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SEPTEMBER, 1894. 


The evolution of the Hepatic*. 

Vice-presidential address before section G, A. A. A. S. 

LUCIEN M. UNDERWOOD. 

There is, perhaps, a natural tendency among specialists to 
magnify the importance of the particular subject or group of 
life forms in which they happen to be specially interested. 
The horticultural botanist, dreaming of the time when the 
world will be reorganized through the products of Ins art, is 
prone to see nothing beyond utility and ornament in plants, 
and it becomes a part of his nature to see some useful char¬ 
acter in forms of vegetation which to others are devoid of 
cither beauty or utility. The economic mycologist, over-im¬ 
pressed with the magnitude of the losses sustained by the uit** 
fortunate agriculturist and fruit grower, is haunted in sleep 
with visions of anthracnose and mildew, anil in his waking 
hours sees little in botany but host-plants bristling with 
asites and Bordeaux mixtures certain to relieve them of their 
incubus. The man with inherent, if not coherent, proclivi¬ 
ties for priority, with a war-like temperament and a strong 

tendency to cross lances, sees in botany one vast battle field 
synonymy in which cohorts of pre-Linnaean binomials, 
hordes ot decapitalization dogmas, hostile homonyms and 
untzian curiosities charge down upon each other in batta 
tons, form and reform in utter confusion. There are some 
microscopic botanists whose degree of specialization never 
Permits them to look outside the limits of an apical cell, an 
others still whose botanical horizon is bounded by the ne o 
*n immersion lens and whose azimuth and right ascension are 
Ca Culated within its limits. We are all more or less inc mei 
o ride our own hobbies in public places, so in performing t c 
mitiai function of this office, I can perhaps do no better than 
bring forth mine. In this way, I shall at least be in touc 1 

* ,th present custom. 

Vol. XIX. —Ho. 6. 

















34S 


The Botanical Gazette. 


[September, 


With no desire, however, to overestimate its importance, 
I wish to place before you the position in the botanical sys¬ 
tem of a comparatively obscure group of plants and to cal! 
your attention for a brief time no less to their own differen¬ 
tiation than to their important relation to the evolution of 
the plant world. I desire to set forth in something of a rea¬ 
sonable way the characters of the group and to correct some 
misunderstandings that have resulted from an imperfect appre¬ 
ciation of its relations. The group commonly known as He- 
paticae has suffered at the hands of general botanists, and through 
them an incomplete and one-sided conception is transmitted 
to the generation of botanical students now coming to their 


maturity. 


The 


average 


text-book of botany emphasizes 


more limited 


strongly the representative character of Marchantia poly* 
morpha. In elementary laboratory guides, this is even made 
to stand as the sole representative of all the bryophytes. in 
those somewhat more comprehensive, it is made a type of the 

group, the Hepaticae, and in even the m°st 
complete it is made to stand pre-eminent as the representa 
tive of this triply developed group of plants, notwithstanding 
the fact that the other members of this trio are vastly more 
important—one in the nature and extent of its developmen 


IC clliu CAICIH *-- * 1 

important relations to the eve 
■■ ■ ■■■ mt ’ One ele- 


opment of the higher groups of the plant world, 
mentary text-book that has in general done much to eeva 

^America during the 

Hepaticae with these 


vav- us atLuum wi mv. I— * rn *)St 

In the liverworts the plant body is far t e 


words: 

part either a true thallus or a thalloid structure 

there 


the standard of botanical teaching in 
past decade opens its account of the 



is a 


differentiation into stem and leaves, etc. 


statement may be taken 
of the group common among 


This 


concept^ 11 


as fairly represent.ng a 

ot the group common among botanists and botanii^ . |j flJC 
The hepatics among us are popularly supposed to e m3 j 

or thalloid plants and Marchantia is regarded as a 


representative. 


I ^ ^ 9 . 

As opposed to this wide-spread ^ 


1 uppuom IV/ ” -- i At* 

tion, it should be noted that as far back as the 
last publication of a general synopsis of tMe H e P at,c ^ w3 ; 
the relative numerical importance of the Marchantia ^ ^ 
only 17 per cent, of the entire group and the mere 


that time has been even more 


largely in the d 1 rection 0^ 


-^ ^ ^ y fc-/ w J. M M. M. V w a a v. * ^ ^ ^ ^ 

represent at once the most numerous and best 



1894] 


The Evolution of the Hepaticce. 


349 


types of the Hepaticae. 1 It would be even less a misrepre¬ 
sentation of the Musci to make its representatives in An- 
dreaea, Phascum or Buxbaumia than to place Marchantia or 
any of its allies as a normal representative of the Hepaticae. 
Armed, however, with such a conception gained from the 
elementary texts and emphasized by the works of reference 
usually accessible in an ordinary laboratory, as for example 
Knv, Strasburger, Sachs, and Goebel, the student goes forth 
into the field to study liverworts and after he has exhausted 
Marchantia and Conocephalus, and has possibly seen a Ric¬ 
ci* 1 - he is usually stranded and knows not what to seek. In 
fact, many are more likely to confuse some such thallose 
lichen, as Peltigera, with liverworts than to look for them 
among leafy forms which their training has not rendered them 
able to properly correlate. The Lophocoleas, the Ccphalo- 
zias, the Frullanias and the Radulas, so elegant in their 
structure as to impress the least aesthetic student with their 
beauty, so diversified in their evolution as to demand the ex- 
crcise of his most active powers of reflection, and withal so 
simple in structure as to render them accessible with a mini- 
mum of microscopic technique—these are a closed volume to 

because of the limitations of his early instruction and im¬ 
pressions. 


The group known since the time of Adanson as the Hepat- 
1( pc stands in a unique position on the boundary line of 
tllallose and leafy plants, and its position is not only inter¬ 
mediate from the structural standpoint, but in its relation to 
t e evolution of the higher plants it stands as a key' or link 
♦-tween the lower and simpler and the higher and more com- 
P ex. The group is not a compact one nor are its component 

flftrmnc 1_ . r . ». . _ . _ 1 J n ,.Kfprl 


l<9 uui CL -- 

groups closely united to each other. It is even to be doubted 
| good reason exists for the separation of the bryophytes 
? to thc two classes Musci and Hepaticae, and it would be 
azardous to attempt their separation as coordinate groups 
°n any rational grounds, even if we leave in question their 
c at * on to the Sphagnaceae.^^^^^^^^ _ 

5 e lative extent of the Jungermaniace® as developed by modern explc» 

genera- su t> s equent study can be seen in a comparison of a few represen a i 


; M «zgeri a .. 
J^Fbocolea 
* ««iochil a 


Species described in 
Synopsis Hepaticarura i844~47- 

. 8 . 

.69. 

. l 79 . 


Species reported by 
Schiffner 1893. 

. 3 6 

.. 149 

.463 



















350 


The Botanical Gazette. 


[September, 


The hepatics possess almost absolutely no utilitarian aspect. 


Beyond the doubtful use of one or two in medicine, and the 


occasional occurrence of one or more tropical species as weeds, 


they are, so far as the physical condition of the human race 


is concerned, an entirely useless group of plants. They do 


not trouble the experiment station botanist, the horticulturist 


finds no use for them, and the general public does not see 


sufficient importance in them to 


subscribe a single shilling 


for the endowment of a laboratory for research in such an 


apparently barren field. And yet from the higher stand¬ 


point of genetic relationship, there is probably no single group 

H ^ ^ ^ ■ A A V I ^ L 


of plants that occupies such an unique position in the plant 


world. What the comprehensive and heterogeneous group 


“Vermes" is to the animal kingdom, the Hepatic® are to 


plants, with this difference, that we have here a much lcs> 


complicated group of organisms with which to deal. 


To understand more fully the relation of the Hepatic* to 


the evolution of the green plants and particularly to their ro c 


in the development of the alternation of phases of reprodud 

tion which has attained such extended proportions in *- 

ferns and other pteridophytes, it is desirable to bring in t‘ e 
review the successive stages in the processes of reproduction 
from the simplest forms upward. For it must be remem re 
that even if the methods of reproduction cannot serve as 1 

means of separating the primary types of the tha °P 1 * V 
in a natural system of classification, they nevertheless rep 
sent the highest function that is manifested in organic 


The successive stages may be characterized as follows. 


I. Among forms whose only method of reproduction 


con¬ 


sists of fission, in which the individual life b^ins with 

-- 1^: _r .___ rp II dlVlSlOO 




completion of the karyokinetic process of cell 
closes when its individuality is lost in the next ^ 


produced, the type of the life history of the organism 


* 'Jr ' , * Ktfflf W 

represented by a straight line whose terminatioi - 


lation to each other. There is no round of l*l e h'~ - ; 


no 


Auiivju tu Lav.il uluci. l iicic 15 ii yj 

cycle of development where fission is the law of repr ^ 


\V*Cr ir "' 

II. Among forms in which conjugation occurs.^^^^ 
successive stages of distinct sexual reproduction o c ^ -*• 

fore thp iHpn of Kicpvnalrf'u been differentia 


IVo 


idea of bisexuality has been aineici**-—;-oi 
purposes seem involved in this process, (0 the . an( j 2 

vitality by the union of elements of separate ^ott 

the production of a structure capable of holding V1 













1894] 


The Evolution of the Hepaticce. 


351 


certainly through critical changes of environment; hence the 
resting-spore. We have here a type of life history where 
continuity commences to curve into a circle and its ends begin 
to unite to form a complete cycle of development. In many 
forms, however, the individual is too hopelessly entangled in 
colony life to be clearly separated. 

III. In forms (like Vaucheria) where the sexual cells arc 
clearly distinguishable from the early commenceirtent of the 
process of reproduction, and the oospore results directly and 
simply from the act of fertilization, the life history of the 


plant may be clearly said to be represented by the circle. 
I he phase of growth is purely a sexual one from spore to 
germinating filament through the production of sexual ap¬ 
paratus to spore again. If asexual reproduction occurs, it 
merely serves to rapidly multiply the plant when favoring en¬ 
vironment makes it possible, and bears no relation to the 
sexual process and is not dependent upon it. 

. Among some of the higher algae occurs the simplest 
form of alternation of phases of reproduction. While there 
are various modifications of the process in minor details in 
man}’ groups of algae, the act of fertilization in certain repre¬ 
sentative forms is followed (1) by the formation of a special 
envelop of cells about the oogone as a specialized protective 
covering, and (2) by the division of the cell contents of the 
oogone into a series of reproductive bodies, an asexual pro¬ 
cess following as a result of a sexual one and therefore de¬ 
pendent on it. The life history here, instead of representing 
* simple cycle of growth, can be best characterized as acotn- 
•nation of two loops each short of a circle, the larger repre¬ 
senting the sexual stage from germinating spore to the com- 
P*etion of the process of fertilization, and the smaller represent- 
l,) g the asexual phase involved in the internal cell division that 
results in the development of the reproductive bodies. The 
called “alternation of generations”, which is nothing more 
. *be succession of phases in the life history of the organ- 

t Copitnences at a point considerably below the lowest 

bryophytes. 

V. ^ be transition from the above condition to tbilTwhicIi 

c find in the lowest archegoniates is a simple one. The ad¬ 
duce manifests itself in the following particulars: (1) i n * c 
otective envelop of the egg cell being developed prior to the 
0 fertilization and not as a result of it; (2) in the some- 





352 


The Botanical Gazette. 


[September, 


what more complex development of the asexual phase (spor- 
ogone) in the formation of a definite multicellular wall and the 
division of the interior by a double process of cell multiplica¬ 
tion. Most of these details even are more or less feebly fore¬ 
shadowed in some of the higher algae. The only modification 
necessary in the diagrammatic representation of the lower bry- 
ophytes as contrasted with that of the higher algae is the rel¬ 
atively greater development of the asexual phase which is 
therefore represented by a proportionally larger loop. The 
lines of specialization which have resulted from the varied 
differentiations of this simple type will be discussed more in 
detail later in this paper. 

VI. The highest development of the principle of alternation 
of phases of reproduction is illustrated by the well known cli¬ 
max reached among the pteridophytes in which the asexual 
phase represents a degree of specialization utterly dispropor¬ 
tionate to the simple sexual phase (prothallus) which has 
scarcely advanced beyond the primitive condition reached b) 
the lowest archegoniates. The diagrammatic representation 

of the life history of the fern is therefore a reversal of that o 
the higher algae, the larger loop representing the highly • 
ferentiated asexual phase and the smaller the simple tha ose 

sexual phase. # 

The high degree of differentiation of the asexual ph ase / ) 
the pteridophytes coupled with the great antiquitjf-offlPB 
group have rendered them a stumbling block to ^any ^ 

have not been careful in tracing their homologies 

olution of the pteridophytes, however it must be 
that the line of descent must be sought, not in a compaf 
of the highly developed asexual phase of the one wit 
simple sporogone of the other but along the line of the st c j 
sexual phase. When we consider this feature of t c ^ ^ 
opment in its proper light, the progress of evolution ^ 
alga to fern is greatly simplified and the distance e' ve ^ 

groups either in the time necessary for the ^ e l° n n tiatior* 
one from the other or in the slight degree of di er j n imud 
manifest in these coordinate phases, is reduced to a nn ^ } 
From higher algae to simple prothallus the transition 

difficult one. In regard to the other feature of t phase 
it maybe suggested that the development of the nsex^^ an( j 

of fern-like plants which dates back to the konifero 115 ’ 
reached a high degree of specialization in the ar 


in mcc* 


remembered 








1894 .] 


The Evolution of the Hepaticce. 


353 


may have been strongly influenced and perhaps rapidly 
evolved by the peculiar environment of precarbonifcrous 
times; at least the statements of the books in reference to the 
excessive amount of carbonic oxide in the atmosphere being 
peculiarly adapted to the growth and development of the 
lower pteridophytes would support such a hypothesis. On 
this point, however, it may be questioned whether the state¬ 
ments of the books do not need some modification. 

I have said that the Hepaticae have undergone a triple dif¬ 
ferentiation. Commencing with a simple thallose plant with 
its unmodified sporogone, it is evident that there are three 
possible lines of specialization: (1) the development of the 
thallus as such; (2) the transformation of the thallus into a 
leafy axis combined with the modification from creeping to 
ascending or erect habit; and (3) the specialization of the 
sporogone at the expense of the thallus. Even a cursory ac¬ 
quaintance with the diverse structures that are developed in 
the group will make it evident that the Hepaticae have im¬ 
proved their opportunity in each of these three possible lines 
and have carried the differentiation of each line to a high de¬ 
gree of perfection. Let us follow out in some detail these 
three lines of development. 

I. The Marchantiales. We must place as lowest in the 
series the group which commences with such simple types as 
Riceia. and Tesselina and ends with the elaborate Marchantia 
*# 4 ''its congeners. Among the lowest types the habit is not 
greatly different from that of the algae, the plants either float¬ 
ing in water or attaching themselves to wet soil. The cap¬ 
sular development in the lower forms moreover is not very 
diverse from that of certain of the higher algae, thesporog*>nc 
>eing without stem and often imperfectly surrounded by a 
capsular wall. As we advance to higher forms, we find not 
only an extensive modification of the thalloid structure neces¬ 
sitating an elaborate system of stomata and in many cases 
jjpccially modified branches for the better accommodation of 

reproductive bodies, but also a striking advance in the 

psular development in which the egg cell develops not only 
a capsule or fertile portion, but also a stalk or sterile portion, 
j*j»»ch with the addition of elaters formed within the capsule, 

serves to distribute the spores. 

^ e [nay note here also two types of differentiation ill t c 
specialized branch that bears the carpocephalum, as it ex- 










354 


The Botanical Gazette . 


[ September, 


plains some seeming anomalies in the fruiting habits of some 
of our common Marchantiaceae. The impression has prevailed 
and is now wide spread that while Marchantia may commonly 
be found in fruit, Conocephalus rarely produces it. The 
fruiting branch of Marchantia is developed before the matur¬ 
ity of the sporogone is reached. This branch is therefore 
firm and consequently persistent. The botanist who only 
rarely comes in contact with plants except as they are pre¬ 
served in herbaria or imbedded in celloidin has considerable 
opportunity to see the fruit bearing branches of Marchantia 
as they are developed, long before the spores are mature and 
persist long after the spores are scattered. On the other 
hand, Conocephalus, whose archegones are fertilized during 
the late summer or early autumn, matures its capsules within 
the carpocephalum before the fruit bearing branch of thethal- 
lus is developed. In this condition it passes the winter and 
with the earliest return of spring the reserve material of the 
thallus rapidly aids in 


sending up 



_ r _ j .. ... _ o „ r . a semi-hyaline slender 

Ibranch which lasts barely long enough to allow the capsules 
to burst through their calyptrae and then withers away, b} 
the time the spring botanist, roused from his hibernation, 
goes forth to search for Anemone or Epigaea, Conocepha us 
has long since scattered its spores, its fruiting branch ' sU!t l 
ered, and the late observer concludes that it rarely pro ucu 
fruit. He who will become a botanist in any broad sense 

must come in contact with nature face to face at all s< ^ son ^ 
and study plants as they grow, as well as in the her ariu • 

and laboratory. The man who sees and studies plants 
as they are represented by dried herbarium fragments ot 
accordance with the stereotyped formula, “treated wit a^ 
per cent, solution of chromic acid, stained in mass wttip 1 
carmine, imbedded in paraffine and cut with a Minot , 
tome,” is sure to get a one-sided notion of the true 

gies of the vegetable world. , nf ; a le< 

While all the minutiae of the relations of the Marc a 
have not been worked out, the following provisiona a ^ ra p 
ment (see diagram opposite) will give some idea o 

finities. u»i-cat* 

From simple forms like Riccia, themselves doubt ess 


siderable advance over the primitive hepatic- 


A cl ftrhtly ft ort 

modification in Ricciocarpus and Tesselina, an y s ^ 

■ ■ Corsinia and Funicularia.^.^ 

former are allied such higher forms as Clevea, Y 


differentiated forms 





The Evolution of the Hcpatica. 


355 


1894.] 


Hypenantrum; from forms allied to the latter we have on the 
one hand Cyathodium and Targionia with their sessile fruit, 
and on the other, Lunularia, Conocephalus and Marchantia, 



Primitive hepatic 

^hich justly may be regarded as the highest thalloid develop 

appears among the Hepaticae. . 

t . H. The yungermaniedes. The second line of d.ffcrent.a- 

to, i among the Hepaticae is in the direction of the - orffia J 5 
0 a leafy axis. From such thalloid forms as AllBiiffc 






356 


The Botanical Gazette. 


[September, 


scarcely developed central axis to such simple modifications 
as appear in Pallavicinia and Metzgeria, in which the central 
axis becomes distinctly differentiated from the plain wing-like 
border a single cell in thickness, it is an easy step to pass to 
such pseudofoliaceous forms as Schiffneria, Fossombronia and 
Haplomitrium. From these forms again it is not difficult to 
pass to some of the simpler leafy axes like Lophocolea, Baz- 
zania, and Jungermania. It is in this group that we find the 
Hepaticae attaining their greatest profusion of structure, the 
most remarkable diversity of foliar development, the widest 
range of adaptation, and the consequent abundance of genera 


and 


- species that span the world from the lone and barren 

island of Kerguelen in the south to the inhospitable region of 
Spitzbergen in the north. Here some three thousand species 
have been developed, and judging from the rapidity of the 

returns, it is evident that the tale is not nearly told. 

It is, of course, impossible, within the limits of the time 
assigned, to attempt to touch upon the numerous features o 
the evolution which this group has undergone in diverse quar¬ 
ters of the world; we can only hint at some of the morestn 
ing by way of illustration. . . 

I. The protonemal development among the Jungermania es 

is usually slight and ephemeral; in only occasional instances 

do we find it persistent. Perhaps the most striking il uS ^ 
tion of this is Protocephalozia, in which the formation o ea ^ 
occurs only as a special development for the protection o 

, ' _ The antherids are borne singly 

axils of rudimentary leaves while the perianth, subten e 


reproductive bodies. 


inal pm 


slender involucral leaves, rises directly' from the ongina ^ ^ 
tonema which represents the entire vegetative con i 1 

the plant. 


plant. i .jy 

. The lines of development leading from thallose 

forms are numerous among the Jungermaniales, an ^ 

them have not yet been definitely' correlated. ,. er . a . f f rn m 
4 . 4.1 _:__• 1!_r as distinct I 


While 


Liiiw lundLCUUw) UIlLb # VV I111C LI1C DC 

forms do not produce their fruit terminally" and J e j C t j ie j/*-/:* 

separated into a distinct family which may be ca e 


geriacecz from its typical genus, there are se ^ W1U . 

which thallose forms lead up toward foliaceous < ^ ^ eVC ;. 

which they agree in the closer relation of sporogo bear 
opme;nt, as well as in the more important fact t ia 


veral instances 


with 











The Evolution of the Hepaticae. 


357 


1894.] 


the sporogone terminal on the main stem or on a branch. 
The line of this character that is best known is perhaps that 
leading up to the Trigonantheae from Zoopsis to Cephalozia. 
From the simplest thallose structure, differing only slightly 
from algae, the various species of Zoopsis become developed 
so as to present the successive modifications of a leaf of a 
single cell, a leaf of two cells, and a leaf of four cells; from 
these steps the passage is easy to such simple two-toothed 
decurrent leaves as we see developed in some of the Ccpha- 
lozias, especially in our common Cephalozia multiflora. The 
fruiting characters in this series are so strikingly alike that 
they have even been united in a single genus. 

3- Perhaps no single group presents so many modifications 
in the diversity of foliar structure as is manifested in the var- 


J 


With 


cells forming a more or less well developed lamina, the great¬ 
est conceivable variety of form coupled with modification 


arising from environment 

fiNMWHiiiiiiiiHII 


has been differentiated, and we 


numerous examples of marvellous adaptation of means to 
end. From these we may note the simple tripartite leaves 
of Blepharostoma made up of simple rows of cells; the intri¬ 
cately divided leaves of Trichocolea and Ptilidium which give 
to the species of those genera their peculiar tomentose ap¬ 
pearance; the ciliary fringes of endless variety that character¬ 
ize the numerous species of Plagiochila; the median lamina 
of Schistocheila recalling a similiar development in Fissidens 
among the true mosses, and above all the innumerable para- 
phyllia of Stephaniella, often covering the entire surface of 
the leaf. These merely indicate a few of the possibilities of 
the foliar development. In the leaf cells themselves, we have 
€ycry grade of compactness, varying from the lax structure 
® Cephalozia, Chiloscyphus and Kantia to the close compact 
structure of Herberta and Gymnomitrium. 

ut beyond all these are the various forms of complication o 

adapted to serve as retainers of moisture. From 

,c simple folds in the leaves of Radula, Scapaniaand Diplophyl- 

u m. we pass to the basal pockets of Lejeunea which are 

sometimes elaborately differentiated, and the water sacs of 

0 u,a, Frullania and more especially Polyotus in which t cy 
sometimes developed in great profusion. As mighty e 
xpected, these peculiar foliar adaptations for holding moist 
re most prominent in those species that have been driven 




353 


The Botanical Gazette. 


[September, 


from their normal habitat on the ground and on decaying 
logs to the bark of trees and even the surface of leaves, 
which in tropical countries are often wholly covered with var¬ 
ious species of Lejeunea, 2 together with an occasional Radula 
and rarely species of other genera. The reputed symbiosis of 
rotifers and other small animals with these water sacs of 
Lejeunea and Frullania has been commented on by many ob- 
servers. 

4. No less remarkable is the development of the perianth 
which serves as a special protection to the maturing sporo 
gone. This is normally free from the uppermost stem leaves, 
which are usually modified from the ordinary form. In cer¬ 
tain genera like Nardia, Marsupella, Schistocheila and Har- 
panthus, the perianth becomes more or less adherent to the 
involucral leaves and in some instances forms a bulbous or 
gibbous enlargement at the base. An exaggeration of this 
bulbous development produces the marsupiocarpous conditio 

found in Kantia, Geocalyx, Tylimanthus and several ot er 
genera, in which the sporogone is developed at the base 0 a 
pendulous pouch which penetrates the substratum, or in t e 
tropical Tylimanthus is hung among the stems of vanoir 
mosses which grow in its vicinity. It is of interest to no 
that this condition has been developed independent y * 1 * 
widely different sections of the family and cannot be: cons' 
ered as forming a tribal alliance by itself as was former, 

maintained. > 

It must now be evident that the Jungermaniales, a ° v _ 

other Hepaticae, are the types in which the most e a 0 ^ 
development has taken place and that they must ^ 

typical representatives of this class. When we a ^ 

great degree of differentiation, the wide-spread 
distribution of the Jungermaniales which has nuently 

ulating almost every available island in the wor , ® 

with endemic species, it becomes evident 
tribute a great antiquity to the group, 
absence of the hepatics in fossiliferous rock:. nintv 

sons, should count as little in determining their an 

III. The Anthocerotales. Having considered t e we 

in which the hepatics have disported themselv es as^ — 

--------r-rvrn^bat 

*1 have only once found our Lejeunea calcarea in India • 
it completely covered a small leaf of Camptosorus growing 1 owing 35 
ravine. This is the first instance known to me of Leje 
epiphyte in northern latitudes. 


that we mus| 

The compa rat; ^ 
for obvious re* 









The Evolution of the Hepaticce. 


359 


> 894 ] 


come finally to the group in which their development has 
looked toward something higher in the plant world. If the 
Marchantiales have elaborated the thallus at the expense of 
other parts, and the Jungermaniales have developed leafy 
axes and exhausted their energies in the elaboration of beauty 
and intricacy of foliar development, the Anthocerotales have 
found a more important line in which to differentiate, namely, 
the development of the sporogonc. And while it has resulted 
in small returns when considered from a hepatic standpoint, 
the results otherwise are commensurate with the whole range 
of higher plants from mosses to Composite. 

In the Anthocerotales, the thallus has undergone only a 
slight differentiation from the primitive type; the sporogone, 
however, develops into a fleshy structure that frequently re¬ 
quires stomata for its transpiration processes. The capsule 
is necessarily a somewhat permanent structure and unlike all 
other bryophytes, develops its spores continuously from above 

downward. 

The ancestors of Anthoceros and Notothylas on the one 
hand, and the Musci on the other, were doubtless the same, 

and the line of separation between them probably commenced 

at an early day, since the elaboration of genera and species 

is no less marked in the Musci than in the foliaceous Hepat¬ 
ic®. ■ % Jsk PCS® 


It has further become evident that the line of development 
°f the leptosporangiate ferns, leading upward to the line of 
the higher plants, is to be sought as a branch from the prifH» 
itive Anthocerotales. While more investigation is necessary 
in this direction, the general relations may be indicated y 
the diagram on the following page. 

The early forms of Anthoceros were not swerved from t cir 

they have continued the development of the sporog 

one at the expense of the thallus and today stand unique 
among the Hepatic®. They differ as widely from all other 
members of the group as do the Musci and Sphagnace* and, 
°r this reason combined with others, the class Hepatic* as 

little __ 1 ceihru 

tion 


reason 


~ - jvji 1UJ LUC! CAlblCIlLC HI UUJ 

m. A reorganization becomes necessary as soon as tte r<. 
®aini||g bryophytes can be properly co-ordinated. 

^ e can then summarize the relations of the Hepatic*. 

!• The group is not of recent origin. This is shown no^ 
\ from the wide-spread geographic distribution o its ma 






3 6 ° 


The Botanical Gazette. 


[September. 


jor group, and its extensive modification into diverse genera, 
but as well by its relations through the Anthocerotales to 
higher groups which have themselves a high antiquity. 



Primitive 


Hepatic 



Algae. 


2. The group is not a compact one, nor is 


j t entirely*" 

groups of the Hepatic® f bovt n 


cumscribed. The three ^iuup ^ th^ 

lined differ as much or more among themselves a ^ (or j 

ing bryophytes differ from them. Ther£ is a ^ present 
new grouping of the bryophytes to accord 




The Evolution of the Hepaticce. 




knowledge. The present grouping into Musci and Hepatic® 
as coordinate classes, is entirely unsatisfactory, and artificial. 

3. In such a triple development as exists among the He¬ 
patic®, no single plant can stand as a type which will fairly 
represent the entire group. If a single plant is to be consid¬ 
ered, however, it would be only fair to make the selection 
from the group which is at once the most highly specialized 
structurally and the most widely represented in all parts of 
the world. To the Jungermaniales, and not to the Marchant- 
iales, belongs this distinction. 

4- We must recognize at least five families among the He¬ 
patic®. Among the Jungermaniace®, it is well to separate 
those forms in which the archegone terminates the growth of 
the shoot from those in which the archegone is distinctively a 
lateral development. The “Jungermaniace® anakrogyn®" 
of Leitgeb and Schiffner, which will include many but not all 
of the “Jungermaniace® thallos® ” of previous writers, may 
well be separated as a distinct family for which we propose 
the name METZGERIACEiE. The older name, Jungerman- 


lace®, may properly be retained for the remaining part of the 
family which includes by far the greater number of genera and 

species. ^ 

5 - The Hepatic® are especially interesting as constituting 
the connecting link in the evolution from thallophytes ;alg®) 
to the higher plants. In this particular, the line of the An- 
thocerotales in which mere vegetative function is sacrificed 
for the sake of reproductive function, represents the royal line 

°f development. 

Te Pauw University , Greencastle , Ind.