial specimens 
blooming abundantly. All in all I have grown 
some 500 hybrids, and of these about 150 speci- 
mens flowered. 

These plants were all of the same type, re- 
sembling in most points the pollen-parent, and 
in some others the pistil-parent of the original 
cross. The most obvious characteristic marks 
are afforded by the flowers, which in 0. muri- 
cata are not half so large as in biennis, 
though borne by a calyx-tube of the same 
length. In this respect the hybrid is like the 
biennis bearing the larger flowers. These may 
at times seem to deviate a little in the direction 
of the other parent, being somewhat smaller 
and of a slightly paler color. But it is very 
difficult to distinguish between them, and if 
biennis and hybrid flowers were separated from 
the plants and thrown together, it is very doubt- 
ful whether one would succeed in separating 
them. 

The next point is offered by the foliage. The 
leaves of 0. biennis are broad, those of 0. muri- 
cata narrow. The hybrid has the broad leaves 
of 0. biennis during most of its life and at the 
time of flowering. Yet small deviations in the 



Unbalanced Crosses 


259 


direction of the other parent are not wanting, 
and in winter the leaves of the hybrid rosettes 
are often much narrower than those of 0. bien- 
nis, and easily distinguishable from both par- 
ents. A third distinction consists in the den- 
sity of the spike. The distance between the in- 
sertion of the flowers of 0. biennis is great when 
compared with that of 0. muricata. Hence the 
flowers of the latter species are more crowded 
and those of 0. biennis more dispersed, the 
spikes of the first being densely crowned with 
flowers and flower-buds while those of 0. biennis 
are more elongated and slender. As a further 
consequence the 0 . biennis opens on the same 
evening only one, two or three flowers on the 
same spike, whereas 0. muricata bears often 
eight or ten or more flowers at a time. In this 
respect the hybrid is similar to the pistil-parent, 
and the crowding of the broad flowers at the 
top of the spikes causes the hybrids to be much 
more showy than either of the parent types. 

Other distinguishing marks are not recorded 
by the systematists, or are not so sharply sepa- 
rated as to allow of the corresponding qualities 
of the hybrids being compared with them. 

This hybrid remains true to the description 
given. In some years I cultivated two gener- 



260 Retrograde Varieties 

ations so as to be able to compare them with 
one another, but did not find any difference. 
The most interesting point however, is the like- 
ness between the first generation, which ob- 
viously must combine in its internal structure 
the units of both parents, and the second and 
later generations which are only of a derivative 
nature. Next to this stands the fact that in 
each generation all individuals are alike. No 
reversion to the parental forms either in the 
whole type or in the single characteristics has 
ever been observed, though the leaves of some 
hundreds, and the spikes and flowers of some 
150 individual plants have been carefully ex- 
amined. No segregation or splitting up takes 
place. 

Here we have a clear, undoubted and rela- 
tively simple, case of a true and pure species- 
hybrid. No occurrence of possible varietal 
characteristics obscures the result, and in this 
respect this hybrid stands out much more 
clearly than all those between garden-plants, 
where varietal marks nearly always play a most 
important part. 

From the breeder’s point of view our hybrid 
Oenothera would be a distinct gain, were it not 
for the difficulty of its propagation. But to en- 
large the range of the varieties this simple and 
stable form would need to be treated anew, by 



Unbalanced Crosses 


261 


crossing it with the parent-types. Such experi- 
ments however, have miscarried owing to the 
too stable nature of the unit-characters. 

This stability and this absence of the split- 
ting shown by varietal marks in the offspring 
of hybrids is one of the best proofs of unisex- 
ual unions. It is often obscured by the accom- 
panying varietal marks, or overlooked for this 
reason. Only in rare cases it is to be met with 
in a pure state and some examples are given of 
this below. 

Before doing so, I must call your attention 
to another feature of the unbalanced unions. 
This is the diminution of the fertility, a phe- 
nomenon universally known as occurring in 
hybridizations. It has two phases. First, the 
diminished chance of the crosses themselves of 
giving full crops of seed, as compared with the 
pure fertilization of either parent. And, sec- 
ondly, the fertility of the hybrids themselves. 
Seemingly, all grades of diminished fertDity 
occur and the oldest authors on hybrids have 
pointed out that a very definite relation exists 
between the differences of the parents and the 
degree of sterility, both of the cross and of the 
hybrid offspring. In a broad sense these two 
factors are proportionate to each other, the 
sterility being the greater, the lesser the affin- 
ity between the parents. Many writers have 



262 


Retrograde Varieties 


tried to trace this rule in the single cases, but 
have met with nearly unsurmountable difficul- 
ties, owing chiefly to our ignorance of the units 
which form the differences between the parents 
in the observed cases. 

In the case of Oenothera muricata x bien- 
nis the differentiating units reduce the fertility 
to a low degree, threatening the offspring with 
almost complete infertility and extinction. 
But then we do not know whether these charac- 
ters are really units, or perhaps only seemingly 
so and are in reality composed of smaller en- 
tities which as yet we are not able to segregate. 
And as long as we are devoid of empirical means 
of deciding such questions, it seems useless to go 
farther into the details of the question of the 
sterility. It should be stated here however, 
that pure varietal crosses, when not accompan- 
ied by unbalanced characters, have never showed 
any tendency to diminished fertility. Hence 
there can be little doubt that the unpaired units 
are the cause of this decrease in reproductive 
power. 

The genus Oenothera is to a large degree de- 
void of varietal characteristics, especially in 
the subgenus Onagra, to which biennis, mur- 
icata, lamarckiana and some others belong. 
On the other hand it seems to be rich in 
elementary species, but an adequate study of 



Unbalanced Crosses 


263 


them has as yet not been made. Unfortunately 
many of the better systematists are in the habit 
of throwing all these interesting forms to- 
gether, and of omitting their descriptive study. 
I have made a large number of crosses be- 
tween such undescribed types and as a rule 
got constant hybrid races. Only one or two 
exceptions could be quoted, as for instance the 
Oenothera brevistylis, which in its crosses al- 
ways behaves as a pure retrogressive variety. 
Instead of giving an exhaustive survey of 
hybrids, I simply cite my crosses between 
lamarckiana and biennis, as having nearly the 
aspect of the last named species, and remaining 
true to this in the second generation without 
any sign of reversion or of splitting. I have 
crossed another elementary species, the Oeno- 
thera hirtella with some of my new and with 
some older Linnean species, and got several 
constant hybrid races. Among these the off- 
spring of a cross between muricata and hirtella 
is still in cultivation. The cross was made in 
the summer of 1897 and last year (1903) I grew 
the fourth generation of the hybrids. These 
had the characters of the muricata in their nar- 
row leaves, but the elongated spikes and rela- 
tively large flowers of the hirtella parent, and 
remained true to this type, showing only slight 
fluctuations and never reverting or segregating 



264 


Retrograde Varieties 


the mized characters. Both parents bear large 
capsules with an abundance of seed, but in the 
hybrids the capsules remain narrow and weak, 
ripening not more than one-tenth the usual 
quantity of seed. Both parents are easily 
cultivated in annual generations and the same 
holds good for the hybrid. But whereas the 
hybrid of muricata and biennis is a stout plant, 
this type is weak with badly developed foliage, 
and very long strict spikes. Perhaps it was 
not able to withstand the bad weather of the 
last few years. 

A goodly number of constant hybrids are de- 
scribed in literature, or cultivated in fields and 
gardens. In such cases the essential question 
is not whether they are now constant, but 
whether they have been so from the beginning, 
or whether they prove to be constant whenever 
the original cross is repeated. For constant 
hybrids may also be the issue of incipient split- 
tings, as we shall soon see. 

Among other examples we may begin with 
the hybrid alfalfa or hybrid lucerne {Medicago 
media). It often originates spontaneously be- 
tween the common purple lucerne or alfalfa 
and its wild ally with yellow flowers and pro- 
cumbent stems, the Medicago falcata. This 
hybrid is cultivated in some parts of Germany 
on a large scale, as it is more productive than 



Unbalanced Crosses 


265 


the ordinary lucerne. It always comes true 
from seed and may be seen in a wild state in 
parks and on lawns. It is one of the oldest 
hybrids with a pure and known lineage. The 
original cross has been repeated by Urban, who 
found the hybrid race to be constant from the 
beginning. 

Another very notorious constant hybrid race 
is the Aegilops speltaeformis. It has been 
cultivated in botanic gardens for more than 
half a century, mostly in annual or biennial 
generations. It is sufficiently fertile and al- 
ways comes true. Numerous records have 
been made of it, since formerly it was believed 
by Fabre and others to be a spontaneous transi- 
tion from some wild species of grass to the ordi- 
nary wheat, not a cross. Godron, however, 
showed that it can be produced artificially, and 
how it has probably sprung into existence 
wherever it is found wild. The hybrid between 
Aegilops ovata, a small weed, and the common 
wheat is of itself sterile, producing no good pol- 
len. But it may be fertilized by the pollen of 
wheat and then gives rise to a secondary 
hybrid, which is no other than the Aegilops 
speltaeformis. This remained constant in God- 
ron ’s experiments during a number of genera- 
tions, and has been constant up to the present 
time. 



266 


Retrograde Varieties 


Constant hybrids have been raised by MU- 
lardet between several species of strawberries. 
He combined the old cultivated forms with newly 
discovered types from American localities. 
They ordinarily showed only the characteristics 
of one of their parents and did not exhibit any 
new combination of qualities, but they came 
true to this type in the second and later gener- 
ations. 

In the genus Anemone, Janczewski obtained 
the same results. Some characters of course 
may split, but others remain constant, and 
when only such are present, hybrid races result 
with new combinations of characters, which are 
as constant as the best species of the same ge- 
nus. The hybrids of Janczewski were quite fer- 
tile, and he points out that there is no good 
reason why they should not be considered as 
good new species. If they had not been pro- 
duced artificially, but found in the wild state, 
their origin would have been unknown, and there 
can be no doubt that they would have been de- 
scribed by the best systematists as species of the 
same value as their parents. Such is especially 
the case with a hybrid between Anemone magel- 
lanica and the common Anemone sylvestris. 

Starting from similar considerations Kemer 
von Marilaun pointed out the fact long ago that 
many so-called species, of rare occurrence. 



Unbalanced Crosses 


267 


standing between two allied types, may be con- 
sidered to have originated by a cross. Surely 
a wide field for abuse is opened by sucb an as- 
sertion, and it is quite a common habit to con- 
sider intermediate forms as hybrids, on the 
grounds afforded by their external characters 
alone, and without any exact knowledge of their 
real origin and often without knowing anything 
as to their constancy from seed. All such ap- 
parent explanations are now slowly becoming 
antiquated and obsolete, but the eases adduced 
by Kerner seem to stand this test. 

Kemer designates a willow, Salix ehrhart- 
iana as a constant hybrid between Salix alba 
and S. pentandra. Rhododendron intermed- 
ium is an intermediate form between the hairy 
and the rusty species from the Swiss Alps, R. 
hirsutum and R. ferrugineum, the former grow- 
ing on chalky, and the other on silicious soils. 
Wherever both these types of soil occur in the 
same valley and these two species approach 
one another, the hybrid R. intermedium is pro- 
duced, and is often seen to be propagating itself 
abundantly. As is indicated by the name, it 
combines the essential characters of both par- 
ents. 

Linaria italica is a hybrid toad-flax between 
L. genistifolia and L. vulgaris, a cross which I 
have repeated in my garden. Drosera obovata 



268 


Retrograde Varieties 


is a hybrid sundew between D. anglica and D. 
rotundifolia. Primula variabUis is a hybrid 
between the two common primroses, P. oifici- 
nalis and P. grandifiora. The willow-herb 
{Epilohmm), the self-heal (Brunella) and the 
yellow pond-lilies (Nuphar) afford other in- 
stances of constant wild hybrids. 

Macfarlane has discovered a natural hybrid 
between two species of sundew in the swamps 
near Atco, N. J. The parents, D. intermedia 
and D. filiformis, were growing abundantly all 
around, but of the hybrid only a group of eleven 
plants was found. A detailed comparison of 
the hybrid with its parents demonstrated a 
minute blending of the anatomical peculiarities 
of the parental species. 

Luther Burbank of Santa Eosa, Califorma, 
has produced a great many hybrid brambles, 
the qualities of which in many respects surpass 
those of the wild species. Most of them are 
only propagated by cuttings and layers, not 
being stable from seed. But some crosses be- 
tween the blackberry and the raspberry {R. 
fruticosus and R. idaeus) which bear good 
fruit and have become quite popular, are so 
fixed in their type as to reproduce their com- 
posite characters from seed with as much regu- 
larity as the species of Rubus found in nature. 
Among them are the “ Phenomenal ” and the 



TJnbalmced Crosses 


269 


“ Primus.” The latter is a cross between the 
Californian dewberry and the Siberian rasp- 
berry and is certainly to be regarded as a good 
stable species, artificially produced. Bell 
Salter crossed the willow-herbs Epilobium tet- 
ragonum and E. montanum, and secured inter- 
mediate hybrids which remained true to their 
type during four successive generations. 

Other instances might be given. Many of 
them are to be found in horticultural and bo- 
tanical journals which describe their system- 
atic and anatomical details. The question of 
stability is generally dealt with in an inci- 
dental manner, and in many cases it is diffi- 
cult to reach conclusions from the facts given. 
Especially disturbing is the circumstance that 
from a horticultural point of view it is quite 
sufficient that a new type should repeat itself in 
some of its offspring to be called stable, and 
that for this reason absolute constancy is rarely 
proved. 

The range of constant hybrids would be 
larger by far were it not for two facts. The 
first is the absolute sterility of so many beauti- 
ful hybrids, and the second is the common occur- 
rence of retrogressive characters among culti- 
vated plants. To describe the importance of 
both these groups of facts would take too much 



270 


Retrograde Varieties 


time, and therefore it seems best to give some 
illustrative examples instead. 

Among the species of Ribes or currant, which 
are cultivated in our gardens, the most beauti- 
ful are without doubt the Californian and the 
Missouri currant, or Rihes sanguineum and R. 
aureum. A third form, often met with, is “ Gor- 
don’s currant,” which is considered to be a 
hybrid between the two. It has some peculiar- 
ities of both parents. The leaves have the gen- 
eral form of the Californian parent, but are as 
smooth as the Missouri species. The racemes 
or flower-spikes are densely flowered as in the 
red species, but the flowers themselves are of a 
yellow tinge, with only a flesh-red hue on the 
outer side of the calyx. It grows vigorously 
and is easily multiplied by cuttings, but it never 
bears any fruit. Whether it would be constant, 
if fertile, is therefore impossible to decide. 

Berberis Uicifolia is considered as a hybrid 
between the European barberry {B. vulgaris) 
and the cultivated shrub Mahonia aquifolia. 
The latter has pinnate leaves, the former undi- 
vided ones. The hybrid has undivided leaves 
which are more spiny than those of the Euro- 
pean parent, and which are not deciduous like 
them, but persist during the winter, a peculiar- 
ity inherited from the Mahonia. As far as I 



Unbalanced Crosses 


271 


have been able to ascertain, this hybrid never 
produces seed. 

Another instance of an absolutely sterile 
hybrid is the often quoted Cytisus adami. It 
is a cross between the common laburnum 
{Cytisus Laburnum) and another species of the 
same genus, (7. purpureus, and has some traits 
of both. But since the number of differentiat- 
ing marks is very great in this case, most of the 
organs have become intermediate. It is abso- 
lutely sterile. But it has the curious peculiar- 
ity of splitting in a vegetative way. It has been 
multiplied on a large scale by grafting, and was 
widely found in the parks and gardens of 
Europe during the last century. Nearly all 
these specimens reverted from time to time to 
the presumable parents. Not rarely a bud of 
Adam’s laburnum assumed all the qualities of 
the common laburnum, its larger leaves, richer 
flowered racemes, large and brightly yellow 
flowers and its complete fertility. Other buds 
on the same tree reverted to the purple parent, 
with its solitary small flowers, its dense shrub- 
like branches and very small leaves. These too 
are fertile, though not producing their seeds as 
abundantly as the C, Laburnum reversions. 
Many a botanist has sown the seeds of the latter 
and obtained only pure common C. Laburnum 
plants. I had a lot of nearly a hundred seed- 



272 


Retrograde Varieties 


lings myself, many of which have already flow- 
ered, bearing the leaves and flowers of the com- 
mon species. Seeds of the purple reversions 
have also been sown, and also yielded the 
parental type only. 

Why this most curious hybrid sports so reg- 
ularly and why others always remain true to 
their type is as yet an open question. 

But recalling our former consideration of 
this subject the supposition seems allowable 
that the tendency to revert is not connected 
with the type of the hybrid, but is apt to occur 
in some rare individuals of every type. But 
since most of the sterile hybrids are only known 
to us in a single individual and its vegetative 
offspring, this surmise offers an explanation of 
the rare occurrence of sports. 

Finally, we must consider some of the so- 
called hybrid races or strains of garden-plants. 
Dahlia, Gladiolus, Amaryllis, Fuchsia, Pelar- 
gonium and many other common flowers afford 
the best known instances. Immeasurable 
variability seems here to be the result of 
crossing. But on a closer inspection the range 
of characters is not so very much wider in these 
hybrid races than in the groups of parent- 
species which have contributed to the origin of 
the hybrids. Our tuberous begonias owe their 
variability to at least seven original parent spe- 



Unbalanced Crosses 


273 


cies, and to the almost incredible number of 
combinations which are possible between their 
characters. The first of these crosses was 
made in the nursery of Veitch and Sons near 
London by Seden, and the first hybrid is ac- 
cordingly known as Begonia sedeni and is still 
to be met with. It has been superseded by sub- 
sequent crosses between the sedeni itself and 
the veitchi and rosiflora, the davisii, the 
clarkii and others. Each of them contributed 
its advantageous qualities, such as roimd flow- 
ers, rosy color, erect flower stalks, elevation of 
the flowers above the foliage and others. New 
crosses are being made continuously, partly be- 
tween the already existing hybrids and partly 
with newly introduced wild species. Only 
rarely is it possible to get pure seeds, and I 
have not yet been able to ascertain whether the 
hybrids would come true from seed. Specific 
and varietal characters may occur together in 
many of the several forms, but nothing is as 
yet accurately known as to their behavior in 
pure fertilizations. Constancy and segregation 
are thrown together in such a manner that ex- 
treme variability results, and numerous beauti- 
ful types may be had, and others may be ex- 
pected from further crosses. For a scientific 
analysis, however, the large range of recorded 
facts and the written history, which at first sight 



274 


Retrograde Varieties 


seems to have no lacunae, are not sufficient. 
Most of the questions remain open and need in- 
vestigation. It would be a capital idea to try 
to repeat the history of the begonias or any 
other hybrid race, making all the described 
crosses and then recording the results in a man- 
ner requisite for complete and careful scien- 
tific investigations. 

Many large genera of hybrid garden-flowers 
owe their origin to species rich in varieties or 
in elementary subspecies. Such is the case 
with the gladiolus and the tulips. In other 
eases the original types have not been ob- 
tained from the wild state but from the cultures 
of other countries. 

The dahlias were cultivated in Mexico when 
first discovered by Europeans, and the chrys- 
anthemums have been introduced from the old 
gardens of Japan. Both of them consisted of 
various types, which afterwards have been in- 
creased chiefly by repeated intercrossing. 

The history of many hybrid races is obscure, 
or recorded by different authorities in a differ- 
ent way. Some have derived their evidence 
from one nursery, some from another, and the 
crosses evidently may have been different in 
different places. The early history of the glad- 
iolus is an instance. The first crosses are re- 
corded to have been made between Gladiolus 



Unbalanced Crosses 


275 


psittadms and G. cardinalis, and between their 
hybrid, which is still known under the name of 
gandavensis and the purpureo-auratus. But 
other authors give other lines of descent. So 
it is mth Amaryllis, which is said by De Graaff 
to owe its stripes to A. vittata, its fine form to 
A. hrasiliensis, the large petals to A. psittacina, 
the giant flowers to A. leopoldi, and the piebald 
patterns to A. pardina. But here, too, other 
authors give other derivations. 

Summarizing the results of our inquiry we 
see in the first place how very much remains to 
be done. Many old crosses must be repeated 
and studied anew, taking care of the purity of 
the cross as well as of the harvesting of the 
seeds. Many supposed facts will be shown to 
be of doubtful validity. New facts have to be 
gathered, and in doing so the distinction be- 
tween specific and varietal marks must be taken 
strictly into account. The first have originated 
as progressive mutations; they give unbalanced 
crosses with a constant offspring, as far as ex- 
perience now goes. The second are chiefly due 
to retrograde modifications, and will be the sub- 
ject of the next lecture. 



Leotxtbe X 


Mendel’s law of balanced cbosses 

In the scientific study of the result of crosses, 
the most essential point is the distinction of the 
several characters of the parents in their combi- 
nation in the hybrids and their offspring. 
From a theoretical point of view it would be 
best to choose parents which would differ only 
in a single point. The behavior of the differen- 
tiating character might then easily be seen. 

Unfortunately, such simple cases do not read- 
ily occur. Most species, and even many ele- 
mentary species are distinguished by more than 
one quality. Varieties deviating only in one 
unit-character from the species, are more com- 
mon. But a closer inspection often reveals 
some secondary characters which may be over- 
looked in comparative or descriptive studies, 
but which reassume their importance in experi- 
mental crossings. 

In a former lecture we have dealt with the 
qualities which must be considered as being due 

to the acquisition of new characters. If we 

276 



Balanced Crosses 


277 


compare the new form in this case with the type 
from which it has originated, it may be seen 
that the new character does not find its mate, 
or its opposite, and it will be unpaired in the 
hybrid. 

In the case of retrogressive changes the vis- 
ible modification is due, at least in the best 
known instances, to the reduction of an active 
quality to a state of inactivity or latency. Now 
if we make a cross between a species and its 
variety, the differentiating character will be 
due to the same internal unit, with no other 
difference than that it is active in the species 
and latent in the variety. In the hybrid these 
two corresponding units will make a pair. But 
while all other pairs in the same hybrid indi- 
viduals consist of like antagonists, only this 
pair consists of slightly unlike opponents. 

This conception of varietal crosses leads to 
three assertions, which seem justifiable by 
actual experience. 

First, there is no reason for a diminution of 
the fertility, as all characters are paired in the 
hybrid, and no disturbance whatever ensues in 
its internal structure. Secondly, it is quite in- 
different, how the two types are combined, or 
which of them is chosen as pistillate and which 
as staminate parent. The deviating pair will 
have the same constitution in both cases, being 



278 


Retrograde Varieties 


built up of one active and one dormant unit. 

Thirdly this deviating pair will exhibit the 
active unit which it contains, and the hybrid 
will show the aspect of the parent in which 
the character was active and not that of the 
parent in which it was dormant. Now the ac- 
tive quality was that of the species, and its 
latent state was found in the variety. Hence 
the inference that hybrids between a species 
and its retrograde variety will bear the aspect 
of the species. This attribute may be fully 
developed, and then the hybrid will not be dis- 
tinguishable from the pure species in its outer 
appearance. Or the character may be incom- 
pletely evolved, owing to the failure of coopera- 
tion of the dormant unit. In this case the hy- 
brid will be in some sense intermediate between 
its parents, but these instances are more rare 
than the alternate ones, though presumably 
they may play an important part in the varia- 
bility of many hybrid garden-flowers. 

All of these three rules are supported by a 
large amount of evidence. The complete fertil- 
ity of varietal hybrids is so universally acknowl- 
edged that it is not worth while to give special 
instances. With many prominent systematists 
it has become a test between species and vari- 
eties, and from our present point of view this as- 
sumption is correct. Only the test is of little 
use in practice, as fertility may be diminished 



Balanced Crosses 


279 


in unbalanced unions in all possible degrees, ac- 
cording to the amount of difference between the 
parents. If this amount is slight, if for in- 
stance, only one unit-character causes the dif- 
ference, the injury to fertility may be so small 
as to be practically nothing. Hence we see that 
this test would not enable us to judge of the 
doubtful cases, although it is quite sufficient as 
a proof in cases of wider differences. 

Our second assertion related to the reciprocal 
crosses. This is the name given to two sexual 
combinations between the same parents, but 
with interchanged places as to which furnishes 
the pollen. In unbalanced crosses of the genus 
Oenothera the hybrids of such reciprocal anions 
are often different, as we have previously 
shown. Sometimes both resemble the pollen- 
parent more, in other instances the pistil-parent. 
In varietal crosses no such divergence is as yet 
known. It would be quite superfluous to ad- 
duce single cases as proofs for this rule, which 
was formerly conceived to hold good for hy- 
brids in general. The work of the older hybrid- 
ists, such as Koelreuter and Gaertner affords 
numerous instances. 

Our third rule is of a wholly different nature. 
Formerly the distinction between elementary 
species and varieties was not insisted upon, and 
the principle which stamps retrograde changes 



280 


Retrograde Varieties 


as the trne character of varieties is a new one. 
Therefore it is necessary to cite a considerable 
amount of evidence in order to prove the asser- 
tion that a hybrid bears the active character 
of its parent-species and not the inactive char- 
acter of the variety chosen for the cross. 

We may pnt this assertion in a briefer form, 
stating that the active character prevails in the 
hybrid over its dormant antagonist. Or as it 
is equally often put, the one dominates and the 
other is recessive. In this terminology the 
character of the species is dominant in the 
hybrid whUe that of the variety is recessive. 
Hence it follows that in the hybrid the latent or 
dormant imit is recessive, but it does not follow 
that these three terms have the same meaning, 
as we shall see presently. The term recessive 
only applies to the peculiar state into which the 
latent character has come in the hybrid by its 
pairing with the antagonistic active unit. 

In the first place it is of the highest import- 
ance to consider crosses between varieties of re- 
corded origin and the species from which they 
have sprung. When dealing with mutations 
of celandine we shall see that the laeiniated 
form originated from the common celandine in 
a garden at Heidelberg about the year 1590. 
Among my oenotheras one of the eldest of the 
recent productions is the 0. brevistylis or short- 



Balanced Crosses 


281 


styled species which was seen for the first time 
in the year 1889. The third example offered 
is a hairless variety of the evening campion, 
Lychnis vespertina, found the same year, which 
hitherto had not been observed. 

For these three cases I have made the crosses 
of the variety with the parent-species, and in 
each case the hybrid was like the species, and 
not like the variety. Nor was it intermediate. 
Here it is proved that the older character dom- 
inates the younger one. 

In most cases of wild, and of garden-varieties, 
the relation between them and the parent-spe- 
cies rests upon comparative evidence. Often 
the variety is known to be younger, in other 
cases it may be only of local occurrence, but 
ordinarily the historic facts about its origin 
have never been known or have long since been 
forgotten. 

The easiest and most widely known varietal 
crosses are those between varieties with white 
flowers and the red- or blue-flowered species. 
Here the color prevails in the hybrid over the 
lack of pigment, and as a rule the hybrid is as 
deeply tinted as the species itself, and cannot be 
distinguished from it, without an investigation 
of its hereditary qualities. Instances may be 
cited of the white varieties of the snapdragon, 
of the red clover, the long-spurred violet {Viola 



282 


Retrograde Varieties 


cornuta) the sea-shore aster {Aster Tripolium), 
corn-rose {Agrostemma Githago), the Sweet 
William {SUene Armeria), and many garden 
flowers, as for instance, the Clarkia pulchella, 
the Polemonium coeruleum, the Veronica longi- 
folia, the gloxinias and others. If the red hue 
is combined with a yellow ground-color in the 
species, the variety will be yellow and the hy- 
brid will have the red and yellow mixture of the 
species as for instance, in the genus Geum. The 
toad-flax has an orange-colored palate, and a 
variety occurs in which the palate is of the same 
yellow tinge as the remaining parts of the 
corolla. The hybrid between them is in all re- 
spects like the parent-species. 

Other instances could be given. In berries 
the same rule prevails. The black nightshade 
has a variety with yellow berries, and the black 
color returns in the hybrid. Even the foliage of 
some garden-plants may afford instances, as for 
instance, the purplish amaranth {Amaranthus 
caudatus). It has a green variety, but the hy- 
brid between the two has the red foliage of the 
species. 

Special marks in leaves and in flowers follow 
the same rule. Some varieties of the opium- 
poppy have large black patches at the basal end 
of the petals, while in others this pattern is en- 
tirely white. In crossing two such varieties, 



Balanced Crosses 


283 


for instance, the dark “ Mephisto ” with the 
white-hearted “ Danebrog,” the hybrid shows 
the active character of the dark pattern. 

Hairy species crossed with their smooth 
varieties produce hairy hybrids, as in some 
wheats, in the campion {Lychnis)^ in Biscutella 
and others. The same holds good for the 
crosses between spiny species and their un- 
armed derivatives, as in the thorn-apple, the 
corn-crowfoot {Ranunculus arvensis) and 
others. 

Lack of starch in seeds is observed in some 
varieties of com and of peas. When such de- 
rivatives are crossed with ordinary starch-pro- 
ducing types, the starch prevails in the hybrid. 

It would take too much time to give further 
examples. But there is still one point which 
should be insisted upon. It is not the systema- 
tic relation of the two parents of a cross, that 
is decisive, but only the occurrence of the same 
quality, in the one in an active, and in the other 
in an inactive condition. Hence, whenever this 
relation occurs between the parents of a cross, 
the active quality prevails in the hybrid, even 
when the parents differ from each other in 
other respects so as to be distinguished as sys- 
tematic species. The white and red campions 
give a red hybrid, the black and pale henbane 
{Hyoscyamus niger and H. pallidus) give a hy- 



284 


Retrograde Varieties 


brid with the purple veins and center in the 
corolla of the former, the white and blue thorn- 
apple produce a blue hybrid, and so on. In- 
stances of this sort are common in cultivated 
plants. 

Having given this long list of examples of the 
rule of the dominancy of the active character 
over the opposite dormant unit, the question 
naturally arises as to how the antagonistic 
units are combined in the hybrid. This ques- 
tion is of paramount importance in the consid- 
eration of the offspring of the hybrids. But 
before taking it up it is as well to learn the real 
signification of recessiveness in the hybrids 
themselves. 

Recessive characters are shown by those rare 
cases, in which hybrids revert to the varietal 
parent in the vegetative way. In other words 
by bud-variations or sports, analogous to the 
splitting of Adam’s laburnum into its parents, 
by means of bud-variation already described. 
But here the wide range of differentiating char- 
acters of the parents of this most curious hybrid 
fail. The illustrative examples are extremely 
simple, and are limited to the active and inactive 
condition of only one quality. 

An instance is given by the long-leaved vero- 
nica {Veronica longifoUa), which has bluish 
flowers in long spikes. The hybrid between 



Balanced Crosses 


285 


this species and its white variety has a blue 
corolla. But occasionally it produces some 
purely white flowers, showing its power of sep- 
arating the parental heritages, combined in its 
internal structures. This reversion is not com- 
mon, but in thousands of flowering spikes one 
may expect to find at least one of them. Some- 
times it is a whole stem springing from the 
underground system and bearing only white 
flowers on all its spikes. In other instances it 
is only a side branch which reverts and forms 
white flowers on a stem, the other spikes of 
which remain bluish. Sometimes a spike even 
differentiates longitudinally, bearing on one side 
blue and on the other white corollas, and the 
white stripe running over the spike may be seen 
to be long and large, or narrow and short in 
various degrees. In such cases it is evident 
that the heritages of the parents remain un-, 
influenced by each other during the whole life of 
the hybrid, working side by side, but the active 
element always prevails over its latent opponent 
which is ready to break free whenever an oppor- 
tunity is offered. 

It is now generally assumed that this incom- 
plete mixture of the parental qualities in a hy- 
brid, this uncertain and limited combination is 
the true cause of the many deviations, exhibited 
by varietal hybrids when compared with their 



286 


Retrograde Varieties 


parents. Partial departures are rare in the 
hybrids themselves, but in their offspring the 
divergence becomes the rule. 

Segregation seems to be a very difficult pro- 
cess in the vegetative way, but it must be very 
easy in sexual reproduction, indeed so easy as 
to show itself in nearly every single instance. 

Leaving this first generation, the original 
hybrids, we now come to a discussion of their 
offspring. Hybrids should be fertilized either 
by their own pollen, or by that of other individ- 
uals bom from the same cross. Only in this 
case can the offspring be considered as a means 
of arriving at a decision as to the internal na- 
ture of the hybrids themselves. Breeders gen- 
erally prefer to fertilize hybrids with the pollen 
of their parents. But this operation is to be 
considered as a new cross, and consequently is 
wholly excluded from our present discussion. 
Hence it follows that a clear insight into the 
heredity of hybrids may be expected only from 
scientific experiments. Furthermore some of 
the diversity observed as a result of ordinary 
crosses, may be due to the instability of the par- 
ents themselves or at least of one of them, since 
breeders ordinarily ‘choose for their crosses 
some already very variable strain. Combining 
such a strain with the desirable qualities of 
some newly imported species, a new strain may 



BcUanced Crosses 


287 


result, having the new attribute in addition to 
all the variability of the old types. In scientific 
experiments made for the purpose of investi- 
gating the general laws of hybridity, such com- 
plex cases are therefore to be wholly excluded. 
The hereditary purity of the parents must be 
considered as one of the first conditions of 
success. 

Moreover the progeny must be numerous, 
since neither constancy, nor the exact propor- 
tions in the case of instability, can be deter- 
mined with a small lot of plants. 

Finally, and in order to come to a definite 
choice of research material, we should keep in 
mind that the chief object is to ascertain the 
relation of the offspring to their parents. Now 
in nearly all cases the seeds are separated from 
the fruits and from one another, before it be- 
comes possible to judge of their qualities. One 
may open a fruit and count the seeds, but ordi- 
narily nothing is noted as to their characters. 
In this respect no other plant equals the com 
or maize, as the kernels remain together on the 
spike, and as it has more than one variety 
characterized by the color, or constitution, or 
other qualities of the grains. A corn-grain, 
however, is not a seed, but a fruit containing a 
seed. Hence the outer parts pertain to the par- 
ent plant and only the innermost ones to the 



288 


Retrograde Varieties 


seedling and therefore to the following genera- 
tion. Fmit-characters thus do not offer the 
qualities we need, only the qualities resulting 
from fertilizations are characteristic of the new 
generation. Such attributes are afforded in 
some cases by the color, in others by the chem- 
ical constitution. 

We will choose the latter, and take the sugar- 
corn in comparison with the ordinary or starch- 
producing forms for our starting point. Both 
sugar- and starch-coms have smooth fruits when 
ripening. No difference is to be seen in the 
young ripe spikes. Only the taste, or a direct 
chemical analysis might reveal the dissimilar- 
ity. But as soon as the spikes are dried, a 
diversity is apparent. The starchy grains re- 
main smooth, but the sugary kernels lose so 
much water that they become wrinkled. The 
former becomes opaque, the latter more or less 
transparent. Every single kernel may in- 
stantly be recognized as belonging to either of 
the types in question, even if but a single grain 
of the opposite quality might be met with on a 
spike. Kernels can be counted on the spike, 
and since ordinary spikes may bear from 300- 
500 grains and often more, the numerical rela- 
tion of the different types may be deduced with 
great accuracy. 

Coming now to our experiment, both starchy 



Balanced Crosses 


289 


and sugary varieties are in this respect wholly 
constant, when cultivated separately. No 
change is to be seen in the spikes. Further- 
more it is very easy to make the crosses. The 
best way is to cultivate both types in alternate 
rows and to cut off the staminate panicles a few 
days before they open their first flowers. If 
this operation is done on all the individuals of 
one variety, sparing all the panicles of the 
other, it is manifest that all the plants will be- 
come fertilized by the latter, and hence that the 
castrated plants will only bear hybrid seeds. 

The experiment may be made in two ways ; by 
castrating the sugary or the starchy variety. 
In both cases the hybrid kernels are the same. 
As to their composition they repeat the active 
character of the starchy variety. The sugar is 
only accumulated as a result of an incapacity 
of changing it into starch, and the lack of this 
capacity is to be considered as a retrogressive 
varietal mark. The starch-producing unit- 
character, which is active in the ordinary sorts 
of corns, is therefore latent in sugar-corn. 

In order to obtain the second generation, the 
hybrid grains are sown under ordinary condi- 
tions, but sufficiently distant from any other 
variety of com to insure pure fertilization. 
The several individuals may be left to pollinate 



290 Retrograde Varieties 

each other, or they may be artificially pollinated 
with their own pollen. 

The outcome of the experiments is shown by 
the spikes, as soon as they dry. Each spike 
bears two sorts of kernels irregularly dispersed 
over its surface. In this point all the spikes 
are alike. On each of them one may see on the 
first inspection that the majority of the kernels 
are starch-containing seeds, while a minor part 
becomes wrinkled and transparent according to 
the rule for sugary seeds. This fact shows at 
once that the hybrid race is not stable, but has 
differentiated the parental characters, bringing 
those of the varietal parent to perfect purity 
and isolation. Whether the same holds good 
for the starchy parent, it is impossible to judge 
from the inspection of the spikes, since it has 
been seen in the first generation that the hybrid 
kernels are not visibly distinguished from those 
of the pure starch-producing grains. 

It is very easy to count the number of both 
sorts of grains in the spike of such a hybrid. 
In doing so we find, that the proportion is 
nearly the same on all the spikes, and only 
slight variations would be found in hundreds 
of them. One-fourth of the seeds are wrinkled 
and three-fourths are always smooth. The 
number may vary in single instances and be a 
little more or a little less than 25j^, ranging, for 



Balanced Crosses 


291 


instance, from 20 to , but as a rule, the aver- 
age is found nearly equal to 25^. 

The sugary kernels, when separated, from the 
hybrid spikes and sown separately, give rise to 
a pure sugary race, in no degree inferior in 
purity to the original variety. But the starchy 
kernels are of different types, some of them 
being internally like the hybrids of the first 
generation and others like the original parent. 
To decide between these two possibilities, it is 
necessary to examine their progeny. 

For the study of this third hybrid generation 
we will now take another example, the opium- 
poppies. They usually have a dark center in 
the flowers, the inferior parts of the four petals 
being stained a deep purple, or often nearly 
black. Many varieties exhibit this mark as a 
large black cross in the center of the flower. In 
other varieties the pigment is wanting, the cross 
being of a pure white. Obviously it is only re- 
duced to a latent condition, as in so many other 
cases of loss of color, since it reappears in a 
hybrid with the parent-species. 

For my crosses I have taken the dark-centered 
“ Mephisto ” and the “ Danebrog,” or Danish 
flag, with a white cross on a red field. The sec- 
ond year the hybrids were all true to the type of 
“ Mephisto.” From the seeds of each artifi- 
cially self -fertilized capsule, one-fourth (22.5%) 



292 Retrograde Varieties 

in each instance reverted to the varietal mark 
of the white cross, and three-fourths (77.5^) 
retained the dark heart. Once more the flowers 
were self-pollinated and the visits of insects ex- 
cluded. The recessives now gave only reces- 
sives, and hence we may conclude that the varie- 
tal marks had returned to stability. The dark- 
hearted or dominants behaved in two different 
ways. Some of them remained true to their 
type, all their offspring being dark-hearted. 
Evidently they had returned to the parent 
with the active mark, and had reassumed this 
type as purely as the recessives had reached 
theirs. But others kept true to the hybrid char- 
acter of the former generation, repeating in 
their progeny exactly the same mixture as their 
parents, the hybrids of the first generation, had 
given. 

This third generation therefore gives evi- 
dence, that the second though apparently show- 
ing only two types, really consists of three dif- 
ferent groups. Two of them have reassumed 
the stability of their original grandparents, and 
the third has retained the instability of the hy- 
brid parents. 

The question now arises as to the numerical 
relation of these groups. Our experiments 
gave the following results : 



Balanced Crosses 293 


Cross 


Mephisto 


Danebrog 


1. Generation 2. Generation 3. Generation 

100% Mephisto 


All Mephistoc 


f77.5% Dorn. 




22.5% Recess. 


9- all hybrids with 
83-68% domi- 
nants and 17- 
32% recessives. 

100% Dane- 
brog. 


Examining these figures we find one-fourth of 
constant recessives, as has already been said, 
further one-fourth of constant dominants, and 
the rest or one half as unstable hybrids. Both 
of the pure groups have therefore reappeared 
in the same numbers. Calling A the specimens 
with the pure active mark, L those with the la- 
tent mark, and H the hybrids, these proportions 
may be expressed as follows : 

This simple law for the constitution of the sec- 
ond generation of varietal hybrids with a single 
differentiating mark in their parents is called 
the law of Mendel. Mendel published it in 
1865, but his paper remained nearly unknown 
to scientific hybridists. It is only of late years 
that it has assumed a high place in scientific 
literature, and attained the first rank as an in- 
vestigation on fundamental questions of hered- 



294 


Retrograde Varieties 


ity. Bead in the light of modern ideas on nnit- 
characters it is now one of the most important 
works on heredity and has already widespread 
and abiding influence on the philosophy of hy- 
bridism in general. 

But from its very nature and from the choice 
of the material made by Mendel, it is restricted 
to balanced or varietal crosses. It assumes 
pairs of characters and calls the active unit of 
the pair dominant, and the latent recessive, 
without further investigations of the question 
of latency. It was worked out by Mendel for a 
large group of varieties of peas, but it holds 
good, with only apparent exceptions, for a wide 
range of cases of crosses of varietal characters. 
Recently many instances have been tested, and 
even in many cases third and later generations 
have been counted, and whenever the evidence 
was complete enough to be trusted, Mendel’s 
prophecy has been found to be right. 

According to this law of Mendel’s the pairs 
of antagonistic characters in the hybrid split up 
in their progeny, some individuals reverting to 
the pure parental types, some crossing with 
each other anew, and so giving rise to a new 
generation of hybrids. Mendel has given a 
very suggestive and simple explanation of his 
formula. Putting this in the terminology of 
to-day, and limiting it to the occurrence of only 



Balanced Crosses 


295 


one differential nnit in the parents, we may 
give it in the following manner. In fertiliza- 
tion, the characters of both parents are not uni- 
formly mixed, but remain separated though 
most intimately combined in the hybrid 
throughout life. They are so combined as to 
work together nearly always, and to have nearly 
equal influence on all the processes of the whole 
individual evolution. But when the time ar- 
rives to produce progeny, or rather to produce 
the sexual cells through the combination of 
which the offspring arises, the two parental 
characters leave each other, and enter sepa- 
rately into the sexual cells. From this it may be 
seen that one-half of the pollen-cells will have 
the quality of one parent, and the other the qual- 
ity of the other. And the same holds good for 
the egg-cells. Obviously the qualities lie latent 
in the pollen and in the egg, but ready to be 
evolved after fertilization has taken place. 

Granting these premises, we may now ask as 
to the results of the fertilization of hybrids, 
when this is brought about by their own pollen. 
We assume that numerous pollen grains fer- 
tilize numerous egg cells. This assumption at 
once allows of applying the law of probability, 
and to infer that of each kind of pollen grains 
one-half will reach egg-cells with the same qual- 



296 Retrograde Varieties 

ity and the other half ovules with the opposite 
character. 

Calling P pollen and O ovules, and represent- 
ing the active mark by P and 0, the latent qual- 
ities by P' and O', they would combine as fol- 
lows: 

P + O giving nniform pairs with the active mark, 

P + O' giving unequal pairs, 

P' + O giving unequal pairs, 

P' + O' giving uniform pairs with the latent mark. 

In this combination the four groups are ob- 
viously of the same size, each containing one- 
fourth of the offspring. Manifestly they corre- 
spond exactly to the direct results of the 
experiments, P O representing the indi- 
viduals which reverted to the specific mark, 
P'-j-O' those who reassumed the varietal 
quality and P-|-0' and P-f-0' those who hybrid- 
ized for the second time. These considerations 
lead us to the following form of Mendel’s 
formula : 

P + O = l/4-Active or 1 A, 

P + O') 

p* + O 1 ~ 1/2-Hybrid or 2 H, 

P' + O' =l/4-Latent or IL, 

Which is evidently the same as Mendel’s 
eiHpirical law given above. 

To give the proof of these assumptions Men- 
del has devised a very simple crossing experi- 



Balanced Crosses 


297 


ment, which he has effected with his varieties of 
peas. I have repeated it with the sugar-corn, 
which gives far better material for demonstra- 
tion. It starts from the inference that if dissim- 
ilarity among the pollen grains is excluded, the 
diversity of the ovules must at once become 
manifest and vice versa. In other terms, if a 
hybrid of the first generation is not allowed to 
fertilize itself, but is pollinated by one of its 
parents, the result will be in accordance with the 
Mendelian formula. 

In order to see an effect on the spikes pro- 
duced in this way, it is of course necessary to 
fertilize them with the pollen of the variety, 
and not with that of the specific type. The 
latter would give partly pure starchy grains 
and partly hybrid kernels, but these would 
assume the same type. But if we pollinate the 
hybrid with pollen of a pure sugar-corn, we 
may predict the result as follows. 

If the spike of the hybrid contains dormant 
paternal marks in one-half of its flowers and in 
the other half maternal latent qualities, the 
sugar-corn pollen will combine with one-half of 
the ovules to give hybrids, and with the other 
half so as to give pure sugar-grains. Hence 
we see that it will be possible to count out direct- 
ly the two groups of ovules on inspecting the 
ripe and dry spikes. Experience teaches us 



298 


Retrograde Varieties 


that both are present, and in nearly equal num- 
bers; one-half of the grains remaining smooth, 
and the other half becoming wrinkled. 

The corresponding experiment could be made 
with plants of a pure sugar-race by pollination 
with hybrid pollen. The spikes would show ex- 
actly the same mixture as in the above case, but 
now this may be considered as conclusive proof 
that half the pollen-grains represent the quality 
of one parent and the other half the quality of 
the other. 

Another corollary of Mendel’s law is the fol- 
lowing. In each generation two groups return 
to purity, and one-half remains hybrid. These 
last will repeat the same phenomenon of split- 
ting in their progeny, and it is easily seen 
that the same rule will hold good for all succeed- 
ing generations. According to Mendel’s prin- 
ciple, in each year there is a new hybridization, 
differing in no respect from the first and 
original one. If the hybrids only are propa- 
gated, each year will show one-fourth of the 
offspring returning to the specific character, 
one-fourth assuming the type of the variety and 
one-half remaining hybrid. I have tested this 
with a hybrid between the ordinary nightshade 
with black berries, and its variety, Solanum 
nigrum chlorocarpum, with pale yellow fruits. 

Eight generations of the hybrids were culti- 



BcAanced Crosses 


299 


vated, disregardmg always the reverting off- 
spring. At the end I counted the progeny of 
the sixth and seventh generations and found 
figures for their three groups of descendants, 
which exactly correspond to Mendel’s formula. 

Until now we have limited ourselves to the 
consideration of single differentiating units. 
This discussion gives a clear insight into the 
fundamental phenomena of hybrid fertilization. 
It at once shows the correctness of the assump- 
tion of unit-characters, and of their pairing in 
the sexual combinations. 

But Mendel’s law is not at all restricted to 
these simple cases. Quite on the contrary, it 
explains the most intricate questions of hybrid- 
ization, providing they do not transgress the 
limits of symmetrical unions. But in this realm 
nearly all results may be calculated beforehand, 
on the ground of the principle of probability. 
Only one more assumption need be discussed. 
The several pairs of antagonistic characters 
must he independent from, and uninfluenced by, 
one another. This premise seems to hold good 
in the vast majority of cases, though rare excep- 
tions seem to be not entirely wanting. Hence 
the necessity of taking all predictions from Men- 
del ’s law only as probabilities, which will prove 
true in most, but not necessarily in all cases. 



300 Retrograde Varieties 

But here we will limit ourselves to normal 
cases. 

The first example to be considered is obvious- 
ly the assumption that the parents of a cross 
differ from each other in respect to two charac- 
ters. A good illustrative example is afforded 
by the thorn-apple. I have crossed the blue- 
flowered thorny form, usually known as Datura 
Tatula, with the white thornless type, desig- 
nated as D. Stramonium inermis. Thorns and 
blue pigment are obviously active qualities, as 
they are dominant in the hybrids. In the 
second generation both pairs of characters are 
resolved into their constituents and paired anew 
according to Mendel’s law. After isolating my 
hybrids during the period of flowering, I counted 
among their progeny: 

128 individuals with blue flowers and thorns 


47 


tf ft 

** without 

54 

u 

** white 

“ and 

21 

(( 

ft ft 

“ without 

250 





The significance of these numbers may easily 
be seen, when we calculate what was to be ex- 
pected on the assumption that both characters 
follow Mendel’s law, and that both are inde- 
pendent from each other. Then we would have 
three-fourths blue offspring and one-fourth in- 
dividuals with white flowers. Each of these 



Balanced Crosses 


301 


two groups would consist of thom-bearing and 
thornless plants, in the same numerical relation. 
Thus, we come to the four groups observed in 
our experiment, and are able to calculate their 
relative size in the following way : 


Proportion 

Blue with thorns 3/4 X 3/4 = 9/16 = 66.26% 9 

Blue, unarmed 3/4X1/4 = 3/16 = 18.75% 3 

White with thorns 1/4 X 3/4 = 3/16 = 18.76% 3 

White, unarmed 1/4X1/4=1/16= 6.26% 1 


In order to compare this inference from Men- 
del ’s law and the assumption of independency, 
with the results of our experiments, we must cal- 
culate the figures of the latter in percentages. 
In this way we find : 

Found. Calculated. 

Blue with thorns 128 = 61% 66.25% 

Blue unarmed 47 = 19% 18.75% 

White with thorns. ... 64 = 22% 18.75% 

White unarmed 21= 8% 6.25% 

The agreement of the experimental and the 
theoretical figures is as close as might be 
expected. 

This experiment is to be considered only as 
an illustrative example of a rule of wide appli- 
cation. The rule obviously will hold good in 
all such cases as comply with the two conditions 
already premised, viz. : that each character 
agrees with Mendel’s law, and that both are 
wholly independent of each other. It is 
clear that our figures show the numerical com- 



302 Retrograde Varieties 

position of the hybrid offspring for any single 
instance, irrespective of the morphological 
nature of the qualities involved. 

Mendel has proved the correctness of these 
deductions by his experiments with peas, and 
by combining their color (yellow or green) with 
the chemical composition (starch or sugar) and 
other pairs of characters. I will now give two 
further illustrations afforded by crosses of the 
ordinary campion. I used the red-flowered or 
day-campion, which is a perennial herb, and a 
smooth variety of the white evening-campion, 
which flowers as a rule in the first summer. 
The combination of flower-color and pubescence 
gave the following composition for the second 
hybrid generation: 


Number 

7o 

Calculation 

Hairy and red 

. 70 

44 

50.26% 

Hairy and white . . . 

. 23 

14 

18.76% 

Smooth and red 

. 46 

23 

18.75% 

Smooth and white . . . 

. 19 

12 

8.25% 

For the combination of pubescence and the 

capacity of flowering 

in the first year I found ; 

Number 

% 

Calculated 

Hairy, flowering 

. 286 

52 

66.26% 

Hairy, without stem. 

. 128 

23 

18.76% 

Smooth, flowering. . . 

. 96 

17 

18.76% 

Smooth, without stem 42 

8 

6.26% 

Many other cases 

have been 

tested by dif- 


ferent writers and the general result is the 



Balanced Crosses 


303 


applicability of Mendel’s formula to all cases 
complying with the given conditions. 

Intentionally I have chosen for the last ex- 
ample two pairs of antagonisms, relating to 
the same pair of plants, and which may he 
tested in one experiment and combined in one 
calculation. 

For the latter we need only assume the same 
conditions as mentioned before, but now for 
three different qualities. It is easily seen that 
the third quality would split each of our four 
groups into two smaller ones in the proportion 
of 34 :14. 

We would then get eight groups of the follow- 
ing composition: 

9/16 X 3/4 = 27/64 or 42.2% 

9/16X1/4= 9/64“ 14,1% 

3/16 X 3/4 = 9/64 “ 14.1% 

3/16 X 1/4 = 3/64 “ 4.7% 

3/16X3/4= 9/64 “ 14.1% 

3/16 X 1/4 = 3/64 “ 4.7% 

1/16X3/4= 3/64 “ 4.7% 

1/16X1/4= 1/64 “ 1.6% 

The characters chosen for our experiment in- 
clude the absence of stem and flowers in the 
first year, and therefore would require a second 
year to determine the flower-color on the per- 
ennial specimens. Instead of doing so I have 
taken another character, shown by the teeth of 
the capsules when opening. These curve out- 



304 Retrograde Varieties 

wards in the red campion, but lack this capacity 
in the evening-campion, diverging only until an 
upright position is reached. The combination 
of hairs, colors and teeth gives eight groups, 
and the counting of their respective numbers of 
individuals gave the following result: 


Teeth 


Hairs 

Flowers 

of capsules 

Number 

% 

Calculated 

Hairy 

red 

curved 

91 

47 

42.2% 

Hairy 

red 

straight 

15 

7.5 

14.1% 

Hairy 

white 

curved 

23 

12 

14.1% 

Hairy 

white 

straight 

17 

8.5 

4.7% 

Smooth 

red 

curved 

23 

12 

14.1% 

Smooth 

red 

straight 

9 

4.5 

4.7% 

Smooth 

white 

curved 

5 

2.5 

4.7% 

Smooth 

white 

straight 

12 

6 

1.6% 


The agreement is as comprehensive as might 
be expected from an experiment with about 200 
plants, and there can be no doubt that a repeti- 
tion on a larger scale would give still closer 
agreement. 

In the same way we might proceed to crosses 
with four or more differentiating characters. 
But each new character will double the number 
of the groups. Four characters will combine 
into 16 groups, five into 32, six into 64, seven 
into 128, etc. Hence it is easily seen that tlie 
size of the experiments must be made larger 
and larger in the same ratio, if we intend to 
expect numbers equally trustworthy. For 



Balanced Crosses 


305 


seven differentiating marks 16,384 individuals 
are required for a complete series. And in 
this set the group with the seven attributes all 
in a latent condition would contain only a 
single individual. 

Unfortunately the practical value of these 
calculations is not very great. They indicate 
the size of the cultures required to get all the 
possible combinations, and show that in ordi- 
nary cases many thousands of individuals have 
to he cultivated, in order to exhaust the whole 
range of possibilities. They further show that 
among all these thousands, only very few are 
constant in all their characters ; in fact, it may 
easily be seen that with seven differentiating 
points among the 16,384 named above, only one 
individual will have all the seven qualities in 
pure active, and only one will have them all in a 
purely dormant condition. Then there will be 
some with some attributes active and others 
latent, but their numbers will also be very small. 
All others will split up in the succeeding genera- 
tion in regard to one or more of their appar- 
ently active marks. And since only in very 
rare cases the stable hybrids can be distin- 
guished by external characters from the un- 
stable ones, the stability of each individual 
bearing a desired combination of characters 
would have to be established by experiment 



306 Retrograde Varieties 

after pure fertilization. MendePs law teaches 
us to predict the difficulties, but hardly shows 
any way to avoid them. It lays great stress on 
the old prescript of isolation and pure fertiliza- 
tion, but it will have to be worked out and ap- 
plied to a large number of practical cases before 
it will gain a preeminent influence in horticul- 
tural practice. 

Or, as Bailey states it, we are only beginning 
to find a pathway through the bewildering maze 
of hybridization. 

This pathway is to be laid out with regard to 
the following considerations. We are not to 
cross species or varieties, or even accidental 
plants. We must cross unit-characters, and 
consider the plants only as the bearers of these 
units. We may assume that these units are 
represented in the hereditary substance of the 
cell-nucleus by definite bodies of too small a size 
to be seen, but constituting together the chromo- 
somes. We may call these innermost repre- 
sentatives of the unit-characters pangenes, in 
accordance with Darwin’s hypothesis of pan- 
genesis, or give them any other name, or we may 
even wholly abstain from such theoretical dis- 
cussion, and limit ourselves to the conception of 
the visible character-units. These units then 
may be present, or lacking and in the first case 
active, or latent. 



Balanced Crosses 


307 


True elementary species differ from each 
other in a number of unit-characters, which do 
not contrast. They have arisen by progressive 
mutation. One species has one kind of unit, 
another species has another kind. On com- 
bining these, there can be no interchange. 
Mendelism assumes such an interchange be- 
tween units of the same character, but in a 
different condition. Activity and latency are 
such conditions, and therefore Mendel’s law 
obviously applies to them. They require pairs 
of antagonistic qualities, and have no connec- 
tion whatever with those qualities which do not 
find an opponent in the other parent. Now, 
only pure varieties afford such pure conditions. 
When undergoing further modifications, some 
of them may be in the progressive line and 
others in the retrogressive. -Progressive modi- 
fications give new units, which are not in con- 
trast with any other, retrograde changes turn 
active units into the latent condition and so give 
rise to pairs. Ordinary species generally 
originate in this way, and hence differ from 
each other partly in specific, partly in varietal 
characters. As to the first, they give in their 
hybrids stable peculiarities, while as to the 
latter, they split up according to Mendel’s law. 

Unpaired or unbalanced characters lie side by 
side with paired or balanced qualities, and they 



308 Retrograde Varieties 

do so in nearly all the crosses made for prac- 
tical purposes, and in very many scientific ex- 
periments. Even Mendel’s peas were not pure 
in this respect, much less do the campions noted 
above differ only in Mendelian characters. 

Comparative and systematic studies must be 
made to ascertain the true nature of every unit 
in every single plant, and crossing experiments 
must be based on these distinctions in order to 
decide what laws are applicable in any case. 



D. EVER-SPOETING VARIETIES 


Lectube XI 

STRIPED FLOWERS 

Terminology is an awkward thing. It is as 
disagreeable to be compelled to make new 
names, as to be constrained to use the old 
faulty ones. Different readers may associate 
different ideas with the same terms, and unfor- 
tunately this is the case with much of the 
terminology of the science of heredity and 
variability. What are species and what are 
varieties? How many different conceptions 
are conveyed by the terms constancy and varia- 
bility? We are compelled to use them, but we 
are not at all sure that we are rightly under- 
stood when we do so. 

Gradually new terms arise and make their 
way. They have a more limited applicability 
than the old ones, and are more narrowly cir- 
cumscribed. They are not to supplant the older 
terms, but permit their use in a more general 
way. 



310 Ever-sporting Varieties 

One of these doubtful terms is the word sport. 
It often means bud-variation, while in other 
cases it conveys the same idea as the old botan- 
ical term of mutation. But then all sorts of 
seemingly sudden variations are occasionally 
designated by the same term by one writer or 
another, and even accidental anomalies, such as 
teratological ascidia, are often said to arise by 
sports. 

If we compare all these different conceptions, 
we will find that their most general feature is 
the suddenness and the rarity of the phenom- 
enon. They convey the idea of something un- 
expected, something not always or not regularly 
occurring. But even “this demarcation is not 
universal, and there are processes that are reg- 
ularly repeated and nevertheless are called 
sports. These at least should be designated by 
another name. 

In order to avoid confusion as far as possible, 
with the least change in existing terminology, 
I shall use the term “ ever-sporting varieties ** 
for such forms as are regularly propagated by 
seed,s ;^nd of pure and not hybrid origin, but 
which d)^rt in nearly every generation. The 
term is a new one, but the facts are for the most 
part new, and require to be considered in 
a new light Its meaning will become clearer 
at once when the illustrations afforded by 



striped Flowers 


311 


striped flowers are introduced. In the follow- 
ing discussion it will be found most convenient 
to give a summary of what is known concerning 
them, and follow this by a consideration of the 
detailed evidence obtained experimentally, 
which supports the usage cited. 

, The striped variety of the larkspur of our 
gardens is known to produce monochromatic 
flowers, in addition to striped ones. They may 
be borne by the same racemes, or on different 
branches, or some seedlings from the same 
parent-plant may bear monochromatic flow- 
ers while others may be striped. Such devia- 
tions are usually called sports. But they occur 
yearly and regularly and may be observed in- 
variably when the cultures are large enough. 
Such a variety I shall call “ ever-sporting.” 

The striped larkspur is one of the oldest gar- 
den varieties. It has kept its capacity of 
sporting through centuries, and therefore may 
in some sense be said to be quite stable. Its 
changes are limited to a rather narrow circle, 
and this circle is as constant as the peculiari- 
ties of any other constant species or variety. 
But within this circle it is always changing 
from small stripes to broad streaks, and from 
them to pure colors. Here the variability is a 
thing of absolute constancy, while the constancy 
consists in eternal changes! Such apparent 



312 Ever-sporting Varieties 

contradictions are unavoidable, when we ap- 
ply the old term to such unusual though not 
at all new cases. Combining the stability and 
the qualities of sports in one word, we may evi- 
dently best express it by the new term of ever- 
sporting variety. 

We will now discuss the exact nature of such 
varieties, and of the laws of heredity which 
govern them. But before doing so, I might 
point out, that this new type is a very common 
one. It embraces most of the so-called variable 
types in horticulture, and besides these a wide 
range of anomalies. 

Every ever-sporting variety has at least two 
different types, around and between which it 
varies in numerous grades, but to which it is 
absolutely limited. Variegated leaves fluctuate 
between green and white, or green and yellow, 
and display these colors in nearly all possible 
patterns. But there variability ends, and even 
the patterns are ordinarily narrowly prescribed 
in the single varieties. Double flowers afford 
a similar instance. On one side the single type, 
on the other the nearly wholly double model are 
the extreme limits, between which the variabil- 
ity is conflned. So it is also with monstrosities. 
The race consists of anomalous and normal in- 
dividuals, and displays between them all possi- 
ble combinations of normal and monstrous 



Striped Flowers 


313 


parts. But its variability is restricted to this 
group. And large as the group may seem on 
first inspection, it is in reality very narrow. 
Many monstrosities, such as fasciated branch- 
es, pitchers, split leaves, peloric flowers, and 
others constitute such ever-sporting varieties, 
repeating their anomalies year by year and gen- 
eration after generation, changing as much as 
possible, but remaining absolutely true within 
their limits as long as the variety exists. 

It must be a very curious combination of the 
unit-characters which causes such a state of 
continuous variability. The pure quality of the 
species must be combined with the peculiarity 
of the variety in such a way, that the one ex- 
cludes the other, or modifies it to some extent, 
although both never fully display themselves 
in the same part of the same plant. A corolla 
cannot be at once monochromatic and striped, 
nor can the same part of a stem be twisted and 
straight. But neighboring organs may show 
the opposite attributes side by side. 

In order to look closer into the real mechan- 
ism of this form of variability, and of this con- 
stant tendency to occasional reversions, it will 
be best to limit ourselves first to a single case, 
and to try to gather all the evidence, which 
can be obtained by an examination of the he- 
reditary relations of its sundry constituents. 



314 


Ever-sporting Varieties 


This may best be done by detennining the de- 
gree of inheritance for the various constituents 
of the race during a series of years. It is only 
necessary to apply the two precautions of ex- 
cluding all cross-fertilization, and of gathering 
the seeds of each individual separately. We do 
not need to ascertain whether the variety as 
such is permanent; this is already clear from 
the simple fact of its antiquity in so many 
cases. We wish to learn what part each in- 
dividual, or each group of individuals with 
similar characters, play in the common line 
of inheritance. In other words, we must 
build up a genealogical tree, embracing several 
generations and a complete set of the single 
cases occurring within the variety, in order to 
allow of its being considered as a part of the 
genealogy of the whole. It should convey to us 
an idea of the hereditary relations during the 
life-time of the variety. 

It is manifest that the construction of such 
a genealogical tree requires a number of sepa- 
rate experiments. These should be extended 
over a series of years. Each should include a 
number of individuals large enough to allow 
the determination of the proportion of the dif- 
ferent types among the offspring of a single 
plant. A species which is easily fertilized by 
its own pollen, and which bears capsules with 



striped Flowers 


315 


large quantities of seeds, obviously affords the 
best opportunities. As such, I have chosen the 
conunon snapdragon of the gardens, Antirrhi- 
num majus. It has many striped varieties, 
some tall, others of middle height, or of dwarfed 
stature. In some the ground-color of the flow- 
ers is yellow, in others it is white, the yellow 
disappearing, with the exception of a large 
mark in the throat. On these ground-colors the 
red pigment is seen lying in streaks of pure car- 
mine, with white intervals where the yellow 
fails, but combined with yellow to make a fiery 
red, and with yellow intervals when that color 
is present. This yellow color is quite constant 
and does not vary in any marked degree, not- 
withstanding the fact that it seems to make 
narrower and broader stripes, according to the 
parts of the corolla left free by the red pig- 
ment. But it is easily seen that this appearance 
is only a fallacious one. 

The variety of snapdragon chosen was of me- 
dium height and with the yellow ground-color, 
and is known by horticulturists as A. majus 
luteum rubro-striatum. As the yellow tinge 
showed itself to be invariable, I may limit my 
description to the red stripes. 

Some flowers of this race are striped, others 
are not. On a hasty survey there seem to be 
three types, pure yellow, pure Ved, and stripes 



316 Ever-sporting Varieties 

with all their intermediate links of narrower 
and broader, fewer and more numerous streaks. 
But on a close inspection one does not succeed 
in finding pure yellow racemes. Little lines of 
red may be found on nearly every flower. They 
are the extreme type on this side of the range 
of variability. From them an almost endless 
range of patterns passes over to the broadest 
stripes and even to whole sections of a pure red. 
But then, between these and the wholly red 
flowers we observe a gap, which may be narrow- 
er by the choice of numerous broad striped in- 
dividuals, but which is never wholly filled up. 
Hence we see that the red flowers are a separate 
type within the striped variety. 

This red type springs yearly from the striped 
form, and yearly reverts to it. This is what in 
the usual descriptions of this snapdragon, is 
called its sporting. The breadth of the streaks 
is considered to be an ordinary case of varia- 
bility, but the red flowers appear suddenly, with- 
out the expected links. Therefore they are to 
be considered as sports. Similarly the red 
forms may suddenly produce striped ones, and 
this too is to be taken as a sport, according to 
the usual conception of the word. 

Such sports may occur in different ways. 
Either by seeds, or by buds, or even within 
the single spikes. Both opposite reversions. 



striped Flowers 


317 


from striped to red and from red to stripes, oc- 
cur by seed, even by the strictest exclusion of 
cross-fertilization. As far as my experiments 
go, they are the rule, and parent-plants that 
do not give such reversions, at least in some of 
their offspring, are very rare, if not wholly 
wanting. Bud-variations and variations within 
the spike I have as yet only observed on the 
striped individuals, and never on the red ones, 
though I am confident that they might appear in 
larger series of experiments. Both cases are 
more common on individuals with broad stripes 
than on plants bearing only the narrower red 
lines, as might be expected, but even on the al- 
most purely yellow individuals they may be seen 
from time to time. Bud-variations produce 
branches with spikes of uniform red fiowers. 
Every bud of the plant seems to have equal 
chances to be transformed in this way. Some 
striped racemes bear a few red flowers, which 
ordinarily are inserted on one side of the spike 
only. As they often cover a sharply defined 
section of the raceme, this circumstance has 
given rise to the term of sectional variability to 
cover such cases. Sometimes the section is 
demarcated on the axis of the flower-spike by a 
brownish or reddish color, sharply contrasting 
with the green hue of the remaining parts. 

Sectional variation may be looked at as a 



318 Ever-sporting Varieties 

special type of bud-variation, and from this 
point of view we may simplify our inquiry and 
limit ourselves to the inheritance of three types, 
the striped plants, the red plants and the red 
asexual variants of the striped individuals. In 
each case the heredity should be observed not 
only for one, but at least for two successive 
generations. 

Leaving these introductory remarks I now 
come at once to the genealogical tree, as it may 
be deduced from my experiments : 



This experiment was begun in the year 1892 
with one individual out of a large lot of striped 
plants grown from seeds which I had purchased 
from a firm in Erfurt. The capsules were gath- 
ered separately from this individual and about 
40 flowering plants were obtained from the 
seeds in the following year. Most of them had 
neatly striped flowers, some displayed broader 
stripes and spare flowers were seen with one- 



Striped Flowers 


319 


half wholly red. Four individuals were found 
with only uniform red flowers. These were iso- 
lated and artificially pollinated, and the same 
was done with some of the best striped indi- 
viduals. The seeds from every parent were 
sown separately, so as to allow the determina- 
tion of the proportion of uniform red individ- 
uals in the progeny. 

Neither group was constant in its off- 
spring. But as might be expected, the type 
of the parent plant prevailed in both groups, 
and more strongly so in the instances with 
the striped, than with the red ones. Or, in 
other words seed-reversions were more numer- 
ous among the already reverted reds than 
among the striped type itself. I counted 2% 
reversion in the latter case, but 24% from the 
red parents. 

Among the striped plants from the striped 
parents, I found some that produced bud- 
variations. I succeeded in isolating these red 
flowering branches in paper bags and in polli- 
nating them with their own pollen, and subjected 
the striped spikes of the same individuals to a 
similar treatment. Three individuals gave a 
sufficient harvest from both types, and these 
six lots of seeds were sown separately. The 
striped flowers repeated their character in 98^ 
of their offspring, the red twigs in only 71j^, the 



320 Ever-sporting Varieties 

remaining individuals sporting into the oppo- 
site gronp. 

In the following year I continued the experi- 
ment with the seeds of the offspring of the red 
bud-variations. The striped individuals gave 
95J^, but in the red ones only 84j< of the progeny 
remained true to the parent type. 

From these figures it is manifest that the 
red and striped types differ from one another 
not only in their visible attributes, but also in 
the degree of their heredity. The striped in- 
dividuals repeat their peculiarity in 90 - 98}^ of 
their progeny, 2 - lOj^ sporting into the uniform 
red color. On the other hand the red individ- 
uals are constant in 71 - 84j^ of their offspring, 
while 16-29% go over to the striped type. Or, 
briefly, both types are inherited to a high degree, 
but the striped type is more strictly inherited 
than the red one. 

Moreover the figures show that the degree of 
inheritance is not contingent upon the question 
as to how the sport may have arisen. Bud- 
sports show the same degree of inheritance as 
seed-sports. Sexual and asexual variability 
therefore seem to be one and the same process 
in this instance. But the deeper meaning of 
this and other special features of our genealog- 
ical tree are still awaiting further investigation. 
It seems that much important evidence might 



striped Flowers 


321 


come from an extension of this line of work. 
Perhaps it might even throw some light on 
the intimate nature of the bud-variations of 
ever-sporting varieties in general. Sectional 
variations remain to be tested as to the degree 
of inheritance exhibited, and the different occur- 
rences as to the breadth of the streaks require 
similar treatment. 

In ordinary horticultural practice it is desir- 
able to give some guarantee as to what may be 
expected to come from the seeds of brightly 
striped flowers. Neither the pure red type, 
nor the nearly yellow racemes are the object 
of the culture, as both of them may be had pure 
from their own separate varieties. In order 
to insure proper striping, both extremes are 
usually rejected and should be rooted out as 
soon as the flowering period begins. Simi- 
larly the broad-striped ones should be re- 
jected, as they give a too large amount of uni- 
form red flowers. Clearly, but not broadly 
striped individuals always yield the most reli- 
able seed. 

Summing up once more the results of our ped- 
igree-experiment, we may assert that the striped 
variety of the snapdragon is wholly permanent, 
including the two opposite types of uniform 
color and of stripes. It must have been so since 
it first originated from the invariable uniform 



322 Ever-sporting Varieties 

varieties, about the middle of the last century, 
in the nursery of Messrs. Vilmorin, and prob- 
ably it will remain so as long as popular taste 
supports its cultivation. It has never been ob- 
served to trangress its limits or to sport into 
varieties without reversions or sports. It fluc- 
tuates from one extreme to the other yearly, al- 
ways recurring in the following year, or even in 
the same summer by single buds. Highly va- 
riable within its limits, it is absolutely constant 
or permanent, when considered as a definite 
group. 

Similar cases occur not rarely among culti- 
vated plants. In the wild state they seem to 
be wholly wanting. Neither are they met with 
as occasional anomalies nor as distinct varie- 
ties. On the contrary, many garden-flowers 
that are colored in the species, and besides this 
have a white or yellow variety, have also 
striped sorts. The oldest instance is probably 
the marvel of Peru, Mirabilis Jalappa, which 
already had more than one striped variety at 
the time of its introduction from Peru into the 
European gardens, about the beginning of the 
seventeenth century. Stocks, liver-leaf {Ee- 
patica), dame’s violet {Hesperis), Sweet Wil- 
liam (Dianthus barbatus), and periwinkles 
(Vinca minor) seem to be in the same condition, 
as their striped varieties were already quoted 



striped Flowers 


323 


by the writers of the same century. . Tulips, hy- 
acinths, Cyclamen, Azalea, Camellia, and even 
such types of garden-plants as the meadow 
crane’s-bill {Geranium pratense) have striped 
varieties. It is always the red or blue color 
which occurs in stripes, the underlying ground 
being white or yellow, according to the presence 
or absence of the yellow in the original color- 
mixture. 

All these varieties are known to be perma- 
nent, coming true during long series of 
successive generations. But very little is known 
concerning the more minute details of their he- 
reditary qualities. They come from seed, when 
this is taken from striped individuals, and 
thence revert from time to time to the corre- 
sponding monochromatic type. But whether 
they would do so when self-fertilized, and 
whether the reversionary individuals are al- 
ways bound to return towards the center of the 
group or towards the opposite limit, remains to 
be investigated. Presumably there is nowhere 
a real transgression of the limits, and never or 
only very rarely and at long intervals of time a 
true production of another race with other he- 
reditary qualities. 

In order to satisfy myself on these points, I 
made some pedigree-cultures with the striped 
forms of dame’s violet (Hesperis matronalis) 



324 Ever-sporting Varieties 

and of Clarkia pulehella. Both of them are 
ever-sporting varieties. The experiments were 
conducted during five generations with the vi- 
olet, and during four with the striped Clarkia, 
including the progeny of the striped and of the 
monochromatic red offspring of a primitive 
striped plant I need not give the figures here 
for the numerical relations between the differ- 
ent types of each group, and shall limit myself 
to the statement that they behaved in exactly 
the same manner as the snapdragon. 

It is worth while to dwell a moment on the 
capacity of the individuals with red flowers to 
reproduce the striped type among their off- 
spring. For it is manifest that this latter qual- 
ity must have lain dormant in them during their 
whole life. Darwin has already pointed out 
that when a character of a grandparent, which 
is wanting in the progeny, reappears in the sec- 
ond generation, this quality must always be 
assumed to have been present though latent in 
the intermediate generation. To the many in- 
stances given by him of such alternative inher- 
itance, the monochromatic reversionists of the 
striped varieties are to be added as a new type. 
It is moreover, a very suggestive type, since the 
latency is manifestly of quite another character 
than for instance in the case of Mendelian hy- 
brids, and probably more allied to those in- 



striped Flowers 


325 


stances, where secondary sexual marks, which 
are as a rule only evolved by one sex, are trans- 
ferred to the offspring through the other. 

Stripes are by no means limited to flowers. 
They may affect the whole foliage, or the fruits 
and the seeds, and even the roots. But all such 
cases occur much more rarely than the striped 
flowers. An interesting instance of striped 
roots is afforded by radishes. White and red 
varieties of different shapes are cultivated. 
Besides them sometimes a curious motley sort 
may be seen in the markets, which is white with 
red spots, which are few and narrow in some 
samples, and more numerous and broader in 
others. But what is very peculiar and striking 
is the circumstance, that these stripes do not 
extend in a longitudinal, but in a transverse 
direction. Obviously this must be the effect of 
the very notable growth in thickness. Assum- 
ing that the colored regions were small in 
the beginning, they must have been drawn out 
during the process of thickening of the root, and 
changed into transverse lines. Barely a streak 
may have had its greatest extension in a trans- 
verse direction from the beginning, in which 
case it would only be broadened and not defi- 
nitely changed in its direction. 

This variety being a very fine one, and more 
agreeable to the eye than the uniform colors, is 



326 Ever-sporting Varieties 

being more largely cultivated in some countries. 
It has one great drawback: it never comes 
wholly true from seed. It may be grown in 
full isolation, and carefully selected, all red or 
nearly monochromatic samples being rooted out 
long before blooming, but nevertheless the seed 
will always produce some red roots. The most 
careful selection, pursued through a number 
of years, has not been sufficient to get rid of 
this regular occurrence of reversionary individ- 
uals. Seed-growers receive many complaints 
from their clients on this account, but they are 
not able to remove the difficulty. This experi- 
ence is in full agreement with the experimental 
evidence given by the snapdragon, and it would 
certainly be very interesting to make a complete 
pedigree-culture with the radishes to test 
definitely their compliance with the rules ob- 
served for striped flowers. 

Horticulturists in such cases are in the habit 
of limiting themselves to the sale of so-called 
mixed seeds. From these no client expects pu- 
rity, and the normal and hereditary diversity 
of lypes is here in some sense concealed under 
the impurities included in the mixture from 
lack of selection. Such cases invite scrutiny, 
and would, no doubt, with the methods of isola- 
tion, artificial pollination, and the sowing of 
the seeds separately from each parent, yield 



striped Flowers 


327 


results of great scientific value. Any one who 
has a garden, and sufficient perseverance to 
make pure cultures during a series of years 
might make important contributions to scien- 
tific knowledge in this way. 

Choice might he made from among a wide 
range of different types. A variety of com 
called “ Harlequin ” shows stripes on its ker- 
nels, and one ear may offer nearly white and 
nearly red seeds and all the possible interme- 
diate steps between them. From these seeds 
the next generation will repeat the motley ears, 
but some specimens will produce ears of uniform 
kernels of a dark purple, showing thus the or- 
dinary way of reversion. Some varieties of 
beans have spotted seeds, and among a lot of 
them one may be sure to find some purely red 
ones. It remains to be investigated what will 
be their offspring, and whether they are due to 
partial or to individual variation. 

The cockscomb (Celosia cristata) has varie- 
ties of nearly till colors from white and yellow 
to red and orange, and besides them some 
striped varieties occur in our gardens, with the 
stripes going from the lower parts of the stem 
up to the very crest of the comb. They are 
on sale as constant varieties, but nothing has 
as yet been recorded concerning their peculiar 
behavior in the inheritance of the stripes. 



326 Ever-sporting Varieties 

being more largely cultivate in some countries 
It has one great drawback: it never comes 
wholly true from seed. It may be grown in 
full isolation, and carefully selected, aU red or 
nearly monochromatic samples being rooted out 
long before blooming, but nevertheless the seed 
will always produce some red roots. The most 
careful selection, pursued through a number 
of years, has not been sufficient to get rid of 
this regular occurrence of reversionary individ- 
uals. Seed-growers receive many complaints 
from their clients on this account, but they are 
not able to remove the difficulty. This experi- 
ence is in full agreement with the experimental 
evidence given by the snapdragon, and it would 
certainly be very interesting to make a complete 
pedigree-culture with the radishes to test 
definitely their compliance with the rules ob- 
served for striped flowers. 

Horticulturists in such cases are in tlie habit 
of limiting themselves to the sale of so-called 
mixed seeds. From these no client expects pu- 
rity, and the normal and hereditary diversity 
of types is here in some sense concealed under 
the impurities included in the mixture from 
lack of selection. Such cases invite scrutiny, 
and would, no doubt, with the methods of isola- 
tion, artificial pollination, and the sowing of 
the seeds separately from each parent, yield 



striped Flowers 


327 


results of great scientific value. Any one who 
has a garden, and sufficient perseverance to 
make pure cultures during a series of years 
might make important contributions to scien- 
tific knowledge in this way. 

Choice might be made from among a wide 
range of different types. A variety of corn 
called “ Harlequin ” shows stripes on its ker- 
nels, and one ear may offer nearly white and 
nearly red seeds and all the possible interme- 
diate steps between them. From these seeds 
the next generation will repeat the motley ears, 
but some specimens will produce ears of uniform 
kernels of a dark purple, showing thus the or- 
dinary way of reversion. Some varieties of 
beans have spotted seeds, and among a lot of 
them one may be sure to find some purely red 
ones. It remains to be investigated what will 
be their offspring, and whether they are due to 
partial or to individual variation. 

The cockscomb (Celosia cristata) has varie- 
ties of nearly all colors from white and yellow 
to red and orange, and besides them some 
striped varieties occur in our gardens, with the 
stripes going from the lower parts of the stem 
up to the very crest of the comb. They are 
on sale as constant varieties, but nothing has 
as yet been recorded concerning their peculiar 
behavior in the inheritance of the stripes. 



328 Ever-sporting Varieties 

Striped grapes, apples and other fruits might 
be mentioned in this connection. 

Before leaving the striped varieties, atten- 
tion is called to an interesting deduction, which 
probably gives an explanation of one of the 
most widely known instances of ever-sporting 
garden plants. Striped races always include 
two types. Both of them are fertile, and each 
of them reproduces in its offspring both its 
own and the alternate type. It is like a game 
of ball, in which the opposing parties always 
return the ball. But now suppose that only 
one of the types were fertile and the other for 
some reason wholly sterile, and assume the 
reversionary, or primitive monochromatic indi- 
viduals to be fertile, and the derivative striped 
specimens to bloom without seed. If this were 
the case, knowledge concerning the hereditary 
qualities would be greatly limited. In fact the 
whole pedigree would be reduced to a mono- 
chromatic strain, which would in each genera- 
tion sport in some individuals into the striped 
variety. But, being sterile, they would not be 
able to propagate themselves. 

Such seems to be the ease with the double 
flowered stocks. Their double flowers produce 
neither stamens nor pistils, and as each indi- 
vidual is either double or single in all its flow- 
ers, the doubles are wholly destitute of seed. 



striped Flowers 


329 


Nevertheless, they are only reproduced by seed 
from single flowers, being an annual or bien- 
nial species. 

Stocks are a large family, and include a won- 
derful variety of colors, ranging from white 
and yellow to purple and red, and with some 
variations toward blue. They eithibit also di- 
versity in the habit of growth. Some are an- 
nuals, including the ten-week and pyramidal 
forms ; others are intermediates and are suitable 
for pot-culture; and the biennial sorts include 
the well-known “ Brompton ” and “Queen ” 
varieties. Some are large and others are small 
or dwarf. For their brightness, durability and 
fragrance, they are deservedly popular. There 
are even some striped varieties. Horticultur- 
ists and amateurs generally know that seed can 
be obtained from single stocks only, and that 
the double flowers never produce any. It is 
not difficult to choose single plants that will 
produce a large percentage of double blossoms 
in the following generation. But only a per- 
centage, for the experiments of the most skilled 
growers have never enabled them to save seed, 
which would result entirely in double flower- 
ing plants. Each generation in its turn is a 
motley assembly of singles and doubles. 

Before looking closer into the hereditary pe- 
culiarities of this old and interesting ever-sport- 



330 


Ever-sporting Varieties 

ing variety, it may be as well to give a short 
description of the plants with double flowers. 
Generally speaking there are two principal 
types of doubles. One is by the conversion of 
stamens into petals, and the other is an anomaly, 
known under the name of petalomany. 

The change of stamens into petals is a grad- 
ual modification. All intermediate steps are 
easily to be found. In some flowers all sta- 
mens may be enlarged, in others only part of 
them. Often the broadened filaments bear one 
or two fertile anthers. The fertility is no doubt 
diminished, but not wholly destroyed. Individ- 
ual specimens may occur, which cannot produce 
any seed, but then others of the same lot may 
be as fertile as can be desired. As a whole, 
such double varieties are regularly propagated 
by seed. 

Petalomany is the tendency of the axis of 
some flowers never to make any stamens or pis- 
tils, not even in altered or rudimentary form. 
Instead of these, they simply continue produc- 
ing petals, going on with this production with- 
out any other limit than the supply of available 
food. Numerous petals fill the entire space 
within the outer rays, and in the heart of the 
flower innumerable young ones are developed 
half-way, not obtaining food enough to attain 



striped Flowers 


331 


full size. Absolute sterility is the natural con- 
sequence of this state of things. 

Hence it is impossible to have races of petal- 
omanous types. If the abnormality happens to 
show itself in a species, which normally prop- 
agates itself in an asexual way, the type may, 
become a vegetative variety, and be multiplied 
by bulbs, buds or cuttings, etc. Some cultivated 
anemones and crowfoots (Ranunculus) are of 
this character, and even the marsh-marigold 
(Caltlia palustris) has a petalomanous variety. 
1 once found in a meadow such a form of the 
meadow-buttercup (Ranunculus acris), and suc- 
ceeded in keeping it in my garden for several 
years, but it did not make seeds and finally 
died. Camellias are known to have both types 
of double flowers. The petalomanous type is 
highly regular in structure, so much so as to be 
too uniform in all its parts to be pleasing, while 
the conversion of stamens into petals in the al- 
ternative varieties gives to these flowers a more 
lively diversity of structure. Lilies have a va- 
riety called Lilium candidum (lore plena, in 
which the flowers seem to be converted into 
a long spike of bright, white narrow bracts, 
crowded on an axis which never seems to cease 
their production. 

It is manifestly impossible to decide how all 
such sterile double flowers have originated. 



332 Ever-sporting Varieties 

Perhaps each of them originally had a congm* 
ent single-flowered form, from which it was pro- 
duced by seed in the same way as the double 
stocks now are yearly. If this assumption is 
right, the corresponding fertile line is now lost; 
it has perhaps died out, or been masked. But 
it is not absolutely impossible that such strains 
might one day be discovered for one or another 
of these now sterile varieties. 

Betuming to the stocks we are led to the con- 
ception that some varieties are absolutely sin- 
gle, while others consist of both single-flowered 
and double-flowered individuals. The single 
varieties are in respect to this character true 
to the original wild type. They never give seed 
which results in doubles, providing all inter- 
crossing is excluded. The other varieties are 
ever-sporting, in the sense of this term pre- 
viously assumed, but with the restriction that 
the sports are exclusively one-sided, and never 
return, owing to their absolute sterility. 

The oldest double varieties of stocks have at- 
tained an age of a century and more. During 
all this time they have had a continuous pedi- 
gree of fertile and single-flowered individuals, 
throwing off in each generation a definite num- 
ber of doubles. This ratio is not at all depend- 
ent on chance or accident, nor is it even variable 
to a remarkable degree. Quite on the contrary 



striped Flowers 


333 


it is always the same, or nearly the same, and 
it is to be considered as an ioherent quality of 
the race. If left to themselves, the single indi- 
viduals always produce singles and doubles in 
the same quantity; if cultivated after some spe- 
cial method, the proportion may be slightly 
changed, bringing the proportion of doubles 
up to 60j^ or even more. 

Ordinarily the single and double members of 
such a race are quite equal in the remainder of 
their attributes, especially in the color of tiieir 
flowers. But this is not always the case. The 
colors of such a race may repeat for themselves 
the peculiarities of the ever-sporting characters. 
It often happens that one color is more or less 
strictly allied to the doubles, and another to 
the singles. This sometimes makes it difficult 
to keep the various colors true. There are cer- 
tain sorts, which invariably exhibit a difference 
in color between the single and the double flow- 
ers. The sulphur-yellow varieties may be ad- 
duced as illustrative examples, because in them 
the single flowers always come white. Hence in 
saving seed, it is impossible so to select the 
plant, that an occasional white does not also 
appear among the double flowers, agreeing in 
this deviation with the general rule of the ever- 
sporting varieties. 

I commend all the above instances to those 



334 Ever-sporting Varieties 

who wish to make pedigree-cultures. The co- 
operation of many is needed to bring about any 
notable advancement, since the best way to se- 
cure isolation is to restrict one’s self to the 
culture of one strain, so as to avoid the inter- 
mixture of others. So many facts remain doubt- 
ful and open to investigation, that almost any 
lot of purchased seed may become the starting 
point for interesting researches. Among these 
the sulphur-yellow varieties should be consid- 
ered in the first place. 

In respect to the great questions of heredity, 
the stocks offer many points of interest. Some 
of these features I will now try to describe, in 
order to show what still remains to be done, 
and in what manner the stocks may clear the 
way for the study of the ever-sporting varieties. 

The first point, is the question, which seeds 
become double-flowered and which single-flow- 
ered plants? Beyond all doubt, the determi- 
nation has taken place before the ripening of the 
seed. But though the color of the seed is often 
indicative of the color of the flowers, as in some 
red or purple varieties, and though in balsams 
and some other instances the most ** highly 
doubled ” flowers are to be obtained from the 
biggest and plumpest seeds, no such rule seems 
to exist respecting the double stocks. Now 
if one half of the seeds gives doubles, and 



striped Flowers 


.335 


tihe other half singles, the question arises, 
where are the singles and the doubles to be 
found on the parent-plant? 

The answer is partly ^ven by the following 
experiment. Starting from the general rule of 
the great influence of nutrition on variability, 
it may be assumed that those seeds will give 
most doubles, that are best fed. Now it is man- 
ifest that the stem and larger branches are in 
a better condition than the smaller twigs, and 
that likewise the first fruits have better chances 
than the ones formed later. Even in the same 
pod the uppermost seeds will be in a compara- 
tively disadvantageous position. This concep- 
tion leads to an experiment which is the basis 
of a practical method much used in France in 
order to get a higher percentage of seeds of 
double-flowering plants. 

This method consists in cutting off, in the first 
place the upper parts of all the larger spikes, in 
the second place, the upper third part of each 
pod, and lastly all the small and weak twigs. 
In doing so the percentage is claimed to go up 
to 67 - 70^, and in some instances even higher. 
This operation is to be performed as soon as the 
required number of flowers have ceased blos- 
soming. All the nutrient materials, destined 
for the seeds, are now forced to flow into these 
relatively few embrj’^os, and it is clear that 



S36 Ever-sporting Varieties 

they will be far better nourished than if no 
operation were made. 

In order to control this experiment some 
breeders have made the operation on the fruits 
when ripe, instead of on the young pods, and 
have saved the seeds from the upper parts sep- 
arately. This seed, produced in abundance, 
was found to be very poor in double flowers, 
containing only some 20-30j^. On the con- 
trary the percentage of doubles in the seed of 
the lower parts was somewhat augmented, and 
the average of both would have given the normal 
proportion of 50%. 

Opposed to the French method is the German 
practice of cultivating stocks, as I have seen it 
used on a very large scale at Erfurt and at other 
places. The stocks are grown in pots on small 
scaffolds, and not put on or into the earth. 
The obvious aim of this practice is to keep the 
earth in the pots dry, and accordingly they are 
only scantily watered. In consequence they 
cannot develop as fully as they would have done 
when planted directly in the beds, and they pro- 
duce only small racemes and no weak twigs, 
eliminating thereby without further operation 
the weaker seeds as by the French method. 
The effect is increased by planting from 6-10 
separate plants in each pot. 

It would be very interesting to make compar- 



striped Flowers 


337 


ative trials of both methods, in order to discover 
the true relation between the practice and the 
results reached. Both should also be compared 
with cultures on open plots, which are said to 
give only 50j^ of doubles. This last method of 
culture is practiced wherever it is desired to 
produce great quantities of seeds at a low cost. 
Such trials would no doubt give an insight into 
the relations of hereditary characters to the 
distribution of the food within the plant. 

A second point is the proportional increase of 
the double-flowering seeds with age. If seed 
is kept for two or three years, the greater part 
of the grains will gradually die, and among the 
remainder there is found on sowing, a higher 
percentage of double ones. Hence we may in- 
fer that the single-flowered seeds are shorter- 
lived than the doubles, and this obviously points 
to a greater weakness of the first. It is quite 
evident that there is some common cause for 
these facts and for the above cited experience, 
that the first and best pods give more doubles. 
Much, however, remains to be investigated be- 
fore a satisfactory answer can be made to these 
questions. 

A third point is the curious practice, called 
by the French “ esimpler,*^ and which consists 
in pulling out the singles when very young. It 
seems to be done at an age when the flower-buds 



338 Ever-sporting Varieties 

are not yet visible, or at least are not far 
enough developed to show the real distinctive 
marks. Children may he employed to choose 
and destroy the singles. There are some slight 
differences in the fullness and ronndness of the 
buds and the pubescence of the young leaves. 
Moreover the buds of the doubles are said to 
be sweeter to the taste than those of the singles. 
But as yet I have not been able to ascertain, 
whether any scientific investigation of this proc- 
ess has ever been made, though according to 
some communications made to me by the late 
Mr. Cornu, the practice seems to be very gen- 
eral in the environs of Paris. In summer large 
fields may be seen, bearing exclusively double 
flowers, owing to the weeding out of the singles 
long before flowering. 

Bud-variation is the last point to be taken up. 
It seems to be very rare with stocks, but some 
instances have been recorded in literature. 
Darwin mentions a double stock with a branch 
bearing single flowers, and other cases are 
known to have occurred. But in no instance 
does the seed of such a bud-variant seem to 
have been saved. Occasionally other rever- 
sions also occur. From time to time speci- 
mens appear with more luxurious growth 
and with divergent instead of erect pods. 
They are called, in Erfurt, “ generals ” on ac- 



striped Flowers 


339 


count of their stiff and erect appearance, 
and they are marked by more divergent horns 
crowning the pods. They are said to produce 
only a relatively small number of doubles from 
their seeds, and even this small number might 
be due to fertilization with pollen of their 
neighbors. I saw some of these reversionary 
types, when inspecting the nurseries of Erfurt, 
but as they are, as a rule, thrown out before 
ripening their seed, nothing is exactly known 
about their real hereditary qualities. 

Much remains to be cleared up, but it seems 
that one of the best means to find a way through 
the bewildering maze of the phenomena of in- 
heritance, is to make groups of related forms 
and to draw conclusions from a comparison of 
the members of such groups. Such comparisons 
must obviously give rise to questions, which in 
their turn will directly lead to experimental in- 
vestigation. 



Lectitbe XII 


UVE-LESAVED CIjOVEB 

Every one knows the “ four-leaved ” clover. 
It is occasionally found on lawns, in pastures 
and by the roadsides. Specimens with five leaf- 
lets may be found now and then in ^e same 
place, or on the same plant, but these are rarer. 
I have often seen isolated plants with quater- 
nate leaves, but only rarely have I observed in- 
dividuals with more than one such leaf. 

The two cases are essentially dissimilar. 
They may appear to differ but little morpholog- 
ically, but from the point of view of heredity 
they are quite different. Isolated quatemate 
leaves are of but little interest, while the occur- 
rence of many on the same individual indicates a 
distinct variety. In making experiments upon 
this point it is necessary to transplant the di- 
vergent individuals to a garden in order to 
furnish them proper cultural conditions and 
to keep them under constant observation. When 
a plant bearing a quatemate leaf is thus 
transplanted however, it rarely repeats the 



Five-leaved Clover 


341 


anomaly. But when plants with two or more 
quatemate leaves on the same individual are 
chosen it indicates that it belongs to a definite 
race, which under suitable conditions may 
prove to become very rich in the anomalies in 
question. 

Obviously it is not always easy to decide 
definitely whether a given individual belongs to 
such a race or not. Many trials may be neces- 
sary to secure the special race. I had the good 
fortune to find two plants of clover, bearing one 
quinate and several quatemate leaves, on an 
excursion in the neighborhood of Loosdrecht in 
Holland. After transplanting them into my 
garden, I cultivated them during three years 
and observed a slowly increasing number of 
anomalous leaves. This number in one summer 
amounted to 46 quatemate and 16 quinate 
leaves, and it was evident that I had secured an 
instance of the rare “ five-leaved ” race which 
I am about to describe. 

Before doing so it seems desirable to look 
somewhat closer into the morphological fea- 
tures of the problem. Pinnate and palmate 
leaves often vary in the number of their parts. 
This variability is generally of the nature of a 
common fluctuation, the deviations grouping 
themselves around an average type in the ordi- 
nary way. Ash leaves bear five pairs, and 



342 Ever-sporting Varieties 

the monntam-ash {Sorhus Avmparia) has six 
pairs of leaflets in addition to the terminal one. 
But this number varies slightly, the weaker 
leaves having less, the stronger more pairs than 
the average. Such however, is not the case 
with temate leaves, which seem to be quite con- 
stant Pour leaflets occur so very rarely that 
one seems justified in regarding them rather as 
an anomaly than as a fluctuation. And this is 
confirmed by the almost universal absence of 
two-bladed clover-leaves. 

Considering the deviation as an anomaly, we 
may look into its nature. Such an inquiry 
shows that the supernumerary leaflets owe their 
origin to a splitting of one or more of the nor- 
mal ones. This splitting is not terminal, as is 
often the case with other species, and as it may 
be seen sometimes in the clover. It is for 
the most part lateral. One of the lateral nerves 
grows out becoming a median nerve of the new 
leaflet. Intermediate steps are not wanting, 
though rare, and they show a gradual separa- 
tion of some lateral part of a leaflet, until this 
division reaches the base and divides the leaflet 
into two almost equal parts. If this splitting 
occurs in one leaflet we get the “ four-leaved ” 
clover, if it occurs in two there will be five leaf- 
lets. And if, besides this, the terminal leaflet 
produces a derivative on one or both of its sides. 



Five-leaved Clover 


343 


we obtain a crown of six or seven leaflets on one 
stalk. Such were often met with in the race I 
had under cultivation, but as a rule it did not ex- 
ceed this limit. 

The same phenomenon of a lateral doubling 
of leaflets may of course be met with in other 
instances. The common laburnum has a va- 
riety which often produces quatemate and 
quinate leaves, and in strawberries I have also 
seen instances of this abnormality. It occurs 
also in pinnate leaves, and complete sets of all 
the intermediate links may often be found on 
the false or bastard-acacia (Robinia Pseud- 
Acacia). 

Opposed to this increase of the number of 
leaflets, and slill more rare and more curious is 
the occurrence of “ single-leaved varieties 
among trees and herbs with pinnate or temate 
leaves. Only very few instances have been de- 
scribed, and are cultivated in gardens. The 
ashes and the bastard-acacia may be quoted 
among trees, and the “ one-leaved ” strawberry 
among herbs. Here it seems that several leaf- 
lets have been combined into one, since this one 
is, as a rule, much larger than the terminal leaf- 
let of an ordinary leaf of the same species. 
These monophyllous varieties are interesting 
also on account of their continuous but often in- 
complete reversion to the normal type. 



344 Ever-sporting Varieties 

Finnate and palmate leaves are no donbt 
derivative types. They most have originated 
from the ordinary simple leaf. The monophyl- 
ly may therefore be considered as a reversion to 
a more primitive state and the monophyllous 
varieties may be called atavistic. 

On the other hand we have seen that these 
atavistic varieties may revert to their nearest 
progenitors, and this leads to the curious con- 
ception of positive and negative atavism. For 
if the change of compound leaves into single 
ones is a retrograde or negative step, the con- 
version of single or ternate leaves into pinnate 
and palmate ones must evidently be considered 
in this case as positive atavism. 

This discussion seems to throw some light on 
the increase of leaflets in the clover. The pea- 
family, or the group of papilionaceous plants, 
has pinnate leaves ordinarily, which, according 
to our premises, must be considered as a deriva- 
tive type. In the clovers and their allies this 
type reverts halfway to the single form, pro- 
ducing only three leaflets on each stalk. If now 
the clover increases its number of leaflets, this 
may be considered as a reversion to its nearest 
progenitors, the papilionaceous plants with pin- 
nate leaves. Hence a halfway returning and 
therefore positive atavism. And as I have al- 
ready mentioned in a former lecture, pinnate 



Fwe-leaved Clover 345 

leaves are also sometimes produced by my new 
race of clover. 

Betuming to the original plants of this race, 
it is evidently impossible to decide whether they 
were really the beginning of a new strain, and 
had originated themselves by some sudden 
change from the common type, or whether 
they belonged to an old variety, which had 
propagated itself perhaps during centuries, 
unobserved by man. But the same diffi- 
culty generally arises when new varieties are 
discovered. Even the behavior of the plants 
themselves or of their progeny does not afford 
any means of deciding the question. The sim- 
plest way of stating the matter therefore, is to 
say that I accidentally found two individuals of 
the ‘ ‘ five-leaved ’ ’ race. By transplanting them 
into my garden, 1 have isolated them and kept 
them free from cross-fertilization with the ordi- 
nary type. Moreover, I have brought them un- 
der such conditions as arc necessary for the full 
development of their characters. And last but 
not least, I have tried to improve this character 
as far as possible by a very rigid and careful 
selection. 

The result of all this effort has been a rapid 
improvement of my strain. I saved the seed 
of the original plants in 1889 and cultivated the 
second generation in the following year. It 



346 


Ever-sporting Varieties 


showed some increase of the anomaly, bnt not to 
a very remarkable degree. In the flowering pe- 
riod I selected four plants with the largest num- 
ber of quatemate and quinate leaves and de- 
stroyed all the others. I counted in the average 
25 anomalous organs on each of them. From 
their seed I raised the third generation of my 
culture in the year 1891. 

This generation included some 300 plants, on 
which above 8000 leaves were counted. More 
than 1000 were quatemate or quinate, the ter- 
nate leaves being still in the majority. But the 
experiment clearly showed that “ four-leaved ” 
clovers may be produced in any desired quan- 
tity, provided that the seed of the variety is 
available. In the summer only three, four and 
five leaflets on one stalk were seen, but towards 
the fall, and after the selection of the best in- 
dividuals, this number increased and came up 
to six and seven in some rare instances. 

The selection in this year was by no means 
easy. Nearly all the individuals produced at 
least some quatemate leaves, and thereby 
showed the variety to be quite pure. I counted 
the abnormal organs on a large group of the 
best plants, and selected 20 excellent speci- 
mens from them, with more than one-third of 
all their leaves changed in the desired manner. 

Having brought my race up to this point, I 



Five-leaved Clover 


347 


was able to introduce a new and far more easy 
mark, afforded by the seedlings, for my selec- 
tions. This mark has since remained constant, 
and has brought about a rapid continuance of 
the improvement, without necessitating such 
large cultures. 

This seedling in the various species of 
clover usually begins with a first leaf above 
the cotyledons of a different structure from 
those that follow. It has only one blade 
instead of three. But in my variety the in- 
crease of the number of the leaflets may extend 
to these primary organs, and make them binate 
or even temate. Now it is obvious that an indi- 
vidual, which begins with a divided primary 
leaf, will have a greater tendency to produce a 
large number of supernumerary leaflets than a 
plant which commences in the ordinary way. 
Or in other words, the primary leaves afford a 
sure criterion for the selection, and this selec- 
tion may be made in the seed-pans. In conse- 
quence, no young individual with an undivided 
primary leaf was planted out. Choosing the 
20 or 30 best specimens in the seed-pan, no 
further selection was required, and the whole 
lot could be left to cross-fertilization by insects. 

The observation of this distinguishing mark 
in the young seedlings has led to the discovery 
of another quality as a starting-point for fur- 



348 Ever-sportmg Varieties 

ther selection. According to the general rule 
of pedigree-culture, the seeds of each individual 
plant are always saved and sowed separately. 
This is done even with such species as the 
clover, which are infertile when self-poUinated, 
and which are incapable of artificial pollina- 
tion on the required scale, since each flower pro- 
duces only one seed. My clover was always 
left free to be pollinated by insects. Obviously 
this must have led to a diminution of the differ- 
entiating characters of the individual plants. 
But this does not go far enough to obliterate 
the differences, and the selection made among 
the seedlings will always throw out at least 
a large part of those that have suffered from 
the cross. 

Leaving this discussion, we may inquire 
closer into the nature of the new criterion af- 
forded by the seedlings. Two methods present 
themselves. First, the choice of the best seed- 
lings. In the second place it becomes possible 
to compare the parent-plants by counting the 
number of deviating seedlings. This leads to 
the establishment of a percentage for every 
single parent, and gives data for comparisons. 
Two or three hundreds of seeds from a parent 
may easily be grown in one pan, and in this 
way a sufficiently high degree of accuracy 
may be reached. Only those parents that give 



Five-lea/ved Clover 


349 


the highest percentage are chosen, and among 
their progeny only the seedlings with -trif oliolate 
primary leaves are planted out. The whole 
procedure of the selection is by this means con- 
fined to the glasshouse during the spring, and 
the beds need not be large, nor do they require 
any special care during the summer. 

By this method I brought my strain within 
two years up to an average of nearly 90 of the 
seedlings with a divided primary leaf. Around 
this average the real numbers fluctuated be- 
tween the maximum of 99)^ and the minimum 
of 70^ or thereabouts. This condition was 
reached by the sixth generation in the year 1894, 
and has since proved to be the limit, the group 
of figures remaining practically the same during 
all the succeeding generations. 

Such selected plants are very rich in leaves 
with four, five and six blades. Excluding the 
small leaves at the tops of the branches, and 
those on the numerous weaker side-branches, 
these three groups include the large majority 
of all the stronger leaves. In su mm er the 
range is wider, and besides many trifoliolate 
leaves the curiously shaped seven-bladed ones 
are not at all rare. In the fall and in the win- 
ter the range of variability is narrowed, and 
at first sight the plants often seem to bear only 
quinquefoliolate leaves. 



348 Eversporting Varieties 

ther seleetion. According to the general rule 
of pedigree-colture, the seeds of each individual 
plant are always saved and sowed separatdy. 
This is done even with such species as the 
clover, whidi are infertile when self-pollinated, 
and which are incapable of artificial pollina- 
tion on the required scale, since each flower pro- 
duces only one seed. My clover was always 
left free to be pollinated by insects. Obviously 
this must have led to a diminution of the differ- 
entiating characters of the individual plants. 
But this does not go far enough to obliterate 
the differences, and the selection made among 
the seedlings will always throw out at least 
a large part of those that have suffered from 
the cross. 

Leaving this discussion, we may inquire 
closer into the nature of the new criterion af- 
forded by the seedlings. Two methods present 
themselves. First, the choice of the best seed- 
lings. In the second place it becomes possible 
to compare the parent-plants by counting the 
number of deviating seedlings. This leads to 
the establishment of a percentage for every 
single parent, and gives data for comparisons. 
Two or three hundreds of seeds from a parent 
may easily be grown in one pan, and in this 
way a sufficiently high degree of accuracy 
may be reached. Only those parents that give 



Five-leaved Clover 


349 


the highest percentage are chosen, and among 
their progeny only the seedlings with trifoliolate 
primary leaves are planted out. The whole 
procedure of the selection is by this means con- 
fined to the glasshouse during the spring, and 
the beds need not be large, nor do they require 
any special care during the summer. 

By this method I brought my strain within 
two years up to an average of nearly 90 ^ of the 
seedlings with a divided primary leaf. Around 
this average the real numbers fiuctuated be- 
tween the maximum of 99)^ and the minimum 
of 70?^ or thereabouts. This condition was 
reached by the sixth generation in the year 1894, 
and has since proved to be the limit, the group 
of figures remaining practically the same during 
all the succeeding generations. 

Such selected plants are very rich in leaves 
with four, five and six blades. Excluding the 
small leaves at the tops of the branches, and 
those on the numerous weaker side-branches, 
these three groups include the large majority 
of all the stronger leaves. In summer the 
range is wider, and besides many trifoliolate 
leaves the curiously shaped seven-bladed ones 
are not at all rare. In the fall and in the win- 
ter the range of variability is narrowed, and 
at first sight the plants often seem to bear only 
quinqnefoHolate leaves. 



350 Ever-sporting Varieties 

I have cultivated a new generation of this 
race nearly every year since 1894, using always 
the strictest selection. This has led to a uni- 
form type, but has not been adequate to produce 
any further improvement. Obviously the ex- 
treme limit, under the conditions of climate and 
soil, has been reached. This extreme type is 
always dependent upon repeated selection. No 
constant variety, in the older sense, has been 
obtained, nor was any indication afforded that 
such a type might ever be produced. On the 
contrary, it is manifest that the new form be- 
longs to the group of ever-sporting varieties. 
It is never quite free from the old atavistic 
type of the trifoliolate leaves, and invariably, 
when external conditions become less favorable, 
this atavistic form is apt to gain dominion over 
the more refined varietal character. Eever- 
sions always occur, both partial and individual. 

Some instances of these reversions may now 
be given. They are not of such a striking char- 
acter as those of the snapdragon. Intermediate 
steps are always occurring, both in the leaves 
themselves, and in the percentages of deviating 
seedlings of the several parent plants. 

On normal plants of my variety the quinque- 
foliolate leaves usually compose the majority, 
when there are no weak lateral branches, or 
when they are left out of consideration. Next 



Five-leaved Clover 


351 


to these come the fours and the sixes, while the 
trifoliolate and seven-hladed types are nearly 
equal in number. But out of a lot of plants, 
grown from seed of the same parent, it is often 
possible to choose some in which one extreme 
prevails, and others with a preponderating 
number of leaves with the other extreme num- 
ber of leaflets. If seed from these extremes are 
saved separately, one strain, that with numer- 
ous seven-bladed leaves will remain true to the 
type, but the other will diverge more or less, 
producing leaves with a varying number of sub- 
divisions. 

Very few generations of such opposite selec- 
tion are required to reduce the race to an 
utterly poor one. In three years I was able to 
nearly obliterate the type of my variety. I 
chose the seedlings with an undivided primary 
leaf, cultivated them and counted their off- 
spring separately after the sowing. I found 
some parents with only 2 - of seedlings with 
divided primary leaves. And by a repeated 
selection in this retrograde direction I suc- 
ceeded in getting a great number of plants, 
which during the whole summer made only 
very few leaves with more than three blades. 
But an absolute reversion could no more be 
reached in this direction than in the normal 
one. Any sowing without selection would be 



352 Ever-sporting Varieties 

liable to reduce the etrain to an average condi- 
tion. 

The production of varietal and of atavistic 
leaves is dependent to a high degree on 
external conditions. It agrees with the gen- 
eral rule, that favorable circumstances 
strengthen the varietal peculiarities, while un- 
favorable conditions increase the number of the 
parts with the atavistic attribute. These in- 
fluences may be seen to have their effect on the 
single individuals, as well as on the generations 
growing from their seed. I cannot cite here all 
the experimental material, but a single illustra- 
tive example may be given. I divided a strong 
individual into two parts, planted one in rich 
soil and the other in poor sand, and had both 
pollinated by bees with the pollen of some nor- 
mal individuals of my variety growing between 
them. The seeds of both were saved and sown 
separately, and the two lots of offspring culti- 
vated dose to each other under the same ex- 
ternal conditions. In the beginning no differ- 
ence was seen, but as soon as the young plants 
had unfolded three or four leaves, the progeny 
of the better nourished half of the parent^plant 
showed a manifest advance. This difference 
increased rapidly and was easily seen in the 
beds, even before the flowering period. 

This experience probably gives an explana- 



Five-leaved Clover 


353 


tion why the qninquefoliolate variety is so 
seldom met with in the wild state. For even if 
it did occur more often, the plants would hardly 
find circumstances favorable enough for the 
full development of their varietal character. 
They must often be so poor in anomalous leaves 
as to be overlooked, or to be taken for instances 
of the commonly occurring quadrifoliolate 
leaves and therefore as not indicating the true 
variety. 

In the beginning of my discussion I have as- 
serted the existence of two different races of 
“ four-leaved ” clovers, a poor one and a rich 
one, and have insisted on a sharp distinction be- 
tween them. This distinction partly depends 
on experiments with clover, but in great part 
on tests with other plants. The previously 
mentioned circumstance, that clover cannot be 
pollinated on a sufficiently large scale otherwise 
than by insects, prevents trials in more than one 
direction at the same time and in the same 
garden. For this reason I have chosen another 
species of cloyer to be able to give proof or dis- 
proof of the assertion quoted. 

This species is the Italian, or crimson clover, 
which is sometimes also called scarlet dover 
{Trifolium incarnatum). It is commonly used 
in Europe as a crop on less fertile soils than 
are required by the red dover. It is annual 



354 Ever-sporting Varieties 

and erect and more or less hairy, and has 
stouter leaves than other kinds of clover. It 
has oblong or cylindrical heads with bright 
crimson flowers, and may be considered as one 
of the most showy types. As an annual it has 
some manifest advantages over the perennial 
species, especially in giving its harvest of hay 
at other seasons of the year. 

I found some stray quatemate leaves of this 
plant some years ago, and tried to win from 
them, through culture and selection, a race that 
would be as rich in these anomalies as the red 
clover. But the utmost care and the most rigid 
selection, and all the attention I could afford, 
failed to produce any result. It is now ten 
years since I commenced this experiment, and 
more than once I have been willing to give it 
up. Last year (1903) I cultivated some hun- 
dreds of selected plants, but though they yielded 
a few more instances of the desired anomaly 
than in the beginning, no trace of a truly rich 
race could be discovered. The experimental 
evidence of this failure shows at least that stray 

four-leaves ’’ may occur, which do not indi- 
cate the existence of a true “ four-” or “ five- 
leaved ” variety. 

This conception seems destined to become of 
great value in the appreciation of anomalies, as 
they are usually found, either in the wild state 



Five-leaved Clover 


355 


or in gardens. And before describing the de- 
tails of my unsuccessful pedigree-culture, it may 
be as well to give some more instances of what 
occilrs in nature. 

Stray anomalies are of course rare, but not 
so rare that they might not be found in large 
numbers when perseveringly sought for. 
Pitcher-like leaves may be found on many trees 
and shrubs and herbs, but ordinarily one or 
only two of them are seen in the course of many 
years on the same plant, or in the same strain. 
In some few instances they occur annually or 
nearly so, as in some individuals of the Euro- 
pean lime-tree (TUia parvifolia) and of the 
common magnolia {Magnolia obovata). Many 
of our older cultivated plants are very rich in 
anomalies of all kinds, and Cyclamen, Fuchsia, 
Pelargonium and some others are notorious 
sources of teratologic phenomena. Deviations 
in flowers may often be seen, consisting of 
changes in the normal number of the several or- 
gans, or alterations in their shape and color. 
Leaves may have two tips, instead of one, the 
mid-vein being split near the apex, and the fis- 
sure extending more or less towards the base. 
Bays of the umbels of umbelliferous plants may 
grow together and become united in groups of 
two or more, and in the same way the fruits of 



356 Ever-Sporting Varieties 

the composites may be united into groups. 
Many other instances could easily be given. 

If we select some of these anomalies for 
breeding-experiments, our results will not agree 
throughout, but will tend to group themselves 
under two heads. Li some cases the isolation 
of the deviating individuals will at once show 
the existence of a distinct variety, which is 
capable of producing the anomaly in any de- 
sired number of instances, only dependent on 
a favorable treatinent and a judicious selection. 
In other oases no treatment and no selection 
are adequate to give a similar result, and the 
anomaly remains refractory despite all our en- 
deavors to breed it. The cockscomb and the 
peloric fox-glove are widely known instances of 
permanent anomalies, and others will be dealt 
with in future lectures. On the other hand 
I have often tried in vain to win an anomalous 
race from an accidental deviation, or to isolate 
a teratologic variety out of more common aber- 
rations. Two illustrative examples may be 
quoted. In our next lecture we shall deal with 
a curious phenomenon in poppies, consisting in 
the change of the stamens into pistils and giving 
rise to a bright crown of secondary capsules 
around the central one. Similar anomalies may 
he occasionally met with in other species of the 
same genus. But they are rare, and may show 



Five-leaved Clover 


357 


the conversion of only a single stamen in the 
described manner. I observed this anomaly in 
a poppy called Papaver commutatum, and sub- 
jected it during several years to a rigid selec- 
tion of the richest individuals. No ameliora- 
tion was to be gained and the culture had to be 
given up. In the same way I found on the bul- 
bous buttercup {Ranunculus hulbosus) a strain 
varying largely in the number of the petals, 
amounting often to 6-8, and in some flowers 
even yet to higher figures. During five succeed- 
ing years I cultivated five generations, often in 
large numbers, selecting always those which 
had the highest number of petals, throwing out 
the remainder and saving the seed only from 
the very best plants. I got a strain of selected 
plants with an average number of nine petals 
in every flower, and found among 4000 flowers 
four having 20 petals or more, coming up even 
to 31 in one instance. But such rare instances 
had no influence whatever on the selection, 
since they were not indicative of individual 
qualities, but occurred quite accidentally on 
flowers of plants having only the average num- 
ber of petals. Now double flowers are widely 
known to occur in other species of the butter- 
cups, both in the cultivated varieties and in 
some wild forms. For this reason it might be 
expected that through a continuous selection of 



358 Ever-aporting Varieties 

the individuals with the largest numbers a 
tendency to become double would be evolved. 
Such, however, was not the case. No propen- 
sity to vary in any definite direction could be 
observed. Quite on the contrary, an average 
condition was quickly reached, and then re- 
mained constant, strongly counteracting all 
selection. 

Such experiences clearly show that the same 
anomaly may occur in different species, and no 
doubt in strains of the same species from dif- 
ferent localities, according to at least two dif- 
ferent standards. The one is to be called the 
poor, and the other the rich variety. The first 
always produces relatively few instances of the 
deviation, the last is apt to give as many of them 
as desired. The first is only half-way a variety, 
and therefore would deserve the name of a half- 
race ; the second is not yet a full constant vari- 
ety, but always fluctuates to and fro between the 
varietal and the specific mark, ever-sporting in 
both directions. It holds a middle position be- 
tween a half-race and a variety, and there- 
fore might be called a middle-race.” But 
the term ever-sporting variety seems more ade- 
quate to convey a right idea of the nature of 
this curious tj^e of inheritance. 

From this discussion it will be seen that the 
behavior of the crimson clover is not to be con- 



Five-leaved Clover 


359 


sidered as an exception, but as a widely occur- 
ring type of phenomenon, occurring perhaps m 
all sorts of teratologic deviations, and in wide 
ranges of species and genera. Hence it may be 
considered worth while to give some more de- 
tails of this extended experiment. 

Ten years ago (1894 - 5) I bought and sowed 
about a pound of seed of the crimson clover. 
Among many thousands of normal seedlings I 
found two with three and one with four cotyle- 
dons. Trusting to the empirical rules of corre- 
lation, 1 transplanted these three individuals in 
order to isolate them in the flowering period. 
One of them produced during the ensuing sum- 
mer one four-bladed and one five-bladed leaf. 
The seeds were saved separately and sown the 
following spring and the expected result could 
soon be seen. Among some 250 individual 
plants I counted 22 with one or two deviations, 
and 10 with from three to nine four- or five- 
bladed leaves. Proportions nearly similar have 
been observed repeatedly. Better nourished in- 
dividuals have produced more deviating leaves 
on one plant, partly owing to the larger number 
of stems and branches, and poor or average 
specimens have mostly been without any aber- 
ration or with only one or two abnormal leaves. 
No further improvement could be attained. 
Quadrifoliolate leaves were always rare, never 



360 Ever-sporting Varieties 

attaining a number that would put its stamp on 
a whole bed. I have endeavored to get some 
six- and seven-bladed crimson clover leaves, but 
in vain; selection, culture of many hundreds of 
individuals, manure, and the beet possible treat- 
ment has not been adequate to produce them. 
Of course I am quite convinced that a repetition 
of my experiment on a far larger scale would 
yield the desired types, but then only in such 
rare instances that they would have no influence 
whatever on the average, or on the improve- 
ment of the race. The eighth generation in the 
year 1903 has not been noticeably better than 
the second and third generations after the first 
selection. 

In comparing this statement with the results 
gained in the experiment with the red clover, 
the difference is at once striking. In one case 
a rich variety was isolated, and, by better 
treatment and sharp methods of selection, was 
brought up in a few years to its highest 
pitch of development. In the other case a very 
weak race was shown to exist, and no amount 
of work and perseverance was adequate to im- 
prove it to any noticeable degree. 

I wish to point out that the decision of what 
is to be expected from deviating specimens may 
become manifest within one or two generations. 
Even the generation grown from the seeds of 



Five4eaved Clover 


361 


the first observed aberrant individuals, if gath- 
ered after sufficient isolation during the period 
of blossoming, may show which type of in- 
heritance is present, whether it is an unpromis- 
ing half-race, or a richly endowed sporting 
variety. I have kept such strains repeatedly 
after the first isolation, and a special case, that 
of cotyledoneous aberrations, will be dealt with 
later. The first generation always gave a final 
decision, provided that a suitable method of 
cultivation for the species under observation 
was found at the beginning. This however, 
is a condition, which it is not at all easy to 
comply with, when new sorts are introduced 
into a garden. Especially so when they had 
been collected in the wild state. Often one or 
two years, sometimes more, are necessary to 
find the proper method of sowing, manuring, 
transplanting and other cultural methods satis- 
factory to the plants. Many wild species re- 
quire more care and more manure in gardens 
than the finest garden flowers. And a large 
number are known to be dependent on very 
particular conditions of soil. 

One of the most curious features of anom- 
alies, which has been learned from accumulated 
instances, is the fact that they obey definite 
laws as to their occurrence on the different 
parts of the plant. Obviously such laws are 



362 


Ever^sporting Varieties 


not apparent as long as each plant produces 
only one or two, or, at most, a few instances of 
the same deviation. On the contrary, any ex- 
isting regularity must betray itself, as soon as 
a larger nnmber of instances is produced. A 
rule of periodicity becomes most clearly mani- 
fest in such cases. 

This rule is shown by no other race in a more 
undoubted and evident manner than by the 
** five-leaved ” clover. Evidently the several 
degrees of deviation, going from three -to seven 
leaflets, may be regarded as responses to differ- 
ent degrees of variation, and their distribution 
over the stems and branches, or over the whole 
plant, may be considered as the manifestation of 
the ever-dianging internal tendency to vary. 

Considered from this point of view, my plants 
always showed a definite periodicity in this dis- 
tribution, which is the same for the whole plant. 
Each of them, and each of the larger branches, 
begin with atavistic leaves or with slight devia- 
tions. These are succeeded by greater devia- 
tions, but only the strongest axes show as many 
as seven leaflets on a stalk. This ordinarily 
does not occur before the height of development 
is reached, and often only towards its close. 
Then the deviation diminishes rapidly, return- 
ing oftmi to atavistic leaves at the summit of the 
stem or brandb. I give the numbers of the 



Five-leaved Clover 363 

leaves of a branch, in their order from the base 
to the top. They were as follows : 

3. 4. 5. 6. 7. 5. 5. 4. 

But this is a selected case, and such regular 
examples of the expected periodicity are rarely 
found. Often one or more of the various steps 
are lacking, or even leaves with smaller num- 
bers may be interspersed among those with 
larger numbers of leaflets. But while the regu- 
larity of the periodicity is in some degree 
diminished by such occurrences, yet the rule 
always holds good, when taken broadly. It 
may be expressed by stating that the bases and 
apices have on the average fewer leaflets on each 
leaf than the middle parts of the stem and 
branches, and that the number of leaflets grad- 
ually increases from the base toward a maxi- 
mum, which is reached in organs on the middle 
or upper part of the axis, and then diminishes 
from this toward the apex. 

This periodicity is not limited to the stems 
and branches, considered singly, but also holds 
good in a comparison made between the 
branches of a single stem, in regard to their rel- 
ative places on that stem. So it is also for the 
whole plant. The first stems, produced by the 
subterranean axis, ordinarily show only a low 
maximum deviation : the next succeeding being 



364 Ever-sporting Varieties 

more divergent and tiie last ones retaming to 
less differentiated forms. 

It is evident that on a given stem the group 
of deviating leaves will be extended upward and 
downward, with the increase of the number of 
these organs. This shows that a stem, or even 
a'plant, promises a higher degree of differentia- 
tion if it commences with its aberration earlier. 
Hence it becomes possible to discern the most 
promising individuals in early youth, and this 
conclusion leads to a very easy and reliable 
method of selection, which may be expressed 
simpiy as follows: the seedlings which com- 
mence earliest with the production of four- and 
five-foliolate leaves are the best and should be 
selected for the continuance of the race. And 
it is easily seen that this mle agrees with that 
given above, and which was followed in my 
pedigree-culture. 

Furthermore it is seen that there is a com- 
plete agreement between the law of periodicity 
and the responses of the deviations to nourish- 
ment and other conditions of life. Weak plants 
only produce low degrees of deviation, the 
stronger the individual becomes, the higher it 
reaches in the scale of differentiation, and the 
more often it develops leaves with five or more 
blades. Whether weakness or strength are de- 
rived from outer causes, or from the internal 



Five-leaved Clover 


365 


succession of the periods of life, is evidently of 
no consequence, and in this way the law of 
periodicity may be regarded as a special in- 
stance of the more general law of response to 
external conditions. 

The validity of this law of periodicity is of 
course not limited to our “ five-leaved ” clover. 
Quite on the contrary it is universal in ever- 
sporting varieties. Moreover it may be ascer- 
tained and studied in connection with the most 
widely different morphologic abnormalities, and 
therefore affords easily accessible material for 
statistical inquiry. I will now give some fur- 
ther instances, but wish to insist first upon the 
necessity of an inquiry on a far larger scale, 
as the evidence as yet is very scanty. 

The great celandine (Chelidonium majus) 
has a very curious double variety. Its flowers 
are simpler and much more variable than in 
ordinary garden-varieties. The process of 
doubling consists mainly in a change of stamens 
into petals. This change is dependent on the 
season. On each stem the earliest flowers are 
single. These are succeeded by blossoms with 
one or two converted stamens, and towards the 
summer this number increases gradually, attain- 
ing 10-11 and in some instances even more 
altered filaments. Each year the same succes- 
sion may be seen repeating itself on the stans of 



366 Ever-sporting Varieties 

the old roots. Double tuberous begonias are or- 
dinarily absolutely sterile throughout the sum- 
mer, but towards autumn the new flowers be- 
come less and less altered, producing some nor- 
mal stamens and pistils among the majority of 
metamorphosed organs. From these flowers the 
seeds are saved. Sometimes similar flowers 
occur at the beginning of the flowering-period. 
Double garden-camomiles (Chrysanthemum in- 
odorum plenissimum) and many other double 
varieties of garden-plants among the great 
family of the composites are very sensitive to 
external agencies, and their flower-heads are 
fuller the more favorable the external condi- 
tions. Towards the autumn many of them pro- 
duce fewer and fewer converted heads and often 
only these are fertile and yield seeds. 

Ascidia afford another instance of this 
periodicity, though ordinarily they are by far 
too rare to show any regularity in their distri- 
bution. However, it is easy to observe that on 
lime-trees they prefer the lower parts of each 
twig, while on magnolias the terminal leaves 
of the branches are often pitcher-bearing. 
Ascidia of the white clover have been found 
in numbers, in my own experiment-garden, 
but always in the springtime. The thick- 
leaved saxifrage (Saxifraga crassifolia) is 
oftmi very productive of ascidia, especially in 



Five-leaved Clover 


367 


the latter part of the season, and as these organs 
may be developed to very different degrees, 
they afford fine material for the study of tiie 
law of periodicity. On a garden-cytisus 
{Cytisus candicans attleyomus) 1 once had the 
good fortune to observe a branch with ascidia, 
which ordinarily are very rare in this species. 
It had produced seven ascidia in all, each 
formed by the conversion of one leaflet on the 
trifoliolate leaves. The first six leaves were 
destitute of this malformation and were quite 
normal. Then followed a group of five leaves, 
constituting the maximum of the period. The 
first bore one small pitcher-like blade, the sec- 
ond and third, each one highly modified organ, 
the fourth, two ascidia, and the last, one leaflet 
with slightly connate margins. The whole 
upper part of the branch was normal, with the 
exception of the seventeenth leaf, which showed 
a slight change in the same direction. All in 
all, the tendency to produce ascidia increased 
from the beginning to the tenth leaf, and de- 
creased from this upward. 

The European Venus* looking-glass was ob- 
served in my garden to produce some quater- 
nate and some quinate flowers on the same spec- 
imens. The quinate were placed at the end of 
the branches, those with four petals and sepals 
lower down. The peloric fox-glove shows the 



368 Ever-sporting Varieties 

highest degree of metamorphy in the terminal 
flowers of the stem itself, ihe weaker branches 
having bnt little tendency towards the forma- 
tion of the anomaly. The European pine or 
Pinus sylvestris ordinarily has two needles in 
each sheath, but trifoliolate sheaths occur on the 
stems and stronger branches, where they prefer, 
as a rule, the upper parts of the single annual 
shoots. CameUia japonica is often striped in 
the fall and during the winter, but when flower- 
ing in the spring it returns to the monochro- 
matic type. 

Peloric flowers are terminal in some cases, 
but occur in the lower parts of the flower-spikes 
in others. Some varieties of gladiolus com- 
mence on each spike with more or less double 
flowers, which, higher up, are replaced by single 
ones. A wide range of bulbs and perennial gar- 
den-plants develop their varietal characters 
only partly when grown from seed and flower- 
ing for the first time. The annual garden-for- 
get-me-not of the Azores {Myosotis azorica) 
has a variety with curiously enlarged flowers, 
often producing 20 or more corolla-segments in 
one flower. But this number gradually dimin- 
ishes as the season advances. It would be quite 
superfluous to give further proof of the general 
validity of the law of periodicity in ever-sport- 
ing varieties. 



Lectxjbe Xm 


PISTIUjODT in poppies 

One of the most cuiions anomalies that may 
be met with in ornamental garden-plants is the 
conversion of stamens into pistils. It is neither 
common nor rare, but in most cases the change 
is so slight comparatively that it is ordinarily 
overlooked. In the opium-poppy, on the con- 
trary, it is very showy, and heightens the orna- 
mental effect of the young fruits after the fad- 
ing of the flowers. Here the central capsule is 
surrounded by a large crown of metamorphosed 
stamens. 

This peculiarity has attracted the attention 
both of horticulturists and of botanists. As a 
rule not all the stamens are changed in this way 
but only those of the innermost rows. The 
outer stamens remain normal and fertile, and 
the flowers, when pollinated with their own pol- 
len, bear as rich a harvest of seeds as other 
opium-poppies. The change affects both the 
filament and the anther, the former of which is 
dilated into a sheath. Within this sheath per- 



370 Ever-sporting Varieties 

feet and more or less numerous ovules may be 
produced. The anthers become rudimentary 
and in their place broad leafy flaps are de- 
veloped, which protrude laterally from the tip 
and constitute the stigmas. Ordinarily these 
altered organs are sterile, but in some instances 
a very small quantity of seed is produced, and 
when testing their viability I succeeded in 
raising a few plants from them. 

The same anomaly occurs in other plants. 
The common wall-flower {Cheiranthus Cheiri) 
and the houseleek (Sempervivum tectorum) are 
the best known instances. Both have repeated- 
ly been described by various investigators. In 
compiling the literature of this subject it is 
very interesting to observe the two contrasting 
views respecting the nature of this anomaly. 
Some writers, and among them Masters in his 
“ Vegetable Teratology ” consider the devia- 
tions to be merely accidental. According to them 
some species are more subject to this anomaly 
than others, and the houseleek is said to be very 
prone to this change. Goeppert, Hofmeister 
and others occasionally found the pistilloid pop- 
pies in fields or gardens, and sowed their seeds 
in order to ascertain whether the accidental 
peculiarity was inheritable or not. On the 
other hand De Omidolle in his “ Prodromus ” 
mentions the pistilloid wall-flowers as a distinct 



Polycephalic Poppies 371 

variety, under the name of Cheiranthus ChetH 
gynantherus, and the analogous form of the 
opium-poppy is not at all an accidental anomaly, 
but an old true horticultural variety, which 
can be bought everywhere under the names of 
Papaver somniferum monstruosum or polyce- 
phalum. Since it is an annual plant, only the 
seeds are for sale, and this at once gives a suffi- 
cient proof of its heredity. In all cases, where 
it was met with accidentally by botanists, it is to 
be assumed that stray seeds had been casually 
mixed with those of other varieties, or that the 
habit had been transmitted by a spontaneous 
cross. 

Wherever opportunity led to experiments on 
heredity, distinct races were found to be in pos- 
session of this quality, while others were not. 
It is of no use to cultivate large numbers 
of wall-flowers in the hope of one day seeing the 
anomaly arise ; the only means is to secure the 
strain from those who have got it. With pop- 
pies the various varieties are so often inter- 
crossed by bees, that the appearance of an acci- 
dental change may sometimes be produced, and 
in the honseleek the pistilloid variety seems to 
be the ordinary one, the normal strain being 
very rare or perhaps wholly wanting. 

Our three illustrative examples are good and 
permanent races, producing their peculiar quali- 



372 Ever-sporting Varieties 

ties regularly and abundantly. In this respect 
they are however very variable and dependent 
on external circumstances. Such a regularity 
is not met with in other instances. Often pedi- 
gree-experiments lead to poor races, betraying 
their tendency to deviate only from time to time 
and in rare cases. Such instances constitute 
what we have called in a former lecture, “ half- 
races,’* and their occurrence indicates that the 
casual observation of an anomaly is not in itself 
adequate to give an opinion as to the chance of 
repetition in sowing experiments. A large 
number of species seem to belong to this case, 
and their names may be found in the above 
mentioned work by Masters and elsewhere. 
But no effort has yet been made to separate 
thoroughly the pistilloid half-races from the 
corresponding ever-sporting varieties. Some 
plants are recorded as being more liable to this 
peculiarity than others. 

Stamens are sometimes replaced by open 
carpels with naked ovules arising from their 
edges and even from their whole inner sur- 
faces. This may be seen in distinct strains of 
the cultivated bulbous Begonia, and more rarely 
in primroses. Here the apex of the carpellary 
leaf is sometimes drawn out into a long style, 
terminated by a flattened spatulate stigma. 

The pistillody of the stamens is frequently 



Polycephalic Poppies 373 

combined with another deviation in the poppies. 
This is the growing together of some of the 
altered stamens so as to constitute smaller or 
larger connate groups. Often two are united, 
sometimes three, four or more. Flowers with 
numerous altered stamens are seldom wholly 
free from this most undesirable secondary 
anomaly. I call it undesirable with respect 
to experiments on the variability of the 
character. For it may easily be seen that 
while it is feasible to count the stamens 
even when converted into pistils, it is not 
possible when groups of them are more or 
less intimately united into single bodies. This 
combination makes all enumeration difficult and 
inaccurate and often wholly unreliable. In 
such cases the observation is limited to a compu- 
tation of the degree of the change, rather than 
to a strict numerical inquiry. Happily the re- 
sponses to the experimental influences are so 
marked and distinct that even this method of de- 
scribing them has proved to be wholly sufficient. 

In extreme instances I have seen all the 
changed stamens of a flower of the opium-poppy 
united into a single body, so as to form a close 
sheath all around the central ovary. Lesser 
sheaths, surrounding one-half or one-third of 
the capsule are of course less rarely met with. 

Leaving this description of the outer appear- 



374 


Ever-sporting Varieties 

ance of Oar anomaly, we may now consider it 
from the doable point of view of inheritance 
and variability. 

The fact of inheritance is shown by the ex- 
perience of many anthors, and by the drcom- 
stance already qnoted, that the variety has been 
propagated from seed for more than half a cen- 
tnry, and may be obtained from various seed- 
merchants. In respect to the variability, the 
variety belongs to the ever-sporting group, con- 
stituting a type which is more closely related to 
the ‘‘five-leaved ” clover than to the striped 
flowers or even the double stocks. 

It fluctuates around an average type with half 
filled crowns, going as far as possible in both 
directions, but never transgressing either limit. 
It is even doubtful whether the presumable 
limits are, under ordinary circumstances, ever 
reached. Obviously one extreme would be the 
conversion of all the stamens, and the other the 
absolute deficiency of any marked tendency to 
such a change. Both may occur, and will prob- 
ably be met with from time to time. But they 
must be extremely rare, since in my own exten- 
sive experiments, which were strictly controlled, 
I never was able to find a single instance of 
either of them. Some of the outer stamens 
have always remained unchanged, yielding 
enough pollen for the artificial pollination of 



Polycephalic Poppies 


375 


the central ovary, and on the other hand some 
rudiments of hardened filaments were always 
left, even if they were reduced to small pro- 
tuberances on the thalamus of the flower. 

Between these extremes all grades occur. 
From single, partially or wholly changed 
stamens upwards to 150 and over, all steps may 
be seen. It is a true fluctuating variability. 
There is an average of between 50 and 100, con- 
stituting a nearly filled crown around the cen- 
tral capsule. Around this average the smaller 
deviations are most numerous and the larger 
ones more rare. The inspection of any bed of 
the variety suffices to show that, taken broadly, 
the ordinary laws of fluctuating variability are 
applicable. No counting of the single individ- 
uals is required to dispel all doubts on this 
point 

Moreover all intermediate steps respecting 
the conversion of the single stamens may nearly 
always be seen. Barely all are changed into 
normal secondary ovaries with a stigma and 
with a cavity filled with ovules. Often the 
stigma is incomplete or even almost wanting, in 
other instances the ovules are lacking or the 
cavity itself is only partially developed. Not 
rarely some stamens are reduced and converted 
into thin hard stalks, without any appearance of 
an ovary at their tip. But then the demar- 



376 Ever-sporting Varieties 

cation between them and the thalamus fails, so 
that they cannot be thrown off when the flower 
fades away, but remain as small stumps around 
the base of the more fully converted filaments. 
This fact would frequently render the enumera- 
tion of the altered organs quite unreliable. 

For these reasons I have chosen a group of 
arbitrary stages in order to express the degree 
of deviation for a given lot of plants. The 
limits were chosen so as to be sufficiently trust- 
worthy and easy to ascertain. In each group 
the members could be counted, and a series of 
figures was reached by this means which al- 
lowed of a further comparison of the competing 
sets of plants. 

It should be stated that in such experiments 
and especially in the case of such a showy crite- 
rion as the pistilloid heads afford after the time 
of fiowering is over, the inspection of the con- 
trolling beds at once indicates the result of the 
experiment. Even a hasty survey is in most 
cases sufficient to get a definite conclusion. 
Where this is not the case, the counting of the 
individuals of the various groups often does not 
add to the evidence, and the result remains un- 
certain. On the other hand, the impression 
made by the groups of plants on the experi- 
menter and on his casual visitors, cannot well 
be conveyed to the readers of his account by 



Polycephalic Poppies 377 

other means than by figures. For this reason 
the result of the experiments is expressed in 
this way. 

I made six groups. The first includes the 
cases where the whole circle is reduced to 
small rudiments. The second shows 1-10 sec- 
ondary capsules. The two following consti- 
tute half a crown around the central fruit, the 
third going up to this limit, the fourth going 
from this limit to a nearly filled circle. Wholly 
filled circles of secondary capsules without gaps 
give the two last degrees, the fifth requiring 
only continuity of the circle, the sixth display- 
ing a large and bright crown all around the 
central head. The fifth group ordinarily in- 
cludes from 90 - 100 altered stamens, while the 
sixth has from 100-150 of these deviating 
parts. 

In ordinary cultures the third and fourth 
group, with their interrupted crowns, predomi- 
nate. Large crowns are rare and flowers which 
at first sight seem to be wholly normal, occur 
only under circumstances definitely known to be 
unfavorable to growth, and to the development 
of the anomaly. 

Having reached by this means a very simple 
and easy method of statmg the facts shown by 
equal lots under contrasting influences, we will 
now make use of it to inquire into the relation 



378 Ever-Porting Varieties 

of this exceptionally high degree of variability 
to the inner and outer conditions of life. 

As a mle, all experiments show the existence 
of such a relation. Unfavorable conditions re- 
duce the numbers of altered stamens, favorable 
circumstances raise it to its highest point. This 
holds true for lots including himdreds of speci- 
mmis, but also for the sundry heads of one bed, 
and often for one single plant. 

We may compare the termmal flower with 
those of the lateral branches on a plant, and 
when no special influences disturb the experi- 
ment, the terminal head ordinarily bears the 
richest crown. If the first has more than 
100 metamorphosed parts, the latter have 
often less than 50 on the same plant. In poor 
soil, terminal heads are often reduced to 10 - 20 
monstrous organs, and in such cases 1 found the 
lateral flowers of the same plants ordinarily 
with less than 10 altered stamens. In some 
cases I allowed the branches of the third and 
fourth degree, in other words, the side twigs of 
the first branches of my selected plants to grow 
out and produce flowers in the fall. They were 
ordinarily weak, sometimes very small, having 
only 5-9 stigmas on their central fruit. Sec- 
ondary capsules were not seen on such flowers, 
even when the experiment was repeated on a 



Polycephalic Poppies 379 

somewhat larger scale and during a series of 
years. 

Among the same lot of plants individual dif- 
ferences almost always occur. They are partly 
due to inequalities already existing in the seeds, 
and partly to the diversity of the various parts 
of the same bed. Some of the plants become 
stout and have large terminal heads. Others 
remain very weak, with a slender stem, small 
leaves and undersized dowers. The height and 
thickness of the stem, the growth of the foliage 
and of the axillary buds are the most obvious 
measures of the individual strength of the 
plant. The development of the terminal flower 
and the size of its ovary manifestly depends 
largely on this individual strength, as may be 
seen at once by the inspection of any bed of 
opium-poppies. Now this size of the head can 
easily be measured, either by its height or cir- 
cumference, or by its weight. Moreover we can 
arrange them into a series according to their 
size. If we do this with the polycephalous vari- 
ety, the relation between individual strength 
and degree of metamorphosis at once becomes 
manifest. The largest heads have the brightest 
crowns, and the number of supernumerary car- 
pels diminishes in nearly exact proportion to the 
size of the fruits. Fruits with less than 50 al- 
tered stamens weighed on an average 5 grams. 



^0 Ever-sporting Varieties 

those with 50-100 snch organs 7 grams and 
those with a bright crown 10 grams, the appen- 
dices being removed before the weighing. Cor- 
responding results have been reached by the 
comparison of the height of the capsules with 
their abnormal surroundings. The degree of 
development of the monstrosity is shown by this 
observation to be directly dependent on, and in 
a sense proportionate to the individual strength 
of the plant. 

The differences between the specimens grown 
from a single lot of seeds, for instance from 
the seeds of one self-fertilized capsule are, as I 
have said, partly due to the divergences which 
are always present in a bed, even if the utmost 
care has been taken to make it as imiform as 
possible. These local differences are ordinarily 
underrated and overlooked, and it is often con- 
sidered to be sufficient to cultivate small lots of 
plants under apparently similar conditions on 
neighboring beds, to be justified in imputing all 
the observed deviations of the plants to heredi- 
tary inequalities. This of course is true for 
large lots, whenever the averages only are com- 
pared. In smaller experiments the external con- 
ditions of the single individuals should always 
be considered carefully. Lots of one or two 
square meters suffice for such comparisons, but 
smaller lots are always subject to chances and 



Polycephalic Poppies 


381 


possibilities, which should never he left out of 
consideration. 

Therefore I will now point out some circum- 
stances, which are ordinarily different on va- 
rious parts of one and the same bed. 

In the first place comes the inequality of the 
seeds themselves. Some of them will germi- 
nate earlier and others later. Those that dis- 
play their cotyledons on a sunny day will he 
able to begin at once with the production of 
organic food. Others appear in bad weather, 
and will thus he retarded in their development. 
These effects are of a cumulative nature as 
the young plants must profit by every hour of 
sunshine, according to the size of the cotyledons. 
Any inequality between two young seedlings is 
apt to he increased by this cumulative effect. 

The same holds good for the soil of the bed. 
It is simply impossible to mix the manure so 
equally that all individuals receive the same 
amount of it from the very beginning. I am in 
the habit of using manures in a dry and pulver- 
ized condition, of giving definite quantities to 
each square meter, and of taking the utmost 
care to get equal distribution and mixture with 
the soil, always being present myself during this 
most important operation. Nevertheless it is 
impossible to make the nourishment exactly 
equal for all the plants of even a small bed. 



3^ Ever~sporting Varieties 

Any ineqnality from this cause will increase 
the difference in the size of the young leaves, 
augment the inequality of their production of 
organic matter and for this reason go on in an 
ever increasing rate. 

Bain and spraying, or on the other hand dry- 
ness of the soil, have stUl greater consequences. 
The slightest unevenness of the surface will 
cause some spots to dry rapidly and others to 
retain moisture during hours and even some- 
times during days. 

Seeds, germinating in such little moist de- 
pressions grow regularly and rapidly, while 
those on the dryer elevations may be retarded 
for hours and days, before fully unfurling their 
seed-leaves. After heavy rains these differ- 
ences may be observed to increase continu- 
ally, and in some instances 1 found that plants 
were produced only on the wet spots, while the 
dry places remained perfectly bare. From this 
the wet spots seem to be the most favorable, but 
on the other hand, seeds may come to germinate 
there too numerously and so closely that the 
young plants will be crowded together and find 
neither space nor light enough, for a free and 
perfect development. The advantage may 
change to disadvantage in this way unless the 
superfluous individuals are weeded out in due 
time. 



Polycephalic Poppies 


383 


From all these and other reasons some plants 
will be favored by the external conditions from 
the beginning, while others will be retarded, and 
the effects will gradually increase until at last 
they become sufficient to account for a consider- 
able amount of individual variability. There 
is no doubt that the difference in the strength of 
the plant and in the size of the capsules, going 
from 5-10 grams for a single fruit, are for the 
most part due to these unavoidable circum- 
stances. I have tried all conceivable means to 
find remedies for these difficulties, but only by 
sowing my seeds in pans in a glass-house have 
I been able to reach more constant and equal 
conditions. But unfortunately such a method 
requires the planting out of the young seed- 
lings in the beginning of the summer, and this 
operation is not without danger for opium-pop- 
pies, and especially not without important influ- 
ence on the monstrosity of the pistilloid variety. 
Consequently my sowings of this plant have 
nearly always been made in the beds. 

In order to show how great the influence of all 
these little things may become, we only have to 
make two sowings on neighboring beds and un- 
der conditions which have carefully been made 
as equal as possible. If we use for these con- 
trolling experiments seeds from one and the 
same capsule, it will soon become evident that 



384 Ever-sporting Varieties 

no exact similarity between the two lots may be 
expected* Such differences as may be seen in 
these cases are therefore never to be considered 
of value when comparii^ two lots of seeds of 
different origin, or under varying conditions. 
No amount of accuracy in the estimation of the 
results of a trial, or in the counting out of the 
several degrees of the anomaly, is adequate to 
overcome the inaccuracy resulting from these 
differences. 

It is certainly of great importance to have a 
correct conception in regard to the influence of 
the surrounding conditions on the growth of a 
plant and on the development of the attribute we 
are to deal with. No less important is the ques- 
tion of the sensibility of the plants to these fac- 
tors. Obviously this sensibility must not be 
expected to remain the same during the entire 
life-period, and periods of stronger and of 
weaker responses may be discerned. 

In the first place it is evident that external or 
inner influences are able to change the direction 
of the development of an organ only so long as 
this development is not yet folly finished. In 
the young flower-bud of the pistilloid poppy 
there must evidently be some moment in which 
it is definitely decided whether the young 
stamen^ will grow out normally or become meta- 
morphosed into secondary pistils. From this 



Polycephalic Poppies 385 

moment no further change of external condi- 
tions is able to produce a corresponding change 
in the degree of the anomaly. The indi- 
vidual strength of the whole plant may still be 
affected in a more or less manifest degree, but 
the number of converted stamens of the flower 
has been definitely fixed. The sensitive period 
has terminated. 

In order to determine the exact moment of 
this termination of the period of sensibility, I 
have followed the development of the flower- 
buds during the first weeks of the life of the 
young plants. The terminal flower may al- 
ready be seen in young plants only seven weeks 
old, with a stem not exceeding 5-6 cm. in 
height and a flower-bud with a diameter of 
nearly 1mm., in which the stamens and sec- 
ondary pistils are already discernible, but still 
in the condition of small rounded protuberances 
on the thalamus. Though it is not possible at 
that time to observe any difference between the 
future normal and converted stamens, it does 
not seem doubtful that the development is so far 
advanced, that in the inner tissues the decision 
has already definitely been taken. In the next 
few days this decision rapidly becomes vis- 
ible, and the different parts of the normal 
stamens and the metamorphosed carpels soon 
become apparent. From this observation it 



384 Ever-Sporting Varieties 

no exact siimlarily between the two lots may be 
expected, Snch differences as may be seen in 
these cases are therefore never to be considered 
of value when comparing two lots of seeds of 
different origin, or under varying conditions. 
No amount of accuracy in the estimation of the 
results of a trial, or in the counting out of the 
several degrees of the anomaly, is adequate to 
overcome the inaccuracy resulting from these 
differences. 

It is certainly of great importance to have a 
correct conception in regard to the influence of 
the surrounding conditions on the growth of a 
plant and on the development of the attribute we 
are to deal with. No less important is the ques> 
tion of tbe sensibility of the plants to these fac- 
tors. Obviously this sensibility must not be 
expected to remain the same during the entire 
life-period, and periods of stronger and of 
weaker responses may be discerned. 

In the first place it is evident that external or 
inner influences are able to change the direction 
of the devdopment of an organ only so long as 
this development is not yet fnlly finished. In 
the young flower-bud of the pistilloid poppy 
there must evidently be some moment in which 
it is definitely decided whether the young 
stamens will grow out normally or become meta- 
morphosed into secondary pistils. From this 



Polycephalic Poppies 385 

moment no further diange of external condi- 
tions is able to produce a corresponding change 
in the degree of the anomaly. The indi- 
vidual strength of the whole plant may still be 
affected in a more or less manifest degree, but 
the number of converted stamens of the flower 
has been deflnitely fixed. The sensitive period 
has terminated. 

In order to determine the exact moment of 
this termination of the period of sensibility, I 
have followed the development of the flower- 
buds during the first weeks of the life of the 
yoimg plants. The terminal flower may al- 
ready be seen in young plants only seven weeks 
old, with a stem not exceeding 5-6 cm. in 
height and a flower-bud with a diameter of 
nearly 1mm., in which the stamens and sec- 
ondary pistils are already discernible, but still 
in the condition of small rounded protuberances 
on the thalamus. Though it is not possible at 
that time to observe any difference between the 
future normal and converted stamens, it does 
not seem doubtful that the development is so far 
advanced, that in the inner tissues the decision 
has already definitely been taken. In the next 
few days this decision rapidly becomes vis- 
ible, and the different parts of the normal 
stamens and the metamorphosed carpels soon 
become apparent. From this observation it 



386 Ever-sportmg Varieties 

can be inferred that the sensitive period of the 
anomaly is limited for the terminal flower-head, 
to the first few weeks of the life of the young 
plants. The secondary heads manifestly leave 
this period at a somewhat later stage. 

In order to prove the accuracy of this con- 
clusion 1 have tried to injure the anomalies 
after the expiration of the first six or seven 
weeks. I deprived them of their leaves, and 
damaged them in different ways. I succeeded 
in making them very weak and slender, without 
being able to diminish the number of the super- 
numerary carpels. The proportionality of the 
size of the central fruit and the development of 
the surrounding crown can often be modified or 
even destroyed by this means, and the apparent 
exceptions from this rule, which are often ob- 
served, may find their explanation in this way. 

In the second place I have tried to change the 
development of the anomaly during the period 
of sensibility, and even in the last part of it 
This experiment succeeded fully when carried 
out within the fifth or sixth week after the be- 
ginning of the germination. As means of in- 
jury I transplanted the young plants. To this 
end I sowed my seeds in pans in unmanured soil, 
planted them out in little pots with richly pre- 
I^ured earth, grew them in these during a few 
weeks and afterwards transferred them to the 



Polycephalic Poppies 387 

beds, taking care that the pots were removed, 
but the balls of earth not broken. 

In consequence of this treatment the plants 
became very large and strong, with luxuriant 
foliage and relatively numerous large flowers 
and fruits. But almost without exception they 
were poor in anomalous stamens, at least so on 
the terminal heads. On a lot of some 70 plants 
more than 50 had less than half a crown of sec- 
ondary capsules, while from the same packet of 
seed the control-plants gave in an equal number 
more than half of filled crowns on all plants with 
the exception of five weak specimens. 

It is curious to compare such artificially in- 
jured plants with the ordinary cultures. 
Strong stems and heavy fruits, which otherwise 
are always indicative of showy crowns, now 
bear fruits wholly or nearly destitute of any 
anomalous change. The commonly prevailing 
rule seems to be reversed, showing thereby the 
possibility of abolishing the correlation between 
individual strength and anomaly by an artificial 
encroachment upon the normal conditions. 

Aside from these considerations the experi- 
ments clearly give proof of the existence of a 
period of sensibility limited to the first weeks of 
the life of the plant for the terminal flower. 
This knowledge enables us to explain many ap- 



388 Ever-sporting Varieties 

parent abnormalities, which may occnr in the 
experiments. 

We now may take a broader view of the pe- 
riod of sensibility. Evidently the response to 
external influences will be greater the younger 
the oi^an. Sensibility will gradually diminish, 
and the phenomena observed in the last part 
of this period may be considered as the last re- 
mainder of a reaction which previously must 
have been much stronger and much readier, pro- 
viding that it would be possible to isolate them 
from, and contrast them with, the other re- 
sponses of the same plant. 

With the light thus cast upon the question, 
we may conclude that the sensitive period com- 
mences not only at the beginning of the germi- 
nation, but must also be considered to include 
the life of the seed itself. From the moment 
of fertilization and the formation of the 
young embryo the development must be sub- 
jected to the influence of external agencies 
which determine the direction it will take and 
the degree of development it will finally be able 
to acquire. Probably the time of growth of 
the embryo and of the ripening of the seed 
correspond exactly to the period of highest 
sensibility. This period is only interrupted 
during the resting stage of the seed, to be re- 
peated in germination. Afterwards the sensi- 



Polpcephalic Poppies 389 

bility slowly and gradually decreases, to end 
with the definite decision of all further growth 
sometime before the outer form of the organ be- 
comes visible under the microscope. The last 
period of life includes only an expansion of the 
tissues, which may still have some influence on 
their final size, but not on their form. This 
has been definitely arrested before the end of 
the sensitive period, and ordinarily before the 
commencement of that rapid development, 
which is usually designated by the name of 
growth, as contrasted with evolution. 

Within the seed the evolution of the young 
plant manifestly depends upon the qualities 
and life-conditions of the parent-plant. The 
stronger this is, and the more favorable circum- 
stances it is placed under, the more food will be 
available for the seed, and the healthier will be 
the development of the embryo. Only well- 
nourished plants give well-nourished seeds, and 
the qualities of each plant are for this reason 
at least, partly dependent on the properties of 
its parents and even of its grandparents. 

From these considerations the inference is 
forced upon us that the apparently hereditary 
differences, which are observed to exist among 
the seeds of a species or a variety and even of a 
single strain or a single parent-plant, may for 
a large part, and perhaps wholly, be the result 



390 Ever-sporting Varieties 

of the life-conditions of their parents and 
grandparents. Within the race all variability 
would in this way be reduced to the effects 
of external circumstances. Among these nour- 
ishment is no doubt the most momentous, 
and this to such a degree that older writers 
designated the external conditions by the term 
nourishment According to Knight nutrition 
reigns supreme in the whole realm of vari- 
ability, the kind of food and the method of nour- 
ishment coming into consideration only in a sec- 
ondary way. The amount of useful nutrition 
is the all-important factor. 

If this is so, and if nutrition decides the de- 
gree of deviation of any given character, the 
widest deviating individuals are the best nour- 
ished ones. The best nourished not only dur- 
ing the period of sensibility of the attribute un- 
der consideration, but also in the broadest sense 
of the word. 

This discussion casts a curious light upon the 
whole question of selection. Not of course 
upon the choice of elementary species or varie- 
ties out of the original motley assembly which 
nature and old cultures offer us, but upon the 
selection of the best individuals for isolation and 
for the improvement of the race. These are, 
according to my views, only the best nourished 
ones. Their external conditions have been the 



Polycephiilic Poppies 


391 


most favorable, not only from the beginning of 
their own life in the field, but also during their 
embryonic stages, and even during the prepara- 
tion of these latter in the life of their parents 
and perhaps even their grandparents. Selec- 
tion then, would only be the choice of the best 
nourished individuals. 

In connection with the foregoing arguments 
I have tried to separate the choicest of the pop- 
pies with the largest crown of pistilloid stamens, 
from the most vigorous individuals. As we 
have already seen, these two attributes are 
as a rule proportional to one another. Excep- 
occur, but they may be explained by some 
hQ^r changes in the external circumstances, as 
I nave also pointed out. As a rule, these ex- 
ceptions are large fruits with comparatively too 
few converted stamens; they are exactly the 
contrary from what is required for a selection. 
Or plants, which from the beginning were 
robust, may have become crowded together by 
further growth, and for these reasons become 
weaker than their congeners, though retaining 
the full development of the staminodal crown, 
which was fixed during the sensitive period and 
before the crowding. I have searched my beds 
yearly for several years in vain to find individ- 
uals which might recommend themselves for se- 
lection without having the stamp of permanent. 



392 Ever-sportiwg Varieties 

OP at least temporarily better, nourishmmit. No 
starting-point for such an independent selection 
has ever been met with. 

Summing up the consequences of this some- 
what extended discussion, we may state it as a 
rule that a general proportion between the in- 
dividual strength and the degree of develop- 
ment of the anomaly exists. And from this 
point of view it is easy to see that all external 
causes which are known to affect the one, must 
be expected to influence the other also. 

It will therefore hardly be necessary to give 
a foil description of all my experiments on the 
relations of the monstrosity to external coi^fe* 
tions. A hasty survey will suffice. 

This survey is not only intended to convey an 
idea of the relations of pistilloid poppies to 
their environment, but may serve as an ex- 
ample of the principle involved. According 
to my experience with a large range of other 
anomalies, the same rule prevails everywhere. 
And this rule is so simple that exact knowledge 
of one instance may be considered as sufficient 
to enable us to calculate from analogy what is 
to be expected from a ^ven treatment of any 
other anomaly. Our appreciation of observed 
facts and the conditions to be chosen for 
intended cultures are largely dependent on such 
calculations. What I am now going to describe 



Polycephalic Poppies 


393 


is to be considered therefore as an experimental 
basis for such expectations. 

First of all comes the question how many in- 
dividuals are to be grown in a given place. 
When sowing plants for experimental purposes 
it is always best to sow in rows, and to give as 
few seeds to each row as possible, so as to in- 
sure all necessary space to the young plants. 
On the other hand the seeds do not all germi- 
nate, and after sowing too thinly, gaps may ap- 
pear in the rows. This would cause not only a 
loss of space, but an inequality between the 
plants in later life, as those nearest the gaps 
would have more space and more light, and a 
larger area for their roots than those growing 
in the imbroken rows. Hence the necessity of 
using large quantities of seed and of weeding 
out a majority of young plants on the spots 
where the greatest numbers germinate. 

Crowded cultures as a rule, will give weak 
plants vdth thin stems, mostly unbranched and 
bearing only small capsules. According to the 
rule, these will produce imperfect crowns of sec- 
ondary pistils. The result of any culture will 
thus be dependent to a high degree on the num- 
ber of individuals per square meter. I have 
sown two similar and neighboring beds with 
the thoroughly mixed seeds of parent-plants of 
the same strain and culture, using as much 



394 Ever-sporting Varieties 

as 2.5 cab. cm. per square meter. On one of the 
beds 1 left all the germinating plants untouched 
and nearly 500 of them flowered, but among 
them 360 were almost without pistillody, and 
only 10 had full crowns. In the other bed I 
weeded away more than half of the young 
plants, leaving only some 150 individuals and got 
32 with a full crown, nearly 100 with half crowns 
and only 25 apparently without monstrosity. 

These flgures are very striking. From the 
same quantity of seed, in equal spaces, by sim- 
ilar exposure and treatment 1 got 10 fully de- 
veloped instances in one and 32 in the other 
case. The weeding out of supernumerary indi- 
viduals had not only increased the percentage 
of bright crowns, but also their absolute num- 
ber per square meter. So the greatest number 
of anomalies upon a given space may be ob- 
tained by taking care that not too many plants 
are grown upon it: any increase of the number 
beyond a certain limit will diminish the prob- 
ability of obtaining these structures. The most 
successful cultures may be made after the max- 
imum number of individuals per unit of area 
has been determined. A control-experiment 
was made under the same conditions and with 
the same seed, but allowing much less for 
the same space. I sowed only 1 cu. cm. on my 
bed of 2 square meters, and thereby avoided 



Polycephalic Poppies 395 

nearly all weeding out. 1 got 120 plants, and 
among them 30 with full crowns of converted 
stamens, practically the same number as after 
the weeding out in the first experiment. This 
shows that smaller quantities of seed give an 
equal chance for a greater number of large 
crowns, and should therefore always be pre- 
ferred, as it saves both seed and labor. 

Weeding out is a somewhat dangerous oper- 
ation in a comparative trial Any one who has 
done it often, knows that there is a strong 
propensity to root out the weaker plants and to 
spare the stronger ones. Obviously this is the 
best way for ordinary purposes, but for com- 
parisons evidently one should not discriminate. 
This rule is very diflScult in practice, and for 
this reason one should never sow more than is 
absolutely required to meet all requirements. 

Our second point is the manuring of the soil. 
This is always of the highest importance, both 
for normal and for anomalous attributes. The 
conversion of the stamens into pistils is in a 
large measure dependent upon the conditions of 
the soil. I made a trial with some 800 flowering 
plants, using one sample of seed, but sowing 
one-third on richly manured soil, one-third on 
an unprepared bed of my garden, and one-third 
on nearly pure sand. In all other respects the 
three groups were treated in the same way. Of 



396 Ever-sportmg Varieties 

the manured plants one-half gave full crowns, 
of the non-manured only one-fifth, and on the 
sandy soil a still smaller proportion. Other 
trials led to the same results. 1 have often made 
use of steamed and ground horn, which is a ma- 
nure very rich in nitrogenous substances. One- 
eighth of a kilo per square nieter is an ample 
amount. And its effect was to increase the 
number of full crowns to an exceptional degree. 

In the controlling trial and under ordinary 
circumstances this figure reached some 50^, 
but with ground horn it came up as high 
as 90^. We may state this result by the 
very striking assertion that the number of large 
crowns in a given culture may be nearly doubled 
by rich manure. 

All other external conditions act in a similar 
manner. The best treatment is required to at- 
tain the best result. A sunny exposure is one 
of the most essential requisites, and in some at- 
tempts to cultivate my poppies in the shade, 1 
found the pistillody strongly reduced, not a 
single full crown being found in the whole lot. 
Often the weather may be hurtful, especially 
during the earlier stages of the plants. I pro- 
tected my beds during several trials by covering 
them with glass for a few weeks, until the young 
plants reached the glass covering. I got a nor- 
mal number of full crowns, some 55%, at a time 



Polycephalic Poppies 397 

when the weather was so bad as to reduce the 
number in the control experiments to 10%. 

It would be quite superfluous to give more de- 
tails or to describe additional experiments. 
Suffice to say, that the results all point in the 
same direction, and that pistillody of the pop- 
pies always clearly responds to the treatment, 
especially to external conditions during the first 
few weeks, that is, during the period of sensi- 
tiveness. The healthier and the stronger the 
plants the more fully they will develop their 
anomaly. 

In conclusion something is to be said about 
the choice of the seed- Obviously it is possible 
to compare seeds of different ori^ by sowing 
and treating them in the same way, giving at- 
tention to all the points above mentioned. In 
doing so the first question will be, whether there 
is a difference between the seeds of strong 
plants with a bright crown around the head and 
those of weaker individuals with lesser develop- 
ment of the anomaly. It is evident that such a 
difference must be expected, since the nutrition 
of the seed takes place during the period of the 
greatest sensitiveness. 

But the experiments will show whether this 
effect holds good against the influences which 
tend to change the direction of the development 
of the anomaly during the time of germination. 



398 Ever-sporting Varieties 

The result of my attempt has shown that the 
choice of the seeds has a manifest influence upon 
the ultimate development of the monstrosity, but 
that this influence is not strong enough to over- 
whelm all other factors. 

The choice of the fullest or smallest crowns 
may be repeated during succeeding generations, 
and each time compared with a culture under 
average conditions. By this means we come to 
true selection-experiments, and these result in 
a notable and rapid change of the whole strain. 
By selecting the brightest crowns 1 have come 
up in three years from 40 to 90 and ultimately 
to 120 converted stamens in the best flower of 
my culture, and in selecting the smallest crowns 
I was able in three years to exclude nearly all 
good crowns, and to make cultures in which 
heads with less than half-filled crowns consti- 
tuted the majority. But such selected strains 
always remain very sensitive to treatment, and 
by changing the Conditions the effect may be 
wholly lost in a single year, or even turned 
in the contrary direction. In other words, the 
anomaly is more dependent on external condi- 
tions during the germinating period than on the 
dioice of the seeds, providing these belong to 
the pistilloid variety and have not deteriorated 
by some crossing with other sorts. 

At the beginning of this lecture 1 stated that 



PolycepTialic Popptes 399 

no selection is adequate to produce either a pure 
strain of brightly crowned flower-heads without 
atavism, or to conduce to an absolute and per- 
manent loss of the anomaly. During a series of 
years I have tested my plants in both directions, 
but without the least effect. Limits are soon 
reached on both sides, and to transgress these 
seems quite impossible. 

Taking these limits as the marks of the 
variety, and considering all fluctuations between 
them as responses to external influences work- 
ing during the life of the individual or govern- 
ing the ripening of the seeds, we get a clear pic- 
ture of a permanent ever-sporting type. The 
limits are absolutely permanent during the 
whole existence of this already old variety. 
They never change. But they include so wide a 
range of variability that the extremes may be 
said to sport into one another, so much the more 
so as one of the extremes is to be considered 
morphologically as the type of the variation, 
while the other extreme can hardly be distin- 
guished from the normal form of the species. 



Leotube XIV 


MONSTBOSITIES 

I have previously dealt with the question of 
the hereditary tendencies that cause monstros- 
ities. These tendencies are not always ident- 
ical for the same anomaly. Two different 
tyx>e8 may, generally, be distinguished. One of 
them constitutes a poor variety, the other a rich 
one. But this latter is abundant and the first 
one is poor in instances of exactly the same con- 
formation. Therefore the difference only lies 
in the frequency of the anomaly, and not in its 
visible features. In discovering an instance of 
any anomaly it is therefore impossible to tell 
whether it belongs to a poor or to a rich race. 
This important qnestion can only be answered 
by direct sowing-experiments to determine the 
d^ree of heredity. 

Monstrosities are often considered as acci- 
dents, and rightfully so, at least as long as they 
are considered from a morphological point of 
view. Physiology of course excludes all acci- 
dentality. And in our present case it shows 

400 



Monstrosities 401 

that some internal hereditary quality is pres- 
ent, though often latent, and that the observed 
anomalies are to be regarded as responses 
of this innate tendency to external con- 
ditions. Our two types differ in the frequency 
of these responses. Bare in the poor race, they 
are numerous in the rich variety. The external 
conditions being the same for both, the heredi- 
tary factor must be different The tendency is 
weak in the one and strong in the other. In 
both eases, according to my experience, it may 
be weakened or strengthened by selection and 
by treatment. Often to a very remarkable de- 
gree, but not so far as to transgress the limits 
between the two races. Such transgression 
may apparently be met with from time to time, 
but then the next generation generally shows 
the fallacy of the conclusion, as it returns more 
or less directly to the type from which the strain 
had been derived. 

Monstrosities should always be studied by 
physiologists from this point of view. Poor 
and rich strains of the same anomaly seem at 
first sight to be so nearly allied that it might be 
thought to be very easy to change the one into 
the other. Nevertheless such chaii^s are not 
on record, and although I have made several at- 
tempts in this line, I never succeeded in passing 
the limit. I am quite convinced that sometime 



402 Ever-sporting Varieties 

a method will be discovered of arbitrarily pro- 
dndiig such, conversions, and perhaps the easi- 
est way to attain artificial mutations may lie 
concealed here. But as yet not the slightest in- 
dication of this possibility is to be found, save 
the fallacious conclusions drawn from too 
superficial observations. 

Unfortunately the poor strains are not very 
interesting. Their chance of producing beauti- 
ful instances of the anomaly for which they are 
cultivated is too small. Exceptions to this rule 
are only afforded by those curious and rare 
anomalies, which command general attention, 
and of which, therefore, instances are always 
welcome. In such cases they are searched for 
with perseverance, and the fact of their rarity 
impresses itself strongly on our mind. 

Twisted stems are selected as a first example. 
This monstrosity, called biastrepsis, consists of 
strongly marked torsions as are seen in many 
species with decussate leaves, though as a rule 
it is very rare. Two instances are the most 
generally known, those of the wild valerian 
(VcUeriana offlcinalis) and those of cultivated 
and wild sorts of teasels {Dipsacus fuUonum, D. 
sylvestris, and others). Both of these I have 
cultivated during upwards of fifteen years, but 
with contradictory results. The valerian is a 
perennial herb, multiplying itself yearly by 



Monstrosities 


403 


slender rootstocks or runners producing at their 
tips new rosettes of leaves and in the center of 
these the flowering stem. My original plant 
has since been propagated in this manner, and 
during several years I preserved large beds 
with hundreds of stems, in others I was com- 
pelled to keep my culture within more restricted 
limits. This plant has produced twisted stems 
of the curious shape, with a nearly straight 
flag of leaves on one side, described by De Can- 
dolle and other observers, nearly every year. 
But only one or two instances of abnormal 
stems occurred in each year, and no treatment 
has been found that proved adequate to increase 
this number in any appreciable manner. I have 
sown the seeds of this plant repeatedly, either 
from normal or from twisted stems, but without 
better results. It was highly desirable to be 
able to oifer instances of this rare and interest- 
ing peculiarity to other universities and mu- 
seums, but no improvement of the race could be 
reached and I have been constrained to give it 
up. My twisted valerian is a poor race, and 
hardly anything can be done with it. Perhaps, 
in other countries the corresponding rich race 
may be hidden somewhere, but I have never had 
the good fortune of finding it. 

This good fortune however, I did have with 
the wild teasel or Dipsacus sylvestris. Twisted 



404 Ever-sporting Varieties 

steins of this and of allied species are often met 
with and have been described by several writers, 
bnt they were always considered as acci- 
dents and nobody had ever tried to cultivate 
them. In the summer of 1885 1 saw among a 
lot of normal wild teasels, two nicely twisted 
stems in the botanical garden of Amsterdam. 
I at once proposed to ascertain whether they 
would 3 rield a hereditary race and had all the 
normal individuals thrown away before the 
flowering time. My two plants flowered in this 
isolated condition and were richly pollinated by 
insects. Of course, at that time, I knew nothing 
of the dependency of monstrosities on external 
conditions, and made the mistake of sowing the 
seeds and cultivating the next generation in 
too great numbers on a small space. But 
nevertheless the anomaly was repeated, and the 
aberrant individuals were once more isolated 
before flowering. The third generation re- 
peated the second, but produced sixty twisted 
stems on some 1600 individuals. The result 
was very striking and quite sufficient for all fur- 
ther researches, but the-normal condition of the 
race was not reached. This was the case only 
after I had discovered the bad effects of grow- 
ing too many plants in a limited space. In the 
fourth generation I restricted my whole culture 
to about 100 individuals, and by this simple 



Monstrosities 405 

means at once got up to 34)^ of twisted st^s. 
This proportion has since remained practically 
the same. I have selected and isolated my 
plants during five succeeding generations, but 
without any further result, the percentage of 
twisted stems fluctuating between 30 and 
about 45 according to the size of the cultures 
and the favorableness or unfavorableness of the 
weather. 

It is very interesting to note that all depends 
on the question whether one has the good for- 
tune of finding a rich race or not, as this pedi- 
gree-culture shows. Afterwards everything de- 
pends on treatment and very little on selection. 
As soon as the treatment becomes adequate, the 
full strength of the race at once displays itself, 
but afterwards no selection is able to improve 
it to any appreciable amount. Of course, in 
the long run, the responses will be the same as 
those of the pistilloid poppies on the average, 
and some influence of selection will show itself 
on closer scrutiny. 

Compared with the polycephalous poppies my 
race of twisted teasels, is much richer in atav- 
ists. They are never absent, and always con- 
stitute a large part of each generation and each 
bed, comprising somewhat more than half of the 
individuals. Intermediate stages between them 
and the wholly twisted stems are not wanting, 



4^ Ever-sporting Varieties 

and a whole series of steps may easily be ob- 
served from sufficiently large cultores. But 
they are always relatively rare, and any lot of 
plants conveys the idea of a dimorphous race, 
the small twisted stems contrasting strongly 
with the tall straight ones. 

A sharper contrast between good representa- 
tives of a race and their atavists is perhaps to 
be seen in no other instance. All the details 
contribute to the differentiation in appearance. 
The whole stature of the plants is affected by 
the varietal mark. The atavists are not, as 
in the case of the poppies, obviously allied with 
the type by a full range of intermediate steps, 
but quite distant from it by their rarity. There 
seems to be a gap in the same way as between 
the striped flowers of the snapdragon and their 
uniform red atavists, while with the poppies 
the atavists may be viewed as being only the 
extremes of a series of variations fluctuating 
around some average type. 

From this reason it is as interesting to appre- 
ciate the hereditary position of the atavists of 
twisted varieties as it was for the red-flowered 
descendants of the striped flowers. In order to 
ascertain this relation it is only necessary to iso- 
late some of them during the blooming-period. 
I made this experiment in the summer of 1900 
with the eighth generation of my race, and con- 



Monstrosities 407 

trived to isolate three groups of plants by the 
use of parchment bags, covering them alter- 
nately, so the flowers of only one group were 
accessible to insects at a time. 1 made three 
groups, because the atavists show two different 
types. Some specimens have decussate stems, 
others bear all their leaves in whorls of three, 
but in respect to the hereditary tendency of the 
twisting character this difference does not seem 
to be of any importance. 

In this way I got three lots of seeds and sowed 
enough of them to have three groups of plants 
each containing about 150-200 well developed 
stems. Among these I counted the twisted indi- 
viduals, and found nearly the same numbers for 
all three. The twisted parents gave as many 
as twisted children, but the decussate ata- 
vists gave even somewhat more, viz., 445^, while 
the ternate specimens gave 375^. Obviously the 
divergencies between these figures are too slight 
to be dwelt upon, but the fact that the atavists 
are as true or nearly as true inheritors of the 
twisted race as the best selected individuals is 
clearly proved by this experience. 

It is evident that here we have a double race, 
including two types, which may be combined in 
different degrees. These combinations deter- 
mine a wide range of changes in the stature of 
the plants, and it seems hardly right to use the 



408 Ever-sportmg Varieties 

same term for such changes as for common 
variations. It is more a contention of opposite 
characters than a true phenomenon of simple 
variability. Or perhaps we might say that it 
is the effect of the cooperation of a very vari- 
able mark, the twisting, with a scarcely varying 
attribute of the normal structure of the stem. 
Between the two types an endless diversity pre- 
vails, but outwardly there are limits which are 
never transgressed. The double race is as per- 
manent, and in this sense as constant, as any 
ordinary simple variety, both in external form, 
and in its intimate hereditary qualities. 

I have succeeded in discovering some other 
rich races of twisted plants. One of them 
is the Sweet William {Dianthus harbatus)^ 
which yielded, after isolation, in the second 
generation, 25^ of individuals with twisted 
stems, and as each individual produces often 
10 and more stems, 1 had a harvest of 
more than half a thousand of instances of this 
curious, and ordinarily very rare anomaly. My 
other race is a twisted variety of Viscaria ocula- 
ta, which is still in cultivation, as it has the very 
consistent quality of being an annual. It yield- 
ed last summer (1903) as high a percentage as 
65 of twisted individuals, many of them repeat- 
ing the monstrosity on several branches. After 
some occasional observations GypsophUa pani- 



Monstrosities 


409 


culata seems to promise similar results. On 
the other hand I have sowed in vain the seeds of 
twisted specimens of the soapwort and the 
cleavewort {Saponaria officinalis and Galium 
Aparine). These and some others seems to be- 
long to the same group as the valerian and to 
constitute only poor or so-called half-races. 

Next to the torsions come the fasciated 
stems. This is one of the most common of all 
malformations, and consists, in its ordinary 
form, of a flat ribbon-like expansion of the stems 
or branches. Below they are cylindrical, but 
they gradually lose this form and assume a flat- 
tened condition. Sometimes the rate of growth 
is imequal on different portions or on the op- 
posite sides of the ribbon, and curvatures are 
produced and these often give to the fasciation 
a form that might be compared with a shep- 
herd’s crook. It is a common thing for fas- 
ciated branches and stems to divide at the 
summit into a number of subdivisions, and ordi- 
narily this splitting occurs in the lower part, 
sometimes dividing the entire fasciated portion. 
In biennial species the rosette of the root-leaves 
of the first year may become changed by the 
monstrosity, the heart stretching in a transverse 
direction so as to become linear. In the next 
year this line becomes the base from which the 
stem grows. In such cases the fasciated stems 



410 Ever-sporting Varieties 

are broadened and flattened from the very be- 
ginning, and often retain the incipient breadth 
throughout their further development Species 
of primroses {Primula japonica and others), of 
buttercups (Ranunculus hulhosus), the rough 
hawksbeard (Crepis biennis), the Aster Tripo- 
lium and many others could be given as in- 
stances. 

Some of these are so rare as to be considered 
as poor races, and in cultural trials do not pro- 
duce the anomaly except in a very few in- 
stances. Heads of rye are found in a cleft 
condition from time to time, single at their base 
and double at the top, but this anomaly is only 
exceptionally repeated from seed. Flattened 
stems of Rubia tinctorum are not unfrequently 
met with on the fields, but they seem to have as 
little hereditary tendency as the split rye 
(Secale Cereale). Many other instances could 
be given. Both in the native localities and in 
pedigree-cultures such ribboned stems are only 
seen from time to time, in successive years, in 
annual and biennial as well as in perennial 
species. The purple pedicularis (Pedicularis 
palustris) in the wild state, and the sunflower 
among cultivated plants, may be cited instead of 
giving a long list of analogous instances. 

On the other hand rich races of flattened 
stems are not entirely lacking. They easily be- 



Monstrosities 


411 


tray themselves by the frequency of the anom- 
aly, and therefore may be found, and tried in 
the garden. Under adequate cultivation they 
are here as rich in aberrant individuals as the 
twisted races quoted above, producing in good 
years from 30 - 40f( and often more instances. I 
have cultivated such rich races of the dandelion 
(Taraxacum officinale) , of Thrincia hirta, of the 
dame’s violet (Hesperis matronalis), of the 
hawkweed (Picris hieracioides) , of the rough 
hawksheard (Crepis hiennis), and others. 

Respecting the hereditary tendencies these 
rich varieties with flattened stems may be put in 
the same category with the twisted races. Two 
points however, seem to he of especial interest 
and to deserve a separate treatment. 

The common cockscomb or Celosia cristata, 
one of the oldest and most widely cultivated 
fasciated varieties may be used to illustrate 
the first point. In beds it is often to be; 
seen in quite uniform lots of large and beau- 
tiful crests, but this imiformity is only se- 
cured by careful culture and selection of the 
best individuals. In experimental trials 
such selection must be avoided, and in doing 
so a wide range of variability at once shows 
itself. Tall, branched stems with fan- 
shaped tops arise, constituting a series of 
steps towards complete atavism. This last 



412 Ever-sporting Varieties 

however, is not to be reached easily. It often 
requires several successive generations grown 
from seed collected from the most atavistic spec- 
imens. And even such selected strains are al- 
ways reverting to the crested type. There is 
no transgression, no springing over into a 
purely atavistic form, such as may be supposed 
to have once been the ancestor of the present 
cockscomb. The variety includes crests and 
atavists, and may be perpetuated from both. 
Obviously every gardener would select the seeds 
of the brightest crests, but with care the full 
crests may be recovered, even from the worst 
reversionists in two or three generations. It is 
a double race of quite the same constitution as 
the twisted teasels. 

My second point is a direct proof of this as- 
sertion, but made with a fasciated variety of a 
wild species. I took for my experiment the 
rough hawksbeard. In the summer of 1895 I 
isolated some atavists of the fifth generation of 
my race, which, by ordinary selection, gave in 
the average from 20 - 40}i of fasciated stems. 
My isolated atavists bore abundant fruit, and 
from these I had the next year a set of some 350 
plants, out of which about 20^ had broadened 
and linear rosettes. This proportion corre- 
sponds with the degree of inheritance which is 
shown in many years by the largest and strong- 



Monstrosities 


413 


est fasciated stems. It strengthens our concln- 
sion as to the innermost constitution of the 
double races or ever-sporting varieties. 

Twisted stems and fasciations are very strik- 
ing monstrosities. But they are not very good 
for further investigation. They require too 
much space and too much care. The calculation 
of a single percentage requires the counting of 
some hundreds of individuals, taking many 
square meters for their cultivation, and this, as 
my best races are biennial, during two years. 
For this reason the countings must always be 
very limited, and selection is restrained to the 
most perfect specimens. 

Now the question arises, whether this mark 
is the best upon which to found selection. This 
seems to be quite doubtful. In the experiments 
on the heredity of the atavists, we have seen 
that they are, at least often, in no manner 
inferior to even the best inheritors of the race. 
This suggests the idea that it is not at all certain 
that the visible characters of a given individual 
are a trustworthy measure of its value as to the 
transmission of the same character to the off- 
spring. In other words, we are confronted with 
the existence of two widely different groups of 
characters in estimating the hereditary tend- 
ency. One is the visible quality of the indi- 
viduals and the other is the direct observation 



414 Ever-sporting Varieties 

of the degree in which the attribute is trans- 
mitted. These are by no means parallel, and 
seem in some sense to be nearly independent 
of each other. The fact that the worst atavists 
may have the highest percentage of varietal 
units seems to leave no room for another ex- 
planation. 

Developing this line of thought, we gradually 
arrive at the conclusion that the visible attribute 
of a varying individual is perhaps the most un- 
trustworthy and the most unreliable character 
for selection, even if it seems in many cases 
practically to be the only available one. The di- 
rect determination of the degree of heredity it- 
self is obviously preferable by far. This degree 
is expressed by the proportion of its inheritors 
among the offspring, and this figure therefore 
should be elevated to the highest rank, as a 
measure of the hereditary qualities. Hence- 
forward we will designate it by the name of 
hereditary percentage. 

In scientific experiments this figure must be 
determined for every plant of a pedigree-culture 
singly, and the selection should be founded ex- 
clusively or at least mainly on it. It is easily 
seen that this method requires large numbers 
of individuals to be grown and counted. Some 
two or three hundred progeny of one plant are 
needed to give the decisive figure for this one 



Monstrosities 


415 


individual, and selection requires the compari- 
son of at least fifty or more individuals. This 
brings the total amount of specimens to be 
counted up to some tens of thousands. In prac- 
tice, where important interests depend upon the 
experiments, such numbers are usually em- 
ployed and often exceeded, but for the culture 
of monstrosities, other methods are to be sought 
in order to avoid these difficulties. 

The idea suggests itself here that the younger 
the plants are, when showing tiieir distinguish- 
ing marks, the more of them may be grown on a 
small space. Hence the best way is to choose 
such attributes, as may already be seen in the 
young seedlings, in the very first few weeks of 
their lives. Fortunately the seed-leaves them- 
selves afford such distinctive marks, and by this 
means the plants may be counted in the 
pans, requiring no culture at all in the gar- 
den. Only the selected individuals need be 
grown to ripen their seeds, and the whole selec- 
tion may be made in the spring, in the glass- 
house. Instead of being very troublesome, the 
determination of the hereditary percentages 
becomes a definite reduction of the size of the 
experiments. Moreover it may easily be effect- 
ed by any one who cares for experimental 
studies, but has not the means required for cul- 
tures on a larger scale. And lastly, there are 



416 Ever-sporting Varieties 

a ninnber of questions about heredity, period- 
icily, dependency on nourishment and other life- 
conditions, and even about hybridizing, which 
may be answered by this new method. 

Seed-leaves show many deviations from the 
ordinary shape, especially in dicotyledonous 
plants. A very common aberration is the multi- 
plication of their number, and three seed-leaves 
in a whorl are not rarely met with. The whorl 
may even consist of four, and in rare cases of 
five or more cotyledons. Cleft cotyledons are 
also to be met with, and the fissure may extend 
varying distances from the tips. Often all these 
deviations may be seen among the seedlings 
of one lot, and then it is obvious that together 
they constitute a scale of cleavages, the ternate 
and quatemate whorls being only cases where 
the cleaving has reached its greatest develop- 
ment. All in aU it is manifest that here we are 
met by one t3q)e of monstrosity, but that this 
type allows of a wide range of fluctuating varia- 
bility. For brevity’s sake all these cleft and 
temate, double cleft and quatemate cotyledons 
and even the higher grades are combined under 
one common name and indicated as tricotyls. 

A second aberration of young seed-plants is 
exactly opposite to this. It consists of the 
union of the two seed-leaves into a single 
organ. This ordinarily betrays its origin by 



Monstrosities 


417 


having two separate apices, but not always. 
Such seedlings are called syncotyledonous or 
syncotyls. Other monstrosities have been ob- 
served from time to time, but need not be men- 
tioned here. 

It is evident that the determination of the 
hereditary percentage is very easy in tricotyl- 
ous or syncotylous cultures. The parent- 
plants must be carefully isolated while bloom- 
ing. Many species pollinate themselves in the 
absence of bees; from these the insects are 
to be excluded. Others have the stamens and 
stigmas widely separated and have to be polli- 
nated artificially. Still others do not lend them- 
selves to such operations, but have to be left free 
to the visits of bees and of humble-bees, this be- 
ing the only means of securing seed from every 
plant. At the time of the harvest the seeds 
should be gathered separately from each plant, 
and this precaution should also be observed in 
studies of the hereditary percentage at large, 
and in all scientific pedigree-cultures. Every lot 
of seeds is to be sown in a separate pan, and care 
must be taken to sow such quantities that three 
to four hundred seedlings will arise from each. 
As soon as they display their cotyledons, they 
are counted, and the number is the criterion of 
the parent-plant Only parent-plants with the 
highest percentages are selected, and out of 



418 Ever-sporting Varieties 

their seedlings some fifty or a hundred of the 
best ones are chosen to furnish the seeds for the 
next generation. 

This description of the method shows that 
the selection is a double one. The first feature 
is the hereditary percentage. But then not all 
the seedlings of the selected parents can be 
planted out, and a choice has to be made. This 
second selection may favor the finest tricotyls, 
or the strongest individuals, or rely on some 
other character, but is unavoidable. 

We now come to the description of the cul- 
tures. Starting points are the stray tricotyls 
which are occasionally found in ordinary 
sowings. In order to increase the chance of 
finding them, thousands of seeds of the same 
species must be inspected, and the range of 
species must be widened as much as possible. 

Material for beginning such experiments is 
very easily obtained, and almost any large 
sample of seeds will be found suitable. Some 
tricotyls may be found among every thousand 
seedlings in many species, while in others ten or 
a hundred times as many plants must be exam- 
ined to secure them, but. species with absolutely 
pure dicotylous seeds are very rare. 

The second phase of the experiment how- 
ever, is not so promising. Some species are rich, 
and others are poor in this anomaly. This dif- 



Monstrosities 


419 


ference often indicates what may be expected 
from further culture. Stray tricotyls point to 
poor or half-races, while more frequent devia- 
tions suggest rich or double-races. In both 
cases however, the trial must be made, and this 
requires the isolation of the aberrant individ- 
uals and the determination of their hereditary 
percentage. 

In some instances the degree of their in- 
heritance is only a very small one. The iso- 
lated tricotyls yield 1 or of inheritors, in some 
cases even less, or upwards to 3 or 4?^. If the 
experiment is repeated, no amelioration is ob- 
served, and this result remains the same during 
a series of successive generations. In the case 
of Polygonum Convolvulus, the black bindweed, 
I have tried as many as six generations without 
ever obtaining more than 3;^. With other 
species I have limited myself to four successive 
years with the same negative result, as with 
spinage, the Moldavian dragon-head {Dracoce- 
phalum moldavicum), and two species of com 
catch-fly {SUene conica and 8, conoidea). 

Such poor races hardly afford a desirable ma- 
terial for further inquiries. Happily the rich 
races, though rare, may be discovered also from 
time to time. They seem to be more common 
among cultivated plants and horticultural as 
well as agricultural species may be used. Hemp 



420 Ever-sporting Varieties 

and mercury (Mercurialis annua) among the 
first, snapdragon, poppies, Phacelia, Helich- 
rysum, and Clarkia among garden-flowers may 
be ^ven as instances of species containing the 
rich tricotylons double races. 

It is very interesting to note how strong the 
difference is between such cases and those which 
only yield poor races. The rich type at once 
betrays itself. No repeated selection is re- 
quired. The stray tricotyls themselves, that 
are sought out from among the original samples, 
give hereditary percentages of a much higher 
type after isolation than those quoted above. 
They come up to 10 - 20^ and in some cases even 
to 40^. As may be expected, individual differ- 
ences occur, and it must even be supposed that 
some of the original tricotyls may not be pure, 
but hybrids between tricotylons and dicotyl- 
ous parents. These are at once eliminated 
by selection, and if only the tricotyls which 
have the highest percentages are chosen for the 
continuance of the new race, the second genera- 
tion comes up with equal numbers of dicotyls 
and tricotyls among the seedlings. The figures 
have been observed to range from 51 - 58^ in the 
majority of the cases, and average 55^, rarely 
diverging somewhat more from this average. 

Here we have the true type of an ever-sport- 
ing variety. Every year it produces in the 



Monstrosities 


421 


same way heirs and atavists. Every plant, if 
fertilized with its own pollen, gives rise to 
both types. The parent itself may be tricotyl- 
ous or dicotylous, or show any amount of 
multiplication and cleavage in its seed-leaves, 
but it always gives the entire range among its 
progeny of the variation. One may even select 
the atavists, pollinate them purely and repeat 
this in a succeeding generation without any 
chance of changing the result. On an average 
the atavists may give lower hereditary figures, 
but the difference will be only slight. 

Such tricotylous double races offer highly 
interesting material for inquiries into questions 
of heredity, as they have such a wide range of 
variability. There is little danger in asserting 
that they go upwards to nearly lOOj^, and down- 
wards to Oj^, diverging symmetrically on both 
sides of their average (50 - 55;^). These limits 
they obviously cannot transgress, and are not 
even able to reach them. Samples of seed con- 
sisting only of tricotyls are very rare, and when 
they are met with the presumption is that they 
are too few to betray the rare aberrants they 
might otherwise contain. Experimental evi- 
dence can only be reached by the culture of a 
succeeding generation, and this always discloses 
the hidden qualities, showing that the double 



422 Ever-sporting Varieties 

type was only temporarily lost, but bound to 
return as soon as new trials are made. 

This wide range of variability between def- 
inite limits is coupled with a high degree of 
sensibility and adequateness to the most di- 
verging experiments. Our tricotylous double 
races are perhaps more sensitive to selection 
than any other variety, and equally dependent 
on outer circumstances. Here, however, I will 
limit myself to a discussion of the former point. 

In the second generation after the isolation of 
stray tricotylous seedlings the average con- 
dition of the race is usually reached, but only 
by some of the strongest individuals, and if we 
continue the race, sowing or planting only from 
their offspring, the next generation will show 
the ordinary type of variability, going upwards 
in some and downwards in other instances. 
With the Phacelia and the mercury and some 
others 1 had the good luck in this one generation 
to reach as high as nearly 90j< of tricotyl- 
ous seedlings, a figure indicating that the 
normal dicotylous type had already become 
rare in the race. In other cases 80j^ or 
nearly was easily attained. Any further 
divergence from the average would have re- 
quired very much larger sowings, the effect of 
selection between a limited number of parents 
being only to retain the high degree once 



Monstrosities 


423 


reached ; so for instance with the mercury, I had 
three succeeding generations of selection after 
reaching the average of 55}^, but their extremes 
gave no increasing advance, remaining at 86, 92 
and 91ft. 

If we compare these results with the effects 
of selection in twisted and fasciated races, we 
observe a marked contrast. Here they reached 
their height at 30 - 40%, and no number of gen- 
erations had the power of making any further 
improvement. The tricotyls come up in two 
generations to a proportion of about 54j^, which 
shows itself to correspond to the average 
type. And as soon as this is reached, only one 
generation is required to obtain a very consid- 
erable improvement, going up to 80 or even 90;^. 

It is evident that the cause of this difference 
does not lie in the nature of the monstrosity, but 
is due to the criterion upon which the selection 
is made. Selection of the apparently best in- 
dividuals is one method, and it gives admirable 
results. Selection on the ground of the hered- 
itary percentages is another method and gives 
results which are far more advantageous than 
the former. 

In the lecture on the pistillody of the poppies 
we limited ourselves to the selection of the finest 
individuals and showed that there is always a 
manifest correlation between the individual 



424 Ever-sporting Varieties 

strength of the plant and the degree of develop- 
ment of its anomaly. The same holds good with 
other monstrosities, and badly nourished speci- 
mens of rich races with twisted or fasciated 
stems always tend to reversion. This rever- 
sion, however, is not necessarily correlated with 
the hereditary percentage and therefore does 
not always indicate a lessening of the degree of 
inheritance. This shows that even in those 
cases an improvement may be expected, if only 
the means can be found to subject the twisted 
and the fasciated races to the same sharp test 
as the tricotylous varieties. 

Much remains to be done, and the principle of 
the selection of parents according to the average 
constitution of their progeny seems to be one of 
the most promising in the whole realm of varia- 
bility. 

Besides tricotylous, the syncotylous seed- 
lings may be used in the same way. They 
are more rarely met with, and in most instances 
seem to belong only to the unpromising half- 
races. The black bindweed {Polygonum Con- 
volvulus), the jointed charlock (Raphanus Rap- 
hanistrum), the glaucous evening-primrose 
{Oenothera glauca) and many other plants seem 
to contain such half-races. On the other hand 
I found a plant of Centranthus macrosiphon 
yielding as much as of syncotylous chil- 



Monstrosities 


425 


dren and thereby evidently betraying the na- 
ture of a rich or double race. Likewise the mer- 
cury was rich in such deviations. But the best 
of all was the Russian sunflower, and this was 
chosen for closer experiments. 

In the year of 1888 I had the good lu^ to 
isolate some syncotylous seedlings and of find- 
ing among them one with 19}^ of inheritors 
among its seeds. The following generation at 
once surpassed the ordinary average and came 
up in three individuals to 76, 81 and even 89?^. 
My race was at once isolated and ameliorated by 
selection. I have tried to improve it further 
and selected the parents with the highest per- 
centages during seven more generations; but 
without any remarkable result. I got figures of 
90^ and above, coming even in one instance up 
to the apparent purity of 100^. These, how- 
ever, always remained extremes, the averages 
fluctuating yearly between 80 -90;^ or there- 
abouts, and the other extremes going nearly 
every year downwards to 50j^, the value which 
would be attained, if no selection were made. 

Contra-selection is as easily made as normal 
selection. According to our present principle it 
means the choice of the parents with the smallest 
hereditary percentage. One might easily im- 
agine that by this means the dicotylous seed- 
lings could be rendered pure. This, how- 



426 Ever-sporting Varieties 

ever, is not at all the case. It is easy to re- 
turn from so highly selected figures as for in- 
stance 95^ to the average about of 50^, as 
regression to mediocrity is always an easy mat- 
ter. But to transgress this average on the 
lower side seems to be as difficult as it is on the 
upper side. 1 continued the experiment during 
four succeeding generations, but was not able to 
go lower than about 10^, and could not even ex- 
clude the high figures from my strain. Parents 
with 65 - 75}( of syncotylous seedlings returned 
in each generation, notwithstanding the most 
careful contra-selection. The attribute is in- 
herent in the race, and is not to be eliminated by 
so simple a means as selection, nor even by a se- 
lection on the ground of hereditary percentages. 

We have dealt with torsions and fasciations 
and with seedling variations at some length, in 
order to point out the phases needing investiga- 
tion according to recent views. It would be 
quite superfluous to consider other anomalies in 
a similar manner, as they all obey the same laws. 
A hasty survey may suffice to show what pros- 
pects they offer to the student of nature. 

First of all come the variegated leaves. They 
are perhaps the most variable of all variations. 
They are evidently dependent on external cir- 
cumstances, and by adequate nutrition the 
leaves may even become absolutely white or 



Monstrosities 


427 


yellowish, with only scarcely perceptible traces 
of green along the veins. Some are very old 
cultivated varieties, as the wintercress, or Bar- 
barea vulgaris. They continuously sport into 
green, or return from this normal color, both by 
seeds and by buds. Sports of this kind are 
very often seen on shrubs or low trees, and 
they may remain there and develop during a 
long series of years. Bud-sports of variegated 
holly, elms, chestnuts, beeches and others might 
be cited. One-sided variegation on leaves or 
twigs with the opposite side wholly green are 
by no means rare. It is very curious io note 
that variegation is perhaps the most universally 
known anomaly, while its hereditary tendencies 
are least known. 

Cristate and plumose ferns are another in- 
stance. Half races or rare accidental cleavages 
seem to be as common with ferns as cultivated 
double races, which are very rich in beautiful 
crests. But much depends on cultivation. It 
seems that the spores of crested leaves are more 
apt to reproduce the variety than those of nor- 
mal leaves, or even of normal parts of the same 
leaves. But the experiments on which 
this assertion is made are old and should 
be repeated. Other cases of cleft leaves should 
also be tested. Ascidia are far more common 
than is usually believed. Bare instances point 



428 Ever-sporting Varieties 

to poor raooB, but the magnolias and lime-trees 
are often so productive of ascidia as to suggest 
the idea of ever-sporting varieties. I have 
seen many hundred ascidia on one lime-tree, and 
far above a hundred on the magnolia. They dif- 
fer widely in size and shape, including in some 
cases two leaves instead of one, or are composed 
of only half a leaf or of even still a smaller part 
of the summit. Bich ascidia-bearing varieties 
seem to offer notable opportunities for scientific 
pedigree-cultures. 

Union of the neighboring fruits and flowers on 
flower-heads, of the rays of the umbellifers or 
of the successive flowers of the racemes of cab- 
bages and allied genera, seem to be rare. 
The same holds good for the adhesion of foliar 
to axial organs, of branches to stems and 
other cases of union. Many of these cases re- 
turn regularly in each generation, or may at 
least be seen from time to time in the same 
strains. Proliferation of the inflorescence is 
very common and changes in the position of 
staminate and pistillate flowers are not rare. 
We find starting points for new investigations 
in almost any teratological structure. Half- 
races and double-races are to be distinguished 
and isolated in all cases, and their hereditary 
qualities, the periodicity of the recurrence of 
the anomaly, the dependency on external circum- 



Monstrosities 429 

stances and many other questions have to be an- 
swered. 

Here is a wide field for garden experiments 
easily made, which might ultimately yield much 
valuable information on many questions of he- 
redity of universal interest. 



Lbctube XV 


DOUBLE ADAPTATIONS 

The chief object of all experimentation is to 
obtain explanations of natural phenomena. 
Experiments are a repetition of things occur- 
ring in nature with the conditions so guarded 
and so closely followed that it is possible to 
make a clear analysis of facts and their 
causes, it being rightfully assumed that the laws 
are the same in both cases. 

Experiments on heredity and the experience 
of the breeder find their analogy in the succes- 
sion of generations in the wild state. The sta- 
bility of elementary species and of retrograde 
varieties is quite the same under both condi- 
tions. Progression and retrogression are nar- 
rowly linked everywhere, and the same laws 
govern the abundance of forms in cultivated 
and in wild plants. 

Elementary species and retrograde varieties 
are easily recognizable. Ever-sporting varie- 
ties on the contrary are far less obvious, and 
in many cases their hereditary relations have 

430 



Dovble Adaptations 


431 


had to be studied anew. A clear analogy be- 
tween them and corresponding types of wild 
plants has yet to be pointed ont. There can be 
no doubt that such analogy exists; the concep- 
tion that they should* be limited to cultivated 
plants is not probable. Striped flowers and va- 
riegated leaves, changes of stamens into carpels 
or into petals may be extremely rare in the wild 
state, but the “ five-leaved clover and a large 
number of monstrosities cannot be said to be 
typical of the cultivated condition. These, how- 
ever, are of rare occurrence, and do not play 
any important part in the economy of nature. 

In order to attain a better solution of the 
problem we must take a broader view of 
the facts. The wide range of variability of 
ever-sporting varieties is due to the presence of 
two antagonistic characters which cannot be 
evolved at the same time and in the same or- 
gan, because they exclude one another. When- 
ever one is active, the other must be latent. But 
latency is not absolute inactivity and may often 
only operate to encumber the evolution of the 
antagonistic character, and to produce large 
numbers of lesser grades of its development. 
The antagonism however, is not such in the ex- 
act meaning of the word; it is rather a mutual 
exclusion, because one of the opponents simply 
takes the place of the other when absent, or sup- 



432 Ever-sporting Varieties 

plements it to the extent that it may be only im- 
perfectly developed. This completion ordinar- 
ily occurs in all possible degrees and thns 
canses the wide range of the variability. Nev- 
ertheless it may be wanting, and in the case of 
the double stocks only the two extremes are 
present 

It is rather difficult to get a clear conception 
of Ihe substitution, and it seems necessary to 
designate the peculiar relationship between the 
two characters forming such a pair by a simple 
name. They might be termed alternating, if 
only it were clearly understood that the alterna- 
tion may be complete, or incomplete in all de- 
grees. Complete alternation would result in 
the extremes, the incomplete condition in the 
intermediate states. In some cases as with the 
stocks, the first prevails, while in other cases, as 
with the poppies, the very extremes are only 
rarely met with. 

Taking such an alternation as a real char- 
acter of the ever-sporting varieties, a wide 
range of analogous cases is at once revealed 
among the normal qualities of wild plants. Al- 
ternation is here almost universal. It is the ca- 
pacity of young organs to develop in two diverg- 
ing directions. The definitive choice must be 
made in extreme youth, or often at a relatively 
late period of development. Once made, this 



Double Adaptations 433 

choice is final, and a further change does not oc- 
cur in the normal course of things. 

The most curious and most suggestive in- 
stance of such an alternation is the case of the 
water-persicaria or Polygonum amphihium. It 
is known to occur in two forms, one aquatic and 
the other terrestrial. These are recorded in 
systematic works as varieties, and are described 
under the names of P. amphibium var. natans 
Moench, and P. amphibium var. terrestre Leers 
or P. amphibium var. terrestris Moench. Such 
authorities as Koch in his German flora, and 
Grenier and Godron in their French flora agree 
in the conception of the two forms as varieties. 

Notwithstanding this, the two varieties may 
often be observed to sport into one another. 
They are only branches of the same plant, 
grown under different conditions. The aquatic 
form has floating or submerged stems with ob- 
long or elliptic leaves, which are glabrous and 
have long petioles. The terrestrial plants are 
erect, nearly simple, more or less hispid 
throughout, with lanceolate leaves and short pe- 
tioles, often nearly sessile. The aquatic form 
flowers regularly, producing its peduncle at 
right angles from the floating stems, but the 
terrestrial specimens are ordinarily seen with- 
out flower-spikes, which are but rarely met with, 
at least as far as my own experience goes. In- 



434 Ever-sporting Varieties 

termediate forms are very rare, perhaps whohy 
wanting, though in swamps the terrestrial 
plants may often vary widely in the direction of 
the floating type. 

That both types sport into each other has 
long been recognized in field-observations, and 
has been the ground for the specific name of 
amphibium, though in this respect herbarium- 
material seems usually to be scant. The mat- 
ter has recently been subjected to critical and 
experimental studies by the Belgian botanist 
Massart, who has shown that by transplanting 
the forms into the alternate conditions, the 
change may always be brought about arti- 
ficially. If floating plants are established on 
the shore they make ascending hairy stems, and 
if the terrestrial shoots are submerged, their 
buds grow into long and slack, aquatic stems. 
Even in such experiments, intermediates are 
rare, both types agreeing completely with the 
corresponding models in the wild state. 

Among all the previously described cases of 
horticultural plants and monstrosities there is 
no clearer case of an ever-sporting variety than 
this one of the water-persicaria. The var. 
terrestris sports into the var. naians, and 
as often as the changing life conditions may 
require it. It is true that ordinary sports oc- 
cur without our discerning the cause and with- 



Double Adaptations 


435 


out any relation to adaptation. This however 
is partly due to our lack of knowledge, 
and partly to the general role that in nature 
only such sports as are useful are spared by 
natural selection, and what is useful we ordi- 
narily term adaptive. 

Another side of the question remains to he 
considered. The word variety, as is now be- 
coming generally recognized, has no special 
meaning whatever. But here it is assumed in 
the clearly defined sense of a systematic va- 
riety, which includes all subdivisions of spe- 
cies. Such subdivisions may be, from a 
biological point of view, elementary species and 
also be eversporting varieties. They may be 
retrograde varieties, and the two alternating 
types may be described as separate varieties. 

It is readily granted that many writers 
would not willingly accept this conclusion. But 
it is simply impossible to avoid it. The two 
forms of the water-persicaria must remain 
varieties, though they are only types of the dif- 
ferent branches of a single plant. 

If not, hundreds and perhaps thousands of 
analogous cases are at once exposed to doubt, 
and the whole conception of systematic varie- 
ties would have to be thrown over. Biologists 
of course would have no objection to this, but 
the student of the flora of any given country 



436 Ever-sporting Varieties 

or region requires the systematic subdivisions 
and should always use his utmost efforts to 
keep them as they are. There is no intrinsic 
difficulty in the statement that different parts of 
the same plant should constitute different va- 
rieties. 

In some cases different branches of the same 
plant have been described as species. So for 
instance with the climbing forms of figs. Un- 
der the name of Ficus repens a fine litHe plant is 
quite commonly cultivated as a climber in flower 
baskets. It is never seen bearing figs. On the 
other hand a shrub of our hothouses called 
Ficus stipulata, is cultivated in pots and makes 
a small tree which produces quite large, though 
non-edible figs. Now these two species are sim- 
ply branches of the same plant. If the repens is 
allowed to climb up high along the walls of the 
hothouses, it will at last produce stipulata- 
branches with the corresponding fruits. Ficus 
radicans is another climbing form, correspond- 
ing to the shrub Ficus uhnifolia of our glass- 
houses. And quite the same thing occurs with 
ivy, the climbing stems of which never flower, 
but always first produce erect and free branches 
with rhombic leaves. These branches have 
often been used as cuttings and yield little erect 
and richly flowering shrubs, which are known in 



Double Adaptations 437 

horticulture under the varietal name of Hede- 
ra Helio) arborea. 

Manifestly this classification is as nearly 
right as that of the two varieties of the water- 
persicaria. Going one step further, we meet 
with the very interesting case of alpine plants. 
The vegetation of the higher regions of moun- 
tains is commonly called alpine, and the plants 
show a large number of common features, dif- 
ferentiating them from the fiora of lower sta- 
tions. The mountain plants have small and 
dense foliage, with large and brightly-colored 
flowers. The corresponding forms of the low- 
lands have longer and weaker stems, bearing 
their leaves at greater distances, the leaves 
themselves being more numerous. The alpine 
forms, if perennial, have thick, strongly de- 
veloped and densely branched rootstocks with 
heavy roots, in which a large amount of food- 
material is stored up during the short summer, 
and is available during the long winter months 
of the year. 

Some species are peculiar to such high al- 
titudes, while many forms from the lowlands 
have no corresponding type on the mountains. 
But a large number of species are common to 
both regions, and here the difference of course is 
most striking. Lotus corniculatus and Coda- 
mintha Acinos, Calluna vulgaris and Campa- 



438 Ever-sporting Varieties 

mda rotundifolia may be quoted as instances, 
and every botanist who has visited alpine re- 
gions may add other examples. Even the edel- 
weiss of the Swiss Alps, Gnaphalvum Leonto- 
podvam, loses its alpine characters, if cultivated 
in lowland gardens. Between such lowland and 
alpine forms intermediates regularly occur. 
They may be met with whenever the range of the 
species extmids from the plains upward to the 
limit of eternal snow. 

In this case the systematists formerly enu- 
merated the alpine plants as forma alpestris, but 
whenever the intermediate is lacking the term 
varietas alpestris was often made use of. 

It is simply impossible to decide concerning 
the real relation between the alpine and low- 
land types without experiments. About the 
middle of the last century it was quite a com- 
mon thing to collect plants not only for her- 
barium-material, but also for the purpose of 
planting them in gardens and thus to observe 
their behavior under new conditions. This 
was done with the acknowledged purpose 
of investigating the systematic significance of 
observed divergencies. Whenever these held 
good in the garden they were considered to be 
reliable, but if they disappeared they were re- 
garded as the results of climatic conditions, 
or of the influence of soil or nourishment Be- 



Double Adaptations 


439 


tween these two alternatives, many writers 
have tried to decide, by transplanting their 
specimens after some time in the garden, into 
arid or sandy soil, in order to see whether they 
would resume their alpine character. 

Among the systematists who tested plants in 
this way, Nageli especially, directed his atten- 
tion to the hawkweeds or Hieracium. On 
the Swiss Alps they are very small and ex- 
hibit all the characters of the pure alpine type. 
Thousands of single plants were cultivated by 
him in the botanical garden of Munich, partly 
from seed and partly from introduced root- 
stocks. Here they at once assumed the 
tall stature of lowland forms. The identical 
individual, which formerly bore small rosettes 
of basal leaves, with short and unbranched 
flower-stalks, became richly leaved and often 
produced quite a profusion of flower-heads on 
branched stems. If then they were trans- 
planted to arid sand, though remaining in the 
same garden and also under the same climatic 
conditions they resumed their alpine charac- 
ters. This proved nutrition to be the cause 
of the change and not the climate. 

The latest and most exact researches on this 
subject are due to Bonnier, who has gone into 
all the details of the morphologic as well as 
of the physiologic side of the problem. 



440 Ever-sporting Varieties 

His purpose was the study of partial variabil- 
ity under the influence of climate and soil. In 
every experiment he started from a single indi- 
vidual, divided it into two parts and planted 
one half on a mountain and the other half on 
the plain. The garden cultures were made 
chiefly at Paris and Fontainebleau, the alpine 
cultures partly in the Alps, partly in the Py- 
renees. From time to time the halved plants 
were compared with each other, and the cul- 
tures lasted, as a rule, during the lifetime of the 
individual, often covering many years. 

The common European frostweed or Helian- 
themum vvlgare will serve to illustrate his re- 
sults. A large plant growing in the Pyrenees in 
an altitude of 2400 meters was divided. One half 
was replanted on the same spot, and the other 
near Cadeac, at the base of the mountain range 
(740 M.). In order to exclude the effect of a 
change of soil, a quantity of the earth from the 
original locality was brought into the garden 
and the plant put therein. Further control- 
experiments were made at Paris. As soon as 
the two halved individuals commenced to grow 
and produced new shoots, the influence of the 
different climates made itself felt. On the 
mountain, the underground portions remained 
strong and dense, the leaves and intemodes 
small and hairy, the flowering stems nearly 



Double Adaptaiions 


441 


procumbent, the flowers being large and of a 
deep yellow. At Cadeac and at Paris the whole 
plant changed at once, the shoots becoming 
elongated and loose, with broad and flattened, 
rather smooth leaves and numerous pale-hued 
flowers. The anatomical structure exhibited cor- 
responding differences, the intercellular spaces 
being small in the alpine plant and large in the 
one grown in. the lowlands, the wood-tissues 
strong in the first and weak in the second case. 

The milfoil {Achillea Millefolium) served 
as a second example, and the experiments were 
carried on in the same localities. The long and 
thick rootstocks of the alpine plant bearing 
short stems only with a few dense corymbs 
contrasted markedly with the slender stems, 
loose foliage and rich groups of flowerheads of 
the lowland plant. The same differences in in- 
ner and outer structures were observed in nu- 
merous instances, showing that the alpine type 
in these cases is dependent on the climate, and 
that the capacity for assuming the antagonistic 
characters is present in every individual of the 
species. The external conditions decide which 
of them becomes active and which remains in- 
active, and the case seems to be exactly paral- 
lel to that of the water-persicaria. 

In the experiments of Bonnier the influence 
of the soil was, as a rule, excluded by trans- 



442 Ever-sporting Varieties 

planting part of the original earth with the 
transplanted half of the plant. From this he 
oonolnded that the observed changes were due 
to the inequality of the climate. This involved 
three main factors, light, moisture and tem- 
perature. On the mountains the light is more 
intense, the air drier and cooler. Control-ex- 
periments were made on the mountains, de- 
priving the plants of part of the light. In va- 
rious ways they were more or less shaded, and 
as a rule responded to this treatment in the 
same way as to transplantation to the plain 
below. Bonnier concluded that, though more 
than one factor takes part in inciting the 
morphologic changes, light is to be consid- 
ered as the chief agency. The response is to 
be considered as a useful one, as the whole 
structure of the alpine varieties is fitted to pro- 
duce a large amount of organic material in a 
short time, which enables the plants to thrive 
during the short summers and long winters of 
their elevated stations. 

In connection with these studies on the in- 
fluences of alpine climates. Bonnier has inves- 
tigated the internal structure of arctic plants, 
and made a series of experiments on growth 
in continuous electric light. The arctic climate 
is cold, but wet, and the structure of the leaves 
is correspondingly loose, though the plants be- 



Double Adaptations 


443 


come as small as on the Alps. Continuous elec- 
tric light had very curious effects; the plants 
became etiolated, as if growing in darkness, 
with the exception that they assumed a deep 
green tinge. They showed more analogy with 
the arctic than with the alpine type. 

The influence of the soil often produces 
changes similar to that of climate. This was 
shown by the above cited experiments of Na- 
geli with the hawkweeds, and may easily be 
controlled in other cases. The ground-honey- 
suckle or Lotus corniculatus grows in Holland 
partly on the dry and sandy soil of the dunes, 
and occasionally in meadows. It is small and 
dense in the first case, with orange and often 
very darkly colored petals, while it is loose and 
green in the meadows, with yellower flowers. 
Numerous analogous cases might be given. On 
mountain slopes in South Africa, and especial- 
ly in Natal, a species of composite is found, 
which has been introduced into culture and is 
used as a hanging plant. It is called Othonna 
crassifolia and has fleshy, nearly cylindrical 
leaves, and exactly mimics some of the crassu- 
laceous species. On dry soil the leaves become 
shorter and thicker and assume a reddish 
tinge, the stems remain short and woody and 
bear their leaves in dense rosettes. On moist 
and rich garden-soil this aspect becomes 



444 


Ever-sporting Varieties 


changed at once, the stems grow longer and 
of a deeper green. Intermediates occur, but 
notwithstanding this the two extremes consti- 
tute dearly antagonistic types. 

The flora of the deserts is known to exhibit 
a similar divergent type. Or rather two types, 
one adapted to paucity of water, and the other 
to a storage of fluid at one season in order to 
make use of it at other times, as is the case with 
the cactuses. Limiting ourselves to the alter- 
nate group, we observe a rich and dense branch- 
ing, small and compact leaves and extraordi- 
narily long roots. Here the analogy with the 
alpine varieties is manifest, and the dryness 
of the soil evidently affects the plants in a sim- 
ilar way, as do the conditions of life in alpine 
regions. The question at once comes up as to 
whether here too we have only instances of 
partial variability, and whether many of the 
typical desert-species would lose their pecu- 
liar character by cultivation under ordinary 
conditions. The varieties of Monardella ma- 
crantha, described by Hall, from the San Ja- 
cinto Mountain, Cal., are suggestive of such 
an intimate analogy with the cases studied by 
Bonnier, that it seems probable that they might 
yield similar results, if tested by the same 
method. 

Leaving now the description of these special 



Double Adaptations 


445 


cases, we may resume our theoretical discus- 
sion of the subject, and try to get a clearer in- 
sight into the analogy of ever-sporting varie- 
ties and the wild species quoted. All of them 
may he characterized by the general term of 
dimorphism. Two types are always present, 
though not in the same individual or in the same 
organ. They exclude one another, and dur- 
ing their juvenile stage a decision is taken in 
one direction or in the other. Now, according 
to the theory of natural selection, wild species 
can only retain useful or at least innocuous 
qualities, since all mutations in a wrong direc- 
tion must perish sooner or later. Cultivated 
species on the other hand are known to be 
largely endowed with qualities, which would 
be detrimental in the wild condition. Mon- 
strosities are equally injurious and could not 
hold their own if left to themselves. 

These same principles may be applied to 
ever-sporting or antagonistic pairs of charac- 
ters. According to the theory of mutations 
such pairs may be either useful or useless. But 
only the useful will stand further test, and if 
they find suitable conditions will become spe- 
cific or varietal characters. On this conclusion 
it becomes at once clear, why natural di- 
morphism is, as a rule, a very useful quality, 
while the cultivated dimorphous varieties 



446 Ever-sporting Varieties 

strike us as something unnatural. The rela- 
tion between cause and effect, is in truth other 
than it might seem to be at first view, but nev- 
ertheless it exists, and is of the highest impor- 
tance. 

From this same conclusion we may further 
deduce some explanation of the hereditary 
races characterized by monstrosities. It is 
quite evident that the twisted teasels are in- 
adequate for the struggle with their tall con- 
geners, or with the surrounding plants. Hence 
the conclusion that a pure and exclusively 
twisted race would soon die out. The fact that 
such races are not in existence finds its expla- 
nation in this circumstance, and therefore it 
does not prove the impossibility or even the im- 
probability that some time a pure twisted race 
might arise. If chance should put such an ac- 
cidental race in the hands of ah experimenter, 
it could be protected and preserved, and hav- 
ing no straight atavistic branches, but being 
twisted in all its organs, might yield the most 
curious conceivable monstrosity, surpassing 
even the celebrated dwarf twisted shrubs of 
Japanese horticulturists. 

Such varieties however, do not exist at pres- 
ent. The ordinary twisted races on the other 
hand, are found in the wild state and have only 
to be isolated and cultivated to yield large num- 



Double Adaptations 


447 


bers of twisted individuals. In nature they are 
able to maintain themselves during long cen- 
turies, quite as well as normal species and va- 
rieties. But they owe this quality entirely to 
their dimorphous character. A twisted race of 
teasels might consist of successive generations 
of tall atavistic individuals, and produce year- 
ly some twisted specimens, which might be de- 
stroyed every time before ripening their seeds. 
Eeasoning from the evidence available, and 
from analogous cases, the variety would, even 
under such extreme circumstances, be able to 
last as long as any other good variety or ele- 
mentary species. And it seems to me that this 
explanation makes clear how it is possible that 
varieties, which are potentially rich in their pe- 
culiar monstrosity, are discovered from time to 
time among plants when tested by experimental 
methods. 

Granting these conclusions, monstrosities on 
the one side, and dimorphous wild species on 
the other, constitute the most striking examples 
of the inheritance of latent characters. 

The bearing of the phenomena of dimorphism 
upon the principles of evolution formulated by 
Lamarck, and modified by his followers to con- 
stitute Neo-Lamarckianism, remains to be con- 
sidered. Lamarck assumed that the external 
conditions directly affected the organisms in 



448 Ever-sporting Varieties 

such, a way as to make them better adapted to 
life, imder prevailing circumstances. Nageli 
gave to this conception the name Theory 
of direct causation ” (Theorie der direc- 
ten Bewirknng), and it has received the ap- 
proval of Von Wettstein, Strasburger and other 
German investigators. According to this con- 
ception a plant, when migrating from lowlands 
into the mountains would slowly be changed 
and gradually assume alpine habits. Once ac- 
quired this habit would become fixed and attain 
the rank of sx}epific characters. In testing this 
theory by field-observations and culture-exper- 
iments, the defenders of the Nagelian principle 
could easily produce evidence upon the first 
point. The change of lowland-plants into al- 
pine varieties can be brought about in numer- 
ous cases, and corresponding changes under 
the influence of soil, or climate, or life-condi- 
tions are on record for the most various charac- 
ters and qualities. 

The second point, however, is as difficult to 
prove as the first is of easy treatment. If after 
hundreds and thousands of years of exposure to 
alpine or other extreme conditions a fixed 
change is proved to have taken place, the ques- 
tion remains unanswered, whether the change 
has been a gradual or a sudden one. Darwin 
pointed out that long periods of life afford a 



Double Adaptations 


449 


chance for a sudden change in the desired di- 
rection, as well as for the slow accumulation of 
slight deviations. Any mutations in a wrong 
direction would at once be destroyed, but an 
accidental change in a useful way would be 
preserved, and multiply itself. If in the course 
of centuries this occurred, they would be near- 
ly sure to become established, however rare at 
the outset. Hence the positive assertion is 
scarcely capable of direct proof. 

On the other hand the negative assertion 
must be granted full significance. If the al- 
pine climate has done no more than produce a 
transitory change, it is clear that thousands 
of years do not, necessarily, cause constant 
and specific alterations. This requirement is 
one of the indispensable supports of the La- 
marckian theory. The matter is capable of 
disproof however, and such disproof seems to 
be atforded by the direct evidence of the pres- 
ent condition of the alpine varieties at large, 
and by many other similar cases. 

Among these the observations of Holter- 
mann on some desert-plants of Ceylon are of 
the highest value. Moreover they touch ques- 
tions which are of wide importance for the 
study of the biology of American deserts. For 
this reason I may be allowed to introduce them 
here at some length. 



450 Ever-sporting Varieties 

The desert of Kaits, in Northern Ceylon, 
nonrishes on its dry and torrid sands some 
species, represented by a large number of in- 
dividuals, together with some rarer plants. 
The commonest forms are Erigeron asteroides, 
Vernonia cinerea, Laurea pinnatifida, Vicoa au- 
rictdata, Heylandia latehrosa and Chrysopo- 
gon montanus. In direct contrast with the or- 
dinary desert-types they have a thin epidermis, 
with exposed stomata, features that ordinarily 
were characteristic of species of moister re- 
gions. They are annuals, growing rapidly, 
blooming and ripening their seeds before the 
height of the dry season. Evidently they are 
to be. considered as the remainder of the flora 
of a previous period, when the soil had not yet 
become arid. They might be called relics. Of 
course they are small and dwarf-like, when com- 
pared with allied forms. 

These curious little desert-plants disprove 
the Nagelian views in two important points. 
First, they show that extreme conditions do not 
necessarily change the organisms subjected to 
them, in a desirable direction. During the 
many centuries that these plants must have ex- 
isted in the desert in annual generations, no 
single feature in the anatomical structure has 
become changed. Hence the conclusion that 
small leaves, abundant rootstocks and short 



Double Adaptations 


451 


stems, a dense foliage, a strongly cuticularized 
epidermis, few and narrow air-cavities in the 
tissues and all the long range of characteris- 
tics of t3npical desert-plants are not a simple 
result of the influence of climate and soil. 
There is no direct influence in this sense. 

The second point, in which Nageli’s idea is 
broken down by Holtermann’s observations, re- 
sults from the behavior of the plants of the 
Kaits desert when grown or sown on garden- 
soil. When treated in this way they at once 
lose the only peculiarity which might be con- 
sidered as a consequence of the desert-life of 
their ancestors, their dwarf stature. They be- 
have exactly like the alpine plants in Bonnier’s 
experiments, and with even more striking dif- 
ferences. In the desert they attain a height 
of a few centimeters, but in the garden they 
attain half a meter and more in height. Noth- 
ing in the way of stability has resulted from the 
action of the dry soil, not even in such a minor 
point as the height of the stems. 

From these facts and discussions we may 
conclude that double adaptation is not induced 
by external influences, at least not in any way 
in which it might be of use to the plant. It 
may arise by some unknown cause, or may 
not be incited at all. In the first case the plant 
becomes capable of living under the altemat- 



452 Ever-sportmg Varieties 

ing circmnstances, and if growing near the 
limits of such regions it will overlap and get 
into the new area. All other species, which did 
not acquire the double habit, are of course ex- 
cluded, with such curious exceptions as those 
of Kaits. The typical vegetation Tinder such 
extreme conditions however, finds explanation 
quite as well by the one as by the other view. 

Leaving these obvious cases of double adap- 
tation, there still remains one point to be con- 
sidered. It is the dwarf stature of so many 
desert and alpine plants. Are these dwarfs 
only the extremes of the normal fluctuating va- 
riability, or is their stature to be regarded as 
the expression of some peculiar adaptive but 
latent quality? It is as yet difficult to decide 
this question, because statistical studies of this 
form of variability are still wanting. The ca- 
pacity of ripening the seed on individuals of 
dwarf stature however, is not at all a uni- 
versal accompaniment of a variable height. 
Hence it cannot be considered as a necessary 
consequence of it. On the other hand the dwarf 
varieties of numerous garden-plants, as for in- 
stance: of larkspurs, snapdragon, opium-pop- 
pies and others are quite stable and thence are 
obviously due to peculiar characteristics. Such 
characteristics, if combined with tall stature 
into a pair of antagonists, would yield a double 



Double Adaptations 


453 


adaptation, and on such a base a hypothetical 
explanation could no doubt be rested. 

Instead of discussing this problem from the 
theoretical side, I prefer to compare those spe- 
cies which are capable of assuming a dwarf 
stature under less uncommon conditions than 
those of alpine and desert-plants. Many weeds 
of our gardens and many wild species have this 
capacity. They become very tall, with large 
leaves, richly branched stems and numerous 
flowers in moist and rich soil. On bad soil, or 
if germinating too late, when the season is 
drier, they remain very small, producing only 
a few leaves and often limiting themselves to 
one flower-head. This is often seen with thorn- 
apples and amaranths, and even with oats and 
rye, and is notoriously the case with buck- 
wheat. Gauchery has observed that the ex- 
tremes differ often as much from one another 
as 1:10. In the case of the Canadian horse- 
weed or Erigeron canadensis, which is widely 
naturalized in Europe, the tallest specimens 
are often twenty-five times as tall as the small- 
est, the difference increasing to greater ex- 
tremes, if besides the main stem, the length of 
the numerous branches of the tall plants are 
taken into consideration. Other instances 
studied by the French investigator are Ery- 
thraea pulchella and Calamintha Acinos. 



454 Ever-sporting Varieties 

Dimorphism is of universal occurrence in the 
whole vegetable kingdom. In some cases it is 
typical, and may easily be discerned from ex- 
treme flutnating variability. In others the con- 
trast is not at all obvious, and a closer 
investigation is needed to decide between the 
two possibilities. Sometimes the adaptive qual- 
ity is evident, in other eases it is not. A large 
number of plants bear two kinds of leaves linked 
with one another by intermediate forms. Often 
the first leaves of a shoot, or those of accident- 
ally strong shoots, exhibit deviating shapes, 
and the usefulness of such occurrences seems to 
be quite doubtful. The elongation of stems and 
linear leaves, and the reduction of lateral or- 
gans in darkness, is manifestly an adaptation. 
Many plants have stolons with double adapta- 
tions which enable them to retain their char- 
acter of underground stems with bracts or to 
exchange it for the characteristics of erect 
stems with green leaves according to the outer 
circumstances. In some shrubs and trees the 
capacity of a number of buds to produce either 
flowers or shoots with leaves seems to be in 
the same condition. The capacity of producing 
spines is also a double adaptation, active on 
dry and arid soil and latent in a moist climate 
or under cultivation, as with the wild and cul- 
tivated apple, and in the experiments of Lo- 



Double Adaptations 455 

thelier with Berberis, Lycium and other species, 
which lose their spines in damp air. 

In some conifers the evolution of horizontal 
branches may be modified by simply turning 
the buds upside down. Or the lateral branches 
can be induced to become erect stems by 
cutting off the normal summit of a tree. Nu- 
merous organs and functions lie dormant un- 
til aroused by external agencies, and many 
other cases could be cited, showing the wide 
occurrence of double adaptation. 

There are, however, two points, which should 
not be passed over without some mention. One 
of them is the influence of sun and shade on 
leaves, and the other the atavistic forms, often 
exhibited during the juvenile period. 

The leaves of many plants, and especially 
those of some shrubs and trees, have the ca- 
pacity of adapting themselves either to intense 
or to diffuse light. On the circumference of the 
crown of a tree the light is stronger and the 
leaves are small and thick, with a dense tissue. 
In the inner parts of the crown the light is 
weak and the leaves are broader in order to 
get as much of it as possible. They become 
larger but thinner, consisting often of a small 
number of cell layers. The definitive forma- 
tion is made in extreme youth, often even 
during the previous summer, at the time of the 



456 


Ever-sporting Varieties 

very first evolution of the young organs within 
the buds. Iris, and Lactuca Scariola or the 
prickly lettuce, and many other plants a|Pord 
similar instances. As the definitive decision 
must be made in these cases long before the di- 
rect influence of the conditions which would 
make the change useful is felt, it is hardly con- 
ceivable how they could be ascribed to this 
cause. 

It is universally known that many plants 
show deviating features when very young, and 
that these often remind us of the characters of 
their probable ancestors. Many plants that 
must have been derived from their nearest sys- 
tematic relatives, chiefly by reductions, are 
constantly betraying this relation by a repeti- 
tion of the ancestral marks during their 
youth. 

There can be hardly a doubt that the general 
law of natural selection prevails in such cases 
as it does in others. Or stated otherwise, it is 
very probable, that in most cases the atavistic 
characters have been retained during youth 
because of their temporary usefulness. Un- 
fortunately, our knowledge of utility of quali- 
ties is as yet very incomplete. Here we must 
assume that what is ordinarily spared by na1> 
ural selection is to be considered as useful. 



Double Adaptations 457 

until direct experimental investigations have 
been made. 

So it is for instance with the submerged leaves 
of water-plants. As a rule they are linear, or 
if compound, are reduced to densely branching 
filiform threads. Hence we may conclude that 
this structure is of some use to them. Now 
two European and some corresponding Amer- 
ican species of water-parsnip, the Sium lati- 
folium and Berula angustifolia with their al- 
lies, are umbellifers, which bear pinnate instead 
of bi- or tri-pinnate leaves. But the young 
plants and even the young shoots when devel- 
oping from the rootstocks imder water comply 
with the above rule, producing very compound, 
finely and pectinately dissected leaves. From a 
systematic point of view these leaves indicate 
the origin of the water-parsnips from ordinary 
umbellifers, which generally have bi- and tri- 
pinnate leaves. 

Similar cases of double adaptation, depend- 
ent on external conditions at different periods 
of the evolution of the plant are very numerous. 
They are most marked among leguminous 
plants, as shown by the trifoliolate leaves of the 
thom-broom and allies, which in the adult state 
have green twigs destitute of leaves. 

As an additional instance of dimorphism and 
probable double adaptation to unrecognized ex- 



458 


Ever-sporting Varieties 


ternal conditions I might point to the genus 
Acacia. As we have seen in a previous 
lecture some of the numerous species of this 
genus bear bi-pinnate leaves, while others 
have only flattened leaf-stalks. According to 
the prevailing systematic conceptions, the 
■ last must have been derived from the first by 
the loss of the blades and the corresponding 
increase of size and superficial extension of the 
stalk. In proof of this view they exhibit, as we 
have described, the ancestral characters in the 
yotmg plantlets, and this production of bi-pin- 
nate leaves has probably been retained at the pe- 
riod of the corresponding negative mutations, 
because of some distinct, though still unknown 
use. 

Summarizing the results of this discussion, 
we may state that useful dimorphism, or dou- 
ble adaptation, is a substitution of characters 
quite analogous to the useless dimorphism' of 
cultivated ever-sporting varieties and the stray 
occurrence of hereditary monstrosities. The 
same laws and conditions prevail in both cases. 



E. MUTATIONS 


Leoxuee XVI 

THE OBIGIH OF THE PELOBIO TOAD-FLAX 

I have tried to show previously that species, in 
the ordinary sense of the word, consist of dis- 
tinct groups of units. In systematic works 
these groups are all designated by the name of 
varieties, but it is usuaUy granted that the 
units of the system are not always of the same 
value. Hence we have distinguished between 
elementary species and varieties proper. The 
first are combined into species whose common 
original type is now lost or unknown, and from 
their characters is derived an hypothetical im- 
age of what the common ancestor is supposed 
to have been. The varieties proper are derived 
in most cases from still existing types, and 
therefore are subjoined to them. A closer in- 
vestigation has shown that this derivation is 
ordinarily produced by the loss of some definite 
attribute, or by the re-acquisition of an appar- 

469 



460 


Mutations 


ently lost characster. The elementary species, 
on the otiier hand, must have arisen by the pro- 
duction of new qualities, each new acquisition 
constituting the origin of a new elementary 
form. 

Moreover we have seen, tiiat such improve- 
ments and such losses constitute sharp limits 
between tiie single unitrforms. Every type, of 
course, varies around an average, and the ex- 
tremes of one form may sometimes reach or 
even overlap those of the nearest allies, but 
the offspring of the extremes always return to 
the type. The transgression is only temporary 
and a real transition of one form to another 
does not come within ordinary features of fluc- 
tuating variability. Even in the cases of ever- 
sporting varieties, where two opposite types 
are united within one race, and where the suc- 
ceeding individuals are continually swinging 
from one extreme to the other, passing through 
a wide range of intermediate steps, the limits 
of the variety are as sharply defined and as free 
from real transgression as in any other form. 

In a complete systematic enumeration of the 
real units of nature, the elementary species and 
varieties are thus observed to be discontinous 
and separated by definite gaps. Every unit 
may have its youth, may lead a long life in the 
adult state and may finally die. But through 



461 


Origin of Peloric Toadflax 

the whole period of its existence it remains the 
same, at the end as sharply defined from its 
nearest allies as in the beginning. Should 
some of the units die out, the gaps between the 
neighboring ones will become wider, as must 
often have been the case. Such segregations, 
however important and useful for systematic 
distinctions, are evidently only of secondary 
value, when considering the real nature of the 
units themselves. 

We may now take up the other side of the 
problem. The question arises as to how species 
and varieties have originated. According to 
the Darwinian theory they have been produced 
from one another, the more highly differenti- 
ated ones from the simpler, in a graduated 
series from the most simple forms to the most 
complicated and most highly organized exist- 
ing types. This evolution of course must have 
been regular and continuous, diverging from 
time to time into new directions, and linking 
all organisms together into one common pedi- 
gree. All lacunae in our present system are ex- 
plained by Darwin as due to the extinction of 
the forms, which previously filled them. 

Since Lamarck first propounded the concep- 
tion of a common origin for all living beings, 
much has been done to clear up our ideas as to 
the real nature of this process. The broader 



462 


Mutations 


aspect of the subject, including the general pedi- 
gree of the animal and vegetable kingdom, may 
he said to have been outlined by Darwin and his 
followers, but this phase of the subject lies be- 
yond the limits of our present discussion. 

The other phase of the problem is concerned 
with the manner in which the single elementary 
species and varieties have sprung from one an- 
other. There is no reason to suppose that the 
world is reaching the end of its development, 
and so we are to infer that the production of 
new species and varieties is still going on. In 
reality, new forms are observed to originate 
from time to time, both wild and in cultivation, 
and such facts do not leave any doubt as to their 
origin from other allied types, and according to 
natural and general laws. 

In the wild state however, and even with cul- 
tivated plants of the held and garden, the condi- 
tions, though allowing of the immediate obser- 
vation of the origination of new forms, are by no 
means favorable for a closer inquiry into the 
real nature of the process. Therefore I shall 
posipone the discussion of the facts till an- 
other lecture, as their bearing will be more 
easily imderstood after having dealt with more 
complete cases. 

These can only be obtained by direct experi- 
mentation. Comparative studies, of course. 



463 


Origin of Peloric Toadflcuc 

are valnable for the elucidation of general prob- 
lems and broad features of the whole pedigree, 
but the. narrower and more practical question as 
to the genetic relation of the single forms to one 
another must be studied in another way, by 
direct experiment. The exact methods of the 
laboratory must be used, and in this case the 
garden is the laboratory. The cultures must 
be guarded with the strictest care and every 
precaution taken to exclude opportunities for 
error. The parents and grandparents and their 
offspring must be kept pure and under control, 
and all facts bearing upon the birth or origin of 
the new types should be carefully recorded. 

Two great difficulties have of late stood in 
the way of such experimental investigation. 
One of them is of a theoretical, the other of a 
practical nature. One is the general belief in 
the supposed slowness of the process, the other 
is the choice of adequate material for experi- 
mental purposes. Darwin’s hypothesis of nat- 
ural selection as the means by which new lypes 
arise, is now being generally interpreted as 
stating the slow transformation of ordinary 
fluctuating divergencies from the average type 
into specific differences. But in doing so it is 
overlooked that Quetelet’s law of fluctuating 
variability was not yet discovered at the time, 
when Darwin propounded his theory. So there 



464 


Mviations 


is no real and intimate connection between these 
two great conceptions. Darwin frequently 
pointed out that a long period of time might be 
needed for slow improvements, and was also a 
condition for the occurrence of rare sports. In 
any case those writers have been in error, ac- 
cording to my opinion, who have refrained from 
experimental work on Ihe origin of species, on 
account of this narrow interpretation of Dar- 
win’s views. The choice of the material is 
quite another question, and obviously all de- 
pends upon this choice. Promising instances 
must be sought for, but as a rule the best way 
is to test as many plants as possible. Many of 
them may show nothing of interest, but some 
might lead to the desired end. 

For to-day’s lecture I have chosen an in- 
stance, in which the grounds upon which the 
choice was based are very evident. It is the 
origin of the peloric toad-flax {Linaria vulgaris 
peloria). 

The ground for this choice lies simply in the 
fact that the peloric toad-flax is known to have 
originated from the ordinary type at different 
times and in different countries, under more or 
less divergent conditions. It had arisen from 
time to time, and hence I presumed that there 
was a chance to see it arise again. If this 
should happen under experimental circum- 



465 


Origin of Peloric Toadflax 

stances the desired evidence might easily be 
gathered. Or, to put it in other words, we must 
try to arrange things so as to be present at the 
time when nature produces another of these 
rare changes. 

There was still another reason for choosing 
this plant for observational work. The step from 
the ordinary toad-flax to the peloric form is 
short, and it appears as if it might be produced 
by slow conversion. The ordinary species pro- 
duces from time to time stray peloric flowers. 
These occur at the base of the raceme, or rarely 
in the midst of it. In other species they are 
often seen at the summit Terminal pelories 
are usually regular, having five equal spurs. 
Lateral pelories are generally of zygomorphic 
structure, though of course in a less degree than 
the normal bilabiate flowers, but they have un- 
equal spurs, the middle one being of the ordi- 
nary length, the two neighboring being shorter, 
and those standing next to the opposite side of 
the flower being the shortest of all. This curi- 
ous remainder of the original symmetrical 
structure of the flower seems to have been over- 
looked hitherto by the investigators of peloric 
toad-flaxes. 

The peloric variety of this plant is character- 
ized by its producing only peloric flowers. No 
single bilabiate or one-spurred flower remains. 



466 


Mutations 


I once had a lot of nearly a hundred spedmens 
of this fine variety, and it was a most cnrions 
and beantifnl sight to observe the many thou- 
sands of nearly regular flowers blooming at the 
same time. Some degree of variability was of 
course present, even in a large measure. The 
number of the spurs varied betweenfour and six, 
transgressing these limits in some instances, but 
never so far as to produce really one-spurred 
flowers. Comparing this variety with the ordi- 
nary type, two ways of passing over from the 
one to the other might be imagined. One would 
entail a slow increase of the number of the 
peloric flowers on each plant, combined with a 
decrease of the number of the normal ones, the 
other a sudden leap from one extreme to the 
other without any intermediate steps. The 
latter might easily be overlooked in field obser- 
vations and their failure may not have the value 
of direct proof. They could never be over- 
looked, on the other hand, in experimental cul- 
ture. 

The first record of the peloric toad-flax is that 
of Zioberg, a student of Linnaeus, who found it 
in the neighborhood of Upsala. This curious 
discovery was described by Budberg in his dis- 
sertation in the year 1744. Soon afterwards 
other localities were discovered by link near 
Gottingen in Germany about 1791 and after- 



467 


Origin of Peloric Toadflax 

wards in the vicinity of Berlin, as stated by 
Batzeburg, 1825. Many other localities have 
since been indicated for it in Europe, and in my 
own country some have been noted of late, as 
for instance near Zandvoort in 1874 and near 
Oldenzaal in 1896. In both these last named 
cases the peloric form arose spontaneously in 
places which had often been visited by botanists 
before the recorded appearance, and therefore, 
without any doubt, they must have been pro- 
duced directly and independently by the ordi- 
nary species which grows in the locality. The 
same holds good for other occurrences of it. 

In many instances the variety has been re- 
corded to disappear after a certain lapse of 
time, the original specimens dying out and no 
new ones being produced. Linaria is a peren- 
nial herb, multiplying itself easily by buds grow- 
ing on the roots, but even with this means of 
propagation its duration seems to have definite 
limits. 

There is one other important point arguing 
strongly for the independent appearance of the 
peloric form in its several localities. It is the 
difficulty of fertilization and the high degree of 
sterility, even if artificially pollinated. Bees and 
humble-bees are unable to crawl into the nar- 
row tubular flowers, and to bring the fertilizing 
pollen to the stigma. Bipe capsules with seeds 



468 


Mutations 


have never been seen in the wild state. The 
only writer who succeeded in sowing seeds of 
the peloric variety was Wildenow and he got 
only very few seedlings. But even in artificial 
pollination the result is the same, the anthers 
seeming to be seriously affected by the change. 
I tried both self-fertilization and cross-pollina- 
tion, and only with utmost care did I succeed 
in saving barely a hundred seeds. In order 
to obtain them I was compelled to operate on 
more than a thousand flowers on about a dozen 
peloric plants. 

The variety being wholly barren in nature, 
the assumption that the plants in the different 
recorded localities might have a common origin 
is at once excluded. There must have been at 
least nearly as many mutations as localities. 
This strengthens the hope of seeing such a mu- 
tation happen in one’s own garden. It should 
also be remembered that peloric flowers are 
known to have originated in quite a number 
of different species of Linaria, and also with 
many of the allied species within the range of 
the Labiatiflorae. 

I will now give the description of my own ex- 
periment. Of course this did not give the ex- 
pected result in the first year. On the contrary, 
it was only after eight years’ work that I had 
the good fortune of observing the mutation. 



469 


Orig^ of Peloric Toadflax 

But as the whole life-history of the preceding 
generations had been carefully observed and 
recorded, the exact interpretation of the fact 
was readily made. 

My culture commenced in the year 1886. I 
chose some plants of the normal type with one 
or two peloric flowers besides the bilabiate ma- 
jority which I found on a locality in the neigh- 
borhood of Hilversum in Holland. I planted 
the roots in my garden and from them had the 
first flowering generation in the following sum- 
mer. From their seeds I grew the second gen- 
eration in three following years. They flow- 
ered profusely and produced in 1889 only one, 
and in 1890 only two peloric structures. I saved 
the seeds in 1889 and had in 1890-1891 the third 
generation. These plants likewise flowered 
only in the second year, and gave among some 
thousands of symmetrical blossoms, only one 
five-spurred flower. I pollinated this flower 
myself, and it produced abundant fruit with 
enough seeds for the entire culture in 1892, and 
they only were sown. 

Until this year my generations required two 
years each, owing to the perennial habit of the 
plants. In this way the prospects of the cul- 
ture began to decrease, and I proposed to try to 
heighten my chances by having a new genera- 
tion yearly. With this intention I sowed the 



470 


Mutations 


selected seeds in a pan in the glasshouse of my 
laboratory and planted them out as soon as the 
young stems had reached a lengtii of some few 
centimeters. Each seedling was put in a sepa- 
rate pot, in heavily manured soil. The pots 
were kept under glass until the beginning of 
June, and the young plants produced during 
this period a number of secondary stems from 
the curious hypocotylous buds which are so 
characteristic of the species. These stems 
grew rapidly and as soon as they were 
strong enough, the plants were put into 
the beds. They all, at least nearly all, 
some twenty specimens, flowered in the follow- 
ing month. 

I observed only one peloric flower among the 
large number present. I took the plant bearing 
this flower and one more for the culture of the 
following year, and destroyed all others. These 
two plants grew on the same spot, and were al- 
lowed to fertilize each other by the agency of 
the bees, but were kept isolated from any other 
congener. They flowered abundantly, but pro- 
duced only one-spurred bilabiate flowers during 
the whole summer. They matured more than 
10 cu. cm. of seeds. 

It is from this pair of plants that my peloric 
race has sprung. And as they are the ancestors 
of the first closely observed case of peloric mu- 



Origin of Peloric Toadflax 471 

tation, it seems worth while to give some details 
regarding their fertilization. 

Isolated plants of Lvnaria vulgaris do not 
produce seed, even if freely pollinated by bees. 
Pollen from other plants is required. This re- 
quirement is not at all restricted to the genus 
Lvnaria, as many instances are known to occur 
in different families. It is generally assumed 
that the pollen of any other individual of the 
same species is capable of producing fertiliza- 
tion, although it is to be said that a critical 
examination has been made in but few instances. 

This, however, is not the case, at least not in 
the present instance. I have pollinated a num- 
ber of plants, grown from seed of the same 
strain and combined them in pairs, and ex- 
cluded the visits of insects, and pollen other 
than that of the plant itself and that of the spec- 
imen with which it was paired. The result was 
that some pairs were fertile and others barren. 
Counting these two groups of pairs, I found 
them nearly equal in number, indicating there- 
by that for any given individual the pollen of 
half of the others is potent, but that of the other 
half impotent. From these facts we may con- 
clude the presence of a curious case of dimor- 
phy, analogous to that proposed for the prim- 
roses, but without visible differentiating marks 
in the flowers. At least such opposite charac- 



472 Mutations 

ters have as yet not been ascertained in the case 
of our toad-flax. 

In order to save seed from isolated plants it is 
necessary, for this reason, to have at least two 
individuals, and these must belong to the two 
physiologically different types. Now in the 
year 1892, as in other years, my plants, though 
separated at the outset by distances of about 20 
cm. from each other, threw out roots of far 
greater length, growing in such a way as to 
abolish the strict isolation of the individuals. 
Any plot may produce several stems from such 
roots, and it is manifestly impossible to decide 
whether they all belong to one original plant or 
to the mixed roots of several individuals. No 
other strains were grown on the same b^d with 
my plants however, and so I considered all the 
stems of the little group as belonging to one 
plant. But their perfect fertility showed, ac- 
cording to the experience described, that there 
must have been at least two specimens mingled 
together. 

Betuming now to the seeds of this pair of 
plants, I had, of course, not the least occasion 
to ascribe to it any higher value than the har- 
vest of former years. The consequence was 
that I had no reason to make large sowings, and 
grew only enough> young plants to have about 
50 in bloom in the summer of 1894. Among 



Origin of Peloric Toadflax 473 

these, stray peloric flowers were observed in 
somewhat larger number than in the previous 
generations, 11 plants bearing one or two, 
or even three such abnormalities. This how- 
ever, could not be considered as a real advance, 
since such plants may occur in varying, though 
ordinarily small numbers in every generation. 

Besides them a single plant was seen to bear 
only peloric flowers ; it produced racemes on sev- 
eral stems and their branches. All were peloric 
without exception. I kept it through the winter, 
taking care to preserve a complete isolation of 
its roots. The other plants were wholly de- 
stroyed. Such annihilation must include both 
the stems and roots and the latter of course re- 
quires considerable labor. The following year, 
however, gave proof of the success of the opera- 
tion, since my plant bloomed luxuriously for the 
second time and remained true to the type of 
the first year, producing peloric flowers ex- 
clusively. 

Here we have the first experimental mutation 
of a normal into a peloric race. Two facts were 
clear and simple. The ancestry was known for 
over a period of four generations, living under 
the ordinary care and conditions of an experi- 
mental garden, isolated from other toad-flaxes, 
but freely fertilized by bees or at times by my- 
self. This ancestry was quite constant as to 



474 


Mutations 


tile pelorio peculiarity, remaining true to the 
wild lype as it occurs everywhere in my country, 
and showing in no respect any tendency to the 
production of a new variety. 

The mutation took place at once. It was a 
sudden leap from the normal plants with very 
rare peloric flowers to a type exclusively 
peloric. No intermediate steps were observed. 
The parents themselves had home thousands of 
flowers during two summers, and these were 
inspected nearly every day, in the hope of find- 
ing some pelories and of saving their seed sep- 
arately. Only one such flower was seen. If 
there had been more, say a few in every hun- 
dred flowers, it might be allowable to consider 
them as previous stages, showing a preparation 
of the impending change. But nothing of this 
kind was observed. There was simply no vis- 
ible preparation for the sudden leap. 

This leap, on the other hand, was full and 
complete. No reminiscence of the former con- 
dition remained. Not a single flower on the 
mutated plant reverted to the previous type. 
All were thoroughly affected by the new attri- 
bute, and showed the abnormally augmented 
number of spurs, the tubular structure of the 
corolla and the round and narrow entrance of 
its throat. The whole plant departed absolute- 
ly from the old type of its progenitors. 



Origm of Peloric Toadflaac 475 

Three ways were open to continue my exper- 
iment. The first was indicated by the abundant 
harvest from the parent-plants of the mutation. 
It seemed possible to compare the numerical 
proportion of the mutated seeds with those 
of normal plants. In order to ascertain 
this proportion I sowed the greatest part of 
my 10 cu. cm. of seed and planted some 2000 
young plants in little pots with well-manured 
soil. I got some 1750 fiowering plants and ob- 
served among them 16 wholly peloric individ- 
uals. The numerical proportion of the muta- 
tion was therefore in this instance to be 
calculated equal to about of the whole crop. 

This figure is of some importance. For it 
shows that the chance of finding mutations 
requires the cultivation of large groups of indi- 
viduals. One plant in each hundred may mu- 
tate, and cultures of less than a hundred speci- 
mens must therefore be entirely dependent on 
chance for the appearance of new forms, even 
if such should accidentally have been produced 
and lay dormant in the seed. In other cases 
mutations may be more numerous, or on the 
contrary, more rare. But the chance of muta- 
tive changes in larger numbers is manifestly 
much reduced by this experiment, and they may 
be expected to form a very small proportion of 
the culture. 



476 


Mutations 


The second question which arose from the 
above result was this. Could the mutation be 
repeated? Was it to be ascribed to some latent 
cause which might be operative more than 
once? Was there some hidden tendency to muta- 
tion, which, ordinarily weak, was strengthened 
in my cultures by some unknown influence? 
Was the observed mutation to be explained by 
a common cause with the other cases recorded 
by field-observations? To answer this question 
I had only to continue my experiment, exclud- 
ing the mutated individuals from any inter- 
crossing with their brethren. To this end I 
saved the seeds from duly isolated groups 
in different years and sowed them at dif- 
ferent times. For various causes I was not 
prepared to have large cultures from these 
seeds, but notwithstanding this, the mutation 
repeated itself. In one instance I obtained 
two, in another, one peloric plant with exclusive- 
ly many-spurred flowers. As is easily under- 
stood, these were related as “ nieces ” to the 
first observed mutants. They originated in 
quite the same way, by a sudden leap, without 
any preparation and without any intermediate 
steps. 

Mutation is proved by this experience to be 
of an iterative nature. It is the expression of 
some concealed condition, or as it is generally 



Origi/n of Peloric Toadflax 477 

called, of some hidden tendency. The real 
nature of this state of the hereditary qualities 
is as yet wholly unknown. It would not be safe 
to formulate further conclusions before the evi- 
dence olfered by the evening-primroses is 
considered. 

Thirdly, the question arises, whether the 
mutation is complete, not only as to the mor- 
phologic character, but also as to the hered- 
itary constitution of the mutated individuals. 
But here unfortunately the high degree of ster- 
ility of the peloric plants, as previously noted, 
makes the experimental evidence a thing of 
great difficulty. During the course of several 
years I isolated and planted together the 
peloric individuals already mentioned, all in all 
some twenty plants. Each individual was nearly 
absolutely sterile when treated with its own 
pollen, and the aid of insects was of no avail. 
I intercrossed my plants artificially, and 
pollinated more than a thousand flowers. Not 
a single one gave a normal fruit, but some small 
and nearly rudimentary capsules were pro- 
duced, bearing a few seeds. From these I had 
119 flowering plants, out of which 106 were 
peloric and 13 one-spurred. The great major- 
ity, .some 90j^, were thus shown to be true to 
their new type. Whether the 10^ reverting 
ones were truly atavists, or whether they were 



478 


Mutations 


only vicinists, caused by stray pollen grains 
from another culture, cannot of course be de- 
cided with sufficient certitude. 

Here I might refer to the observations con- 
cerning the invisible dimorphous state of the 
flowers of the normal toad-flax. Individuals of 
the same type, when fertilized with each other, 
are nearly, but not absolutely, sterile. The 
yield of seeds of my peloric plants agrees fairly 
well with the harvest which I have obtained 
from some of the nearly sterile pairs of indi- 
viduals in my former trial. Hence the sugges- 
tion is forced upon us that perhaps, owing to 
some unknown cause, all the peloric individuals 
of my experiment belonged to one and the same 
type, and were sterile for this reason only. If 
this is true, then it is to be presumed that all 
previous investigators have met the same con- 
dition, each having at hand only one of the two 
required types. And this discussion has 
the further advantage of showing the way, 
in which perhaps a full and constant race of 
peloric toad-flaxes may be obtained. Two indi- 
viduals of different type are required to start 
from. They seem as yet never to have arisen 
from one group of mutations. But if it were 
possible to combine the products of two muta- 
tions obtained in different countries and under 
different conditions, there would be a chance 



479 


Origin of Peloric Toadflax 

that they might belong to the supposed opposite 
types, and thus be fertile with one another. 

My peloric plants are still available, and the 
occurrence of this form elsewhere would give 
material for a successful experiment. The 
probability thereof is enhanced by the experi- 
ence that my peloric plants bear large capsules 
and a rich harvest of seeds when fertilized from 
plants of the normal one-spurred race, while 
they remain nearly wholly barren by artificial 
fertilization with others. .1 suppose that they 
are infertile with the normal toad-flaxes of tiieir 
own sexual disposition, but fertile with those of 
the opposite constitution. At all events the 
fact that they may bear abundant seed when 
properly pollinated is an indication of success- 
ful experiments on the possibility of gaining a 
hereditary race with exclusively peloric flowers. 
And such a race would be a distinct gain for 
sundry physiologic inquiries, and perhaps not 
wholly destitute of value from an horticultural 
point of view. 

Returning now to the often recorded occur- 
rence of peloric toad-flaxes in the wild state and 
recalling our discussion about the improb- 
ability of a dispersion from one locality to 
another by seed, and the probability of inde- 
pendent origin for most of these cases, we are 
confronted with the conception that a latent 



480 


Mutations 


tendency to mutation must be universally 
present in the whole species. Another observa- 
tion, although it is of a negative character, 
gains in importance from this point of view. 
I refer to the total lack of intermediate steps 
between normal and peloric individuals. If 
such links had ordinarily been produced pre- 
vious to the purely peloric state they would no 
doubt have been observed from time to time. 
This is so much the more probable as lAnaria 
is a perennial herb, and the ancestors of a 
mutation might still be in a flowering condi- 
tion together with their divergent offspring. 
But no such intermediates are on record. The 
peloric toad-flaxes are, as a rule, found sur- 
rounded by the normal type, but without inter- 
grading forms. This discontinuity has already 
been insisted upon by Hofmeister and others, 
even at the time when the theory of descent was 
most under discussion, and any link would 
surely have been produced as a proof of a slow 
and continuous change. But no such proof has 
been found, and the conclusion seems admissible 
that the mutation of toad-flaxes ordinarily, if 
not universally, takes place by a sudden step. 
Our experiment may simply be considered as a 
thoroughly controlled instance of an often re- 
curring phenomenon. It teaches us how, in the 



Origm of Peloric Toadflaas 481 

main, the peloric mutations mnst be assumed to 
proceed. 

This conception may still be broadened. We 
may include in it all similar occurrences, in 
allied and other species. There is hardly a 
limit to the possibilities which are opened up by 
this experience. But it will be well to refrain 
from hazardous theorizing, and consider only 
those cases which may be regarded as exact 
repetitions of the same phenomenon and of 
which our culture is one of the most recent in- 
stances on record. We will limit ourselves to 
the probable origin of peloric variations at 
large, of which little is known, but some evi- 
dence may be derived from the recorded facts. 
Only one case can be said to be directly analo- 
gous to our observations. 

This refers to the peloric race of the common 
snapdragon, or Antirrhinum majus of our gar- 
dens. It is known to produce peloric races from 
time to time in the same way as does the toad- 
flax. But the snapdragon is self-fertile and so 
is its peloric variety. Some cases are rela- 
tively old, and some of them have been recorded 
and in part observed by Darwin. Whence they 
have sprung and in what manner they were 
produced, seems never to have been noted. 
Others are of later origin, and among these one 
or two varieties have been accidentally pro- 



482 


Mutations 


duced in the nursery of Mr. Chr. Lorenz in 
Erfurt, and are now for sale, the seeds being 
guaranteed to yield a large proportion of 
peloric individuals. The peloric form in this 
case appeared at once, but was not isolated, and 
was left free to visiting insects, which of course 
crossed it with the surrounding varieties. 
Without doubt the existence of two color-varie- 
ties of the peloric t3rpe, one of a very dark red, 
indicating the “ Black prince ” variety as the 
pollen-parent, and the other with a white tube 
of the corolla, recalling the form known as 
“ Delila,” is due to these crossings. I had last 
year (1903) a large lot of plants, partly normal 
and partly peloric, but evidently of hybrid 
origin, from seeds from this nursery, showing 
moreover all interme^ate steps between nearly 
wholly peloric individuals and apparently nor- 
mal ones. I have saved the seeds of the iso- 
lated types and before seeing the flowers of 
their offspring, nothing can be said about the 
purity and constancy of the type, when freed 
from hybrid admixtures. The peloric snap- 
dragon has five small unequal spurs at the base 
of its long tube, and in this respect agrees with 
the peloric toad-flax. 

Other pelories are terminal and quite regular, 
and occur in some species of Linaria, where I 
observed them in Linaria dalmatica. The 



Origin of Peloric Toadflax 483 

terminal flowers of many branches were large 
and beautifully peloric, bearing flve long and 
equal spurs. About their origin and inher- 
itance nothing is known. 

A most curious terminal pelory is that of the 
common foxglove or Digitalis purpurea. As we 
have seen in a previous lecture, it is an old 
variety. It was described and flgured for the 
first time by Vrolik of Amsterdam, and the 
original specimens of his plates are still to be 
seen in the collections of the botanic garden of 
that university. Since his time it has been 
propagated by seed as a commercial variety, 
and may be easily obtained. The terminal 
flower of the central stem and those of the 
branches only are affected, all other flowers 
being wholly normal. Almost always it is ac- 
companied by other deviations, among which a 
marked increase of the number of the parts of 
the corolla and other whorls is the most strik- 
ing. Likewise supernumerary petals on the 
outer side of the corolla, and a production of a 
bud in the center of the capsule may be often 
met witli. This bud as a rule grows out after 
the fading away of the flower, bursting through 
the green carpels of the unripe fruit, and pro- 
ducing ordinarily a secondary raceme of flow- 
ers. This raceme is a weak but exact repetition 
of the first, bearing symmetrical foxgloves all 



484 


Mutations 


along and terminating in a peloric structure. 

On the branches these anomalies are more or 
less reduced, according to the strength of the 
branch, and conforming to the rule of perio- 
dicity', given in our lecture on the “ five-leaved ” 
clover. Through all this diminution the peloric 
type remains unchanged and therefore becomes 
so much the purer, the weaker the branches on 
which it stands. 

I am not sure whether such peloric flowers 
have ever been purely pollinated and their seed 
saved separately, but I have often observed 
that the race comes pure from the seed of the 
zygomorphic flowers. It is as yet doubtful 
whether it is a half race or a double race, and 
whether it might be purified and strengthened 
by artificial selection. Perhaps the determina- 
tion of the hereditary percentage de- 
scribed when dealing with the tricotyls might 
give the clue to the acquisition of a higher 
specialized race. The variety is old and widely 
disseminated, but must be subjected to quite a 
number of additional experiments before it can 
be said to be sufficiently understood. 

The most widespread peloric variety is that 
of gloxinia. It has erect instead of drooping 
flowers; and with the changed position the 
structure is also changed. Like other pelories 
it has five equal stamens instead of four un- 



Origin of Peloric Toadflax 485 

equal ones, and a corolla with five equal seg- 
ments instead of an upper and a lower lip. It 
shows the peloric condition in all of its fiowers 
and is often combined with a small increase 
of the number of the parts of the whorls. 
It is for sale under the name of erecta, and 
may be had in a wide range of color-types. It 
seems to be quite constant from seed. 

Many other instances of peloric flowers are 
on record. Indian cress or Tropaeolum majus 
loses the spur in some double varieties and 
with it most of its symmetrical structure; it 
seems to be considered justly as a peloric mal- 
formation. Other species produce such anom- 
alies only from time to time and nothing is 
known about their hereditary tendency. One 
of the most curious instances is the terminal 
flower of the raceme of the common laburnum, 
which loses its whole papilionaceous character 
and becomes as regularly quinate as a common 
buttercup. 

Some families are more liable to pelorism 
than others. Obviously all the groups, the 
flowers of which are not symmetrical, are to be 
excluded. But then we find that labiates and 
their allies among the dicotyledonous plants, 
and orchids among the monocotyledonous ones 
are especially subjected to this alteration. In 
both groups many genera and a long list of spe- 



486 


Mutations 


* 

cies could be quoted as proof. The family of the 
labiates seems to be essentially rich in terminal 
pelories, as for instance in the wild sage or 
Salvia and the dead-nettle or Lamium. Here 
the pelories have long and straight corolla- 
tubes, which are terminated by a whorl of four 
or five segments. Such forms often occur in 
the wild state and seem to have a geographic 
distribution as narrowly circumscribed as in 
the case of many small species, Those of the 
labiates chiefly belong to southern Europe and 
are unknown at least in some parts of the other 
countries. On the contrary terminal pelories 
of Scrophularia nodosa are met with from time 
to time in Holland. Such facts clearly point 
to a common origin, and as only the terminal 
flowers are affected by the malformation, the 
fertility of the whole plant is evidently not seri- 
ously infringed upon. 

Before leaving the labiates, we may cite 
a curious instance of pelorism in the toad-flax, 
which is quite different from the ordinary 
peloric variety. This latter may be considered 
from a morphologic standpoint to be owing to 
a five-fold repetition of the middle part of the 
underlip. This conception would at once ex- 
plain the occurrence of five spurs and of the 
orange border all around the corolla-tube. We 
might readily imagine that any other of the five 



Origm of Peloric Toadflax 487 

parts of the corolla could be repeated five-fold, 
in which case there would be no spur, and no 
orange hue on the upper corolla-ring. Such 
forms really occur, though they seem to be more 
rare than the five-spurred pelories. Very little 
is known about their frequency and hereditary 
qualities. 

Orchids include a large number of peloric 
monstrosities and moreover a wild pelory 
which is systematically described not only as a 
separate species but even as a new genus. It 
bears the name of Uropedium lindenii, and is 
so closely related to Cypripedium caudatum 
that many authors take it for the peloric variety 
of this plant It occurs in the wild state in 
some parts of Mexico, where the Cypripedium 
also grows. Its claims to be a separate genus 
are lessened by the somewhat monstrous con- 
dition of the sexual organs, which are described 
as quite abnormal. But here also, interme- 
diates are lacking, and this fact points to a 
sudden origin. 

Many cases of pelorism afford promising ma- 
terial for further studies of experimental muta- 
tions. The peloric toad-flax is only the proto- 
type of what may be expected in other cases. 
No opportunity should be lost to increase the as 
yet too scanty evidence on this point. 



leotube xvn 


THE PBODUCIIOK OF DOUBLE FLOWEBS 

Mutations occur as often among cultivated 
plants as among those in the wild state. Gar- 
den flowers are known to vary markedly. 
Much of their variability, however, is due to 
hybridism, and the combination of characters 
previously separate has a value for the breeder 
nearly equal the production of really new qual- 
ities. Nevertheless there is no doubt that some 
new characters appear from time to time. 

In a previous lecture we have seen that 
varietal characters have many features in com- 
mon. One of them is their frequent recur- 
rence both in the same and in other, often very 
distantly related, species. This recurrence is an 
important factor in the choice of the material 
for an experimental investigation of the nature 
of mutations. 

Some varieties are reputed to occur more 
often and more readily than others. White-col- 
ored varieties, though so very common, seem for 
the most part to be of ancient date, but only few 

488 



Production of Double Flowers 489 

have a known origin, however. Withont any 
doubt many of them have been found in a wild 
state and were introduced into culture. On the 
other hand double flowers are exceedingly rare 
in the wild state, and even a slight indication of 
a tendency towards doubling, the stray petaloid 
stamens, are only rarely observed growing wild. 
In cultivation, however, double flowers are of 
frequent occurrence; hence the conclusion that 
they have been produced in gardens and nur- 
series more frequently than perhaps any other 
type of variety. 

In the beginning of my experimental work I 
cherished the hope of being able to produce a 
white variety. My experiments, however, have 
not been successful, and so I have given them 
up temporarily. Much better chances for a 
new double variety seemed to exist, and my en- 
deavors in this direction have finally been 
crowned with success. 

For this reason I propose to deal now with 
the production of double flowers, to inquire 
what is on record about them in horticultural 
literature, and to give a full description of the 
origin thereof in an instance which it was my 
good fortune to observe in my garden. 

Of course the historical part is only a hasty 
survey of the question and will only give such 
evidence as may enable us to get an idea of the 



490 


Mutations 


chances of success for the experimental worker. 

In the second half of the seventeenth century 
(1671), my countryman, Abraham Hunting, pub- 
lished a large book on garden plants with many 
beautiful figures. It is called “ Waare Oeffen- 
inge der Planten,” or “ True Exercises With 
Plante.” The descriptions pertain to ordinary 
typical species in greater part, but garden- 
varieties receive special attention. Among 
these a long list of double flowers are to be seen. 
Double varieties of poppies, liverleaf {Hepa- 
tica)f wallflowers (Cheiranthus) y violets, CaU 
tha, Althaea, Colchicum, and periwinkles 
(Vinca), and a gfeat many other common flow- 
ers were already in cultivation at that time. 

Other double forms have been since added. 
Many have been introduced from Japan, espe- 
cially the Japanese marigold, Chrysanthemum 
indicum. Others have been derived from Mexi- 
co, as for instance the double zinnias. The 
single dahlias only seem to have been originally 
known to the inhabitants of Mexico. They 
were introduced into Spain at about 1789, and 
the first double ones were produced in Louvain, 
Belgium, in 1814. The method of their origin 
has not been described, and probably escaped 
the originators themselves. But in historical 
records we find the curious statement that it 
took place after three years* work. This indi- 



Production of Double Flowers 491 

cates a distinct plan, and the possibility of 
carrying it to a practical conclusion within a 
few years’ time. 

Something more is known about other cases. 
Garden anemones, Anemone coronaria, are said 
to have become double in the first half of the 
last century in an English nursery. The owner, 
Williamson, observing in his beds a flower with 
a single broadened stamen, saved its seeds se]> 
arately, and in the next generations procured 
beautifully filled flowers. These he afterwards 
had crossed by bees with a number of colored 
varieties, and in this way succeeded in produc- 
ing many new double types of anemone. 

The first double petunia is known to have sud- 
denly and accidentally arisen from ordinary 
seed in a private garden at Lyons about 1855. 
From this one plant all double races and varie- 
ties have been derived by natural and partly by 
artificial crosses. Carriere, who reported this 
fact, added' that likewise other species were 
known at that time to produce new double varie- 
ties rapidly. The double fuchsias originated 
about the same time (1854) and ten years later 
the range of double varieties of this plant had 
become so large that Carriere found it impos- 
sible to enumerate all of them. 

Double carnations seem to be relatively old, 
double corn-flowers and double blue-bells being 



492 


Mutations 


of a later period. A long list could easily be 
made, to show that during the whole history of 
horticulture double varieties have arisen 
from time to time. As far as we can judge, 
such appearances have been isolated and sud- 
den. Sometimes they sprang into existence in 
the full display of their beauty, but most com- 
monly they showed themselves for the first time, 
exhibiting only spare supernumerary petals. 
Whenever such sports were worked up, a few 
years sufiSced to reach the entire development 
of the new varietal attribute. 

From this superficial survey of historical 
facts, the inference is forced upon us that the 
chance of producing a new double variety is 
good enough to justify the attempt. It has fre- 
quently succeeded for practical purposes, why 
should it not succeed as well for purely scien- 
tific investigation? At all events the type rec- 
ommends itself to the student of nature, both 
on account of its frequency, and of the apparent 
insignificance of the first step, combined with 
the possibility of rapidly working up from this 
small beginning of one superfluous petal to- 
wards the highest degree of duplication. 

Compared with the tedious experimental pro- 
duction of the peloric toad-flax, the attempt to 
produce a double flower has a distinct attrac- 
tion. The peloric toad-flax is nothing new ; the 



Production of Double Flowers 493 

experiment was only a repetition of what pre> 
smnably takes place often within the same 
species. To attempt to produce a double 
variety we may choose any species, and of 
course should select one which as yet has not 
been known to produce double flowers. By 
doing so we will, if we succeed, produce some- 
thing new. Of course, it does not matter 
whether the new variety has an horticultural in- 
terest or not, and it seems preferable to choose 
a wild or little cultivated species, to be quite 
sure that the variety in question is not already 
in existence. Finally the prospect of success 
seems to be enhanced if a species is chosen, the 
nearest allies of which are known to have pro- 
duced double flowers. 

For these reasons and others I chose for my 
experiment the com-marigold, or Chrysanthe- 
mum segetum. It is also called the golden corn- 
flower. In the wheat and rye fields of central 
Europe it associates with the blue-bottle or blue 
corn-flower. It is sometimes cultivated and the 
seeds are offered for sale by many nursery- 
men. It has a cultivated variety, called grandi- 
florum, which is esteemed for its brilliancy and 
long succession of golden bloom. This variety 
has larger flower-heads, surrounded with a 
fuller border of ray-florets the species belongs 
to a genus many species of which have pro- 



494 


Mutations 


duoed double varieties. One of them is 
the Japanese marigold, others are the carir- 
nctum and the imhricatum species. Nearly 
allied are c[uite a number of garden-plants with 
double flower-heads, among which are the 
double camomiles. 

My attention was first drawn to the structure 
of the heads and especially to the number of the 
ray-florets of the com-marigold. The species 
appertains to that group of composites which 
have a head of small tubular florets surrounded 
by a broad border of rays. These rays, when 
counted, are observed to occur in definite num- 
bers, which are connected with each other by a 
formula, known as “ the series ” of Braun and 
Schimper. Iii this formula, which commences 
with 1 and 2, each number is equal to the sum 
of the two foregoing figures. Thus 5, 8 and 13 
are very frequent occurrences, and the following 
number, 21, is a most general one for apparent- 
ly full rays, such as in daisies, camomiles, i4rm<?a 
and many other wild and cultivated species. 

These numbers aye not at all constant. They 
arc only the averages, around which the real 
numbers fluctuate. There may even be an over- 
lapping of the extreme, since the fluctuation 
around 13 may even go beyond 8 and 
21, and so on. But such extremes are only 
found in stray flowers, occurring on the same 



Production of Double Flowers 495 

individuals with the lesser degrees of deviation. 

Now the marigold averages 13, and the 
grandiflorum 21 rays. The wild species is pure 
in this respect, but the garden-variety is not. 
The seeds which are offered for sale usually 
contain a mixture of both forms and their 
hybrids. So I had to isolate the pure types 
from this mixture and to ascertain their con- 
stancy and mutual independency. To this end 
I isolated from the mixture first the 13-rayed, 
and afterwards the 21-rayed types. As the 
marigolds are not sufficiently self-fertile, and 
are not easily pollinated artificially, it seemed 
impossible to carry on these two experiments at 
the same time and in the same garden. I de- 
voted the first three years to the lower form, 
isolated some individuals with 12 - 13 rays out of 
the mixture of 1892 and counted the ray-florets 
on the terminal head of every plant of the en- 
suing generation next year. I cultivated and 
counted in this way above 150 individuals and 
found an average of exactly 13 with compara- 
tively few individuals displaying 14 or only 12 
rays, and with the remainder of the plants 
grouped symmetrically around this average. I 
continued the experiment for still another year 
and found the same group of figpires. I was 
then satisfied as to the purity of the isolated 
strain. Next year I sowed a new mixture in 



496 


Mutations 


order to isolate the reputed pure grandiflorum 
type. During the beginning of the flowering 
period I ruthlessly threw away all plants dis- 
playing less than 21 rays in the first or terminal 
head. But this selection was not to be consid- 
ered as complete, because the 13-rayed race may 
eventually transgress its boundary and come 
over to the 21 and more. This made a second 
.selection necessary. On the selected plants 
all the secondary heads were inspected and 
their ray-florets counted. Some individuals 
showed an average of about 13 and were de- 
stroyed. Others gave doubtful figures and 
were likewise eliminated, and only 6 out of a 
lot of nearly 300 flowering plants reached an 
average of 21 for all of the flowers. 

Our summer is a short one, compared with the 
long and beautiful summer of California, and it 
was too late to cut off the faded and the open 
flowers, and await new ones, which might be 
purely fertilized after the destruction of 
all minor plants. So I had to gather the seed 
from flowers, which might have been partially 
fertilized by the wrong pollen. This however, 
is not so great a drawback in selection experi- 
ments as might be supposed at first sight. The 
selection of the following year is sure to elim- 
inate the offspring of such impure parentage. 



Production of Double Flowers ^7 

A far more important principle is that of the 
hereditary percentage, already discussed in our 
lecture on the selection of monstrosities. In 
our present case it had to he applied only to the 
six selected plants of 1895. To this end the seeds 
of each of them were sown separately, the ray- 
florets of the terminal heads of each of the 
new generation were counted, and curves and 
averages were made up for the six groups. 
Five of them gave proof of still being mixtures 
and were wholly rejected. The children of the 
sixth parent, however, formed a group of uni- 
form constitution, all fluctuating around the de- 
sired average of 21. All in all the terminal 
heads of over 1500 plants have been subjected 
to the somewhat tedious work of counting their 
ray-florets. And this not in the laboratory, but 
in the garden, without cutting them off. Other- 
wise it would obviously have been impossible to 
recognize the best plants for preservation. 1 
chose only two plants which in addition recom- 
mended themselves by the average number of 
rays on their secondary heads, sowed their 
seeds next year separately and compared the 
numerical constitution of their offspring. 
Both groups averaged 21 and were distributed 
very symmetrically around this mean. This re- 



498 


Mutations 


suit showed that no further selection could be 
of any avail, and that I had succeeded in purify- 
ing the 21-rayed grandiflorum variety. 

It is from this grandiflorum that I have finally 
produced my double variety. In the year 1896 
I selected from among the above quoted 1500 
plants, 500 with terminal heads bearing 21 or 
more rays. On these I counted the rays of all 
the secondary heads about the middle of August 
(1896) and found that they had, as a rule, 
retrograded to lower figures. On many thou- 
sands of heads only two were found having 22 
rays. AU others had the average number of 21 
or even less. I isolated the individual which 
bore these two heads, allowed them to be fertil- 
ized by insects with the pollen of some of the 
best plants of the same group, but destroyed the 
remainder. 

This single exceptional plant has been the 
starting point of my double variety. It was not 
remarkable for its terminal head, which exhib- 
ited the average number of rays of the 21-rayed 
race. Nor was it distinguished by the average 
figure for all its heads. It was only selected 
because it was the one plant which had some 
secondary heads with one ray more than all the 
others. This indication was very slight, and 
could not have been detected save by the 
cotmting of the rays of thousands of heads. 



Production of Double Flowers 499 

But the rarity of the anomaly was exactly the 
indication wanted, and the same deviation 
would have had no signification whatever, had it 
occurred in a group fluctuating symmetrically 
around the average figure. On the other hand, 
the observed anomaly was only an indication, 
and no guarantee of future developments. 

Here it should be remarked that the indica- 
tion alluded to was not the appearance of the 
expected character of doubling in ever so slight 
a measure. It was only a guide to be followed 
in further work. The real character of double 
flower-heads among composites lies in the pro- 
duction of rays on the disk. No increase of the 
number of the outer rays can have the same sig- 
nificance. A hasty inspection of double flower- 
heads may convey the idea that all rays are ar- 
ranged around a little central cluster of disk- 
florets, the remainder of the original disk. But 
a closer investigation will always reveal the 
fallacy of this conclusion. Hidden between 
the inner rays, and covered by them, lie the 
little tubular and fertile florets everywhere 
on the disk. They may not be easily seen, but 
if the supernumerary rays are pulled out, the 
disk may be seen to bear numerous small 
florets at intervals. But these intervals 
are not at all numerous, showing thereby that 
only a relatively small number of tubes has been 



500 


Mutations 


converted into rays. This conversion is ob- 
viously the true mark of the doubling, and be- 
fore traces of it are found, no assertion what- 
ever can be given as to the issue of the pedigree- 
experiment 

Three more years were required before this 
first l>ut decisive trace was discovered. During 
these years I subjected my strain to the same 
sharp selection as has already been described. 
The chosen ancestor of the race had flowered in 
1896, and the next year I sowed its seeds only. 
From this generation I chose the one plant with 
the largest number of rays in its terminal head, 
and repeated this in the following year. 

. The consequence was that the average num- 
ber of rays increased rapidly, and with it the 
absolute maximum of the whole strain. The 
average came up from 21 to 34. Brighter and 
brighter crowns of the yellow rays improved 
my race, until it became difficult and very time- 
consuming to count all the large rays of the bor- 
ders. The largest numbers determined in the 
succeeding generations increased by leaps from 
21 to 34 in the first year, and thence to 48 and 66 
in the two succeeding summers. Every year I 
was able to save enough seed from the very best 
plant and to use it only for the continuance of 
the race. Before the selected plants were al- 
lowed to open the flowers from which the seed 



Production of Double Flowers 501 

was to be gathered, nearly the whole remaining 
culture was exterminated, excepting only some 
of the best examples, in order to have the re- 
quired material for cross-pollination by insects. 
Each new generation was thereby as sharply 
selected as possible with regard to both parents. 

All flower-heads were of course closely in- 
spected. !Not the slightest indication of real 
doubling was discovered, even in the summer of 
1899 in the fourth generation of my selected 
race. But among the best the new character 
suddenly made its appearance. It was at the 
commencement of September (1899), too late 
to admit of the seeds ripening before win- 
ter. An inspection of the younger heads 
was made, which revealed three heads 
with some few rays in the midst of the disk on 
one plant, the result of the efforts of four years. 
Had the germ of the mutation lain hidden 
through all this time? Had it been pres- 
ent, though dormant in the original sample 
of seed ? Or had an entirely np'<^ crcation taken 
place during my -cohtinuous endeavors? Per- 
haps as their^ more or less immediate re- 
sult ? It is obviously impossible to answer these 
questions, before further and similar experi- 
ments shall have been performed, bringing to 
light other details that will enable us to reach a 
more definite conclusion. 



502 


Mutations 


The fact that the origination of sudi forms 
is accessible to direct investigation is proven 
quite independently of all further considera- 
tions. The new variety came into existence at 
once. The leap may have been made by the 
ancestor of the year 1895, or by the plant of 
1899, which showed the first central rays, or 
the sport may have been gradually built up dur- 
ing those four years. In each case there was a 
leap, contrasting with the view which claims a 
very long succession of years for the develop- 
ment of every new character. 

Having discovered this first trace of doubling, 
it was to be expected that the new variety would 
be at once as pure and as rich as other double 
composites usually are. Some effect of the 
crossing with the other seed-bearing individuals 
might still disturb this uniformity in the follow- 
ing year, but another year’s work would elim- 
inate even this source of impurity. 

These two years have given the expected re- 
sult. The average number of the rays, which 
isd already arisen from 13 34 now at once 

came up to 47 and 55, the last iSgure being the 
sum of 21 and 34 and therefore *he probable 
uttermost limit to be reached before absolute 
doubling. The maximum numbers came as high 
as 100 in 1900, and reached even 200 in 1901. 
Such heads are as completely double as are the 



Production of Double Flowers 603 

brightest heads of the most beautiful double 
commercial varieties of composites. Even the 
best white camomiles (Chrysanthemum ino- 
dor um) and the gold-flowers or garden-mari- 
golds (Calendula officinalis) do not come nearer 
to purity since they always have scores of little 
tubular florets between the rays on their disks. 

Real atavists or real reversionists were seen 
no more after the first purification of the race. 
I have continued my culture and secured last 
summer (1903) as many and as completely 
doubled heads as previously. The race has at 
once become permanent and constant. It has of 
course a wide range of fluctuating variability, 
but the lower limit has been worked up to about 
34 rays, a figure never reached by the grandi- 
forum parent, from which my new variety is 
thus sharply separated. 

Unfortunately the best flowers and even the 
best individuals of my race are wholly barren. 
Selection has reached its practical limit. Seeds 
must be saved from less dense heads, and no 
way has been found of avoiding it. The ray- 
florets are sterile, even in the wild species, and 
when growing in somewhat large numbers on 
the disk, they conceal the fertile flowers from 
the visiting insects, and cause them also to be 
sterile. The same is the case with the best cul- 
tivated forms. Their showiest individuals are 



504 Mutations 

barren, and incapable of the reproduction of the 
race. 

This last is therefore, of necessity, always 
continued by means of individuals whose devia- 
tion from the mean average is the least. But 
in many cases the varieties are so highly dif- 
ferentiated that selection has become quite su- 
perfluous for practical purposes. I have al- 
ready discussed the question as to the actual 
moment, in which the change of the grandiflor- 
um variety into the new plenum form must be 
assumed to have taken place. In this respect 
some stress is to be laid on the fact that the im- 
provement through selection has been gradual 
and continuous, though very rapid from the first 
moment. But with the appearance of the first 
stray rays within the disk, this continuity sud- 
denly changed. All the children of this original 
mutated plant showed the new character, the 
rays within the disk, without exception. Not 
on all the heads, nor even on the majority of the 
heads on some individuals, but on some heads all 
gave clear proof of the possession of the new 
attribute. This was present in all the repre- 
sentatives of the new race, and had never been 
seen in any of their parents and grandparents. 
Here there was evidently a sudden leap, at 
least in the external form of the plants. And it 
seems to me to be the most simple conception. 



Production of Double Flowers 505 

that this visible leap directly corresponded to 
that inner change, which brought about the com- 
plete inheritability of the new peculiarity. It 
is very interesting to observe how completely 
my experience agrees with the results of the 
observations of breeders at large. No doubt 
a comparison is difficult, and the circumstances 
are not adequate to a close study. 

Isolation and selection have been applied com- 
monly only so far as was consistent with the re- 
quirements of practical horticulture, and of 
course a determination of the hereditary per- 
centage was never made. The disregard of this 
feature made necessary a greater length of time 
and a larger number of generations to bring 
about the desired changes. Notwithstanding 
this, however, it has been seen that double va- 
rieties are produced suddenly. This may have 
occurred unexpectedly or after a few years’ ef- 
fort toward the end desired. Whether this 
sudden appearance is the consequence of a 
single internal differentiating step, or of the 
rapid succession of lesser changes, cannot yet 
be made out. The extreme variability of dou- 
ble flowers and the chance of their appearance 
with only slight indications of the previous pet- 
aloid alterations of a few stamens may often re- 
sult in their origin being overlooked, while 
subsequent generations may come in for full no- 



506 


Mutations 


tice. In the greater number of cases recorded 
it remains doubtful whether the work said to be 
done to obtain a new double variety was done 
before the appearance of these preliminary indi- 
cations or afterward. 

In the first case, it would correspond with 
our selection of large numbers of fiorets in the 
outer rays, in the second however, with the or- 
dinary purification of new races from hybrid 
mixtures. 

In scientific selection-experiments such cross- 
es are of course avoided, and the process of 
purification is unnecessary, even as in the 
Chrysanthemum culture. The first generation 
succeeding the original plant with disk-rays was 
in this respect wholly uniform and true to the 
new type. 

In practice the work does not start from such 
slight indications, and is done with no other 
purpose in view than to produce double flowers 
in species in which they did not already exist. 
Therefore it is of the highest importance to 
know the methods used and the chances of suc- 
cess. Unfortunately the evidence is very scanty 
on both points. 

Lindley and other writers on horticultural 
theory and practice assert that a large amount 
of nourishment tends to produce double flow- 
ers, while a culture under normal conditions. 



Production of Double Flowers 507 

even if the plants are very strong and healthy, 
has no such effect. But even here it remains 
doubtful whether it applies to the period before 
or after the internal mutation. On the other 
hand success is not at all to be relied upon, nor 
is the work to be regarded as easy. The in- 
stances of double flowers said to be obtainable 
at will, are too rare in comparison with the 
number of cases, where the first indication of 
them was found accidentally. 

Leaving all these doubtful points, which will 
have to be cleared up by further scientific in- 
vestigation, the high degree of variability re- 
quires further discussion. It may be considered 
from three different points of view according 
to the limit of the deviation from the average, 
to the dependency on external conditions and to 
periodicity. It seems best to take up the last 
two points firsts 

On a visit to a nursery at Erfurt I once in- 
spected an experiment with a new double varie- 
ty of the common blue-bottle or blue corn-flow- 
er. The plants were dependent on the weather 
to a high degree. Bad weather increased the 
number of poorly filled flower-heads, while 
warm and sunny days were productive of beau- 
tiful double flowers. The heads that are borne 
by strong branches have a greater tendency to 
become double than those of the weaker ones. 



508 


Mutations 


and towards the autumn, when all those of the 
first gronp are faded away, and only a weak 
though large section of the heads is still power- 
ing, the whole aspect of the varietjs-l^adually 
retrogrades. The same law of dependency and 
I)eriodicity is prevalent everywhere. In my 
own cultures of the improved field-marigold I 
have observed it frequently. The number of the 
ray-florets may be considered as a direct re- 
sponse to nourishment, both when this is deter- 
mined by external circumstances, and when it 
depends on the particular strength of the 
branch, which bears the head in question. It is 
a case exactly similar to that of the supernumer- 
ary carpels of the pistilloid poppy, and the de- 
ductions arrived at with that variety may be 
applied directly to double flowers. 

This dependency upon nourishment is of high 
practical importance in combination with the 
usual effect of the doubling which makes 
the flowers sterile. It is a general rule that the 
most perfect flowers do not produce seed. At 
the height of the flowering period the external 
circumstances are the most favorable, and the 
flowering branches still constitute the stronger 
axes of the plants. Hence we may infer that 
sterility will prevail precisely in this period. 
Many varieties are known to yield only seeds 
from the very last flowers, as for instance some 



Production of Double Flowers 609 

double begonias. Others bear only seed on their 
weaker lateral branches, as the double camomile, 
or become fertile only towards the fall, as is 
often the case with the above quoted Erfurt va- 
riety of the blue-bottle. As far as I have been 
able to ascertain, such seeds are quite adequate 
for the reproduction and perpetuation of the 
double varieties, but the question whether there 
are differences between the seeds of the more 
or less double flowers of the same plants still 
remains open. It is very probable, from a the- 
oretical point of view, that such differences ex- 
ist, but perhaps they are so slight, as to have 
practically no bearing on the question. 

On the ground of their wide range of varia- 
bility, the double varieties must be regarded as 
pertaining to the group of ever-sporting forms. 
On one side they fluctuate in the direction to- 
wards such petalomanous flowers as are borne 
by the stocks and others, which we have pre- 
viously discussed. Here no trace of the fertile 
organs is left. But this extreme is never reach- 
ed by petaloid double flowers. A gap remains 
which, often overlooked, always exists, and 
which sharply separates the two types. On the 
other hand the alteration of the stamens grad- 
ually relapses to perfectly single flowers. Here 
the analogy with the pistillody of the poppies 
and with the “ five-leaved ** clover is obvious. 



510 


Mutations 


This conception of the inner nature of double 
flowers explains the fact that the varietal mark 
is seldom seen to be complete throughout larger 
groups of individuals, providing these have not 
been already selected by this character. 
Tagetes africana is liable to produce some 
poorly filled specimens, and some double va- 
rieties of carnations are offered for sale with the 
note that the seed yields only 80% of doubles. 
With Chrysanthemum coronarium and blue-bot- 
tles this figure is often announced to be only 
about 50^. No doubt it is partly due to im- 
purities, caused by vicinism, but it is obviously 
improbable that the effect of these impurities 
should be so large. 

Some cases of partial reversion may be inter- 
preted in the same way. Among the garden 
anemones. Anemone coronaria, there is a va- 
riety called the “ Bride,” on account of its pure 
white flowers. It is for sale with single and 
with double flowers, and these two forms are 
known to sport into one another, although they 
are multiplied in the vegetative way. Such cases 
are known to be of quite ordinary occurrence. 
Of course such sports must be considered as 
partial, and the same stem may bear both types 
of flowers. It even happens that some partic- 
ular flower is partly double and partly single. 
Mr. Krelage, of Haarlem, had the kindness to 



Production of Double Flowers 511 

send me such a curions flower. One half of it 
was completely double, while the other half was 
entirely single, bearing normal and fertile sta- 
mens in the ordinary number. 

The same halfway doubling is recorded to 
occur among composites sometimes, and from 
the same source I possess in my collection a 
head of Pyrethrum roseum, bearing on half of 
its disk elongated corolla tubes, and on the 
other half the small disk-florets of the typical 
species. 

It is a current belief, that varieties are im- 
proved by continued culture. I have never been 
able to ascertain the grounds on which this con- 
viction rests. It may be referred either to the 
purity of the race or to the complete develop- 
ment of the varietal character. In the first case 
it is a question of hybrid mixtures from which 
many young varieties must be freed before be- 
ing placed on the market. But as we have al- 
ready seen in a former lecture, this requires 
only three or four years, and afterwards the 
degree of purity is kept up to the point which 
proves to be the most suitable for practical 
purposes. The complete development of the 
varietal character is a question restricted to 
ever-sporting varieties, since in white flowers 
and other constant varieties this degree is va- 
riable in a very small and unimportant meas- 



512 


Mutations 


nre. Hence the double flowers seem to afford 
a very good example for this discussion. 

It can be decided by two facts. First by a 
consideration of the oldest double varieties, and 
secondly by that of the very youngest. Are the 
older ones now in a better condition than at the 
outsetf Have they really been gradually im- 
proved during the centuries of their existence f 
Obviously this can only be answered by a com- 
parison of the figures given by older writers, 
with the varieties as they are now in culture. 
Hunting’s drawings and descriptions are now 
nearly two centuries and a half old, but 1 do not 
find any real difference between his double va- 
rieties and their present representatives. So 
it is in other cases in which improvements by 
crossing or the introduction of new forms does 
not vitiate the evidence. Double varieties, as 
a rule, are exactly the same now, as they were 
at the time of their first introduction. 

If this were otherwise one would expect that 
young double varieties should in the main dis- 
play only slight grades of the anomaly, and 
that they would require centuries to reach their 
full development. Nothing of the kind is on 
record. On the contrary the newest double 
sorts are said to be not only equal to their prede- 
cessors, but to excel them. As a rule such claims 
may be exaggerated, but not to any great extent. 



Production of Double Flowers 513 


This is proven in the simplest way by the re- 
sult of our own experiment. 

In the double field-marigold we have the very 
first generation of a variety of pure and not 
hybrid origin. It shows the new attribute in 
its full development. It has flower-heads near- 
ly as completely filled as the best double varie- 
ties of allied cultivated composites. In the sec- 
ond generation it reached heads with 200 rays 
each, and much larger numbers will seldom be 
seen in older species on heads of equal size. I 
have compared my novelty with the choicest 
double camomiles and others, but failed to dis- 
cover any real difference. Improvement of the 
variety developed in the experiments carried on 
by myself seems to be excluded by the fact 
that it comes into conflict with the same difficul- 
ty that confronts the older cultivated species, 
viz. : the increasing sterility of the race. 

It is perfectly evident that this double mari- 
gold is now quite constant. Continuously va- 
rying about a fixed average it may live through 
centuries, but the mean and the limits will al- 
ways remain the same, as in the case of the 
ever-sporting varieties. 

Throughout this lecture I have spoken of 
double flowers and double flower-heads of com- 
posites as of one single group. They are as 
nearly related from the hereditary point of 



514 


Mutations 


view, as they are divergent in other respects. 
It would be superfluous to dwell any longer 
upon the difference between heads and flowers. 
But it is as well to point out, that the term dou- 
ble flowers indicates a motley assemblage of dif- 
ferent phenomena. The hen-and-chicken daisy, 
and the corresponding variety of the garden- 
oineraiia {Cineraria cruenta)^ are extremes on 
one side. The hen-and-chicken type occurs 
even in other families and is known to produce 
most curious anomalies, as with Scabiosa, the 
supernumerary heads of which may be pro- 
duced on long stalks and become branched 
themselves in tlie same manner. 

Petalody of the stamens is well known to be 
the ordinary type of doubling. But it is often 
accompanied by a multiplication of the organs, 
both of the altered stamens and of the petals 
themselves. This proliferation may consist in 
median or in lateral cleavages, and in both 
cases the process may be repeated one or more 
times. It would be quite superfluous to give 
more details, which may be gathered from any 
morphologic treatise on double flowers. But 
from the physiologic point of view all these 
cases are to be considered as one large group, 
complying with previously given definitions of 
the ever-sporting varieties. They are very va- 
riable and wholly permanent. Obviously this 



Production of Double Flowers 515 

permanency a^ees perfectly with the concep- 
tion of their sudden origin. 



Lectuee xvni 


NEW SPECIES OF OENOTHERA 

In our experiments on the origin of peloric 
varieties and double flowers we were guided in 
the choice of our material by a survey of the 
evidence already at hand. We chose the types 
known to be most commonly produced anew, 
either in the wild state or under the conditions 
of cultivation. In both instances our novelty 
was a variety in the ordinary sense of the word. 
Our pedigree-culture was mainly an experi- 
mental demonstration of the validity of conclu- 
sions, which had previously been deduced from 
such observations as can be made after the ac- 
cidental birth of new forms. 

From these facts, and even from these pedi- 
gree-experiments, it is scarcely allowable to 
draw conclusions as to the origin of real spe- 
cies. If we want to know how species originate, 
it is obviously necessary to have recourse to 
direct observation. The question is of the high- 
est importance, both for the theory of descent, 
and for our conception of the real nature of 

516 



New Species of Oenothera 517 

systematic affinities at large. Many authors 
have tried to solve it on the ground of compara- 
tive studies and of speculations upon the bio- 
logic relations of plants and animals. But in 
vain. Contradiction and doubt still reign su- 
preme. All our hopes now rest on the result of 
experiments. 

Unfortunately such experiments seemed sim- 
ply impossible a few years ago. What is to 
guide us in the choice of the material? The 
answer may only be expected from a consid- 
eration of elementary species. For it is obvious 
that they only can be observed to originate, and 
that the systematic species, because they are 
only artificial groups of lower unities, can never 
become the subject of successful experimental 
inquiry. 

In previous lectures we tried to clear up the 
differences existing between nearly related ele- 
mentary species. We have seen that they af- 
fect all of the attributes of the plants, each of 
them changing in some measure all of the or- 
gans. Nevertheless they were due to distinct 
unities and of the lowest possible degree. Such 
unit-steps may therefore be expected to become 
visible some time or other by artificial means. 
On the other hand, mutations as a rule make 
their appearance in groups, and there are many 
systematic species which on close inspection 



518 


Mutations 


have been shown to be in reality composite as- 
semblages. Boses and brambles, hawkweeds 
and willows are the best known examples. Vio- 
lets and Draba verna, dandelions and helian- 
themtims and many other instances were dealt 
with in previous lectures. Even wheat and bar- 
ley and com afford instances of large groups 
of elementary species. Formerly mixed in 
the fields, they became separated during the 
last century, and now constitute constant races, 
which, for brevity’s sake, are dealt with under 
the name of varieties. 

In such groups of nearly allied forms the sin- 
gle members must evidently be of common or- 
igin. It is not necessary for them to have orig- 
inated all in the same place or at the same time. 
In some cases, as with Draba verna, the present 
geographic distribution points to a common 
birthplace, from whence the various forms may 
about the same period have radiated in all direc- 
tions. The violets on the other hand seem to 
include widely diffused original forms, from 
which branches have started at different times 
and in different localities. 

The origin of such groups of allied forms 
must therefore be the object of our research. 
Perhaps we might find a whole group, perhaps 
only part of it. In my opinion we have the 
right to assume that if Drcba and violets and 



New Species of Oenothera 519 

others have formerly mutated in this way, oth- 
er species must at present be in the same 
changeable condition. And if mutations m 
groups, or such periodic mutations should be 
the rule, it is to be premised that these periods 
recur from time to time, and that many species 
must even now be in mutating condition, while 
others are not. 

It is readily granted that the constant condi- 
tion of species is the normal one, and that mu- 
tating periods must be the exception. This fact 
does not tend to increase our prospect of dis- 
covering a species in a state of mutability. 
Many species will have to be tested before find- 
ing an instance. On the other hand, a direct trial 
seems to be the only way to reach the goal. No 
such special guides as those that led us to the 
choice of pelories and double fiowers are avail- 
able. The only indication of value is the pre- 
sumption that a condition of mutability might 
be combined with a general state of variability 
at large, and that groups of plants of very uni- 
form features might be supposed to be constant 
in this respect too. On the contrary, anomalies 
and deviations if existent in the members of 
one strain, or found together in one native lo- 
cality of a species, might be considered as an 
indication in the desired direction. 

Few plants vary in the wild state in such a 



520 


Mutations 


measure as to give distinct indications. All have 
to be given a trial in the garden under conditions 
as similar as possible to their natural environ- 
ments. Cultivated plants are of course to be 
excluded. Practically they have already under- 
gone the experience in question and can not be 
expected to change their habits soon enough. 
Moreover they are often of hybrid origin. The 
best way is to experiment with the native plants 
of one’s own country. 

I have made such experiments with some hun- 
dred species that grow wild in Holland. Some 
were very variable, as for instance, the jointed 
charlock {Raphanus Baphanistrum) and the 
narrow-leaved plantain (Plantago lanceolata). 
Others seemed more uniform, but many species, 
collected without showing any malformation, 
subsequently produced them in my garden, 
either on the introduced plants themselves or 
among their offspring. From this initial ma- 
terial I have procured a long series of heredi- 
tary races, each with some peculiar anomaly for 
its special character. But this result was only 
a secondary gain, a meager consolation for the 
negative fact that no real mutability could be 
discovered. 

My plants were mostly annuals or biennials, 
or such perennials as under adequate treatment 
might produce flowers and seeds during their 



521 


New Species of Oenothera 

first summer. It would be of no special use to 
enumerate them. The negative result does not 
apply to the species as such, but only to the in- 
dividual strain, which I collected and cultivated. 
Many species, which are quite constant with us, 
may be expected to be mutable in other parts 
of their range. 

Only one of all my tests met my expectations. 
This species proved to be in a state of mutation, 
producing new elementary forms continually, 
and it soon became the chief member of my ex- 
perimental garden. It was one of the evening- 
primroses. 

Several evening-primroses have at different 
times been introduced into European gardens 
from America. From thence they have spread 
into the vicinity, becoming common and exhibit- 
ing the behavior of indigenous types. Oenoth- 
era biennis was introduced about 1614 from 
Virginia, or nearly three centuries ago. 0. 
muricata, with small corollas and narrow 
leaves, was introduced in the year 1789 by 
John Hunneman, and 0. suaveolens, or sweet- 
scented primrose, a form very similar to the 
biennis, about the same time, in 1778, by 
John Fothergill. This form is met with in dif- 
ferent parts of France, while the biennis and 
muricata are very common in the sandy regions 
of Holland, where I have observed them for 



522 


Mutations 


more than 40 years. They are very constant 
and have proven so in my experiments. Be- 
sides these three species, the large-flowered 
evening-primrose, or Oenothera lamarckioma, 
is fonnd in some localities in Holland 
and elsewhere. We know little concerning 
its origin. It is supposed to have come 
from America in the same way as its con- 
geners, but as yet I have not been able to 
ascertain on what grounds this supposition 
rests. As far as I know, it has not been seen 
growing wild in this country, though it may 
have been overlooked. The fact that the 
species of this group are subject to many sys- 
tematic controversies and are combined by dif- 
ferent writers into systematic species in differ- 
ent ways, being often considered as varieties 
of one or two types, easily accounts for it 
having been overlooked. However, it would be 
of great interest to ascertain whether 0. la- 
marckiana yet grows in America, and whether 
it is in the same state of mutability here as it 
is in Holland. 

The large-flowered evening-primrose was also 
cultivated about the beginning of the last cen- 
tury in the gardens of the Museum d’Histoire 
Naturelle, at Paris, where it was noticed by 
Lamarck, who at once distinguished it as an un- 
described species. He wrote a complete desorip- 



523 


New Species of Oenothera 

tioh of it and his type specimens are still pre- 
served in the herbarium of the Museum, where 
I have compared them with the plants of my 
own culture. Shortly afterwards it was re- 
named by Seringe, in honor of its eminent dis- 
coverer, whose name it now bears. So Lamarck 
unconsciously discovered and described himself 
the plant, which after a century, was to become 
the means of an empirical demonstration of his 
far-reaching views on the common origin of all 
living beings. 

Oenothera lamarckiana is considered in 
Europe as a garden-plant, much prized for 
parks and ornamental planting. It is cultivated 
by seed-merchants and offered for sale. It has 
escaped from gardens, and having abundant 
means for rapid multiplication, has become wild 
in many places. As far as I know its known 
localities are small, and it is to be presumed 
that in each of them the plant has escaped sep- 
arately from culture. It was in this state that 
I first met with this beautiful species. 

Lamarck’s evening-primrose is a stately 
plant, with a stout stem, attaining often a height 
of 1.6 meters and more. When not crowded the 
main stem is surrounded by a large circle of 
smaller branches, growing upwards from its 
base so as often to form a dense bush. These 
branches in their turn have numerous lateral 



524 


Mutations 


branches. Most of them are crowned with 
flowers in snmmer, which regularly succeed each 
other, leaving behind them long spikes of young 
fruits. The flowers are large and of a bright 
yellow color, attracting immediate attention, 
even from a distance. They open towards 
evening, as the name indicates, and are pollin- 
ated by humble-bees and moths. On bright days 
their duration is confined to one evening, but 
during cloudy weather they may still be found 
open on the following morning. Contrary to 
their congeners they are dependent on visiting 
insects for pollination. 0. biennis and 0. 
muricata have their stigmas in immediate con- 
tact with the anthers within the flower-buds, and 
as the anthers open in the morning preceding 
the evening of the display of the petals, fecun- 
dation is usually accomplished before the in- 
sects are let in. But in 0. lamarchiana no 
such self-fertilization takes place. The stigmas 
are above the anthers in the bud, and as the 
style increases in length at the time of the 
ox>ening of the corolla, they are elevated above 
the anthers and do not receive the pollen. Or- 
dinarily the flowers remained sterile if not vis- 
ited by insects or pollinated by myself, although 
rare instances of self-fertilization were seen. 

In falling off, the flowers leave behind them 
a stout ovary with four cells and a large number 



525 


New Species of Oenothera 

of young seeds. The capsule, when ripe, opens 
at its summit with four valves, and contains 
often from two to three hundred seeds. A hun- 
dred capsules on the main stem is an average 
estimate, and the lateral branches may ripen 
even still more fruits, by which a very rapid dis- 
semination is ensured. 

This striking species was found in a locality 
near Hilversum, in the vicinity of Amsterdam, 
where it grew in some thousands of individuals. 
Ordinarily biennial, it produces rosettes in the 
first, and stems in the second year. Both the 
stems and the rosettes were at once seen to be 
highly variable, and soon distinct varieties 
could be distinguished among them. 

The first discovery of this locality was made 
in 1886. Afterwards I visited it many times, 
often weekly or even daily during the first few 
years, and always at least once a year up to 
the present time. This stately plant showed the 
long-sought peculiarity of producing a number 
of new species every year. Some of them were 
observed directly on the field, either as stems 
or as rosettes. The latter could be transplanted 
into my garden for further observation, and 
the stems yielded seeds to be sown under like 
control. Others were too weak to live a suffi- 
ciently long time in the field. They were dis- 
covered by sowing seed from indifferent plants 



526 


Mutations 


of the wild locality in the garden. A third 
and last method of getting still more new spe- 
cies from the original strain, was the repetition 
of the sowing process, by saving and sowing 
the seed which ripened on the introduced 
plants. These various methods have led to the 
discovery of over a dozen new types, never pre- 
viously observed or described. 

Leaving the physiologic side of the rela- 
tions of these new forms for the next lecture, 
it would be profitable to give a short descrip- 
tion of the several novelties. To this end they 
may be combined under five different heads, ac- 
cording to their systematic value. The first 
head includes those which are evidently to be 
considered < as varieties, in the narrower sense 
of the word, as previously given. The second 
and third heads indicate the real progressive 
elementary species, first those which are as 
strong as the parent-species, and secondly a 
group of weaker types, apparently not destined 
to be successful. Under the fourth head I shall 
include some inconstant forms, and under the 
last head those that are organically incomplete. 

Of varieties with a negative attribute, or real 
retrograde varieties, I have found three, all of 
them in a flowering condition in the field. I 
have given them the names of laevifolia, brevi- 
stylis and nanella. 



627 


New Speeds of Oenothera 

The laevifolia, or smooth-leaved variety, was 
one of the very first deviating types found in 
the original field. This was in the summer of 
1887, seventeen years ago. It formed a little 
group of plants growing at some distance from 
the main body, in the same field. 1 found some 
rosettes and some flowering stems and sowed 
some seed in the fall. The variety has been 
quite constant in the field, neither increasing 
in number of individual plants nor changing 
its place, though now closely surrounded by oth- 
er Lamarckianas. In my garden it has proved 
to be constant from seed, never reverting to the 
original lamarckiana, provided intercrossing 
was excluded. 

It is chiefly distinguished from Lamarck’s 
evening-primrose by its smooth leaves, as the 
name indicates. The leaves of the ori^nal form 
show numerous sinuosities in their blades, not 
at the edge, but anywhere between the veins. 
The blade shows numbers of convexities on 
either surface, the whole surface being undu- 
lated in this manner; it lacks also the bright- 
ness of the ordinary evening-primrose or 
Oenothera biennis. 

These undulations are lacking or at least very 
rare on the leaves of the new laevifolia. Or- 
dinarily they are wholly wanting, but at times 
single leaves with slight manifestations of this 



528 


Mutations 


character may make their appearance. They 
warn ns that the capacity for such sinuosities 
is not wholly lost, but only lies dormant in the 
new variety. It is reduced to a latent state, ex- 
actly as are the apparently lost characters of 
so many ordinary horticultural varieties. 

Lacking the undulations, the laevifoUa-le&veB 
are smooth and bright. They are a little nar- 
rower and more slender than those of the La- 
marckiana. The convexities and concavities of 
leaves are said to be useful in dry seasons, 
but during wet summers, such as those of the 
last few years, they must be considered as very 
harmful, as they retain some of the water which 
falls on the plants, prolonging the action of the 
water on the leaves. This is considered by some 
writers to be of some utility after slight show- 
ers, but was observed to be a source of weak- 
ness during wet weather in my garden, pre- 
venting the leaves from drying. Whether the 
laevifolia would do better under such circum- 
stances, remains to be tested. 

The flowers of the laevifolia are also in a 
slight degree different from those of Lamarck- 
tana. The yellow color is paler and the petals 
are smoother. Later, in the fall, on the weaker 
side branches these differences increase. The 
laevifolia petals become smaller and are often 
not emargiaated at the apex, becoming ovate 



529 


New Species of Oenothera 

instead of obcordate. This shape is often the 
most easily recognized and most striking mark 
of the variety. In respect to the reproductive 
organs, the fertility and abundance of good seed, 
the laevifoUa is by no means inferior or superior 
to the original species. 

0. brevistylis, or the short-styled evening- 
primrose, is the most curious of all my new 
forms. It has very short styles, which bring 
the stigmas only up to the throat of the calyx- 
tube, instead of upwards of the anthers. The 
stigmas themselves are of a different shape, 
more flattened and not cylindrical. The pollen 
falls from the anthers abundantly on them, and 
germinates in the ordinary manner. 

The ovary which in lamarckiana and in 
all other new forms is wholly underneath the 
calyx-tube, is here only partially so. This 
tube is inserted at some distance under its 
summit. The insertion divides the ovary into 
two parts : an upper and a lower one. The up- 
per part is much reduced in breadth and some- 
what attenuated, simulating a prolongation of 
the base of the style. The lower part is also 
reduced, but in another manner. At the time 
of flowering it is like the ovary of lamarckiana^ 
neither smaller nor larger. But it is reached 
by only a very few pollen-tubes, and is there- 
fore always incompletely fertilized. It does 



530 


Mutations 


not fall o£P after the fading away of the 
flower, as unfertilized ovaries usually do ; 
neither does it grow out, nor assume the upright 
position of normal capsules. It is checked in its 
development, and at the time of ripening it is 
nearly of the smne length as in the beginning. 
Many of them contain no good seeds at all ; from 
others 1 have succeeded in saving only a hun- 
dred seeds from thousands of capsules. 

These seeds, if purely pollinated, and with 
the exclusion of the visits of insects, reproduce 
the variety entirely and without any reversion 
to the lamarckiana type. 

Correlated with the detailed structures is the 
form of the flower-buds. They lack the high 
stigma placed above the anthers, which in the 
lamarckiana, by the vigorous growth of the 
style, extends the calyx and renders the flower- 
bud thinner and more slender. Those of the 
brevistylis are therefore broader and more 
swollen. It is quite easy to distinguish the in- 
dividuals by this striking character alone, al- 
though it differs from the parent in other par- 
ticulars. 

The leaves of the 0. brevistylis are more 
rounded at the tip, but the difference is only pro- 
nounced at times, slightly in the adult rosettes, 
but more clearly on the growing summits of the 
stems and branches. By this character, the plants 



New Species of Oenothera 531 

may be discerned among the others, some weeks 
before the flowers begin to show themselves. 

But the character by which the plants may 
be most easily recognized from a distance in the 
field is the failure of the fruits. They were 
found there nearly every year in varying, but 
always small numbers. 

Leaving the short-styled primrose, we come 
now to the last of our group of retrograde va- 
rieties. This is the 0. nanella, or the dwarf, and 
is a most attractive little plant. It is very short 
of stature, reaching often a height of only 20- 
30 cm., or less than one-fourth of that of the par- 
ent. It commences flowering at a height of 10- 
15 cm., while the parent-form often measures 
nearly a meter at this stage of its development. 
Being so very dwarfed tiie large flowers are all 
the more striking. They are hardly inferior 
to those of the lamarckiana, and agree with 
them in structure. When they fade away 
the spike is rapidly lengthened, and often be- 
comes much longer than the lower or vegetative 
part of the stem. 

The dwarfs are one of the most common mu- 
tations in my garden, and were observed in the 
native locality and also grown from seeds saved 
there. Once produced they are absolutely con- 
stant. I have tried many thousands of seeds 
from various dwarf mutants, and never ob- 



532 


Mutations 


served any trace of reversion to the lamarch- 
iana type. I have also cultivated them in suc- 
cessive generations with the same result. In 
a former lecture we have seen that contrary to 
the general run of horticultural belief, varieties 
are as constant as the best species, if kept free 
from hybrid admixtures. This is a general rule, 
and the exceptions, or cases of atavism are ex- 
trmnely rare. In this respect it is of great inter- 
est to observe that this constancy is not an ac- 
quired quality, but is to be considered as innate, 
because it is already fully developed at the very 
moment when the origmal mutation takes place. 

From its first leaves to the rosette period, 
and through this to the lengthening of the stem, 
the dwarfs are easily distinguished from any 
other of their congeners. The most remarkable 
feature is the shape of the leaves. They are 
broader and shorter, and especially at the base 
they are broadened in such a way as to become 
apparently sessile. The stalk is very brittle, 
and any rough treatment may cause the leaves 
to break off. The young seedlings are 
recognizable by the shape of the first twO' or 
three leaves, and when more of them are pro- 
duced, the rosettes become dense and strikingly 
different from others. Later leaves are more 
nearly like the parent-type, but the petioles re- 
main short. The bases of the blades are fre- 



533 


New Species of Oenothera 

quently almost cordate, the laminsB themselves 
varying from oblong-ovate to ovate in ontline. 

The stems are often quite unbranched, or 
branched only at the base of the spike. Strong 
secondary stems are a striking attribute of the 
lamarckiana parent, but they are lacking, or 
almost so in the dwarfs. The stem is straight 
and short, and this, combined with the large 
crown of bright flowers, makes the dwarfs emi- 
nently suitable for bed or border plants. Un- 
fortunately they are very sensitive, especially 
to wet weather. 

Oenothera gigas and 0. rubrinervis, or the 
giant, and the red-veined evening-primroses, are 
the names given to two robust and stout spe- 
cies, which seem to be equal in vigor to the 
parent-plant, while diverging from it in strik- 
ing characters. Both are true elementary 
species, differentiated from lamarckiana in 
nearly all their organs and qualities, but not 
showing any preponderating character of a 
retrograde nature. Their differences may 
be compared with those of the elementary 
species of other genera, as for instance, of 
Draba, or of violets, as will be seen by their 
description. 

The giant evening-primrose, though not taller 
in stature than 0. lamarckiana, deserves 
its name because it is so much stouter in all re- 



534 


Mutations 


spects. The stems are robust, often with twice 
the diameter of lamarckiana throughout. The 
intemodes are shorter, and the leaves more 
numerous, covering the stems with a denser 
foliage. This shortness of the intemodes ex- 
tends itself to the spike, and for this reason the 
flowers and fruits grow closer together than on 
the parent-plant. Hence the crown of bright 
flowers, opening each evening, is more dense 
and more strikingly brilliant, so much the more 
so as the individual flowers are markedly larger 
than those of the parents. In connection with 
these characters, the flower-buds are seen to be 
much stouter than those of lamarckiana. The 
fruits attain only half the normal size, but are 
broader and contain fewer, but larger seeds. 

The rubrinervis is in many respects a coun- 
terpart to the gigas, but its stature is more 
slender. The spikes and flowers are those of 
the lamarckiana, but the bracts are narrower. 
Bed veins and red streaks on the fruits afford 
a striking differentiating mark, though they are 
not absolutely lacking in the parent-species. 
A red hue may be seen on the calyx, and even 
the yellow color of tiie petals is somewhat deep- 
ened in the same way. Young plants are often 
marked by the pale red tinge of the mid-veins, 
but in adult rosettes, or from lack of sunshine, 
this hue is often very faint. 



New Species of Oenothera 535 

The leaves are narrow, and a curious feature 
of this species is the great brittleness of the 
leaves and stems, especially in annual individ- 
uals, especially in those that make their stem 
and flowers in the first year. High turgid- 
ity and weak development of the mechanical 
and supporting tissues are the anatomical cause 
of this deficiency, the bast-fibers showing thin- 
ner walls than those of the parent-type under 
the microscope. Young stems of rvbrinervis 
may be broken off by a sharp stroke, and 
show a smooth rupture across all the tissues, 
while those of lamarckiana are very tough and 
strong. 

Both the giant and the red-veined species are 
easily recognized in the rosette-stage. Even the 
very young seedlings of the latter are clearly 
differentiated from the lamarckiana, but often 
a dozen leaves are required, before the dif- 
ference may be seen. Under such circumstances 
the young plants must reach an age of 
about two months before it is possible to 
discern their characters, or at least before 
these characters have become reliable enough 
to enable us to judge of each individual 
without doubt. But the divergencies rapidly 
become greater. The leaves of 0. gigas are 
broader, of a deeper green, the blade more 
sharply set off against the stalk, all the ro- 



536 


Mutations 


settes becoming stout and crowded with leaves. 
Those of 0. ruhrinervis on the contrary are 
thin, of a paler green and with a silvery white 
surface; the blades are elliptic, often being 
only 2 cm. or less in width. They are acute 
at the apex and gradually narrowed into the 
petiole. 

It is quite evident that such pale narrow 
leaves must produce smaller quantities of or- 
ganic food than the darker green and broad 
organs of the gigas. Perhaps this fact is ac- 
countable partly, at least, for the more robust 
growth of the giant in ttie second year. Per- 
haps also some relation exists between this dif- 
ference in chemical activity and the tendency 
to become annual or biennial. The gigas, as a 
rule, produces far more, and the ruhrinervis 
far less biennial plants than the lamarckiana. 
Annual culture for the one is as unreliable as 
biennial culture for the other. Ruhrinervis 
may be annual in apparently all specimens, in 
sunny seasons, but gigas will ordinarily remain 
in the state of rosettes during the entire 
first summer. It would be very interesting 
to obtain a fuller insight into the relation 
of the length of life to other qualities, but 
as yet the facts can only be detailed as 
they stand. 

Both of these stout species have been found 



637 


New Species of Oenothera 

quite constant from the very first moment of 
their appearance. I have cultivated them from 
seed in large numbers, and they have never re- 
verted to the lamarcMana. From this they 
have inherited the mutability or the capacity of 
producing at their turn new mutants. But they 
seem to have done so incompletely, changing in 
the direction of more absolute constancy. This 
was especially observed in the case of rtihri- 
nervis, which is not of such rare occurrence as 
0. gigas, and which it has been possible to study 
in large numbers of individuals. So for in- 
stance, “ the red-veins ” have never produced 
any dwarfs, notwithstanding they are produced 
very often by the parent-type. And in crossing 
experiments also the red-veins gave proof of the 
absence of a mutative capacity for their produc- 
tion. 

Leaving the robust novelties, we may now 
take up a couple of forms, which are equally 
constant, and differentiated from the parent- 
species in exactly the same manner, though by 
other characters, but which are so obviously 
weak as to have no manifest chance of self- 
maintenance in the wild state. These are the 
whitish and the oblong-leaved evening-prim- 
roses or the Oenothera albida and oblonga. 

Oenothera albida is a very weak species, with 
whitish, narrow leaves, which are evidently in- 



538 


Mutations 


capable of prodnoing sufficient quantities of or- 
ganic food. The young seedling-plants are soon 
seen to lag behind, and if no care is taken of 
them they are overgrown by their neighbors. 
It is necessary to take them out, to transplant 
them into pots with richly manured soil, .and 
to give them all the care that should be given 
to weak and sickly plants. If this is done fully 
grown rosettes may be produced, which are 
strong enough to keep through the winter. In 
this case the individual leaves become stronger 
and broader, with oblong blades and long 
stalks, but retain their characteristic whitish 
color. 

In the second year the stems become relative- 
ly stout. Not that they become equal to those 
of lamarckiana, but they become taller than 
might have been expected from the weakness of 
the plants in the previous stages. The flowers 
and racemes are nearly as large as those of the 
parent-form, the fruits only a little thinner and 
containing a smaller quantity of seed. From 
these seeds I have grown a second and a third 
generation, and observed that the plants remain 
true to their type. 

0. ohlonga may be grown either as an annual, 
or as a biennial. In the first case it is very 
slender and weak, bearing only small fruits and 
few seeds. In the alternative case however, it 



539 


New Species of Oenothera 

becomes densely branched, bearing flowers on 
quite a number of racemes and yielding a full 
harvest of seeds. But it always remains a small 
plant, reaching about half the height of that of 
lamarckiana. 

When very young it has broader leaves, but 
in the adult rosettes the leaves become very nar- 
row, but fleshy and of a bright green color. 
They are so crowded as to leave no space be- 
tween them unoccupied. The flowering spikes 
of the second year bear long leaf-like bracts 
under the first few flowers, but those arising 
later are much shorter. Numerous little cap- 
sules cover the axis of the spike after the fading 
away of the petals, constituting a very striking 
diiferentiating mark. This species also was 
found to be quite constant, if grown from pure 
seed. 

We have now given the descriptions of seven 
new forms, which diverge in different ways from 
the parent-type. All were absolutely constant 
from seed. Hundreds or thousands of seedlings 
may have arisen, but they always come true 
and never revert to the original 0. lamarckiana 
type. From this they have inherited the condi- 
tion of mutability, either completely or partly, 
and according to this they may be able to pro- 
duce new forms themselves. But this occurs 
only rarely, and combinations of more than one 



540 


Mutations 


type in one single plant seem to be limited to the 
admixture of the dwarf stature with the charac- 
ters of the other new species. 

These seven novelties do not comprise the 
whole range of the new productions of my 0. 
lamarckkma. But they are the most interest- 
ing ones. Others, as the 0. semilata and the 0. 
leptocarpa are quite as constant and quite as 
distinct, but have no special claims for a closer 
description. Others again were sterile, or too 
weak to reach the adult stage and to yield seeds, 
and no reliable description or appreciation can 
be given on the groimd of the appearance of 
a single individual. 

Contrasted with these groups of constant 
forms are three inconstant types which we now 
take up. They belong to two different groups, 
according to the cause of their inconstancy. In 
one species which I call 0. lata, the question 
of stability or instability must remain wholly 
unsolved, as only pistillate flowers are produced, 
and no seed can be fertilized save by the use of 
the pollen of another form, and therefore by 
hybridization. The other head comprises two 
fertile forms, 0. scintUlans and 0. elliptica, 
which may easily be fertilized with their own 
pollen, but which gave a progeny only partly 
similar to the parents. 

The Oenothera lata is a very distinct form 



New Species of Oenothera 641 

which was found more than once in the field, and 
recently (1902) in a luxuriant flowering speci- 
men. It has likewise been raised from seeds 
collected in different years at the original sta- 
tion. It is also wholly pistillate. Apparently the 
anthers are robust, but they are dry, wrinkled 
and nearly devoid of contents. The inner wall 
of cells around the groups of pollen grow out 
instead of being resorbed, partly filling the 
cavity which is left free by the miscarriage of 
the pollen-grains. This miscarriage does not 
affect all the grains in the same degree, and 
under the microscope a few of them with an ap- 
parently normal structure may be seen. But the 
contents are not normally developed, and I have 
tried in vain to obtain fertilization with a large 
number of flowers. Only by cross-fertilization 
does 0. lata produce seeds, and then as freely as 
the other species when self-fertilized. Of course 
its chance of ever founding a wild type is pre- 
cluded by this defect. 

0. lata is a low plant, with a limp stem, bent 
tips and branches, all very brittle, but with 
dense foliage and luxuriant growth. It has 
bright yellow flowers and thick flower-buds. 
But for an unknown reason the petals are apt to 
unfold only partially and to remain wrinkled 
throughout the flowering time. The stigmas 
are slightly divergent from the normal type, 



54^ Mutations 

also b^ng partly united with one another, and 
laterally with the summit of the style, but with- 
out detriment to their function. 

Young seedlings of lata may be recognized by 
the very &st leaves. They have a nearly or- 
bicular shape and are very sharply set off 
against their stalk. The surface is very un- 
even, with convexities and concavities on both 
sides. This difference is lessened in the later 
leaves, but remains visible throughout the whole 
life of the plant, even during the flowering sea- 
son. Broad, sinuate leaves with rounded tips 
are a sure mark of 0. lata. On the summits of 
the stems and branches they are crowded so as 
to form rosettes. 

Concerning inheritance of these characteris- 
tics nothing can be directly asserted because of 
the lack of pollen. The new type can only be 
perpetuated by crosses, either with the parent- 
form or some other mutant. I have fertilized 
it, as a rule, with lamarckiana pollen, but have 
often also used that from nanella and others. In 
doing so, the lata repeats its character in part of 
its offspring. This part seems to be independ- 
ent of the nature of the pollen used, but is very 
variable according to external circumstances. 
On the average one-fourth of the offspring be- 
come lata, the others assuming the type of the 
poUen-parent, if this was a lamarckia/na or 



New Species of Oenothera 543 

partly this type and partly that of any other of 
the new species derived from lamarckiana, that 
might have been used as the pollen-parent. This 
average seems to be a general rule, recurring 
in all experiments, and remaining unchanged 
through a long series of successive generations. 
The fluctuations around this mean go up to near- 
ly and down nearly to lj<, but, as in other 
cases, such extreme deviations from the aver- 
age are met with only exceptionally. 

The second category includes the inconstant 
but perfectly fertile species. I have already 
given the names of the only two forms, which 
deserve to be mentioned here. 

One of them is called scintillans or the shiny 
evening-primrose, because its leaves are of a 
deep green color with smooth surfaces, glistening 
in the sunshine. On the young rosettes these 
leaves are somewhat broader, and afterwards 
somewhat narrower than those of 0. lamarck- 
iana at the corresponding ages. The plants 
themselves always remain small, never reaching 
the stature of the ancestral type. They are 
likewise much less branched. They can easily 
be cultivated in annual generations, but then 
do not become as fully developed and as fertile 
as whQU flowering in the second year. The 
flowers have the same structure as those of the 
lamarckiana, but are of a smaller size. 



544 


Mutations 


Fertilizing the flowers artificially with their 
own pollen, excluding the visiting insects by 
means of paper bags, and saving and sowing 
the seed of each individual separately, fur- 
nishes all the requisites for the estimation of the 
degree of stability of this species. In the first 
few weeks the seed-pans do not show any un- 
equality, and often the young plants must be re- 
planted at wider intervals, before anything 
can be made out with certainty. But as soon 
as the rosettes begin to fill it becomes mani- 
fest that some of them are more backward than 
others in size. Soon the smaller ones show 
their deeper green and broader leaves, and 
thereby display the attributes of the scintUlans. 
The other grow faster and stronger and exhibit 
all the characteristics of ordinary lamarcki- 
anas. 

The numerical proportion of these two groups 
has been found different on different occasions. 
Some plants give about one-third scintUlans 
and two-thirds lamarcJciana, while the progeny 
of individuals of another strain show exactly 
the reverse proportion. 

Two points deserve to be noticed. First the 
progeny of the scintUlans appears to be mutable 
in a large degree, exceeding even the lamarcki- 
ana. The same forms that are produced most 
often by the parent-family are also most ordi- 



New Species of Oenothera 545 

narily met with among the offspring of the 
shiny evening - primrose. They are oblonga, 
lata and naneUa. Oblonga was observed at 
times to constitute as much as 1% or more of 
the sowings of scintillans, while lata and 
nanella were commonly seen only in a few 
scattering individuals, although seldom lacking 
in experiments of a sufficient size. 

Secondly the instability seems to be a con- 
stant quality, although the words themselves are 
at first sight, contradictory. I mean to con- 
vey the conception that the degree of instability 
remains unchanged during successive genera- 
tions. This is a very curious fact, and strongly 
reminds us of the hereditary conditions of 
striped-flower varieties. But, on the contrary, 
the atavists, which are here the individuals 
with the stature and the characteristics of the 
lamarckiana, have become lamarckianas in 
their hereditary qualities, too. If their seed is 
saved and sown, their progeny does not contain 
any scintillans, or at least no more than might 
arise by ordinary mutations. 

One other inconstant new species is to he 
noted, but as it was very rare both in the field 
and in my cultures, and as it was difficult of cul- 
tivation, little can as yet be said about it. It is 
the Oenothera elliptica, with narrow eUiptical 
leaves and also with elliptical petals. It re- 



546 


Mutations 


peats its type only in a very small proportion 
of its seed. 

All in aU we thus have a group of a dozen new 
types, springing from an original form in one 
restricted locality, and seen to grow there, 
or ari fling in the garden from seeds collected 
from the original locality. Without any doubt 
the germs of the new types are fully developed 
within the seed, ready to be evolved at the time 
of germination. More favorable conditions in 
the field would no doubt allow all of the de- 
scribed new species to unfold their attributes 
there, and to come into competition with each 
other and with the common parents. But ob- 
viously this is only of secondary importance, 
and has no influence on the fact that a number 
of new tyi)e8, analogous to the older swarms of 
Draba, Viola and of many other polymorphous 
species, have been seen to arise directly in the 
wild state. 



Lectubb XIX 


EXFEBIMEKTAL FEDIGBEE-OULTXTBES 

The observation of the production of mutants 
in the field at Hilversum, and the subsequent 
cultivation of the new types in the garden at 
Amsterdam, gives ample proof of the mutability 
of plants. Furthermore it furnishes an analogy 
with the hypothetical origin of the swarms of 
species of Draba and Viola, Last hut not least 
important it affords material for a complete 
systematic and morphologic study of the new- 
ly arisen group of forms. 

The physiologic laws, however, which gov- 
ern this process are only very imperfectly re- 
vealed by such a study. The instances are too 
few. Moreover the seeds from which the mu- 
tants spring, escape observation. It is simply 
impossible to tell from which individual plants 
they have been derived. The laevifolia and the 
brevistylis have been found almost every year, 
the first always recurring on the same spot, the 
second on various parts of the original field. It 
is therefore allowable to assume a common 

547 



548 


Mutations 


origin for all the observed individuals of either 
strain. Bnt whether^ besides this, similar 
strains are produced anew by the old lamarchi- 
ana group, it is impossible to decide on the sole 
ground of these field-observations. 

The same holds good with the other novelties. 
Even if one of them should germinate repeated- 
ly, without ever opening its fiowers, the possi- 
bility could not be excluded that the seeds might 
have come originally from the same capsule but 
lain dormant in the earth during periods of un- 
equal length. 

Other objections might be cited that can only 
be met by direct and fully controlled experi- 
ments. Next to the native locality comes the ex- 
perimental garden. Here the rule prevails that 
every plant must be fertilized with pollen of its 
own, or with pollen of other individuals of 
known and recorded ori^n. The visits of in- 
sects must be guarded against, and no seeds 
should be saved from flowers which have been 
allowed to open without this precaution. Then 
the seeds of each individual must be saved and 
sown separately, so as to admit of an apprecia- 
tion, and if necessary, a numerical determina- 
tion of the nature of its progeny. And last but 
not least the experiments should be conducted 
in a similar manner during a series of successive 
years. 



Experimental Pedigree-Cultures 549 

I have made four Buch experiments, each com> 
prising the handling of many thousands of in- 
dividual plants, and lasting through five to nine 
generations. At the beginning the plants were 
biennial, as in the native locality, but later I 
learned to cultivate them in annual genera- 
tions. They have been started from different 
plants and seeds, introduced from the original 
field into my garden at Amsterdam. 

It seems sufficient to describe here one of 
these pedigree-cultures, as the results of all four 
were similar. In the fall of 1886 I took nine 
large rosettes from the field, planted them to- 
gether on an isolated spot in the garden, and 
harvested their seeds the next year. These nine 
original plants are therefore to be considered 
as constituting the first generation of my race. 
The second generation was sown in 1888 and 
flowered in 1889. It at once yielded the ex- 
pected result. 15000 seedlings were tested 
and examined, and among them 10 showed 
diverging characters. They were properly 
protected, and proved to belong to two new 
types. 5 of them were lata and 5 ncmella. 
They flowered next year and displayed all the 
characters as described in our preceding lec- 
ture. Interm^iates between them and the gen- 
eral type were not found, and no indication of 
their appearance was noted in their parents. 



550 


Mutaiiom 


They came into existence at once, fully equipped, 
without preparation or intermediate steps. No 
series of generations, no selection, no struggle 
for existence was needed. It was a sudden leap 
into another type, a sport in the best acceptation 
of the word. It fulfilled my hopes, and at once 
gave proof of the possibility of the direct obser- 
vation of the origin of species, and of the ex- 
perimental control thereof. 

The third generation was in the main a repeti- 
tion of the second. I tried some 10000 seed- 
lings and found three lata and three nanella, or 
nearly the same proportion as in the first in- 
stance. But besides these a ruhrinervis made 
its appearance and fiowered the following year. 
This fact at once revealed the possibility that the 
instability of lamarckiana might not be re- 
stricted to the three new types now under obser- 
vation. Hence the question arose how it would 
be possible to obtain other types or to find them 
if they were present. It was necessary to 
have better methods of cultivation and examina- 
tion of the young plants. Accordingly I de- 
voted the three succeeding years to working on 
this problem. 

I found that it was not at all necessary to 
sow any larger quantities of see^.^ but that the 
young plants must have room enough to develop 
into full and free rosettes. Moreover I ob- 



Experimental Pedigree-Cultures 551 

served that the attributes of lata and nmella, 
which I now studied in the offspring of my first 
mutants, were clearly discernible in extreme 
youth, while those of ruhrinervis remained con- 
cealed some weeks longer. Hence 1 con- 
cluded that the young plants should be examined 
from time to time until they proved clearly to be 
only normal lamarckiana. Individuals ex-' 
hibiting any deviation from the type, or even 
giving only a slight indication of it, were forth- 
with taken out of the beds and planted separate- 
ly, under circumstances as favorable as possible. 
They were established in pots with well-manured 
soil and kept under glass, but fully exposed to 
sunshine. As a rule they grew very fast, and 
could be planted out early in June. Some of 
them, of course, proved to have been erroneous- 
ly taken for mutants, but many exhibited new 
characters. 

All in all I had 334 young plants which did 
not agree with the parental type. As I exam- 
ined some 14000 seedlings altogether, the result 
was estimated at about 2.5j^. This proportion 
is much larger than in the yields of the two first 
generations and illustrates the value of im- 
proved methods. No doubt many good muta- 
tions had been overlooked in the earlier observa- 
tions. 

As was to be expected, lata and naneUa 



552 


Mutations 


were repeated in this third generation (1895). 
I was sure to get nearly all of them, without any 
important exceptions, as I now knew how to de- 
tect them at almost any age. In fact, I found 
many of them; as many as 60 nanella and 73 
lata, or nearly .5^ of each. Buhrinervis also 
recurred, and was seen in 8 specimens. It 
was much more rare than the two first-named 
types. 

But the most curious fact in that year was 
the appearance of oblonga. No doubt I had 
often seen it in former years, but had not at- 
tached any value to the very slight differences 
from the type, as they then seemed to me. I 
knew now that any divergence was to be es- 
teemed as important, and should be isolated for 
further observation. This showed that among 
the selected specimens not less than 176, or more 
than 1% belonged to the dhlonga type. This 
type was at that time quite new to me, and it had 
to be kept through the winter, to obtain stems 
and flowers. It proved to be as uniform as its 
three predecessors, and especially as sharply 
contrasted with lamarckiana. The opportuni- 
ty for the discovery of any intermediates was as 
favorable as could be, because the distinguish- 
ing marks were hardly beyond doubt at the time 
of the selection and removal of the young plants. 
But no connecting links were found. 



Experimental Pedigree-Cultures 553 

The same holds good for alhida, which ap- 
peared in 15 specimens, or in 0.1;^, of the whole 
culture. By careful cultivation these plants 
proved not to be sickly, but to belong to a new, 
though weak type. It was evident that I had 
already seen them in former years, but having 
failed to recognize them had allowed them to be 
destroyed at an early age, not knowing how to 
protect them against adverse circumstances. 
Even this time I did not succeed in getting them 
strong enough to keep through the winter. 

Besides these, two new types were observed, 
completing the range of all that have since been 
recorded to regularly occur in this family. 
They were scintillans and gigas. The first 
was obtained in the way just described. The 
other hardly escaped being destroyed, not hav- 
ing showed itself early enough, and being left in 
the bed after the end of the selection. But as 
it was necessary to keep some rosettes through 
the winter in order to have biennial flowering 
plants to furnish seeds, I selected in August 
about 30 of the most vigorous plants, planted 
them on another bed and gave them sufficient 
room for their stems and branches in the follow- 
ing summer. Most of them sent up robust 
shoots, but no difference was noted till the first 
flowers opened. One plant had a much larger 
crown of bright blossoms than any of the others. 



554 


Mutations 


As soon as these flowers faded away, and the 
young fruits grew out, it became clear that a 
new type was showing itself. On that indica- 
tion 1 removed all the already fertilized flowers 
and yonng fruits, and protected the buds from 
the visits of insects. Thus the isolated flowers 
were fertilized with their own pollen only, and 
I could rely upon the purity of the seed saved. 
This lot of seeds was sown in the spring of 1897 
and yielded a uniform crop of nearly 300 young 
gigas plants. 

Having found how much depends upon the 
treatment, I could gradually decrease the size of 
my cultures. Evidently the chance of discover- 
ing new types would be lessened thereby, but the 
question as to the repeated production of the 
same new forms could more easily and more 
clearly be answered in this way. In the follow- 
ing year (1896) I sowed half as many seeds as 
formerly, and the result proved quite the same. 
With the exception of gigas all the described 
forms sprang anew from the purely fertilized 
ancestry of normal Lamarckianas. It was now 
the fifth generation of my pedigree, and thus I 
was absolutely sure that the descendants of the 
mutants of this year had been pure and without 
deviation for at least four successive genera- 
tions. 

Owing partly to improved methods of seleo- 



Experimental Pedigree-Cultures 555 

tion, partly no doubt to chance, even more mu- 
tants were found this year than in the former. 
Out of some 8000 seedlings I counted 377 deviat- 
ing ones, or nearly which is a high propor- 
tion. Most of them were ohlonga and laia, the 
same types that had constituted the majority in 
the former year. 

Alhida, nanella and rubrinervis appeared in 
large numbers, and even scintillans, of which 
I had but a single plant in the previous genera- 
tion, was repeated sixfold. 

New forms did not arise, and the capacity of 
my strain seemed exhausted. This conclusion 
was strengthened by the results of the next 
three generations, which were made on a much 
smaller scale and yielded the same, or at least 
the mutants most commonly seen in previous 
years. 

Instead of giving the figures for these last 
two years separately, I will now summarize my 
whole experiment in tiie form of a pedigree. In 
this the normal lamarckiana was the main line, 
and seeds were only sown from plants after suf- 
ficient isolation either of the plants themselves, 
or in the latter years by means of paper bags 
enclosing the inflorescences. I have given the 
number of seedlings of lamarckiana which were 
examined each year in the table below. Of 
course by far the largest number of them were 



556 


MutaJtions 


thrown away as soon as they showed their dif- 
ferentiating characters in order to make room 
for the remaining ones. At last only a few 
plants were left to blossom in order to perpet- 
uate the race. I have indicated for each genera- 
tion the number of mutants of each of the ob- 
served forms, placing them in vertical columns 
underneath their respective heads. The three 
first generations were biennial, but the five last 
annual. 


FCDIOBEE OF A MUTATINO FAMILT OF OENOTHKBA LAHABCKIAKA 
UT THB EXFEBIHXNTAI. OABOEN AT AJISTEBDAK. 


Generi 

0.gig. 

albida 

obi. 

rubrin. 

Lam. 

nanella 

lata* 

scint. 

VIIL 


5 

1 

0 

1700 

21 

1 


VII. 



9 

0 

3000 

11 



VL 


11 

29 

3 

1800 

9 

5 

1 

V. 


25 

135 

20 

8000 

49 

142 

6 

IV. 

1 

15 

176 

8 

14000 

60 

73 

1 

IIL 




1 

10000 

3 

3 


XL 





15000 

5 

5 



L 9 

It is most striking that the various mutations 
of the evening-primrose display a great degree 
of regularity. There is no chaos of forms, no 
indefinite varying in all degrees and in all direc- 
tions. Quite on the contrary, it is at once evi- 
dent that very simple rules govern the whole 
phmiomenon. 

1 shall now attempt to deduce these laws from 



Experimental Pedigree-Cultures 557 

my experiment. Obviously they apply not only 
to our evening-primroses, but may be expected 
to be of general validity. This is at once 
manifest, if we compare the group of new mu- 
tants with the swarms of elementary forms 
which compose some of the youngest systematic 
species, and which, as we have seen before, are 
to be considered as the results of previous mu- 
tations. The difference lies in the fact that the 
evening-primroses have been seen to spring 
from their ancestors and that the drabas 
have not. Hence the conclusion that in com- 
paring the two we must leave out the pedigree of 
the evening-primroses and consider only the 
group of forms as they finally show themselves. 
If in doing so we find suflScient similarity, we are 
justified in the conclusion that the drabas and 
others have probably originated in the same way 
as the evening-primroses. Minor points of 
course will differ, but the main lines cannot have 
complied with wholly different laws. All so- 
called swarms of elementary species obviously 
pertain to a single type, and this type includes 
our evening-primroses as the only controlled 
case. 

Formulating the laws of mutability for the 
evening-primroses we therefore assume that 
they hold good for numerous other correspond- 
ing cases. 



558 


Mutations 


I. The first law is, that new elementary spe- 
cies appear suddenly, without intermediate, 
steps. 

This is a striking point, and the one that is in 
the most immediate contradiction to current 
scientific belief. The ordinary conception as- 
sumes very slow changes, in fact so slow that 
centuries are supposed to be required to make 
the differences appreciable. If this were true, 
all chance of ever seeing a new species arise 
would be hopelessly small. Fortunately the 
evening-primroses exhibit contrary tendencies. 
One of the great points of pedigree-culture is the 
fact that the ancestors of every mutant have 
been controlled and recorded. Those of the last 
year have seven generations of known lamarck- 
iana parents preceding them. If there had been 
any visible preparation towards the coming mu- 
tation, it could not have escaped observation. 
Moreover, if visible preparation were the rule, 
it could hardly go on at the same time and in the 
same individuals in five or six diverging direc- 
tions, produdng from one parent, gigas and no- 
nella, lata and rubrinervis, oblonga and albida 
and even scintiUans. 

On the other hand the mutants, that constitute 
the first representatives of their race, exhibit 
all the attributes of the new type in full display 
at once. No series of generations, no selecticm. 



Experiment(U Pedigree-Cultures 559 

no straggle for existence are needed to reach 
this end. In previous lectures I have mentioned 
that I have saved the seeds of the mutcmts 
whenever possible, and have always obtained 
repetitions of the prototype only. Beversions 
are as absolutely lacking as is also a further de- 
velopment of the new type. Even in the case of 
the inconstant forms, where part of the progeny 
yearly return to the stature of lamarckiana, in- 
termediates are not found. So it is also with 
lata, which is pistillate and can only be prop- 
agated by cross-fertilization. But though the 
current belief would expect intermediates at 
least in this case, they do not occur. I made a 
pedigree-culture of lata during eight successive 
generations, pollinating them in different ways, 
and always obtained cultures which were partly 
constituted of lata and partly of lamarckiana 
specimens. But the latas remained lata in all 
the various and most noticeable characters, 
never showing any tendency to gradually revert 
into the original form. 

Intermediate forms, if not occurring in the 
direct line from one species to another, might be 
expected to appear perhaps on lateral branches. 
In this case the mutants of one type, appearing 
in the same year, would not be a pure type, but 
would exhibit different degrees of deviation 
from the parent The best would then have to 



560 


Mutations 


be chosen in order to get the new type in its pure 
condition. Nothing of the kind, however, was 
observed. All the o61o«^a-mutants were pure 
oblongas. The pedigree shows hundreds of 
them in the succeeding years, but no difference 
was seen and no material for selection was af- 
forded. All were as nearly equal as the in- 
dividuals of old elementary species. 

n. New forms spring laterally from the 
main stem. 

The current conception concerning the origin 
of species assumes that species are slowly con- 
verted into others. The conversion is assumed 
to affect all the individuals in the same direction 
and in the same degree. The whole group 
changes its character, acquiring new attributes. 
By inter-crossing they maintain a common line 
of progress, one individual never being able to 
proceed much ahead of the others. 

The birth of the new species necessarily 
seemed to involve the death of the old one. This 
last conclusion, however, is hard to understand. 
It may be justifiable to assume that all the in- 
dividuals of one locality are ordinarily inter- 
crossed, and are moreover subjected to the same 
external conditions. They might be supposed 
to vary in the same direction if these conditions 
were changed slowly. But this could of course 
have no possible influence on the plants of the 



Experimental Pedigree-Cultures 561 

same species growing in distant localities, and 
it would be improbable they should be affected 
in the same way. Hence we should conclude 
that when a species is converted into a new type 
in one locality this is only to be considered as 
one of numerous possible ones, and its alteration 
would not in the least change the aspect of the 
remainder of the species. 

But even with this restriction the general be- 
lief is not supported by the evidence of the even- 
ing-primroses. There is neither a slow nor a 
sudden change of all the individuals. On the 
contrary, the vast majority remain unchanged; 
thousands are seen exactly repeating the orig- 
inal prototype yearly, both in the native field 
and in my garden. There is no danger that 
lamarckiana might die out from the act of mu- 
tating, nor that the mutating strain itself would 
be exposed to ultimate destruction from this 
cause. 

In older swarms, such as Draba or Helianthe- 
mum, no such center around which the various 
forms are grow'^ is r. aii<>3wn. Are we to con- 
clude therefore cuA'! tne main strain has died 
out? Or is it perhaps concealed among the 
throng, being distinguished by no peculiar char- 
acter ? If our gigas and ruhrinervis were grow- 
ing in equal numbers with the lamarckiana in 
the native field, would it be possible to decide 



562 > 


Mutations 


which of th^ was the progenitor of the others? 
Of course this could be done by long and tedious 
crossing-es^rnnents, showing atavism in the 
progeny, and thereby indicating the common 
ancestor. But even this capacity seems to be 
doubtful and connected only with the state of 
mutability and to be lost afterwards. Therefore 
if this period of mutation were ended, probably 
there would be no way to decide concerning the 
mutual relationship of the single species. 

Hence the lack of a recognizable main stem in 
swarms of elementary species makes it impossi- 
ble to answer the question concerning their com- 
mon origin. 

Another phase of the opposition between the 
prevailing view and my own results seems far 
more important. According to the current be- 
lief the conversion of a group of plants growing 
in any locality and flowering simultaneously 
would be restricted to one type. In my own ex- 
periments several new species arose from the 
parental form at once, giving a wide range of 
new forms at the same timeumd under the same 
conditions. 'to '• 

m. New elementary species attain their full 
constancy at once. 

Constancy is not the result of selection or of 
improvement It is a quality of its own. It can 
neither be constrained by selection if it is absent 



Experimental Pedigree-Cultures 563 

from the beginning, nor does it need any natural 
or artificial aid if it is present. Most of my 
new species have proved constant from the first. 
Whenever possible, the original mutants have 
been isolated during the flowering period and 
artificially self-fertilized. Such plants have al- 
ways given a uniform progeny, all children ex- 
hibiting the type of the parent. No atavism 
was observed and therefore no selection was 
needed or even practicable. 

Briefly considering the different forms, we 
may state that the full experimental proof has 
been given for the origin of gigas and ruhriner- 
vis, for albida and oblonga, and even for nch 
nella, which is to be considered as of a varietal 
nature ; with lata the decisive experiment is ex- 
cluded by its unisexuality. Laevifolia and 
brevistylis were found originally in the field, 
and never appeared in my cultures. No obser- 
vations were made as to their origin, and seeds 
have only been sown from later generations. 
But these have yielded uniform crops, thereby 
showing that there is no ground for the assump- 
tion that these two older varieties might behave 
otherwise than the more recent derivatives. 

Scintillans and elliptica constitute exceptions 
to the rule given. They repeat their character, 
from pure seed, only in part of the offspring. I 
have tried to deliver the scintiUans from this 



5j64 


Mutations 


incompleteiiess of heredily, but in vain. The 
snoceedii^ generations, if produced from true 
representatives of the new type, and with pure 
fertilization, have repeated the splitting in the 
same numerical proportions. The instability 
seems to be here as permanent a quality as the 
stability in other instances. Even here no se- 
lection has been adequate to change the original 
form. 

rV. Some of the new strains are evidently ele- 
mentary species, while others are to be consid- 
ered as retrograde varieties. 

It is often difficult to decide whether a given 
form belongs to one or another of these two 
groups. I have tried to show that the best 
and strictest conception of varieties limits 
them to those forms that have probably 
originated by retrograde or degressive steps. 
Elementary species are assumed to have been 
produced in a progressive way, adding one 
new element to the store. Varieties differ from 
their species clearly in one point, and this is 
either a distinct loss, or the assumption of a 
character, which may be met with in other 
species and genera. Laevifolia is distin- 
guished by the loss of the crinkling of the 
leaves, hrevistylis by the partial loss of the 
epigynous qualities of the flowers, and nanella is 
a dwarf. These three new forms are tiierefore 



Experimental Pedigree-Cvltures 565 

considered to constitute only retrograde steps, 
and no advance. This conclusion has been fully 
justified by some crossing experiments with 
hrevistylis, which wholly complies with Men- 
del’s law, and in one instance with nanella, 
which behaves in the same manner, if crossed 
with rubrinervis. 

On the other hand, gigas and rubrinervis, ob- 
longa and albida obviously bear the characters 
of progressive elementary species. They are 
not differentiated from lamarckiana by one or 
two main features. They diverge from it in 
nearly all organs, and in all in a definite though 
small degree. They may be recognized as soon 
as they have developed their first leaves and re- 
main discernible throughout life. Their char- 
acters refer chiefly to the foliage, but no less to 
the stature, and even the seeds have peculiari- 
ties. There can be little doubt but that all the 
attributes of every new species are derived from 
one principal change. But why this should af- 
fect the foliage in one manner, the flowers in 
another and the fruits in a third direction, re- 
mains obscure. To gain ever so little an insight 
into the nature of these changes, we may best 
compare the differences of our evening-prim- 
roses with those between the two hundred ele- 
mentary species of Draba and other similar 
instances. In doing so we find the same main 



566 


Mutations 


feature, the minute differences in nearly all 
points. 

V. The sflnte new species are produced in a 
large number of individuals. 

This is a very curious fact. It embraces two 
minor points, viz: the multitude of similar mu- 
tants in the same year, and the repetition there- 
of in succeeding generations. Obviously there 
must be some common cause. This cause must 
be assumed to lie dormant in the LamarcManas 
of my strain, and probably in all of them, as no 
single parent-plant proved ever to be wholly 
destitute of mutability. Furthermore the dif- 
ferent causes for the sundry mutations must lie 
latent together in the same parent-plant. They 
obey the same general laws, become active under 
similar conditions, some of them being more 
easily awakened than others. The germs of the 
oblonga, lata and nanella are especially ir- 
ritable, and are ready to spring into activity at 
the least summons, while those of gigas, riibri- 
nervis and scintiUans are far more difficult to 
arouse. 

These germs must be assumed to lie dormant 
during many successive generations. This is 
especially evident in the case of lata and nanella, 
which appeared in the first year of the pedigree- 
culture and whi(fii since have been repeated 
yearly, and have been seen to arise by mutation 



Experimented Pedigree-Cultures 567 

also during the last season (1903). Only gigas 
appeared but once, but then there is every rea- 
son to assume that in larger sowings or by a pro- 
longation of the experiments it might have made 
a second appearance. 

Is the number of such germs to be supposed 
to be limited or unlimited f My experiment has 
produced about a dozen new forms. Without 
doubt 1 could easily have succeeded in getting 
more, if I had had any definite reason to search 
for them. But such figures are far from favor- 
ing the assumption of indefinite mutability. 
The group of possible new forms is no doubt 
sharply circumscribed. Partly so by the mor- 
phologic peculiarities of lamarckiana, which 
seem to exclude red flowers, composite leaves, 
etc. No doubt there are more direct rea- 
sons for these limits, some changes having taken 
place initially and others later, while the present 
mutations are only repetitions of previous ones, 
and do not contribute new lines of development 
to those already existing. This leads us to the 
supposition of some common original cause, 
which produced a number of changes, but which 
itself is no longer at work, but has left the af- 
fected qualities, and only these, in the state of 
mutability. 

In nature, repeated mutations must be of far 
greater significance than isotated ones. How 



568 


Mutations 


great is Uie chance for a single individual to be 
destroyed in the struggle for life? Hundreds 
of thousands of seeds are produced by la- 
marckkma annually in the field, and only 
some slow increase of the number of specimens 
can be observed. Many seeds do not find the 
proper circumstances for germination, or the 
young seedlings are destroyed by lack of water, 
of air, or of space. Thousands of them are so 
crowded when becoming rosettes that only a few 
succeed in producing stems. Any weakness 
would have destroyed them. As a matter of 
fact they are much oftener produced in the seed 
than seen in the field with the usual unfavorable 
conditions ; the careful sowing of collected seeds 
has given proof of this fact many times. 

The experimental proof of this frequency in 
the origin of new tyx)es,>seems to overcome many 
difficulties oflFered by the current theories on the 
probable ori^n of species at large. 

VI. The relation between mutability and fluc- 
tuating variability has always been one of the 
chief difficulties of the followers of Darwin. The 
majority assumed that species arise by the slow 
accumulation of slight fluctuating deviations, 
and the mutations were only to be considered as 
extreme fluctuations, obtained, in the main, by a 
continuous selection of small differences in a 
constant direction. 



Experiment(U Pedigree-Cultures 569 

My cultures show that quite the opposite is 
to be regarded as fact. All organs and all quali- 
ties of lamarckiana fluctuate and vary in a 
more or less evident manner, and those which I 
had the opportunity of examining more closely 
were found to comply with the general laws of 
fluctuation. But such oscillating changes have 
nothing in common with the mutations. Their 
essential character is the heaping up of slight 
deviations around a mean, and the occurrence of 
continuous lines of increasing deviations, link- 
ing the extremes with this group. Nothing of 
the kind is observed in the case of mutations. 
There is no mean for them to be grouped around 
and the extreme only is to be seen, and it is 
wholly unconnected with the original type. It 
might be supposed that on closer inspection each 
mutation might be brought into connection with 
some feature of the fluctuating variability. But 
this is not the case. The dwarfs are not at all 
the extreme variants of structure, as the fluctua- 
tion of the height of the lamarckiana never de- 
creases or even approaches that of the dwarfs. 
There is always a gap. The smallest specimens 
of the tall type are commonly the weakest, ac- 
cording to the general rule of the relationship 
between nourishment and variation, but the 
tallest dwarfs are of course the most robust 
specimens of their group. 



670 


Mutations 


Fluctnatingyariabilily, as a rule, is subject to 
reversioxu The seeds of the extremes do not 
produce an offspring which fluctuates around 
their parents as a center, but aroimd some point 
on the line which combines their attributes with 
the corresponding characteristic of their ances* 
tors, as Vilmorin has put it. No reversion ac- 
companies mutation, and this fact is perhaps the 
completest contrast in which these two great 
types of variability are opposed to each other. 

The offspring of my mutants are, of course, 
subject to the general laws of fluctuating varia- 
bility. They vary, however, around their own 
mean, and this mean is simply the type of the 
new elementary species. 

Vn. The mutations take place in nearly all 
directions. 

Many authors assume that the origin of spe- 
cies is directed by unknown causes. These 
causes are assumed to work in each single case 
for the improvement of the animals and plants, 
changing them in a manner corresponding 
in a useful way to the changes that take 
place in their environment. It is not easy to 
imagine the nature of these influences nor how 
they would bring about the desired effect. 

This difficulty was strongly felt by Darwin, 
and one of the chief purposes of his selection- 
theory may be said to have been the at- 



Experimental Pedigree-Cultures 571 

tempt to surmount it Darwin tried to re- 
place the unknown cause by natural agencies, 
which lie under our immediate observation. 
On this point Darwin was superior to his 
predecessors, and it is chiefly due to the clear 
conception of this point that his theory has 
gained its deserved general acceptance. Accord- 
ing to Darwin, changes occur in all directions, 
quite independently of the prevailing circum- 
stances. Some may be favorable, others detri- 
mental, many of them without signiflcance, 
neither useful nor injurious. Some of them 
will sooner or later be destroyed, while others 
will survive, but which of them will survive, 
is obviously dependent upon whether their 
particular changes agree with the existing 
environic conditions or not. This is what 
Darwin has called the struggle for life. 
It is a large sieve, and it only acts as 
such. Some fall through and are annihilated, 
others remain above and are selected, as the 
phrase goes. Many are selected, but more are 
destroyed ; daily observation does not leave any 
doubt upon this point. 

How the differences originate is quite another 
question. It has nothing to do with the theory 
of natural selection nor with the struggle for 
life. These have an active part only in the ac- 
cumulation of useful qualities, and only in so 



572 


Mutations 


far as they protect the bearers of such charac- 
ters against being crowded out by their more 
poorly constituted competitors. 

However, the differentiating characteristics 
of elementary species are only very small. How 
widely distant they are from the beautiful adap- 
tative organizations of orchids, of insectivorous 
plants and of so many others ! Here the differ- 
ence lies in the accumulation of numerous ele- 
mentary characters, which all contribute to the 
same end. Chance must have produced them, 
and this would seem absolutely improbable, even 
impossible, were it not for Darwin’s ingenious 
theory. Chance there is, but no more than any- 
where else. It is not by mere chance that the 
variations move in the required direction. They 
do go, according to Darwin’s view, in all direc- 
tions, or at least in many. If these include the 
useful ones, and if this is repeated a number of 
times, cumulation is possible; if not, there is 
simply no progression, and the type remains 
stable through the ages. Natural selection is 
continually acting as a sieve, throwing out the 
useless changes and retaining the real improve- 
ments. Hence the accumulation in apparent- 
ly predisposed directions, and hence the 
increasing adaptations to the more specialized 
conditions of life. It must be obvious to any 
one who can free himself from the current ideas. 



Experimental Pedigree-Cultures 573 

that this' theory of natural selection leaves the 
question as to how the changes themselves are 
brought about, quite undecided. There are two 
possibilities, and both have been propounded by 
Darwin. One is the accumulation of the slight 
deviations of fluctuating variability, the qther 
consists of successive sports or leaps taking 
place in the same direction. 

In further lectures a critical comparison of 
the two views will be given. To-day I have only 
to show that the mutations of the evening-prim- 
roses, though sudden, comply with the demands 
made by Darwin as to the form of variability 
which is to be accepted as the cause of evolution 
and as the origin of species. 

Some of my new types are stouter and others 
weaker than their parents, as shown by gigas 
and albida. Some have broader leaves and 
some narrower, lata and ohlonga. Some have 
larger flowers (gigas) or deeper yellow ones 
(ruhrinervis), or smaller blossoms (scintillans)^ 
or of a paler hue (albida). In some the cap- 
sules are longer (rubrinervis) , or thicker 
(gigas), or more rounded (lata), or small (oh- 
longa), and nearly destitute of seeds (brevi- 
stylis). The unevenness of the surface of the 
leaves may increase as in lata, or decrease as in 
laevifolia. The tendency to become annual pre- 
vails in rubrinervis, but gigas tends to become 



574 


Mutations 


biennial. Some are rich in pollen, while sdn- 
tiUans is poor. Some have large seeds, others 
small. Lata has become pistillate, while 
hrevistylis has nearly lost the faculty to pro- 
duce seeds. Some undescribed forms were 
quite sterile, and some 1 observed which pro- 
duced no flowers at all. From this statement it 
may be seen that nearly all qualities vary in op- 
posite directions and that our group of mutants 
affords wide material for the sifting process of 
natural selection. On the original field the 
laevifolia and hrevistylis have held their own 
during sixteen years and probably more, with- 
out, however, being able to increase their num- 
bers to any noticeable extent Others perish 
as soon as they make their appearance, or a 
few individuals are allowed to bloom, but prob- 
ably leave no progeny. 

But perhaps the circumstances may change, 
or the whole strain may be dispersed and spread 
to new localities with different conditions. Some 
of the latter might be found to be favorable to 
the robust gigas^ or to rubrinerms, which re- 
quires a drier air, with rainfall in the spring- 
time and sunshine during the summer. It would 
be worth while to see whether the climate 
of California, where neither 0. lamarckiana 
nor 0. biennis are found wild, would not exactly 



Experimental Pedigree-Cultures 575 

suit the requirements of the new species rubri- 
nervis and gigas. 

Note. — Oenotheras are native to America and all 
of the species growing in Europe have escaped from 
gardens directly, or may have arisen by mutation, or 
by hybridization of introduced species. A fixed 
hybrid between O. cruciata and O. biennis constituting 
a species has been in cultivation for many years. 
The form known as O. biennis in Europe, and used 
by de Vries in all of the experiments described in these 
lectures, has not yet been found growing wild in 
America and is not identical with the species bearing 
that name among American botanists. Concerning 
this matter Professor de Vries writes under date of 
Sept. 12, 1905: “The ‘biennis’ which I collected in 
America has proved to be a motley collection of forms, 
which at that time I had no means of distinguishing. 
No one of them, so far as they are now growing in 
my garden is identical with our biennis of the sand 
dunes. ’ ’ The same appears to be the case with 
O. muricata. Plants from the Northeastern American 
seaboard, identifiable with the species do not entirely 
agree with those raised from seed received from 
Holland. 

O. Lamarckiana has not been found growing wild 
in America in recent years although the evidence at 
hand seems to favor the conclusion that it was seen 
and collected in the southern states in the last century. 
(See MsuiDougal, Vail, Shull, and Small. Mutants 
and Hybrids of the Oenotheras. Publication 24. 
Carnegie Institution. Washington, D. 0., 1905.) 

EnrroB. 



liXSOTXTBE XX 


THE OBIGIK OF WILD SPECIES AND VABIETIE8 

New species and varieties occur from time to 
time in the wild state. Setting aside all theo- 
retical conceptions as to the common origin of 
species at large, the undoubted fact remains that 
new forms are sometimes met with. In the case 
of the peloric toad-flax the mutations are so 
numerous that they seem to be quite regular. 
The production of new species of evening-prim- 
roses was observed on the field and afterwards 
duplicated in the garden. There is no reason 
to think that these cases are isolated instances. 
Quite on the contrary they seem to be the pro- 
totypes of repeated occurrences in nature. 

If this conception is granted, the question at 
once arises, how are we to deal with analogous 
cases, when fortune offers them, and what can 
we expect to learn from them? 

A critical study of the existing evidence seems 
to be of great importance in order to ascertain 
the best way of dealing with new facts, and of 
estimating the value of the factors concerned. 

576 



577 


Origin of Wild Species 

It is manifest that we must be very careful and 
conservative in dealing with new facts that are 
brought to our attention, and every effort should 
be made to bring additional evidence to light. 
Many vegetable anomalies are so rare that 
they are met with only by the purest 
chance, and are then believed to be wholly 
new. ' When a white variety of some common 
plant is met with for the first time we generally 
assume that it originated on that very spot 
and only a short time previously. The discov- 
ery of a second locality for the same variety at 
once raises the question as to a common origin 
in the two instances. Could not the plants of 
the second locality have arisen from seeds 
transported from the first? 

White varieties of many species of blue-bells 
and gentians are found not rarely, white-flower- 
ing plants of heather, both of Erica Tetralix and 
Calluna vulgaris occur on European heaths; 
white flowers of Brunella vulgaris, Ononis re- 
pens, Thymus vulgaris and others may be seen 
in many localities in the habitats of the colored 
species. Pelories of labiates seem to occur 
often in Austria, but are rare in Holland ; white 
bilberries {Vaccinium MyrtUlus) have many 
known localities throughout Europe, and nearly 
all the berry-bearing species in the large heath- 
family are recorded as having white varieties. 



678 


Mutations 


Are we to assume a single origin for all the 
representatives of such a variety, as we have 
done customarily for all the representatives of 
a wild species } Or can the same mutation have 
been repeated at different times and in distant 
localities? If a distinct mutation from a given 
species is once possible, why should it not occur 
twice or thrice? 

A variety which seems to be new to us may 
only appear so, because the spot where it grows 
had hitherto escaped observation. Lychnis 
preslii is a smooth variety of Lychnis diurna 
and was observed for the first time in the year 
1842 by Sekera. It grew abundantly in a grove 
near Mimchengratz in southern Hungary. It 
was accompanied by the ordinary hairy type of 
the species. Since then it has been observed to 
be quite constant in the same locality, and some 
specimens have been collected for me there late- 
ly by Dr. N&nec, of Prague. No other native 
localities of this variety have been discovered, 
and there can be no doubt that it must have 
arisen from the ordinary campion near the spot 
where it still grows. But this change may have 
taken place some years before the first discov- 
ery, or perhaps one or more centuries ago. 
This could only be known if it could be proved 
that the locality had been satisfactorily investi- 
gated previously, and that the variety had not 



679 


Origin of Wild Species 

been met with. Even in this case only some> 
thing would be discovered about the time of the 
change, but nothing about its real nature. 

So it is in many cases. If a variety is ob- 
served in a number of specimens at the time 
of its first discovery, and at a locality not 
studied previously, it takes the aspect of an old 
form of limited distribution, and little can be 
learned as to the circumstances under which it 
arose. If on the contrary it occurs in very 
small numbers or perhaps even in a single in- 
dividual, and if the spot where it is found is 
located so that it could hardly have escaped pre- 
vious observation, then the presumption of a re- 
cent origin seems justified. 

What has to be ascertained on such occasions 
to give them scientific value? Three points 
strike me as being of the highest importance. 
First, the constancy of the new type; secondly, 
the occurrence or lack of intermediates, and last, 
but not least, the direct observation of a re- 
peated production. 

The first two points are easily ascertained. 
Whether the new type is linked with its more 
common supposed ancestor by intermediate 
steps is a query which at once strikes the bota- 
nist. It is usually recorded in such cases, and 
we may state at once that the general result is, 
that such intermediates do not occur. This is 



580 


Mutations 


of the highest importance' and admits of only 
two explanations. One is that intermediates 
may be assmned to have preceded the existent 
developed form, and to have died out after- 
wards, But why should they have done so, 
especially in cases of recent changes? On the 
other hand the intermediates may be lacking 
because they have never existed, the change 
having taken place by a sudden leap, such as the 
mutations described in our former lectures. It 
is manifest that the assumption of hypothetical 
intermediates could only gain some probabil^y 
if they had been found in some instance. Si^e 
they do not occur, the hypothesis seems wholly 
unsupported. 

The second point is the constancy of the new 
type. Seeds should be saved and sown. If the 
plant fertilizes itself without the aid of insects, 
as do some evening-primroses, the seed saved 
from the native locality may prove wholly pure, 
and if it does give rise to a uniform progeny the 
constancy of the race may be assumed to be 
proved, provided that repeated trials do not 
bring to light any exceptions. If the offspring 
shows more than one type, cross-fertilization is 
always to be looked to as the most probable 
cause, and should be excluded, in order to sow 
pure seeds. Garden-experiments of this kind, 
and repeated trials, should always be combined 



Origin of Wild Species 


581 


with the discovery of a presumed mutation. In 
many instances the authors have realized the 
importance of this point, and new types have 
been found constant from the very beginning. 
Many cases are known which show no rever- 
sions and even no partial reversions- This fact 
throws a distinct light on our first point, as it 
makes the hypothesis of a slow and gradual de- 
velopment still more improbable. 

My third point is of quite another nature and 
has not as yet been dealt with. But as it ap- 
peals to me as the very soul of the problem, 
it seems necessary to describe it in some detail. 
It does not refer to the new type itself, nor to 
any of its morphologic or hereditary attributes, 
but directly concerns the presumed ancestors 
themselves. 

The peloric toad-flax in my experiment was 
seen to arise thrice from the same strain. Three 
different individuals of my original race showed 
a tendency to produce peloric mutations, and 
they did so in a number of their seeds, exactly 
as the mutations of the evening-primroses were 
repeated nearly every year. Hence the infer- 
ence, that whenever we find a novelty which is 
really of very recent date, the parent-strain 
which has produced it might still be in existence 
on the same spot. In the case of shrubs or 
perennials the very parents might yet be found. 



582 


Mutations 


But it seems probable, and is especially proved 
in the case of the evening-primroses, that all 
or the majority of the representatives of the 
whole strain have the same tendency to mutate. 
If this were a general rule, it would suffice to 
take some pure seeds from specimens of the 
presumed parents and to sow and multiply the 
individuals to such an extent that the mutation 
might have a chance to be repeated. 

Unfortunately, this has not as yet been done, 
but in my opinion it should be the first effort of 
any one who has the good luck to discover a new 
wild mutation. Specimens of the parents 
should be transplanted into a garden and fertil- 
ized under isolated conditions. Seeds saved 
from the wild plant would have little worth, as 
they might have been partly fertilized by the 
new type itself. 

After this somewhat lengthy discussion of the 
value of observations surrounding the discovery 
of new wild mutations, we now come to the de- 
scription of some of the more interesting cases. 
As a first example, I will take the globular- 
fmited shepherd's purse, described by Solms- 
Laubach as Capsella heegeri. Professor 
Heeger discovered one plant with deviating 
fruits, in a group of common shepherd's purses 
in the market-place near Landau in Germany, 
in the fall of 1897. They were nearly spher- 



Origin of Wild Species 


583 


ical, instead of flat and purse-shaped. Their 
valves were thick and fleshy, while those of the 
ordinary form are membranaceous and dry. 
The capsules hardly opened and therefore dif- 
fered in this point from the shepherd’s purse, 
which readily loosens both its valves as soon as 
it is ripe. 

Only one plant was observed ; whence it came 
could not be determined, nor whether it had 
arisen from the neighboring stock of Capsella 
or not. The discoverer took some seed to his 
garden and sent some to the botanical garden 
at Strassburg, of which Solms-Laubach is the 
director. The majority of the seeds of course 
were sowed naturally on the original spot. The 
following year some of the seeds germinated 
and repeated the novelty. The leaves, stems and 
flowers were those of the common shepherd’s 
purse, but no decision could be reached concern- 
ing the type of this generation before the first 
flowers had faded and the rounded capsules had 
developed. Then it was seen that the heegeri 
came' true from seed. It did so both in the 
gardens and on the market-place, where it was 
observed to have multiplied and spread in some 
small measure. The same was noted the fol- 
lowing year, but then the place was covered with 
gravel and all the plants destroyed. It is not 
recorded to have been seen wild since. 



584 


Mutations 


Intennediate forms have not been met with. 
Some slight reversions may occur in the autumn 
on the smallest and weakest lateral branches. 
Such reversions, however, seem to be very rare, 
as I have tried in vain to produce them on large 
and richly branched individuals, by applying all 
possible inducements in the form of manure 
and of cutting, to stimulate the production of 
successive generations of weaker side branches. 

This constancy was proved by the experi- 
ments of Solms-Laubach, which I have repeated 
in my own garden during several years with 
seed received from him. No atavists or deviat- 
ing specimens have been found among many 
hundreds of flowering plants. 

It is important to note that within the family 
of the crucifers the form of the capsule and the 
attributes of the valves and seeds are usually 
considered to furnish the characteristics of 
genera, and this point has been elucidated at 
some length by Solms-Laubach. There is, how- 
ever, no sufiicient reason to construe a new 
genus on the ground of Heeger’s globular- 
fruited shepherd’s purse; but as a true elemen- 
tary species, and even as a good systematic 
species it has proved itself, and as such it is de- 
scribed by Solms-Laubach, who named it in 
honor of its discoverer. 

Exactly analogous discoveries have been 



585 


Origin of Wild Species 

made from time to time with other plants by 
different writers. Near Wageningen, in Hol- 
land, I found Stellaria Holostea apetala in the 
year 1889, and near Horn in Lippe (Germany) 
Capsella Bursa-pastoris apetala, both in a very 
few specimens on a single spot. Whether these 
were mutations or introductions remains of 
course uncertain. About the same time I dis- 
covered near Hilversum in Holland a smooth 
variety of the evening campion. Lychnis vesper- 
tina, forming a very small group of individuals 
in a field, where the hairy type was common. 
It was sown in my garden and proved pure and 
constant, without intermediates. As the local- 
ity had been repeatedly and carefully investi- 
gated by me, I trust to be justified in the asser- 
tion that I gathered the very first individuals of 
the variety. The stock soon was overgrown by 
surrounding shrubs and died out, and now only 
the cultivated offspring are available, as in the 
case of Heeger’s shepherd’s purse. 

A very curious instance of spontaneous muta- 
tions is afforded by a peculiarity of some even- 
ing-primroses and their allies. This peculiarity 
is shown by the petals remaining minute and 
assuming a linear shape. The character is de- 
veloped as a specific one in Oenothera cruciata. 
This plant owes its name to the shape of the 
petals, which form a slender cross in the flower, 



586 


Mutations 


instead of displaying a bright yellow cnp. 
0. cradaia grows in the Adirondack Mountains, 
in the states of New York and Vermont, and 
se^s to be abundant there. It has been intro- 
duced into botanical gardens and yielded a num- 
ber of hybrids, especially with 0. biennis and 0. 
lamarchiana, and the narrow petals of the 
parent-species may be met with in combination 
with the stature and vegetative characteristics 
of these last named species. 0. cruciata has a 
purple foliage, while biennis and lamarchiana 
are green, and many of the hybrids may in- 
stantly be recognized by their purple color. 

The curious attribute of the petals is not to be 
considered simply as a reduction in size. On 
anatomical inquiry it has been found that these 
narrow petals bear some characteristics which, 
on the normal plants, are limited to the calp:. 
Stomata and hairs, and the whole structure of 
the surface and inner tissues on some parts of 
these petals are exactly similar to those of the 
calyx, while on others they have retained the 
characteristics of petals. Sometimes there 
may even be seen by the naked eye green longi- 
tudinal stripes of calyx-like structure alter- 
nating with bright yellow petaloid parts. For 
these reasons the cruciata character may be con- 
sidered as a case of sepalody of the petals, or of 
the petals being partly converted into sepals. 



587 


Origin of Wild Species 

It is worth while to note that as a monstrosity 
this occurrence is extremely rare throughout the 
whole vegetable kingdom, and only very few 
instances have been recorded. 

Two cases of sudden mutations have come to 
my knowledge, producing this same anomaly in 
allied species. One has been already alluded to ; 
it pertains to the common evening-primrose or 
Oenothera biennis, and one is a species belong- 
ing to another genus of the same family, the 
great hairy willow-herb or Epilobium kirsutum. 
I propose to designate both new forms by the 
varietal name of cruciata, or cruciaium. 

Oenothera biennis cruciata was found in a 
native locality of the 0. biennis itself. It con- 
sisted of only one plant, showing in all its flow- 
ers the cruciata marks. In all other respects it 
resembled wholly the biennis, especially in the 
pure green color of its foliage, which at once 
excluded all suspicion of hybrid origin with the 
purple O. cruciata. Moreover in our country 
this last occurs only in the cultivated state in 
botanical gardens. 

Intermediates were not seen, and as the plant 
bore some pods, it was possible to test its con- 
stancy. I raised about 500 plants from its seeds, 
out of which more than 100 flowered in the first 
year. The others were partly kept through the 
winter and flowered next year. Seeds saved in 



588 


Mutations 


both seasons were sown on a large scale. Both 
the first and the succeeding generations of 
the offspring of the original plant came true 
without any exception. Intermediates are 
often found in hybrid cultures, and in them the 
character is a very variable one, but as yet they 
were not met with in progeny of this mutant. 
'All these plants were exactly like 0. biennis, 
with the single exception of their petals. 

EpUobium hirsutum cruciatum was discov- 
ered by John Basor near Woolpit, Bury St. Ed- 
munds, in England. It fiowered in one spot, 
producing about a dozen stems, among large 
quantities of the parent-species, which is very 
common there, as it is elsewhere in Europe. 
This species is a perennial, multiplying itself by 
underground runners, and the stems of the 
new variety were observed to stand so close to 
each other that they might be considered as the 
shoots of one individual. In this case this spee- 
imen might probably be the original mutant, as 
the variety had not been seen on that spot in 
previous years, even as it has not been found 
elsewhere in the vicinity. 

Intermediates were not observed, though the 
difference is a very striking one. In the cru- 
ciate flowers the broad and bright purple petals 
seem at first sight to be wholly wanting. They 
are too weak to expand and to reflex the calyx 



Origin of Wild Species 


589 


as in the normal flowers of the species. The 
sepals adhere to one another, and are only 
opened at their summit by the protruding pis- 
tils. Even the stamens hardly come to light. 
At the period of full bloom the flowers convey 
only the idea of closed buds crowned by the con- 
spicuous white cross of the stigma. Any inter- 
mediate form would have at once betrayed itself 
by larger colored petals, coming out of the 
calyx-sheath. The cruciate petals are small 
and linear and greenish, recalling thereby the 
color of the sepals. 

Mr. Easor having sent me some flowers and 
some ripe capsules of his novelty, I sowed the 
latter in my experimental garden, where the 
plant flowered in large numbers and with many 
thousands of flowers both in 1902 and 1903. 
All of these plants and all of these flowers re- 
peated the cruciate type exactly, and not the 
slighest impurity or tendency to partial rever- 
sion has been observed. 

Thus true and constant cruciate varieties 
have been produced from accidentally observed 
initial plants, and because of their very curious 
characters they will no doubt be kept in 
botanical gardens, even if they should event- 
ually become lost in their native localities. 

At this point I might note another observation 
made on the wild species of Oenothera cruciata 



590 


Mutations 


from the Adirondacks. Through the kindness 
of Dr. MacDougal, of the New York Botanicfd 
Garden, I received seeds from Sandy Hill near 
Lake George. When the plants, grown from 
these seeds, flowered, they were not a uniform 
lot, but exhibited two distinct types. Some had 
linear petals and thin flower-buds, and in 
others the petals were a little broader and the 
buds more swollen. The difference was small, 
but constant on all the flowers, each single plant 
clearly belonging to one or the other of the two 
types. Probably two elementary species were 
intermixed here, but whether one is the sys- 
tematic type and the other a mutation, remains 
to be seen. 

Nor seem these two types to exhaust the range 
of variability of Oenothera cruciata. Dr. B. L. 
Bobinson of Cambridge, Mass., had the kind- 
ness to send me seeds from another locality in 
the same region. The seeds were collected in 
New Hampshire and in my garden produced a 
true and constant cruciata, but with quite differ- 
ent secondary characters from both the afore- 
said varieties. The stems and flower-spikes and 
even the whole foliage were much more slender, 
and the calyx-tubes of the flowers were notice- 
ably more elongated. It seems not improbable 
that Oenothera cruciata includes a group of 
lesser unities, and may prove to comprise a 



591 


Origin of Wild Species 

swarm of elementary species, while the original 
strain might even now be still in a condition of 
mutability. A close scrutiny in the native re- 
gion is likely to reveal many unexpected 
features. 

A very interesting novelty has already been 
described in a former lecture. It is the Xan- 
thium wootoni, discovered in the region about 
Las Vegas, New Mexico, by T. D. A. CockereU. 
It is similar in all respects to X. commune, but 
the burrs are more slender and the prickles 
much less numerous, and mostly stouter at their 
base. It grows in the same localities as the 
X. commune, and is not recorded to occur else- 
where. Whether it is an old variety or a recent 
mutation it is of course impossible to decide. 
In a culture made in my garden from the seed 
sent me by Mr. Cockerell, I observed (1903) that 
both forms had a subvariety with brownish 
foliage, and, besides this, one of a pure green. 
Possibly this species, too, is still in a mutable 
condition. 

Perhaps the same may be asserted concerning 
the beautiful shrub. Hibiscus Moscheutos, ob- 
served in quite a number of divergent types by 
John W. Harshberger. They grew in a small 
meadow at Seaside Park, New Jersey, in a 
locality which had been undisturbed for years. 
They differed from each other in nearly all the 



502 


Mutations 


organs, in size, in the diameter of the stems, 
which were woody in some and more fleshy in 
others, in the shape of the foliage and in the 
flowers. More than twenty types could be dis- 
tinguished and seeds were saved from a num- 
ber of them, in order to ascertain whether they 
are constant, or whether perhaps a main stem in 
a mutating condition might be found among 
them. If this should prove to be the case, the 
relations between the observed forms would 
probably be analogous to those between the 0. 
lamarckiana and its derivatives. 

Many other varieties have sprung from the 
type-species under similar conditions from time 
to time. A fem-leaved mercury, Mercurialis 
aimua lacmiata, was discovered in the year 1719 
by Marchant. The type was quite new at the 
time and maintained itself during a series of 
years. The yellow deadly nightshade or Atropa 
Belladonna lutea was found about 1850 in the 
Black Forest in Germany in a single spot, and 
has since been multiplied by seeds. It is now 
dispersed in botanical gardens, and seems to be 
quite constant. A dwarf variety of a bean, 
Phaseolus lunatus, was observed to spring from 
the ordinary type by a sudden leap about 1895 
by W. W. Tracy, and many similar cases could 
be given. 

The annual habit is not very favorable for 



593 


Origin of Wild Species 

the discovery of new forms in the wild state. 
New varieties may appear, but may he crowded 
out the first year. The chances are much 
greater with perennials, and still greater with 
shrubs or trees. A single aberrant specimen 
may live for years and even for centuries, and 
under such conditions is pretty sure to be dis- 
covered sooner or later. Hence it is no won- 
der that many such cases are on record. They 
have this in common that the original plant 
of the variety has been found among a vast 
majority of representatives of the correspond- 
ing species. Nothing of course is directly 
known about its origin. Intermediate links 
have as a rule been wanting, and the seeds, 
which have often been sown, have not yielded 
reliable results, as no care was taken to pre- 
serve the blossoms from intercrossing with their 
parent-forms. 

Stress should he laid upon one feature of 
these curious occurrences. Relatively often 
the same novelty has been found twice or thrice, 
or even more frequently, and under conditions 
which make it very improbable that any relation 
between such occurrences might exist. The 
same mutation must have taken place more than 
once from the same main stem. 

The most interesting of these facts are con- 
nected with the origin of the purple beech, which 



594 


Mutations 


is now so universally cultivated. I take the fol- 
lowing statements from an interesting historical 
essay of Prof. Jaggi. He describes three orig- 
inal localities. One k near the Swiss village, 
Bnch am Irchel, and is located on the Stamm- 
berg. During the 17th century five purple 
beeches are recorded to have grown on this spot. 
Four of them have died, but one is still alive. 
Seedlings have germinated around this little 
group, and have been mostly dug up and trans- 
planted into neighboring gardens. Nothing is 
known about the real origin of these plants, but 
according to an old document, it seems that 
about the year 1190 the purple beeches of Buch 
were already enjoying some renown, and at- 
tracting large numbers of pilgrims, owing to 
some old legend. The church of Embrach is said 
to have been built in connection with this legend, 
and was a goal for pilgrimages during many 
cmituries. 

A second native locality of the purple beech 
is found in a forest near Sondershausen in 
Thiiringen, Germany, where a fine group of 
these trees is to be seen. They were mentioned 
for the first time in the latter half of the 
eighteenth century, but must have been old spec- 
imens long before that time. The third locality 
seems to be of much later origin. It is a forest 
near Boveredo in South Tyrol, where a new 



Origin of Wild Species 


595 


university is being erected. It is only a century 
ago that the first specimens of the purple beech 
were discovered there. 

As it is very improbable that the two last 
named localities should have received their pur- 
ple beeches from the first named forest, it seems 
reasonable to assume that the variety must have 
been produced at least thrice. 

The purple beech is now exceedingly common 
in cultivation. But Jaggl succeeded in showing 
that all the plants owe their origin to the orig- 
inal trees mentioned above, and are, including 
nearly all cultivated specimens with the sole ex- 
ception of the vicinity of Buch, probably derived 
from the trees in Thuringen. They are easily 
multiplied by grafting, and come true from 
seed, at least often, and in a high proportion. 
Whether the original trees would yield a 
pure progeny if fertilized by their own pol- 
len has as yet not been tested. The young seed- 
lings have purple seed-leaves, and may easily be 
selected by this character, but they seem to 
be always subjected in a large measure to 
vicinism. 

Many other instances of trees and shrubs, 
found in accidental specimens constituting a 
new variety in the wild state, might be given. 
The oak-leaved beech has been found in a forest 
of Lippe-Detmold in Germany and near Ver- 



596 


Mutations 


sailles, whence it was introduced into horticul- 
ture by Carriere. Similarly divided and cleft 
leaves seem to have occurred more often in the 
wild state, and cut-leaved hazels are recorded 
from Rouen in France, birches and alders from 
Sweden and Lapland, where both are said to 
have been met with in several forests. The 
purple barberry was found about 1830 by Ber- 
tin, near Versailles. Weeping varieties of 
ashes were found wild in England and in Ger- 
many, and broom-like oaks, Quercus pedun- 
culata fastigiata, are recorded from Hessen- 
Darmstadt, Calabria, the Pyrenees and other 
localities. About the real origin of all these 
varieties nothing is definitely known. 

The “ single-leaved ” strawberry is a variety 
often seen in botanical gardens, as it is easily 
propagated by its runners. It was discovered 
wild in Lapland at the time of Linnaeus, and 
appeared afterwards unexpectedly in a nursery 
near Versailles. This happened about the year 
1760 and Duchesne tested it from seeds and 
found it constant. This strain, however, seems 
to have died out before the end of the 18th cen- 
tury. In a picture painted by Holbein (1495- 
1543); strawberry leaves can be seen agreeing 
exactly with the monophyllous type. The va- 
riety may thus be assumed to have arisen inde- 



Origin of Wild Species 


597 


pendently at least thrice, at different periods 
and in distant localities. 

From all these statements and a good many 
others which can be found in horticultural and 
botanical literature, it may be inferred that 
mutations are not so very rare in nature as is 
often supposed. Moreover we may conclude 
that it is a general rule that they are neither 
preceded nor accompanied by intermediate 
steps, and that they are ordinarily constant 
from seed from the first. 

Why then are they not met with more often? 
In my opinion it is the struggle for life which is 
the cause of this apparent rarity ; which is noth- 
ing else than the premature death of all the in- 
dividuals that so vary from the common type of 
their species as to he incapable of development 
under prevailing circumstances. It is obvious- 
ly without consequence whether these deviations 
are of a fluctuating or of a mutating nature. 
Hence we may conclude that useless mutations 
will soon die out and will disappear without 
leaving any progeny. Even if they are pro- 
duced again and again by the same strain, but 
under the same unfavorable conditions, there 
will be no appreciable result 

Thousands of mutations may perhaps take 
place yearly among the plants of our immediate 
vicinity without any chance of being discovered. 



598 


Mutations 


We are trained to the appreciation of the dif- 
ferentiating marks of systematic species. When 
have succeeded in discerning these as given 
by our local flora lists, we rest content. Meet- 
ing them again we are in the habit of greeting 
them with their proper names. Such is the 
satisfaction ensuing from this knowledge that 
we do not feel any inclination for further in- 
quiry. Striking deviations, such as many 
varietal characters, may be remarked, but then 
they are considered as being of only secondary 
interest. Our minds are turned from the deli- 
cately shaded features which differentiate ele- 
mentary species. 

Even in the native field of the evening-prim- 
roses, no botanist would have discovered the 
rosettes with smaller or paler leaves, constitut- 
ing the first signs of the new species. Only by 
the guidance of a distinct theoretical idea were 
they discovered, and having once been pointed 
out a closer inspection soon disclosed their 
number. 

Variability seems to us to be very general, but 
very limited. The limits however, are distinct- 
ly drawn by the struggle for existence. Of 
course the chance for useful mutations is a very 
small one. We have seen that the same muta- 
tions are as a rule repeated from time to time 
by the same species. Now, if a useful mutation. 



599 


Origin of Wild Species 

or even a wholly indifferent one, might easily be 
produced, it would have been so, long ago, and 
would at the present time simply exist as a sys- 
tematic variety. If produced anew somewhere 
the botanist would take it for the old variety 
and would omit to make any inquiry as to its 
local origin. 

Thousands of seeds with perhaps wide circles 
of variability are ripened each year, but only 
those that belong to the existing old narrow 
circles survive. How different would Nature 
appear to us if she were free to evolve all her 
potentialities I 

Darwin himself was struck with this lack of 
harmony between common observations and the 
probable real state of things. He discussed 
it in connection with the cranesbill of the 
Pyrenees {Geranium pyrenaicum). He de- 
scribed how this fine little plant, which has never 
been extensively cultivated, had escaped from a 
garden in Staffordshire and had succeeded in 
multiplying itself so as to occupy a large area. 
In doing so it had evidently found place for an 
uncommonly large number of plantlets from its 
seeds and correspondingly it had commenced to 
vary in almost all o^ans and qualities and 
nearly in all imaginable directions. It dis- 
played under these exceptional circumstances a 
capacity which never had been exceeded and 



600 


Mutations 


which of course would have remained concealed 
if its multiplication had been checked in the or- 
dinary way. 

Many species have had occasion to invade new 
regions and cover them with hundreds of thou- 
sands of individuals. First are to be cited 
those species which have been introduced from 
America into Europe since the time of Colum- 
bus, or from Europe into this country. Some of 
Ibem have become very common. In my own 
country the evening-primroses and Canada flea- 
bane or Erigeron canadensis are examples, and 
many others could be given. They should be 
expected to vary under these circumstances in 
a larger degree. Have they done so? Mani- 
festly they have not struck out useful new char- 
acters that would enable their bearers to found 
new elementary species. At least none have 
been observed. But poor types might have 
been produced, and periods of mutability might 
have been gone through similar to that which is 
now under observation for Lamarck’s evening- 
primrose in Holland. 

From this discussion we may infer that the 
chances of discovering new mutating species are 
great enough to justify the utmost efforts to 
secure them. It is only necessary to observe 
large numbers of plants, grown under circum- 
stances which allow the best opportunities for 



Origin of Wild Species 


601 


all the seeds. And as nature affords such op- 
portunities only at rare intervals, we should 
make use of artificial methods. Large quan- 
tities of seed should be gathered from wild 
plants and sowed under very favorable condi- 
tions, giving all the nourishment and space re- 
quired to the young seedlings. It is recom- 
mended that they be sown under glass, either in 
a glass-house or protected against cold and rain 
by glass-frames. The same lot of seed will be 
seen to yield twice or thrice as many seedlings 
if thus protected, compared with what it would 
have produced when sown in the field or in the 
garden. I have nearly wholly given up sowing 
seeds in my garden, as circumstances can be 
controlled and determined with greater ex- 
actitude when the sowing is done in a glass- 
house. 

The best proof perhaps, of the unfavorable 
infiuence of external conditions for slightly de- 
teriorated deviations is afforded by variegated 
leaves. Many beautiful varieties are seen in 
our gardens and parks, and even com has a 
variety with striped leaves. They are easily re- 
produced, both by buds and by seeds, and they 
are the most ordinary of all varietal deviations. 
They may be expected to occur wild also. But 
no real variegated species, nor even good 
varieties with this attribute occurs in nature. 



602 


Mutations 


On the other hand occasional specimens with a 
single variegated leaf, or with some few of them, 
are actually met wilh, and if attention is once 
drawn to this question, perhaps a dozen or so 
instances might be brought together in a sum- 
mer. But they never seem to be capable of 
further evolution, or of reproducing themselves 
sufficiently and of repeating their peculiarity in 
their progeny. They make their appearance, 
are seen during a season, and then disappear. 
Even this slight incompleteness of some spots 
on one or two leaves may be enough to be their 
doom. 

It is a common belief that new varieties owe 
their origin to the direct action of external 
conditions and moreover it is often assumed that 
similar deviations must have similar causes, and 
that these causes may act repeatedly in the same 
species, or in allied, or even systematically dis- 
tant genera. No doubt in the end all things 
must have their causes, and the same causes 
will lead under the same circumstances to the 
same results. But we are not justified in deduc- 
ing a direct relation between the external con- 
ditions and the internal changes of plants. 
These relations may be of so remote a nature 
tiiat they cannot as yet be guessed at. There- 
fore only direct experience may be our guide. 

Summing up the result of our facts and dis- 



Origin of Wild Species 


603 


cussions we may state that wild new elementary 
species and varieties are recorded to have 
appeared from time to time. Invariably this 
happened by sudden leaps and without interme- 
diates. The mutants are constant when prop- 
agated by seed, and at once constitute a new 
race. In rare instances this may be of sufficient 
superiority to win a place for itself in nature, 
but more often it has qualities which have led to 
its introduction into gardens as an ornamental 
plant or into botanical gardens by reason of the 
interest afforded by their novelty, or by their 
anomaly. 

Many more mutations may be supposed to be 
taking place all around us, but artificial sowings 
on a large scale, combined with a close exam- 
ination of the seedlings and a keen appreciation 
of the slightest indications of deviation seem 
required to bring them to light. 



Lectubes XXI 


MUTATIONS IN HOETICULTUBE 

It is well known that Darwin based his theory 
of natural selection to a large extent upon the 
experience of breeders. Natural and artificial 
selection exhibit the same general features, yet 
it was impossible in Darwin's time to make a 
critical and comparative analysis of the two 
processes. 

In accordance with our present conception 
there is selection of species and selection within 
the species. The struggle for life determines 
which of a group of elementary species shall sur- 
vive and which shall disappear. In agricultural 
practice the corresponding process is usually 
designated by the name of variety-testing. 
Within the species, or within the variety, the 
sieve of natural selection is constantly eliminat- 
ing poor specimens and preserving those that 
are best adapted to live under the given condi- 
tions. Some amelioration and some local races 
are the result, but this does not appear to be of 

much importance. On the contrary, the selec- 

604 



Mutations in Horticulture 


605 


tion within the race holds a prominent place in 
agriculture, where it is known by the imposing 
term, race-breeding. 

Experience and methods in horticulture differ 
from those in agriculture in many points. 
Garden-varieties have been tested and separated 
for a long time, but neither vegetables nor 
flowers are known to exhibit such motley groups 
of types as may be seen in large forage crops. 

New varieties which appear from time to time 
may be ornamental or otherwise in flowers, and 
more or less profitable than their parents in 
vegetables and fruits. In either case the dif- 
ference is usually striking, or if not, its culture 
would be unprofitable. 

The recognition of useful new varieties being 
thus made easy, the whole attention of the 
breeder is reduced to isolating the seeds of the 
mutants that are to be saved and sown separate- 
ly, and this process must be repeated during 
a few years, in order to produce the quantity of 
seed that is needed for a profitable introduction 
of the variety into commerce. In proportion to 
the abundance of the harvest of each year this 
period is shorter for some and longer for other 
species. 

Isolation in practice is not so simple nor so 
easy an affair as it is in the experimental gar- 
den. Hence we have constant and nearly un- 



606 


Mutations 


avoidable cross-fertilizations with the parent- 
form, or with neighboring varieties, and conse- 
quent imparity of the new strain. This impurity 
we have called vicinism, and in a previous lec- 
ture have shown its effects upon the horticul- 
tural races on one hand, and on the other, on the 
scientific value that can be ascribed to the ex- 
I)erience of the breeder. We have established 
the general rule that stability is seldom met 
with, but that the observed instability is always 
open to the objection of being the result of vicin- 
ism. Often this last agency is its sole cause; 
or it may be complicated with other factors 
[without our being able to discern them. 

Though our assertion that the practice of the 
horticulturist in producing new varieties is lim- 
ited to isolation, whenever chance affords them, 
is theoretically valid, it is not always so. We 
may discern between the two chief groups of 
varieties. The retrograde varieties are con- 
stant, the individuals not differing more frtoi 
one another than those of any ordinary species. 
The highly variable varieties play an important 
part in horticulture. Double flowers, striped 
flowers, variegated leaves and some others yield 
the most striking instances. Such forms have 
been included in previous lectures among the 
ever-sporting varieties, because their peculiar 
diaracters oscillate between two extremes, viz. : 



Mutations m Horticulture 607 

the new one of the variety and the correspond- 
ing character of the original species. 

In such cases isolation is usually accompanied 
by selection: rarely has the first of a double, 
striped or variegated race well filled or richly 
striped flowers or highly spotted leaves. 
Usually minor degrees of the anomaly are seen 
first, and the breeder expects the novelty to de- 
velop its features more completely and more 
beautifully in subsequent generations. Some 
varieties need selection only in the beginning, 
in others the most perfect specimens must 
be chosen every year as seed-bearers. For 
striped flowers, it has been prescribed by Vil- 
morin, that seeds should be taken only from 
those with the smallest stripes, because there is 
always reversion. Mixed seed or seed from 
medium types would soon yield plants with too 
broad stripes, and therefore less diversified 
flowers. 

In horticulture, new varieties, both retrograde 
and ever-sporting, are known to occur almost 
yearly. Nevertheless, not every novelty of the 
gardener is to be considered as a mutation in 
the scientific sense of the word. First of all, 
the novelties of perennial and woody species are 
to be excluded. Any extreme case of fluctuat- 
ing variability may be preserved and multiplied 
in the vegetative way. Such types are desig- 



608 


Mutations 


nated in horticulture as varieties, though ob- 
viously they are of quite another nature than 
the varieties reproduced by seed. Secondly, a 
large number, no doubt the greater number 
of novelties, are of hybrid origin. Here we 
may discern two cases. Hybrids may be 
produced by the crossing of old types, either 
of two old cultivated forms or newly intro- 
duced species, or ordinarily between an old 
and an introduced variety. Such novelties are 
excluded from our present discussion. Sec- 
ondly, hybrids may be produced between a true, 
new mutation and some of the already existing 
varieties of the same species. Examples of this 
obvious and usual practice will be given further 
on, but it must be pointed out now that by such 
crosses a single mutation may produce as many 
novelties as there are available varieties of the 
same species. 

Summarizing these introductory remarks we 
must lay stress on the fact that only a small part 
of the horticultural novelties are real mutations, 
although they do occur from time to time. If 
useful, they are as a rule isolated and multiplied, 
and if necessary, improved by selection. They 
are in many instances, as constant from seed as 
the unavoidable influence of vicinism allows 
them to be. Exact observations on the origin, 
or on the degree of constancy, are usually lack- 



Mutations in Horticulture 


609 


ing, the notes being ordinarily made for com- 
mercial purposes, and often only at the date of 
introduction into trade, when the preceding 
stages of the novelty may have been partly for- 
gotten. 

With this necessary prelude I will now give a 
condensed survey of the historical facts relat- 
ing to the origin of new horticultural varieties. 
An ample description has been given recently 
by Korshinsky, a Russian writer, who has 
brought together considerable historical mate- 
rial as evidence of the sudden appearance of 
novelties throughout the whole realm of garden- 
plants. 

The oldest known, and at the same time one 
of the most accurately described mutations is 
the origin of the cut-leaved variety of the 
greater celandine or Chelidonium majus. This 
variety has been described either as such, or as 
a distinct species, called Chelidonium laciniatum 
Miller. 

It is distinguished from the ordinary species, 
by the leaves being cut into narrow lobes, with 
almost linear tips, a character which is, as we 
have seen on a previous occasion, repeated in 
the petals. It is at present nearly as commonly 
cultivated in botanical gardens as the C. majus, 
and has escaped in many localities and is ob- 
served to thrive as readily as the native wild 



610 


Mutations 


plants. It was not known until a few years be- 
fore the close of the 16th century. Its history 
has been described by the French botanist, Bose. 

It was seen for the first time in the garden of 
Sprenger, an apothecary of Heidelberg, where 
the C, majus had been cultivated for many 
years. Sprenger discovered it in the year 1590, 
and was struck by its peculiar and sharply de- 
viating characters. He was anxious to know 
whether it was a new plant and sent specimens 
to Olusius and to Plater, the last of whom 
transmitted them to Caspar Bauhin. These 
botanists recognized the type as quite new and 
Bauhin described it some years afterwards in 
his Phytopinax under the name of Chelidonium 
majus foliis quernis, or oak-leaved celandine. 
The new variety soon provoked general interest 
and was introduced into most of the botanical 
gardens of Europe. It was recognized as quite 
new, and repeated search has been made for it 
in a wild state, but in vain. No other origin 
has been discovered than that of Sprenger ’s 
garden. Afterwards it became naturalized in 
England and elsewhere, but there is not the 
least doubt as to its derivation in all the ob- 
served cases. 

Hence its origin at Heidelberg is to be con- 
sidered as historically proven, and it is of course 
only legitimate to assume that it originated in 



Mutations in Horticulture 


611 


the year 1590 from the seeds of the C. majus. 
Nevertheless, this was not ascertained by 
Sprenger, and some doubt as to a possible intro- 
duction from elsewhere might arise. If not, 
then the mutation must have been sudden, oc- 
curring without visible preparation and without 
the appearance of intermediates. 

From the very first, the cut-leaved celandine 
has been constant from seed. Or at least it has 
been propagated by seed largely and without 
difficulty. Nothing, however, is known about it 
in the first few years of its existence. Later 
careful tests were made by Miller, Eose and 
others and later by myself, which have shown 
its stability to be absolute and without rever- 
sion, and it has probably been so from the begin- 
ning. The fact of its constancy has led to its 
specific distinction by Miller, as varieties 
were in his time universally, and up to the pres- 
ent time not rarely, though erroneously, be- 
lieved to be less stable than true species. 

Before leaving the laciniate celandine it is to 
be noted that in crosses with C. majus it follows 
the law of Mendel, and for this reason should 
be considered as a retrograde variety, the more 
so, as it is also treated as such from a mor- 
phological point of view by Stahl and others. 

We now come to an enumeration of those 
cases in which the date of the first appearance 



612 


Mutations 


of a new horticultural variety has been record- 
ed, and I must apologize for the necessity of 
again quoting many variations, which have pre- 
viously been dealt with from another point of 
view. In such cases 1 shall limit myself as 
closely as possible to historical facts. They have 
been recorded chiefly by Verlot and Carriere, 
who wrote in Paris shortly after the middle of 
the past century, and afterwards by Darwin, 
Korshinsky, and others. It is from their writ- 
ings and from horticultural literature at large 
that the following evidence is brought together. 

A very well-known instance is that of the 
dwarf variety of Tagetes sipwofa, which arose in 
the nursery of Vilmorin in the year 1860. It 
was observed for the first time in a single indi- 
vidual among a lot of the ordinary Tagetes sig- 
nata. It was found impossible to isolate it, but 
the seeds were saved separately. The majority 
of the offspring returned to the parental type, 
but two plants were true dwarfs. From these 
the requisite degree of purity for commercial 
purposes was reached, the vicinists not being 
more numerous than lOj^ of the entire number. 
The same mutation had been observed a year 
earlier in the same nursery in a lot of Saponaria 
calahrica. The seeds of this dwarf repeated the 
variety in the next generation, but in the third 
none were observed. Then the variety was 



Mutations in Horticulture 


613 


thought to be lost, and the culture was given up, 
as the Mendelian law of the splitting of varietal 
hybrids was not known. According to our pres- 
ent knowledge we might expect the atavistic de- 
scendants of the first dwarf to be hybrids, and 
to be liable to split in their progeny into one- 
fourth dwarfs and three-fourths normal speci- 
mens. From this it is obvious that the dwarfs 
would have appeared a second time if the strain 
had been continued by means of the seeds of the 
vicinistic progeny. 

In order to avoid a return to this phase of the 
question, another use of the vicinists should at 
once be pointed out. It is the possibility of in- 
creasing the yield of the new variety. If space 
admits of sowing the seeds of the vicinists, a 
quarter of the progeny may be expected to come 
true to the new type, and if they were partly 
pollinated by the dwarfs, even a larger number 
would do so. Hence it should be made a rule to 
sow these seeds also, at least when those of the 
true representatives of the novelty do not give 
seed enough for a rapid multiplication. 

Other dwarfs are recorded to have sprung 
from species in the same sudden and unexpected 
manner, as for instance Ageratum coeruleum of 
the same nursery, further Clematis ViticeUa 
nana and Acer campestre nanum. Prunus Ma- 
haleb nana was discovered in 1828 in one 



614 


Mutations 


specimen near Orleans by Mme LeBrun in a 
large culture of Mahaleh. Lonicera toitar- 
ica nana appeared in 1825 at Fontenay-aux- 
Boses. A tall variety of the strawberry is 
called “ Giant of Zuidwijk ” and originated at 
Boskoop in Holland in the nursery of Mr. van 
de Water, in a lot of seedlings of the ordinary 
strawberry. It was very large, but produced 
few runners, and was propagated with much dif- 
ficulty, for after six years only 15 plants were 
available. It proved to be a late variety with 
abundant large fruit, and was sold at a high 
price. For a long time it was prominent in 
cultures in Holland only. 

Varieties without prickles are known to have 
originated all of a sudden in sundry cases. 
Gleditschia sinensis, introduced in 1774 from 
China, gave two seedlings without spines in the 
year 1823, in the nursery of Oaumzet. It is 
curious in being one of the rare instances where 
a simultaneous mutation in two specimens is 
acknowledged, because as a rule, such records 
comply with the prevailing, though inexact, be- 
lief that horticultural mutations always appear 
in single individuals. 

From Korshinsky^s survey of varieties with 
cut leaves or laciniate forms the following cases 
may be quoted. In the year 1830 a nurseryman 
named Jacques had sown a large lot of elms. 



Mutations in Horticulture 


615 


TJlmus pedunculata. One of the seedlings had 
cut leaves. He multiplied it by grafting and 
gave it to the trade under the name of Z7. 
pedunculata urticaefolia. It has since been 
lost 

Laciniate alders seem to have been produced 
by mutation at sundry times. Mirbel says that 
the Alnus glutinosa laciniata is found wild in 
Normandy and in the forests of Montmorency 
near Paris. A similar variety has been met 
with in a nursery near Orleans in the year 1855. 
In connection with this discovery some discus- 
sion has arisen concerning the question whether 
it was probable that the Orleans strain was a 
new mutation, or derived in some way from the 
trees cited by Mirbel. • Of course, as always in 
such cases, any doubt, once pronounced, affects 
the importance of the observation for all time, 
since it is impossible to gather sufficient his- 
torical evidence to fully decide the point. The 
same variety had appeared under similar cir- 
cumstances in a nursery at Lyons previously 
(1812). 

Laciniated maples are said to be of relatively 
frequent occurrence in nurseries, among seed- 
lings of the typical species. London says that 
once 100 laciniated seedlings were seen to orig- 
inate from seed of some normal trees. But in 
this case it is rather probable that the presumed 



616 


Mutations 


normal parents were in reality hybrids between 
the type and the laciniated form, and simply 
split according to Mendel’s law. This hy- 
pothesis is partly founded on general consider- 
ations and partly on experiments made by my- 
self with the cut-leaved celandine, previously 
alluded to, which I crossed with the type. The 
hybrids repeated the features of the species and 
showed no signs of their internal hybrid con- 
stitution. But the following year one-fourth 
of their progeny returned to the cut-leaved 
form. If the same thing has taken place in the 
case of Loudon’s maples, hut without their 
hybrid origin being known, the result would 
have been precisely what he observed. 

Broussonetia papyrifera dissecta originated 
about 1830 at Lyons, and a second time in 1866 
at Fontenay-aux-Eoses. The cut-leaved hazel- 
nuts, birches, beeches and others have mostly 
been found in the wild state, as I have already 
pointed out in a previous lecture. A similar 
variety of the elder, Sambucus nigra laciniata, 
and its near ally, Sambucus raccmosa laciniata, 
are often to be seen in our gardens. They have 
been on record since 1886 and come true from 
seed, but their exact ori^ seems to have been 
forgotten. Cut-leaved walnuts have been known 
since 1812; they come true from seed, but are 
extrmnely liable to vicinism, a nuisance which is 



Mutations in Horticulture 


617 


ascribed by some authors to the fact that often 
on the same tree the male catkins flower and faU 
olf several weeks before the ripening of the 
pistils of the other form of flowers. 

Weeping varieties afford similar instances. 
SopJiora japonica pendula originated about 
1850, and Gleditschia triacanthos pendula some 
time later in a nursery at Chateau-Thierry 
(Aisne, France). In the year 1821 the bird’s 
cherry, or Prunus Padus, produced a weeping 
variety, and in 1847 the same mutation was ob- 
served for the allied Prunus Mahaleh. Numer- 
ous other instances of the sudden origin of 
weeping trees, both of conifers and of others, 
have been brought together in Korshinsky’s 
paper. This striking type of variation includes 
perhaps the best examples of the whole his- 
torical evidence. As a rule they appear in large 
sowings, only one, or only a few at a time. Many 
of them have not been observed during their 
youth, but only after having been planted out 
in parks and forests, since the weeping charac- 
ters show only after several years. 

The monophyllous bastard-acacia originated 
in the same way. Its peculiarities will be dealt 
with on another occasion, but the circumstances 
of its birth may as well be given here. In 1855 
in the nursery of Deniau, at Brain-sur-l’Au- 
thion (Maine et Loire), it appeared in a lot of 



618 


Mutations 


seedlmgB of the typical species in a single in- 
dividnal. This was transplanted into Ihe Jar- 
din des Plantes at Paris, where it flowered and 
bore seeds in 1865. It must have been partly 
pollinated by the surrounding normal repre- 
sentatives of the species, since the seeds yielded 
only one-fourth of true offspring. This propor- 
tion, however, has varied in succeeding years. 
.Briot remarks that the monophyllous bastard- 
acacia is liable to petaloid alterations of its 
stamens, which deficiency may encroach upon 
its fertility and accordingly upon the purity of 
its offspring. 

Broom-like varieties often occur among trees, 
and some are known for their very striking re- 
versions by buds, as we have seen on a previous 
occasion. They are ordinarily called pyramidal 
or fastigiate forms, and as far as theif history 
goes, they arise suddenly in large sowings 
of the normal species. The fastigiate birch was 
produced in this way by Baumann, the Abies 
concolor fastigiata by Thibault and Keteleer at 
Paris, the pyramidal cedar by Paillat, the analo- 
gous form of WelUngtonia by Otin. Other in- 
stances could easily be added, though of course 
some of the most highly prized broom-like trees 
are so old that nothing is known about their 
origin. This, for instance, is the case with the 
pyramidal yew-tree, Taxus baceata fastigiata. 



Mutations in Horticulture 


619 


Others have been found wild, as already men- 
tioned in a former lecture. 

An analogous case is afforded by the purple- 
leaved plums, of which the most known form is 
Prunus Pissardi. It is said to be a purple va- 
riety of Prunus cerasifera, and was introduced 
at the close of the seventies from Persia, where 
it is said to have been found in Tabris. A simi- 
lar variety arose independently and unex- 
pectedly in the nursery of Spath, near Berlin, 
about 1880, but it seems to differ in some minor 
points from the Persian prototype. 

A white variety of Cyclamen vernum made its 
appearance in the year 1836 in Holland. A sin- 
gle individual was observed for the first time 
among a large lot of seedlings, in a nursery near 
Haarlem. It yielded a satisfactory amount of 
seed, and the progeny was true to the new type. 
Such plants propagate slowly, and it was only 
twenty-seven years later (1863) that the bulbs 
were offered for sale by the Haarlem firm of 
Krelage & Son. The price of each bulb was 
$5.00 in that year, but soon afterwards was re- 
duced to $1.00 each, which was about thrice the 
ordinary price of the red variety. 

The firm of Messrs. Krelage & Son has 
brought into commerce a wide range of new 
bulb-varieties, all due to occasional mutations, 
some by seed and others by buds, or to the acci- 



620 


Mutations 


dental transference of new qualities into the 
already existing varieties by cross-pollination 
through the agency of insects. Instead of giv- 
ing long lists of these novelties, I may cite the 
black tulips, which cost during the first few 
years of their introduction about $25.00 apiece. 

Horticultural mutations are as a rule very 
rare, especially in genera or species which have 
not yet been brought to a high degree of varia- 
bility. In these the wide range of varieties and 
the large scale in which they are multiplied of 
course give a greater chance for new varieties. 
But then the possibilities of crossing are like- 
wise much larger, and apparent changes due to 
this cause may easily be taken for original mu- 
tations. 

The rarity of the mutations is often proved 
by the lapse of time between the introduction 
of a species and its first sport. Some instances 
may be given. They afford a proof of the length 
of the period during which the species remained 
unaltered, although some of these alterations 
may be due to a cross with an allied form. 
Eryfhrina Crista-gaUi was introduced about 
1770, and produced its first sport in 1884, after 
more than a century of cultivation. Begonia 
semperflorens has been cultivated since 1829, 
and for half a century before it commenced 
sporting. The same length of time has elapsed 



Mutations in Horticulture 


621 


between the first culture and the first variation 
of Cramhe mariti/ma. Other cases are on rec- 
ord in which the variability exhibited itself 
much sooner, perhaps within a few years after 
the original discovery of the species. But such 
instances seem, as a rule, to be subject to doubt 
as to the concurrence of hybridization. So for 
instance the Iris lortetii, introduced in the year 
1895 from the Lebanon, which produced a white 
variety from its very first seeds. If by chance 
the introduced plants were natural hybrids be- 
tween the species and the white variety, this ap- 
parent and rather improbable mutation would 
find a very simple explanation. The length of 
the period preceding the first signs of variability 
is largely, of course, due to divergent methods 
of culture. Such species as Erythrina, which 
are perennial and only sown on a small scale, 
should not be expected to show varieties very 
soon. Annual species, which are cultivated 
yearly in thousands or even hundreds of thou- 
sands of individuals, have a much better chance. 
Perhaps the observed differences are largely 
due to this cause. 

Monstrosities have, from time to time, given 
rise to cultivated races. The cockscomb or 
Celosia is one of the most notorious instances. 
Cauliflowers, turnips and varieties of cabbages 
are recorded by De Candolle to have arisen in 



622 


Mutations 


culture, more than a century ago, as isolated 
monstrous individuals. They come true from 
seed, but show deviations from time to time 
which seem to be intimately linked with their 
abnormal characters. Apetalous flowers may 
be considered as another form of monstrosity, 
and in Salpiglossis sinuata such a variety with- 
out a corolla made its appearance in the year 
1892 in the nursery of Vilmorin. It appeared 
suddenly, yielded a good crop of seed and 
was constant from the outset, without any sign 
of vicinism or impurity. 

In several cases the origin of a variety is ob- 
scure, while the subsequent historical evidence 
is sudi as to make an original sudden appear- 
ance quite probable. Although these instances 
offer but indirect evidence, and will sooner or 
later lose their importance, it seems desirable 
to lay some stress on them here, because most of 
these cases are very obvious and more striking 
than purely historical facts. Sterile varieties 
belong to this heading. Sometimes they bear 
fruit without kernels, sometimes flowers with- 
out sexual organs, or even no flowers at all. In- 
stances have been given in the lecture on 
retrograde varieties; they are ordinarily as- 
sumed to have originated by a leap, because it is 
not quite clear how a loss of the capacity for the 
formation of seeds could have been slowly accu- 



Mutations in Horticulture 623 

mulated in preceding generations. An interest- 
ing case is afforded by a sterile variety of com, 
which originated some time ago in my own pedi- 
gree-cultnres made for another purpose, and 
which had begun with an ear of 1886. The first 
generation from the original seeds showed noth- 
ing particular, but the second at once produced 
quite a number of sterile plants. The sterility 
was caused by the total lack of branches, includ- 
ing those bearing the pistillate flowers. The 
terminal spikes themselves were reduced to 
naked spindles, without branches, without flow- 
ers and even almost without bracts. 

In some individuals, however, this negative 
character was seen to give way at the tip, show- 
ing a few small naked branches. Of course it 
was impossible to propagate this curious form, 
but my observations showed that it sprang into 
existence from known ancestors by a single step 
or sudden leap. This leap, however, was not 
confined to a single specimen; on the contrary 
it affected 40 plants out of a culture of 340 
individuals. The same phenomenon was re- 
peated from the seeds of the normal plants in 
the following year, but afterwards the mon- 
strosity disappeared. 

The Italian poplar affords another instance. 
It is considered by some authors as a distinct 
species, Populus italica, and by others as a 



624 


Mitiations 


broom-like variety of the Popuhis nigra, from 
which it is distinguished by its erect branches 
and other characters of minor importance. It 
is often called the pyramidal or fastigiate 
poplar. Its origin is absolutely unknown and 
it occurs only in the cultivated state. In Italy 
it seems to have been cultivated from the 
earliest historical times, but it was not intro- 
duced into other countries till the eighteenth 
century. In 1749 it was brought into France, 
and in 1758 into England, and to-day it 
may be seen along roads throughout cen- 
tral Europe and in a large part of Asia. But 
the most curious fact is that it is only observed 
in staminate specimens ; pistiUate trees have not 
been found, although often sought for. This 
circumstance makes it very probable that the 
origin of the broom-like poplar was a sudden 
mutation, producing only one individual. This 
being staminate, it has been propagated ex- 
clusively by cuttings. It is to be admitted, 
however, that no material evidence is at hand 
to prove that it is not an original wild species, 
the pistillate form of which has been lost by 
vegetative multiplication. One form only of 
many dioecious plants is to be found in cultiva- 
tion, as for instance some South American 
species of Rites. 

Total lack of historical evidence concerning 



Mutations in Horticulture 


625 


the origin of a variety has sometimes been con- 
sidered as sufficient proof of a sudden origin. 
The best known instance is that of the renowned 
cactus-dahlia with its recurved instead of in- 
curved ray-florets. It was introduced from 
Mexico into the Netherlands by Van den Berg of 
Jutphaas, under the following remarkable cir- 
cumstances. In the autumn of 1872 one of his 
friends had sent him a small case, containing 
seeds, bulbs and roots from Mexico. From 
one of these roots a Dahlia shoot developed. 
It was cultivated with great care and bloomed 
next year. It surprised all who saw it by 
the unexpected peculiarity of its large rich 
crimson flowers, the rays of which were re- 
versed tubular. The margins of the narrow 
rays were curved backwards, showing the bright 
color of the upper surface. It was a very 
showy novelty, rapidly multiplied by cuttings, 
and was soon introduced into commerce. It has 
since been crossed with nearly all other avail- 
able varieties of the Dahlia, giving a large and 
rich group of forms, bound together by the 
curious curling of the petals. It has never been 
observed to grow in Mexico, either wild or in 
gardens, and thus the introduced individual has 
come to be considered as the first of its race. 

I have already mentioned that the rapid pro- 
duction of large numbers of new varieties, by 



626 


Mutations 


means of the crossing of the offspring of a 
single mutant with previously existing sorts, is 
a very oonunon feature in horticultural prac- 
tice. It warns us that only a small part of the 
novelties introduced yearly are due to real mu- 
tations. Further instances of novelties with 
such a common origin are the purple-leaved 
dahlias, the gooseberries without prickles, the 
double petunias, erect gloxinias and many 
others. Accumulation of characters, acquired 
in different races of a species, may easily be 
effected in this way; in fact it is one of the im- 
portant factors in the breeding of horticultural 
novelties. 

I have alluded more than once in this lecture 
to the question, whether it is probable that mu- 
tations occur in one individual or in more. 
The common belief among horticulturists is 
that, as a rule, they appear in a single plant. 
This belief is so widespread that whenever a 
novelty is seen for the first time in two or more 
specimens it is at once suggested that it might 
have originated and been overlooked in a previ- 
ous generation. Not caring to confess a lack 
of dose observation, the number of mutants 
in such cases is usually kept secret. At least 
this statement has been made to me by some of 
the horticulturists at Erfurt, whom I visited 
some years ago in order to learn as much as 



Mutations in Horticulture 627 

possible abont the methods of production of 
their novelties. Hence it is simply impossible 
to decide the question on the basis of the ex- 
perience of the breeders. Even in the case of the 
same novelty arising in sundry varieties of the 
same species, the question as to common origin, 
by means of crossing, is often hard to decide, 
as for instance in moss-roses and nectarines. 
On the other hand, instances are on record 
where the same novelty has appeared at differ- 
ent times, often at long intervals. Such is the 
case with the butterfly-cyclamen, a form with 
wide-spreading petals which originated in 
Martin’s nursery in England. The first time it 
was seen it was thought to be of no value, and 
was thrown away, but when appearing for a 
second time it was multiplied and eventually 
placed on the market. Other varieties of Cycla- 
men, as for instance the crested forms, are also 
known to have originated repeatedly. 

In concluding this series of examples of hor- 
ticultural mutations, I might mention two 
cases, which have occurred in my own experi- 
mental garden. The first refers to a tubular 
dahlia. It has ray-florets, the ligules of which 
have their margins grown together so as to 
form tubes, with the outer surface correspond- 
ing to the pale under-surface of the corolla. 

This novelty originated in a single plant in a 



628 


Mutations 


culture from the seed of the dwarf variety 
“ Jules Chretien.” The seeds were taken from 
introduced plants in my garden, and as the 
sport has no ornamental value it is uncertain 
whether this was the first instance or whether 
it had previously occurred in the nursery at 
Lyons, from whence the bulbs were secured. 
Afterwards it proved true from seed, hut was 
very variable, exhibiting rather the features of 
an ever-sporting variety. 

Another novelty was seen the first time in 
several individuals. It was a pink sport of the 
European, cranesbill. Geranium pratense. It 
arose quite unexpectedly in the summer of 1902 
from a striped variety of the blue species. It 
was seen in seven specimens out of a lot of about 
a hundred plants. This strain was introduced 
into my garden in 1897, when I bought two 
plants under the name of Geranium pratense 
album, which however proved to belong to the 
striped variety. From their seeds I sowed in 
1898 a first generation, of which a hundred 
plants flowered the next year, and from their 
seeds I sowed in 1900 the lot which produced 
the sport. Neither the introduced plants nor 
their offspring had exhibited the least sign of a 
color-variation, besides the blue and white 
stripes. Hence it is very probable that my nov- 
elty was a true first mutation, the more prob- 



Mutations in Horticulture 


629 


ably so since a pink variety would without doubt 
have a certain horticultural value and would 
have been preserved if it had occurred. But as 
far as I have been able to ascertain, it is as yet 
unknown, nor has it been described until to-day. 

Summing up the results of this long, though 
very incomplete, list of horticultural novelties 
with a more or less well-known origin, we see 
that sudden appearances are the rule. Having 
once spnmg into existence the new varieties are 
ordinarily constant, except as affected by 
vicinism. Details concerning the process are 
mostly unavailable or at least are of very doubt- 
ful value. And to this it should be added that 
really progressive mutations have hardly been 
observed in horticulture. Hence the theoretical 
value of the facts is far less than might have 
been expected. 



Leotubb XXII 


8TSTEMATI0 ATAVISM 

The steady cooperation of progression and re- 
trogression is one of the important principles 
of organic evolution. I have dwelt upon this 
point more than once in previous lectures. I 
have tried to show that both in the more im- 
portant lines of the general pedigree of the 
vegetable kingdom, and in the numerous lateral 
branches ending in the genera and species virith- 
in the families, progression and retrogression 
are nearly always at work together. Your at- 
tention has been directed to the monocotyledons 
as an example, where retrogression is every- 
where so active that it can almost be said to be 
the prevailing movemmit. Seduction in the veg- 
etative and generative organs, in the anatomical 
structure and growth of the stems, and in sun- 
dry other ways is the method by which the 
monocotyledons have originated as a group 
from their supposed ancestors among the lower 
dicotyledonous families. Betrogression is the 
leading idea in the larger families of the group, 

630 



Systematic Atavism .631 

as for instance in the aroids and the grasses. 
Retrograde evolution is also typical in the high- 
est and most highly differentiated family of the 
monocotyledons, the orchids, which have but 
one or two stamens. In the second place I have 
had occasion more than once to assert that retro- 
gression, though seemingly consisting in the 
disappearance of some quality, need not, as a 
rule, be considered as a complete loss. Quite on 
the contrary, it is very probable that real losses 
are extremely rare, if not wholly lacking. Ordi- 
narily the loss is only apparent, the capacity 
becomes inactive only, but is not destroyed. The 
character has become latent, as it is commonly 
stated, and therefore may return to activity and 
to the full display of its peculiarity, whenever 
occasion offers. 

Such a return to activity was formerly called 
atavism. But as we have seen, when dealing 
with the phenomena of latency at large, sundry 
cases of latency are to be distinguished, in order 
to get a clear insight into these difficult proc- 
esses. 

So it is with atavism, too. If any plant re- 
verts to a known ancestor, we have a positive 
and simple case. But ancestors with alternate 
specific marks are as a rule neither historically 
nor experimentally manifest. They are only 
reputed to be such, and the presumption rests 



632 


Mutations 


upon the systematic affinity between the deriva- 
tive species and its nearest probable allies. 
Such reversions are now to be examined at some 
length and may be adequately treated under the 
head of systematic atavism. To this form of 
atavism pertain, on the basis of our definition, 
those phenomena by which species assume one 
or more characters of allies, from which they 
are understood to have descended by the loss of 
the character under discussion. The phenom- 
ena themselves consist in the production of 
anomalies and varieties, and as the genetic 
relation of the latter is often hardly beyond 
doubt, the anomalies seem to afford the best in- 
stances for the study of systematic atavism. 
This study has for its chief aim the demonstra- 
tion of the presence of the latent characters, and 
to show that they return to activity suddenly 
and not by a slow and gradual recovery of the 
former features. It supports the assertion 
that the visible elementary characters are es- 
sentially an external display of qualities carried 
by the bearers of heredity, and that these 
bearers are separate entities, which may be 
mingled together, but are not fused into a 
chaotic primitive life-substance. Systematic 
atavism by this means leads us to a closer ex- 
amination of the internal and concealed causes, 
which rule the affinities and divergencies of 



Systematic Atavism 633 

allied species. It brings before us, and empha- 
sizes the importance of the conception of the 
so-called unit-characters. 

The primrose will serve as an example. In 
the second lecture we have seen that the old 
species of Linnaeus, the Primula veris, was 
split up by Jacquin into three smaller ones, 
which are called P. oificinalis, P. elatior and P. 
acaulis. From this systematic treatment we 
can infer that these three forms are assumed to 
be derived from a common ancestor. Now two 
of them bear their flowers in bracted whorls, 
condensed into umbels at the summits of a scape. 
The scapes themselves are inserted in the axils 
of the basal leaves, and produce the flowers 
above them. In the third species. Primula 
acaulis, this scape is lacking and the flowers are 
inserted singly in the axils on long slender 
stalks. For this reason the species is called 
acaulescent, indicating that it has no other 
stem than the subterranean rootstock. But on 
closer inspection we observe that the flower- 
stalks are combined into little groups, each 
group occupying the axil of one of the basal 
leaves. This fact at once points to an analogy 
with the umbellate allies, and induces us to ex- 
amine the insertion of the flowers more crit- 
ically. In doing so we find that they are united 
at their base so as to constitute a sessile umbel. 



634 


Mutations 


The scapes are not absolutely lacking, but only 
reduced to almost mvisible rudiments. 

Belying upon this conclusion we infer that all 
of the three elementary species have umbels, 
some pedunculate and the others not On this 
point they agree with the majority of tiie allied 
spemes in the genus and in other genera, as for 
instance in Androsace. Hence the conclusion 
that the common ancestors were perennial 
plants with a rootstock bearing their flowers 
in umbels or whorls on scapes. Lacking in the 
Primula vem, these scapes must obviously have 
been lost at the time of the evolution of this 
form. 

Proceeding on this line of speculation we at 
once see that a very adequate opportunity for 
systematic atavism is offered here. According 
to our general conception the apparent loss of a 
scape is no proof of a corresponding internal 
loss, but might as well be caused simply by 
the reduction of the scape-growing capacity to 
a latent or inactive state. It might be awak- 
ened afterwards by some unknown agency, and 
return to activity. 

Now this is exactly what happens from time 
to time. In Holland the acaulescent primrose 
is quite a common plant, filling the woods in the 
spring with thousands of clusters of bright yel- 
low flowers. It is a very uniform type, but in 



Systematic Atavism 


635 


some years it is seen to return to atavistic con- 
ditions in some rare individuals. More than 
once I have observed such cases myself, and 
found that the variation is only a partial one, 
producing one or rarely two umbels on the same 
plant, and liable to fail of repetition when the 
varying specimens are transplanted into the 
garden for further observation. But the fact 
remains that scapes occur. The scapes them- 
selves are of varying length, often very short, 
and seldom long, and their umbels display the 
involucre of bracts in a manner quite analogous 
to that of the Primula officinalis and P. elatior. 
To my mind this curious anomaly strongly sup- 
ports the view of the latent condition of the 
scape in the acaulescent species, and that such a 
dormant character must be due to a descent 
from ancestors with active scapes, seems to be in 
no need of further reiteration. Beiuming to 
activity the scapes at once show a full develop- 
ment, in no way inferior to that of the allied 
forms, and only unstable in respect to their 
length. 

A second example is afforded by the bracts 
of the crucifers. This group is easily distin- 
guished by its cruciform petals and the group- 
ing of the flowers into long racemes. In other 
families each flower of such an inflorescence 
would be subtended by a bract, according to the 



636 


Mutations 


general mle that in the higher plants side 
branches are situated in the axils of leaves. 
Bracts are reduced leaves, but the spikes of the 
crudferouB plants are generally devoid of 
than. The flower-stalks, with naked bases, 
seem to arise from the common axis at indefinite 
points. 

Hence the inference that crucifers are an ex- 
ception to a general mle, and that they must 
have originated from other types which did 
comply with this rule, and accordingly were in 
the possession of fioral bracts. Or, in other 
words, that the bracts must have been lost dur- 
ing the original evolution of the whole family. 
This conclusion being accepted, the accidental 
re-apparition of bracts within the family must 
be considered as a case of systematic atavism, 
quite analogous to the re-appearance of the 
scapes in the acaulescent primrose. The sys- 
tematic importance of this phenomenon, how- 
ever, is far greater than in the first case, in 
which we had only to deal with a specific char- 
acter, while the abolition of the bracts has be- 
come a feature of a whole family. 

This reversion is observed to take place ac- 
cording to two widely different principles. On 
one hand, bracts may be met with in a few 
stray species, assuming the rank of a specific 
character. On the other hand they may be seen 



Systematic Atavism 


637 


to occur as an anomaly, incompletely developed, 
often very rare and with all the appearance of 
an accidental variation, hut sometimes so com- 
mon as to seem nearly normal. 

Coming now to particular instances, we may 
turn our attention in the first place to the genus 
Sisymbrium. This is a group of about 50 species, 
of wide geographic distribution, among which 
the hedge mustard {S. offidnalis) is perhaps the 
most common of weeds. Two species are re- 
puted to have bracts. Sisymbrium hirsutum and 
S. supinum. Each flower-stalk of their long 
racemes is situated in the axil of such a bract, 
and the peculiarity is quite a natural one, corre- 
sponding exactly to what is seen in the inflor- 
escence of other families. Besides the Sisym- 
brium some sis other genera afford similar 
structures. 

Erucastrum pollichii has been already allud- 
ed to in a former lecture when dealing with the 
same problem from another point of view. As 
previously stated, it is one of the most manifest 
and most easily accessible examples of a latent 
character becoming active through systematic 
atavism. In fact, its bracts are found so often 
as to be considered by some authors as of quite 
normal occurrence. Contrasted with those of 
the above mentioned species of Sisymbrium, 
they are not seen at the base of all the flower- 



638 


Mutaiions 


stalks, bnt are limited to the lowermost part of 
the raceme, adorning a few, often ten or twelve, 
and rarely more flower-stalks. Moreover they 
exhibit a feature which is indicative of the pres- 
ence of an abnormality. They are not all of the 
same size, but decrease in length from the base 
of the raceme upward, and Anally slowly dis- 
appear. 

Besides these rare cases there are quite a 
number of cruciferous species on record, which 
have been observed to bear bracts. Penzig 
in his valuable work on teratology gives a 
list of 33 such genera, many of them repeat- 
ing the anomaly in more than one species. 
Ordinary cabbages are perhaps the best known 
instance, and any unusual abundance of nour- 
ishment, or anomalous cause of growth seems 
to be liable to incite the development of bracts. 
The hedge garlic or garlic mustard (Alliaria), 
the shepherd's purse, the wormseed or Erysi- 
mum cheiranthoides and many others afford 
instances. In my cultures of Heeger’s shep- 
herd’s purse, the new species derived at Lan- 
dau in Germany from the common shepherd’s 
purse, the anomaly was observed to occur more 
than once, showing that the mutation, which 
changed the fruits, had not in the least affected 
this subordinate anomalous peculiarity. In all 
these cases the bracts behave as with the Eru- 



Systematic Atavism 


639 


castrum, being limited to the base of the spike, 
and decreasing in size from the lower flowers 
upward. Connected with these atavistic bracts 
is a feature of minor importance, which how- 
ever, by its almost universal accompaniment of 
the bracts, deserves our attention, as it is indica- 
tive of another latent character. As a rule, the 
bracts are grown together with their axillary 
flower-stalk. This cohesion is not complete, nor 
is it always developed in the same degree. 
Sometimes it extends over a large part of the 
two organs, leaving only their tips free, but on 
other occasions it is limited to a small part of 
the base. But it is very interesting that this 
same cohesion is to be seen in the shepherd’s 
purse, in the wormseed and in the cabbage, as 
well as in the case of the Erucastrum and most 
of the other observed cases of atavistic bracts. 
This fact suggests the idea of a common origin 
for these anomalies, and would lead to the 
hypothesis that the original ancestors of the 
whole family, before losing the bracts, exhibited 
this peculiar mode of cohesion. 

Bracts and analogous organs afford similar 
cases of systematic atavism in quite a number 
of other families. Aroids sometimes produce 
long bracts from various places on their 
spadix, as may be seen in the cultivated 
greenhouse species, Anthurium schereerianum. 



640 Mutations 

Poppies have been recorded to bear bracts 
analogous to the little scales on the flower-stalks 
of the pansies, on the middle of their flower- 
stalks. A similar case is shown by the yellow 
foxglove or Digitalis parviflora. The foxgloves 
as a mle have naked flower-stalks, without the 
two little opposite leafy organs seen in so many 
other instances. The yellow species, however, 
has been seen to produce such scales from time 
to time. The honeysuckle genus is, as a rule, 
devoid of ^e stipules at the base of the petiole, 
but Lonicera etrusca has been observed to 
develop such organs, which were seen to be free 
in some, but in other specimens were adnate 
to the base of the leaf, and even connate with 
those of the opposite leaf. 

Other instances could be given proving that 
bracts and stipules, when systematically lack- 
ing, are liable to reappear as anomalies. In 
doing so, they generally assume the peculiar 
characters that would be expected of them by 
comparison with allied genera in which they are 
of normal occurrence. There can be no doubt 
that their absence is due to an apparent loss, 
resulting from the reduction of a formerly 
active quality to inactivity. Besuming this ef- 
fective state, tile case attains the value and sig- 
nificance accorded to systematic atavism. 

A very curious instance of reduced bracts, de- 



Sjfstematic Atavism 641 

veloping to uniisual size, is afforded by a variety 
of com, which is called Zea Mays cryptosperma, 
or Zea Mays tunicata. In ordinary com the 
kernels are surrounded by small and thin, incon- 
spicuous and membranaceous scales. Invisible 
on the integrate spikes, when ripe, they are 
easily detected by pulling the kernels out. In 
cryptosperma they are so strongly developed as 
to completely hide the kernels. Obviously they 
constitute a case of reversion to the characters 
of some unknown ancestor, since the com is the 
only member of the grass-family with naked 
kernels. The var. tunicata, for this same rea- 
son, has been considered to be the original wild 
form, from which the other varieties of corn 
have originated. But as no historical evidence 
on this point is at hand, we must leave it as it is, 
notwithstanding the high degree of attractive- 
ness attached to the suggestion. 

The horsetail-family may be taken as a fur- 
ther support of our assertion. Some species 
have stems of two kinds, the fertile being 
brownish and appearing in early spring before 
the green or sterile ones. In others the stems 
are all alike, green and crowned with a cone- 
like spike of sporangia-bearing scales. Mani- 
festly the dimorphous cases are to be considered 
as the younger ones, partly because they are 
obvious exceptions to the common mle, and 



642 


Mntations 


partly because the division of labor is indicative 
of a higher degree of evolution. But sometimes 
these dimorphic species are seen to revert to the 
primary condition, developing a fertile cone at 
the summit of the green summer-stmn. 1 have 
had the opportunity of collecting an instance of 
this anomaly on the tall Equisetum telmateja 
in Switzerland, and other cases are on record in 
teratological literature. It is an obvious ex- 
ample of systematic atavism, occurring sud- 
denly and with the full development of all the 
qualities needed for the normal production of 
sporangia and spores. All of these must be 
concealed in a latent condition within the young 
tissues of the green stems. 

More than once I have had occasion to deal 
with the phenomenon of torsions, as exhibited 
by the teasels and some other plants. This 
anomaly has been shown to be analogous to the 
cases described as double adaptations. The 
capacity of evolving antagonistic characters is 
prominent in both. The antagonists are as- 
sumed to lie quietly together while inactive. 
But as soon as evolution calls them into activity 
they become mutually exclusive, because only 
one of them can come to full display in the same 
organ. External influences decide which of the 
two becomes dominant and which remains dor- 
mant. This decision must take place separately 



Systematic Atavism 643 

for each stem and each branch, but as a rule, 
the stronger axes are more liable to furnish 
anomalies than the weaker. 

Exactly the same thing is true of double 
adaptations. Every bud of the water-persi- 
caria may develop either into an erect or into a 
floating stem, according as it is surrounded by 
water or by relatively dry soil. In other cases 
utility is often less manifest, but some use may 
either be proved, or shown to be very probable. 
At all events the term adaptation includes the 
idea of utility, and obviously useless contriv- 
ances could hardly be brought under the same 
head. 

We have also dealt with the question of 
heredity. It is obvious that from the flowers of 
the floating and erect stems of the water-persi- 
caria seeds will result, each capable of yielding 
both forms. Quite the same thing was the case 
with the teasels. Some 40}t of the progeny pro- 
duce beautifully twisted stems, but whether the 
seed was saved from the most completely 
twisted specimens or from the straight plants 
of the race was of no importance. 

This phenomenon of twisting may now be 
considered from quite another point of view. 
It is a case of systematic atavism, or of the re- 
acquirement of some ancient and long-lost qual- 
ity. This quality is the alternate position of 



644 


Mutations 


the leaves, which has been replaced in the teasel- 
family by a grouping in pairs. In order to 
prove the validity of this assertion, it will be 
necessary to discuss two points separately, viz. : 
relative positions of the leaves, and the manner 
in which the alternate position causes the stems 
to become twisted. 

Leaves are affixed to their stems and branches 
in various ways. Among them one is of 
wide occurrence throughout the whole realm 
of the higher plants, while all the others are 
more rare. Moreover these subordinate ar- 
rangements are, as a rule, confined to definite 
systematic groups. Such groups may be large, 
as for iustance, the monocotyledons, that have 
their leaves arranged in two opposite rows in 
many families, or small, as genera or subdivi- 
sions of genera. Apart from these special 
cases the main stem and the greater part of the 
branches of the pedigree of the higher plants 
exhibit a spiral condition or a screw arrange- 
ment, all leaves being inserted at different 
points and on different sides of the stem. This 
condition is assumed to be the original one, 
from which the more specialized types have 
been derived. As is usual with characters in 
general, it is seen to vary around an average, 
the spiral becoming narrower and looser. A 
narrow spiral condenses the leaves, while a 



Systematic Atavism 


645 


loose one disperses them. According to snch 
fluctuating deviations the number of leaves, in- 
serted upon a given number of spiral circuits, is 
different in different species. In a vast major- 
ity of cases 13 leaves are found on 5 circuits, 
and as we have only to deal with this propor- 
tion in the teasels we will not consider others. 

In the teasels this screw-arrangement has dis- 
appeared, and has been replaced by a decussate 
grouping. The leaves are combined into pairs, 
each pair occupying the opposite sides of one 
node. The succeeding pairs alternate with one 
another, so as to place their leaves at right 
angles. The leaves are thus arranged on the 
whole stem in four equidistant rows. 

On the normal stem of a teasel the two mem- 
bers of a pair are tied to one another in a com- 
paratively complicated way. The leaves are 
broadly sessile and their bases are united so as 
to constitute a sort of cup. The margins of 
these cups are bent upward, thereby enabling 
them to hold water, and after a rainfall they 
may be seen filled to the brim. It is believed 
that these little reservoirs are useful to the 
plant during tiie flowering period, because they 
keep the ants away from the honey. Consider- 
ing the internal structure of the stem at the base 
of these cups we find that the vascular bundles 
of the two opposite leaves are strongly con- 



646 


Mutations 


nected with one another, constituting a ring 
which narrowly surrounds the stem, and which 
would impede an increase in thickness, if such 
were in the nature of the plant. But since the 
stems end their existence during the summer of 
their development, this structure is of no real 
harm. 

The grouping of the leaves in alternate pairs 
may be seen within the bud as well as on the 
adult stems. In order to do this, it is necessary 
to make transverse sections through the heart 
of the rosette of the leaves of the first year. 
If cut through the base, the pair exhibit connate 
wings, corresponding to the water-cups ; if cut 
above these, the leaves seem to be free from one 
another. 

In order to compare the position of leaves 
of the twisted plants with this normal arrange- 
ment, the best way is to make a corresponding 
section through the heart of the rosette of the 
first year. It is not necessary to make a micro- 
scopic preparation. In the fall the changed dis- 
position may at once be seen to affect the central 
leaves of the group. All the rosettes of the 
whole race commence with opposite leaves; 
those that are to produce straight stems remain 
in this ocmdition, but the preparation for twist- 
ing begins at the end of the first year as shown 
by a special arrangement of the leaves. This 



Systematic Atavism 


647 


disposition may then be seen to extend to the 
very center of the rosette, by use of microscop- 
ical sections. Examining sections made in the 
spring, the original arrangement of the leaves 
of the stem is observed to continue until 
the beginning of the growth of the shoot. 
It is easy to estimate the number of leaves cor- 
responding to a given number of spiral circuits 
in these sections and the proportion is found to 
indicate 13 leaves on 5 turns. These figures 
are the same as those given above for the ordi- 
nary arrangement of alternate leaves in the 
main lines of the pedigree of the vegetable king- 
dom. 

Leaving aside for the moment the subsequent 
changes of this spiral arrangement, it becomes 
at once clear that here we have a case of sys- 
tematic atavism. The twisted teasels lose their 
decussation, but in doing so the leaves are not 
left in a disorderly dispersion, but a distinct new 
arrangement takes its place, which is to be 
assumed as the normal one for the ancestors 
of the teasel family. The case is to be consid- 
ered as one of atavism. Obviously no 
other explanation is possible, than the sup- 
position that the 5-13 spiral is still latent, 
though not displayed by the teasels. But in 
the very moment when the faculty of decussa- 
tion disappears, it resumes its place, and be- 



648 


Mutations 


comes as prominent as it must once have been in 
the ancestors, and is still in that part of their 
offspring, which has not become changed in this 
respect. Thus the proof of our assertion of 
systematic atavism is, in this case, not obtained 
by the inspection of the adult, but by the investi- 
gation of the conditions in an early stage. 
It rmnains to be explained how the twisting may 
finally be caused by this incipient grouping of 
the leaves. Before doing so, it may be as well 
to state that the case of the teasel is not an iso- 
lated one, and that the same conclusions are 
supported by the valerian, and a large num- 
ber of other examples. In early spring some 
rosettes show a special condition of the 
leaves, indicating thereby at once their atavism 
and their tendency to become twisted as soon 
as they begin to expand. The Sweet William 
or Dianthus barbatus affords another instance; 
it is very interesting because a twisted race 
is available, which may produce thousands of 
instances developed in all imaginable degrees, 
in a single lot of plants. Viscaria oculata 
is another instance belonging to the same fam- 
ily. 

The bedstraw {Galium) also includes many 
species which from time to time produce twist- 
ed stems. I have found them myself in Hollmid 
on Galium verum and G. Aparine. Both seem 



Systematic Atavism 


649 


to be of rare occurrence, as 1 have not suc- 
ceeded in getting any repetition by prolonged 
culture. 

Species, which generally bear their leaves in 
whorls, are also subjected to casual atavisms of 
this kind, as for instance the tall European 
horsetail, Equisetvm Tehnateja, which occasion- 
ally bears cones on its green summer stems. 
Its whorls are changed on the twisted parts into 
clearly visible spirals. The ironwood or Cas- 
uarina quadrivalvis is sometimes observed to 
produce the same anomaly on its smaller lateral 
branches. 

Coming now to the discussion of the way in 
which the twisting is the result of the spiral dis- 
position of the leaves, we may consider this ar- 
rangement on stems in the adult state. These 
at once show the spiral line and it is easy to fol- 
low this line from the base up to the apex. In 
the most marked cases it continues without in- 
terruption, not rarely however, ending in a 
whorl of three leaves and a subsequent straight 
intemode, of which there may even be two or 
three. The spiral exhibits the basal parts of the 
leaves, with the axillary lateral branches. The 
direction of the screw is opposed to that of the 
twisting, and the spiral ribs are seen to cross the 
line of insertion of the leaves at nearly right 
angles. On this line the leaves are nearer 



650 


Mutations 


to one another than would correspond to the 
original proportion of 5 turns for 13 leaves. 
In fact, 10 or even 13 leaves may not rarely 
be counted on a single turn. Or the twist 
may become so strong locally as to change the 
spiral into a longitudinal line. On this line 
all inserted leaves extend themselves in the 
same direction, resembling an extended flag. 

The spiral on the stem is simply the continua- 
tion of the spiral line from within the rosettes 
of the first year. Accordingly it is seen to be- 
come gradually less steep at the base. For this 
reason it must be one and the same with this 
line, and in extreme youth it must have pro- 
duced its leaves at the same mutual distances as 
this line. Transverse sections of the growing 
summits of the stems support this conclusion. 

From these several facts we may infer that 
the steepness of the spiral line increases on the 
stem, as it is gradually changed into a screw. 
Originally 5 turns were needed for 13 leaves, 
but this number diminishes and 4 or 3 or even 2 
turns may take the same number of foliar 
organs, xmtil the screw itself is changed into a 
straight line. 

■This change consists in an unwinding of the 
whole spiral, and in order to effect this the stem 
must become wound up in the opposite direc- 
tion. The winding of the foliar screw must 



Systematic Atavism 


651 


curve the longitudinal ribs. The straighter 
and steeper the screw becomes, the more the 
ribs will become twisted. That this happens in 
the opposite direction is obvious, without fur- 
ther discussion. The twisting is the inevitable 
consequence of the reversal of the screw. 

Two points remain to be dealt with. One is 
the direct proof of the reversal of the screw, the 
other the discussion of its cause. The first may 
be observed by a simple experiment. Of course 
it proceeds only slowly, but all that is necessary 
is to mark the position of one of the younger 
leaves of a growing stem of a twisting indi- 
vidual and to observe the change in its posi- 
tion in a few hours. It will be seen to have 
turned some way around the stem, and finally 
may be seen to make a complete revolution in 
the direction opposite to the screw, and there- 
by demonstrating the fact of its uncurling. 

The cause of this phenomenon is to be sought 
in the intimate connection of the basal parts of 
the leaves, which we have detailed above. The 
fibrovascular strands constitute a strong rope, 
which is twisted around the stem along the 
line on which the leaves are inserted. The 
strengthening of the intemodes may stretch this 
rope to some extent, but it is too strong to be 
rent asunder. Hence it opposes the normal 
growth, and the only manner in which the inter- 



652 


Mutatww 


nodes may adjust themselves to the forces which 
tend to cause their expansion is by straighten- 
ing the rope. In doing so they may find the re- 
quired space, by growing out in an unusual 
direction, bending their axes and twisting the 
ribs. 

To prove the validity of this explanation, a 
simple experiment may be given. If the fibro- 
vascular rope is the mechanical impediment 
which hinders the normal growth, we may try 
the effect of cutting through this rope. By this 
means the hindrance may at least locally 
be removed. Now, of course, the operation 
must be made in an early stage before, 
or at the beginning of the period of growth, 
in every case before the uncurling of the 
rope begins. Wounds made at this time are apt 
to give rise to malformations, but notwithstand- 
ing this difficulty I have succeeded in giving the 
necessary proof. Stems operated upon become 
straight where the rope is cut through, though 
above and under the wounded part they go on 
twisting in the usual way. 

Sometimes the plants themselves succeed in 
tearing the rope asunder, and long straight in- 
temodes divide the twisted stems in two or more 
parts in a very striking manner. A line of tom 
leaf-bases connects the two parts of the screw 
and gives testimony of what has passed within 



Systematic Atavism 653 

the tissues. At other times the straighteuing 
may have taken place directly internal to a leaf, 
and it is tom and may be seen to be attached to 
the stem by two distinct bases. 

Summing up this description of the heredi- 
tary qualities of our twisted teasels and of their 
mechanical consequences, we may say that the 
loss of the normal decussation is the cause of all 
the observed changes. This special adaptation, 
which places the leaves in alternating pairs, re- 
placed and concealed the old and universal ar- 
rangement on a screw line. In disappearing, it 
leaves the latter free, and according to the rule 
of systematic atavism, this now becomes active 
and takes its place. If the fibrovascular con- 
nection of the leaf-bases were lost at the same 
time the stems would grow and become straight 
and tall. This change however, does not occur, 
and the bases of the leaves now constitute a con- 
tinuous rope instead of separate rings, and 
thereby impede the stretching of the intemodes. 
These in their turn avoid the difficulty by twist- 
ing themselves in a direction opposite to that 
of the spiral of the leaves. 

As a last example of systematic atavism I will 
refer to the reversionary changes, afforded by 
the tomatoes. Though the culture of this plant 
is a recent one, it seems to be at present in a 
state of mutability, producing new strains, or 



654 


Mutations 


assuming the featares of their presnmable an- 
cestors. In his work ** The Survival of the Un- 
like,** Bailey has given a detailed description of 
these various types. Moreover, he has closely^ 
studied the causes of the changes, and shown 
the great tendency of the tomatoes to vicinism. 
By far the larger part of the observed cases of 
running out of varieties are caused by acciden- 
tal crosses through the agency of insects. Even 
improvements are not rarely due to this cause. 
Besides these common and often unavoidable 
changes, others of greater importance occur 
from time to time. Two of them deserve to be 
mentioned. They are called the “ Upright ” and 
the ** Mikado types, and differ as much or 
even more from their parents than the latter do 
from any one of their wild congeners. Their 
characters come true from seed. The ** Mika- 
do race or the Lycopersicum grandifolium (L. 
latifolium) has larger and fewer leaflets than 
the slender and somewhat flimsy foliage of the 
common form. Flat or plane blades with de- 
current margins constitute another character. 
This variety, however, does not concern our 
present discussion. The upright type has stiff 
and self-sustaining stems and branches, resem- 
bling rather a potato-plant thw a tomato. 
Hence the name Lycopersicum solanopsis or L. 
validum, under which it is usually described. 



Systematic Atavism 655 

The foliage of the plant is so distinct as to yield 
botanical characters of sufficient importance to 
justify this specific designation. The leaflets 
are reduced in numbers and greatly modi- 
fied, and the flowers in the inflorescence are re- 
duced to two or three. This curious race came 
in suddenly, without any premonition, and the 
locality and date of its mutation are still on 
record. Until some years ago it had not made 
its appearance for a second time. Obviously it 
is to be considered as a reversionary form. 
The limp stems of the common tomatoes are in 
all respects indicative of the cultivated condi- 
tion. They cannot hold themselves erect, but 
must he tied up to supports. The color of 
the leaves is a paler green than should he ex- 
pected from a wild plant. Considering other 
species of the genus Solatium, of which the 
Lycopersicum is a subdivision, the stems are as 
a rule erect and self-supporting, with some few 
exceptions. These, however, are special adapta- 
tions as shown by the winding stems of the 
bitter-sweet. 

From this discussion we seem justified in con- 
cluding that the original appearance of the up- 
right type was of the nature of systematic 
atavism. It differs however, from the already 
detailed cases in that it is not a monstrosity, nor 
an ever-sporting race, but is as constant a form 



656 


Mutations 


as the best variety or species. Even on this 
gronnd it must be considered as a representa- 
tive of a separate group of instances of the uni- 
versal rule of systematic reversions. 

Of late the same mutation has occurred in the 
garden of G. A. White at Washington. The 
parent form in this case was the Acme,” of 
the ordinary weak and spreading habit of 
growth. It is known as one of the best and most 
stable of the varieties and was grown by Mr. 
White for many years, and had not given any 
sign of a tendency towards change. Seeds 
from some of the best plants in 1899 were sown 
the following spring, and the young seedlings 
unexpectedly exhibited a marked difference 
from their parents. Prom the very outset they 
were more strong and erect, more compact and 
of a dai^er green than the “ Acme.” When 
Ihey reached the fruiting stage they had devel- 
oped into typical representatives of the Lyco- 
persicum solanopsis or upright division. The 
whole lot of plants comprised only some 30 
specimens, and this number, of course, is too 
small to base far-reaching conclusions upon. 
But all of the lot showed this type, no 
true “ Acme ” being seen among them. The 
fruit differed in flavor, consistency and color 
from that of the parent, and it also ripened 
earlier than the latter. No seed was saved from 



Systematic Atavism 


657 


these plants, but the following year the 
“ Acme ” was sown again and found true to its 
type. Seeds saved from this generation in 1900 
have, however, repeated the mutation, giving 
rise to exactly the same new upright form in 
1901. This was called by its originator “ The 
Washington.’* Seeds from this second muta- 
tion were kindly sent to me by Mr. White, and 
proved true to their type when sown in my 
garden. 

Obviously it is to be assumed in the case of 
the tomatoes as well as in instances from 
other genera cited, that characters of an- 
cestors, which are not displayed in their 
progeny, have not been entirely lost, but are still 
present, though in a latent condition. They 
may resume their activity unexpectedly, and at 
once develop all the features which they for- 
merly had home. 

Latency, from this point of view, must be one 
of the most common things in nature. All or- 
ganisms are to be considered as internally 
formed of a host of units, partly active and 
partly inactive. Extremely minute and almost 
inconceivably numerous, these units must have 
their material representatives within the most 
intimate parts of the cells. 



Lbotubb XXIll 


TAZOKOMIO AN0MAX1E8 

The theory of descent is founded mainly 
on comparative studies, which have the ad- 
vantage of affording a broad base and the 
convincing effect of concurrent evidence 
brought together from widely different sources. 
The theory of mutation on the other hand rests 
directly upon experimental investigations, and 
facts concerning the actual descent of one form 
from another are as yet exceedingly rare. It is 
always difficult to estimate the validity of con- 
clusions drawn from isolated instances selected 
from the whole range of contingent phenomena, 
and this is especially true of the present case. 
Systematic and physiologic facts seem to indi- 
cate the existence of universal laws, and it is not 
probable that the process of production of new 
species would be different in the various parts 
of the animal and vegetable kingdoms. More- 
over the principle of unit-characters, the pre- 
eminent significance of which has come to be 
more fully recognized of late, is in full harmony 

668 



Taxonomic Anomalies 659 

with the theory of sudden mutations. Together 
these two conceptions go to strengthen the ‘pro1^ 
ability of the sudden origin of all specific char- 
acters. 

Experimental researches are limited in their 
ext{ *4, and the number of cases of direct obser- 
vation of the process of mutation will probably 
never becbme large enough to cover the whole 
field of -410 theory pf'^escent. Therefore it will 
always be necessar^^lfco show that the similarity 
between observed afid other cases is such as to 
lift above all doubt the assertion of their result- 
ing from the same causes. 

Besides the direct comparison of the muta- 
tions described in our former lectures, with the 
analogous cases of the horticultural and natural 
production of species and varieties at large, an- 
other way is open to obtain the required proof. 
It is the study of the phenomena, designated by 
Casimir de Candolle by the name of taxo- 
nomic anomalies. It is the assertion that char- 
acters, which are specific in one case, may be 
observed to arise as anomalies or as varieties in 
other instances. If they can be shown to be 
identical or nearly so in both, it is obviously 
allowable to assume the same origin for the 
specific character and fo^ the anomaly. In 
other terms, the specific marks may be consid- 
ered as having originated according to the laws 



660 


Mutations 


that govern the production of anomalies, and 
we may assume them to lie within reach of our 
experiments. The experimental treatment of 
the origin of species may also be looked upon as 
a method within our grasp. h 

The validity and the significance lese 
considerations will at once become clear,' if we 
choose a definite example. The broadest and 
most convincing one app«,’^s to me v’5 be af- 
forded by the cohesion oi ,ie petals in gamo- 
petalous flowers. Accordiiig to the current 
views the families with the petals of their 
flowers united are regarded as one or two main 
branches of the whole pedigree of the vege- 
table kingdom. Eichler and others assume 
them to constitute one branch, and therefore one 
large subdivision of the system. Bessey, on the 
other hand, has shown the probability of a sep- 
arate origin for those groups which have in- 
ferior ovaries. Apart from such divergencies 
the connation of the petals is universally recog- 
nized as one of the most important systematic 
characters. 

How may this character have originated? 
The heath-family or the Ericaceae and their 
nearest allies are usually considered to be the 
lowest of the gamopetalous plants. In them the 
cohesion of the petals is still subject to rever- 
sionary exceptions. Sudi cases of atavism may 



Taxonomic Anomalies 


661 


be observed either as specific marks, or in the 
way of anomalies. Ledum, Monotropa and Py- 
rola, or the Labrador tea, the Indian pipe and 
wintergreen are instances of reversionary 
gamopetalism with free petals. In heaths 
(Erica Tetralix) and in rhododendrons the 
same deviation is observed to occur from time 
to time as an anomaly, and even the common 
Rhododendron ponticum of our gardens has a 
variety in which the corolla is more or less 
split. Sometimes it exhibits five free petals, 
while at other times only one or two are entirely 
free, the remaining four being incompletely 
loosened. 

Such cases of atavism make it probable that 
the coherence of the petals has ori^ally arisen 
by the same method, but by action in the op- 
posite direction. The direct proof of this con- 
clusion is afforded by a curious observation, 
made by Vilmorin upon the bright and large- 
flowered garden-poppy, Papaver bracteatum. 
Like all poppies it has four petals, which are 
free from one another. In the fields of Messrs. 
Vilmorin, where it is largely cultivated for its 
seeds, individuals occur from time to time which 
are anomalous in this respect. They exhibit a 
tendency to produce connate petals. Their 
flowers become monopetalous, and the whole 
strain is designated by the name of Papaver. 



662 


Mutations 


bracteatum monopetcdum. Henry de Vilmorin 
had the kindness to send me some of these 
plants, and they have flowered in my garden 
during several years. The anomaly is highly 
variable. Some flowers are quite normal, ex- 
hibiting no sign of connation; others are wholly 
gamopetalous, the four petals being united from 
their base to the very margin of the cup formed. 
In consequence of the broadness of the petals 
however, this cup is so wide as to be very 
shallow. 

Intermediate states occur, and not infre- 
quently. Sometimes only two or three petals 
are united, or the connation does not extend the 
entire length of the petals. These cases are 
quite analogous to the imperfect splitting of 
the corolla of the rhododendron. Givii^ free 
rein to our imagination, we may for a moment 
assume the possibility of a new subdivision of 
the vegetable kingdom, arising from Vilmorin ’s 
poppy and having gamopetalous flowers for its 
chief character. If the character became fixed, 
so as to lose its present state of variability, 
such a group of supposititious gamopetalous 
plants might be quite analogous to the corre- 
sponding real gamopetalous families. Hence 
there can be no objection to the view, that the 
heaths have arisen in an analogous manner from 
their polypetalous ancestors. Other species of 



Taxonomic Anomalies 


663 


the same genus have also been recorded to pro- 
duce gamopetalous flowers, as for instance, 
Papaver hybridum, by Hoffmann. Poppies are 
not the sole example of accidental gamopetaly. 
Linnaeus observed the same deviation long ago 
for Saponaria oHidnalis, and since, it has been 
seen in Clematis Vitalba by Jaeger, in Peltaria 
alliacea by Schimper, in Silene aamvlata by Bo- 
reau and in other instances. No doubt it is not 
at all of rare occurrence, and the origin of the 
present gamopetalous families is to be consid- 
ered as nothing extraordinary. It is, as a mat- 
ter of fact, remarkable that it has not taken 
place in more numerous instances, and the mal- 
lows show that such opportunities have been 
available at least more than once. 

Other instances of taxonomic anomalies are 
afforded by leaves. Many genera, the species of 
which mainly bear pinnate or palmate leaves, 
have stray types with undivided leaves. 
Among the brambles, Rubus odoratus and 
R. ftexuosus may be cited, among the aralias, 
Aralia crassifolia and A, papyriferaf and 
among the jasmines, the deliciously scented 
sambac {Jasminum Samhac). But the most 
curious instance is that of the telegraph-plant, 
or Desmodium gyrans, each complete leaf of 
which consists of a large terminal leaflet and 
two little lateral ones. These latter keep up, 



664; 


Mutations 


night and day, an irregular jerking movement, 
which has been compared to the movements of 
a semaphore. Desmodium is a papiliona- 
ceous plant and closely allied to the genus 
Medysarum, which has pinnate leaves with 
numerous pairs of leaflets. Its place in the 
system leaves no doubt concerning its origin 
from pinnate-leaved ancestors. At the time of 
its origination its leaves must have become re- 
duced as to the number of the blades, while the 
size of the terminal leaflet was correspondingly 
increased. 

It might seem difficult to imagine this great 
change taking place suddenly. However, we are 
compelled to familiarize ourselves with such hy- 
pothetical assumptions. Strange as they may 
seem to those who are accustomed to the concep- 
tion of continuous slow improvements, they are 
nevertheless in complete agreement with what 
really occurs. Fortunately the direct proof of 
this assertion can be given, and in a case 
which is narrowly related, and quite parallel to 
that of the Desmodium, since it affects a plant 
of the same family. It is the case of the 
monophyllous variety of the bastard-acacia or 
Robinia Pseud-Acacia. In a previous lecture 
we have seen that it originated suddenly in a 
French nursery in the year 1855. It can be 
propagated by seed, and exhibits a curious de- 



Taxonovnic Anomalies 


665 


gree of variability of its leaves. In some in- 
stances these are one-bladed, the blade reaching 
a length of 15 cm., and hardly resembling those 
of the common bastard-acacia. Other leaves 
produce one or two small leaflets at the base of 
the large terminal one, and by this contrivance 
are seen to be very similar to those of the Des- 
modium, repeating its chief characters nearly 
exactly, and only differing somewhat in the rela- 
tive size of the various parts. Lastly real in- 
termediates are seen between the monophyllous 
and the pinnate types. As far as I have been 
able to ascertain, these are produced on weak 
twigs under unfavorable conditions ; the 
size of the terminal leaflet decreases and the 
number of the lateral blades increases, showing 
thereby the presence of the original pinnate 
type in a latent condition. 

The sudden origin of this ** one-leaved ” 
acacia in a nursery may be taken as a prototype 
of the ancient origin of Desmodium. Of 
course the comparison only relates to a single 
character, and the movements of the leaflets are 
not affected by it. But the monophylly, or rath- 
er the size of the terminal blade and the reduc- 
tion of the lateral ones, may be held to be suf- 
ficiently illustrated by the bastard-acacia. It 
is worth while to state, that analogous varieties 
have also arisen in other genera. The ** one- 



666 


Mutations 


leaved strawberry bas already been referred 
to. It originated from the ordinary type in 
Norway and at Paris. The walnut likewise, has 
its monophyllous variety. It was mentioned 
for the first time as a cultivated tree about 1864, 
but its origin is unknown. A similar variety of 
the walnut, with “ one-bladed ” leaves but of 
varying shapes, was found wild in a forest near 
Dieppe in France some years ago, and appeared 
to be due to a sudden mutation. 

Something more is known concerning the 
** one-bladed ” ashes, varieties of which are 
often seen in our parks and gardens. The com- 
mon form has broad and deeply serrate leaves, 
which are far more roimded than the leaflets of 
the ordinary ash. The majority of the leaves 
are simple, but some produce one or two smaller 
leaflets at their base, closely corresponding in 
this respect to the variations of the ** one- 
bladed ” bastard-acacia, and evidently indicat- 
ing the same latent and atavistic character. In 
some instances this analogy goes still further, 
and incompletely pinnate leaves are produced 
with two or more pairs of leaflets. Besides 
this variable type another has been described 
by Willdenow. It has single leaves exclusive- 
ly, never producing smaller lateral leaflets, 
and it is said to be absolutely constant 
fr<nn seed, while the more variable types 



Taxonomic Anomalies 


667 


seem to be also more inconstant when propa- 
gated sexually. The difference is so striking 
and affords such a reliable feature that Koch 
proposed to make two distinct varieties of them, 
calling the pure type Fraxmus excelsior mono- 
phylla, and the varying trees F. excel, exhetero- 
phylla. Some writers, and among them WUl- 
denow, have preferred to separate the “ one- 
leaved ” forms from the species, and to call 
them Fraxinus simplicifolia. 

According to Smith and to Loudon, the “ one- 
leaved ” ashes are found wild in different dis- 
tricts in England. Intermediate forms have not 
been recorded from these localities. This 
mode of origin is that already detailed for the 
laciniate varieties of alders and so many other 
trees. Hence it may be assumed that the “ one- 
leaved ” ashes have sprung suddenly but fre- 
quently from the original pinnate species. The 
pure type of Willdenow should, in this case, 
be considered as due to a slightly different 
mutation, perhaps as a pure retrograde variety, 
while the varying strains may only be ever- 
sporting forms. This would likewise explain 
part of their observed inconstancy. 

In this respect the historic dates, as collected 
by Korshinsky, are not very convincing. Vi- 
cinism has of course, almost never been exclud- 
ed, and part of the multiformity of the offspring 



668 


Mutations 


must obviously be due to this most universal 
agency. Indirect vicinism also plays some part, 
and probably affords the explanation of some 
reputed mutative productions of the variety. 
So, for instance, in the case of Sinning, who aft- 
er sowing the seeds of the common ash, got as 
large a proportion as 2^ of monophyllous trees 
in a culture of some thousand plants. It is 
probable that his seeds were taken partly from 
normal plants, and partly from hybrids between 
the normal and the “ one-bladed ” type^ assum- 
ing that these hybrids have pinnate leaves like 
their specific parent, and bear the characters of 
the other parent only in a latent condition. 

Our third example relates to peltate leaves. 
They have the stalk inserted in the middle of 
the blade, a contrivance produced by the conna- 
tion of the two basal lobes. The water-lilies 
are a well known instance, exhibiting sagit- 
tate leaves in the juvenile stage and changing 
in many species, into nearly circular pel- 
tate forms, of which Victoria regia is a very 
good example, although its younger stages do 
not always excite all the interest thej deserve. 
The Indian cress {Tropaeolum)^ the marsh- 
pennywort or Hydrocotyle, and many other in- 
stances could be quoted. Sometimes the peltate 
leaves are not at all orbicular, but are elon- 
gated, oblong or elliptic, and with only the lobes 



Taxonomic Anomalies 


669 


at the base united. The lemon-scented Eucor 
lyptus citriodora is one of the most widely 
known cases. In other instances the peltate 
leaves become more or less hollow, constituting 
broad ascidia as in the case of the crassulaceous 
genus Umbilicus. 

This connation of the basal lobes is universal- 
ly considered as a good and normal specific 
character. Nevertheless it has its manifest 
analogy in the realm of the anomalies. This is 
the pitcher or ascidium. On some trees it is of 
quite common occurrence, as on the lime-tree 
{Tilia parvifolia) and the magnolia {Magnolia 
obovata and its hybrids). It is probable that 
both these forms have varieties with, and others 
without, ascidia. Of the lime-tree, instances are 
known of single trees which produce hundreds 
of such anomalous leaves yearly, and one such a 
tree is growing in the neighborhood of Amster- 
dam at Lage Vuursche. I have alluded to these 
cases more than once, but on this occasion a 
closer inspection of the structure of the ascidium 
is required. For this purpose we may take the 
lime-tree as an example. Take the shape of the 
normal leaves in the first place. These are cor- 
date at their base and mainly inequilateral, but 
the general shape varies to a considerable ex- 
tent. This variation is closely related to the 
position of the leaves on the twigs, and shows 



670 


Mutations 


distinct indications of complying with the gen- 
eral law of periodicity. The first leaves are 
smaller, with more ronnded lobes, the subse- 
quent leaves attain a larger size, and their lobes 
slightly change their forms. In the first leaves 
the lobes are so broad as to touch one another 
along a large part of their margins, but in or- 
gans formed later this contact gradually dimin- 
ishes and the typical leaves have the lobes wide- 
ly separated. Now it is easily understood that 
the contact or the separation of the lobes must 
play a part in the construction of the ascidia, 
as soon as the margins grow together. Leaves 
which touch one another, may be affected by 
the connation without any further malforma- 
tion. They remain flat, become peltate and ex- 
hibit a shape which in some way holds a mid- 
dle position between the pennyworts and the 
lemon-scented eucalyptus. Here we have 
the repetition of the specific characters of these 
plants by the anomaly of another. Whenever 
the margins are not in contact, and become con- 
nate, notwithstanding their separation, the blade 
must be folded together in some slight degree, 
in order to produce the required contact. This 
is the origin of the ascidium. It is quite super- 
fluous to insist upon the fact that their width 
or narrowness must depend upon the corre- 
sponding normal form. The more distant the 



Taxonomic Anomalies 


671 


lobes, the deeper the ascidium will become. It 
should be added that this explanation of the dif- 
ferent shapes of ascidia is of general validity. 

Ascidia of the snake-plantain or Plantago 
lanceolata are narrow tubes, because the leaves 
are oblong or lanceolate, while ttiose of the 
broad leaved species of arrowhead, as for in- 
stance, the Sagittaria japonica, are of a conical 
shape. 

From the evidence of the lime-tree we may 
conclude that normal peltate leaves may have 
originated in the same way. And from the fact 
that pitchers are one of the most frequent 
anomalies, we may conclude that the chance of 
producing peltate leaves must have been a very 
great one, and wholly sufficient to account for 
all observed cases. In every instance the pre- 
viously existing shape of the leaf must have de- 
cided whether peltate or pitcher-like leaves 
would be formed. As far as we can judge pel- 
tate anomalies are quite uninjurious, whilS as- 
cidia are forms which must impede the effect of 
the light on the leaf, as they conceal quite an 
important part of the upper surface. In this 
way it is easily conceivable that peltate leaves 
are a frequent specific character, while ascidia 
are not, as they only appear in the special cases 
of limited adaptation, as in the instances of the 
so called pitcher-plants. The genera Nepenthes, 



672 


Mutations 


Sarracenia and some others are very well 
known and perhaps even the bladderworts or 
Utricularia might be included here. 

The reproduction of specific characters by 
anomalous ascidia is not at all limited to the 
general case as described above. More minute 
details may be seen to be duplicated in the same 
way. Proofs are afforded on one side by in- 
complete ascidia, and on tlie other by the double 
cups. 

Incomplete ascidia are those of the Nepenthes. 
The leaf is divided into three parts, a blade, a 
tendril and the pitcher. Or in other words, the 
limb produces a tendril at its summit, by means 
of which the plant is enabled to fasten itself to 
surrounding shrubs and to climb between their 
branches. But the end of this tendril bears a 
well-formed um, which however, is produced 
only after the revolving and grasping move- 
ments of the tendril have been made. Some 
species have more rounded and some more 
elongated ascidia and often the shape is seen to 
change with the development of the stem. The 
mouth of the um is strengthened by a thick rim 
and covered with a lid. Numerous curious con- 
trivances in these structures to catch ants and 
other insects have been described, but as they 
have no relation to our present discussion, we 
shall abstain from dealing with them. 



Taxonomic Anomalies 


673 


Likewise we must refrain from a consid- 
eration of the physiologic qualities of the ten- 
dril, and confine our attention to the combina- 
tion of a limb, a naked midvein and an ascidium. 
This combination is to be the basis of our dis- 
cussion. It is liable to be produced all of a sud- 
den. This assertion is proved by its occurrence 
as a varietal mark in one of our most ordinary 
cultivated plants. It is the group known as 
Croton, belon^ng to the genus Codiaeum. 
A variety is called interruptum and another ap- 
pendiculatum, and these names both relate to 
the interruption of the leaves by a naked mid- 
vein. The leaves are seen to be built up of three 
parts. The lower half retains the aspect of a 
limb; it is crowned by a vein without lateral 
nerves or blade-like expansions, and this stalk 
in its turn bears a short limb on its summit. The 
base of this apical limb exhibits two connate 
lobes, forming together a wide cup or ascidium. 
It should be stated that these interruptum varie- 
ties are highly variable, especially in the rela- 
tive size of the three principal parts of the leaf. 
Though it is of course conceded that the ascidium 
of Nepenthes has many secondary devices 
which are lacking in Croton, it seems hardly al- 
lowable to deny the possibility of an analogous 
origin for both. Those of the Croton, according 
to our knowledge regarding similar cases, must 



674 


Mutations 


have arisen at once, and hence the conclusion 
that the ascidia of Nepenthes are also originally 
due to a sudden mutation. Interrupted leaves, 
with an ascidium on a naked prolongation of the 
midvein, are by no means limited to the Croton 
varieties. As stray anomalies they have often 
been observed, and I myself had the oppor- 
tunity of collecting them on magnolia, on clover 
and on some other species. They are additional 
evidence in support of the explanation given 
above. 

In the same way double ascidia may be made 
use of to explain the foliar cups of the teasels 
and some other plants, as for instance, some 
European snakeroots {Eryngium maritimum 
and E. campestre), or the floral leaves of the 
honeysuckle. The leaves on the stems of the 
teasels are disposed in pairs, and the bases of 
the two leaves of each pair are connate so as 
to constitute large cups. We have alrjeady men- 
tioned these cups, and recall them in the present 
connection to use them as a prototype of the 
double ascidia. These are constituted of two op- 
posite leaves, accidentally connated at their base 
or along some part of their margins. If the 
leaves are sessile, the analogy with the teasels 
is complete, as shown, for instance, in a case 
of Cotyledon, a crassulaceous plant which is 



Taxonomic Anomalies 


675 


known to produce such cups from time to time. 
They are narrower than those of the teasel, but 
this depends, as we have seen for the one- 
leaved ” ascidium, on the shape of the original 
leaf. In other respects they exactly imitate the 
teasel cups, showing thereby how these cups 
may probably have originated. 

In numerous cases of anomalies some acci- 
dental structures are parallel to specific char- 
acters, while others are not, being obviously in- 
jurious to their bearers. So it is also with the 
double ascidia. In the case of stalked leaves 
the two opposite stalks must, of course, consti- 
tute a long and very narrow tube, when growing 
together. This tube must bear at its summit 
the conical ascidium produced by the two con- 
nate limbs. At its base however, it includes the 
terminal bud of the stem, and frequently the 
tube is so narrow as to impede its further de- 
velopment. By this contrivance the double as- 
cidium assumes a terminal position. Instances 
have been observed on magnolia, in Boehmeria 
and in other cases. 

Flowers on leaves are of rare occurrence. 
Notwithstanding this, they constitute specific 
characters in some instances, accidental anoma- 
lies in others. Hehvingia rusciflora is the most 
curious and best knovm instance. It is a 
little shrub, belonging to the Cornaceae, and 



676 


Mutations 


has broad elliptical undivided leaves. On 
the middle of the midvein these leaves are seen 
to bear small clusters of flowers; indeed this 
is the only place where flowers are produced. 
!Ba(di cluster has from 13 - 15 flowers, of which 
some are staminate and home on stalks, while 
others are pistillate and nearly sessile. These 
flowers are small and of a pale greenish color 
and yield small stone-fruits, with a thin 
coating of pulpy tissue. As the name indicates, 
this mode of flowering is closely similar to that 
of Ruscus, which however, does not bear its 
flowers and berries on real leaves, but on leaf- 
like expansions of the twigs. Phyllonoma rws- 
cifolia, a saxifragaceous plant, bears the same 
specific name, indicating a similar origin of the 
flowers. Other instances have been collected by 
Casimir de Candolle, but their number is very 
small. 

As a varietal mark, flowers on leaves like- 
wise rarely occur. One instance however, is 
very remarkable, and we have already dealt 
with it, when treating of constant varieties, and 
of the lack of vicinism in the case of species 
with exclusive self-fertilization. 

It is the “ Nepaul-barley ” or Hordeum tri- 
furcatum. The leaves, which in this case bear 
the adventitious flowers, are the inner scales of 
the spikelets, and not on green leaves as in the 



Tcmonofnic Anomalies 


677 


cases already alluded to. But this of course 
makes no real difference. The character is 
variable to a high degree, and this fact indicates 
its varietal nature, though it should be recalled 
that at least with the Hehoingia, the majority of 
the leaves are destitute of flowers, and that in 
this way some degree of variability is present 
in this normal case too. 

All in all there are three sorts of “ Nepaul- 
barley.” They have the same varietal mark, 
but belong to different species of barley. These 
are differentiated according to the number of 
the rows in which the grains are seen on the 
spikes. These numbers may be two, four or six, 
giving rise to the specific names of Hordeum dis- 
tichum, tetrastichum and hexastichum. Whether 
these three varieties are of independent, but 
parallel ori^n, or are to be considered as due to 
a single mutation and subsequent crosses is not 
known, all of them being of ancient origin. 
Historic evidence concerning their birth is 
wholly wanting. From analogy it would seem 
probable that the character had arisen by a mu- 
tation in one of the three named species, and 
had been transferred to others by means of ac- 
cidental crosses, even as it has been artificially 
transmitted of late to quite a number of other 
sorts. But however admissible this conception 
may seem, there is of course no real objection 



678 Mutations 

to'ihe assumption of independent and parallel 
mutations. 

For the purpose of a comparison with the 
Helwingia t3rpe we are however, not at all con- 
cerned with the species to which the trifurca- 
tum variety belongs, but only with the varietal 
mark itself. The spikelets may be one-, two- or 
three-flowered, according to the species. If we 
dioose for further consideration the hexasti- 
chum type, each spikelet produces three nor- 
mal flowers and afterwards three normal grains. 
Morphologically however, the spikelet is not 
homologous to those parts of other grasses 
which have the same name. It is constituted of 
three real spikelets, and thus deserves the name 
of a triple construction. Each of these three 
little organs has its normal pair of outer scales 
or glumae. These are linear and short, ending 
in a long and narrow spine. Those of the mid- 
dle-most spikelets stand on its outer side, while 
those of the lateral part are placed transversely. 
In this way they form a kind of involucre 
around the central parts. The latter consist 
of the inner and outer palets or scales, each two 
of which include one of the flowers. The outer 
palet is to be considered as the metamorphosed 
leaf, in the axil of which the flower is produced. 
In the common sorts of barley it bears a long 
awn, giving thereby its typical aspect to the 



Taxonomic Anomalies 


679 


whole spike. The axillary flower is protected on 
the opposite side by a two-keeled inner palet. 
Each flower exhibits three stamens and an 
ovary. In the six-rowed barley all the three 
flowers of a triple spikelet are fertile, and each 
of them has a long awn on the top of the outer 
palet. But in the two-rowed species only the 
middle-most flower is normal and has an awn, 
the two remaining being sterile and more or less 
rudimentary and with only very short awns. 
From this description it is easily seen that the 
species of barley may be distinguished from one 
another, even at a casual glance, by the number 
of the rows of the awns, and therefore by the 
shape of the entire spikes. This striking fea- 
ture, however, does not exist in the “ Nepaul- 
barley.” The awns are replaced by curiously 
shaped appendices, which are three-lobed. The 
central lobe is oblong and hollow, and forms a 
kind of hood, which covers a small supernumer- 
ary floret. The two lateral lobes are narrower, 
often linear and extended into a smaller or 
longer awn. These awns are mostly turned 
away from the center of the spike. The central 
lobe may sometimes bear two small florets, but 
ordinarily only one is to be found, and this is 
often incomplete, having only one or two 
stamens, or is different in some other way. 



€80 


Mutations 


These narrow lateral lobes heighten the abnor- 
mal aspect of the whole spike. 

Hiey are only produced at a somewhat ad- 
vanced stage of the development of the palet, 
are nnited to one another and to the central 
part by strong veins, which form transversal 
anastomoses at their insertion. The length of 
these awns is very variable, and this quality is 
perhaps the most striking of the whole variety. 
Often they reach only 1-2 mm., or the major- 
ity may become longer and attain even 1 cm., 
while here and there, between them, longer ones 
are inserted, extending in some instances even 
as far as 3 cm. from the spike. Their trans- 
verse position in such cases is strikingly con- 
trasted with the ordinary erect type of the 
awns. 

These lateral lobes are to be regarded, from 
the morphologic point of view, as ditferentiated 
parts of the blade of the leaf. Before they are 
formed, or coincidently with the beginning of 
their development, the summit of the central 
lobe becomes hollow, and the development of 
the supernumerary flower commences. In dif- 
ferent varieties, and especially in the most re- 
cent crosses of them, this development is ex- 
cessively variable. 

The accidental flower arises at some distance 
beneath the summit of the scale, on its middle 



Taxonomic Anomalies 


681 


vein. The development begins with the protra> 
sion of a little scale, and the flower itself is 
situated beneath this scale, and is to be pro- 
tected by it and by the primary scale, but is 
turned upside down at the same time. Op- 
posite to this organ, which represents the outer 
palet of the adventitious flower, two little swol- 
len bodies are evolved. In the normal flowers 
of barley and other grains and grasses their 
function is to open the flowers by swelling, and 
afterwards collapse and allow them to close. 

In the adventitious flowers of the “ Nepaul- 
barley,*’ however, this function is quite super- 
fluous. The stamens occur in varying numbers ; 
typically • there are three, but not rarely 
less, or more, are seen. In some instances the 
complete double whorl of six, corresponding to 
the ancestral monocotyledonous type, has been 
found. This is a very curious case of sys- 
tematic atavism, quite analogous to the Iris 
pallida abavia, previously alluded to, which 
likewise has six stamens, and to the cases g^ven 
in a previous lecture. But for our present dis- 
cussion it is of no further intere^st. The ovary 
is situated in the middle of the flower, and in 
some instances two have been observed. This 
is also to be considered as a case of atavism. 

All these parts of the adventitious flower are 
more or less subject to arrest of development 



682 


Mutations 


in a later stage. They may even sometimes be- 
come abnormaL Stamens may unite into pairs, 
or carpels bear four stigmas. The pollen-sacs 
are as a rule barren, the mother-cells under- 
going atrophy, while normal grains are seen but 
rarely. Likewise the ovaries are rudimentary, 
but Wittmack has observed the occasional 
production of ripe grains from these abnormal 
florets. 

The scale is seldom seen to extend any far- 
ther upwards than the supernumerary flower. 
But in the rare instances where it does pro- 
long its growth, it may repeat the abnormality 
and bear a second floret above the first. This of 
course is generally much weaker, and more rudi- 
mentary. 

Baciborsky, who has lately given a full and 
very accurate description of this anomaly, lays 
great stress upon the fact that it is quite use- 
less. It is perhaps the most obviously useless 
structure in the whole vegetable kingdom. Not- 
withstanding this, it has come to be as complete- 
ly hereditary as any of the most beautiful adap- 
tations in nature. Therefore it is one of the 
most serious objections to the hypothesis of 
slow and gradual improvements on the sole 
ground of their usefulness. The struggle for 
life and natural selection are manifestly in- 
adequate to give even the slightest indication of 



Taxonomic Anomalies 


683 


an explanation of this case. It is simply im- 
possible to imagine the causes that might have 
produced such a character. The only way out 
of this difficulty is to assume that it has arisen 
at once, in its present apparently differentiated 
and very variable condition, and that, being 
quite uninjurious and since it does not decrease 
the fertility of the race, it has never been 
subjected to natural selection, and so has saved 
itself from destruction. 

But if we once grant the probability of the 
origin of the “ Nepaul-barley ” by a sudden mu- 
tation, we obviously must assume the same in 
the case of the Helwingia and other normal in- 
stances. In this way we gain a further support 
for our assertion, that even the strangest 
specific characters may have arisen suddenly. 

After having detailed at some length those 
proofs which seem to be the most striking, and 
which had not been previously described with 
sufficient detail, we may now take a hasty survey 
of other contingent cases. In the first place the 
cruciate flowers of some onagraceous plants 
should be remembered. Small linear petals oc- 
cur as a specific character in Oenothera crth 
data of the Adirondacks, but have been seen to 
arise as sudden mutations in the common even- 
ing-primrose (0. biennis) in Holland, and in the 
willow-herb {EpUobium hirsutum) in England. 



684 


Mutations) 


Leaves placed in whorls of three are very rare. 
The oleander, juniper and some few other 
plants have temate whorls as a specific char- 
acter. As an anomaly, temate whorls are far 
more common, and perhaps any plant with op- 
posite leaves may from time to time produce 
them. Baoes rich in this abnormality are 
found in the wild state in the yellow loose- 
strife or Lysimachia vulgaris, in which it is 
a very variable specific character, the whorls 
varying from two to four leaves. In the 
cultivated state it is met with in the myrtle 
or Myrtus communis, where it has come to be 
of some importance in Israelitic ritual. Crisped 
leaves are known in a mallow, Malva crispa, and 
as a variety in cabbages, parsley, lettuce and 
others. The orbicular fruits of Heeger’s shep- 
herd’s pni^ (CapseUa heegeri) recall similar 
fruits of other cruciferous genera, as for in- 
stance, Camelina. Screw-like stems with wide 
spirals are specific in the flower-stalks of 
Cyclamen and Vallisneria, varietal in J uncus 
effusus spiralis and accidental in Scirpus lacus- 
tris. Dormant buds or small bulbs in inflo- 
rescences ai'e normal for wild onions. Polygo- 
num viviparum and others, varietal in Poa 
alpina vwipara and perhaps in Agave vivi- 
para, and accidental in plantains {Plantago 
lanceolata), Saadfraga umbrosa and others. 



Tasoonontic Anomalies 


685 


Cleft leaves, one of the most general anomalies, 
are typical in Boehmeria hiloba. The adnation 
of the peduncles of the inflorescences to the 
stem is typical in Solanum and accidental in 
many other cases. 

It seems quite superfluous to add further 
proof. It is a very general phenomenon that 
specific characters occur in other genera as 
anomalies, and under such circumstances that 
the idea of a slow evolution on the ground of 
utility is absolutely excluded. No other ex- 
planation remains than that of a sudden muta- 
tion, and once granted for the abnormal cases, 
this explanation must obviously likewise be 
granted for the analogous specific characters. 

Our whole discussion shows that mutations, 
once observed in definite instances, afford the 
most probable basis for the explanation of spe- 
cific characters at large. 



Leotube XXIV 


XHB HTF0THE8IS OF PBBIODIO MUTATIONB 

The prevailing belief that slow and gradual, 
nearly invisible changes constitute the process 
of evolution in the animal and vegetable king- 
dom, did not offe:^ a strong stimulus for experi- 
mental research. * No appreciable response to 
any external agbncy was of course to be ex- 
pected. Responses were supposed to be pro- 
duced, but the corresponding outward changes 
would be too small to betray themselves to the 
investigator. 

^he direct observation of the mutations of 
the evening-primrose has changed the whole 
aspect of the problem at once. It is no longer 
a matter dealing with purely hypothetical con- 
ditionsJ Instead of the vague notions, uncer- 
tain hopes, and a priori conceptions, that have 
hitherto confused the investigator, methods of 
observation have been formulated, suitable for 
the attainment of definite results, the general 
nature of which is already known. 

To my mind the real value of the discovery 

ess 



Periodic Mutations 


687 


of the mutability of the evening-primrose lies 
in its usefulness as a guide for further work. 
The view that it might be an isolated case, lying 
outside of the usual procedure of nature, can 
hardly be sustained. On such a supposition it 
would he far too rare to be disclosed by the 
investigation of a small number of plants from 
a limited area. Its appearance within the lim- 
ited field of inquiry of a single man would have 
been almost a miracle. 

The assumption seems justified that analo- 
gous cases will be met with, perhaps even in 
larger numbers, when similar methods of ob- 
servation are used in the investigation of plants 
of other regions. The mutable condition may not 
be predicated of the evening-primroses alone. 
It must be a universal phenomenon, although 
affecting a small proportion of the inhabitants 
of any region at one time: perhaps not more 
than one in a hundred species, or perhaps not 
more than one in a thousand, or even fewer may 
be expected to exhibit it. The exact proportion 
is immaterial, because the number of mutable 
instances among the many thousands of species 
in existence must be far too large for all of 
them to be submitted to close scrutiny. 

It is evident from the above discussion that 
next in importance to the discovery of the pro- 
totype of mutation is the formulation of meth- 



688 


Mutations 


ods for bringing additiooal instances to light. 
These methods may direct effort toward two dif- 
ferent modes of investigation. We may search 
for mutable plants in nature, or we may hope 
to induce species to become mutable by artificial 
methods. The first promises to yield results 
most quickly, but the scope of the second is 
much greater and it may yield results of far 
more importance. Indeed, if it should once be- 
come possible to bring plants to mutate at our 
will and perhaps even in arbitrarily chosen di- 
rections, there is no limit to the power we may 
finally hope to gain over nature. 

What is to guide us in this new line of work? 
Is it the minute inspection of the features of the 
process in the case of the evening-primroses? 
Or are we to base our hopes and our methods on 
broader conceptions of nature’s laws? Is it the 
systematic study of species and varieties, and 
the biologic inquiry into their real hereditary 
units? Or is the theory of descent to be our 
starting-point? Are we to rest our conceptions 
on the experience of the breeder, or is perhaps 
the geologic pedigree of all organic life to open 
to us better prospects of success? 

The answer to all such questions is a very 
simple one. All possibilities must be considered, 
and no line of investigation ignored. For my- 
self I have based my field-researches and my 



Periodic Mutations 


689 


testing of native plants on the hypothesis of 
nnit-characters • as deduced from Darwin’s 
Pangenesis. This conception led to the expec- 
tation of two different kinds of variability, one 
slow and one sudden. The sudden ones known 
at the time were considered as sports, and 
seemed limited to retrograde changes, or to 
cases of minor importance. The idea that 
sudden steps might be taken as the principal 
method of evolution could be derived from the 
hypothesis of unit^characters, but the evidence 
might be too remote for a starting point for ex- 
perimental investigation. 

The success of my test has given proof to the 
contrary. Hence the assertion that no evidence 
is to be considered as inadequate for the pur- 
pose under discussion. Sometime a method of 
discovering, or of producing, mutable plants 
may be found, but until this is done, all facts of 
whatever nature or direction must be made use 
of. A very slight indication may change for- 
ever the whole aspect of the problem. 

The probabilities are now greatly in favor of 
our finding out the causes of evolution by 
a close scrutiny of what really happens in na- 
ture. A persistent study of the physiologic 
factors of this evolution is the chief condition 
of success. To this study field-observations 
may contribute as well as direct experiments, 



690 


Mutations 


microscopical mvestigaiions as well as extended 
pedigree-cnltures. The cooperation of many 
workers is required to cover the field. Some- 
where no doubt the desired principle lies hid- 
den, but until it is discovered, all methods must 
be tried. 

With this conception as the best starting- 
point for further investigation, we may now 
make a brief survey of the othtT phase of the 
problem. We shall try to connect our observa- 
tions on the evening-primroses with the theory 
of descent at large. 

We start with two main facts. One is the 
mutability of Lamarck’s primrose, and the sec- 
ond is the immutable condition of quite a num- 
ber of other species. Among them are some 
of its near allies, the common and the small- 
flowered evening-primrose, or Oenothera bien- 
nis and O. muricata. 

From these facts, a very important question 
arises in connection with the theory of descent. 
Is the mutability of our evening-primroses tem- 
porary, or is it a permanent condition T A dis- 
cussion of this problem will give us the means of 
reaching a definite idea as to the scope of our 
inquiries. 

Let us consider the present first. If mutabil- 
ity is a permanent condition, it has of course no 
beginning, and moreover is not doe to the 



Periodic Mutations 


691 


agency of external circumstances. Should this 
be granted for the evening-primrose, it would 
have to be predicated for other species found in 
a mutable state. Then, of course, it would be 
useless to investigate the causes of mutability 
at large, and we should have to limit ourselves 
to the testing of large numbers of plants in 
order to ascertain which are mutable and 
which not. 

If, on the other hand, mutability is not a per- 
manent feature, it must once have had a begin- 
ning, and this beginning itself must have had an 
external cause. The amount of mutability and its 
possible directions may be assumed to be due to 
internal causes. The determination of the mo- 
ment at which they will become active can never 
be the result of internal causes. It must be as- 
signed to some external factor, and as soon as 
this is discovered the way for experimental in- 
vestigation is open. 

In the second place we must consider the past. 
On the supposition of permanency all the ances- 
tors of the evening-primrose must have been 
mutable. By the alternative view mutability 
must have been a periodic phenomenon, produc- 
ing at times new qualities, and at other times 
leaving the plants unchanged during long suc- 
cessions of generations. The present mutable 
state must then have been preceded by an im- 



692 


Mutaiions 


mutable condition, bnt of course thousands of 
mutations must have been required to produce 
the evening-primroses from their most remote 
ancestors. 

If 'we take the species into consideration 
that are not mutable at present, we may ask 
how we are to harmonize them with each of 
the two theories proposed. If mutability is 
permanent, it is manifest that the whole pedi- 
gree of the animal and vegetable kingdom is to 
be considered as built up of main mutable lines, 
and that the thousands of constant species can 
only be taken to represent lateral branches of 
the genealogic tree. 

These lateral branches would have lost the 
capacity of mutating, possessed by all their an- 
cestors. And as the principle of the hypothesis 
under discussion does not allow a resumption of 
this habit, they would be doomed to eternal con- 
stancy until they finally die out. Loss of muta- 
bility, under this conception, means loss of the 
capacity for all further development. Only 
those lines of the main pedigree which have 
retained this capacity would have a future; all 
others would die out without any chance of pro- 
gression. 

If, on the othef hand, mutability is not pemia- 
nmit, bnt a periodic condition, all lines of the 
genealogic tree must be assumed to show alter- 



Periodic Mutations 


693 


natively mutating and constant species. Some 
lines may be mutating at the present moment; 
others may momentarily be constant. The mu- 
tating lines will probably sooner or later revert 
to the inactive state, while the powers of de- 
velopment now dormant may then become awak- 
ened on other branches. 

The view of permanency represents life as 
being surrounded with unavoidable death, the 
principle of periodicity, on the contrary, fol- 
lows the idea of resurrection, granting the 
possibility of future progression for all living 
beings. At the same time it yields a more hope- 
ful prospect for experimental inquiry. 

Experience must decide between the two main 
theories. It demonstrates the existence of poly- 
morphous genera, such as Draba and Viola and 
hundreds of others. They clearly indicate a 
previous state of mutability.- Their systematic 
relation is exactly what would be expected, if 
they were the result of such a period. Perhaps 
mutability has not wholly ceased in them, but 
might be found to survive in some of their mem- 
bers. Such very rich genera however, are not 
the rule, but are exceptional cases, indicating 
the rarity of powerful mutative changes. 

On the other hand, species may remain in a 
state of constancy during long, apparently dur- 
ing indefinite, ages. 



694 


Uviationa 


Many facts plead in favor of the constancy 
of species. This principle has always been 
recognized by systematists. Temporarily the 
current form of the theory of natural selec- 
tion has assumed species to be inconstant, ever 
flhnng in g and continuously being improved and 
adapted to the requirements of the life-condi- 
tions. The followers of the theory of descent 
believed that this conclusion was unavoidable, 
and were induced to deny the manifest fact that 
species are constant entities. The mutation 
theory gives a clew to the final combination of 
the two contending ideas. Beducing the change- 
ability of the species to distinct and probably 
short periods, it at once explains how the 
stability of species perfectly agrees with the 
principle of descent through modification. 

On the other hand, the hypothesis of mutative 
periods is by no means irreconcilable with the 
observed facts of constancy. Such casual 
changes can be proved by observations such as 
those upon the evening-primrose, but it is ob- 
vious that a disproof can never be given. The 
principle grants the present constani^ of the 
vast majority of living forms, and only claims 
the exceptional occurrence of definite changes. 

Proofs of the constancy of species have been 
given in different ways. The high degree of 
similarity of the individuals of most of our 



Periodic Mutations 


695 


species has never been denied. It is observed 
throughout extended localities, and during long 
series of years. Other proofs are afforded by 
those plants which have been transported to dis- 
tant localities some time since, but do not ex- 
hibit any change as a result of this migration. 
Widely dispersed plants remain the same 
throughout their range, provided that they be- 
long to a single elementary species. Many 
species have been introduced from America into 
Europe and have spread rapidly and widely. 
The Canadian horsetail {Erigeron canadensis) y 
the evening-primrose and many other instances 
could be given. They have not developed any 
special European features after their introduc- 
tion. Though exposed to other environmental 
conditions and to competition with other spe- 
cies, they have not succeeded in developing 
a new character. Such species as proved ade- 
quate to the new environment have succeeded, 
while those which did not have succumbed. 

Much farther back is the separation of the 
species which now live both in arctic regions 
and on the summits of our highest mountain- 
tops. If we compare the alpine flora with the 
arctic plants, a high d^ee of similarity at once 
strikes us. Some forms are quite identical; 
others are slightly different, manifestly repre- 
senting elementary species of the same sys- 



696 


Mutations 


tematic tyi)e. Still others are more distant or 
even belong to different genera. The latter, 
and even the diverging, though nearly allied, 
elem^tary species, do not yield adequate evi- 
dence in any direction. 

Iliey may as well have lived together in 
the long ages before the separation of the now 
widely distant floras, or have sprung from a 
common ancestor living at that time, and subse- 
quently have changed their habits. After ex- 
cluding these unreliable instances, a good num- 
ber of species remain, which are quite the same 
in the arctic and alpine regions and on the sum- 
mits of distant mountain-ranges. As no trans- 
portation over such large distances can have 
brought tiiem from one locality to the other, no 
other explanation is left than that they have 
been wholly constant and unchanged ever since 
the glacial period which separated them. Ob- 
viously they must have been subjected to widely 
changing conditions. The fact of their stability 
through all these outward changes is the best 
proof that the ordinary external conditions do 
not necessarily have an influence on spedfic evo- 
lution. They may have such a result in some 
instances, in others they obviously have not. 
Many arctic forms bearing the specific name of 
dlpmus justify this conclusion. Astragalus al- 
frinus, Phleum alburn, Hieracium alpmum and 



Periodic Mtdations 


697 


others from the northern parts of Norway may 
be cited as examples. 

Thus Primvla imperialis has been found 
in the Himalayas^ and many other plants of the 
high mountains of Java, Ceylon and north- 
ern India are identical forms. Some species 
from the Oameroons and from Abyssinia have 
been found on the mountains of Madagascar. 
Some peculiar Australian types are represented 
on the summit of Kini Balu in Borneo. . None of 
these species, of course, are found in the inter- 
vening lowlands, and the only possible explana- 
tion of their identity is the conception of a com- 
mon post-glacial origin, coupled with complete 
stability. This stability is all the more remark- 
able as nearly allied but sli^tly divergent 
forms have also been reported from almost 
all of these localities. Other evidence is 
obtained by the comparison of ancient plants 
with their living representatives. The re- 
mains in tombs of ancient Egypt have al- 
ways afforded strong support of the views of 
the adherents of the theory of stability, and to 
my mind they still do so. The cereals and fruits 
and even the flowers and leaves in the fimeral 
wreaths of Bameses and Amen-Hotep are the 
same that are still now cultivated in Eg3rpt. 
Nearly a hundred or more species have been 
identified. Flowers of Acacia, leaves of Mimth 



698 


Mutations 


sops, petals of Nymphaea may be cited as in-' 
stances, and they are as perfectly preserved as 
the best herbarium-specimens of the present 
time. The petals and stamens retain their orig- 
inal colors, displaying them as brightly as is 
consistent with their dry state. 

Paleontologic evidence points to the same 
conclusion. Of course the remains are incom- 
plete, and rarely adequate for a close compari- 
son. The range of fluctuating variability should 
be examined first, but the test of elementary 
species given by their constancy from seed can- 
not, of course, be applied. Apart from these 
difficulties, paleontologists agree in recognizing 
the very great age of large numbers of species. 
It would require a too close survey of geologic 
facts to go into details on this point. Suffice it 
to say that in more recent Tertiary deposits 
many species have been identified with living 
forms. In the Miocene period especially, the 
similarity of the types of phanerogamic plants 
with their present offspring, becomes so striking 
that in a large number of cases specific distinc- 
tions rest in greater part on theoretical con- 
ceptions rather than on real facts. For a long 
time the idea prevailed that the same species 
could not have existed through more than one 
geologic period. Many distinctions founded 
on this belief have since had to be abandoned. 



Periodic Mutations 


699 


Species of algae belonging to the well-pre- 
served group of the diatoms, are said to have 
remained unchanged from the Carboniferous 
period up to the present time. 

Summing up the results of this very hasty 
survey, we may assert that species remain un- 
changed for indefinite periods, while at times 
they are in the alternative condition. Then at 
once they produce new forms often in large 
numbers, giving rise to swarms of subspecies. 
All facts point to the conclusion that these pe- 
riods of stability and mutability alternate more 
or less regularly with one another. Of course 
a direct proof of this view cannot, as yet, be 
given, but this conclusion is forced upon us by 
a consideration of known facts bearing on the 
principle of constancy and evolution. 

If we are right in this general conception, we 
may ask further, what is to be the exact place 
of our group of new evening-primroses in this 
theory! In order to give an adequate answer, 
we must consider the whole range of the obser- 
vations from a broader point of view. First of 
all it is evident that the real mutating period 
must be assumed to be much longer than the 
time covered by my observations. Neither the 
beginning nor the end have been seen. It is 
quite obvious that Oenothera lamarckima 
was in a mutating condition when I first 



700 


Mutations 


saw it, seventeen years ago. How long had 
it been sof Had it commenced to mutate after 
its introduction into Europe, some time ago, or 
was it already previously in this state! It 
is as yet impossible to decide this point. Per- 
haps the mutable state is very old, and dates 
from the time of the first importation of the 
species into Europe. 

Apart from all such considerations the period 
of the direct observations, and the possible 
duration of the mutability through even more 
than a century, would constitute only a moment, 
if compared with the whole geologic time. 
Starting from this conception the pedigree of 
our mutations must be considered as only one 
small group. Instead of figuring a fan of mu- 
tants for each year, we must condense all the 
succeeding swarms into one single fan, as might 
be done also for Draba verna and other poly- 
morphous species. In Oenothera the main stem 
is prolonged upwards beyond the fan; in the 
others the main stem is lacking or at least 
undiscemible, but this feature manifestly is only 
of secondary importance. We might even pre- 
fer the image of a fan, adjusted laterally to 
a stem, which itself is not interrupted by this 
branch. 

On this principle two further considerations 
are to be discussed. First the structure of the 



Periods Mviations 


701 


fan itself, and secondly the combination of suc- 
ceeding fans into a common genealogic tree. 

The composition of the fan as a whole in- 
cludes more than is directly .indicated by the 
facts concerning the birth of new species. They 
arise in considerable quantities, and each of 
them in large numbers of individuals, either in 
the same or in succeeding years. This multiple 
origin must obviously have the effect of 
strengthening the new types, and of heightening 
their chances in the struggle for life. Arising 
in a single specimen they would have little 
chance of success, since in the field among thou- 
sands of seeds perhaps one only survives and 
attains complete development. Thousands or 
at least hundreds of mutated seeds are thus re- 
quired to produce one mutated individual, and 
then, how small are its chances of surviving! 
The mutations proceed in all directions, as I 
have jwinted out in a former lecture. Some are 
useful, others might become so if the circum- 
stances were accidentally changed in definite 
directions, or if a migration from the ori^al 
locality might take place. Many others are 
without any real worth, or even injurious. 
Harmless or even slightly useless ones have 
been seen to maintain themselves in the field 
during the seventeen years of my research, as 
proved by Oenothera laevifolia and Oeno- 



702 Mutations 

thera brevistylis. Most of the others quickly 
disappear. 

This failure of a large part of the productions 
of nature deserves to be considered at some 
length. It may be elevated to a principle, and 
may be made use of to explain many diffi- 
cult points of the theory of descent. If, in 
order to secure one good novelty, nature must 
produce ten or twenty or perhaps more bad 
ones at the same time, the possibility of im- 
provements coming by pure chance must be 
granted at once. All hypotheses concerning the 
direct causes of adaptation at once become su- 
perfluous, and the great principle enunciated by 
Darwin once more reigns supreme. 

In this way too, the mutation-period of the 
evening-primrose is to be considered as a proto- 
type. Assuming it as such provisionally, it may 
aid ns in arranging the facts of descent so as to 
allow of a deeper insight and a closer scrutiny. 
AJil swarms of elementary species are the re- 
mains of far larger initial groups. All species 
containing only a few subspecies may be sup- 
posed to have thrown off at the outset far more 
numerous lateral branches, out of which how- 
ever, the greater part have been lost, being 
unfit for the surrounding conditions. It is 
the principle of the struggle for life between ele- 
mentary species, followed by the survival of the 



Periodic Mutations 


703 


fittest, the law of the selection of species, which 
we have already laid stress upon more than 
once. 

Our second consideration is also based upon 
the frequent repetition of the severed mutations. 
Obviously a common cause must prevail. The 
faculty of producing nanella or lata remains the 
same through all the years. This faculty must 
be one and the same for all the hundreds of mu- 
tative productions of the same form. When 
and how did it originate? At the outset it must 
have been produced in a latent condition, and 
even yet it must be assumed to be continuously 
present in this state, and only to become active 
at distant intervals. But it is manifest that 
the original production of the characters of 
Oenothera gigas was a phenomenon of far great- 
er importance than the subsequent accidental 
transition of this quality into the active state. 
Hence the conclusion that at the beginning of 
each series of analogous mutations there must 
have been one greater and more intrinsic mu- 
tation, which opened the possibility to all its 
successors. This was the origination of the 
new character itself, and it is easily seen that 
this incipient change is to be considered as the 
real one. All others are only its visible ex- 
pressions. 

Considering the mutative period of our even- 



704 


MutaHoiM 


in^primrose as one unit-stride section in the 
great genealogic tree, this period includes two 
nearly related, but not identical changes. One 
is the production of new specific characters in 
the latent condition, and the other is the bring- 
ing of them to light and putting them into active 
existence. These two main factors are conse- 
quently to be assumed in all hypothetic concep- 
tions of previous mutative periods. 

Are all mutations to be considered as limited 
to such periods? Of course not Stray muta- 
tions may occur as well. Our knowledge con- 
cerning this point is inadequate for any deSnite 
statement. Swarms of variable species are 
easily recognized, if the remnants are not too 
few. But if only one or two new species have 
survived, how can we tell whether they have 
originated alone or together with others. This 
difficulty is still more pronounced in regard to 
paleontologic facts, as the remains of geolc^c 
swarms are often found, but the absence of 
numerous mutations can hardly be proved in 
any case. 

I have more than once found occasion to lay 
stress on the importance of a distinction be- 
tween progressive and retrograde mutations in 
previous lectures. All improvement is, of 
course, by the first of these modes of evolution, 
but apparent losses of organs or qualities are 



Periodic Midations 


705 


perhaps of still more universal occurrence. Pro- 
gression and regression are seen to go htmd in 
hand everywhere. No large group and proba- 
bly even no genus or large species has been 
evolved without the joint agency of these two 
great principles. In the mutation-period of the 
evening-primroses the observed facts give direct 
support to this conclusion, since some of the 
new species proved, on closer inspection, to be 
retrograde varieties, while others manifestly 
owe their origin to progressive steps. Sudi 
steps may be small and in a wrong direction; 
notwithstanding this they may be due to the 
acquisition of a wholly new character and there- 
fore belong to the process of progression at 
large. 

Between them however, there is a definite 
contrast, which possibly is in intimate connec- 
tion with the question of periodic and stray mu- 
tations. Obviously each progressive change is 
dependent upon the production of a new charac- 
ter, for whenever this is lacking, no such muta- 
tion is possible. Ketrograde changes, on the 
other hand, do not require such elaborate pre- 
liminary work. Each character may be con- 
verted into the latent condition, and for all we 
know, a special preparation for this purpose is 
not at all necessary. It is readily granted that 
such special preparation may occur, because the 



706 


Mutaiiona 


great xnimberB in which our dwarf variety of the 
Oenothera are yearly produced are suggestive 
of each a con<Htion. On the other hand, the 
laevifolia and hrevistylis mutations have not 
been repeated, at least not in a visible way. 

From this discussion we may infer that it is 
quite possible that a large part of the progres- 
sive changes, and a smaller part of the retro- 
grade mutations, are combined into groups, ow- 
ing their origin to common external agencies. 
Hie periods in which such groups occur would 
constitute the mutative periods. Besides them 
the majority of the retrograde changes and 
some progressive steps might occur separately, 
each being due to some special cause. De- 
gressive mutations, or those which arise by 
the return of latent qualities to activity, would 
of course belong with the latter group. 

This assumption of a stray and isolated pro- 
duction of varieties is to a large degree sup- 
ported by experience in horticulture. Here 
there are no real swarms of mutations. Sud- 
den leaps in variability are not rare, but then 
they are due to hybridization. Apart from this 
mixture of characters, varieties as a rule appear 
separately, often with intervals of dozens of 
years, and without the least suggestion of a com- 
mon cause. It is quite superfluous to go into 
details, as we have dealt with the horticultural 



Periodic Mutations 


707 


mutations at sufficient length on a previous oc- 
casion. Only the instance of the peloric toad- 
flax might be recalled here, because the historic 
and geographic evidence, combined with the re- 
sults of our pedigree-experiment, plainly show 
that peloric mutations are quite independent of 
any periodic condition. They may occur any- 
where in the wide range of the toad-flax, and the 
capacity of repeatedly producing them has 
lasted some centuries at least, and is perhaps 
even as old as the species itself. 

Leaving aside such stray mutations, we may 
now consider the probable constitution of the 
great lines of the genealogic tree of the evening- 
primroses, and of the whole vegetable and ani- 
mal kingdom at large. The idea of drawing up 
a pedigree for the chief groups of living organ- 
isms is originally due to Haeckel, who used this 
graphic method to support the Darwinian the- 
ory of descent. Of course, Haeckel’s genealogic 
trees are of a purely hypothetic nature, and have 
no other purpose than to convey a clear concep- 
tion of the notion of descent, and of the great 
lines of evolution at large. Obviously all de- 
tails are subject to doubt, and many have ac- 
cordingly been changed by his successors. These 
changes may be considered as partial improve- 
ments, and the somewhat picturesque form of 
Haeckel’s pedigree might well be replaced by 



708 


Mutations 


more simple plans. Bat the changes have by no 
means removed the doabts, nor have they been 
able to supplant the general impression of dis- 
tinct groups, united by broad lines. This 
feature is very essential, and it is easily seen to 
correspond with the conception of swarms, as 
we have deduced it from the study of the lesser 
groups. 

Oenealo^c trees are tiie result of comparative 
studies; they are far removed from the results 
of experimental inquiry concerning the origin of 
species. What are the links which bind them 
together t Obviously they must be sought in 
the mutative periods, which have immediately 
preceded the present one. In the case of 
evening-primrose the systematic arrangenry 
of the allied species readily guides us in the^d 
limitations of such periods. For ma^^ 
the species of the large genus of Oenothera 
groax)ed in swarms, the youngest or most recv'>it 
of which we have under observation. Its imme- 
diate predecessor must have been the subgenns 
OnagrOf which is considered by some authors as 
consisting of a single systematic species, Oenoth- 
era biennis. Its multifarious forms point to a 
common origin, not only morphologically but 
also historically. Following this line backward 
or downward we reach another apparent muta- 
tion-period, whidi includes the ori^n of 



Periodic MiUations 


709 


the group called Oenothera, with a large nmn- 
ber of species of the same general type as the 
OnagrartoTme. Still farther downward comes 
the old genns Oenothera itself, with numerous 
subgenera diverging in sundry characters and 
directions. 

Proceeding still farther we might easily con- 
struct a main stem with numerous succeeding 
fans of lateral branches, and thus reach, from 
our new empirical point of view, the theoretical 
conclusion already formulated. 

Paleontologic facts readily agree with this 
conception. The swarms of species and va- 
rieties are found to succeed one another like so 
many stories. The same images are repeated, 
and the single stories seem to be connected by 
the main stems, which in each tier produce the 
whole number of allied forms. Only a few pre- 
vailing lines are prolonged through numerous 
geologic periods ; the vast majority of the lat- 
eral branches are limited each to its own storey. 
It is simply the extension of the pedigree of 
the evening-primroses backward through ages, 
with the same construction and the same lead- 
ing features. There can be no doubt that we 
are quite justified in assuming that evolution 
has followed the same general laws through the 
whole duration of life on earth. Only a mo- 
ment of their lifetime is disclosed to ns, but it 



710 


Mt^aiions 


is quite sufficient to enable ns to discern the 
laws and to conjecture the outlines of the whole 
scheme of evolution. 

A grave objection which has often, and 
from the very outset, been urged against Dar- 
win’s conception of very slow and nearly im- 
perceptible changes, is the enormously long time 
required. If evolution does not proceed any 
faster than what we can see at present, and if 
the process must be assumed to have gone on 
in the same slow manner always, thousands of 
millions of years would have been needed to de- 
velop the higher types of animals and plants 
from their earliest ancestors. 

Now it is not at all probable that the duration 
of life on earth includes such an incredibly 
long time. Quite on the contrary the lifetime 
of the earth seems to be limited to a few 
millions of years. The researches of Lord Kel- 
vin and other eminent physicists seem to leave 
no doubt on this point Of course all esti- 
mates of this kind are only vague and approx- 
imate, but for our present purposes they may 
be considered as sufficiently exact. 

In a paper published in 1862 Sir William 
Thomson (now Lord Kelvin) first endeavored to 
show that great limitation had to be put upon 
the enormous demand for time made by Lyell, 
Darwin and other biologists. From a consider- 



Periodic Mutations 


711 


ation of the secular cooling of the earth, as de- 
duced from the increasing temperature in deep 
mines, he concluded that the entire age of the 
earth must have been more than twenty and less 
than forty millions of years, and probably much 
nearer twenty than forty. His views have been 
much criticised by other physicists, but in the 
main they have gained an ever-increasing sup- 
port in the way of evidence. New mines of 
greater depth have been bored, and their tem- 
peratures have proved that the figures of Lord 
Kelvin are strikingly near the truth. George 
Darwin has calculated that the separation of 
the moon from the earth must have taken place 
some fifty-six millions of years ago. Geikie has 
estimated the existence of the solid crust of the 
earth at the most as a hundred million years. 
The first appearance of the crust must soon have 
been succeeded by the formation of the seas, 
and a long time does not seem to have been re- 
quired to cool the seas to such a degree that life 
became possible. It is very probable that life 
originally commenced in the great seas, and that 
the forms which are now usually included in the 
plankton or floating-life included the very first 
living beings. According to Brooks, life must 
have existed in this floating condition during 
long primeval epochs, and evolved nearly all the 
main branches of the animal and vegetable king- 



712 


Mut(Uions 


dom before RinkiTig to the bottom of the sea, and 
later producing the vast number of diverse 
forms which now adorn the sea and land. 

All these evolutions, however, must have been 
very rapid, especially at the beginning, and to- 
gether cannot have taken more time than the 
figures given above. 

The agency of the larger streams, and the 
deposits which they bring into the seas, afford 
further evidence. The amount of dissolved 
salts, especially of sodium chloride, has been 
made the subject of a calculation by Joly, and 
the amount of lime has been estimated by 
Eugene Dubois. Joly found fifty-five and Du- 
bois thirty-six millions of years as the probable 
duration of the. age of the rivers, and both fig- 
ures correspond to the above dates as closely 
as might be expected from the discussion of evi- 
dence so very incomplete and limited. 

All in all it seems evident that the duration of 
life does not comply with the demands of the 
conception of very slow and continuous evolu- 
tion. Now it is easily seen, that the idea of 
successive mutations is quite independent of 
this difficulty. Even assuming that some thou- 
sands of characters must have been acquired in 
order to produce the higher animals and plants 
of the present time, no valid objection is raised. 
The demands of the biologists and the results of 



Periodic Mutations 


713 


the physicists are harmonized on the ground of 
the theory of mutation. 

The steps may be surmised to have never been 
essentially larger than in the mutations now 
going on under our eyes, and some thousands of 
them may be estimated as sufficient to account 
for the entire organization of the higher forms. 
Granting between twenty and forty millions 
of years since the beginning of life, the intervals 
between two successive mutations may have 
been centuries and even thousands of years. As 
yet there has been no objection cited against this 
assumption, and hence we see that the lack of 
harmony between the demands of biologists and 
the results of the physicists disappears in the 
light of the theory of mutation. 

Summing up the results of this discussion, we 
may justifiably assert that the conclusions de- 
rived from the observations and experiments 
made with evening-primroses and other plants 
in the main agree satisfactorily with the in- 
ferences drawn from paleontologic, geologic 
and systematic evidence. Obviously these ex- 
periments are wonderfully supported by the 
whole of our knowledge concerning evolution. 
For this reason the laws discovered in the ex- 
perimental garden may be considered of great 
importance, and they may guide us in our fur- 
ther inquiries. Without doubt many minor 



714 


Mutaiions 


points are in need of correction and elaboration, 
but such improvements of our knowledge will 
gradually increase our means of discovering 
new instances and new proofs. 

The conception of mutation periods produc- 
ing swarms of species from time to time, among 
which only a few have a chance of survival, 
promises to become the basis for speculative 
pedigree-diagrams, as well as for experimental 
investigations. 



F. FLUCTUATION 


Lbctube XXV 

OENEBAli liA.WS OF FLUCTUATION 

The principle of unit-characters and of ele- 
mentary species leads at once to the recognition 
of two kinds of variability. The changes of 
wider amplitude consist of the acquisition of 
new units, or the loss of already existing ones. 
The lesser variations are due to the degree of 
activity of the units themselves. 

Facts illustrative of these distinctions were 
almost wholly lacking at the time of the first 
publication of Darwin’s theories. It was a bold 
conception to point out the necessity for such 
distinction on purely theoretical grounds. Of 
course some sports were well known and fluc- 
tuations were evident, but no exact analysis of 
the details was possible, a fact that was of great 
importance in the demonstration of the theory 
of descent. The lack of more definite knowl- 
edge upon this matter was keenly felt by Dar- 

716 



716 


Fluctuations 


win, and exercised much influence upon his 
views at various times. 

Quetelet’s famous discovery of the law of 
fluctuating variability changed the entire situa- 
tion and cleared up many difficulties. While a 
clear conception of fluctuations was thus gained, 
mutations were excluded from consideration, 
being considered as very rare, or non-existent. 
They seemed wholly superfluous for the theory 
of descent, and very little importance was at- 
tached to their study. Current scientific belief 
in the matter has changed only in recent 
years. Mendel’s law of varietal hybrids is 
based upon the principle of unit-characters, and 
the validity of this conception has thus been 
brought home to many investigators. 

A study of fluctuating or individual variabil- 
ity, as it was formerly called, is now carried on 
chiefly by mathematical methods. It is not my 
purpose to go into details, as it would re- 
quire a separate course of lectures. I shall con- 
sider the limits between fluctuation and muta- 
tion only, and attempt to set forth an adequate 
idea of the principles of the first as far as they 
touch these limits. The mathematical treat- 
ment of the facts is no doubt of very great value, 
but the violent discussions now going on be- 
tween mathematicians such as Pearson, Kap- 
teyn and others should warn biologists to ab- 



Laws of Fluctuations 


717 


stain from the use of methods which are not 
necessary for the furtherance of experimental 
work. 

Fortunately, Quetelet’s law is a very clear 
and simple one, and quite sufficient for our con- 
siderations. It claims that for biologic phe- 
nomena the deviations from the average comply 
with the same laws as the deviations from the 
average in any other ease, if ruled by chance 
only. The meaning of this assertion will be- 
come clear by a further discussion of the facts. 

First of all, fluctuating variability is an al- 
most universal phenomenon. Every organ and 
every quality may exhibit it. Some are very 
variable, while others seem quite constant. 
Shape and size vary almost indefinitely, and the 
chemical composition is subject to the same law, 
as is well known for the amount of sugar in 
sugar-beets. Numbers are of course less liable 
to changes, but the numbers of the rays of mn- 
bels, or ray-florets in the composites, of pairs of 
blades in pinnate leaves, and even of stamens 
and carpels are known to be often exceedingly 
variable. The smaller numbers however, are 
more constant, and deviations from the quinate 
structure of flowers are rare. Complicated 
structures are generally capable of only slight 
deviations. 

From a broad point of view, fluctuating varia- 



718 


Fluctuations 


bility falls under two heads. They obey quite 
the same laws and are therefore easily confused, 
but with respect to questions of heredity they 
should be carefully separated. They are des- 
ignated by the terms individual and partial 
fluctuation. Individual variability indicates 
the differences between 'individuals, while 
partial variability is limited to the devia- 
tions shown by the parts of one organ- 
ism from the average structure. The same 
qualities in some cases vary individually and in 
others partially. Even stature, which is as 
markedly individual for annual and biennial 
plants as it is for man, becomes partially variant 
in the case of perennial herbs with numbers of 
stems. Often a character is only developed once 
in the whole course of evolution, as for instance, 
the degree of connation of the seed-leaves in 
tricotyls and in numerous cases it is impos- 
sible to tell whether a character is individual or 
partial. Consequently such minute details 
are generally considered to have no real im- 
portance for the hereditary transmission of the 
character under discussion. 

Fluctuations are observed to take place only 
in two directions. The quality may increase or 
decrease, but is not seen to vary in any other 
way. This rule is now widely established by 
numerous investigations, and is fundamental to 



Laws of Fluctuations 


719 


the whole method of statistical inyestigation. 
It is equally important for the discussion of the 
contrast between fluctuations and mutations, 
and for the appreciation of their part in the 
general progress of organization. Mutations 
are going on in all directions, producing, if they 
are progressive, something quite new every 
time. Fluctuations are limited to increase and 
decrease of what is already available. They 
may produce plants with higher stems, more 
petals in the flowers, larger and more palatable 
fruits, but obviously the first petal and the first 
berry cannot have originated by the simple in- 
crease of some older quality. Intermediates 
may be found, and they may mark the limit, but 
the demonstration of the absence of a limit is 
quite another question. It would require the 
two extremes to be shown to belong to one unit, 
complying with the simple law of Quetelet. 

Nourishment is the potent factor of fluctuat- 
ing variability. Of course in thousands of cases 
our knowledge is not sufScient to allow us to ana- 
lyze this relation, and a number of phases of the 
phenomenon have been discovered only quite 
recently. But the fact itself is thoroughly mani- 
fest, and its appreciation is as old as horticul- 
tural science. Knight, who lived at the begin- 
ning of the last century, has laid great stress 
upon it, and it has since influenced practice in a 



720 


Fluctuations 


large measure. Moreover, Knight pointed out 
more than once that it is the amount of nourish- 
ment, not the quality of the various factors, that 
mcerdses the determinative influence. Nourish- 
ment is to he taken in the widest sense of the 
word, including all favorable and injurious ele- 
ments. Light and temperature, soil and space, 
water and salts are equally active, and it is the 
harmonious cooperation of them all that rules 
growth. 

We treated this important question at some 
length, when dealing with the anomalies of the 
opium-poppies, consisting of the conversion of 
stamens into supernumerary pistils. The de- 
pendency upon external influences which this 
change exhibited is quite the same as that shown 
by fluctuating variability at large. We inquired 
into the influence of good and bad soil, of sun- 
light and moisture and of other concurrent fac- 
tors. Especial emphasis was laid upon the 
great differences to which the various individ- 
uals of the same lot may be exposed, if moisture 
and manure differ on, different portions of the 
same bed in a way unavoidable even by the most 
careful preparation. Some seeds germinate on 
moist and rich spots, while their neighbors are 
impeded by local dryness, or by distance from 
manure. Some come to light on a sunny day, 
and increase their first leaves rapidly, while on 



Laws of Fluctuations 


721 


the following day the weather may be unfavor- 
able and greatly retard growth. The individual 
differences seem to be due, at least in a very 
great measure, to such apparent trifles. 

On the other hand partial differences are 
often manifestly due to similar causes. Con- 
sidering the various stems of plants, which mul- 
tiply themselves by runners or by buds on the 
roots, the assertion is in no need of further 
proof. The same holds good for all cases of 
artificial multiplication by cuttings, or by other 
vegetative methods. But even if we limit our- 
selves to the leaves of a single tree, or the 
branches of a shrub, or the flowers on a plant, 
the same rule prevails. The development of 
the leaves is dependent on their position, wheth- 
er inserted on strong or weak branches, exposed 
to more or less light, or nourished by strong or 
weak roots. The vigor of the axillary buds 
and of the branches which they may produce is 
dependent upon the growth and activity of the 
leaves to which the buds are axillary. 

This dependency on local nutrition leads to 
the general law of periodicity, which, broadly 
speaking, governs the occurrence of the fluctuat- 
ing deviations of the organs. This law of pe- 
riodicity involves the general principle that 
every axis, as a rule, increases in strength when 



722 


Fluctuations 


growing, but sooner or later reaches a maximum 
and may afterwards decrease. 

This periodic augmentation and declination is 
often boldly manifest, though in other cases it 
may be hidden by the effect of alternate influ- 
ences. Pinnate leaves generally have their 
lower blades smaller than the upper ones, the 
longest being seen sometimes near the apex 
and sometimes at a distance from it Branches 
bearing their leaves in two rows often afford 
quite as obvious examples, and shoots in gen- 
eral comply with the same rule. Germinating 
plants are very easy of observation on this 
point When they are very weak they produce 
only small leaves. But their strength gradually 
increases and the subsequent organs reach 
fuller dimensions until the maximum is at- 
tained. The phenomenon is so common that its 
importance is usually overlooked. It should be 
considered as only one instance of a rule, which 
holds good for all stems and all branches, and 
which is everywhere dependent on the relation 
of growth to nutrition. 

The rule of periodicity not only affects the 
size of the organs, but also their number, when- 
ever these are largely variable. Umbellate 
plants have numerous rays on the umbels of 
strong stems, but the number is seen to decrease 
and to become very small on the weakest lateral 



Laws of Fluctuations 


723 


branches. The same holds good for the number 
of ray-florets in the flower-heads of the com- 
posites, even for the number of stigmas on the 
ovaries of the poppies, which on weak branches 
may be reduced to as few as three or four. 
Many other instances could be given. 

One of the best authenticated cases is the de- 
pendency of partial fluctuation on the season 
and on the weather. Flowers decline when the 
season comes to an end, become smaller and less 
brightly colored. The number of ray-florets in 
the flower-heads is seen to decrease towards the 
fall. Extremes become rarer, and often the 
deviations from the average seem nearly to dis- 
appear. Double flowers comply with this rule 
very closely, and many other cases will easily 
occur to any student of nature. 

Of course, the relation to nourishment is dif- 
ferent for individual and partial fluctuations. 
Concerning the first, the period of development 
of the germ within the seed is decisive. Even 
the sexual cells may be in widely different condi- 
tions at the moment of fusion, and perhaps this 
state of the sexual cells includes the whole mat- 
ter of the decision for the average characters of 
the new individual. Partial fluctuation com- 
mences as soon as the leaves and buds begin to 
form, and all later changes in nutrition can 
only cause partial differences. All leaves. 



724 


Fluctuations 


buds, branches, and flowers must come under 
the influence of external conditions during the 
juvenile period, and so are liable to attain a de- 
velopment determined in part by the action of 
these factors. 

Before leaving these general considerations, 
we must direct our attention to the question of 
utility. Obviously, fluctuating variability is 
a very useful contrivance, in many cases at 
least. It appears all the more so, as its relation 
to nutrition becomes manifest. Here two as- 
pects are intimately combined. More nutrient 
matter produces larger leaves and these are in 
their turn more fit to profit by the abundance of 
nourishment So it is with the number of 
flowers and flower-groups, and even with the 
numbers of their constituent organs. Better 
nourishment produces more of them, and there- 
by makes the plant adequate to make a 
fuller use of the available nutrient substances. 
Without fluctuation such an adjustment would 
hardly be possible, and from all our notions of 
usefulness in nature, we therefore must recog- 
nize the efSciency of this form of variability. 

In other respects the fluctuations often strike 
ns as quite useless or even as injurious. The 
numbers of stamens, or of carpels are dependent 
on nutrition, but their fluctuation is not known 
to have any attraction for the visiting insects. 



Laws of Fluctuations 


725 


If the deviations become greater, they might 
even become detrimental. The flowers of the 
St. Johnswort, or Hypericum perforatum, 
usually have five petals, but the number varies 
from three to eight or more. Bees could hardly 
be misled by such deviations. The carpels of 
buttercups and coliunbines, the cells in the cap- 
sules of cotton and many other plants are vari- 
able in number. The number of seeds is there- 
by regulated in accordance with the available 
nourishment, but whether any other useful pur- 
pose is served, remains an open question. Vari- 
ations in the honey-guides or in the pattern of 
color-designs might easily become injurious by 
deceiving insects, and such instances as the 
great variability of the spots on the corolla of 
some cultivated species of monkey-flowers, for 
instance, the Mimulus quinquevulnerus, could 
hardly be expected to occur in wild plants. For 
here the dark brown spots vary between nearly 
complete deficiency up to such predominancy as 
almost to bide the pale yellow ground-color. 

After this hasty survey of the causes of fluc- 
tuating variability, we now come to a discussion 
of Quetelet’s law. It asserts that the deviations 
from the average obey the law of probability. 
They behave aa if they were dependent on 
chance only. 

Everyone knows that the law of Quetelet can 



726 


Fluctuations 


be demonstrated the most readily by placing a 
snfScient number of adult men in a row, arrange 
ing them according to their size. The line pass- 
ing over their heads proves to be identical with 
tbq.f. given by the law of probability. Quite 
in the same way, stems and branches, leaves and 
petals and even fruits can be arranged, and 
they will in the main exhibit the same line of 
variability. Such groups are very striking, and 
at the first glance show that the large majority 
of the specimens deviate from the mean only to 
a very small extent. Wider deviations are far 
more rare, and their number lessens, the greater 
the deviation, as is shown by the curvature 
of the line. It is almost straight and horizontal 
in the middle i)ortion, while at the ends it 
rapidly declines, going sharply downward at 
one extreme and upward at the other. 

It is obvious however, that in these groups 
the leaves and other organs could conveniently 
be replaced by simple lines, indicating their size. 
The result would be quite the same, and the lines 
could be placed at arbitrary, but equal dis- 
tances. Or the sizes could be expressed by fig- 
ures, the compliance of which with the general 
law could be demonstrated by simple methods 
of calculation. In this manner the variability 
of different organs can easily be compared. 

Another method of demonstration consists in 



Laws of Fluctuations 


727 


gronping the deviations into previously fixed 
divisions. For this purpose the variations 
are measured by standard units, and all the in- 
stances that fall between two limits are consid- 
ered to constitute one group. Seeds and small 
fruits, berries and many other organs may 
conveniently be dealt with in this way. As an 
example we take ordinary beans and select them 
according to their size. This can be done in 
different ways. On a small piece of board a 
long wedge-shaped slit is made, into which seeds 
are pushed as far as possible. The margin of 
the wedge is calibrated in such a manner that the 
figures indicate the width of the wedge at the 
corresponding place. By this device the figure 
up to which a bean is pushed at once shows its 
length. Fractions of millimeters are neglected, 
and the beans, after having been measured, are 
thrown into cylindrical glasses of the same 
width, each glass receiving only beans of equal 
length. It is clear that by this method the 
height to which beans fill the glasses is ap- 
proximately a measure of their number. If now 
the glasses are put in a row in the proper se- 
quence, they at once exhibit the shape of a line 
which corresponds to the law of chance. In this 
case however, the line is drawn in a different 
manner from the first. It is to be pointed out 
that the glasses may be replaced by lines in- 



728 


Fluctuations 


dicating the height of theif contents, and that, 
in order to reach a more easy and correct state- 
ment, the length of the lines may simply be made 
proportionate to the number of the beans in 
each glass. If such lines are erected on a com- 
mon base and at equal distances, the line which 
unites their upper ends will be the expression of 
the fluctuating variability of the character under 
discussion. 

The same inquiry may be made with other 
seeds, with fruits, or other organs. It is quite 
superfluous to arrange the objects themselves, 
and it is sufficient to arrange the flgures in- 
dicating their value. In order to do this a 
basal line is divided into equal parts, the de- 
marcations corresponding to the standard-units 
chosen for the test The observed values are 
then written above this line, each finding its 
place between the two demarcations, which in- 
clude its value. It is very interesting and 
stimulating to construct such a group. The 
first figures may fall here and there, but very 
soon the vertical rows on the middle part of 
the basal line begin to increase. Sometimes 
ten or twenty measurements will suffice to make 
the line of chance appear, but often indentations 
will remain. With the increasing number of 
the observations the irregularities gradually 



Laws of Fluctuations 729 

disappear, and the line becomes smoother and 
more uniformly curved. 

This method of arranging the figures directly 
on a basal line is very convenient, whenever ob- 
servations are made in the field or garden. 
Very few instances need be recorded to obtain 
an appreciation of the mean value, and to show 
what may be expected from a continuance of 
the test. The method is so simple and so 
striking, and so wholly independent of any 
mathematical development that it should be ap- 
plied in all cases in which it is desired to ascer- 
tain the average value of any organ, and the 
measure of the attendant deviations. 

I cite an instance, secured by counting the 
ray-florets on the flower-heads of the com-mari- 
gold or Chrysanthemum segetum. It was that, 
by which I was enabled to select the plant, which 
afterwards showed the first signs of a double 
head. I noted them in this way: 

47 

47 62 
41 54 68 
44 60 62 75 
36 45 58 65 72 — 99 

Of course the figures might be replaced in 
this work by equidistant dots or by lines, but 
experience teaches that the chance of making 
mistakes is noticeably lessened by writing down 



730 


Fluctmtions 


the figures themselves. Whenever decimals are 
made use of it is obviously the beet plan to kecip 
the figures themselves. For afterwards it often 
becomes necessary to arrange them according 
to a somewhat different standard. 

Uniting the heads of the vertical rows of fig- 
ures by a line, the form corresponding to Que- 
telet’s law is easily seen. In the main it is 
always the same as the line shown by the meas- 
urements of beans and seeds. It proves a dense 
crowding of the single instances around the 
average, and on both sides of the mass of tiie 
observations, a few wide deviations. These be- 
come more rare in proportion to the amount of 
their divergency. On both sides of the average 
the line begins by falling very rapidly, but then 
bends slowly so as to assume a nearly horizon- 
tal direction. It reaches the basal line only be- 
yond the extreme instances. 

It is quite evident that all qualities, which 
can be expressed by figures, may be treated in 
this way. First of all the organs occurring in 
varying numbers, as for instance the ray-florets 
of composites, the rays of umbels, the blades of 
pinnate and palmate leaves, the numbers of 
veins, etc., are easily shown to comply with 
the same general rule. Likewise the amount 
of chemical substances can be expressed 
in percentage numbers, as is done on a large 



Laws of Fluctuations 


731 


scale with sugar in beets and sugar-canei, with 
starch in potatoes and in other instances. 
These figures are also found to follow the same 
law. 

All qualities which are seen to increase and 
to decrease may be dealt with in the same man- 
ner, if a standard unit for their measure- 
ment can be fixed. Even the colors of fiowers 
may not escape our inquiry. 

If we now compare the lines, compiled from 
the most divergent cases, they will be found to 
exhibit the same features in the main. Ordi- 
narily the curve is symmetrical, the line sloping 
down on both sides after the same manner. But 
it is not at all rare that the inclination is 
steep on one side and gradual on the other. This 
is noticeably the case if the observations relate 
to numbers, the average of which is near zero. 
Here of course the allowance for variation is on- 
ly small on one side, while it may increase with- 
out distinct limits on the alternate slope. So it 
is for instance with the numbers of ray-florets 
in the example given on p. 729. Such divergent 
cases, however, are to be considered as excep- 
tions to the rule, due to some unknown cause. ' 
Heretofore we have discussed the empirical 
side of the problem only. For the purpose 
of experimental study of questions of hered- 
ity this is ordinarily quite sufficient The in- 



732 


Fluctuations 


quiiy into the phenomenon of regression, or of 
the relation of the degree of deviation of the 
progeny to that of their parents, and the selec- 
tion of extreme instances for multiplication are 
obviously independent of mathematical consid- 
erations. On the other hand an important in- 
quiry lies in the statistical treatment of these 
phenomena, and such treatment requires the 
use of mathematical methods. 

Statistics however, are not included in the 
object of these lectures, and therefore 1 shall 
refrain from an explanation of the method of 
their preparation and limit myself to a general 
comparison of the observed lines with the law 
of chance. Before going into the details, it 
should be repeated once more that the empirical 
result is quite the same for individual and for 
partial fluctuations. As a rule, the latter occur 
in far greater number, and are thus more easily 
investigated, but individual or personal aver- 
ages have also been studied. 

Newton discovered that the law of chance can 
be expressed by very simple mathematical cal- 
culations. Without going into details, we may 
at once state that these calculations are based 
upon his binomium. If the form (a -|- b)" is cal- 
culated for some value of the exponent, and if 
the values of the coefficients after develop- 
ment are alone considered, they yield the basis 



La/u}s of Fluctuations 


73$ 


for the construction of what is called the line or 
curve of probability. For this construction the 
coefiScients are used as ordinates, the length of 
which is to be made proportionate to their value. 
If this is done, and the ordinates are arranged 
at equal distances, the line which unites their 
summits is the desired curve. At first glance it 
exhibits a form quite analogous to the curves 
of fluctuating variability, obtained by the meas- 
urements of beans and in other instances. Both 
lines are symmetrical and slope rapidly down in 
the re^on of the average, while with increasing 
distance they gradually lose their steep incli- 
nation, becoming nearly parallel to the base at 
their termination. 

This similarity between such empirical and 
theoretical lines is in itself an empirical fact. 
The causes of chance are assumed to be innu- 
merable, and the whole calculation is based on 
this assumption. The causes of the fluctuations 
of biological phenomena have not as yet been 
critically examined to such an extent as to allow 
of definite conceptions. The term nourishment 
manifestly includes quite a number of separate 
factors, as light, space, temperature, moisture, 
the physical and chemical conditions of the soil 
and the changes of the weather. Without doubt 
the single factors are very numerous, but 
whether they are numerous enough to be treated 



734 


Fluctuations 


as mnumerable, and thereby to explain the laws 
of fluctuations, remains uncertain. Of course 
the easiest way is to assume that they combine 
in the same manner as the causes of chance, and 
that this is the ground of the similarity of the 
curves. On the other hand, it is manifestly of 
the highest importance to inquire into the part 
the several factors play in the determination 
of the curves. It is not at all improbable that 
some of them have a larger influence on indi- 
vidual, and others on partial, fluctuations. If 
this were the case, their importance with respect 
to questions of heredity might be widely ditfer- 
ent. In the present state of our knowledge the 
fluctuation-curves do not contribute in any 
large measure to an elucidation of the causes. 
Where these are obvious, they are so without 
statistics, exactly as they were, previous to 
Quetelet’s discovery. 

In behalf of a large number of questions con- 
cerning heredity and selection, it is very desir- 
able to have a somewhat closer knowledge of 
these curves. Therefore I shall try to point out 
their more essential features, as far as this can 
be done without mathematical calculations. 

At a first glance three points strike us, the 
average or the summit of the curve, and the ex- 
tremes. If the general shape is once denoted by 
the results of observations or by the co^- 



Lmos of Fluctuations 


735 


cients of the binomium, all further details seem 
to depend upon them. In respect to the average 
this is no doubt the case ; it is an empirical value 
without need of any further discussion. The 
more the number of the observations increases, 
the more assured and the more correct is this 
mean value, hut generally it is the same for 
smaller and for larger groups of observations. 

This however, is not the case with the ex- 
tremes. It is quite evident that small groups 
have a chance of containing neither of them. 
The more the number of the observations in- 
creases, the larger is the chance of extremes. As 
a rule, and excluding exceptional cases, the ex- 
treme deviations will increase in proportion to 
the number of cases examined. In a hundred 
thousand beans the smallest one and the largest 
one may be expected to differ more widely from 
one another than in a few hundred beans of the 
same sample. Hence the conclusion that ex- 
tremes are not a safe criterion for the discus- 
sion of the curves, and not at all adequate for 
calculations, which must be based upon more 
definite values. 

A real standard is afforded by the steepness 
of the slope. This may be unequal on the two 
sides of one curve, and likewise it may differ for 
different caaes. This steepness is usually meas- 
ured by means of a point on the half curve and 



736 


Fluctuations 


for this purpose a point is chosen which lies 
exactly half way between the average and the 
extreme. Not however half way with respect to 
the amplitude of the extreme deviation, for on 
this ground it would partake of the uncertainty 
of the extreme itself. It is the point on the 
curve which is surpassed by half the number, 
and not reached by the other half of the num- 
ber of the observations included in the half of 
the curve. This point corresponds to the im- 
portant value called the probable error, and 
was designated by Galton as the quartile. For 
it is evident that the average and the two quar- 
tiles divide the whole of the observations into 
four equal parts. 

Choosing the quartiles as the basis for cal- 
culations we are independent of all the second- 
ary causes of error, which necessarily are in- 
herent in the extremes. At a casual examina- 
tion, or for demonstrative purposes, the ex- 
tremes may be prominent, but for all further 
considerations the quartiles are the real values 
upon which to rest calculations. 

Moreover if the agreement with the law of 
probability is once conceded, the whole curve is 
defined by the average and the quartiles, and 
the result of hundreds of measurements or 
countings may be summed up in three, or, in 



Lems of Fhictuations 737 

the case of symmetrical curves, perhaps in two 
figures. 

Also in comparing different curves with one 
another, the quartiles are of great importance. 
Whenever an empirical fluctuation-curve is to be 
compared with the theoretical form, or when 
two or more cases of variability are to be con- 
sidered under one head, the lines are to be 
drawn on the same base. It is manifest that 
the averages must be brought upon the same 
ordinate, but as to the steepness of the line, 
much depends on the manner of plotting. Here 
we must remember that the mutual distance of 
the ordinates has been a wholly arbitrary 
one in all our previous considerations. And 
so it is, as long as only one curve is considered 
at a time. But as soon as two are to be com- 
pared, it is obvious that free choice is no longer 
allowed. The comparison must be made 
on a common basis, and to this effect the quar- 
tiles must be brought together. They are to lie 
on the same ordinates. If this is done, each 
division of the base corresponds to the same 
proportionate number of individuals, and a 
complete comparison is made possible. 

On the ground of such a comparison we may 
thus assert that fluctuations, however different 
the organs or qualities observed, are the same 
whenever their curves are seen to overlap one 



738 


Fluctuations 


another. . Furthermore, whenever an empirical 
curve agrees in this manner with the theoretical 
one, the fluctuation complies with Quetelet’s law, 
and may be ascribed to quite ordinary and uni- 
versal causes. But if it seems to diverge from 
this line, the cause of this divergence should be 
inquired into. 

Such abnormal curves occur from time to 
time, but are rare. Unsymmetrical instances 
have already been alluded to, and seem to be 
quite frequent. Another deviation from the 
rule is the presence of more than one summit. 
This case falls under two headings. If the ray- 
florets of a composite are counted, and the fig- 
ures brought into a curve, a prominent summit 
usually corresponds to the average. But next 
to this, and on both sides, smaller summits are 
to be seen. On a close inspection these summits 
are observed to fall on the same ordinates, on 
which, in the case of allied species, the main 
apex lies. The specific character of one form 
is thus repeated as a secondary character on an 
allied species. Ludwig discovered that these 
secondary summits comply with the rule discov- 
ered by Braun and Schimper, stating the rela- 
tion of the subsequent figures of the series. 
This series gives ^ the terms of the dis- 
position of leaves ^ in general, and of the 
bracts and flowers, on the composite flower- 



Loms of Fluctuations 


739 


heads in our particular case. It is the 
series to which we have already alluded 
when dealing with the arrangement of the leaves 
on the twisted teasels. It commences with 
1 and 2 and each following figure is equal to 
the sum of its two precedents. The most com- 
mon figures are 3, 5, 8, 13, 18, 21, higher cases 
seldom coming under observation. Now the 
secondary summits of the ray-curves of the 
composites are seen to agree, as a rule, with 
these figures. Other instances could readily be 
given. 

Our second heading includes those cases 
which exhibit two summits of equal or nearly 
equal height. Such cases occur when dif- 
ferent races are mixed, each retaining its own 
average and its own curve-summit. We have al- 
ready demonstrated such a case when dealing 
with the origin of our double com-chrysantbe- 
mum. The wild species culminates with 13 rays, 
and the grandiflorum variety with 21. Often 
the latter is found to be impure, being mixed 
with the typical species to a varying extent. 
This is not easily ascertained by a casual in- 
spection of the cultures, but the true condition 
will promptly betray itself, if curves are con- 
structed. In this way curves may in many in- 
stances be made use of to discover mixed races. 

Double curves may also result from the inves- 



740 


Fluctuations 


tigation of true double races, or ever-sportiug 
varieties. The striped snapdragon shows a 
curve of its stripes with two summits, one cor- 
responding to the average striped flowers, and 
the other to the pure red ones. Such cases may 
be discovered by means of curves, but the con- 
stituents cannot be separated by culture-exper- 
iments. 

A curious peculiarity is afforded by half- 
curves. The number of petals is often seen 
to vary only in one direction from what should 
be expected to be the mean condition. With 
buttercups and brambles and many others there 
is only an increase above the typical five; 
quatemate flowers are wanting or at least are 
very rare. With weigelias and many others the 
number of the tips of the corolla varies down- 
wards, going from five to four and three. Hun- 
dreds of flowers show the typical five, and de- 
termine the summit of the curve. This drops 
down on one side only, indicating unilateral 
variability, which in many cases is due to a 
very intimate connection of a concealed sec- 
ondary summit and the main one. In the 
case of the bulbous buttercup. Ranunculus bid- 
hosus, I have succeeded in isolating this second- 
ary summit, although not in a separate variety, 
but only in a form, corresponding to the type 
of ever-sporting varieties. 



Laws of Fhictuations 


741 


Beoapitulating the results of this too con- 
densed discussion, we may state that fluctua- 
tions are linear, being limited to an increase and 
to a decrease of the characters. These changes 
are mainly due to differences in nourishment, 
either of the whole organism or of its parts. 
In the first case, the deviations from the mean 
are called individual; they are of great impor- 
tance for the hereditary characters of the 
offspring. In the second case the deviations 
are far more universal and far more striking, 
but of lesser importance. They are called par- 
tial fluctuations. 

All these fluctuations comply, in the main, 
with the law of probability, and behave as if 
their causes were influenced only by chance. 



Lecture XXVI 


ASEXUAL MULTIPLICATION OF EXTREMES 

Fluctuating variability may be regarded from 
two different points of view. The multiformity 
of a bed of flowers is often a desirable feature, 
and all means which widen the range of fluctua- 
tion are therefore used to enhance this feature, 
and variability affords specimens, which sur- 
pass the average, by yielding a better or larger 
product. 

In the case of fruits and other cultivated 
forms, it is of course profitable to propagate 
from the better specimens only, and if possible 
only from the very best. Obviously the best are 
the extremes of the whole range of diverging 
forms, and moreover the extremes on one side of 
the group. Almost always the best for practical 
purposes is that in which some quality is 
strengthened. Cases occur however, in which 
it is desirable to diminish an injurious pecul- 
iarity as far as possible, and in these instances 
the opposite extreme is the most profitable one. 

These considerations lead us to a discussion 

742 



Multiplication of Extremes 743 

of the results of the choice of extrmes, which it 
may be easily seen is a matter of the greatest 
practical importance. This choice is generally 
designated as selection, but as with most of the 
terms in the domain of variability, the word 
selection has come to have more than one mean- 
ing. Facts have accumulated enormously since 
the time of Darwin, a more thorough knowl- 
edge has brought about distinctions, and di- 
visions at a rapidly increasing rate, with which 
terminology has not kept pace. Selection in- 
cludes all kinds of choice. Darwin distin- 
guished between natural and artificial selection, 
but proper subdivisions of these conceptions are 
needed. 

In the fourth lecture we dealt with this same 
question, and saw that selection must, in the first 
place, make a choice between the elementary 
species of the same systematic form. This 
selection of species or species-selection was the 
work of Le Couteur and Patrick Shirreff, and is 
now in general use in practice where it has re- 
ceived the name of variety-testing. This clear 
and unequivocal term however, can hardly be 
included under the head of natural selection. 
The poetic terminology of selection by nature 
has already brought about many difficulties that 
should be avoided in the future. On the other 
hand, the designation of the process as a natural 



744 


Fluctuations 


selection of species complies as closely as possi- 
ble with easting terminology, and does not 
seem liable to any misunderstanding. 

It is a selection between species. Opposed to 
it is the selection within the species. Manifest- 
ly the first should precede the second, and if this 
sequence is not conscientiously followed it will 
result in confusion. This is evident when it 
is considered that fluctuations can only appear 
with their pure and normal type in pure strains, 
and that each admixture of other units is liable 
to be shown by the form of the curves. More- 
over, selection chooses single individuals, and a 
single plant, if it is not a hybrid, can scarcely 
pertain to two different species. The first 
choice therefore is apt to make the strain pure. 

In contrasting selection between species with 
that within the species, of course elementary 
species are meant, including varieties. The 
terms would be of no consequence if only right- 
ly understood. For the sake of clearness we 
might designate the last named process with 
the term of intra-specific selection, and