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THE JOURNAL OF 
AGRICULTURAL SCIENCE 



CAMBRIDGE UNIVERSITY PRESS 

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THE 

JOURNAL 

OF 

AGRICULTURAL SCIENCE 

EDITED FOR THE PLANT BREEDING AND ANIMAL NUTRITION RESEARCH INSTITUTES AT CAMBRIDGE, 
AND THE ROTHAMSTED RESEARCH INSTITUTES BV 

Professor R. H. BIFFEN, M.A., F.R.S., Cambridge 

Sir a. D. HALL, K.C.B., M.A., LL.D., F.R.S., Ministry of Agriculture, London 

F. H. A. MARSHALL, Sc.D., F.R.S., Cambridge 

Sir E.J. RUSSELL, D.Sc, F.R.S., Rothamsted Experimental Station, Harpenden 

Professor T. B. WOOD, C.B.E., M.A., F.LC, F.R.S., Cambridge 

IN CONSULTATION WITH 

B. C. ASTON, Department of Agriculture, Wellington, New Zealand 

Dr C. a. barber, C.I.E., School of Agriculture, Cambridge 

Professor B. T. P. BARKER, M.A., National Fruit and Cider Institute, Long Ashton, Bristol 

W, BATESON, M.A., F.R.S., John Innes Horticultural Institute, Merton, Surrey 

J. R. CAMPBELL, B.Sc, Department of Agriculture, Dublin 

I. B. POLE EVANS, Department of Agriculture, Pretoria, South Africa 

F. B. GUTHRIE, Department of Agriculture, Sydney, N.S.W. 

Professor J. HENDRICK, B.Sc, Marischal College, Aberdeen 

Sir T. H. MIDDLETON, K.B.E., C.B., M.A., The Development Commission, London 

Dr frank T. SHUTT, F.I.C, Experimental Farms, Ottawa, Canada 

Professor W. SOMERVILLE, M.A., D.Sc, School of Rural Economy, Oxford 

Dr a. C. TRUE, Department of Agriculture, Washington, D.C., U.S.A. 

Sir FRANCIS W.'iTTS, K.C.M.G., Barbados 

Dr H. J. WHEELER, American Agricultural Chemical Co., Boston, Mass., U.S.A. 



VOLUME XII 1922 



CAMBRIDGE 

AT THE UNIVERSITY PRESS 
1922 






PRINTED IN QREAT BRITAIN 



CONTENTS 

Part 1 (January 1922) 

PAGE 

Newton, Robert. A comparative study of winter wheat 

varieties with especial reference to winter-killing . . 1 

GooDEY, T. On the susceptibihty of clover and some other 
legumes to stem-disease caused by the eelworra, Tylenchus 
dipsaci, syn. devastatrix, Kiihn. (With Plate I) . . 20 

Salaman, R. N. and Lesley, J. W. Genetic studies in 

potatoes: sterihty. (With Plate II) .... 31 

Crowther, Charles and Woodman, Herbert Ernest. A 

study of nitrogen metabohsm in the dairy cow . . 40 

Armstrong, S. F. The Mendelian inheritance of susceptibihty 
and resistance to yeUow rust {Puccinia glumarum, Erikss. 
et Henn.) in wheat ........ 57 

Woodman, Herbert Ernest and Hammond, John. Note 
on the composition of a fluid obtained from the udders of 
virgin heifei-s ......... 97 

Part 2 (April 1922) 

Murray, Alan J. The chemical composition of animal bodies. 

(With 1 Text-figure) 103 

Taylor, William and Husband, Alfred D. The effect on 

the percentage composition of the milk of (a) variations 

in the daily volume and (6) variations in the nature of 

the diet. (With 4 Text-figures) Ill 

Tocher, J. F. The citric solubihty of mineral phosphates. 

(With 8 Diagrams) 125 

Woodman, Herbert Ernest. Comparative determmations 

of the digestibihty and metabolisable energy of green 

oats and tares, oat and tare hay and oat and tare silage 144 , 
Whittles, C. L. A note on the classification of soUs on the 

basis of mechanical analyses. (With 11 Text-figures) . 166 
Salaman, Redcliffe N. The Influence of size and character of 

seed on the jdeld of potatoes. (With 4 Text-figures) . 182 
Engledow, F. L. and Shelton, J. P. An investigation upon 

certain metrical attributes of wheat plants . . .197 



vi Contents 

Pakt 3 (JuLV 1922) 



PAOK 



Deighton, Thomas. Some investigations on the electrical 
method of soil moisture determination. (With 6 Text- 
figm-es) . . . . . . 207 

WooD.MAN, Herbert Ernest. The chemistry of the strength 

of wheat Hour . . . . . . . .231 

IvANOFF, E. 1. On the use of artificial msemination for zoo- 
technical purposes in Russia ...... 244 

Capstick, J. W. and Wood, T. B. The effect of change of 
temperature on the basal metabolism of swine. (W^ith 
4 Text-figures) ........ 257 

HoRTON, E. and Salmon, E. S. The fungicidal properties of 

certain spray-fluids. Ill ...... 269 

CoLLms, S. H. and Thomas, B. The sugars and albuminoids 

of oat straw 280 

Robinson, Gilbert Wooding. Note on the mechanical 

analysis of humus soils 287 

Jones, S. G. A bacterial disease of turnip (Brassica napus). 

(With Plate III) 292 

Robinson, Gilbert Wooding. A new metiiod for the 
mechanical analysis of soOs and other dispersions. (Willi 
4 Text-figures) 300 



Part 4 (October 1922) 

Amos, Arthur and Williams, Gwilym. Temperature and 

other factors affecting the quahty of silage . . . 323 
Amos, Arthur and Woodman, Herbert Ernest. An in- 
vestigation into the changes which occur during the 
ensilage of oats and tares ...... 337 

Comber, Norman M. The availability of mineral plant food. 

A modification of the present hypothesis . . . 363 
Comber, Norman M. A modified test for sour soils . . 370 
Comber, Norman M. The flocculation of soils. Ill . . 372 
Hammond, John. On the relative growth and development 
of various breeds and crosses of pigs. (With 5 Text- 
figures) 387 



Vol. XII. Parti 



January, 1922 



THE 



JOURNAL 

OF 

AGRICULTURAL SCIENCE 



EDITED FOR THE PLANT BREEDING AND ANIMAL NUTRITION RESEARCH INSTITUTES AT CAMBRIDGE, 
AND THE ROTHAMSTED RESEARCH INSTITUTES BY 

Professor R. H. BIFFEN, M.A., F.R.S., Cambridge 

Sir a. D. HALL, K.C.B., M.A., F.R.S., Ministry of Agriculture, London 

F. H. A. MARSHALL, Sc.D., F.R.S., Cambridge 

E. J. RUSSELL, D.Sc, F.R.S., Rothamsted Experimental Station, Harpenden 

Professor T. B. WOOD, C.B.E., M.A., F.LC, F.R.S., Cambridge 

IN CONSULTATION WITH 

B. C. ASTON, Department of Agriculture, Wellington, New Zealand 

Dr C. a. barber, C.I.E., School of Agriculture, Cambridge. 

Professor B. T. P. BARKER, M.A., National Fruit and Cider Institute, Long Ashton, Bristoi 

W. BATESON, M.A., F.R.S., John Innes Horticultural Institute, Merton, Surrey 

J. R. CAMPBELL, B.Sc, Department of Agriculture, Dublin 

1. B. POLE EVANS, Department of Agriculture, Pretoria, South Africa 

F. B. GUTHRIE, Department of Agriculture, Sydney, N.S.W. 

Professor J. HENDRICK, B.Sc, Marischal College, Aberdeen 

Sir T. H. MIDDLETON, K.B.E., C.B., M.A., The Development Commission, London 

Dr FRANK T. SHUTT, F.I.C, Experimental Farms, Ottawa, Canada 

Professor W. SOMERVILLE, M.A., D.Sc, School of Rural Economy, Oxford 

Dr a. C. true. Department of Agriculture, Washington, D.C., U.S.A. 

Sir FRANCIS WATTS, K.C.M.G., Barbados 

Dr H. J. WHEELER, American Agricultural Chemical Co., Boston, Mass., U.S.A. 




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Volume XII JANUARY, 1922 Part I 

-i^ UJRA R? 

NEW \<)UV 
BUTANICAL 



A COMPARATIVE STUDY OF WINTER WHEAT 

VAIIIETIE8 WITH ESPECIAL REFERENCE TO 

WINTER-KILLINGS 

By EGBERT NEWTON, M.S., B.S.A. 

UniversiUj of Albert n, Edmontmi. 

INTRODUCTORY. 

Winter wheat, where it can be safely grown, usually outyields spring 
varieties quite markedly, but unfortunately ib is much more restricted 
in distribution, due to its liability to winter-kiUing. Much progress has 
been made with this and other crops in breeding for cold resistance by 
empirical methods. It would appear, however, that greater and more 
certain progress would be made if the nature of cold resistance in plants 
were well understood. This subject has long been of interest to physio- 
logists, and in its practical applications is of widest importance. The 
northern limit of profitable growth of our staple crops marks also the 
limit of profitable exploitation of our agricultural lands. The southern 
farmer has likewise to meet the problems of the frost-killing of fruit 
buds and flowers and the more tender winter cereals. 

HISTORICAL. 

The progress of our knowledge of the nature of cold resistance and 
frost effects has been reviewed quite fully at different times by Abbe(i), 
Blackman(5), Chandler (O) and others. Of the earlier investigations it 
will be sufficient to note here in their order the most significant. 

The theory put forward in 17.37 by Duhamel and Buffon(ii) that 
death from cold was due to rupturing of the cell walls by expansion on ice 
formation, is of historical interest. It was almost a century later that 
Goeppert(i3) found ice formation to occur in the intercellular spaces. 
Sachs (.■?8) showed this to be the usual occurrence, and developed the 
view, now generally considered erroneous, that disorganisation took 

■ This study was carried on in the lalioratory of Dr R. A. Gortner, Chief of the Division 
of Agricultural Biochemistry, University of Miimesota, to whom grateful acknowledgement 
is made for kind help and direction. The work was aided by election to the Shevlin 
Fellowship. 

Journ. of Agric. Sci. xn 1 



2 Winter Wheat Varieties and Winfr r-Killing 

place on thawing, and might be prevented by warming very slowly, 
allowing time for rcabsorpHon of the water by the cell. 

Later Miiller-Thiirgau(:«) proved that this ice formation in the 
tissues was necessary for freezing to death, and concluded that death 
was due to the consequent desiccation of the protoplasm. This 1i ypothesis 
received support from Matruchot and .Molliard (2fi), who demonstrated 
the identity of the modifications in cell structure produced by frost, 
plasmolysis and desiccation. The work of (ireeley(iT) supplied similar 
evidence. MezOi) opposed the theory of death by desiccation, since his 
investigations indicated that all solutes crystallise out at a temperature 
not lower than — G C. He concluded that cold desiccation must there- 
fore be complete at this temperature, and cannot explain injury to plants 
which resist much lower temperatures. He advanced instead the theory 
of a fatal minimum temperature for each plant. 

Gorke (14) showed another important effect of the withdrawal of water, 
namely, the precipitation of certain proteins by the increasing con- 
centration of the cell sap, aided by its increasing acidity on cooling. He 
also showed that the precipitation occurred at varying temperatures for 
plants of varying degrees of hardiness. This was ascribed by Scliaffnit(i(i) 
to the splitting in varying degrees during the hardening process of 
com])le.\ proteins into simjiler. less readily precipitated forms. 

Lidforss (2(!) found most hardy plants to have their starch reserves 
converted to sugar during the winter, and beheved this an adaptation 
for cold resistance, the sugar having a protective action in preventing 
the precipitation of the proteins. Schaffnit ( lo) tested the effect of adding 
sugars and various other substances to plant saps and to egg albumen 
solution, and was able to modify very greatly the precipitation by 
freezing. Equally striking results were secured by Ma.\imov(:<0) in 
increasing the hardiness of sections of red cabbage and Tradescantia by 
freezing them in solutions of either organic or inorganic substances, 
provided these were non-to.\ic and had a low eutectic point. 

Recent Progress. 

Recent inve.stigations have dealt nuiinly with the hypotheses noted 
above, extending them in several important respects. Attempts have 
also been made to determine the correlation of various physical, chemical, 
physiological and morphological characters with apparent frost hardiness. 

Several workers have drawn attention to the possible importance of 
the fact that plant sap is contained in cells of capillary dimensions. 
D' Arsonval (3) estimated the osmotic pressure in very small cells at 



R. Newton 3 

1000 atmospheres, and notes that by the apphcation of increasinp; 
pressure the sohdification point of water can be lowered indefinitely. 
In buds with small cells, dense tissues and meagre water content. 
Wiegand (49) found no ice at — 18° C, though in most buds it was present 
in large quantity. He concluded that the degree of cold necessary to 
cause the separation of ice is proportional to the force which holds the 
water in the tissues. Lewis and Tuttle(25) reported that Hving leaves of 
Pi/rola wrapped around the bulb of a mercury thermometer undercooled 
to ~ 32-l° C. before ice formation took place. On the other liand, it 
has been a universal observation since the time of Goeppert(]3) that ice 
may form in the tissues without injury to hardy plants, so that under- 
cooling is not of itself a sufficient explanation of hardiness. 

The water content of tissues is related to structure, and it has been 
shown by several investigators (2, 4, 24, 37, in, 13, 14) that dry matter con- 
tent is directly correlated with hardiness. 8inz (44) and Beach and Allen ( 1 ) 
noted also the importance of structures resisting desiccation, while 
Pantanelli(35) found injury from frost to be always proportionate to 
loss of water from the tissues, even when freezing was done in a saturated 
atmosphere. 

Between the concentration of the cell sap and winter hardiness, 
Ohlweiler (34) and Chandler (6) found a direct relationship; Salmon and 
Fleming (39), working with winter cereals, found none. Pantanel]i(35) 
partly reconciled the conflicting evidence by reporting a relationship 
in some crops and none in others, including wheat. Probably the sap 
of all plants increases in concentration during the hardening process, 
but not necessarily in proportion to the degree of hardiness attained. 
However, the earlier evidence as to the importance of the accumulation 
in the sap of substances of a protective nature, especially sugars, has 
received further support. Gassner and Grimme(i2) and Akerman and 
Johansson (2) reported that hardy varieties of \vinter wheat and other 
grains were richer in sugar, the differences between varieties corre- 
sponding to differences in degree of hardiness. Pantanelli (35) found that 
sugar was rapidly used up during exposure to low temperatures, and 
that hardiness was related to the quantity of sugar retained by the plant. 
The association of sugar accumulation with hardening by cold has been 
pointed out again by Rosa (37) and Coville(7). 

On the other hand, Harvey (Hi) found that cabbages acquired hardi- 
ness on five days' exposure to + 3° C, before any great change occurred 
in the carbohydrate equihbrium. He beHeves the principal effect of the 
hardening process to be a change in the constituents of the protoplasm, 

1—2 



4 Winter Wheat Varieties aixl Winti r-KiHiiKj 

as indicated by an increase in the amino-acid content, and, on freezing 
the sap, by less precipitation of the proteins. He measured the increase 
in hvdrogen-ion concentration of the sap on cooling, and was able to 
produce bhe same relative precipitation of proteins by adding equivalent 
i|uantitie8 of acid. However, the ease of precipitation of proteins by 
freezing apparently cannot always be taken as an index of hardiness, 
since Chandler (fi) was uniible to find any difference in this respect between 
the sap of tender and hardy twigs of fruit trees. Again, it should perhaps 
1)1' remarked that the fraction of the total proteins present in the ex- 
pressed sap is rather small, and of this only 31-2 per cent, at most is 
reported by Harvey as precipitated by freezing the juice of iinliardened 
cabbage. The extent to whicii this justifies a generalisation with regard 
to the probable behaviour of the proteins within the cell may be regarded 
as problematic. 

There is some evidence that stability of the dormant condition may 
be an important protective adaptation. Lidforss ('-'6) noted that a suc- 
cession of warm days caused regeneration of starch from sugar, with 
an increase in susceptibility to cold. Chandler (6) found some varieties 
of peaches to have a longer rest period than others and to be started 
into growth more slowly by warm periods in the winter. Evidently 
varieties which can maintain continuous dormancy during the danger 
period must have a distinct advantage. 

Our present concept of the causes of winter-killing nuiy be briefly 
summarised. Without doubt, the ultimate cause of death by freezing 
must be the disorganisation of the protoplasm. Irreversible coagulation 
or precipitation of the colloidal protein constituents may be caused by 
increase in concentration of electrolytes in the cell sap on withdrawal of 
water, or by increase in acidity, or by both factors acting together. The 
critical minimum temperature necessary to bring this about must be 
profoundly modified by rate of cooliug, especially if this be slow enough 
to give time for the hardening process, and by the presence of substances 
which protect the proteins from precipitation. Split ling of the proteins 
during hardening may be a protective adaptation. Since the funda- 
mental feature of the disturbance produced by freezing is withdrawal 
of water from the cell, intracelhilnr adaptations to resist desiccation 
must be of prime importance. 



K. Newton 5 

EXPERIMENTAL. 
The Problem. 

The present study seeks to establish a chemical or ijhvsico-chemical 
measurement of hardiness for winter wheat varieties. A number of 
varieties originated or selected by the Department of Plant Breeding of 
the University of Minnesota, and known to vary considerably in hardi- 
ness, were compared with reference to the physical constants of the 
cell sap, the content of amino nitrogen, water-soluble nitrogen and total 
nitrogen, and the content of sugars and starch. AH materia! used was 
grown in field plots under normal conditions. Since it was desired to 
compare the varieties in the hardened condition rather than to study the 
hardening process, collections were not made until after the advent of 
freezing weather. 

A preliminary study of physical constants was carried out with eight 
varieties. Subsequent stud}^ was confined to four of these, two hardy 
and two tender. One variety, Minhardi, was collected from two plots 
some distance apart, and these are reported separately as the effect of 
location was quite marked, 

Metho]is. 

Collection of Samples. All the samples of one series were collected 
from the field the same afternoon, though with the exception of the 
first series the leaves were frozen solid when collected, so that changes 
due to vital activities would be very slight. The plants were growing in 
rows, which were carefully gone over for the removal of dead leaves 
before taking the samples. For the collection of November 12, 1920, 
ib was necessary first to brush off a Hght covering of snow. As the leaves 
were cut, they were thrown on a wire screen for the removal of adhering 
bits of dirt and ice, then transferred at once to tight glass containers. 
Samples of approximately KIO grams were collected in duphcate, one 
lot for the study of physical constants, the other for analysis for nitrogen 
and carbohydrates. All samples were kept frozen until used. 

Physical Constants. The depression of the freezing point of the hrst 
collection was determined by the thermoelectric method, the accuracy 
of which has been shown by White (I7). The convenient arrangement of 
apparatus illustrated by Harvey (20, Fig. ]) was used. The leaves were 
packed into a section of thin-walled glass tubing 2 cm. long, in which 
they were held in place by a small rubber band, the thermocouple then 
being inserted in the centre. Undercoohng seldom amounted to more 



<i W iiifrr Whad \ (iiicdts kikI Wijifi r-Killini/ 

tlian 2° C. and was corrected for in the usual way. By this method 
(hiphcates often varied as much as 0-03° C, and in later collections it 
was abandoned in favour of the standard Beckmann method, by which 
it was always possible to obtain checks agreeing within O-Ol^ C. 

The work of Dixon and Atkins (lO), e.xtended by Gortner, Lawrence 
and Harris (lu), has shown the necessity of rendering the cell membranes 
permeable by freezing the tissue previous to sap extraction in order that 
a representative sample may be obtained. However, having regard bo 
the observation of Harvey (i!») that freezing permanently lowered the 
hvdrogeu-ion concentration of cabbage juice, and (-1) that on the other 
hand a certain amount of dilution did not affect this value, the samples 
of the first collection were not frozen before, expressing the sap, as it 
was desired to study particularly the relationship of this constant to 
liardiness. fiut the following coni^Jarisons of sap exjiressed from duplicate 
samples with and witliout previous freezing indicated that for wheat at 
least Harvev's observation does not hold true. 



V'iir-icty 


Not fro/.fu 


Frozen 




pH 


/-H 


.Miiiiiai'di 


()-."),S0 


(>-37ti 


HutTuni 


(r4li5 


(i-28i» 


radi.i 


(i-47r) 


u-i'sy 



Therefore in hiter collections preliminary freezing of the tissues was 
carried out, and the expressed sap used for all constants studied. 

The technique of (iortner and Harris (if)) was followed in the main. 
The rubber-stoppered bottles containing the samples were packed in 
a slushy mixture of ])ulverised ice and salt in an earthenware jar, which 
fitted snugly inside a well-insulated "tireless cooker." Jn this condition 
the contents remained frozen solid until required for use. never in any 
case for less than \'2 hours. For the freezing mixture, coinmou salt was 
used at first, and later calcium chloridi". To thaw th(> samples, tlie bottles 
were placed under running water, then rinsed with distilled water and 
wiped dry before ojiening. The leaves were folded in pieces of strong 
cotton previously boiled in three changes of distilli'd water and dried 
free from dust, and the sap expressed either in a hydraulic press under 
400 atmospheres pressure, or in a large hand screw press with a small 
steel cup which permitted the application of heavy pressure. The parts 
of the press with which the juice came in contact w6re kept coated with 
a thin layer of paraffin wax. 

The depression of the freezing point was first determined with a 
Beckmann apparatus. Then the conductivity was measured with a, 



K. Newton 7 

Wheatstoiie bridoe, using a Freas conductivity cell, and finally the 
hydrogen-ion concentration was determined by means of standard Leeds 
and Northrup potentiometric equipment. Both of the latter determina- 
tions were carried out at 25° C. in a constant temperature room. Usually 
the work on any particular sample was completed within an hour of 
expressing the juice. 

PreparuUon of Samples for Analysis. As the samples for analysis 
were collected in the field they were placed directly in tared one-litre 
erlenmeyers with rubber stoppers. They were frozen when collected, and 
kept in that condition overnight. Immediately after thawing in the 
laboratory next day, samples for the determination of dry matter were 
weighed out; then in addition, sufficient material was removed to leave 
exactly 100 grams in each fiask. To tills was added 1-5 grams of pure 
precipitated calcium carbonate for the neutrahsation of plant acids, and 
sufficient 95 per cent, alcohol to make the final concentration 80 per cent, 
after allowing for the dilution due to water in the leaves. The samples 
were then boiled half an hour under reflux condensers, and put away 
tightly stoppered until a convenient time for analysis. The procedure 
from thawing to boiling was carried out with the utmost expedition. 

The advantage of using calcium carbonate as noted above has been 
discussed by Spoehr(}.5). Davis, Daish and Sawyer (9) have pointed out 
the necessity for rapid destruction of enzymes. In this connection the 
present study afforded opportunity for sonu^ observations of interest. 
An additional quantity of one variety was collected for experimentation 
in methods. Part of this was left five days in an ice chest, and was then 
put through the regular preparative and analytical procedure. In Table 1 
the results are compared with those for the same material disposed of 
promptly after collection. When it is considered that the tissues were 
not crushed or injured to any appreciable degree, the effect of enzyme 
action even in such cold storage conditions is very striking. 

Drij Matter. Triphcatc samples of approximately 5 grams of green 
material were dried to constant weight in a vacuum oven at 98° C. 

Total Nitrogen. The total nitrogen was determined by the Kjeldahl- 
Gunning- Arnold method, using the residues from the dry matter deter- 
minations. 

Extraction of Sugars and Soluble Nitrogen. Large extractors of the 
Soxhlet type were made by drilling a small hole close to the bottom of 
a 750 c.c. wide-mouthed bottle, and fitting in a glass siphon tightly by 
making a ground glass joint or by wedging it with a collar of rubber 
tubing. The bottle was closed with a large rubber stopper, in which were 



fi Wiiitrr W/ic(if \'<trli(ics (uid W'liifci-A'i/liiii/ 

fitted two reflux coudensers and a bent glass tube leading to the distillinji 
flask below. The siphon also passed through the stopper of the distilling 
flask. The samples were transferred to one of these extractors and ex- 
tracted with 8U per cent, alcohol on a steam bath for 30 hours, by which 
time the Molisch a-napthol test on the alcohol in the extractor always 
became entirely negative. In transferring material from one container 
to another, the emptied container was thoroughly rinsed with hot 
alcoiiol. 

The extract was concentrated in the apparatus illustrated by Van 
Siyk(>(ifi. Fitr. I) under a pressure of less than 30 mm., with the dis- 
tilling flask in a water bath at a temperature of Uf to 50° C. When 
reduced to a volume of 7') to ItXlt-.c. about 200 c.c. of distilled water 
was added and the solution reconcent rated to get rid of the last traces of 
alcohol. This precaution was found necessary since the presence of 
alcohol affected the subsequent determination of amino nitrogen. The 
recoucent rated extract was then transferred to a 'jrjO cc. volumetric 
flask by Altering through a pad of cheesecloth in a small funnel, making 
it nearly to volume by several successive washings of the distilling flask 
with small portions of boilingwater. Apad of cheesecloth four layers thick 
was found the most satisfactory filter for removing the solid particles 
of chlorophyll which separated out. All otlier materials tried clogged 
at once. The extract was then cooled to room temperature and made up 
to volume. 

All volumetric flasks and jjipettes used throughout the analyses were 
standardised in true cubic centimetres at 20° C. 

Amino Nitnuferi. The amino nitrogen was determined by the usual 
Van Slyke apparatus, using 10 c.c. portions of the extract, filtered for 
removal of fine particles which had escaped the cheesecloth filter. Since 
preliminary trials had given a somewhat higher yield when deamination 
was continued for 30 minutes instead of the usual live minutes, the former 
period was adopted. Of this time, shaking was done during the first 
mintite and the last two minutes. 

Water-Solubh Nitrogen. The total water-soluble nitrogen in the 
alcoholic extract was determined by the Kjeldahl-(4unning-Arnold 
method, using 10 c.c. portions of the concentrated extract, filtered as 
for amino nitrogen. 

Oleariny Extract for Sugar Analysis. After the portions required for 
nitrogen determinations had been removed, the remainder of the extract 
was cleared with dry powdered lead acetate. The dry defecation method, 
first proposed by Horne(a), has tlie advantage not only of largely 



R. Newton 

eliiiiinatiug the error clue to the voluiiu' of the precipitate, but also of 
obviating the necessity of mailing to vohune a second time. The leatl 
acetate was added in small (juantities at a time, successive small portions 
of the extract being filtered oft and tested for completeness of precipita- 
tion. The solution was then filtered through a dry filter paper and 
deleaded with a minimum quantity of powdered sodium oxalate, fol- 
lowing the same technique as for clarihcation. A second filtration through 
a dry filter paper completed the preparation of the extract for sugar 
analysis. 

Reducing Sugars. The reducing sugars were determined by the very 
excellent method recently devised by Shaffer and Hartmann (42), in which 
the cuprous oxide is determined directly by iodo-thiosulphate titration 
in the presence of an excess of potassium o.xalate. The oxalate inhibits 
the reaction of cupric ions with soluble iodides. The reduction of Fehling's 
solution is carried out under the standard conditions prescribed for 
Miinson and Walker's method (Official Methods, A.O.A.C.) and the sugar 
corresponding to the quantitv of cuprous oxide read from the tables. 
By connecting the gas burners witli water manometers, and carefully 
calibrating them in conjunction with the flasks used for the reductions, 
it was found possible to keep within 10 seconds of the four minutes 
prescribed for bringing the solution to boiling. 

The thiosulphate was standardised against pure copper by an ada[)ta- 
tion of the simple method proposed by Peters (36). Triplicate standardisa- 
tions by this method varied less than ()•(>] mg. copper per c.c. N/10 thio- 
sulphate. 

The accuracy of this sugar method was tested witii pure dextrose 
obtained from the Bureau of Standards. Duplicate portions of 100 mg. 
and of 150 mg. of the anhydrous sugar were weighed out. dissolved in 
water and carried through the analytical {)rocedure, with the following 
results : 



ixtruse jjRscuL 


DL'.\tru.s(' ii 


100 


'.l!»S 


100 


<1!I0 


150 


1411-4 


150 


141I-2 



The nuijority of the sugar determinations made fell within the limits of 
these quantities. Aliquots of 10 c.c. of the cleared extract were used 
for the reductions. 

Sucrose. The sucrose was determined by the increase in reduction 
on inversion of the cleared extract. For inversion the citric acid method 
of Davis and Daish(8) was employed. Comparative tests with invertase 



10 



Winfer Whctd Varieties and Wintir-Killiiaj 



and witli the oftiiial liydrochloric acid nipthod jjavo results varyiug by 
less tJian U-5 per cent, of tlie ((uantitv found. It appears, therefore, that 
sucrose was the only disaccharide present in the leaves. 

Starch. A qualitative test for starch, with the usual iodine-potassium 
iodide solution, was made on the dried, ground residue from the alcohol 
extraction. 



Tabic 1. ChuMjt's in aminu nilroyen, lolul soluble nUrvgen and stujars of 
winter wheal leaves during 5 datfs' storage in ice chest. 



Aniinii niliuyrii 
VVaUii -solii bio iiitioHcii 
Keduciiig .siigui' as clextiosu 
Invert sugar as suci'o.sc ... 
Total sugar as dextrose . . . 



Fresh leaves 


Stored leaves 




perecutage 


percentage 


Percentage 


green weight 


green weight 


change 


0-050 


00(>7 


+ :}4-0 


0157 


0-2:i7 


■fSl-O 


a-286 


4- 174 


+ 27-0 


4-574 


iWK 


- 52-0 


7-943 


(i-40-' 


- lU-4 



Table 11. Physical constants of sap of ivinter wheat leaves. 
Collcctod October 29, 1920*. 



Variety Classification 


A 


/' 


pH 


Turkey 


Tender 


2-08 


24-;i;i 


ii-:j(jO 


Kan red 


Tender 


1-97 


2:!-(iS 


l>-()32 


Minhar'di {ii) 


Very hardy 


2-11 


25-:j5 


U-.528 


Minliardi {h) 


V(My hardy- 


2- 15 


25-s:! 


(i-.">SO 


Buffuni 


Very hardy 


2-21 


2(1-55 


()-4{i5 


Odessa 


Very hard\^ 


2-09 


25- 11 


l>-457 


Padui 


Wry hardy 


2-05 


24-(>:( 


(i-475 


Mintnrki ... 


Hardy 


2-(17 


24-S7 


ll-5:i() 


Itei R,.i,lv... 


Tender 


2-02 


24-2S 


i)-o:J2 



* A delirniined ilirectly in tissue by tlu-rnioelectric method; i>H. determined on sap 
expressed after grinding tissue without pievioiis freezing. 



Tabic ill. J'hi/sical constants (f sap of irintcr irlieat leaves. 



Variety A 1' 

Collection of November 12 
Turkey ... 2-26 27-15 



Kanred 
Aliiihardi («) 
Minhardi (h) 
ButTum 



2-.15 
2-5(i 
2-44 
2-08 



28-23 
30-74 
29-30 
32-17 



A' ■: lU^ 
1920*. 

iisi; 

14-31 
13-25 
14-87 
14-83 



Collection of December 9, 1920t. 
Turkey ... 1-99 23-92 14-94 



Kanred 
Minhai-di (u) 
Minhardi \b) 
Buffuni 



1-42 
1-83 
1-69 
1-60 



17-08 
22-00 
20-32 
19-24 



14-04 
13-93 
15-02 
13-35 



/,H 



.")S4U 
li-201 
6-078 
6086 
5-980 



5-486 
5-557 
5,548 
5-733 
5.593 



* iSap e.\i)i'essed under ])ressure of 400 atmospheres after freezing tissues. 

-f- Sap expressed by large hand screw press afttir boiling tissues in pressure Uusks. 



II. Newton 



I I 



Table IV. Tlie role of suyars and eledrohjles in oamolic pressure. 



Variety P P, 

Collfftiuii of November 12, 
Turkey ... 27-15 11-5U 



Kanred 
Miiihardi (") 
MinharcU (6) 
Buffum 



28-23 
30-74 
29-30 
32- 17 



9-51 
11-54 
10-51 
12-32 



P - l\ 
1920. 
15-(i."> 
I.S-72 
19-2(1 
IS- 79 
19-85 



10' A' . 10' 



11-86 
14-31 
13-25 

14-87 
14-83 



10-15 
18-07 
17-89 
19-34 
20-71 



P-P> 

K X 10' 

1-32 
1-31 
1-45 
1-20 
1-34 



P-P, 

A-„ ■: 10' 



0-97 
1-04 
1-07 
0-97 
0-90 



Average ... 29-52 11-08 
t'oUection of December 9, 



Turkey 
Kanred 
Mmhardi (u) 
Miivliardi (h) 
Buffum 



23-92 
17-08 
22-00 
20-32 
19-24 



7-49 
5-40 
7-91 
0-5!( 
7-27 



18-44 
1920. 
10-43 
ll-(iS 
14-09 
13-73 
11-97 



13-82 



14-94 
14-04 
13-93 
15-02 
13-35 



18-43 



17-98 
15-97 
16-80 
17-69 
10-04 



1-34 



1-10 
0-83 
1-01 
0-91 
0-90 



l-OO 



0-91 
0-73 
0-84 
0-78 
0-75 



AveraKe 



20-51 



6-93 



13-58 



14-20 



16-91 



0-95 



0-80 



Table V. Nitrogen of ivinler wheat leaves. 









Water- 


soluble 








Dry Amino nitrogen 


nitrogen 


Total nitrogen 




matter 
content 


.\ 


/ 






V 




Ureen Dry 


Green 


Dry 


Green 


Dry 


Variety 


0/ 

/o 


o/ o/ 

/O /O 


% 


% 


0/ 

/o 


0/ 

/o 


Collection of November 12, 1920. 










Turkey 


37-54 


0-054 0-14 


(»120 


0-34 


1-394 


3-71 


Kanred 


32-89 


0-045 014 


0-129 


0-39 


1-242 


3-78 


Minhardi {a) 


37-99 


0-051 (t-13 


0-161 


0-42 


1-416 


3-73 


Minhardi {b) 


33-51 


0-048 0-14 


0-1.53 


0-4(( 


1-228 


3-60 


Buffum 


35-83 


0-040 0-13 


0-141 


0-39 


1-184 


3-30 


Collection of December 9, 1920. 










Turkey 


29-65 


0-049 0-17 


0-1.59 


0-54 


1-179 


3-98 


Kanred 


25-48 


0-050 0-20 


0-134 


0-53 


0-936 


3-07 


Minhardi {u) 


31-74 


0-058 0-18 


0-192 


0-60 


1-276 


4-02 


Minhardi (b) 


28-20 


0065 0-23 


0-175 


0-(i2 


1-049 


3-72 


Buffum 


29-17 


0-058 0-20 


0-149 


0-51 


0-938 


3-22 


Table VI. Sugar content 


of ivinter wheat leaves. 






Keducingsugai 


■ Invert 


sugar 


Total ! 


sugar 




Dry 


as de-xtrose 


as sucrose 


as dextrose 




matter 
content 


A 






/. 






. Green Dry 


t 
Green 


Dry 


Green 


Dry 


Variety 


O,' 

/o 


o/ o/ 
/o /o 


% 


% 


% 


% 


Collection of November 12, 1920. 










Turkey 


. 37-64 


2-992 7-97 


5-301 


14-13 


8-397 


22-37 


Kanred 


. 32-89 


3-090 939 


3-900 


11-86 


7-0.55 


21-45 


Minhardi (a 


) 37-99 


3-237 8-52 


4-797 


12-63 


8-127 


21-39 


Minhardi (b\ 


) 33-51 


3-335 9-95 


4-351 


12-98 


7-760 


23-16 


Bufium 


. 35-83 


3-308 9-23 


5-799 


16-19 


9-219 


25-73 


Collection of December 9, 1920. 










Turkey 


. 29-65 


2-347 7-92 


3-.598 


12-14 


6-004 


20-25 


Kanred 


. 25-48 


1-840 7-22 


2-660 


10-44 


4-540 


17-82 


Minhardi (a 


) 31-74 


2-579 8-13 


3-356 


10-57 


6-991 


18-88 


Minhardi (b 


^ 28-20 


2-027 7-19 


3-391 


12-03 


5-472 


19-40 


Buffum 


. 29-17 


2-163 7-42 


3-772 


12-93 


5-997 


20-56 



12 Wilder Wluat Varieties aitil Winter- Killing 

DISCUSSION. 

The depression of the freezing point A, the corresponding osmotic 
pressure P, and the hydrogen-ion concentration of the sap of the samples 
collected October 29 are given in Table II. The osmotic j)ressiires recorded 
are based on the freezing ])oint data, use being made of tiie ]iublished 
tables of Harris and (!or^ner(l^). The hydrogen-ion concentration is 
expressed in terms of pW value as read from the tables of Schmidt and 
Hoagland(4i). A classification of varieties, as determined by survival 
under field conditions during a nund^er of years, was supplied i)y the 
Department of Plant Breeding and is included in the table. It will be 
seen that in this collection at least there are no significant variations in 
the constants reported which could be correlated with the relative hardi- 
ness of varieties. 

The same absence of correlation in pliysiial constants, including 
specific conductivity A', holds true for the collection of Novendjcr VI. 
reported in Table HI. It may be noted, however, that the concentration 
of the sap had increased somewhat in the varieties used. In the collection 
of December 9, included in the same table, all varieties exhibit a faUing 
off in the depression of the freezing point and corresponding osmotic 
pressure, probably due in part to simple dilution of the sap, as the 
moisture content of the tissue was greater. One variety, Kanred, fell 
off in this respect appreciably more than the rest. It is perhaps note- 
worthy that this variety winter-killed somewhat more tiian tlie others 
during the year of this test. 

An unexpected difficulty was encountered in expressing the sap from 
the sam])les collected Decend)er 9. The samples were frozen by the 
method already described, using a freezing mixture of pulverised calcium 
chloride and snow mixed in the ju'oportions wliich should give theoreti- 
cally a cryohydrate mixture with a corresponding temperature of 
— 54-9° C. After seven iiours' freezing, the samples were thawed under 
running water, and refrozen for a period of 1 1 hours. They were thawed 
again under the tap. Even after this treatment it was found impossible 
to express more than 2 to 3 c.c. of juice from 100 grams of material under 
400 atmospheres pressure. Further, the plants retained their bright 
green colour instead of a.ssuming the w'atersoaked appearance character- 
istic of fiost-kiiled tissuc^s. The data of Table V show that these samples 
contained a lower percentage of dry matter than did the earlier collection, 
consequently the failure to express the sap was not due to lack of moisture 
in the tissues but apparently to a failure to break down the colloidal 



R. Newton IH 

complex of the protoplasm and to increase the permeabihty of the cell 
by freezing. Since the permeability of the tissues had not been affected 
by freezing, it was decided to attempt to destroy the colloidal complex 
and increase permeability by ])lacing the material in a closed pressure 
flask and heating it in a boiling water bath. The juice was then expressed 
as readily by the hand press as by the hydraulic press, 30 to -10 c.c. 
(about the usual amount) being collected from each sample. 

These observations give rise to some very important considerations. 
In the first place, the wheat plants were apparently not killed by ex- 
posure to temperatures lower than normally obtain in many places 
where they suffer severe winter-killing. The specific temperature must 
be only one of a number of factors involved. It is also apparent that the 
hardening process continued long after the advent of freezing weather, 
as this difficulty was not met with in the collection of November 12. 
Further, and contrary to the findings of a number of workers, hardening 
was not in this case associated with an increase in the dry matter content, 
since as already noted the water content was greater in the collection 
of December 9. Nor was it associated with an increase in sugar content; 
this value had decreased, as will be seen later. 

Most significant is the evident tenacity with which the hardened 
tissue grips its water content. Wiegand (18) noted that as the temperature 
falls the quantity of water separating in the form of ice becomes con- 
stantly less and less. The same author develops the theory that the 
passage of water from the cell during freezing is due to an equalising of 
the force of imbibition, acting from the outer cell membrane to the centre 
of the system ; this follows as a consequence of the disturbance of equi- 
librium set up by the force with which the formation of ice crystals 
takes water from the surface of the cell. Wiegand supports the view that 
death is due to drying of the protoplasm beyond its critical water content. 
Evidence of other workers as tu the importance of resistance to desicca- 
tion has been presented in an earlier section of this paper. Whatever may 
be the precise mechanism by which withdrawal of water brings about 
disorganisation of the protoplasm, it seems clear at least that hardiness 
must be intimately connected with forces which oppose this desiccation. 
In the light of our present knowledge of the properties of colloids, it 
seems most probable that the principal force is imbibition. 

Spoehr (45) found that in cacti the pentosans increase with decreasing 
water supply. MacDougal(37) also points out that the conversion of the 
diffusible sugars to the mucilaginous pentosans is one of the alterations 
which may result in the cell as a consequence of partial desiccation. The 



14 Wliitir Wlnnt Vftrirflcs hikI \Vi iiI< r-f\illing 

latter author pictures plant protoplasm as a pentosan-proteiu colloid, 
and considers that the character and amount of the pentosans largely 
determine the hydration reactions of the protoplast. Winter conditions 
where the soil freezes solid are really xerophytic conditions, since the 
plant's usual water supply is cut ofT. Having this in mind, it may be 
reasoned from the evidence of MacDougal and Rpoehr that under winter 
conditions pentosans would accumulate in the cell, contributing largely 
to the formation of a protoplasmic gel of high imbibitioiml powers. 
Investigation of this point will be reserved for a later paper. 

The relative importance of sugars and electrolytes in osmotic pressure 
is considered in Table IV. Unfortunately there is no known method 
whereby the relative proportions of osmotic pressure contributed by 
electrolytes and non-electrolytes can be calculated accuratelv from con- 
ductivity and freezing point data. These proportions have sometimes 
been estimated by taking tlie value for electrolytes as equal to that of 
a solution of potassium chloride having the same conductivity. But it is 
manifestly unjustifiable, as Miss Haynes(22) has pointed out, to assume 
that the cell sap electrolytes are dissociated to the same extent as potas- 
sium chloride, and produce ions of the same mobility. In the present 
instance the sugar percentages were known and these were assumed to 
represent the non-electrolyte materials. The theoretical osmotic pressure 
exerted by the sugars is calculated from the quantities of reducing sugars 
and sucrose determined by analysis to be present. The difTerence between 
this value P^ and the total osmotic pressure P (i.e. P— P,) may be 
attributed chiefly, though probably not entirely, to electrolytes. In the 
coliec'tion of November 12, the sugars present were sufficient to account 
for an average of about .38 per cent, of the osmotic pressure: in that of 
December 9, for about 34 per cent. 

The probable effect of non-electrolytes in depressing the conductivity 
cannot be determined by ordinary viscosity measurements, as these do 
not distinguish between substances in molecular solution and colloids, 
and the latter substances, as is well known, do not interfere appreciably 
with conductivity^. However, the correction suggested by Miss Haynes 
for the depression of the conductivity by the sugar content of the sap 
has been applied to the observed values. The corrected specific con- 
d)i(tivity A'„ is derived from the observed \-;iIue K . hx the formula 

lOOA" 
'""^lOO-oa;' 
where n = 2 (constant for sugar) and x — per cent, sugar in sap. 

' Fur i'xam])l(', spp Af.rson (2H), Table V. 



R. Newton 15 

The ratio of the value P — P, to the corrected vahie for specific con- 
ductivity ( X 10^) is given in the last column of the table. This should 
be a constant in case the cell sap electrolytes in each variety were identical 
in composition, and the effect of solutes other than sugars on the mobility 
of the ions can be considered equal for all varieties. The ratio of P — P., 
to the observed value for conductivity is given in the adjoining column, 
in order that the effect of the correction for sugar content may be seen. 
For the earlier collection the ratio, based on the corrected values for 
conductivity, varies from 0-96 to 1-07, and averages 1-00, but for the 
later collection it falls off somewhat, ranging from 0-73 to 0-91 with an 
average of 0-80. Possibly the heating of these later samples to lOO^ C. 
had released ions which would otherwise have remained adsorbed by 
cell colloids, thus increasing somewhat the value of A', though Mason's 
results (28, Table VI) suggest that such an increase would probatily 
have been very small. In any case, the diminution in the value of P — P, 
in the later collection is so decided as to make it unlikely that the possible 
disturbing factors introduced by the heating could account entirely for 
the failure of K to diminish correspondingly. Furthermore, the content 
of soluble protein (see Table V) is small and relatively constant, and the 
hydrogen-ion concentration is Cjuite constant, so that the possibility 
of any considerable variation in conductivity due to protein salts and 
organic acids may be excluded. The evidence suggests that substances 
other than electrolytes, and variable in nature, must contribute somewhat 
to the quantity P — P^, or in other words that sugars are probably not 
the only non-electrolytes which contribute to the osmotic values. 

The amino nitrogen, water-soluble nitrogen and total nitrogen in per- 
centage of green and dry weights are given in Table V. The percentage 
of dry matter content is also included. It cannot be said that any of the 
figures exhibit a marked correspondence to differences in degree of 
hardiness. The increase in the water content of the collection of Decem- 
))pr is accounted for by a mild rainy period of some days" duration 
which occurred during the previous week. It has been remarked already 
that Kanred killed somewhat more than the other varieties during the 
season of this experiment, and this variety was lowest in dry matter 
content. However, in the hght of the evidence already presented, it 
seems possible that our view of the nature of the correlation between dry 
matter content and hardiness may require modification. A smaller 
water content is naturally associated with the smaller cells and denser 
tissues characteristic of the slower growth in late autumn, so that in 
general hardened tissues would be expected to contain less moisture than 



16 Winter Wheat Varieticfi rnid Winter- Kill Inn 

imhardened tissues. But iu coiiiparin;:: liardcncd tissues of different 
varieties, assuniinj; them to be of similar structure, the moisture content 
is perliaps larfjely a function of the relative imbibitional powers of the 
cell colloids and the defrrec of ])reviows exposure to modifyiui; environ- 
mental factors, for example, desiccating agents such as winds and low 
temperatures. It seems, therefore that both the magnitude and order 
of the values in any particular series of samples may be affected bv the 
weather conditions preceding the date of collection. 

The fundamental importance of resistance to withdrawal of water 
does not, of course, exclude the possibility of an important relationship 
between the character or .state of the proteins and the secondary effects 
following desiccation. In this instance, though the percentages do not 
correspond uniformly to the known hardiness, yet Minhardi, the hardiest 
variety used, liad somewhat the largest content of water-soluble nitrogen. 
All varieties show an increase in amino nitrogen and water-soluble 
nitrogen in tlic later collection. This is in harmony with the evidence of 
Harvey (i!i) that s])litting of the proteins is associated with tjic hardening 
process. 

The high content of sugars, especially sucrose, reported in Tabic \'l. 
is cjuite remarkaljle. It has been noted already that sucrose was ap- 
parently the only disaccharide {)resent. But liere again the varieties 
could not be classified according to hardiness on the basis of the values 
found. All suffered a loss between the collections of November 12 and 
December 9, the percentage falling lowest in Kanrcd. The greater degree 
of killing in this variety thus lends support to the observation of Pan- 
taneUi (•■«) that luirdiness was proportional to the (piantitv of sugar 
retained during exposure to low temperatures. 

A qualitative test for starch on the dried, ground residue Irom the 
alcohol extraction gave entirely negative results in every case. This is 
as expected from the observations of Miyake (32), Lidforss (26) and others. 

The above discussion indicates that we are still far from an exact 
analysis of the factors influencing winter hardiness, but certain of the 
observations, notably the failure of freezing the tissues to break down 
the protoplasmic .structure in the hardened jilants, are very suggestive. 
Furtlier investigation of tliis iilicnomcmm will be carried oul in the near 
future. 



R. Newton 17 



SUMMARY. 



1. A number of varieties of winter wheat, known to van' consider- 
ably in degree of winter hardiness, were compared in the hardened 
condition with reference to the physical constants of the cell sap, and 
the content of dry matter, nitrogen, sugars and starch. 

2. No constant relation was found between depression of the freezing 
point, specific conductivity, or hydrogen-ion concentration of the cell 
sap and relative frost hardiness. 

3. Sugars accounted for .^f to 38 per ceni'. of the total osmotic 
pressure of the sap. 

4. The ratio of that part of the osmotic pressure not due to sugars 
(i.e. P— PJ to the corrected specific conductivity ( >; lO-'') is not a 
constant. For the samples collected November 12, this ratio varied from 
0-9G to 1-07 (average 1-(K>) and for those collected December 9, from 0-73 
to 0-91 (average 0-80). 

5. The relation between dry matter content and hardiness was not 
constant, though one of the two tender varieties had the lowest per- 
centage. 

6. All varieties increased in amino nitrogen and water-soluble 
nitrogen during the hardening process. The hardiest variety had the 
largest content of water-soluble nitrogen, but the relation was not uniform 
throughout the series. 

7. The sugar content did not correspond uniformly with the known 
hardiness. The percentage decreased between November 12 and Decem- 
ber 9, falhng lowest in one of the two tender varieties. 

8. Sucrose is an important storage^ material and is apparentlv the 
only disaccharide present. 

9. All varieties were entirely free from starch. 

10. The colloidal complex of the cell of the fullv hardened tissue 
could not be broken down by exposure to the teinperature of a calcium 
chloride-snow cryohydric mixture (theor. = — 54-9° C). 

11. The hardened tissue retains its water content with great force. 
From tissue containing about 70 per cent, of moisture no appreciable 
amount of sap could be expressed by 100 atmospheres" pressure, even 
after severe preliminary freezing. 



JouTQ. of Agric. Sci. xii 



18 Winter Wheat Varieties and Winter- KUlliui 



KKKERENCES. 

(1) Ahbk, C. Kxp. Sla. Record, 6 (1895), p. 777. 

< o 

(2) Akerman, a., and Johansson, H. tSuerUjen Utsmleforenim/s TiiUkriJI, 27 (I!I17). 

p. 77. 

(3) d'Arsoxvai,, M. Compt. Hend. Acad. Set. Paris, 133 (l!iol), p. 84. 

(4) Beach, S. A., and Allen, F. W., Jr. lounAgr. Exp. .Sin. Ue.ienrrh Hull. 21 ( 1015). 

(5) Blackman, F. F. New I'hyl. 8 (1909), p. 354. 

((i) Chandlkr, W. H. Missouri Agr. Exp. Sla. Research Bull. 8 (1913). 

(7) CoviLLE, F. V. ./. Agr. Research, 20 (1920), p. 151. 

(8) Davis, W. A., ;ui<l Daisu. A. .1. ./. Agr. Sci. 5 (1913), p. 437. 

(9) Davis, W. A., Daish. A. J., and Sawvkk, G. C. ./. Agr. Sci. 7 (lOlfi), p. 2.55. 

(10) Dixon, H. H., and Atkins. \V. K. G. Sci. Froc. Roi/. Dublin Soc... X.S. 13 (1913), 

p. 422. 

(11) DiHAMKL DF MoNCEAU, H. L., and BUFFON, G. L. L. Mem. Mulli. el I'lii/.'!. 

Acfiil. Roy. Sci. Paris (1737), p. 273. Cited by Chandler (6). 

(12) Gassner, O., and Grimmk. ('. Rer. Deut. Bol. (lexell. 31 ( 1913), p. 507. 

(13) GoEPPERT, H. K. IJeher flie WiirincevlirickebiiKi in dem I'fliiiizen. too/.- ( I H30). 

('itc<l l)y Chandler (0). 

(14) GoKKK, H. fMiiilw. Ver.^:. Shit. 65 (I90(i), (). 149. 

(15) GoRTNER, II. A., and Harris, J. A. PlmU World, 17 (19U). ji. td. 

(16) G'oRTNEK, \l. A.. Lawrence, J. \'.. and Harris, ,]. A. liiorhmi. Hull. 5 1 191(1), 

p. 139. 

(17) (iRBELEV, A. W. .4»(e;-. ./. PJii/.tiot. 6 (1901), p. 122. 

(18) Harris, J. A., and Gortner, R. A. Awer. .1. Bol. 1 (1914), p. 75. 

(19) Harvey, R. B. ./. Agr. Research, 15 (I9IS). |i. ,S3. 

(20) Bat. Oaz. 67 (1919), p. 441. 

(21) Amer. ./. Bol. 9 (1920), p.- 21 1. 

(22) H a YNEs. Dorothy, /iior/ic?)!. ./. 13 (1919), p. 1 1 1. 

(23) HoRNE, W. D. ./. Amer. ('hem. Soc. 26 (1904). p. ISli. 

(24) Johnston, E. S. Amer. ./. Bol. 6 (1919). p. 37.'!. 

(25) Lewls, p. J., and Tuttle, Gwynethk M. AidkiI.'! Bol. 34 ( I92o). p. (05. 

(26) LiDFOBSS, B. L^inds Univ. Ar-t-ih: 2 (1907), No. 1.3. 

(27) MArDoii<i.\L, T). 'P. Carnegie fnsl. Wash. Pub. 297 (1920). 

(28) Mason, T. G. Sci. Proc. Hoy. Oiiblin Soc. X.S. 15 (1919), p. (i51. 

(29) Matruchot. L., and .AfoM.lARn, M. Compt. Rend. Acad. Sci. Parii. 130 (1900), 

p. 788; 132 (1901). p. 49.5. 

(30) Maximov, N. a. Ber. Deut. Bol. OcieU. 30 (1912). i)p. 52. 293, .504. 

(31) Mez, C. Flora, 94 (1905), p. 89. 

(32) Miyake, Kuchi. Bol. (laz. 33 (1902), p. .321. 

(33) Muller-Thuroau, H. Uindw. .Jahrb. 9 (1880). p. 133; 15 (IS8(i). p. 453. 

(34) Dhi.wkiler, VV. W. Mi.'.-.muri liol. Gard., Ann. Heporl, 23 (1912). p. 101. 

(35) Pantanelli, F. Alii delln Reale Academia dei lAncei. Ser. .5, 27 (1918), p|). 126, 

148; 28(1919), p. 20.5. Ahs. in Inl. Her. Sci. Pnicl. Agr. 9 (1918), p. 1416; 
10(1919), p. 844. 

(36) I'KTERs, A. \V. ./. Amer. Chem. Soc. 34 (1912). p. 422. 



R. Newton 19 

(37) Rosa, J. T., Jr. Proc. Amer. Soc. Uorl. Sci. 16 (I'Jl'J), p. liJO. 

(38) Sachs, J. Latidw. Vers. Stat. 2 (1860), p. 107. 

(39) Salmon, S. C, and Fleming, F. L. ./. A(ji: Resmrc.h 13 (1918), p. 497. 

(40) SCHAPFNIT, E. Mitt. Kaiser WUMms inst. Landiv. Rroinbm/, 3 (I9I(»), p. 91!. 

(41) Schmidt, C. L. A., and Hoagland, 1). R. Univ. Cat. Pali. Phi/si,,/. 5 (1919). 

(42) Shaffer, P. A., and Hartm.\nn, A. F. .7. Biol. Cheiii. 45 (1921). i>. .■U9. 

(43) Shutt, F. T. Trans. Roy. Soc. Can. Ser. 2, 9 (1903). .sect. 4. p. 149. 

(44) SiNZ, E. ./. Landw. 62 (1914), p. 301. 

(45) Spoehe, H. A. Carnegie Inst. Wash. PkIk 287 (1919). 

(46) Van Slykb. D. D. ./. Biol. Ohem. 10 (1911), p. \r>. 

(47) WinTK, W. P. Plii/sirul Revieiv, 31 (1910), p. I;i.'>. 

(48) WiEfiANU, K. M. Plant Worhl. 9 (19(l(i). pp. 2.",. 107. 

(49) Bot. Gaz. 41 (1006), p. 373. 



(Received Aiifjusl -IGlh. 1921.) 



2—2 



ON THE SUSCEPTIBILITY OF CLOVKi; AM) SOMK 

OTHER LEGl'MES TO STEAJ- DISEASE CAUSEJ) BY 

THE EELWORM, TYLENCHUS DIPSACI, 8YN. 

DE VA ST A TRIX, K t^H N. 

By T. COODEV, D.Sc. 

DepartmenI of Helmintholof/y, London School of Tropical Medicine, 

hite of I he Rothmnsted Experimental Station. 

(With P1m(.' 1, and Tables I and II in Text.) 



CONTENTS. 






PAOE 


Tntioduetion 


. 20 


Tlie pai-asite 


. 21 


DfHoriptioii of tlif disi'asc 


22 


lOxppriiiH'iilal 


. 23 


Disfussion .... 


. 28 


RcflTl'IU'CS .... 


. .W 



i.XTHoDrc'i'rox. 

Tt has l)een known for a number of years that red clover and rertain 
other cultivated leuuniinous plants, besides many other non-le<iuminous 
ones, are subject to attack from the eelworin, Ti/Ienchiis dipKocl. 

KUhn (1881) jjave an account of the disease produced in clover and 
lucerne. Later on Ritzema-Bos (1892) showed that the worm attacking 
clover was morpholooically indistinoui.shable from that attacking rye. 
oats, hyacinth, carnation and several other cultivated |)Uints and certain 
weeds. In England Miss Ormerod (1880-1 900) dealt with the subject in 
many of her annual reports and gave a good account of the symptoms 
})roduced by Tylenrhiis dipsaci. ])oiutiug out in 1899 the difFerences 
between these symptoms and tliose prodiK I'd hv tlie fungus Sclfirotinin 
trifolionim. 

More recently Amos (1919) has published a paper dealing witli i.lie 
difficulties of growing clover, in which lie states in general terms the 
comparative susceptibilitv of a number of different kinds of clover and 
other leguminous plants. Also Byars (1920) and Smith (1919) liave ipiite 



T. GOODKY 21 

recently given accoiint.s of the serious damage to red i/lover in certaiii 
areas of the norbh-west States in the United States of America due to 
Ti/lenchus dipsaci. 

A detailed investigation of the parasitism of Tylenvhu.s dipsaci seemed 
highly desirable, and as a beginning the question of the susceptibiUty of 
a number of clovers and other legumes to attack from the worm was 
taken up. 

In the following pages, which arc to be looked upon as a preliminary 
communication only, an account is given of the attempt which I have 
made to obtain a numerical expression of susceptibiHty and arrive at 
some figure which may be considered as an index of susccptibiliti/ for a 
given kind of clover or other host plant. 

The investigation was undertaken in 1920 when I was acting as 
lielminthologist on the staff of the Institute of Plant Pathology at the 
Rothamsted Experimental Station, Harpenden, whilst some of the 
material has been worked up since I was transferred to this laboratory. 

I wish to acknowledge my indebtedness to Mr R. A. Fisher of the 
Rothamsted Laboratory for kindly working out the Standard Error in 
connection with the percentages of deformed seedUngs, and for some 
suggestions. My best thanks are also due to Mr Arthur Amos who helped 
me by supplying diseased clover plants and to Messrs Sutton & Sons 
who very kindly sent the seeds used in these experiments. 

THE PARASITE. 

The parasite causing the disease is a small nematode worm belonging 
to the family AnguiUulidnc. popularly known as eelworms. It is not 
my intention in the present paper to give a detailed description of the 
worm; this has been done by many previous investigators whose works 
may be consulted: good accounts of it are to be found in Ritzema-Bos 
(1892) and Marcinowski (1909). 

The adults are visible to the naked eye when seen suitably illuminated, 
and measure from one milhmetre to one and three-quarter millimetres in 
length. The widest part of the body is about one-fortieth of the total 
length. 

The sexes are distinct and the males are on the whole a little shorter 
and narrower than the females. Although, as stated above, the worm lias 
been described many times previously, there is still need for much 
information concerning the structure of several of its organs. Moreover, 
we need to know exactly how the parasite gains access into the tissues 
of the host plant, and also how it uses the chitinous stylet which it carries 



•2'2 S(i'jn-(/it«(it>i vdiiKcd bij I Ik h'tin'onii 

in till' biutal t-avitv. It is usually assuiiu'd that it is by means of this 
organ that it pierces plant tissues and then penetrates into the plant, 
and that havinj^ once got inside it uses its stylet to puncture the cells 
amongst which it is l^-ing. and feeds on the cell sap which it sucks out 
from them. 

All this, however, needs much further investigation, I think, especially 
when one remembers the power pos.sessed by the infective larvae of the 
human ])arasite Anoi/losloma dmxJenale of boring through the skin without 
the aid of anv piercing mouth armature. Moreover, no one. as far as 
1 know, has ever obser\'ed the stylet of Tifletichus dipsaci in use as a 
piercing organ. It is a very small structure, being 12-15 microns in 
length, and t he point is so fine that it can only be seen under the very high 
magnification of an oil-immersion lens. In all my numerous examinations 
of diseased clover i>lants. l)oth fresh and ])reserved. 1 have never found 
the stylet exserted from the anterior end of the body. 

Another point: it is a matter of observation that the parasite, in .some 
way or other as }et not understood, causes an increase in the size of 
parenchymatous cells of the host plant, and this also requires further 
investigation. Kitzema-Bos suggested that it was due to a secretion 
poured out by the worm, and considered the spatulate posterior portion 
of the oesophagus as probably the seat of the secreting gland; the matter 
is, however, still very obscure. It is hoped that later on one may be 
enabled to take up the elucidation of these interesting problems. 

DESCKll'TlON OF THE DISEASE. 

In regard to a suitable name for this disease, the term Sicni (/i.va/.ve 
sliould be used, thus keeping in line with the German expression >Slock- 
krankheit for the same condition. 'Die term Stem-rot is already in use 
as the name of tlie fungal disease of clover caused by Sclerotinia Iri- 
folioniin, see Anu)s (1919) and Cotton (1920). 

Admittedly the two names are sufficiently alike to lead to the ])ossi- 
biiity of confusion in nomenclature for two very different pathological 
conditions, but 1 would suggest that the confusion might be avoided by 
the use of another name for the fungal disease which is not strictly con- 
fined to the stem as is the eelworm disease, but attacks the whole of the 
foliage of the plant. 

The term Foliw/e-rol of clurcr. or Clorer rot would be j)referable to 
Stem-rot, which is not an exact descriptive designation. It is of interest 
to note that the Germans have avoided confusion by the use of the word 
Klcekrebu for the fungal tlisease. 



T. (;ooDKY 23 

Tlio followinjj; is a brief account of tlie rliicf cliaractpri.stics of flic 
two diseases, the differences between wliicli are fairly well shown in tlic 
two pliotograpLs at the end of this paper. 

Stem (lisea>ie caused by Ti/lencliKs dipsaci is chiefly characterised by 
a stimtinfi a.nd deforming of the plant accompanied by much swclhug 
of the leaf stalks at their base and of the stipules. The older leaves die 
back and new leaves which develop, though frequently numerous, have 
very short stalks, and the leaf blades are twisted and much wrinkled. 
The leaf stalks and stipules are also very much discoloured. The plant 
gradually dies back and is eventually killed, though the parasite does 
not attack the root. 

The disease spreads slowly from an infective centre and persists 
throughout the year, being most noticeable perhaps during the winter 
and spring when the leafage is not profuse. 

Foliage rot of clover, or Clover rot, due to the fungus, differs from t he 
eelworni disease in the appearance of the affected plants. The foliage 
is first attacked and becomes covered with a white mould or niycehum 
which causes the leaves and stems to turn brown and rot rapidly. The 
spread of the disease is rapid, sweeping over a whole field in a few days, 
especially when favoured by mild damp weather during autunm and 
winter. There is no stunting or swelhng of the affected parts but just 
a collapse and decay of the foliage followed by attack on the roots. 

If not too badly attacked, a second crop of clover may spring up from 
the unkilled roots and a fair yield may be obtained. 

The disease does not apparently continue to attack the clover during 
spring and summer. 

A certain amount of confusion seems to exist among agriculturists 
as to the differences between these two diseases, b^it to anyone who has 
seen the two conditions in the held the differences are very marked and 
unmistakable. The confusion is partly exphcable on account of the 
frequent association of saprophytic eelworms along with the fungal 
foliage-rot disease. All these eelworms are different, however, from the 
disease producing Tylenchus dipsaci and are free- living soil nematodes 
which liave invaded the rotting clover tissue and have there found a 
highly favourable medium for growth and multiplication. 

EXPERIMENTAL. 

!^ome preliminary experiments were carried out in which several 
seedhngs of red clover, about 10 days old and showing the first true leaf, 
were each inoculated with a single egg containing a well developed larva. 



24 SU Ill-dim (isi rtiHsa/ //// fJn hJi Inoriii 

'J'lio inoiuliition was (-arried out by means of a fine capillary glass pipette. 
Later examination and dissection of seedlings revealed the fact that 
mature and sexually difTerenliated worms were d<'veloped in from 
24 to 30 days from the date of inoculation. 

Several experiments were also made in which clovers of different 
kinds were grown on soil heavily infected wnth Ti/lenchu^ dipsaci. It was 
invariably found that the seedlings of red clover showed a high per- 
centage ol affected planfs which possessed, at first, swollen hj'pocotyls 
and later on became stunted and deformed with small wrinkled leaf- 
blades. 

Kollowini; these early experiments the main experiment which forms 
the basis of this paper was set up. 

The soil used was that from around the roots of diseased red c^lover 
from the Universitj' Farm at Cambridge, which had i)een kept for about 
two months at the bottom of a small galvanised iron bin. All the plants 
had died down and become withered and brown. 

The soil was crumbled up finely and the tops of the plants were chopjjcd 
up finely and thoroughly mixed into the soil, with which also a small 
proportion of silver sand was incorporated. 

This mixture, which it was considered would be highly infective for 
Tylenchuf! dip.mci, was put in a layer about one inch deep on the top 
of Hoosfield .soil plus lOper cent, sand in f O-ineh glazed pots, thus forming 
a shallow layer of infective soil close to the top of the pot. 

Each pot was divided into four quadrants for economy of space by 
means of glass partitions pressed down into the soil. 

One hundred seeds of each of the following were sown, each in its 
quadrant, and covered with a thin layer of .sand. 

Red clover — Enghsh, French, Canadian. Wild Knglish. 

C'oiv-grass — English . Swedish . 

Alsikc clover — English, Canadian. 

While clover — Sutton's Mammoth. Wild Cotswold. Wild Kentish, 
English. Dutch AVhite. 

Kidncif celcli, Sainfoin. Lucerne (Provence), Trejoil. 

All the seeds were sown on the same day, June 1st. The ])ot s were then 
carefully watered and put out in the wire-covered enclosure and there 
left for the seedlings to grow under the same conditions of temperature, 
light, air, moisture, etc. It was hoped by giving throughout all the 
pots uniform conditions of soil in which the parasites were as equally 
di.stributed as could be arranged, and by lea\nng them under the same 
climatic conditions in all cases, that anv differences shown in the inci- 



\ (tOODEY 



•in 



denco of attack by Ti/lenr/nis would be due to differences of suscepti- 
bility to the jtarasite. That this was a reasonable and sound assumption 
is borne out, I think, by the results obtained. 

On July 8th, that is, after 37 days, all the seedlings were harvested, 
counted, and after being separated into deformed and health}' in ap- 
pearance, were separately jiickled in 70 per cent, alcohol. 

The figures obtained in this way enabled me to arrive at Ihe per- 
centage of deformed seedlings in each case, as shown in the following 
table. 

Taljle [. Showing Ihe ninnherf: of heallhi/ (uul ilcfunned nvedlinys, 
ihe percenlage of (leforined, and Ihe sliindard error. 

No. of .seedling's 

' , i'ciri'ntage of Stiiudiiiil 



iviiiil of plant 


Healthy 


Deformed 


Total 


deformed 


enor 


Hal chinr: 












Knglisli 


:i', 


41 


71) 


.■)4 


±5-7 


French 


L'(; 


III 


S7 


70- 1 1 


14-!) 


Wild English 


IS 


47 


li.") 


72-3 


-5-5 


Canadian 


10 


lil 


StI 


70-25 


:14-S 


Cow-fjrass : 












Englisli 


.. Xi 


•.V.) 


72 


54-1 


.■)-il 


Swedish 


20 


37 


li3 


58-7 


:Jy- 


Al-^^-ike rloi'cr : 












English 


.. 71 


12 


S3 


144 


J:3-!l 


Canadian 


(iO 


23 


S3 


27-7 


l,4'l) 


White, clover: 












Sutton's Mammoth . 


711 


!l 


ss 


10-2 


' 3'2 


English 


r,:', 


1(1 


1)3 


ir)S7 


J:4-0 


\Vild Cotswold 


1- 


II) 


S2 


12-2 


30 


\yild Kentish 


1 1 


III 


S7 


ll-.-> 


i.3-4 


Kidneif rclch 


.. :!l 


42 


7.3 


00-0 


_..")• S 


i^aiiifoin 


.js 


13 


71 


I.S-3 


^4-0 


Lucerne (Provence) 


lis 


4 


72 


:,-i 


+ 2-7 



Trefoil 



41 



41 



These figures of ]iercentage infection give one a rough indication of 
the susceptibihty of the different kinds of clovers, etc., but it was 
thought that if one could estimate the numbers of Tylenchus in a series 
of deformed seedHngs one would be able to arrive at some expression 
for the intensity of infection or intensity of susceptibihtv in eacli case. 

With this end in view I examined all the deformed seedlings and 
selected the ten most deformed in each case, and then proceeded to the 
dissection of these in order to obtain the contained Tylenchus. 

Each seedhng was carefully dissected by means of needles, with the 
aid of a binocular dissecting microscope. This, of course, was a slow 



2*t SU'iH-iliseaxc (•(Dined l>ii Ihi A't/icunii 

proci'ss, but it, was loiind quite ]>r;ictic;ibli', :iiu| coiiiparalively fow of tiie 
worms were damaged or broken during these operations. Each seedling 
was placed in a shallow glass capsule iu distilled water, and bit by bit 
tlisspcted so as to free tlie tissues from the contained parasites wliich were 
then left in the water whilst the vegetabh; matter was gradually removed. 

After the dissection the nematodes were collected, concentrated and 
trnnsferred to a microscope slide oi- slides as the case might require, and 
then e.xaniiued under the microscope, i^'or the purposes of collection 
1 first of all used glass capillary pipettes, bub later on abandoned these 
and used the centrifuge which proved very servicealile. The resulting 
drop for examination thus contained adults of both se.xes, larvae in 
many stages of development, and numerous eggs. In making my exami- 
nations I recorded separately the numbers of males, females and larvae : 
eggs were not counted. A record was also kept of whatever other kinds of 
nematodes might be present with the Ti/lenchus. These, however, do not 
concern us in the present paper. 

In the case of those varieties which gave a large number of deformed 
seedhngs, the ten most deformed were, as stated above, selected for 
dissection, whilst iu the other cases as for example, lucerne, sainfoin, 
white clover, where only a few seedhngs were deformed, the \^liole of 
them were dissected. 

In the case of lucerne only four seedhngs were defornieil. hut none 
of these revealed any adult Tyleiichvx on dissection. 

Since the same number of seedlings was not dissected tiiroughoul, 
it became necessary to decide arbitrarily on some number to take as an 
average in arriving at the index of susceptibility, and for this purpose 
the number of deformed lucerne seedlings was chosen, i.e. four. 

Since also index of susceptibihty was being interpreted as equivalent 
to intensity of susceptibility, the four highest totals of males plus fcnuiles 
were taken and an average made of these, the resultant figure being 
called the index of susceptibility. Whether the males and females 
counted are the progeny of a single fertilised female, thus giving a 
reproduction figure, or whether they are the result of an invasion of the 
tissues of the host by numerous larvae which have attained sexual 
differentiation and maturity witliin the seedling, the data available are 
not sufficient for one to say, since we do not know enough of the life- 
history of the parasite to say definitely which is the infective larval stage. 

The figure arrived at in each case gives us, I think it will be agreed, 
an expression of the suitability of the host plant for the needs of the 
parasite, and this is what the investigation was designed to reveal. 



'W (JOODEY I'T 

Table 11. Sliowiiuj (lie four liighesl counts of male andfenude 'I'ylenchi iii 
seeiUiny.'i, the aceraije of llie loluh of Uiene giviiuj the index of suscepti- 
bility in each case. 

Name of plant Males Females Total 

Med liuLLr, Eu'Aiah 



Avci-ayc I!JO index of suseeptibilily 

Yin/ t/ui'tc, Freneli 



Average ... 
Ikil doixr. Willi En-lisli 



Averaii.- ... 
lied doixr. (.'anai-liau 



Avei'ane ... 
t'utc-tjia-'is, Enyliali 



Avei-aj,'C ... 
Co(v-'jnt-'i-:y, yu'ci-liali 



Average ... 
Alsike duccr, Eiinlisli 



Average ... 
AlsilcL clijixr, Uaiuuliaii. 



Average ... 
While ilorcr, .Sutton's Mainniotli Jiil 
Wliite dover, English ... 



Average ... ... ... 4-75 



l(i:i 


i:tii 


■2:vj 


!)l> 


lilt 


nil 


IH> 


II III 


iiiii 


OS 


!):5 


KH 






I!JO 


11(1 


:2.'')l 1 


:',iii) 


i;;i 


!l(i 


1 .j',.i 


11 


HIS 


I5i 


!l 


i+il 


14!) 






■2or> 


;:'' 


IIJ 


1 17 

1 <■) 


■ 1 '. 1 


1 -ill 
141' 


I7J 


:{(t 


ll(i 


ui; 






Hill 


S7 


:!17 


1114 


7-) 


ISO 


L'.")- 


(i.S 


L'lil 


:!:!!' 


Itii 


ISO 


1'7(1 






:5i(i 


1 


M 
1 1 


117 ■ 


4 


i; 


Ill 


.) 


!l 


11 






:5S-2r, 


v.> 


.Sll 


I2i.l 


.".;"> 


!is 


l.^:i 


:•'.) 


lu 


I2lj 


IIKI 


Hill 


2(1(1 






1117 


III 


III 


L'd 


III 

1 " 


J.") 
1 ■> 


'!- 


1 .1 


1 _ 

U 


:i4 






2.S-.-J 


IS 


:!ii 


4S 


l(i 


4li 


(12 


7 


17 


24 


n 


!l 


14 






37 


ml 

i; 
1 


nil 

1 
o 


nil 

III 
(j 


2 


— 


2 


— 


1 


1 



28 



Stem-disease caused hif the Eehrorm 
'I'ahlc II (continued). 



Name of |)laiit 
H'hik clover, W'ild (.'ejtswoM 

Avcnigf ... 
While cloicr, Willi KeiitiBli 



■Malfs 

~} 

1 
1 


Females 

7 
7 

1 


Total 

S 
2 


2 


1 

3 


5-5 index of Muxccptiliility 

1 
5 



41 


(17 


lOH 


It 


7.S 


121' 


sr, 


1:27 


212 


95 


US 


2i:i 






Ui-ilo 


i 


li 

• ) 


Id 


7 


ii 


10 


— 


2 


2 






7 


nil 


nil 


nil 


nil 


nil 


nil 



Average ... 

Kiilnci/ rclch 

Average 

Sainfoin ... 

Averajre ... 
Lucerne ... 
Trefoil 

BISCUSSIOX. 

Jn a hioloiiical iuvestitiation of this character it is practically im- 
possible to repeat the experiments exactly, and consequently one would 
not expect to get the same figures in a repeat experiment. 

Nevertheless, one would, I think, obtain figures having the same 
relative significance, and for this reason the figures put forward above 
as indices of susceptibility may be taken as representing approximately 
the relative susceptibilities of the dift'eront clovers, etc. to 7'//. dipsad 
attack. 

An examination of the figures shows that all the varieties of red 
clover tested are very susceptible to attack and fall into a common 
group (1) to which also belong cow-grass (Swedish) and kidney vetch. 

Arranged in order of intensity of susceptibility we have them as 
follows: 



lied clover (Canadian) ... 
(French) 
(English) 

Cow-grass (Swedish) 

Kidney vetch 

Red clover (Wild English) 



.•$ll> 'i 
20.5 I 



190 ,, , 

163-75 I 

100 



T. GooDBY -29 

Widely separated from this group we have another one (2) much less 
susceptible, comprising 

Cow -grass (English) ... 38-2", | 

AJsike clover (Canadian)... I!7 - f (roup 2. 

Alsike flovfi- (Englisli) ... iS-.", ) 

The great disparity between the figures for the Swedish and the 
English cow-grass is remarkable and somewhat surprising, and suggests 
tjie need for much further investigation along these lines. 

A further group (3) comprises varieties which are but very sliglitly 
susceptible to attack, viz. : 

Sainfoin ... ... ... 7 ) 

White clnvfM- (Wild Cot.swold) ry'y | ^, „„ , 

(English) ... 4-7.-. '"^""P-'- 

(Wild Kontish) 2 ) 

Lastly we have a group (4) made up of 

White rluver (Sutton's .Mammoth)) 

Lucerne [ I iroup 4. 

Trefoil ) 

which appear to be iusu.sceptible to attack. 

A comparison of the indices of susceptibility with the percentages 
of deformed seedlings shown in Table I reveals the fact that all the 
members of Group I have a high percentage of deformed seedhugs. 
Canadian red clover, having the highest index of susceptibihty, has also 
the highest percentage of deformed seedlings. The parallel does not hold 
throughout the group, however, for Wild EngHsh red clover, which has 
the second highest percentage of deformed seedlings, has the lowest 
index of susceptibihty in CTroup 1 . 

The low index of susceptibility shown by English cow-grass, compared 
with its high percentage of deformed seedlings, is an otitstanding excep- 
tion to the parallelism of high inde.x of susceptibility with high per- 
centage of deformed seedlings. 

In the case of Groups 2 and ?> it is not possible to establish a 
parallel when we have cases like English alsike clover with a lower 
perci'ntage of deformed seedlings I ban either English white clover or 
sainfoin, and a much higher index of susceptibihty than either of these. 

These results are in general agreement with those of Amos (1919, 
pp. 8 and 9), except as to one or two details. He never found sainfoin 
attacked, whilst I find that the seedlings are very slightly susceptible 
to attack. 

Tlie results have a practical bearing of considerable importance to 
the farmer whose land is infested with Tylenchun dipsaci, and whose 
red clover is therefore hable to attack from this parasite. 



'^>0 Stcni-diMase com^eff fi// the Eclworm 

If he wishes to avoid Stem disease lie should not sow red clover, 
fow-ijrass or alsike clover, but should make use of trefoil, lucerne, 
sainfoin or a larjje white clover, such as Sutton's Mammoth White. 

Recommendations similar to the above liavc been made before, 
notably by Amos (J919, p. 9), but they are so obviously the proper and 
hopeful lines to adopt that they will bear repetition and reiteration. It 
is no use attemptino; to fiet rid of the eelworm disease if red clover, cow- 
grass, alsike clover and kidney vetch are sown on infected land. 



RKrKRK.XCKS. 

(1) Amos, A. (191 it). Tlu: IJitliculties of growing lied f'lovor — Clover .Sieknes.s iiiul 
other Causes of Failure. Journ. Roy. Agr. Soc. Eng. 79, pp. 68-88. 

(2) Byars, \j. p. (1920). A Xematode Disease of Red Clover and SIrinvherrv in llie 
Pacific Nortli-we.it. I'liyloprithologi/, 10, No. 2. p. III. 

(:!) Cotton, A. I). (1020). Clover Stem Rot (Sclfrnliiiia Irifolionim ICrik.). Juxrt). 
Ministry of Aiji: 26. \o. 12. .March, pp. 1241-1244. 

(4) KiJHN, J. (18S1 ). Das Lii/.crn;ilehcii (Tylenrhii-i HiireiiMernii). Deiilsche hinthr. 
Prexxe, 8, p. ,S2. 

(5) IVIarcinowski, K. (1009). Parasitiseh und semiparasitiseh an I'llanzeii lebeudc 
Nematodeii. Arbe.iten mm der Kaiseriirlien liioh(jisclien Aiiiloll fiir Land- iiinl 
Forslimrt.schiiJ'1, 7, Heft 1. jip. 5()-()7. 

(()) Ormerod, E. .a. (1887-1899). lieporls on Injurious In.sect,i. 

(7) ]ilTZERLV-Bos, .1. (1892). L'.Vngiiillule de la Tige (Tylenchus ilenislalri.r Kidin), 
etc. Archives dn Musee Teyler, Haarlem, 3, p. 161 and p. .545. 

(8) Smith, R. H. (1919). A Preliminary Note concerning a Serious Nematode Di-sea-sc 
of Red Clover in tlie Xorth-western States. Journ. Econ. J'Jiit. 12, So. ti. pp. 460- 
462. 



KA'PLANATION OF I'LATI-; I. 

Fitl. 1. Photograph nf pni-tinns ol jilanl iif icd clover suffernitr from Stem disease ea\iaed 
in' Tyhnclms dipsaci, showing; the cjiarat'teristieally swollen ir;if stalks ixntX stipules 
at .1 and B. 

Fill. 2. Photograph of a whole plant of red clover suffering from Foliage-rot caused by the 
fungus Hclerotiniii Irifolionim. The white mycelium oau he .seen spreading on to the 
surface of the .soil, whilst tlw eollap.sed nature of the leaf and leaf-slalks is well shown. 



[Received September Gth, 1021. 



JOURNAL OF AGRICULTURAL SCIENCE. Vol. XII. Part 



PLATE I 




Fig. I. 




Fig. 2. 



r4ENETIC STUDIES IN POTATOES; STERTLTTY. 

By R. N. SALAMAN, M.A., M.D.. Burh'n. Herts. 

AND 

J. W. LESLEY, M.A., Phi,vl Brcfdliii/ Innlihih\ Ctitiliridjir Universi///. 

(Witli Plato IL) 

Male sterility in potatoos, that is tlio ahsenco of pollon from the antliors, t" 
has been shown by one of us (8arlaiiuin(i)) to behave as a recessive to 
male fertility. The present paper is an account of some further experi- 
ments in the genetics of this character, particularly of crosses between 
two varieties in which the reciprocals give difTerent results. 

Both quantity and quaUty of pollen were estimated by methods 
similar to those used by 8alaman{i). Four empirical grades of quantity 
were employed, viz. "abundant." "medium," "small" and "very few 
grains." The quality of the pollen was determined by mounting a sample 
in water and examining microscopically. Under this treatment living 
and presumably healthy grains swell up, appear spherical and translu- 
cent, whilst the pores become prominent. Such grains are termed "good." 
Bad grains are generally smaller, irregular in outline, and often appear 
quite empty. 

Even the best samples of pollens which we have seen contain a con- 
siderable proportion of empty grains. The projiortion of good grains was 
determined approximately by counting. 

The Relation between Qitaltty and Qitantity of Pollen. 

.4 close correlation was found to exist between qiiantity and quality 
of pollen as indeed was observed by P]ast(2) and Salaman(i). In general 
the larger the quantity the higher the proportion of good grains. The 
constant presence of "abundant" pollen is a sure sign of a large propor- 
tion of good grains. Similarly the lowest grade of quantity — "very few 
grains" — is proof of the absence of good pollen. Of the intermediate 
grades "medium" quantity was generally associated with poor quality 
pollen. The grade which we describe as "small" rarely contained any 
good grains. Perhaps " medium " quantity is best counted as potentially ^ 
fertile, the "small" quantity as potentially sterile. 



32 Genetic Studies in Potatoes: Sterilitfi 

lu some families the ditiiculty of classification was considi'iablc, and 
a satisfactory method of dealing with a quantitative and variable char- 
acter such as the present has yet to be discovered. In some few cases 
only the quantity of pollen was recorded but as a rule both quantity 
and quality were estimated on three or four different dates; especially 
was this so when flowering was continued over a long period (this varied 
in different seedlings from one to over fourteen weeks). 

Frequently the repeated observations both of quantity and quality 
of ))()ilen agreed closely in different flowers on the same plant but in 
some cases this was not so. Little is known of the factors causing such 
variations. The variation of quantity is chiefly to be ob.^erved in sterile 
or partially fertile plants, and may he, in part, a result of the irregular 
and delayed ripening of the anthers cliaracteristic of such ])laiits. We 
iiud the quality of pollen sometinu's deteriorates considerably after the 
flower has been open for five or si.\ days, but apart from that there are 
inherent differences in the degree of fertility. For instance, Edgecote 
Purple invariably shows abundant pollen of high quality and may be 
termed fully fertile. Edzell Blue on the other hand is somewhat variable 
in quantity, usually only "medium" and the quality is correspondingly 
inferior. 

We have not attempted to measure small (|uantitative differences 
but only lai'ge differences of a more obvious kind. The methods of esti- 
mation are, of course, appro.ximate and not suitable for accurate measure- 
ment, but are sufficiently effective in determining large differences. 
Rapidity of execution is also a ('onsideration when over three hundred 
microscopic examinations need to be made in the flowerinu' ])eriod. 

Material u.sed. 

Three cultivated varieties formed the basis of the breeding experi- 
ments. They are characf erised as follows : 

( 1) E (I f/ecote Purple. The male organs are I'lillv fertile. Imvinu a.hnndant 
pollen of good quality of which at least 'J5 per cent, consists of ]ierfect 
grains. It forms berries and seed freely by luitural self-pollination. Our 
stock of this was brought by Professor Biffen Ironi \Viit>liii-c. where it 
maintains a. fairly high yield although grown year aftei' year withoni 
the usual renewal by means of Scotch or other seed. 

(2) Myatt's Ashleaf. The male organs are fully fertile like the pre- 
ceding. It likewise forms berries and .seed, self-setting freely. 

(3) Edzell Blue. The male organs are fertile but not fully so, being 
considerably less fertile than either of the two preceding varieties. Both 



R N. Salaman and J. W. Lesley 



33 



quantity and quality vary considerably, but as a rule it is "medium, ' 
containing about 5 per cent, f^ood grains. Forms berries but sparingly, 
such berries having fewer seeds than the preceding. 

Parchment bags and the usual precautions were used unless expressly 
noted to the contrary. The seed from each berry was kept separate, 
which served as a useful check when self-set or "natural" berries were 
used. 

More than 200 selfed seedhngs were raised from Edgecote Purple and 
many of these carried on to the second year by tubers. Twenty-five plants 
flowered which were recorded as follows : 

Abundant ... 20 Small ... ... 1 

Medium ... 3 Very few grains 1 

All of the nine examined qualitatively contained good pollen (see Table I). 
Two plants, one with "small" ([uantity, the other with "very few 
grains,"' were only once recorded and are of doubtful significance. Fer- 
tility, which has already been shown to be recessive in the potato, here 
probably breeds true in accordance with expectation. Five individuals 
formed self-set berries. 

Table I. 



Abundant 



Medium 



Small 



Per cent. good. 





< 


f^ 


Kdsecote Purple selfed ... 


20 


.3 


Edzcll Blue selfed 


S 


(i 


Ednecote Purple x Myatt's 






AsUeaf 


1!) 


:{ 


Myatt's Aslileaf x Edge- 






cote Purple 


i:{ 




Edzell Blue x Myatt's Asli- 






leaf 


8 


4 


Edgecote Purple x Edzell 






Blue 


4+ 




f 2 from Edgecote Purple 






X Edzell Blue 


15 




Edzell Blue x Edgecote 






Purple ... 


13 


10 



1 n 

72 ^ tC 


0~ 


I- 


(i- 11 


- 10- 





I- 


0- 


11- 


10- 





1 1 

■A 4 




2 


1 

2 1 


3 

1 

.5 






2 
1 




1 
3 




:! 10 


I 


1 


1 1 


34 

7 












1 


8 18 


2 


5 




3 


4 










(i 



Some 200 selfed seedlings from Myatt's Ashleaf were raised, mostly 
in 1921 which was a disastrous year for potato seedlings in this district. 
Of these only two flowered, both having "abundant" pollen of which 
some at least was certainly good. The evidence here is very meagre and 
merely shows that Myatt's Ashleaf gives fertile offspring when selfed. 

In the case of Edzell Blue only self-set or "natural" seed has been 
available notwithstanding that about 100 flowers were self fertilised 

Joum. of Agric. Sci. xii 3 



34 Genetic Studies in rntiifnes: Sferilifif 

luulor baj;s. The seed from tlip natural berries was sowu separately 
,i;ivin<^ 150 seedlings; but eight plants from one berry proved from other 
evidence to be the result of a cross and were therefore not included, 
otherwise the results are consistent and trustworthy. Twenty-one plants 
flowered and were classified as follows: 

Abundant ... 8 Small ... ... 3 

Medium ... G Nil I 

The qualitative results are shown in Table I. It was noted that 
even the fertile plants, unlike those from Edgecote Purple selfed, were 
apt to vary considerably in different flowers and on different dates both 
in quantity and quality of pollen. Although itself fertile Edzell Blue 
selfed actually throws a large proportion of .sterile offspring, a result 
which contrasts strongly with that obtained from Edgecote Purple. A 
somewhat similar appearance of sterility is recorded by Salaman(i) in 
certain lines derived from a fertile Sutton's Flourball. We shall .submit 
an explanation after the much fuller evidence from crosses has been 
given. 

Two hundred seedlings were raised from the cross — Edgcote Purple x 
Myatt's Ashleaf in 1921. Of the F^ plants 22 flowered, consisting of 

Abundant ... 19 Medium ... 3 

All were fertile and contained at least 20 per cent, of good grains. 

A similar number of seedlings were raised from the reciprocal cross 
— Myatt's Ashleaf ■: Edgcote Purple — of which 13 flowered. All were 
fully fertile. The results from this cross are at once intelligible and 
harmonise with the few selfed data available, fertility behaving as a 
recessive. 

The cross — Edzell Blue x Myatt"s Aslileaf — was raised in 1920, and 
grown on in 1921 when a further sowing was also made. Of the 163 
plants grown 25 flowered and were recorded as: 

Abundant jiollen 8 Small ... ... 3 

Medium jjoileu 4 Very few grains 10 

As in the case of Edzell Blue selfed the quantity varied considerably in 
different records from the .same individual. Unfortunately the quality 
of pollen here was only examined in three cases (see Table I). It is 
clear, however, that a large proportion of sterile plants result from this 
cross between two fertiles. 

In 1919 the crosses — Edzell Bhie x Edgecote Purple and Edgecote 
Purple ;< Edzell Blue — were made. In the families raised in 1920 there 



R. N. Salaman and J. W. Lesley 35 

was no significant difference eitlior in tlie number of seeds per berry or 
in the germination of the seed or in the mortahty among seedhngs. 
Neither flower nor tuber colour showed any significant difference. 

Two types of inflorescence occurred in these famihes. In the " simple '' 
type (see plate) the primary axis divides into several (usually two) 
secondary axes, each of which forms a scorpioid cyme. In the " compound "' 
type (see plate), however, the two or more secondary axes divide again, 
forming tertiary axes and some of these divide so that axes of the fourth 
or fifth order are formed each of the ultimate branches forming a 
scorpioid cyme as before. Similar types of inflorescence have been 
studied by Crane (8) in tomatoes. The proportions of these two types 
in the present case showed no significant difference in the reciprocal 
crosses. 

The proportion of plants which flowered in Edgecote Purple >: Edzell 
Blue, however, was nearly double that in the reciprocal family. (In 
1920, 23 per cent, as against 13 per cent. ; in 1921, 72 per cent, as against 
37 per cent.) Both families were equally vigorous. In the late summer 
when many of the plants had ceased to flower several seedlings in Edge- 
cote Purple :■' Edzell Blue were seen to bear berries, often a dozen or 
more on a plant. In the reciprocal cross, on the contrary, extremely 
few plants had berries and these in but small numbers^. It occurred to 
us that this difference might be due to a difference in pollens, as seed 
and berry production in potatoes is frequently determined by pollen 
(of. Stuart(3)). As a first step, all the available pollens were examined. 
In Edgecote Purple x Edzell Blue all the 18 plants tested had "abundant" 
pollen. This was in accord with the frequent presence of self-set berries 
in this family. In the reciprocal cross 1.5 plants were recorded where 
pollen was described as follows: 

Abundant ... 1 Small ... ... 8 

Medium ... 1 Very few grains 5 

Only one plant was "abundant" as against the entire 18 in the 
reciprocal family. A remarkable difference in the male organs of the 
reciprocal cross thus came to fight, a difference which is paralleled by 
previously observed difference in fruit and seed jiroduction. Both 
famihes were grown on by tubers in 1921 and a further sowing made of 
1919 seed of the cross Edzell Blue x Edgecote Purple. 

' The berries both from Edgecote Purple •: Edzell Blue and Edzell Blue y Edgecote 
Purple contained seed. The average germination capacity was 90 % and the lowest 38 %. 
We are indebted to Mr Saunders of the National Institute of Agricultural Botany for 
testing the seeds. 

3—2 



36 Genetic Studies in Potatoes; Steri/iti/ 

From the cross Edgecote Purple x Edzell Blue 41 plants flowered. 
Both quantity and quality of pollen were repeatedly tested; all were 
fully fertile. The constant production of "abundant" pollen of high 
quaUty was a characteristic of every plant. The results from separate 
berries were consistent and the observations of 1920 were therefore fully 
confirmed (see Table I). 

An F2 family from a fully fertile F^ plant from this cross was raised 
in 1921 and 15 plants flowered. All had "abundant" pollen of high 
(jiiality (sec Table I). Thus there is no evidence here of sterility arising 
either in ^1 or -Fj- 

In Edzell Blue < Edgecote Purple grown on 19 plants flowered; both 
quantity and quahty were again repeatedly observed with the following 
results : 

Abundant ... 13 Small 8 

Medium ... 10 Very few grains 1 8 

In the qualitative test (Table 1) only four of the plants showed any con- 
siderable proportion of good grains; the majority of jilants tested had 
no good grains. Again the results from separate berries were consistent. 
The difference in berry production which first attracted our attention 
was as remarkable in 1921 as in the previous year. In Edgecote Purple 
X Edzell Blue over 50 per cent, of the individuals bore self-set berries, 
often in the greatest profusion ; of those grown under more favourable con- 
ditions at Oruiskirk, actually 20 out of 28 (over 90 per cent.) bore berries. 
In the family Edzell Blue x Edgecote Purple only si.x plants bore self- 
set berries and here it is interesting to note the correlation between good 
quality pollen and the setting of natural berries. All of the four plants 
having good pollen had self-set berries, but only one of the sixteen plants 
having no good pollen had self-set berries and even these were probably 
due to insect-borne pollen. These figures give no idea of the contrast in 
quantity of berries per plant which was even more remarkable (see 
Plate). That there is no evidence of female sterility here is indicated by 
the presence of natural berries on the six plants and on two others which 
set seed when artificially crossed with fertile plants. 

It has therefore been shown that whilst Edgecote Purple x Edzell 
Blue gives a wholly fertile Fj^ the reciprocal cross gives some sterile and 
some fertile plants. 



R. N. Salaman and J. W. Lesley 37 

Discussion. 

The two main facts to which we wish to draw attention are: 

(1) The appearance of sterile (or female) plants from the fertile 
variety, Edzell Blue, when selfed and from crosses between it and other 
fertiles, Myatt's Ashleaf and Edgecote Purple. 

(2) The different results obtained in F^ from a reciprocal cross. 
The evidence certainly points to a particular one of the three varieties 

as the principal agent introducing sterility. Both Edgecote Purple and 
Myatt's Ashleaf are themselves remarkably fertile. They have been 
crossed reciprocally and gave a wholly fertile Fj^; there is some evidence 
that when selfed they give fertile offspring. With Edzell Blue it is other- 
wise. It is itself only moderately fertile. Both selfed and crossed with 
Myatt's Ashleaf it gives a majority of sterile offspring. It is noteworthy 
that sterihty has arisen in both cases where Edzell Blue is the mother 
parent. It behaves as a sterile when used as female and as a fertile 
when used as a male parent. 

In plants male sterihty arising from a cross between fertile parents 
is, of course, a well-known occurrence, but in the present case sterility 
arises from a cross in one direction but not in the other. 

This difference in the reciprocal cross between Edzell Blue and Edge- 
cote Purple points to some difference in the eggs and pollen of one or 
both of the parents. The evidence seems to point strongly to such a 
difference in the sexual cells of Edzell Blue. It is not impossible that in 
Edzell Blue the sterihty is attached to the cytoplasm of the egg, but 
that the generative nucleus of the pollen grain carries the basis of fer- 
tihty. As sterihty normally behaves as a dominant we should then ex- 
pect all the F^ to be sterile where Edzell Blue is the mother. This, how- 
ever, was not so. A few were fertile, but we know of no evidence sug- 
gesting that the cytoplasm of eggs may differ in constitution. Indeed 
the heterogeneity of the eggs suggests segregation. It is more likely that 
a factor or factors are at work which are localised in the nucleus. 

As_sierility is dominant it would seem that the eggs of Edzell Blue 
are of two kinds, some — possibly half — carrying male sterihty, the re- 
mainder carrying male fertihty. The data at present available only give 
an approximate idea of the proportions. The pollen on the other hand 
all carries fertility. Following the same hypothesis both eggs and pollen 
of Edgecote Purple and Myatt's Ashleaf would appear to carry fertihty. 

In order to account for the difference between the eggs and pollen 
of Edzell Blue we suggest that at some stage of development a process 



38 Genetic Studies hi Potatoes; Steriliti/ 

of segregation has occurred at which the basis of sterihty has dropped 
out of the hneage of the tuale germ cells. On the other hand the germ 
lineage of the eggs is unaffected so that male sterility is present in some 
of the egg cells and is absent from others ; this may well be merely the 
result of normal segregation. Possibly in the developing bud at the time 
when the male organs of the flower are being differentiated a differentia- 
tion of genetic characters takes place. This hypothesis affords an ex- 
planation of the rather paradoxical male fertility of Edzell Blue in spite 
of its containing the dominant element of male sterility. For as a result 
of the premature segregation the primordia of the antliers would only 
contain the basis of fertility and are therefore able to form good pollen. 
It would account for the fertility of t\ and F2 from the cross Edgecote 
Purple X Edzell Blue and for the fertihty of the reciprocal crosses be- 
tween Edgecote Purple x Myatt's Ashleaf. The F-^ result from the cross 
Edzell Blue x Myatt's Ashleaf which was similar to that of Edzell Blue 
X Edgecote Purple is also intelhgible on the above hypothesis. A diffi- 
culty is met however in the result from Edzell IMue selfed. According to 
the theory about half the eggs carry sterility and the other half fertility 
while all the pollen carries fertihty. Consequently selfing should give 
half sterile and half fertile offspring, i.e. the same result as Edzell Blue 
< Edgecote Purple. But the data (Table I) indicate an excess of fertiles. 
The numbers are small but the discrepancy demands further investiga- 
tion. Again, no explanation is afforded of the rather imperfect pollen 
production of Edzell I51ue. 

To sum up it appears that in male sterile varieties the eggs either all 
carry male sterility or some carry male sterility and the remainder male 
fertility. The eggs of male fertile varieties (except Edzell Blue) and the 
pollen of all male fertile varieties tested carry male fertility. As sterility 
behaves as a dominant the F^ from a cross, sterile x fertile, consists of 
all steriles or partly of .sterile and partly of fertile plants. 

Miss Saunders (4) in her classical experiments with Matthiula has 
shown that the pollen of certain "singles" is all of one kind, but that the 
eggs are of two different kinds with respect to the "doubling" factors. 
Other experiments (5) suggest that in Petunia the pollen is heterogeneous 
and the ovules homogeneous for a "singleness" factor. The present data 
point to an explanation of the former kind in potatoes. 

If we regard a male-sterile plant as a functional female it follows 
that the gametes of Edzell Blue are differentiated in regard to sex, the 
eggs carrying either Hermaphroditism (cj Fertility) or Femaleness (o 
Sterility) and the sperms all Hermaphroditism (cJ Fertility). 



JOURNAL OF AGRICULTURAL SCIENCE. Vol. XII. Part I. 



PLATE II 





Fig. 1 



Fig. 2 




Fig. 3 



R. N. Salaman and J. W. Lesley 39 

Tliat a process of differentiation jjrior to normal segregation may 
occur in plants is shown by the work of Bateson(6) and (7) and others. 
In the present case there is reason to suspect a segregation by which 
sterility is dropped out of the germ lineage of the sperms but not of the 



In concluding it is a pleasure to acknowledge the help and encourage- 
ment given us by Prof. R. H. Biffen and the willing assistance of Miss 
E. Hagger at Barley and Mr Hamilton at Cambridge. 



REFERENCES. 

(1) Salaman, R. N. Limi. 8oc. Jourii. Botany, 39, Oct. 1910. 

(2) East, E. M. Rep. of the Agronomist, 1907, Conn. Agr. Expt. Sta. 

(3) Stuart, W. U.S. Dept. of Agr. Bull. 195, \^15. 

(4) Saunders, E. R. Journ. of Genetics, 1, No. 4, 1911. 

(5) Journ. of Genetics, 1. No. 1, 1910. 

(6) Bateson. Journ. of Genetics, 5, No. 1, 1915. 

(7) Journ. of Genetics, 6, No. 2, 1916. 

(8) Crane, M. B. Journ. of Genetics, 5, No. 1, 1915. 



EXPLANATION OF PLATE II. 

Fig. 1. "Simple" cymose system of male-steiilo F^ jjlant from Edzell Blue x Edgeoote 
Purple. 

Fig. 2. " Compound" cymose system of male-sterile F^ plant from Edzell Blue x Edgeeote 
Purple showing variation from the less "compound" type at the apex to the more 
"compound" type at the base of the shoot. 

Fig. 3. Bunch of self -set berries developed from a compound mflcjrescence of male-fertile 
Fj^ plant from Edgeeote Purple ;■: Edzell Blue. 



(Received November 3rd, 1921.) 



A STUDY OF NITROGEN METABOLISM 
IN THE DAIRY COW. 

By CHARLES CliOWTHEH. .\1.A., rii.JJ. 
AND HERBERT ERNEST WOODMAN, D.Sc, Pii.l). 

The work outlined in the present communication icas carried out during 
the years 1916-19 in the Institute for Research in Animal Nutrition of the 

University of Leeds. 

In an earlier conunuiiicatioii' dealing with the results of a series of 
digestibility determinations carried out by us with two sheep, attention 
was directed to the fact that, w^hen the averages for consumption and 
excretion of nitrogen in the different periods were arranged in the order 
of increasing nitrogen consumption, the retention of nitrogen in the body 
of the sheep rose only up to a certain point and then fell. The essential 
data are reproduced below: 



Period Nature of ration 

1 Hay I palm kernel oake I 

IV Hay alone 

II Hay + palm kernel cakes I and 1 1 

V Hay + extracted palm k. meal ... 

Ill Hay + undec. cotton cake 

VI Hay + dried yeast 

It will be noted that each sheep showed the maximuni retention of 
nitrogen in Period II, in which about 12 gni. digestible nitrogen, or 
roughly 17 gm. total nitrogen (= 106 gm. total crude protein) per head 
per day (= 2-4 kg. total crude protein per 1000 kg. live-weight) were 
consumed. In the periods following this in the table, as the nitrogen- 
consumption increases the nitrogen-retention falls steadily. 

These results suggest that, judged by nitrogen-retention, there is an 
optimum point of protein supply, above or below which nitrogen-reten- 
tion is reduced. It was realised, however, that this series of observations 
could not be regarded as in any way conclusive on this point, in view of 
' Journ. ofAgric. Sci. 8 (1917), 447. 





Average 


per day 




' 




Nitroger 


L retained 


Nitrogen digested 


{ -f ) or lost ( - ) 
by sheep 


8heep 1 


Sheep 2 


Sheep 1 


Sheep 5 


gm. 
U-88 


gm. 
7-38 


gm. 
-0-37 


gm. 
1-94 


9-0!) 


9-61 


+ 1-93 


214 


11-4(1 


l-'-48 


-H3-80 


4-7G 


Vl-li 


1312 


+ .3-33 


2-1.') 


i2;n 


12-9() 


■f3-25 


3-7(i 


1810 


18-28 


+ 2-94 


l-S.'i 



C. Crowtfier and H. E. Woodman 41 

the varying sources of protein-supply in the different periods, and the 
fact that the order in which tlie diverse rations were fed was not that of 
increasing nitrogen-content. It woukl be ei(ually legitimate, for example, 
to account for the reduced nitrogen-retention in Periods III and VI, by 
assuming the proteins of cottonseed cake and yeast respectively to be of 
lower metabolic efRciency than those of palm kernel cake. 

Both alternatives engaged our interest, as we were at the time con- 
templating a comprehensive study of the nutritional requirements of 
the dairy cow, in which, as is well-known, protein-supply plays a part 
of outstanding importance. It has been established that up to a certain 
point increased protein consumption leads to increased secretion of 
milk. Does this point coincide with that of maximum retention of nitro- 
gen in the body? Does the amount of food-protein recj[uired to produce 
the latter vary with the qualitative character of the ration? Is the 
maximum of nitrogen-retention constant for any one individual or 
variable according to the feeding? Before attempting to secure answers 
to these questions we decided first to test whether, by feeding cows on 
rations of the same qualitative composition, but of successively increasing 
protein-content, and determining tlie nitrogen-retention, we could detect 
an optimum of protein-supply, such as had been suggested by the records 
of the sheep experiments. Further, in order to avoid the complications 
that pregnancy and lactation would introduce, we selected as test animals 
two fully grown Shorthorn cows, not in calf, and not producing milk. 

FIRST EXPERIMENT. 
(196 days, November, 1916— June, 1917.) 

For reasons stated later this experiment cannot be regarded as en- 
tirely satisfactory and consequently need only be dealt with in outhne. 

The two cows were first brought approximately into nitrogenous 
equihbrium on a daily ration of 141b. "seeds" hay, supplying about 
122 gm. nitrogen. After determining over a given period the daily 
balance between the amounts of nitrogen consumed and excreted, the 
ration was increased by adding 2 lb. maize meal per day (containing 
about 13 gm. nitrogen) and the effect on the nitrogen balance was then 
investigated. This was followed by several further experimental periods, 
in each of which the ration was increased by 2 lb. maize meal. 

The general arrangements for the experiment and the methods of 
analysis, etc., followed were similar to those described in detail later in 
this paper. 



42 J Sfiidji of Nitroijen Metabolism, in tin Dairy Con- 

111 all changes of feeding a transitional period of at least nine days 
was allowed, whilst the experimental period consisted of at least twelve 
days, giving a minimum period of three weeks between each change. 
The essential data obtained are summarised in Table T. 

Table I. 
Cow A. (Initial weight. W?,^ II).) 















Gain ( -^ ) or 






Daily ration 




Loss ( - ) of 








A 




Total N consumed 
per day 


N by cow 
per day 


?criod 


Duration 


JI^ 




Maize 




days 


lb. 




lb. 


«m. 


gm. 


1 


24 


14 







12in 


- 8-2 


11 


32 


14 




2 


1341 


+ 7-6 


III 


21 


14 




4 


1.51-8 


+ 181 


IV 


21 


14 




6 


1G8-4 


+ 20-6 


\' 


28 


14 




8 


l()l-0 


+ 10-4 


VI 


21 


16-5 




,S 


172-4 


+ 11 


\11 


28 


16-5 




10 


1 S.-)-7 


+ 60 


VIII 


21 


16-5 




12 


201-9 


+ 17-8 


IX 


.31 


16-.5 




1(1* 


l!)4-3 


+ 15-7 




Cow 


B. (Ir 


litial 


weight, 959 lb.) 




1 


32 


14 







124-3 


+ 50 


11 


32 


14 




2 


133-3 


+ 8-4 


III 


21 


14 




4 


148-9 


+ 18-9 


IV 


21 


14 




6 


1G4-3 


+ 20-4 


V 
VI 

vu 


28 


14 




8 


161-4 


+ 18-1 


28 


14 




10 


170-3 


+ 21-0 


VIII 


— 


— 




— 


— 


— 



* The concentrated food diirini; this period consisted of 91b. maize + 1 lb. linseed cake. 

The investigation proceeded quite smoothly up to Period V, when it 
became necessary to draw a fresh consignment of hay. This proved un- 
fortunately to be decidedly poorer in nitrogen than the previous con- 
signment, and conse(|uently, despite the added 2 lb. of maize, the nitro- 
gen consumption for Period V worked out rather less than for Period IV. 
In order to overcome this difficulty the basal ration of hay was increased 
for Period VI to 16-5 lb. per day, the maize meal being retained as in 
Period V at 81b. Unfortunately, although Cow A consumed the increased 
ration of hay satisfactorily, Cow B could not be induced to do so, and in 
consequence this cow had to be kept for the remainder of the experiment 
on the lower ration (14 lb.) of hay, so that from this point the records 
of the two cows were not strictly comparable. 

Further difficulty was experienced towards the end of the experiment 
in inducing the cows to consume the rations completely and it was ob- 
vious that we were approaching the limits of their ajipetitcs. This was the 



C. Crowthbr and H. E. Woodman 43 

more marked with Cow B, and for this reason we were obliged to reject 
the records of this cow for Periods VI and VIII. 

If the data for nitrogen-retention be examined, it will be seen that 
with each cow up to Period IV there were distinct indications that the 
daily retention of nitrogen was approaching a maximum value and, but 
for the regrettable difficulty with the hay, it seems probable that this 
limit would have been reached in Period V, since in the later periods, 
despite increased intake of nitrogen, no higher retention than that of 
Period IV was recorded. A slight increase is indicated with Cow B in 
Period VII but it will be noted that the nitrogen intake in this case was 
practically the same as for Cow A in Period IV, so that the maximum 
retention of nitrogen under the conditions of experiment would seem to 
be associated with a nitrogen intake of roughly 170 gm. per day {= 1060 
gm. crude protein). Taking the average weight of the cows for Period V 
this represents a daily intake of crude protein of 2-34 kg. per 1000 kg. 
live-weight, or almost exactly the same figure as was dedxiced for the 
sheep from the data obtained in the digestibility trials. This confirmation 
is particularly interesting in that the diets in the different periods of the 
sheep tests varied considerably in qualitative character, and the con- 
clusion suggests itself that, when fed along with hay, the proteins of 
maize, cottonseed, palm kernels and yeast are of equal value so far as 
capacity to effect protein storage in the body is concerned. 

It would appear therefore from these experiments that for the last- 
named purpose the optimum protein-supply in the food is in the neigh- 
bourhood of 2-4 A-(/. crude protein, or say hi kg. digestible crude protein 
per 1000 kg. live-weight. This, of course, appUes only to animals such as 
those under test which were not subject to any losses of nitrogen other 
than those voided in faeces and urine, and were free from any exceptional 
internal needs for protein such as arise during pregnancy. 

It will be noted from Table I that the duration of the different periods 
varied from 21 to 32 days. It was anticipated that a period of 21 days 
would afford ample time for the re-establishment of nitrogen equilibrium 
after the disturbance due to change of ration. It soon became evident, 
however, that this was not the case, and the records of Periods IV to VI 
bring this out clearly. For reasons already given the nitrogen-consump- 
tion remained relatively constant throughout these three periods, which 
may therefore be grouped together as one long period. Viewed in this 
light it is seen that the establishment of nitrogen equilibrium is a much 
slower process than we had assumed, the nitrogen-retention persisting, 
though at a steadily diminishing rate, throughout the whole interval of 



44 A SftKfi/ of Xifrof/en Metabolmn in the JJnirij Cow 

70 days. In tliis particular, therefore, our scheme of experiiuent would 
appear to have been defective in that the change of ration from period 
to period was evidently made before the influence of the earlier ration on 
nitrogen-retention had been exhausted. Accordingly, before proceeding 
further with the comprehensive programme of experimental work on 
these lines which lay before us, we thought it desirable to make a more 
prolonged study of nitrogen-retention under conditions of roughly con- 
.staiit nitrogen-consumption, and a further experiment was undertaken 
in November, 1917, and developed later into a study of nitrogen-retention 
during pregnancy and lactation, the whole experiment covering a period 
of two years. 

SECOND EXPERLAIEXT. 

(November, 1917 — November, 1919.) 

(icneral Plan of Experiment. 

Two Siiorthorn cows, C and D, similar to those used for the first 
experiment, both "dry" and not in calf, were weighed and placed on a 
daily ration consisting of 20 lb. "seeds" hay. The nitrogen-balance in 
both cows was followed continuously, except for the one week monthly 
during which the cows were weighed and an interval of 10 weeks 
at the end of the first year. After a period of 302 days (including 
255 days for which the nitrogen-balance records were obtained) during 
which both cows received identical treatment. Cow D was put to 
the bull, whilst Cow C remained unserved as control. The nitrogen- 
balance measurements were continued for both cows tjiioughout the 
period of jjregnancy of Cow D and subsequent parturition, and were 
further extended well into the period of lactation. For Cow D the experi- 
ment extended over periods of 302 days "dry"' and not in calf, 2Sf davs 
"dry" but in calf, and 136 days in milk, a total of 722 day.s throughout 
the whole of which period Cow C was maintained dry and not in calf. 
Samples for nitrogen-balance determinations were taken on 54() days 
during this period. 

Both this and the foregoing experiment were carried out in a building 
specially designed for work of this character. The floor was of cement, 
graded and grooved to secure ra]>id drainage, each cow-stall being pro- 
vided with a separate drain, so arranged that the drainage could be easily 
collected for purposes of weighing and sampling. Preliminary tests 
showed that any liquid falling on the floors of the stalls could be recovered 
within 2 or 3 per cent., whilst by spraying the floors occasionally with 



C. Crowthbr and H. E. Woodman 45 

water a still higher degree of completeness could, be obtained in the 
recovery of urinary nitrogen. 



E.rpni'mcntal detail.';. 

Collection, Sampling and Analysis of Faeces. The faeces were collected 
into weighed covered buckets. The 2-i-hours' collection was weighed, 
thoroughly mixed, and by quartering, reduced to a small sample. One- 
tenth of the daily faeces was preserved in a closed vessel with the 
addition of a little toluene. In this manner, composites were made up 
twice weekly, representing the collection over three and four days respec- 
tively. Preliminary tests had shown that the loss of nitrogen was inap- 
preciable when the faeces were stored in this manner over a period of 
several days. The composite samples were well mixed and small samples 
were drawn from the bulk for analysis. The nitrogen-content was deter- 
mined in triplicate by means of the Kjeldahl method. 

Collection, Sampling and Analysis of Urine. The urine was collected 
in weighed buckets, the drainage being assisted by frecjuent spraying of 
the floors with water. No litter was used in the stalls. The daily output 
of urine was weighed and, after thorough stirring, one-tenth of the total 
weight was ladled out, acidified with 20 c.c. H0SO4 (1:1) and preserved in 
a Winchester bottle. Composites were made up in this way twice weekly 
and the nitrogen-content of the samples was determined by the Kjeldahl 
method. Under the conditions of collection the faeces were always con- 
taminated with urine, and the urine was diluted to some extent by the 
water used in spraying. This was immaterial, however, as it was only 
required to measure the total voided nitrogen. 

Length of periods and 'weighing of cows. The jseriods were mainly 
of about 18 days' duration. At the end of each period the cows were 
weighed on three successive days under comparable conditions. 

Feeding of cows and analysis of foodstuffs. The hay was fed in four 
equal allowances during the day, care being taken that the cows had 
consumed the hay completely before being left for the night. Water 
was given ad lib. Composite samples of the feeds were made up by 
reserving weighed representative samples daily. Two independent hay 
composite samples were made up in each period, and the dry matter and 
nitrogen-contents of these were determined, the mean results for the 
two samples being used in the calculation of the nitrogen-balances. 
From time to time representative samples were made up from the period 
composites and complete analyses were carried out. Moisture deter- 



46 A Study of yitriHjeii Metabolisni in the Dairy Cow 

minations were made daily on independent hay samples, since this factor 
was found to be sul)ject to consitleiable variation. 

Analysis of milk. Cow J) was milked twice daily during its period of 
lactation and half-weekly com])osites were made up. The sam])les were 
preserved by the addition of one or two drops of formalin. The deter- 
mination of the nitrogen in the milk samples was carried out in duplicate 
by the Kjeldahl method. 

The experiments were carried out at the Manor Farm, (iarfortii, 
(Experimental Farm of the University of Leeds and the Yorkshire 
Council for Agricultural Education). The care of the animals was in the 
experienced hands of Mr H. J. Hargraves, N.D.A., to whom we are 
greatly indebted for the skill and accuracy with which this important 
side of the work was carried out. 

Table II. Analysis of seeds hay and linseed cake composile. 
(Calculated on dry matter.) 
Seeds hay 



Days i-epresented 
by sample ... 


1-08 


69-194 


195-295 


296^99 


500-660 


661-722 


Linseed 
cake 


Crude protein ... 


12-46% 


12-41% 


11-08% 


12-86% 


10-27% 


10-29% 


3318% 


True protein ... 


10-25 


1103 


9-75 


11-45 


8-73 


9-17 


23-86 


Ether extract ... 


1-52 


1-95 


1-79 


1-65 


1-65 


1-55 


10-15 


Nitrogen-free 
















extractives ... 


50-23 


45-68 


51-50 


48-50 


49-23 


49-92 


38-95 


Crude til)re 


28-90 


33-42 


29-64 


30-94 


31-82 


31-22 


10-71 


Ash 


0-89 


0-54 


5-99 


6-05 


7-03 


7-02 


7-01 



It will he noted that the composition of the hay, and in particular, its 
content of protein, were subject to considerable variation during the 
course of tlie trial. This rendered neces.sary, in the later stages of the 
experiment, a slight increase in the amount of hay fed per day, in order 
to maintain the amount of protein consumed per day at its initial level. 
Another factor disturbing to some extent and difficult to regulate was 
the great variation to which the moLsture-content of the hay was subject 
from day to day. For these reasons it was impossible to avoid an ap- 
preciable variation in the nitrogen-.supply without recourse to methods 
which the resources at our disposal did not permit. It will be seen from 
the second column of Table III what the extent of this variation was. 

Comments on Tabic III (First Main Period of Experiment). 

We cannot attempt to tabulate here in detail the whole of the data 
accumulated day by day during the trial. The figures given in Table 1 1 1 
therefore represent daily averages for the difFerent periods, the nitrogen- 
balance columns giving the average daily gain or loss of nitrogen by the 



C. Crowther and H. E. Woodman 



47 



cows for each respective jjeriod. The weight columns give the gain or 
loss of weight of the cows over the whole period. 

Table III. 
Sunuiiurij of nitroyen-halances for Cow C and Can' D up to da// 295. 

Daily ration: 20 llj. seeds hay (average dry matter per day = 7600 gm. ). 
Cow C Cow D 





N con- 


Total N 


Mean 


^ 


Total N 


Mean 


-^ 




sumed 


voided 


nitrogen- 




voided 


nitrogen - 


Change 


Period 


(average 


(average 


balance 


Change in 


(average 


balance 


in 


in days 


per day) 


per day) 


per 


day 


weight 


per day) 


per day 


weight 




gm. 


gm. 


g 


m. 


lb. 


gm. 


gm. 


lb. 


1- 19 


1360 


130-1* 


+ 


5-9 


-13| 


132-4* 


+ 3-0 


-43 


23- 47 


1511 


143-7 


-1- 


7-4 


- 5* 


139-7 


-I-11-4 


-1-15 


52- 08 


144-5 


139-2 


+ 


5-3 


+ llf 


136-2 


+ 8-3 


+ lli 


72- 8!) 


152-9 


1.50-3 


j- 


2-(i 


- ^ 


147-7 


-1- 5-2 


- 1 


93-110 


151-8 


1.50-2 


4- 


1-6 


+ 2 


148-2 


-f 3-0 


+ 121 


1 14-131 


148-0 


151-2 


_ 


2-6 


+ 30^ 


148-9 


- 0-3 


+ e| 


135-152 


152-3 


149- 1 


+ 


3-2 


.> 


140-8 


-f ,5-5 


+ 15 


150-173 


148-9 


1.50-9 


- 


20 


Tioi 


145-4 


-i- 3-5 


-f253 


177-194 


147-3 


147-S 


- 


0-5 


- 3| 


142-5 


+ 4-8 


-14j 


198-215 


105-3 


1.55-6 


+ 


9-7 


+ lo!i 


151-8 


^-13-5 


-1-19 


219-230 


141-8 


1430 


- 


1-2 


+ 22| 


141-0 


+ 0-8 


+ 33 J 


240-257 


136-6 


135-0 


-f 


1-0 


+ 7 


130-2 


+ 6-4 


-flO 


201-270 


146-5 


135-9 


+ 


10-0 


+ 15§ 


135-7 


-flO-8 


+ 4 


282-295 


138-7 


134- 1 


+ 


4-6 


+ n 


1310 


+ 7-7 


+ 24f 



Analytical Total N 
days consumed 

2.55 37,016 gm. 



Condensed suni.tnanj. 
Total N retained 



Nett change of weight 



Cow D 




Cow C 




Cow 


D 




571 gm. 




-1- 109 lb. 




+ 118^ 


, lb. 




1 milk (c-( 


JW.-5 


not quite d] 


■y 


at beginning 


of 


( Cow C. 


1: 


.'29 lb. 










1 Cow D. 


1: 


260 lb. 











Cow C 
800 gm. 

* Includes small amount of nitrogen tnn 
trial). 

Initial weights of eow^ 



According to current views on protein metabolism we might expect 
to find, on introducing a given ration supplying protein in excess of the 
requirements of the basal metabolism, that nitrogen storage took place 
at the outset, but that the rate of storage steadily fell until nitrogen- 
equilibrium was re-established. This process is clearly evident in the 
records of our two cows. Taking Cow C for example, and overlooking 
the first 20 days as preliminary, it will be seen that the nitrogen-retention 
steadily fell and nitrogenous equilibrium was ultimately roughly estab- 
lished, though not until the lapse of about 90 days. Subsequently, 
between days 93 and 194 the cow was in almost perfect nitrogen-equi- 
librium, but this was then disturbed by a rise in nitrogen-consumption 
due to an abrupt rise in the protein-content of the hay. The effect of 



48 A Study o/yitrugen Metaholisin in t/ic Ddirij Cow 

this seems to have passed away ((uickly and between days 219 and 257 
iiitiogeii-eqiiilibriuin again prevailed. Thus, but for the abnormal period 
of days 198-215, e(juilibrium was maintained over a period of 164 days. 
It was all the more surprising therefore in the subsequent periods from 
day 261 to day 295 to tind that nitrogen storage was again taking place, 
a phenomenon of which the explanation is not very ob^aous. It certainly 
cannot be attributed to more than a small extent to the comparatively 
small rise in nitrogen-consumption in the ])eriod of days 261-278. 

The record of Cow D is very similar for the first part of the period, 
the nitrogen-retention falling steadily until the 100th day or thereabouts 
when nitrogen-equilibrium was established. The jjeriod from the 114th 
to the 131st day shows an almost perfect nitrogen-balance, but subse- 
quently a curiously persistent small retention of nitrogen was recorded 
throughout the remaining 164 days, increasing appreciably, as in the 
case of Cow C, in the last stages of the period. 

Over the whole period, out of 37-6 kg. nitrogen consumed by each 
cow, Cow C retained 8(i() gm. and Cow D 1571 gm., whilst the gains in 
live-weight were 109 lb. and 118 lb. respectively. 

No clear correlation is evident between the nitrogen-balances and the 
weight changes. For instance, between days 114 and 131, Cow C showed 
a daily negalire nitrogen-balance of 2-6 gm. and an Increase in weight of 
30j lb. for the period. Between days 72 and 89, however, where the cow 
f/ained 2-6 gm. of nitrogen daily, the weight of the cow suffered a loss of 
3?5 lb. for tiie period. 

The extremely irregidar variation of the figures in the nitrogen- 
balance and weight columns, and the disconcerting rise in the nitrogen- 
retention after 240 days of relatively uniform feeding, show clearly the 
danger of placing too much reliance on conclusions drawn from the results 
of short-perjod experiments with cattle. A three-weeks' period in work 
of this character is obviously far too short. 

Comments on Table IV (Second Main Period of Experiment). 

Cow D was put to the bull on September 6, 1918 (day 303), and the 
measurements of the nitrogen-balances were suspended until November 
8, 1918 (day 366), This break in the measurements was unfortunate, 
since, on resumption of the trials, distinct indications were obtained 
that the protein metabolism of Cow D had undergone a marked dis- 
turbance in the early stages of pregnancy. Up to day 295, Cow D had 
shown throughout a uniforndy higher positive nitrogen-balance than 
Cow C. On resumption, however, Cow D was found to be distinctly in 



C. Crowther and H. E. Woodman 



49 



nitrogen deficit, whereas Cow C still retained a positive nitrogen-balance. 
If the nitrogen-balances throughout w'ere plotted graphically against the 
days of duration of the trial, it would be found that the curves for the 

Table IV. 

Summarji of nilro(/en-balances during period of pregnancy of Cow D. 

(Days 36G-575.) 

Daily ration: 

Gorv C (to day 558): 20 lb. seeds hay* (average dry matter per day = 7340 gm.). 
Cow D (to day 407): 20 lb. seeds hay (average dry matter per day = 7250 gm.). 

(Day 408-562); 21 lb. seeds haj' (average dry matter per day = 7740 gin.). 



Cow C 



Cow D 



Period 

in 
days 

,366-383 

387-407 

41(5-432 

436-153 

457-474 

478^95 

499-523 

534-558§ 

562-575 



N con- 
sumed 
(average 
per day) 

gm. 
143-7 
144-6 
1.36-8 
138-9 
1.50-2 
152-6 
149-1 
145-2 
146-6 



Total N 

voided 

(average 

per day) 

gm. 
132-8 
131-8 
129-9 
1441 
160-0 
154-8 
161-6 
148-4 
141-6 



Mean 

daily 

nitrogen- 

balance 

gm. 
-1-10-9 
4-12-8 
-I- 6-9 

- 5-2 

- 9-8 

- 2-2 
-12-5 

- 3-2 
+ 5-0 



Change 
in 

weight 
fur 

period-l- 
ib. 

4-32 

- % 

+ H 

-m 

+ 5J 

-m 

- 3s 
-1-20 



N con- Total N Mean 

sumed voided daily 

(average (average nitrogen - 

per day) per day) balance 



gm. 
143-7 
144-6 
143-6 
14.5-8 
1.57-7 
160-2 
156-6 
145-6 
149-4 



gm. 
148-6 
145-7 
144-5 
143-8 
15.5-9 
1.5.5-1 
154-7 
140-8 
131-4 



:m. 
4-9 
1-1 
0-9 
20 
1-8 
5-1 
1-9 
4-8 



-1-18-0 



Change 

in 
weight 

for 
periodj 

lb. 
-13| 

-Hl2f 
+ 25i 
-F21i 
-1-19 
■t-22 
+ 26i 
4-104 
•fl5S 



Condensed summary. 
CowC 



CowD 



Number of 

analytical 

days 

174 
428 



Total N 
consumed 

gm. 
25,309 
62,925 



Total N 
retained 
or lost 

gm. 
- 50 
-t-816 



Nett change 
in live- 
weight 

lb. 
-18J 

4-9111 



Total N 
consumed 

gm. 
24,019 



Total N 
retained 
or lost 

gm. 
4-386 



Nett change 
in live- 
weight 

lb. 
4-139-4 



* From day 562 started feeding new consignment of hay. This proved poorer in nitro- 
gen and ration for days 562 to 575 was consequently altered, and average consumption 
as follows: 

Cow C: 21-4 lb. hay 4- -43 lb. linseed cake ( =87.50 gm. dry matter per day). 
Cow D: 21-8 lb. hay 4- -43 lb. linseed cake ( =8920 gm. dry matter per day). 

t Weight of Cow C at beginning of period, 1378 lb. 

X Weight of Cow D at beginning of period, 1407 lb. 

§ The records for Cow D in this period relate only to days 534-544. This cow was 
withdrawn from trial between days 544 and 558 on a"count of slightly swollen hocks. 

II Does not include weight changes from August 29 to October 31, 1919, during which 
period no determinations of nitrogen-balance were made. 

two cows intersect shortly after service of Cow D ; previous to this, the 

curves run approximately parallel. Thus, on a diet more than sufficient 

for its protein requirements in the ante-pregnant period, Cow D, as a 

Journ. of Agric. Sci. xii 4 



50 A Shiflfi of Xifroficn Metaho/iniii in tli< Dah-ij Coir 

result of changos in the early stages of pregnancy, was suffering a loss of 
protein. 

This behaviour is in accord with the findings in other investigations 
carried out on different species. Murlin^ investigated the weekly nitrogen- 
balances in a ]jregnant bitch and showed that there was a large loss 
of maternal protein, commencing immediately after conception and 
continuing for six weeks. Only during the last two weeks before parturi- 
tion was there a marked conservation of protein, as manifested in the 
pronounced nitrogen-retention. Murlin attributed the destruction of 
maternal protoplasm which accompanies the development of the foetus 
to the necessity for providing "hereditary building stones for the laying 
down of the youthful protoplasm in accordance with the type character- 
istic of the species." 

The diet of Cow D was increased by 1 lb. seeds hay per day on day 
408 and later again on day 502 (see Table IV). This slight increase 
enabled the cow to begin to retain nitrogen. Reference to Tables \\ and 
V shows that the rate of storage, however, was not very considerable 
until within three or four weeks of partTirition. During this time, al- 
though the amount of nitrogen excreted in tlic faeces remained roughly 
at its former level, yet tiie nitrogen ajjpearing in the urine underwent a 
marked diminution. This was a consequence of protein-retention. Ex- 
amining the period as a whole, it would appear that the demands made 
on the food protein for the single purpose of foetal development were 
relatively small, since the average rate of nitrogen-retention was only 
about 2-4 gm. per day. 

The behaviour of Cow C, dry and not in calf, during this period con- 
trasted curiously with its behaviour in the preceding period, when it 
was able to make a distinct gain of protein and body-weight. In this 
period, though receiving approximately the same ration, Cow C suffered 
a slight loss of protein and its weight dropped about 18 lb. These results 
serve to illustrate further the uncertainty of short period work with 
animals. 

Comments on Table V (Third Main Period of the Experiment). 

In Table V are given the full experimental details for the period im- 
mediately preceding and following the calving of Cow D. Particulars of 
mUk-yield, etc., for this and the following period will be found in Table 
VIII. For some days after parturition, each day's collections of urine, 
faeces and milk from Cow D were analysed separately. 

' A'meriran Journal of Phii.noloqii, 1910, xxvii 177. 



C. Crowther and H. E. Woodman 



51 



Table V. Nitrogen-balances for Cow D in period of parlurition. 

Daily ration: 21-5 lb. of seeds hay + linseed cake (for amounts on difi'crcnt days 

see Table). 







Consumed 




Nitrogen 


voided 










.V 






. 






Daily 
nitrogen- 


Days of 


Lb. of 


Total dry 


% 


In 


In 


In 




period 


cake 


matter 


Total N 


faeces 


urine 


milk 


Total 


balance 






Sia. 


gm. 


gm. 


gm. 


gm. 


gm. 


gm. 


580-581) 


1* 


9,104 


141S 


76-1 


.50-3 




126-4 


+ 15-4 


587 


1 


9,174 


142-5 


— . 


1.58-6t 


51-11 


481-5 


( - 99-5 


588 


1 


8,973 


1400 


143-7 


40-4 


87-7) 


1 - 99-5 










(2 davs) 










589 


1 


9.033 


140-8 


90-0 


61-1 


100 


251-1 


-110-3 


590 


8 


11,826 


280-3 


98-9 


88-2 


105-7 


292-8 


- 12-5 


591 


8 


11,832 


280-4 


94-6 


88-8 


76-2 


259-6 


+ 20-8 


692 


6 


10,960 


239-5 


114-5 


111-1 


79-5 


30.5-1 


- 65-6 


593 


6 


11,024 


240-4 


129-3 


99-3 


81-7 


310-3 


- 69-9 


594 


6 


11,010 


248-1 


91-4 


125-5 


78-2 


29.5-1 


- 47-0 


595 


8 


11,718 


286-4 


100-8 


108-2 


78-4 


287-4 


- 1-0 


596 


8 


11,730 


286-6 


101-9 


102-1 


76-5 


280-5 


+ 6-1 


597 


8 


11,830 


288-1 


103-4 


lOS-0 


74-8 


286-2 


+ 1-9 


598-603 


8 


11,715 


286-5 


111-6 


111-2 


69-2 


292-0 


- 5-5 


Average from part 


urition 


252-5 


102-2 


103-5 


76-8 


282-5 


- 30-0 



Average including N of calf 
and afterbirth ... 



91-8 



... 252-5 _ _ _ 344.3 

* 1 lb. linseed cake contained 399-0 gm. dry matter and 19-93 gm. N. 
I This figure gives N of urine + fluids + washings. Loss in weight of Cow D durmg this 
period was 161 lb. 

Cow D calved on the morning of June 17th, 1919 (day 587), the 
period of gestation being 284 days. The weight of the calf was 84 lb. 
Estimating the protein-content of the calf at 16 per cent.^, its nitrogen- 
content would be 975 gm. The placental fluid, urine and washings were 
collected together and analysed. The placenta weighed 11-5 lb. and had 
a nitrogen-content of 74-6 gm. {= 1-43 per cent. N in placenta). 

Taking the figure 2-4gm. as representing the rate of storage of nitrogen 
per day during the period of i^regnancy, it follows that the total storage 
of nitrogen by Cow D during the period of gestation was apjjroximately : 

Up to day 579 ... ... 665 gm. 

From day 580 to parturition 108 ,, 
Total 773 „ 
The losses of nitrogen during parturition were approximately: 

In calf ... ... ... 975 gm. 

In placenta, etc. 

Total 



75 



1050 



Vide Armsby, The Nutrition of Farm Animals, p. 62. 



4—2 



52 A Studji of Nitrogen Metabolism in tin' Ihih-ij Cmr 

This figure represents a iiiiniimiiu estimate, since it does not include 
the nitrogen of the fluids, wliich were collected with the urine and not 
analysed separately. Thus, whereas 1050 gni. nitrogen had been stored 
as tissue in the form of calf and placenta. Cow D had been able, on a 
ration only very slightly heavier than that which served for its protein 
requirements when not in calf, to obtain 773 gm. from its food for this 
purpose. The deficit of 277 gm. must have been supplied from the 
maternal protein at the average rate of about 1 gm. per day. 

A cow in calf is thus able to maintain a positive nitrogen-balance on 
a ration differing only slightly from that requisite for nitrogenous equi- 
librium in the ante-pregnant period, though under such circumstances, 
it may have to supply from its own protein a fraction of the nitrogen 
necessary for foetal growth, and thus be unable to build up the desirable 
reserves during pregnancy to enable it to come into lactation with a 
good milk flow ca])able of being sustained over a long period. More 
generous feeding than was given in this investigation is obviously 
necessary in actual farm practice, especially in view of the heavy negative 
nitrogen-balances shown by Cow D in the days following parturition. 

For the first three days after calving it was thought inadvisable to 
increase the ration, but on the fourth day (day 590) the allowance of 
linseed cake was raised to 8 lb. This immediately checked the loss of 
nitrogen from the body, but as the cow at this stage could barely con- 
sume the ration, the allowance of linseed cake was reduced two days 
later (day 592) to 6 lb., whereupon a marked nitrogen deficit was again 
established. On day 595 the allowance of linseed cake was again raised 
to 8 lb. and nitrogen-equilibrium was practically restored, this changing 
to nitrogen-retention when on day G08 a further 1 lb. of cake was given 
{vide Table VI). 

For the period covered by Table V Cow C, dry and not in calf, was 
again in nitrogen deficit (see below) following a short period of nitrogen 
storage from day 502 to 575. 

N consumed N voided Mean daily Change in 
(average (average nitrogpn- weight for 
Daily ration (days 580-603) per day) per day) balance period 

gm. gm. gm. lb. 

215 lb. hay + 1 lb. linseed cake 143-8 ISoO - U-8 +2i 

Comments on Table VI (Fourth Main Period of E.xperiment). 

It will be noted from Tables V and VI that a positive nitrogen- 
balance was not estabUshed in Cow D until three weeks after parturition. 
It was then consuming daily aiiout .3.30 gm. nitrogen and was yielding 
about 27 lb. of milk, containing roughly GO gm. N per day. That the 



C. f*ROWTHER AND H. E. WoODMAN 



53 



ration was then ample for the extra requirements of milk production 
was evidenced by the consistent positive nitrogen- balances recorded. 
Towards the end of the trial, when the daily yield of milk had fallen 
below 20 lb. (containing about 48 gm. N) the amount of cake fed daily 
was reduced to 5 lb. This resulted in the estabUshment of a decided 
negative nitrogen-balance. 



Summary of nitrogen-balaii 
Daily ration; 21-5 lb. seeds 



Table VI. 
ces for Cow D during period of lactation. 

hay + linseed cake* (for amounts see Table). 







Consumed 




N voided 












(average 


per day) 


(average 


per day) 




Mean 


Change 


Days 
















daily 














\ 


in 


of 


Lb. of 


Total dry Total 


In 


In 


In 




nitrogen - 


■weight 


period 


cake 


matter 


N 


faeces 


urine 


milk 


Total 


balance 


period 






gm. 


gm. 


gm. 


gm. 


gm. 


gm. 


gm. 


lb. 


608-624 


9 


12,013 


329-9 


107-2 


153-8 


.59-9 


320-9 


-1- 9-0 


- f 


629-645 


9 


12,0.39 


3499 


109-1 


169-2 


58-9 


337-2 


-I-12-7 


•f 15J 


650-6.59 


10 


12,440 


340-5 


112-8 


161-4 


57-4 


331-6 


•f 8-9 


- If 


66.5-680 


ot 


11,952 


323-5 


111-9 


143-4 


.53-6 


308-9 


+ 14-6 


-33f 


685-701 


/ 


11,1.53 


287-7 


106-2 


124-6 


54-7 


285-5 


+ 2-2 


-1- 5 


706-722 


.J 


10,370 


241-3 


97-4 


106-5 


48-7 


252-6 


-11-3 


- 2J 






( 


Condensed Summary f 


or Cow 


D. 






Analytical 


days 


Total N consumed 


Total N retained Nett change i 


in weight 








gm 






gm. 




lb. 






608-624 


29,131 




-1- 536-8 




-18 






546 




96,051 




-1-2091 




+ 78H 






546 




96,051 




-f 10411) 









* 1 lb. cake contained 400 gm. dry matter and 21 gra. nitrogen (approx. average for 
whole lactation period). 

t Amount of cake reduced to 9 lb. on day 068. 

t See note ([!) Table IV. 

§ Including N of calf and placenta (estimated at minimum of 1050 gm.). 

During this period of about 90 analytical days in the lactation period, 
Cow D actually retained about 537 gm. of nitrogen and only lost 18 lb. 
body-weight. For the whole trial of 546 experimental days, it will be 
seen that this cow consumed about 96,000 gm. nitrogen and of this 
retained 1040 gm. {i.e. slightly over 1 per cent.), this being roughly the 
amount of nitrogen absorbed in foetal development and lost from the 
body at parturition. 

It was originally intended to continue the experiment through the 
whole period of lactation, but circumstances rendered this impracticable. 

It is of interest to compare in the case of Cow D for the peiiod sub- 
sequent to calving (Tables V, VI) the consumption of nitrogen over and 
above "equihbrium requirements" with the amount of nitrogen secreted 
in the milk. For this purpose we may take the "equilibrium require- 



54 A Study 


of Nitrogen 


Mctaholis, 


in ill tin 


Dalrif Cow 


ment," judged 1 


)\ the previous 


records of the cows, 


at roundly 145 gm. 


per day. 


Surplus X 
consumed (total 






Nitrogen- 




N-145gm.) 


N in milk 


Ratio of 


balance 


Day 


(average 


(average 


surplus N 


(average 


number 


per day*) 


per day*) 


to milk N 


per day) 




gm. 


gm. 




gm. 


590-591 


135 


91 


1-5: 1 


+ 4-1 


592-594 


98 


SO 


1-2: 1 


-60-9 


595-603 


142 


li 


20: 1 


- 2-9 


608-645 


195 


.-)!) 


3-3: 1 


+ 10-8 


650-659 


195 


57 


3-4: 1 


+ 8-9 


665-680 


178 


.'")4 


3-3: 1 


+ 14-6 


685-701 


143 


55 


26: 1 


+ 2-2 


706-722 


96 

# 


49 
To nearest gm. 


20:1 


-11-3 



It is clearly evident why during days 592-594 a heavy nitrogen 
deficit w'as recorded, since the "surplus" nitrogen, even without allow- 
ance for digestibility, was barely greater than the nitrogen removed 
from the body in the milk. Even in the period, days 595-603, when the 
"surplus" nitrogen was roughly twice that secreted in the milk, equi- 
librium was barely established, and again later, in the period, daj's 
706-722, when a similar proportion prevailed, nitrogen deficit again set 
in. In the intervening jjeriods when the proportion was well over 3:1a 
substantial nitrogen-retention was effected. 

It would appear therefore that in order to prevent loss of nitrogen 
from the body of the lactating cow the "surplus" nitrogen must amount 
to well over twice the amount of nitrogen secreted in the milk. This is a 
condition which may well be difficult to satisfy in practice. Cow D was 
only a moderate milker (about 28 lb. milk daily at maximum), and yet 
it required the heavy and highly nitrogenous rations indicated to prevent 
loss of nitrogen from the body. With the more liberal milk-flow so often 
achieved with the modern dairy cow it would be even more difficult to 
secure nitrogen-equihbrium, if not indeed beyond the food-consuming 
capacity of the cow. This is fully in accord with practical experience of 
the difficulty of maintaining the "condition" of the milch cow in the 
early stages of lactation. 

The full details for Cow C (dry and not in calf) are not given for this 
period, as they present no new features of interest. The establishment 
of a po.sitive nitrogen balance is noteworthy, since on the same ration 
in the preceding period, a decided negative balance was recorded. An 
examination of the figures for the complete trial shows, however, that 
Cow C had been able to store about 1000 gm. of nitrogen from the 
81,000 gm. consumed. 



C C*ROWTHKR AND H. E. WoODMAN 



55 



Table VII. 
Condensed summary for Cow C between the days 608 and 722. 

Daily ration: 21-5 lb. seeds hay + 1 lb. linseed cake. 

Analytical Total N Total N Nett change 

days consumed retained of weight 

lb. 
+ 13f 
+ 107 



94 

546 



Total N 
consumed 

gm. 
14,039 
81,015 



gm. 
+ 472 
+ 1005 



Days from 
calving 

1 

2 
3 

4 
5 
6 

7 • 

8 

9 

10 

11 
12-14* 
15-17 
22-24 
25-28 
29-31 
32-35 
36-38 
43-45 
46-49 
50-52 



Daily 
yield 

lb. 
3-62 
8-75 
20-09 
28-87 
25-56 
27-91 
28-56 
28-93 
29-71 
29-19 
29-87 
29-56 
28-25 
26-79 
26-85 
27-36 
27-21 
27-35 
26-72 
26-75 
26-14 



Table VIII. Mtll- records of Cow D. 



N 

/o 
3-110 
2-210 
1-097 
0-807 
0-657 
0-628 
0-631 
0-596 
0-582 
0-578 
0-552 
0-525 
0-531 
0-507 
0-494 
0-472 
0-477 
0-490 
0-479 
0-498 
0-498 



N in 
milk 

gm. 
.51-07 
87-73 
KMXKI 
105-711 
76-17 
79-52 
81-74 
78-22 
78-44 
76-.52 
74-80 
70-40 
68-07 
61-63 
60-20 
58-57 
58-88 
60-80 
5813 
00-45 
59-07 



Days from 
calving 

53- 56 

57- 59 

64- 66 

67- 70 

71- 73 

79- 81 

82- 84 

85- 87 

88- 91 

92- 94 

99-101 

102-105 

106-108 

1U9-112 

113-115 

120-122 

123-126 

127-129 

130-133 

1.34-136 



Daily 
yield 

lb. 
26-34 
25-75 
24-80 
24-95 
25-77 
23-25 
22-70 
22-49 
22-27 
22-32 
21-62 
22-50 
20-92 
22-44 
21-66 
19-37 
19-50 
18-,59 
19-28 
18-. 54 



N 

% 
0-499 
0-497 
0-485 
0-511 
0-510 
0-509 
0-511 
0-534 
0-523 
0-529 
0-555 
0-547 
0-5.56 
0-545 
0-552 
0-570 
0-558 
0-569 
0-549 
0-575 



N in 
milk 

gin. 
59-58 
56-75 
54-57 
57-83 
59-63 
53-70 
52-40 
54-50 
53-87 
53-57 
54-40 
.55-85 
.52-73 
55-50 
,54-17 
.50-07 
49-35 
48-00 
48-03 
48-37 



From analysis of composite milk samples. 



SUMMARY. 

This communication deals with the results of two experiments in 
which the "nitrogen-balance," or difference betweezi nitrogen-consump- 
tion and nitrogen-excretion by the cow, has been studied over prolonged 
periods, starting with the "dry" cow, not in calf, proceeding through the 
whole period of pregnancy and well into the period of active lactation. 

Experiment 1 was performed throughout with the two cows, " dry "' 
and not in calf, receiving a basal ration of hay to which was added in- 
creasing amounts of maize meal with a view to securing a progressively 
increasing consumption of nitrogen. This experiment lasted 196 days, 
during which period determinations of the nitrogen- balance were made 
on 90 days. 

Experiment 2 was carried out similarly with two cows, and covered 
a period of 722 days, including 546 days on which determinations of the 
nitrogen-balance were made. Throughout the whole of this period one 



56 A Study of Nitrogen Metabolism i)i tlie Dalrij Cov 

cow (Cow C) was maintained "dry" and not in calf, as control cow, 
whilst the other cow (Cow D) after 302 days became pregnant and its 
record was followed throughout the stages of pregnancy and parturition 
and for the first 13C days of active lactation. 

The outstanding features of the results are as follows: 

(1) With the progressive increase of nitrogen-consumption beyond 
the fundamental requirements of the dry cow the rate of nitrogen-reten- 
tion steadily increases to a maximum and then falls. The maximum 
appears to be attained under the con<litions of our experiment with a 
protein-supply in the neighbourhood of 2-4 kg. crude protein per 1000 kg. 
live-weight. There are indications that this figure may be independent 
of the nature of the foods fed along witli hay. 

(2) When the cow is maintained ujion a ration which causes an initial 
nitrogen-retention the rate of retention falls steadily, but a very pro- 
longed period — up to 90-100 days — may be necessary before nitrogen- 
equihbrium is attained. 

(3) Even after nitrogen-equilibrium is estaliUshed and a relatively 
constant nitrogen-consumption is maintained, there may arise from time 
to time considerable deviations from equilibrium either in the positive 
or negative direction. It would appear therefore that for reliable work 
of this character long experimental periods are essential. 

(4) The very earliest stages of pregnancy are marked by a profound 
disturbance of nitrogen metabolism, the requirement for maintenance 
of nitrogen -equilibrium being very sensibly increased. This additional 
requirement persists at a steadily reduced rate for some 1.") to 20 weeks, 
after which it is very small. Over the whole jieriod of pregnancy the 
average rate of nitrogen-retention was only about 2-4 gm. per day. 

(5) During parturition and for a few days subsequently the output 
of nitrogen is very great and more than can be restored rapidly by food- 
consumption. With the experimental cow, giving barely three gallons 
of milk per day at most, some two to three weeks elapsed after calving 
before nitrogen-equilibrium was restored. 

(6) It would appear that to maintain nitrogen-equilibrium during 
lactation, the food must supply from twice to three times the amount 
of nitrogen secreted in the milk, in addition to that required for the 
maintenance of equilibrium in the "dry" state. This represents a food- 
consumption which would be difficult to attain in the case of cows giving 
large yields of milk, and accounts for the familiar difficulty of main- 
taining the "condition" of such cows in the earlier stages of lactation. 

{Received l&th November, 1921.) 



THE MENDELIAN INHERITANCE OF SUSCEPTI- 
BILITY AND RESISTANCE TO YELLOW RUST 
{PUCCINI A GLUM ARUM, ERIKSS. ET HENN.) IN 

WHEAT. 

By S. F. ARMSTRONG, B.A., F.L.S. 
(Cambridge University Plant Breeding Institute.) 



Contents. 

Section I. INTRODUCTION 

(a) Historical 

(6) Itust scale adopted 

((■) The soil 

(rf) Weather records . 

(e) The parent wheats 

Section II. THE EXPERIMENTAL RESULTS, 1917-1920 

1. The Fj plants, 1917 

2. The F^ generation, 1918 

(A) Climatic conditions in 1918 ....... 

(B) Spread of rust during 1918 

(C) Results obtained: in the F, generation ...... 

3. The F^ cultures, 1919 

(A) Climatic conditions, manuring, and growth of the cultures in 1919 . 

(B) Spread of rust during 1919 ....... 

(C) Results obtained from the F^ cultures ...... 

4. Summary of the F^ results 

5. Application of the F^ results to the F^ statistics . 

6. Results obtained from F2, F^, F^ cultures, etc., in 1920 . 

Section III. SOME OP THE FACTORS WHICH MAY INCREASE OR 
DIMINISH SUSCEPTIBILITY TO RUST ATTACK 
Introduction 

(a) Effect of climatic conditions 

(b) Food supply 

(f ) New combinations of parental characters .... 

(d) Variation of susceptibility in hybrid wheats 

(e) Possible effect of environment upon the fungus . 

CONCLUSIONS 

APPENDIX 

LIST OF PAPERS REFERRED TO IN THE TEXT .... 



58 
61 
01 
01 
63 



03 
64 
64 
64 
65 
07 
07 
08 
69 
75 
76 
78 



81 

82 
82 
89 
90 
91 

92 
94 
96 



58 Mendelian Inheritance and Yelloiv Rust In Wheat 



Section I. INTRODrCTIOX. 

The present paper may, at first sifjht, a])pear to contain nuicli that is 
irrelevant to tlie subject as indicated in the title. But, whilst the primary 
object throughout was to trace the inheritance of susceptibility and 
resistance to rust attack, experience shows that a study of the environ- 
mental conditions is also essential for a correct understanding of this 
problem. 

The unusual weather, and other circumstances in 1919, led to such 
an abnormal growth of the wheat cultures, that it was felt necessary to 
present all the available evidence which would throw any hght upon 
the condition of the host plants, the spread of rust, and the greater 
severity of its attack in that year. For these reasons, details which are 
usually ignored in the treatment of a subject from the genetic point of 
view, e.g. such as refer to soil, manuring, and weather, have been in- 
cluded. 

(a) Historical. 

A large number of investigations have been carried out bearing on 
the question of the susceptibihty and resistance of plants to rust attack, 
and the more common cereal rusts es])ecially have received much atten- 
tion. A great deal of this work has been concerned with the histology of 
the rusts, in which the phenomena of inoculation and infection have 
been studied under various conditions, and attempts made to discover 
the primary causes of immunity and susceptibility. Our knowledge of 
this branch of the subject is based largely upon the investigations of 
Ward (15-20), Pole Evans(5), Miss Gibson(7), Miss Marryat(iO), and Eriks- 
son (4). 

The suggestion that immunity depended upon certain slight ana- 
tomical differences, e.g. thicker cell walls, fewer or smaller stomata, more 
or longer hairs, etc., was proved to be incorrect by the researches of 
Marshall Ward(i9) on the Brown Rust [Puccinia dispersa) in the genus 
Bromus. Ward showed that the curves of infectibihty and those indi- 
cating the various anatomical differences, not only failed to correspond, 
but showed no relation whatever. This led to the conclusion tliat im- 
munity and susceptibility are not directly determined by the anatomy 
of the host plant, but depend u])on physiological reactions between the 
protoplasm of the parasite and the cells of the host. 

From the experimental evidence obtained, Ward concluded that 
"infection and resistance to infection depend on the power of the fungus 



S. F. Armstrong 59 

protoplasm to overcome the resistance of the cells of the host by means 
of enzymes or toxins, and reciprocally, on that of the protoplasm of the 
cells of the host to form an ti- bodies which destroy such enzymes or 
toxins "(19). In another place Ward (18) was careful to point out that, 
" The failure to find any structural or mechanical explanation of the 
phenomenon (in the sense here imphed) does not necessarily involve the 
assumption that there is no mechanism in the hving plant which is 
answerable for the obstruction, or aid, to infection exhibited by the 
species. It only points to the conclusion that the mechanism is of that 
more refined and subtle nature which determines such fundamental 
properties as specific relationship, variation, heredity, and other bio- 
logical phenomena." 

These quotations from Ward's papers have been made because, in 
the first place, they represent the final con-elusions of an investigator 
whose work in this direction has never been surpassed; and further, if 
these conclusions are correct it is reasonable to expect that such features 
as immunity, etc., should be subject to the general laws of heredity. 

Ward (20, p. 37) also inoculated the fohage of Rivet wheat — which is 
only shghtly susceptible to Yellow Rust — with the uredospores of that 
fungus; at the same time he inoculated a very susceptible variety (Red 
King), and hybrid plants obtained from a cross between these varieties. 
Microscopical examination of serial sections showed that inoculation 
and infection very readily occurred in the very susceptible parent and 
the hybrids. In the case of the resistant variety (Rivet) it was found 
that the uredospores germinated, and sent their germ tubes into the 
stomata as frequently, or nearly so, as they did into the more susceptible 
wheats. Up to the fourth or fifth day after entry the course of events 
was also similar, but invariably after this period a process of complete 
degeneration was observed in the hyphae, and the parasite failed to 
establish itself. The host cells in the immediate neighbourhood of such 
hyphae were generally collapsed and their contents disintegrated. From 
a comparison with experimentally starved hyphae, Ward concluded that 
the hyphae in this resistant wheat were undergoing death-changes either 
as the result of starvation or poisoning. 

These observations have been confirmed and extended by other 
workers. Miss Gibson (7) showed that the mere inoculation of the wrong 
host plants by the uredospores is quite a common occurrence among the 
Uredineae. She found that in such cases the germ tube enters the stoma 
as in a normal infection, but that after a period of about four days or 
less the resulting hypha becomes exhausted and dies. Her work emphasized 



60 Mendelian Inheritance and YeUoio Rnst in Wheat 

the imfortunce of distinguishuig between mere inoculation and infection 
proper, and showed that it is the power of the hyphae to form haustoria 
which must be taken as the real index of the infective capacity of the 
rusts. Later, Miss Marryat(iO) carried out a very useful comparative 
histological examination of the foliage of certain immune and susceptible 
wheats which had been inoculated with Yellow E,ust. Her results fully 
confirmed Ward's previous work, and also clearly proved that different 
degrees of imnniiiity exist, as is indicated by the relative length of the 
struggle which goes on between the fungus and the host cells before 
the former is defeated. 

Extensive breeding experiments in recent years have taught us that 
characters like rust resistance, which are the outcome of complex physio- 
logical processes, are nevertheless subject to the laws of Mendehan 
inheritance. Colour in plants and baking "strengtli" in wheat are 
examples of this. With reference to colour, Miss Wheldale(2i) says: 
"There is little doubt that the formation of anthocyanin does involve 
a series of progressive reactions each of which is controlled by a certain 
enzyme." Also Keeble and Armstrong(9) present what they beheve to 
be convincing evidence in favour of the hypothesis "that pigmentation 
is the outcome of the action of oxydase on chromogen." Yet, in spite 
of the complexity of the reactions involved, tlie appearance of definite 
colours has been shown by numerous experiments to obey the Jlendelian 
laws. 

The foundations of our knowledge concerning the inheritance of rust 
resistance were laid some years ago by Biffen(i, 2 and 3) in England, and 
Nilsson-Ehle{ii) in Sweden. Biffen's experiments showed that resistance 
to Yellow Rust was inherited as a sim])lo Mendelian recessive character. 
Thus, in a cross between a susceptible and an immune variety, the 
hybrids were all as badly rusted as the susceptible parent. In the F^ 
generation one-quarter of the plants were highly resistant or immune, 
while the remainder were rusted to various extents. Unfortunately, in 
the F^ generation many of BifTen's cultures suffered from various causes, 
and the mortahty was so high as to render the results inconclusive in 
certain respects. It was clear that rust-free F, plants produced only 
rust-free individuals in the next generation, and also that some of the 
susceptible F2S gave rise to susceptible plants only. But there still 
remained considerable doubt as to the behaviour of the progeny of the 
su.sceptible F2 plants taken as a whole. The primary object of the work 
here described was to clear up the points of uncertainty just referred to. 
It was decided to go over the whole ground from the beginning, and, 



8. P. Armstrong (51 

if possible, to carry the experiments out on a larger scale, and over a 
longer period than had previously been done. 

(6) Rust scale adopted. 

In recording the severity of rust attack, an arbitrary scale was 
employed similar to that used by Eriksson (4) and Biffen(2). In the 
present case the relative extent of attack was indicated as follows: 
= a rust-free plant; l=a slight attack; 2 = a moderate attack; 
3 = a bad attack ; and 4 = a very severe attack. When examining the 
F^ crop, it became apparent that a considerable proportion of the plants, 
though not completely rust-free, showed only the merest traces of 
attack. It was thought advisable to distinguish these from the dis- 
tinctly rusted individuals grouped under grade 1, and they were therefore 
given a special mark (Ix). 

Such a scale, of course, can only indicate the relative extent of rust 
attack in a given season. In an exceptionally bad rust year (e.g. liHO), 
plants placed in grade 3 may be as severely attacked as those which 
are placed in grade 4 in another season; and similar seasonal fluctuations 
may occur among the other grades. But, although the method is not 
perfect, it appears to be the only practical one that can be used under 
field conditions where thousands of plants have to be examined in a 
comparatively short time. Further, this scale has been found sufficiently 
reUable for the purpose in view, and it has therefore been adhered to 
throughout the whole of these investigations. 

(c) The soil. / 

The soil in the cages (on which all the cultures were grown up to 
the end of 1919) may be described as a medium gravelly loam. A sample 
of the top soil to a depth of seven inches was taken in September 1919, 
and the analysis showed that it contained an ample supply of plant 
food materials in an available form. 

Apart from a light top-dressing of superphosphate apphed in the 
spring of 1917, it had received no manure since 1910. Since the last- 
mentioned year it had been hand-dug, and always carried a cereal crop. 

(d) Weather records. 

Records of the weather are given in Table I. These were taken at 
the University Botanic Garden about a mile and a half distant. In 
addition, daily notes were taken of the weather conditions at the Uni- 
versity Farm. 



62 Mendelian Inheritance and Yelloiv Rust in Wheat 



Table J. Rainfiill, Sunshine, and Mean Temperature at Cambridge from 
January to July for the yearn 1917 to Ut20. 





Total rain 


Average daily: 




Sunshine 


Mean 


temperature 


Year and moiitlis 


inches 


hours 


Centigrade degrees 


1917 










January to March 


3-83 


108 




1-9 


April 


1-52 


4-27 




5-2 


May 


1-30 


7-39 




140 


June 


1-95 


7-20 




16-6 


July 


446 


7-39 




165 


Total 


1312 




1918 










January to March 


3B5 


2-89 




5-2 


April 


3-26 


300 




6-6 


May 


216 


6-84 




130 


Juno 


1-20 


710 




13-2 


July 


2-56 


6-39 




16-2 


Total 


12-83 




1919 










January to March 


2-88 


1-81 




2-5 


April ' 


2-57 


3-77 




6-7 


May 


0-23 


8-35 




12-9 


June 


1-41 


7-73 




14-2 


July 


308 


3o5 




13-9 


Total 


10-17 




1920 










January to March 


3-9(i 


310 




61 


April 


3-44 


2-90 




91 


May 


l-4(i 


7-84 




12-7 


June 


1-24 


7-73 




14-9 


July 


2-91 


5-29 




14-5 


Total 


1301 





Instead of looking merely at the monthly totals or averages, it appears 
better to consider separately the more or less distinct "weather periods" 
into which each season was naturally divided. This enables one to 
appreciate better the effect of the weather upon the growth of the host 
plants, and also its efiect upon the general prevalence and spread of 
rust. The weather is thus briefly described under each season in 
Section II. 



8. F. Armstrong 63 

(e) The parent wheats. 

The varieties of wheat chosen for the main experiment were Wil- 
hehnina and American Chib. It is of interest to note that these varieties 
differ in several important respects, e.g. : 

W ilhdmina American Cliih 

Beardless ear Bearded ear 

Medium-lax ear Dense ear 

White chaff Red chaff 

Medium-short straw Long straw 

Starchy grain Fhnty grain. 

Under equal conditions American Club also matures earUer than Wil- 
helmina. The main point in this connection, however, is that under 
normal conditions American Club is immune to Yellow Rust, whilst 
the other variety is moderately susceptible. 

Both varieties are susceiDtible to the Brown Rust (P. iriticina, Erikss.), 
but, fortunately, this species did not interfere with the observations on 
Yellow Rust. Brown Rust does not usually make its appearance in the 
uredo stage in the Cambridge district before the middle of June. Again, 
so long as the host remains green there is no difficulty in distinguishing 
the one rust from the other. Occasionally, when the fohage of a plant is 
beginning to shrivel up, some doubt may occur; but such cases are rare. 

In June 1916, the cross (No. 120) Wilhelmina ? American Club ^ was 
made. About 20 grains were obtained, and these were planted in the 
breeding cage on September 30th. 

Section II. THP] EXPERIMENTAL RESULTS. 1917—1020. 

(1) The F-^ plants, 1917. 

The F^ plants had ample space and grew vigorously during 1917, 
a season that was remarkable for the comparative mildness of the rust 
attack in the Cambridge district. 

Hot weather was general from May until the end of July, and the 
rainfall was moderate except during July, which was a very wet month 
(see Table I). The F-^ plants had a moderate attack of Yellow Rust, and 
were harvested about the middle of August. 

A portion of the grain from these plants was sown on November 9th 
in rows numbered 1 to 42. In the following year on February 26th a 
further sowing was made in rows numbered 43 to 82. The object in 
making two sowings was partly to lengthen the period during which 



64 3Iendelian Inheritance and YeUoiv Rust in Wheat 

observations could be made in 1918, and partly to see whether any 

difference in respect of the severity of attack would occur on the more 
advanced and less advanced plants respectively. A portion of the prain 
from the F^ plants was saved for sowinj; in successive seasons, and in 
this way 7^, generations from the same hybrids were raised in HUB, 
1919 and 1920. 

(2) TlIK 7'^ CENKRATION, 1918. 

(A) Climalic conditionn in 1918. 

Monthly records of the rainfall, etc., during the growing season are 
given in Table I. The following brief description is taken from daily 
observations, and will serve to indicate the general character of the 
season. 

The month of April was very wet, with a high average percentage 
of atmospheric humidity, and less than the normal amount of sunshine. 
During May the weather was normal, and the wheats made steady 
progress. May 3rd to 22nd was a warm period during which some heavy 
showers fell; this period ended with a thunderstorm and heavy rain 
on the 23rd. This was foIlf)\ved by a fine warm period which lasted until 
June 17th. By this date the plants were beginning to need rain, but they 
had not been checked in any way. 

From June 18th to 2r)th the weather was for tlie most part cool and 
wet. Warm weather followed from June 26th to July 8th, and then came 
a period of dull, mild, wet weather which lasted until .Inly 28th. 
July 29th to August Kith was a tine, warm period. 

It will be seen that tlie season was divided into several comparatively 
short alternating periods of fine and wet weather. This led to a steady 
and normal growth of the plants and they were harvested in good con- 
dition during the last-mentioned period. 

(B) Spread of rust during 1918. 

Pustules of Yellow Rust were first seen on April 8th, and by May 18th 
its spread had become general: but the intensity of its attack was still 
of a slight nature. It continued to spread very gradually until the end 
of May, but so slow was its progress that at this date it was feared the 
season might prove unsuitable for reliable statistics to be taken of the 
F^ crop. Towards the end of May, however, it began to spread very 
rapidly, and by June 21st this rust was very prevalent throughout the 
cages. By the last-mentioned date th<! foliage of the more susceptible 
plants was clothed with pustules. 



S. p. Armstrono 65 

The followiiifi records illustrate the progress of tlie rust attack during 
1918: 

The autumn sown poi'tion of the F., crop contained 829 plants, of 
which 627 were finally I'usted. Of these "finally rusted" individuals, 
54 per cent, were attacked by June 10th to 13th; 90 pei' cent, by June 
29th; and 100 per cent, by July 30th. 

The progress of the rust attack in 1918 is further illustrated by the 
notes on the two varieties given below. 

Willtelmiiin. (01 plants). 

iVIay 18th, a little rust seen. 

June 1st, 23 per cent, of the plants slightly rusted. 
June 8th, 81 per cent, of the plants rusted. 
June 21st, 100 per cent, of the plants rusted. 

Extra Squarehead II (29 plants). 

April 8th. one pustule on the culture. 

May 18th, a few jjlants shghtly rusted. 

June 1st, 34 per cent, of the plants slightly rusted. 

June 8th, 65 per cent, rusted. 

June 21st, 100 ^Jer cent, rusted. 

These observations show that Yellow Rust spread most rapidly in 
1918 during the last week in May and the first three weeks in June. 

(C) Results obtained in the F^ f/eneralio)) (1918). 

From the middle of March onwards all the F^ plants and the parent 
cultures were kept under observation. By June 8th over 80 per cent, of 
the plants in an adjacent plot of Wilhelmina wheat were rusted, and it 
was therefore decided to start at once a .systematic examination of the 
^2 plants. 

The method of recording results was as follows: 

Each plant received a number to indicate the number of the i-ow and 
also its position in the row: e.g. 40/10 referred to the tenth plant in 
the fortieth row, and so on. This made all subsequent references easy. 
Each plant was then carefully examined leaf by leaf, and the presence 
or absence of rust attack entered in a note-book according to the 
previously mentioned scale. 

The autumn sown plants were examined in this way at three different 
periods, viz. First, from June 10th to 13th; agaiti from June 29th to 
July 3rd; and lastly, from Jidy 30th to August 3rd. 

Journ. of Agric. Soi. xii 5 



66 Mendelian Tnheritonce and Yellotv Rust in Wheat 

Rows 43 to 82 (sown February 1918) were examined at two different 
periods, viz. June 15tli to ITth, and again July I6tli to 29tli. 

By the end of July the plants were beginning to mature, and, after 
making the final examination of the autumn-sown crop, it was found that 
the spring-sown portion was too far advanced for another examination 
to be made. In each case the final examination was made only a few 
days previous to the ripening of the plants. 

Tabiu 1 1. Rcmillx from, fjradiiu/ the Fn plants ( l'.)18) ucroyiling to t/ir erlent 
of the rtiKl. attack. (Cross No. 120.) 



Date of 
sowin}; 


Total 
No. of 
]ilant.s 




Extent of the rust attack 




Xone 


Traee Slight .Moderate Jiail 


\'erv severe 


Autumn : 

Nov. !Uli. 11117 


829 


202 


fi!) 210 102 117 


119 


■Spring: 

Feb. 2()th, 1918 


731 


145 


98 181 132 89 


80 



Totals l.'>()0 347 107 391 294 200 155 

The final condition of the F.^ generation is shown by Tal)]!' II. Of 
829 plants in the autumn-sown portion, 202 remained rust-free through- 
out the season, while the remaining (i27 plants showed evidence of more 
or less susceptibility. This is a close approximation to the 3 : 1 Mendelian 
ratio. 

In the spring-sown portion, it will be obsen^ed, the proportion of 
completely rust-free individuals was considerably less tiian one-fourth 
of the total number, but, on the other hand, the proportion of plants 
bearing only traces of rust was much higher than in the autumn-sown 
crop. 

The whole F^ generation contained 1213 rusted and 347 rust-free in- 
dividuals. If the badly rusted plants (giades 3 and 4) be separated from 
those that wei(( lijss severely attacked, we obtain the following totals: 

Attack, bad to very severe 361 plants 
Attack, moderate or less 852 plants 
Entirely free from rust 347 plants 

While these figures do not show a very rlose approximation to the 
simple Mendelian ratio, they are certaiidy very suggestive of it. Fuither 
consideration of these figures is deferred until the later results have been 
given. 



S. F. Armstrong 67 

(3) The F, cultures. 1919. 

Since it was impossible to deal with sufficiently large F^ cultures 
raised from all the Fn plants, a number of the latter were chosen so as to 
include individuals showing every grade of attack, as well as a number 
of those that had remained rust-free. Altogether 198 F.^ plants were 
taken, and the grain sown in tiie autumn of 1918. 

(A) Climatic rondi/io)}f:, nidiuiring, avd qrnuih nf Ihr niltiirex in 1919. 

Monthly records of the weather are given in Table T. The season 
proved a most trying one for the plants, there being three prolonged 
periods of extreme chmatic conditions. 

The fir.st of these was from January IStJi to February 13th, during 
which the ground was frozen and snow-covered. So unfavourable was 
the spring weather that as late as the beginning of May the cultures 
were still in a very backward condition. Before they had sufficient time 
to recover they were faced by a period of drought which lasted from 
May 13th until June 19th. Throughout this period of 38 days the average 
daily sunshine was 10-1 hours, but the total rainfall only 6-2 mm. Indeed 
the total fall of rain from May 1st until June 19th amounted to onlv 
8-9 mm., i.e. 0-35 inch during .50 days. 

On May 27th a top-dressing of nitrate of soda was apphed to all the 
cultures, at the rate of 4 cwt. per acre. It was hoped that this heavy 
apphcation would counteract the drought effects to some extent as soon 
as rain fell. However, rain did not fall in sufficient cjuantitv to carrv tlie 
nitrate into the soil until 23 days later. By June i7th it appeared prob- 
able that most of the cultures would be ruined, as many of the plants 
were in a critical condition and the basal foHage was dying off. Three 
days later (June 20th) a heavy fall of rain carried the nitrate to the roots. 
The change was sudden and most marked, for by June 23rd most of the 
plants showed a notable recovery, and soon afterwards they began to 
send up numerous side tillers. 

The period of drought referred to was immediately followed by a 
lengthy period of the very oppo.site conditions. From June 20th until 
the end of July the weather was cool, dull, and moist. During this time 
(42 days) 4-4 inches of rain fell, but the average daily sunshine was only 
3-6 hours. One of the general effects of this weather — combined with the 
action of the nitrate — was to delay greatly the ripening of the plants. 



68 Mendellaii Inheritance and Yellov Rust in Win ni 

(15) Spread of ru.sl during 1!U9. 

Yellow Rust W.1S observed for the first time on May 8tli, a luontli 
later than in tlie previous year. During May, and up to about the 20th 
of June, its s])rea(l was very slow, except in the case of very susceptible 
varieties and cultures. This difference in regard to the "|ieriod of in- 
fection" was very remarkable. For example, a variety of wheat which 
may be referred to as "B"" was grown alongside tlie f\ cultures, and 
proved to be extremely susceptible to Yellow Rust. Se\'eral of the 
plants were rusted by May 16th, i.e. fairly early in the period of drought. 
By May 24th almost every plant bore numerous pustules, and on the 
31st of May, out of 136 plants in the plot, 135 were excessively rusted. 
A large plot of another variety (Sudanese wheat) was grown in tlie 
neighbourhood, and this was also attacked very early by Yellow Rust. 
This attack was so severe that, by the middle of .Tune, all the plants were 
prematurely destroyed, and no grain was formed. 

These cases are here referi'ed to because the attacks developed with 
great intensity durivg n period of drought, and afforded a striking contrast 
to the scarcely perceptible attacks made at the same time on moderately 
susceptible varieties. They demonstrate that the more susceptible varieties 
are liable to an earlier successful attack than less susceptible kinds; and 
also that, on very susceptible wheats at least, Yellow Hu.st is quite 
capable of making rapid progress in the tissues of tlie liost during the 
hottest weather we are likely to experience in this country. 

Similar differences as regai-ds the period of infection were observed 
among the Fg cultures. By June 14th rust was spreading rapidly on all 
those cultures which finally proved to be pure susceptibles; on the others, 
there was either no rust at all, or its progress was very slow (see Table XI). 

In order that all the plants might be exposed to an equal chance of 
infection, on the evening of June 13th all the cultures were sprayed with 
water teeming with fresh uredospores of Yellow Rust obtained from 
a neighbouring crop. This procedure was {>robal)ly quite unnecessary, 
since the pure susceptible cultures (already containing many attacked 
plants) were well scattered over the entire experimental area. Almo.st 
immediately after the fall of rain on June 2()th, a distinct increase in 
the rate of rust-spread was noticed, and during the cool, moist weather 
which prevailed in July tiie attack developed into an epidemic of llie 
greatest severitv the writei' has ever seen. 



8. F. Armstron« 6i> 

((J) Re.'iidls obtained from (he t\ cidtures (191'J). 

(a) General. Tlie spring drought proved a very severe test, for all 
the cultures, and some ol them, which were on rather poorer ground, 
had to be abandoned. Ample material was provided by the remaining 
170 cultures which contained some 8500 plants. These cultures were 
examined in regular order, and the first appearance of rust on each noted. 
Immediately an attack was observ^ed, all the plants were numbered, and 
the rusted ones indicated in a book. The cultures were repeatedly ex- 
amined, from the first week in May until the end of .luly or later, to 
see to what extent the attack had spread. At. the last examination the 
intensity of attack on each plant was noted as in 1918. 

The conditions under which the plants were grown proved so favour- 
able to rust attack tliat. almost without exception, the cultui'es were 
more severely rusted than their F^ parents Jiad been in the jjrevious year. 
This is indicated to some extent by the results given in Tables III to VII. 
Cultures raised from badly rusted F., plants were still more severely 
attacked in 1919. It wiU be seen also that, in the 69 cultures which gave 
evidence of segregation, very few plants actually remained rust-free. 

Table III. Results of analt/sis of the F^ cultures (1919) 
grown f 7-0 in rust-free F.2 plants. 

Extent of the rust attack at final e.vaniination 
Plants (28th July to 11th August) 



Culture 

No. 


in 
culture 


None 


Trace 


flight 


M oderate 


Bad 


Very severe 


66/9 


49 


49 





— 


— 


— 


— 


11/21 


28 


28 


— 


— 


— 


— 


— 


2/10 


45 


44 


1 


— 


— 


— 


— 


19/12 


46 


41) 


6 


— 


— 


— 


— 


2/18 
82/14 

8/17 
68/19 
29/1.5 


41 
25 

60 
42 
43 


27 
1 
25 
13 
111 


(1 
14 
(1 
(i 
II 


12 
10 
20 
18 
11 


.1 

15 

4 

14 


1 


— 


57 /S 


62 


1) 


11 


41 


10 


— 


— 


Totals 


441 


243 


38 


112 


45 


3 


— 


26/22 

28/24 

3/1 

15/5 


7 
42 
51 
34 





7 



1 
7 
II 

1 


4 
■*."> 
19 
18 


o 

8 

25 

8 


2 

7 


— 


24/3 


19 


1 


I.I 


4 


11 


3 


— 


25/9 


29 











11 


111 


o 


22/27 


30 


— 


— 


— 


11 


14 


,5 



{b) Cultures raised from rust-free F^ plants. Seventeen of these cultures 
were grown, but in only two of theni did every plant remain absolutely 
free from attack. Of these seventeen cultures, the first ten in Table III 



70 Meiideliaii Inheritance and Yellow Rust in Wheat 

suffered least from drought, and their growth was almost normal; if wc 
limit our attention for the moment to these we note the following facts: 
(1) they all remained perfectly free from rust up to about July 8th 
(see Table XI); (2) cultures 66/9 and 11/21 were entirely rust-free until 
maturity; and (3) the other eight cultures each contained some plants 
that were attacked to various extents. In most cases these attacks were 
of a shght character only, though three plants out of a total of 364 had 
actually bad attacks. Careful observation showed that the parasite did 
not thrive on the plants in tliese cultures, except in the rare cases just 
noted. The pustules, though often numerous, were abnormally small, 
and a large proportion of them failed to burst the epidermis, or only 
did so as the foliage was beginning to shrivel up. Owing to the difficulty 
in making due allowance tor tiie milder nature of the attack, as distinct 
from the relative number of pustules borne, it is probable that the sus- 
ceptibihty of some of these plants has been overstated by the grades 
accorded to them. Moreover, a comparison of these cultures with the 
homozygous susceptible ones growing alongside showed that the rekUive 
difference in the extent of rust attack was as great as had existed between 
their respective F., parents in the previous season. 

Cultures 26/22, 28/24, 3/1, 15/5, and 24/3 are grouped by themselves 
in Table III because they were much affected by drought, and their 
growth was far from normal. Although linally rusted to a greater extent 
than the first ten cultures, hke them they remained uninfected till as 
late as July 8th, and the evidence strongly suggests that they were also 
derived from "genetically immune" F.,'s. 

It was obvious that the extent to which the power of resistance was 
disturbed varied largely from culture to culture, and also among plants 
in the same culture. Further, the greatest "disturbance" occurred in 
those cultures that were most affected by drought, and possibly this 
may also partly explain why the attack varied so widely on ilift'erent 
individuals. Although it is impossible to state the exact extent of this 
■' disturbance, '" from the evidence obtained it seems safe to conclude 
that it was sufficient to allow "genetically iniinuiie" plants to become 
either slightly or in some cases moderately attacked. This must be borne 
in mind when considering the remaining Fj results. 

Biffen(3, p. 123) found in his experiments that the immune F., jilants 
bred true to that character; and in the present case, when all the experi- 
mental evidence was taken into consideration, the only conclusion one 
could arrive at was that these fifteen cultures were "immune" in the 
genetic sense, although in uiauy instances the plant's power to resist 



8. F. Ahmstkong 71 

attack had been nioditied or partially broken down. This greater or le.s.s 
degree of predisposition to attack was probably due to the interaction 
of other causes or "factors '" such as are discussed later under section III. 

The last two cultures in Table III (25/9 and 22/27) were attacked 
considerably beyond the average, thougli not nearly so severely as the 
pure susceptible cultures were. They were probably the progeny of 
heterozygous susceptible plants that escaped infection in 1918. 

(c) Twelve cultures (Table IV) were raised from F.^^ plants which 
showed only traces of attack. Three of these proved highly resistant 
and compared closely in this respect with the iirst fifteen cultures given 
in Table III. One of these (82/9) was further tested on a large scale; 
forty-seven F^ cultures were grown containing some 850 plants, all of 
which proved highly resistant in 1920. It is therefore reasonable to 
conclude that the two cultures, 31/23 and 70/13, were also the offspring 
of homozygous "immune" plants, although these plants showed traces 
of attack in 1918. 

Table IV. Results of amdysis of F-^ riiUares (1919) grown from F^ plants 
whicJi had onlij traces of rust attack in the previous season. 

Extent of the nist attaek at final examination 
Plants (28th July to 11th August) 



Culture in 
No. cultuie 


None 


Trace 


.Slight 


A 

Moderate 


Bad 


Very severe 


12/20 48 


— 


— 


1 


9 


17 


21 


14/18 54 


— 


— 


4 


29 


14 


7 


9/0 53 


— 


— 


6 


32 


9 


6 


16/15 67 


— 


— 


•> 


51 


12 


■t 


10/10 2B 


— 


— 


3 


14 


9 


— 


72/7 53 


1 


— 


21 


21 


9 


1 


32/1 40 


9 


(1 


11 


14 


5 


1 


66/1 63 


20 


.s 


13 


14 


7 


1 


41/17 (44) 
























Totals: 404 


30 


8 


61 


184 


82 


39 


[8 cultures] 


^ 






^ 




1 




99 






305 




31/23 48 


4 


— 


24 


20 








70/13 44 


2 


7 


30 


5 


— 





82/9 61 


— 


10 


49 


2 


^ 






The other nine cultures gave evidence of segregation into shghtly, 
moderately, and badly rusted types, and were clearly the offspring of 
heterozygotes for rust resistance. In eight of these the plants were fully 
graded and included 99 individuals with a shght attack, or none, and 
305 with a moderate or bad attack. 

(d) Of the cultures raised from only shghtly rusted -^2'^' ^^ gave 
distinct evidence of segregation (Table V). Twenty-two of these plants 



I'l Mendd'uiH I nlierltancc and Ycllutn Ruxf In Wheat 

were graded at the final examination, and these contained "291 individuals 
with only a slight attack or none, and 893 on which the attack was either 
moderate, bad, or very severe. These numbers are very close to the 
3 : 1 Mendelian ratio. Of the other cultures in this group, seven showed 
much less evidence of segregation, but, as the majority of the plants in 
each case were much less severely attacked than those of the homozygous 
susceptible cultures growing alongside, it is probable that these were 
the offspring of heterozygotes. 

Two other cultures, 1/3 and 38/22, proved to be as resistant as the 
first 15 given in Table 111. 



Table ^ . Analyaii: of F-j cullitres (191'.)) (jivwujrom F<, plants which had 
a slight attack of rust in 1918. 

Extent of the rust attack at filial cxamiiiation 
Plants (28th July to 1 1th August) 

OiJture in * , 

No. culture None Trace Slight Moderate Bad Very severe 

2/8 52 12 — 9 20 8 3 

7/15 48 II — 9 5 12 1 

9/3 7(t 15 — 22 28 4 1 

11/3 51 11 — 7 26 5 2 

07/10 54 12 — 6 10 11 15 

67/11 73 n 3 12 24 8 15 

13/13 lit 21 9 9 8 2 

39/7 87 — — 15 48 14 10 

41/16 48 — — 8 28 6 6 

52/13 48 — — 8 24 10 fi 

52/23 67 _ _ 13 31 17 6 

56/14 65 — — 20 21 l> IS 

72/2 44 — — 5 13 7 19 

72/12 50 — — 3 15 12 20 

9/18 29 — — 7 12 9 1 

10/9 49 _ _ 5 23 15 6 

17/13 66 — — 20 42 4 

17/24 62 — — 10 43 7 2 

22/1 48 — — 2 30 16 

23/17 50 — — 3 21 25 1 

24/15 31 — — 1 10 IS 2 

8/5 43 — — 1 2S 10 4 

30/11 (63) 

32/16 (34) 

33/23 (44) 

38/6 (32) 

Totals: 1184 93 3 195 511 238 144 

[22 cultures] ' ^^ — — ' "^ v ' 

291 893 

(e) Si.xty-threc cultures were raised from F^ plants which had been 
moderately attacked. Fourteen of these proved to be homozygous 
susceptibles, for every plant in these I 1 cultures (791 plants in all) was 
either badly or very severely iiisted. 



S. F. AUMSTRONG 73 

Thirty-one cultures gave clear evidence of .segregation, thougli only 
nine of these actually contained any rust-free plants at maturity. 
Details of rust attack on each plant in '2i of these cultures are given in 
Table VI. It will be noted that the extent of "'disturbance of resistance" 
varied considerably fi'oni culture to culture. In the first four given in 
this table, it was practically non-existent; in the next four it was ap2)reci- 
able, while in most of the others it was very great. Nevertheless, the 
very wide difference between the nature of the attack in the extreme 
grades, and the proportion of cases of intermediate attack, indicated 
that JVIeudehan segregation had occurred in all these cultures. 

Table VI. Results of analysis of the F.^ ciiliures (1919) raised from F., 
plants which had a moderate rust attack in 1918. //; this tabic are 
grouped 24 cultures which gave clear evidence <f segregation. 

Extent of the rust attack at final examination 





Plants 




(28th July 


to 11th August) 




( Iiiitriiro 


in 














No. 


culture 


None 


Trace 


Slight 


Moderate 


Bad 


Very severe 


08/ lU 


05 


15 


o 


I 


10 


12 


25 


1/15 


42 


U 


— 


25 


5 


1 





14/6 


32 


8 


— 


1 


18 


4 


1 


67/9 


57 


10 


1 


5 


6 


9 


20 


55/2 


119 


5 


— 


17 


53 


19 


25 


68/5 


39 


4 


— 


2 





11 


16 


71/14 


52 


1 


1 


26 


14 


7 


3 


4/1 


112 


1 


— 


23 


03 


18 


7 


57/2 


04 


— 


— 


3 


16 


43 


o 


2/9 


42 


— 


. — 


3 


27 


8 


4 


8/13 


40 


— 


— 


•> 


20 


9 


3 


8/15 


71 


— 


— ■ 


13 


40 


1.-. 


3 


11/10 


34 


— 


— 


1 


18 


10 


5 


12/3 


52 


— 


— 


2 


23 


20 


7 


18/2 


48 


— 


— 


3 


34 


s 


3 


18/4 


55 


— 


— 


1 


17 


33 


4 


28/13 


40 


— 


— 


8 


9 


15 


8 


40/5 


40 


— 


— 


4 


24 


14 


4 


40/17 


44 


— 


— 


16 


25 


2 


1 


54/4 


78 


— 


— 


5 


55 


10 


o 


24/18 


39 


— 


— . 


2 


2 


15 


20 


73/8 


76 


— 


— 


4 


23 


20 


29 


77/10 


57 


— 


— 


15 


14 


10 


12 


78/2 


55 


— 


— 


9 


21 


13 


12 


Totals: 


1359 


55 


4 


191 


549 


338 


222 



250 1109 

(339-7) (1019-3) 

In addition to tlie above, seven otlier cultures gave clear evidence of segregation, but 
full records of rust on each plant were not made. 

Most of the remaining 18 cultures had suffered very severely from 
drought. In these segregation was much less evident, the attack varying 
from a moderate to a veiy severe one. They were, however, distinctly 



74 MendeliiiH Inkerilance and I'lilui'' Hnxt In Whral 

intermediate between the homozygous susceptible and "imuiune" 
cultures in regard to their rusted condition, and, taking their abnormal 
growth into consideration, one is probably correct in concluding that 
they were the offspring of F., heterozygotes. 

(/) Nineteen cultures were grown from i\ phmts which had been 
badly rusted in 1918. Fifteen of these proved to be homozygous sus- 
ceptibles, every plant being either badly or very severely attacked. One 
culture (14/2) was seriously affected by di'ought, but was 2)robabiy also 
of the same genetic constitution for susceptibility. The three other 
cultures, 74/12, 6/4, and 31/1, gave clear evidence of segregation. 

{(j) The 24 cultures raised from very badly rusted i\ plants all 
proved to be homozygous snsceptibles. In each of these all the plants 
were distinctly worse attacked than their parents had been in the pre- 
vious season (Tabic VII). 

Table VJl. Results from 21 7'^^ vultures (1919) raised from F^ plaids 
wkicJi were very badly rusted in 1918. Every plant in this grouj) of 
cultures was very severely rusted in 1919. 

Percentage of plants rusted 



C'ultino 


Plants 
in 


Kust HrsL 


.May 


June 


July 


July 28tli 


No. 


culture 


seen 


16tli to 3Ist 


14th to ISth 


4tli to 10th 


to Aug. 9th 


9/li) 


33 


May 28 


6 


33 


91 


UMI 


14/21 


34 


„ 16 


6 


82 


100 


100 


27/21 


54 


,. 17 


4 


88 


100 


101) 


28/ U 


33 


„ 17 


3 


81 


100 


lOO 


29/(i 


21 


., 17 


5 


72 


10(( 


100 


31/7 


44 


,. 17 


2 


20 


75 


100 


.•i3/2 


23 


„ 29 


12 


62 


83 


100 


34/ 1;! 


24 


., 28 


12 


63 


100 


100 


42/5 


33 


„ 31 


3 


51 


93 


100 


.54/l(> 


20 


., 29 


10 


45 


85 


100 


55/17 


47 


., 29 


13 


49 


98 


100 


57/3 


62 


., 19 


1 


50 


97 


lOd 


1)4/20 


24 


„ 27 


8 


50 


100 


loo 


1)8/ 12 


44 


„ 29 


4 


57 


98 


10<t 


7.')/ 11 


26 


22 


8 


92 


100 


100 


80/11 


15 


Z 27 


20 


73 


100 


100 


Hi cnilUnf.s 


537 . 


Average % = 


7-3 


598 


94-9 


KHI 


29/2 


22 


May 28 


__ 


_ 





loo 


41/5 


25 


„ 29 


— 


— 


— 


UK) 


15/7 


34 


., 16 


— 


— 


— 


100 


16/2 


32 


„ 28 


— 


— 


— 


100 


8'1() 


34 


„ 28 


— 


— 


— 


100 


4U/20 


23 


„ 19 


— 


— 


— 


100 


3/11 


30 


June 7 


— 


— 


— 


100 


81/12 


20 


., 7 


— 


— 


— 


100 


24 cultures 


757 













8. F. Ali.MSTKONG ' 75 

{h) Order of "JirsL appearance" of rust on the different cultures. It is 
interesting to notice the order in which the i^g cultures became infected. 
This is shown in Table XI. As early as Ma.}' 17th, 13-2 per cent, of the 
pure susceptible cultures were infected. At that date, none of the homo- 
zygous "immune" cultures, and only 3-1 j)er cent, of those in which 
segregation occurred, contained any infected plants. By June 1 1th, all 
the pure susceptible cultures were badly attacked, but as )'et no sign of 
infection was observed on the homozygous ■'immune" cultures, while 
an intermediate percentage of the segregating cultures were infected. 
By July 12th, 93-7 per cent, of the last-mentioned cultures were attacketl, 
but only a trace of rust was then present on one plant in all the homo- 
zygous "immune "' cultures. These results are in the order of expectation 
if susceptibihty and immunity are inherited in simple Mendehan fashion. 

The fact that the F^ cultures were of three kinds was emphasized, 
not only by the ""dates of first infection," but also by the rate at which 
rust spread throughout the cultures. There was not sufficient time to go 
fully into this matter, but the figures given in Table VII will serve to 
indicate how rapidly the infection spread among the plants in the pure 
susceptible cultures. In these, the great majority of the plants were 
very badly rusted by July 1th to 10th, whereas no rust was to be found 
on the pure "immune"' cultures at that time. Although full statistics 
were not obtained from the segregating cultures, it was clear that the 
rate of rust spread was of an intermediate character in these. 



4. Summary of the F-^ re.sult.s. 

The general results obtained from the F.^ cultures may be briefly 
summarized as follows : 

(A) Up to as late as July 10th the cultures were sharply divided into 
three groups: 

1. Those in which every plant was severely attacked. 

2. Those in which no trace of attack was to be found. 

3. Those in which the extent of attack varied very markedly from 
plant to plant, some of the plants being rust-free. 

(B) The homozygous susceptible (f .) cultures were all characterized 
by: 

((/) A comparatively early infection. 

(b) A very rapid spread of the disease. 

(c) An exceptionally severe attack on every plant. 



70 Mendclian hilierltance aiul Yelloiv Jiusf in Whral 

(C) The lioniozj'jious "iuiiiimic" cultures {'!.) wtue characterized by: 
(a) Kemarkable resistance to attack under the most adverse external 

conditions. 

(6) Extreme lateness of infection where it occurred. 

(c) The comparatively mild nature of llie attack (and in some cases 
its complete absence). 

(D) The cultur(!s in u liich segregation occurred (3.) took generally an 
ijitermediate position as regards the period of infection and rate of rust 
spread; though liiuilly a proportion of the plants were as severely rusted 
as those in the pure susceptible cultures. 

The 5() cultures in which segregation was clear, and for which full 
statistics are available, contained 3045 plants, of which 2385 were either 
moderately or badly rusted, while 660 had only a slight attack or none. 
The numbers 2284 : 761 would exactly represent the 3 : 1 Mendehan 
ratio, and if it exists here it follows that 101 plants out of a probable 
761 recessives were rusted beyond the slight extent indicated by grade 1 , 
i.e. 13-2 per cent. But this degree of "disturbance in rust resistance" 
is quite comparable with that which occurred in the 15 homozygous 
"immune"' cultures given in Table 111 where, out of a total of 594 plants, 
114, or ID per cent., were rusted beyond grade 1. Furtlier, since the F^ 
results have shown that these 15 cultures wi^re the progeny of genetically 
immune parents, there is sufficient evidence to show that such genetically 
immune plants may under very adverse conditions be subject to a mild 
attack. This being the case, it appears safe to conclude that in the 
above-mentioned segregating cultures one-quarter of the plants were 
genetically immune, and that these cultures were the product of F.^ 
heterozygotes for rust resistance. 

5. Application of thk F^ results to the i^.^ .statlstics. 

Table VIII gives a summary of the results obtained from all the F^ 
cultures. It will be seen that it is comparatively easy to pick out homo- 
zygous susceptible and immune types in the F^ generation by merely 
selecting the extreme cases of attack or non-attack. On the other hand, 
one cannot be so sure about the constitution of the moderately rusted 
individuals, for in this particular instance nearly one-quarter of these 
proved to be pure susceptibles. IMost of the slightly rusted plants of 
1918, however, turned out to be heterozygotes. Finally, a ])lant that 
bears traces of attack in one season may be shown by its offspring to be 
a geneticalh' iinnninc iii(li\idu:il, w liile a rust-free ])lant niny occasionally 
be proved a heterozygote which has eseajietl infection. 



S. F. Armstrong 



77 



In considering the F^ results it was seen tiiat the 1 : "2 : 1 ratio was 
not very closely approached, though the figures strongly suggested its 
existence. The numbei' of iiist-free and badly rusted plants were, taken 
together, consideraldy less than those placed in the intermediate grou]). 
The jDrobable explanation is that this deviation arises partly from the 
difficulty in determining the exact extent of attack by inspection only, 
and partly from the existence of other factors which are capable of 
modifying the degree of attack. 



Table VII 1. SuDimari/ of resvltf fnihi 170 Fg rulfiires in 1919. 

Condition of the F^ cultures, 1919 
Extent of rust Numlier of , ' 



attack on the F., F^ cultures All plants C'rtntained susceptible All plants 

])arents in 1918 raised, 1919 susceptible and resistant plants rust resistant 

Very bad 24 -u — — 

Bad 19 1() 3 — 

Moderate (!.•? 14 49 — 

SU^ht :!5 — 33 2 

Traces 12 — 9 3 

None 17 — 2 15 



Totals 



170 



54 



96 



20 



Table IX. Ajiproximale genetic consiitutimi of the Fo f/eneration [avtumn- 
sown portion) as regards susceptibility to Yellow Rust. These figures 
are arrived at hg the direct application of the F^ results. 



Number of F^ plan 

placed in each grac 

for rust attack* 


ts 
le 

Results in F^ 


A])i)roxiniate genetic constitution of 

the F^ crop as indicated by 

the F^ results 


4 3 2 1 


1 


r f 


DD 


DR RR 


09 








100",, proved DD 


(19 


— — 


I 
'17 








)S4 .. DD 
(Hi ., DR 


98 


19 — 


U 


52 






J 22 „ DD 

J78 .. DR 


35 


127 — 


o 







94 ., DR 
(1 ,. RR 


— 


197 

— 13 


09 


75 „ DR 
25 „ RR 


— 


52 — 
— 17 


2( 


)2 12 „ DR 

88 „ RR 


— 


24 — 
— 178 




Totals: 


202 


419 208 






T 


he 


: 2 : 1 ratio would be: 


(207) 


: (414) : (2071 



78 Mendelian Inheritance and Yelloin Rusf in Wheat 



If, however, the results obtained from the F^ cultures are applied to the 
number of plants placed in the different grades of attack in the Fo, we find 
that the 1:2:1 ratio is very clearly demonstrated. The details of this 
iipphcatioii are set out in Tables IX and X, and show that the probable 
composition of the aiitiiinn-sown portion was approximately: 

■2i)-2 DD : 419Z)/? : 208 RR, 

and (if tli(> sprinji-sown ]K)rtion of the Fo generation: 
189-7 DD : ;378-2 DR : Hi.'M RR. 

Table X. Approximate genetic constitution of the F^ generation {spring- 
sown portion) as regards susceptibility to Yellow Rust. The.'^e figures 

are arrived at bi/ the direct application of the F^ results. 



Xiiiiilx'r iif A'j plan 

|)l!i<^«'(l in each gra( 

for rust attack* 

A 


ts 
Ir 

RcsnUs ill /■'., 

) 


Approxiiiiatt' <;f'nPtir ronstitntion of 

tlif I''., prop as inflioak'd liy 

the ^'3 results 

A 


4 3 2 1 

1 


1 


T ( 


DD DR 


nil 


4- 








100",, proviMl /)?) 


Sfi — 


— 


i: 








184 .. DD 
|l(i .. /)R 


74-7 — 
14-:! 


— 


!2 






22 ., DD 

7S .. D/{ 


20 — 

— m:! 


— 


u 


U 




liU .. Dl! 
I C. .. Jill 


— 17n 


II 


1 

9S 


175 ., DIt 
|25 ., UK 


— 73-5 


24-5 


1- 


.-. (12 .. Dl! 

/SS .. HI! 


— 17-4 


127-r. 




Totals: 


189-7 :578-2 


1631 








riK 


1:2:1 ratio would be 


(183) : (:?r.,->) : 


(183) 



* For rust grades see p. Gl. 

The total number of plants was 1560, and the numbers expected 
according to the 1:2:1 ratio are (;}9()) : (780) : (:59()). Applying the F3 
results to the wliole F^ crop, we (Ind tlie following cotn])osition indicated : 

391-7 homozygous susceptible individuals. 

797-2 heterozygous susceptible individuals. 

.'>71-1 homozygous imnmne individuals. 

6. Results obtained from F2, F^ and ^^4 ctiltures, etc., in 1920. 

Tli(^ foregoing results were supplemented by further data obtained 
(luring 1920. All the rust cultures of that year were grown on the Uni- 



S. F. Armstrong 79 

versity Seed Farm near Cambridge. The ground, wliich had received 
a dressing of 10-12 loads of farmyard manure and had been cropped with 
potatoes in the previous year, was in good condition for wheat growing. 
Cultures of tlie Fo, F^ and F^ generations of the cross Wilhelmina 
X American Club were raised, in addition to others. 

During the winter 1919-1920 abnormally mild weather was almost 
continuous. One interesting feature associated with this mild weather 
was that freshly formed uredospores of Yellow Rust were found from 
the first week in October, 1919, onward to the following summer on 
certain susceptible wheats which had been sown at the end of August, 
1919. During the spring and summer of 1920 the weather was favourable 
to the normal growth of the cultures (see Table I). 

Yellow Rust attack was general amongst the field cultures at a very 
early date, and by the beginning of May in many of the susceptible 
cultures all the plants were rusted. By the first week in June the attack 
was at its Jieight. 

(n) Further Fn statiMici nhUiined in 1920. 

In raising the i^., generation (cross No. 120) in 1918, no attempt was 
made to keep separate the grain of the several F^ plants. In a later 
cross, however (Brooker's x American Club, cross No. 154), this was done, 
and several distinct F^ famihes were raised in 1920. Two of these 
families were examined in the same manner as the F^ of cross No. 1 20 
had been in 1918 with the following results: 

A population of 198 7^., individuals raised fi'oni a moderately rusted 
f J plant contained 42 badly rusted plants and fO whicli remained abso- 
lutely rust-free. On the remaining plants, the rust varied from the 
merest trace up to a moderate attack. 

The second i^, family consisted of 2-58 individuals and was raised 
from an F-^ plant which had a shght attack only. It contained 62 badly 
rusted and 61 perfectly rust-free plants, the remaining 135 indixaduals 
being attacked to not more than a moderate extent in any case. 

These figures indicate that similar results are obtained whether the 
analysis be made upon the progeny of separate i^j plants or upon the 
offspring of several ^''j^'s combined. 

The small F^ crop of the original Wilhelmina x American Club cross 
grown in 1920 contained 114 plants, and by the end of July it was found 
that 86 of these were rusted and 28 were rust-free. Of the rusted plants 
six had a much severer attack than Wilhelmina grown under similar 
conditions. 



80 Mendeliau Inheritance and Yellow Btisf in Wheal 

{b) Direct aiial/jsis of un F., Ihroiujh the F^ results, 1920. 

A small Fn crop of the same parentage (Wilhelmina x American 
Club) consistiiij; of 86 plants was raised in 1919. No attempt was made 
to grade these for rust attack as it was decided to grow an F.^ culture 
from each plant and to use the F^ data for placing each F.^ plant in its 
proper category for susceptibihty or resistance. These 86 F^>^ were 
raised in 1920. In 22 of these cultures all the plants were readily su.s- 
ceptible; 20 others contained only rust-free or highly resistant plants, 
while the remaining 44 cultures consisted of readily susceptible and 
resistant plants. The infeience is that the A', grown in 1919 consisted 
of 20 rust- resistant plants, 44 impure susceptible and 22 pure susceptible 
individuals. In four of the pure susceptible F-^ cultures all the plants 
were excessively attacked. 

(c) Results from F^ cidliires. 
(Cross No. 120. Wilhelmina x American Club.) 

A considerable number of F^ cultures were grown in 1920. Twenty- 
seven of these were raised from plants taken at random out of the wholly 
susceptible F^ cultures of the previous year. Without exception these 
F^ plants (433 altogether) were badly rusted. 

Thirty-.six F^ cultures were grown from plants which had been 
extracted from obviously segregating F^ cultures. Space will not allow 
a full iircount of the results, but they showed definitely that the three 
genetic types — pure resistant, pure susceptible and impure susceptible 
—were present in the F^ cultures. At the same time they indicated 
again that some allowance must be made for fluctuations in suscepti- 
bihty due to season and other external conditions. The 19 F^'f. raised 
from rust-free F^ plants consisted entirely of rust-resistant individuals. 
Similarly all the extracted badly rusted F^ plants produced badly rusted 
F^ cultures, while slightly or moderately rusted F.-^ j)lants gencniJlN- 
produced cultures in which rusted and rust-free plants occurred. 

Two hundred and eighty-eight F/^ cultures were raised from F.^ 
plants which were the offspring of rust-free F.;, individuals. 

Some of these were picked from cultures like 66/9, 11/21, 2/10 and 
19/12 (Table III) in which all the plants were completely or almost 
completely rust-free in 1919. 

The F^ plants nimTbered several thousands and it was impossible 
to examine each individual very closely, but a general inspection showed 
that all the plants were either rust-free or possessed a very high degree 
of resistance. 



S. F. Armstrong 81 

Many plants were purposely taken from cultures 15/5, 24/3, 29/15, 
57/8, etc. (Table III), in which rust-resistance had apparently been dis- 
turbed or "broken down" under the adverse conditions prevailing in 
1919. A few of these extracted jPg's had, indeed, been badly rusted, 
e.g. 15/5/15, 24/3/18, etc. Nevertheless in 1920 all the F^ plants proved 
to be either completely rust-free or highly resistant. 

Table XI. Progress uf infedion bi/ Yellow Rust on the various F-^ cidlmes 
in 1919. (Cross No. 120.) 169 cultures*. 

Percentage of cultures on wliich infection had occurred 
for the weekly periods ending 



t\ Number May June July Final examination 

cultures of ^''3 , ^' , '• , , * , July 28th to 

1919 cultures 17th 24th 31st 7th Uth 21st 2Sth 5th 12th August 1 1th 

DD\ 5.3* 13-2 340 773 94-3 100 — — — — — 

DK'a 'Mi 3-1 15-6 22-4 49-0 61-4 IJ4-5 80-2 81-2 93-7 100 

lilCs 20 Of 90 

* One culture omitted because no record of date of first attack was made. 

t Only one small pustule seen on one plant by this date out of a total of 817 [ilants. 

Section- 111. .SOME OF THK FACTORS WHICH JIAV IXCREASIC Oil 
DIMINISH SUSCEPTIBILITY TO RUST ATTACK. 

Introduction. 

In the previous section of this paper it was seen that a sharply defined 
1:2:1 ratio was not directly found in the F.^ generation in 1918, 
although the Fg results showed that it undoubtedly existed. The varia- 
tions observed in the F^, and from season to season, appear to indicate 
that, in addition to the inherited factors which primarily determine 
resistance, etc., there exist other factors which may tend either to 
increase or reduce a plant's predispo.sition to attack. 

The now generally accepted view is, that immunity is due to the 
production of specific toxins or anti-toxins which have the power to 
neutraUze the action of the attacking fungus. If this is correct, an im- 
mune plant is one whose normal metabolism provides such a substance, 
whilst a susceptible plant is one which is either unable to form such a 
substance at all, or can only do so to an ineffective extent. But even 
in the case of a plant which is able to produce such protective substances, 
it is obvious that such production may be subject to modification as 
regards quantity, rate of formation, etc. There is, indeed, evidence to 
show that a state of complete immunity depends not only upon the 
inherited factor for resistance, but also upon a properly balanced con- 

Joura. of Agric, Soi. xu 6 



H'2 Meiuh'luni I iiln rlttnicr ((ml Yellow Rf(st in Wlmd 

ditioii of the plant's normal nu'taholisni. For example, American Club, 
thoufjh normally immuiio, has been found to develop pustules of 
Yellow ]?ust under abnormal conditions of gro\vth(iO) or nutrition (12). 
It is therefore probable that any factor or factors which bring about a 
condition of growth unfavourable to the production of those substances 
upon which immunity depends, may lead to a greater or less degree 
of susceptibility. Ward(20) especially emphasized the fact that "the 
physiological condition of the host is always a factor of prime import- 
ance" in considering the beliaviour of the host towards the parasite. 

Since all physiological processes are dependent upon both internal 
(inherited) and external factors, in matters of this kind we must be 
careful to distinguish between the inherited and non-inherited factors 
concerned in bringing about the net result. Consequently, in trying to 
discover the causes of the "disturbance in rust resistance" as observed 
for example in 1 919, we nuist recognize the possible effects of: 

(1) External environmental factors. 

(2) Inheritable factors (other than those prinuirily concerned in 
causing resistance, etc.) which lead to fresh combinations of parental 
features in the hybrid and its descendants. These will now be con- 
sidered. 

(a) Effect ok climatic conditions. 

The greater severity of attack in 1919 is partly explained by the 
different weather in the two seasons. That of 1918 favoured a regular 
and normal development of the plants. On the other hand the cultures 
of 1919, while still in a backward condition, were subjected first to a 
7 weeks" drought, and afterwards to G weeks of almost continuous dull, 
cool, wet weather. 

During both years records were taken of the extent of the Yellow Rust 
attack on 13 distinct varieties of wheat grown in the cages. In eight 
cases the attack was more severe in 1919 than in 1918; on four varieties 
it was of about the same intensity, and in one case it was slightly less 
severe. This and other evidence support the behef that the abnormal 
weather of 1919 was partly responsible for the more pronounced attack 
in that year. 

(h) Food supply. 

It was, however, clear that the greater intensity of attack on the 
F^ cultures in 1919 was not due solely -or even chiefly — to tlu' different 
weather conditions. The increased severity of attack was far moie pro- 
nounced on these than on the standard varieties growing alongside. 



S. F. Armstrong 8:1 

while the only known difference in environmental conditions was that 
of food supply. The rust-cultures had all received a heavy dressing of 
nitrate of soda, whereas the other plots were unmanured. The nitrate 
was carried to the roots of the plants when their Very existence was in 
the balance at the end of the drought (June "20th). Thus the nece.s.sary 
supply of moisture, and also a large quantity of available nitrogen, were 
simultaneously presented to the plants. It is very important to note, 
therefore, that the change from a critical condition to a state of active 
growth was as sudden as it was pos.sible to be. The "second growth" — 
which also occurred on the unmanured wheats — was stimulated to an 
enormous extent on the F^'s, and the cultures assumed the very dark 
green colour characteristic of plants receiving an excess of nitrogen. 
The maturation of the plants was also considerably delayed. These 
conditions evidently in some way afforded a greater opportunity for 
rust attack, for it was precisely during this period of delayed maturation 
that the great epidemic of the season developed. 

Nitrogenous manures, especially when greatly in excess of other 
fertihzers, are well known to be very effective in increasing the severity 
of rust attack. Biff'en(3) has pointed out that, on the Rothamsted wheat 
plots, rust attack is invariably encouraged where ammonium salts or 
nitrates are continuously applied in heavy doses. Spinks(i2) also showed 
that susceptibility to Yellow Rust is increased by the use of large quan- 
tities of available nitrogen, while plants which are semi-starved as regards 
nitrogen may exhibit a considerable degree of resistance. Further, as 
Spinks and others have shown, some salts, e.g. salts of potassium and 
especially lithium salts, may markedly reduce susceptibihty. The 
question of food supply is therefore certainly of great importance in 
connection with the observed fluctuations in susceptibility. 

In connection with this question of food supply, it may be noted 
that during the present experiments there appeared to be a difference 
in susceptibility between "interior" and "exterior" plants in the same 
pure susceptible cultures. Records of the first plants to be attacked were 
made on 23 of the homozygous susceptible cultures given in Table VII. 
At the time of "first infection" these cultures contained 642 "interior," 
and 124 "exterior" plants. By June 7th the number of infections noted 
on "interior" plants was 35, i.e. 5-4 per cent., while at the same date the 
infected "exterior" plants numbered 20, i.e. 16-1 per cent. Similarly, 
in 12 other pure susceptible cultures, by the end of May it was found that 
7-3 per cent, of the "exterior" plants were attacked, but only 2-3 per 
cent, of the "interior" plants. The number of early infections were 

6—3 



84 Mendiiiun InlKritance tniii Yrlhnr Rust In Wlniif 

therefore relatively three times as numerous on the "exterior" as on 
the "interior" plants. 

An experiment was planned in order to find out if possible to what 
relative extent such "circumstances as wide spacing and large amounts 
of available nitrogen were responsible for the increased severity of attack 
observed. The varieties included in the test were tlie two parent wheats 
Wilhelmina and American Club and the following extracted F^ tjrpes 
descended from these parents: 

GG/'djd, a rust-resistant type, with white chaff and beardless medium- 
lax ears (a resistant Wilhelmina type). 

82/14/a, a rust-resistant type, witli red chaS and beardless medium- 
lax ears. 

75/7 /c, a susceptible type, with wliite chaff, and dense bearded ears 
(a white chaffed susceptible American Club type). 

75/1 1/(^, a dense eared, bearded, susceptible type with red chaff'. 
(This was practically a susceptible American Club.) 

Four beds, A, B, C, and D, each 4 feet wide, were laid out, and each 
variety was sown across these in a single row 16 feet long. A space of 
() inches was allowed between each row, but the grains were sown 2 inches 
apart on beds A and D, and 12 inches apart on B and C. The grain was 
sown on November 2'lth, 1919, and a fairly uniform plant was obtained. 

On May 4th, 1920, beds A and B were top-dressed witli nitrate of 
soda at the rate of 7 cwt. ))er acre. It should be noted that, although 
beds C and D received no nitrate, the soil was in good condition after 
the potato crop of the previous year; the comparison to be made was not 
between starved and overfed plants, but between plants grown under 
normal and abnormal conditions as regards space and nitrogenous 
manuring. 

Yellow Rust was first seen on May 7th on one or two plants of 75/11/rf 
and Wilhelmina (exterior row) in each case on bed A. By May 12th rust 
attack had become general on all the susceptible varieties, the only 
difference being that it was of a less pronounced character on Wilhelmina. 
At that date no sign of attack could be found on any of the resistant 
varieties although their foliage was literally ])owdered daily with nredo- 
spores from their susceptible neighbours. 

The condition of the plants on May 21st and June 2nd is shown in 
Table XII in which the numerator of each fraction indicates the number 
of plants rusted out of the total surviving plants of each variety on each 
bed (given as the denominator). 



8. P. Armstrong 85 

General conditiov of the plants on May 2\st, 1920. 
The plants on bed A were of a dark green colour and growing 
vigorously; they were about 2 feet high, and owing to the close planting 
and strong growth the shoots were densely crowded together. Mildew 
was abundant, especially on Wilhelmina and 6fi/9/rf. 

Table XII. Effects of wide planting and heavi/ application of Nitrate upon 
wheats susceptible and resistant to Yellow Rust. Grain soivn Nov. 2itk, 
1919. Nitrate of soda applied May 4th, 1920, at the rate of 7 c.wt. per 
acre. 



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* In these cases the plants were only "flecked.' 



86 Meriflelian Inheritance and Yelloir Jinst in WJimf 

On beds B and C the plants were also makinj; a very strong growth. 
Owing to the large amount of space available, numerous tillers were 
formed and the shoots were spreading out obliquely. 

On bed D the plants were about 18 inches high, erect, and of a light 
green colour. They had tiliored much le.ss freely than the plants on the 
other beds. 

Table XII shows that on this date all the plants of American Club 
and of the two extracted resistant types (altogether '20F> plants) were 
still entirely free from infection. Taking the proportion of plants infected 
and the severity of attack into consideration, Burbank's was distinctly 
the most susceptible type, 08 out of 72 plants being badly attacked. The 
proportion of rusted plants in Wilhelmina and the two extracted sus- 
ceptible types were very similar, hut the attack ou'Wilheimina was less 
severe; the actual numbers were: in 7."j/7/f, .34 rusted out of 40 plants; 
in 75/11 /(Z, 33 rusted out of 43 plants; and in Wilhelmina. 91 rusted out 
of 121 plants. 

Confining our attention for the moment to the susceptible varieties, 
we get some idea of the e.xtent to which "wide spacing,"' etc., apparently 
favour rust attack. 

The effect of "wide spacing'" is seen by comparing beds C and D. 
On bed D, out of 107 plants of the susceptible varieties, 73 were rusted, 
i.e. 68 per cent. On bed 0, 21 out of a total of 23 susceptible plants were 
rusted, i.e. 91 per cent. 

The effect of the heavy dose of nitrate is seen from a comparison of 
beds A and D ; on the former, out of 1 24 plants of the susceptible varieties, 
111 were rusted, i.e. 89-5 per cent, as compared with 68 per cent, on D. 

The combined effect of "spacing'' and "nitrate" is seen by-comparing 
beds B and D. On the former, 21 out of 22 susceptible plants were rusted, 
i.e. nearly 100 per cent, against the 68 per cent, on D. 

It is clear from these and other observations that very widely spaced 
plants are more hable to an early infection than are closely planted 
individuals — other conditions being equal. A partial explanation for 
this possibly lies in the fact that widely spaced plants tiller more freely, 
and so ofltcr a much greater area of leaf surface to infection than more 
crowded individuals. On the other hand the percentage of early in- 
fections on the closely planted bed A was as high as on the widely spaced 
bed C, and it is unlikely that this effect was brought about by the in- 
creased tillering of the plants on A. The increased susceptibihty of plants 
receiving heavy doses of nitrogenous manures or extra space for growth 
appears to depend rather upon the increased or modified food-supply 
offered. 



8. F. Armstrong 87 

Condilion <if the phints on June 2nd, 1 920. 

By this date rust attack was at its height and the state of the beds 
was very interesting (Table XII). 

It will be seen that every plant of Burbank's, Wilhelmina, and the 
two extracted susceptible types was rusted. On Wilhelmina the attack 
was generally speaking of a moderate character; on the other susceptible 
varieties it was very severe. The two extracted rust-resistant types and 
American Club continued to show very high resistance to attack, but 
in a few cases this resistance had apparently been more or less broken 
down. These cases will be noticed after first comparing the number of 
such apparent "breakdowns'" on the different beds. 

On bed D there were 83 plants of the immune varieties, and these 
all remained completely rust-free ; not the shghtest sign of infection could 
be found throughout the season. 

On bed C only one plant was "flecked" out of a total of 14. Out of 
15 plants on B 7 either bore pustules or were "flecked," while on bed A 
17 plants were either "flecked" or bore pustules out of 93 individuals. 
The percentage of more or less successful attacks at this date on beds 
D, C, A and B was therefore respectively 0, 7, 18 and 40. These results 
point in the same direction as those given above for the number of 
early infections recorded among the susceptible varieties on the same 
beds. 

These cases of infection were distributed among the "immune" 
varieties as follows: 17 cases occurred out of the 118 American Club 
plants; 6 occurred amongst the 45 plants of 66/9/f/; while only 2 cases 
were met with out of 42 plants of 82/14/a. 

The following particulars may be given of the individual plants 
concerned. 

American Club. On bed C (row (i) 1 jilant was slightly flecked. On 
bed A (row 2) 3 plants were clearly flecked though no pustules were 
formed. In row 6, out of 22 plants, 6 showed signs of infection. Plant 
No. 5 had a pronounced attack — though chiefly confined to one leaf. 
On this single blade, 71 well-developed pustules were counted, every one 
shedding spores, in addition to 17 other unbroken pustules. Plant Ifi, 
besides being flecked, bore three large pustules, one of which was shedding 
spores. Plant 19 had 7 well-developed pustules, 4 of which were broken, 
besides numerous flecks. Plants 6, 10 and 22 were flecked. In row 10, 
plant 2 was flecked and bore 47 pustules, many of which were broken. 
Plant 9 bore flecks and 2 unbroken pustules. Plants 12 and 15 were 



88 MendeUan Inheritance and Yelloir Rust in Whnil 

also flecked, and the former had 8 pustules, some ol wliich shed 
spores. 

On bed B (row 2), 1 jilaiit was slightly flecked, and another bore a 
few unbroken pustules on one blade. In row 10 the 4 plants remained 
free from infection. In row 6 there were only 2 plants; one of these had 
14 leaves badly attacked and on these over 200 pustules were counted, 
many of which were freely shedding spores. Some weeks later it was 
discovered that this plant was also infected wnth Bunt (Tilhtia cariefsy. 

Turning next to the extracted resistant types it is seen that the 
plants of (}&j9/d (row 4) on beds C and D were completely resistant on 
June 2nd; further, they remained immune to the end of the season. 
On bed A, 4 plants out of 19 had sHght attacks, in each case a few 
pustules were formed, some of which were broken. On B, 2 out of the 
3 plants had a few slight "flecks," but no pustules were seen. On the 
whole therefore this extracted f\ type was distinctly more resistant than 
its resistant parent (American Club) under these abnormal conditions. 

All the plants of the extracted resistant type 82/14/'/ (row 8) re- 
mained free from any trace of infection throughout on beds A, C and D. 
The 2 plants on bed B each had a shght attack on one blade. On one of 
these the attack was confined to the leaf-tip where the tissue was dying 
off. This extracted type was then decidedly more stable in its resistance 
than American Club. 

In summing up, it may be repeated that the conditions under w^hich 
these plants were grown were much more unfavourable to rust resistance 
than those Ukely to be met with in general farm practice. This is especi- 
ally true of beds A and B. During the latter part of May and throughout 
June the susceptible varieties produced enormous quantities of uredo- 
spores and the alternating rows of resistant cultures were literally 
powdered all over day by day with fresh spores. It is conceivable that 
an occasional spore may possess more than the average power for bringing 
about an infection, and with such iiuge numbers of inoculations occurring 
day by day it is not surprising that now and then infection should have 
been accomphshed. 

But the evidence shows that the success of the parasite was of a 
very limited nature. Later observations indicated that the position on 
June 2nd was the worst reached during the year. Not only did the fungus 

' Since then another similar case has been observed. In an F, culture (from the cross 
Wilhelmina x American Clul)) raised from an immune F^ plant all except one plant were 
rust-free. This odd plant wa.s very severely attacked by rust, ajid was also found to be in- 

fecteit with Hunt. 



8. F. Armstrong 89 

fail to infect any other plants, but even the infection areas already noted 
did not spread, and the tissues lying around such areas gradually died 
off and with them the parasite also. Numerous brown dead patches 
in the tissue remained, but clearly the hosts were the victors in the 
struggle. 

The experiment shows that, while heavy doses of nitrate do lead to 
an intensification of rust attack on susceptible varieties, such treatment 
of normally immune wheats fails actually to break down or destroy their 
resistant powers. Under such treatment, however, the struggle which 
goes on between invader and host is seriously prolonged and may lead 
to an appreciable loss of leaf-tissue in the latter. 

(r) New combinations of parental characters. 

It was clear, however, that, in addition to such external factors as 
those mentioned above, other causes were concerned in affecting the 
plants" susceptibiUty. In the same season (1919), and under the same 
external conditions, some of the homozygous susceptible cultures and 
plants were more severely attacked than others. Similarly, among the 
homozygous "immune" cultures (and plants) great differences existed 
in regard to the degree of re.sistance shown. Two of these cultures (66/9 
and 11/21), containing 77 plants, actually came through this most un- 
favourable season, and in spite also of the heavy apphcation of nitrate, 
matured off absolutely free from Yellow Bust infection. Two other cultures, 
including 91 plants, survived the test almost equally well, only 7 plants 
showing any sign of attack. These cultures did not escape by maturing 
off earUer than the rest, for they were not ripe until the second week in 
August. In the other pure "immune" cultures, however, while some 
plants were rust-free or had traces only, the majority had a slight attack, 
and a number were moderately rusted. 

The above facts are only exphcable on the assumption that the 
differences are partly due — at least indirectly — to other inherited features. 
It was observed that new combinations of such characters as ear shape, 
chaff colour, bearded or beardless condition, etc., appeared to be without 
effect upon a plant's susceptibihty. But this does not involve the as- 
sumption that all combinations of other characters are hkewise \vithout 
effect. In a paper recently published Hayes (8) points to some evidence 
of Unkage between rust resistance and certain morphological characters 
in the offspring resulting from crosses between Triticum vulgare and 
varieties of T. durum and T. dicoccunt. It is, indeed, extremely probable 



90 Menddicw Tulurltance and Ytllov Riixf in Whtat 

that fresh coiiiljinations of those features which more especially alTect 
the plants laetabohsm may also modify its power of resistance. The 
parents of the cross under consideration were dissimilar in respect of 
several such characters, e.g. fohage, period of ripening, and probably 
also in root-range. As 13iflen(3) has pointed out, when segregation occurs 
fresh combinations of these various features result, and consequently 
the metabolism of such offspring is affected in various ways. The resulting 
root-range may be disproportionate to the new leaf-area, a slower rate 
of maturation prolongs the period of possible attack, and so on. Most 
important of all, it must not be overlooked that physiological features 
are also inherited, and recombinations of these may produce unexpected 
results. 

While some of these new combinations may bring about increased 
susceptibility, there was evidence that others may reduce it. or stabilise 
the inherited resistance. This fact has also been independently noted by 
Hayes (8) in his experiments. These effects are realized not only in the 
Fo, but also in any subsequent generation in which such combinations 
of features are iidierited, or arise. A consideration of such points as 
these enables one to understand partly, at least, why statistics of rust 
attack on an i^g generation (from a cross between susceptible and im- 
nume parents) seldom give a close approximation to the 1:2:1 
Mendelian ratio. 



{(l) Variation of .susceptibility in hybrid wheats. 

The view that the re-combination of parental characters may lead 
to a modification of a plant's predisposition to attack is further supported 
by the various degrees of susceptibihty posse.ssed by hybrids. It has 
been stated by several observers tliat hybrid wheats are usually as 
susceptible to rust as the more susceptible jiarent. Instances, however, 
are known to the writer in which the attack was distinctly more severe 
on the hybrid, and also other cases in which it was much less severe. 

In order to make a strict eom])arison on this point, certain liybrids 
were grown alongside their parents in 1911) under exactly the same con- 
ditions as to time of sowing, space allowance, etc. One of these crosses 
was between American Club and a very susceptible race No. 109/1. Of 
the 14 hybrids, none had more than a slight attack at the final examina- 
tion on July 31st, while all the plants of 109/1 were badly rusted. 

Another cro.ss was made between a moderately susceptible variety 
(Brooker's) and American Club. Sixty-eight t\ plants were raised in 



S. F. Ahmstbong 91 

1919. Rust varied from mere traces up to a mild attack on the hybrids 
whilst the susceptible parent had a moderately bad attack. 

As far as these results go, they indicate that crosses between a 
normally immune variety hke American Club and a susceptible variety 
give rise to hybrids whose inherited susceptibility is of an intermediate 
nature. 

This, however, does not appear to hold good when some degree of 
susceptibihty is possessed by both parents. In a further cross (No. 155) 
between Wilhelmina and Persian Black (a variety of T. dicoccum), the 
33 Fi plants raised were all very severely attacked. Both parents 
grown alongside under exactly the same conditions had only a moderate 
attack. Possibly the much increased severity of attack in this case may 
be due to the fact that there is a tendency for the hybrids of this cross 
to be sterile. 

Two other cases may be mentioned: Rivet (T. turgidum — shghtly 
susceptible) crossed with Persian Black (moderately susceptible), and 
Rivet crossed with Chinese White — a very early maturing susceptible 
variety — produced hybrids which were much more severely rusted than 
either of the parents. 

In the three last-mentioned crosses none of the parent varieties are 
completely resistant to attack, and as the other differences between them 
are unusually great and numerous, it is possible that the increased 
susceptibility of the hybrids may be largely due to the altered meta- 
bolism of the plants. 

(e) Possible effect of environment upon the fungus. 

In conducting these investigations, it has not been forgotten that the 
cause of the disease is also a hving organism favoured, or disfavoured, 
by factors similar to those that affect the host, and that it must therefore 
also receive consideration in dealing with the question of variation in 
susceptibility of the host. 

Undoubtedly weather conditions affect the general spread of the 
fungus according as they favour the vitality, dissemination, and ger- 
mination of its spores, or otherwise. But apart from this, the writer has 
had no evidence in the field that the parasite is directly aided in its 
attacks by one kind of weather rather than another. The spread of the 
disease in susceptible plants was as rapid during the hot, dry period from 
May 13th to June 19th in 1919 as it was in the cool, damp period from 
June "JOth to July 31st of the sa!ne year. 



02 Mendellan Inheritmice and Yelloir Rust in Wlieat 

It has been supposed that increased virulence is gained by a rust 
after passinj^ one stage of its hfe-history on a congenial host. For example, 
Pole-Evans (U). working with P. graminis, beUeved that his experiments 
showed [a) "that the t\ from a cross between a susceptible and an 
immune wheat is more susceptible to rust attack than its susceptible 
parent," and (6) "that the rust which passes tiirough a liybrid plant 
produces a far more severe infection than the rust from the susceptible 
parent." Neither of these conclusions, however, appear to carry much 
weight since the wheat employed as the "immune" parent proved on 
some occasions to be moderately susceptible. As the present investiga- 
tions have shown, hybrids which result from tlie crossing together of 
two more or less susceptible varieties are generally more susceptible 
than either of their parents. The second conclusion referred to has re- 
cently been negatived by the experiments of Staknian(i:^) who worked 
with the same rust. Stakman's evidence showed that the patliogenicity 
of rusts is not easily changed by host-influence. He says "although many 
attempts were made to increase the virulence of biologic forms on resistant 
hosts, the results indicated that rust-forms do not gradually adapt them- 
selves to resistant or semi-congenial hosts." 

Since rust spores probably vary as regards their capacity for infection, 
an occasional spore may be able to bring about a more or less successful 
infection on a host plant which is capable of complete resistance in tiie 
vast majority of cases. In this way ])erhaps the partial or temporary 
bieakdown of rust-resistance may be partly accounted for. At present, 
however, the bulk of the experimental evidence indicates that it is to 
the physiological condition of the liost, rather than to any increased 
virulence on the part of the parasite, that variations in a ])lant"s sus- 
ceptibility are due. Changes in the metabohsm of the possible host are 
brought about in various degrees by the interaction of both inherited 
and non-inherited factors, and it is suggested that such changes may lead 
to a diminished resistance by proving unfavourable to the formation 
of those products upon which inmiunity depends. 



CONCLUSIONS. 

The evidence obtained from the investigations described demonstrates: 
1. That immunity and susceptibility to Yellow liust attack are 
inheritable features in wheat. 

"2. That susceptibility and immunity behave as unit-characters, and 



8. F. Armstrono 93 

depend primarily upon definite factors which are inherited according 
to the simple Mendehan law. 

3. That segregation leads to the occurrence in the F^, generation of 
susceptible and immune individuals in tlie proportion of 3 : 1. 

4. That the immune F2 plants breed true to that character. 

5. That one-third of the susceptible F.^ plants are homozygous for 
susceptibihty and breed true, and that the remaining two-thirds are 
heterozygous for susceptibility and give rise to offspring in which rusted 
and rust- resistant plants occur as in the ^''2 • 

6. That homozygous susceptible plants are distinguishable from 
heterozygotes quite as much by an earlier and more rapid spread of 
infection as by the final extent of attack. 

7. That a plant's predisposition or resistance to attack is, neverthe- 
less, subject to greater or less modification from the interaction of various 
other causes. There is evidence for this in the fact that a badly rusted 
plant may prove to be heterozygous for susceptibility, whilst a moderately 
rusted individual may be shown to be homozygous for the same feature. 

8. That the relative difference in resistance between homozygous 
susceptible and "immune" plants remains approximately the same even 
when the external conditions are favourable to an extremely severe 
attack. 

9. That while new combinations of characters may lead indirectly to 
increased susceptibihty, there is evidence to show that the reverse effect 
may be produced. In some instances the inherited immunity was in 
some way so stabihsed that the most favourable conditions for rust 
attack failed to bring about the shghtest degree of infection. 

10. That breeding for rust resistance may proceed with every as- 
surance of success, and that even the production of new races as stable 
for immunity as American Club itself is by no means an impossible task. 

The evidence further indicates: 

11. That a cross between a normally immune and a susceptible 
wheat produces a hybrid in which the inherited susceptibihty is probably 
of an intermediate nature. 

12. That the causes referred to above under clause 7 probably include 
any factor which is capable of modifying the plant's metabohsm to an 
appreciable extent, and embrace 

(a) Inherited factors leading to fresh combinations of morpho 
logical or physiological features, and 

(6) Non-inherited environmental factors. 



94 Mciuldliin I iiln i'iUdh-c and Yilhnv Riisl in WIk tit 

APPENDIX. 

An allempl. lo estimate the Reduction of Yield due to . 
Yellow Rust attack. 

Various estimates have been given as to the probable loss of fjrain 
due to rust attack, but most of these appear to be little more than guesses. 
It is, of course, certain that rust attack may be so severe as to destroy 
the host plants altogether, but such super-susceptible races do not enter 
into general cultivation in countries where they are Hable to attack. The 
question to be answered is, What is the approximate reduction in yield 
of those varieties which, though capable of being generally cultivated 
are nevertheless subject to a moderate or occasionally a bad attack? 

A favourable opportunity occurred to test this point in 19'20. 

A variety of wheat known as "Jap" has been grown on small plots 
at Cambridge for the last 15 years. It was formerly used as a parent, but 
ill recent years has been discarded for tiiis i)ur|)ose owing partly to the 
inferior nature of its straw and jiartly because of its susceptibility to 
V'ellow Rust. A small culture has, however, been grown on each year, 
and in 1918, when the parent stocks were examined as to their com- 
parative susceptibility, it was noticed that the "Jap" culture consisted 
of plants which varied widely in this respect. Looking at the plot as 
a whole, it appeared to be suffering from a moderate rust attack, but 
when examined in detail, certain plants were seen to be rust-free. A final 
inspection of the culture in July showed that it contained 38 rusted and 
14 rust-free individuals. Six of the rusted and four of the rust-free 
plants were saved, and from these separate cidtures were grown in the 
following year. Owing to the extremely favourable conditions for rust 
attack in 1919 the cultures raised from the rusted plants were attacked 
with great severity, and even those grown from the rust-free plants had 
a slight attack. The relative difference in their power of resistance 
appeared to be the same as in 1918. All the cultures were of the "Jap" 
type as regards straw, ear-shape, etc., and if morphological diflerences 
existed they were too slight to be apparent to the naked eye. The only 
observed difference apart from rust resistance was in the period of "ear- 
emergence," there being some 10 days between the earhest and latest in 
this respect. Rust susceptible and resistant cultures were included in 
both the early and late groups. 

One plant (3/16/29) was saved from a pure susceptible culture (3/16), 
and also one plant (1/4/10) from a resistant culture (1/4), and a plot of 
each was raised in 1920; a similar plot was grown from the original 



8. F. Armstrong f>5 

mixed stock of "Jap." On May 12th, 1920, out of 57 plants in culture 
3/16/29, 41 were attacked by Yellow Rust; on the same date the 66 plants 
in culture 1/4/10 were free from infection. Culture 3/16/29 was about 
7 days earlier than the other, and all the plants in it were rusted by 
June. Only a few slight traces of attack and some " flecked" plants 
were found on culture 1/4/10 before harvesting. 

The original intention in growing these cultures was merely to see 
whether the extracted types bred true to resistance and siisceptibihty 
respectively, but, at harvest-time, they seemed to offer very favourable 
material on which to determine the loss directly due to Yellow Rust. 
In the first place, their identical — or almost identical — morphological 
features appeared to afford safe ground as a basis for such a comparison. 
Again each culture had remained free from attack by Brown Rust or 
other fungi up to the time the plants were pulled — July 23rd — so that the 
difference in yield was chiefly, if not entirely, due to the presence or 
absence of Yellow Rust. Further, each plot was sown on the same day. 
grown under identical conditions side by side, and no loss of grain had 
occurred at harvest-time. In one respect only there was a sUght cUiTerence 
between the cultures, viz. in the number of plants per row, this being 
due to the rather poorer germination of the grain in the susceptible 
cultures. The results were as follows: 





Culture of 


Culture 


Culture 




"Original Mixed 


1/4/10 


3/16/29 




Jap" 


"Resistant" 


"All susceptible 


Rows 


3 


4 


4 


Plants 


4.5 


66 


57 


Plants per row- 


15 


16-5 


14-2 


Total weight of ears (grams) 


310 


555 


245 


Weight per ))lant (grams) ... 


6-9 


8-4 


4-3 


Percentage relative weights: 








(a) Per plant 


821 


100 


51-2 


(b) Per unit area ... 


741 


100 


44 



It will be seen that the weight of ears in the "mixed" culture was 
reduced by 18 per cent, per plant, and by nearly 50 per cent, per plant 
on culture 3/16/29. The reduction per unit area was still greater in each 
case. Had the grain been threshed out and weighed separately, it is 
certain that the differences would have been still more striking, but this 
unfortunately was not done. 

These figures indicate that a variety of wheat having on the average 
a moderate degree of susceptibihty (comparable with, say, Square Head's 
Master) may give a yield at lea.st 25 per cent, below that obtainable 
from almost precisely the same form when rendered rust-resistant. 



96 Mcndefldii hiln ritdiia ftml Ydlmi- /'ii.sf ill win lit 

LIST OF I'APERS REFEHREI) TO I.\ THK TKXT. 
(I 



(2 
(3 
(4 
(6 

(7 
(8 

(f» 
(10 

(11 
(12 

(l.-i 

(14 

(15 
(16 
(17 
(18 
(19 

(20 

(21 



BiFFKN, K. H. (IIK).")). -Menders Laws of Inheritance and \\ lieal llreediiig. 
Joum. Agric. Sci. 1, 1. 

(1907). Studies in (lie liiheiitniiee of Disease Resistance. Joum. Agric. 

Sci. 2, 109. 

(1912). Studies iiil he I iilieritaiue of Disease Resistance. Part II. Jourii. 

Agric. Sci. 4, 421. 

Eriksson, J. (1896). Die Oelreiderotile. 

Evans, I. B. P. (1907). The Cereal Rusts. Annah of Bolutiij, 21, 447. 

(1911). South African Cereal Rusts, with observations on the Problem 

of Breeding Ru.st -resistant Wheats. Jourii. Agric. Sci. 4, 9;'). 

(iiBsoN, Miss ('. M. (1904). Notes on Infection Experiments with various 
Tredineae. New Plii/lnlogi.il. 3, 184. 

Haves, H. K. and others (1920). (Jenetics of Rust Resistance in crosses of 
varieties of Tritieum vulgare with varieties of T. durum and T. dieoccum. Joum. 
Agric. Res. 19. 523. 

Keebi.e and Armstkonc; (Hti.'J). The Role of Oxydases in the Formation of 
tlie .Anthocyanin Pigments of Plants. Joum. Oeitelic.t. 2, 277. 

Marrvat, DoROTirEA ('. 10. (1907). Notes on the Infection and Histology of 
two Wheats immune to the attacks of Puccinia glumarum. Joum. Agric. Sci. 
2, 129. 

NrL.ssoN-EHLE (1909). Kreuzunguniersiichungen an Haje.r und Weizen. 

SpiNK.s, (J. T. (19i:5). Factors affecting Susceptibility to Disease in Plants. 
Joum. Agric. Sci. 5, 231. 

Stakman, E. ('. and others (1918). Plastieity of Biologic Forms of I'uccima 
graminis. Joum. Agric. ffp.s-. 15, 221. 

Vavilov, N. I. (1914). Immunity to Fungous Diseases as a Physiological test 
in Genetics and Systematics, exemplified in Cereals. .Joum. Oenelic.i, 4. 49. 

Ward, H. xMarshall (1890). Croonian Lecture. Proc. Roy. Soc. 47. 

'1902). Proc. Rnij. Soc. 69. 4.-)l. 

(1902). Proc. Roy. Soc. 71. l;i8 

(1902). Proc. Camb. Phil Soc. 11, part o. 

(1902). On the relations between Host and Parasite in the Bromes anil 

their Brown Rust (P. disper.'ia). Annals of Botany, 16. 233. 

(1905). Recent researches on the Parasitism of ['"ungi. Annals of Botany, 

19, 1. 

Wheldale, Miss M. (191 I). On the Formation of .Anthoevaiiin. .Joum. Genetics, 
1, 133. 



{Received October 8th, 1921.) 



NOTE ON THE COMPOSITION OF 

A FLUID OBTAINED FROM THE 

UDDERS OF VIRGIN HEIFERS 

By HERBERT ERNEST WOODMAN, Pji.D., D.Sc, 
AND JOHN HAMMOND, M.A. 

{From fJie Institute, for the Study of Animal Nutrition, 
School of Agriculture, Cambridge Universitg.) 

The secretion of milk by the mammary glands normally follows a period 
of pregnancy, but numerous cases have been cited in the literature of 
secretion which takes place in animals that have never borne young. 
Non-pregnant bitches frequently secrete milk several weeks after 
oestrus (1), and a secretion, apparently similar to milk, takes place after 
pseudo-pregnancy in rabbits (2). No quantitative analyses have been 
made of these secretions to show whether they possess the characteristics 
of true milk or colostrum. 

The origin and significance of colostrum itself, as distinct from milk, 
is also in doubt, and its formation has variously been attributed to: 
(1) The break up of the central cells of the alveolus, or as a result of their 
initial activities; (2) The filtration of lymphatic secretion through the 
walls of the alveoli mixing with the milk formed by the cells. Recent 
work on the proteins of colostrum (3) has shown that although the 
caseinogen and albumin must be elaborated by the mammary gland, 
yet the globulin, which is present in large amount in the colostral 
secretion, is in every respect identical with the globulin of blood serum. 

There also exists the possibility that colostrum results from the 
partial absorption of the more diffusible milk constituents, the secretion 
of which has been taking place to a small extent some time previously. 

It was therefore of considerable interest to find, during a study which 
is being made by one of us (J. H.) of the development of the udder of 
the cow, that the galactophoroiis sinuses and ducts of virgin heifers of 
some 1| to 21 years of age contained very frequently a fluid which could 
often be expressed from the nipples in quite considerable amounts. The 
object of the present work was to investigate the composition of the 
secretion and its possible relation to colostrum and to milk. 

It has been suggested by several writers (i) that the mammary gland 

Journ. of Agric. Sci. xn. 7 



98 Fluid obtained from. Udders of Virgin Heifers 

undergoes a cycle correlated with that existing in the ovaries and 
culminating at oestrus by a swelling of the mammary gland. Since 
heifers have periodic corpora lutea and a well-marked ovarian cycle, 
it might be supposed that the former acted in much the same way as 
those of pseudo-pregnant rabbits, but to a smaller extent. It was not 
unreasonable therefore to suppose that this Ouid was secreted just before 
the period of oestrus in heifers, but attempts to prove this so far have 
been without success. The fluid can be drawn off from tlie udder at any 
period of the cycle, and the amount varies considerably according to 
the individual. In animals killed at various periods of the oestrous cycle, 
there was an indication that more existed just before the oestrous period 
than at any other time. But individual cases were also found which did 
not show this behaviour. 

The secretion of milk has been attributed to the removal of the 
stimulus which caused the mammary gland to develop. Thus Lane- 
Claypon and Starling (-5) and others have attributed this action to the 
foetus, but Marshall and Hammond (2) found that the corpus luteuni 
caused the growth of the mammary gland in the rabbit, and that milk 
was produced whenever the gland had developed to a sufhcient extent. 

The removal of the causative stimulus in heifers cannot, however, 
be the cause of the secretion, as the fluid has been found in the udders 
of previously virgin heifers pregnant 'i-A montlis, at a time when the 
corpus luteum is still large and active. 

The problem thus presented itself: Is the secretion similar to that of 
colostrum and milk, resulting from the activity of the cells of the alveoh, 
or is it merely an exudation of lymph filling up the galactophorous 
sinuses, which have been formed by the development of the mammary 
gland? If the latter hypothesis be found correct, then at what stage 
in the development of the mammary gland do the typical constituents 
of milk first appear? 

Chemical investigation of the fluid. 

In all, four samples of the fluid were examined. The first two samples 
were obtained from heifers which had never been served, whilst the 
third and fourth samples were taken from the udders of the heifers 
during the first three weeks of pregnancy. 

The amount of fluid was only small, ea(^h heifer contributing on an 
average about 7 c.c. to the supply. The liquid was slightly opaque in 
appearance, though not possessing the dense opaqueness of milk. A 
slight sediment settled out on standing, but the fluid passed fairly 



H. E. Woodman and J. Hammond 1H) 

readily tlirough a filter paper, the filtrate tlieu being almost clear aud 
possessing the appearance of a protein solutiou. It was slightly viscous, 
gave a foam on shaking and did not show the amphoteric reaction of 
fresh milk, but was very faintly alkaline to both litmus and phenol- 
phthalein. 

A preliminary investigation of the first two samples was carried out 
as follows. A' small volume of the fluid was diluted with distilled water 
and one drop of acetic acid was added. On shaking, a white flocculent 
precipitate settled out in a manner characteristic of the separation of 
caseinogen from milk by this method. This was filtered off and was 
shown to be a protein by the usual tests. Furthermore, it answered to 
all the characteristic tests for caseinogen. (1) It was insoluble in water 
but dissolved readily in dilute soda and in lime-water aud was rejireciiji- 
tated by the addition of a drop of acetic acid. (2) When fused with a 
mi.vture of KgCOg and KNO3, the solution obtained on extracting the 
residue with water gave a strong phosphate test with nitric acid and 
ammonium molybdate. (3) The freshly precipitated protein was com- 
pletely soluble in excess of acetic acid. 

Further tests were made in order to ensure that the substance was 
not a nucleoprotein, which class of bodies gives most of the general 
reactions of the phosphoproteins. The presence of nucleoproteins in such 
a fluid would, moreover, not be at all surprising, especially if it resulted 
from the filtration of lymph through the walls of the alveoH. That the 
protein was caseinogen, however, and not a nucleoprotein was shown 
by: (1) The readiness with which it sjilit off its phosphorus as inorganic 
phosphate by mild alkahne hydrolysis. Under these conditions, nucleo- 
proteins do not yield phosphoric acid, the phosphorus remaining bound 
up in the nucleic acid group (li). (2) The behaviour of the fluid towards 
rennet. To 5 c.c. of the fluid were added 2 c.c. rennet extract. On placing 
in a bath at 10°, only a slight turbidity resulted after two minutes. On 
the further addition of two drops of calcium chloride solution to the 
mixture, however, the turbidity increased aud a curdy precipitate 
settled out. A clear mixture of 5 c.c. fluid, 2 c.c. rennet extract and 
1 c.c. calcium chloride solution was placed in a bath at 40°. In a few 
seconds, a turbidity spread throughout the hquid, followed by a rapid 
separation of curdy precipitate. This behaviour was consistent with the 
presence of caseinogen in the fluid, the rennet producing, in the presence 
of calcium salts, a precipitate of insoluble calcium caseate from the 
soluble calcium caseinogate. (3) The absence of any insoluble nuclein 
residue when the protein was submitted to peptic digestion. 



loo Fluid ohlaincd J'roiii Udders of Viryln Ilfifira 

The filtrate rcmaiuing after separation of the caseinogen was heated 
a short time in boihug water. This caused coagulation and the substance 
which separated in this manner was shown to be protein by the ordinary 
tests. The nature of the coagulable ])roteins was investigated in the 
following manner. After separating the caseinogen from another portion 
of the fluid, the clear filtrate was made exactly neutral by means of 
NjlO NaOH and was then saturated with inagnesiuiii suljjhate. The 
protein which was salted out by this ])n)cess was filtered olV and re- 
dissolved in water. On saturating this solution with magnesium sulphate, 
the protein was again throw n out. It possessed therefore the character- 
istics of a globuhn. 

The filtrate from the globulin was next acidified with acetic acid. 
A further precipitate of protein was obtained, its mode of isolation proving 
it to be an albumin. As far as it was po.ssible to judge from the tests, 
the fluid contained rather more globulin than albumin. 

The liquid remaining after removal of caseinogen by acetic acid and 
albumin and globulin by coagulation still answered to the biuret test 
and gave an appreciable precipitate with tannic acid. It still contained 
nitrogenous bodies of a simpler type, amongst which was a proteose, 
since a further precipitate was obtained on saturating the liquid with 
ammonium sulphate. The existence of non-protein nitrogen in the fluid 
was borne out by subsequent analysis. 

The fluid, after removal of proteins, was found to exert a slight 
reducing action when boiled for some time with Fehling's solution. The 
osazone, which was only obtained in small amount and with difficulty, 
had the characteristic appearance of lactosazone under the microscope. 
A sample of milk, tested similarly, showed ready and copious reduction 
of Fehling's solution and gave a good yield of lactosazone without diffi- 
culty. In all the samples of fluid examined, it was only possible to 
demonstrate the presence of lactose in small amounts. 

A prehminary extraction of the fluid with ether showed it to contain 
a small amount of fat. Sample 4 was found, by the Paper Coil method, 
to contain about 0-6 per cent, of a sohd yellow fat. This was saponified 
by boihug a short time with caustic soda. After acidifying, extracting 
with ether and allowing the solvent to evaporate, the residue possessed 
the characteristic odour of butvric acid. It followed that tlie fat in the 
fluid was the product of mamuuiry synthesis. 

The fluid did not contain any detectable amount of mucin, since 
this would have shown as gelatinous strands on the addition of acetic 
acid. The precipitate thus obtained w^as, however, perfectl}- flocculent 



H. E. Woodman and J. Hamjmond 



101 



and was, moreover, completely dissolved by the addition of excess of 
acetic acid. Mucin remains undissolved under these conditions. The per- 
fectly flocculent character of the precipitate obtained on adding alcohol 
to the fluid and stirring precluded the possibility of the presence of 
pseudo-mucins in the fluid. No other glucoproteins were found in the 
fluid, since on hydrolysing the total protein with hydrochloric acid, no 
reducing sugars were formed. 

The main constituents of the fluid were, therefore, caseinogen, 
globulin and albumin, with traces of fat, lactose and simpiler nitrogenous 
substances (proteoses). In view of the obvious importance of the fluid 
in its relationship to the ultimate colostrum and milk secretions, it was 
advisable, as fat as was possible, to conduct a quantitative enquiry. 
Unfortunately, no one sample obtained was large enough to permit of 
a complete analysis being carried out on it. The following figures were, 
however, obtained and give some idea of the quantitative composition 
of the fluid. The data for milk and a sample of colostrum containing 
roughly the same amount of protein are appended for comparison. 



Sa. 


nipl 


es 1 and 


•> 






Total jjrotcin 
Caseinogen 
Coagulable pi 


(total N y. 0-37 
'oteins 


) 5-82 
... 1-70 
... 3-29 


0/ 

/o 






,Sa 


III pie 3. 












Fluid 


Colostrum' 


Milk= 


Total protein (N-. 0-37) 

Caseinogen 

Globulin' 

Albumin 


0-37 % 
2-50 „ 
2-2S „ 
1-00 „ 


(MS % 
3-2.5 „ 
1-97 „ 
0-70 „ 




2-90 % 
Trace 
0-60 „ 




>Sa 


^itple 4. 












Fluid 


Milk' 


Colostrum^ 


ypecific gravity 
Total solids ... 

Ash^ 

Fat' 




1-014 

8-80 % 
0-80 ., 
0-63 .. 


1-032 

1- -«J /o 

0-75 „ 

3-40 „ 




1-050 

14-19 % 

0-96 „ 

4-21 „ 



' Crowther and Raistrick, Bloch. J., 10, 435. 1916. The sample represented the fourth 
milking after parturition. - Fleischmann. 

' The globulin was separated from the liquid, remaining after removal of caseinogen 
with acetic acid, by neutraUsing with N/10 NaOH and saturating with magnesium sulphate. 
After filtering, tlie precipitate was well waslicd witli saturated magnesium sulphate 
solution and its amount estimated by tlie Kjcldalil method. The albumin was isolated 
from the filtrate by acidifying with acetic acid and standing in boiUng water for a short 
time. " Fleischmann. 

^ Eugling. Sample taken 48 hours from parturition and contained about 6 % protein. 

" The ash gave the reactions for phosphate .and calcium. 

' Paper Coil method. 



1()"2 Fluid ubtdiiicd Jroiii Uddtrx uj Vinjiii lleij'ers 

Conclusions. 

A secretion lias hocii found to occur in small amount in tlie udders 
of virgin heifers which contains the characteristic proteins of colostrum, 
together with sUght amounts of fat, lactose and proteose. It follows 
that the initiation of mammary gland activity in the dairy cow is not 
necessarily dependent on pregnancy, but may be associated with the 
occurrence of the oestrous cycle. The processes which result in the elabora- 
tions of proteins would appear to be the most active iu this early stage 
of the glands activity, since only small amounts of fat and sugar seem 
to be formed. 

The fluid bears, on account of its globulin content, a closer relation 
to colostrum than to milk. The question arises as to whether the secretion 
continues to accumulate throughout pregnancy, or whether it undergoes 
gradual reabsorption. It is hoped to gain information on this and other 
points by following the changes in the yield and composition of the 
fluid at regular periods throughout the progress of pregnancy. 

REFERENCKS. 

(1) Mausilvll and HaLNAn. I'roc. Jtoyal Sue. 15., 89, lillT. 

(2) Hammond iind Maushall. Proc. Royal Hoc. 15., 87, lit! 1. 

(3) Woodman. Bioch. J., 15, 187, 1921. 

(4) Marsh.\ll. The I'hi/nioloyi/ oJUeproduclion, Low\on. I!(l(). 

(5) Lane-Claypon and Stakuno. Proc. Royal Soc. ii., 77, I'JOU. 
(0) Plimmek. Practical Urganic and Blo-Cliemislry, p. 4(10. 



{Received Januari/ ]''>/li, 1922.) 



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CONTENTS 



{Hirudo medic iftalis). — The Cockroach {Prripiamta amfru:aHA).~~'Y\\c Frcsh*Wjtcr Crayfish (AstfKHs) and The 
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Common Marine Mussel {Afy/tins eJulis). — The Lancelet {Ampkiaxus, syn. B ram hies Utna iafu:eoiatus). — The 
Spiny Dogfish [Acantkias. syn. Saualus) or ihe Spotted Dogfish {Scyiiium), a.ul the Skate {Haia). — The Frog 
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{LepHS cunicutus). — A Classification of the above Types.— Index. 



(II'. I-' '.HT 

Volume XII April, 1922 Part II 



THE CHEMICAL COMPOSITION 
OF ANIMAL BODIES 

By J. ALAN MURRAY, B.Sc. 

University College, Reading. 

(With 1 Text-figure.) 

In a previoiLs communication (i) the author pointed out that the chemical 
composition of the bodie.s of farm animals is determined when the per- 
centage of fat is known; for the composition of the uou-fatty matter is 
practically the same in all, it is not affected by the " condition" (fatness) 
and it varies only to a slight extent with the age of the animals. The 
averages, in round numbers, deduced from Lawes and Gilbert's analyses (2) 
were as follows: 





Ash 


Protein 


Water 


Young (growing) animals 
Adults 


... i 
(i 


20 

0-) 


76% 
72% 



These conclusions were necessarily more or less tentative in character 
because the data referred to only ten animals in all. viz., two pigs, three 
cattle and five sheep. More extensive data, recently to hand, aft'ord a 
striking confirmation of the general thesis and enable us to determine 
the influence of age and the individual variation with greater precision. 

Haecker(3) records separate analyses of the whole bodies of 49 indi- 
viduals (cattle) ranging from about 100 lb. to 1500 lb. live weight and 
from 3-.5 percent, to 35 per cent, of body fat. Swanson(4) records separate 
analyses of the whole bodies of 36 individuals (pigs) ranging from about 
201b.to4001b.live weight and from 5 per cent, to 60 per cent, of body fat. 

In Haecker's experiments the animals were arranged in groups ac- 
cording to size with intervals of about 100 lb. average live weight between 
them. The mean values for each group are shown in Table I below*. 

The empty body weight is, of course, the live weight minus the 
refuse, i.e. the contents of stomach, intestines and urinary bladder. The 
fat-free empty weight is the weight of non-fatty matter in the actual 
body. It is found from the empty body weight by 

m = M(100 - F)/100 
or, directly from the live weight, by 

m = M'(100- F ~ /J)/100, 

Jouin. of Agric. Sci. xii . 8 



104 The ('li('iiii(i(l ( 'nijijHisiliini of .[ ninidl liotUes 





t 


lublr 1. 


I'diiiiJOsUivti uj W/ioli lidd 


as (Cattle). 




No. 


I.ivc 
weight 

lb. 


body" 


Fat free 
empty 


Fat in 
empty 


LV>iii|>uBition n{ nun-fatty matter 


in 


1 


1 1 




group 


weight 


weight 


body 


Ash 1 


I'rf'toiti 


W.-.t.r 


I'lA 




lb. 


lb. 


% 


U 


ft 


U 




5 


107 


900 


86-4 


4-00 


4-44 


20-72 


74-84 


4-69 


4 


207 


163-2 


153-5 


6-01 


4-71 


20-36 


74-93 


4-33 


4 


301 


2461 


218-5 


11-19 


4-83 


21-13 


74-03 


4-37 


5 


416 


339-5 


303-8 


10-55 


4-86 


21-59 


73-55 


4-45 


5 


504 


418-1 


360-7 


13-73 


4-89 


22-19 


72-91 


4-55 


3 


614 


493-7 


424-5 


13-97 


5-33 


22-58 


72-08 


4-46 


4 


708 


587-8 


490-2 


16-57 


5-36 


22-31 


72-33 


4-15 


3 


815 


692-1 


563-8 


18-52 


5-20 


23-08 


71-72 


4-43 


3 


905 


774-5 


587-6 


24-08 


5-48 


23-27 


71-25 


4-24 


4 


1008 


880-7 


643-6 


26-91 


5-41 


23-41 


71-18 


4-31 


3 


1108 


976-3 


663-8 


3203 


5-62 


24-13 


70-25 


4-29 


3 


1204 


1077-0 


728-8 


32-32 


5-46 


23-66 


70-88 


4-:»3 


I 


1302 


1 150-5 


776-6 


32-50 


5-60 


23-40 


7100 


4-18 


I 


1413 


1237-0 


834-1 


32-58 


5-21 


23-95 


70-84 


4-60 


1 


1508 


1352-9 


843-9 


37-59 


5-14 


25-19 


69-66 


4-90 



79 












78 


— \ 










^ 












fo77 












3} 
























'' 












■1 76 






















g 
























S 












0) 












1 75 


X \ 








■ 


























^ 










f 


o 74 




f 




















a 












0) 












u 












S 73 




\^x 








Cu 












<v 




^S. X 








.^72 




X^X,^^ 








^ 












71 






X 


■*f^ "*" 




70 




1 1 


1 1 


X 

1 1 
1 i 





TOO 200 300 400 500 600 700 800 900 1000 1b. 
Fat-free empty wciglit 
Fig. 1 



J. Alan Murray 105 

where F and R are respectively the percentages of fat and refuse in the 
empty weight M and in the live weight M' respectively and ///. is the 
fat-free empty weight. 

It will be seen, on reference to the table, that the percentage of 
water in the non-fatty matter diminishes progressively as age (weight) 
increases, and the percentages of ash and protein are correspondingly 
increased. There appears to be no consistent relationship between the 
ratio of protein to ash and the age of the animal ; the variation observed 
must therefore be ascribed to individuality, i.e. to unknown causes. The 
mean value of the ratio PjA is 4-392 ± 0-215*. In other words, protein 
forms from 79 per cent, to 84 per cent, of the dry substance of the 
non-fatty matter and ash the remaining 16 per cent, to 21 per cent. 
The mean percentages of these ingredients may therefore be found by 
the formulae 

P = U-815 (lOU - W); A = 0-185 (100 - W) 

where P, A and W are the percentages of protein, ash and water respec- 
tively in the non-fatty matter. 

It only remains therefore to find an expression for determination of w. 
It is obvious that the relationship of water to weight is not one of simple 
proportion; but when the points are plotted out a definite order can be 
clearly discerned. The smooth curve in the diagram (Fig. 1 ) corresponds 
to the formula w = 90Hr '"''*"'', where m is the fat-free body weight (lb.) 
and w is the percentage of water in the same. The points corresponding 
to the mean vahies of the observed data are indicated by ^- and it will 
be seen that the curve passes through or near to most of them. The 

mean deviation, jr, S (d), (of all the individual cases) from the curve is 

0-71. 

In order to test these conclusions the composition of the three cattle 
analysed by Lawes and Gilbert was calculated from the live weight 
and percentage of fat and the results are given for comparison with the 
observed data in the table below. 

The discrepancies between the observed and calculated results do 
not exceed the limits of individual variation in Haecker's data. In the 
case of the two oxen they are attributable mainly to deviation from the 
mean ratio of protein to ash. In the case of the calf they are attributable 
mainly to deviation from the curve of relationship of water to weight. 



s/y- 



((/-) = 0-319. 



106 Tlie Chemical Coiitposltion of Aii'nnnl liodies 

Tabic 11. Coiiijwsitiuii uf Adtiul Bodies. 

Fat calf Half-fat ox Fat ox 





Calculated 


■ -^ 
Observed 


Calculated 


Observed 


Calculated 


Observe 


Water ... 


0/ 

/o 
... 62-79 


o/ 
o 

05- Hi 


o/ 

/o 

5.5-71 


o/ 

o 

5()10 


O' 

o 
47-79 


o/ 
48-40 


Protein . . . 


... 17-80 


15- 70 


1914 


18-08 


Ki-45 


15-42 


Ash ... 


4-06 


3-92 


4-3.5 


508 


3-74 


417 


Fat 


... (1.5-29) 


1.1-29 


(20-80) 


20-80 


(3202) 


3202 




K)0-00 


100-07 


1(K»-00 


100-0(> 


10000 


1 0001 


Hefiise ... 





3-2 





8-2 





lid 


Fasted live 


weight (lb.) 


2r)9 




1232 




Ul'.l 



The coiupo.sition o( the lattciiing increa.se (oxen) calculated from tlie 
data actually recorded by Lawes and Gilbert is as follows: 

Fat 94-54%, Water .j-49 %, Protein O-G %, Ash - ()-«4 %. 

The percentages of water and protein in the increase might be regarded 
as an indication of growth, but as the animals were four years old it is 
improbable that any increase in size occurred, or that such increase, if 
it did occur, would beaccom])anied by a loss of 1-71 lb. of ash ingredients. 
Further, as the ratio of water to protein in the increase is 9/1 whereas 
in the whole body it is only 3/1 it is more reasonable to attribute the 
apparent increase in non-fatty constituents to difference in composition 
of the two animals. The individual variations revealed by Haecker's 
data are more than sufficient to justify this assumption. The inference 
therefore is that, in fully grown animals the fattening increase consists 
entirely of fat. Tiiis, of course, is acceptable on other grounds, but those 
who have maintained it have had to do so in the face of numerical data 
which could lie (|uoted against it and i>f w hich. liitlicrto. lu) satisfactory 
explanation was fcuthcomiiig. 

It is to be expected that iu other animals I lie compo.siiioii of t lie uou- 
fatty matter will alter with age iu much the same manner as in cattle, 
and the author anticipated no difficulty in tracing this relationship in 
pigs from Swanson's data. A preliminary survey, however, indicated 
that these results might be affected by the differences in feeding as well 
as by the age and individuality of the animals, and that the variations 
due to these combined causes would make it difficult clearly to distin- 
guish the influence of any one. The best that could be done, it seenu'd, 
was to divide the data into three groups as shown in the table below. 

It appears that the ratio of protein to ash in pigs is higher than in 
cattle, but the percentage of water in the non-fatty matter alters with 
age not only in the same manner but even in the same degree. The latter 



J. Alan Murray 



107 



inference, however, must be to a large extent discounted in view of the 
magnitude of the probable errors. It could not have been deduced from 
Swanson'.s data alone and until confirmed liy further evidence it must 
be regarded as hypothetical. 

Table III. Influence of Age (Pigs). 

(.'(imposition of non-tatty matter 





No. of 
animals 




^ 






empty weight 


Ash 


Protein 


Water 


PIA 


Under 60 Ih. 


10 


4-15 + 0-87 


19-03^2-55 


76-834312 


4-60 


6U-1(X» „ 


10 


3-91 ! 0-36 


19-89 i 1-35 


76-02 L 1-41 


5-09 


UIO-170 .. 


11 


4-01 0.30 


20-90 (1-96 


7509 1-04 


5-21 



The test of comparison with Lawes and tiilbcrt"s data is not con- 
clusive, but, so far as it goes, it indicates that the inference is perhaps 
more reliable than might be supposed. For this purpose the percentage 
of water in the non-fatty matter was calculated, as before, by the 
formula w = 90y;r'°^*"^; but owing to the difference in the ratio of 
protein to ash different coefficients must be used for these ingredients, 
thus 

P = 0-83 (100 -^W);A= 0-l('i (100 - W). 



The results are as follows: 



Store pig 



Fat pig 







Calculated 


Observed 


Calculated 


Observed 


Water 
Protein . . . 
Ash 
Fat 




. 58-28 

. 14-28 

2-86 

. (24-.59) 


58-15 

14-45 

2-82 

24.59 


42-71 
11-13 

2-22 
(43-94) 


43-01 

11-35 

1-72 

43-94 


Live weight 


(lb.) 


— 


94 


— 


185 



In the following table the data are grouped according to the kind of 
food consumed by the animals. 

Table IV. Influence of Food (Pigs). 



Food 


No. 

of 

animals 


Empty 
weight 


Fat-free 
empty 
weight 


Fat in 

live 
weight 


Composition of non-fatty matter 


Ash 


Protein 


Water 


PIA 


Corn alone 


5 


lb. 

80-27 


lb. 
47-45 


o/ 
36-69 


o/ 

o 

3-56 




17-93 


o, 
78-51 


6-03 


Corn and ash ... 


5 


130-74 


68-25 


37-03 


4-16 


17-39 


78-45 


4-17 


Corn and protein 


10 


217-94 


109-31 


48-01 


3-54 


21-34 


75-12 


li-07 


Corn, ash and | 
protein ...\ 


5 


226-74 


118-57 


45-5.5 


4-41 


21-17 


74-42 


4-82 



In order to interpret these results correctly it is necessary to make 
allowance for the difference in size, i.e. to compare them with data 



108 The Chonical Comjiosition <>/ Aniinnl Jio(/ies 

calculated for animals of the same size by means of the formula above, 
as follows: 





Corn aliiiit' 


Com and ash 


Com and protein 


Corn, asli and 
protein 




Cald 


Obseril 


Card 


ObserM 


Car.l 


Obser'd 


Cal'd 


Obserd 


Water 

Protein 

Ash 


/O 

78-25 

18-12 

3-63 




78-51 

17-93 

3-58 


77-21 
18-98 

:! SI 


78-45 
17-39 

lie. 


75-91 

20-07 

102 


75-'l2 

21-34 

3-54 


o 

75-68 

20-26 

406 


o/ 

/o 

74-42 

2117 

4-41 



The correspondence between the observed and calculated data is, 
throughout, as close as could be expected in any circumstances. The 
inference therefore is that the differences which do occur should be 
attributed to individual variation and that the effect of the additions 
to the food was nil. It is to be observed, however (Table IV), that the 
addition of ash to the corn has reduced the ratio of protein to ash whereas 
the addition of protein has produced no appreciable alteration in that 
ratio. When ash and protein are added together the ratio is reduced only 
about half as much as by addition of ash alone. When the results are 
stated as percentages of the several ingredients these effects are obscured 
by the large amount of water present. Swanson remarks that the addi- 
tion of protein and ash accelerates the growth of the animal but does 
not affect its composition. 

The only data relating to sheep at present available are those of 
Lawes and Gilbert and. as these refer to only five individuals, they are 
inadequate for purposes of the present investigation. They may, however, 
be used to test the applicability of the formula deduced for cattle. Thus 
it is found that the ratio of protein to ash (-1-3) is practically the same 
but the coefficient in the formula for water must be reduced, i.e. 
w = 87»r "'*'''. Calculated on this basis the results are as follows: 

Fat-free live weight (lb.) 50-63 70-82 73-84 74-20 123-80 

Fat (per cent, of live weight) ... 28-50 23-50 18-70 .35-60 45-80 

Ratio of protein to ash 4-43 4-34 4-67 4-34 3-75 

W'ater(percent. of non- 1 observed 75-91 74-42 76-10 74-63 71-80 

fatty matter) ... (calculated 75-46 74-56 74-40 74-42 73-07 



Amount of Body Fat. 

In farm animals generally the ratio of fat to non-fatty matter varies 
within wide limits. It depends lai-gely upon the quantity and quality 
of the food and, to that extent, it can be controlled. Elsewhere(i) the 
author has inferred that the maximum amount of body-fat is about 



J. Alan Murray 109 

liO per cent, of the live weight. This estimate was based on the increase 
ill basal katabohsm, determined by Armsby("'), in an ox. Pigs probably 
have a smaller capacity for food than ruminants of the same size; but, 
on the other hand, the food which is customary and suitable for them 
has a much higher productive index (ratio of dynamic to total energy). 
It was recognised that the result depends upon these factors and that 
any animal would require an indefinite time to attain the maximum 
degree of fatness of which it is capable under any given conditions. The 
fact that over 60 per cent, of body fat was recorded in two cases in 
Swanson's data indicates that the theoretical maximum is probably 
higher for pigs than for ruminants. At any rate it disposes of the objec- 
tion that the estimated maximum (60 per cent.) is far beyond what had 
hitherto been recorded. The theoretical minimum of body fat is zero. 
The lowest recorded in the data under consideration is 5-27 per cent, in 
the pigs and 3-64 per cent, in the ruminants. There is no reason to 
believe that these records are the lowest attainable in living animals. 

Attention may be called to the fact that the diminishing percentage 
of water in the non-fatty matter coincides with diminishing rate of 
growth and to the possible connection between these phenomena. The 
biological significance of the constants in the formula for water may also 
prove a matter of interest to pliysiologists. 

Summary. 

Animal bodies are composed of fat and non-fatty matter. The relative 
proportions of these two ingredients vary within wide limits but can be 
controlled by food. The non-fatty matter consists of water, protein and 
ash. The percentage of water varies with the age of the animal in a 
definite manner. This has been determined with tolerable certainty for 
cattle. The available evidence indicates that the same formula is applicable 
to pigs and, with .slight modification, also to sheep, but these inferences 
require confirmation. The ratio of protein to ash is the same in sheep 
as in cattle but in pigs it is higher. In any case it does not alter with 
the age of the animal but it may be influenced to a certain extent by 
the food. Individual variation is wider in pigs than in ruminants. The 
average composition of the whole body at any stage can be calculated 
when the live weight and percentage of fat in it are known. 



110 The Chemical Composition of Animal Bodies 



i:k1'KRFA'('rs. 

(1) MruKAV. J. A. lOlfl. Meat Produclion. .I„iir». Ai/rir. ,SV,. 9. I>art 2, 174. 

(2) I.AWKs and Gilbkrt. Rothcim-slfil MemoirK, 3. 

(3) Hakckkk, T. L. 1920. Investigations in Beef I'rodiiclion. liuU. 193, I'niv. 

Minnesota Agiie. Ex per. Sta. 

(4) SwANSON, r. 0. 1921. Krteet of Rations on Developnu'nt of I'igs. Joiirn. Aijric. 

lies. 21. .5. 
(.')) Arm.sby, H. p. 1917. InHuenee of the Degree of Fatness of Cattle ujioii tlieir 
Utilisation of Peed. Jowrn. Agric. Rex. 11, 10. 



{Received 18 Janiuiri/, 1922.) 



THE EFFECT ON THE PERCENTAGE COMPOSITION 
OF THE MILK OF (a) VARIATIONS IN THE DAILY 
VOLUME AND {!>) VARIATIONS IN THE NATURE OF 

THE DIET. 

By WILLIAM TAYLOE, M.D., D.P.H. {Carnegie Research Scholar), 
AND ALFRED D. HUSBAND, A.I.C. 

(From the Rowett Research Institute, Aberdeen.) 

(With 4 Text-figures.) 

The study of lactation has ahiiost always been undertaken from one of 
two very diverse points of view, the physiological and the commercial. 
The chief aim of the physiologist has been to determine, either the origin 
of the various constituents of the milk and the method of their elabora- 
tion, or the extent to which internal secretions affect the flow of milk 
by their initiation, inhibition or stimulation of milk secretion. From the 
commercial or agricultural point of view, on the other hand, the chief 
interest has centred round the problem of the production of butter fat, 
and a very large number of experiments have been conducted to deter- 
mine by what method of feeding a cow could be caused to give the 
maximum yield of milk with the highest percentage of fat. 

Much of this work is of great value, but in many cases the fat is the 
only constituent of the milk which has been determined separately, the 
other constituents having been estimated together as milk solids other 
than fat. 

With regard to the diets, unless the calorific consumption is stated, 
a simple addition of extra protein or fat to a ration does not allow of a 
judgment being formed as to whether the alteration in the daily volume 
and percentage composition of the milk is due to protein or fat per se, or 
simply to an increase in the calorific value of the ration. This considera- 
tion would appear to have been lost sight of in some cases. 

The most complete investigation of the influence on the percentage 
composition of the milk of feeding with an excess of one of the energy- 
yielding constituents of the food is that of Voit(i), who worked with a 
bitch. He found that, while an excess of one constituent in the food 



11 "2 PerecntfUfe Composttioit of Milk 

teiulod to uive ;i slijilit iucrease in tlic percentage of that constituent in 
the milk, the deviation from the normal was comparatively slight. 

The work done since V'oit's time has produced rather contradictory 
results. For example, Ingle (2) found that a protein rich diet increased 
both the yield of milk and the percentage of fat, while Crowther(3) 
found that a food rich in protein gave a decrease in the yield but an 
inc-rease in the fat content. Again, Jordan and Jenter(4) show that the 
amount of fat in the food is without influence on the percentage of fat 
in cows" milk, while Morgan, Berger and FingerUng("i) found that a fat 
poor diet produced in goats a milk with a low percentage of fat. 

There is difficulty in correlating contradictory results such as these, 
and the difficulty is increased where there is uncertainty as to the calorific 
value of the food digested and absorbed, and, further, when no account 
has been taken of the probable influence on the percentage composition 
of a change in the daily volume of milk secreted. In the voluminous 
literature on milk there is very Uttle reference to the influence of volume 
on composition — except in the case of the fat — and it is possible that this 
may explain some of the contradictory results obtained by different 
workers on the question of the influence of ditt'erent diets, 

PRESENT IXVESTIGATIOX. 

The present investigation was undertaken to determine : 

A. To what extent variations in the daily volume (or rate of secre- 
tion) of the milk were accompanied by variations in its percentage 
composition. 

B. To what extent the percentage composition of the milk could be 
influenced by diet. 

The experimental animal was the goat, and throughout the investiga- 
tion the milking was done at 9 a.m. and 5 p.m. The total volume of the 
24 hours' secretion of milk was measured, mixed and anal)'sed daily, the 
percentages of total protein, casein, albumin plus globulin, non-protein 
nitrogen, fat, lactose and ash being determined. 

METHODS OF ANALYSIS. 

Total Protein. The total nitrogen was estimated by the Kjeldahl 
method, the protein factor G-38 being used for the determination of total 
protein. 

Casein. The casein was precipitated with acetic acid and filtered off, 
after which tlie nitrogen was determined by the Kjeldahl method, the 
same protein factor. (!-38, being made use of. 



W. Taylor and A. D. Husband 



113 



Albumin and Globulin. These were precipitated by tannic acid from 
the filtrate obtained in the estimation of casein, after which they were 
estimated together as described above for casein. 

Non-Protein Nitrogen. This was estimated by the difference between 
the percentage of total protein and the sum of the percentages of casein, 
albumin and globulin. 

Fat. By the Soxhlet method. 

Lactose. Fehhng's method and Benedict's method were both made 
use of; but in the individual experiments one method was adhered to 
throughout. 

A.sh. By the ordinary method of ignition. 

EXPERIMENTAL. 

A. The Effect of Variations in Volume on the Percentage Com- 
position OP THE Milk, with an Animal on a Diet of Constant 
Composition. 

Experiment I. (Analytical Data, Table I.) 
In this experiment a series of milk analyses was carried out from 
day to day in the case of a goat fed on a diet of hay and a mixture of 
meals made from locust beans, earth nuts and oats, this mixture being 
sweetened with sugar. The animal was allowed to eat to its appetite, 
but the nature of the diet was constant throughout. Owing to the con- 
finement, the monotonous diet and the advanced stage of lactation, the 
volume of the milk fell steadily throughout the experiment with, as a 
rule, but slight variations from day to day. 

Table I. 











Alb 


jmin 


Non- 
















+ 


protein 










Volume 


Protein 


Casein 


globulin 


nitrogen 


Fat 


Lactose 


Ash 




c.e. 


0' 

/o 


o/ 

/O 


o- 


/o 


% 


o/ 
/o 


o/ 


1 


310 


4-50 


307 


1-20 


0-23 


4-54 


4-26 


0-98 


2 


290 


4-73 


3-38 




14 


0-21 


4-85 


4-28 


0-97 


3 


320 


4-.50 


3- 12 




15 


0-23 


5-24 


4-24 


0-98 


4 


310 


4-39 


301 




15 


0-24 


5-80 


4-21 


0-94 


5 


2.55 


4-59 


319 




I(i 


0-23 


5-55 


419 


0-94 


6 


250 


4-72 


334 




20 


0-18 


5-12 


4-24 


0-90 


7 


245 


4-82 


3-37 




24 


0-21 


5-56 


4-24 


0-98 


8 


240 


4-80 


3-41 




24 


0-21 


502 


4-35 


0-97 


9 


225 


500 


3-,54 




28 


019 


5-38 


4-30 


100 


10 


235 


4-89 


3-39 




28 


0-21 


5-76 


4-26 


0-98 


11 


185 


5-25 


3-70 




35 


0-20 


5-56 


4-21 


100 


12 


190 


5-17 


3-63 




36 


019 


6-01 


4-30 


102 


13 


220 


4-82 


3-39 




25 


0-18 


0-86 


4-26 


0-97 


14 


240 


4-.54 


314 




24 


010 


6-37 


4-26 


108 


15 


170 


501 


3-52 




25 


0-25 


0-30 


4-20 


0-98 


10 


145 


5-40 


3-79 




30 


0-24 


5-94 


4-30 


104 



114 



Percentage Composition of Mill: 



Haiiiiniiii(l and Ha\vk(ii), ami otluTs, liavc shown that an inverse 
relationship exists between the percentage of fat and the daily volume. 
This was well brou<;ht out, but it may be seen from ¥\'^. 1 that the 
percentage of protein also varied inversely as the volume with a regu- 
larity at least equal to that of the fat, though the extent of the variation 
was less marked. The percentage of lactose maintained a very constant 
level, varying between M!) per cent, and A-'M) ))er cent. Tiic percentage 
of ash, which varied from 0-94 per cent, to 1-(I8 per cent., may l)e seen 
from the analytical data to have shown a tendency to rise with the fall 
in volume towards tlie end of the e.xperuiient . 



10 11 12 13 14 15 16 Days 



6% -^ 



300i-p-> 




■ Fat 



riiitrui 



Lactose 



Volume 
lOOc.c.-* 

Fig. 1. Showiiii-' the effect of variatiims in voliiiiie oi\ tlie percentage 
composition of tlie milk. 

Experiment II. (Analytical Data, Table II.) 

The fluctuations in volume from day to day having been compara- 
tively slight in the preceding experiment, advantage was taken in this 
case of the decrease in yield brought about by an absence of food, and 
the increase which follows the resumption of feeding. 

A goat was fed for eight days on an unrestricted diet of hay and 
oatmeal, and on the 9th and 10th days no food was taken. PVom the 
11 til dav onward the feeding was resumed. 



W. Taylor and A. D. Husband 115 

Table II. 

Volume Protein Fat Lactose Ash 

n p o/ 0/ O 0/ 



1 


500 


2-97 


3-95 


4-33 


0-82 


o 


480 


309 


4-32 


407 


0-84 


3 


460 


307 


4-08 


412 


0-88 


4 


470 


3-00 


4-09 


4-00 


0-87 


5 


470 


2-91 


4-45 


4-00 


0-89 


6 


460 


2-95 


4-47 


4-07 


0-79 


7 


460 


2-98 


4-53 


4-07 


0-83 


8 


460 


2-93 


3-95 


4-07 


0-79 


9 


350 


3-02 


5- 17 


3-80 


0-80 


10 


50 


9-24 


1016 


2-31 


1-37 


11 


340 


2-88 


5-40 


4-00 


0-98 


12 


350 


2-52 


4-81 


4-23 


0-91 


13 


320 


2-93 


5-53 


4-20 


0-94 


14 


230 


3-23 


5-98 


4-21 


0-96 


15 


275 


2-93 


5-71 


405 


0-89 


l(i 


300 


2-77 


5- 16 


3-82 


0-90 


17 


275 


2-97 


4-97 


412 


0-92 



The tollowinji extract from tlie analytical data brings out very clearly 
the inter-relation.shij] of volume and composition. 

Volume Protein Fat. Lactose Ash 

,. ,. o o O O' 

*^-^- o O O n 

Last dav before starvation ... 460 2-93 3-95 407 0-79 

Second dav of „ ... 50 9-24 1016 2-31 1-37 

after 3.X) 2-52 4Sl 4-23 O'.ll 

It will be seen that with the great fall in volume on the second day 
of starvation there was a rise in the percentages of all the constituents 
of the milk, with the exception of the lactose, the percentage of which 
came down with the volume. 

The percentage of fat, as was e.xpected, showed a marked rise, but 
the percentage of protein was found to rise markedly also ; and the 
percentage of ash, although affected to a less extent, distinctly increased 
with the great and sudden fall in the volume of milk. 

The lactose, a constituent of the milk the percentage of which is 
normally very constant, showed, on the other hand, a percentage de- 
crease as definite as the percentage increase in the protein, fat and ash. 

With the renewed consumption of food the daily volume of milk 
increased, with, at the same time, a close approximation to its previous 
percentage compo.sition. 

Experiments III and IV. (Analytical Data, Tables III and IV.) 

These experiments were conducted to determine whether the inter- 
relationship of volume and composition, maintained during Exps. I and 
II, would still hold good during the physiological increase and decrease 



116 Percentage Conipositum of Mill, 

in volume wliich takes place at the commencement and cessation of 
lactation respectively. 

Table 111. 











Alhumin 


Non- 
















■f 


protein 










\(iliiiue 


Protein 


Casein 


"lobulin 


nitrOKcn 


Kat 


Lactose 


Ash 




c.c. 


/o 


o/ 
/o 


% 


% 


% 


% 


O' 
n 


1 


1.30 


508 


302 


2-66 


0-30 


807 


3-65 


0-81 


3 


250 


411 


2-.i5 


1-37 


019 


5-56 


4-39 


0-79 


5 


330 


407 


2-59 


1-31 


017 


5-91 


4-70 


0-81 


7 


3t)5 


3-88 


2-45 


1-25 


0-18 


5-70 


4-72 


0-78 


i» 


400 


3()5 


2-44 


1-05 


Olf) 


608 


502 


0-68 


11 


500 


3-81 


2-49 


1-08 


0-18 


5-18 


5- 10 


0-76 


13 


430 


3-62 


2-29 


1-03 


0-30 


5-22 


506 


0-75 










Table IV. 
















Albumin 


Non- 
















■¥ 


protein 










\'()liime 


Protein 


Casein 


globulin 


nitrogen 


Fat 


Lactose 


Ash 






o/ 


o/ 


o/ 


o/ 


O- 


0/ 


O' 




c.c. 


,0 


/o 




/o 


.0 


/o 


/o 


1 


400 


5-36 


4-26 


0-93 


0-17 


5-53 


406 


0-92 


•> 


340 


5-65 


4-55 


0-98 


012 


6-02 


406 


0-96 


3 


275 


(il7 


4-91 


1-05 


0-21 


6-53 


4-24 


0-96 


4 


250 


0-52 


5-25 


114 


0-13 


7-83 


4- 16 


0-99 


o 


210 


0-60 


5-30 


1-20 


0-16 


7-20 


4-05 


101 


(i 


185 


7-14 


5-59 


1.39 


0-16 


7-96 


4-05 


1-02 


7 


110 


8-08 


6-38 


1-.55 


0-15 


8-86 


4 16 


112 


8 


80 


801 


0-84 


1-66 


0-11 


8-63 


3-71 


M3 


9 


55 


8-47 


(i-61 


1-73 


0-13 


9-70 


3-(l2 


108 


10 


35 


9-96 


7-5(> 


2-28 


0-12 


11-36 


3-07 


1-30 


U 


45 


10-46 


7-64 


2-61 


0-21 


10-94 


2-27 


1.33 


12 


35 


8-96 


6-50 


2-45 


0-01 


9-31 


2-li2 


119 


13 


30 


9-22 


6-68 


2-57 


y 


8-40 


2-89 


1-20 


14 


20 


9-20 


4-90 


4-20 


0-10 


9-44 


2-35 


1-36 


15 


25 


906 


5-88 


306 


0-12 


9-06 


2-27 


1-18 


16 


15 


9-88 


6-64 


3-21 


003 


9-08 


2-20 


1-36 


17 


15 


10-88 


7-28 


3-56 


0-04 


9-49 


2-20 


1-42 


18 


.5 


11-20 


7-64 


3.16 


? 


7-65 


— 


1-41 



It may be seen from Figs. 2 and 3 that tlie changes in the percentage 
composition of the milk which accompanied alterations in volume, due 
to these causes, were the same in nature as the changes which accom- 
panied the fluctuations in volume brought about in the preceding experi- 
ment by the two days' starvation. 

(During E.xp. Ill, commencement of lactation, a milk analysis was 
carried out only on alternate days.) 

As a result of these and other similar experiments, not described here 
for reasons of economy of space, it seemed possible to formulate the 
following general principle : That, on a diet of constant composition, the 
percentages of all the (-oustituents of the milk, with the exception of 
the lactose, tend to vary inversely as the daily volume of milk secreted ; 



AV. Taylor and A. D. Husband 



117 



auil that the percentage of lactose, whih^ uoriiially very coustant, tends 
to vary directly as the voliune, this tendency being particularly apparent 
at the beginning and end of lactation. 



11 13 Doys 




Prut fill 

100c.c._^ 

Fig. 2. Begiiiniiig of Lactation. 

1 2 3 4. 5 6 7 8 9 101112131415161718 Days 

PioteiD 



1 0°;. 



400c.e.-> 




Fat, 



200c.c.-> 



Oc.o.-^ 



Lactose 



Volume 



Fis. 3. End of Lactation. 



118 Percentage Composition of Milk 

B. The Influence of Diet on the Volume and Percentage 

Composition ok tiik Mii.k. 

Experiment V. (Analytical Data, Table V.) 

The above prin(i])le haviiii: been established on a diet of constant 
composition, it was desired to see to wliat extent it niiyht be departed 
from on diets which were abnormally hi<ih in some one of tlie three 
enerjjy-yielding constituents of the food, viz., protein, fat and carbo- 
hydrate. 

Table V. 

(Average daily volume and average percentage com])osition of the 
milk for each dietary period.) 











Allnirnin 

1 


Non. 
protein 










\'olunie 


I'rotiMn 


Casein 


glol)nIin 


nitrogen 


Kat 


Lactose 


Ash 


Nature of Oiet 


o.c. 


"„ 


o/ 
o 


o 


0' 

o 


o/ 
.o 


,0 


0/ 

o 


High f.it (14 days) 


;iit.'-) 


4- 14 


3-20 


0-94 


0-20 


4-40 


4-23 


0-90 


Normal (!) days) 


:!!!» 


4(i() 


3-39 


1-27 


0-23 


.5-33 


3-90 


110 


High protein ( l(i days 


) :m 


4-34 


3-23 


Ml 


0-39 


3 23 


41)."> 


0-93 


Normal (.'> day.s) 


380 


4-42 


3-43 


0-99 


(l-2(i 


4-40 


3-91 


108 


High r-arbohydratel 
(13 day's) )' 


439 


4-42 


334 


l-OS 


Oil) 


3-52 


4-17 


0'92 



(In ciilculatiug the average percentage of protein the iioii-proteiii 
nitrogen was not included.) 

To do this the normal calorific intake of the goat was first estimated 
by feeding her for 20 days on an unlimited and congenial diet of known 
composition, weighing the amount of food left over at the end of each 
day, and finally calculating the average daily calorific consumption. On 
this basis each of the experimental diets was made up. 

In this experiment, a high fat, a high ])rotein and a high carbohydrate 
diet were given, a period of normal diet intervening between each period 
of special diet. The average daily volume of the milk has been worked 
out for each dietary period, and against this has been set out the average 
percentage composition of the milk for the corresponding period. The 
first two days after each change of diet have, however, been omitted 
in the calculation of these averages. For reasons of space the results of 
the individual milk analyses from day to day have not been given in 
the tables, hut only the average daily volume and average percentage 
composition for each dietary period. (For details of diets, see Table VI.) 



W. Taylor and A. D. Husband 



119 



Table VI. 
High Fat Diet. 



Hay 

Earth nuts 243 

Oatmeal 102 

Locust bean meal 2ti(j 

Sui,'ar 7 1 



)gms.' 



(Protein 121-7 gms. 

Fat 136-2 „ 

I Carbohydrate .599-9 „ 



Hiijli Protein Diet. 



Hay 560 gms. ) (Protein 305-1 gms. 

Plasmon 300 "„ [ = -^ Fat 41-2 ., 

Oatmeal 335 .. ] (Carbohydrate .504-5 „ 



High Carbohydrate Diet. 

Hay 586 gms. 

Locust bean meal 374 „ 
Maize meal 531 „ 

Oatmeal 9.S „ 



(Protein 105-3 gms. 

J Fat 40-3 „ 

(Carbohydrate 933-2 „ 



= 4225 calories. 



= 3702 calories 



= 4633 calories. 



The result of this experiment can most clearly be seen by consulting 
Fig. 4. In this graph the horizontal lines represent average volumes and 
average percentages, the sloping lines connecting the various horizontal 
levels representing the two days at the beginning of each dietary period 
which have been left out in the calculation of the averages. 



5% 



700 e.c. 




300 c^ 



Fig. 4. Showing the effect of diets of different composition on the volunie 
and percentage composition of the milk. 
Journ. of Agric. Sci. xii 



120 Percentage CoinposUioit of Milk 

It will be seen that jn no case was there a direct increase in the per- 
centage of that constituent of the milk corresponding to the constituent 
of the diet which was present in excess. The protein, fat and ash all 
tended to vary, albeit to different degrees, inverseh-, and the lactose 
directly, as the daily volume of milk secreted. It is true that with the 
different diets variations in the percentage composition of the milk were 
produced, but these variations were of such a nature, and took place 
to such a degree, as could be accounted for by the variations in the rate 
of secretion, and, therefore, in the daily volume of the milk. 

Fig. 4 brings out very clearly the direct relationsiiip existing between 
the percentage of lactose and the daily volume of milk secreted. 

Several different feeding experiments were carried out with, in every 
case, results similar to those stated above. In one of these it was con- 
sidered that a high protein diet had markedly stimulated the rate of 
milk secretion. In this experiment, tliercfore, it is worthy of note, the 
high protein diet was made up in such a way that it was of lower calorific 
value than either the high fat diet which preceded it, or the high carbo- 
hydrate diet which followed it. The greatest secretion of milk, however, 
was got on the diet of lowest calorific value, viz., the high protein diet. 
The following are the main features of the diets set out against the average 
daily volumes of milk obtained. 

Volume of 
C'aloritiu value of diet milk 

High fat diot ... 4230 calories (containing 136 gms. 400 c.c. 

of fat) 
High protein diet ... 3700 calories (containing 305 gnis. 540 c.c. 

of protein) 
High carbohydrate diet 4630 calories (containing 933 gms. 440 c.c. 

of carbohydrate) 

There is one constituent, however, not of the milk but in the milk, 
the percentage of which was found to have a direct relationship to diet, 
viz., the non-protein nitrogen. This was estimated by the difference in 
the figures for the percentage of total protein and the sum of the per- 
centages of casein, albumin and globulin. Wliilc not protein, therefore, 
it is expressed separately in terms of protein, in view of the fact that 
it was included in the estimation of nitrogen from which tfie percentage 
of total protein was calculated. It was found to vary from about 0-1 
per cent, to 0-4 per cent, with the amount of protein taken in the food. 
(This is being dealt with in another })ubUcation.) 



W. Taylor and A. D. Hitsband 121 

DISCUSSION OF RESITLTS. 

It seems justifiable to conclude from the results of these experiments, 
that with the exception of the non-protein nitrogen, which is not a 
product of the mammary gland, diet has no direct influence on the 
percentage composition of the milk. It has. however, an indirect influence 
by reason of its effect on the daily volume, but the percentages in which 
the various constituents of the milk will be present in any particular 
daily volume, obtained by some special method of feeding, will be the 
same as those in which they would be present in the same daily volume 
were it obtained in the ordinary course of lactation. 

Indeed, the inverse relationship of percentage of fat and daily volume 
is so unvarying on the average, as Tocher (7) points out in the case of the 
cow — in his statistical analysis of milk records, where he deals with the 
milk of thousands of cows — that it may be stated, and illustrated by a 
graph, with the mathematical precision of a proposition in Euclid. He 
says: "It will be seen that there is a direct proportional relationship 
between quantity and average quality. 

"Given two known values of average quahty for any two types of 
quantity, a straight line joining the two values of average quality and 
extended on either side will give the average quahties for all other types 
of quantity, average quahty being represented in value by a straight 
line proportional to its value standing at right angles to the base line 
of quantity at a point corresponding to its appropriate type of quantity." 

By the term " quality "' in the above statement is understood, of 
course, the percentage of fat. 

While this is true of the fat it is probably no less true of the protein. 
Throughout the present investigation the percentage of protein in the 
milk and the daily volume varied inversely with a regularity at least equal 
to that of the fat. It is true that these percentage variations were not 
so marked as in the case of the fat, the inverse rise and fall with each 
variation in volume having been less, as a rule, but they took place from 
da)^ to day with an equal consistency if to a less degree, even during 
periods of special dieting. 

The probabihty is, therefore, that it will be found from a statistical 
analysis of milk records — when the requisite data become available — 
that the relationship of average percentage of protein to each particular 
daily volume can be formulated as clearly and precisely in the case of 
this constituent of the milk as has been done by Tocher in the case of 
the fat. It is true that in a graph the hne representing the fat and that 

9—2 



122 Percentage Comjfosition of Mil h 

representing the protein would be at different angles, as the protein 
neither rises nor falls with variations in volume to the same extent as 
the fat, but the likeUhood is that where Tocher uses the word "quality" 
the words "percentage of protein" might be substituted, without im- 
pairing the accuracy and applicability of the statement. 

During the present investigation the individual protein constituents 
were estimated as casein on the one hand, and albumin plus glol)ulin 
on the other, and it was found that, from day to day, the casein and 
albumin plus globulin were present in varying proportions. Sometimes, 
when there was a rise in the percentage of protein, it was found that this 
was due chiefly to the casein; and again, on some other occasion, the 
albumin and globulin would be found to have contributed largely to the 
rise. Despite these irregularities, however, it was found that there was 
a tendency for the casein on the one hand, and the albumin plus globulin 
on the other, to maintain individually, as well as in combination, an 
inverise percentage relationship to volume ; and, consequently, these 
protein constituents of the milk were found present in larger percentages 
at the beginning and end of lactation than during the period when it 
was at its height. 

With regard to the ash, this was found to he the least variable of the 
constituents of the milk, but the analytical data for E.xps. II and V 
show that where there was a marked fluctuation in volume the percentage 
of a.sh .showed an inverse relationship to it. 

The relationship of lactose to volume is not so apparent as that of 
the protein or fat. Crowther and Euston(S) say: "It will be seen that 
the percentage of sugar, after rising a httle with the early stages of lacta- 
tion, fell steadily throughout the rest of the period." While due credit 
must be given for this observation it nuiy be pointed out that the per- 
centage of lactose is only indirectly connected with the period of lacta- 
tion. Its real relationship is to volume, and the accuracy of the words 
"steadily throughout" would seem to depend on the evenness with 
which the volume rises at the commencement of lactation, the evenness 
with wliich it is maintained, and the evenness with which it falls at the 
end of lactation. During the present investigation, where there were 
wide variations in volume at the height of lactation, due either to dieting 
or starvation, the percentage of lactose was found to vary also, and 
showed a direct relationship to it — as may be seen in Fig. 4. 

The inter-relationship of vohime and com])osition suggests a theory 
of milk secretion which may be put forward here, and on wliich further 
work is being carried out. 



W. Taylor and A. D. Husband 123 

Vau der Laan(9) shows that a state of osmotic equihbrium exists 
between the blood and the milk, and that this equahtv of osmotic pressure 
persists even in diseases of the udder. As lactose is the substance which 
is likely to play the most considerable part in determining the osmotic 
pressure in the milk, the osmotic pressure in the blood is likely to be 
expressed to a very great degree by the percentage in which this con- 
stituent is present in the milk ; and as, normally, the osmotic pressure 
in the blood must be considered to be a constant, with but slight varia- 
tions from day to day, it is to be expected that an equal constancy 
will prevail in the percentage in which the lactose is present in the milk. 
It has been found that, while the percentage of lactose tends to vary 
directly as the daily volume, at the height of lactation these variations 
are normally so shght that an approximately constant percentage is 
maintained. The conclusion to be drawn is not that the lactose is 
elaborated till it reaches this practically constant percentage, but that 
it is kept down to this constant level by the rate of secretion of the milk. 
The suggested theory of secretion is, therefore, that the elaboration of 
lactose produces a flow of milk by a process of osmosis. This would explain 
why. at the height of lactation, the percentage of lactose varies but 
slightly and tends to do so directly as the daily volume, at the same time 
reducing the percentages of all the other constituents of the milk by 
a process of dilution — hence their inverse percentage relationship to 
volume. 

coxcLrsioxs. 

1. The percentage composition of the milk seems to be determined 
by its rate of secretion. 

2. The percentages of protein, fat and ash vary inversely, and the 
percentage of lactose varies directly, as the daily volume, the greatest 
variation being .shown by the fat and the least by the inorganic elements. 

!5. There is an inverse relationship between the percentage of lactose 
and the percentages of all the other constituents of the milk, this being 
particidarly apparent in the case of the fat. 

4. Diet has no direct influence on the percentage composition of the 
milk, except in the case of the non-protein' nitrogen which is not a product 
of the mammary gland. Diet has, however, an indirect influence by 
reason of its efiect on the daily volume. 

5. A high protein diet would appear to stimulate the rate of secretion 
of the milk. 



124 Percentage Composition of Milk 

6. It is suggested that the quantity of lactose elaborated hy the 
uiainmary gland controls the daily volume of the milk, and that, there- 
fore, the rate of its elaboration controls the rate of milk secretion. 

We wish to express our indebtedness to Dr .1. B. Orr, who suggested 
this research, for constant encouragement and advice during the progress 
of the work. 

KF.I'i:i!KX(i:.s. 

(1) VoiT. Zeilschnjl far B'whijk, 1 8(19, 5, p. 122. 

(2) Ingle. Bull. Yorks. Coll., Leeds, No. 2.'). Mtdl. Cited by Hainnioml and Hawk, 

Joiirii. A(inr. Sci., 1917, 8, p. 139. 
(:i) C'rowther. Univ. of Leeds, Bull. Xo. 44, 1903. Cited by Hammond and Hawk, 
./onni. Agric. Sci., 1917, 8, p. 139. 

(4) Jordan and Jenter. New York Agric. Kxper. Station. 1901. Bull. No. 197. 

Cited by Lusk, The Science of NiUrition, 1917, p. 393. 

(5) Morgan, Beroer and Fincjerling. LandwirUchaJt. Venuchaatal, 1904, 41, 

p. 1. Cited by Lusk, The Science of Nutrition, p. 393. 
((!) Hammond and Hawk. Studies in Milk Scciction. .Jottrn. of Aqric. Sci.. 1917, 
8. J). 139. 

(7) TooHER. Investigation into. Milk Yield of .Ayrshire Cows. Trans. High.and Agric. 

Soc. of Scot., 1919, 31, p. 237. 

(8) Crowther and Ruston. Variation in the Composition of Cows' Milk witb the 

Advance of Lactation. Trans. High, and Agric. Soc. of Scot , 191 1. 23. p. 93. 

(9) Van der Laan. Biochein. Zeil.tch., 1919. 73. p. 313-2.5. 



{Received 6 January 1922.) 



THE CITRIC SOLUBILITY OF MINERAL 
PHOSPHATES 

By J. F. TOCHER, D.Sc, F.I.O. 

Consulting Chemist to the HiyhlunA and Agrieidtural Societij oj Scotland; 
Lecturer on Statistics, Vnirersity of Aberdeen. 

(With 8 Diagrams.) 

I. INTRODUCTORY. 

The Fertilisers and Feedin.ii Stuffs Act 1906, Section 10, defines the 
expressions "soluble" and "insoluble" to mean that the fertilising con- 
stituent is soluble or insoluble in water, or, if specified in the invoice, 
to mean that the fertilising constituent is soluble to the extent guaranteed 
in a solution of citric acid, or other solvent, of the prescribed strength. 
In particular the section defines the percentage of soluble phosphate and 
the percentage of insoluble phosphate to mean respectively the percentage 
of tribasic phosphate of Ume equivalent which has been, or that which 
has not been, rendered soluble. "Citric solubihty" under the Act is 
further and more definitely defined in the FertiHsers and Feeding Stuffs 
General Regulations 1906 as follows : 

"When, in an invoice relating to hasic slag or basic superfhos-phate, 
it is specified that a certain percentage of the phosphate contained in 
the basic slag or superphosphate is soluble in citric acid, this shall be 
taken to mean that it is capable of being dissolved to the extent of such 
percentage when 5 grams of the fertiliser and 500 cubic centimetres of 
water, containing 10 grams of citric acid, are continuously agitated in 
a flask or bottle of about 1 htre capacity for the period of half an hour 
at the ordinary temperature." 

It is clear from these regulations that "citric solubihty" refers to 
ba.sic slags and "basic superphosphates "^ and that the citric solubihties 
of basic slags and of basic superphosphates have to be determined at 
"room" temperature by means of a 2 per cent, solution of citric acid, 
the duration of contact being limited to half an hour in a quantity of 

^ The seller need not, unless he chooses to do so, f^ive any (guarantee of citric .solubility. 



126 The Citric SoJiihility of Mi ii end FJio.yjJuifes 

the fertiliser exactly one half in amount of citric acid present. The basis 
of this test is evidently the work of Wa<;ner and appears to be of a wholly 
empirical character. .Since Wagner's method has been adopted as an 
official test, citric solubiUty has been studied by a number of different 
workers. Stead^ found that for normal basic slags the solubihty increased 
with the amount of silica present. He also .showed that citric solubility 
was associated with the degree of fineness of the powder. Kobertson- 
.studied the degree of solubihty of mineral phosphates in citric acid using 
the official test. He shows that mineral phosphates arc completely 
soluble iu 2 per cent, citric acid solution if a sulticient number of extracts 
are made by successive lialf liour contacts. Robertson in his conclusions 
states that "Even a small amount of free lime or calcium carbonate 
decreases substantially the solubihty of mineral phosphates as judged 
by the citric acid test. When a large amount of calcium carbonate or 
free hme is present, the citric acid test as commonly practised, is a test 
for hme and not for phosphates. It is important in this respect to dis- 
tinguish between free hme and calcium carbonate, and hme actually 
entering into the composition of the phosphate. The higher the percentage 
of hme actually entering into the phosphate compound, the higher the 
citric solubihty of the phosphate." He has also shown that fluor-spar 
greatly decreases citric solubility in slag and concludes that the official 
test gives no true idea of the solubility of the pho.sphate in slag. He states 
that "one of the effects of fluor-spar is to cause the formation of a phos- 
phate which does not contain silica in combination as is the case with 
high citric soluble slags." The effect of fusing with fluorides apparently 
is that a compound of silicon and fluorine is formed leaving lime and 
phosphorus in combination. Dixon^ made a study of the citric solubihty 
of various bone phosphates. In his case he varied the citric acid con- 
centrations and with a constant weight of fertihser he found that in 
every case the stronger the citric acid solution the greater was the amount 
of phosphate dissolved. Ramsay* prepared pure tricalciuni phosphate 
by mixing three equivalents of CaO with one equivalent of PoOj and 
show-ed that 91 per cent, of the total phosphoric acid content of the 
pure tricalciuni phosphate was soluble in the prescribed 2 per cent, 
citric acid solution in 30 minutes. He also showed that the simple 
addition of calcium carbonate reduced citric solubility. Russell and 
Prescott^ studied the (•itri(' solubihty of the phosphates of the soil. They 



' Trans. Faraday Soc. 16, I'art 2. - Soc. Cliem. Ind. No. 4, 35. 

' Journ. ofAgric. Sci. 1906, Part 4. ^ Ibid. June, 1917. ' Ibid. Sept. 191U. 



J. F. Tocher 



1-27 



found a greater solubility for short periods of contact when compared 
with long periods and established the fact that adsorption of phosphate 
took place during long periods of contact. 

II. CITRIC SOLUBILITY— OFFICIAL AXD OTHKRWLSE. 

The writer was attracted to this subject by the fact that the citric 
solubihty of certain commercial phosphates was determined in a dilute 
citric acid solution ((»-"2 per cent.) and not by means of the 2 per cent, 
solution prescribed by the official test for slags. 

Samples of ground mineral phosphate are occasionally guaranteed to 
contain as much as 50 per cent, "citric soluble" phosphate. To the un- 
wary this might be taken to mean that the sample contained 50 per cent, 
"citric soluble" phosphate as determined by the official test for slags 
and "basic superphosphates" prescribed in the Regulations. As a matter 
of fact, however, the citric solubility in this case was determined for 
the sellers by agricultural analysts by agitating for half an hour 5000 
parts of a solution of citric acid (0-2 per cent, strength) with 1 part of 
the sample. That is to say the amount of the citric acid employed was 
one-tenth of the amount officially prescribed while the proportion of 
fertihser was 50 times less than the proportion prescribed as may be 
seen from the following table (Table I). 



Table I. 



Test 
Official quantities ... 
Quantities for private test 
i.e. ... 



Citric 

acid 
10 grams 

1 gram 
10 grams 



Fertiliser 
.5-0 grams 
O-I gram 
10 ,. 



Total 

volume 

.500 c.c. 

.500 „ 

5000 „ 



The following results (Table II) were obtained on using the official 
citric solubihty test on samples of ground mineral phosphate and basic 
slag: 

Table II. 





Basic slags 

A 




• 


Mineral 


, phosj^hate 










Percent. 


' 






Percent. 


Citric 






of total 


Citric 






of total 


sol. 


Total 




phos. 


sol. 


Total 




phos. 


phos. 


phos. 


Fineness 


dissolved 


phos. 


phos. 


Fineness 


dissolved 


27-94 


30-59 


84-8 


91-3 


21-92 


04-80 


64-7 


33-8 


28-21 


31-00 


79-0 


91-0 


18-26 


55-86 


85-1 


32-7 


4-82 


19-35 


76-0 


24-9 


20-39 


57-84 


84-5 


35-3 


6-36 


25-55 


74-1 


24-5 


19-72 


57-98 


82-9 


340 


22-68 


23-60 


93-6 


96-1 


21-53 


58-51 


98-0 


36-8 


28-54 


39-10 


85-4 


73-0 


19-30 


01-92 


88-0 


31-3 



128 The Citric Soliihilifi/ of Mineral PJwsphates 

The results of this table show that when mineral phosphate is as 
finely ground as basic slag a fair amount of phosphate is rendered " citric 
soluble"' by the official method but the "citric solubility" of mineral 
phosphates appears generally to be much less than the citric solubility 
of slags, when this test is apphed. 

irr. TITK SCHK^rK of KXrKRTMKXTAI. WORK. 

The citric solubility uf mineral phosjihates was accordingly studied 
at "room" temperature over a period of 30 minutes agitation: 

(1) In varying dilution, the quantities of acid and mineral phosphate 
being constant. 

(2) In varying concentrations of acid, the volume of fluid and the 
weight of mineral phosphate being constant. 

(3) With varying amounts of the phosphatic fertihser, the volume 
of the fluid and the concentration of acid being both constant. 

In order to compare the citric .solubility of mineral phosphates under 
the above conditions, with the citric solubiUty of a pure phosphatic 
compound, a fourth series of experiments was conducted, namely, 

(4) the solubihty of dicalcium phosphate in dilute hydrochloric acid. 
It is evident that whatever be the value of determining the j)ro- 

portion of citric soluble phosphate in a phosphatic fertiliser, it is neces- 
sary, for comparative purposes, if other conditions are similar, that the 
test should be applied in the same way and with the same proportions of 
citric acid or of other acid and of fertiliser as prescribed officially, for 
basic slags and basic superphosphates. 

Other conditions are, of course, open to study. For example we could 
have two of the above factors varying differently with a series of constant 
values for the third factor. The citric solubility of tricalcium phosphate 
and other pure phosphatic compounds could be studied and the results 
compared with the results from the above four series. The writer has 
not been able to carry out these latter experiments. He therefore sub- 
mits the results of experimental work under the above four heads'. 

' The writer has to acknowledge his indebtedness to Mi .lnhn I']. Ritchie, M.A., B.Sc., 
A. I.e., who has performed the necessary analytical determinations in the exi)eriments 
on mineral phosphates, and has also given valuable assistance in preparing the memoir. 
He has also to thank Mr W. T. H. Williamson, B.Sc., A.I.C., for the determinations in 
the case of dicalcium phosphate. 



J. F. Tocher 



129 



IV. EXPERIMENTS WHERE THE QUANTITIES OF MINERAL PHOSPHATE 
AND CITRIC ACID USED WERE CONSTANT AND THE DILUTION 
WAS VARIED. 

In order to determine the variability in citric solubility of mineral 
phosphate with varying dilutions of citric acid, a series of experiments 
was conducted with different dilutions shaking for half an hour, the time 
prescribed in the official test. The quantities of citric acid and of mineral 
phosphate used are indicated in the following table (Table III). Let 
m-^ = amount of citric acid used, itio ^ amount of mineral phosphate 
used, and ni^ = volume of fluid used. In tliis series the ratio rn^jm^ was 
made constant (and equal to 2) in order to secure that the effect of the 
presence of Ca(0H)2 and of CaCOj and other hydrates and carbonates, 
on the citric acid concentration was of a constant character. Throughout 
this series of experiments 10 grams citric acid and 5 grams mineral 
phosphate were used, the volume being varied as shown in Table III. 

Table III. Quantities of ininend phosphate and citric acid used are 
constant — dilution, i.e. degree of concentration, varies. 

5 grams mineral phospliate 
10 grams citric acid 



1 

Exp. 


2 

Vol. of 
sol. 


3 4 

Wt. of Phosphate 

dissolved. Grams per 

volume stated 


5 

Pliosphate 
dis.solved 
per cent, 
of sample 

as 
Ca,(PO,), 


6 7 

Percentage dis- 
solved of total 
phosphate con- 
tent 


8 9 

:Molecular concentration of 

phosphate at end of 30 

minutes. Gram-mols. 

per litre 


Observed 

as 
Ca,(PO,), 


Tlieory 
Ca3(P0.), 


Observed 


Theory 


Observed 


Theory 


1 
2 

3 
4 
5 


500 

625 

833 

1250 

2500 


0-9620 
1-0210 
1-0875 
1-2080 
1-4070 


0-9697 
1-0215 
1-0907 
1-1990 
1-4030 


19-24 
20-42 
21-75 
24-16 
28-14 


29-8 
31-7 
33-7 
37-5 
43-6 


30-1 
31-7 
33-8 
37-2 
43-5 


0-006206 
0-005270 
0-004210 
0-003117 
0-001815 


0006256 
0-005272 
0-004222 
0-003094 
0-001810 



60 i 



oo 

gp;' 



a a 
§■3 



20 



in (.'iihio ("'clitimetrcs 



500 1500 2500 

Diagram 1. See columns 8 and 9, Table III. 



sag 

S^-2 24 
Sfea 22 

"So- 



Voiunic in ('nl>ic Centimetres 



500 1500 

Diagram 2. See column 5, 



2500 
Table III. 



130 The Citric SolnhiUty of Mineral Phosphates 

It is seeu from these results that the hi^'hcr the dilution of citric 
acid, with mjin.^ kept constant, the greater is the proportion of citric 
solubility of tho jihosphato expressed as a percentafze of the weifiht of 
the sample (coluiim 5. Tal)le III). Bassett' considers that the compound 
usually present in mineral phosphates is hydroxyapatite which may be 
written |Ca3(P04)2l3C'a(()H)^. Ho also thinks it probable that hydroxy- 
apatite is the only calcium phosphate that can permanently exist under 
normal soil conditions. It forms the stable solid phase over a ran^'c of 
acidity of great practical importance, as it can exist in contact with 
faintly acid, neutral or alkaline solutions. An attempt has been made to 
fit a theoretical curve to this series of experiments on the assumptions 
that there is equilibrium at the end of the experiment and that the 
following equation represents the reaction : 

Ca03Ca3(P04)2+ .'^HaCeHsO,, H20i^CaH,(PO,)2+ SCaHCgHsO, 

+ 2Ca3(POA+H,p (1) 

Of course other equilibrium equations including dicalcium phosphate can 
be written from which the same mass action equation can be deduced. 
The above equation is merely given as a suggestion. 

The sample of mineral phosphate contained a proportion of COj 
equivalent to 0-G5 gram of calcium carbonate in 5 grams of the sample. 
Hence 1-36 grams of citric acid would be used up in the formation of 
citrates, leaving 8-64: grams of acid available to attack the phosphatic 
compound. If the original acid concentration is taken to be proportional - 
to the concentration at ecpiilibrium, a constant should be obtained on 
applying the law of mass action. A good agreement between theory and 
observation is obtained on this hypothesis. If w = molecular concentra- 
tion of acid after alkaline lime has been neutrahsed ; m = molecular con- 
centration of phosphate (expressed as tricalcium phosphate) at the end 
of 30 minutes agitation then we should have y^jic^ = k. The last two 
columns (columns 8 and 9, Table III) show the observed molecular con- 
centrations and the theoretical values on the basis of above equation. 
A good fit is also obtained using the equation u*l{w — u)\w — 2m) wIumi 
the theoretical values are found by Horner's method. Diagrams 1 and 
2 show in graphical form the results of Table III. 

' Trans. Chem. Soc. 1017, 111. 

- The values of u from the equation m*'(wi - 3«)' show ureater cliver<;ence.s from observa- 
tional values than the values obtained from either of the equations civen in the text. Tho 

ratio ^ varies from -72 to -SO, showint; that the original concentration is nearlv 

w 

proportional to concentration at the end of 30 minutes shaking. Whatever the reason, the 
formula u'jiv^ gives by far the best fit to the results. 



J. F. Tocher 



.181 



A second set of experiments was carried out in which the ratio 
mjm^ = 10 instead of 2, that is, in each case 10 times more citric acid 
than phosphate was used in each separate experiment. The undernoted 
table (Table IV) shows the quantities used and the results obtained. 
This set of experiments when plotted against the theoretical curve ex- 
pressed in equation (1) was found to be a very bad fit. In order to deter- 
mine the best fitting equation the ratio of the exponent x to the exponent 



c in the general equation C ■ 



l\u'' 



k.M 



- was determined where C, l\ and k^ 



are constants. The ratio — was found to be egixal to 1-0669 

mean 2: 



16/15. 



The following table (Table IV) and accompanying diagrams (Diagrams 3 
and 4) show the observed results and those reached from the ecpiation, 

C = --j^ , or log C = 1 6 log u — 1 5 log w. 

Table IV. Quantities of mineral phosphate and citric acid constant — 

dilution, varied. 



1 10 grams citric acid 

( 1 gram mineral phosphate 



1 

Exp. 




Vol. of 
solution 


3 4 

Weight of phosphate 
dissolved as GajPjOg 


5 
Percent, 
dissolved 
of total 
Ca,,P20, 
content 


6 
Phosphate 
dissolved 
per cent, 
of weight 
of sample 


7 8 

Molecular concentration 
at end of 30 minutes 




Observed 


Theory 


Observed 


Theory 


1 
2 
3 
4 
5 
6 


500 

625 

833 

1250 

2500 

5000 


0-5376 
0-5472 
0-5610 
0-5708 
0-59.55 
0-6180 


0-5388 
0-5464 
0-5565 
0-5705 
0-.5960 
0-6220 


83-3 

84-8 
87-0 
88-5 
92-3 
95-S 


53-76 
54-72 
56-10 
57-08 
59-55 
61-80 


0003468 
0-002824 
0-002172 
0-001472 
0000768 
0-000399 


0-003476 
0-002820 
00021.54 
0001473 
0-000769 
0-000401 



c.-, 30 
oO 






20 



£•3 10 






N'uluinc in Cubic Cclitiiiicdcs 



;-S 500 2500 5000 

Diagram 3. See columns 7 and 8, Table IV. 



03 s a 

^ "" o 

111 

COS 
%^ 

-SO 



54 



/ Volume in Cubic Centiuietres 



500 " 2500 5000 

Diagram 4. See column 6, Table IV. 



132 The Citric Solxbility of Mineral P/iosphates 

Experiment 6 of Table IV is an experiment identical in character with 
the private test already mentioned (see Table I). The results of experi- 
ments parallel to this experiment were used by certain sellers to describe 
the citric solubility of the mineral phosphate put on the market. It 
will be seen that Exp. 6 falls naturally into its place among the experi- 
ments given in Table IV. The amount of phos])hate dissolved amounts 
to (52-2 per cent, of the weight of mineral pliospliatc tested while the 
same phosphate, analysed in accordance with the official test (Table III, 
Ex]). 1) shows a citric solubility of 19-24 per cent. If we consider the 
proportion dissolved in relation to the total amount of phosphate present 
expressed as tricalcic phosphate it is found that, by the official method 
29-83 per cent, of the total Ca^P.^Og content is dissolved, while by the 
private test (at great dilutions, see Table IV) 95-8 per cent, of the total 
CagP-^Og content was dissolved. These results show what might naturally 
be expected, namely, a much higher solubility of mineral phosphate in 
the experiments where the constant ratio m^jni^ = 10 (Table IV) was 
used than where mjm.^ = 2 (Table III) was used. In other words if 
mjm2 is nuide large enough we should reach the limit of 100 j)er cent, 
citric solubility for all very high dilutions. 

The results in Table II show that, using the official test on both slags 
and iniueral phosphates, slags generally show a higher citric solubility 
tliaii mineral phosphates. If the uiiodicial test (Exp. (1. Tal>le IV) was 
universally applied to slags we should have similar liigh solubility figures, 
in other words the citric solubility at high dilution would be practically 
100 per cent, and the only item of information whicii would be valuable 
to the purchaser would be the actual proportion of phosphate, expressed 
as tricalcium phosphate, present in the fertihser. In some slags the citric 
solubility in terms of total phosphate content is as much as 90 per cent. 
(see Table I) and therefore the actual increase on dilution must be 
necessarily small compared with the increase in citric solubility on 
dilution of any mineral phosphate. 

The undernoted table (Table V) shows the average composition of 
five commercial mineral pho.sphates^. The sixth (Egyptian) was analysed 
in my laboratory. 

Since calcium carbonate is present in varying ))roportions in com- 
mercial mineral phosphate it is clear that with a constant initial molecular 
concentration of citric acid, varying quantities of citric acid will be 
available to attack the insoluble phosphate. For example, suppose we 
selected two dift'erent varieties of mineral phosphate, ground to the same 
1 Robertson, J.S.C. I. ,35, p. 218. 



Makatea 


Florida 










Island 


Pebble 


Alfrerian 


Gafsa 


Tunisian 


Egyptian 


52-38 


47- 10 


40-13 


43-30 


48-40 


^46-81 


38-24 


31-50 


27-27 


25-35 


26-13 


29-52 


1-69 


3-04 


0-70 


5-50 


9-03 


9-42 


1-46 


1-0(1 


0-72 


3-26 


0-98 


— 


3-30 


2-41 


3-28 


4-39 


3-21 


2-0(i 


1-01 


Mill 


2-50 


4-08 


4-25 


2-78 


1-35 


1-itO 


2-02 


1-72 


0-90 


0-77 


0-28 


7 03 


8-12 


7-56 


4-65 


7-73 


0-20 


4-42 


3-17 


3-94 


2-45 


0-91 



.1. F. TociiER 133 

degree of fineness, and containing the same proportions of liydroxy- 
apatite but quite different proportions of calcium carbonate. The sample 
wliich contained the smaller (|uantity of calcium carbonate would show 
a higher citric solubility than the second sample which contained a 
higher proportion of calcium carbonate, due to the presence of a relatively 
large proportion of free citric acid in the former. 

Table V. Composition of Mineral Phosphates. 



Cak-iura o.xide 
Phosphoric acid ... 
Carbon dio.\ide 
Moisture ... 
Combined moisture and) 

organic matter ... \ 
Ferric and ahiminium j 

o.xides ... ... ( 

Magnesium oxide ... 

Sand 

Undetermined 

Citric solubility is not necessarily a te.st of the availability of the 
phosphate to the plant in the soil. If the sample is finely ground and 
has a low citric solubihty, the lowness of the citric solubihty in the case 
of mineral phosphate would mainly be due ( 1 ) to the presence of alkahne 
material which would neutralise a large proportion of the citric acid, 
leaving the residue to act on the phosphate and (2) to the chemical 
constitution of the phosphatic mineral. In the case of slags the citric 
solubility would be mainly dependent on ( 1 ) the compounds of fluorine 
as shown by Robertson, (2) the presence of alkaline lime as shown by 
Ramsay, and (3) the chemical constitution of the phosphatic compound 
in the slag. It has yet to be shown that the phosphate in mineral phos- 
phate is not utiUsed by the plant as readily and as efiiciently as the 
phosphate from slags. In other words the exact chemical composition of 
the phosphatic compounds in the various mineral phosphates and slags 
has, in each case, to be demonstrated. It appears to be necessary to 
test the citric solubihty of phosphates of knoivn composition against their 
availability in the soil as shown by yield of crop. The results would then 
show how far, if at all, citric solubihty is a measure of availability in 
the soil. Since the commercial fertilisers tested contain varying quantities 
of alkaline Hme, fluorides and other interfering substances, and since 
the chemical constitution of the fertihsers is incompletely known, the 
writer can see no scientific validity in the use of citric solubihty as a 
measure of availability. The three practical tests appear to be : 



134 The Citric Solahility of Mineral Phosphates 

(1) Total phosphatic content. 

(2) Degree of fineness of the powder. 

(3) Presence or absence of substances capable of inhibiting growth. 
A fourth test of scientific, as well as practical, value would be a test 
demonstrating the constitution of the iihosphatic compounds in the 
fertiliser. 

If citric solubility cannot be regarded as a useful and practical test 
for mineral phosphate it is still less valid as a comparative test for slags 
and mineral phosphates alike owing to the varying composition of slags 
and to their widely different chemical compo.sition and constitution 
when compared with mineral phosphates. 

In regard to the chemical constitution of phosphatic fertihsers it has 
already been noted that hydroxyapatite is considered by Bassett as the 
chemical compound probably present in mineral phosphate. Alorison 
states^ that the molecular ratio of phosphoric anhydride to calcium 
oxide P-jOj/CaO is 1/.5 in slags and supports Stead's conclusions that the 
phosphatic content in basic slags consists of a chemical union of tetra- 
calcium phosphate and monocalcium silicate (CaO)4P205CaOSi02. On 
the other hand the ratio of phosphoric anhydride to calcium oxide 
in Bassett's hydroxyapatite is 'ij\0 — 1/3 J. Morison also deals with the 
effect of free lime on the citric solubility of slags and shows that the 
greater the amount of free lime in a slag the greater is the total solubility 
after three extractions. On the other hand Ramsay- shows that about 
91 per cent, of the total pho.sphoric acid in pure tricalcium phosphate is 
soluble in the prescribed 2 per cent, citric acid solution. This degree of 
solubihty is very similar to the degree of solubility of the best grades of 
slags (see Table I). He also shows that by the simple addition of calcium 
carbonate to pure tricalcium phosphate the citric solubihty is reduced 
fmm 91 to 84 per cent. This is naturally to be expected and the apparent 
greater solubility of phosphate with increase of lime content found by 
Morison must be due to other causes. It should be noted that the 
quantities of free lime present in Morisons samples are relatively small. 
The increase in solubility with an increase of silica and the decrease in 
solubihty in the presence of fluorides have already been mentioned. 
Robert.sou finds that calcium carbonate decreases substantially the solu- 
bility of phosphates as judged by the 2 per cent, citric acid test. The exact 
effect of the presence of calcium carbonate or calcium hydroxide on the 
solubility of phosphate of a known composition can of course be found 

' Juiini. Ayil. Sci. 1909. 
= Ibid. 8, p. 277. 



J. F. Tocher 1:35 

a jwiori. The difficultv arises when the composition of the phosphates is 
unknown and when other interfering substances are present. Since the 
nature of the substances present are unknown, equations expressing the 
law of mass action cannot be written down in these cases. 

The following table (Table VI) shows the average compo.sition of 
some commercial slags as given by Collins {Chemical Fertilisers, p. 122). 

Table VI. Composition of Slags. 

12 3 4 5 

Total P-A IL'-IJO 20-49 O-O'J 17-57 19-35 

SiUca 17-(i9 10-12 13-49 7-77 12-12 

Lime 3S-02 46-81 40-43 52-22 44-75 

Magnesia 4-24 2-92 5-01 1-94 0-11 

Mansanese o.xide ... 7-39 4-38 5-41 9-37 4-68 

Iron" 12-89 9-98 13-83 8-13 9-10 

These latter tables (Tables V and VI) show in a general wa)' the 
differences between slags and mineral pho.sphates. These two classes of 
fertihsers contain non-jihosphatic residues differing in chemical com- 
position, and residues which are common to both in different proportions. 
The results of tliis section show that citric solubility is merely a special 
case of the law which has been proved to hold for the solubihty of a 
definite chemical substance in dilute acids and it can always be stated 
a prion when the conditions are known for a definite substance in a 
definite dilution. When, however, we pass from a single substance to 
mixtures of varying composition citric solubility cannot be descriptive 
■of available jihosphate of definite composition. The reason for this lies 

(1) in the unknown changes which take place in the initial molecular 
concentration of the citric acid, due to the formation of calcium and 
other citrates from the carbonates and hydrates present in the fertiliser, 

(2) in the unknown changes which take place on agitating phosphatic 
fertihsers of varying composition and (.3) in the known effects produced 
by the presence of fluorides and of silica. 

V. EXPERIMENTS IN WHICH THE VOLUME OF FLUID AND THE WEICiHT 
OF MINERAL PHOSPHATE ARE BOTH CONSTA.XT. THE VARYIN(i 
FACTOR BEINC4 ACID CONCENTRATION. 

We shall now consider condition (2) namely, where the amount of 
mineral phosphate (m.^) and the volume of fluid (iii.^) are both constant, 
i.e. jWg/Wg = constant, while the amount of citric acid is varied. 

The following series of experiments was carried out with a constant 
weight of mineral pho.sphate (5 grams) in varying concentrations of citric 
acid in a constant volume of 500 c.c. The undernoted results (Table VII) 

Journ. of Agrio. Sci. xii 10 



V,]i) The C'dric Sohihiliti/ of Mineral J'/iosp/Ki/cs 

show that if the acidity is expressed as the molecular conceutruliuu ol 
citric acid at the end of 30 minutes shaking, K — u^jifi fairly accurately 
describes the solubility of the phosphates at the acid concentrations 
named. 

Table VII. Amount of miner nl phosphate present and voluine constant — 

aci(Jit>i varies. 

m^j)iu = 100; vol. =.'500 c.c. =m^: m., -miiu'ial iiliuspliiite ^5 grums 



I 


2 


3 


4 


6 


7 


8 9 


Exp. 


Wt. citric 
acid in 
500 c.c. 


Aciility lis 
citric acid 
at end of 
30 minutes 


Wt. of plio.spliate 

dissolved as 
CajPjO, in 500 c.c. 


Per 

centago 
dissolved 
of total 
CajP.O, 
content 


ea,P.O. 
found 

percent. 

of phos- 
pliute 
taken 


Molecular concentra- 
tion of phosphate at 
end of 30 minutes 




Observed 


Theory 


Observed 


Theory 


1 


10 grms. 


8-87 grms. 


0-9675 


0-9492 


300 


19-35 


-006242 


-006124 


9 


8 „ 


7-02 „ 


0-8119 


0-7958 


25-2 


16-24 


-005238 


-005134 


3 


•' - 


5-11 „ 


0-6743 


0-6250 


20-9 


13-48 


-0043.50 


-004032 


i 


4 „ 


z-2r, „ 


0-449r) 


0-4470 


13-9 


8-99 


-002900 


-002884 


5 


•) 


1-34 „ 


0-2176 


0-2300 


6-7 


4-35 


-001404 


-001484 


6 


1 ., 


0-49 „ 


0-1020 


0-1082 


3-2 


2-04 


-000658 


-000698 



oo 60 

lo:=°- 

gco 30 

II 20 
If '0 



.^' 



^' 



If '0/' 

oja Wiijjht of Citric Acid in .">( 
1 2 3 4 5 6 7 8 
rt:»»......» -: vj„.v «,,l «., w ..., 



."iOOc.c. 

"4 5 6 7 8 9 10 

;rain 5. See columns H and 0, 
n 



15 



Sfl 



§fe=. 
"Sob 






W(i"lil of ('ilric Acid in .')(X)c.c. 



2345678 9 10 
Diagram (>. See column 7, Tal>le VII. 



Oiagi 

Table VI] . 

The acconipanyini; diagrams (Diagrams 5 and (i) sliow the results of 
Table VII. These results show clearly increasing citric solubility with 
increasing acid concentration but with constant weight of mineral phos- 
phate in a constant volume. In a citric solubility test, used as a measure 
of availability, it seems necessary therefore to show that a two per cent, 
solution is the concentration of citric acid best suited for the utilisation 
of phosphate by the plant. Would it not be more in accordance with 
scientific practice firstly, to a.scertain the constitution of the ])liosphatic 
fertilisers, and secondly, to dptermine wliat rolo concentration has in the 
life history of the plant? 



J. F, ToCHEH 



VI. Ii;XPERBrEXTS WITH CONSTANT VOLUME AND CONSTANT CONCEN- 
TRATION OF ACID BUT WITH VARYING QUANTITIES OF MINERAL 
PHOSPHATES. 

In the first set of experiments fairly high constant vakies of mjnu 
were used. We shall now consider the effect of making mjm^ small, 
nij^ and iii^ being in this case constant and m.^ the variable. If m^Jm^ 
is made small enough we should have a citric solubility practically zero 
for all dilutions. An example indicating the approach to the latter con- 
dition is given in the following table (Table VIII) where the third set 
of conditions is observed. (See also Diagrams 7 and 8.) 

Table VIII. Amount of citric acid and volume constant — amount of 
mineral phosphate (»(.,) used varied. 



Exp 

I 

3 
4 



Wt. of min- 
eral phos- 
phate taken 

5 grams 
10 ., 
20 „ 
40 „ 



■-= = 50 



(10 grains citric aciil = mj 
^500c.c. volume = Hi, 



Ratio 



1 

0-.5 

0'25 



Acidity ex- 
pressed as 
citric acid 

at end of 30 
minutes 

8-87 
8-50 
7-6.5 
5-98 



Amount of 

pliosphate 

dissolved as 

CajP.O, 

0-970.5 
0-86(30 
0-6070 
0-4110 



Mol. cone, of 

phospliate 

dissolved at 

end of 30 

minutes 

-UU(i2Ul 
-00.5.5S7 
-003916 
-002652 



Citric solubility 
expressed as 

Ca3P3*^)a per cent. 

of pliosphate 

taken 

19-41 
8-66 
3-04 
1-03 



.a 
a 



60 



3 cd 

go 

a « 

o > 



Wei;;lU of Miner; 
taken — < Jciini-- 



1 l'lios|iluite 



5 10 IE 
Diasrram 7. 



20 25 30 35 
See Table VIII. 



20 



l-i 
^ 3 fl 



IZ 10 



2S.& 

■son 

St 



5- 



;lit of Mineral ' 

^|d^ate taken — t^ranis 



5 10 15 20 25 30 3£ 40 
Diagram 8. See Table VIII. 



If the mineral phosphate contained merely tri- or di-calcium phos- 
phate and was quite free from Ca(OH)a, CaO or CaCOj and also was in 
excess, mere variations in the quantity taken would have had little or 
no effect on the amount of citric acid present at the end of the period of 
shaking. The presence of Ca(0H)3 naturally reduces the acid concentra- 
tion with the result that, while 19-41 per cent, of the 5 grams mineral 
phosphate was dissolved only 1-03 per cent, mineral phosphate was dis- 

10—2 



138 The Citric Solubility of Mineral Phosphates 

solved wlu'ii 40 gnuns of the fertiliser were taken. It is thus shown, whicli 
is also apparent a jyriori, that citric solubility depends on the quantity 
of mineral pliosphato or slag used. With iiuantities like .50 grams or 
100 grams of mineral phosphate the citric solubihty would be extremely 
small. On what theoretical grounds are quantities like 5 grams (official 
test) in the case of slag and 1 gram (private test) in the case of mineral 
phosphate used to determine the availability of pho.sphate in the soil? 

Hi 

\'II. JHK l.VCOMPLETEXESS OI' 'IHE REACTIONS. 

All the foregoing results have been considered from the standpoint 
of the amount of phosphate dissolved per cent, of the weight of mineral 
phosphate taken. It is desirable, however, to consider the amount of 
phosphate dissolved in relation to the amount theoretically obtainable 
if the reaction were complete. We cannot say definitely what the reaction 
is but we know that the equation in Section 1 V' gives a suitable prediction 
formula. Suppose we put the question : What proportion of the amount 
indicated l)y this equation is obtained in each separate experiment? We 
know from theory that the hydrogen ion concentration of an acid is 
increased by dilution and we should therefore expect (/realer proportions 
of the. possible total amounts at higher dilutions than at lower dilutions. 
Let us consider the first series of experiments from this standpoint. If 
the citric acid concentration at the beginning of the reaction was 3w gram- 
molecules and the reaction went completely, according to the equation 
given in Section IV we should have w gram-molecules of monocalcium 
phosphate formed, equivalent to ic gram-molecules of tricalcium phos- 
phate. Hence for the completed reaction we should have iv gram- 
molecules of citric acid giving 1/3 «' gram-molecules of tricalcium phos- 
phate. Suppose we find only y gram-molocules of tricalcium ])hosphatc 

then -^-^ is the percentage of tiie theoretical amount which has 

been found. Tlie following table (Table IX) shows the concentration of 
the citric acid, the theoretical amount of phosphate obtainable in a 
complete reaction according to the equation, the actual amount of phos- 
phate obtained, as gram-molecules of tricalcium phosphate per litre, and 
the percentage of the theoretical amount of phosphate obtainable. 

It is seen that this percentage is practically identical with the per- 
centage in col, 5 of Table III. Indeed the numbers in col. 5 of that 
table multiplied by 1-016 give the percentage in col. 4 of Table IX. This 
arises from the following considerations. If a^ be the weight of phosphate 



J. F. Tocher 139 

dissolved aad «2 = weight of mineral phosphate taken for the particular 
dilution v then 100 — = Pi= amount of phosphate dissolved as a per- 

centage of amount of mineral phosphate taken. The number of gram- 

,,...,,.. , , . 10 1000 

molecules oi citne acid per litre in each case may be written -rr-^r x = ic 

^ ■' 2]0 r 

where v is the dilution. The amount of phosphate theoretically obtainable 

expressed as tricalcium phosphate is therefore «'/3 = x gram-molecules 

per litre. The amount of phosphate found also expressed as tricalcium 



phosphate in gram-molecules per litre is 



310 



1000 

V 



y- 



Table IX. Table .showing atnount of pliosphale found per cent, of 
amount theoreticaUij obtainable, at various dilxtionfi on basis of equation, 
Section IV. 

Gram-molecules per litre 



;x|K 


Concentra- 
tion of 
citric acid 


Pliospliatc 
theoretically 
obtainable 
in complete 

reactions 


Plios]iliate 
actually 
obtained 


Phosphate 

founil per 

cent, of 

amount 

theoretically 

obtainable 


1 


•09.52 


•0317 


•0186 


1955 


2 


■07G2 


•02.5-i 


•01.58 


20-75 


3 


•0572 


•0191 


•0126 


2210 


4 


•0381 


•0127 


•0094 


24-55 


n 


•0190 


■1)003 


•0054 


28^59 



Now the number of gram-molecules dissolved expressed as a per- 
centage of the number of gram-molecules theoretically obtainable is 
clearly 



y X 100 = p, X 



63a, 



P2- 



X ^ ' 310 

In the series under consideration a, = 5 ^^^ thus we have 

63 



Ih = Pi 



62 



10 16 7^1. 



With increasing values of a^ it is known that a smaller series of values 
of jjj would be obtained (see Table VIII). For example, if 40 grams of 
mineral phosphate were taken then p.^^ = Sjjj (approximately). The results 
in Table IX merely illustrate the well-known fact that solubihty depends 
on the hydrogen ion concentration. They further show that it is mis- 
leading to adopt a particular set of weights to test citric solubility and 
to express the solubility in terms of the weight of mineral phosphate taken 
for the experiment, if it is intended to judge the equality of a phosphatic 
fertiliser by the result so obtained. 



140 The Citric Sofiibilit!/ of Mineral P/iosp/idtea 

Vril. DICALCIUM PHOSPHATE EXPERIMENTS. 

The observed amount of phosphate dissolved by citric acid per cent, 
of the theoretical amount for a completed reaction found in these experi- 
ments may be contrasted with corresponding figures obtained from the 
interaction between a pure substance likedicalcium phosphate and hydro- 
chloric acid. A series of experiments was conducted with this end in 
view. In each experiment a constant ([uantity (25 grams) of precipitated 
dicalcium phospliate (Calir042H20) was shaken for half an hour in a 
constant volume (500 c.c.) of water. The proportion of hydrochloric 
acid was varied as shown in Ta])k' X. Tlie following results were obtained : 

Table X. 





Volume constant = 500 c.c. ; 


dicalcium pho 


sphate = 25 


grams 




I 


11 


III 


IV 




V 




Original 

concentration 

of 11 CI. 

Gram niols. 

per litre 


Concentration 

of phoj^plmte 

after shaking. 

(granvmols. 

raH,{P(>4)2 

per litre) 


Theoretical 
concentratiou 
of phospjiate 

't ~ : — 7:7 X )'• 
l+2t 


Grams of dicalcium phosphate 
dissolved JXT litre 


xi>. 


Observed 




Theory 


1 


' -2856 ^ 


•1299 


■1325 


44^69 




45-58 


2 


•2285 


•1058 


•1060 


3640 




3646 


:i 


•1713 


•0792 


•0795 


27^24 




27-35 


4 


■1142 


•0547 


•0530 


18-82 




18-23 


'i 


■0571 


•0265 


•02G5 


912 




912 


(> 


■0286 


•0124 


(li:!:! 


4-27 




4-58 



These results show the decreasing percentage of phosphate di.s.solved 
with decreasing acid concentration as usually obtained in such experi- 
ments. The result, however, to be contrasted with the corresponding 
previous results, is the relative completeness of the reaction as seen in 
cols. I and II of the above table (Table X). Since there is excess of 
dicalcium phosphate the undernoted equation may be taken to represent 
the reaction namely, 

2 CaH PO4 ! 2 1 1( '1 1; ( 'aH4(P04)2 + CaCl^ (2) 

In this equation two molecules of hydrochloric acid are used up to 
produce one molecule of monocalcium phosphate and one molecule of 
calcium chloride. Hence if we start with w gram-molecules of hydro- 
chloric acid we shall have, for a completed reaction, liv gram-molecules 
of monocalcium phosphate, the substance determined. If iv = molecular 
concentration of iiydrochloric^ acid per litre at the beginning of the 
experiment and u -^ molecular concentration of phosphate expressed as 
Ca3(F04).2 per litre at the end of 30 minutes shaking when equilibrium 
may be presumed in this case to be established, then according to the 



J. F. Tocher 141 

law of mass action we should expect k = ujw — 2m to describe the ex- 
perimental results. An inspection of col. Ill (Table X) will show that 
the formula reasonably fits the data. No account has been taken of the 
degree of ionisation in the above equilibrium equation. The extent of 
the reverse action, 

CaH,(P04).l;CaHP0, + H3PO4, 
has also been neglected. 

If the degree of ionisation of liydrochloric acid is taken into account 
together with the fact that a minute Cjuantity of calcium hydroxide was 
found to be present in the dicalcium phosphate used it is found that 2m 
is slightly greater than hi as may be seen on inspection of Table XI 
(col. IV). The value of 'liijw varies from 1-008 to 1-039, the average 
value being 1-0228 and theory requires this ratio to be equal to unity 
for a completed reaction. 

Table XI. 



I 




II 


III 


IV 


Concentration 


of 








dissociated HCl 


Gram-mols. 






(gram-mols. per 


litre) 


CaH,(P04)2 




2m 


= w 




= M 


2« 


w 


■2576 




•1299 


•2.598 


1^0085 


•2087 




■ 1058 


•2116 


b0139 


•1573 




■0792 


•1584 


b0070 


•1053 




■0.547 


•1094 


1^0389 


•0514 




•0265 


•0530 


10311 


■0239 




■0124 


•0248 


10377 



The work in this section is intended merely to illustrate the approxi- 
mation to a completed reaction in the case of a known phosphate. More 
detailed work is necessary and a fuller con.sideration of the theory is also 
necessary in order to give a complete physico-chemical explanation of 
the phenomena. 

IX. f«i\CLUSIO\S. 

(1) If constant weights of sample and of citric acid are used in a 
series of experiments, the only quantity varied being the volume, the 
quantity of phosphate dissolved per cent, of weight of sample taken 
increases with increasing volumes. With 5 grams of sample and 10 grams 
of citric acid, the citric solubihty varied from 19-24 to 28-14 per cent, of 
weight of sample. With 1 gram of sample and 10 grams of citric acid, 
the citric solubihty varied with increasing dilution from 53-8 to 61-8 per 
cent, of weight of sample. The effect of the presence of alkahne lime was 
ehminated by maintaining mjm^ at a constant value and with increasing 
dissociation as a result of increasing dilution increasing percentages of 



142 The Citric Sohihility of Mineral PJioxphnteii 

phosphate were dissolved (i.e., percentages of mineral phosphate taken). 
The molecular concentration on the other hand (i.e. number of gram- 
molecules per litre) decreased with increasing dilution. It is not held 
that the equations describing the results are valid for concentrations or 
dilutions outside those used in these experiments. 

(2) If a constant weight of sample and a constant volume are used 
in a series of e.xperiments, the concentration of citric acid being varied 
from 1 gram to 10 grams, the citric solubilities varied from 4-4 to 19-4 
per cent, of weight of sample taken. That is to say, citric solubility in- 
creased, as we should e.\pe(t, with increased acid concentration at con- 
stant volume and with a constant weight of hydroxyapatite. 

(3) If a constant weight of citric acid and a constant volume are used 
in a series of experiments, the quantities of sample being varied from 
experiment to experiment, the citric solubilities decreased from 19 to 
1 per cent, of weight of sample taken. These decreases are due (1) to the 
presence of Ca(0H)2 in the molecule of hydroxyapatite, {'!) to the presence 
of Ca(0H)2, CaO or CaCOg in the free condition and (3) to the fact that 
the results are expressed in terms of mineral phosphate taken for analysis. 

(4) It is seen that, other conditions being constant, citric solubility 
depends upon an unlimited choice of constant values of any two factors, 
together with an unlimited number of values of the third varying factor. 
If, therefore, a citric solubility test has to be adopted, the theoretical 
condition determining the relative quantities of sample, acid and volume 
must be found, otherwise the test has no practical value. Wagner has 
not supplied any theoretical basis for selecting the specified constant 
quantities of the three factors. We can, therefore, at will select for slags 
suitable values of sample, acid and volume to secure high citric solubility 
values. We can, however, select at will quite different values of sample, 
acid and volume which will give equally high citric solubility values for 
mineral phosphates. Further, we could select for both slags and mineral 
phosphates suitable values of sample, acid and volume which would 
give, on the one hand, perfect citric solubihty (100 per cent.) or, on the 
other hand, no citric solubihty at all. 

(5) The citric solubility of mineral phosphate has been contrasted 
with the solubility of a pure substance, dicalcium phosphate, in hydro- 
chloric acid. It is shown that with the dilutions used and with an excess 
of dicalcium phosphate the reaction is practically complete. Since there 
is an excess of dicalcium phosphate it has been assumed that the main 
substance present at the end of the reaction is monocalcium phosphate. 

(6) Citric solubility, if apphed to fertilisers may in a certain degree 



J. F. Tocher 143 

be a measure (1) of fineness of grinding as already pointed out by other 
workers, but it seems necessary also to postulate similarity of composition 
in comparing degrees of fineness in practice, (2) of tlie presence or 
absence of alkaline substances in fertilisers approximately of the same 
composition and ground to the same degree of fineness, (3) of the presence 
or absence of fluorides as well as alkaline substances in slags and (4) of 
the differences in the constitution of the phosphatic compounds in finely 
ground fertilisers containing approximately the same proportions of ex- 
traneous substances. 

None of these conditions are realisable in practice because the propor- 
tions and the actions of extraneous substances are generally undeter- 
mined and because the nature of the phosphatic compound present is 
either unknown or is not given. Further we can with any phosphatic 
fertiliser irrespective of its composition and constitution, use concentra- 
tions or dilutions to get any value of citric solubihty we please. Citric 
solubihty is therefore an unreliable empirical test of the agricultural 
value of mineral phosphates and slags. It has yet to be .shown that high 
citric solubihty is a measure of the presence of phosphate in a readily 
available condition for plant growth, or is an indication of the presence 
of a highly citric soluble phosphatic compound of a known chemical 
constitution. We are driven, therefore, to the conclusion that the only 
practical tests of value of phosphatic fertilisers from the agricultural 
standpoint are : 

(1) Total phosphatic content. 

(2) Degree of fineness of grinding. 

(3) Freedom from injurious substances and of substances inhibiting 
plant growth. 

The eft'ect of using dift'erent kinds of pho.sphatic fertilisers on yield 
of turnip crop, where the same amount of fertihsers, expressed as tri- 
calcium phosphate, is apphed in each case forms the subject of a separate 
communication. 

{Received December 23rrf, 1921.) 



COMPARATIVE DETERMINATIONS OF THE DIGES- 
TIBILITY AND METABOLl SABLE ENERGY OF 
GREEN OATS AND TARES, OAT AND TARE 
HAY AND OAT AND TARE SILAGE. 

By HERBERT ERNEST WOODMAN, Ph.D., D.Sc. 

{From the Institule for the Study of Aninud Nutrition, 
School of Agriculture, Cambridge University.) 

In a recent comnniiiicationi, the results of au investigation into the 
digestibiUtv of oat and tare silage were recorded. The desirabihty, how- 
ever, of extending the scope of this initial work was recognised, in view 
of attempts which are being made to re-establish on a large scale the 
practice of ensilage in this country. 

Before incurring the initial e.xpense involved in the setting up of a 
silo, the farmer is justly entitled to ask and receive answers to such 
questions as the following : 

(1) What are the precise conditions under which the production of 
a palatable silage of good quahty can be guaranteed ? 

(2) What is the magnitude of the losses of nutrient matter sustained 
by the crop when stored in the silo? Are such losses greater or smaller 
than those which accompany storage in the haystack? 

(3) Does the green forage suffer any marked diminution in digesti- 
bility and nutritive value during its conversion into silage, and what are 
the relative merits of the silo and the haystack in this respect? 

(4) What are the best kinds of forage to be grown in this country for 
the purposes of ensilage? 

In America, where the practice of ensilage has been well established 
on a very large scale for many years, numerous trials have been carried 
out at the various E.vperiment Stations with a view to throwing light on 
these questions. The conditions obtaining in that country, however, are 
markedly dilTerent from Enghsh conditions. The maize plant is the forage 
which is widely grown in America for the production of silage, and it has 
been found to be in every respect excellently adapted to this purpose. In 
this country, however, httle success has so far attended the efforts to 

* Wood and Woodman, Joum. of Agric. i'ci. 11, 304, 1921. 



H. E. Woodman 145 

grow and utilise maize forage for ensilage, and consequently the attention 
of agriculturists has been directed towards the discovering of other crops 
which are suitable for being grown for silage. A large measure of success 
has attended these efforts. Aniosi, for instance, has shown that a mixed 
crop of oats and tares jjossesses all the characteristics for the successful 
inclusion of the jDractice of ensilage in the ordinary farm routine. 

It would, therefore, be unsafe to assume that the results obtained in 
American trials with maize forage apply with equal force to the methods 
of ensilage which are being adopted in this country. Concurrently with 
the extension of the practice, it is necessary to prosecute enquiries with 
a view to obtaining satisfactory answers to such ci[uestions as those 
enumerated above. Investigations are proceeding in all these directions 
at Cambridge, and the work to be detailed in the present communication 
was undertaken in order to obtain a direct comparison of the digestibility 
of oat and tare silage not only with oat and tare hay, but also with the 
green oats and tares from which both hay and silage had been produced. 
Such information must be taken into account when coming to a decision 
as to the relative merits of ensihng and hay making. 

From prior considerations, it would be natural to presume that the 
processes of hay and silage making would result in a diminution of the 
digestibility of the ingredients of the green forage, since it seems reason- 
able to assume that whatever fermentative or bacterial changes take 
place, do so mainly at the expense of the more readily assimilated con- 
stituents. The characteristic change which occurs when green forage is 
packed into the silo involves the destruction of carbohydrates with the 
formation of organic acids, hke lactic and acetic acids. This is the result 
of fermentation mainly brought about by the enzymes of the plant cells 
and by bacteria. Since the more ea.sily assimilated carbohydrates are 
hable to be used up in this process, it would be anticipated that the 
residual carbohydrate ingredient of the silage would have a diminished 
digestibiUty. On the other hand, the percentage of digestible ether 
extractable material in the forage will be augmented by the formation 
of the organic acids, although the net result of the change must involve 
loss of nutritive value. This loss, however, need not necessarily, on theo- 
retical grounds, be considerable, since these changes are quickly arrested 
after the development of a sufficient degree of acidity. In any case, it 
should be remembered that all types of roughage suffer similar destruction 
of soluble carbohydrates during the time they stagnate in the rumen of 
the animal. 

1 Amos, Journ. of the Farmers' Chih, Part 2, 1920. 



146 Oat and Tare Silage 

Similar considerations arise when forage is dried in the field and stored 
in the stack. If this could be carried out without undue fermentation 
takiiij; ])la(p. then there seems no particular reason why tlie mere drvinp 
clown should result in any appreciable depression of the dij^estibility. In 
the usual practice of hay making, however, field fermentation and heat- 
ing in the stack tend to deprive the forage of quite considerable amounts 
of its more easily assimilated organic matter, and the usual effect is to 
cause a decrease in the digestibihty of the protein and the nitrogen- 
free extractives. 

The pos.sibility must not be lost sight of that the changes which occur 
in the silo and the haystack may be accompanied by an actual increase 
in the digestibility of the less easily assimilated ingredients of the green 
forage. For instance, evidence is not lacking that the heating which 
occurs both in the silo and the haystack leads to an increase in the 
digestibility of the crude fibre constituent. 

The changes which affect the protein ingredient of ensiled forage, 
resulting in an increase in the amount of amino acids, may be expected 
to lead to an increase in the "ease" of digestibility of the material, 
rather than to an increase in the actual protein digestion <-ocfficient, 
since the same type of change is readily brought about in the digestive 
tract of the animal. The palatable and succulent nature of good silage 
sliould give it a distinct advantage over the dried fodder in regard to 
the ease ^\-ith which the animal is able to digest it. Like other succulent 
foods, silage is reputed to have a beneficial effect on the digestive organs, 
although, of course, a poor quality of silage possessing undue acidity 
may have the reverse effect. 

The available data in connection with digestibihty trials on corn 
forage agree substantially with the foregoing considerations. The follow- 
ing table gives the average digestion coefficients obtained in a large 
number of American trials for corn silage and green and cured corn 
fodder^. 



Forage 


Dry 

matter 


A.sli 


Protein 


Crude 
(ibre 


N-free 
extractives 


Ether 
extract 


Green corn fodder, ",„ 
Cured corn fodder, "„ 
Corn silage, % 


68 
66 
66 


35 
34 
31 


61 
55 
53 


61 
66 
67 


74 
69 
70 


74 
72 
81 



These figures afford some idea of the relative digestibilities of the 
different ingredients of the three types of fodder, although it is not 
certain that in every case the results were obtained by strictly comparable 
trials. It will be noted that there is no appreciable difference in the 

1 Henry, Feeds and Feeding, 1902, p. 248. 



H. E. AVOODMAN 147 

digestibility ol: the com silage and dry corn fodder, the most marked 
difference being in the case of the ether extract, as would be anticipated. 
Both stored fodders are somewhat less digestible than the green fodder, 
although it is of interest to note that in the case of the crude fibre, the 
percentage digestibility shows an increase in the case of both the silage 
and the dried corn fodder. It is also noteworthy that drying and ensiling 
do not appear to depress the digestibihty of the nitrogen-free extract to 
any marked extent. 

General Arrangement of Experiment. 

For the purpose of the digestion trials, a plot of about 1600 square 
yards was measured off from a large field of oats and tares situated on the 
Howe Hill Experimental Farm at Cambridge. Within the hmits of the 
experimental plot, the growth of the crop was, to the eye, of a reasonably 
uniform character. 

In order to bring out in the sharjaest manner possible any differences 
in the digestibilities of the three types of foodstuff', it was decided that 
the experiment should consist of three main periods in which ample 
rations of the green forage, hay and silage, unmixed with concentrates, 
should be fed successively and their respective digestibihties determined 
directly. In the earlier work on oat and tare digestibihty, doubt was felt 
as to the desirability of keeping the sheep for a period of three weeks on 
an acidic food Uke silage alone, and the possibihty of digestive disturb- 
ance was avoided by feeding a smaller ration of silage together with a 
basal ration consisting of meadow hay and a httle linseed cake. This 
procedure necessitated the carrying out of digestibility measurements on 
the basal ration and the calculation of the silage digestibihty by difference. 
In this experiment, however, no difficulty was encountered in main- 
taining the sheep during the three weeks of experiment on an ample 
ration of silage alone. The quahty of the silage was good and the sheep 
from the outset consumed the ration quite readily without suffering the 
slightest discomfort. Indeed, it was noteworthy that less difficulty was 
experienced with the feeding during the silage period than in the green 
fodder and hay periods. When the green fodder was introduced into the 
diet, one of the sheep showed at first a tendency to be shghtly "blown," 
but by judiciously cutting down the amount fed for some days, this 
difficulty was overcome and a very satisfactory trial was obtained. In 
the hay period, one of the sheep displayed an inabihty to consume the 
entire ration, and consequently the digestibihty of the hay was deter- 



148 Oat and Tare Silage 

miued on a smaller ration tliau was previously designed. Reference will 
be made to this point again at a later stage. 

It was thus possible, by avoiding basal rations, to measure the 
digestibiUty of the silage directly on a much larger quantity of material 
than could possibly have been fed in an indirect method of determination, 
and, moreover, the conditions obtaining throughout the whole trial were 
thus made comparable. 

The green oats and tares period began on .Tune IG. 1921. Samples 
of about 25 lbs. were cut from the plot daily by means of a sickle and 
were passed through the chaffing machine before being fed to the sheep. 
During the few hours over which it was necessary to store the material, 
it was spread out in a thin layer on a concrete floor to prevent " heating," 
which occurred fairly readily when the cut fodder was kept in bulk in 
bags. The .samples for analysis were taken at the .same time as the rations 
for the whole day were weighed out. Moisture determinations were 
carried out on the representative .samples every two days during the 
analytical period, the dry matter from such determinations being 
utihsed in the making up of the period composite sample. The gradual 
increase of dry matter in the maturing crop is illustrated by the following 
figures obtained during the fourteen days' experimental period : 

Days 1-2 3-4 5-6 7-8 9-10 11-12 13-14 

Dry matter, % 2900 30-95 33-69 32-55 33-23 33-55 34-32 

As the approach of the crop to maturity was probably accompanied 
by a gradual diminution in the digestibihty of the forage, it was necessary, 
in order to secure a fair comparison with the hay and silage, that the 
parts of the plot reserved for the liay and silage should be cut halfway 
through the green oats and tares period. This was accordingly done and 
the material to be converted into silage was carted without delay, passed 
through the usual cutting machine and then packed tightly into a small 
experimental silo reserved for this purpose. Further particulars will be 
given when the details of the silage period are discus.sed ; it is sufficient 
to note here that all the conditions for making the silage were .satis- 
factory and material of an excellent quaUty was obtained when the silo 
was opened at a later date. The making of the hay was not attended with 
similar good fortune. The first two days during which the forage was 
drying in the field were beautifully fine and sunny, but a sudden thunder- 
storm shortly before the time for carting rendered the sample quite unfit 
for use in a comparative trial with the silage. It was therefore necessary 
to use another sample of oat and tare hay which had been carted before 



H. E. Woodman 149 

the storm, but whicli lia,d been cut at the same time as the forage on the 
experimental f>lot. It came from a neighbouring part of the field, but, 
as will be seen later, this circumstance detracted somewhat from the 
strictly comparative nature of the trials. The hay sample was finally 
packed tightly into a meadow haystack standing in a Dutch barn and 
a thick layer of straw was pressed compactly on top, so that the water 
vapour generated by the hea.ting in the stack should pass into the straw 
and not condense in the upper portions of the hay, thus causing it to 
mould. 

The experimental procedure in the trials was, in the main, identical 
with that adopted in the earlier work on oat and tare silage digestibility. 
The Hainan harness was again employed with success, and there can be 
little doubt that, from the point of view of convenience, safety and com- 
fort for the sheep, it is distinctly superior to the orthodox " funnel and 
bag" harness. 

The analytical period in all three cases consisted of fourteen days, 
this being preceded by a preliminary period of seven days. Bi-weekly 
composites of urine and faeces were made, nitrogen estimations being 
carried out on these samples. Determinations of dry matter were made 
on aliquot portions of the faeces samples, the dried residues being pre- 
served in air-tight bottles to be utilised in the making up of the period 
composite samples for complete analysis. Separate period urine com- 
posites were kept for dry matter estimations and the determination of 
the energy content by means of the bomb calorimeter. They were pre- 
served by the addition of chloroform. 

In the hay period, the daily rations for the whole period were weighed 
out previously into paper bags from the bulk of chaffed hay, the samples 
for complete analysis and moisture determinations being drawn at the 
same time. In the silage period, as in the green forage period, moisture 
determinations were made on representative samples every two days, 
the dried material being made up into the composite samples for com- 
plete analysis. It was not considered necessary to carry out determina- 
tions of nitrogen on the fresh silage samples, since in the earlier work 
with oat and tare silage, it was noted that no measurable loss of nitrogen 
occurred during the drying down of silage. 

In order to gain a trustworthy comparison of the digestion coefficients 
of the protein constituents of the three foodstuft's, it was essential to 
take into account the well-established fact that the faeces do not con- 
sist solely of undigested food residues, but that the latter are largely 
contaminated by nitrogenous metabohc products which have been 



160 Oat and Tare Silage 

secreted into tlie alimentary tract and escaped re-absorption. Thus the 
protein digestion coefficients as determined directly represent minimum 
values, and in view of the possibility of this disturbinjr factor operating 
unequally in the trials with the difTerent fodders, it was deemed advisable 
to correct the protein digestibilities by basing them on the amount of 
pepsin-insoluble nitrogen in the faeces. Accordingly, determinations of 
the pepsin-insoluble nitrogenous constituents of the faeces were made in 
all three cases. The error occasioned by the presence of metaboUc pro- 
ducts in the faeces affects, of course, the accuracy of the digestion co- 
efficients of all the foodstulT ingredients, but it falls with especial weight 
upon the protein and ether extract. No satisfactory and reliable method 
for correcting the ether extract digestibihty has so far been evolved^. 

The sheep were weighed at the beginning and end of each period and 
account was kept of the nitrogen balance. The wethers employed were 
the same as were used in the earlier work on oat and tare silage. A study 
of the results shows an extraordinarily good agreement between the sets 
of figures obtained for the two sheep. Such agreement is not often met 
with in work with animals, and it would appear that the two sheep 
selected for the purpose possessed almost equal digestive capacity. 

The writer's thanks are due to his as.sistant, Mr V. .T. Aylett, for the 
skilful manner in which lie took charge of the animals and for tJie care 
with which he carried out the analytical work in connection with the 
digestibihty trials. 

Table I . Dclaih of ratian-s. 





Daily 


Dry matter 


Period 


ratinn 


HI ration 




t,'[n. 


nm. 


Gropn oats and tares 


40(){) 


1 2S)il-0 


Oat and tare hay 


1000 


839-6 


Oat and tare silage 


3000 


8190 



In planning the rations for the trials, it was, for obvious reasons, 
intended that the sheep should receive roughly the same weight of dry 
matter per day throughout. This object, however, was not attained for 
the following reasons. The first moLsture determinations carried out on 
preliminary samples of the green oats and tares showed them to have a 
drv matter content of about 27 per cent. A diet of 4000 gm. of this 
fodder contained therefore about 1080 gm. of dry matter. By the end of 
the j)erio(l, however, the thy matter content of the crop rose to over 
34 per cent, and the mean percentage for the analytical ])erio(l was 

' For fuller information on this jmint, see Crowlher and Woodman, Jniini. of Agric. 
Sci. 8, 434, 1917. 



H. E. Woodman 151 

32-47 per ceut. The dryness of the crop was probably connected with the 
droughty season during which it was approaching maturity. TJie con- 
sequence of this gradual increase in the percentage of dry matter was 
that the sheep received a larger allowance of dry matter during the 
period than was intended. Further, it was noted during the prehminary 
feeding of the oat and tare hay, that one of the sheep was unable to con- 
sume comfortably more than about 1000 gm. per day. There was no 
alternative, therefore, but to cut down the daily ration to this amount, 
and as a consequence, the amount of silage given in the daily ration 
during the third period had to be kept at the hay dry matter level, since 
it was desired, above all, to obtain a clean-cut comparison between the 
hay and the silage. The possible effect of these circumstances on the 
strict comparativeness of the trials will be discussed later. 

(Ireem Oats and Tares Period. 

Condition of crop during trial. The crop consisted of autumn-sown 
oats and tares grown upon clay land. Equal quantities of grey winter 
oats and tares were planted, but the tares predominated at the time 
of the trial. Owing to the exceptionally dry summer, the crop was 
short in the straw and .stood well. The oats were just coming into milk 
and the tares were in full flower. The condition of the crop was therefore 
almost ideal for cutting for liay, but was somewhat premature, according 
to the customary practice, for silage. It follows that the conditions of 
the trial slightly favoured the green oats and tares and the hay rather 
than the silage. 

Table II. Composition of green oats and tares composite 
samjile {calculated to dry matter). 





0/ ■ 
/o 


Crude protein 


10-83 


Ether extract ... 


302 


Nitrogen-free extractives 


50-22 


Crude fibre 


28-12 


Ash 


7-81 



Average moisture content of green oats and tares = 67-53 °/g. 

Average amount of dry matter in green oats and tares per day = 1299-0 gm. 

Table III. Average weight and composition of faeces. 

Sheep I Sheep II 

gm. gm. 

Weight of fresh faeces daily 1483 1576 

Weight of dry matter daily 469-37 474-85 

Joum. of Agric. Sci. xii 11 



152 



Oat and Tare Silage 
Table III {cont.). Composition of dry maUer. 



Crude protein* ... 

Ether extract ... 
Nitrogen-free e.xtraetivcs 
('rude fibre 

Asli 

Pcpsin-HCl insoluble protein 

* Crude protein as dcterinini-d on fresh faeces 



Tabic 1\'. Digesiihility of green ouls and lures. 

Daily ration: 4000 gni. green oats and tares. 
Sheep 1. 



HEEP I 


Sheep II 


o/ 


o/ 


/o 


,o 


11-52 


9-54 


4-01 


3-99 


31-93 


3315 


40- IS 


40-84 


12-30 


12-48 


5-24 


5-17 


3-65 


3-15 



(Jnnsumed (green oats 

and tares) 
Voided ... 

Digested 

Digestion (-oeHieicnts, "{, 



Total 

dry 

matter 



129!)-(IO 
409-37 

829-63 
63-80 



Organic Crude 



matter 
gm. 



1197-55 
411-30 

786-19 
65-65 



protein 
m. 



Ether 
extract 



140-09 
54-13* 

86-56 
01-53 



39-24 
18-82 

20-42 
52-04 



N-free 




extrac- 




tives 




gm. 


gm. 


652-35 


305-27 


149-87 


188-59 


502-48 


176-68 


77-03 


48-37 



Sheep II. 



* Calculated on nitrogen of fresh faeces. 

I'rulcin digcslibilil// cvrrcded for metnhnlic nitrogen. 

SuKKp I Sheep II 

Protein coiisuniod, i;ni. ... ... ... 140-69 

Pepsin-insoluble protein \iiided, f.'m. ... 24-59 

Protein digested, gm. ... ... ... 116-10 

Corrected digestion coefficient, % ... 82-52 

Mean corrected digestion eoeliieient, % 82-5 



140-69 
24-55 

11614 
82-55 



Ash 
gm. 



1(11-45 
58-01 

43-44 

42-82 



Consumed (green oats 

and tares) 
Voided 


129900 
474-85 


1107-55 
415-59 


140-09 
49-65* 


39-24 
18-95 


652-35 
157-41 


365-27 
193-93 


101-45 
59-26 


Digested 

Digestion eoeliicicnts, "„ 


824- 15 
63-44 


781-96 
65-29 


91-04 
li4-70 


20-29 
51-71 


494-94 

75-87 


171-34 
46-91 


42-19 
41-59 


Mean digestion coi^lf., "„ 


03-7 


65-5 


63-1 


51-9 


76-5 


47-6 


42-2 



The Siitisfactory a<ireompnt displayed by the results for the two shee]) 
will be noted and also that the agreement in the case of the protein 
digestion coetiicicnts becomes still more marked after the large correction 
for metabolic nitrogen has been made. 



H. E. Woodman 153 

Table V. Percentages of digeslible nutrients in green oats and 
tares (calculated to drij matter). 

By combining the results of the digestibility trial with the tiguies giving the composition 
of the green oats and tares, it is possible to calculate the percentages of digestible 
nutrients in the forage (dry matter). 

/o 
Crude jjrotein* ... ... ... ... 6-83 

Ether extract 1-57 

Nitrogen-free e.xtractives ... ... 38-42 

Crude fibre 13-39 

Production starch equivalent (Kellner) 

per 100 lbs. clry oats and tares ... 44-92 

* Apparent digestion coefficient of protein employed in calculation. 

Table VI. Nitrogen balance during period, 
and, weights of sheep. 

Daily ration N consumed N voided 

4000 gm. green Av. per , ' > Av. daily 

oats and tares day In faeces In urine Total N balance 

gm. gm. gm. gm. gm. 

Sheep 1 22-.51 8-66 1100 19-66 +2-85 

Sheep II 22-51 7-94 12-18 20-12 +2-39 

Sheep I Sheep II 

St. 11). St. lb. 

June 16, 1921 9 4 10 1 

July 7, 1921 9 2| 10 1 

Change in weiglit - 1 ^ 

Whilst it is unsafe to base conclusions in connection with the utihsa- 
tion of food protein from short period experiments, it is satisfactory to 
note that the forage diet provided a satisfactory maintenance ration 
for the animals. 

Oat and Tare Hay Period. 

Condition of fodder at time of feeding. Reference has already been 
made to the unfortunate circumstance which rendered necessary the 
rejection of the hay from the experimental plot and the employment 
in.stead of an unspoilt sample from another part of the field. The con- 
ditions under which the material was stacked have also been described. 
The small stack weighed about 5 cwt. ; the outer portions, which were 
shghtly spoilt by mould, were rejected and a shoe of about li cwt. was 
cut down the middle (October 7, 1921). The sample was chaffed and the 
sampUng and feeding were carried out in the manner already described. 

The hay was mainly of a nice green coh)ur, shghtly bleached in places 
by the sun. It had no smell of heating in the stack, but retained the 
natural aroma of the herbage, characteristic of green hay. The crop was 
cut at an ideal time for hay, the oats being just in milk and the tares in 

11—2 



154 (Jitt (did Tare Si Inge 

full flower. The leaf had been well saved and the fodder could be described 
as "a useful sample of hay, although perhaps uot of the very best 
quality ^" A mechanical analysis carried out on a representative sample 
of the hay showed it to contain rouyhly 30 per cent, by weight of oats 
and 70 per cent, of tares. 

Taljlc \ II . ( 'ttni position of oal and tare liai/ comjjosile 
sample (calculated to drij iixitlcr). 

rriidc protein ... ... KMM) 

Kthor extract 20!t 

N'itrogen-free extractives t.">SI 

Crude fibre 2".)07 

Ash 9-13 

Average muisture content of oat and tare liay - l(i'04 "/q. 

Average amount of dry matter ill oat and tare iiay per day = 839-() gm. 

Attention has already been drawn to the reasons why the amount of 
dry matter fed ])or (lav during this ])eriod was smaller than in the pre- 
ceding period. The liigh percrntage of protein in the hay, as compared 
with the green forage, must also be noted. It would be expected that the 
Jiay dry matter would contain rather more protein than the dry matter 
of the green oats and tares, since, as a result of field fermentation and 
lieating in the stack, losses of non-nitrogenous organic matter occur. 

Table VUl. Average weight and composition of faeces. 

Sheep I Sheep II 

Weiglit of fresh faeee.s daily, gm. 601 701 

Weight of dry matter daily, gm. 291-73 290-80 

Composition of dri/ mailer. 

Sheep I Sheep II 

o/ o/ 

O CI 

Crude protein* 12-13 12-.')-t 

Ether extract 3-77 3-77 

Nitrogen-freo extractives ... 37-31 37-83 

Crude film- 34-20 34-2.5 

Ash \2r)9 11-0! 

PepsinHCl insoluble protein ... (i-21 <>-4(l 

* Crude protein as determined on 
/rc.«ft faeces ... ... ... 002 5-43 

The increase in the percentage of protein cannot, however, be wholly 
accounted for in this way, and the explanation is probably to be found 
in the fact that the hay was not. for reasons already stated, taken from 

' The writer's colleague. Mr .•Vrlhur Amos, M.A., very kindly cxj)ressed his opinion.^ 
regarding the quality of the hay and the silage used in these trials. 



H. E. Woodman 



1 .15 



the experimental plot, but came from another part of the held where 
the growth of the crop was not quite uniform with that of the experi- 
mental crop. That the crop was not quite uniform within the limits of 
the ex23erimeutal plot itself is evidenced by the fact that the silage was 
also shghtly richer in protein than would be anticipated from a study of 
the losses of carbohydrates in the silo. It is not considered, however, 
that these circumstances materially affect the main conclusions to be 
drawn from the experiment, though they illustrate the extra difficulties 
introduced into work dealing with a mixed crop. 



Table IX. DigestibilUy of oat and tare hay. 

Daily ration: 1000 gm. oat and tare hay. 
Sheep I. 



(onsunipd (oat and tare 

liay) 

Voided ... 

Digested 

Digestion coi'fticiiMita. "„ 



Consumed (oat and tarf 

liav) ... 
Voidi'd 

Digested 

Digestion ooeHicients, "„ 

Mean digestion coeff., % 



Total 

dr,y 

matter 



S39-00 
291-73 

-)47-87 
(15 -2 5 



Organic 

matter 

gm. 



7G2!I4 
2r)!5-00 

507-94 
(iO-58 



Crude 

protein 

gm. 



110-70 
30-18* 

SU-52 
09-00 



Ether 

extract 

gm. 



17-55 
11-00 

G-55 
37-32 



N-free 
extrac- 
tives 
gm. 



384-G2 

108-84 

275-78 
71-70 



Crude 
fibre 



244-07 
99-77 

144-30 
.TO- 1 2 



SuEEr II. 



Sheep I 


Sheep II 


116-70 


110-70 


18-12 


IH-99 


98-58 


97-71 


84-48 


83-73 



84-1 



Ash 
gm. 



839-60 


762-94 


116-70 


17,55 


384-02 


244-07 


296-80 


262-34 


38-06* 


11-19 


112-28 


101-65 


542-80 


500-60 


78-64 


(;-36 


272-,34 


142-42 


64-05 


65-62 


67-39 


36-24 


70-81 


58-35 


65-0 


06-1 


68-2 


36-8 


71-3 


58-7 



76-66 
36-73 

39-93 

52-09 



76-60 
34-46 

42-20 

55-05 

53-0 



* Calculated on nitrogen in fnsh faeces. 

Correction of ■protein d,igestibiUti/ for metabolic nitrofjen. 



Protein consumed, gm. ... 
Pepsin-insoluble protein voided, gm. ... 
Protein digested, gm. 
Corrected digestion coefficient, % 

Mean corrected digestion coefficient, % 



The results again show good agreement between the two sheep. They 
will be discussed in detail at a later staiie. 



156 <><(t Olid Tare Sila(/e 

Table X. Percentages of digest ihle nutrients in oat and 
tare hay sample {calculated to dry mailer). 



Oudp protein* 9-48 

Ether extract 0-77 

Nitrogen-free extractives 32-66 

Crude libre ... ... 1700 

Production stareli equivalent (Kellner) per 100 lbs. dry oat and tare hay =43-24. 

* Ap))arent digestion coefficient used in calculation. 

Tnl)l(' XI. Nitrogen balance during period 
and weights of sheep. 

Daily ration N consumed N voided Av. daily 

1000 gni. oat Av. per , * < N 

and tare hay day In faeces In urine Total balance 

gm. gm. gm. gm. gm. 

Sheep I 18-67 5-79 11-23 1702 +1-65 

Sheep II 18-67 6-09 12-18 18-27 -(-0-40 

Sheep I Sheep II 

St. lb. St. lb. 

Oct. 13, 1921 9 4 10 8 

Nov. 3, 1021 9 1 9 12 

Change in weight -3 - 10 

It is scarcely a matter for surprise tliat tlie slieep during this period 
lost a little weight, since the ration was scarcely up to maintenance 
requirements, owing to the necessity which arose of having tg cut down 
the amount of hay to secure complete consumption. Both sheep, how- 
ever, showed a sUght retention of protein during the trial. 

Oat and Tare Silage Period. 

Quality of silage used in experiment. The condition of the crop at the 
time of cutting (June 23, 1921) has already been described. The material 
was carted within three hours of cutting, so that Uttle or no wilting was 
allowed to take place. The silage was made in a miniature wooden silo^, 
which was 4 feet in diameter and 6 feet high and rested on a foundation 
of gault clay. The forage was first cut by the usual chaif-cutter and then 
filled into the small silo, precautions being taken that the material settled 
down compactly. A thick layer of soil was placed on top. The silo was 
opened on Nov. 8, 1921, and after rejecting the small amount of waste 

' A number of such experimental silos have been erected on the Howe Hill Farm in 
connection with work being carried out by Mr A. Amos and the writer on the making of 
silage mider controlled conditions, an account of which will be published shortly. 



H. E. Woodman 157 

material on top, silage of excellent quality was encouutered. It possessed 
a good green colour and a pleasant "fruity" odour, the smell of butyric 
acid beinr;: entirely absent. The silage as fed contained very few tare 
pods and no tare seeds, nor did the oat husks contain any solid food 
material. The sheep consumed it readily; the surplus was fed to stock, 
and it was observed that they ate it with relish and throve upon it. 

Fresh samples of silage for feeding were taken every day and the top 
of the silo was covered by a tarpaulin during the experiment. As the 
trial proceeded, the quality of the silage fell oft' slightly, owing probably 
to the slowness with which it was being used up. The last portions were 
not quite so green and "fruity," hut still were of good quality and quite 
free from butyric acid. 

AiKihjf^is uffiiJiifie ciiract. In order to gain some insight into the nature 
of the changes which had occurred during ensilage of the green crop, 
aqueous extracts of the silage were submitted to analysis. A 2()0 gm. 
sample of the silage was submitted to extraction by shaking for four 
hours in a shaking machine with GUO c.c. of distilled water. The extract 
was filtered first through hnen, the residue being well squeezed out, and 
then through a filter paper. 1.50 c.c. of the aqueous extract were made 
up to 500 c.c. with alcohol. This occasioned the separation of a small 
amount of precipitate, which settled readily, and the resultant clear 
alcohol liquid was submitted to analysis by the Foreman titration 
method^. Fuller details regarding the analysis of silage extracts will be 
given in another communication. 

Table XII. Analijsis of silage extract. 
(The data roter to 100 gm. of the fresh silage — moisture content = 72-9 °,',.) 

c.c. iV/10 

Total acid radicles (free and combined) ... 316'1 

Amino acids and amides of asparagine type 104-2 

Total organic acids of lactic and acetic type 211-9 

Organic acids volatile in steam ... ... 56-6 

Non-volatile organic acids ... ... ... 155-3 

Volatile bases ... ... ... ... 18-1 

Calculated as acetic acid, the percentage of volatile organic acids in 
the fresh silage works out at 0-34 per cent. This, of course, is reckoned 
as moisture by the customary method of determining dry matter, but 
allowance has been made for it in all the data tabulated here in connection 
with silage digestibiUty. To do this involved slight assumptions, which, 
however, could only possibly aft'ect the result to an inappreciable extent. 

1 Foreman, Bioch. Joarii. 14, 451, 1920. 



158 Out and Tare Silage 

Table XIII. ComjMsilion of oat and tare silage composite 
sample {calculated to moisture-free material). 



Crude i)rot<»iii ... ... 12-55 

Kther e.xtiac-t 4-32 

Nitrogen-free e.\trai:live.s 45-57 

(,'rudc fibre ... ... 29-44 

Ash 8-12 

Average moisture content uf oat and tare silage -72-70 %. 

Average amount of dry matter in oat and tare silage per day = 819-0 gm. 

Table XIV. Average weight and composition of faeces. 



Weight of fresh faeces daily, gni. 
Weight of dry matter daily, gm. 

Composition of dry 
matter 

Crude protein* ... 
Ether extract 
Nitrogen-free extractives 
Crude fibre 

Ash 

Pepsin-insoluble jirotein 

♦Crude protein a.s determined on 
fresh faeces 



Sheep I 


Sheep II 


569 


631 


291-73 


297- 10 


Sheep I 


Sheep II 


/o 


% 


1202 


11-00 


3-27 


3-12 


37-15 


37-75 


35-03 


35-23 


12-53 


12-90 


5-76 


5-65 



6-38 



5-64 



Table XV. Digestibility of oat and tare silage. 

Daily ration : 3000 gm. silage. 

Sheep I. 









Total 
dry 

matter 


Organic 
matter 


Crude 
protein 


Ether 
extract 


N-free 
extrac- 
tives 


Crude 
fibre 


Ash 
gm. 








gm. 


gm. 


gm. 


gm. 


gm. 


gm. 


Consumed (oat 


and tare 
















silage) 






819-00 


752-50 


102-78 


35-38 


373-23 


241-11 


66-50 


Voided . 






291-73 


2,55-18 


36-25* 


9-54 


108-38 


102-19 


36-55 


Digested 






527-27 


497-32 


66-53 


25-84 


264-85 


138-92 


29-95 


Digestion 


coefficients, % 


64-38 


66-09 


64-73 


73-04 


70-96 


57-62 


45-04 







Sheep II. 










Consumed {oat and tare 

silage) 
Voided ... 


81900 
297- 10 


752-50 
258-77 


102-78 
35-56* 


35-38 
9-27 


373-23 
11216 


241-11 
104-66 


66-50 
38-33 


Digested 

Digestion coefficients, "^ 


521-90 
63-72 


493-73 

65-61 


67-22 
65-40 


26-11 
73-80 


261-07 
69-95 


136-45 
56-59 


28-17 
42-36 


Mean digestion eoeff., "„ 


64- 1 


6.-)-9 


65-1 


73-4 


70-5 


57-1 


43-7 



Calculated on nitrogen of fresh faeces. 



H. E. Woodman 159 

The percentage of etlier extract i.s uot as large as would be expected 
from a study of the figures obtained for the organic acids in the silage 
extract. The difference is not wholly accounted for by the fact that a 
portion of the acids must exist in combination with bases, and it seems 
to indicate the occurrence in the silage of substances of an acidic nature 
which are not extracted by ether. Evidence that this might be the case 
was obtained during the titration of the extract with N/IO alkali. As 
the neutrality point was approached, a yellow colour developed in the 
originally almost water-clear solution. This point is being investigated 
further. 

Protein digestibility corrected for metabolic nitrogen. 

Sheep I Sheep II 

Protein consumed, gm. 102-78 102-78 

Pepsin-insoluble protein voided, gm. 16-80 16-79 

Protein digested, gm 85-98 8.5-99 

Corrected digestion coetticient, % ... 83-66 8.S-66 

Mean corrected digestion coefficient % 83-7 

As in the other two trials, there is little fault to find with the agree- 
ment shown by the two sets of coefficients. 

Table XVI. Percentages of digestible nutrients in the oat 
and tare silage sample {calculated to dry matter). 

0/ 
/O 

Crude protein ... ... 8-17 

Ether extract 3-17 

Nitrogen-free extractives 32-13 

Crude Bbre 16-81 

Ash 3-55 

Production starch equivalent (KeUner) per 100 lbs. dry silage = 45-59. 

Table XVII. Nitrogen balance during period 
and weights of sheep. 



Daily ration 
3000 gm. oat 
and tare silage 


N consumed 

Av. per 

day 


II 






N voided 




Av. daily 

N 
balance 


1 faeces 




In urine 


Total 


Sheep I 
Sheep II 


gm. 
16-45 
16-45 




gm. 
5-80 
5-69 




gm. 

9-88 

10-40 


gm. 
1.5-68 
16-09 


gm. 
+ 0-77 
+ 0-36 








Sheep : 


I Sheep II 








Nov. 14 
Dec. 5, 

Change 


, 192 
1921 

in w« 


St. 

1 9 

8 

sight 


lb. 

6 

12 

-8 


St. lb. 

10 5 

9 8 

-11 







Both sheep lost weight in this period, but no conclusions can be 
drawn from this as to the relative feeding values of hay and silage. The 



160 Oat and Tare Silage 

periods were too short and tlie sheep were not on controlled diets previous 
to the different trials. The sheep would readily have consumed a heavier 
diet of silage, l)ut it was desired to keep the amount of drv matter con- 
sumed per day rou^^hly the same as in the hay period. P>ot1i animals 
were rouijlily in nitrt)f^enous eiiuililnium during this peridd. 

Table Will. Siiiiiiiitiri/ of digestihllili/ n-sull.'^. 
1. Oonipai'isdii of dijiestimi eoellieients. 











Oat and tare 




< Jreen oats 


Oat and 


Oat and 


silage 




and t-ares 


tare iiay 


tare silatie 


(1920-21) 






/O 


",i 


.o 


Dry mattor 


03-7 


fW-O 


(ill 


iw-S 


Organic mattor 


(ir,r, 


(!(■• 1 


(»■!» 


r.5-8 


Cnnlr pidtciii (}i|)|)an'iu) 


(i:!- 1 


tiSl' 


0.5- 1 


07-2 


('null- protein (i-orrcc-led) 


H-2-r, 


84- 1 


83-7 


— 


Ether extriiet 


51-9 


3{i-8 


73-4 


78-9 


Nitrogen-fret' extractives 


76-) 


71-3 


70-5 


52-2 


Cnule HIjre 


470 


58-7 


571 


49-7 


Ash 


42-2 


53-6 


43-7 


50-2 



2. Percentages of digest ilile nutrients (calculated to dry matter) 
starch equivalents. 











Oat and tare 




Oreen oats 


Oat and 


Oat and 


silage 




and tares 


tare hay 


tare silage 


(1920-21) 




/o 


o 


o 


/o 


Crude protein 


0-83 


9-48 


817 


10-91 


Ether extract ... 


l-.'57 


0-77 


317 


3-35 


Nitrogen-free extractives 


38-42 


32-(iti 


3213 


19-47 


Crude fibre 


13-39 


17(11) 


16-81 


10-39 


l'r(]dnction .starch eiiuiva-l 










lent jier KM) llis. of dry 


44-92 


43-24 


45-59 


33-4 


fodder... ... ... ) 











Discussion of results. In the fourth column are given the ligures 
obtained from digestibiUty trials with the same sheep on the previous 
year's crop of oat and tare silage. These results were not corrected for 
the volatile acid content of the silage. They differ materially from the 
results obtained in the present investigation, the pre^^ous year's silage 
possessing on the whole a markedly lower digestibility. This difference 
comes out strikingly in the cases of the dry matter, organic matter, 
nitrogen-free extractives and fibre, whilst the protein and ether extract 
fractions possess similar digestibiUties. The previous year's silage was 
much richer in protein (16-2/5 per cent, on dry matter) than the 1921-22 
crop (12-55 per cent.), and this is reflected in the table giviug tJie amounts 
of digestible nutrients. The wide difference in the amoimts of dige.stible 
carbohydrates in the two silage .samples is also noteworthy, whilst the 
lower nutritive value of the previous year's silage is evidenced by the 
difference between the values of the starch equivalents. 



(1) Black winter oata sown. 

(2) Crop out on July 12, 1920. It w'as quite 
mature. Oats had just passed milk 
stage and tares were well seeded. 

(3) Crop allowed to wilt one or two day.s 
before carting. 

(4) Silage made in commercial silo; maxi- 
mum temj^erature of fermentation wa.s 
35° C. Silage brown in colour with 
somewhat pungent odour. 

(5) Seeds of both oats and tares in silage 
contained much solid food material. 



H. E. Woodman 161 

It is of interest to examine the possible reasons for these wide 
variations in the results for the two silages, since obviously a practical 
point of some importance is involved. The differences in the procedures 
by which the two crops were produced are noted below in parallel 
columns. 

Sn,.u;E 1920-21. Silage 1921-22. 

(1) Grey winter oats sown. 

(2) Croji cut on June 23, 1921. Crop was 
immature and ideal for hay. Oats were 
just commg into mUk and tares were in 
full flower. 

(3) Crop carted within three hours of 
cutting. 

(4) Silage made in miniature ailo. Tempera- 
ture of fermentation did not exceed 
25° C. Silage green in colour with 
pleasant fruity smell. 

(5) Silage contained very few tare pods and 
no tare seeds, and oat husks did not 
contain solid food material. 

The first set of conditions is customarily regarded as ideal for silage. 
The results of this investigation, however, indicate that early cutting 
and carting without wilting may lead to a great gain in palatability, 
digestibility and nutritive value of the silage, although, of course, the 
actual weight of forage carted may be somewhat smaller per acre. 

The chief results obtained in the present exjDeriment on the compara- 
tive digestibilities of the three types of fodder are, with the exception of 
the protein figures, in fair agreement with the results obtained in 
American investigations with corn forage. These results, which are the 
averages from a large number of trials, not necessarily strictly compara- 
tive, have been summarised earlier in the paper. It will be noted that 
the digestibilities of the total dry matter, total organic matter and crude 
protein are of a similar order in all three cases. The uncorrected figures 
for protein digestibihty indicated that the hay protein was distinctly 
more digestible than the protein of the silage and the green fodder, but 
on taking into account the metabohc nitrogen of the faeces, the in- 
equaUties are almost wiped out. 

It would be anticipated that striking differences would occur in the 
digestion coefficients of the ether extracts. The ether extract of the green 
forage is about half absorbed; in the case of the hay, the availability 
sinks to about 37 per cent., whilst with the silage ether extract, which 
contains the easily assimilated organic acids, the relatively high figure of 
73 per cent, is reached. It is not to be assumed, however, that the organic 
acids of the silage possess the nutritive quahties of the soluble carbo- 
hydrates of the green fodder from which they have arisen during ensilage. 



162 Oat miff Tare Silar/e 

Furthermore, it must Ix' borm- in mind tliat in not one of the three cases 
does the ether extract consist wholly of true fat. and also that the fat 
dijjostion coefficients are lialtlo to be subject to error, in view of the fact 
that the faeces always contain ether soluble material arising from meta- 
bohc products and not from actual food residues. 

The nitrogen-free extractives of the hay and the silage are approxi- 
mately of equal digestibihty, although in both cases the digestibility is 
lower than that of the corresponding fraction of the green forage. The 
depression of digestibility in this respect during the conversion of the 
crop into hay and silage is not, however, so great as has sometimes been 
supposed. 

It is interesting to note that the fibre constituent of the hay and silage 
is almost equally digested, whereas that of the green crop possesses an 
appreciably lower digestibihty. This finding confirms the supposition 
that heating in the stack and the silo leads to a definite increase in the 
dige.stibility of the crude fibre. In view of the fact that such fodders 
contain relatively large amounts of fibre, this increase of digestibility 
becomes of con.sidcrable significance. 

Attention should be called to the fact that whereas in the hay and 
silage periods almost equal amounts of dry matter were fed per day, yet 
in the green oats and tares period a much larger allowance of dry matter, 
for reasons already gone into, was consumed by the sheep. It is well 
known that animals tend to digest their food with somewhat less com- 
pleteness when the ration undergoes any marked increase in bulk. This 
variation is not necessarily very pronounced. Indeed, if it were, then 
the digestion coefficients based on feeding definite rations (usually sub- 
maintenance in such tests) could only possess a limited value. It is only 
fair, however, in comparing the green fodder digestion coefficients with 
those of the hav and the silage, to regard them as being minimum values, 
and to assume that if a ration of green fodder more comparable in dry 
matter content with the hay and silage rations had been fed. slightly 
higher values would liave been obtained. Tliis does not affect greatly the 
luain conclusion that the digestibility of the ]iay and silage dry matter 
compares very favourably with that of the green fodder dry matter. 

The findings outlined above are substantially confirmed by a study 
of the tabulated starch equivalents, which give the nutritive value of 
100 lbs. dry fodder for production in terms of lbs. of starch. If anything, 
these results point slightly in favour of the silage. 

The results giving the actual percentages of digestible nutrients in 
the dry foodstuffs, whilst not strict!}- comparable owing to slight non- 



II. R. WOOD.AIAN 1H3 

uniforniity iu the growth of the oat aud tare crop, show clearly that both 
hay and silage contain somewhat more digestible protein and fibre and 
rather less digestible nitrogen-free extractives than the green crop. The 
amounts of digestible ether extract vary within wide limits, the hay 
figure being very low and the silage figure relatively high. 

In commenting on the decrease of digestibihty which is assumed to 
occur when a green crop is ensiled, Henry and Morrison^ write: "The 
exceedingly favourable results from silage feeding are therefore due to 
the palatability of tiie silage, its beneficial eft'ect on the liealtli of the 
animals and the fact that less feed is wasted than when dry fodder is 
used." The results of this investigation indicate, however, that a con- 
tributory factor of great importance is the fact that the silage possesses 
a digestibility and a nutritive value which are only slightly, if at all, 
inferioi- to those possessed b}' the green forage from which it has been 
produced. 

Comparison of Metabolisable Eneruy of Greex Oats and 
Tares, Oat and Tare Hay and Oat and Tare Silage. 

In order to e.xtond the comparisons already outlined, it was decided 
to make determinations of the metabolisable energy of the three types 
of fodder. The metabolisable energy may be regarded as that portion of 
the gross energy of a foodstuff which is available for utilisation in the 
body of the animal; it does not, however, represent the true value of the 
foodstuft' for general production purposes, since further deductions are 
necessary in allowing for the energy used up in the processes of mastica- 
tion aud digestion. The metabohsable energy is ascertained by deducting 
from the gross energy of the food.stufi the losses of energy from the body 
in the form of the hquid, sohd and gaseous excreta; its determination 
involves, therefore, the carrying out of bomb calorimetric experiments 
on the foodstuft', dry faeces and dry matter of the urine. The course of 
the determinations will be gathered from a study of the following tables. 

Table XIX. Details of urine output during trials. 
Sheep I Sheep II 



Period 

Green oats and tares 
Oat and tare hay 
<Jat and tare silage 



Average 

daily 
amount 


Mean 
dry 

matter 


Average 

daily 
amount 


Mean 
dry 

matter 


c.e. 


/o 


c.e. 


(_)/ 


1140 
1826 
20.51 


(i-18 
3(10 
2-63 


1288 

954 

1812 


5 '68 
7-04 

3-2r, 



Feeds and Feeding, p. 51, 1917. 



164 



Oat and Tare Silage 



Tabic XX. Drij mutter balances per 100 gm. dry matter cotisumed. 

Sheep I Sheep II 



Average 
daily 
Diy matter dry matter 
Period consumed of faeces 


Average 

daily 

drj' matter 

of urine 


Average 

daily 

dry mattei 

of faeces 


Average 
daily 
- dry matter 
of urine 




gm. 


gm. 


gm. 


gm. 


gm. 


Gi-een oats and tares 
Oat and tare hay 
Oat and tare silage 


100 
100 
100 


3613 
34-75 
35-62 


5-42 
7-83 
6-59 


36-55 
35-35 
36-28 


5-63 
8-68 
7-19 


Table XXI. 


Heats of combustion per gm 


. nf drij miMer. 




Green oats and tares 4244 cals 
Oat ami tare hay 4211 „ 
Oat and tare silage* 4338-3 „ 








■ 


Sheep I 




Sheep 


II 


Period 


I^riue dry 
Faeces matter 
cals. cals. 


Urine dry 
Faeces matter 
cals. caLs. 


(Jrcen oats and tares 
Oat and tare hay ... 
(Jat and tare silage 


4317 
4511 
4517 


lU.'jO 
1708 
2100 


4326 
4441 
4413 


2059 
189t) 
2216 



* Allowance made for volatile a(-ids as acetic acid (Iiiat 
= 3490 cals.— Berthelot). 



I if conil Hist ion of acetic acid 



Table XXII. Energy balances per 100 gm. dry matter consumed. 

Sheep II 



Sheep I 



Period 

Green oats and tares 
Oat and tare hay 
Oat and tare silage 



G loss 
energy of 
foodstulf 

ral.-. 

424-4 
421-1 
433-83 



Loss of 

energy 

in faeces 

Cals. 

1.5.5-97 
156-76 

u;ns9 



Loss of 

energy 

in urine 

Cals. 

10-62 
13-37 

13-84 



Loss of 

energy 

in fiieces 

Cals. 

158-12 
156-99 
160- 10 



The above figures enable the metabolisable energy per 10(1 II 
foodstufi to be calculated. The results are expressed in therms 
= 1000 Cals.). 

Talilc XXIIl. Metabolisable energy per 100 lbs. dry foodstuff . 



Lo.ss of 
energy 
in urine 

Cals. 

1 1,59 

16-40 

I .'. O.T 

b,s. of dry 
(1 therm 





Green oats and tares 
therms 


Oat and tare hay 
therms 


Oat and tare silage 
therms 


Sheep 1 
Sheep 11 


116-94 
115-53 


113-84 
112-36 


117-.-.3 
116-93 


Mean 


116-23 


113-10 


117-23 



It \vill be noted that the agreement between the results for the sheep 
is again qiute satisfactory. The above figures, however, still require cor- 
rection for the energy lost in the gaseous excreta, which could not, of 



H. E. WuOD.MAN H).T 

course, be measured under the conditions of this experiment. Recourse 
was therefore had to the correction figure given by Armsby^, namely, a 
deduction of 60-1 Cals., was made per 100 gm. of digested carbohydrates. 
In this way, the following figures were obtained, which are compared with 
figures given in the second column, which have been calculated by the 
use of Armsby'.s factor by multiplying the digestible organic matter by 
1-588. 

Table XXIV. Corrected melaholisahle energies compared 
with calculated values {per 100 lbs. dry fodder). 

Experimental C'alculiitcd 

figure figure 

therms tlierms 

Creeu uats ami tares 102-10 'Jobl 

( )at and tare liav 09-55 95-23 

Oat and tare silage 10.3-89 95-72 

The values obtained by the use of Armsby's factor are thus uniformly 
lower than the experimental figures. 

The above results are in h-irmony with the conclusions drawn from 
a study of the digestibihty and nutritive value of the fodders. As between 
the hay and the silage, the advantage appears to rest with the silage. 
In order to obtain the actual productive energy of the foodstufi's (Net 
Energy Values), it would be necessary to make a further subtraction 
corresponding with the energy used up in mastication and digestion and 
ultimately lost as heat from the body (Increment of Heat Production). 
It may be presumed that this consideration would operate still further 
to the advantage of the silage, since it is reasonable to suppose that less 
energy will be used up in the mastication and digestion of the soft and 
succulent silage, than in the corresponding processes with the dry and 
coarse hay fodder. 

In conclusion, the writer would Uke to take this opportunity of 
acknowledging his indebtedness to Professor T. B. Wood, C.B.E., M.A., 
F.R.S., for nnich valuable advice during the course of this investigation; 
also to Mr Arthur Amos, M.A., who not only supervised the making of 
the hay and the silage, but also supphed the writer with many interesting 
and useful details concerning the growing of the crop and the quality of 
the respective fodders. 

1 Nvlrttioii of Farm Ainnmls, p. 030. ' 



{Received February 20th, 1922.) 



A NOTE ON THE CLASSIFICATION OF SOILS 
ON THE BASLS OF MECHANICAL ANALYSES. 

15 Y C. L. WHITTLES, 

School of Agricullure, Cambridge. 

(With Eleven Figures.) 

Although many schemes have been proposed for a classification of soils', 
not any single one seems to have found general acceptance. It is, how- 
ever, generally agreed that with any method, a final subdivision based 
on the texture of the soil is highly de.sirable, even though it only be the 
sands, loams, and clays of common jjarlance. (Jranted then that a 
classification based on mechanical analyses is called for — though not 
necessarily as the j)riiiiary division into groups — it is here proposed to 
examine some of tJie various methods so far put forward for dealing with 
the results of mechanical analyses. Tables of analytical results in them- 
selves are unwieldy and make decidedly iminteresting reading. The com- 
parison of a large number of soils is a slow and tedious proce.-^s, if it is 
accomphshed only by a study of the figures. 

Hope and Carpenter(22) have devised a method by whicii one can 
rapidly refer a soil to one of twelve types. In their classification the 
particles are classified into four groups, the limiting dimensions of which 
are given in Table I. 

Table I. Hope and Carpenter's Classification of Parlides. 

Limiting diameter in mm. 





Ingredient 


Maximnm 


.Minimi 


1. 


Coarse sand 


10 


0-28 


2. 


Fine- sand 


0-28 


004 


3. 


Silt 


004 


001 


4. 


Fine siU and clay 


001 


— 



Four broad divisions are distinguished according as one or other of 
these fractions occurs in the largest percentage. Each of these divisions 
is subdivided into three classes according as one or other of the three 
remaining fractions pre])onderates. Each ingredient is represented by 
a number (1, 2, 3 or 1), and the type is named by placing the division 

• See Bibliography. 



C. L. Whittles 167 

number first, followed by the appropriate class number. This is sum- 
marised in Table II. They point out that each type has a correspondinrj 
type into which it can merge by inappreciable degrees, the transforma- 
tion being effected by interchange in the proportions in the ingredients 
which are of primary and secondary importance respectively, e.g. 1 , 2 
to 2, 1. On the other hand, they can diverge far from each other in 
character. Other relationships are pointed out of which the most im- 
portant perhaps is the change in the secondary ingredient, as for example 
from i, 2 to 1, 3. 

Table II. Hall and Carpenter s Classifivaiion of Soils. 



Primary ingredient 


Secondary inaredient 




(division) 






(class) 


Type 






(-• 


Fine sand 


1,2 


. Coarse sand 




3- 


Silt 


1,3 






(4. 


Fine silt and clay 


1,4 






!^- 


Coarse sand 


■2,1 


. Fine sand 




Silt 


2,3 






[i. 


Fine silt and clay 


2,4 






1. 


Coarse sand 


3,1 


. Silt 




. 2. 


Fine sand 


3,2 






i. 


Fine silt and clay 


3,4 






1. 


Coarse sand 


4,1 


. Fine silt and 


clay 


, 2. 


Fine sand 


4,2 






3. 


Silt 


4,3 



The earliest reports of mechanical analyses were often illustrated by 
photographs of the actual fractions obtained. The sand, silt, etc., were 
placed in small phials of uniform size, and the predominance of the bulk 
of the material in certain grades served to give a more vivid idea as to 
the meaning of the figures of the analysis. The method at that time had 
its value, for the purpose of a mechanical analysis was not so well known 
then as now. Hilgard's text-book (21) and the early bulletins of the U.S. 
Department of Agriculture contain illustrations of this type. 

It is only a short step from the use of the actual fractions to that of 
shaded blocks. In Whitney's report on the tobacco soils of Maryland (57) 
a general summary of the types is given in diagrammatic form in which 
three grades are distinguished by different shading, viz. sand, silt and 
clay. 

In order to compare several soils or soil types on the same diagram 
the method of plotting the percentage of each grade against an arbitrary 
scale of grades has frequently been adopted. Differences are here far 
more obvious than resemblances, and their correct interpretation is 
almost as difficult as that of the figures themselves. The plotting of the 

Journ. of Agric. Sci. sn 12 



lo- 3 



168 Clas,siJicatioH of Soils 

summatiou percentage against either an arbitrary scale, a natural scale 
of mean diameters (7), or more conveniently tlir logarithms of the mean 
diameters, is to be preferred. By this means a very complete representa- 
tion of the analysis can be made, and the gradual gradation from type 
to type clearly seen. 1ml t he method becomes unintelligible if any number 
of soils are plotted on one diagram. A number of soil types arc shown in 
Fig. 1 , where the summation percentages are plotted against the logarithms 



Limit oi" EngmshFinrEarth 




lo.'OOOl ■ 



IWfil 



U.S. Eai'ly Market Garden 

Market Garden 

U.S. Market Garden 

Sheep and liarley 

Cherries and Fine Hops 

Tobacco 

Potato 



.. Orcliards 

•— .■ — «- Coarse Hops 

• • • • TT.S. Wheat 

. ■ >. Wheat 

l'..S. Wheat and Grass 

U.S tira=s and Wh^at 



Fig. 1. Comparison of types liy enmniation i\irvcs. 

of the mean diameters of the groups, the points so obtained being joined 
up by a smooth curve. The value -0001 mm. has been taken as the lower 
hraiting value of the dimensions of the clay group. This is purely an 
arbitrary proceeding. The proportion of "colloid" clay could here be 



V. L. Whittles Kjti 

shown with great advantage. In this connection the u.se of ultra-filtration 
methods might give valuable information. 

The curves for the fighter soils rise steeply and then flatten out, those 
for the heavier soils are flat at first and rise steeply later. Two particular 
appfications of these curves are of importance : 

{]) Two soils, analysed according to different systems of grouping of 
particles may be compared exactly. 

(2) The analytical results may be transformed from one system to 
another by reading oft' the values at the points at which the curve cuts 
the mean diameter of the selected classes. 

Baker (7) has devised two values for describing a soil from its mechani- 
cal analysis plotted in this way. This is of value for catalogue and descrip- 
tive purposes, but is not so well adapted for the preparation of drift 
maps as is the triangular method. In this method only three clas.ses of 
particles can be considered, which may be conveniently termed Coarse, 
Medium and Fine respectively. The question now arises as to which two 
limiting values shall be chosen for the separation of the Medium class 
from the Coarse and Fine grades respectively. Considering Fig. 1 we 
find that: 

U.S. Bureau of Soils take -0:3 and •()02!'). 
Wilsdon(58) takes -02.5 and -Odl. 

It is here suggested that, taking into consideration the known 
properties of the various grades, the curves are best characterised by 
their intercepts on the lines for -12 and -006. On this basis we have, on 
the usual English system: 

Coarse (fine gravel + coarse sand) 
Medium (fine sand + silt) 
Fine (fine silt -1- clay). 

Triangular Methods. 

In the method adopted by the U.S. Bureau of Soils the proportions of 
clay and silt are plotted along each of two axes at right angles. By joining 
the 100 points on these lines a right-angled triangle is formed. This is 
then conventionally divided up into compartments as shown in Fig. 2. 
The scheme of classification is given in Table III. 

Wilsdon has suggested a modification of this method whereby the 
proportion of the third constituent — the sand — may be read off directly 
from the diagram. The percentages of sand, silt and clay are plotted on 
an equilateral triangle. The detailed procedure is given in connection 

12—2 



170 Classification of Soils 

Table 111. U.S. Bureau of Soil's Classifitation. 



Coarse sand 
Mcdiuni sand 
Fine sand 
Sandy loam 

Fine sandy loam 

Loam 

iSilt loam 
Clay loam 
Sandy clay 

Sill clay 
Clay 



Fine 

gravel 

2-1 



Coarse " 
sand 
1-5 
mm. 



Medium 
sand 



More than 25 "„ (1+2) 

More than .W "„ (1+2 + 3) 

Less than 20 "„ (1+2) I 

More than 20% (1+2-t 3) 

Less than 20 "o (1+2 +3) 
More than 20'?;, (1+2 + 3) 

Less than 20% (1+2 + 3) 



Fine 

sand 

■25-10 

mm. 



Very fine 

sand 

■10-05 

mm. 



Silt 
•05-005 

mm. 



Clay 
•005-0 



0-15 \ 0-10 % 

Less than 20 "i, (G + 7) 

0-15% I 0-10% 
Less than 20 % (6 + 7) 



0-15% I 0-10% 
Less than 20% (6 +7) 

10%-35%|5%-15", 
More than 20 "„ ((> H 7 
l.*'S8 than 50 % (6 + 7) 



More than 20 "„ (6 + 7) 
Less than 50 "„ (6 + 7) 

Less than 15%-25",, 
55 % (6) 
More than 50% (6 + 7) 



More than 
55 % (6) 

•2.T o' _r,,-, q/ 



I>ess than 
25 % (7) 

25 %-35 



More than 60 % (6 + 7 1 



Less than 
25 % (6) 



More than 
20 % (7) 



Less than 60 % (6 + 7) 



More than 
55 % (6) 



25%- 
35 % (7) 



More than 
35 *^' (7) 
More than 60% (6 + 7) 



witli a furtlier inoditication. Soils arc clas.'iifipd into fmirtecii uroiips, th« 
liiiiiting 2)r()porti()ii.s are giveu iu Table 1\', and illustrated grajiliically 
in Fig. 3. 

Atteiitiou is directed to the following considerations in connection 
with this method : 

1. Only a comparatively small area of the whole triangle is employed. 

2. The crop types are not so well differentiated as in that of the 
U.S. Bureau of Soils. 



I 



i 



C L. Whittles 



171 



Table IV. Classification of Soils (Wilsdon). 







Percentage 






Sand 


Silt 


Clay 


DesiTiptirin 


(+004 mm.) 


(+0002 mm.) 


( -0002 mm.) 


Sand 


+ 75 


-25 


-25 


Sandy Itiani I 


+ B0 


-40 


-10 


„ II 


+ IJ0 


-30 


-20 


Heavy sandy loam 


-75 


-20 


-30 


Loam I 


+ 45 


+ 30 


-10 


„ II 


-45 


+ 45 


-10 


„ III 


-60 


+ 20 


-20 


,. IV 


-50 


+ 30 


-20 


„ V 


-40 


+ 40 


-20 


Silt 


-30 


+ 50 


-20 


Heavy silt loam 


-20 


+ 50 


-30 


Clay loam I 


-60 


-40 


-30 


>— 


+ 20 


+ 30 


-30 


Clay 


-70 


-70 


+ 30 



A + sign is placed before a minimum limit, and a - sign before a maximum. 



"'"/or 



20° 



\ al-.S. GiaiK 


^y ^ and Wheat \. 


\ Cuv \^ 


• U.S. Wieat \ 
,. ,Wlwat ami Grass \ 


Ci.AV Loam \^ 


^-1lS. Whea\ •^''"'^^- ""1" 
^' • Orchard* 


SiT.TV C'LAV I.CIAM \^ 


.S.VNOY LO.VMS \ 

,. ^Tobacco 
^ •Sh.q. and BaiU (hemes 


\ 


Sm.T 1,0AM \^ 


»U.S .Ma. kit (iaidiii i.'ii,;. 
• .Maikil tiardeii Jl„[,^ 


\ 


•is Ka]lv .Market Garden 
SaSUS 


\ 



-'»°/o ^"'°/o 

Fig. 2. Comparison of types by U.S. method. 



1110° /o 




Cr.AY 



Cr.AV Loam I 



Ci.AV Loam 11 

\ 



• Wliea t 

•l.'K Wheat^l.oAM n'.LoAM V' 
Sandy Loam\ Loam \ ^Coai'^XHops 



Potato 



MI 



lOep and Barley^ 

_ ^.Market lialdell 
VS. Kail? Market (!arH>-ii 



To^iae,-.. 



-• -lolKie. 
^ Cherried and Vi 
Loam I 



ine Hops 
\ Loam H 




SaMi.. II in nini 



.Silt XI 002 niui. 



Fig. 3. Comparison of t^'pes by Wilsdon's method. 



172 Classification a/ Soils 

3. It is difficult to associate each of the three clioseu groups with 
distinct properties in regard to their relation to the movements of 
water (49). 

4. Luxmore(2!i) has shown that many properties of soils can be 
correlated witli the proportion of particles havinfj; a maximum diameter 
of 0-01 mm. 

5. Takinf; into account the insensible degrees by which any given 
type merges into another, are we justified in laying down limiting per- 
centages for classes of soils? A soil with a given analysis behaving as 
a sandy loam in a district of deficient rainfall becomes a loam with a 
medium rainfall, and a heavy loam with a very high rainfall. The influence 
of the amounts of organic matter and of calcium carbonate cannot be 
ignored. 

6. Different analysts, working on the same sample of soil frequently 
— as often as not — obtain discordant results for the clay and fine silt 
fractions, though they will agree as to the total amount of these two 
grades present. 

7. The rapidity with wliich a large number of samples can be 
analysed if the determination of the clay is omitted is an important 
point. 

8. The curves for the sunuuat ion percentages are better characterised 
by the proposed limits. 

The various limiting diameters of the three classes are shown in 
Table V. 

Table V. Classification of particles. 

Limits of diameters in millimetres 

. * , 



Coarse (sandl Medium (silt) Fine (clay) 



System Maximum Minimum Maximum Minimum Maximum Minimum 

American 20 005 005 OOOf) 0005 — 

Wilsdon 10 004 004 0002 0002 — 

Proposed 30 0-2 0-2 001 001 — 

[Or possibly — 0-2 0-2 0-02 002 — ] 

Atterberg (44) has suggested the limits -2, -02 and -002, and there 
appears to be fairly strong evidence that a geometrical progression is 
the type of classification required. As English analysts do not recognise 
the hmit 0-02, the nearest English point (0-01) has been adopted here 
provisionally. The result obtained wifh the types previously considered 
is showm in Fig. 4. 



C. L. Whittles 



173 



The actual procedure adopted for plotting the results can be seen 
from the following example : 



8-9 



Fine gravel u a , .,- „ ,, 

Coarslsantl 170 , -'■^- ^''^'^'^■ 

^r '"""' III I 30-3. Medinm. 

Fine silt 24-5 1 .-,„ „ „. 

Clay 4-4 , ~^-^- ^""^ 



Fine ^OOl linn. 
Fine Siltl 
Clay 




ass\an(l Wheat 



Wheat and 
Wheat '''"^^ 



Ab 
Sheepand Barley* 



'^' ,«('oarse Hop 

Orchard .^tX ■^Vhe; 

]5^ •T(d)acc 



Chenies and 
I'otato Kiin, Woj.s 
U.S. Alarkel (iaiden ^ ^ 

U.S. I'^arl^ aiarket (iardeii 



CoARSE>0'2uim. 
I Fine (iravelj 
[Coarse Sand| 



0-2uim. Mkdu'im O'Ol mm. 

)Fine Sand| 
tSilt I 



Fig. 4. Comparison of types by proposed method. 

In Fig. 5 the side of the equilateral triangle ABC is 100 units, the 
apices represent 100 per cent, of the respective ingredients. 

From B along BA cut oft' BP = 25-9 units 
„ A „ AB „ AQ=30-3 „ 
„ A „ AC „ AR= 28-9 -„ 

From P, Q and R draw PA', QY and RZ parallel with BC, AC and 
AB respectively to form the triangle pqr. 

Then any point on the line PA' represents 25-9 per cent, of the coarse 
particles, on QY 30-3 per cent, of the medium particles, and on RZ 28-9 
per cent, of the fine particles. 



174 Clamficatioi) of Soil x 

Then tlie centre S of the triangle pqr, obtained by bisecting the base 
angles is the requirefl point. This construction avoids the necessity for 
raising the percentages arithmetically so that they total 100. In general 
they will be less than 100, for the losses on solution and ignition are not 
included in the amounts plotted. 

Soils with a high content of organic matter or of calcium carbonate 
cannot be compared by their position on the triangle alone. By the 
employment of an arbitrary colour scale, the organic matter content, or 
the acidity expressed in terms of titration values or of hydrogen ion 
concentration could be shown simultaneously with its approximate 
mechanical analysis. Rainfall and other climatic data arc obviously 
open to a similar method of treatment. 

In order that the position of a point on the diagram may be rapidly 
interpreted, a diagram showing the proportions of each of the three 
ingredients present, by steps of 10 per cent, has been prepared. By 
super-imposing this on any of the soil diagrams the limits of the groups 
can rapidly be read off. 

The amount of variation permissible in a mechanical analysis for 
survey purposes has been investigated by Robin.son(3;t). The analyses of 
the two yields, (a) uiiiforin, (h) too variable, are shown in Fig. 5. Atten- 
tion is drawn to this in order that an idea may be obtained as to the 
value that is to be assigned to any amount of scatter in a diagram. 

The general arrangement of the soil types is indicated in Fig. 4. The 
triangle has been divided up into three main divisions (marked in solid 
lines) according as one or other of the three ingredients predominates. 
Each division is subdivided into two classes (by dotted lines) according 
as one or other of the remaining two constituents is in excess. The inter- 
relationship between class and class is thus proportional to the length 
of the dividing line. They may merge into one another or diverge widely. 
For convenience of reference the classes nuiy be named A^, B^, Bq, 
Cfj, C^Y and A^,, respectively as shown. 

Fig. 6 shows a number of wheat soils from almost every geological 
formation. It will be noticed that they tend to be more or less concen- 
trated around those selected by Hall and Russell as typical. The lighter 
soils of Norfolk on which wheat is grown, though the soils are not par- 
ticularly well adapted to the crop, merge into the typical wheat group, 
which apparently lies near the boundary of B^. and C,, . The soils in 
Cg are on the whole more typically grass than arable (12, 16, n, 19,20,29, 

31, 36, 40). 

Barley soils are illustrated in Fig. 7. The crop is grown on soils of the 



C. L. Whittles 
c; 



175 



Fine Silt] 




(Fine Gravel 

Coarse Sand 



\i 

Fine Sand| 
Silt I 



Fig. 0. Wheat soils. 



176 



Classification of Soils 




Fig. 7. Barley soils. 



Coavsor 



/ 


V' 


> 


^^^. varu'tios. \ 


/ 


A,., 




• varieties % . \ 
• ®j • \ 

''^ .. .- \ 


/' 






t \ 



Fig. 8. Hop soils. 



C. L. Whittles 



177 



®TypiCcal Soils, quoted by Hall and Jfiisse 
• Other typical soils, from vaiions sources 

Soils on wliich crop is "irow n, tlioii"li 
soil not really topical oltlii' vv< 
©Ditto (quoted by Hall and Hussell) 




Fi". 9. Orchard soils. 




Fig. 10. Potato soils. 



178 



Classificatio)} of Soils 



three classes Ajj, B;^ and B^., but it is only the ligliter soils of the latter 
class that can carry sheep. 

Hop soils are illustrated in Fig. 8, and Orchard soils in Fig. 9. The 
comparison of these two types made by Hall and iiiissell(i!i) is clearly 
illustrated. 'J'lie orchard soils in Cjj, apart from the extreme case quoted 
by Hall and liussell from the Weald Clay, are all grassed orchards, and 
according to the Bristol Reports (U, 14, 55) suffer from canker to a greater 
or less extent. Evidently these soils are really too heavy for fruit. 

In Fig. 10 a number of potato soils are shown. The limiting factor 
for a potato soil, low content of coarse silt, is not brought out very well 
by this method (1, lo, 2o, 41). 




-Market garden soils. 



The Biggleswade Market Garden soils (35) which are most typical are 
shown in Fig. 11. Those which have been utilised on account of economic 
reasons have been omitted. Hall and Russell's Merton Alluvial .soils 
a])pr().\imate more closely to the i^igglcswade type than does the Wey- 
bridge, but these are both more of the Market Garden type than the 
Bagshot Windlesham and the Thanets from Swanley and Greenhythe. 



C. I.. Whittles 179 

Application to the Preparation of Maps. 

If each, of the tliree primary colours be taken to represent one of the 
three constituents (Coarse, Medium, and Fine), then to any position ou 
the triangle is a corresponding definite colour, produced by a combina- 
tion of the three primary colours in the same proportions. Any desired 
degree of differentiation may be attained by using a sufficiently large 
number of combinations. Steps of 5 per cent, would give 231 types, and 
this would be sufficiently accurate for all purposes, as will be seen from 
a consideration of Fig. 5. For the preparation of the drift maps of a 
district, stejjs of 10 per cent, giving 66 types would probably be sufficient. 
The proportion of stones and gravel, chalk, organic matter, etc., could 
be shown by dots or shading. Maps of the soil and subsoil prepared on 
these hnes would be of great value. 

In conclusion, the writer begs to tender his thanks to all those who 
have suppUed him with data and other help. 

A Bibliography on Soil Classification, with data for soil types. 

(1) AsHBY. .S. F. ( 190.")). A Contribution to the study of Factor.s affecting tlie Quality and 

C'(jinposition of Potatoes. Jour. Aijric. Sci. 1, 350. 

(2) Atterbeku, a. (1908). On Metliods of clay analysis. A'. Luiullhr. Ahul. Hniull. ocli 

Tidsl-r. 47, Nos. 5-0. 

(3) (1909). The constituents of mineral .soils; the analysis, classitioation and 

prmcipal properties of clay soils. Comjit. Rend. Conf. Inicnml. Aijrog^ol. [Buda- 
pest], 1. 

(4) (1912). Mechanical soil analysis and classification of iSvvedish mineral soils. 

A'. Landihr. Akad. Hand!, och Tidsh: 51, No. 0; Internat. Mill. Bodciik. 2, No. 4. 

(5) (1916). The classification of humus-free and huifius-poor mineral soils of 

Sweden according to their consistencies. Internat. Mitt. Bodenk. 6. 

(ij) Atteeberg, a. and Joiian.s,son (1916). The classification of the mineral soils of high 

humus content of Sweden. Internat. Mitt. Bodenk. 6. 
(7) Baker, H. A. (1920). Investigation of the mechanical constitution of loose arenaceous 

sediments by tlie method of elutriation. Geological Magazine, 57, Nos. 7-9. 
(S) BjjArlvkke, K. O. (1901-2). On the Classification of Soils. Berg. Norges. Laiidbr. 

Hoiskolen Virks, App. 
(9) Chulnoky, E. von (1909). Soil type as determined by climatic zones. Compt. Rend. 

Conf. Internat. Agroge'ol. [Bndapcst], 1, l(i3-176. 

( 10) Coffey, G. N. ( 1916). The present status and future development of soil classification. 

Jour. Atner. Soc. Agron. 8, 239. 

(11) FiPPiN, E. 0. (1911). The practical classification of soils. Proc. Atner. iSoc. Agron. 3, 

70-89. 

(12) Foreman, F. W. (1907). Soils of Cambridgeshire. Jour. Agric. Sei. 2, No. 2, 161. 

(13) CJiMMiNGHAM, C. T. (1912). Annual Report of the National Frnil and Cider Institute. 



180 Classitication of Soils 



(14) GiMMlNCHAM, ('. T. and Gkovk (1019). Annual Report of llie National Fruit and Cider 

Institute. 

(15) Glinka, K. (1914). Dir. Typen dcr BodtnbiUlumj (Berlin). 

(16) Goodwin, W. The Snih of NoHinyham.ihirc. 

(17) Haooard, H. R. (1902). Rural England. (Maps uf soils and crops.) 

(18) Hall, A. D. (1912). The value of soil analyses to the farmer. Jour. Roy. Agric. Hoc. 73. 

(19) Hall, A. U. and Russell, E. J. (1911). Tin: Agriculture and Soils of Kent, Surrey 

and Sugscjc. 
(20) (1911). Soil Surveys and Soil Analyses. Jour. Agric. Sci. 4, No. 2, 182. 

(21) Hiloard (190(i). Soils. 

(22) Hope, G. 1). and ('AKrENTKR, P. H. (1915). Siujgcst ions for the inanurial treatment of 

tea soils. (Indian Tea Association. Calcutta.) 

(23) Inkev, B. de (1910). Nomenclature and classification of soil types. // Conf. Agrogeol. 

Internal. Sl(x-kh(>hn. Resume' (l). 

(24) KossowiTSCH (1912). Die Srhwarzerde. 

(2">) Kossovacn, P. (1900). The genesis of soils and the principles of a genetic soil classi- 
fication. Zhur. Opuitn. Agroti. {Russ. Jour. Kxpt. Landw.), 7, No. 4, 478. 

(20) (1910). The soil forming processes and the main principles of soil classification. 

Zhur. Opuitn. Agron. (Russ. Jour. Expt. Landw.), 11, No. 5. 

(27) Lagatu, H. (1903). Vetude des terres el les cartes agronomiques (Montpelier). 

(28) (190.5). Classification and nomenclature of soils according to mineralogical 

constitution. Compl. Renrl. Acad. Sci. (Paris), 141, No. 6, 363. 

(29) LuxMooRE. Soils uf Dorset. 

(30) MiiRc:o(;c'l. Die Bodenzonen Rumdniens. 

(31) Newman, L. F. (19121. Soils and Agriculture of Norfolk. Trans. Sarfolk- and Soru-tch 

Naturali.fts Society, 9, 349. 

(32) Pendleton, R. L. (1919). Are soils mapped under a given type name by the Bureau 

of Soils Method closely similar to one another? Univ. Col. Pubs. Agr. Sci. 3, 
No. 12. 

(33) Ramann, K. (1920). />V)./.'Hi-»H</(; (Berlin). 

(.34) (1918). Hodenbildung und Budeneinleilung (MvrWn). 

(35) RiGG, T. (191H). Soils and Crops of the Market Garden District of Biggleswade. Jour. 

Agric. Sci. 7, No. 4, 385. 

(36) Robinson, t;. VV. (1913). Soils nf Shropshire. 

(37) (1917). Studies on the Palaeozoic soils of North Wales. Jour. Agric. Sci. 8, 

No. ,3, 338. 

(38) Robinson, G. W. and Hill (1919). Further Studies on the Palaeozoic soils of North 

Wales. Jour. Agric. Sci. 9, No. 3, 259. 

(39) Robinson, G. W. and Lloyd, W. E. (1915). On the Probable Error of Sampling in 

Soil Survey. .lour. Agric. Sci. 7, No. 2, 144. 

(40) RuEoo, L. H. Farming of Dorsetshire. Jour. Royal Agric. Soc. 15, 389. 

(41) Russell, E. J. (1921). Soil Conditions and Plant Growth. 

(42) Sauer, C. 0. (1918). A soil classification for Michigan. Ann. Rjit. .Mich. Acad. Sci. 

20. 

(43) Schreiner, O. and Skinner. .1. J. (191S). The Triangle System for fertilizer experi- 

ments. Jour. .-imcr. Soc. Agron. 5, No. 10. 225. 

(44) SciiucHT, F. (1914). Report of the meeting of the International Commission for the 

mechanical and physical examination of soil. Internat. Mitt. Bodenk. 4, No. 1. 

(45) Sibirtzev (1895). Genetic classification of soils. Memoirs of the Itistit. of Agric. and 

Forest, at Novo- Alexandria, Oovemment of LiMin, 9, pt. 2, 1-23. 



C. L. WllITTLKS 181 

(40) iSiBiKTZEV (1897). L'ctudc des sols de la Russie. Comjrci Ge'ologiqiie Inicniationale, 
SI Pe'tersboiirg. 

(47) (1898). Brief survey of the chief soil types of Russia. Memoirs of the Instil. 

of Agric. and Forest, at Novo-AIerandria, Government of Lublin, 11, jit. 3. 

(48) SiLVA, L. A. Rebello da (1907). Classification of Soils. Rec. Agron. [Portugal]. 

5. No. 10, 294-301. 

(49) Smith, A. (1917). Relation of the Methanioal Analysis to tlie Moisture Equivalent 

of Soils. Soil Science, 4, 471. 

(50) Tebbutt, L. (1920). Freneli Agricultural Soil Maps. Jour. Min. Agric. 27, No. 1. 

(51) Treitz, p. (1909). What is weathering? Conipt. Rend. Conf. Iiilcrnnt. Agroge'ol. 

[Budapest], 1, 131-161. 

(52) TuLAiKOPP, N. (1908). Genetic Classification of Soils. Jour. Agric. Sci. 3, No. 1, 80. 

(53) TuMiN, G. (1910). Mechanical analysis and cartographic grouping of rocks and soils. 

Ezhe^. Geol. i. Min.. Ro.<i.ni, 12. 

(54) Vy.soT.SKi, G. N. (1906). On climatic basis of classification of soils. Pochcooycdijenie 

[Pe'dologie], pp. 1-18. Abs. in Zliur. Ojiuitn. Agron. [Russ. Jour. E.rjil. Landw.], 
8 (1907), .536. 

(55) Wallace (1920). Annual Report National Fruit and Cider Institute. 

(56) Weibull, M. (1907). An investigation of soils of Southern Sweden. A'. Laiidtbr. 

Akad. Handl. och Tid.dr. 46, Nos. 2-3, 107-178. 

(57) Whitney- (1892). Report on Soils of Maryland. U.S. Weatlrr Bureau liiiU. No. i. 

(58) WiLSDON, B. H. (1919). The Need and Objects of a Soil Survey in the Punjaub. 

Agric. Jour, of India, 14, pt. 2, 281. 



(Received Febrtmr// 'I'Ind, 1922.) 



THE INFLUENCE OF SIZE AND CHARACTER 
OF SEED ON THE YIELD OF POTATOES. 

By KEDC'LIKFE N. SALA.MAN, .M.A., M.D., 
Barley, Ilerls. 

(With Four Text-figures.) 

The rosults of a preliiiiiuary iuvesligatiou ou tliis subject', in wliicli 
single plots were used, which were pubUshed in 1921, tended to show 
that the following inferences, in respect to the relation of size and type 
of tuber-set to crop, might be drawn. 

1. The size of the crop varied directly with the weight of the set up 
to a certain point, viz. 2 ozs., the crop then sinking slightly to a more or 
less constant level, whilst the weight of the set increased. 

2. The crop residting from the planting of large sets with secondary 
outgrowths exceeded that from all other types of sets and was as much 
as 25 Y>eT cent, more than that derived from sets of equal size without 
outgrowths. 

3. The proportion of heav}- ware in a crop varied inversely with the 
size of the tuber-set, and was not materially affected by the existence or 
otherwise of outgrowths on the set. 

4. The tendency to form outgrowths was not conveyed by tuber. 
The problem was re-investigated in 1921. As in the previous year, 

the Potato used was the variety Barley Bounty^, the crop of which had 
been grown in Scotland the previous season. The experimental plot was 
situated on the writer's farm at Barley, on a piece of ground which sloped 
gradually from east to west. The western end was shghtly more clayey 
than the eastern portion, but on the whole the soil was of a uniform 
type of loam and had been specially chosen on that account. The area 
of the ground on which the experimental sets were planted was 17-5 feet 
X 400 = 777 sq. yards. It was deeply cultivated: no stable manure was 

' Salaimin, R. N., Journ. of the Ministry of Agric. Vol. xxvni, April 1021. 
- This is a wart immune variety raisi-il by the author in 1911 wliich is very resistant 
to roll and mosaic and partially so to Phytophthora. It is not yet on the market. 



R. N. Salaman 1S3 

used, but it was sown with tlie following artiiiciai.s : superphospliate 
84 lbs., sulphate of ammonia 2(1 lbs., and kainit 28 lbs. The guard rows 
were treated in like manner. 

Eleven classes of seed tubers were selected, boxed and sprouted, on 
the same date. In each class the seed was weighed, pound by pound, so 
that there was a check both as to size and individual weight. Thus, 
ehminating as far as possible, any source of error arising from ine(iuahty 
of seed within each class, an error which has vitiated some otherwise 
valuable work in past years. 

Class A. Tubers weishing 0-6 oz. or 2l> to 1 lb. 

B. ., „ 1-33 ozs. „ 12 

C. „ ., I'-O „ „ 8 
D- „ ,. -'-66 „ „ 6 

E. „ „ 4-0 „ „ 4 

F. ,. ,. .5-33 „ „ 3 
U. Mixed unselecteil seed tubers. 

H. VVlicile tiiljers with outgrowtlis weigliiiig 2 ozs. eaeli. 

I. Tlie erown ends from tubers with lateral outgrowths 

w^eighiiig 1-66 ozs. each. 
J. Cut sets with outgrowths weighing 2 ozs. each. 
K. Qut sets with outgrowths, weighing 1'2.5 ozs. each. 

All tuber-sets presented short, strcuig sprouts and no blind sets were 
planted. 

Of these classes, B, C, D and G were present in sufficient quantity 
to plant five rows of 100 tubers each. A and E filled three rows respec- 
tively of 100 tubers each. F was sufficient for one full row and part of 
another. H, J and K were present only in sufficient quantities to plant 
part rows of each. It should be noted that in a standard plot, viz. a row 
100 feet long, not only was the number of sets the same, but in respect 
to any class, the total weight of sets was e.xactlv the same. 

Th.e experiment was planned on the checker-board system (see Fig. 1 ), 
but in place of square plots, single rows were used. As the variety was 
the same throughout, no need was felt for guard rows of some neutral 
variety between the rows, but surrounding the whole experiment were 
rows of the variety Golden Wonder, each section containing 100 tubers. 
On the northern side two rows of Golden Wonder were succeeded by a 
crop of barley, on the south the two rows were followed by more potatoes. 

The rows were exactly two and a half feet apart and the tubers were 
sown by hand, the distance between the centres of every two consecutive 
tubers being one foot. The spacing between tubers was carefully con- 
trolled by actual measurement as each tuber was planted. The covering 
in, first hoeing, and earthing up were done by horse labour. 

Joum. of Agric. Sci, xn. 13 



1<S4 liijhieair of Sad Wriij/if, etc. mi llt< I'dIiUo Crop 

Tlic ])l()t was so arranged tliat these seven rows, witli their two border 
rows on either side, eleven in all, ran from east to west. Each of the seven 
rows were subdivided by stakes at intervals of 100 feet making four such 
groups of 100 feet on end. 

The smaller lots were all planted in the lowest grou]) of rows and 
were so ])lauted that F, A and K together contained 100 tubers and made 
one complete row. whilst IT, J and 1 cliil the same in a ncighhouring 
row. 

(Jood intentions notwitlistanding, the plot proved to he anything but 
e({uable in character. As the drought proceeded it became increasingly 
clear that the lowest lying, i.e. eastern end, was favoured by more 
residual moisture in its rather more friable soil, and probably by a 
greater precipitation of dew, the influence of which on the colour and 
size of the plants was exceedingly clear. On the other hand, there was 
no apparent difference in tlie soil condition from north to south. It is 
true that the outermost row of Golden Wonder against the crop of Barley 
was even more impoverished than its neighbour or either of the guard 
rows on the .southern side of the plot, but this was undoubtedly due to 
the too close proximity of a vigorous cereal cro]). E'H passaiil it should 
be noted that two guard rows are insufficient as a jirotectiou to an experi- 
mental plot against a foreign_cro]), but tpiite sufficient as against another 
potato crop. 

Besides the exhausting effect of the drought, there was a frost on 
.luue I'Jth which nipped the leaves of several plants in all parts of the 
plot, whilst towards harvesting time surface caterpillars in search of 
moisture wrought considerable havoc on the tubers. No single set failed 
to produce a ])lant of some size. 

From April 19th, the day the tubers were sown, until they were 
harvested in October, no rain whatever (barring a slight shower in 
October) fell on the experimental ground, although heavy rain had fallen 
elsewhere in the parish during August. The potatoes were raised by hand 
on October 19th, exactly six months after planting, weighed at once and 
stored in separate bags. The analysis of the crop was made in January 
of this year. 

In Fig. I the plots are shown diu.grammatically. In the iourtli row, 
lots H and 1 in reality formed ])arts of the sanu' row as .1. and lots K 
and F parts of the same row as A. They are only placed in the diagram 
alongside each other for the sake of clearness. In each plot the return of 
cro]) per .set, i.e. the hundredth jiart of the total crop, is shown blocked 
in black, the actual figures are given in Schedule I at the cud of the 



R N. Salaman 



185 



n 



I 



I 



ill I , . 



I I 



ill 



w 



» 
o 



ll I 



I I 



I ill I 



I 



o 



H J I 



urn 




z<- 



-< M 



; ih. 



•lb 



I I ■! I ' I ' I I I I I M I I I - 



50 5 10 15 16 

Fifi. 1. 



13—2 



186 liijlmiici' of S(((l Wdijht, clc. on the rofdfu Crop 

paper, in the case of tlie smaller lots in the lowest row, the return per 
tuber set is calculated after correcting for the lesser number of plants. 

As there was no disease in the tubers at all, there being but very 
little in this part in 1921, and the variety itself exhibiting considerable 
resistance to I'hytophthora, no allowance was needed for this possible 
source of error. If the diagram lie studied it will appear that: 

(rt) Tliere is much less variation in tlie crop return on the guard rows 
both as regards plots alongside and plots above or below eacli (jther, 
than there is in the case of the A-K series. 

{b) That whilst yields in the outermost guard row on the north side 
are uniformly less in all four of its divisions than those of its inner 
neighbour, those of the latter do not materially differ from those of the 
two guard rows on the south side, which, in their turn, are almost com- 
pletely ahke. 

(c) The variation between the uj)i)er and lower divisions in the guard 
rows, more especially the inner northern and the two southern rows, is 
such that the crop is gradtially increased from east to west so that that 
of the latter is twice the value of that of the former rows. On the other 
hand, the returns of any of the four rows sliows no appreciable variation 
from north to south. 

Turning to the A-K series, it will be seen that B, C, D and (f are 
represented at least once in every row, so that in their case the variation 
in the soil condition which nuinifested itself is, in its effect on crop, 
neutralised. 

In respect to A. E and F we are on less sure ground, but as will be 
seen later, it is ])ossil)le to arrive at results in respect to them wliich would 
appear to be almost equally satisfactor}'. 

The first problem was to find the standard deviation of differences. 
As B, C, D and G occur in all rows, tl.e pairs BC, BD, Bb, CD, Cb, CG 
were taken first. Whenever B, C or D was duplicated in a given row, 
both possible pairs were taken, but throughout, only pairs in the same 
row were considered. To tliis group of thirty-five pairs was added 
fifteen composed of the pairs EB, EC, and ED, each occurring four 
times, and E(! which occurs three times. Thus ten pairs of varieties gave 
fifty pairs of plots, each pair in the same row. 

The standard deviation thus obtained is I-IO lbs., which allows of a 
probable error for one 2>air of 2-77, or for four jmirs of l-;58. 

There is next the difficulty of obtaining comparable mean yields for 
each variety. The data for B and C are : 





R. N. Salaman 




Row 


B 


C 


1 


19-5 


21-5, 28-25 


2 


26 


31-5 


3 


32-5, 39 


35-5 


4 


56 


51 



187 



If we average these results as they stand, C will be given two plots 
in the poor row 1, and B two plots in the good row 3. The average of 
B will thereby tend to be made greater than the average of C. This will 
not do. Where any variety had more than one plot in a row, the figures 
for these plots were therefore replaced by their mean, and the average 
calculated from the four resulting figures. In this way we get the com- 
parable or standardised yields for B, C, D and ( > : 





Standardised yield, 


B 


34-3 


C 


35-7 


D 


41-6 


G 


40-6 



The yields of B, C and D are in the same order as size of set, and the 
difference (7-3 lbs.) between the greatest and least is over five times the 
probable error of the dift'erence (1-4) — taking this probable error as based 
in effect on only four pairs of plots. 

But there remain A, E and F of the variety used for testing the effect 
uf size of set. A has plots only in rows ], 3 and 4: hence the averages 
obtained in the same way as above for A and for the plots in the same 
rows of B, C and D are not comparable with the standardised figures 
above; and we want a comparable figure. 

This was obtained in the following way: on the three pairs of plots 
available, the total yield of A was 76-5, and of B 111-2. The standardised 
yield of B is 34-3. An estimated standardised yield of A may therefore 
be put at 76-5 x 34-3 ^ 111-2 or 23-6. From the similar figures for C, 
D and G we obtain estimates of 24-5, 24-3 and 24-4. These figures are all 
fairly close together, and we may take their mean, 24-2, as a fairly close 
estimate of the standardised yield of A. Standardised estimates for E 
and F were similarly obtained, viz. E, 47-5. and F, 67-3. 

These figures increase without a break from the smallest sets A, to 
the largest sets F, so there can be no doubt about the result. For B, C 
and D, as already stated, the probable error of a difference is about 
1-4 lbs. For A, E and F. owing to the method of estimation, we cannot 
state a precise probable error, But if the probable error of the difference 



1S8 hijlin lire of S('<<l Wrli/ht, <fc. on titr Potato Crop 

between A ami K be as large as 3 lbs., the actual difference between their 

yields is over fourteen times this. 

The standardised mean yields for each of the seed classes A to can 

now be irivon: 

A -IX-l E 47-5 

B 34-3 F 67-3 

C 35-7 G 40-6 

D 11-C 

and are shown diagrammatically in Fiji. 2, from which it is clear that the 
crop increases directly willi tlie weijiht of the tuber set. If the mean is 
taken of the values of the series A-F, we obtain the figure 41-8 for the 
mean yield of the si.x seed classes, which corresponds very closely with 
40-6, the standardised yield for G, the seed class where tubers are planted 
without any conscious selection. This close approximation is of particular 
interest, for it not only confirms the general correctness of the calcula- 
tions, but it shows that the choice of the six seed classes A-F probably 
covers all the chief possibilities ilUustrating the variation of yield arising 
from seed weight differences. 

Sfandnnli-'cd yields in pounds per set 



16 
15 
14 
13 
12 
11 
10 

9 

8 

7^ 

6 

5 

4H 



1 ■ 



lib 



inilh 



B 



d size 



C D E F G 

Fip. -1. 

Middleton^ also found a positive correlation between yield 
of set but only dealt with three sizes. 

The 19-21 results differ in one respect from those of 1920, where the 
2 ozs. set produced the maximum yield, whereas in this year the yield 
increases pari passu with the weight of the set. It may well be that the 
latter result is the generally correct one. but the possibility must not be 

' Middleton, T. H., Guide to Experiment condvcled at Burgo)/ne\<! Farm, etc., Camb. 
Univ. Dept. of Agiicidtiirc, 1907. 



R. N. 8ALAMAN 1.S9 

overlooked that in a normal season the sets weighing 2 ozs. or thereabouts 
might again prove to be the best, and that the advantage accruing to 
heavier sets in 1921 is due indirectly to the great drought, when the 
absence of moisture in the soil gave a fictitious value to tlie heavier tuber- 
sets because of the greater quantity of moisture contained in and about 
their relatively larger bulk. 

The lots H, J and K. representing the tuber-sets classes with out- 
growths, produced crops of 50, (il-6 and 50 lbs. respectively. In the 1920 
trials the outgrowth tuber-sets were whole and weighed 6 ozs. each, and 
produced a crop 25 per cent, bigger than any other class of seed. In this 
year's experiment there were no large tubers with outgrowths. Indeed, 
the latter, on any size tubers were rare. 

The outstanding feature is the high yield of class J, the cut sets with 
outgrowths of average weight 2 ozs. This exceeds the yield of H or K 
by 14-6, which is five times the probable error for a single pair, and 
although it is true that the probable error for a plot of 65 tuber-sets is 
greater than for one of 100, yet a difference as great as here observed 
cannot be regarded as other than very significant. 

Assuming, therefore, as we may. that the excess of yield of the .T 
class over that of H or K is to be referred to the difference of kind in 
the seed set, it becomes of interest to consider what this difference really 
consists in. 

In class .1, the only buds left are those eyes on the secondary out- 
growth, whilst there are 2 ozs. of flesh for their shoots to feed on in their 
early stage. In class H we have whole tubers of the same weight as the 
J class, but here the outgrowth is only a part, and that a minor one, of 
the whole tuber, and the shoots arising from it have to compete for 
nourishment with those arising from the other eyes of the tuber, and 
hence have not the initial advantage which the J class enjoys. 

Class K consists of isolated outgrowths with but small quantities of 
tuber material to feed on and is, in a season such as that of 1921, at a 
distinct disadvantage. 

Class I consists of the rose or crown ends of the tubers from which 
the cut sets of J and K have been removed. Their average weight was 
1-66 ozs. There is no reason to expect that these sets should possess any 
greater advantage than any other tuber-set of the same size which was 
devoid of outgrowth. Indeed, in respect to weight of tuber-set the yield 
that might be expected would be something between that given by classes 
B and C in the same row, say 52 lbs. However, the reahsed yield of 40 lbs. 
is sufiicientlv widelv removed from this figure to suggest a difference of 



190 fnjiiienee of Seed Weight, etc. on the Potato Crop 

significance, and one is tempted to sec in this reduced yield a confirmation 
of the conclusions reached by Middieton* that in general, cut sets were 
inferior in cropping capacity to whole tubers. 

As in 1920, so again in 1921, the realised crops from each class were 
analysed in the following manner: 

A ]() lb. sample was weighed out on a spring balance and was then 
sorted into the following classes: 

Tubers weighing 



2 to the 


11). 


Tubers 


weighing 


11 


to the 


lb. 


3 








>) 


16 






4 








>j 


18 






5 








j> 


20 






6 








>> 


24 






7 








)? 


30 






8 








5) 


36 















under tliis weight 




2 

















It was found that when this subdivision was made and the individual 
groups summated, they always came to a figure within a little of lOi lbs., 
the excess being due to error of the balance in weighing small lots. It is 
for this reason that the relative proportion of the different classes sliown 
in Figs. 3 and 4 is calculated to lOj lbs. It should be realised that in 
each of these classes into which the crop has been subdivided, the tubers 
are practically of exactly equal weight and size. The actual figures are 
given in Schedule II. 

Although in all the sani])les, division into all the 1 7 classes was carried 
out — as far as the material in each case allowed — it was found that for 
practical purposes it was better to re-group the findings into four classes: 

1. Tubers of 3-33 ozs. and over. 

2. ,, over 2 ozs. and under 3-33 ozs. 

3. ,, „ I oz. „ 2 ozs. 

4. ,, under 1 oz. 

As regards classes B, C, D and G, the mean value of each weight 
group in the crop was readily determined, always, however, taking the 
mean of the determination where two examples of a class occurred in 
one and the same of the four rows in the experimental plot. 

In regard to A, E and F. the same method in determining the mean 

' Middleton, T. H. Guide. In K.r/ierinnnis conilurlcd nl liiiiyni/iic's Fartn, etc, (amb. 
Univ. Dept. (if Agriciilliiri', I'.KIT. 



R. N. Sal AM AN 



191 



value of each weight group was appHed as was used to determine their 
standardised mean yields. 

The results are shown in Fig. 3. Concentrating on the production of 
heavy ware (Class 1 of the weight series rendered sohd black in the 
figure) it will be seen that, except for a very shght increase, viz. -5 per 
cent., of this class in the B series over the A, there is a steady decrease 
of heavy ware with every increase of weight of the seed. 



10-6 lb 

10-5' 

10- 




7 
6 
5 
4 
3 
2 

1 

■5 



C D 

Fig 3. 

A. Sets weighing -6 oz. each. E. Sets weighing 40 ozs. eaeli. 

B. „ ,, 1-33 ozs. „ F. „ „ 5-33 ozs. „ 

C. ,, ,, 20 ozs. ,, 0. ,, unselected. 
J). ,, ,, 2'()6ozs. ,, 

^^^^^H Represents the weight of tubers of 3-33oz3. and over in every lOJlb. sample. 
^^^^ ,. ,. ,. 2.0OZS. „ 

wzm. •' " '■ 1°^ 

„ less than loz. in wt. „ ,, 



192 lojinence of Seed Weight, etc. on tin Potnto Crojt 

Turning to tlie production of the lighter tubers in the yields, two 
facts emerge. In the series A-D, the quantity of "chats" decreases in 
direct ratio with the weight of the set, and therefore in the same ratio 
as that of the " ware" in the same yield. On the other hand, in the E and 
F tuber-set series the amount of " chats " is much in excess of that found 
in any of the A-D groups. So that it would appear from these results to 
be very clearly demonstrated that heavy sets, weighing 1 ozs. and over, 
not only give greatly reduced ([uantities of useful heavy ware, hut also 
return in tlieir produce an altogether exce-^sive proportion of useless 
chats in comparison with the yields rendered by tuber-sets of smaller 
size. This result is entirely in accord with that obtained in the favourable 
season of 1920, when the sets weighing 4 ozs. and over produced roughly 
twice as many chats, and one-third or more less ware, than the sets of 
lighter weight. 

A similar analysis of the yields was made of the tuber-sets groups 
H, I, .1 and K, and the results are shown in Fig. 4, where they are placed 
in comparison with all the other groups represented in the same portion 
of the experimental plot. In this series the outstanding fact is the 
enormous proportion, viz. 4U per cent., of heavy ware produced by the 
K series. If reference be made to Kig. 1 it will be seen that series K 
and F were grown in the same line in the same portion of the experi- 
mental plot, and so may be fairly compared. The F series, however, are 
tuber-sets of 5-:53 ozs., whilst the K are outgrowths of 1-25 ozs. in weight, 
and the great disproportion, between 5 per cent, and 40 per cent, of the 
whole sample, the quantities of heavy ware produced by them res{)ec- 
tively, is confirmatory evidence of the previous deduction, that the 
Ughter the weight of the tuber-set, the greater the proportion of heavy 
ware produced. 

This relation of size of set to quantity of heavy ware was observed 
by Sir Thomas Middleton^, but liis results were unknown to the author 
till after this paper was written. 

No explanation is advanced either of this relation or of that between 
the weight of set and the weight of the total crop, but it is permissible 
to suggest that both phenomena may be related to the le.sser maturity of 
small tubers. 

In each of the analyses of crops made, — and many were duplicated — 
record was kept of the presence of secondary outgrowths on the tubers. 
Doubtless owing to the fact that this particular i)iece of land never 

' Midilleton, T. H., "Potato Ex]K'rinu'ntH at l{iiii;o\ lie's Farm, Impingtoii, Ciiinbs.," 
The Pdldlo Year liuok, 1907. 



R. N. 8ALAMAN 



1 90 



received any of the late rains enjoyed by other parts, there were but 
very few, and they of very small size. It was found that their presence 
was not correlated with any feature such as size of tuber, nor were they 
any more frequent in the group H, I, J or K than in those of the series 
A-F. As in 1920, no evidence is forthcoming that such growths are 
conveyed by tubers from one generation to another. 




I 




A B C D F G H I 



Fi.L'. 4. 
A — G. As liefoie. 
H. Whole tubers with outgrowths, 2 ozs. eacli. 

I. Crown ends from tubers with outgrnwtlis. l-finzs. each. 

J. Cut sets witli outgrowths, 2 ozs. each. 
K. Cut sets with outgrowths. 1-25 ozs. eaeli. 



H^HjjjJI Represents the weight of tubers of 3-33 ozs. and over in e\erv lOi H>. sample 
„ ,, ,, less than loz. in wt. ,, ,, 



194 Infuence of Seed WelgJtt, etc. an the Potato Crop 

The results attained in 1921, which so closely bear out those su{i;gested 
by the experiment of 1920, may be briefly summarised: 

1. The total yield varies directly with the wcijjht of the tuber-set. 

2. That small sets under 1 oz. in weight, although giving a great 
return in proportion to tlieir weight, and a high proportion of heavy 
ware, are unccononiical. 

3. That taking into consideration the total weight of seed used, the 
proportion of heavy ware produced and the total yield, sets of 2 ozs. in 
weight are the most remunerative. 

4. Cut sets consisting of secondary outgrowths weighing 2 ozs., and 
whole sets with similar outgrowths of the same weight to a lesser extent, 
produce considerably heavier crops than any other type of set, and at 
the same time produce a high quantity of heavy ware. 

5. There is an inverse ratio between the size of the seed set and 
the percentage of heavy ware in the resulting crop. 

6. The productivity of secondary growth, as well as 'the high pro- 
portion of heavy ware, yielded by small tuber-sets, may be correlated 
with immaturity of the seed tuber. 

7. There is no correlation between the presence of secondary growth 
in the seed set and the existence of the same in the resultant crop. 

Schedule I. Showing the weights of crops in poiinrls of each seed 
class in the experi»wntal area, including the (luard Rows. 



Guard 


lOWH 














Guard 


rows 


4 


3 
11-5 


A 


B 


C 


D 


K 


G 


C 2 


1 


9-.'5 


12-5 


19-5 


21-5 


26-5 


35-5 


30-5 


28-25 10-5 


10-5 




Ifio 


D 


E 


F 


C 


B 


D 


G 




10 


32-25 


37 


49-25 


31-5 


20 


39 


35-25 10 


20 




17-4 


B 


C 


A 


G 


D 


E 


B 
39 21 




11(1 


.32-5 


35-5 


27 


39-25 


48-25 


48-25 


10-5 






C 


G 


H' 


D 


B 


G 


A^ 




10 


24 


r>i 


50-5 


7-5 
P 
8 
J» 
42 


50 


50 


58 


18-5 27 

Fs 
10-5 

K« 
20 


24-5 






1.^ seta plan 
20 


ted. 




' A. 

6 F, 


50 sets planted. 
10 






' J, 


05 


» 






•K, 


,40 


*i 





1{. N. Salaman 195 

Schedule II. Analysis of crops of each of the seed classes as they occur in 
the experimental area, showing the amount in pounds in each weight 
grade excepting the 'chats^ under 1 oz. out of sample weighing l()-5 lbs. 

Tubers weighing over 3-3 ozs. 
A B C D E (J C 















(1 


1) 





D 


E 


K 


c 


H 


U 


G 











•5 











B 


C 


A 


G 


i) 


E 


B 



■i-2 



2 


1-25 


•5 


■5 


1 


H 


D 


B 


G 


A 


2-5 


1 Ij 


2-33 


;i-5 


2 


1 
1-3 








F 
■5 


J 

1 








K 
4 



Tubers weighing over 2 ozs 



A 


B 


C 


D 


E 


G 


C 


2 


1 


2-5 


1-5 


1-5 


1-5 


2-5 


D 


£ 


F 


C 


B 


D 


G 


2-6 


1 


1-5 


1-75 


1-5 


3 


2-37 


15 


C 


A 


G 


D 


E 


B 



4 


3-5 


4-5 


3-25 


3-75 


2 


3 


C 


G 


H 


D 


B 


G 


A 


G 


GO 


3!l 
I 
3-3 

J 
4-5 


61 


5-83 


7 


4 
F 
4 
K 
6 



Tubers weighing over 1 oz 



A 


B 


C 


D 


E 


G 


C 


4-5 


5-5 


G 


5-5 


5 


5-5 


7 


D 


E 


F 


C 


B 


D 


G 


7-6 


5-5 


G 


G-5 


6 


8 


6-75 


B 


C 


A 


G 


D 


E 


B 



7-75 


7-5 


7 


8-25 


7-75 


5-5 


7-5 


C 


G 


H 


D 


B 


G 


A 


9-5 


91 


7-3 

I 

8 

J 

8 


9 


9 


10 


8 
F 
7 
K 
9 



i(() hitiucnce of Seed Weight, etc. on tin Potato Crop 



DESCRIPTION OF FIGURES. 

Fig. 1. ^5lio\v.s the plots as actually laid out. In the lowest row it should bo understood 
that Lots H, I and J formed one row, and A, F and K another. The blackened portion 
represents the yield j)er set in pounds, in each plot. 

fig. 2. Represents the standardised 3fields per set in each of the classes of seed weight A-G. 

Fig. 3. The crops from A-G are analysed as to the weight groui)s into which their con- 
stituent tubers fall. The figure represents the standardised mean of the various groups 
in each of the classes. 

Fig. 4. The analysis of croj)s of all -seed classes in the fourth or western .section of the 
experimental plot showing the relation of tlie special classes H, I, J and K to the 
normal. 

The writer has great pleasure iu acknowledjjiiifi his deep obligation 
to Mr Udny Yule, C.B.E., M.A., F.R.S., who most kindly worked out 
and elucidated the statistical data iu this paper. 



(Received Februur// llth, 1922.) 



AN INVESTIGATION UPON CERTAIN METRICAL 
ATTRIBUTES OF WHEAT PLANTS. 

By F. L. ENGLEDOW, M.A. 

PIkh/ Breeding liiiilituk', Sc/khiI of Agrioiltiire, Caiiihr'uhjc. 

AND J. P. SHELTON, 

Farrer Memorial Scholar, Sydiw//. 

( 'ONTENTS. 

PAGE 

§ T. Introdiu'tiun ........... 197 

§11. Material and iMethod 199 

§ 111. The Ghime-Longtli : Raeliis-Leiigtii Ratio 200 

§ I\'. Concerning the Inter-relatiunshij) of the Tillers of a I'lant in regard 

to certain Measurable Characters ...... 202 

§ V. The Relation of Weight of Seed Sown to the Resulting Phint . . 203 

Conclusions ........... 204 

Bibliography 205 

§ I. Introduction. 

In dealing with the Inheritance of Ghmie-Leugth (Engledowii)] there 
were encountered certain problems relating to metrical characters. As 
it appeared that these problems must attach to all genetic work upon a 
metrical basis, they were made the subject of a separate inve.stigation. 
A simple account of some of the difficulties experienced in connection 
with Glume-Length Inheritance will serve to formulate the problems. 

It is necessary first to set forth the reasons which lefl to a genetic 
investigation upon glume-length. To the glume itself no intrinsic interest 
attached. The prime motive was to forge some sharper weapon than 
eye-judgment for the separation of "genetic types" mF^fi etc., and for 
more critical study of segregation. Rigid measurement, and classification 
solely by measurement, might, it was felt, provide such a weapon. Alike 
to eye-judgment and to measurement, "fluctuation" was certain to be 
an obstacle; but both observation and inference united to suggest that 
the length of the glume of the wheat plant was less liable to fluctuation 
than were most of its other observable attributes. There was the addi- 
tional advantage that glume-length could be measured accurately and 



198 Metrical Attributes of Wheat Plants 

with facility. These two reasons, then, led to its adoption. Overlap of 
distributions is the form in which the difficulty of fluctuation makes 
itself felt. To counter overlap, two wndely differing parent form.< were 
selected, viz. the T. durum known as Kubanka (mean glume-length in 
England£il0-5 mm.), and the distinctive T. polonicum or Polish Wheat 
(mean glume-length in England £i 30-5 mm.). Greatly as these forms 
diverged in glume-length, their distributions nevertheless showed a slight 
overlap. In the F.,, the parental types reappeared in a "shifted" form. 
With them, and intermediate between them, came a heterozygote. 
Consequently the glume-length distribution of the whole F, took a 
trimodal form which, defying analysis on the basis of rigid measurement, 
enforced a reversion to eye-judgment. It was quite obvious that the 
wide "'fluctuation'" in glume-length was due to the occurrence in the 
parental and segregate populations of a certain number of very poorly 
grown plants. To reject such plants would have been disastrous and to 
include them was to confuse distributions and inhibit analysis. Plants 
of this kind were poor in every _way and, roughly speaking, the less the 
stature of a plant, the shorter were its leaves, its ears, its glumes, etc. 
This very patent fact suggested that instead of making, for every plant, 
an absolute measurement, there should be made some form of "com- 
pensated" measurement. In short, every plant should be "handicapped." 
"Length-of-rachis"' was selected as the basis of the "handicap." The 
working hj'pothesis was that a big, thri^^ng. plant had long ears (i.e. great 
rachis length) on which were borne proportionately long glumes. Per 
contra, small plants would be small "all round" and it seemed not 
unlikely that the ratio — length of glume : length of rachis —would 
exhibit a smaller plant-to-plant fluctuation than would absolute glume- 
length. To test the constancy of this ratio, then, became the first object 
of investigation. 

A phenomenon designated by the term "shift" was observed in the 
F2 of the Pohsh x Kubanka cross. It consisted in the appearance in F^ 
of two groups of plants, each in number about a quarter of the whole F2 
population, and having respectively a complete eye-resemblance to the 
parental (F„) forms. In mean glume-length, however, the F^ Kubanka 
type .slightly exceeded the F^, while the F^ Polish type was 25 per cent, 
shorter than the Fq. Explanations of "shift" could be based upon 
"modification by cros.sing" [cf. Ruggles-Gates(3)] or upon "minor 
nmltiphnng factors," but yet another explanation seemed possible. The 
embryos and endosperms from which grew the Fo Polish-type plants, 
were nourished by F^ (i.e. heterozygous and intermediate) plants. 



F. L. EnCtLkdow and J. P. Shelton 199 

Upbringing by such a ""foster mother'' might have some predetermining 
influence and might be the cause of "shift" [for a fuller consideration 
see Engledowd). pp. 127-8]. This explanation is based upon a belief 
that there is a fairly close relationship between the weight, composition, 
etc. of the mother seed, and the attributes (glume-length included) of 
the resulting plant. To test this relationship liecame a second object of 
investigation. 

Many morphological and economic attributes of plants may be 
metrically represented in a number of different ways. Cereal plants 
illustrate this point. As generally grown a jilaut has a main axis and a 
number of axillary shoots or tillers. To obtain an expression of the 
glume-length, rachis-length, ratio of grain to straw etc. for a population 
of any variety, it is possible to confine observation to one ear-bearing 
stalk per plant. The largest, the first formed, or a random ear may be 
chosen: or every ear of the plant may be included and the observations 
for the whole plant be averaged. Labour is minimised if only one ear 
per plant be observed but the available number of observations is 
increased by the inclusion of every ear. Differing sets of circumstances 
have led sometimes to the one practice and sometimes to the other and 
it is clear that the justification of each in its own circumstances, mu.st 
re.st upon the relationships which prevail among the tillers of the indi- 
vidual plant. These relationships formed the third part of the enquiry. 

§ II. Material and Method. 

The strains of Polish and Kubanka were the ones used in the glume- 
length investigation. They are both old and carefully kept pure lines. 
The seed for each variety was obtained from forty plants of the 1919 
harvest. The main ear of every one of these plants was measured for 
rachis-length and glume-length and all of the grains were weighed and 
separately labelled. Sowing (in 1920) was completed in one day and 
both germination and growth were good and of as great uniformity as 
is usually attainable under the conditions of careful experiment. At 
harvest (1920), every ear of every plant was separately collected, and 
later on its rachis-length and glume-length were determined. Previously 
it had been usual to measure only one glume per ear [see Engledow(i), 
pp. 111-2], but for this investigation both glumes of the "median" 
spikelet of each side of the ear {i.e. four glumes per ear) were measured. 
The average of these four measurements is, hereinafter, referred to as 
"glume-length." 

Journ. of Agric. Soi. xii 1'^ 



200 Metrical Anribates of ^VlKat PlauLs 

§ 111. The Glume Length : Rachis-Length Ratio. 

As a pifliininary to further work, the correlation between glume- 
length and rachis-h'ngth was evahiated from data obtained from the 
iyi4 crop of the two pure lines. There were 15U plants of each pure hne 
and the coefhcients of correlation (r) were: 

Polish = + 0-295 ± 0-050, 
Kubanka = + 0-469 ± 0-043. 

It seemed not improbable that the lowness of the correlations was due 
to the fact that the experimental plants were not alike in respect of 
the total number of ears (or tillers) produced per plant.~ Consequently 
tiie 1920 plants — the ones observed in the main investigation — were 
classified as "one-ear." "two-ear," etc. plants and the correlation between 
glume-length and rachis-length was evaluated for the separate classes. 
In the case of every class, the main ear only of every plant was dealt 
with in the correlations. Table I contains the correlation coefficients (r): 

Table I*. Coefficients of Correlation between Glume-Length at\d Rachis- 

Lenglh for one-car, ttco-ear, and three-ear Polish and Kubanka jdant^. 

(Only the main ear of the plant was observed.) 





No. 


of eai-s 


No. of 




Variety 


pel 


• plant 


j)lants 


r 


Polisli 




1 


310 


0-918 ±0006 


r.ilisli 




o 


HO 


0-768 ±0020 


I'.ili.sli 




;s 


;{.s 


0-8.52 JO-OSO 


KubanUa 




1 


1'0.5 


0-7,51 ±0-020 


Kniianka 




2 


107 


0-717:,. 0-032 


Kllliauka 




:! 


o5 


0-494 ±0-069 



* All tho cori'olatioiis in llic labk- are jjusitive. The unit of nieasuroMiont throughout' 
is 1 mm. 

The values of the correlations are high, botli absolutely and in 
relation to their own probable errors but even a correlation of unity 
lietween two variables does not imply a constant ratio between them 
unless tlie regression lines pass througii the origin (0 . 0). This fact 
was well illustrated by the results obtained when the ratio glume- 
length/rachis-length was evaluated for individual ])lants. The ratio 
iluctuated as wildly as did the glume-length and to show this it is 
necessary to give no more than the coefficients of variation (viz. 
V = 100a/ 3/, where a = standard deviation and M = mean). These are 
given in Table II. 



F. L. Engledow and J. P. Shelton 201 

Table 11. Coefficients of Variation for 01 Nine-Length, Baehis-Lengtli and 
the Ratio of these two quantities in Polish and Kiibanhi ivheats. 



CiiefRcicnt. of vaiiation of 



Variety iiiid No. of ears , — 

no. of plants ])er plant (ihinie-lengtli Rachis-length Ratio 

Poliali (:)1<;) 1 ]7-13±0-47 25-77±0-74 l.'-)-47 -l:0-4:? 

Polish (110) 2 S-5()±0-39 13-8.3±0-l!4 10-S:?:i 04!1 

Kuhanka (20")) 1 10-I8±0-34 20-43±0-71 18-L'niO(>3 

Kiihanka (107) 2 8-40 |:0-.3n Id-SSi-O-SO 12-.58-J:0-.^lt 

It is therefore to he concluded that this particular "compensated" 
ratio possesses no value either to the geneticist for a critical study of 
variation or to the plant breeder for the discrimination of closely re- 
sembling agricultural strains. 

Despite this record of failure, it is felt that "compensated" observa- 
tions {i.e. some form of ratio) ofi'er still the only alternative to "abso- 
lutely (unattainably?) uniform conditions of growth" as a means of 
removing the masking effects of "fluctuation."" It is not to be expected 
that the random choice of two characters — e.g. leaf-width and grain- 
length — will serve as a basis for compensation or handica]) and ])rovide 
a con.stant ratio. Manifestly, in seeking constancy, one should endeavour 
to find two "lengths" (or other attributes) which are determined by 
the same causes and during the same time-period. In glume- and 
rachis-lengths, it would seem, these requirements are as likely to meet 
fulfilment as in any pair of attributes of the wheat plant to which one 
could point. This granted, there follows the regrettable but not surprising 
conclusion that "lengths'" are such vague expressions of the real 
"nature'" of a plant variety, of its physiological activities, as to be of 
little value in attempts to determine accurately its modes of inheritance. 

The employment of "ratios"' by genetici.sts has usually been dictated 
not so much by a desire to achieve "compensation"" as by the necessity 
of devising representations for elusive attributes like leaf-shape, etc. 
The work of Martin-Leake (S) upon Cotton, of Balls (6) upon the same 
plant, and of Groth(7) upon the Tomato afford examples; but in all 
these cases fluctuation has played its customary havoc. 

In outline, the "handicap"" principle for plants is strictly analogous 
to that followed in flat-racing. Horses are handicapped so that they 
may afford an exciting "bunch" at the winning-post. It is required to 
"bunch"' metrical observations upon a plant population {i.e. to minimise 
fluctuation) but it seems probable that a really successful "handicap"' 
will have to be a complex one. It will, in fact, have to be applied not 



202 Metrical Attributes of Wheat Plants 

simply to tin- "eiul-iJiotluct " (tlit- inature plant) but to the more iiu- 
portant life-stages by whicli tlie end-product is determined. 

<j \\. The Inter-r?:i,ationship.s of the Tillers of a Plant 

IN REGARD TO CERTAIN MEASURABLE CHARACTERS. 

Glume-length, rachis-length, and the ratio of these two, were deter- 
mined for every ear of every plant of Polish and Kubanka (1920 erop). 
Ear-to-ear correlations (same plant) are given in Table III. It is plain 
that first and second ears are more closely correlated than first and 
third; further, correlations for rachis-length are slightly higher than 
those for glume-length. Of the actual coefficients of correlation it may 
be said that they are statistically significant but are not very high (their 
general value is about | ()-."3). 

Table III. Ear-to-ear Correlations on the Indiridunl Plant. 

Value o( r for 

Variety and ^ — '• ■ -., Ears per 

no. of plants /■ for fJluraelength Rachis-length Ratio plant 

Polish (110) ICiirs 1 .-xnd L> OvWl j.0().">0 0-66.5:;; 0036 0-5l2±0-047 2 

I'olish (38) Ears 1 and :! (1-42!) j;()0S9 0-439±0-080 0-428±0-089 3 

Kubanka (107) Ears 1 and 2 0-,Wni0042 0-li.">!ti0037 0-699±0-033 2 

The first inference from these iigures seems to be that, when dealing 
with the glume or with any similar ear-character, it is essential to confine 
the observations to one ear per plant. In that, as a very general rule, 
the ear of the main stalk is formed first and attains the greatest growth, 
it is the best ear of the plant for observation. This inference from the 
facts of inter-tiller correlation naturally leads one to ask whether, in 
furtherance, it would be well to limit the experimental population to 
plants which all possess the same total number of tillers or which all 
ripen the same number of ears. Upon this point further evidence is 
available and it is set forth in Table IV. The facts are quite clear and 

Table IV. Mean Values for the main tillers of plants grouped 
according to the number of ears -per plant. 

Mean value (main tillers only) of 

• " ^ -^ 

Olnme-length Rachis-length Ratio 

26-.->!017 !)2-I±0-90 0-298±0-002 

30-0±017 118-4±l-0.i 0-262±0-002 

I0-9±00.5 58-0±0-50 0-196i;0-002 

ll-7-i;000 68-5 + 0-7.5 0-17o±0-001 

rather striking. Although only the main tiller was observed in the case 
of every plant, the one-ear and two-ear plants give very different results. 



Variety and 


No. of ears 


no. of plants 


per ))lan( 


Polish (316) 


1 


Polish ( 1 10) 


>> 


Kubanka (205) 


1 


Kubanka (107) 


'2 



F. L. Englbdow and J. P. Shelton 203 

Both for Polish, aud Kubauka, ghiiiie- and rachis-leugths are greater 
in the case of two-ear than in the case of one-ear plants; and since the 
dif^'erence is more marked for rachis than for glume, the "ratio" is 
lower for the two-ear plants. 

A difference is, perhaps, to be anticipated for, within limits, the 
more vigorous the plant the more tillers it produces: and the facts 
displayed in Table IV make it appear that greater vigour is evinced in 
"all-round"' form — not only more tillers but bigger ones (larger glumes 
and rachis). This "co-fluctuation" of the attributes rachis-length. glume- 
length, and number of tillers, encourages one to think that in such 
attributes is to be found a means of estimating degree of growth and of 
comparing and contrasting different pure lines. There may still be room 
for hope but no progress is possible until "fluctuation" has been dealt 
with and, as far as this case goes, the mathematical handling of attribute 
measurements (use of ratios, etc.) has been valueless. 

It has been inferred that observation should be confined to the main 
ear of the plant and this inference, if valid, is not without interest from 
the point of view of yield-investigations. When, in seeking higher- 
yielding forms, an F2, is raised from two parental strains, it is almost 
essential to cast out what are believed to be the "inferior" segregates. 
Even if there be no casting of Fj plants, the process must be applied 
to the resulting F^ families for otherwise available time and ground- 
space become inadequate. In actual practice " casting" by eye-judgment 
has attained some very conspicuous successes but there is now a tendency 
to try to substitute an accurate "method" in its place. If those attri- 
butes which are considered to govern yield behave in a way analogous to 
that described for glume-length, etc., then the best tiller and not the 
whole plant should be the basis of estimation. In the field, however, 
small tillers as well as large go to make a crop, and whatever form of 
judgment of F2, plants is evolved, it must of course, in some way, pay 
due regard to tillering power. 

§ V. The Relation of Weight of Seed Sown 
TO THE Resulting Plant. 

It has been explained in the introduction that there existed a special 
reason for attempting to determine the influence upon the plant of the 
weight and composition of the seed from which it grew. Apart from this, 
in a great mass of literature [for a very full summary see Kidd and 
West (8)], there is evidence which justifies the suppo.sition that much of 
the troublesome "fluctuation" is induced by lack of uniformity of seed. 



204 Metrical Affn'hntes of Wliiat Plants 

As a contributory test of this point, correlations were evaluated between 
weight of mother-seed and glume-length, rachis-length, and their ratio 
in the resulting plants. Preliminary investigation having shown an 
absence of conolatioii for a population of jiinnts having different numbers 
of ears, attention was confined to single-car plants. Talilc \' contains 
the results. 

Table \ . Correlation between Weight of Mother Seed and the Characters of 
the Resulting Plant. (Only one-ear plants are included.) 



Varii'tj' and 



Correlation between weight of mother seed and 



no. of plants Glume-length Rachis-length Ratio 

Polish (.316) 0-O(55±OO38 0043-0038 OOOOi — 

Kuhanka (20.5) 0-262i0-a44 0-1.57±0-04li 0003±0-047 

The supposed relation between weight of mother-seed and glume- 
length, etc., is thus emphatically negatived. Mere weight of seed is not — 
save at the lower extreme — likely to be of great physiological importance 
and the belief in its importance (vide literature above mentioned) is, 
perhaps, largely due to the form, of ex])eriment often adopted — the 
removal of a portion of the endosperm, work with non-pure lines, 
fewness of observations and so on. No embryo during germination uses 
the whole of the reserve food with which it has been provided and 
reserves beyond a certain amount must be simply "surplus." That 
"quality" of endosperm may be important still remains a possibility 
and evidence exists to this effect. This possibility is the only remaining 
basis for the explanation of "shift" of which an account is given in the 
introduction. With the general principle that good, sound, seed must be 
sown to reap a good crop, there is common agreement, but beyond this, 
even in genetic work and in face of the danger of fluctuation, there seems 
no need to go. The weighing of a vast number of seeds in order that 
seeds all of the same weight may be .sown, seems, from the facts above 
recorded, not to be worth while. 

Conclusions. 

The conclusions which follow hold in strictness — failing further test — 
only for the year, the locality, and the wheat varieties concerned in the 
investigation. Since, however, the residts iwe fairly emphatic, they 
seem likely to prove applicable in principle to other circumstances. 

(i) Glume-length and rachis-length in both Polish and Kubanka 
"Wheats are very highly correlated. 



F. L. Engledow and J. P. Siielton 'JOS 

(ii) Nevertheless, the ratio of these two quantities has about as big 
a coefficient of variation as the absolute glume-length. 

(iii) Therefore, despite contrary expectations, the ratio appears to 
be of no special value in investigation. 

(iv) Among the tillers of any one plant correlations e.xist for glume- 
length, rachis-length, and ratio. Their general value is about + 0-5 and 
consequently when dealing with attributes of this kind observation 
should be confined to the main stalk of every plant. 

(v) It is desirable further, to restrict the experimental population 
to ])lants all of which produce the same number of tillers. 

(vi) Weight of mother-seed, for a reasonably good seed sample, 
seems not to determine in any observable degree the growth of the 
resulting plant as judged in general by glume-length, rachis-length, and 
the ratio of these two. 

(vii) The great labour of picking out for sowing a sample of seeds 
all of one weight in order to reduce "fluctuation"' among the resulting 
plants, seems not likely to be repaid. 



BIBLIOGRAPHY. 

(1) Engledow, F. L. (1920). The lulieritance of Glume-Length and Grain-Length 

in a Wheat Cross. Journ. Genelics, 10, No. 2. 

(2) Haklan, H. V. (1920). Daily Development of Kernels of Hanuchen Barley from 

Flowering to Maturity at Aberdeen, Idaho. Journ. Agric. Research, 19, No. 9. 

(3) Gates, R. Ruggles (1915). On the ModiKcation of Characters by Crossing. 

Am. Nat. 49. 

(4) Engledow, F. L. (1920). Inheritance in Barley, No. I. Joiirii. Ornelirs, 10, No. 2, 

ajid No. II. Journ. Agric. Sci. 11, 1921. 

(5) JIabtin Leake, H. Studies in Indian Cotton. Journ. Griirlics. 1. 
(0) Balls, W. L. (1909). Studies of Egyptian Cotton. 

(7) CJroth. Bulletins of the New Jersey Experiment Station, Nos. 228, 238, 239, 242, 

278. 

(8) KiDD, F. and West, C. (1919). Physiological Predetermination; the Influence 

of the Physiological Condition of the Seed upon the Course of the Subsequent 
Growth and upon the Yield. Ann. App. Biol. 5, Nos. 3 and 4. 



{Received 1st June, 1921.) 



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Volume XII JULY, 1922 Part III 

tJOTANiCAR, 

SOME INVESTIGATIONS ON THE ELECTRICAL 
METHOD OF SOIL MOISTURE DETERMINATION. 

By THOMAS DEIGHTON, M.A., B.Sc. 

(School of Agriculture, Cambridge.) 

(With Six Text-Figures.) 

The investigations described in the following pages had their origin in 
a desire to find some method of moisture determination in the soil 
which would not require the taking of samples, with a view to some 
further experiments on the cultivation of the soil in root-crop pro- 
duction. 

Tentative work on these hues was commenced in America in 1887 
by Professor Milton Whitney (i) who employed an earth battery con- 
sisting of alternate copper and zinc plates buried in the soil, connected 
through a galvanometer. Later in Bull. No. 6, "Division of Soils," 
U.S. Dept. Agriculture the same author further develops this method 
of moisture determination. 

In 1897 M. Whitney and T. H. Means (2) published an accoimt of 
some experiments in which they determined the specific resistance of 
various soils, making a correction for packing error, and showed that 
this varied considerably for different soils. The authors plotted the 
resistance against the moisture in various soils and found that the curves 
obtained "agree in the main with an hyperbolic curve except that they 
are more or less rotated," and they discovered that "it requires from 

1 to 3 per cent, more water to produce the same change in the resistance 
of some soils than in others." To this paper is appended a table for the 
reduction of soil resistances to a standard temperature. In the experi- 

;ments a compensating temperature cell was used. 
C2 The following year F. D. Gardner (3) dealt with the use of under- 
ground cables on ploughed land and gave results of an extended series 
^ of measurements of soil moisture by the electrical method compared 
c.Jwith determinations by drying on the same plots. The results, though 
J.-J considered satisfactory by the author, show a mean difference of about 

2 per cent, in the moisture content between the two methods of working. 
The maximum difference was as high as 4-3 per cent. 

Journ. of Agrio. Soi. xil 15 



208 The Electrical Method of Soil Moistnre Determination 

In 1899 L. J. Briggs{4) described improved instruments and electrodes 
and introduced a condenser in parallel witli that arm of the bridge 
adjacent to the soil resistance, which would throw the small capacity 
found in the soil and the condenser capacity on opposite sides of the 
bridge with respect to the telephone receiver. 

I have found a reference to some work by R. 0. E. Davis (Trans. 
Arner. Electrochem. Soc. 17 (1910), 391-403), in which he is said to have 
found the resistance of soils within the limits 10-20 per cent, of moisture 
to be inversely as the moisture content. Unfortunatel)- the original of 
this paper is not to be obtained here, but the result thus stated is at 
variance with Whitney's results which experiments to be described in 
this paper fully confirm. 

The electrical method has never been popular on this side of the 
Atlantic for several reasons, notably the discrepancy in the results 
attained by Gardner using the two methods in a parallel series of experi- 
ments and the failure of the investigators to deal satisfactorily with the 
question of movement of salts in the soil. 

Preliminary Experiments. 

Apparatus. The experiments which follow were made on a small plot 
of ground on the south side of the School of Agriculture at Cambridge. 
It had been dug over a short time previously and was not ideal for the 
purpose as a thin layer of builder's refuse from the building of the school 
rendered it less homogeneous than cultivated farm land. It had, however, 
the merit of being conveniently situated with regard to the laboratory, 
and the results obtained upon it appear to justify the conclusion that 
no great error was introduced by this lack of uniform texture. 

For the measurement of the resistance an ordinary post-office pattern 
Wheatstone's bridge was employed, with an induction coil from which 
the condenser had been removed to avoid any possibility of polarisation 
of the electrodes, and a telephone receiver. As a source of energy two 
small storage cells were used. At first a large coil giving a frequency 
of something under 30 per second was put in, but this was afterwards 
changed for a smaller one with a frequency rather over 100 per second, 
as it was found much easier to estimate the minimum of sound with 
this. The condenser in parallel with the bridge arm used by Briggs was 
dispensed with, being found unnecessary for the attainment of the degree 
of accuracy aimed at. 

The electrodes employed were formed from cored electric arc light 
carbons 9" long and I" diameter. The tapered ends of these were ground 



T. DeiOxHTON 209 

down to form roughly a paraboloid of revolution, a shape found most 
satisfactory by Briggs (I.e.) for maintaining contact with the soil. The 
core was then drilled out for about an inch from the end and the cavity 
tilled with melted caoutchouc and sealing wax, a mixture which main- 
tained its position in the cavity and rendered good service for insulating 
the end of the core throughout the experiments. The opposite end was 
then scored and an inch of the core drilled out. A thread was tapped 
on to the inside of the cavity and a copper wire sealed in with fusible 
alloy. The top was then covered with sealing wax. The whole of the 
outside of the electrode, except a band one inch wide round the para- 
boloidal surface at the bottom, which was to act as the electrode surface, 
was then insulated by painting with two coats of "Duroprene"" and 
thoroughly dried for two or three days at about 50° 0. As the experi- 
ments progressed this insulation was found un.satisfactory and in cases 
where it was necessary to leave the electrodes a considerable time buried 
another type was adopted which will be described in a later paper. 

There appears to be a theoretical objection to the use of metal 
electrodes of any kind in direct contact with the soil which has not 
hitherto been noticed by workers in this field : namely that polarisation 
is very likely to take place even when an alternating current is employed 
unless the frequency is very high, since the free metallic ions are not 
completely returned to the electrode on reversal; and in some cases 
rapidly form double salts which are not decomposed on reversal. In 
these cases polarisation may occur even at frequencies of 40,000 per min. 
Owing to its abiUty to absorb gases a carbon electrode is self-depolarising 
to a sufficient extent to nullify the first effect and the second does not 
arise. The phenomenon mentioned is well known to electro-chemists (5). 

Local Variations in Resistance. It was desirable before proceeding 
further to find whether the resistance was the same under like conditions 
in different parts of the plot. The method of experiment was simply 
to push two such electrodes as have been described into the soil of the 
plot to the desired depth at a definite distance apart; a preliminary test 
having shown that the contact error in this, while not negligible, did 
not seriously affect the results. The same pair of electrodes was then 
moved to another part of the plot and placed at the same depth and the 
same distance apart. The results for a depth of 7" at 3" interval are 
shown in Fig. 1, which may be taken to represent the plot, which was 
about '22' X 30' in extent with the observations entered in the place in 
which they were taken. Subsidiary experiments proved that the obser- 
vations were sufficiently close together to justify the insertion of the 

15—2 



210 The Electrical Method of Soil Moisture Deterimnation 

lines of equal resistance as shown. These results are quite in accordance 
with the observations of Gardner (I.e.), who in attempting to standardise 
a pair of electrodes on an experimental plot found, by actually drying 
samples, that the moisture content at any depth might vary over a 
small area by as much as 7| per cent. Although moisture contents were 
not determined in the present case it will be seen from the resistance- 
moisture observations given later in this paper (Table VII) that such 
variations are sufficient to accoimt for the different resistances observed, 
although it should be remembered that other factors may also be 
operative, such as variations in the soluble salt content — especially of 
nitrates — from point to point in the plot. 



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Fig. 1. Local variations of resistance on plot at 7" depth. 

The Effect, of Distance apart of the Electrodes. Gardner (I.e.) made 
numerous experiments on this matter by burj'ing two large electrodes 
15' apart, and a series of smaller ones at distances from J" to 18" apart, 
15' from each of the larger ones. He then took the resistance between 
the large pair and between the smaller ones, singly, and each of the 
larger ones. He adds " From these measurements it was a simple matter 
to calculate the resistance due to each of the individual electrodes at 



T. Deighton 211 

a distance of 15 ur more feet. By adding the values of any two of the 
small electrodes thus found, the resistance is obtained which they would 
have if 15 feet apart." A table is given showing the actual resistance 
between the small electrodes at their actual distance apart and the 
calculated resistance between them when 15' ajDart. He concludes that 
"when the electrodes are 15 ft. apart 98 per cent, of the resistance is 
encountered within 9 inches of the surface of each electrode and the 
intervening 13i ft. of soil causes only 2 per cent, of the total resistance." 
Briggs (I.e.) states that the resistance is practically confined to volumes 
of soil not exceeding 6" in diameter with the electrodes as centres. If 
this be so, there should be no important variation on increasing the 
distance apart beyond 6"; but both Gardner's results quoted below 
(Table I), and those of the present author on a more extended scale, 
show a quite appreciable change beyond this point. 

Table I. Excerpt from Gardner s table. 

Distance Resistance between standard 

apart electrodes* 

5" 928 

8" 934 

12' 968 

18" 979 

* Gardner calls this column (the numbers being given as percentages 92-8 etc.), 
"Relation of observed to calculated resistance." By making the resistance 1000 ohms 
at 15' the standard and reducing the other resistances to this the same figures are obviously 
obtained. 

Gardner's experiments were all made at one depth and the author 
therefore carried out a series of measurements of the effect of distance 
apart of the electrodes on the resistance of the soil at varying depths, 

Table II. Effect of Distance Apart of Electrodes on Resistance 
at various Depths. 



Distance 






Resistances, 


in 


thousanc 


Is of ohms at 






apart of 
electrodes 










'. 








1" depth 


2" depth 


3" depth 


4' 


■' depth 


5" depth 6" 


' depth 


7" depth 


2" 


100 


92 


33 




15,7 


11,0 


8,7 


6,2 


3" 


60 


27 


17,o 




14,0 


11,9 


11,9 


8,5 


4" 


75 


34,5 


15,5 




10,4 


8,o 


6,4 


5,2 


6" 


85 


25,5 


14,0 




9,4 


7,o 


5,3 


4,0 


9" 


51 


22,o 


11,3 




7,2 


5,9 


4,9 


4,4 


12" 


45 


15,5 


9.1 




7,o 


5,8 


5,o 


4,6 


18" 


SO 


22 


lO.q 




7,5 


5,5 


4,5 


3,S 


27" 


70 


20,9 


13,9 




8,2 


6,5 


5,2 


4,o 



the results of which are given in Table II. There appears to be a tendency 
for the resistance to fall to a minimum when the electrodes are about 



212 The Electrical Method of Soil Moisture Detenu! nation 

]"2" apart at shallow depths while in the case of depths about 0" the 
minimum is found when a distance apart of about 18" is reached. 

The Effect of Depth. The following experiment was made to determine 
the effect of depth unhampered by other considerations. A very dry 
soil was sifted through a 3 mm. sieve to extract .stones and packed as 
uniformly as possible into a pot. Two electrodes 4" apart were then 
sunk to different depths in it and the resistance measured. It was thus 
shown that tlie resistance between them was approximately halved by 
sinking to a depth of 4". A repetition of the experiment after .saturating 
the soil gave a result quite in accordance since in this case there must 
have been some moisture gradient due to the action of gravity on the 
water in the pores of the soil. The observations are sho\\Ti in Table III. 

Table 111. Effect of Depth in Uniform Soil. 

Depth of centre of Resistance in oiims 

elei^trode below , ■ -^ ^ 

.soil surface Dry Saturated 

1" 12.5.000 550 

2' 102,000 460 

3" 72,000 260 

4" 66,000 200 

Electrode Values. A further series of experiments was undertaken to 
determine whether it was really pos.sible to assign values to the electrodes 
on a system similar to that employed by Gardner. For this purpose 
equal sized electrodes were set out at the four corners of a six-inch 
square and at a depth of G". The distance apart agrees witli Briggs' 
figure for the volume of soil concerned in the resistance measurements. 
Observations were then taken in all po.ssible ways between them. In 
Table IV the results are shown, — in the last two columns we have the 
resistances observed and parallel with these the resistances as calculated 
from the first four observed resistances by Gardner's method, e.g. the 
electrodes being equal, if R^ is the resistance due to the electrode A, 
Ri, that due to the electrode B, and R^ that due to the electrode C; and 
if Rat,. Rac ^ifl Rbc are the resistances observed between A and B, A and C, 
and B and C respectively, we have 

.'. -Ra + ^6 + ^c = Rab + Rac, 

whence R^ = R<^ + ^a^ -JR^ + ^q) ^ 



T. Deighton 213 

but R, + F, = B,,. 



^ab + "ac ~ ^ic 



Similarly R^ and R,. may be determined and R,i will equal i?^,, — R^- 
Obviously R^^ and R^^ can then be calculated. As will be seen no 
very good agreement is attained. 

Table IV. Resistances, observed and calculated, on 6" square. 













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5500 


5330 



This method of calculation gave results more in accordance with 
the observations when seven electrodes were set out in the angular 
points of a regular hexagon with the seventh in the middle, in such a 
manner that the distance between any adjacent pair was the same = 18" 
corresponding to (Gardner's limit: the value of an electrode being de- 
termined as the mean of the results obtained from two or three triangles. 
As these results are very length v and of no importance in themselves 
they are omitted. The calculated and observed results agreed to about 
100 ohms in 3000. It will be seen later that in an infinite isotropic 
medium the calculation should give the result desired, the variations 
are therefore most probably due to local aelotropic conditions. 

Resistance at greater Distances. The question of what happens at 
distances much exceeding 18" was investigated by the author, once as 
a continuation of the 7" depth observations of Table II and once inde- 
pendently of these. The results, given in Table V, show a slow increase 
of resistance beyond 18" up to quite long distances. We are therefore 
driven to conclude that had Gardner actually measured the resistance 
between two of the smaller electrodes at 15' instead of merely calculat- 
ing it he would not have concluded that the intervening ISi' of soil 
accounted for only 2 per cent, of the resistance at 15', the rest being 
due to the 9" of soil about the electrodes. 

It will be observed that in Exp. 2 there is no minimum at 18". There 
is here no real discrepancy, the occurrence of a minimum being a possible 



214 The Electrical Met hud uj' Soil Moisture Deteriitinatiun 

and not a necessary pheaomenon, as will be shown from theoretical 
considerations later on in tliis paper. 

Table V. Resistances at greater Distances. 



listanco 


E.\p. 1 


Exp. 2 


Distance 


Exp. 1 


Exp. 2 


4" 


r,200 


2400 


3' 


— 


3200 


6" 


4000 


2300 


4' 


4500 


3700 


9- 


4400 


2600 


6' 


5200 


4100 


12" 


4G0U 


ao.w 


8' 


— 


2250* 


18" 


;!800 


3000 


9' 


5400 


— 


2' 


— 


3700 


12' 


— 


4300 


27" 


4000 


— 


10' 


— , 


5400 



* I am \ituible fully l(j account for this lower figure; several subsequent tests about 
the same place gave results in the neighbourhood of 3600. 

To summarise the results to this point, we find (hat the pot experi- 
ment appears to favour Briggs' theory, the fact that agreement between 
calculated and observed resistances, even when the calculation was 
made from a single triangle, was better in the hexagon than in the 
square speaks more in favour of (Jardner's limit being correct. On the 
other hand neither theory explains the increase of resistance at distances 
exceeding 18", the minima observed in Table II, nor why these minima 
should appear at greater distances as the depth increases. 

Thk Path of thk Current. 

Experimental. It seemed probable that a more satisfactory result 
might be attained by casting overboard the idea, really no more than a 
convenient fiction, of the resistance being due to the soil in the im- 
mediate neighbourhood of the electrodes and considering the whole mass 
of soil about them. 

An experiment was devised the object of which was to determine 
at what depth below the line joining the elet^trodes a conducting layer 
would appreciably affect the resistance between them. For this purpose 
a beaker of about 600 c.c. capacity (Fig. 2) was taken and four scales 
of inches were gummed up the sides of it. Inside this lay a clean per- 
forated metal plate of nearly the diameter of the beaker so that the 
curved-in sides of the vessel would just keep it off the bottom. Through 
the centre of this plate was passed a glass tube carrying a copper con- 
ductor which was soldered to the underside of the plate. At the top, 
the tube made connection with a funnel by means of about an inch of 
rubber tube, but the copper wire passed out at the side and the opening 
was rendered watertight with sealing wax. Tlie beaker was then filled 
up to the 2" mark with pure dry sand and five subsidiary electrodes of 



T. Deighton 



215 



copper wire were buried therein at the 11" level. The rest of the beaker 
was filled with the same saud very shghtly damped so as to have a 
resistance of about 11,000 ohms between the main electrodes, consisting 
of solder spheres on the ends of thick copper wires, placed 2^" apart in 
the sand at the 3|" level. The subsidiary electrodes were connected to 
a ring conductor surrounding the apparatus and this was joined through 
a galvanometer to a single dry cell the other terminal of which made 
connection with the wire from the metal plate at the bottom. The main 
electrodes were connected through the bridge to the secondary of the 
induction coil. The sensibility of the galvanometer was such that when 




Fig. 2. Apparatus and connections in Beaker Experiment. 

one subsidiary electrode was placed in conducting connection with the 
metal plate the needle moved only a fraction of the distance across the 
scale, so that all five electrodes would have to be in use to give anything 
like a complete cross swing. 

Hence on pouring a solution of an electrolyte (very dilute hydrochloric 
acid) down the funnel, it was possible to see if the surface of the 
solution rising by capillary attraction was sensibly plane or whether it 
was depressed or humped up at the centre; the condition for a plane 
surface being that a sudden complete cross swing of the galvanometer 
needle should be observed at the moment the water line visible on the 



216 Tlie Electrical Method of Soil Moist lar Deteriiii nation 

outside reached the 1|" mark. In the experiment this was observed 
quite sharply and it was therefore assumed that the liquid surface in 
the capillaries was sensibly plane. The dampiu^j of the sand above had 
not been carried so far as to interfere with packing and it was therefore 
presumed that this condition was equally satisfied above. The resistance 
unplugged in the standard arm of the bridge was 10,000 ohms, so that 
the effect awaited as the solution gradually rose was a sudden cessation 
of sound in the receiver, followed immediately by a sudden increase. 
This also gave a very sharp indication when tin' water line read on the 
four scales round the beaker was s(jmething between }/ and \" below 
the line of the main electrodes, the readings were 3g", 3j", 3", 3^". Thus 
when the conducting surface reached a level of somewhat more than \" 
below that of the two electrodes the resistance between them fell by 
about 10 per cent. From this result it appears probable that the current 
density which is concentrated in the line joining the two electrodes 
becomes rapidly less on moving away from this part of the field, though 
probably not as quickly as the result appears at first sight to suggest, 
as the conductivity is only increased over a comparatively small part of 
the region surrounding the line of the electrodes. 

The following experiment, originally performed as a means of con- 
firming the above result, is described not so much for any value it has 
in itself, as on account of the justification it seems to supply for the 
assumptions made in the short mathematical investigation which follows. 
A tray was taken in which moist sand was laid out in a lamina l" thick. 
Electrodes were placed 61" apart in this and the width of the conducting 
layer was gradually cut down by the insertion of wooden partitions on 
each side of the line of the electrodes at varying distances. The increase 
in resistance with decrease in width of the conducting layer was quite 
in accordance with expectations, becoming much greater as the electrodes 
were approached, while remaining practically unchanged at considerable 
distances. The results are given later in Table VI. 

Theoretical. It is shown by Mascart and Joubert(fi) that the resistance 
between two electrodes immersed in an unlimited isotropic conducting 
medium depends only on the medium and the form and dimensions of 
the electrodes, and is doubled if the medium is limited by an infinite 
plane passing through the electrodes, i.e. if the medium extends on one 
side only of this plane. On account of the comphcated nature of the 
considerations involved they omit any consideration of the problem 
when the bounding plane passes to one side of the line of the electrodes. 
It will suliice lor our purpose however if we can determine in some 



T. Deighton 



•217 



simple manner the volume of soil through which the practically important 
portion of the current flows. 

The method of attacking the problem adopted by Mascart and 
Joubert, viz. by electrical flux and tubes of How leads to complications 
when applied to cases other than the two selected. Since we are using 
an alternating current, we may probably treat the matter from the 
electrostatic point of view at any one moment, instead of considering 
it generall}' from electrodvnamic considerations, without any serious 
error. 

X 













^^ 
























^ 






















^^ 


"~^^ 








__p 


^^ 


"-. z 












/ 












^ -^ ^ 


























%' 


y^ " 


^^ 




^"^^ 


.^-^-^^ 




^y^ 






^^\^ \ 






^y 






Y \ 


y 




^^^ 






\ 


/ 










N 


/ ^ 










N 


/ ^-^ 










\ 


/ ^^ 










\ 


/ ^^ 










\ 


A i^e 






c 




\ 
\ 








p' 







Let A and B (Fig. 3) be two electrodes, supposed small, in an isotropic 
conducting medium. We may assume that at any moment an ion at 
any point P in the median plane PC'P' is subject to two forces, one acting 
from A, represented in magnitude and direction by PX, and one towards 
2?, represented in magnitude and direction by FY . These wnll be equal 
at any point in PVP' and will have a resultant FZ which may be taken 
to represent the force tending to move the ion at the moment which 
will be proportional to the current, since assuming Ohms law, the mean 
velocity of the ions resolved in the direction in which the force acts 
varies as the force. 

Thus the current density at any point on the median plane FCF' 
will be proportional to FZ at that point. 



218 Tite Electrical Method of Soil Moisture Determination 

Now if the angle BAP -= 6 we have in three dimensions 

px = py cc ^ Jp^, = ^Acle^er "" '"'" ^' 

if AC remains constant. 

Hence PZ - (PX + PY) cos 6 oc cos^ 6. 

Precisely the same result is obtained from a consideration of the 
equipotential surfaces. Since the electrification of the electrodes at any 
moment will be equal and opposite the median plane is the equipotential 
surface V = 0. 

On either side of this will be equipotential surfaces V = + dV and 
V = — dV and the current across the median plane therefore will be 
inversely proportional to the distance x along a line of force between 
these two surfaces^, since this is a measure of the resistance assuming 
the medium isotropic. It makes no difference in this consideration 
whether we take the momentary state or put V in virtual volts and the 
current in virtual amperes. We have then that the current across the 

median plane at the point P, is equal to K . 

Now considering spheres round the electrodes V = j^ where r is 
the radius of the sphere, whence 

V 

and since x is inclined at an angle = 6 to the direction of r 

X = dr sec d 

= — ,- r^ sec ddV 

= _ ^^ysec^edV. 

Hence when the potential difference at the ends of x is constant = 2dV 
we have 

X oc sec* 6, 

whence current across the median plane at P x cos' 6 as before. 

Thus the fraction of the total current passing outside any tore^ 

' This may be considered a straight line. 

- The lines of force are known to be circular arcs vide Masoart and Joubert, Electricity 
and Magnetism, 1, p. 205. 



T. Deighton 



219 



formed by the revolution of a line of force AQPB about the axis AB 
will vary as: 



tan e cos3 9 (W 
(since the circumference of the tore in the median plane is 'IvCP oc tan 6) 

sin 6 COS" d (19 



cos2 9 d (COS 9) = i cos3 9. 

Thus the fraction of the total current passing outside any tore oc cos^ 9 
and the fraction passing inside any tore cc (1 — cos^ 9). 

It follows from this that 35-7 per cent, of the current passes outside 
the sphere whose poles are the electrodes. 

Proceeding in a similar way we have for a lamina 

1 1 



PX = PY cc 



oc cos 9 



AP AC sec 9 
if AC is constant. 

Therefore the fraction of the total current passing outside any portion 
of the lamina enclosed by two lines of force of equal length on opposite 
sides oi AB varies as 



(1 + cos2^)f/0 = 



cos- 9 d.9 
"1„ 1 . 



77 

4 



in 2^ 



Table VI. Results of Tray Experiment, Observed and Cahulated. 

Resistance 



Extent of sand on 


^ 


Corrected for 


Calculated from 


each side of line 


Mean of three 


temperature and 


the above 


of electrodes 


actually observed 


evaporation 


formula 


oc 


— 


— 


18,400 


7i" 


18,500 


18,600 


18,600 


5i" 


19,100 


19,.500 


19,800 


4rV' 


20,100 


20,000 


20,700 


31" 


20,800 


22,000 


22,200 


2r 


23,400 


2.5.000 


24,400 


If" 


27,100 


29,700 


36,800 



As will be seen from Table VI this agrees very well with the results 
obtained in the experiments ^\'ith the tray of moist sand described above. 



220 The Electrical Method of Soil Moisture Determination 

The observation at 1|" is doubtless aSected by the nearer a^jproach to 
a three dimensional condition and the fact that the electrodes were not 
small in comparison with the mdth of the field thus restricted. The 
correction for evaporation was made by interpolation from the original 
and a final observation at 1\". We see then that no grave error is likely 
to have been introduced by the assumptions made at the beginning of 
this section. 

This being so we are probably not far wrouj^ in inter])reting our soil 
phenomena in terms of the calculation made for the three dimensional 
case, more especially as it explains all the phenomena observed. Each 
electrode may obviously still be considered to possess a definite re- 
sistance value of its own at any stated distance, and calculations based 
on these values will still yield approximately correct results but slight 
differences will doubtless appear according to the direction in which the 
second electrode lies. Since with increasing distance apart local differ- 
ences in specific resistance will tend to cancel out in their effects it is 
clear why a better agreement was obtained in the hexagon than in the 
square. The result of the pot experiment is explainable on either theory, 
but it is noteworthy that the theory agrees with the halving of the re- 
sistance at 4" depth. Calculation actually shows an external residue of 
current of about 8 per cent, but since the surface is plane it follows that 
a considerable portion of this would, in the circumstances of the experi- 
ment, be included. The steady but slow increase of resistance as the 
electrodes are moved further apart beyond 18" is explained by the 
cutting off by the air layer of regions of increasing current density. 
Combining this with the fact of the existence of a moisture gradient in 
the soil we obtain an explanation of the minima observed in the plot 
trials (Table II) since, starting with the electrodes in close proximity 
and gradually moving them apart the fir.st effect is to cause a fall in 
resistance by causing the current to dip down into lower moister layers. 
After a time however, with increa.sing distance, the non-conducting air 
laver above begins to cut into regions of greater and greater current 
density till the resistance introduced by this more than compen.sates 
for the other effect. In the second series of experiments in Table V there 
is no minimum. These were made at the end of the long drought of 1921 
and it appears probable that the second effect overbalanced the first 
from the beginning, owing to the moisture gradient in the soil being 
less steep. An explanation is also afforded of the increase of the distance 
apart at minimum resistance with increasing depth since it will in this 
case be necessar}' to move the electrodes further apart before the air 



T. Deighton 221 

layer begins to affect the couduction between them to a similar extent. 
The result obtained in the beaker experiment is easily understood since 
the surface of the conducting layer being plane, only small segments 
of tores carrying an appreciable fraction of the current pass through 
this layer, and the segment is less the greater the current density in 
the tores. An attempt to solve the matter completely by mathematics 
led in all cases to expressions integrable only over restricted ranges or 
in very slowly converging series, putting this method of procedure out 
of court for practical purposes. A series of rough approximations led 
to results not out of keeping with those obtained. 

CONCLUSION.S FROM ABOVE ExPERI.MENT.S. 

These results are of practical importance as they show what may and 
what may not be expected from this method of moisture determination. 
It is clear in the first place that what is obtained is the mean resistance 
of a volume of soil which may for practical purposes be considered as 
of rather greater extent than a sjahere whose poles are the electrodes, 
something the shape of an apple with the electrodes at the calyx and 
stalk, since the fraction of current passing outside a selected tore falls off 
very sharply beyond d = 45°, and soon becomes negligible. The moisture 
content will also refer to this volume of soil and local and depth varia- 
tions will be obliterated. If therefore we desire to measure the moisture 
content at any depth we must place the electrodes at such a distance 
apart that the moisture gradient can be considered uniform in the 
volume of soil concerned when the deficiency above the level of the 
electrodes will be counterbalanced by the excess below this level. More- 
over if the distance is more than a few inches it will be necessary to take 
account of the tendency of the current to dip down into the moister 
layers, or to continue the simile above, of the downward bend in the 
core of the apple. Secondly the electrodes should really be of such a 
size that they may be considered small in comparison with the distance 
apart as otherwise the calculations do not strictly hold and the new 
conditions ought to be investigated afresh. The necessity of obtaining 
good contact with the soil puts a practical limit to the size of the electrode 
and it was found in consequence that 3" apart is about the lower limit 
for the electrode distance. The distance apart must moreover be chosen 
with a view to confining the current or such part of it as matters to the 
portion of soil concerned, e.g. a distance of 15'-20', while probably giving 
illuminating information on forest land would usually be quite useless 
in ordinary arable farming. Finally it seems possible that considerable 



•222 The Electrical Method of Soil Moixtiirc Deterinlnation 

use might be made of the method in arid sandy regions for determining 
the approximate depth at which the water table lies, e.g. supposing the 
depth of this were 50' — starting with electrodes 6" deep say and a short 
distance apart on increasing the distance the resistance would gradually 
increase to a point but on reaching a distance apart of about 200' the 
beaker experiment would lead us to expect a fairly sharp fall due to the 
water at 50' depth. A few observations would suffice to determine at 
what fraction of the distance apart when the resistance falls the water 
table would be found. It is perhaps worthy of note in this connection 
that the resistance of earth returns in telegraphy is very low; though of 
course, as large plates are usually buried for this purpose, we should not 
erpect anything like the resistances encountered in the soil experiments. 

Resistance-moisture Curves. 

Experiments were made in the laboratory to determine the character 
of the resistance-moisture curve. Artificial mixtures, natural sands and 
soils were employed and results obtained in accordance with those of 
Whitney (^c), except that at low moisture contents definite discon- 
tinuities were observed. 

The method of carrying out the experiments was alike in all cases. 
500 grams of the soil or other substance used was placed in a wooden 
box whose internal dimensions were 2|" x 6" x 2^" and the electrodes, 
small carbon cones, were placed at each end. An extra amount of the 
same sample was used as a reserve from which samples removed for 
moisture determinations could be replaced, maintaining the original 
weight of dry soil. The hygroscopic moisture was found not to affect 
the resistance within the capacity of the instruments used; that is to 
say the air dry substance had in all cases a resistance under the con- 
ditions of experiment exceeding one megohm. As wetting a sample in 
such a way as to render it only slightl)- moist is difficult the following 
plan was adopted: the sample was wetted slightly with distilled water 
and then thoroughly mixed, after which it was warmed to about 30° C. 
and allowed to cool again once or twice. This seemed to distribute the 
moisture evenly through the mass and was preferred to the alternative 
of gradually drying out a saturated mass as its character is changed by 
this treatment. The damp sample was then placed in the box and packed 
down to a constant leveP — a thermometer placed in the middle of the 
mass enabled the temperature to be read and the resistance was taken 

' Great clifTicultv was found in this in the case of the boulder einy; the observations 
were less satisfactory on this account. 



T. Dkighton 



2-23 



when this liad fallen to some point but shghtly above room temperature, 
the same temperature being employed throughout any one series of 
determinations. A sample was taken out from the middle of the mass 
after each resistance reading and the moisture in it determined by drying 
at 110° C. About 15 to '20 determinations were made in this way for 
each sample. It was not, however, found possible to carry the moisture 
content up to saturation since near this point the water tended to oose out 
from the bottom of the bo.x. The results obtained with one soil are given 
in Table VII. If plotted out they yield hyperbolas, but if, instead of 

Table VII. Result.s of Resistance Moisture Detenu 'mat ions on a 
tijpical soil (Greensand). 

Hygroscopic moisture 1-4 % 



Moi.stui'c "(J 


Resistani-c 


iluisture ",, 


Resistance 


dry weight 


in olims 


dry weight 


in ohms 


2-3 


1.100,00(( 


71 


16,800 


2-9 


:j!iU,OUO 


7-6 


11,700 


3-4 


257,000 


8-9 


8,920 


3-6 


208,000 


9-6 


6,200 


4-4 


130,000 


10-7 


5,050 


4-9 


114,000* 


11-6 


3,950 


5-1 


(>0,000 


12-5 


3,490 


5-3 


lll,.")0O* 


13-0 


3,270 


5-7 


:i!i,ooo 


14-2 


2,.50O 


5-8 


70,9110* 


18-6 


1,870 


6-6 


19,200 







plotting directly, we plot the logarithm of the moisture expressed in 
percentage dry weight, less the hygroscoi^ic moisture, against the loga- 
rithm of the resistance observed we obtain the curves shown in Figs. 
4, 5 and 6: whence it is clear that at low moisture contents the curve 
is discontinuous at any rate at one point, the existence of the first point 
of discontinuity is disputable owing to the small number of observations. 
It will be observed that the type of curve is different for the artificial 
mixtures to what it is for the natural soils and sands taken. In the 
former case the resistance falls sharply at first, then less so and finally 
sharply again, in the latter the reverse holds — slowly at first, then more 
quickly, and slowly at the end. 

It would appear that there ought to be no sharp angle between the 
different regions as shown in the curves. It was felt however that as 
the accuracy of the measurements was not sufficiently great to justify 
the use of them as a basis for the discussion of this matter greater 
clearness would be attained by drawing the fines as shown. 

The facts seem explainable as follows : — In the case of pure sand and 
artificial mixtures we may assume that there is no measurable amount 

Joum. of Affric. Sci. xii 16 



224 The l-Jltctrical Method of Soil Moisture Detenu i nation 

of colloid present, while in the natural calcareous sand (coarse) a 
mechanical analysis showed 0-45 per cent, clay and the other sands and 
soils used contained considerably more than this. Now in the case 
where we have no colloid present we should expect little or no reduction 
of resistance until the 5()/x/x film thickness of Quincke (7) is passed since 
Terzaghi (8) has shown that there is no brownian movement and therefore 
presumablv but little if any ionic movement in this layer. Owing to 
evaporation it was found impossible to obtain any results in this region. 

Pure sand w. high resistance water 
„ w. low „ 

>. + 1 % marble w. high reeiBlance water 
„ „ w. low ,. 

+ ij % marble 




17 18 19 00 01 02 03 04 

Log. ot % water over hygroscopic 
Fig. 4. 

Beyond this the addition of water might be expected to cause a more 
rapid fall than in the third stage where it vnW be sensibly inversely pro- 
portional to the moisture content up to the point at which surface 
tension begins to overcome the force of adhesion ^ When surface tension 

^ For in this case the surfaoe of electrode wetted will be directly proportion.il to the 
thickness of the moisture layer, thus if H is the radius of a particle, supposed spherical, 
and IR the thickness of the water film upon it and if ti is the number of contacts between 



T. Deighton 



•22b 



begins to take effect however the tendency is to concentrate the extra 
moisture added in the interstices where one particle touches another or 
the electrode surface and therefore we may expect that the resistance 
will vary inversely as some function of the moisture content. Experi- 
mentally it was found to vary approximately as the inverse square of 
the moisture as had been found iireviouslv bv Whitney. 



COABSt CALCAHEOUS SAN3 




18 19 GO 01 07 03 04 

Log. of % water over hygroscopio 

Fig. 5. 

A tentative explanation of the second series of cases where the 
particles are covered by a colloid substance was originally elaborated 
on the theory that the conductivity of a substance in the gel stage would 
be less than that of the same substance under similar conditions as a sol. 
Recent work by Miss Laing and Prof. McBainO) however shows that 

the several particles and the electrode the area wetted a:n[(R + AiJ)^ -iJ^] =2ni?. AiJ 
neglecting higher powers of Ai?. If in is the moisture content nR.\R cctiRm. But for 



any electrode obviously n oc 



1 



Resistance = 



1 



R conductivity area wetted 

experimental results agree with this in the region dealt with. 



oc - . The 



16- 



226 The Electrical M<t/i(><l of Soil Moisture DetermiiKitiini 

iu the case of sodium oleute the gel stage has under similar conditions 
of concentration and temperature the same conductivity as the sol. The 
similarity of nature between this and the silica gel, with which we are 
most probably dealing, suggests that a like phenomenon would be ob- 
served here. Fortunately Laing and McBain's work itself suggests an 
alternative explanation. They found the conductivity of the soap-curd 
was much lower than that of the tran.sparent gel or sol and distinguisli 



6 0- 
58 
5 6 
5 4 

5 2 

6 
■18 





36 


<D 








1 


3 6 
















•M 










o 






39 


bl) 




O 




hJ 


3J0 



"®- 




MiAM*CI 



_L 



I '®.l 



16 17 18 19 00 01 02 03 04 05 06 07 08 09 lO '1 12 1 '3. 1' 

Log. of % water over hygroscopic 

Fig. 6. 

sharply between coagulation and gelation. Thus in the tirst stage we 
may be merely increasing the degree of hydration of the fibres of the 
silica coagulum, in the second stage where the curve descends more 
steeply we have a passage from a coagulum to a gel in which t he resistance 
falls not only on account of the water added but also because the specific 
resistance of the gel is less than that of the coagulum. finally when the 
coagulum is all converted into gel we have the third stage due to pro- 
gressive dilution of the gel or sol, it being immaterial which is present. 



T. Deighton -l-n 

The principal objection to this is the fact that no stage corresponding 
to the curd stage in soaps has been observed in sihca or other similar 
gels hke gelatine; but if the curd fibres in soap had been transparent 
instead of white it is by no means certain that they would have been 
observed, and in this case since silica crystals are transparent while 
soap crystals, of which the curd is thought to consist, are white, it seems 
not impossible that silica curds may exist in the gel under certain con 
ditious and yet have remained unnoticed uj:) to the present ; only further 
experiment can decide the matter. Laing and McBain found the specific 
conductivity of the curd to increase with concentration, but as the highest 
concentration employed was -QN no deduction germane to the present 
case can be made from this. 

It is worth mentioning that the first kink in the curve seems to be 
related in some way with the "unfree" water of Bouyoucos(iO). The 
mean of his values for various sands is 1-6 per cent, which is in good 
agreement with the moisture at the first kink in the sands dealt with 
here, which varies from 1 to 2 per cent. In the soils we have greensand 
4-4 per cent., glacial loam 3-2 per cent, and boulder clay 8-4 per cent, 
at the first kink. Bouyoucos' averages for unfree water in sandy loams 
and clays come out 4-4 per cent, and 12-2 per cent. 

As regards the effect of the resi.stance of the distilled water used 
with artificial mixtures this is quite what one would expect. In natural 
sands and soils, salts are present in sufficient quantity completely to 
mask any eft'ect due to this cause. 

It appears then, that for any pair of electrodes it should be possible 
to construct an empirical curve from which, given the resistance between 
them in any definite place the moisture content can at once be deduced. 
The degree of accuracy attainable in practice would probably not be as 
great as the lie of the observations about the curves would lead one to 
expect as, apart from the error in sampling a large volume of soil for 
standardisation purposes, the hysteresis eft'ects on wetting and drying 
the colloids would undoubtedly have some effect. Moreover, the curve 
obtained for the greensand seems to indicate another possible source of 
error which might prove very serious. The portion drawn with a dotted 
line^ was obtained quite by accident, after the last observation on this, 
an abnormal fall in resistance was noted — the author therefore went 
backwards and obtained the full fine curve. On adding water afterwards 
this curve was consistently followed and it was found impos,sible to pro- 
ceed again along the dotted portion. Thus there seems to be a possibility 

^ Corresponding observations marked with an asterisk in Tal>le VII. 



228 The Electrical Metliotl of Soil Jfoisfiin J)efenninafioit 

under exceptional circuinstiURes of izetting a nietastable condition of 
some kind; possibly due, if the theory adumbrated is true, to something 
of the nature of a supersaturation of the coagulum — or, more probably, 
a time factor comes in, Lainj; and McBain having found that the con- 
ductivity of a newly formed curd falls oil for a long time after its forma- 
tion, thus we might expect a similarly retarded recovery if water is 
added too rapidly. The probability of this is increased by the fact that 
these workers found that the best way to obtain the gel was to warm 
the curd very slowly. This error would in this case be unlikely to appear 
in soil work. 

The agreement of the last portion of the curve as to slope in all 
cases seems to show that in general at moisture contents exceeding 
10 per cent, or thereabouts the American formula holds good approxi- 
matelv and we mav therefore use it in the form given by Gardner, viz. : 



'^-y^' 



where W = per cent, moisture at time of standardisation, 
R = the resistance corresponding to W, 
i?j = the resistance observed, 
and Wi = the per cent, moisture corresponding to the resistance R^, 
provided always that we do not lose sight of the sources of error noted 
above and of the limitations of the method dealt with earlier in this paper. 
There remains the question of the effect of movement of soil salts 
in the soil which, if considerable, may either vitiate the method alto- 
gether, or render it too cumbrous for use by necessitating a too frequent 
standardisation of the electrode. Experiments are proceeding on tliis 
matter, but from the extreme slowness of the method adopted for this 
purpose, the full results are not likely to be available for some time. It 
may be stated however that the material so far to hand seems to indicate 
that where a soil is protected from rain these salt movements do not 
affect the moisture determination by as much as one half per cent. 

I take this o])])oi'tunit v of tiianking all those who by their unfailing 
interest, help and encouragement have enabled me to bring this in- 
vestigation to its present position. Among these I owe a special debt 
of gratitude to Mr J. W. Capstiek. O.B.E., M.A., D.Sc. for continuous 
advice and sympathetic criticism throughout the whole time that the 
experiments were in progress. 



T. Deighton 229 

Summary. 

In this paper an examination is made of the processes operative and 
the limits of accuracy of the electrical method of determining soil moisture. 

The resistance over a small plot is found to vary under similar 
conditions and it is concluded that these differences are mo.st probably 
due to actual differences in moisture or other factors. 

The effect of the distance apart of the electrodes is investigated and 
a probability of a minimum resistance between two electrodes being 
observed under certain conditions is indicated. 

The use of electrode values in computing soil resistances is discussed 
and criticised. 

The path of the current in the soil is investigated mathematically 
and it is shown that the results obtained accord well with the observed 
facts. 

It is concluded that the method gives the mean water content of a 
volume of soil somewhat greater than a sphere whose poles are the 
electrodes. The practical limits of the method are indicated. 

Certain resistance-moisture curves obtained in the laboratory are 
discussed and it is concluded that while at water contents above 
10 per cent, the relation found by the American investigators holds good 
— viz. that the resistance varies inversely as the square of the moisture 
content; at lower water contents than this one and possibly two dis- 
continuities appear in the curve. 

These discontinuities are reversed in the case of artificial mi.xtures 
not containing colloids. 

A tentative explanation of these phenomena is given. 



REFERENCES. 

(1) Whitney, M. Some Physical Properties of Soil in their Relation to Moisture 

and Crop Distribution. U.S. Dept. Agric, Weather Bureau Bull. No. 4, 1892. 

(2) Whitney, M. and Means, T. H. An Electrical Method of determining the 

Soluble Salt Content of Soils. U.S. Dept. Agric, Dimsion of Soils, Bull. 
No. 8, 1897. 

(3) Gardner, F. D. The Electrical Method of Moisture Determination in Soils; 

Results and Modifications in 1897. U.S. Dept. Agric, Division of Soils, 
Bull. No. 12, 1898. 

(4) Beigqs, L. J. Electrical Instruments for Determining the Moisture, Tem- 

perature, and Soluble Salt Content of Soils. U.S. Dept. Agric, Division of 
Soils, Bull. No. 15, 1899. 



230 The Electrical Method of Soil Moisture Determination 

(o) Leblanc, AF. and Schick. Wechselstromelectrolyse. ZeiLichr. f. Phys. Chem. 

46 ( I<tO:i). 213; also LciB, A. Zeilschr. f. EUclrochem. 12 ( 19W)). 79. 
(0) M.iSCART, E. and Joubert, J. Electricity and Magneiism. 1, 206. [Eng. TraiLs. 

by E. Atkinson, London, 1883.] 

(7) Quincke, G. Ann. d. Phys. u. Chem. 5 Reiho, Bd. 17 (1809). 413. 

(8) Terzaohi, Ch. New facts about surface friction. The. Physical Perieu; 16 

(1920), Xo. 1. 

(9) Laino, jr. E. (.Miss) and McBain. .). W. The Investigation of Sodium Oleate 

.solutions in the three Physical States of third, Sol and Gel. Trans. Chem. 
Soc. 117 (1920), 1500. 
(10) BoUYOUCOS, G. J. Measurement of inactive or unfree Moisture in the Soil by 
means of the Dilatometer Method. Joiini. Afjric. Re.i. 8 (1917), 19.">. 



(Received April IMi, 1922.) 



THE CHEMISTRY OF THE STRENGTH 
OF WHEAT FLOUR. 

By HERBERT ERNEST WOODMAN, Ph.D., D.Sc. 

{From, the Animal Nutrition Institute, School of Agriculture, 
Cambridge University. ) 

It is well known that different flours vary enormously in respect of the 
size and shape of loaf they yield on baking. The factor which determines 
the quahty of flour in this connection has been termed "strength" and 
the latter has been defined as "the capacity of flour for making large 
well-piled loaves "(i). 

Many views have been held from time to time regarding the ex- 
planation of flour strength from the chemical standpoint. The earliest 
view was that strength was determined by the gluten content of the 
flour, which by virtue of its tenacity was able to retain in the bread 
the carbon dioxide produced as a result of the activity of the yeast. 
Many cases, however, were investigated where flours possessing a high 
gluten content were not so strong as a flour with a low content of gluten. 
Furthermore, no accepted regularity has been found to exist between 
the strength of flours and the water-holding or gas retaining capacity 
of their glutens. 

Attention was next directed to the consideration of the individual 
proteins in the gluten of flour, namely, gliadine and glutenine. It was 
found that measurements of the absolute amounts of gliadine showed 
no correlation with strength. Neither was it possible to show any con- 
sistent relationsship between strength and the ratio of ghadine to glutenine 
in the gluten. It was suggested by Hall (2) that gliadine might not be 
a definite substance and that the gliadine contained in very strong 
flours might be different from that in weak flours. Wood (3), however, 
prepared and examined samples of gliadine from strong and weak flours 
and concluded, on the grounds of their content of amide nitrogen, that 
the proteins from both sources were identical. Indirect determinations 
of the amide nitrogen of the glutenines of weak and strong flours led to 
the conclusion that the glutenine protein in different flours was one and 



232 The Chenihtrii of tin StniH/f/i of W/irat Flour 

the same substance. It was therefore not possible, on the available 
evidence, to explain the difference in the loaf-iiiakinti; qualities of different 
flours by reference to their protein content. 

A valuable contribution to the study of the subject was made, when 
Wood (3) resolved the conception of flour strength into two factors: 

1. Tii(> factor of strength which determines the shape of the loaf. 

^- J) ;• >j I! size ,, ,, 

The results obtained by this investigator justified the conclusion that 
the capacity of a flour for giving off gas wjien incubated with yeast 
and water is the factor which in the first instance determines the size 
of the loaf. The latter depends not so much on the amount of sugar 
present in the flour as such, but on the diastatic capacity of the flour, 
which gives rise to continued sugar formation and consequently con- 
tinued gas evolution in the dough. The same worker also showed that 
the properties of gluten in regard to coherence and elasticita^ were 
subject to considerable modification by the concentration of acid, alkali 
or salt in the solution with which it was in contact, and he suggested 
that these properties have an important bearing on the shape of the 
loaf. A knowledge of the acidity and soluble .salt content of a flour should 
therefore afford a clue to that factor of strength wliich decides whether 
the flour will make a good-.shaped loaf. 

The information obtained in the investigation referred to above has 
been applied with success in several pha.ses of the milling industry. The 
view has long been held, however, by Professor Wood himself, that in 
view of the improvement of tlie methods employed in protein research, 
the question of the identity or non-identity of the corresponding gluten 
proteins in weak and strong flours should be re-investigated. It is now 
recognised that two proteins may be quantitatively identical with regard 
to their amino-acid content and yet be two distinct proteins, by virtue 
of dift'erences in the order of hnkage of the amino-acids within the protein 
molecules. Such a case is furnished by the caseinogens of cow's and 
sheep's milk. Though it is possible to show that these proteins are 
distinct sub.stances(i), yet by the ordinary chemical methods of analysis 
they are indistinguishable. 

It is clear, then, that any chemical method which is to be emplo3'ed 
to decide on the identity or non-identity of related proteins must be 
such as to take into account the pos.sibility of differences connected with 
the order in which the constituents of the proteins are linked up within 
the molecules. Such a method is the Racemisation Method, which has 
been used recently in the investigation of the corresponding proteins of 



H. E. Woodman 233 

blood serum, colo.stnun and milk (•'>). The method depends on the be- 
haviour of proteins in dilute ulkaline solution. When such solutions are 
kept at 37° C, they suffer a progressive diminution in the value of their 
optical rotatory power as a result of a keto-enol tautomerism of the 
= CH — CO — groups in the protein complex. If the specific rotations 
of the solution be plotted against the time in hours during which the 
reaction has been allowed to proceed, then the readings fall on a perfectly 
smooth curve. It is found that the rotation sinks rapidly at first, then 
more slowly and subsequently after about 250 hours attains a practically 
constant value. The process thus results in the partial racemisation of 
the protein, and the graphs thus obtained are referred to as racemisation 
curves. 

Since individual proteins display specific behaviour quantitatively 
when racemised with dilute soda, it follows that the method may be 
used to test the identity or non-identity of related proteins. Thus, if 
two proteins are to be pronounced identical, then if racemised under 
the same conditions, their solutions must show the same initial rotation, 
the same final rotation and the same rate of diminution of rotation. 
They must also continue to display identical optical behaviour if the 
concentration of the alkah or protein in the solution is varied. On the 
other hand, if two proteins are not identical, this will be revealed by their 
possessing distinct sets of racemisation curves. 

In the investigation to be outlined in the present communication, 
samples of gliadine and glutenine have been isolated from typical strong 
and weak flours and have been investigated comparatively by means 
of the racemisation method. The results obtained are very suggestive 
in relation to their bearing on the existing ideas of flour strength, since 
it has been shown that whereas the gliadines from weak and strong 
flours are identical proteins, yet the glutenines prepared from the same 
sources appear to be two distinct chemical individuals. 

Preparation of Proteins. 

1. Gliadine and glutenine from strony flour. 

The flour used for this purpose was a typically strong flour milled 
exclusively from Northern Manitoba Wheat. The method used for the 
isolation of the proteins was in its essentials the same as that described 
by Osborne (fi). The bulk of the starch and soluble constituents was 
removed by enclosing the flour in a muslin bag and kneading the material 
in a stream of running water, the process being completed by thoroughly 



234 Thr ('hriiilxtrij of the Sfrftif/f/i of Wlimt Flour 

kueadiiig the gluten under a large volume of distilled water. The re- 
sultant characteristically sticky gluten was broken up into small pieces 
and extracted with alcohol, the alcohol added being such as to give, with 
the water in the gluten, a solvent containing 70 per cent, of alcohol by 
volume. After standing for 48 hours with frequent shaking, the super- 
natant alcoholic solution of gUadine was filtered ofT and the residue was 
repeatedly extracted with successive portions of 70 per cent, alcohol 
until the amount of gliadine going into solution was inappreciable. 

The combined filtrates were then concentrated in vacuo at 50° C, 
care being taken to keep the gliadine in solution by adding small portions 
of alcohol from time to time. The concentrated solution was cooled 
and poured slowly, with constant stirring, into a large volume of ice- 
cold distilled water containLiig about 10 grin, salt per litre. A gummy 
mass separated out which collected on the glass rod. This was repeatedly 
washed with distilled water, dis.solved in 70 per cent, alcohol and the 
solution filtered until water clear. After concentrating the solution 
in vacuo at 50° C, the syrupy residue was cooled and poured into 
absolute alcohol. It was found that complete separation of the gliadine 
could only be obtained by this method after stirring a Uttle salt into the 
alcoholic hquid. The addition of ether also enabled the gliadine to 
separate completely. 

The process of dissolving the gliadine preparation in 70 per cent, 
alcohol, filtering, concentrating in vacuo and precipitating by means of 
absolute alcohol was carried out in all three times, the final precipitation 
being effected by a mixture of ether and absolute alcohol, this resulting 
in the gliadine separating in a flocculent condition. The protein was then 
dried by washing successively with absolute alcohol and anhydrous ether 
and was filially obtained as a white powder which dissolved completely 
in 70 per cent, alcohol to give a water clear solution. As a result of the 
method of preparation, it contained a little salt as impurity. 

The gluten residue, after extraction of the gfiadine with 70 per cent, 
alcohol, was allowed to dry at room temperature and then powdered. 
It was then further extracted with alcohol, the gliadine-free residue 
being shaken with successive portions of ether to remove fat. After 
air-drying, the material was shaken with sufficient 0-2 per cent. KOH 
to effect solution. The extract was filtered, great difficulty being ex- 
perienced in obtaining a clear filtrate. From the latter the glutenine 
was precipitated by means of very dilute hydrochloric acid, the amount 
of acid requisite for flocculent precipitation being determined by a pre- 
liminary test on a small bulk of the alkaline solution. The precipitate 



H. E. Woodman 235 

obtained in this manner was exhaustively extracted with 70 per cent. 
alcohol to remove traces of gliadinn. It was then redissolved in the 
minimum amount of ()-2 per cent. KOH, filtered clear and the glutenine 
reprecipitated in the manner already described. The process of pre- 
cipitating the protein fnjm alkaline solution was carried out in all four 
times, and after each precipitation, the glutenine was extracted with 
70 per cent, alcohol to ensure complete removal of gliadine. After the 
final precipitation, the glutenine was well washed with, distilled water 
and was obtained as a white powder bv successive washings with 
absolute alcohol and anhydrous ether. The preparation gave a water 
clear solution in 0-2 per cent. KOH and an exhaustive extraction of a 
sample of the material showed that it was entirely free from gliadine. 
It contained, as a result of the method of isolation, a small amount of 
potassium chloride as impurity. 

2. Gliadine and f/hitcnine fmn) iveak Jlnur. 

The flour used as the starting point for the preparation of these 
proteins was one which had been milled exclusively from English wheat. 
The same methods were employed as those outlined in the preparation 
of the proteins from Manitoba flour. 

The gluten of the Enghsh flour differed materially from that of 
Manitoba flour in respect of its physical properties. Whereas the latter 
was sticky and coherent, the former lacked coherency and resembled 
putty in its consistency. 

Much bigger percentage yields of the proteins were obtained from 
the Manitoba flour than from the Enghsh flour. 

Method of investigating the behaviour op the protein.s 

WITH dilute alkali. 

The protein .samples were first finely ground up and then dried in 
vacuo over calcium chloride for several days. The amount of ash-free 
protein in each sample was determined by means of the Kjeldahl method, 
the nitrogen content of the gliadine samples being multiplied by the 

factor - and that of the glutenine samples by yyIiq ■ 

In the case of the gliadine .samples, the first series of determinations 
were carried out in the following manner. Exactly 1 grm. of the dry 
protein was weighed out into a 50 c.c. flask containing a little distilled 
water. 2-5 c.c. of N NaOH (or Nj2 NaOH as the case may be) were then 
slowly run in from a pipette. After mixing gently, the volume was 



2;>6 The Clumistnj of the Sfniu/fh of Wheat Flour 

made up to the 50 c.c. mark with distilled water and the flask was placed 
in an incubator kept at 37° C. When the protein was completely in 
solution, the liquid was filtered quickly into a small flask, which was 
then stoppered and kept in the incubator. From time to time, the optical 
rotation of the alkaline solution was determined in a Ir/- polar! metric 
tube, using a Schmidt and Haensch instrument and sodium light. This 
procedure was continued for about 300 hours, when the value had 
become practically constant. Graphs were then con.structed .showing 
the progress of the racemisation, the ordinates representing specific 
rotation values and the abscissae the number of hours during which the 
reaction had been allowed to proceed. 

In carrying out the determinations in the above manner, some delay 
always occurred in eft'ccting complete solution of the gliadine in the 
alkali. The difliculty was satisfactorily overcome in the following way. 
The 1 grm. sample of dry protein in the 50 c.c. flask was first dissolved 
in 10 c.c. of 70 per cent, alcohol. The 25 c.c. of .standard soda were then 
slowly run in, the flask being gently shaken during the process. The 
volume was then made up to 50 c.c. with distilled water and the flask 
was placed in the incubator. A clear solution was obtained in a few 
minutes by this method. 

The racemisation data of the glutenine samples were obtained in a 
somewhat similar manner. 1 grm. samples of the dry protein were 
weighed into 50 c.c. flasks containing a little distilled water. The 25 c.c. 
of standard soda were then run in slowly and the flask was gently 
shaken. A jelly like mass was first obtained, which quickly liquefied 
when the flask was put in the incubator. The volume was then made 
up to the 50 c.c. mark with distilled water and the polarimetric readings 
were taken as described above. 

Investigation of the gliadine samples. 
1. Specific rotations in 70 per cent, alcohol. 

2 per cent, solutions of the gliadine preparations in 70 per cent, 
alcohol were examined by means of the polarimeter with the following 
results: 

Gliadine from Manitoba flour [ajy^ = — 93-60°. 
,, EngUsh „ [a]/, = - 93-78°. 

Osborne (6) gives the value of — 92-28° for the specific rotation of gliadine 
in 80 per cent, alcohol. 



H. E. Woodman 



237 



It will be noted that the gliadine.s from the strong and weak flours 
display no difference in respect of their rotations in 70 per cent, alcoholiu 
solution. 

2. Data obtained in the racemisation of the gliadme samples. 



Manitoba tlour gUadine 
2 % in xV/2 NaOH 



English Hour gliadine 
2 % in Nj-l NaOH 



Time in hours 


Specific rotation 


Time in liours 


Specific rotation 


2 


-110-5° 


2 


-111-0 


5 


- 106-8 


5 


- 106-3 


9 


- 104-1 


9 


- 1040 


24 


- 96-8 


241 


- 96-3 


49 


- 89-0 


49 


- 89-5 


74 


- 84-1 


73 


- 83-9 


101 


- 78-8 


101 


- 79-5 


125 


- 75-1 


124 


- 75-6 


169 


- 71-5 


170 


- 71-3 


242 


- G7-3 


240 


- 67-() 



In the series of determinations recorded under 3, 4, -5 and 6, the 
weighed out samples of protein were first dissolved in a measured 
volume of 70 per cent, alcohol as described before the addition of the 
standard alkali. 



3. 

Manitoba fiour ghadlne 
2 % in Nj2 NaOH (alcohol present) 



English flour gliaduie 
I in iV/2 NaOH (alcohol present) 











Time in hours 


Specific rotation 


Time in hours 


Specific rotation 


1 


- 109-4° 


1 


- log-o" 


5 


- 98-3 


5 


- 97-8 


9 


- 930 


9 


- 93-2 


24 


- 86-2 


24 


- 86-7 


48 


- 80-5 


48 


- 80-6 


74 


- 76-2 


72 


- 76-2 


125 


- 72-6 


124 


- 72-1 


170 


- 69-4 


170 


- 68-9 


240 


- 66-0 


242 


- 65-6 



6. 



Manitoba flour gliadine 
2 % in Nji NaOH (alcohol present) 



EngUsli flour gUadine 
2 % in Nji NaOH (alcohol present) 



Time in hours 


Specific rotation 


Time in hours 


Specific rotation 


1 


-110-5° 


1 


-110-8° 


5 


-103-1 


5 


- 103-1 


9 


- 100-0 


9 


- 99-3 


25 


- 94-7 


24 


- 94-3 


48 


- 90-5 


48 


- 90-5 


96 


- 88-4 


97 


- 88-0 


119 


- 86-8 


120 


- 86-5 


168 


- 84-7 


170 


- 84-0 


244 


- 82-0 


242 


- 81-7 



■238 The Chninsh-ii of the Sfntif/f/' "J' W'/naf llmtr 

The above deteniiination.s wore carried out at least in duplicate and 
the results were confirmed by independent investigation of further 
samples of the two gliadines prepared from the same flours. 

It will readily be seen from the above data that the gliadines from 
the two types of flour display throughout identical optical behaviour 
when racemised by dilute alkali at 37°. This fact is brought out more 
strikingly if the graphs representing the course of raceniisation be con- 
structed. For each set of experimental conditions, it will be found that 
one smooth curve can be drawn to satisfy equally the two sets of readings 
for the Manitoba and English flour gliadines. Such slight discrepancies 
as may occur fall within the general error of e.xperiment. 

When racemised by means of Nj'l NaOH, each gliadinc solution 
possesses an initial s])ecific rotation of about — 114° (taken from graph ^). 
The rotations of both solutions diminish fairly rapidly and at an equal 
rate during the first 24 hours; tlie rate of diminution in each case then 
falls off equally and after 240 hours, when the value of the rotation has 
become practically constant, the two solutions possess an e(|ual specific 
rotation of about — (57°. 

The presence of the small ainoujit of alcohol in the second series of 
determinations e-xerts a striking elTec't on the rate of racemi.sation and 
affects both gUadines in an equal degree. The effect is best studied by 
constructing the graphs. The rate of racemisation during the first 
24 hours for iV/2 NaOH is much quicker when alcohol is present than 
when it is absent. In the presence of the alcohol, the specific rotation 
during the first 24 hours sinks from — 114° to — 86°, whereas when no 
alcohol is present, the corresponding diminution is from — 114° to about 
— 97°. After about 50 hours, however, the two curves begin to come 
together again and almost coincide after about 250 hours. The presence 
of alcohol causes Nj^ NaOH to effect a greater reduction in specific 
rotation during the first day than does iV/2 NaOH without alcohol. 
These curves cro.ss after about .'}5 hours and from this point the rate of 
diminution with the weaker alkali is relatively slow. The reason for the 
effect thus produced by the alcohol, which resembles that of a catalyst, 
requires further investigation. For the purposes of this enquiry, it is 
sufficient to note that under the three different sets of conditions, the 
gliadines from the weak and strong flours display the same optical 
behaviour during racemisation. This fact is taken as evidence of the 
identity of the two gliadines. A final test on a mixed sample of the two 

^ The graphs are init rrprnthu-ed lioro, as they are not necessary in enabling the 
essential conehisions tu he drawn. 



H. E. Woodman 239 

gliadines gave readings which fell on the racemisation curves which the 
two proteins have been shown to possess in common. 

3. Vombining weights of the gliadines. 

Foreman (7) has shown that aqueous-alcohohc solutions of certain 
amino-acids containing about 85 per cent, alcohol can be titrated accu- 
rately with alkali in the presence of phenolphthalein. The amino groups 
under these conditions display no basicity to phenolphthalein and the 
carboxyl groups can therefore be estimated by titration. 

On the basis of this observation, it seemed probable that the basic 
effect of the free amino groups in the ghadine molecule towards phenol- 
phthalein might be held in abeyance when the protein was dissolved in 
alcohol, thus permitting of the direct estimation of the free carboxyl 
groups in the molecule by titration with alkali. Accordingly, 2 per cent. 
solutions of the gliadines in 80 per cent, alcohol were titrated with 
iV/10 NaOH in the presence of phenolphthalein, and the following results 
were obtained : 

Manitoba flour gliadine 1 grm. dry, ash-free protein required 1-95 c.c. 

A7I0 NaOH. Combining weight = 5128. 
Enghsh ,, „ 1 grm. dry, ash-free protein required 1-99 c.c. 

iV/10 NaOH. Combining weight = 5026. 
It follows that both gliadines possess the same combining weight, the 
difference recorded being due to experimental error. This fact affords 
further confirmation of the identity of the gliadines. 

The data recorded above possess an additional interest when con- 
sidered in conjunction with the minimum molecular weight ascribed to 
gliadine by Osborne (8) on the assumption that the molecule contains 
five atoms of sulphur, viz. 15560. It would thus appear probable that 
the ghadine molecule contains three or a multiple of three free carboxyl 
groups. 

Investi(!ation of the glutenine samples. 

1. Specific rotation in iV/25 NaOH. 

0-5 per cent, solutions of the glutenines in iV/25 NaOH were examined 
by means of the polarimeter with the following results : 

Glutenine from Manitoba flour [a]^, = — 99-5°. 
., English „ [a]^, = - 78-8°. 

2. Similar differences in the optical properties of the glutenines were 
observed during the racemisation of the proteins by means of iV/2 NaOH 
at .37° C. 

Joum. of Agric. Sci. xn 17 



240 The Chemist ri/ of the Strength of Wheat Flour 



Munitoba Hon 


r glutenine 


English ti 


lour glutenine 


2 % in 


AT- 


I NaOH 


2% in 


5l 


2 NaOH 


Time in hours 




1 
Specific rotation 


Time in hours 




Specific rotation 


1 




- 930° 


1 




-740'= 


5 




-850 


5 




-67o 


9 




-79-5 


9 




-62-9 


24 




-71-0 


24 




-57-0 


48 




-60-5 


49 




-500 


72 




-55-5 


72 




-45-9 


96 




-51-2 


98 




-41-5 


143 




-470 


144 




-370 


190 




-44-0 


192 




-350 


240 




-41-5 


242 




-32-5 



."5. The following data show the behaviour of the glutenines when 
racotuised with N/i NaOH at 37° C. 



Manitoba flour glutenine 
2 % in A74 NaOH 



English Hour glutenine 
2 % in A74 NaOH 











Time in hours 


Specific rotation 


Time in hours 


Specific rotation 


2 


- 940° 


2 


- 77-0° 


9 


- 85-5 


9 


-71-6 


24 


-78-6 


25 


-650 


96 


-67-8 


96 


- 57-5 


144 


-63-5 


143 


-540 


242 


-57-0 


240 


-48-5 



The differences in optical behaviour displayed by the glutenines 
during racemisation with Xj'2 and iV/4 NaOH point to the conclusion 
that the glutenine of strong flour is a different protein from that con- 
tained in weak flour. Two objections, however, may be raised against 
the evidence on which this conclusion is based. 

1. In view of the difficulty of effecting complete separation of two 
proteins from each other, it is possible that the samples of glutenine are 
still associated with small amounts of gliadine. and that the high rotation 
values obtained with Manitoba Hour glutenine as compared with English 
flour glutenine may be explained on the grounds that the former glutenine 
contains more of the high rotating gliadine than does the latter. 

2. It has not been demonstrated that the glutenines are extracted 
from the glutens without change. It is possible that the 0-2 per cent. 
KOH used in the isolation of the glutenine may cause, even at the room 
temperature, a slow Taceinisati(m of the proteins and thus render un- 
certain any conclusions which may be drawn as a result of the optical 
behaviour of the final samples with dilute alkali at 37° C. 

The first objection cannot be sustained, liowever, since a study of 
the initial rotations of the proteins in alkali shows that the Manitoba 
flour glutenine would have to contain relatively large amounts of 
gliadine to account for its optical behaviour on this assumption. Ex- 



H. E. Woodman 241 

hauistive extractions of the sample with 70 per cent, alcohol failed to 
reveal the presence of even traces of ghadine. 

In view of the second possible objection, the following tests were 
carried out. A 0-5 per cent, solution of Manitoba flour glutenine in 
0-2 per cent. KOH, to which was added a drop of toluene, was allowed 
to stand at room temperature for about a month and the specific rota- 
tion was determined from time to time. The initial specific rotation 
was — 95-0", and during the period of the trial this value did not suffer 
any measurable diminution. It is reasonable to assume, therefore, that 
the optical properties of the glutenines were not affected as a result of 
their mode of extraction by means of 0-2 per cent. KOH. 

Moreover, the rate of diminution of rotation of a 0-5 per cent, solution 
of Manitoba flour glutenine in N/25 NaOH when kept at 37° C. was 
exceedingly slow, as is evidenced by the following series of determina- 
tions : 

Time in hours Specific rotation 

2 - 990' 

25 -97-0 

98 -910 

267 -79-0 

It will be observed that the specific rotation of the Manitoba flour 
glutenine solution had barely fallen to the initial value of the specific 
rotation of the English flour glutenine even after standing 267 hours 
at 37° C. 

Both objections become untenable in view of the fact that similar 
investigations carried out on further samples of tlie glutenines from the 
same flours yielded confirmatory results. If the differences observed 
between the two glutenines arise from the operation of factors involved 
in the objections 1 and 2, then it would be a remarkable coincidence 
if such factors should operate with exactly equal eft'ect in the case of the 
independent samples which were examined. 

The results of the investigation may therefore be interpreted as de- 
monstrating the non-identity of the glutenines from strong and weak 
flours. 

If, as seems probable, the characteristic physical differences between 
the glutens of the two flours are related to the differences existing be- 
tween the glutenine fractions, then it would at first sight appear feasible 
to produce a "strong" gluten by preparing a moist mixture of English 
flour gliadine with Manitoba flour glutenine, or a "weak" gluten by 
mixing together Manitoba flour gliadine with English flour glutenine. 
Attempts to demonstrate this possibihty, however, met with no success, 

17—2 



24-_' The Chemistry of the Sfrcnfff/i of Whmf Flour 

the reasons being twofold : 1 . It is not possible by grinding.' the ])roteins 
together to effect the same intimacy of mixture as occurs naturally in 
the flour. 2. The physical properties of the proteins themselves have 
probably been considerably modified during the process of their isolation 
as a result of prolonged contact witii different reagents (alcohol, ether, 
alkali, etc.). 

The view has been put forward by Kosutany(!») that glutenine is 
derived from gliadine by the splitting off of water. The i)uantitative 
work of Osborne in connection with the hydrolysis of these proteins has 
shown beyond doubt that they are two absolutely distinct substances, 
and a comparison of the racemi.sation data for the glutenines with those 
of the gliadines confirms Osborne's view. The gliadines exhibit distinctly 
different optical behaviour during racemisation from that displayed by 
the glutenines. 

Summary and Conclu.sioxs. 

The gliadine and glutenine proteins from typical strong and weak 
wheat flours have been isolated and investigated by comparative methods. 

The gUadines from the two sources have been showTi to be identical 
proteins. This conclusion, which is in harmony with the earlier results 
obtained by Wood, has been arrived at on the following grounds: 

1. The identity of their optical behaviour when racemised by dilute 
alkali at 37° C. under three different sets of conditions. 

2. The identity of their specific rotations in 70 per cent, alcohol. 

3. The identity of their combining capacities for alkali, as determined 
by titration in 80 per cent, alcoholic solution by means of iV/10 NaOH 
to phenolphthalein. 

The glutenines from the two types of flour have been showTi to be 
two distinct substances, this conclusion being based on their different 
optical behaviour during racemisation by dilute alkali. 

It is suggested that the existing ideas on flour strength require 
modification to include the facts recorded in this investigation. It is 
desirable to retain the dual conception of strength as put forward by 
Wood. The factor which determines the size of the loaf is most probably 
connected with the diastatic capacity of the flour, as was suggested by 
this investigator. On the other hand, the factor which determines the 
shape of the loaf and which appears to be directly related to the physical 
properties of the gluten of the flour, is possibly dependent on the par- 
ticular glutenine mechanism possessed by the wheat. 

The results of this investigation suggest that the strong wheat 
synthesizes one type of glutenine and the weak wheat a different type, 



H. E. Woodman 24:] 

whilst wheats of intermediate strength may contain varying proportions 
of the two glutenines. To a certain extent also, as was demonstrated 
by Wood, the physical state of the gluten will be conditioned by the 
acidic and soluble salt content of the flour. 

It is not claimed that the above explanation can be regarded as final, 
since there seems no particular reason to hmit the number of possible 
glutenines to two, nor indeed is it feasible to rule out, on the available 
evidence, the possibility of the existence of more than one gliadiue 
amongst the wheats. It is hoped to continue the investigation further 
along these lines. 

It has been shown that ghadine possesses a combining weight of 
approximately 5000, and from this the conclusion has been drawn that 
the ghadine molecule contains three or a multiple of three free carboxyl 
groups. 

It has been demonstrated that a solution of glutenine in 0-2 per cent. 
KOH undergoes no measurable diminution in optical rotation on standing 
over a long period at room temperature and that only a slow change 
occurs in iV/25 alkahne solution at 37°. It thus appears probable that 
proteins can be extracted by means of 0-2 per cent. KOH without 
suffering change, provided the alkahne extracts are kept cool. 

The writer would hke to avail himself of this opportunity to exjjress 
his thanks to Professor T. B. Wood, C.B.E., M.A., F.R.8., at whose 
instance this investigation was undertaken and whose advice throughout 
has been of material assistance. Also to Dr. A. E. Humphries, with 
whose help the writer was able to secure the samples of flour used for 
the preparation of the proteins. The sample of Manitoba flour was 
supphed by Messrs John White and Sons and the English flour by 
Messrs Soundy and Co. To both these firms the writer's thanks are due. 

REFERENCES. 

(1) HuMPHBiES and BrFFEN. J. Agric. Sci. 2, 1, 1907-8. 

(2) Hali,. Report of Home-gromn Wheat Committee, 1905-6. 

(3) Wood. J. Agric. Sci. 2, 139, 1907-8. 

.1. Agric. Sci. 2, 267. 1907-8. 

(4) Dudley and Woodman. Biochem. J. 9, 97, 1915. 

(5) Woodman. Biochem. .J. 15, 187, 1921. 

(6) Abderhalden. Handbiich der bioch. Arbeitsmethoden, 2, 320, 1909. 

(7) Foreman. Biochem. J. 14, 451, 1920. 

(8) Osborne. The Vegetable Proteins, p. 70 (1909). 

(9) Kosutany. J. Landw. 51, 130, 1903. 

[Received June 6th, 1922.) 



ON THE USE OF ARTIFICIAL INSEMINATION 
FOR ZOOTECHNICAL PURPOSES IN RUSSIA. 

By E. I. IVANOFF, 

Director of the Central Experimental Breeding Station for 
DonieMic Animals, Moscow, Russia. 

One of the greatest problems of Russia's present economic policy is the 
restoration and development of farming, and in particular, cattle- 
farming. The war and revolution have, together with other things, 
destroyed enormous numbers of cattle, horses, pigs, etc., and thoroughly 
undermined the meat industry, as well as the sources of supply of 
working animals. A decrease of 50 % below the former numbers of 
horses is the common state of things. The preservation of cattle-farms 
and studs is seldom met with, and the number of stock-producing animals 
is at least ten times less than formerly. The terrible drought threatens 
to bring into this sphere of national wealth even greater destruction. 
At the same time there can be no doubt that without the restoration 
and maintenance on a definite level of stud and cattle-farming, Russia 
cannot return to full economic activity. The present-day state of things 
demands that every effort be made, every possibility found and utilised, 
for increasing the number of domestic animals and for improving the 
methods of breeding and the breeds themselves. 

Mass-breeding of domestic animals must certainly go hand-in-hand 
with mass-improvement of the breeds. If indiscriminate raising of 
animals was unprofitable before the war, at the present time, with 
undreamt-of prices of fodder and labour, it is certainly a loss. 

The greatest obstacle in the way of a successful solution of the above 
problems is the shortage of progenitors suitable for stud and cattle- 
farms. Let us take for example horse-breeding. Before the war, the 
number of thorough-breds in Russia was not even 1 %, and for one 
stud-stallion, there were 600 mares. At present the difference between 
the demand and supply of valuable stallions can be expres.sed approxi- 
mately as 1 : 3000. But the number of mares served by one stallion in 
the pairing season is from 10-40, seldom higher, and on an average 25-30. 



E. I. IvANOPF 245 

Consequently, in order to jirovide for all the available mares stud- 
stallions, it woidd be necessary either to increase the number of the 
latter at least a hundred times, or to increase the productivity of the 
present number as many times. The former, in view of the present 
economic conditions, cannot be realised even to the extent of 1 % of the 
requirements; the latter, though not fully, yet to a considerable degree 
can be reached by putting systematically into wide practice the method 
of artificial insemination which enables more than 300 mares to be 
inseminated during the pairing season by one stallion, instead of 25-30. 
The same applies to all other live stock. 

The aim of the present article is to show what has been achieved in 
Russia with this method and to indicate the possibilities connected with 
the practical side of this work. 

Under the term "artificial insemination" as applied to Mammals, 
and in particular domestic animals, is understood the introduction, by 
artificial means, of the semen of the male into the vagina of the female. 
The seminal cells or spermatozoa can be introduced either (1) in their 
natural medium, i.e. in the secretion of accessory sexual glands, or (2) in 
an artificial medium (physiological solution, Locke's fluid, serum, etc.). 
In either case the essential conditions of fertilization are the natural 
fundamental jirocesses and conditions: the maturity of sexual products, 
for examjale, their viability, etc. must remain unchanged. The only 
difEerence is that in artificial insemination the fate of the secreted male 
sexual cells is held in the hands of man, who can divide the collected 
material into parts and inject it into the female sexual organs by means 
of instruments (catheter, syringe). Thus, in the case of Mammals, strictly 
speaking, it is not a method of artificial fertilization, but of artificial 
insemination. 

The possibiUty of artificial impregnation by means of natural sperm 
was demonstrated long before my work by the famous Italian man of 
science, Spallanzani. The small number of carefully worked experiments 
on animals and lack of experience on the technical side for a long time 
prevented this method from gaining due importance in the practices of 
applied zoology. 

With regard to the second method of insemination, i.e. by means of 
an artificial medium, the very possibility of such a method was denied 
by some until my works appeared. Those who wish to get acquainted 
with the history and technical side of the subject will find detailed in- 
formation in these works and in the memoirs referred to at the end of this 
paper. ...... . . .. . , 



240 Artijirial Insemination 

The practical iiu])()itaiice of artificial insemination of domestic 
animals is to be found in the possibility by means of this method to 
utilize the seminal fluid, secreted by the male when covering the female, 
for the purpose of inseminating a number of other females (10-20) who 
are "on heat"; to combat the barrenness of females caused by various 
mechanical obstructions (stenosis of the neck of the womb, deflexion of 
the neck of the womb, polypi, etc.); to cro.ss animals dirt'ering very 
greatly in size and weight; to cross various ty]ies of animals (horses with 
asses or zebras, cows witii bisons or aurochs, etc.); to utilize the repro- 
ductive capacity of a valuable male in case of fatal injury or even death 
of the latter resulting from causes of a non-infectious kind. (In the 
latter circumstance, the seminal fluid is collected from the excised .se.xual 
glands of the male, diluted with some solution beneficial to the life of 
the seminal cells, and injected like natural seminal fluid into the vagina 
of the female.) 

One of the great advantages of artificial insemination is to be found 
in the fact that it dispenses with the necessity of bringing a valuable 
male into close contact with an unknown female, as the semen can be 
obtained vnth the aid of a well-known female or one specially selected 
for the purpose. This circumstance is particularly important in areas 
where such diseases as dourine, glanders, etc. are met with. 

We must also point out that in artificial insemination when the 
presence of trypanosomes is suspected in the sperm, the possibility of 
making the seminal liquid free from infection without killing the sperma- 
tosomes, has in principle been proved. 

Finally, in artificial insemination the whole process takes place under 
the control of the microscope, which makes it possible to determine in 
every individual case before insemination the actiuil degree of mobility 
of the seminal cells and their number. This enables the breeder to follow 
and to determine the jjroductive abilities of the male before his stud 
career commences, and not after, as was usually tlie case in natural 
insemination. 

The greatest j)ractical importance of the method of artificial insemina- 
tion is to be found in the possibiUty of applying it for purposes of mass- 
raising of domestic animals and fullest utilization of particularly valuable 
males. In order to secure for this method wide practical aj)plication it 
was necessary to work out simple and safe technical means, to verify 
them on a sufficient number of animals, ascertain the number of possible 
inseminations from one "leap," the percentage of positive results, the 
strength, fecundity and working ability of the young, and convince one- 



E. I. IVANOFF 247 

self that this method will not create an attitude of mistrust in the peasant 
population. 

Many years were devoted to these joroblems — beginning with my 
first experiments on the Dubrovski stud-farm in 1899. The practical 
work was carried on in the great majority of cases on horses. On cattle, 
chiefly on sheep, artificial insemination was practised to a fairly large 
extent, but usually with a scientific purpose. Experiments were also 
conducted on dogs, foxes, rabbits, birds and other animals. In the 
following, I shall submit data only from work on horses. 

In the history of the development of this work in Russia, two main 
stages must be noted, the first being the period of experimental pre- 
jmratory work on the problem under laboratory conditions (Institute 
of Experimental Medicine, Zoological Laboratory of the Academy of 
Science), and under conditions of practical life from 1899-1909 (on the 
special exj^erimental station of the Department of State Stud-Farming, 
in the Government of Orel, Livenski district, village of Mijnee-Dolgoe, 
and on the estate of Askania-Nova, in the Government of Taurida, 
formerly belonging to Faltzfein). Only after dealing with the fundamental 
problems and printing the results of the experiments, had the task of 
advocating this method for wide use been undertaken. The Government 
opened a special laboratory with a physiological section and a zoo- 
technical station, in Askania-Nova, attached to the Laboratory of the 
Veterinary Department, where from 1909 special theoretical and practical 
courses of study were pursued on the physiology and biology of insemina- 
tion and a body of specialists, mainly veterinary surgeons, was being 
trained for the practical a^jplication of this method on stud-farms and 
pairing stations. 

PreiJaratory experimental work was carried out apart from other 
animals on 579 horses, and during that period, together with problems 
of direct, practical interest (percentage of conceptions from artificial 
insemination, number of possible inseminations from one "leap," etc.) 
problems were experimentally investigated which have a more remote 
connection with stud-farm interests. As the manner of carrying out the 
exjjeriments and their results were made clear in my book Artificial 
Insemination of Domestic Animals, published also in German, I shall 
confine myself here to a very bare outHne. 

The above work shows that artificial insemination enables the 
number of mares inseminated by one stallion during the pairing season 
to be increased on an average ten times, and the percentage of foaling, 
if the work is done correctly and under conditions usual on pairing 



24H Aiiifirldl IiiaciniiKttloii 

stations (stallion of undoui)te(l fertility, mares healthy, pairing season 
about three months, condition of mares ascertained and repeated in- 
semination effected) is higher than in natural coition with the very same 
stallions and reaches on an average 78 % . Single insemination, without 
repeated injections to follow it during the period of " heat," gives only 
25 % of conceptions. Conception as a result of the mare being insemi- 
nated outside the period of "heat" is an exception. In cases of persistent 
barrenness, due to some anatomical irregularity in the construction of 
the mare's genital organs, artifical insemination is a very efficient means 
of bringing about conce])tiou. The technical side of artificial in.semination 
is sufficiently simple to be used under conditions prevalent on Russian 
pairing stations, to say nothing of stud-farms, and can be applied not 
only to horses but also to other domestic animals. Artificial insemination, 
when the necessary precautions are taken, removes the possibility of 
infection. Pregnancy and delivery are normal. The young in appearance, 
size, strength, capacity for work and fertility do not deviate from the 
normal, and such broods have produced a number of winners on the race- 
course (Dubrovski stud-farm), and in Askania-Nova over 50 horses, 
produced by artificial insemination, were bought for the cavalry and 
artillery at highest prices. Finally, it was proved beyond doubt that the 
peasants are quick to learn the advantages of such a method and that 
its wide use all over Russia is ultimately, therefore, fairly certain. 

With the establishment in 1909 of the above-mentioned laboratory 
(Physiological Section of the Laboratory of the Veterinary Department 
and Zootechnical Station in Askania-Nova) the aims of wliich, in addition 
to the investigation of scientific and practical problems of the physiology 
and biology of insemination, included also the popularization of the 
method of artificial insemination and aid for institutions and persons 
desirous of using this method — the possibility of acquiring fuller and 
wider knowledge of the method was afforded to specialists (veterinary 
surgeons and zootechnicians) and amateurs. A special course of lectures 
was given here on the physiology and biology of insemination, on problems 
of heredity, and practical work was done on artificial insemination of 
domestic animals. During the period from 1909 to 1919 over 400 persons, 
mainly veterinary surgeons, availed themselves of the opportunity of 
becoming familiar with artificial insemination. Some of these people 
have made practical use of this method. 

The work of the physiological section, in particular the work in 
connection with artificial insemination, attracted attention abroad, and 
a number of specialists (professors and surgeons) were sent to Russia 



E. T. IvANOFK 249 

to gain acquaintance with this method {vide Review of the Activities of 
Phi/siological Section during 1909-1913, p. 22). • 

In 1914 the work was interrupted in consequence of the army's 
demand for veterinary surgeons, and many of the latter had no oppor- 
tunity of submitting the results of their work in 1913. 

The work done in Russia represents the first attempt to use artificial 
insemination in mass-raising of domestic animals, an attempt, as will 
be seen later, by no means perfect in regard to conditions; without 
systematic organization or strict compliance with definite instructions. 
The laboratory in my charge was a purely consultative institution. As 
was subsequently shown, that state of things made possible a great 
number of very material and injurious digressions from the technical 
method elaborated by me, and the work was often confined to one or 
two visits of the veterinary surgeon to a stud-farm, once or twice a week 
(in the course of one, two, or three weeks) and in the majority of cases 
was regarded as a side-issue. 

The data at our disposal refer only to the period 1909-1913 (data 
for the latter year are by no means complete) and were collected partly 
by means of a questionnaire, partly from reports of the Rural Councils. 
The questionnaire contained a number of questions, the answers to 
which should have given a clear idea of the conditions and results of 
the work. In deahng with the material of the questionnaire only those 
enquiry forms were made use of, the information of which was sufficiently 
full and left no suspicion as to the correctness of figures. 

The above material shows the general state of things to be as follows: 
during the period 1909-1913 inclusive, the method of artificial insemina- 
tion has been used in more than 30 governments of European Russia and 
in Siberia. , - . . ■ . •■ • 

Even in those cases where artificial insemination was introduced, 
not on private initiative, but as a measure of mass-improvement of 
the peasants' horses (governments of Kherspn, Ekaterinoslav, Taurida, 
Bessarabia), the organization and management of this work suffered 
from all kinds of irregularities; for example, at the head of affairs were 
often found persons without any or with second-hand knowledge of the 
subject, incompetent people; every worker could at his discretion intro- 
duce various changes into the organization or technical side of the work. 
Particularly injurious with regard to the percentage of conceptions was 
the idea that it is possible to carry out work successfully without regard 
to the absence of "heat" in the mare; also excessive simplification of the 
technical side, including in some cases the use, instead of index-cylinders 



250 Artifieial Insemination 

aud pharmaceutical scales, of implements suitable only for home use. 
As artificial insemination of horses was included in the daily work of 
veterinary surgeons, often being done without any remuneration, only 
one day a week was often devoted to it, and sometimes the whole work 
did not go further than one or two visits of the surgeon. For anyone 
familiar with the conditions of pairing it is clear that work is impossible 
under such circumstances, as, apart from the method of insemination, 
they must lead to a considerable reduction of the percentage of concep- 
tions, owing to the impossibility of repeating the insemination on the 
fresh appearance of "heat" in the mare. In other cases, the lowering of 
the proportion of conceptions was due to injections into the womb being 
repeated every 7-9 days, wliicli was bound to cause an early abortion 
where conception had already set in. Further, at many stations for 
artificial insemination, stallions were used which were known to be un- 
suitable for this purpose, as in natural insemination the percentage of 
conceptions from them did not exceed 13 and in some cases was less 
than 4. It is true that, as has been ascertained, the percentage of 
conceptions from the same stallions with artificial insemination rose from 
4 to 11, from 5 to 22, from 13 to 21, but the use of such specimens was 
bound to lower the general proportion of conception from artificial 
insemination. Finally, artificial insemination was performed mainly on 
mares very unreliable from the breeder's point of view, or known to be 
sterile. 

The work was carried on chiefly on Rural Councils' pairing stations, 
in villages tens, and sometimes hundreds, of miles distant from town or 
railway station. 

During the period 1909-1913 artificial insemination was performed, 
according to the data supplied by the questionnaire, on 6804 horses*. 

In 1909 on 3 stations 57 horses. 



1910 „ 8 


)) 


288 


1911- „ 31 


J> 


2285 


1912 „ 41 


j?> 


3397 


1913 „ 17 


>? 


777 



The information for 1913, as pointed out above, is by no means 
complete. 

With regard to the normal condition of the young, freedom from 
infection of the sexual organs of the mares in the practice of artificial 
insemination, low proportion of abortions, etc., the data supplied by the 

' The above figurea refer only to European Russia. 



E. I. IVANOFF -251 

questionnaire are of a very uniform character and confirm all the con- 
clusions arrived at in the preliminary experimental work. Artificial 
insemination during the above short period succeeded in gaining the 
confidence of the ])opulation. In some cases the number of horses brought 
to the pairing station during one pairing season ran into hundreds. It 
has been ascertained that the number of mares fertilized during the 
pairing season by one stallion can average 300 and over when the method 
of artificial insemination is used. Sometimes the data of the question- 
naire sup])ly indications that the young born were of a superior type, or 
in any case perfectly sound. 

Only one case of deformity is recorded out of over 2000 foals born, 
which proijortion is quite normal. 

As regards the proportion of positive results, the figures, as one could 
expect from the foregoing, are by no means uniform. The percentage of 
conceptions varies between 4 and 907 and averages about 40. 



For 1909 the proportion of conceptions was 40 % 

„ 1910 „ „ „ 40-3 % 

1911 35-5°, 



• 

1912 41-4 "/ 

1913 4''-3 °/ 

When we look into that disparity in the results of the work of difierent 
people, we find that it was caused by those irregularities, which crept 
into the work, as the data of the questionnaire clearly show. For 
example, if we were to divide the material at our disposal into two 
sections, one under the heading "Artificial insemination performed on 
mares in period of 'heat,'" and the other "Artificial insemination per- 
formed regardless of presence or absence of 'heat,'" we should find that 
in the first group, where a number of other irregularities and deviations 
from proper conditions of work remained and only that factor of "in- 
semination without 'heat'" was excluded, the proportion of positive 
results equalled 49 % , while in the second group, where that factor 
remains, the percentage of positive results was 28. 

When we examine in both these groups the influence of the factor 
of duration of the pairing season, we find that when 

The duration of pairing season is The % of conceptions 
Less than one month for 1st group 38-6 

., 2nd „ 19 

Over one month ,, 1st „ 54 

„ 2nd „ 29 



262 Artijirial Insemination 

With more careful organization of the work and reliable parents, the 
proportion of conceptions from artificial insemination reached in the 
work of my pupil-practitioners not only the figures shown above (78 %), 
but even exceeded them, rising to 87-88 and even 90 % . 

Table I. 

Artilicial inscminatiiiri took place under the following conditions: (I) the mares were 
*'on heat," (2) the pairing period for artificial insemination was lonyer than one month, 
(3) the complement of marcs was the usual one for a stud-farm, no mare being known to 
be sterile, (4) the stallions were kno^Ti to be reliable. 



a 



o c " 



ESj aS Eg S 

fS.2 J.S f2 f 

Year, Kovernment, district, station 0*^5 "S— o"^ o „ 

anil name of person in charge do« ox ds 02 a — 

of operations ^XS '^u ^.* ZS o^g5 

1912. Don Army Province, 
Provalski Army Stud-Farm, 

vet. surgeon V.'Y. Kartasheif So 17 11 2 ()0-7 

1913. Don Army Province, 
Provalski Army Stud-Farm, 

vet. surgeon V.V. Kartashcff 31 22 3 (5 88-0 

1910. Govt, of Saratoff, dis- 
trict and town of Kuznetzk, 
pairing station, vet. surgeon 

N. A. Zhukoii 3(i 25 II 09-4 

1911. (jiovt. of Saratoff, dis- 
trict and town of Kuznetzk, 
pairing station, vet. surgeon 

N. A. Zhukoff ... ... 27 17 10 62-9 

1912. Govt, of Saratoff, dis- 
trict and town of Kuznetzk, 
pairing station. \et. surgeon 

N. A. Zhukoff ... ... 10 7 3 700 

1912. Govt, of Kharkoff, dis- 
trict of Akhtyrsk, estate of 
Konig Bros., Trostinnetz, 

assistant-surgeon Gafner ... 32 28 4 87-5 

1913. Govt, of Kharkotf, dis- 
trict of Aklityrsk, estate of 
Konig Bros., Trostinnetz, 

assistant-surgeon Gafner ... 43 39 4 90-7 

Total ... ... ... 209 \na 40 8 771 

It is clear from the above table that the proportion of conceptions in 
artificial insemination is usually higher than that in natural pairing of 
the same progenitors. 

The following table of results of artificial insemination of hor.ses on 
the zooteclmical station of Askania-Nova (1912) illustrates that fact 
still more clearly. 



E. I. IVANOFF 



253 



Table II. 

Results of artificial insemination of 

horses on the zootechnioal station 

of Askania-Nova in 1912 



Results of natural insemination 

by the same stallions in 

the same year 





NvT 


of mares 




' 


' 




No. of mares 




sub 


iected to 


No. of 


"(, of 


o/ nf 


No. of 


subjected to 


Name of 


artificial 


in- 


concep- 


concep- 


concep- 


concep- 


natural in- 


stallion 


seminat 


ion 


tions 


tions 


tions 


tions 


semination 


Harry 




11 




9 


81-8 


40 


2 


5 


Freiherr 




7 




4 


57-1 


.50 


2 


4 


Irkutsk 




11 




11 


100 


— 


— 


— 


Wallenstein 




4 




4 


100 


50 


4 


8 


Gadai-Zille 




6 




3 


.'50 


.33-3 




6 



Total 



39 



31 



84-1) 



43-4 



10 



23 



Thus, the practical work of veterinary surgeons, carried out on some 
thousands of horses in various parts of Russia and generally under very 
primitive conditions, bears out all the fundamental conclusions of the 
preliminary investigations and shows the great usefulness and value of 
artificial insemination of domestic animals for the population. 

Reports and the material of the enquiry clearly indicate that where 
the work was conducted more or less succes.sfully, where the veterinary 
surgeon was able to devote to the artificial insemination of horses 
sufficient time and attention, there the number of horses inseminated 
durinc the pairing .season on one station reached sometimes 850, and the 
majority of these in such a case were peasants' horses. In the estimation 
of Rural Councils (Zemstvos) that work was gaining greater and greater 
importance, and in the year before the war meetings and conferences 
were being convened for the special purpose of discussing the problems 
of more efficient organization of the work of artificial insemination, in 
connection with mass-improvement and mass-raising of stocks of horses 
and other domestic animals; also for the purpose of preparing a definite 
plan of work and publishing special instructions binding for all those 
doing practical work in the subject (governments of Kherson, Taurida, 
Bessarabia, etc.). 

The interruption of the work, which was getting into stride and 
assuming large proportions, was due entirely to the war and revolution, 
and as soon as problems of organization in cattle-farming again came to 
the front, artificial insemination became a matter of prime importance, 
as shortage of procreators was the greatest obstacle in the way of all 
former endeavours. 

Already in 1919 at one of the All-Russian conferences of zootech- 
nicists of the Department of Cattle-farming of the People's Commissariat 



254 Artificial 1 nsi ininatloii 

of Agriculture, aud later on, at the subsequent AU-Russian conferences 
on practical horse-breeding, the question of introducing the method of 
artificial insemination was considered to be of immediate imjjortance. 
However, lack of instruments, which were lost during the revolution, 
and the general economic and political -situation prevented work being 
commenced at once. The Collegium of the P. C. A. decided to open a 
"Central Experimental Station for investigating the problem of raising 
domestic animals," and one of its fundamental practical aims was the 
organization of the woik of artificial insemination. Ju 1921 the station 
received a great number of enquiries and re(]uests for instruments for 
artificial insemination of horses from the Don Province, Kuban Province, 
Turkestan, governments of Voionezh, Smolensk, and other places. In 
some places, like the Don Province, or government of Voronezh, it was 
proj)Osed to place the work of artificial insemination on a broad basis. 
In the Don Province a special laboratory has been opened ; in the govern- 
ment of Voronezh there are equipped stations, but the number of in- 
.struments and suitable horses is insufficient. Owing to the accumulation 
of imavoidable and unfavourable circumstances, the work of artificial 
insemination of horses could not be commenced in the spring of this 
year (1922), mainly in consequence of the impossibility of obtaining in 
])roper time instruments ordered abroad. By spring 1923 the training 
of a staff of specialist-technicians should be completed and a number of 
stations opened, in the first place, for the artificial insemination of horses. 
With the practical devel()])ment of this method are clo.sely ccmnected 
also its economic possibilities. The price of good progenitors should rise 
and cattle and stud-farming should attract the attention of the popula- 
tion and of ca])italists who should find here a good investment. While 
formerly horse-breeding, for example, was in Russia by no means a 
])rofitable business, but rather a necessity or a hobby, at the ])reseut 
time, when a stallion during the pairing season can bring a return several 
times greater than its cost and leave the owner a profit of some hundreds, 
and sometimes thousands, of gold roubles, the advantage of breeding 
a good stock is obvious'. In such circumstances there is a possibility 
of attracting to the work of mass-breeding and improving the stocks of 
domestic animals private enterprise, granting it one or another privilege 
and guarantee eliminating great risks. It would be possible to try to 

' Kxample: expenses in connection witli equipment of station for artitioial insemination 
200 gold roubles, cost of two .stallions, 1000 g.r., upkeep of horses for four uiontlis, iOO g.r., 
wages to groom for four months, 200 g.r., stabling, 100 g.r., total, 1700 g.r. 

Receipts: artificial insemination of 600 mares at 5 g.r. per mare; total, 3000 g.r. 



E. I. IVANOFP 255 

create in Russia great liorse and cattle-ranches. In spite of the losses 
during the war and revolution, there are still in Russia millions of 
domestic animals. The females are preserved in greater numbers and the 
main shortage is in males. The latter could partly be brought from abroad 
and partly increased in number through artificial insemination. In any 
case Russia, with her enormous open spaces, her extraordinary variety 
of climate, soil, geographical surface, her wealth of still untouched 
zootechuical material and the millions of her population — chiefly peasant 
population — provides endless opportunities for the development of all 
kinds of animal-breeding on a large scale, from horse-breeding to, and 
including, the breeding of deer and silver foxes, in the case of which 
artificial insemination acquires particular importance, as foxes are 
monogamous. 

It must also be remembered that with the use of artificial insemination 
on domestic animals we not only gain material advantage, but also save 
time. Formerly, in order to create a local breed or even a considerable 
uniform herd, from one or another valuable progenitor, it required a 
period of several decades. Now, with artificial insemination, this can 
be. achieved in a much shorter period of time, and a surplus of progeny 
makes possible a more careful selection. 

Artificial insemination is bound in the near future to assume additional 
import.ance in the zootechuical practice in connection with the solution 
of two fundamental problems now being investigated, namely (1) in- 
creasing the number of females fertilized during the pairing season 
through artificial insemination by one male, and (2) preserving for some 
time and forwarding to distant places the seminal solution. 

The first 2>roblem has already been to some extent solved by my 
experiments and the observations of my pupils, veterinary surgeons, and 
for practical application it needs only to be verified on a number of 
animals. 

The second problem, theoretically quite reasonable, needs for its 
solution the investigation of a number of questions. 

The possibility of preserving alive the seminal ceils of Mammals 
outside the organism for many days and even weeks has been demon- 
strated by the work in our laboratory, as well as by other investigators ; 
this, however, is true only of seminal cells taken, with precautions of 
sterihzation, directly from the epididymes of the seminal gland. In this 
case it is sufficient to prevent them from drying up and to place them in a 
temperature of 1 or 2° C. But for practical purposes, it is most important 
to preserve the seminal cells not in the above state, but in the medium 

Journ. of Agric. Sci. xu 18 



256 Artijicial Insemination 

of the secretions of the accessory sexual glands (natural sperm). In this 
medium there can be no question of sterilization and, what is particularly 
important, the seminal cells coming into contact with the secretions of 
the accessory sexual glands change their biological properties — acquiring 
a maximum of energy and dying in a comparatively short time (a few 
hours). Some methods of elucidating the nature of factors determining 
these properties are already mapped out and the solution of this problem, 
we are entitled to think, is only a question of time. 

There remain a few words to be said on the development of the 
technical side of the work. In view of certain inconveniences connected 
with the sterilization of the sponge collecting the sperm when tlie male 
covers the female, I have substituted for the 2 % solution of sodium 
carbonate a solution of spirits of wine (60-65 %) in which the sponge is 
kept about an hour, then thoroughly cleansed with sterilized water, and 
finally washed several times (being repeatedly squeezed out in the press) 
with a sterilizing physiological solution of kitclien salt, or a 10 % 
solution of refined sugar. This method of sterilization has been used in 
practical work by veterinary surgeons since 1911. Before this innovation 
was recommended for actual use, it underwent a number of suitable 
tests and investigations in the laboratory and on the experimental 
station in Askania-Nova which have shown its usefulness. 



LITERATURE. 

Heape. The Artificial Insomination of Mammals {Proc. Roy. Soc. 61, 1897). 

■ The Artificial Insemination of Mares {Veterinarian, 1898). 

IvANOFF. De la F^condation Artificielle chez les Mammiferes {Arch, des Sciences Biol. 
12, 1907, St Petersburg). 

De la Kcondation Art. clicz los Animaux domestiques {Arch, de Vet. Sci. 1910, 

St Petersburg). 

Die Kunstiiche Befnichiung der Haustiere, Hannover, 1912. 

Beschreibung von Ilybriden, etc. {Zeitschr. f. Induktive Abslammungs- und 

Vererbungslehre, 16, 1916). 
Marshall. The Physiology of Reprodiiction, 2nd ed., London, 1922. 
MabsH;\ll and Croslani). Sterility in Marcs, etc. {Journ. of Board of Agric. 24, 1918). 
Wolf. The Survival of Motility in Mammalian Spermatozoa {Journ. of Agric. Sci. 

11, 1921). 



{Received June '21st, 1922.) 



THE EFFECT OF CHANGE OF TEMPEPvATURE 
ON THE BASAL METABOLISM OF SWINE. 

By J. W. CAPSTICK, O.B.E., M.A., 

Felloiv of Trinitij College, 

AND 

T. B. WOOD, C.B.E., M.A., F.R.S., 

Drapers Professor of Agriculture. 

{From the Animal Nutrition Institute, School of 
Agriculture, Cambridge.) 

Introduction. 
It has long been generally accepted that an animal requires more food 
in cold weather than in hot weather, that, in fact and within certain 
limits, an animal's food requirement increases as the temperature falls. 
The number of precise measurements however of the effect of change of 
temperature on food requirement is very small, and it was with the 
object of extending the knowledge of this important subject that the 
following investigation was undertaken. 

The writers' attention was directed to the subject by a paper by 
Armsby and Fries on " Net Energy Values and Starch Values " which 
appeared in this Journal in 1919'. 

In this paper Armsby and Fries point out that their Net Energy 
and Kellner's Starch Equivalents really measure the same thing, namely 
the amount of energy in feeding stuffs which is available to the animal 
for physiological purposes. They claim further however that this net 
energy only is available for maintenance, and that any excess of energy 
above this amount is converted at once into heat ivhich is of no value to 
the animal. 

The point will perhaps be made clearer by a concrete instance, and 
since figures on the subject are lacking in the case of swine, it may be 
permissible to supply them for a steer. 

Armsby states that the basal metabolism of a 1,000 lb. steer is about 
six therms or 6,000 calories per day. Most European authorities agree 
that 14 lbs. of average meadow hay supplies a maintenance ration for a 

' 1 This .Journal, 9, 182. 

18—2 



258 Basal Metabolism of Swine 

1,000 lb. steer. Now 14 lbs. of average meadow hay supplies about 
11,500 calories of mctabolisable energy and about 6,000 calories of 
net energy. Armsby and Fries contend that only the 6,000 calories of 
net energy are of service to the animal, the remaining 5,500 calories 
being wasted. Many European writers, amongst them one of the authors 
(T. B. W.), have assumed that under certain conditions the whole 
11,500 calories may be of service to the steer, the 6,000 calories of net 
energy sufficing for physiological purposes, which presumably will not 
vary greatly witli changes of temperature, and the balance of 5,500 
calories .saving the oxidation of further material to meet the increa.sed 
energy required to maintain body temperature in unusually cold 
surroundings. It is significant to note that whilst Armsby's measure- 
ments were made in general in a calorimeter at about 65° F. or summer 
temperature, most European experiments on the maintenance of steers 
have been made in uiiheated stalls or sheds at winter temperatures of 
between 40° F. and 50° F. Such a difference in temperature, amounting 
to from 8 to 14" C. may possibly account for the difference of opinion 
between American and European investigators. It was with the hope 
of throwing some light on this point that the writers undertook the 
investigation described in the following pages. Unfortunately their 
calorimeter was not large enough to allow of experiments with a 1,000 lb. 
steer. The experiments were therefore carried out on a hog. 

The investigation also deals with another point. Previous investiga- 
tions on the effect of temperature on metabolism have shown that at 
ordinary temperatures an animal maintains its body temperature 
approximately constant by the rearrangement of its blood circulation. 
When the air temperature is low, the blood is deflecttid from the skin to 
the internal organs: the skin gets cold and loses less heat, but the internal 
temperature is maintained. When the air temperature is high much 
blood is sent through the skin where it loses much heat and cools the 
internal organs. 

This method of regulation is however insufficient to maintain a con- 
stant body temperature when the air temperature falls below a certain 
point which has been called the critical temperature. Below this point, 
a fall in the air temperature necessitates the oxidation of further 
material. The basal metabolism will therefore attain a minimum at the 
so-called critical point. Below this point it will increase by the heat 
value of the extra material oxidised. 



J. W. Capstick and T. B. Wood 259 

Experimental. 

The experiments described below were carried out in the large calori- 
meter described by one of the writers (J. W. C.) in a previous number 
of this Journal'. As the method of working is fully described in that 
paper nothing need be said here as to the details of the manipulation. 

The exjjeriments were made on a Large White pedigree hog bred by 
Mr K. J. J. Mackenzie on the Cambridge University Farm. The hog 
was born on January 2(jth, 1921, and was castrated on April 1st. The 
experiments began at the end of November when the hog was 10 months 
old and continued to the following April. 

The food given to the hog was of the .same general character through- 
out the experiments and was gradually increased so as to be roughly 
proportional to the two-thirds power of his weight. As an indication of 
the nature and amount of his food, he received when his weiffht was 

o 

300 lbs. the following daily ration in two meals : 

2 lbs. sharps, 2 lbs. barley meal, 

1^ lbs. bean meal, 1 lb. maize meal, 

1 lb. fish meal. 

In the intervals between the fasting periods, which lasted from four 
to six days, he was kept in a small paddock in the open air with a shelter 
of wattle hurdles. In severe weather he was put in a sty in the labora- 
tory. As he stripped his paddock bare of vegetation very quickly he was 
given a little green food each day. 

The care of the hog was in the hands of Capt. J. S. Morgan who kept 
him in excellent condition throughout. The fact that the hog gained 
157 lbs. in weight in the course of the experiments, which lasted 140 
days, in spite of his being without food for about a quarter of that time, 
is sufficient indication that the fasts had no ill-effect on his health. 

The hog was put in the calorimeter about 9 a.m. and remained 
there in darkness and without food, usually for five days. Regular sup- 
plies of water were introduced from outside. During this period readings 
were taken whenever the galvanometer curve showed that he had been 
asleep for a sufficiently long time to get rid of the effects of muscular 
activity. From these readings the heat evolution was calculated. No 
analyses were made of the excreta nor was the respiratory exchange 
observed. 

After each fasting period he was given about a fortnight to recover 

1 This Journal, 11. 1921, 408. 



260 Banal Metabolism of Sivine 

before being put in the caloiimeter again. This proved to be long 
enough to keep him in good health. 

The heat given off by the hog was measured in the usual way by 
observing the rise of temperature of a stream of water circulating round 
the calorimeter, additions being made for the latent heat of the water 
vapour brought out in the ventilating air, for the sensible heat brought 
away by the ventilating air and for leakage of heat through the walls 
of the calorimeter. 

Details of the apparatus and the methods of measurement are given 
in the paper quoted above. It is sufficient to say here that the rise of 
temperature of the circulating water is measured by a thermoelectric 
couple which traces a continuous record on a Cambridge and Paul Thread 
Recording Galvanometer. This continuous record has proved to be a 
very valuable feature of the apparatus. The writers consider that it has 
enabled them to obtain more accurate measurements of the true Resting 
Metabolism than have been obtained hitherto. 

The curve shows at a glance whether the hog is asleep or nul, how 
long he has been asleep and whether his metabolism is rising or falling. 
The slightest movement of the hog is recorded at once and the nature 
of the hump on the curve often reveals its cause. An instance of this is 
given in Fig. 1. 

Moreover there are occasional lapses in the apparatus. An electric 
current may fail through a bad contact or other cause. The thermostat 
may strike work through a heater burning out, dirty mercury causing 
the relay to go out of action, etc. After some experience it has been 
found that all these have their ch.iracteristic effects on the curve, so that 
an observer watching the galvanometer can go at once to the source of 
the trouble and remove it before any harm is done. 

In the earlier experiments the hog was very regular in his habits. 
He seldom slept in the day-time but kept in continual motion, his 
metabolism being very irregular and mounting gradually higher until 
about 5.30 or 6 p.m. when he went to sleep, and usually did not stir 
antil about 6 o'clock on the following morning, except that at some 
time in the earlier part of the night he stood up to empty his bladder. 

Fig. 1 is the curve obtained on the second day of the experiment 
which began on January 5. It has been chosen as showing several of the 
characteristic features of these curves. The irregularity of the curve in 
the day-time is much the same as is found in most of the curves, except 
on the first day of the fast when the hog often slept a part of the day. 

The small hump at lO.oO p.m. is due to the hog's rising to empty 



Journal uf Agricultural ycienue, Vul. Xii. Part 3 



Jun 


Utli, 1< 


)>2 














































■ 
















.- ■ 


*-^ 






-.- ^ 


\ 
















■" 




'"Xv.^ ■ 










,- 


-■---. 




.■.■~-- 


■-■' 


_ 'f 























































































9 10 II Noon 1 2 3 4 5 6 7 8 



between pp. 200^21) 1 



Jan. Vth, \9-2-2 



Mid I 2 3 4 5 6 7 



9 10 



J. W. Capstick and T. B. Wood 261 

his bladder. Its shape is quite characteristic of urination. The warm 
urine falling on the floor of the calorimeter causes a rapid rise in the 
temperature of the outlet water followed by an etjually rapid fall as the 
urine cools. This fall is checked by the rise of metabolism due to the 
movement of the hog, which does not show itself so quickly as the rise 
due to the warm urine. 

The peak at 1.15 a.m. was caused by a small movement of the hog. 

It is obvious that it is impossible to take any measurements of the 
resting metabolism in the day-time or the earlier part of the night. 
When the hog has gone to sleep it takes many hours for the metabolism 
to sink to its correct resting value uncomplicated by the effects of 
muscular activity. The fall during the night is not entirely due to 
recovery from the day's activity. It is prolonged by the lag in the galva- 
nometer readings arising from the heat capacity of the calorimeter. 
This heat capacity, whilst not altering the total area of a hump, 
reduces its height and sjireads it over a greater time. Further it is 
known that the body temperature in man falls to a minimum in the early 
hours of the morning and it is possible that there is a similar fall in swine 
which would in itself cause a fall in the heat evolution during the night. 

The final conclusion from the study of these galvanometer curves is 
that it is only on rare occasions that observations of the resting meta- 
bolism free from the effect of muscular activity can be made at any 
other time than in the early hours of the morning. 

The galvanometer records have been taken continuously through the 
whole period of the fast. The readings of the various thermometers, etc. 
needed for calculating the heat evolution have in general not been 
taken during the day. Through the night they have been taken at 
hourly or occasionally at half-hourly intervals, unless the curve showed 
that the readings would be useless. At the end of each day the curve 
and the record of the readings were carefully studied to find the time 
or times at which the metabolism most nearly approached a steady 
minimum. It is not possible to be biased in making the selection for 
the calculation is so long and involves so many readings that it is quite 
impossible to foresee the result before the calculation is completed. 
Most frequently only one point was selected from the day's records — 
occasionally two or three — on a few occasions no point showed sufficient 
steadiness. The metabolism was in a few cases calculated at points 
within 24 hours of the hog's entering the calorimeter, but these early 
readings have less weight than those taken later. The hog never really 
settled down until the second night. 



262 



Banal Afefabolism of Strine 



Experiments have been made at a series of temperatures ranging 
from 10-3° C. to 23-7° C. 

It is not possible to state exactly what was the temperature of the hog's 
surroundings. Take for instance the experiment at what we have called 
13'3° in Fig. 2. The water entered the circulating pipe at 13'3° and left it 
at 13".5°. The average temperature of the calorimeter body was therefore 
somewhere between these teniperatnre.s. The ventilating air entered 
the calorimeter at 12'4° and left at 14•4^ What then was the effective 
temperature of the calorimeter from the point of view of the hog's 
metabolism ? One can only make a guess. In order to have something 
definite the writers have adopted the temperature of the inlet water as 
defining the temperature of the hog's surroundings, fully realising that 
the actual effective temperature is probably a little different. The point 
is not one of any great consequence as the critical temperature is rather 
indefinite. It is not strictly a temperature but a set of circumstances of 
which temperature is the most important, for air circulation, humidity, 
etc. are not without effect. 

Table I. 

The time is given in hours since the last meal. 

In the 23'7° experiment the earlier readings were lost through a 

defect in the galvanometer circuit. 



Date Dec. 4 


Date Dec. 19 


Date Jan. 8 


Wei" 


;ht 


216 lbs 


Weig 


;ht 231 lbs 


Weight 252 lbs 


Temp. 


li-A" 


Temp. 16-9° 
Time Metabolism 


Temp. 
Time M 


10-3° 


Time 


Metabolism 


etabolism 


14 




2-927 


41 




2-058 


19 


.3-188 


43 




2-139 


67 




1-869 


42 


2-374 


66 




1-926 


90 




1-702 


66 


2-227 


93 




1-852 


114 




1-725 


90 


2105 


116 




1-833 












140 




1-851 












Date Feb. 5 




Date Feb. 25 




Date Mar. 22 


Date Apr. 23 


Weight 293 lbs 




Weight 306 lbs 




Weight 342 lbs 


Weight 373 lbs 


Temp. •20-4'' 




Temp. 


13-6° 




Temp. 


12-8° 


Temp. 23-7" 


'ime Metabolism 




Time Metabolism 




Time Metabolism 


Time Metabolis 


35 1-927 




45 


2-221 




28 


2-647 


63 1-870 


39 1-904 




68 


2-019 




88 


2-438 


84 1-750 


65 1-702 




93 


1-955 




58 


2-266 




.14 1-.562 




113 


1-936 




108 
134 


2-126 
2-115 





Table I shows the whole of the observations that have been made. 
At the head of each section is given the date on which the hog left the 
calorimeter, his weight at thf 



end of the fast before receiving his first 



J. W. Capstick and T. B. Wood 



26^ 



meal and the temijerature of the inlet water. Below these data is given 
the calculated metabolism in kilogram-calories per minute at various 
numbers of hours from the hoy's last meal. 



3 2 
3-1 



2 9 



2-6 
2-5 



5 2 4 

a 



S 2 3 



2 2 
2 1 
20 
1-9 
IS 
1-7 
1-6 
1-5 




■ "0 10 20 30 40 50 60 70 80 'JO 100 HO 120 '30 140 

Hours since last meal 

Fig. 2. 

Fig. 2 shows the results in Table I plotted on a single diagram. 
The ordinates are calories per minute and the abscissae are hours since 
the last meal. The 12'8° curve is raised '3 cal. and the 23"7° curve is 
raised '5 cal. to keep them clear of the other curves. 



264 Basal Metabolism of Swine 

It will be soeii that the points tall very well on a series of similar 
curves. The fact that the divergences of the points from the curves are 
so small atifoi'ds some evidence of the general accuracy of the measure- 
ments and supports the belief of the writers that they have obtained 
the true resting metabolism. 

The curves show a very close similarity to each other as regards 
their shape. This similarity formed the subject of a paper read by the 
writers before the Royal Society. The paper has been printed in the 
Proceedings of the Roijul Society' and nothing need be said on the 
matter here. 

The circumstances of the experiment at 23"7' made it impossible to 
get more than two satisfactory observations and these were both taken 
before the hog had (juite reached his basal metabolism. The basal meta- 
bolism was therefore obtained in this case by drawing a curve through 
the two observed points parallel to the remaining curves. This procedure 
seems to be justified by the conclusions reached in the paper read before 
the Royal Society. 

Inspection of the curves shows that in every case the terminal hori- 
zontal part, which gives the basal metabolism, is reached between 90 
and 100 hours after the last meal. Tangl" states that the hogs with 
which he worked reached their basal metabolism in 72 hours. In the 
present experiments there was always a perceptible fall after 72 hours. 
From some experiments which the writers are cai'rying out at present it 
would seem that age has an etiect on the time at which the basal meta- 
bolism is reached, for a young hog weighing about 35 lbs. reaches his 
basal metabolism in about two days. 

The basal metabolism is found graphically from the curves in Fig. 2 
and is tabulated in the fifth column of Table II below. 

Table II. 
Summary for Critical Temperature. 



Date 








liasal 




Age 


Corrected 










meta- 


Reduced Reduced 


correction 


basal 


1921 


Age 


Temp. 


Weight 


bolism 


to 300 lbs to 13-3" 


to 420 days 


metabolism 


Dec. 4 


312 days 


13-3° C. 


216 lbs 


1-840 


2-291 2-291 


-•391 


1-900 


,, 19 


327 ,, 


16-9° C. 


231 „ 


1-715 


2-057 — 


- -290 


1-767 


1922 
















.Jan. 8 


347 ,, 


10-3»C. 


2.52 ,, 


2-102 


2-361 — 


- -195 


2-166 


Feb. 5 


375 „ 


20-4° C. 


293 ,, 


1-570 


1-595 — 


- -092 


1-.503 


„ 2.5 


395 „ 


13-6° C. 


.306 „ 


1-940 


1-914 1-937 


-■038 


1-876 


Mar. 22 


420 „ 


12-8°C. 


342 ,, 


2-120 


1-943 1-905 





1-943 


Apr. 23 


452 „ 


23-7° C. 


373 ,, 


1-720 


1-489 — 


-H-OlO 


1-499 




' Froc. 


li.S. B, 94, 


35. 




= Biol. Zeitsch. 44. 





J. W. Capstick and T. B. Wood 



265 



Before the measurements can be used for finding the critical tem- 
perature they must be corrected to a standard weight and a standard age. 

The standard weight chosen is 300 lbs., as this lies almost half-way 
between the extremes of weight. In making the correction it is assumed 
that the metabolism is proportional to the hog's surface area and that the 
area is proportional to the two-thirds power of the weight. 

The basal metabolisms in the sixth column of Table II are calculated 
from those in the fifth column on these assumptions. 

In order to provide data for a possible age correction observations of 
the basal metabolism were made in the neighbourhood of 13° C. on 
December 4, February 25 and March 22. These three were at 13-3°, 
13"6° and 12'8° respectively. The difference is not great, but as they 
fall at a part of the range where the change of metabolism with tem- 
perature is considerable they should be corrected to the same temperature 
before they are used for finding the age correction. 



2 4 


— 


2-2 


V 


20 


^^^^^^^ 


1 8 


" 


16 


- 


1'4 


1 1 1 1 1 1 1 1 



300 320 340 360 380 400 420 440 460 
Age in daj'S 

Fig. 3. 

This correction requires a knowledge of what it was the object of the 
experiments to find — namely, the relation between basal metabolism 
and temj^erature — and it is somewhat illogical to make such a correction 
at this stage. As however the correction is quite small it is not likely 
that any appreciable error will be made by assuming for this purpose 
that there is a linear relation connecting the metabolism and tempera- 
ture between 10-3° and 20-4°. This gives a fall of -077 calories per Centi- 
gi-ade degree, and using this value we have the corrected metabolisms 
shown in the seventh column of Table II. The final curve of Fig. 4 
shows that a linear relation is not far from the truth. 

Fig. 3 shows the result of plotting the basal metabolism at 13-3° 



266 



Basal MefahoUsm of Sivine 



against the hog's age in days. It appears that at the end of the experiments 
age had almost ceased to have any effect. 

Wi' liave ne.xt to correct all the metabolisms in the sixth column of 
Table 11 to some one date. It is immaterial what date is chosen. The 
writers have selected March 22 when the hog was 420 days old. 

The corrections to be added or subtracted are given in the eighth 
column of Table II. In making these corrections it has been assumed 
that the effect of increasing age on the curve connecting metabolism 
and temperature is to cause it to move bodily downwards always keeping 
the same shape. It may be that it would be more correct to assume 
that the various points on the curve move downwards in the same 
proportion. 




2 4 6 8 10 12 14 16 18 20 22 24 

Degrees Centigrade 
Fig. 4. 

The writers see no adequate theoretical reason for preferring either 
of these methods to the other. For the present purpose it makes very 
little difference which method is used. The point might be worth in- 
vestigating experimentally, but it would be difficult to secure the 
necessary accuracy. 

We have finally the coi-rected values of the basal metabolism shown 
in the last column of Table II and plotted against temperature in Fig, 4. 

The points fall very well on the curve with the exception of that at 
16"9° which is 6J percent, too high. The writers are unable to account for 



J. W. Capstick and T. B. Wood 267 

this anomaly except on the grounds that the experiment at 16'9" was 
unsatisfactory throughout. The hog was scarcely ever really quiet 
throughout the whole fasting period with the result that the galvano- 
■ meter curve was less regular than usual. It should be noted that errors 
due to the hog would almost certainly cause the observed metabolism 
to be too high, whilst experimental errors would be indifferently high 
and low. There was also an instrumental failure on the last day of the 
16'9' experiment. One of the electrical heaters in the thermostat burnt 
out and there was a great disturbance of the curve before the fault 
could be remedied. 

The remaining points however are sufficiently consistent to enable 
the writers to state that the critical temperature is very near to 21° C. — 
remembering, however, what has been stated above, that the real average 
temperature of the hog's surroundings may be somewhat different. 

This conclusion agrees very well with that reached by Tangl who 
states that he found the critical temperature to be between 20° and 23°. 

The actual metabolism at the critical temperature is I'SO calories 
per minute for a 300 lb. hog or 2,160 calories per day. 

The exact relation between a hog's surf;\ce area and his weight is 
not known. Tangl accepts Voit's formula A = 9-02 IF". This gives 904 
calories per day per square metre, which is near the value generally 
adopted for human beings. 

The values of the basal metabolism at different temperatures have a 
practical interest for pig breeders as they enable us to calculate the 
maintenance ration at various temperatures. 







Table III. 










Basal metabolism 




Basal 


metabolism 


Temp. 


of a 300 lb. 


hog 


Temp. 


of a 


300 lb. hog 





3-10 




12 




2-01 


2 


2-92 




14 




1-84 


4 


2-74 




16 




1-70 


6 


2-56 




18 




1-59 


8 


2-38 




20 




1-51 


10 


2-19 




22 




1-50 



Table III gives the metabolism of a 300 lb. hog at intervals of 2° 
from 0° C. to 22° C. The metabolism between 10° and 20° is taken from 
the full curve in Fig. 4. Actual observations of the metabolism could 
not be made at very low temperatures as the temperature of the town 
supply water did not permit of the calorimeter being set to anything 
below 10°. In order to get an estimate of the metabolism below 10° it 
is therefore necessary to use the uncertain expedient of extrapolation. 



268 Basal Metabolism of Swine 

As the observed curve is nearly a straight line below about 16" it 
has been continued backwards in a straight line to 0°, the dotted line 
being the part of the curve obtained by extrapolation. The values of 
the metabolism in Table III are taken from this extended curve. 

It may be presumed that in so far as the extrapolated values are in 
error, the error is on the side of their being too low since the observed 
part of the cui-ve is concave upwards. The}' will however provide a 
sufficient approximation for our present purpose. 

It will be seen that the maintenance ration at 0° is more than 
double that at 22°, and both these temperatures are not unfrequontly 
met with on farms in this countiy. 

Conclusions. 

The critical temperature of the hog under experiment was approxi- 
mately 21" C. 

At this temperature his basal metabolism was a minimum and 
amounted to 2,160 calories in 24 hours when he was 420 days old and 
weighed 300 lbs. This corresponds to 904 calories per day per square 
metre of body surface. 

As the temperature of his surrounding.s fell below 21° C, the basal 
metabolism increased at the rate of about 4 per cent, per degree Centi- 
grade, which corresponds to an increase of about 40 per cent, for a 
temperature difference of 10°C. which is commonly found between 
summer and winter conditions. 

Thus, if the same law holds in the case of a steer whose basal meta- 
bolism at 18° C. or summer temperature is 6,000 calories, his basal 
metabolism at 8° C. in an open yaid in winter would be 9,000 calories. 

The suggestion is that the increase of 3,000 cahjries is met b}' the 
utilisation of the thermic energy of the coarse fodder included in his 
ration. 

{Received June 2^th, 1922.) 



THE FUNGICIDAL PROPERTIES OF CERTAIN 
SPRAY-FLUIDS. III. 

By E. HORTON and E. S. SALMON, 
Research DepartiTient, S.E. Agric. College, Wye, Kent. 

As an aid to the elucidation of the problem of the exact fungicidal value 
of a mixture of lime-suljjhur and arsenate of lead — a matter of great 
importance to the practical fruit-grower — spraying experiments were 
carried out during 1921 with certain spray-fluids containing arsenic or 
lime-sulphur and its constituents. 

Method. In order to ascertain within narrow limits the fimgicidal 
value of any solution, it is obviously necessary to maintain as fixed a 
biological standard as possible. To ensure this, the fungus used in com- 
parative experiments should be in the same stage of development and, 
if it is a parasite, the host-plant used should also be " standardised " as far 
as possible — since it has been shown(2) that the same stage of a fungus 
may be more easily killed when on the older leaves of a plant than on 
the younger. 

In all the experiments described below, the fungus used was Sphaero- 
theca Huniuli (DC.) Burr., and the stage selected for spraying was the 
young, "powdery," conidial stage produced on young leaves, at the 
3rd to 9th node, of rooted cuttings of hop-plants {Humulus Lupulus, 
Linn.) grown in an unheated greenhouse. To escape as far as possible 
variation on the side of the host-plant, with possible consequent effects 
on the vigour of the parasitic fungus, all the plants used were clone- 
plants, i.e., plants raised vegetatively by cuttings taken from one indi- 
vidual hop-plant. The general methods of sprajdng and of the examina- 
tion of the sprayed leaves, etc. have been described in previous articles 
(1, 2). In order to secure complete wetting of the fungus, calcium casein- 
ate (1 per cent.) was added to the solutions used. 

Where care is taken to obtain in this way strictly similar biological 
conditions of parasitic fungus and host-plant, it becomes possible, as 
shown below, to determine within narrow limits the fungicidal value of 
a solution. In all the experiments described below "powdery" conidial 



270 Funf/icidal Properties of Certain Sprnij-Flidih. 

patches of <S'. Humuli were selected for spraying on one leaf at a node, 
while the similar patches of mildew on the other leaf at the same node 
served as "controls." 

The experiments carried out fall into two classes: viz. (1) those in 
which arsenical solutions were used; and (2) those in which lime-sulphur 
or its constituents were used. 

1. Experiments with Solutions containing Arsenic. 

Several investigators have stated from time to time that arsenic 
possesses some fungicidal power. Waite(:)), who appears to have been 
the first to have discovered this, stated in 1910 that arsenate of lead 
"seems to possess considerable fungicidal value, though probably not 
enough to be depended upon for general use." Similar statements have 
been made by Cliuton( l) and Watkins(5). Wallace, Blodgett and Hesler(6) 
considered that arsenate of lead was "about as effective as lime-sulphur" 
in controlling apple-" scab" (Venturia inaequalis) in the orchard; but 
state that in laboratory experiments with germinating spores of apple- 
"scab," "brown rot" and Sphaeropsis, arsenate of lead was found to 
have only "a weak fungicidal value." Morse has repeatedly claimed 
fungicidal powers for arsenate of lead; in 1914 he stated(7) that "arsenate 
of lead paste controlled apple scab as well as Bordeaux mixture and lime- 
sulphur," and, from observations made on trees in sprayed orchards, 
that "even small or medium applications of arsenate of lead possess a 
distinct fungicidal value"; in 1915, the conclusion was drawn(S), again 
from observations made in sprayed orchards, that "arsenate of lead was 
less efficient in controlling scab than the standard fungicides, but still 
noticeable." In 1916 Morse stated(!i) that arsenate of lead alone controls 
apple-" scab" on the fruit (apple) as well as, or better than, lime-sulphur 
mixed with arsenate of lead, but added that "laboratory experiments 
by Mr M. Shapovalov failed to show for arsenate such high fungicidal 
properties as the field experiments indicated. Germination of conidia 
of the fungus {Venturia inaequalis) placed in similar dilutions of the 
poison was reduced and retarded, but by no means prevented." In 1918, 
Morse, in recording(io) the results of spraying experiments in apple 
orchards, stated that "the use of arsenate of lead alone as a spray re- 
duced the amount of scab on the foliage from 90 to 95 per cent." Sanders, 
in 1917, from spraying trials made in the orchard, recorded(H) that "the 
arsenate of lime alone seems to be almost as valuable a fungicide as the 
arsenate of lead alone." On the other hand, the .statement has been made 
by Pickett(i2) that arsenate of lead has practically no fungicidal value. 



E. HORTON AND E. S. SALMON 271 

As will be seen from the above, the statements as to the fungicidal 
value of arsenic rest on observations made in the field, except in two cases 
where experiments were made with germinating spores. We have not 
been able to find in the literature of the subject a single case in which the 
experimenter has used arsenical solutions of varying strengths on a 
fungus kept under close observation and determined the necessary 
strength for complete fungicidal action. 

Materials used. Sodium arsenates. In the first instance the sodium 
hydrogen arsenate Na.2HAs04 and trisodium arsenate solutions were 
prepared by neutralising a solution of a known weight of pure arsenic 
acid with the theoretically necessary weights of sodium hydroxide 
(Exjjeriments 2.3, 25, 27). Afterwards pure Na2HAs047H.,0 was pre- 
pared by cr3^stallisiug the commercial dodecahydrate above 20°, and the 
trisodium arsenate was prepared from it by treating the solution with 
the calculated weight of sodium hydroxide solution and crystallising. 
The amount of arsenic in these salts was estimated by distiUing with 
cuprous chloride and hydrochloric acid and titrating the distillate with 
iodine (Experiment 41). 

Calcium Arsenates. In the first instance sprays of the required con- 
centration of these substances were prepared simply by taking a solution 
of the corresponding sodium salt of double the required strength and 
diluting to double the volume with a solution of the necessary amount 
of calcium chloride (E.xperiments 19, 20, 22, 28). The spray solution of 
course contained sodium chloride (which at so great a dilution was prob- 
ably quite without eft'ect on the hop leaf) as well as the calcium arsenate. 
In this method of preparation (with dilute solutions) calcium chloride 
produces a precipitate with sodium hydrogen arsenate but the precipitate 
dissolves on dilution; with trisodium arsenate the precipitate is insoluble. 

For later experiments two calcium arsenates were prepared, the first 
by treating a solution of 11-5 grams of calcium chloride in 25 c.cm. of 
water with a solution of 32 grams of crystallised disodium hydrogen 
arsenate (Na2HAs047H20), the second by adding a solution of calcium 
chloride of the same strength to a solution of 31 grams of crystallised 
disodium hydrogen arsenate which had been previously treated with a 
solution of 4 grams of pure sodium hydro.xide. In each case the precipitate 
was filtered on a Buchner funnel, thoroughly washed with cold water and 
dried in the air at room temperature. For the purpose of spraying the 
calculated quantities of these arsenates were weighed out, triturated with 
water and the suspension diluted (partly with 10 per cent, calcium 
caseinate solution) to the required strength (Experiments 31. 33, 34). 

Jcum. of Agric. Soi. xn 19 



272 Fnngiddal Properties of Certain Spray-Fluids 

Experiment 23. Disodium arsenate (containing 0-096 per cent. AsgOj). 
On the first day (24 hours) after spraying, all the mildew-patches on all 
the sprayed leaves were barren and apparently dead, while these on the 
control leaves were very vigorous and densely "powdery."" By the third 
day after spraying, the fungicidal nature of the solution was clearly 
evident. Each spot of mildew was con.spicuous as a dead, white mycelial 
patch. There was also a brown patch of dead leaf-cells, sometimes corre- 
sponding in size with the area of the dead myceHum, sometimes smaller. 
The healthy parts of the leaf showed no trace of injury. 

Exjjeriment 27 bis. Disodium arsenate (0-024 per cent. AsjOj). 

Experiment 41. Disodium arsenate (0-02 per cent. As^Og). 

Both the above solutions proved fungicidal ; no leaf -cells underlying 
the mildew-patches were killed by the solution. 

Experiment 25. Trisodium arsenate (containing 0-077 per cent. 
AsoOj). The fungicidal effect of the solution was clearly evident 24 hours 
after spraying. By the third day, on some of the leaves, small brown, 
"burnt"' patches of leaf-ceils, underlying the mildew-patches, had 
appeared, similar to those noticed in Experiment 23 (see above). 

Experiment 20. Dicalcium arsenate (0-096 per cent. As,j05). By the 
fourth day all the mildew-patches on the sprayed leaves were dead; 
those on the " control " leaves (sprayed with 1 per cent, calcium caseinate) 
were very vigorous and densely powdery. No trace of "scorching" 
occurred on the sprayed leaves. 

Experiment 22. Dicalcium arsenate (0-048 per cent. AS2O5). On the 
first day (24 hours) after spraying, the mildew-patches on all the sprayed 
leaves (four) were dead — the mycelium, although still white, was com- 
posed of hi/phae in a floccoso-collapsed condition. All the mildew-patches 
on the "control" leaves (four), which had been left unsprayed, were very 
vigorous and densely "powdery." 

Experiment 28. Dicalcium arsenate (0-024 per cent. AsjOg). On the 
second day after spraying most of the mildew-patches were barren — a 
very few patches, however, bore a few weak conidiophores at their edges. 
The mildew-patches on the "control" leaves (unsprayed) were all very 
vigorous and densely "powdery." By the seventh day no further growth 
of the mildew had taken ])lace. By the thirteenth day the mildew-patches 
were all killed; on three leaves there were small, distinct, "scorched" 
areas of dead leaf-cells limited to the places where the mildew had 
occurred (cf. Experiment 23). The general appearance of the sprayed 
leaves suggested that the solution used was just fungicidal. 

Experiment 33. Dicalcium arsenate (0-01 per cent. AsgOj). The solu- 



E. HORTON AND E. S. SALMON 273 

tion exerted a slight checking action on the mildew-patches on two of 
the five sprayed leaves ; on the remaining three leaves the mildew-patches, 
on the fourth day after spraying, were as ''powdery" as those on the 
"control" leaves (unsprayed). The solution at this strength, then, was 
practically non-fungicidal. 

Experiment 19. Tricalciiun arsenate (0-076 per cent. AsjOj). By the 
fourth day after spraying the mildew-patches on all the sprayed leaves 
(five) were barren and apparently dead; on the "control" leaves (five), 
sprayed with 1 per cent, calcium caseinate, all the mildew-patches were 
very vigorous and densely " powdery." By the sixteenth day it was clear 
that the solution had been completely fungicidal. No trace of "scorch- 
ing" appeared anywhere on the leaves. 

Experiment 31. Tncalciinn arsenate (0-02 per cent. As^Oj). By the 
third day several of the mildew-patches on four of the (seven) sprayed 
leaves had developed fresh conidiophores at the edges of the patches — 
a clear indication that the solution was not quite fungicidal ; on three of 
the leaves the patches were all barren. At this date all the mildew- 
patches on the seven "control" leaves, which had been sprayed with 
1 per cent, calcium caseinate, were very vigorous and densely " powdery." 
At the end of the experiment, i.e., on the twelfth day, the condition of 
the mildew on the sprayed leaves was as follows: leaf (1), (2), (3), at the 
4th, 5th, 6th nodes; clustered conidiophores round the edges of all the 
patches, while the nujcelium was barren and probably dead at the centre 
of each patch. This condition indicates that the solution used was of a 
not quite fungicidal strength. Leaf (4) at the 3rd node, and leaf (5) at 
the 5th node; the mildew-patches now bearing densely cluistered "pow- 
dery" conidiophores at their edges — indicating that the solution was 
almost non-fungicidal. Leaf (6) and (7), at the 6th and 7th nodes: many 
of the patches remained permanently barren and were probably killed; 
a few developed weak scattered conidiophores at their edges. Here the 
solution proved almost but not quite fungicidal. In previous experi- 
ments (2) it had been found that a "powdery" patch of mildew is easier 
to kill when growing on an older leaf than on a younger leaf. 

Experiment 34. Tricalcium arsenate (0-01 per cent. AsgOg). By the 
seventh day only a slight checking action on the growth of the mildew 
was evident, most of the patches now bearing densely clustered, more or 
less "powdery" conidiophores. It was clear that the solution at this 
strength is practically non-fungicidal. 



19—2 



•274 Fungicidal Properties of Certain Spray-Fluids 

2. Experiments with "Lime-Sulphur" and its Constituents. 

Tliese experiments — preliminary to a contemplated study of the 
fungicidal and insecticidal properties of a mixture of lime-sulphur and 
arsenates — were for the purpose of ascerta,imng to which constituent or 
constituents of lime-sulphur the fungicidal property of this spray-fluid 
is due, and also to determine the exact strength of such constituents 
fungicidal for the "powdery" conidial stage of S. Humidi. 

It was found(20) that the addition of a solution of calcium caseinate 
— a substance first used with a fungicide, apparently, by Vermorel and 
Dantony(i3) — increased the wetting powers of lime-sulphur so satis- 
factorily that its fungicidal properties at various dilutions could be 
accurately measured. Concordant results were obtained when a solution 
of lime-sulphur of a certain strength, to which a solution of calcium 
caseinate had been added, was compared, using the method described 
below, with a hme-sulphur solution alone of the same strength. Some of 
the details of these experiments may be given here, since they serve also 
to show the close approximation of the lower hmit of the fungicidal con- 
centrations and the upper hmit of the non-fungicidal concentrations of 
hme-sulphur for the particular fungus. 

The method employed was — since a soap solution cannot be used 
with hme-sulphur for chemical reasons — first to spray the mildew with a 
1 per cent, soft soap solution (which removed the air entangled among 
the conidia and conidiopkores and wetted all the parts), then to spray 
thoroughly with water to remove the soap solution, and immediately 
afterwards with the hme-sulphur solution. Observations showed that 
the treatment with soft soap and then with water had no deleterious 
effect on the mildew, since by the fourth day after treatment (and often 
earher) the sprayed mildew-patches were fully as vigorous and as 
powdery as the imsprayed ones on the "control" leaves. 

In the following two experiments the Ume-sulphur solution was 
applied after the preliminary treatment described above. A commercial 
brand of hme-sulphur ("Sulfinette") of 1-30 sp. gr. and containing 
16-57 per cent, of polysulphide sulphur was used. 

Experiment 10. Lime-sulphur, 1 part to 99 parts of water (0-16 per 
cent, polysulphide sulphur). The solution proved completely fungicidal. 
Experiment 9. Lime-sulphur, 1 : 199 (0-08 per cent, polysulphide 
sulphur). On the fourth day after sprajnng the mildew- patches were all 
barren. By the sixth day scattered conidiophores had appeared from 
some of the patches, while the remaining patches were still barren. These 



E. HoRTOX AND B. S. Salmon 275 

conidiophores persisted to the end of the experiment (14 days). Lime- 
sulphur at this strength (0-08 per cent, polysulphide sulpliur) appeared 
to be just breaking down in fungicidal efficiency. 

In the corresponding experiments the same brand of hme-sulphur 
was used mixed with a solution of calcium caseinate. 

Experiment 14. Lime-sulphur, 1 : 99 (0-16 per cent, polysulphide 
sulphur) and 1 per cent, calcium caseinate. The solution proved com- 
pletely fungicidal within 24 hours after spraying; and the same was the 
case when 0-5 per cent, calcium caseinate was used. 

Experiment 1.5. Lime-sulphur, 1 : 149 (0-11 per cent, polysulphide 
sulphur) and 1 per cent, calcium caseinate. Complete fungicidal action 
resulted. 

Experiment 16. Lime-sulphur, 1 : 199 (0-08 per cent, polysulphide 
sulphur) and 1 per cent, calcium caseinate. On the tenth day after 
spraying, a few of the mildew-patches had produced fresh, clustered 
conidiophores, and others, scattered conidiophores; many of the patches 
were dead. It was clear that at this strength the solution was not quite 
fungicidal. 

A reference to the hterature of the subject seemed to show that 
chemists were not in complete agreement as to what chemical compounds 
constitute the spray-fluid universally known as lime-sulphur (compare 
Van Slyke, Hedges, and Bosworth(i4); Tartar(i5); Ramsay (16); Thompson 
and Whittier{i7); Bodnar(i8); Chapin(i9)). The following compounds, 
which are known or suspected constituents, were tried singly: calcium 
sulphate, sulpliite, thiosulphate, hydroxyhydrosulphide and polysul- 
phide (probably pentasulphide). The result of each experiment is given 
below. 

Materials used. Calcium sulphate. A saturated solution of this salt 
was prepared by neutrahsing a boiUng solution of 2 grams of pure 
sulphuric acid in 250 c.cm. of water with a slight excess of carefully 
purified precipitated calcium carbonate, filtering the hquid and allowing 
the filtrate to cool. The spray was prepared by mixing the filtrate with 
enough calcium caseinate solution to give a 1 per cent, concentration of 
the latter. 

Experiment 32. Calcium sulphate (saturated solution) and 1 per cent. 
calcium caseinate. Clustered conidiophores were re-formed on all the 
mildew-patches by the second day, and by the fourth day the patches on 
the sprayed leaves were as " powdery " as those on the " control " leaves. 
Calcium sulphite. A solution of 25 grams of crystalhsed sodium 
sulphite in the minimum amount of water was added to a solution of 



276 Fungicidal Properties of Certain Spray-Fluids 

23 grams of calcium chloride (prepared from twice reprecipitated calcium 
carbonate) in a small volume of water. A white flocculent precipitate 
formed which quickly became powdery. Thi.s was filtered on a Buchner 
funnel, thoroughly wa.shed with cold water and whilst still wet was trans- 
ferred to a beaker with 250 c.cm. of water and stirred mechanically for 
an hour. The solid was then allowed to settle and the supernatant liquid 
filtered. For spraying 90 c.cm. of this solution were mi.xed with 10 c.cm. 
of calcium caseinate solution (10 per cent.). 

Experiment 36. Calcium sulphite (saturated solution) and 1 per cent, 
calcium caseinate. Exactly the same result was obtained as in E.xperi- 
ment 32, described above. 

A saturated solution of calcium sulphite having proved to be non- 
fungicidal, a suspen.sion of the solid sulphite was adjusted (by means of 
titration with standard iodine solution) to contain 5 grams in 90 c.cm. 
of liquid and this 90 c.cm. treated with 10 c.cm. of 10 per cent, calcium 
caseinate solution for .spraying. 

Experiment 40. Calcium sulphite (su.spension), 5 per cent., and 1 per 
cent, calcium caseinate. Exactly the same result was obtained as in 
E.xperiment 32, described above. 

Calcium thiosulphale. The preparation of a small quantity of the pure 
salt is rendered difficult by its high solubility in water, and an attempt 
to obtain it by double decomposition of calcium chloride with sodium 
thiosulphate failed through the inferior solubility of sodium chloride. 
By stirring a mixture of 27 grams of pure barium thiosulphate 
(BaSgOj.HgO) and 16 grams of pure calcium sulphate (CaS04) in 250 
c.cm. of water for 10 hours and then filtering, a solution was obtained 
which gave a reaction for sulphate but not for barium and on titration 
with standard iodine solution proved to contain 1-321 grams of thio- 
sulphate sulphur per 100 c.cm. This solution contained only calcium 
thiosulphate and calcium sulphate and the latter had been proved non- 
fungicidal. Ordinary commercial lime-sulphur solution contains roughly 
1-5 per cent, of thiosulphate sulphur per 100 c.cm.. so that the wash 
obtained by diluting with 29 parts of water contains 0-05 per cent, of 
thiosulphate sulphur. A spray solution containing the same amount of 
sulphur (as calcium thiosulphate) was prepared by diluting 3-78 c.cm. 
of this calcium thiosulphate .solution with water, adding 10 c.cm. of 
10 per cent, calcium caseinate solution and making up to 100 c.cm. This 
was applied (Experiment 38) and proved to be quite non-fuugicidal. 

A solution ten times as strong was prepared by adding 10 c.cm. of 
calcium caseinate solution (lO per cent.) to 37-85 c.cm. of the calcium 



E. HORTON AND E. 8. SALMON 277 

thiosulphate solution and diluting to 100 c. cm. This was applied (Ex- 
periment 35) and some fungicidal action was observable. The patches 
on the sprayed leaves were all barren on the second day after spraying; 
by the fourth day conidiophores had begun to be developed from some 
of the patches, and by the seventh day clustered conidiophores either 
covered these patches or had developed round their edges. The solution 
thus proved ultimately non-fungicidal. 

Calcium hydroxyhydrosulphide. A concentrated solution of calcium 
hydrosulphide was prepared in the manner described by Divers and 
Shimidzu {Chem. Soc. Trans. 1884, 45, 272) by bubbling hydrogen 
sulphide through a suspension of pure calcium hydroxide in water, fresh 
lime being added at intervals as the liquid becomes clear. A pale yellow- 
solution was obtained which was diluted for analysis and use. The mono- 
sulphide sulphur was estimated by Chapin's method. 

Commercial lime-sulphur solution (concentrated) contains about 
6 per cent, of monosulphide sulphur. Hence a wash diluted to the extent 
of 1 in 150 (which we found to be the minimum fungicidal strength for 
hop-mildew) will contain 0-04 per cent, of monosulphide sulphur. Ac- 
cordingly spray solutions (each containing 10 c.cm. per 100 c.cm. of the 
10 per cent, calcium caseinate solutions) were prepared by diluting this 
calcium hydrosulphide solution so as to contain the required amount of 
monosulphide sulphur. 

Experiment 27. 0-04 per cent, monosulphide sulphur and 1 per cent. 
calcium caseinate. The solution was non-fungicidal; conidiophores were 
re-formed 24 hours after the spraying, and the patches were densely 
"powdery" by the fourth day. 

Experiment 30. 0-34 per cent, monosulphide sulphur and 0-5 per cent, 
calcium caseinate. The solution was non-fungicidal; the patches bore 
fresh conidiophores by the second day, and became "powdery" soon 
afterwards. 

Experiment 29. 0-85 per cent, monosulphide sulfihur and 0-5 per cent, 
calcium caseinate. On the second day after spraying, the patches were 
practically obhterated by the deposit from the spray-fluid and were 
barren. By the fifth day conidiophores had begun to develop from most 
patches (chiefly from their edges), even where the deposit had completel}^ 
covered the patch. By the ninth day it was quite evident that the 
solution was non-fungicidal, most of the patches being as powdery as 
those on the " control " leaves. 

Calcium pohjsulphide. Calcium hydrosulphide solution was prepared 
as described above and the monosulphide sulphur estimated. A measured 



278 Fungicidal Projjerties of Certain Spray-Fluids 

m 

portion of the concentrated solution was heated on a water-bath with 
excess of powdered sulphur until no more dissolved, when the red liquid 
was decanted and preserved. The polysulphide sulphur in this solution 
was estimated by Chapin's nietliod. 

Commercial hme-sulphur solution contains about 25 grams per 100 
c.cm. of polysulphide sulphur and thus gives 0-33 per cent, of polysul- 
phide sulphur in a 1 in 75 dilution. The calcium polysulphide solution 
was diluted to contain 0-33 per cent, of polysulphide sulphur. 

Experiment 43. Calcium poli/.sulphide (0-33 per cent, polysulphide 
sulphur) and 1 per cent, calcium caseinate. The solution proved fungi- 
cidal, the fungicidal effect being evident by the fourth day after spraying. 

The experiments described above tend to show that the only con- 
stituent of lime-sulphur solution which has appreciable fungicidal power 
(at the strength at which this solution is used in practice) is calcium 
polysulphide. 

This result is in agreement with the previous work(i,i') with am- 
monium polysulphide solutions. 

Summary. 

The following solutions were tested with respect to their fungicidal 
properties towards the " powdery,"' conidial stage of S. Humuli on young 
hop-leaves in the greenhouse : 

(1) Disodiuni arsenate, containing 0-096 per cent. AsjOj proved 
fungicidal and killed also patches of leaf-cells underlying the mildew- 
patches, but did not otherwise injure the leaf. A solution containing 
0-02 per cent. AsgOg was fungicidal without killing any leaf-cells. 

(2) Trisodium arsenate containing 0-077 per cent. AS2O5 proved 
fungicidal. 

(3) Dicalcium arsenate, containing 0-048 per cent. AS2O5 proved 
fungicidal : containing 0-024 per cent. AsoOj the solution was apparently 
just fungicidal, but with 0-01 per cent. AsgOj the solution was practically 
non-fungicidal. 

(4) Tricalcium arsenate containing 0-076 per cent. AsgOg is fungi- 
cidal; containing 0-02 per cent. AS2O5 it possesses some fungicidal value, 
but with 0-OT per cent. As^Og it is practically non-fungicidal. 

(5) The following constituents of hme-sulphur wash proved non- 
fungicidal: calcium sulphate, sulphite, thiosulphate, hydroxyhydro- 
sulphide. 

(6) Calcium polysulphide, at a strength of 0-11 per cent., proved 
fungicidal. 



E. HORTON AND E. S. SALMON 279 



BIBLIOGRAPHY. 

(1) Eyre, J. V. and Salmon, E. S. The Fungicidal Properties of Certain Spray- 

fluids (Journ, Agric. Science, 7, 473-507 (1910)). 

(2) Eyre, J. V., Salmon, E. S. and Wormald, L. K. Idem, II (I.e. 9, 284-307 

(1919)). 

(3) Waite, M. B. Experiments on the Apple with some New and Little-known 

Fungicides (1/..S'. Dept. Agric. Circ. 58 (i'.)lO)). 

(4) Clinton, G. P. Tests of Summer Sprays on Ajiples, Peaches, etc. (Connecticut 

Agric. Exper. Station, Thirtij-fifth Ann. Rep. 1911, 347-100 (1912)). 

(5) Watkins, O. S. Tests of Lime-Sulphur, Bordeaux mixture and other Sprays 

(Illinois State Circ. 159 (1912)) (Abstr. in U.S.A. Dept. Agric. Exper. Stat. 
Record, 28. 48 (1913)). 

(6) Wallace, E., Blodgett, F. M. and Heslek, L. R. Studies of the Fungicidal 

Value of Lime-Sulphur Preparations {Agric. Exper. Stat. Cornell Univ. (New 
York) Bull. 290 (1911)). 

(7) Morse, W. J. Spraying Experiments and Studies on Certain Apple Diseases 

in 1913 [Maine Slat. Bull. 223) {Thirtieth Ann. Rep. Maine Agric. Exper. Stat. 
1914, 1-24 (1914)). 

(8) Morse, W. J. and Shapov.alov, M. Apple Spraying Experiments in 1914 

{Maine Stat. Bull. 240) {Thirty-first Ann. Rep. Maine Agric. Exper. Stat. 1915, 
177-190). 

(9) Morse. W. J. Arsenate of Lead as a Fimgicide for Apple Scab (Phytopathology, 

6, 118 (1916)). 

(10) Apple Spraying Experiments in 1916 and 1917 (Maine Stat. Bull 271) 

(Thirty-fourth Ann. Rep. Maine Agric. Exper. Stat. 1918, 101-128). 

(11) Sander.s, G. E. Arsenate of Lead cs. Arsenate of Lime {Proc. Entomol. Soc. 

Nova Scotia, 1916, 40-45 (1917)). 

(12) Blair, J. C. et alii. Field Experiments in Spra3ring Apple Orchards. General 

Summary by B. S. Pickett (Univ. of Illinois Agric. Exper. Stat. Bull. 185 
(1916)). 

(13) Vermorel, V. and Dantony', E. Sur les bouillies fongicides mouiUantes {C. R. 

156, 1475-1470 (1913)). 

(14) Van Slyke, L. L., Hedges, C. C. and Bosworth, A. W. A Chemical Study of 

the Lime-Sulphui' Wash {N. Y. Agric. Exper. Stat. Bull. 319 (1909)). 

(15) Tartar, H. V. and Bradley, C. E. On the Composition of Lime-Sulphur Spray 

(Journ. Indust. and Engin. Chem. 2, (1910) (Oregon Stat. Research Bull. 3 
(1914)). 
(10) Ramsay', A. A. The Preparation and Composition of Lime-Sulphur Sprays 
(.lourn. Agric. Science, 6, 194-202 (1914)). 

(17) Thompson. F. and Whittier, A. C. The Composition of Lime-Sulphur Solutions 

(Delaware Stat. Bull. 105 (1914)). 

(18) BoDNAR, J. Chemische Zusammensetz.ung und Wertbestimmung von Schwefel- 

kalkbriihe (Chem. Zeit. 39. 715 (1915)). 

(19) Chapin, R. M. The Chemical Composition of Lime-Sulfm- Animal Dips (U.S. 

Dept. Agric. Bull. 451 (1916)). 

(20) Salmon, E. S. and Horton. E. Lime-Sulphur and Calcium Caseinate as a 

Fungicide (Joxirn. Min. Agric. 28, 995-999 (1922)). 



{Received July 2\st. 1922.) 



THE SUGARS AND ALBUMINOIDS OF OAT STRAW. 

By S. H. COLLINS and B. THOMAS. 

Agricultural Department, Armstrong College, Newcastle-on-Tyne. 

The newer knowledge of nutrition shows that cereals and seed products 
are deficient in calcium, sodium, chlorine, and unknown substances, called 
fat-soluble A and water-soluble B sometimes referred to as "vitamines" 
or "accessory food factors." 

McCollum(i) in America, has gone the length of proving by actual 
experiment that cows and their calves can be raised to perfection on 
nothing but the complete maize plant, although maize grain is well 
known as a very incomplete food. In spite of his demonstration, and in 
spite of the obvious fact that nothing could be more like grass than an 
entire cereal plant and tlu^refore suited to herbivora, very few practical 
or theoretical agriculturists recognise that straw is the most likely thing 
in the world to correct for the deficiencies of grain feeding. The diffi- 
culty is to get straw that is eatable. The practical fanner, when he 
happens to get a good sample, accepts it as a gift of fate and is content 
to turn it into profit for himself as soon as he can. The object of the 
enquiry, or rather the series of enquiries of which this forms a part, is 
to adopt the more scientific mode of procedure and endeavour to find 
out what differences of feeding value naturally occur in oat straw, and 
which of the conditions needed for high feeding value could be repeated 
at will, and what light such investigation threw on the old question of 
why farmers in some districts can fatten cattle on swedes and straw 
whilst in other districts it is found impossible. Oat straw is plentiful in 
this country and is probably well suppUed with the so-called food 
accessories, that is the things that the grains lack; the problem at issue 
is how to get more of the eatable kind and less of the uneatable kind. 
Provided that the straw is eaten in fair quantity, the possible diminution 
of growth power, by partial destruction of vitamines due to keeping 
straw in the stack, is of no practical importance because of the large 
amount of the straw. 

The first subject attacked was the sugar content, but it was found 
during the progress of the investigations that the albuminoids were 



S. H. Collins and B. Thomas 281 

equally promisintr as a subject of enquiry. It is worthy of note that 
whereas the chief digestible carbohydrate of oat grain is starch, which 
is condensed dextrose, the sugar of the straw is chiefly laevulose. In 
other words, straw supplies the feeding deficiency of oat grain, if cane 
sugar, which is a condensed form of both sugars together, is considered 
the complete food sugar. 

Samjjles of oat straw from many parts of Great Britain have been 
examined for their chief constituents and as far as possible the conditions 
under which the straw was grown have been recorded. From the results 
obtained, averages of groups of results are given in the following notes. 
The general method of analysis follows common practice for oil, albu- 
minoids, fibre and ash. The estimation of laevulose has been described 
by one of us (2), the estimation of the other sugars being by Fehling's 
volumetric method. At times the method of Ling (3) was used for an 
end point but in most cases the solutions were sufficiently free from 
colour to render Ling's indicator superfluous. At times the oat straws 
were extracted with ether to remove some substances that prevented 
the cuprous oxide from setthng(4) but in most cases these precautions 
proved unnecessary. Nevertheless the authors consider that both 
methods are very valuable at times when difficulties arise. As regards 
Ling's indicator the authors found that a simpler recipe worked even 
better. A small ball rolled up from about haK a yard of flower wire was 
placed in a test tube with 2 c.c. hydrochloric acid and 2 c.c. water and 
boiled for one minute. A small sjjoonful (about | gni.) of ammonium 
sulpho-cyanide was added and allowed a minute or two to stand and 
cool. This indicator kept, in its original test tube with the residue of 
the iron wire, very well for a week or two, since fresh iron dissolved as 
fast as oxidation took place. Also carbon oxysulphide is formed which 
acts as a reducing agent. In practice it is better to make fresh indicator 
daily. In early samples pentoses were looked for, but either none or 
the merest traces could be found. From the polarimetric readings and 
other properties the unidentified sugar appears to be mostly dextrose. 

The albuminoids are the usual N / %\ figures. All the early samples 
were also treated so as to give the ammonia volatile with steam and 
10 per cent, potash and the nitrogen insoluble in various "protein pre- 
cipitants." In the end it was found that the N precipitated by basic 
lead acetate and the N volatile as NH3 by steam and potash almost 
exactly added up to the total N and that other N precipitants were 
uncertain. Further the amount of "non-albuminoid" nitrogen as de- 
duced from such estimations was too small in amount to have much 



282 Tlie Siigara and Albuminoids of Oat Straio 

practical value. Normal leail acetate gave concordant results but left 
a considerable fraction unaccounted for. Copper hydrate gave very dis- 
cordant results. The (N x 6J) precipitated by basic lead acetate added 
to the (N •; 6J) volatile with steam and potassium hydroxide gave a 
result on the average of 70 tests of -QUO per cent, above the total (N x 6^). 
The average difference between the sum of those two parts and the whole, 
neglecting signs, was -184 per cent. Of the 70 samples thus fully analysed 
the average "albuminoids" was 3-26 per cent, and the average ''amides" 
was -29 per cent, or only 8-9 per cent, of the total. 

I. Effect of Manure on the Composition of Oat Straw. 

The compilation of averages of large numbers of trials, such as these, 
presents many difficulties. Classification is often rather difficult and 
some observ'ations must be rejected as not capable of classification. By 
dividing the results of the analysis of oat straw into three groups we 
find the following figures. Unless otherwise expressed the results have 
been calculated from 1919, 1920 and 1921 crops. 

A. 35 samjiles of oat straw grown with very much organic nitrogen 
such as ploughed in leas, apparently rich, omitting doubtful "clover 
takes" but including land with heavy dressings of dung. 

I.aevuloso ... 
Total sugar 
Albuminoids 

B. 29 samples of oat straw top dressed witli suljahate of ammonia. 

Laevulose 1U2 "„ +-21 

Total sugar 3-28 ±-24 

Albuminoids 2-54 ±"12 

C. 21 samples of oat straw grown with little if any nitrogenous 

manure in any form. 

Laevulo.se 1-65% i-28 

Total sugar 3-47 ±-45 

Albuminoids 2-57 ±-16 

The combinations of these results which give significant diflferences 
are; Much organic nitrogen gives an oat straw richer in albuminoids 
than that given by httle or no nitrogen, to the extent of 1-27 % ± -22, 
as judged by 56 tests. Much organic nitrogen gives an oat straw richer 
in albuminoids than that given by sulphate of ammonia top dressings, 
to the extent of 1-30 % ± -21, as judged by 64 tests. Organic nitrogen 
manures give oat straw richer in albuminoids than that given by all 
other manures, to the extent of 1-28 % ± -17, as judged by 85 tests. 

Other probable results are: Organic nitrogen manures depress the 
amount of laevulose in oat straw to the average extent of -59 % ± -21. 



1-05 % 


±11 


2-51 


±•24 


3-84 


-"-■13 



S. H. Collins ato B. Thomas 283 

Sulphate of ammonia is better than organic nitrogen for sugar pro- 
duction but only to a small extent. 

II. Effect of Districts. 

It was quite impossible to do more than select a few farms to re- 
present large areas. The conclusions arrived at can by no means be 
supposed to refer to the whole of the district alluded to. In some cases 
personal knowledge permitted the farms to be well scattered, so that 
County Durham is fairly well represented, but the district called Scotland 
is merely an average of a few results from Aberdeen and Edinburgh and 
is therefore merely a name for places well to the north of Northumberland. 
Similarly Yorkshire is represented almost entirely by Garforth, only a 
few other places in the county being among the hst of farms from which 
samples were obtained. The .•southern counties district is more wide- 
spread, as it includes Essex, Herts, Bucks, Hants, Wilts, Derby and 
Notts, and may fairly represent "the South" from a north country- 
man's point of view. 

In spite of these drawbacks in the classification, a useful comparison 
may be made with the following results. 

Albuminoids in Oat Straw in Different Districts. 

Moving from North to South : 

Scotland with 2U samples gives 3-23 % ± -10. 

Northumberland and Durham with 26 samples gives .■M.5 % ± -14. 

Cumberland and Westmorland with 15 samples gives 4-42 % ± -1.5. 

Yorkshire with 27 samples gives 3-09 % ± -08. 

Southern Counties with 34 samples gives 2-74 % ± -09 . 

The outstanding result is the much higher amount of albuminoids in 
Cumberland and Westmorland. Oats are there a very important crop 
as they receive nmch more maniire than is customary in other parts. 
They frequently follow old leas and often receive much direct apphcation 
of dung. Stock are moreover the central feature of the system of farming 
and much care is taken of the beasts. Owing to the damper chmate 
it is possible that the roots of the oats go on absorbing nitrogen to a 
late stage and hence keep on accumulating nitrogen; but the average 
figures for non-albuminoid nitrogen are not especially high, so that some 
other explanation must be looked for. The superiority of the oat straw 
on the farms tested in Cumberland and Westmorland can hardly be 
attributed to any other cause than an increased amount of available 
nitrogen in the soil. 



284 The Sugars and Alhntninoids of Oaf Strair 

If we put Cumberland and Westmorland aside and compare the other 
districts there is at once the striking result that albuminoids increase 
directly with latitude. The difference between the Scottish figure, and 
those from the southern counties is marked and is quite in accordance 
with the popular impression that straw can be fed in Scotland in a way 
in which it cannot be fed in the south of England. At Cockle Park one 
experiment with different seed dates showed that the total nitrogen in 
the crop per acre was not very different; with autumn sown oats, the 
large crop of grain took nearly all the nitrogen, hut the spring sown 
oats gave only half the grain yield and left a straw very rich in albu- 
minoids. It follow.s that in Scotland with its shorter growing season 
the grain will not be able to exhaust the straw to the same extent as it 
would in England and that therefore Scottish oat straw will on the 
average contain more albuminoids than English oat straw. The con- 
clusion is in close accord with the results based on the statistics. 

A partial answer is here given to the well-known question : .why can 
cattle be fattened on straw and roots in Scotland and not in the south 
of England? It is due to the superiority of north country straw in 
albuminoids. Quite possibly along with the albuminoids may go those 
httle understood food accessory sub.stances already alluded to. Swedes 
and turnips are very poor in albuminoids and the superiority of northern 
straw in this respect may be the determining factor. At Cockle Park, in 
feeding trials on hay, the determining factor is often the percentage of 
albuminoids. North country hay is poor in albuminoids whereas north 
country oat straw is relatively ricli, or one might say south country 
hay is relatively rich and south country straw relatively ])oor. These 
two facts together go a long way to explain the respective practices in 
feeding cattle. The variation in the albuminoids in oat straw grown in 
different districts may possibly be partly due to rainfall. In Scotland, 
Northumberland, Durhami and Yorkshire the average rainfall at the 
places where the oats were grown was about 30 inches, but the Cumber- 
land and Westmorland areas have an average rainfall about 15 inches 
and the southern counties area about 27 inches. Among other causes 
of high proportions of albuminoids may be placed a good supply of 
water. Oats that are cut green will often be cut green because the season 
is wet with the result that the straw contains more albuminoids. Hence 
the cattle relish the straw and the farmer says that the straw is "sweet" 
but it is rich in albuminoids and not particularly rich in sugar. 



S. H. Collins and B. Thomas 285 

The District in which Oats are groimi and the amount of Si i gar 
in the Straw. 

Seasonal influences play such a great part in sugar production and 
content that 1920 and 19"21 do not give the same relationships. 

In 1920, Cumberland and Westmorland headed the list and Northum- 
berland and Durham were only a little behind the four northern counties, 
giving total sugar 4-48 % ± -29 with the rest of Great Britain at 
1'69 % ± -12. In 1921 however the southern counties gave 4-76 % ± -34 
and the four northern counties 1-80 % ± -15 the average of all except 
the southern counties being 1-44 % ± -10. From these results it is 
clear that the southern counties made good use of the dry season of 
1921. 

As in former years samples of oat straw which contain much total 
sugar also contain much laevulose, so that the laevulose varies from 
50 to 70 per cent, of the total sugar, but when the total sugar is low in 
amount laevulose is often absent. On the average of all results, poor 
and rich, the laevulose is a little under 50 per cent, of the total but even 
then it is the commonest sugar, since the remainder is divided between 
cane sugar and dextrose and perhaps traces ot other sugars. 

General Conclusions. 

Fine weather during harvest appears essential for obtaining high 
percentages of sugar. Sugar gradually disappears from straw after 
harvest. When straw is very dry the loss is small, but if damp, sugar 
is readily lost. Under average practical conditions high sugar content 
is not common but, under careful management, oat straw six months 
old has given very high figures for sugar. Roiighly it might be said 
that the more nitrogen a soil contains the more albuminoids there will 
be in the straw, but much will depend on the amount of grain produced. 

The general impression obtained during the course of these investi- 
gations is that the reason why feeding oat .straw and swedes is so suc- 
cessful in one district and not in another may be summed up in the 
phrase "good husbandry." AVhen a farmer understands and is keen 
on cattle he obtains more dung, which gives him better quality straw 
and roots. Feeding these again skilfully to more beasts gives hnn still 
more and still richer dung until in the limit of practice he is able to feed 
beasts almost entirely on straw and roots because both are rich in 
albuminoids. The lowest figure for albuminoids is 1-12 per cent, and the 
highest 8-05 per cent. ; a variation more than enough to explain any 



286 The Sugars <in<l Alhiuinnouh oj Oaf Straw 

difference in feeding value. Poor samples of hay are often below 8 per 
cent, albuminoids. The highest total sugar is 9-74 per cent, and the 
lowest 0-33 per cent. Old leas ploughed out and plenty of muck give 
high albuminoids; fine harvest weather gives sugars. It is good manage- 
ment that secures the benefits of these improvements in composition. 

The Value of Research Grants. 

Twenty-two years ago one of us started to answer the question 
"why can cattle be fattened on roots and straw in Scotland and not in 
England? " Limitation of time restricted the enquiry to hnes which 
looked promising, with little direct result altliough the experience has 
in the end proved very valuable. Thanks to a Special Research Grant 
from the Jlinistry of Agriculture, a very moderate extra expenditure 
has enabled the enquiry to be prosecuted in a complete manner. Out 
of this came the idea that perhaps it was the albuminoids in the straw 
that was the foundation on which an answer could be given; further 
work has shown that that is undoubtedly the case, as far as the main 
part of the answer is concerned. Nevertheless the sugar is important 
in both swedes and straw and contributes a great deal to the feeding 
value, but probably it is the albuminoids in the straw that make the 
chief difference between the practice of north and south. 

BIBLIOGRAPHY. 

(1) McCoLLTiM. Tlie Newer Knowledge of Nutrition (^la.cMiM^i.n), -p. 100. 

(2) Collins. The Estimation of Laevuloso (Fructose) in Straw. J. S.C.I. 1922, 

p. 56. T. 

(3) Lino and Jones. V'oluiiu-tric Estimation of Reducing Sugars. Analyst, 1908, 

p. 160. 

(4) Collins and Spilleb. Sugar in Oat Straw and Cattle Food. J.S.C.T. 1920, 

p. 66. T. 

(Received July 5th, 1922.) 



NOTE ON THE MECHANICAL ANALYSIS 
OF HUMUS SOILS. 

By gilbert WOODING ROBINSON, M.A. 

Adviser in AgricuUuml Chemistri/, University College 
of North Wales, B<t.ngor. 

It is generally recognised that the mechanical analysis of soils containing 
large quantities of organic matter presents considerable difficulties and 
that in the case of peaty soils mechanical analysis can have Httle 
significance. Apart from the masking effect of organic matter on soil 
properties which will naturally vitiate any correlations with mechanical 
composition, the actual dispersion of humus soils is difficult owing to the 
cementing action of humified organic matter, whereby soil particles are 
aggregated together into compound structures which resist ordinary 
methods of dispersion. Various methods have been suggested for the 
destruction of organic matter as a preliminary to mechanical analysis. 
Atterberg^ recommends the use of alkaline sodium hypobromite solution. 
In the case of diatomaceous soils, however, oxidation of the organic 
matter with hot nitric acid {d. 1-14) is recommended. For soils free 
from calcium carbonate the use of hydrochloric acid (d. 1-12) is suggested. 

In view of the reactive character of some of the finer soil constituents 
these and similar methods would appear to be open to objection. Any 
acid treatment is certain to result in the partial solution of clay and 
finely divided minerals, whilst alkaline treatment results in the attack 
of silica or colloidal silicic acid. 

The soils of North Wales are generally higii in organic matter and 
the writer has long suspected that the figures for clay obtained in the 
ordinary mechanical analysis might be too low and that a certain 
amount of clay was reckoned wath the other fractions. Two circum- 
stances favoured this view. In the first place, the majority of the soils 
of this area are derived from rock material w^hich might be expected 
to furnish rather heavy soils. Further the analyses of the hydrochloric 
acid extracts for such soils show high figures for silica, iron oxide and 
aluminium oxide such as might be expected from clay soils. 

■ Int. Mitt. Bodeiikunde, 1912, 2, 312-342. 
Joum. of Agric. Soi. xii 20 



•288 Note on the Mechanical Ajiali/sis of Humus Soils 

Attempts were therefore made to effect the destruction of organic 
matter without attacking clay or fine mineral particles. This requires of 
course a neutral reagent. Th; first oxidising agent tried was ammonium 
persulphate. Considerable oxidation of the organic matter can be 
effected by the use of this reagent in aqueous solution but the sulphuric 
acid liberated dissolves mineral material and it is necessary to maintain 
neutrality by repeated additions of alkali. There is the further dis- 
advantage of the large quantities of ammonium sulphate introduced 
whicii has to be removed before the soil can be subjected to mechanical 
analysis. With this somewhat inconvenient method, however, it was 
found that considerably higher figures were obtained for the clay fraction 
than by the ordinary method. Some results obtained on a typical Welsh 
soil using different methods of dispersion may now be given. 

I'rcliiniiiary treatment Clay % 

l)r<Unarv method 6-9 

One hour digestion with HCl (d. 112) 13-5 

Digestion «ith NaBiO (Atleiherg) 10-.")* 
Ammonium persuljihate oxidation (10 : 20). 

No neutralisation 1304t 
Ammonium persulphate oxidation {'> : 20). 

Maintained approx. neutral 160 

* 7-58 "{, of material dissolved. f ''"^S °o of material dissolved. 

Microscopical examination of the fractions obtained showed striking 
differences. The fine silt and silt obtained by the ordinary method con- 
tained considerable quantities of amorphous material. The same fractions 
obtained after preliminary oxidation were seen to consist entirely of 
crystaUine mineral matter. Similar fractions are obtained from raw 
clays and soils poor in organic matter. 

The use of ammonium persulphate proved inconvenient in practice 
and hydrogen j)en)xide was therefore tried as an oxidising agent. After 
.some prehniiiiary trials it was found that the most convenient method 
of oxidising was as follows. Ten grams of soil are weighed into a beaker 
of 600-700 c.c. capacity. Fifty c.c. of hydrogen peroxide (20 vols.) are 
added and the beaker placed on a boiling water bath. A vigorous 
reaction soon takes place with considerable frothing owing to the evolu- 
tion of oxygen. The contents of the beaker are stirred from time to 
time. After about 30 minutes the reaction dies down and a further 
25 c.c. of peroxide are added, the froth adhering to the sides of the 
beaker being washed down with a small volume of water. After a further 
15-20 minutes' heating the reaction is generally complete and frothing 



G. W. Robinson 289 

ceases. In the case of soils with large j^roportions of organic matter, more 
peroxide will be needed. The beaker is then removed from the water bath 
and, after adding about 100 c.c. of water, boiled for about 15 minutes. 
A considerable oxidation of organic matter has now taken place and 
the oxidised material acquires the yellowish or light brown colour of a 
non-humous subsoil. The contents of the beaker remain approximately 
neutral so that no solution of mineral matter may be apprehended. In 
order to form some idea of the effect of this oxidation on the soil organic 
matter two soils were oxidised. After filtration and washing the residual 
material was dried and the loss on ignition determined. The filtrate and 
washings were evaporated to dryness and the amount of soluble organic 
matter determined. A separate experiment was also carried out in which 
the gaseous products were collected in normal sodium hydroxide and the 
amount of carbon dioxide estimated by double titration. The amount 
of organic matter completely oxidised to carbon dioxide was found by 
multiplying the weight of carbon found as carbon dioxide by 2, assuming 
as a first approximation that the organic matter contained 50 per cent. 
of carbon. The results obtained were as follows: 

Loss on ignition t).\idised Soluble 

Soil Loss on ignition after oxidation to T'O., org. matter 

Cili 2.5-4 8-1 o-,5 10-8 

4T 101 40 1-9 3 7 

It \vill be seen that the original organic matter is approximately 
accounted for by the unoxidised matter and the products of oxidation. 

A number of soils thus oxidised were submitted to mechanical 
analysis. The result of the treatment is to break down the compound 
particles very thoroughly and the separation of the fine gravel and 
coarse sand by means of the 100 mesh sieve is very easily effected with 
very little trituration. Generally speaking the sedimentations were 
carried out twice without the addition of ammonia and then as in the 
ordinary method. It may be added that the soluble products of oxidation 
would appear to be deflocculating in their action and quite considerable 
quantities of clay can be obtained without the use of ammonia. The 
following table shows the results obtained for a number of soils by the 
ordinary method including the usual preliminary treatment with HCl, 
and also by the hydrogen peroxide method, in which this acid treatment 
is omitted. 



20- 



290 Note on tlir JJcc/uaiical A/nili/t<i,>< of JJ mints Soils 

Ab. 4 B Ab. B S F 2 A F 2 B G 26 A C 3li A 



Soil 


Ord. 


H,0, 


Ord. Hj.Oj 


Ord. HjO, 


Ord. 


H,0, 


Ord. 


H.O, 


Ord. H,0, 


Fine gravel 


3-8 


3-3 


30 2-8 


— 


— 


•4 


38 


40 


7-8 10-3 


Coarae sandj 
Fine sand ( 


29-5 


29-5 


.33-8 331 


81 8-3 


4-6 


6-5 


\4-8 
)5-2 


5-2 
81 


12-3 7-8 
20-5 15.-. 


SUt 


18-3 


15*5 


190 13-8 


22-1 20-8 


20-9 


20-7 


23-2 


1 3-7 


15-6 140 


Fine silt 


28(i 


23-2 


260 19-5 


32-9 25-4 


,340 


27-4 


34-6 


26-8 


23-4 297 


Clay 


8-2 


17-9 


6-3 17-6 

^ -/ ' 

1-3 


201 283 

V J 

3-5 


28-7 


320 


3-8 


13-2 

1 


5-6 9.-. 


Moisture 




2-3 


3-2 




3-3 


2-6 


Org. matter 


100 


90 


10-9 


5 


•4 


2, 


5-4 


10-3 



Totals 100-7 101-7 US 4 97-1 97-G 97-2 96-8 95-6 104 1 99-7 98-1 99' 



Soil 


Ord. 


H,0, 


Ord. 


H,0, 


(ii.l. 


ILol 


Ord. 


H,0, 


Ord. 


H,0. 


Fine gravel 


6-6 


1-4 


40 


3-2 


5-2 


4-6 


■9 


■8 


37 


4-1 


Coarse sand 


2.1-7 


27-9 


20-5 


380 


22-5 


24-9 


23-6 


25-3 


11-8 


12-2 


Fine sand 


27-1 


20-4 


29-7 


210 


270 


18-7 


26-8 


21-4 


32-8 


18-6 


Silt 


10-8 


10-5 


14-8 


10-5 


15-7 


12-5 


160 


12-0 


20-0 


17-5 


Fine silt 


10-7 


17-7 


10-1 


17-2 


12-5 


19-0 


13-2 


15-7 


131 


19-0 


Clay 


3-8 


6-8 

V 

■2 


3-S 


8-0 


4-2 


7-5 


3-5 


9-3 


:!•:', 


130 

> 


Moisture 


4 


• 2 


•>. 


1 


3-8 


2 


•6 


Org. matter 


8-1 


10-9 


8-7 


9-6 


110 



Totals 980 980 98-0 98-0 97-9 980 97-4 97-9 98-3 97-0 

It will be noticed that in every case there is an increase in the amount 
of clay obtained. Tn other words the effect of the oxidation has been 
to increase the degree of dispersion of the soil. That this effect was not 
an apparent increase in the clay owing to higher visco-sity of tJie aqueous 
solution of the oxidation products was shown by a viscosity determina- 
tion on a filtrate obtained from an oxidation. The ^^scosity was sensibly 
the same as for pure water and it may be assumed tliat tlie difference 
is due to an actual dispersion of complex particles which are not broken 
uy) in the ordinary method of dispersion. The hydrogen-peroxide dis- 
persion has of course been effected without preliminary acid treatment, 
in the case of the soils used. Possibly it might be desirable to include 
the acid treatment in the case of soils containing much carbonate. It 
is worthy of remark that the clay hquor obtained by the peroxide method 
is strikingly different from that obtained by the ordinary method. On 
agitation, it shows a satin-like effect owing to the reflection of hght 
from minute crystaUine particles. This effect is not shown by the clay 
liquor from soils in the ordinary method. Similar results are obtained 
with fine silt suspensions. It is also noticed that on flocculation of the 
clay hquor a smaller volume of flocculated material is obtained than in 
the ordinary method. 



(t. W. Robinson 291 

No attemj)t lias been made to follow the chemical changes involved 
in the oxidation of soil organic matter by hydrogen peroxide. It may be 
mentioned that the soluble compounds formed appear to form a very 
suitable medium for the development of moulds and fungi as, when 
exposed to air, they quickly become covered with a scum on which 
growths appear. The products of oxidation would be well worthy of 
chemical examination. 

The results obtained particularly in the case of Welsh soils indicate 
that the figures obtained for clay by the ordinary method may be mis- 
leading and that there are considerable quantities of 'clay' which are 
wrongly grouped with the coarser fractions. In other words the ordinary 
method fails to secure the prime particle structure. This defect in the 
standard method may operate to some extent even in soils with smaller 
amounts of organic matter, for in every case larger figures were obtained 
for the clay after peroxide treatment. 

Treatment with peroxide offers a convenient means of removing 
organic matter from soil without altering the mineral portion. In these 
experiments it was not found possible to remove all the organic matter. 
Complete removal might be effected by successive treatment with 
peroxide. It would appear, however, that the humified organic matter 
is completely oxidised or rendered soluble for the dark colour is removed 
even from peat soils and the oxidised soil has the appearance of a raw 
subsoil. The unoxidised material in such cases appears to consist entirely 
of structural organic matter, a circumstance which suggests that only 
humified matter is attacked. 



{Received July Sth, 1922.) 



A BACTERIAL DISEASE OF TURNIP 
{BRASSICA NAPUS). 

By S. G. JONES, M.Sc. 
Lecturer in Botany, University College of Wales, Aberystwyth. 

(With Plate ill.) 

Of recent years a disease of root-crops known to farmers in Nortli Wales 
is one in which the heart or core of the root is converted into a soft 
putrid mass but which leaves the rind and mature foliage intact. The 
disease is prone to appear on land treated with lime as a pre%'entive 
against the roots being attacked by Plasmodiophora hrassicae or when 
the land has received a heavy dressing of nitrogenous fertiUzers. It is 
common knowledge that nitrogenous manures have a tendency to force 
the crop and so produce watery, sappy roots which easily fall prey to 
disease. Recently it was brought to the writer's notice by one of the 
County Organizers for Agriculture in Wales that some of the farmers 
in his area were strongly disinclined to lime the land for root-crops 
because this treatment was favourable to the appearance of "soft-rot." 
There is probably some modicum of truth in this contention, for as will 
be seen below, the writer in the investigation of the present disease 
found that the organism isolated refused to grow on any media which 
were not neutral or alkaline. The writer observed and investigated this 
disease on a crop of white turnips grown on the farm of the I'niversity 
College of North Wales and the land here had received a dressing of 
nitrate of soda. A casual glance at the crop did not show anything 
unusual, in fact judging from the amount of green foliage the crop looked 
very healthy. Closer examination however showed that the very young 
leaves at the centre of the crown had been destroyed thus forming a tiny 
wound into which one could push a probe without obstruction to the 
depth of some three or four inches. The fully expanded leaves very 
effectively concealed the wound and the disease seemed evidently con- 
fined to the internal tissues leaving the foliage and rind quite firm even 
up to time of harvesting the crop. Indeed the extent of damage was 
only fully revealed at the time of lifting when the harvester's knife 



S. a. Jones 293 

lopped off the foliage only to discover tiiat the roots were bad. A diseased 
root cut in vertical section showed a Hask-shaped, soft, putrid core 
surrounded by a brown zone abutting on the healthv tissue (Fig. 1). 
The disease never made further progress into the rind nor into the lower 
part of the root and this would therefore account for the healthy turges- 
cent appearance of the fohage since the vascular tissue in the root and 
rind would still be functional. Such were the external features of most 
of the diseased jilants but in addition numerous cases were found where 
the entire apical bud had been destroyed thus forming a large wound 
only however to be concealed by no fewer than three, often five secondary 
crowns all bearing healthy luxuriant foliage (Fig. 2). There were also 
found numerous diseased roots with all foliage intact, but bearing deep 
cracks in the rind above ground; these were probably examples of 
"burst" roots a condition frequently found in sappy roots exposed to 
sudden weather changes. In all these types however the internal appear- 
ance of the diseased roots was precisely the same — the soft-rot was 
always confined to the core of the root and in addition there was always 
present the brown-coloured zone at the boundary of the diseased area. 
A white-rot of turnips similar to the one now described has been attri- 
buted by Potter to an organism Pseudomonas destructans (Potter). He 
states that plants attacked by this parasite "can be recognised by the 
drooping yellowish leaves, the older leaves being tlie first to show any 
indications of disease; they gradually flag and droop to the ground, at 
the same time becoming yellow and shrivelled in appearance. The leaves 
next in age gradually exhibit the same signs of premature decay and this 
proceeds until finally the young leaves at the growing point succumb; 
the entire rosette of leaves perishes, and the whole root becomes a soft, 
putrid mass, which eventually collapses etc." In the present disease, 
however, the external appearances of the diseased plants showed features 
very different from those accompanying the one described by Potter 
and these were deemed sufficiently striking to warrant further investi- 
gation. 

It has been a matter of extreme difficulty to detect the initial mode 
of attack of this disease on the plants in the field. The writer has not 
been able to investigate this important point and the evidence gathered 
from the farmers is most conflicting. One noticed that the turnip plants 
were to all appearances dead, with the leaves flat on the ground as if 
the cattle had been lying on them but that on a subsequent visit he had 
found the crop to all appearances fully recovered only to find however 
at the time of harvesting that the roots were bad. Another said that 



294 A Bacterial Disease of Turnip (Brassica Napiiis) 

he had also seenjthe leaves drooping but that the seeming recovery of 
the fohage was due to new growth from secondary crowns. At the 
College farm the writer found intermixed in tlie drills along with diseased 
roots numerous healthy-looking plants possessing brown, dry, empty 
cavities with no sign of the pasty mass ever having been present; such 
plants invariably harboured slugs or their ova. These plants had, like 
the types of diseased roots already described, either the young foUage 
at the growing point destroyed or the foliage of the apical bud had 
entirely disappeared with the wound thus formed completely healed and 
surrounded by luxuriant fohage from secondary crow^ns. 

The Nature of the Disease. 

With a view to determine the nature of the pasty mass in the core, 
small quantities of it, taken from several affected plants were placed 
in a httle sterile water in a watch-glass. Microscopic examination of 
the turbid water showed isolated cells and cell-clusters floating in the 
liquid. There were no traces of protozoa such as are described by 
Priestley or of fungal hyphae. A small quantity of the liquid taken up 
on a sterile platinum looji and smeared on a cover-glass showed when 
stained a dense mass of bacteria. Cultures were then prepared for 
isolating the organisms. 

Methods. 

The sterihzation of apparatus and media was effected in the usual 
way. In the first instance nutrient gelatine acidified to 1 per cent, 
normal hydrochloric acid was employed but this medium w'as found 
unsuitable; then turnip-juice gelatine of natural acidity and neutralized 
was also used. Growth on these media, however, proved so inferior to 
that produced on beef-extract-peptone-gelatine neutrahzed with sodium 
hydrate that this was exclusively employed in the preparation of pure 
cultures. Precautions were taken to ensure its constant composition and 
uniformity of treatment in sterihzation. 

Diseased plants from which cultures were to be taken were thoroughly 
washed free from soil and placed for 15 minutes in a weak solution of 
corrosive subhmate. Without removing the chloride the- roots were cut 
open with a sterile knife from root-tip to crown, the root being inverted 
in order as far as possible to avoid contamination with foliage epiphytes. 
Petri-dish cultures were then carried out in the usual way and the 
several colonies transferred to agar-slants. 

The next step was to prepare sterile blocks of turnip for inoculation 
from the agar-streak cultures. By means of a platinum hook inocidations 



8. a. Jones 295 

were eflected from the agar-streaks into small excavations made at the 
centre of the blocks. After an incubation period of 15 to 24 hours at 
20° C. most of the blocks showed a whitish-grey transparency around 
the inoculated part. In the more juicy blocks, the afiiected area, in 
24 hours, would be about the size of a sixpence. After further incubation 
for 24 hours they had become completely diseased; during the next 
two or three days they assumed a yellowish hue and after a week a 
brown colour. The organisms causing the rot in the blocks had been 
derived from the agar-streaks which had been taken from round, whitish- 
grey hquefying colonies. Repeated cultures from field material showed 
that the colonies effective on the turnip blocks were of this type. Poured 
plates taken from successfidly inoculated blocks showed the colonies in 
crowded growth to be small, those situated below the surface of the 
gelatine being smaller. On a thinly sown jjlate the colonies were large, 
circular, with much hquefaction in the centre. Magnified under the 
low power of the microscope they showed a finely, closely fibrillated 
margin; within the margin was a narrow finely-granular zone, then a 
narrower denser granular band forming a very faint concentric circle 
within which was a wide zone gradually diminishing in a granular 
density towards the centre. The saucer-like depression contained massed 
bacterial debris floating in a thinly granular hquid. Buried colonies 
were small, round, fibrillated at the margin and homogeneously granular. 

The Organism .4nd its Flagell.\tion. 

After repeated cultures had been made in nutrient gelatine from the 
diseased blocks there remained no doubt that a pure culture had been 
obtained. Cover-sUp preparations of the organisms stained with carbol- 
fuchsin showed them to be rod-like in form and of varying length. Single 
specimens were short with rounded ends and pairs were frequently seen. 
Hanging-drop cultures in bouillon from several young agar-slants showed 
the organisms to be actively motile. After repeated attempts to stain 
the flagella, it was found effective to transfer the organism from agar- 
streaks of not more than 12 hours' growth into a number of small petri- 
capsules half-filled with sterile, filtered water kept at the same tem- 
perature as that in which the agar-cultures were incubated. The cover- 
sHps were placed in series of six in a large petri-dish bearing the corre- 
sponding number of the culture. A sterile platinum loop was then dipped 
into the small capsule and the drop quickly deposited on the cover-shp, 
six preparations being taken from the same capsule. These were air-dried 



•296 A Bacterial Disease of Turnip (Brassica Xapus) 

by iminediatelv placing the petri-dishes in an incubator at GO '. LoefHer's 
method of staining was first employed \vithout success, but with this 
method, the organisms showed uniform staining, except at one pole 
which was somewhat hyaline. When however the mordant was made 
sUghtly alkahne with caustic-soda (J c.c. of 1 per cent, alkali per 10 c.c. 
of tannin) most of the shdes after staining showed the presence of a 
single long polar Hagellum. Van Ermengen's stain, pre])ared according 
to the usual formula, also showed the presence of the cihum. No varia- 
tion in the number or .situation of tlie flagella was seen. 

Infection Experiment.s. 

The next step was to establisli the disease in healthy plants. It was 
decided to carry out infection of healthy plants by employing cultures 
from inoculated blocks. Preparations were accordingly made for inocu- 
lating a series of blocks from young cultures taken from the agar-streak 
tubes that had last been employed in the flagella staining. The latter 
process had entailed repeated failures and fresh attempts always involved 
the use of fresh subcultures. It was reckoned that the tubes now em- 
ployed for inoculating the turnip blocks contained cultures which had 
passed through some 20 generations over the medium. After the usual 
period of incubation, the inoculated blocks showed little or no signs of 
disease. Some of the blocks showed a slight browning around the 
inoculated part and made no further advance; others did not appear 
to have taken the disease at all. It seemed that the organism had either 
lost its virulence in its repeated passages through the medium, or that 
the turnip, through prolonged cultivation had passed over into a state 
of resistance to attack. It was therefore decided to submit sterile blocks 
of turnip to special treatment on the lines followed by Laurent for 
rendering resistant tubers sensitive to bacterial attack, by immersing 
them in alkaline solutions. Accordingly the blocks were first soaked for 
an hour, some in 0-25 per cent., some in 0-.5 per cent, and others in 
1 per cent, caustic-soda solutions. They were then transferred to sterile 
test-tubes and inoculated from the same agar-streak cultures that had 
been employed on the supposed resistant blocks. After prolonged incuba- 
tion the parasite made no more progress on the blocks thus treated than 
on the control ones which had only been soaked in water previous to 
inoculation. It was therefore concluded that the organism had lost 
virulence by so many passages through the artificial medium. When, 
however, another series of turnip blocks was inoculated from an agar- 



S. G. Jones 297 

culture derived directly from diseased material the usual signs of attack 
and rotting of the blocks took place. 

As above mentioned the farmers who had witnessed the attack in 
the fields said tiiat the disease had been preceded by a sudden collapse 
of the foliage. This reported phenomenon at once suggested infection 
of the leaves by way of the stomata or water-pores. Experiments were 
carried out on a number of plants in the following way. Uninjured leaves 
(attached to the plant) of varying ages were plunged into water in a 
series of petri-dishes to which had been added pure cultures of the 
organism from bouillon. The leaves were left immersed for an hour. 
In some plants they were first steriUzed with weak mercuric chloride 
which afterwards was removed by repeated plunging into sterile water; 
in others, no surface sterihzation was employed. The leaves of the control 
plants were also treated in the same way. These experiments failed to 
show any infection of the foUage. The writer is strongly of opinion that 
infection is preceded by mechanical injury through some such agency 
as leaf -cutting insects or slugs and the very earliest signs of tlisease in 
the very numerous cases seen in the field were the softening and water- 
soaked appearance of the young fohage. Further inocidation experi- 
ments were carried out by first .moistening the young foliage at the 
growing point and then depositing a pure culture from bouillon. The 
root was then covered over with a bell-jar plugged at the top with 
cotton-wool. These experiments invariably failed despite the greatest 
care being taken to keep the inoculated part moist. Accordingly the 
tender foliage at the growing point was pinched off with a sterile forceps 
and into the wound thus made a pure culture of the organism was de- 
posited, the wound being covered over with a piece of steriUzed cotton- 
wool, and the whole plant again covered over as before. This method 
of inoculation was always successful but the progress of the disease 
varied somewhat in different plants. The extent of attack was deter- 
mined from time to time by probing the cavity with a platinum wire. 
When a depth of some four inches had been reached the plants were 
cut open in vertical section. Those in which the pulp was watery showed 
the characteristic whitish-grey mass accompanied by the marginal brown 
discoloration. Other roots of a drier spongy texture showed a diseased 
core of a uniform brown colour. This difference of colour in the diseased 
parts suggested an idea that it might bear some relation to the water 
content of the cells and intercellular system or in other words to the 
extent of aeration of the tissues. During the earlier stages of the investi- 
gation it was noticed that when the inoculated turnip blocks in the test- 



298 A Bacterid! DlHeaae of Turnip (Brassica Napus) 

tubes were examined at intervals, some were always found to be more 
advanced in disease than others. Those which were spongy in appearance 
were brown or yellowish-brown in colour but the more succulent blocks 
were always wliitish-f;rey. The difference of coloration in the diseased 
tissues may therefore be due to oxidation. Further proof of this was 
established by the appearance of the diseased blocks in the tubes after 
incubation periods of 24 hours, 48 hours, and 7 days. At first they 
showed a whitish-grey transparency around the inoculated part; later, 
they had become almost completely diseased but still whitish-grey, 
but after 7 days the blocks were considerably changed and distinctly 
brown in colour. The darkened colour-, however, was only seen in those 
portions of the blocks exposed to the air in the tubes; the basal portions 
immersed in a little water were still light in colour. Still further evidence 
proving the discoloration to be due to oxidation was obtained by the 
following experiment. Two conical flasks with side tubes, plugged and 
sterilized in the autoclave were partially filled with sterile blocks about 
a cubic centimetre in size, and a little sterile water added. Two rubber 
stoppers which had previously been boiled in mercuric chloride and 
dipped in sterile water carried a bent tube, reaching to within half-an- 
inch of the turnip blocks. Into each a small fragment of diseased turnip 
was inserted, tlie stoppers quickly replaced and sealed with paraffin wax, 
sterile rubber connections furnished with pinch-cocks were slipped over 
the side and the bent tubes. The flasks were connected each to three 
similar flasks containing a mixture of pyrogallic acid and potash. 
A current of air was then drawn through the series of flasks for 15 
minutes. The rubber connections of the turnip-flasks were then closed 
with the pinch-cocks and the flasks detached. From one turnip-flask 
the pinch-cocks were removed, and the tube-ends closed with sterile 
cotton-plugs. Both flasks were then incubated at 20° C. for a week. 
After 24 hours the blocks around the diseased fragment of turnip intro- 
duced showed the usual whitish-grey transparency. At the end of the 
week the contents of the cotton- plugged flask had become brown in 
colour, whereas the blocks in the sealed flask, all diseased, still remained 
whitish-grey in colour, and showed no sign whatever of browning, nor 
did they show any change of colour even after several weeks. Inci- 
dentally the experiment shows the organism to be facultative anaerobic. 
Further evidence of this property is given below. 

As previously stated the discoloration in the field plants was con- 
fined to a distinct zone, between the healthy and diseased tissues. It 
is possible that the disintegration of the tissues following upon disease 



8. a. Jones -ifUt 

would be attended by a collajjsing of the cells, so that access of air 
through the diseased core would be prevented and thus hinder atmo- 
spheric oxidation. At the time of infection in the field, the plants would 
be actively growing and drawing upon the minerals in the soil. It is 
conceivable that one or more of these substances would have an oxidizing 
efiect on the bacterial .secretions in the diseased tissues, causing a dis- 
coloration at the margin of the diseased area. E. F. Smith states that 
Laurent, experimenting with different fertihzers on potatoes upon plots 
which had been treated with sodium nitrate and sulphate of ammonia 
produced tubers, which when inocidated with an organism (beheved to 
be B. coli) gave a " black zone between the attacked and healthy tissues. 
As this stain was not noticed elsewhere, Laurent attributed it to the 
nitrogenous product formed by the bacteria at the expense of the 
tissues." 

Relation of Parasite to Ho.st. 

The relation of the organisms to the tissues of the host was first 
determined by examination of the diseased pulp of the field plant. 
A small quantity of the pulp mounted on a slide and gently pressed down 
with the cover-glass showed the cells to be completely isolated. The 
cell-walls were, however, intact and presented no appearance of being 
swollen. Numerous reticulated vascular strands were also seen with 
their walled prosenchymatous elements attached in places. The bacteria 
were generally seen outside the cells, but a few cells were so completely 
occupied by them that they appeared black amongst the contiguous 
imoccupied cells. Examination of the diseased pidp of inoculated plants 
showed exactly the same phenomena. Such densely occupied cells with 
the contiguous cells containing few or no bacteria were also seen in the 
microtomed sections of inoculated material. 

Field material was fixed in Flemming's solution and in Carnoy's 
acetic-alcohol. Small pieces of the diseased roots were cut to include 
the healthy tissue, the brown zone, and the loose \)\\\\). The shdes made 
from the material fixed in the Flemming mixture showed almost the 
complete loss of the soft pulp in the prolonged process of washing. The 
alcohol-fixed material was therefore employed. The pieces selected for 
paraffin embedding included all the tissues from the periphery to the 
soft pulp. Transverse and longitudinal sections were cut on the micro- 
tome to a thickness of 4fi and mounted on shdes thinly coated with 
white of egg. Considerable difficult}' was experienced in the differential 
staining of the tissues and the bacteria respectively. The organisms 



300 A Bacterial Disease of Taniip (lirassicii Nai>iis) 

stained easily with tlie aiiilin dyes, particularly carbol-fuchsin, followed 
by differentiation in alcohol, showing the bacteria to advantage. Another 
method was to stain for 12 hours in HofFniann-blue saturated with 
picric acid, and after washing in 50 per cent, alcohol, to immerse for 
three minutes in carbol-fuchsin. This showed the tissues blue and the 
bacteria red, but the staining was not always uniform and hence the 
method was unreHable. After repeated attempts with various dyes 
satisfactory results were obtained by the use of Heidenhain's iron-alum- 
liaeraatoxylin followed by eosin in dove-oil. Tliis showed the bacteria 
black and the cell- walls light red. 

When the slides were exainincd under the Iow-jkiwci- of the micro- 
scope, the bacteria were seen to be apparently e.xclusively confined to 
the intercellular system of the medulla, and the disintegration of the 
tissues to be brought about by the dissolution of the middle lamella. 
Some cells in the same region were seen to be densely filled with bacteria, 
relatively few or none being present in contiguous cells, thus repeating 
the features already observed in the examination of the diseased pulp. 
Some of the xylem elements also seemed to be occupied by bacteria. 
The microscopic examination of microtomed sections derived from 
artificially inoculated roots revealed an exactly similar invasion of the 
tissues to that seen in the field material. Tlie bacteria abounded in 
the intercellular spares of the inner tissues; occasional parenchyma 
cells were densely filled with bacteria, whereas the peripheral tissues were 
intact. 

Separation ok thk Bacteria from their Products. 

The separation of the by-|)roducts from the bacteria was then 
attempted. A two-litre flask containing a little water and sterilized by 
intermittent steaming was half filled with sterile blocks of turnip, a 
diseased block from a test-tube dropped in, and the flask quickly plugged. 
After four days' incubation at 20° the whole of the contents had been 
reduced to a pulpy putrid mass with a highly offensive odour. This was 
pressed through a piece of coarse linen and the turbid filtrate passed 
through filter-paper. The grey-coloured liquid was then divided into 
two portions — one portion was passed through a Berkefeld filter which 
had been sterihzed for several hours in the hot-air oven and allowed to 
cool. The clear pale yellow filtrate was poured into a number of small, 
sterile test-tubes and corked with sterilized rubber bungs. To the other 
portion was added four times its bulk of 80 per cent, alcohol. After 
24 hours a heavy flocculent precipitate had been formed. The super- 



8. U. Jones 301 

natant liquid was then siphoned out, the precipitate collected and 
washed with absolute alcohol. After careful drying in the incubator at 
20° it was digested in 100 c.c. of sterile distilled water for three hours. 
The liquid was then passed through the Berkefeld filter. A clear pale 
yellow filtrate was again j^roduced and poured into a number of sterile 
tubes plugged with cotton-wool and protected by rubber caps. The 
action of the two filtrates upon living turnips was then tried in the 
following way. Thin sections of turnips were placed in small petri- 
capsules, into some was poured the filtrate obtained from the pulp, into 
others the filtrate from the watery digest of the alcohohc precipitate. 
Other capsules coiatained sections in sterile water. Microscopic examina- 
tion after 24 hours showed no differences between several preparations 
mounted and the control sections from the sterile water and examination 
again after several days showed no change in the appearance of the 
sections. Twelve tubes of the filtrates from both sources were employed 
upon the sterile turnip sections without any signs of loosening of the 
cells. The action of the filtrates upon a 1 per cent, starch solution was 
then tried, but the blue coloration after adding iodine still remained 
even after prolonged action. Tf an enzymic jiroduct capable of separating 
the parenchyma of the turnip was present in the diseased pulp, its power 
of action seemed to have been destroyed in the filter. A new series of 
experiments on similar lines was performed using a Muencke bacteria 
filter. This filtrate was again ineffective in loosening the tissues. The 
filtrates obtained from the watery digests of the alcohohc precipitates 
obtained from both bouillon and glucose-bouillon seemed to be quite 
inert in their action on the tissues. The use of the porcelain filters was 
then discontinued and the alternative method tried of treating the 
bacterial products with antiseptics. A solution of chloroform was em- 
ployed. The culture treated was the turbid filtrate obtained directly 
from the putrid mass formed from diseased turnip. The coarser portions 
of the pulp were removed as before by pressing through a cloth and 
merely filtering the liquid through filter-paper. An equal volume of the 
chloroform solution was then added to the filtrate and the flask vigorously 
shaken at frequent intervals. To determine the sterility of the product 
inoculations into tubes of nutrient gelatine were taken and poured into 
petri-dishes. At the same time thin sterile sections of turnip were 
treated with the product. After 24 hours" immersion the tissues had 
become disintegrated and further the poured plates were sterile. 



302 .1 Bart I' r ltd Disease 0/ Turnip (Brassica Napns) 

Characters of the Organism. 

Habit. Causes a whitish-grey rot in turnip. 

Morphology. Bacteria l-3ju, to 3fi x -lofi to •9/x with a single 
polar flagellum. On sugar-rich media it forms long, unequally seg- 
mented filaments. 

Relation to Oxygen. Evidence for aerobism: Large surface colonies 
and rapid growth on the surface of the media, buried colonies small; 
gelatine stab funnel-shaped: rapid decay of turnip in the cotton-plugged 
flasks and tubes. Evidence for anaerobism: Slight growth on recently 
steamed agar-slopo tubes cultivated by Buchner'.s method for anaerobes; 
general turbidity in liquid media enclo.sed in Durham and Fermentation 
tubes; growth in gelatine stab after sealing mouth of track; decay of 
turnip blocks in a sealed flask. 

Growth on Gelatine Media. Surface colonies large, round, whitish- 
grey, margin fibrillated. Liquefies gelktin; stab-culture funnel-shaped 
in 24 hours, spreading to wall of tube in 48 hours, liquefaction nearly 
complete. Li the sealed track liquefaction not complete. Colonies on 
litmus-lactose and litmus-glucose-gelatine produce faint pink margin; 
on chalk-lacto.se and chalk-glucose-gelatine, hyaline ring; ])oor growth 
on acidified medium. 

Growth on Agar Media. Surface colonics round or sliglitly lobed, 
opalescent; sometimes spreading, filmy areas formed; deep colonies oval 
or spindle-shaped. Growth on agar-streak spreading and filmy. Good 
growth along agar-stab, spreading at surface. Colonies on litmus-lactose 
and litmus-glucose-agar produced jiink rnnigiii; or clialk-lacto.se and 
chalk-glucose-agar hyaline border. 

Growth i.v Bouillon. Rendeivs bouillon turbid, forming a heavy 
sediment; no pellicle; maximum turbidity in neutral and feebly alkahne 
broth; neutral reaction to litmus; with 2 per cent, glucose, lactose, and 
cane-sugar turbidity in open and closed ends of Durham and Fermenta- 
tion tubes, producing acid reaction without evolution of gas. In Pasteur's 
solution with cane-sugar turbiditv only in open end of tubes. 

Growth in Nitrate Solution. In Giltay and Aberson's culture 
fluid strong nitrite reaction after 24 hours with iodine-sulphuric-starch 
test, with formation of ammonia (Nessler's Test). Heavy sediment formed 
and film on surface of culture. Control tubes gave neither reaction. 

Growth in Nitrogen- Free Solution. No turbidity; after seven 
days, petri-cultures in gelatine inoculated from it produced very few 
colonies. Growth therefore feeble. 



8. (r. Jones 



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21 



304 .1 BdrtirldJ Disra.^r of Turin'/) (Brassica Napus) 

PARAisiTisM. Produces a soft -rot in swede, potato, carrot, radish 
and cabbage. No growth on beetroot. 

Ferments. Pectinase ; diastatic and peptonising ferments produced. 

Re.\ctiox of Bv-PROnrcTS. Diseased pulp neutral or feebly alkaline; 
bouillon neutral; acid produced in sugar media: production of ammonia 
in the vegetable media. COg evolved from diseased pulp. 

Reaction to Stains. Stains easily with various auilin dyes and by 
Gram's method. With Loeffler's flagella stain, one pole hyaline. 

rONCLUSION. 

While tlie organism under consideration has many characters in 
common with Pseudomonas campestris (Smith) and with Bacillus 
Oleracea (Harrison) it is clearly most nearly related to Pseudomonas 
destructans (Potter). The writer is of opinion that it is a varietal form 
of the latter. Of the differences mentioned in the table the most striking 
is the mode of attack of the disease while the root retains its shape, 
with the rind firm and the mature foliage healthy. 

This investigation was carried out in the Laboratory of Agricultural 
Botany, University College, Bangor. It was taken up at the instance 
of Prof. J. Lloyd Williams (formerly Adviser at Bangor) who had ob- 
served this disease on farms in North and South Carnarvonshire, but 
his enquiries in the other Counties failed to bring to light any other 
instances of its occurrence, although many cases were observed of other 
rots of swede and turnip. To him the writer wishes to express great 
indebtedness for guidance and kindly ad\'ice and also to Professor 
R. G. White by whose courtesy he had access to the ].,aboratory and 
the College Farm. 

LITERATURE. 

(1) Caeruthers and Smith. Journal of Botany, 39 (1901). 

(2) GnuNGHAM, C. T. Formation of Calcium Carbonate by bacteria in the soil. 

Journ. Agric. 8ci. 4. 

(3) Johnson and Adams. Bacterial Kot in Turnips and other Brassicas in Ireland. 

Economic Proc. of the Royal Dublin Society, 2, Xo. 1. 

(4) Potter, M. C. («) On a bacteiial disease of the Turnip (Br. Xapus). Proc. of 

Royal Hoc id y. 67. 

(b) On the parasiti^^m of Pseudontoiias deslructan.s. Proc. of 

Royal Society, 70. 

(c) A brief review of Bacteriological Research in Phytopathology. 

Science Progress, 5. 

(d) Bacterial diseases of Plants. Journ. of Agric. Sci. 4. 

(e) Brown Rot of Swedes. Journ. of Bd. of Agric. 10. 

( / ) On a method of checking Parasitic Diseases in Plants. 
Journ. Agric. Sci. 3. 



JOURNAL OF AGRICULTURAL SCIENCE. Vol. XII. Part 



PLATE 111 




-t -^,_ * , 




F.g. 2 



e 








-'*««>-" 




* I 




Fig. 3 



8. (i. Jones 305 

(5) Pkiestley and Lechmere. A bacterial disease of Swedes. Joiirii. A(iric. Sri. 3. 

(6) Smith, Erwin F. Bacteria in Relation to Plant Diseases (Washington), 1, 2 and 3. 

(7) Taylor, T. H. Cabbage Top in Swedes. University of Leeds and The Yorkshire 

Council for Agricidlnral Education, No. 82. 



EXPLANATION OF PLATE IIL 

Fig. I. Diseased turnip with tlie young foliage of tlie growing point absent. Tiie plant 
had been left in the open and only removed at the time of winter ploughing. The 
rind had liecome hard, dry, and cracked. A small quantity of the shrunken pasty 
mass is shown. 

Fig. 2. Appearance of the crown of a plant with six secondary shoots. The aperture 
enclosed by them is surrounded also by leaf scars, which evidently belonged to the 
decayed apical bud. 

Fig. 3. Sections across the leaf-crowns of diseased plants. 



{Received June I'dlh, 1922. 



21—2 



A NEW METHOD FOR THE MECHAXTCAL 

ANALYSIS OF SOILS AND OTHER 

DISPERSIONS. 

By gilbert WOODING ROBINSON, M.A. 

Adviser in Agricultural Chemislry, University College 
of North Wales, Bangor. 

Introduction. 

Attention has been given of recent years to the possibility of devising 
methods of mechanical analysis which shall express the mechanical 
composition of a soil or clay by a continuous curve. The standard 
methods of mechanical analysis, as for example that followed in England, 
can of course be used to obtain such curves, but with the comparatively 
small number of fractious separated, very little detail can be inserted. 
Any multiplication in the number of fractions nnist ine\'itably be 
attended by an increase of experimental errors, and the problem must 
therefore be attacked by other methods. 

Od^n has devised an elegant method whereby the mechanical analysis 
of a soil or clay can be derived from an experimental curve showing the 
rate of accumulation of sediment from a column of material in sus- 
pension^. The weight of material is automatically registered from time 
to time and from the curve obtained a mass distribution curve is derived 
which gives a detailed representation of the composition of the material 
under examination. Wiegner'" has applied the theoretical principles of 
the Oden method in a very simple apparatus consisting essentially of 
a U-tube system in which a column of sedimenting suspension is balanced 
against a column of pure water. As the material falls below the point 
at which the water tube joins the fall tube, the specific gravity of the 
suspension decreases, resulting in a corresponding fall in the water 
column. The lieight of the water column is read from time to time and 

» Int. Mitt. Bodenkunde, 191"). 5, 2.57-311 : Koll. Zeit. 19U), 18, S.-J-^tS; Tram. Faraday 
Soc. 1922, 17. 327-348: Nefedof, ./. Exp. Lanilw. 1902. 3, 421-449, (nitlin.s a method 
similar in prinriple to that of Oden. but apparently purely empirical. 

• Lantlio. Vrrstirh.i SIfnf. 1918,91,41. 



G. W. Robinson 307 

by appropriate calculation the experimental results can be thrown into 
the form of curves similar to those obtained by Oden's instrument. Both 
Oden's and Wiegner's methods have found apphcations in the study of 
dispersions 1. 

A serious drawback to Oden's apjaaratus is its expense. While it is 
of the highest value for the critical investigation of comparatively small 
numbers of samples, it can hardly come into use for routine work as 
the resources of an ordinary provincial institution would scarcely be 
equal to the outlay involved in setting up more than one such instru- 
ment and only comparatively small numbers of soils could be dealt with. 
Wiegner's apparatus is cheaper and could b}' modifications^ be made to 
give results of considerable accuracy. But here the time factor is serious. 
Using, as is necessary, a column about a metre long, several days would 
be required to obtain information as to the finer fractions which exert 
such an important effect on the properties of the soil. 

In the present work the writer has attempted to devise a method 
capable of giving more detailed data than the ordinary sedimentation 
methods and which, though not giving continuous curves, avoids the 
drawbacks of the Oden and Wiegner methods and can be used for 
standard mechanical analysis with great saving of time. 

Before discussing the new method of mechanical analysis a few 
remarks may be made on the expression of mechanical composition by 
means of curves. The simplest method of expressing the results of a 
mechanical analysis is to plot summation percentages* against particle 
sizes. Such a method is however almost useless in the case of highly 
dispersed substances, because in order to show the complete range the 
most characteristic particle sizes are cramped together near the «/-axis. 
A better distribution will be obtained by using the logarithms of particle 
sizes. The end of the curve corresponding to zero size is of course at 
— 00 but in practice a very manageable type of curve will be obtained^. 

Since the separation of particles of diameter smaller than -2 mm. is 
universally based on the principle of subsidence, whereby fractions are 
distinguished by their different setthng velocities in water, there are 
good reasons for using logarithms of setthng velocities instead of 
logarithms of particle sizes. In the ensuing treatment this method is 
used, the velocities being calculated in ordinary c.G.s. units. The same 

1 Roll. Zeit. 1920,26. 100-121; ibul. 1920,26, 121^138. J. Landw. 1921, 69. 5-32. 

- As for instance in the method of reading the lieight of the water column. 
' i.e. percentages of material of a given particle size or smaller. 
* Ct. Whittles, /. Agric. Sci. 1922. 12, 166-181. 



308 Michdnlral A/iali/s!s of Soils ttiid otiter DispevslouK 

type of curve will be given and it will diispense with any assumption as 
to the size, shape and density of the settling particles. 

In this connexion, the probable effect of the gel coating which has 
been postulated for the finer particles of a soil or clay on the sedimen- 
tation of such material is worthy of consideration. It has been suggested 
that such coatings are not to be considered as uniform and discrete but 
as concentric shells of increasing degree of hydration. As an approximate 
basis of calculation let us assume that the emulsoid coating has the 
same density as the water in which the particles are suspended. What 
vnW be the effect of this coating on the settling velocity? If a be the 
radius of the falling particle and d the thickness of the gel coating or 
shell, then the velocity of fall of the particle in the absence of any coating 
is given by 

using the usual notation and assuming the density of water = 1, and 
the velocity of the coated particle by 

_2 gja + dy- 

where p^ is the mean density of the coated particle. 

weight of particle + shell 
volume 

|7ra»p + |7r[(a + df - a'] 



weight of particle + shell 

Now pi= — - -.. 

'^ volume 



fn{a+df 
a^p + [(a + df - o»] 



{a + df 

_ 2 g{a + df \a?p + [(a + rf)3-a'] _ ] 
lli.n ^^__. _ .^ - \a + df j 

^2 flr a ^(p-l) 
9'ij' a+d ' 

v^a + d 

" Vi a ' 

a 
or i"o = V, 



a+d' 

It will be seen that the presence of a coating of appro.vimatcly the 
same density as the suspension medium will have a marked effect on 
the velocity of fall. The low velocities corresponding to the finer fractions 



G. W. Robinson :]09 

will thus be conditioned not simply by the actual particle sizes but by 
the magnitude of the gel coating. The writer hopes to return to this 
point in a later paper. In the meantime it is suggested that the left 
hand portion of the curve in the case of clay soils may relate to such 
coated particles rather than to particles bounded by a sohd surface. 
By using log v instead of log particle size, the necessity for a decision 
as to the significance of these small velocities is postponed. 

It is of course obvious that the expression of the mechanical com- 
position of a soil or clay by a curve of this type offers a way out of the 
appalhng confusion created by the diversity of conventions used in 
different countries. Since practically all the methods in use are based 
on the principle of sedimentation, curves can easily be obtained if the 
settling velocities are known. Whether the principle is applicable to 
methods in which separation is effected by currents of water of varying 
velocity, as in the Hilgard method, the writer is unable to decide. As 
a first appro.ximation, it would appear that the method is applicable. 

We have assumed that the viscosity coefficient in the Stokes' equation 
is constant. With varying temperatures this is of course not the case. 
This difficulty can however easily be solved if a standard temperature 
be adopted, say, 15° C. By putting the viscosity coefficient of water at 
that temperature equal to unity and calculating the viscosities at other 
temperatures'^ with reference to this, the correction can be applied. Thus 
if results obtained at var3dng temperature are to be compared, it will 
be necessary to use log (v x specific viscosity) instead of log v. 

Theory of New Method. 

A fundamental assumption underlying all methods of mechanical 
analysis by sedimentation is that particles in a column settle inde- 
pendently of each other. That there are Hmits to this assumption is 
obvious. According to Oden this condition is fulfilled in suspensions of 
concentration not greater than 1 per cent.'^ Wiegner, on the other hand, 
brings evidence to show that concentrations of more than 5 per cent. 
can be used without serious inaccuracy, which may be due to the 
dangerous principle of compensating errors. 

Let us assume a suspension of soil or other granular material to 
consist of a number of fractions, a, b, c, etc., each uniform in itself, 
having hmiting velocities, i\, i\, v^, etc., respectively, and present in 

' For the effect of temperature on the viscosity coefficient of water, see Hosking, 
Phil. Mat). 1907, 17. 509; ihid. 1909. 18, 260. 
- Int. Mia. Bodenlninde, 1915, 5, 276. 



310 Mechanical Anah/'n's of Soils and other DinpevHlmis 

concentrations, A^, A^, A^. etc., respectively such that "ZA = C'^, the 
total concentration. Then if the fractions settle independently of each 
other, each fraction will behave as a separate column uniform in con- 
centration from top to bottom and we may represent the state of affairs 
at the beginning of sedimentation as in the upper diagram of Fig. 1, 
the relative amount or partial concentration of each fraction being 
represented graphically by the thickness of its column on the diagram. 



b 



{ 



B 




Fig. 1. Diagrammatic representation of sedimentation. 

As sedimentation proceeds each column will fall bodily at its own 
appropriate velocity and the disposition after settling has proceeded for 
a certain time may be represented by the lower figure of the diagram. 
The black portion below the line CD will represent the amount of each 
fraction accumulated on the bottom of the sedimenting vessel, while 
the concentration of the suspension at any depth will be given by the 
total width of columns at that depth. Thus at depth d, the concen- 
tration will be equal to the sum of the partial concentrations of the 



' Or Zi.-l + organic n\nftpr = C in the rase of nrdinarv Hiiila. 



Gr. W. Robinson 



311 




fractions, a to e, having velocities less than d/t. The ratio of the concen- 
tration at depth d after time t to the total concentration at the beginning 
of the experiment will thus give the proportion of material having 
velocities less than d/t. By determining the concentration for diilerent 
values of djt the data are obtained for a summation curve showing the 
relation between percentage of material and log setthng velocity. 

Experimental. 

The method used consists in allowing a soil suspension of known 
concentration to settle in a cyhndrical vessel and withdrawing samples 
for appropriate values of depth/time. By suitable choice of depth and 
time the concentration and hence the percentage of particles 
corresponding to any desired velocity can be obtained. 
Generally speaking a htre measuring cyhnder about 40 cm. 
in height and 6 cm. in diameter is used. There is of course no 
necessity to use a graduated vessel: any cyhnder of uniform 
cross section and suitable dimensions may be used. Samphng 
of the suspension is carried out by means of a 20 c.c. pipette 
passed through a cork or shive and adjusted so that when 
the cork rests on the top of the cyhnder the point of the 
pipette is at the desired depth below the surface of the hquid 
(see Fig. 2). The column having settled for the required time 
the pipette, previously adjusted for depth, is closed at the top 
with the finger, in order to avoid samphng the upper layers, 
and lowered very carefully till the cork rests on the top of 
the cyhnder. The finger is then removed and 20 c.c. of the 
suspension withdrawn. Every precaution is of course taken 
to avoid shaking or mixing the layers of the suspension at 
the point of sampling. With a column of the dimensions 
mentioned the withdrawal of 20 c.c. causes a fall in level 
of about 7 mm. This probably represents the extreme error 
in samphng. It is assumed that the 20 c.c. of suspension withdrawn 
represents the concentration at the point of the pipette. Probably the 
liquid comes mainly from above, but to some extent from below this 
point. A separate experiment with a column which had settled for 
several weeks and which had formed clearly defined strata, showed that 
it was possible to pipette to within 2 to 3 mm. of a stratum without 
disturbance. It will be shown later that an error of a few milhmetres 
in samphng involves a neghgible error in the final result. Careful manipu- 
lation is of course necessary in this operation. The 20 c.c. of suspension 

21—5 



Fig. 2. 
Method of 
sampling. 



312 Mechanical Aufdi/sis of Soils and other Diapermnis 

is delivered into a fiat porcelain dish wliich lias been previously ignited 
and weighed. Dishes ordinarily used for the estimation of total solids 
in milk are convenient for the purpose. The sample is taken to dryness 
on the water bath and, if the estimation is to be made on unignited 
material, weighed after attaining constant weight. Ordinarily it is 
ignited in a muffle, an operation which only takes a few minutes at red 
heat, and weighed after coohng in a desiccator. From the weight of 
ignited material the concentration of the sample of suspension is calcu- 
lated. By sampling in such a way that successively smaller values of 
depth/time are used, the same suspension may be shaken up and sampled 
over and over again. The partial concentration of any fraction at a 
given depth is unaltered until the top of the fraction column has sunk 
below that depth, as will be seen by reference to Fig. 1. The removal 
of a sample of suspension does not therefore aiiect the concentration of 
the suspension with respect to fractions of smaller velocities. 

In an actual experiment a 2-5 per cent, suspension of a clay was 
prepared by shaking up 100 grams of powdered clay for 24 hours with 
2 litres of water containing 100 c.c. of 1 per cent, sodium carbonate 
solution and making up finally to 4 litres. A litre cylinder was then 
filled to within 3-4 era. of the top with the well mixed suspension and 
after again shaking for a minute, allowed to stand for six minutes. 
A 20 c.c. sample was then withdrawn at 36 cm. depth as described above. 
After drying and ignition, the weight of ignited material was found to 
be -376 gram. Subtracting -005 gram for the amount of sodium car- 
bonate in 20 c.c, we have the nett weight of ignited material as -371 gram 
and the concentration of the suspension at the point sampled, 1-855 
per cent. The original concentration being 2-5 per cent., we find that 
the concentration of the suspension at 36 cm. after six minutes is 

r855 

•jr~^ X 100=74-2 per cent, of the original concentration. In other 

words 74-2 per cent, of the clay, reckoned as ignited material, has a 
settbng velocity less than -1 cm. /sec. Other determinations were made 
for successively smaller velocities and the residts are set out in Table I. 
For the sake of brevity the w-eight of ignited material is given after 
subtraction of the -005 gram of .sodium carbonate. 

In Fig. 3 cui-ves are shown for the clay of the experiment just 
described and for a few other ty})ical clays and soils. The vertical dotted 
lines, ^I, B, and t', are the ordinates corresponding to clay, fine silt, and 
silt, respectively, according to their settling velocities in the Enghsh 
method. In order to bring the fine sand, coarse sand and fiiie gravel 



G. W. Robinson 



313 



Table I. London Clay. 2-5 per cent, suspension in -025 per cent, 
sodium carbonate solution. Temperature 12-1G°. 











Ignited 




%of 










material 


Concen- 


original 


Time 


Deptli 


Velocity 




in 20 c.c. 


tration 


concen- 


sees. 


cms. 


cm./sec. 


log V 


gms. 


u 

/O 


tration 


360 


36 


•1000 


1^0000 


0^371 


b855 


74-2 


600 


20 


•0333 


2^5227 


0^358 


1-790 


71-6 


600 


6 


■0100 


20000 


0325 


1-625 


65-0 


6000 


20 


•0033 


3^5227 


0^293 


1-465 


58-6 


6000 


6 


•0010 


3^0000 


0252 


1-260 


.50-4 


60000 


20 


■O0033 


4-.5227 


0^220 


1100 


44^0 


60000 


6 


•01 1010 


4^0000 


0^178 


0-890 


356 


600000 


20 


■000033 


.^•5227 


0135 


0-675 


270 


600000 


6 


•000010 


5^0000 


0093 


0^465 


18-65 



100 




5 Log (' 3 1 1 3 

Fig. 3. Summation Curves showing Composition of Typical Soils and Clays. 



314 Mechanical Analysis of Soils and other Dispersions 

into the diagram, their velocity values were calculated on the assump- 
tion that they obey Stokes' law and that the diameter of particle repre- 
sented by the upper limit of the silt is -04 mm. The lines thus obtained 
are D, E, and F, respectively and are inserted for the sake of com- 
pleteness. By taking into account the coefficient of viscosity and using 
glycerine-water mixtures, these points on the di.stribution curve might 
be obtained by the above method. It is however simpler to use the 
sieve method to fill in the right hand portion of the curve. It may be 
added that the data of an ordinary mechanical analysis are given 
graphically by the difference between successive intercepts on the 
ordinates A, B, C, etc. For example the fine silt is given by the difference 
between the intercept on B and the intercept on A, the silt by the differ- 
ence between the intercept on C and the intercept on B and so on. 

By suitable choice of depths and times any required degree of detail 
can be secured in any part of the curve. If a large number of points 
are required it is convenient to prepare a large volume of suspension 
and work with a number of separate cyhnders. The details may be left 
to the convenience and ingenuity of individual operators. Possibly a 
more convenient, though scarcely less expensive, method of sampling 
may be devised. Any measurable physical property of dispersions which 
depends on concentration may be considered in this connexion. For 
very dilute suspensions it is possible that a nephelometric method might 
be devised. 

The method may find its best use as a substitute for the present 
standard method of mechanical analysis. The suggested procedure in 
this case is as follows. The air dried sample is treated with A'jb hydro- 
chloric acid exactly as in the ordinary method, using however 20 grams 
instead of 10 grams of soil. The fine gravel and coarse sand are separated 
in the ordinary way and the finer material passing the 100 mesh sieve 
is shaken with 600-700 c.c. of water and 50 c.c. of 10 per cent, ammonia 
in an end over end shaker for two to four hours, the longer period being 
necessary in the case of soils with much organic matter. After shaking, 
the suspension is made up to one Utre, which is equivalent to 2 per cent., 
reckoning on the original material. The following determinations are 
then made successively by the method described above. 



JtelJth 


Time 


Velocity 


Giving 


cm. 


hrs. 


min. 


cm./sec. 


percentivjie of 


(o) 30 





5 


01 


silt + fine silt + clay 


(6) 12 





20 


001 


tine silt + clay 


(c) (i 


16 


40 


00001 


clay 


or 7-2 


20 


■ 






or 81) 


24 










(4. W. Robinson 315 

Lastly to determine the tine sand, the suspension remaining after 
the last sampUng is poured away to about 200 c.c. without shaking up 
the sediment. The remaining suspension and sediment are then washed 
into a beaker and the fine sand determined by the ordinary method, 
using the 10 cm. and 100 seconds, or 7-5 cm. and 75 seconds sedimen- 
tation. 

The following figures are the results of an actual determination on 
a Pennant Grit soil from CTlamorganshire : 

By ordinary method Fiue gravel ... ... ^'6% 

Coarse sand ... ... 20-1 

Moisture ... ... 4-2 

Organic matter ... ... 10-2 

Total 391 

So that fine sand + silt + fine silt + clay should = 100 - 39'1 =60-9 (1). 

By new method, using 2 "(, suspension. 

For 5 mins. and 30 cm., weight of ignited material iu 20 c.c. = -112 gm. 
Therefore concentration =5 x -112 = -560 %. 

Therefore silt + fine silt + clay = '^-^^''-^-°^ = 28-0 % (2). 

Similarly for 20 mins. and 12 cm., ignited material = -065 gm. 

Concentration = -325 % and fine silt + clay = =16-25 % (3). 

Similarly for 20 hrs. and 7-2 cm. ignited material = -019 gm. 

Concentration =-095 % and clay = ," =4-75 % (4). 

Subtracting (4) from (3). fine sat = ll-5 %. 

Subtracting (3) from (2). silt =11-7.5 "o- 

Subtracting (2)from (1) fine sand = 32-9 %. 

By direct sedimentation at end of e.xperiment, tine sand = 32-5 %. 

Effect op Variations in Conditions of Working. 

In order to form some idea as to the latitude allowable in the con- 
ditions of working the following points were investigated. 

(«) Effect of concentration. A number of determinations were made 
on a clay suspension of varying concentrations. Results are given for 
different times and depths. 



Depth 6 cm. 
Time 10 mins. 



Concentration 


Percentage 


of original 


of original 


suspension 


concentration 




1 -50% 


63-0 




-625 


61-0 




1-00 


620 


1. 1 


2-00 


63-2 


ns. ! 


2-50 


64-0 




4-00 


63-1 




'5-00 


65-7 



316 Mechanical Analysis of Soils and other Dispersions 

i -50 530 

Depth t3 cm. 1 100 51-5 

Time 100 mins. 'i 200 52-2 

1 400 490 

„ .,1- (100 450 

Depth lo cm. 2-00 44-2 

T.mr 240 mms. ] g.^,, ^g.3 

,, ,, , f 100 37-5 

Depth 7 cm. \ gg.^, 

T,.ne 27 hours | g.^^ ^,._ 

The variations in the results obtained with varyin<; concentrations 
are not serious when the nature of mechanical analysis and the nature 
of the material under examination is taken into account. In the standard 
Phighsh method the concentration used is about 2 per cent. In \'iew of 
the small weights to be dealt with in very dilute suspensions and the 
consequent magnification of weighing errors, it was decided to use 
2 per cent, suspensions as a general rule and in the comparisons given 
later of the results by the new method with those by the old method, 
this concentration was used. 

(h) Diameter of column. The diameter of the column may be ex- 
pected to have some effect on the result obtained since, apart from any 
boundary effect, the fall in height due to the removal of liquid will be 
greater in narrow columns. The following experiment senses to test 
this point. 

Chiy suspension 25 %. Time 19-5 hrs. Dejjth 9 em. 

Diameter of cvlinder Weight of ignited material 
7-7 cm. -102 gm. 

60 -101 

4-6 102 

3-4 098 

The last cylinder was an ordinary 250 c.c. measuring cylinder. It 
would appear that with J litre, litre and 2 litre cylinders consistent 
results may be obtained and that the diameter of the cylinder is im- 
material. In general, a litre or \ litre cylinder was used. 

(c) Equivalence of Depth/Time ratio. Theoretically the same con- 
centration should be obtained for different times and depths provided 
that the ratio depth/time, i.e. the hmiting velocity is constant. This 
point is investigated in the following experiments. 

Kaolin. 2-5 % suspension in -025 "„ sodium carbonate. 

Weight of ignited 

Depth Time material 

cm. hours gra. 

5 5 -165 

19-5 19-5 169 

Clay. 2-5 % suspension in -025 % sodium carbonate. 

4 1 -254 
12 3 253 

5 18-75 -178 
18 68 177 



G. W. Robinson 



:n7 



{d) Errors Id Depth of Saniplijuj. Tlie effect of errors in depth of 
sampling may be best demonstrated by considering the nature of the 
vertical concentration gradients in a column of suspension after varying 
times. A series of curves showing the relation between depth and con- 
centration for different times can readily be derived from the summa- 
tion curve for the material under consideration. For example if it be 
known from the summation curve that 50 per cent, of the material has 



100 




2 





2 Lot; V 


20 


30 


40 im. 
L)c|itli 



Fig. 4. Concentratiiin Gradients at Different Ueptlis. 

a limiting velocity less than -01 cm. per second (log v = 2-0000), then 
at depth 10 cm. after 1000 seconds, the concentration will be 50 per 
cent, of the original concentration. A series of concentration gradients 
for a clay is shown in Fig. 4. AB is the summation curve and the 
curves I. II, III, IV, and V give the percentages of the original concen- 
tration at different depths for 10 sees., 1 min., 10 mins., 100 mins., and 



318 Mechcuiical Anali/six of Soils and oflirr Dixpersioiu 

1000 mins. respectively. The log f abscissae refer of course to the 
summation curve AB. and tlie depth abscissae to the concentration 
curves. 

It will he seen that the change in concentration witji depth after 
any given time is very gradual below the first few centimetres. Thus, 
after ten minutes, the concentration in the case illustrated only changes 
about 2-5 per cent, of the total concentration between 10 cm. and 
20 cm. With longer times the gradient becomes rather steeper. Errors 
of the order of a few millimetres in depth of sampling have thus very 
little effect on the concentration obtained. This of course only holds 
so long as the material under experiment has a fairly smooth summation 
curve. With a material having an irregular type of curve, depth errors 
might be more serious. 

Similar considerations can be developed for the time and tem- 
perature error. 

The errors introduced by the above variations in working conditions 
though scarcely negligible are nevertheless not serious when the character 
of the material is considered and it may be doubted whether they are 
of significance from the point of view of the genetics and physical pro- 
perties of soils and clays. The Oden method is of course less exceptionable 
from the point of view of delicacy and must be used where critical data 
are required. The method described in the present paper could of course 
be made to give results strictly comparable among themselves. It is 
however desirable to have a method which can admit of some latitude 
to suit the convenience of individual worlvcrs and which has to that 
extent and within reasonable limits the character of an absolute method. 

Agreement with Re.sults obtained by the Standard Method. 

In view of the enormous number of results accumulated by the older 
method, it would be a doubtful advance to suggest a new method, even 
though more convenient and accurate, if the results obtained by it could 
not be used for comparison with the older results. A considerable number 
of determinations were therefore made by the new method and the 
results compared with those already obtained by the old method. In 
the following table the residts of this comparison are given. For con- 
venience of statement only three values are given, namely, clay, fine 
silt, and silt. The same method of dispersion was used throughout except 
in the case of certain clays, which contained practically no organic matter 
and were dispersed in -02.5 per cent, sodium carbonate. 



(1. W. Robinson :119 

Table II. Comparison of Results hi/ Old and New Methods. 

Silt 



fcloil or 




Clay 


Pine silt 

A 


clay 


OlcT 


New 


01(1 


New 


A 43 A 


9-5 


10-8 


26-8 


26-8 


A 55 A 


10-5 


101 


21-7 


21-7 


F2B 


29-0 


28-7 


340 


34-0 


D44A 


3-5 


5-9 


381 


38-0 


G8 


13-3 


16-6 


240 


20-0 


D 10 


13-9 


13-6 


57-6 


57-9 


C34 


3-9 


4-0 


13-6 


13-5 


Dll 


2-7 


3-8 


14-6 


14-4 


D73 


5-8 


2-4 


22-6 


22-2 


D49 


20 


2-2 


12-2 


9-3 


Llangoed clay 


43-4 


48-4 


30-7 


30-8 


Ruabon 


25-8 


23-2 

(38-2 


44-4 


44-4 

(26-4 


London clay 


400 


37-2 
(38-4 
[24-2 


22-6 


2G-4 
(27-4 
(46-8 


Kaolin 


235 


^23-6 

I23-8 


48-4 


46-4 

(47-2 




(110 


121 


245 


28-7 


Ab. 4 


^10-5 
(l3-0 


11-75 


26-0 


26-5 




130 


25-9 


26-2 



Old 


New 


150 


15-0 


131 


13-2 


20-9 


20-R 


15-8 


15-9 


18-4 


18-4 


9-3 


9-2 


100 


100 


7-2 


70 


131 


17-4 


8-2 


120 


3-9 


3-9 


17-5 


17-4 




fl2-6 


11-7 


13-4 




12-4 




16-2 


13-7 


• 17'8 




15-8 


17-7 


180 


18-7 


17-3 


lS-5 


17 3 



The agreement between the two series of results is generally close 
and not unsatisfactory when it is considered that mechanical analysis 
by the older method is hable to considerable errors. On the average, 
putting the figures obtained by the old method as 100, the new method 
gives 102-7 for the clay, 100 for the fine silt and 99-6 for the silt. It 
would thus appear that there is no appreciable constant error in com- 
paring results by the two methods. In view of the large number of 
manipidations recj^uired in the old method, there are more occasions for 
error than in the new , and any serious disagreement is at least as likely 
to be due to errors in the former as in the latter method. 

It will be noticed that the most serious disagreements are in the case 
of light soils. To secure a perfect comparison it would be necessary to 
secure that the prehminary dispersion is exactly the same in both 
methods. In the standard method the material is repeatedly triturated 
after each pouring off. The method provisionally adopted for dispersion 
in the new method, namely a 2 to 4 hour shaking in an end over end 
shaker would appear to give a comparable degree of dispersion. The 
longer period is apparently necessary in the case of soils rich in organic 
matter. Dispersion by sodium carbonate^ gave good results with raw- 
clays but was unsatisfactory with soils containing much organic matter. 

1 Cf. .Joseph and Martin, ./. Agnc. Sei. 1921, 11, 29,3-303. 



320 Mechanical Aualiisia of Soils and other Dispersions 

Conclusion. 

The method of mechanical analysis above described has two recom- 
mendations. It is more expeditious and economical than the standard 
method. Granted that the new method gives reliable results, its adoption 
would remove one of the (gravest objections against the jiresent method, 
namely its laboriousness. With the new method it has been found 
possible in the writer's laboratory to carry out six mechanical analyses 
in a day. With pro])er organisation there should be no difficulty in 
carrying out 35-40 analyses in a week. Anyone familiar witli the routine 
of the older methods will realise that it would be impossible to deal witii 
such numbers single handed. There is the further consideration of 
economy in the use of beakers, filters, etc., to say nothing of the dis- 
tilled water, ammonia and hydrochloric acid required. On the other 
hand the suggested method requires careful manipulation. Working 
with 2 per cent, suspensions, an error of 1 mgm. in weighing corresponds 
to -25 per cent, in the result obtained. It is doubtful if the method would 
commend itself for teaching purposes. 

The new method mav be used within limits for obtaining continuous 
curves such as are obtained by the Oden and Wiegner methods. Pro- 
vided temperature conditions are controlled it is easily possible to carry 
the distribution curve for a soil or clay considerably beyond the limits 
of clay as defined by the standard method, and the constitution of the 
finer fractions can thus be investigated over ranges hitlierto scarcely 
explored^. An application may also be found in the investigation of 
changes in degree of dispersion consequent on manuring, cultivation 
and season. 

With regard to the errors of the method it may be remembered that 
the experiments recorded were carried out in ordinary measuring 
cylinders. These are rarely uniform in cross section. With perfectly 
cylindrical columns, no doubt, better results would be obtained. With 
regard to temperature effects, no attempt was made to secure rigid 
control of temperature conditions. As in the ordinary method, the 
settling took place in an ordinary laboratory \vith its unavoidable 
vicissitudes of temperature. Care was however taken to avoid the 
proximity of sources of heat. In certain cases where the settling columns 
were in the vicinity of radiating surfaces, unsatisfactory results were 
obtained. Generally speaking for the longer periods the columns were 

' A considerable number of clays have, in fact, been followed by this method as far 
as log 0= 7, which appears to be near the lower limit. 



a. W. Robinson 321 

put away in a large cupboard in a room without any burners or other 
sources of heat. The possibihty of convection currents was thus avoided 
as far as possible. 

By a suitable choice of depths and times the method could be readily 
adapted to systems of fractionation other than that in use in this country. 
In the American systems, where the numbers of fractions separated are 
large, the amount of work involved and the possibiUties of error are 
serious. The above method might be of use in such cases. By setting 
out the results as summation curves the mechanical analyses by any 
system of grading could be obtained by interjjolation. 

Summary. 

(1) The expression of mechanical composition by means of con- 
tinuous curves is discussed. It is suggested that a convenient repre- 
sentation will be obtained by showing summation percentage as a 
function of the logarithm of settling velocity. 

(2) The effect of a gel coating on the setthng velocity of a particle 
is examined and it is shown that a reduction in velocity takes place 
which is a simple function of the thickness of the gel coating. 

(3) A method is outhned by which the mechanical composition of a 
soil or clay is derived from determinations of the concentration of a 
settling suspension for different values of depth/time. 

(4) A shortened method for mechanical analysis is described which 
gives results in good agreement with results obtained by the present 
standard method. 

(5) The effect of various modifications in conditions of working is 
discussed. 

(6) The nature of the concentration gradients in a settling column 
of a suspension is examined. It is shown that below the first few centi- 
metres the change in concentration with depth is very gradual. 

(Received July 8th, 1922.) 



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Volume Xil 0CT013EK, 1922 Part IV 

- LiS i t.AKY 

NidW YOWC 
aOTAM tCAIL 

TEMPERATURE AND OTHER FACTORS AFFECTlNCi 
THE QUALITY OF SILAGE. 

By ARTHUR AMOS, M.A. 
AND THE LATE GWILYM WILLIAMS, M.A., N.D.A. 

(Schoul of Agriculture, Cambridge University.) 

Introduction. 

In 1883 Mr George Fry, F.L.S.^ described a series of observations which 
he had made upon silage. From these he drew the conclusion that if 
the conditions of silage making were such that the temperature exceeded 
45° C. sweet brown silage resulted, but that if the temperature failed 
to rise above 40° C. then sour silage with a rather repulsive odour was 
produced. These results were obtained in the type of silos then commonly 
in use, which varied in depth generally between 12 and 18 feet, frequently 
had a considerable surface area and were filled comparatively slowly. 

In 1884 Dr Augustus Voelcker, F.R.S.- confirmed Mr Fry's ex- 
perience with silage in the regulation and maintenance of a proper 
temperature and mentions 125° F. (51-o° C.) as being the point below 
which sweet or hay fermentation does not take place. He further stated 
that sweet silage keeps only a short time on exposure to air, whereas 
sour silage may keep {J-9 months exposed to air. 

In 1886, Dr J. A. Voelcker^ described the making of sweet silage by 
ensuring the temperature of fermentation rising to 122° F. = 50° C, 
"the point which Mr George Fry considers must be reached to get sweet 
silage."' 

M. Goffart^, however, is quoted as follows: "My maize, my green 
rye, my fodders of every kind have scarcely changed colour after eight 
or ten months of ensilage."' From this it is obvious that the silage of 
M. Gofi'art, which had "scarcely changed colour" was very different 
material from the "sweet brown silage" advocated by Fry. 

Babcock and Russell'^ state that " the popular opinion that good silage 
can only be made with considerable heat is erroneous."" Good silage 

1 Agricultural Gazette, Aug. 27th, 1883, Nov. 26th, 1883 and April Uth, 1884. 
cvj " Voelcker. Journal of the Eoijul Agricultural Society, \%M. 
^ ' Voelcker. Il>id. 1886. ^ Silos for British Crops by the sub-editor of the Fivld. 

_^ ^ Babcock and Russell. Wisconsin Agricultural Experiment Station, I7th and 18th 

J " Annual Report, 1900. 
_., Journ. of Agric. Sci. xii 22 



324 Tcnipenditn' qff'cctiii;/ the Qiiatif;/ of Silage 

was made by them in .small retainers at temperatures which did not 
exceed 80°F. = 27°C.; thus, as the authors say, "disproving Fry's 
theory, that a temperature of at least 120° F. was essential for good 
silage." 

Many American and other experimenters have obtained similar 
results, of which may be quoted those of Neidig'. In this case the 
maximum temperature recorded at the centre as distinct from the top 
surface of the silo was 91° F. = 33° C, and good silage resulted. 

When in 1917 the authors began to study silage-making in the 
American type of tower silo, agricultural opinion in England still re- 
tained the distinction between "sweet"' and "sour" silage which Fry 
had enunciated and did not realize the possibilities of other types of 
silage. For this reason, as well as for the fact that silage produced in 
the experimental silo at Cambridge varied very greatly not only from 
year to year, but also in different parts of the same silo, it became 
apparent that, before reliable feeding experiments with silage could be 
conducted, it was necessary firstly to define the different types of silage 
w hich were capable of being produced, and secondly to define the con- 
ditions under which each tyj)e could be produced. 

The observations in this paper are divided into two parts. The first 
part concerns those made upon silage produced by a large number of 
silage growers in the Eastern Counties and elsewluTe, from which a few 
characteristic examples have been described. The second part describes 
a more accurate series of observations made in the experimental silo at 
Cambridge. 

In the earlier years the late Mr G. Williams co-operated but his 
untimely death in 1920 prevented him from helping to complete the 
work. 

QUAIJTATIVE OBSERVATIONS MADE ON SILAOE PRODUCED BY 
FARMERS UNDER VARIOUS CONDITIONS. 

1. On farms belonging to Mr .T. Thistleton Smith, Kakenham, 
Norfolk. 

Mr Thistleton Smith farms light to medium land, u])on which the 
silage crops generally stand well. The crop mi.xture consists of wheat, 
oats, and tares, which is allowed to become fairly mature before cutting 
(the oats being past the milk stage and the tares well seeded). If the 
crop is succulent it is allowed to wilt a few hours before being ensiled. 

' Neidig. "Chemical Changes in .Silage ferniontation." lowii Agric. Kxp. Utation, 
Research Bulletin, No. Iti. 



X. Amos and G. Williams 325 

The resulting silage over a period of years and in several silos has been 
of a yellowish-brown to brown colour with an acid though quite pleasant 
smell. The silage has been readily eaten by all classes of stock, which 
have invariably thriven upon it. 

This is much the most common type of silage now being produced in 
the Eastern Counties of England and appears to be universally produced 
in tower silos from a mature crop which is reasonably dry when ensiled. 

2. In two silos belonging to Mr F. W. D. Robinson, Beccles, Suffolk, 
1919-1920. 

The crops in this case were oats and tares grown upon hght land. 
They were cut in a medium condition of maturity, the oats being in 
milk and the tare pods full-grown in length but with immature seeds. 
The crops were ensiled immediately after cutting. The resulting silage 
possessed a green colour with a smell which was neither "sweet" nor 
"sour"; it can best be described as "fresh" and "fruity.'" Stock ate 
it greedily and throve upon it. 

It would seem highly probable that M. Goffart's " crops of every kind 
which had scarcely changed colour after 8 or 10 months of ensilage" 
must have been of this character. 

3. On Mr Arnold Oliver's farm at Bures in Suffolk. 

In two successive years 1919 and 1920 the silos were filled with oat 
and tare crops cut in a medium condition of maturity, and under con- 
ditions very similar to those prevailing in Mr Robinson's silos. 

In each case the crop was ensiled immediately after cutting and 
produced a green silage with the same "fruity" smell observed with 
Mr Robinson's silage. In 1920 a maximum thermometer was inserted 
about the middle of the silo and this recorded 30'^ 0. 

4. On General Adlercron's farm at Culverthorpe, near Grantham. 
In 1920 the silo was filled dTiring September and October from a 

late-sown oat and tare crop which was badly laid. The crop had grown 
to a great length and was semi-rotten close to the ground. Much rain 
fell during the ensiling process. The resulting silage was dark brown 
almost black in colour and possessed the most objectionably sour 
pungent smell. So tenaciously did this smell chng to anything touching 
it that the writer, who had occasion to handle some, was unable to get 
the taint from his hands for 36 hours. This silage was eaten by cattle 
but without rehsh. 

It is satisfactory to record that in the season 1921-22 beautiful silage 
has been produced on this farm by ensiling under conditions similar to 
those adopted by Mr J. Thistleton Smith. 



326 Teinperatare a^'eeiiiKj the Qualifi/ of SUagc 

5. Silage made by Capt. Nicoll of Alresford in 1920. 

Tlie crop was slightly overmature when cut, but not badly laid; 
during the greater part of the filling the crop was allowed to wilt after 
cutting and frequently got very wet with rain, but during the last two 
days of filhng the crop was ensiled directly after cutting. 

The top part coinciding with the dry period of filhng of the silo 
produced very good silage upon which the cattle throve, but the bottom 
coinciding with the wet period of filUng was poor silage and the cattle 
fell away whilst feeding upon it. 

In 1921, the silo was filled throughout with freshly cut material and 
the product was excellent: green in colour with the characteristic 
"fruity" smell. 

G. Silage made from immature crops on Mr Alfred Amos' farm at 
Wye, Kent. 

Maize was grown for several years in succession from 1899 to 1904 
and ensiled in a tower silo, but the variety grown — American Horse 
Tooth — failed to ripen sufficiently for ideal silage purposes, rarely getting 
beyond the flowering stage. Under these conditions the silage was in- 
variably "sour"' with a pungent clinging smell. The cattle ate it, but 
not greedily and did not thrive greatly upon it. 

In 1921, a crop of winter oats which had grown very rankly and 
was hkely to be badly laid before harvest was cut oil between May 8th 
and 10th when a foot to 15 inches high, and put into a clamp silo after 
wilting for 24 hours. The crop was of course very immature. The re- 
sulting silage was of a greenish ohve colour with a most objectionable 
smell, similar to that described in General Adlercron's silage. The silage 
was fed to dairy cows in late summer, being scattered on the grass during 
the severest part of the drought in that year. The cows did not eat it 
greedily until the smell had partially blown away, but after lying in 
the sun for an hour the silage was readily eaten. The cows kept in good 
condition, milked well and no taint was noticeable in the milk. 

7. Silage made in a stave silo in Sussex in 1920. 

The crop consisted of oats and tares in which a large proportion 
of charlock was growing. This was allowed to become very mature 
before cutting, so that the charlock had set seeds, which were almost 
ripe, and produced stems which were hard and woody. The crop after 
cutting was allowed to wilt 24 to 48 hours and was consequently very 
dry when ensiled. This fact combined with the woody character of the 
charlock stems prevented the chaffed crop being adequately packed by 
trampling, so that much air was included. 



A. Amos and G. Williams 827 

When the silo was opened numerous tiny patches of mould were 
found throughout the whole depth of the silo and of necessity became 
mingled \vith the rest when thrown down for feeding. This silage was 
very dark brown almost black in colour, possessed a strong smell of 
ammonia and was musty. Cattle, when fed upon it, only ate it under 
compulsion unless they were able to pick out pieces uncontaminated 
with mould. 

SiLARE AT Cambridge, 1917-1921. 

The silo has been partially or completely filled each of the five years 
during the period, and in addition a silage stack was made in 1918. 
Careful records were kejDt of the crop as ensiled and of the silage as 
taken out. In many cases moisture content has been recorded by means 
of weighed samples enclosed in wire netting sample-bags. 

Temperature has been recorded by two methods. In the first a 
hollow iron gas-pipe was driven into the silage after the silo had been 
filled. A thermometer was then lowered to different levels in the silage, 
allowed to remain till it had taken up the temperature of the sur- 
rounding silage, quickly pulled out and the temperature read off. 
Readings were made at different depths at daily or longer intervals. 
The length of the gas pipe was never more than 8 ft. It is obvious, 
therefore, that the temperatures of the surface 8 ft. only could be 
ascertained by this plan. The method is open to the further criticism, 
that the silage is constantly settling; if, therefore, the tube is driven 
in 8 ft. from the surface one day> and the silage settles, the tip of the 
tube is no longer 8 ft. from the surface. In the observations recorded 
the tube was driven in to the full depth after trampling the silage at 
the time of the first reading and was not driven in further as the silage 
settled. The temperature readings on subsequent days were therefore 
taken at depths which corresponded approximately with the same layers 
of silage as those from which the temperature was taken on the first day. 

In the second method maximum thermometers were buried in the 
silo at more or less regular intervals as the filhng of the silo proceeded. 
These were carefully corked within short lengths of iron gas pipe to 
prevent breakage, and placed just beneath sample bags put in at the 
same time. The thermometers were recovered as the silage was used and 
the maximum temperatures recorded. 

In 1917 the silo was filled with a crop of oats and tares cut when 
fairly mature, the oats being well in milk and the tares with full-growTi 
pods and the seeds beginning to dent the pods. The crop, which was 



328 Temperature atfecting the Quality of Silage 

lodged but not badly laid, was cut on July 16th and 17th in dull weather, 
a quarter of an inch of rain fell on each of July l~th and 18th and inter- 
fered with the coinmencement of filling on the hitter day. Filling had 
to be stopped on -hily 19th, when the silage cutter broke down. 

The percentage of moisture in the green crop as filled to the silo 
varied from 70-3 per cent, at the bottom when the crop though wilted 
contained some added rainwater, to only 64-6 per cent, at the top when 
the crop was wilted and dry. 

The following table gives a record of the daily temperature readings 
on the centigrade scale for ten days after filling, and subsequently at 
longer intervals of time. 

Table I. imi cwf. 





Tcmiieniture 


Tcinperaturc 


Temperature 




at 6 ins. 


at 2 ft. 


at 5 ft. 


Date 


"C. 


°C. 


"C. 


July 20 


26 


— 


— 


„ 21 


49 


33 


27 


22 


60 


34 


29-5 


", 23 


OSS 


35-5 


32 


,. 24 


63 


40 


33 


„ 25 


6;">-;') 


460 


34-5 


„ 26 


62-.'> 


47 


35 


„ 27 


(>4r. 


49-5 


35 


„ 29 


63-5 


48 


36-5 


„ 30 


— 


49-5 


.36-5 


Aug. 2 


— 


49-5 


36-5 


,. 5 


— 


— 


37 


Oct. 1 








31-5 


„ 23 


— 


— 


27 


Nov. 3 


— 


— 


26-5 


.. 1.5 


— 


— 


24-5 



Except on July "2()tli. when the reading was made at 9 a.m., the 
thermometer readings were taken at or near 5 p.m. After July 29th in 
the case of the (i ins. depth and August .")th in the case of the 2 ft. depth, 
readings ceased to be taken because it was impossible to ascertain the 
corresponding depth, and moreover temperature changes were only those 
due to cooling. 

When the silo was opened on November r2th and subsequent days 
it was found that the level at which the (J in. temperatures had been 
taken consisted of s])oilt mouldy material from which much of the 
moisture had been driven out by the heat. The range of temperature 
therefore of 60° to 65° corresponded with moulding of the silage. 

The silage taken from the 2 ft. depth, where the temperature rose 
to 49° C, had a uniform dark brown colour with a characteristic ''sweet" 
pleasant smell similar to that of an overheated hay stack, and was evi- 
dently comparable to the '"sweet" silage described by Fry in earlier days. 



A. Amos and G. WilliajMS 329 

The silage taken from tlie 5 ft. depth, where the maximum tem- 
perature did not exceed 37-5° C, was of a much paler brown colour with 
a strong, somewhat acid, flavour, similar to that described in Mr J. 
Thistletou Smith's silos. 

Two feet from the bottom of the silo where doubtless the temperature 
of fermentation was lower though records were not obtained, the colour 
was still brown but the smell was much more pungent and very un- 
pleasant, and similar to that described in General Adlercrons silo. The 
smell was most tenacious and when handled tainted the hands so that 
even washing with soap and water failed to remove the unpleasant smell 
for several hours. This silage in contrast with the previous two types 
was not relished by stock. 

In the light of later experience, it seems probable that the chief 
factor contributing to this condition was the rainfall upon July 17th and 
1 8th, causing a certain amount of decomposition of the green crop in 
the field, and resulting in some rainwater being conveyed to the silo 
with this part of the crop. 

In 1918 the silo was filled at the bottom with rye and tares and with 
oats and tares at the top ; both crops were autumn sown. The rye and 
tares stood well whereas the oat and tare crop was somewhat but not 
badly laid. Cutting commenced on July 1st when the rye was rather 
old, the grain being full-grown but soft and the glumes dry; the tare 
seeds were denting the pods which were well developed; the oats were 
forward in milk. The crop was cut 24 to -18 hours in advance of filling. 
This continued from July "2nd to July 5th, when the silo was full. It 
was left over the week-end to settle and refilled on July 8th with oats 
and tares cut the same day. During the whole period of filling the 
weather was beautifully sunny and no rain fell. 

The following table gives a record of temperatures taken at or about 
5 p.m. each day at first at daily and later at longer intervals. 

Table II. 1918 crop. 



Date 
July 





Temperature 


Temperature 


Temperature 




at 1 it. 


at 4 ft. 


at 8 ft. 


;e 


°C. 


°C. 


°C. 


9 


37 


32 


45 


10 


41 


34 


42-5 


11 


47 


34-5 


41 


12 


47-5 


35 


40 


13 


47 


35-5 


39-75 


14 


47-5 


35-5 


39-5 


16 


49 


36-25 


38-75 


18 


46-5 


35-75 


38 


21 


45-75 


35-5 


37-5 



330 Temperatnrc afeci'nuf the QuaHtji of Sildf/e 

The silo was opened on November J 0th wlieii it was found that the 
silage at 1 ft. deep, the level of the first set of temperature readings, was 
of dark hrown colour with a "sweet" pleasant smell in every way similar 
to that immediately below the to]) of the silo in the previous year although 
this part of the silo was filled with freshly cut crop. The maximum 
temperature recorded at this depth was 49° C. and the silage contained 
72 per cent, of moisture when taken out. It is in fact almost invariably 
the case when a silo is filled with oats and tares or some similar crop 
that, after the mouldy surface is removed, a shallow layer of "sweet"' 
silage is found; this, however, in most cases rapidly gives place to silage 
of different character. 

At 4 ft. deep, where the temperature did not exceed 36-25° C, the 
character of the silage was of pnlnr brown colour and had a pleasant 
smelling though acid flavour. 

At 8 ft. deep the temperature records are higher than at 4 ft., and 
starting at the comparatively high figure of 4.')° C. on July 9th fall con- 
tinuously to .Tuly 21st. The explniuition of this apparent paradox is 
that the 8 ft. level di])])ed just below the top layer put into the silo on 
July Gth. This being easily accessible to air from July .")th to July 8th, 
during the interval of the filling of the silo, fermented readily and so 
reached a high temperature before the silo was refilled on the latter day. 
It is quite probable indeed that 4^i' V. was not the true maximum, for 
some cooling may have occurred before the thermometer was inserted 
on July 9th. The silage at this depth was similar to that at the 1 ft. 
level in that it was "sweet" with a dark brown colour, but the crop 
having been cut a couple of days before filling the silage was much drier. 

In this same silo five sample bags were put at regular intervals 
during filling, and below each bag a maximum thermometer was placed. 
Table III gives in the first column the number of the bag, in the 
second the condition of the crop when ensiled, in the third the per- 
centage of moisture in the green crop, in the fourth the maximum 
temperature, in the fifth the ])ercentage of Tuoisture in the silage, and 
in the last column tlu' type of silage produced. 





Tab 


le III. 1919 crop. 










% "f 


Maximum 


%o£ 




lo. of 




moisture 


temp. 


moisture 


Typo of 


bag 


Material 


green crop 


"C. 


silage 


silage 


.5 


Oats and tares, no wiltin<r 


71-7 


47 n 


71-6 


Sweet dark brown 


4 


., wiUed 4 lirs. 


7 15 


.•i7 


7.5-6 


Acid light 


3 


., L'4 „ 


(•,-,■■> 


.■!.-) 


(>9I 


.. " .. 


2 


,. 48 „ 


(i(>(i 


;n 


<i9G 


>. 


1 


Rye and tares, ,, 24 „ 


(w + 


30 


G9-8 


»» »» 



A. Amos and G. Williams 331 

Taking bag 5 first, because this was nearest to the top, and conse- 
quently taken out first, it was found to be situated within I ft. of the 
surface and so corresponded with the conditions discussed in relation 
to the silage 1 ft. deep in Table II. The sample contained a fair amount 
of moisture, nearly 72 per cent., and reached a maximum temperature 
of 47°-5 C. The silage produced was characteristically "sweet"' with 
pleasant smell and dark brown colour. 

The silage in bag 4, which reached a maximum temperature of 
37° C, had an acid though pleasant smell. It was situated not far below 
the level where the break in filling the silo occurred and doubtless for 
this reason the temperature is above those in samples Nos. 3, 2 and 1. 

The silage in bags 3, 2 and I was in eacli case produced from a crop 
which had been consideral)ly wilted in dry weather and contained only 
about (15 per cent, of moisture when ensiled. The maximum temperatures 
were respectively 35° C, 31° C. and 30° C, and in each case a yellowish 
brown silage resulted with an acid, typically silage, smell. This was 
pleasant and by no means tenacious hke the smell of the silage from the 
bottom of the silo in the previous year. These samples seem to be 
typical of silage jiroduced in tower silos from fairly mature crops which 
are allowed to wilt under dry weather conditions before being ensiled. 
The silage is not "sweet" in the sense of the earlier writers and neither 
is it "sour" enough to be un])leasant. It is readily eaten by stock which 
thrive well upon it. 

In 1918 a silage stack was also made from a crop of spring-sown oats 
and tares. This was cut on .luly 20th, allowed to wilt for 24 hours, 
and built into a circular stack 12 ft. in diameter. The stack heated 
greatly, the maximum tem])erature in the bottom half of the stack — 
ascertained by the use of the same hollow gas pipe with thermometer 
previously described, but thrust horizontally into the stack — proved to 
be .58° C, whilst that of the top half rose to as much as 75° C. The 
whole of the stack was composed of sweet silage, for the most part dark 
brown, but in some jilaces, where the heat was greatest, almost black 
in colour. 

This silage was readily eaten by cattle, but the losses in fermenta- 
tion only, as ascertained from two sample bags, amounted to 19 and 
21 jDer cent, of the dry weight respectively. So great a loss indicates 
that silage made at such high temperatures is uneconomical. 

In 1919 the silo was filled with a spring-sown oat and tare mixture. 
Cutting commenced on August 4th and was completed on August 5th. 
Filling was carried out on August 5th, 6th, 7th and 8th. The crop was 



IV. Mtl 


1) rn>p. 






% of 


Maxiinum 


%of 




moisture 


temp. 


moisture 


'J'y]ie of 


;reen croji 


° C. 


silago 


Hiluge 


57-3 


40 


()0() 


Sweet dark brown 


()7-l 


.30 


711 


Acid lifrht „ 


05-7 


30 


7 Mi 


•» »> •* 


G9-7 


345 


73-0 


'» »» »» 


70-1 


31 


73-8 


»» t» ?• 


72-(i 


305 


7.5-7 


Sour dark ., 



'•V.Vl Teu^xraiinc <(i)(cfiii>j the QnulUij i)j' Sikaje 

luirly well lU'vuloped, the oats just pas.sing out of the milk stage aud the 
tares with full-grown pods and half-grown seeds. The crop stood up 
fairly well, but a slight shower of rain, amounting only to -01 in., fell 
on the crop on the evening of August 4th after the first days cutting. 
The rest of tiie filling period was fine though dull. 

In consequence of the rain on August 4th, the fodder in bags 1 to 5, 
Table IV, was slightly wetted by rain after cutting, but with the excep- 
tion of bags 1 and 2, was dry again before ensiling. 

Tabit 

No. of 
bag Material 

7 Oats and tares, wilted 3 days 
f> .. .. .. 2 „ 

5 ,, .. ., 3 „ 

4 „ ., ., 2 ,. 

3 „ M .. 2 „ 

2 Oats and tares, wilted 1 day, 

but wet with rain 
1 Oats and tares, not wilted, 79-8 24 83-4 „ „ „ 

wet with rain 

Table IV is compiled in exactly the same way as Table III. 

When the silo was opened it was again found that the topmo.st bag. 
No. 7, near the surface, contained "sweet" dark brown silage and this 
was associated with a maximum temperature of fermentation, taken just 
below the bag, of Hi" C. It is probable that the maximum temix'rature 
within the bag would have been a few degrees above this point. 

Bag 6, which had been cut in dry weather and allowed to wilt two 
days before ensiling reached a maximum temperature of 30° ('. and 
contained typical liglit brown acid silage with a pleasant smell. 

Bags 5, 4 aud 3 whicli had been slightly wetted with rain after 
cutting and then left long enough to dry oflt the rainwater before ensiling, 
produced silage very similar to that in bag (i. 

Bag 2, whicli contained a small amount of rainwater when ensiled, 
contained a slightly unpleasantly sour silage and bag I . wliich was 
next to the floor of the silo and was very wet when ensiled, contained 
the characteristic unpleasantly sour pungent brown silage. The thermo- 
meter indicated that the maximum temperature in this case was only 
24° C, due partly to proximity to the floor of the silo and partly to the 
exclusion of air from the wet material containing as it did 80 per cent, 
of moisture. It must also be recorded that in the season 1919 the drain 
in the floor of the silo was intentionally closed so that no drainage was 
possible. This may have contributed to the souring of the bottom silage. 



A. Amos and G. Williams 
Table V. 1920 crop. 







"„ of 


.Maximum 


''' (if 




No. of 




moisture 


temp. 


moisture 


Tyjje of 


bag 


Material 


green crop 


"V. 


silage 


silage 


7 


Oats and tares, no wilting 


(J9G 


35-5 


7!-.-) 


Acid light brown 


li 


t)ats, tares and beans, wilted 


(iS-1 


31-5 


70 


Acid yellow- 




() hours 








lirown 


5 


Oats, tares and peas, wilted 
hours 


(it) 


32-5 


70-4 


Acid yellow- 
brown 


4 


Oats and tares, wilted 24 hrs. 


70 


33 


69-7 


Acid light brown 


3 


„ 48 ,. 


I14S 


3()-2 


02-8 


,, ,. 


o 


Oats and tares, cut days 
before filUnt;. Soaked with 
rain 


72-5 


31-3 


72-9 


"Sour" dark 
brown 



1 ., ., „ figi 305 71 « 

In 1920 the silo was filled with a cro]) of autumn sown oats and tares, 
except for two small quantities of material which contained in addition 
peas and beans respectively. The crop was well advanced when cut, the 
oats being just past the milk stage, the tare pods full grown in length, 
with seeds denting the pods. The pea seeds were full-grown in size though 
still soft, and the bean seeds were not quite full-grown. Cutting com- 
menced on July 3rd, but much rain fell during the next five days, so 
that filling was impossible till July 9th. The following Table VI gives 
the rainfall for the ])eriod. 

Table VI. Raiiifnll 1920. 

July 



4 


014 in. 


July S 


0-44 in. 


July 12 


nil 


5 


0-.'")(i ., 


9 


nil 


,. 13 


nil 


() 


OM „ 


„ 10 


0(14 „ 


„ 14 


005 in, 


7 


010 ,. 


., 11 


0-((5 ,, 


„ 15 


nil 



Bag No. 7, which was situated 2 ft. 6 in. below the surface of the 
silage, was made from the oat and tare crop; this had been ensiled shortly 
after cutting. The temperature of fermentation was considerable, 
35°-5 C, owing to its proximity to the surface and consequent access 
of air. This silage had a pleasant acid smell and was much relished by 
the stock. 

Bags Nos. C) and 5, containing beans and peas respectively, mixed 
with the oats and tares were in each case wilted only six hours, but the 
crops were dry and fairly mature before cutting, so that their moisture 
content as filled was low, 68-1 per cent, and 66 per cent, respectively. 
In each case good silage resulted characterised by a pale yellow-brown 
colour with a pleasant acid smell : this was greatly relished by the stock, 
the pea, oat and tare silage being particularly good. 

The silage in bag No. 4 was cut on July 12th and allowed to wilt 
24 hours; that in bag No. 3 was cut on July 10th, wetted with slight 



334 Trnipenitwe affect Iikj the Qiudiitj of Sihuje 

showers on tliat day and the morning of July 11th, but the afternoon 
was dry and sunny so that the crop when ensiled on July 12th was free 
from rainwater. Each of these produced light brown silage with an acid 
but not unpleasant smell. None the less it was not so good as that in 
Nos. 5 and (!. 

Bags Nos. 2 and 1 contained material which had been cuf on July .'kd, 
but owing to very wet weather remained in the field till July 9th before 
ensiling. A certain amount of decom])osition occurred in the field, and 
the crop was ensiled whilst it still contained some rainwater, the total 
moisture contents being 72-5 per cent, and f)9-l per cent, respectively. 
The silage from these bags was of the characteristically unpleasant 
"sour" variety, previously described; it possessed a dark brown colour 
and a pungent smell which clung to hands or clothes brought into 
contact with it; the maximum temperatures recorded with these samples 
amounted only to 30° C. to 31" C. Experimental cattle, when fed upon 
it, failed to thrive well. 

Table VTl. 1921 crof. 

"„ i)f Miixiiuiiin "„ nf 
Nci. of moisture teiii[) inoistiirc f.'^'Pf "f 

l>au Material green ero|) ■" ('. silage silage 

"-' Oats and tares, wilted lirs. (i7-4 34-5 70-6 Green and "fruity" 

I ., , not wilted 7()-.") 24-.5 69-7 

In 1921 the crop was ensiled in perfect weather, warm and dry, 
except that on the night previous to the first day's cutting -OC) in. of rain 
fell, so that the material in bag 1 contained a small amount of rain- 
water. The crop was not very mature, the tares being in full flower 
and the oats ju.st in milk. Wilting throughout the filling was reduced 
to a minimum, the croj) being cut only a short time before ensiling. 
Both bags, and in fact the whole of the silage, was of excellent quality. 
The silage had an olive colour with a tint of green throughout, though 
in some parts the green was more pronounced than in others. The smell 
was entirely dilTerent from that previously obtained; it had no suggestion 
of sourness, although it was made from sappy and rather immature 
material, nor had it any pungent odour, but it possessed a kind of 
"fruity" smell suggestive of pear drops and combined with this the 
smell of freshly cut lawn grass. When fed to stock it was ravenously 
eaten and under experimental conditions has given excellent feeding 
results^. 

It is to be remarked when such freshly cut material containing large 
quantities of moisture is ensiled that much juice may be expressed and 

' The results of this feeding experiment will be puliliahed shortly. 



A. Amos and G. Williams '^V>l^ 

lost from vvoodeu silos. The juice may ruu to waste and after putrefaction 
produce unpleasant smells in the yard or it may be given to cattle or 
pigs as a liquid. 

Conclusions. 

1. Many different types of silage may be produced from the same 
crop according to the conditions of ensiling; the characteristics of the 
resulting silage varying not only in physical and chemical but also in 
feeding properties. 

2. The following types of silage have been differentiated and some 
of the conditions of their production ascertained. 

((/) "Sweet" dark brown silage. This type of silage is produced when 
the temperature of fermentation rises above 45°-50° C. ; it has not been 
produced below 45° C. It is frequently produced in stack silage to which 
air has ready access, but not generally in tower silos except in a shallow 
layer (i in. to '2 ft. thick just below the mouldy surface to which air has 
ready access. This silage has a dark brown colour varying in intensity 
according to the temperature of fermentation and a sweet pleasant smell 
resembhng that of heated hay. It is readily eaten by stock, but has 
generally lost a considerable proportion of its food value through exces- 
sive heating. 

(b) Acid light-brown or yellow-brown silage is i>roduced in tower silos 
from crops which are moderately mature when cut and allowed to wilt 
for varying periods according to the initial dryness until the moisture 
content of the crop approximates 70 percent. The maximum tempera- 
ture of fermentation is generally between 30° and 37° C. 

This silage has a yellowish brown to brown colour with an acid 
though pleasant smell probably largely due to acetic acid, the yellowish 
types being generally the more pleasant. 

This type of silage is eaten greedily by stock, which thrive upon it 
and is to be commended. 

{(■) Green "fruity" silage is produced in tower silos from crops which 
are cut in the earlier stages of maturity, from the time of full flower till the 
seeds are half formed. The crop must also be ensiled soon after cutting. 
The temperature of fermentation is low and may vary from 22° C. to 
34° C. This type has a green to olive green colour with a smell that is 
neither "sweet" nor "sour," but can best be described as "fresh" and 
"fruity." It is greedily eaten by stock, which thrive greatly upon it, and 
Woodman^ has recently shown that its digestible properties are very high. 

Green silage suffers from one practical disadvantage; large quantities 
1 Woodman. This Journal, 12, Part II, April 1922. 



336 TeiiijK ridnrc tijf'crfing the Quality of Sihuje 

of juice are liable to drain away from the silage and carry with them 
soluble food material, which if allowed to accumulate in the yard under- 
goes fermentation and ])r()duces a smelly mass of putrid material, if, 
however, the juice is collected cattle and pigs readily drink it. This 
problem is receiving further study. 

{d) Sour silage is j)roduced under at least two different sets of con- 
ditions. It may be ])roduced from an immature and succulent crop, or 
it may be produced from a crop which has been cut and then saturated 
by rain before ensiUng, especially when the crop has become laid and 
partially rotten at the base before cutting. 

Sour silage has a dark brown or olive brown colour witli a pungent 
and most un])l('asaiit smell ])ossibly due to butyric acid. Cattle will 
eat this, but not readily and do not generally thrive upon it. 

(e) Musty silage. One case only of tliis type had been recorded, in 
which an over-ripe crop containing much charlock was allowed to wilt 
and become over-dry before ensiling. A number of tiny mouldy centres 
were produced in which ammonia was generated. 

This silage has a dark bro\\ii almost black colour and has a musty 
ammoniacal smell. Stock refused to eat it or ate it only under com- 
2)ulsiou. 

3. The classiiication of silages given ai)ove is admittedly superficial, 
but it may serve to pave the way for the chemist, the plant phj^siologist 
or perhaps the bacteriologist to produce similar types of silage under 
well defined conditions and so make the distinctions more absolute. 
For the successful practice of ensilage in this country it is fundamental 
that the conditions by which each type of silage may be produced should 
be accurately known. 

4. In the past persons conducting feeding experiments in this 
country have rarely attempted to define the type of silage used, and 
conflicting results have been obtained. When it is further noted that 
the quality of silage at different parts of a silo may be, and frequently 
is, fundamentally different, it is of the utmost importance that these 
facts should be recorded in future feeding experiments. 

Our acknowledgements are due to the Ministry of Agriculture who 
have financed this study, to Messrs English Bros, of Wisbech who 
generously i)resented the experimental silo and to Prof. Biffen and his 
farm managers Messrs TI. Y. Sliei-ingham and N. Langridge who have 
facilitated the ex])eriments u|ion tin- Plant Breeding Farm at Cambridge. 

(Received August 7th, I92"2.) 



AN INVESTIGATION INTO THE CHANGES WHICH 

OCCUR DURING THE ENSILAGE OF 

OATS AND TARES. 

By ARTHUR AMOS, M.A. 
AND HERBERT ERNEST WOODMAN, Ph.D., D.Sc. 

{School of AgricitUnrc, Vanibridijc U nircrsilij.) 

Introduction. 

The practice of ensilage has been rapidly gaining adherents in the 
British Isles since Mr Cxeorge Jaques began to advocate the oat and tare 
crop for this purpose in 1913. In view of this fact, it becomes increasingly 
important for the scientist to be in a position to supply the ])ractitioner 
with facts from which he may be able to calculate the probable economy 
of the system before investing the nece.ssary capital in a silo. One of 
us^ has already made such a tentative calculation based upon a some- 
what limited knowledge of those facts. It is the purpose of these experi- 
ments to amplify knowledge in one direction, namely, in that of the 
chemical changes which occur during the ensilage of oats and tares, so 
that one may know what are the losses and what the gains, if any, in 
chemical constituents during the process. 

One of us'^ has recently shown that it is possible to produce at least 
five distinct types of silage from the same crop. It is, therefore, equally 
important to be able to state definitely which of these occasion the least 
net loss during ensilage, and to endeavour by controlling the factors 
concerned to reduce to a minimum the losses in the making of those 
types of silage which appear most economical. 

The experiences gained with maize silage in America and elsewhere, 
useful though they be, do not bear directly upon the present problem of 
oat and tare silage, because the chemical composition of the two crops 
is very different. 

Prehminary work was begun in 19f8 when the late Mr Gwilym 
Williams assisted on the chemical side of the work, but in the earlier 

' Ensilage by Aitliiir Amos, .louriial of Funiurs Clnb, March l'J20. 
- Amos and Williams, This Volume, p. 323. 



3r{8 (}(il 1111(1 Tare SUdijc 

years progress was limited by the failure of some of the methods of 
investigatiou. In the first season high grade linen bags, such as are 
used by seedsmen in distributing seeds, were used as containers, but 
proved defective because the fabric perished as a result of the fer- 
mentation in the silo. Next fine-meshed galvanised wire netting was 
tried, but though in the first year the juices of the silage produced 
no effect upon this nuiterial, in subsequent years this was not the case 
and consequently accurate weighing of the contained sample became 
impossible. In the experiments now to be described, loosely woven jute 
bags, made of the same material as commonly employed for chaff bags, 
were used, and this has proved perfectly suitable. During this pre- 
liminary period certain progress was made in chemical methods which 
have been of use in the present investigation. It has, however, been 
thought undesirable to publish the earlier results in detail because of 
the uncertainties above mentioned. 

Saiii|)les of silage described in this ])a])er were made in two cases 
from the commercial silo used on tiie Plant Breeding Farm at Cambridge; 
in the remainder from three small wooden cylindrical silos, measuring 
6 ft. high and 4 ft. in diameter, which have given highly satisfactory 
experimental results. In some measure experimental silos of this size 
constitute a new departure; they are free from the objection commonly 
used again.st bottles of silage, that the bulk- under ex])eriment is so small 
that any rise in temperature is immediately dissipated, and yet they 
enable the experimenter to vary at will one factor only, a condition which 
is difficult indeed to accomphsh by varying tiie jHisition of the sample 
bags in a large commercial silo. 

These small silos were constructed of I in. boards, tongued and 
grooved and kept tightly pressed together by three circular iron hoops 
which were capable of being easily tightened by suitable screws. The 
wood was of plain deal, tarred externally for purposes of preservation. 
The silos were placed in a shady .situation and the floor of each con- 
sisted of j)uddied gault clay. At the time of filling metal extensions 
i ft. high made of iron sheeting were fitted to the top of each silo. 

The sample bags, as previously stated, consisted of loosely woven 
jute, measuring 3 ft. (J in. long by '1 ft. in breadth; these contained 
about 2 cwt. of green fodder under average conditions of wetness. When 
filled with fodder these dimensions were considerably contracted, so that 
in no case were they within 6 ins. of the walls of the silo when placed 
in position. 

Immediately beneath each sam})le bag was placed a maximum 



A. A.MOS AXI) H. E. WooD.MAN oo5> 

thermometer encased within a piece of iron gas piping for protection. 
]3abcock and Russell ^ have shown that such fermentations as produce 
increase of temperature in the silo take place very rapidly and that the 
maximum temperature is generally reached within four or five days. 
The use of a maximum thermometer therefore gives a useful indication 
of the vigour of the fermentation, jjrovided the heat is not rapidly lost 
by conduction. 

The results upon opening proved that good silage was capable of 
being made in these small silos, and in two out of the three cases the silage 
differed very slightly, if at all, from that produced commercially; more- 
over, the wa.stage due to spoilt material at the top compared favourably 
with that of commercial practice, and in the case of silage made from 
freshly-cut, succulent crop, the amount of spoilt nuiterial on top measured 
only i in. in thickness. 

Object of the Experime^t.s. 

The purpose of the present investigation was two-fold; firstly to 
determine the effect of varying the moisture content, both by the wilting 
of the crop after cutting and by allowing rain to fall upon the crop in 
the field, upon the quality of the silage produced, and so to ascertain how 
far this factor influences the producing of different types of silage; and 
secondly to ascertain the nature and magnitude of the chemical changes 
which occur when these different types of silage are made and to obtain 
a comparison of the fermentation losses involved in each case, as well 
as any benefits which may accrue from such fermentation. Further 
details of the chemical objects of the experiment are given later. 

Description of Crop. 

The crop utilised for the experiment was autumn-sown and was 
seeded at the rate of If bushels of tares and I5 bushels of grey winter 
oats per acre. In the dry summer of 1921 there was approximately 
equal growth of oats and tares at time of cutting, but no separation 
of the crop was made. The crop used for the samples was cut at recorded 
times between June 21st and 23rd, at which time the maturity of the 
crop was perhaps ideal for making hay, but would generally be considered 
slightly immature for silage. The oats were then well past flower, 
some being in milk, others having not quite reached this stage; the tares 

^ Babcock and Russell, llth anrt lS//( Annual Report, Wisconsin AgriciiUnral Experi- 
ment illation. 

Joum. of Agrio. Soi. xii 23 



340 Out and Tare Silcuje 

were ill full flower witli a few pods half an inch in length. The whole 
crop stood perfectly and was of excellent quality. 

The weather at the time of cutting formed part of the long drought 
in 1921, so that generally soil and crop were very dry, but -06 in. rain 
fell in the night previous to the commencement of operations on 
June 21st. June 21st was flull and tine, but June 22nd to June 26th 
were scorching days. During the night of June 2()th a shar]) thunder- 
storm fell, measuring -22 in. of rain, and about half this quantity next 
day. Samples Nos. 1, 2 and 3 were cut in the early morning of June 21st 
and were chafl'ed and ensiled without delay. Thus they contained some 
added rainwater, as Table 1 shows, and contained only 23-5 per cent, 
dry matter when ensiled. Samples Nos. 4 and 5 were cut at the same 
time, but allowed to wilt for 24 hours before ensihug, and lost moisture 
so that they contained 35-7 per cent, of dry matter. Sample No. G was 
cut at 8 a.m. on .June 23rd — a scorching day — and allowed to wilt six 
hours before ensiling, whilst Samples Nos. 7 and 8 were cut on June 23rd, 
dried by wilting in hot sun till June 2(5th, then wetted by the thunder- 
storm and linalh' ensiled on .June 27th, when they then contained 37-8 
per cent, of dry matter, indicating that they must have been very dry 
before the rainfall. It is important to note that the crop used in Sami)les 
Nos. 7 and 8 showed no sign of rotting or putrefaction as a result of the 
rain, a condition that not infrequently occurs when a laid croj) of oats 
and tares becomes wet with rain after cutting. 

FlLLIN(i OF Sll.OS AND S.\iMPl,E BaG8. 

All the fodder was ehafi'ed with a I'apec silage cutter before ensiling. 
Before filling the sample bags and taking a sample of the original fodder, 
a suitable quantity of chaffed crop was shot down upon a smooth con- 
creted floor and well mixed by turning. From this well-mixed heap a 
7 lb. biscuit tin of fodder was filled by taking small handfuls from 
different parts of the heap. The lid was closed at once and the sample 
sent down to the laboratory for analysis. The sample bags were im- 
mediately filled by taking portions at random from the same heap, tied 
U]), numbered and weighed. Sometimes more than one sample bag was 
filled from the same chaffed sample when rei|uired for immediate use 
in different silos or different parts of the same silo: in this way some 
economy was made in the number of control samples to be analysed 
and the resulting silage samples were more comparable. 

In filling the small silos, chaffed oats and tares were first put in 
until, when well trodden, the height of fodder in the silo was about 2 ft. ; 



A. Amos and H. E. Wuodjiax 341 

then a nest was hollowed out into which was first put a short length of 
iron gas tubing containing a maximum thermometer. Immediately on 
top of the thermometer was placed a sample bag. Then more chaf1:'ed 
fodder was trodden in until the height of the fodder reached 4 ft., at 
which level a second sample bag was placed with maximum thermometer 
as before. More chaft'ed fodder was added and trampled until with the 
aid of the extensions previously described the toj) of the silage reached 
(j ft. 6 in. or 7 ft. in height. The silo was then left '24 hours to settle, 
after which about 6 in. of soil was thrown on top for the purpose of 
excluding air. Eventually the silage settled until at the time of opening 
the level of the tojj of the silage was about 5 ft. 

Two sample bags put into the big silo were provided with similar 
maximum thermometers, and in addition a 4 ft. length of stout string 
was tied at one end to the bag and at the other to a short thatching peg. 
The men filling the silo were instructed to keep pulling up the peg as 
long as possible, so that when the silage was being used the peg might 
come into view before the sample bag and so give warning of the 
proximity to the sample. 

Opening of the Silos. 

The small silos were opened at convenient times during November, 
by which time all fermentation had long since ceased and the tem- 
perature had for the most part cooled down nearly to that of the pre- 
vailing air temperature. Notes were made of the condition of successive 
layers in the silos as these were emptied, and so soon as a bag was 
exposed it was removed, cleaned and weighed. The bag was then quickly 
emptied, cleaned and weighed again; the difference between these two 
weights giving the net weight of contained silage. The silage, emptied 
from the bag, was then quickly mixed together, a sample taken from 
this, placed in a tin, and sent down to the laboratory for analysis. 

The two sample bags in the commercial silo were retrieved soon after 
the markers came into view and whilst the general level in the silo was 
still one to two feet above the bags. 

When silo 1 was opened on November 10th, it was found that there 
was no more than 4 in. of spoilt material at the top of the silo; then 
14 in. of good silage was removed before the first bag (bag No. 2) was 
reached. This silage possessed a distinctly green colour and a pleasant 
odour with no suggestion of sourness. The aroma can best be described 
as "fruity."' Bag 1 was taken out on November 15th. It was situated 

23—2 



Kinall silu 1 


C'OIIUH. 


Small silo 2 


C'omiii. 


Small silo 3 






silo 


A 




silo 


A 


\~ 


2 


3 


( 

4 


5 


6 


7 8 











24 


24 


6 


96 96 


13 


i;! 


13 


16-5 


16-5 


16-5 


14-5 14-5 


24-.-. 


22r> 


24-5 


23-5 


24-5 


34-5 


32-5 39-0 


715-5:! 


7(io3 


76-53 


64-28 


64-28 


67-40 


62-24 62-24 


7()l)5 


75-56 


69-31 


06-17 


66-25 


70-07 


63-46 {a) 02-06* 
{!)) 60-50 


■u-\ 


262-4 


262-9 


334-0 


323-6 


287-8 


293-8 294-0 


2I4(i 


227-3 


232-9 


306-5 


294-3 


267-0 


264-2 2(5-9 



842 (fdl 1111(1 Tare Siluijc 

about 2 ft. l)elo\v bag '1 aud possessed the .same pleasant ■'fruity' suiell 
but the colour, though still green, was not quite so good. 

Bag 3, which was taken from the same sample of crop as bags 1 and '1, 
was retrieved from the big silo on March 28th, and when opened was 
found to contain silage very similar to that taken from silo No. 1. It 
possessed an olive green colour and a^ pleasant, slightly "fruity"' smell. 

Table 1. 



No. of bai; 

Iiitorvrtl li<-t\vei!ii cutting 

aiul ensiling (hours) 
Initial t(MUiH'r-ature (° (.'.) 
.Maximum tompci-atui-e (" ('.) 
% moisture a.s ensiled 
% moisture after ensiling 

Dry matter as ensiled (ozs.) 
Dry matter after ensiling 

(ozs. ) 
% loss of ilry matter 13-2 13-4 11-4, 8-2 91 7-2 lO-o l(i-5 

* (n) Unsjjoilt sample, (b) Spoilt sample. 

An examination of Table I shows that the conditions of silage in 
samples 1, 2 and -'5 are very similar, except in one respect. They were 
ensiled at the same initial and maximum temperatures, which latter was 
very low, the quality of silage was very similar, and the jiercentage loss 
of dry matter was rather high in all cases. The one condition which 
varied greatly. was the percentage of moisture in the final product; this 
in the two samj)les in the small silo remained practically the same as 
in the original crop, whereas in the big silo the percentage of moisture 
fell from TO-u per cent, at the beginning to 09 per cent, at the end, 
indicating that the superimposed weight of silage in the tall silo had 
caused some of the moisture to be expressed and this drained away. 

The drainage licjuid was not analysed, but similar drainage in other 
years has contained varying quantities, between 4 and 10 per cent., of 
soluble material and is therefore an im])ortant source of loss during 
ensilage whenever it occurs. 

As before mentioned, the percentage loss of dry matter in each of 
these three sam])les was high, namely, 13-2 ])er cent, and l."5-4 per cent, 
in the small silo, aud 11-4 per cent, in the large silo. 

There seems no very obvious reason to account for the greater loss 
of dry material from the small silo than from the similar sample in the 
large silo, especially in view of the fact that httle, if any, water drained 



A. Amos and H. E. Woodman 34:3 

from the former whilst drainage must have been considerable from the 
latter. 

Silo No. 2 was opened on November 17th; it had been filled from a 
croij which had been cut 24 hours before ensiling, and was consequently 
much drier when ensiled, containing only (i4-3 per cent, of moisture. 
There were 8 or 9 in. of spoilt mouldy material on top, doubtless due 
to the drier crop being more difficult to press down by the soil covering 
for the exclusion of air. The silage in bags Nos. 4 and 5 contained in 
this silo was practically identical. It was olive brown in colour with 
no trace of the green colour found in bags 1, 2 and 3, and had no trace 
of the "fruity" smell associated with these. The smell, on the other 
hand, though pleasant, was distinctly acidic and was characteristic of 
much commercial silage made from similar crops under similar con- 
ditions. The rise in temperature as recorded by the maximum thermo- 
meters was again low, rising only from 16°-r) C. to 23°-5 C. and 24°-5 C. 
in each case. This is lower than the tem])erature commonly recorded 
with similar silage, for which the maximum temperature is normally 
about 30 " C. In both cases the moisture percentage increased during 
ensilage, a result occasioned by the disapjaearance of some of the dry 
matter during the process, and not by addition of water, for the silos 
were kept covered to protect from rainwater. 

Finally the loss of dry matter during ensilage in this case was con- 
siderably less than in the first three samples, a fact wliich suggests that 
drying the crop for 24 hours before ensiling is desirable. It should, 
however, be remembered that when this is done two other sources of 
loss in the field may be occasioned, namely, that due to respiration and 
to the breaking oft of the leaves as the crop dries. 

Bag () contained a sample which was allowed to dry for six hours 
only on a scorching hot day after cutting. It contained only 67-4 per 
cent, of moisture when ensiled, but this increased to 70 per cent, in the 
silo, partly by loss of dry matter during fermentation, and possibly also 
owing to absorption of moisture from other layers in the silo which were 
moister. In this case the maximum temperature rose to 34°-5 C, and 
yet the loss of dry matter was only 7-2. The silage produced imder these 
conditions had a pale brown colour with just a suggestion of green about 
it, and possessed a smell which was faintly fruity with little or no acidic 
smell. It was by no means typical silage and was characteristic only 
of a very small layer in the silo. Possibly this represented a transition 
stage between the green "fruity" silage below and the brown acidic 
silage about this layer in the silo. 



:>44 0(i( (iikI Tare Si/(t(/c 

Small silo No. '.i had been tilled from a part of the crop which was 
cut on June 23rd and left in the sun to dry during June 23rd, 24th and 
2yth, by which time it was three parts made into hay. However, during 
the night of June 25th and 26th, a thunder.storm occurred, which pre- 
cipitated -22 in. of rain and wetted the croj) considerably. June 2Gth 
was dull and about •]() in. of rain fell. On June 27th a part of the crop 
was carted in early morning and ensiled in one of the small silos. This 
crop, in spite of the rain on the previous day, contained only l)2-2 ])er 
cent, of moisture when ensiled. 

The silo was opened on November 29th. when it was found that a 
considerable (l('])th, about 18 in., of spoilt mouldy material had to be 
removed from the top before the good silage was reached: even at this 
dejith the silage iie.xt tlie walls was mouldy and occasional spots of mould 
were found throughout the whole mass. This mouldiness was due in 
part probably to infection in the field as a consequence of the rain, and 
in part also to the fact that owing to the dryness of the material it could 
not be packed so tightly in the silo. 

When bag No. 8, situated in the top half of the silo, was removed 
it was found that the ma.ximum thermometer immediately below it had 
recorded a temperature of 39° C. J'robably the temperature in the bag 
itself would have been a few degrees higher. The contents of this bag 
were partly good and partly mouldy; approximately two-thirds were 
good. This had a yellow-brown colour and an aroma very similar to that 
of heated hay. It was in fact "sweet" silage. The loss of drv matter 
in fermentation was high, 16-5 per cent. This was due in part to the 
excessive heat of fermentation and in part to the acticm of the moulds 
present. 

Bag No. 7 at the bottom part of this silo contained a few small spots 
of nu)uld. It had reached a maximum temperature of 32^-.") C. It had 
a yellow-brown colour with a very slight indistinctive smell, with no 
suggestion of acid to the nose. It appeared different from any type of 
silage commonly met in practice. The loss of dry matter during fermen- 
tation amounted only to 10 per cent. 

P'rom experience gained from other sources it appears that the most 
desirable type of silage is the green "fruity" silage produced in bags 
1 and 2 in the small silo, and bag 3 at the bottom of the large silo. This 
type of silage seems to be produced when a fresh green crop in an early 
Btage of maturity (soon after flowering) is ensiled, with little or no 
previous wilting, at a low temperature, at or about 2.5° C. The results 
of these experiments suggest that with this type a considerable loss of 



A. Amos and PI. E. Woodman 845 

dry matter may result from the process, especially if much drainage of 
sap occurs. Bag No. 6 at the top of the large silo produced a silage 
bordering upon this type, and was ensiled under somewhat similar con- 
ditions as to freshness — it was cut only six hours before ensihng — but 
the maximum temperature recorded in this bag probably accounts for 
the alteration in type. 

The acid brown type of silage produced in bags 4 and 5 in the second 
small silo is characteristic of much commercially made silage, and is 
also a valuable type of silage. This is made generally from a moderately 
dry crop, dried either by wilting or by allowing the crop to matiire and 
so become drier before cutting. The analytical figures show a remarkably 
low loss of dry matter in these two samples, only 8-2 per cent, and 9-1 
per cent. The small loss is certainly a point in favour of this type of 
silage. 

The silage in small silo No. 3 is not typical of commercial silage and 
therefore no important conclusions can be drawn except perhaps that 
rain washed fodder as well for its tendency to become mouldy, as for 
the washing of food material from it by rain in the field, cannot be 
expected to jiroduce first class silage. 

Methods of Analysis. 

The analysis of the green crop and silage samples was carried out 
in the following manner. The percentage of dry matter was determined 
by drying down representative samples of 200 grms. to constant weight 
in the steam oven. The estimation was carried out in duphcate and the 
dry residues were finely ground in a mill, allowed to air-dry for several 
days and then submitted to complete analysis. This involved deter- 
minations of moisture, crude, true and pepsin-HCl soluble protein, 
"amides," ether-extract, crude fibre, ash and nitrogen-free extractives. 
The results in every case were calculated to dry matter. When calcu- 
lating the amount of ether extract in the silage samples, it was necessary 
to make a correction for the volatile organic acids which are lost during 
the process of drying down. 

The analysis of the samples was left in the hands of Mr F. J. Aylett, 
to whom the writers would like to express their thanks for his careful 
work in this connection. 

In order to gain a further insight into the nature of the changes 
which occur during the ensilage of green forage, analyses were also 
carried out on aqueous extracts of the green crop and silage samples. 
Representative 200 grms. samples of the material were weighed out into 



.'MG Oat and Tare Silage 

wide-necked bottles of about 1200 c.c. capacity. To the material was 
then added 500 c.c. of distilled water (previously boiled and cooled) and 
the bottle was sto])|)ered with a rubber bung and vigorou.sly shaken in 
a shaking machine for four hours. The resulting dark brown coloured 
extract was filtered first through musHn. the residual material being 
well squeezed out. and then through a filter paper. 150 c.c. of the 
aqueous extract was then made up to 500 c.c. with alcohol; this caused 
the separation of a small amount of precipitate, which settled readily. 
The clear liquid, which was slightly yellow in colour, was then filtered 
oil' through a dry filter paper and submitted to analysis by means of 
the Foreman alcohol titration method. 

The amounts given in the following description of the method refer 
to the analy.sis of the silage extracts; the determinations on the green 
crop extracts were carried out on larger volumes, since the ingredients 
to be estimated were only present in relatively small amounts in such 
extracts. 

10 c.c. of the alcoholic li(|uid were diluted with .50 c.c. alcohol and 
the solution was titrated with .V/10 NaOH in the presence of phenol- 
phthalein. When the neutral jjoint was reached, 12 c.c. of a ne\itral 
aqueous formalin solution were added, whereon the pink colour was dis- 
charged and the addition of one or two drops of iV/10 NaOH was necessary 
to restore neutrality. The total titre of ^V/IO NaOH gave a measure of 
the total acid grouj)s, free and combined, in the extract. It is im])ortant 
to remember that amino acids and amides of the asparagine type are 
also included in this measurement. The small amount of alkali re<]uisite 
to restore neutrality after the addition of formalin has been shown by 
Foreman to be an indication of the amount of dibasic amino acids and 
proline present in the solution. 

The titration method of Foreman also enabled the amounts of amino 
acids and volatile bases in the extracts to be determined. To 50 c.c. of 
the alcoholic liquid in a 500 c.c. distillation flask was added an amount 
of iV/10 NaOH sufficient to produce neutrality. The contents of the 
flask were then submitted to steam distillation, a vigorous current of 
COj-free steam being passed through for about five minutes. The bases 
with the alcohol were caught in 10 c.c. N jlO HCl which had ])reviously 
been pipetted into the receiver. The excess of acid in the contents of 
the receiver was determined by titration with iV/10 NaOH in the presence 
of alizarin and the amount of acid equivalent to the volatile bases 
estimated by dift'erence. The liquid remaining in the flask, which is 
alkaline after the distillation owing to the hydrolysis of the salts of 



A. Amos and H. E. Woodman :>47 

amino acids, was cooled, diluted with distilled water and titrated with 
iV/10 HCl to phenolphthalein, the amount of free alkaH in the flask being 
equivalent to the amino acids in the original 50 c.c. of alcoholic liquid'. 

In order to obtain the amount of volatile organic acids in the alcoholic 
liquid. .10 c.c. were pipetted into a 500 c.c. distillation flask and an 
amount of N/iO RSO^ shghtly in excess of the equivalent to the volatile 
bases was added. The contents of the flask were then submitted to 
steam distillation, in every case 500 c.c. of distillate being collected. 
The acidity of the di.stillate was determined by titrating with N/U) 
NaOH to phenolphthalein. 

The results thus obtained, in conjunction with the moisture content 
of the material, enabled the amounts of the different ingredients in the 
original material to be calculated. The results were expressed in the 
following manner: 

e.cV 

Total aciflic groups, free and comiiinecl A 

Amino acifLs and aniide.s of asparagine type B 

Total organic acitis of lactie and ac-etie type .\-B 

Organic acids volatile in steam ( ' 

Non-volatile organic acids A -B-(.' 

Volatile bases I) 

Several advantages attach to the use of the above method of dealing 
with silage extracts which are not jjossessed by the titration methods 
previously in use. 

( 1 ) The titration of total acidity is carried out in a liquid which is 
almost water clear, the light yellowish brown colour of the alcoholic 
liquid practically disappearing on further dilution with alcohol. The 
end point in the titration is much more satisfactory than that obtained 
when direct titration of diluted aqueous extracts is resorted to. 

(2) On treating the aqueous extract with alcohol as described above, 
proteins, albuminoses, etc. are precipitated. This treatment therefore 
removes certain classes of substances which might interfere with the 
determination of the simpler constituents. 

{?)) The determinations of the amino acids and volatile bases are 
carried out in one operation. A knowledge of the relative amounts of 
these con.stituents is of value in studying the degree of putrefaction 
which may have occurred in samples of spoilt silage^. 

(-1) Alcoholic silage extracts jtrepared in the manner described can 
be kept over long ])eriods without undergoing change. 

' For a full account of the technique and significance of the Foreman method, the 
original publication should be consulted (Foreman. Biorh. J . 14, 4.51. 1920). 
- Foreman and Graham-Smith, J. Hygiene, IS, 109, 1917. 



]4S 



Oat ami Tart Silage 



Table II. Showing clianges in contenl of dry matter, volatile and non- 
volatile organic acidx, amino acids and volatile baxcs undergone by the 
out and tare crop in the I'arious .silos per 1000 grnis. dry oats and tares. 

Silo I. 





Green oats 








and tares 


Bag 1 silage 


Bag 2 silage 




c.c. -V 


c.c. .V 


c.c. .V 


Volatile organic acids 


9-0 


299-0 


194-9 


Non-volatile organic acids 


.337-0 


923-2 


986-6 


Amino acids 


75-0 


472-5 


433 1 


Volatile bases 


17-0 


116-4 


108-3 


Dry matter 


1000 gms. 


868-5 gms. 


866-2 gms. 



Silo II. 





(ircen oats 

and tares 

c.c. .V 


Bag 4 silage 
c.c. .V 


Bap 5 silage 
e.e. .V 


Volatile organic acids 
Nonvolatile organic acids 
Amino acids 
Volatile bases 


7-0 

309-0 

.-)5-() 

19-0 


268-9 

601-1 

444-2 

89-0 


284-7 

534-8 

493-9 

90-0 



])rv maUer 



1000 gms. 



917- 



009-5 gms. 



Sil( 



Volatile organic acids 
Non-volatile organic acids 
/\mino acids 
Volatile bases 
Dry matter 



Volatile organic acids 
Non-volatile organic acids 
Amino acids 
\'olatile bases 
Dry matter 



llrfoii rtiita 


Bag 7 
silage 
c.c. X 




Bag 8 silage 




and tares 


Unspoilt 
c.c. .V 


S|X)ilt 
c.c. .V 


Total 
c.c. A' 


ti-0 
243-0 

43-0 

230 
1000 gins. 


121-4 
503-6 

288-7 
84-5 
899-3 gms. 


113-1 9-2 
2()8- 1 69-8 
174-1 69-8 
63-5 .56-4 
516-5gms. 318-5gm.s. 


122-3 
337-9 
243-9 
119-9 
835-0 gm; 




Big silo. 








Green 


oats and tares 




Oat and tare silage 


Bags 
c.c. .V 


Bag~6 
c.c. .V 


Bags 
c.c. X 


Bagfi 
c.c. A' 


9-0 6-0 

337-0 247-0 

75-0 37-0 

17-0 14-0 

1000 gms. 1000 gms. 


215-4 
900-2 
365-2 
106-3 
886-0 gms. 


304-2 
761-5 
437-8 
92-8 
927-5 cms. 



A. Amos and H. E. Woodman 34:9 



Table III. Condituenis of silage extract expressed as 
percentages of moisture-free silage. 

of bag 1 i; 3 4 5 6 7 8 





0- 

/o 


o 


o. 


o/ 


o/ 
/o 


0' 

/o 


() 


Unspoilt Spoilt 

t > o 


Volatile organic aeiils* 


2-07 


i-3r> 


1-40 


l-7(i 


1-88 


1-97 


0-81 


1-31 ()I7 


Non-volatili- org. acidst 


(io3 


7'22 


6-11 


311 


2-51 


5-17 


2-85 


2-48 — 


Amino acidsj 


4-76 


4-38 


3(;i 


4-24 


4-75 


413 


2-81 


2-95 1-92 


Volatile bases]; 


117 


109 


lUo 


85 


0-87 


(••88 


0-82 


1-08 l-.j;") 



* r'ak'ulatecl as acetic acid. 

f Calculated as lactic acid (see table given later under "Changes suffered by Ether 
Extract"). 

.■f Calculated as crude protein. 

Comments on Tables II and III. The significance of the above data 
will be dealt with fully in the general discussion of the results. At this 
point, it is only desired to call attention to the following: 

1. In all the bags containing normal silage, the non- volatile acids 
preponderated largely in amount over the volatile organic acids. 

'2. Where moulding of the silage occurred (as in bag 8), the volatile 
and non-volatile organic acids were not simply neutralised by the basic 
decomposition products of the jDrotein constituent, but were actually 
destroyed. This is in agreement with the observations of Dox and 
Neidig^ and the behaviour is further exemplified by the results of an 
analysis carried out on a samjde of mouldy silage from the top of silo II: 

CO. N 

Volatile organic acids — 

Non-volatile organic acids 2ri-9 

Amino acids 1(1-7 

Volatile bases UiO 

In this case, all the volatile organic acids and most of the non-volatile 
had disappeared as a result of mould activity. The meaning of the high 
ratio of volatile bases to amino acids will be discussed later. 

3. The results for bag 3 silage are, as anticipated, quite normal, 
although this bag was allowed to remain in the big silo some mouths 
after the other bags had been removed. 

' Dox and Ncidig, iJcNcri/r/i BiiUeliii. No. 10, Iowa Experiment Station. 



350 



Out aiul Tare Sihuje 



Table IV. Amounts of constituents of green oats and tares and oat 
and tare silage contained in bag I and bag '2 (sil-o I). 

Analysis of samples (i-alciilatod tu dry matter). 









Green oats 


Bag I 


Bag 2 








and tares 




silage 

O' 


silage 

o 


fVuile jirotein 






121.-. 




12-27 


. o 
12-01 


Ether extract* 






:!r.!i 


3-12 


3-21 


N-free e.xtractives 






oOGT 


47-92 


47-<>2 


Crude fibre 






25- 10 


27-75 


27-87 


Ash 






8-49 


8-94 


8-09 


True protein 






9-20 


.1-03 


5-7G 


'"Amides" 






2-9.1 


7-24 


«-8.-) 


Pepsin-HCl soluble 


protei 


in 


1002 


943 


9-90 


I'rotein digestion eoeHicit 


■nts (/// rilro) 


,S2-.-. 


7(i-9 


78-5 



* Not taking into account the volatile organic acids of the silage. 



Bagl 



Bag 2 









\ 


f 




^ 




C.reenoats 


Oat and 




Green oats 


Oat and 


% 




and tares 


tare silage 


increase 


and tares 


tare silage 


increase 




()■/.. 


oz. 


nr loss 


oz. 


oz. 


or loss 


Moist material 


1053-0 


919-0 


- 12-7 


1118-0 


930-0 


- 16-8 


Dry matter* 


247-1 


214-0 


- 13-2 


202-4 


227-3 


- 13-4 


Ortianic matter* 


226-1 


19.5-S 


^ 13-4 


240-1 


207-8 


- 13-5 


Crude protein 


.30-0 


25-8 


- 140 


31-9 


28-3 


- 11-3 


Ether extract* 


8-9 


10-9 


+ 22-5 


9-4 


10-2 


+ 8-5 


N-free extractives 


12.-.-2 


100-8 


- 19-5 


1330 


lOG-8 


- 19-7 


Crude lihre 


(J20 


.58-3 


- 5-9 


05-8 


62-5 


- 5-0 


Ash 


210 


18-8 


- 10-5 


22-3 


19-5 


- 12-5 


Ti-ue protein 


22-7 


10-t) 


- 53-3 


24-2 


12-9 


- 4(i-7 


'■ -Amides" 


7-3 


15-2 


' 108-2 


7-7 


15-4 


-1- 1000 


Pepsin- KCl soluhio 


24-8 


19-S 


- 20-1 


2«-3 


22-2 


- 15-6 


prt)tein 















* -Mlowanee made for silage \'ohitiIe organic acitts as acetic acid- Amount of silage 
dry uuitler in bags calculated as residue after drying at 100° C: 210-3 oz. (bag 1) and 
224-3 oz. (bag 2). 



A. Amu?; and H. E. Woudman 



351 



Table V. Amounts of con.slitiii'nts of green oats and tares and oat 
and fare silaye contained in bag i and bag 5 (silo II). 

Analysis of samples (calculated to dry matter) 







Green oats 


Bag 4 


Bago 






and tares 
o 


silage 
o 


silage 
o 


Crude protein 




/o 
11-37 


12-81 


(1 
1309 


Ether extract* 




3-95 


3-18 


?.ir) 


N-free extractives 




49-93 


48-62 


47- 10 


Crude fibre 




2703 


26-81 


27-76 


Ash 




7-72 


8-58 


8-90 


True protein 




8-89 


6-75 


6-93 


"Amides" 




2-48 


606 


616 


PepsinHCl soluble 


protein 


9-35 


9-97 


10-57 


Protein digestion coefiicients {in vitro} 


82-2 


77-8 


80-7 



* Not taking into account the volatile organic acids of the silage. 







Bag 4 






Bag 5 








^^ 






A 






Green oats 


Oat and 


o 


Green oats 


Oat and 


",' 




and tares 


tare silage 


increase 


and tares 


tare silage 


increase 




07.. 


oz. 


or loss 


oz. 


oz. 


or loss 


Moist material 


93.50 


9060 


- 3-1 


906-0 


872-0 


- 3-7 


Dry matter* 


3.340 


306-.) 


- 8-2 


323-6 


294-3 


- 9-1 


Organic matter* 


308-3 


280-7 


- 8-9 


298-6 


26S-(i 


- 10-0 


Crude protein 


38-0 


38-6 


-f 1-6 


368 


37-8 


+ 2-7 


Ether extract* 


13-2 


14-9 


+ 12-9 


12-8 


14-5 


+ 13-3 


N-free extractives 


166-8 


14()-4 


- 12-2 


161-0 


136-1 


^ 15-8 


Crude fibre 


90-3 


80-8 


- 10-5 


87-4 


80-2 


- 8-2 


Ash 


2.5-7 


25-8 


+ 0-4 


25-0 


■25-7 


+ 2-8 


True protein 


29-7 


20-3 


- 31-7 


28-S 


20-0 


^ 30-6 


"Amides" 


8-3 


18-3 


+ 120-5 


8-0 


17-8 


+ 122-5 


Pepsin-HCl soluble 


31-2 


30-0 


- 3-9 


30-3 


30-5 


+ 0-7 


protein 















* Allowance made for silage volatile organic acids as acetic acid. Amount of silage 
dry matter in bags calculated as residue after drying at 100° C. : 301-3 oz. (bag 4) and 
288-9 oz. (bag 5). 



352 



(hit mill Tan' Silaye 



Table VI. Amounts of consliliients of green oats and tares and cat 
and tare silage contained in bag 3 and bag 6 (big silo). 

Analysis of samples (calculated to dry matter) 

Ureen oats aad tares Oat and tare silage 



Bag 3 



Bag (i 



Bags 



Bag G 



Crude protein 






12-15 


10(52 


10-99 


ll-5(i 


Ether extract* 






3r>i) 


3-38 


3-37 


3-05 


N-free extractives 






50()7 


52-27 


50-(i5 


50-88 


Crude fibre 






2510 


25-94 


26-81 


26-20 


Ash 






8-49 


7-79 


8-18 


8-31 


True protein 






9-20 


812 


5-14 


5-03 


"Amides" 






2-95 


2-50 


5-85 


6-53 


Pepsin-HCl soluble 


i>i'otein 




1002 


8-77 


8-29 


9-01 


Protein digestion coefficients 


{in vilro) 


82-5 


82-6 


75-4 


77-9 



* Mot taking volatile organic acids of silage into account. 



Bag 3 



Bag 6 





Green oats 


Oat and 


0/ 

o 


Green oats 


Oat and 


\ 

O' 

o 




and tares 


tare silage 


increase 


and tares 


tare silage 


increase 




oz. 


oz. 


or loss 


oz. 


oz. 


or loss 


Moist material 


11200 


7.59-0 


- 32- 1 


SS3-(» 


80-i() 


, 1-0 


Dry matter* 


262-9 


232-9 


-11-4 


287-8 


2()7-(l 


- 7-2 


Organic matter* 


240-6 


214-1 


-11-0 


265-4 


245-2 


- 7-6 


Crude ])rotein 


31-9 


25-2 


-210 


30-6 


30-3 


- 10 


Ether extract* 


9-5 


11-0 


-f 15-8 


9-7 


13-1 


+ 35-1 


N-free extractives 


1.33-2 


116-3 


-12-7 


150-5 


1.33-2 


- 11-5 


Crude fibre 


6(i-0 


61-6 


- 6-7 


74-6 


68-6 


- 8-0 


Ash 


22-3 


18-8 


- 1.5-7 


22-4 


21-8 


- 2-7 


True protein 


24-2 


11-8 


-51-2 


23-4 


13-2 


- 43-6 


"Amides" 


7-7 


13-4 


+ 74-0 


7-2 


171 


+ 137-5 


Pepsin- HCl soluble 


26-3 


19-0 


-27-7 


25-2 


23-6 


- 6-3 


protein 















* Allowance made for silage volatile organic acids as acetic acid. Anmunt of silage 
dry matter in bags calculated as residue after drying at 100° C: 229-6 oz. (bag 3) and 
261-8 oz. (bag 6). 



A. Amos and 11. E. Woodman 



853 



Table VII. Anmiuils of constiluenls vf i/rceii, uais and lares ami out 
and tare silage in bag 7 and bag S (silo III). 



Analysis of samples (calculated to chy matter) 



Ba" 8 .si la'' 











tJreen oats 


Bag 7 




r ^ 


^ 












and tares 


silage 


Unspoilt 


Spoilt 












0/ 


/o 




o,' 


0/ 












/O 




/o 


,0 




Crmle protein 








11-97 


13-34 




12-68 


15o5 




Etlier extract* 








3-87 


2-81 




2-70 


2-88 




N-free extracti 


vcs 






45-43 


44-49 




40- 15 


38-59 




t'rudc tibre 








3014 


30- 10 




29-82 


31 -.32 




Ash 








8-59 


9-20 




8-05 


11 (iO 




True protein 








8-32 


7-40 




7-19 


11-73 




"Amides" 








3 05 


5-88 




5-49 


3-82 




Pepsin-HCl sul 


ublc 


protein 




1010 


10-47 




902 


9-02 




Protein digestion coefficients 


{in uitro) 


84-4 


78-5 




75-9 


01-9 






* Not taking 


volatile ( 


Drganic acids of silage into account. 












Bag 7 








Bag 8 












A 








A 










Cireen 


Oat 


^ 


f 
CJreen 








'' 






oats 


and 


(1 
(J 


oats 


Un- 






"i, 






and 


tare 


increase 


and 


spoilt 


8|joilt 




increase 






tares 


silage 


or 


tares 


silage 


silage 


Total 


or 






07.. 


oz. 


less 


oz. 


oz. 


oz. 


oz. 


loss 


Moist material 




778-(l 


7230 


7-1 


780'0 


4010 


238-0 


039-0 


-18-1 


Dry matter* 




-'93 8 


204-2 


1(1-0 


294() 


1521 


93-8 


245-9 


- 1 0-5 


Organic matter* 




:;(i8l> 


240- 1 


100 


209:! 


1391 


.S2-9 


2220 


-170 


Crude protein 




3.-)-2 


350 


0-0 


35 3 


19-0 


140 


330 


- 4-8 


Ether extract* 




11-4 


9-4 


17-0 


11-4 


(i-O 


2-7 


8-7 


- 23-7 


N-free extractives 




133-5 


1100 


12-7 


133-8 


09-3 


30-2 


105-5 


-211 


Crude fibre 




88-5 


79- 1 


100 


88 '8 


448 


29-4 


74-2 


- 10-5 


Ash 




25-2 


24- 1 


4-4 


25-3 


130 


10-9 


23-9 


- 5-0 


True protein 




24-5 


190 


- 20-0 


24-5 


10-8 


11-0 


21-8 


-11-0 


"Amides" 




10-7 


15-4 


+ 44-0 


10-8 


8'2 


3I> 


11-8 


-i- 9-3 


Pepsin-HCl soluble protei!i 


29-7 


27-4 


- 7-7 


29-8 


14-5 


9(1 


23-5 


-211 


* Allowance made for 


silatre volatile organic acids as 


acetic acid. Am 


nurit of sil 


age dry 


matter in 


bag 7 calcndated as 


resi< 


lue after 


drying : 


It 100° C.=: 


202-1 oz. 


In bag 


; 8: 150-2 


oz. (uns 


poilt) and 


93-8 ozs. (spoilt). 
























7 


8 


-I-29-8 


- 25-4 


-92-3 


+ 5-0 


- 5-2 


-190 



Discussion of Results. 
I. Moisture and dry matter ehanges daring ensilage. 

Numlier of bag 1 2 3 4 5 

(_'hange of moisture content -101-5 -152-9 -331-0 -1-5 -4-7 

(oz.) 
Percentage change of - 12-0 - 17-9 - 38-0 -0-2 -0'8 

moisture content 

The above figure.s are of interest owing to the fact that certain of the 
soluble constituents of the silage are lo.st in the juice draining away from 
the silo. The losses in the silo are obviously compounded of two main 
factors: 1. Fermentation losses. 2. Losses in the juice draining away. 
Thus, where excessive drainage occurs, the percentage loss of dry 
matter may be high. 



354 Old (Hid Tan SiL(((j< 

Such cases arc funiishod by bags 1 and '1 (silo 1) ami bag li (big silo). 
The reasons for the large losses of moisture from these bags are twofold : 
1 . The green fodder carried an appreciable amount of superficial moisture 
owing to its having been rained on just previous to cutting. 2. The 
oats and tares were cut in an immature condition and were as a conse- 
quence exceedingly "sappy." No wilting was allowed to take place 
befoie filling the material into the bags and the moisture content was 
therefore mucli liigher than that of the material in bags 1, d, 7 and 8. 

It is clear that the relatively high losses of dry matter from bags 
] and 2, as compared with those from bags 1 and "j, are to be attributed 
to the extra losses occasioned by drainage. It follows, therefore, that 
whilst green "fruity" silage of an excellent quality was obtained by 
preserving the unwilted, immature forage, yet the excessive drainage, 
consequent on "sappiness," led to a needlessly high percentage loss of 
dry matter. 

A study of the figures obtained for bags 4 and 5, which were filled 
with wilted oats and tares and from which little or no juice was lost 
by drainage, indicate that the actual fermentation losses need not 
exceed 8 i) per cent, of the original dry matter present. 

The large loss of moisture which occurred in bag 3 has already been 
referred to in an earlier section of the paper. The gain of moisture in 
bag G is explained by the fact tliat the bag was placed in tiiu big silo 
and was surrounded by material po.ssessing a higher moisture content. 
The infiltration of juice has to somi^ extent augmented tlu- amount of 
dry matter present in the bag, so that the net loss of dry matter as a 
result of fermentation is low, namely 7 per cent. 

It is of interest to note the high percentage loss of dry matter which 
occurred as a result of spoihng in bag 8, amounting to 16-5 per cent. 

II. Changes suffered 6// the nitroyvnuas constituents. 

It is obvious that during the conversion of the green crop into silage 
a profound change takes place in the character of the nitrogenous con- 
stituents, mainly resulting in the splitting up of a large proportion of 
the true protein into simple soluble ])roducts of the amino acid type. 
For example, only about i 1 i)er cent, of the crude protein in the bag I 
silage was in the form of true protein, whereas the true protein in the 
green oats and tares represented 7() per cent, of the total nitrogenous 
constituents. The figures in this connection for the material in the 
different bags are as follows: 



Xumbur of ban 



Amount of true j Green oats I 
protein exjiressed ; and tares ) 
as percentage of : (Jat and ] 
crude protein ) tare silage j 



los AND H. E. Woodman 


:J55 


12 3 4 5 


7 S 




Unspoilt Spoilt 


75-7 7:)-7 7.5-7 7S-2 7S-2 7()-5 


70U 7UU 70-U 


410 45-7 4i;« 52-7 52-il 43-5 


5(j-U 5li-7 75-4 



The hydrolytic changes affecting the true protein constituent appear 
to proceed to the greatest extent during the ensilage of the moist un- 
wilted oats and tares. Thus in bags 1, 2 and 3, containing unwilted 
material, the change caused a disap])earance of roughly 50 per cent, of 
the true protein, this being associated with an increase in the amount 
of "amides" of about 100 per cent, in the case of bags 1 and 2 and 
74 per cent, in the case of bag .3. A bigger increase in the amount of 
"amides" would undoubtedly have been registered had it not been for 
the loss of soluble nitrogenous constituents in the large volumes of juice 
draining away from these bags, since in bags 4 and 5, containing wilted 
oats and tares, and where little or no drainage occurred, a .splitting up 
of 30 per cent, of the true protein was accompanied by a 120 per cent, 
increase in the amount of "amides." The shghtly wilted material in 
bag 6, which was converted into silage possessing a high moisture content 
compared with that of the silage of bags 4 and .5 and which suffered no 
losses on account of drainage, suffered a large loss of true protein 
(44 per cent.) and the "amides" were augmented to the extent of 138 
per cent. 

The material filled into bags 7 and fS had obviously been subject to 
change during the time it lay out in the field, since only 70 per cent, of 
the crude protein was in the form of true protein. The changes in the 
character of the nitrogenous constituents were not nearly so far reaching 
in these bags as with the material in the other bags. In bag 7, only a 
fifth of the true protein was hydrolysed and the "amides" were only 
increased by 44 per cent. In bag 8, where extensive spoihng occurred, 
only II per cent, of the true protein disappeared and the "amides" 
were only augmented to the extent of 9 per cent. In the actual spoilt 
portion of bag 8 silage, the true protein formed a larger proportion of 
the total crude protein than was the case in the original oats and tares 
placed in the bag, the rotting of the material having to a large extent 
used up the "amides." 

The above results indicate therefore that the ensiling of "sappy" 
unwilted forage leads to conditions which are favourable to the ex- 
tensive splitting up of true protein into "amides." From the nutritive 
standpoint, it is uncertain whether this can be considered advantageous. 

Jonrn. of Agric. Sci. xn 24 



856 



Oat and Tare Silage 



By combining the results obtained in the analysis of the dry matter 
of the saniph's with those obtained in the titration of the extracts, it is 
possible to ascertain in what form the "amide " fractions of the foodstuffs 
existed. 

Per 100 grins, dry matter (nitrogen expressed throughout as protein) 
Bag 1 Bag 2 Bag 3 Bag 4 





Cireen 




(irecn 


Green 




Green 




crop 


Silage 


erop Silage 


crop 


Silage 


crop Silage 




o/ 
/o 


/o 


o/ o/ 
A) /o 




o/ 
/o 


0/ o/ 
/o /o 


Amino acid.s, etc. 


oil 


4-7() 


Oil 4-38 


on 


301 


008 4-24 


Volatile bases 


002 


1-17 


002 109 


()()2 


10.5 


003 0-85 


True amides 


2-82 


1-31 


2-82 1-38 


2-82 


119 


2-37 0-97 




Ba 


J55 


Bag 


Ba 


g" 


Bag 8 




Green 




(ireen 


Green 




Green Silage 




crop 


Silage 


crop Silage 


crop 


Silage 


crop , * ^ 

Unspoilt Spoilt 




o/ 


0/ 


IV 0/ 


o/ 


0/ 


O' O' o/ 

/o /o /o 




/o 


/o 


-o /o 


/o 


/O 


Amino acids, etc. 


008 


4-74 


005 4-13 


006 


2-81 


006 2-95 1-92 


\'olatiU' l>ases 


003 


0-87 


002 0-88 


003 


0-82 


003 108 1-55 


True amides 


2-37 


0-55 


2-43 1-52 


3-54 


2-25 


3-54 1-46 0-35 



The amino acids (with amides of the asparagine type) and volatile 
bases are determined by titration of the extracts. The result obtained 
by subtracting the sum of these from the "amides"' as determined in 
the analysis of the dry matter of the samples has been designated "true 
amides"; i.e. amides which do not contain a free carboxyl grouj) and 
thus escape determination during titration of the extracts. 

It is of interest to note that amino acids and amides hke asparagine 
comprise only a very small fraction of the "amide" constituent of green 
oats and tares. This fact is in harmony with the conception that these 
substances represent stages in the synthesis of plant protein and there- 
fore exhibit no tendency to accumulate in the plant. 

The outstanding features of the silage "amide" figures are: 1. A big 
increase in the amount of amino acids, these forming, in the case of 
unspoilt samples, the bulk of the "amides" of the silage. 2. An increase 
in the amount of volatile bases. 3. A decrease in the amount of "true 
amides." The increase in the volatile bases is probably explained by 
the production of ammonia by a hydrolytic change affecting the "true 
amides." Thus, in bag 1, 1-5 percent, "true amides" disappeared and 
1-15 per cent, volatile bases made their a])pearance. The figures for 
bag 8, where spoiling occurred, are excej)tionai. in the case of the spoilt 
portion of bag 8 silage, the amounts of amino acids and "true amides" 
were low, whereas the amount of volatile bases was relatively high. 



A. Amos and H. E. Woodman 357 

Such features may be regarded as the chemical evidence of tipoihng, the 
volatile bases having made their appearance as a result of the destruction 
of amino acids. In the production of good silage, the main changes 
aflecting the nitrogenous constituents are probably brought about by 
proteolytic enzymes and an investigation of the material reveals a high 
ratio of amino acids to volatile bases. The rotting of silage is evidenced 
by a low ratio. The ratio in the case of bag 7 silage affords evidence 
of the slight degree of spoiling which actually did occur in this bag. 
A further ilhi.stration is seen in the figures already given for the titration 
of the extract of the spoilt silage samjjle from the top of silo II. Here 
the volatile bases are actually present in excess of the amino acids, the 
ratio of amino acids to bases being roughly 1 : 1-6. 

In bags I, 2 and 3, where large quantities of juice were lost by 
drainage, there were appreciable losses of crude protein, probably in 
the form of "amides" dissolved in the juice. In bags 4, 5, G and 7, 
where little or no juice was lost by drainage, only small changes in the 
crude protein constituent were recorded. The slight gain of protein in 
bags 4 and 5 arose probably from experimental error (difficulty of 
accurate samphng, etc.). It may safely be assumed that if silage can be 
made without excessive drainage from the silo, then the loss of crude 
protein will be small. A twofold problem awaits satisfactory solution 
if the practice of ensilage is to develop on a sound economical basis: 
1. The prevention of excessive drainage from the silo. "2. The possible 
utilisation of silage juice in feeding. Both these questions are receiving 
attention at the present time. 

In every case the crude protein digestibility of the green oats and 
tares (as determined in vitro) suffered a slight depression as a result of 
ensilage. A study of the data points to the probability that the de- 
pression of protein digestibihty is greatest where large losses of the easily 
assimilated "amides" occur as a result of drainage. Where spoiling 
occurs, as in bag 8, the decrease in protein digestibility may be con- 
siderable. 

III. Changes suffered by the Ether Extract. 

In all the bags, with the exception of bags 7 and 8, the amount of 
ether soluble material was augmented as a result of the changes under- 
gone by the green forage during ensilage. The increase was very variable 
in amount and apparently bore no relation to the percentage loss of 
nitrogen-free extractives. Thus, in bag 4, where about 12 per cent, of 
the nitrogen-free extractives disappeared, there was a 13 per cent. 



358 Oat and Tare Silarje 

increase in the ether extract, whereas in bag 6, an ahnost equal i)ei- 
centage destruction of nitrogen-free extractives was accompanied by a 
35 per cent, increase in the amount of ether extract. 

The results obtained in this regard for bags 1 and 2 were curious. 
In both bags the percentage loss of nitrogen-free extractives was about 
19 per cent.; in bag 1, however, the increase of ether extract was 23 per 
cent., the corresponding figure for bag 2 being only about 9 per cent. 
As bag 2 occupied the ujjper half of the small silo, it is ])ossible that a 
portion of the volatile organic acids escaped as a result of "heating," 
since analysis of the extracts showed that the bag 2 silage was iiiuch 
poorer in respect of volatile acids than was the bag 1 silage. 

In bags 7 and 8, where spoiling occurred, there was an appreciable 
decrease in the amount of ether extract during ensilage. It follows that 
where silage undergoes rotting, the process is attended by losses of ether 
soluble material. It has already been demonstrated that the organic 
acids are readily destroyed during the spoiling of silage by moulds. 

If the figures for the ether extracts be compared with those obtained 
in the titration of the organic acids in the extracts, certain interesting 
facts are disclosed which merit further investigation. The figures ob- 
tained for the green crop extracts show that the green oats and tares 
contained an appreciable amount of non-volatile material which titrated 
with iV/IO NaOH in the presence of phenolphthalein. The amount of 
volatile acidic constituent was negligible. The nature of the non-volatile 
acidic constituent was not ascertained. It was observed, however, that 
during titration of the green croj) extracts, a strong yellow colour de- 
veloped, which intensified as the neutral point was approached. It is 
probable tliat the oats and tares contain a constituent which reacts 
with the soda producing the colour change, and the soda used up in 
this reaction accounts for the high non-volatile acidic figure obtained 
for the green crop. As this phenomenon was noticed in an equal degree 
during the titration of the silage extracts, it follows that this constituent 
escapes destruction during ensilage, and thus it is not feasible to cal- 
culate the whole titration figure for non-volatile acidity in the silage in 
terms of lactic acid. It was further noted that the spoiling of silage by 
moulds occasioned the destruction of the constituent in question. 

The following table gives a comparison of the percentages of ether 
extract in the dried silage samples with th(> iion-voIatile acidity calculated 
as lactic acid, after subtracting from the uon- volatile acid titration 
figure the corresponding figure for the green oats and tares. 



A. Amos and H. E. Woodman 359 

Per lUOgrma. dry oat and tare silage: 

Bags 1 2 3 4 G 7 S 

Unspoilt 
sample 

Non-volatUe acidity calculated 0-53 7-22 6-11 311 2-51 5-17 2'85 2-48 

as lactic acid, % 
Ether extract in dry matter, o„ 3-12 3-21 3-37 3-18 3-15 305 2-81 2-70 

It would be anticipated that the amount of ether extract in the 
silage after drying at 100° would show some correspondence with the 
amount of non-volatile acidity calculated as lactic acid. This was the 
case in the material of bags 4, 5 and 7 and in the unspoilt portions of 
bag 8. Wide discrepancies occur, however, in the figures for the silage 
in bags 1, 2, 3 and 6, warranting the assumption that a very different 
acidic fermentation has taken place in these bags from that which 
occurred in the remaining bags. It is clearly impossible to assume that 
the non-volatile acid in these bags was lactic acid wholly. In this con- 
nection, it is interesting to remember that bags 1, 2 and 3 contained 
unwilted material, and bag 6 slightly wilted material, and that the 
fermentative processes in these bags went on therefore under much 
moister conditions than obtained in the other bags. The question is 
worthy of further investigation, since excellent samples of silage were 
obtained from bags 1, 2 and 6. It is probably incorrect to assume that 
lactic acid is the only non-volatile organic acid which may arise as a 
result of fermentative changes in the silo. 

IV. Changes suffered bi/ the crude fibre constituent. 

In every case, a loss of crude fibre was recorded as a result of ensilage, 
the loss varying from about 5 per cent, in the case of the unwilted oats 
and tares to about 10 per cent, in the case of the wilted material. In 
the case of the spoilt sample in bag 8, the loss of crude fibre was as much 
as 16-5 per cent, of the original amount of fibrous constituent in the bag. 

The question arises as to the type of action in the silage process 
which results in the disappearance of crude fibre. The explanation is 
probably to be found in work carried out by Voelcker^, who found that 
the following change occurs when straw chaff is mixed with a small 
quantity of green rye or tares (1 ton straw chaft' to about 1 cwt. of rye 
or tares) in the spring or summer and the mixture is allowed to ferment 
until the autumn. 

The untreated straw contained 23-7 per cent. N.-free extractives and 
54 per cent, crude fibre. 

The fermented straw contained 45-8 per cent. N.-free extractives and 
34-5 per cent, crude fibre. 

1 Voelcker, ./. of the R. Agric. Soc. of Eng. 7, 85, 1871. 



360 Oat (iiul Tare Silaye 

It is tlius obvious that the fermentation to which the straw was 
submitted had the effect of converting an appreciable amount of the 
cellulose of the straw into a form which could be dissolved during the 
process of determining the percentage of crude fibre. The conversion of 
crude fibre into nitrogen-free extractives involved a distinct improve- 
ment in the feeding value of the straw. 

From the results of the present investigation, it appears probable 
that the cellulose of thi^ green oats and tares undergoes to some e.\tent 
a similar breakdown during ensilage, resulting in a gain of nitrogen-free 
extractives and a corres|)ondiiig decrease in the amount of crude fibre. 
Indeed, the nitrogen-free extractives so formed may conceivably undergo 
further change with the production of organic acids, although this may 
not hap])en if the green forage develops acidity rapidly in the early 
stages of storage in the silo. 

It should be pointed out that the oats and tares used in this in- 
vestigation were cut in an immature condition, so that the optimum 
conditions obtained for observing possible changes affecting the fibrous 
constituent. To what extent the cellulose of mature forage would be 
subject to such changes is uncertain, though Voelcker' s work indicates 
that similar changes would occur. The ])oint is under investigation. 

The clianges modifying the cellulose constituent during ensilage of 
fodder are of great importance from the jjoint of view of nutritive value. 
The gain is twofold: 1. Part of the fibre breaks down into nitrogen-free 
extractives (and, to some extent possibly, to organic acids), i. The 
residual crude fibre itself possesses a greater digestibility tlian the 
original crude fibre in the green oats and tares^. 

V. Changes Kiijjered bi/ the nitrogen -free extractives. 

In no case was the loss of nitrogen-free extractives less than 11 per 
cent, of this constituent originally present in the bags. The biggest 
losses were registered in bags 1 and 2, the diminution being roughly 
19-5 per cent, in each bag. It is significant, in view of the remarks 
contained in the preceding paragraph, that the amount of crude fibre 
disappearing in these bags was much smaller than in the remaining bags. 

The results for bag 8 show that the rotting of a silage sam|)lc may 
lead to large losses of nitrogen-free extractives. 

VI. Changes suffered by inorganic constituents. 

Large losses of inorganic salts may occur during ensilage owing to 
the sohibli" portions escaping in the juice. Where little drainage occurs, 

' VVoodmiui, J. Ayric. Hci. 12, 144, 1922. 



A. Amos and H. E. Woodman ;361 

the loss of these constituents is not appreciable. These facts must be 
considered in conjunction with the importance attaching to the inorganic 
salt content of a foodstuff from the nutritional standpoint. If, for 
example, silage is to be utilised in feeding dairy cows, it is undesirable 
that the green crop should sustain large losses of inorganic salts during 
ensilage. 

Summary. 

Experiments have been described which had primarily as their object 
the investigation of the effect of varying moisture content in the green 
oat and tare crop on the type of silage produced from such forage. The 
magnitude of the changes affecting the constituents of the green crop 
under the different conditions of ensilage have also been detailed. 

The main conclusions are summarized below: 

(1) The ensihng of a fresh green crop in an early stage of maturity 
(soon after flowering) with Httle or no previous wilting, and with a fer- 
mentation temperature in the neighbourhood of 25° C., leads to condi- 
tions which favour the production of green "fruity" silage. The results 
of the experiments suggest that with this type, a considerable loss of 
dry matter may result from the process, especially if much drainage of 
sap occurs. The same conditions appear to be favourable to the ex- 
tensive splitting up of true protein into soluble nitrogenous products; 
more than 50 per cent, of the true protein of the green crop may be 
transformed into "amides," an appreciable pro]iortion of which may be 
lost, together with inorganic salts, in the drainage juice. 

Thus, though green "fruity" silage is much relished by stock and 
possesses excellent feeding value, yet its production may be accom- 
panied by substantial losses of crude protein and soluble salts. Loss by 
drainage should therefore be obviated. 

(2) The ensihng of a moderately dry crop, dried either by wilting 
or by allowing the crop to mature, produces conditions which favour 
the production of the acid brown type of silage. The production of this 
type of silage is accompanied by a relatively low loss of dry matter, the 
amount of juice drainage from the silo being very much smaller than 
that occurring during the production of green "fruity" silage. Approxi- 
mately .30 per cent, of the true protein of the green crop is spht up into 
"amides." 

(3) The ensiling of material which has undergone prolonged wilting 
and extensive rain-washing does not produce a good quality of silage, 
and the forage displays a tendency to become mouldy during the process. 



;J62 Oat and Tan S'daye. 

Where moulding occurs, the volatile and non-volatile organic acids are 
not simply neutralised by basic products, but are actually destroyed. 
The process is accompanied by large losses of dry matter, the "amides," 
nitrogcn-frce extractives and ether extract being extensively destroyed. 
C'liemical evidence of the spoiling of silage by mould development is 
afforded by a study of the ratio of amino acids to volatile bases in the 
silage extract. In good silage, the ratio is high; in spoilt silage, the 
volatile bases may be present actually in excess of the amino acids. 

(I) In all the samples of normal silage investigated, the non-volatile 
organic acids were ])resent in good excess of the volatile organic acids. 
Evidence has been brought forward warranting the assumption that the 
acidic fermentation during the formation of green "fruity" silage is 
markedly different from that accom])anying the production of brown 
acidic silage, and it appears jirobable that lactic acid is not the only 
non-volatile organic acid which may arise as a result of the fermentative 
action in the silo. 

(.5) The increases in the amount of ether extractable material as a 
result of ensilage are very variable in the different experiments and bear 
no relation to the ])ercentage losses of nitrogen-free extractives. 

((!) In every case, the crude protein digestibility of the green oats 
and tares (as determined in vitro) has been shown to suffer a slight 
depression during ensilage. 

(7) The outstanding features of the silage "amide" ligures as com- 
pared with the corresponding figures for tlie green croj) are: («) a large 
increase in the amount of amino-acids, these forming the bulk of the 
"amides'" of the silage; (b) an increase in the amount of volatile bases, 
the latter consisting probably of ammonia which has arisen us a result 
of hydrolytic changes affecting amides originally present in the green 
crop. 

(8) Results have been obtained which suggest tliat the cellulose of 
green oats and tares undergoes to some extent a breakdown during 
ensilage, resulting in a gain of nitrogen-free extractives and a corre- 
sponding decrease in the amount of crude fibre. Furthermore, as has 
been demonstrated in a [irevioiis communication, the crude fibre re- 
maining in the silage possesses a greater digestibility than that originally 
present in the green forage. 



{Received Aligns! 7l/i. I!)'2'2.') 



THE AVAILABILITY OF MINERAL PLANT FOOD. 

A MODIFICATION OF THE PRESENT HYPOTHESIS. 

By NORMAN M. COMBER. 

{Department of Agriculture, The Urdversity, Leeds.) 

The Present Hypothesis. 

Scientific soil researches have pussed through one fairly well defined 
phase. The important and pioneer work of empirical field trial has 
established the main physical and chemical requirements of crops and 
laid down the routine method of examining soil amendments. 

The researches of recent years have inaugurated a second phase : an 
enquiry into the constitution of the soil and into the mechanism of the 
growth of plants in soil. In connection with this second phase of soil 
investigations much progress has been made on the botanical side in 
developing knowledge of the mechanism of processes which go on inside 
the plant, and in the last decade views of the constitution of the soil have 
changed fundamentally. But the relation of the plant to the soil has 
received very scanty consideration in modern literature. Views on that 
subject are very much as they were after Daubeny's publication in 1845. 
Outstanding work has been done by Dyer^, by Cameron and Whitney-, 
and by HalP and his collaborators. There have been some changes of 
interpretation and some differences of opinion, but the fundamental 
assumption that the soil solution is the nutrient medium of the plant, 
that the state of solution is necessary to availability has remained almost 
unquestioned. 

The basis of practically all teaching on the chemistry of soil fertility 
and on the value of fertiUzers, is the behef that nutrient substances pass 
into solution in the soil water externally to the plant and subsequently 
diffuse into the root hairs. Much well-known discussion has arisen about 
the solvents concerned, particularly about the possible excretion of 
organic acids by the plant. 

' Tran.-i. Chem. Sue. 189-t, 65. 

= U.S. Dept. Aijrk. Bureau vj Soils Bull 1903. No. 22. 

3 Phil. Trans. 1913. 



3G4 The Arailabili/i/ of Mineral Phmt luxnl 



The Inadequacy of the Present Hypothesis. 

There ;ire a number of facts wliieh are difficult to reconcile with this 
hypothesis. 

1. The relatio)! of the composition of the soil solution to the mineral 
elements taken up, and the water transpired, by plants. In obvious and 
natural accordance with the view that the soil solution is the nutrient 
solution of the plant, many attempts have been made to express or dis- 
place this solution from the soil, and by its analysis to ascertain the 
essential chemical knowledjj;e of the fertility of the soil concerned. The 
results of these experiments show that the ratio of certain mineral ele- 
ments assimilated by plants to the water transpired is greater than the 
ratio of these elements to the water in which they are dissolved in the soil. 
Hall' has calculated that if the potash taken up by a clover C'rop is 
assumed to have been dissolved in the water transpired, the calculated 
solution is far more concentrated in respect of potash than solutions 
obtained from the soil. Raniiinn- makes a similar observation but arrives 
at a different conclusion. H;ill deduces that the dissolved material enters 
the plant from the soil solution at a greater rate than the water. Ramann 
is apparentlv unable to reconcile this view with the laws of diffusion and 
concludes that the i)lant takes material from the soil other than that 
which is in solution. 

2. The absorption of iron by plants. Iron is a necessary element for 
plant growth. All plants take up a certain amount from the soil. The 
amount necessary is relatively small, but it is difficult to see how even 
this small amount can exist in sol id inn in soils containing a high percentage 
of (thalk. 

3. The nvailabilil 1/ of phosphates. This is probably the greatest 
difficulty of all. Tlic value of various phosphatic substances to plants is 
not by any means in accordance with the present hypothesis. Basic slag 
and certain mineral phosphates are sparingly soluble and are yet valual)le 
phosphatic fertilizers. The evaluation of these substances entirely on a 
solubility basis has not been an un(iualified success. Their usefulness as 
phosphatic fertilizers is often comparable to that of a water soluble 
phosphate. 

Tlie phosphates of iron and aluminium are in a curious position in the 
literature. On t he one hand it is normally taught that these are insoluble 

» '/'At Soil. 19-20. 

- Lamlir. VirSlul. 1<)10, 88. 



N. M. doMHRR 365 

and of little use to the plant, and that the formation of these phosphates 
in superphosphates diminishes the value of the material to the plant. 
On the other hand, direct ex])erimenti leaves no doubt that phosphates 
of iron and aluminium are very useful to the plant as sources of phos- 
phorus. There seems to be a prejudice, which prevails in spite of experi- 
mental evidence to the contrary, that sparing solubility must mean a low 
availabilitv. The e.xperimental fact is that sparint^ly soluble phosphates 
are often easilv available, and the inevitable conclusion is that solubility 
is not the dominatinji' condition of availability. 

A Modification of the Present Hypothesi.s. 

The hypothesis that all material entering the plant from the soil first 
becomes dissolved in the soil water and then diffuses into the root hair, 
arose on the basis of two fundamental beliefs. First, the physiological 
belief that only material in true solution can diffuse through the cell 
protoplasm and second, the belief that the soil is a simple system of 
particles moistened by a solution. Now tliese two fundamental concep- 
tions have become modified. Becaxise of the modifications and also 
because of the cbscrepancies already noted between the facts and the 
hypothesis, it is desirable that the hypothesis should be reconsidered. 

The absorption of colloids hi/ the plant. As a first point in the recon- 
sideration it may be noted that the teaching that only material in true 
solution can diffuse into the plant cells is not unquestionably true. There 
is some eviflence that less highly dispersed material can enter. Czapek- 
definitely states that colloids can enter the plant cells. "Die lebende 
Plasmahaut ist nicht nur fiir echte Losungen, sondern auch fiir kolloide 
Losungen durchlassig." He refers to the passage of dyestuffs and of fat 
emulsions into plant cells. Pfeffer^ records the diffusion of silicic acid 
into the cell sa]) of plants. 

There is also some recent experimental evidence in favour of the 
absorption of colloidal silica by plants. Jennings* describes a series of 
experiments in which wheat seedlings were grown in water solutions to 
which were added various absorbing substances. When colloidal silica 
gel was used there was a marked increase in growth and in drv matter, 
and it was clearly shown that the plant had absorbed silica. 

' See Marais, Soil Set. 1922, 13, No. .") ;uui bibliography. 
" Biochemie der PJIanzeii, 1M3. 
' Tlw Ptiysioloyij uf Plants. 1900. 
« Soil Set. 1919, 7. 



gill. 


(1 
. it 


0-2628 


5-3 


()-4()()9 


16-0 


0-jt>35 


31 


10540 


20-2 


0-5743 


2-8 


1-1404 


22-8 


0-9l)8S 


2-0 


1 -4235 


31 3 



360 T/ir Arai/dhifili/ of Minerdl Plant FiukI 

The followini;; are some of Jennings' figures: 

Dry weights and silica contents of wheal seedlings grown in nutrient 
solutions and in nutrient solutions containing silica (Jennings). 

Dry weight Silii-a in 
of tops dry iiiatt<'r 

XT 1 - * 1 i- o- L -II- ( witliout silit-a 

Nutrient solution 8.) pts per million , ,. ■ , ,, 

' ' I + silica gel 1 "„ 

.,-,, < without silica 

( + silica gel 1 ",j 

-„„ (without silica 

.. ^>00 ,, -. .|. t I II 

I + silica gel I "„ 

|.N.,.. (without silica 

" " ] -f- silica gel 1 ",, 

Thus it appears that colloidal j^els can enter the plant, and entering 
the plant from the soil they may carry with them absorbed substances. 

The essential elements for plant growth. It is commonly held that there 
arc ton essential elements involved in the growth of plants. That tenet 
implies tliat all other elements universally found in plants grown in soil 
are there by accident. That this teaching has not been thoroughly 
acceptable is well known and from a studv of plants grown in soil it has 
been contended tliat sili(ton and a number of other elements are essential. 
The argument for ten essential elements and no more is, of course, the 
fact that apparently normal ])!ants can l)e grown in water solutions with- 
out the introduction of any detectalile tia('e of elements other than the 
well-known ten. That fact proves that only ten elements are required for 
the growtli of plants in water solutian. The application of the same con- 
clusion to plant growth in soil is entirely dependent upon the assumption 
that the mechanism of feeding is the same in the soil as in water solution. 
If the mechanism of feeding is different the chemical requirements may 
well be different too. If, for instance, silica acts as a kind of carrier of 
mineral substances to plants grown in soil, silicon will be an essential 
element for that purpose. By considering the possibihty of a mode of 
absorption from soil different from that which obtains in the case of 
plants grown in water solution, some explanation of the additional ele- 
ments always present in soil-grown plants may be found. 

The relation of the root hairs In the soil particles. Another point arises 
from the modified view- of the constitution of the soil. Whereas the soil 
system was formerly regarded as merely a system of moistened particles 
it is now regarded as a system of particles which are coimected with the 
external aiul free water by gel material. Some attention has been given 
to the bearing of this conception of the soil on transpiration and the 



N. M. CoMBKH 367 

water content of plants '^. Its bearing on the mineral nutrition of plants 
still awaits consideration. 

Now it is a well-known Ijotanical fact that when the root hair comes 
into contact with a soil particle the outer la)'er of the root hair is trans- 
formed into a mucilage and an indissoluble attachment is made with the 
soil particle. One relation of the soil colloids to the plant is here apparent. 
The soil particle is coated with iiydrophilous colloid. The root hair be- 
comes coated with hydrophilous colloid. By the union of these colloids 
the plant and the soil particles become cemented together. Tlie particles 
so attached to the plant cannot be removed without damage to the root 
hairs. 

Underlying the present teaching is the conceptiou of the root hair 
"dipping into" the soil solution, and taking up its nutrient material in 
exactly the same way as it does from experimental water culture solutions. 
It seems, however, important to acknowledge the fact that by the union 
of their respective colloids the plant and the soil form one si/stcm and not 
I wo si/steni.? in mere contact, and to admit the possibility that the mechanism 
of the nutrition of plants grown in soil is not necessarily and entirely the 
same as the mechanism of the nutrition of plants grown in water solution. 
The physical possibilities of the union of the plant and the soil. The 
migration of ions in the colloidal complex by which the plant and soil are 
united has been discussed by Casale^. He argues that positive and negative 
colloids exist in the soil and that the charge on them is due to their 
throwing off anions and cations respectively. The negative colloids are 
dominant and absorb the positive colloids. The colloids of the plant, 
according to Casale, throw off hydrogen ions and are negatively charged, 
but less so than the soil colloids. Hence there is a potential difference 
between soil and plant and a migration of cations from the soil to the 
plant accordingly. Equilibrium is never reached, because the cations 
pass on into the plant by a similar electrical mechanism. 

Sufficient seems to be known about the different electrical charges on 
various parts of the plant cells to indicate that a migration of ions under 
difference of electrical potential probably plays an important part in 
plant nutrition and cannot be left out of account in a consideration of 
the availabihty problem. 

The chemical possibilities of the union of the plant and the soil. When 
the root hair and the soil particle are cemented together there is an 
obvious possibility of the cell sap of the root hair dissolving material 

1 See Sludl, rmiix. Faraday Soc. 1922, 17. 

= Slaz. spa: agr. ital. 1921, 54; J.C.S. Abs. (i), 1922, 509. 



368 Thr A railabi/ifi/ of Afineral Planf Food 

from the soil aggregate without any excretion of acid into the soil 
generally. The cell sap and the soil particles to which the cell is cemented 
are in such contact as to admit the direct dissolution from particular 
particles by the sap of the ])articulur cells attached thereto. 

Organic acids have a far greater solvent power for many mineral 
substances than minoral ;i(-ids have. Oxalic acid will dissolve much larger 
amounts of iron from the soil tlian hydrochloric acid. Calcium phosphate 
is much more soluble in citric, acetic, lactic and malic acids than in 
hydrochloric or nitric acids. But it must be noticed that the solution of 
mineral matter by the sap and nmciiagc of plant cells is not to be re- 
garded as essentially an acid dissolution. Many organic compounds 
besides acids will dissolve iron and aluminium compounds and phos- 
phates. Tricalcic phosphate, for example, is much more soluble in water 
containing starch, glue, sugars and many other organic bodies. 

This effect of organic matter on the solubility of phosphates and of 
compounds of iron and aluminium is very well known and in soil 
phenomena it must be far reaching. It affords a satisfactory explanation 
of the uptake of iron fi-oiu cluilky soils, for numy organic compounds 
have a high solvent power for iron over a wide range of both acid and 
alkaline reaction. The enormous amount of oxalate in lichens growing on 
limestone is not without significance in this connection. 

The availability of sparingly soluble phosphates becomes more in- 
telligible if it is supposed that the root hairs become cemented to the 
particles thus admitting the absorption of colloidal phosphate and the 
direcl dissolution of the particle by the organic solvents concerned. .\lso 
it is easy to see the connection between the root habit of wild white clover 
and its special response to the presence of these sparingly soluble 
phosphates. 

The available mineral phosphates have, according to the argument 
of a succeeding paper^, a hydrophilous surface with which the root hair 
can make its attachment. The unavailable phosphates appear not to 
have a colloidal surface. Ferric phosphate loses its colloidal properties 
on ignition and it also, according to Prianischnikow- becomes unavailable 
for the plant. Aluminium phosphate retains its colloidal properties after 
ignition and it remains available for the plant. 

There are, therefore, strong indications that colloidal properties in 
sparingly soluble mineral plant food are of first importance, perhaps 
enabhng the plant to absorb colloidal matter; certainly enabling the 

• ThLs \'oluine, p. .372. 
- liicd. CciUr. 1905, 34. 



N. M. Comber 3<i9 

root hair to make its natural attachment. Tiie importance of such pro- 
perties has already received some recognition commercially: a process 
has recently been patented^ whereby "insoluble phosphates... are con- 
verted to a colloidal form and rendered suitable for use as manures by 
treatment with a large quantity of water and about 0-1 to 0-3 per cent, 
of a mineral acid or alkali in a high speed disintegrator... substances 
which act as protective colloids, e.g. tannin, or salts of lysalbinic acid or 
humic acid, or the like, may also be added."' 

According to the differences in the composition of the cell sap and of 
the mucilage developed by the root hair, so plants will vary in their 
power of attachment to mineral particles and in their power to dissolve 
material from the particles to which they are attached. There is no 
measure of availability apart from the plants concerned and the con- 
ditions of their growth. 

Summary. 

The assumption that plants feed in the soil j ust as they feed in water 
culture solution is unjustified and contrary to the facts. In modification 
of the usual hypothesis two possibihties are discussed. 

1. The absorption of colloids by the plant. 

2. The union of the root hair with soil and other mineral particles 
(so that the plant and the soil form one system) and the dissolution of 
the particle by the organic matter of the root hair so attached. 

1 See J. Hoc. Chan. hid. I'.lL'i', 41, Nu. 10, 385 a. 



{Received August 11///. 1922. 



A MODIFIED TEST FOR SOUR SOILS. 

By NORMAN M. COMBER. 

{Deparlmcnt of Agriculture, The Universilij, Leeds.) 

It was ruuently suggested' by the writer that tlie neutral salt test for 
sourness iu soils could be adapted for rapid qualitative ])urposes by using 
an alcoholic solution of potassium thiocyanate. This reagent becomes 
coloured in contact with soils deficient in strong bases, because of the 
presence of iron among the weak bases which are brought into solution 
from such soils by neutral salts. 

This thiocyanate test appears to have been used quite extensively 
in this country, in Denmark and Scandinavia: and one attempt- has 
been made in America to nuike it a quantitative lime-requirement method. 

The use of this test by farmers and others not in close contact with 
a chemical laboratory is very restricted on account of the difficulty of 
obtaining either the alcohol or the thiocyanate. Also, the reagent is 
expensive and highly ))oisonous. A minor inconvenience is the necessity 
of drying the soil: freshly sampled soils often (!ontain enough water to 
destroy the colour. 

Some less restricted modification of the test was therefore sought , and 
it was found that an aqueous solution of potassium salicylate is a useful 
substitute for an aU'oholic solution of the thiocyanate. 

In the absence of large amounts of mineral acids, salicylic acid and 
its salts give a violet colour with traces of ferric salts. In aqueous solution 
this test for iron is far more delicate than the thiocyanate te.st. Aqueous 
solutions of ferric salts are found to give the violet colour with salicylic 
acid in dilutions too great to admit of coloration by thiocyanate. 

When, therefore, a solution of potassium salicylate is applied to a 
soil which yields iron to neutral salt solutions, the appearance of this 
violet colour in the solution might be expected. Accordingly the action 
of this reagent was examined in the first instance on twelve soils known 
to be sour apd to respond to the thiocyanate test, and on twelve soils 

1 Thia Journal, 1920, 10. 

- Carr, Jown, Ind. Enxj. Chcm. VX1\, 13, Xo. 10. 



N. M. Comber 371 

known not to be sour. A red colour developed in a few minutes in the 
solutions in contact with the sour soils and a yellow or brownish-yellow 
colour in the others. Tliis brownish-yellow colour is apparently developed 
in all cases, and the red colour arising from the sour soils is due to the 
combination of the brownish-yellow and violet colours. 

During the last nine months the test has been applied to a large 
number of soils and its indications agree with those of the thiocyanate 
test. 

The colour developed by aqueous potassium salicylate is seldom so 
deep as that developed by alcoholic thiocyanate, and the soil takes longer 
to settle from the water than from the alcohol. 

A 5 per cent, solution of salicylate is one of convenient concentration, 
but more concentrated solutions give a quicker indication. 

[Received August IWi, 1922.) 



Journ. of Agric. Sol xn 26 



THE FLOCCULATION OF SOILS. Til. 

By NORMAN M. COMBER. 
(Department of Agriculture, The University, Leeds.) 

In the previous papers' it has been deduced that the fiocculation of soil 
particles by calcium hydroxide is the net result of its deflocculating action 
on the cores of the particles and its precipitating action on the colloidal 
matter. Calcium hydro.xide will deflocculate or flocculate according to 
which of these actions is dominant. 

In the present communication further support of the earlier deductions 
is offered from experimental observations on 

(i) The fiocculation of particles other than soil particles. 

(ii) The effect of colloidal silica on the suspensibility of particles. 

(iii) The effect of concentration on the relative flocculating powers 
of calcium hydroxide and calcium chloride. 

(iv) The relative hme absorbing capacities of the core and of the 
colloidal surfaces of soil particles. 

(v) The effect of heat on soils. 

Experimental. 

A. The fiocculation of particles other than soil particles. 

1. Experiments such as those described in the first of these papers 
were made with a variety of relatively insoluble powders, in order to 
ascertain whether any substances other than clay were precipitated from 
their suspensions better by calcium hydroxide than by a neutral calcium 
salt. It was difficult to get very durable suspensions of many of these 
powders. However, such e-xamination as could be made indicated that 
the abnormal fiocculation by calcium hydroxide was not shoum in sus- 
pensions of zinc oxide, zinc carbonate, ferric oxide, barium sulphate, 
ferric phosphate (ignited), lead carbonate and Canadian apatite. It was 
shown in suspensions of aluminium phosphate (unignited or ignited), 

» Journ. Agric. Sci. 1920, 10 (4); 1921, 11 (4). 



N. M. Comber 373 

ferric phosphate (imignited), basic slags (after the removal of free base), 
finely powdered raw bones, and rock phosphates^ (after removal of free 
hme). 

2. Aluminium phosphate suspensions were subjected to further ex- 
amination. With three different samples, two purchased and one prepared 
in the laboratory, most of the experiments were carried out that have 
been described in the two previous papers in connection with clay 
suspensions. The aluminium phosphate behaved in many respects like 
clay. It was flocculated by calcium compounds better in alkaline than 
in neutral suspensions; the use of ammonium hydroxide in conjunction 
with a calcium salt produced a much larger volume of coagulum than 
when the calcium salt was used alone ; at very low concentrations calcium 
hydroxide was inferior to calcium chloride as a flocculant, and a con- 
centration of ferric chloride could be found which gave an optimum 
flocculation. 

B. The effect of colloidal silica on the suspen.sibilit!/ of small particles. 

Reference has been made in the earlier papers to the effect of very 
small amounts of colloidal silica on the flocculation of suspensions of 
ferric oxide. 

The ef[ect of siUca on the suspensibility of jDarticles has been frequently 
noticed throughout these experiments. Specific observations were made 
by weighing out 0-25 gm. portions of the powder concerned, suspending 
one portion in f c.c. distilled water and the other in 10 c.c. of a silica 
sol containing 0-0031 gm. SiO.j in the 10 c.c. 

The silica increased in a marked manner the suspensibility of two 
different samples of ferric oxide, zinc carbonate, ignited soil particles, 
kaohns and other lean clays. With other sub-stances, e.g. zinc phosphate, 
powdered granite, powdered felspar, no eft'ect was visible. 

C. The effect of concentration on the flocculating poiver of calcium 

hydroxide. 

In the previous paper an experiment was described which shows that 
in very low concentrations, calcium hydroxide has a flocculating power 
less than that of calcium chloride, while at higher concentrations the 
reverse is true. Similar experiments with other clays and with kaolin 
have shown a similar result. Two of these experiments will be quoted. 

1. A London Clay subsoil was extracted with 5 per cent. HCl, and 
thoroughly washed. One portion of the extracted subsoil was shaken 

' Nine mineral phosphates were kindly sujiplied by Dr G. Scott Robertson. 

25—2 



374 The Flocculation of Soils. ITJ 

with water and allowed to settle. The clay was then decanted. The re- 
maining portion was treated with excess of lime water and left for one 
day with frequent shaking. This portion was then filtered and washed 
with hot water until the washings gave no colour with phenolphthalcin. 
It was then shaken with water and allowed to settle after which the clay 
was decanted. Two suspensions of the clay were thus obtained, one 
depleted of its easily soluble bases and the other with as much lime as it 
could retain against a hot water washing. These suspensions were then 
adjusted so that 100 c.c. of each contained 0-2270 gm. clay (weighed after 
ignition). The relative effect of Ca (OHjj and CaCL^ in various concentra- 
tions was then observed on 10 c.c. portions of each of these suspensions. 
It was found that the suspension.s of the acid extracted clay were 
flocculated better by the Ca(0H)2 at all concentrations above about 
A^/450, while the suspension of clay after treatment with Ca(0H)2 was 
flocculated better by Ca{0H)2 at all concentrations above A^/1000. 

The amount of lime already held by the soil clearly affects the con- 
centration of added Ca(0H)2 above which the abnormal effect of that 
hydroxide is manifested. 

It must also be remarked that the clay which had been treated with 
lime water and washed remained suspended in the control tubes very 
much longer than the clay which had been extracted by acid and washed. 

2. A similar comparison of the flocculating powers of Ca(0H)2 and 
CaCl2 was made with two different clays, one a fat Halifax clay and the 
other a lean kaolin. The suspensions used contained 0-3044 gm. ignited 
clay in 100 c.c. In the exjieriment with the fat clay the superior floc- 
culating power of Ca(0H)2 was operative and very -pronounced at all 
concentrations above N/500. In the experiment with the kaoUn the 
superior flocculating power of Ca(0II)2 could be seen at all concentra- 
tions above iV/1000: in the course of one or two minutes, however, the 
neutral and alkaline suspensions were alike. The phenomenon could be 
seen with the lean clay but was not very pronounced. 

Similar experiments with other clays showed that the superior floccu- 
lating power of Ca{OH)o at higher concentrations was always more 
pronounced in suspensions of fat clays than in suspensions of lean clays. 

D. The relative lime absorbing capacities of the core and of the 
colloidal surface of soil particles. 

1. When a soil has been extracted with acid, its base absorbing 
power and its power to decompose calcium carbonate are usuallv in- 



N. M. Comber 375 

creased. Experiments made by Sciiolleubergeri indicate, however, that 
there is a limit to the increase in base absorbing power which is brought 
about by acid extraction. Working with a Clyde clay he found the base 
absorbing power increased with the concentration of the acid used up to 
an acid concentration of about N/2-5, but greater concentrations of acid 
failed to produce any further increase in the base absorbing power. 
With a Miami clay loam Schollenberger found that extraction with iV/10 
acid brought the soil to its maximum base absorbing power. 

The strong indication of these results is that the base absorbing power 
of soils as measured by the ordinary "lime requirement" methods, is a 
phenomenon exclusively confined to the colloidal surface of soil particles 
and is not to any appreciable extent a simple and direct reaction with 
the structural minerals forming the cores of the particles, as is suggested 
by Sulhvan- and others. 

In further examination of the point, seven soils were taken at random 
and samples of each, after passing the 1 mm. sieve were extracted for one 
day under similar conditions with HCl of various concentrations. 35 gm. 
soil and 100 c.c. acid were used for each extraction. The soils were filtered, 
washed, and air dried. The "lime requirement"' was determined by the 
Hutchinson-McLennan method. The figures are as follows and fully con- 
firm Schollenberger's results. 

Table I. 
"Lime Requirements" of soils after extraction with HCl of various 

concentrations. 
{CaCOs per 100 of Soil.) 

Soil 



Concentra- 


Medium 












Millstone 


tion of 


subsoil 


Heavy 


Light 


Millstone 


Millstone 


Millstone 


grit soil 


HCl 


(Chelms- 


soil 


soil 


grit soil 


grit soil 


grit soil 


(Knares- 




ford) 


(Batley) i 


((.Tarforth) 


(Leeds) 


(Sheffield) 


(Shipley) 


borough) 


N/IQO 


Nil 


0-74 


— 


— 


— 


— 


— 


NI50 


0-08 


104 


0--2?, 


— 


0-39 


— 


— 


N/IO 


0-55 


MO 


0-33 


(I-.32 


0-73 


0-54 


0-41 


Nji 


0-54 


— 


0-33 


0-32 


0-75 


0-.55 


043 


N/3 


— 


MO 


0-33 


— 


— 


0-.5.5 


— 


N 


0-54 


MO 


0-30 


0-33 


0-75 


0-55 


0-43 


2N 


0-53 


— 


— 


— 


0-75 


— 


— 


ION 


O-iJO 


104 


0-27 


— 


— 


— 


— 



2. Attempts were made to carry out similar experiments with ortho- 
clase felspar and with powdered granite, but the base absorbing powers 
of these after acid extraction were so small that the attempt was 

1 Soil Science,, 1917, 3. ^ U.S. Oeol. Survey Bull. 1907, 312. 



376 The Flocculation of Solh. Ill 

abandoned. After extraction with iV/3 acid the felspar showed a " lime 
requirement" of 0-01 per cent. CaCOj and the granite showed no "hrae 
requirement ' measurable by the Hutchinson- McLennan method. 

E. The effect of heat on soil aggregates. 

It has been contended in these papers that the aggregation of soil 
particles is brought about and maintained by the binding or cementing 
action of gel material. If this is true, one of the first effects of heating a 
soil will be tlie dehydration, slirinkage and cracking of the gels and 
presumably a loosening of the aggregate and a consequent increase in 
the exposed surface. 

It is well known that heating a soil under certain conditions increases 
the soluble matter^. The experiments recorded in this section have been 
made in order to find evidence for or against the view that this increase 
is in part due to the increased surface exposed by the destruction of the 
cementing gels. 

1. («) It has been claimed by Fraps^ that after the ignition of a soil 
for a few minutes over a bunsen flame the amounts of iron, aluminium 
and phosphorus soluble in dilute IIC'l arc increased. Repetitions of these 
experiments with a number of English soils abundantly confirm Fraps' 
results. For example, the following figures show the weights of FegOj and 
AUOg extracted from 100 gm. London Clay subsoil by 250 c.c. Njiy HCl 
before and after 5 minutes' ignition. 





Unignited 


Ignited 


Fe.O, 


26 mgm. 


186 mgm. 


ALO^ 


174 ., 


.530 „ 



(i) In order to test qualitatively the elTect of the partial ignition of 
soils and other systems, on the solubility of iron in dilute acid, equal 
amounts of the material under examination were weighed out, and one 
portion ignited over a bunsen flame for a few minutes. Each portion was 
then extracted with the same volume of iV/5 HCl for 15 minutes and 
filtered. 1 c.c. of a standard solution of NH4CNS was added to equal 
volumes of the filtrates and the colours compared. In this way an 
increase in the solubility of iron in dilute acid was shown to be brought 
about by the partial ignition of a large number of soils, sub.soils and clays, 
and of some synthetic systems to be presently described. 

(c) Experiments similar to the foregoing were made using KgFeCgNg 
as the reagent, and it was found that a considerable amount of ferrous 
iron in the acid solution resulted from partial ignition. 

• For n review of the literature see Gu.stapon, Soil Science, 1922, 13. 
' Journ. Iml. Hiujin. Chem. 1911, 3; J.C.S. Abstracts, ii. 1912. 



N. M. Comber 377 

{d) It is well known that ignition ultimately depresses the solubihty 
of iron and other soil constituents. Clearly therefore the rise in solubility 
— or rather in the amount dissolved — takes place only in the early stages 
of ignition. By means of the colorimetric test the relative amounts of 
iron extracted from soils and clays after ignition for various times was 
measured. In nearly all the soils and clays examined the solubility of 
iron in acid was on the dechne before 10 minutes of ignition over a bunsen 
flame. Only in one experiment with a very fat clay did the increase 
continue for as long as 10 minutes. The following arbitrary figures are 
typical. 

Table II. 

Relative amounts o/Fe extracted by N/HClfrom soils ignited for 

different times. 







5 mins 


10 mins 




Unignited 


ignition 


ignition 


A 


10 


2-8 


1-9 


B 


1-0 


3-2 


2-5 


C 


1-0 


2-5 


10 



(e) One of two equal portions of a clay subsoil was partially ignited. 
Each portion was then extracted with A^/5 HCl. Equal volumes of the 
filtrates were boiled, cooled and titrated with N/5 NaOH using first 
methyl orange and then phenolphthalein. The difference between the 
methyl orange reading and the phenolphthalein reading was then taken 
as a measure of the acid-salt-forming bases (FcgOg and AI2O3) in solution, 
and the difference between the phenolphthalein reading and the titre of 
the original acid was taken as a measure of the neutral-salt- forming bases 
which had gone into solution. 

The experiment was also carried out with the same subsoil at its 
maximum base absorbing power (that is, after extraction with acid as 
previously described). 

The following table shows, in respect of two subsoils, the actual 
differences of burette readings for 100 c.c. filtrate and the ratios calcu- 
lated therefrom. 

Table III. ■ ■ 

Relative amounts of neutral- salt-forming bases {n) and acid-salt-forming 
bases (a) extracted from tivo subsoils, before and after ignition, by iV/5 HCl. 

Before ignition After ignition 

A A 

r f ^ I — ■ ^ 

Burette readings Burette readings 

, '^- , Ratio , * ^ Ratio 

n a n : a « a n : a 

A Original subsoil 19-2 3-6 1:019 10-8 l.i-S 1:1-43 

E.xtraoted „ 3-2 7-2 1 : 2-25 5-6 32-0 1 : 5-70 

B Original subsoil 30-8 9-2 1 : 0-30 21-2 40-4 1 : 1-91 

Extracted „ 92 160 1:1-74 11-2 47-2 1:4-21 



378 The Flocculation of Soils. Ill 

Clearly therefore the sohibility of the acid-salt-forming bases is in- 
creased by ignition to a much greater extent than the neutral-salt-forming 
bases. Indeed the neutral-salt-forming bases dissolve to a less extent 
after ignition of the original subsoils. 

2. The thiocyanate test was appUed to a number of soils before and 
after a partial ignition. Soils containing excessive amounts of organic 
matter or of chalk showed no reaction with alcohoUc thiocyanate after 
ignition, but with 30 mineral soils taken at random the reaction with 
thiocyanate was increased. Those soils which gave no colour before 
ignition did so after, and those which gave a colour before ignition gave 
a much more intense colour after. 

3. The effect of partial ignition on the base absorbing power, as 
measured by the Hutcliinson-McLennan "Hme requirement" method, 
was examined in a number of experiments. Two 20 gm. portions of each 
sample were weighed out and one portion ignited over a bunsen flame 
for 5 minutes. "Lime requirement" determinations were then made on 
the original and on the partially ignited portions. The results are shown 
in Table IV. 

Table IV. 

The effect of 5 minutes' ignition on tlie "lime requirement" of soils 

and subsoils. 

(CaCOs per 100 of Soil.) 











:— 


e 




a 














o 


o _ 




o_ 


•a 


a 




, , 


2 o 




<n 


TS'SO 


'3 


= '3 


c 


%-3 




■3 3 
0) o 


"5 

3) 
t 


£ 
-3 


isa 

-25<N 


CD 

>> 

> 

as 


ime subso 
ter extrac 
Ith N/2 H 


-2 


S-3 

O 3 

U 00 




si 


a £ 


& 


S 




X 


tS'S S 




io 3 


Before 




















ignition 


0-28 


Nil 


0-41 


004 


0-78 


Nil 


1-36 


on 


Nil 


ignition 


013 


Nil* 


Nil* 


007 


0-42 


016 


0-60 


001 


006 



* The concentration of the bicarbonate solution was increased. 

Normal soils showed a lower base absorbing power after partial 
ignition and this effect was very much greater when much organic 
matter was present. Subsoils containing no organic matter .showed a 
greater base absorbing power after partial ignition. The same subsoils, 
however, after extraction with dilute acid showed a lower base absorbing 
power. 

4. A number of experiments were carried out with pure substances 
in search for some synthetic system of known constitution which also 



N. M. Comber 379 

showed an increment in the amount of iron dissolved in dilute acid after 
partial ignition. 

(a) Ferric oxide or hydroxide was obtained in a variety of ways. 
Two purchased samples (one red and one brown), the dried precipitates 
obtained by adding NH4OH, NaOH, and KOH to solutions of FeClj both 
in hot solution and in the cold, and the gels obtained by evaporating 
ferric hydroxide sols were all used. They showed a continuous decrease 
in the solubility of iron in N/5 HCl during ignition. 

(6) Three 50 gm. portions of ferric oxide were weighed out. One was 
shaken with 100 c.c. di.stilled water and then treated with 200 c.c. 
Ca(0H)2 solution. Another was shaken with 100 c.c. silica sol (containing 
2-085 gm. SiOa in the 100 c.c.) and precipitated with 200 c.c. Ca(0H)2 
solution. The remaining portion was shaken with 100 c.c. silica sol and 
200 c.c. distilled water were added. Each of these systems was then 
evaporated to dryness on the water bath, and the relative amounts of 
iron extracted by N/5 HCl before and after 2 minutes' ignition was 
observed. The ignition decreased the amount of iron dissolved where 
only Ca(0H)2 had been added, but increased it about threefold in the 
two other cases. 

The amount of iron dissolved from the unignited material in which 
silica had been used was very much less than where only Ca(0H)2 was 
used. 

When the silica sol or the precipitate formed by adding Ca(0H)2 
thereto, was evaporated separately from the ferric oxide and then in- 
timately mixed with it, there was no increase by ignition, but always a 
decrease, in the amount of iron dissolved by dilute acid. 

These experiments were repeated many times with three different 
samples of ferric oxide, and with similar results. 

An increase in the amount of iron dissolved by dilute acid was also 
observed in the products obtained by suspending ferric oxide in a dilute 
solution of waterglass and adding a solution of AICI3 , and by suspending 
ferric oxide in AICI3 and adding NH4OH. 

Wherever the ferric oxide particles were cemented together by 
gelatinous precipitates, a partial ignition increased the amounts of iron 
dissolved by acid, just as is observed in soils. 



380 The Flocculation of Soils. Ill 

Discussion. • 

The jlucculation of particles other than soil particles. 

The only substances, in the random collection examined, which 
showed the same anomalous flocculation by calcium hydroxide, as clay, 
were certain phosphates. Su.spensions of the phosphates of aluminium 
and of iron, as well as .some natural calcium phosphates, arc flocculated 
by calcium salts very much better from alkaline than from neutral 
suspensions. 

The similar behaviour of clay and of these phosphates seems to lend 
support to the explanation of the abnormal flocculation by calcium 
hydroxide which has been advanced in the earlier papers. Calcium salts 
added to a dilute ammoniacal solution of a phosphate, produce a volu- 
minous gelatinous precipitate very similar to that produced in dilute 
ammoniacal solutions of sihca. Further, the phosphates of aluminium, 
iron and calcium are well known to exist quite commonly in the colloidal 
gel form. The action of calcium hydroxide on the colloidal surfaces of 
these phosphates is analogous to its action on the colloidal surfaces of 
silicates and is susceptible to a similar explanation. 

Powdered apatite is crystalhne, without colloidal properties, and it 
does not show the flocculation anomaly either before or after extraction 
with cold dilute acid. 

The colloidal condition of phosphates and sihcates is undoubtedly 
related to their solubility and to their availability to the plant. This 
aspect of the subject is discussed in a separate paper. 

The respective rdles of the core and of the colloidal surface. 

Assuming the truth of the earlier deduction that calcium hydroxide 
has a dual action on .soil particles (a deflocculating action on the cores of 
the particles and a precipitating action on the emulsoid surface) it is clear 
that the deflocculating action may dominate the precipitating action in 
at least two circumstances: 

(i) When the amount of emulsoid matter is small relatively to the 
core. 

(ii) When the amount of calcium hydroxide is insufficient to cause 
a maximum precipitation with the colloidal matter. 

The first of these circumstances has already been demonstrated and 
discussed. The second has now been demonstrated experimentally, for it 
has been shown that when the concentration of the flocculant is very low 
clay suspensions are flocculated less readily by calcium hydroxide than 



N. M. Comber 381 

by a neutral calcium salt. lu these low concentrations the calcium 
hydroxide is insufficient to produce a dominating precipitating action on 
the surface colloids and the deflocculatiug action on the cores prevails. 

The concentration above which calcium hydroxide becomes the better 
flocculant is much less with a lean clay than with a fat clay. In a lean 
clay, where the proportion of effective emulsoid matter is low, less 
calcium hydroxide is required to cause the maximum precipitation. But 
because the amount of emulsoid matter is relatively small, the superior 
calcium hydroxide flocculation is never very marked. In a fat clay the 
relative effective amounts of emulsoid matter is high and more calcium 
hydroxide is required to cause precipitation. Experiment shows that 
emulsoid colloids such as silica protect the particles of some substances 
and stabilize their suspensions. A fat clay contains a large amount of the 
protective and stabihzing colloid and more colloid is accordingly required 
to coagulate it, and precipitate the suspension. Also, because there is so 
much emulsoid matter in the fat clay the abnormal effect of calcium 
hydroxide, when it is attained, is very pronounced. 

This subject may now be considered from an entirely different view- 
point. 

If a clay is treated with an excess of calcium hydroxide, it is floccu- 
lated. Two or three washings, however, will reverse the flocculation (see 
Appendix, paragraph 2), but no ordinary amount of washing with pure 
water will deplete the soil of hme from the "lime requirement" point of 
view. Again, therefore, it is clear that a certain easily removed excess of 
calcium hydroxide is necessary to maintain the flocculated condition of 
wet clay. 

Quite crudely, but in order to arrive at a more precise conception, it 
may be assumed that when lime has been absorbed by a sour clay, there 
is at one extreme a part of the lime, correcting the sourness, which is not 
removable by ordinary water washing, and at the other extreme a part, 
causing flocculation, which is easily removed by water washing. 

It might be supposed that the lime which is held irreversibly (or 
relatively so) has reacted with the core of the particle, while the easily 
reversed absorption is an action of the colloidal surface. That view, 
however, is untenable, for experimental evidence has been described to 
show that by extraction with dilute acid a soil may easily be brought to 
a maximum base absorbing power. Acid of concentration considerably 
below normal, will usually remove all the base which can be afterwards 
replaced by shaking with calcium bicarbonate. Extraction of the soil 
with more concentrated acid, which will more effectually attack the 



382 The Flocculation of Soils. Ill 

minerals of the cores of the particles causes no increase in the base 
absorbing power of the remaining soil. The absorbed bases are easily 
soluble in dilute acid and their extraction brings the soil at once, and 
decidedly, to its maximum base absorbing power. From this it seems 
justifiable to conclude that the absorption of hme which is measurable 
by titration methods is solely confined to the surface colloids. The 
insignificant amount of lime absorbed by powdered granite, after ex- 
traction with acid, also goes to show that the unweathered and crystalhne 
minerals have little to do with the absorption of lime under such con- 
ditions as those of the Hutchinson-McLennan "lime requirement" 
determination. 

It is not suggested that these minerals are not reactive but that any 
part they play in base absorption is small. Powdered and extracted 
crystalline minerals and rocks do show a shght absorptive power. But 
even this may be due to the colloidal surface, for the grinding of rocks — 
particularly the wet grinding of rocks — has a decomposing effect similar 
to weathering. This is apparent from the classical work of Daubree^ and 
the more recent work of Cushman*. 

The whole of the absorption of lime — reversible and irreversible — is 
therefore a phenomenon associated with the colloidal surface. Until 
sufficient lime has been apphed to react with that surface, the lime may 
exercise a deflocculating action because of the combined effects of the 
decreasing hydrogen ion concentration and the uncoagulated colloid 
stabihzing the particles. 

After a soil has been treated with excess of calcium hydroxide, washing 
with water readily removes lime at first, but as the amount of lime gets 
less it becomes more difficult to remove it. The actual process of washing 
a soil at the pump after treatment with calcium hydroxide until the 
filtrate no longer colours phenolphthalein, is a long one. The colour pro- 
duced by phenolphthalein becomes very gradually fainter in successive 
washings and in such a way as to make it clear that the operation is not 
one of merely washing away an excess of the hydroxide in solution, like 
the washing away of hydrochloric acid after treatment of a soil therewith. 
During the washing, calcium hydroxide is being removed less and less 
effectively from the colloidal surface in which it is in some way held. 

The retention of hme by this colloidal surface seems to fall on the 
borderhne between the physical phenomenon of a reversible absorption 
and the chemical formation of compounds such as Way's double silicates, 

' ComiA. Html. 1857, 44. 

« U.S. Dept. Agric. Bur. Chem. Bulletin, 1905, 92. 



N. M. Comber 383 

which are slowly hydrolysed on washing. The full discussion of the re- 
tention of lime by soils is therefore impossible until more is known about 
these borderline phenomena on the one hand and about the actual con- 
stitution of the soil colloids on the other. Meanwhile it seems clear that 

(i) The absorption of lime is mainly confined to the colloidal surface. 

(ii) The absorptive power must be largely satisfied before lime causes 
the abnormal flocculation of clay. 

The partial ignition of soils. 

Ignition and solubility. Quite independent evidence that the particles 
making up the soil aggregates are bound by the cementing action of their 
gelatinous surfaces, is found in the experiments on the ignition of soils. 
The experiments show in the first place that partial ignition normally 
increases the amounts of iron, aluminium, etc. which are extracted by 
dilute acid. This increase can only be due to one of two general causes. 
Either the elements concerned are transferred by ignition to some other 
chemical combination or to some other physical state of higher solubility 
in acid, or else the amount of effectively exposed surface is increased. 
The formation of more soluble compounds is most improbable. It is 
scarcely likely that ferrous iron, ferric iron, aluminium and phosphorus 
would all be converted to more soluble compounds, and in any case the 
formation of more soluble forms of iron and aluminium compounds by 
ignition is the very opposite of usual experience. 

Ferric hydroxide powder obtained in a variety of ways failed to show 
any increased solubihty on ignition. WTien, however, the particles of 
ferric hydroxide were suspended in a suitable solution and precipitated 
so that they became aggregated by some gelatinous substance such as 
silica or alumina, the first effect of ignition was to increase the amount of 
iron dissolving in acid. 

The conclusion is that the increased dissolution is due to the drying 
up of the colloidal matter, the separation of the particles and the conse- 
quent exposure of a larger surface to the acid subsequently added. 

This increase in the amount dissolved is not a true increase in 
solubility. Ignition depresses the solubility of iron, etc. In the early 
stages of ignition, however, the effect of increased surface more than 
counteracts that depression of solubiUty. 

Ignition and base absorbing power. The base absorbing power of 
various soils and subsoils, before and after 5 minutes' ignition, was 
examined by the Hutchinson-McLennan method. The results recorded in 
Table IV present three cases for consideration. 



384 The Floccnlation of So i/s. Ill 

1. Subsoils containing no organic matter and from which the absorbed 
bases have been removed by dilute acid, show a decreased base absorbing 
power after partial ifjnition. This is the simplest and most obvious case. 
It has been previously argued that the power to absorb base rests chiefly 
with the colloidal gel matter of the soil. This colloidal matter will be 
dehydrated and its colloidal state (eventually) destroyed by ignition. In 
accordance with the argument it is found that an early eSect of ignition 
is the depression of the base absorbing power. 

2. Untreated subsoils, containing no organic matter, but containing 
absorbed lime, show an increased base absorbing power after 5 minutes' 
ignition. The inference is as follows. In the original uuignited material 
the whole of the absorptive power of the surface colloids of the subsoil 
aggregate is satisfied or nearly so. On ignition the aggregate is disrupted 
by the .shrinkage of the colloids and in the first stages of such disruption 
new surfaces, whose absorptive power is not satisfied, are exposed. Such 
new surface will lose its absorbing power as ignition proceeds, but in the 
first stages of ignition the development of new surface more than counter- 
acts the destruction of its colloidal state. The subsoil aggregate may show 
no lime requirement at all as an aggregate for the absorptive power of the 
outer surface of the aggregate may be fully satisfied with lime. When the 
aggregate becomes broken the surfaces of the particles are exposed and 
their exposure takes place before their absorptive power is lost. After 
a short ignition, therefore, a sub!5oil free from organic matter and 
which originally has no base absorbing power shows a base absorbing 
power. 

This consideration fully supports the earlier views that lime reacts 
with the colloidal surface forming a precipitate which entangles and 
binds the particles. The complete formation of such an absorption com- 
pound will clearly take place only over the outer surface of the resulting 
aggregate. 

This view is also in accordance with the fact that after ignition it is 
the acid-salt-forming bases rather than the neutral-salt-forming bases 
which dissolve to a greater extent in acid. 

3. Soils containing organic matter show a marked decrease in base 
absorbing power after partial ignition. Now, humus undoubtedly plays 
an important part in the absorption of lime by the .soil colloids. On 
ignition its colloidal state will be destroyed very rapidly. Where humus 
is present therefore the decline in base absorbing power on ignition will 
at first be very rapid and may easily overbalance the increase due to new 
surface exposure. Moreover, the lime absorbed by the humus will 



N. M. Comber 385 

presumably be liberated during the combustion of the humus and remain 
in the residue as free base. 

These considerations seem to afford an adequate explanation of the 
experimental facts that the base absorbing power of soils containing 
organic matter falls during partial ignition and that the fall is very great 
when much organic matter is present. The original peaty soil had a high 
" hme requirement," but after 5 minutes' ignition it increased the con- 
centration of the bicarbonate solution very considerably. 

It will be noted that normal mineral soils, after partial ignition, show 
a lower base absorbing power but an enhanced reaction with thiocyanate. 
The reason of this is quite obvious in view of the fact that the proportion 
of the iron and aluminium to the calcium which present themselves for 
dissolution in acid is increased by partial ignition. The actual power to 
absorb lime from bicarbonate, and presumably potassium from potassium 
thiocyanate, is less, but after the potassium has been absorbed the free 
thiocyanic acid attacks a relatively greater proportion of iron and 
aluminium. 

Summary. 

In support and extension of the conclusions drawn in the earlier 
papers the following facts and deductions are submitted : 

1. The only sparingly soluble substance, from a random collection 
examined, whose suspensions showed the same abnormal flocculation by 
calcium hydroxide that is shown by clay, were certain phosphates of iron 
aluminium and calcium. The abnormal flocculation of these phosphates is 
open to an explanation quite analogous to that already advanced for the 
flocculation of clay. 

2. Until the amount of calcium hydroxide added to a suspension of 
clay or phosphate reaches a certain amount its abnormal flocculating 
power is not manifested. The amount required to produce the abnormal 
flocculation is greater for a fat clay than for a lean one. This is in agree- 
ment with the view that the abnormal flocculation is caused by a coagula- 
tion of emulsoid matter, for obviously such coagulation will not become 
dominant until a sufficient amount of the precipitant has been added. 

3. The lime absorbed by a soil can be wholly and completely removed 
by a dilute acid treatment which cannot very appreciably decompose the 
unweathered minerals. It is therefore concluded that the absorption of 
lime by a soil is an absorption by the soil colloids and not by the un- 
weathered minerals. 



386 The Flocculation of Soils. Ill 

4. The ignition of a soil for a few minutes over a bunsen flame in- 
creases the amounts of iron and aluminium dissolved by acid. Evidence 
is brought to show that this is due to a destruction of the colloids which 
bind the particles together, and a consequent exposure of a larger surface. 

5. The effect of a partial ignition on the base absorbing power of soils 
and subsoils is described and the results are claimed to be in agreement 
with the view that the particles in the aggregates are bound together by 
gelatinous colloidal matter. 

Appendix. 

The preparation of clay suspensions. 

For experimental work on flocculation it is frequently necessary to 
prepare clay suspensions without the use of excess of ammonia solution 
which is employed in routine mechanical analysis. Two notes on the 
making of such suspensions are appended : 

1 . In order to obtain, after sedimentation, the maximum amount of 
clay in suspension it is necessary to adjust the relative amounts of soil, 
etc. and water. All soil and clay particles are largely aggregated. If 
therefore the proportion of clay to water is very large the deflocculated 
particles are entrained by the aggregates and the whole settles down 
leaving clear water above. On the other hand, if the proportion of clay 
to water is small the amount of clay in suspension will be small. 

This can be strikingly demonstrated by arranging a series of tubes 
containing a large amount of a stiff clay at one end and gradually 
decreasing amounts through the series. If water is then added to the 
same height in each tube, it is found after agitation that the supernatant 
liquid is quite clear in a few minutes where the amount of solid is greatest. 
It becomes gradually more turbid down to a certain point in the series 
beyond which it becomes less turbid again. 

Only by such trial can the most suitable relative amounts of solid to 
water be ascertained. 

2. An almost neutral suspension of clay is easily prepared by ex- 
tracting the soil with dilute acid, washing, agitating with excess of lime 
water, filtering at the pump and thoroughly washing with hot water. 
The wet soil will then give good clay suspensions. 

Soils treated in this way, or after extraction with acid, should not be 
dried after washing if a maximum clay suspension is required. 



(Received August llth, 1922.) 



ON THE RELATIVE GROWTH AND DEVELOPMENT 
OF VARIOUS BREEDS AND CROSSES OF PIGS. 

By JOHN HAMMOND, M.A. 

{InsLilule of Aninud Nulrilkni, School of Agriculture, Cmtihruhje.) 

iNTRODUCTiON. 

Few reliable figures (i) exist at the present time wliicli show the relative 
qualities of the various British breeds of pigs in respect of their ability 
to put on weight and the relative proportions of meat and offal in the 
carcases. Weights and carcase percentages of German breeds have been 
published by the German Agricultural Society (2). 

An investigation based on the records of the Smithtield Club's Fat 
Stock Show was therefore undertaken to determine the relative merits of 
the various breeds. 

Hitherto most of the work which has been done on the growth and 
fattening of farm animals has been based on the chemical composition 
of the body ; this, however, does not altogether show the economic side 
of the question as it fails to differentiate between parts of different value 
and edibility. 

In all interpretations of the results of this investigation given below 
it should be remembered that the animals exhibited were all in a fat con- 
dition and that the Show is essentially a butchers' show. The averages 
quoted for the dift'erent breeds will be maximum averages for the best 
animals of the breed; the commercial specimens of the breed would 
normally fall below this average but there is no reason to suppose that 
the relative positions of the breeds would be affected thereby. 

The results in general show the rate of growth and carcase percentage 
of the different breeds at 3, 5, 7, 9 and 11 months old; data on the rate 
of maturity is also presented as well as figures which show the changes 
that have been made in breeds during the last few years. 

In order to determine the actual amount of edible meat produced it is 
necessary also to know the weights of muscle, fat and bone in the carcase, 
but there are no data on this point in the records of the Show and this 
remains to be discussed in another investigation. 

Journ. of Agric. Sci. sii 26 



388 Groirth ami Development of Breeds inul Crosses of Pigs 

The available published data on the proportions of meat and bone 
in the carcase, collected from the literature, is given below from which 
it would appear that the proportion of bone varies in different breeds 
and decreases with age. CornevinO) has shown that the live weight of 
the wild boar contains 3-9 per cent, of bone whereas the Craonnaise breed 
contains only 2-6 per cent. Long(i) quotes experiments by McMurtree 
who found that the carcase of a Poland China 11 months old and 
weigliing 340 lbs. contained 8-4 per cent, bone, 39-4 per cent, muscle and 
45-5 per cent, fat, whereas a Berkshire 9 months old and weighing 245 lbs. 
contained 9-3 per cent, bone, 42-7 per cent, muscle and 41-G per cent. fat. 
Wellman(5) found that a Berkshire 3 weeks old and weighing 10 lbs. con- 
tained 13'5 per cent, bone, whereas one of 9 weeks old and weighing 26 lbs. 
contained 11-9 per cent, bone and a Large White of about 15 months old 
and weighing 319 lbs. contained 9-1 per cent. bone. The following figures 
have been calculated from data ])iiblish(Ml by Tschirwinsky(t>). 

.\ge Live weight "„ of 
No. Breed weeks lbs. skeleton 

1. Windsor \, ,.,. 10 161 18-6 

2. .. from same htUr „„ „, .„„ 



4. Large White |, ..,, 9 24-3 

., •=■ Jirora same Mttcr .,., _. ,. 



28 751 10-3 

170 



While some of the discrepancies between different authorities may be 
accounted for by the various methods adopted in cleaning the skeleton 
before weighing, yet on the whole the proportion of meat to bone varies 
considerably both with breed and with age. 

Material and Methods. 

The investigation was conducted in the same way as that previously 
described for cattle (7) and sheep (8) and consisted of a statistical treat- 
ment of the records of the Fat Stock Show held by the Smithfield Club at 
Islington from the year 1901 (when the classes for pigs were restarted) until 
the year 1913 inclusive. I am indebted to Mr E. J. Powell the Secretary 
of the Club who has kindly supplied me with these records. 

Two series of competitions for pigs exist (1) The Live Classes, and 
(2) The Carcase Classes. 

In the first Series — Lire Classes — a record is kept only of the age and 
gross weight of the animals. This .series is divided into classes for breeds 
and crosses of different ages, the sex not being specified, each pen con- 
sisting of two pigs. Classes also exist for ])orkers not exceeding 100 lbs. 
weight in which the age is not limited. In addition there are classes for 
single pigs of the different breeds under 12 months old. 



John Hammond 389 

In the second series — Carcase Classes — wliicli were started in 1903, a 
record is kept not only of the live weight and age of the pig but also the 
weights of the carcase and pkick after the animal had been killed. Tliis 
series is divided only into classes for pigs of different weights; in some 
cases in addition there being an age limit as well. Each entry consists of 
a single pig only. The entries for this series are very small compared with 
the number of exhibits in the live classes especially in view of the fact 
that the carcase test is the ultimate object for which the pigs were 
bred. 

The weights of the animals and carcases have been carefully taken by 
the officials of the Club under the supervision of the Stewards. For the 
details of the methods of slaughter and dressing of the carcases I am 
indebted to jVIr Charles Bone who has been responsible for these and who 
has kindly furnished me with information on these points. 

Neither in the Live Classes nor in the Carcase Classes is there any 
specification of sex. Henry (9) found that boar pigs weighed slightly more 
than sows, but Danish (lO) experiments have shown very little difference 
between the sexes. 

The details given in the records of the Show have been treated 
statistically so as to give information on the points it was desired to 
investigate. Weights throughout have been given in lbs. and decimals 
of a pound, and ages in months and weeks. 

As the single pig classes would naturally attract the exceptional 
animals it was thought better to keep them separate. The fact that in 
the porker classes the weight was limited but not the age was not con- 
sidered to be of sufficient importance to warrant separate treatment and 
they have been grouped by their age; breeds maturing early would be 
exhibited in this class at a younger age than those of the late maturing 
breeds. 

In order to avoid confusion when discussing the results of the in- 
vestigation below, the following account gives the methods by which the 
various tables in the text have been compiled. 

Table I has been prepared from the records of the Show direct. As 
each pen consists of two pigs the total has been halved to obtain the 
weight of individual pigs. The divisions into age groups correspond more 
or less with classes at the Show, the bulk of the porkers falling into the 
"under 3 months" and "3-5 months" groups wliile the majority of the 
classes "not exceeding 9 months" and "not exceeding 12 months" fall 
into the groups " 8-9 months " and " 10-12 months " respectively. A few 
of the former constitute part of the " 6-7 months " group. The single pig 

26—2 



390 Groivth and Development of Breeds and Crosses of Pigs 

classes have been ke})t separate and are shown at tlic I'ud of the tabic 
Averages calculated from less than 10 individuals are shown in italic 
type. 

Table II has been calculated from Table 1 by dividing the weight by 
the number of weeks old (counting 4 weeks to a month). The weight at 
birth, owing to lack of data on this point, has been taken as zero. The 
numbers of individuals from which the results have been calculated are 
also given so that an estimate can be made of the reliability of the 
average. Averages calculated from less than 10 individuals are shown in 
italic type. 

Tabic III has been compiled from Table 1 by adding or subtracting 
the number of weeks growth (see Table II) reijuired to correct for age. 
Averages calculated from less than U) individuals are shown in italic 
type. The probable error of the mean has been calculated in several 
cases and is shown in Table 1 V. 

Table A. Probable error of mean (pen of two), lbs. 



Months old— 


3 


;-) 


7 


9 


11 


Liu-go White 
Berkshire 


3- 03 

2-7t> 


3-48 
1-3I) 


12-89 


4-30 
0-98 


512 
2-51 



Table IV has been prepared from the records of the Carcase Classes 
direct. Results averaged from less than 5 individuals are shown in italic 
type. The parts into which the pig is divided on slaughter are as follows: 

Carcase. Includes the head, feet and skin (but not hair or claws). 
The skin varies in thickness in different types of ])igs(U). Henseler(i-) in 
a starved Bavarian belted sow of 79 lbs. found that it was li per cent, 
of the live weight and CoUn (13) that it was lO- 1 per cent, in a pig weighing 
64 lbs. Within a breed the proportion would j)r()bably decrease with the 
increasing size of the animal. 

Pluck. Consists of the pluck proper — heart, liver, lungs, diaphragm, 
oesophagus and trachea — and in addition the caul fat. thus differing from 
the pluck of cattle and sheep. The total percentage is very similar to that 
found by Holm(i4) in Danish pigs of the same weight. 

" Unaccounted for.'' This is the difference between the sum of the two 
foregoing parts and the live weight; it consists mainly of stomach and 
intestines and their contents, but also includes blood, hair, spleen, 
pancreas and genitals as well as the weight lost on cooling. 

In order to give some idea of how the weight of the Pluck and " Un- 
accounted for" is distributed among the dift'erent organs the following 
Table B has been prepared: 



John Hammond 



391 






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Tlie differences between authorities may be due partly to variations 
in method but are largely affected by differences in the size and age of 
the animals. The liver of the pig at birth is much larger in proportion 
(3 per cent, of liver) than it is at a year old (1 per cent, of liver). It will 
be noticed too that the proportion of the stomach and intestine contents 
increases from about 2-5 per cent, at birth to about 1 1 per cent, at 3 
months old and then decreases again to about 2-5 per cent, at a year old. 

Table V has been calculated from Table lY in the same way that 
Table 11 has been jjrepared from Table I. Averages from less than 
5 individuals are shown in italic type. Tlic four breeds from which the 
average at the base of tiie table has been calculated are as follows: Large 
White, Large Black, Berkshire and Middle White. The breed average 
only has been considered and not the number of individuals in each breed. 

Table. VI has been prepared from Table IV in the same way as Table 1 1 1 
has been calculated from Table I. Averages from less than 5 indiNaduals 
are shown in italic type. The average at the base of the table refers to 
the same four breeds as in the preceding table. 

Table VII has been compiled from Table VI by calculating the weight 
of the carcase or part as a percentage of the live weight. Averages from 
less than 5 individuals are shown in italic type. The average at the base 
refers to the same four breeds as stated in Table V. 

Table VIII has been (uilculated from the averages of the four breeds 
given at the base of Table VI. The method used is described in the text 
(see p. 402). 

Table IX has been prepared from Table 111 by calculating the weights 
at various ages as percentages of the weights at 1 1 months old. The single 
pig classes at 9 months are shown as a percentage of the single pig classes 
at 11 months. Figures calculated from less than 10 individuals on either 
side are shown in italic type. 

Table X has been compiled from Table VI by calculating the weights 
at various ages as percentages of the weight at 11 months old. Figures 
calculated from less than 5 individuals on either side are shown in italic 
type. 

Table XI has been prepared from the Live Class records of tlie Show 
direct. All doubtful and second cross animals have been ehminated. 
Averages calculated from loss than 10 individuals are shown in italic 
type. 

Table XII has been calculated from Table XI in the same way that 
Table II has been calculated from Table 1. Figures from less than 10 
individuals are shown in italic type. 



John Hammond 393 

Table XIII has been compiled from Table XI in the same way that 
Table III has been prepared from Table I. The mean weights between 
the two breeds have been taken from Table III. Averages from less than 
10 individuals are shown in italic type. 

Table XIV has been calculated from Table XIII in the same way that 
Table IX has been prepared from Table III. Figures calculated from less 
than 10 individuals on either side are shown in italic type. 

I'able X V has been prepared from the records of the Carcase Classes 
direct. All second and doubtful crosses have been eliminated. All 
figures are shown in italic type as in no case is the average calculated 
from more than 5 individuals. 

Table XVI has been compiled from Table XV by showing the per- 
centage of the carcase or part as a percentage of the live weight. All 
figures are given in itahc type as in no case is the average calculated from 
more than 5 individuals. 

Table XVII has been prepared from the records of the Live Classes of 
the Show after correction of each for age as described for Table III. 
Figures calculated from less than 10 individuals are shown in italic type. 

Table XVIII has been compiled from the records of the Carcase 
Classes after correction of each for age as described for Table III. 
Averages from less than 5 individuals are shown in italic type. 

Table XIX has been calculated from the records of the Live Classes 
of the Show after the weight of each pen of 2 pigs had been corrected for 
age as described in Table III. 

Table XX has been calculated from the records of the Carcase Classes 
of the Show after the weight of each animal had been corrected for age 
as described in Table III. 

Table XXI has been compiled from the records of the Carcase Classes 
of the Show by calculating for each animal the carcase and parts as a 
percentage of the live weight. Individuals were then classified into tliree 
equal groups — high, average and low — according to the live weight or 
percentage of the part they were grouped by. The averages for each of 
these groups were then calculated. Each different age group as shown in 
Table IV was treated separately in this way and then all the age groups 
were combined and their average is given in this table. The numbers of 
animals dealt with in each group were as follows: high 74, average 75, 
low 75. 



394 Growth and Development of Breeds and Crosses of Pigs 

Results. 

The results obtained are considered in sections below under various 
headings which it was considered might have an eSect on growth and 
development — breed, age, early maturity, cross-breeding, selection, 
individual variation and correlation. In general, the results obtained 
from the Live Classes for actual gross weight have been considered first 
followed by the proportional development and weights of the various 
organs as obtained from the Carcase Classes. 

Breed. No satisfactory explanation has yet been offered why one 
animal or breed should produce meat more economically than another. 
Armsby and Fries (18) have shown that it does not depend on differences 
in digestive power; their experiments indicated that the well-bred animal 
had a lower maintenance requirement than a scrub, due to the hitter's 
more nervous disposition and greater restlessness. 

Feeding tests for the economy of gain in different breeds of pigs made 
at the Ontario College of Agriculture (if») have failed to show any uniform 
difference between breeds as so much depended on the strain used. 
Carlyle{20), however, who compared Berkshires with Razorbacks or semi- 
wild swine found that the latter required more feed per unit gained. 
Similar results were obtained by Diffloth(2i) when comparing Suffolk pigs 
with those of a fJerman breed. 

It is rather in the utilization than in the absorption of food that breeds 
differ; variations in utilization will be seen below. Little or nothing is 
known as to whether the underlying physiological differences in the 
metabolism of different breeds are due to variation in heat loss by the 
skin as shown by Wood and ]Iill(22) or to differences in the glycogenic 
coefficient of the blood controlled by the glands of internal secretion. 
Liihring(23) states that it is possible to distinguish between the different 
breeds of pigs by the protein differentiation method. 

Table I shows the average ages and weights of the different breeds of 
pigs as compiled from the records of the Live Classes. The following 
Table II shows these weights translated into lbs. per week gained since 
birth. The weight at birth has been neglected owing to the absence of 
data for the dift'orent British breeds. Carmichael and Rice(2i) found that 
the average birt h weights of breeds in America ranged from 2-25 lbs. for 
Duroc- Jerseys to 2-6 f lbs. for Berkshires but it was considerably affected 
by other factors such as litter size, sex, age of sow, etc. Meek (25) states 
that the birth weight varies from 1'.5 lbs. to 4-5 lbs. and Henr\M26) that 
the variation is from 1-3 lbs. to 3-1 lbs. 



John Hammond 



395 









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390 (ji-oirth and Development of Breedx and Croftsea of Pigx 

T;il)lc 111. Comparatirc wrifjIitK of different breeds i)f piijs -Iba. 







Pen 


of 2 classes 




Single pig 

A 


classes 


Ago in months 


3 


r> 


7 


9 


11 


f ^ 

9 


11 


Lincolnshire Curly Coatod 


7J 


_ 


341 


404 


510 


465 


483 


Large Wliite 


,S(i 


107 


— 


390 


481 


421 


490 


Large Black 




— 


— 


305 


371 


470 


— 


470 


Somersetshire 




— 


13S 


— 


340 


430 


— 


436 


Tamworth 




— 


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2.97 


334 


414 


34!) 


404 


Berkshire... 




Sf) 


uu 


21H 


337 


402 


327 


404 


Middle White 




77 


118 


210 


325 


384 


— 


385 


SmaU Black 




— 





— 





37!) 





37/i 


Dorset 




— 


— 


— 


— 


— 


23S 


349 


Small Wliitc 




— 


— 


151 


216 


273 


— 


— 



In Table I it will be seen that there is variation in the average age at 
which the difTerent breeds were exhibited so that the figures arc not 
strictly comparable. 

Corrections have therefore been made for this from the rate of growth 
shown in Table II and the comparative weights of breeds at the common 
ages of 3, 5, 7, 9 and 11 months are given in Table III and it is to this 
table that reference is made below. 

The breeds in Table HI are arranged in order of tlieir weight at 
1 1 months old, the mature size of the breed ; the differences in the relative 
order at the other ages are due to variations in the rate of maturity and 
will be discussed below. 

The Lincolnshire Curly Coated (averaging 510 lbs.) is the heaviest 
breed with the Large Wliite next some 30 lbs. fighter while the Large 
Black follows closely weighing some 10 lbs. less. 

There is then a rather large drop of 50 lbs. to the Tamworth. with the 
Berkshire some 10 lbs. below and the Middle White about 20 lbs. fighter 
still. There is then a very big gap of some 1 10 lbs. to the now almost 
extinct Small White. 

A few animals described as the Somersetshire breed (probably 
Gloucester Old Spots) come midway between the Large Black and the 
Tamworth in size ; while a few called Small Blacks and Dorsets are sfightly 
fighter than the Middle Wliites. 

Much work on the comparative slaughter weight of pigs has been done 
by Hofman-Bang, Morkeberg and Lund (27) in Denmark and has been 
mainly directed to testing two breeds, the Large White and Native 
Danish and their crosses. These tests, which give data of gain in five 
weight per unit of food (consumed up to the age of approximately 200 days 
and 200 lbs. live weight, conclude with carcase weights at that age only 
and show consistent results in that the carcase weight of the Large White 



& 



John Hammond 397 

is about 2 per cent, greater thau tliat of tlie Native Danish. The investiga- 
tion which was practical in nature was however limited to pigs of this age, 
so does not show differences due to age. 

Seniinler(2s) found that the carcase weights of Berkshires were on the 
average higher than those of German native breeds of the same type. 
Henry (29) quotes from Cuvier that the intestine length of the wild boar 
is 9 times the body length whereas that of the domestic boar is 13-5 times 
and he found himself that in fat hogs it was 21 times. No weights are 
given, however, and it does not follow that in<-reased length means in- 
creased weight; if the diameter were decreased the absorptive area 
would still be greater and the weight of contained foodstufi's the same or 
less. Henseler's(i2) data shows that a starved pig of 9 months old had 
an intestine length 18-1 times the body length, whereas in a well-fed pig 
of the same age and from the same litter the length was only 16-9 times; 
moreover, the intestine was 4-95 per cent, of the hve weight in the starved 
animal, whereas it was only 2-8 per cent, in the well-fed. 

The average weights of pigs killed in the carcase competitions are 
shown in Table IV which also gives tlie numbers exhibited and their 
average age. These figures have been translated into lbs. per week in- 
crease which are shown in Table V. The birth weight has been neglected 
as the weights of the different breeds at birth were not known. Owing to 
differences in age the weights of the different breeds given in Tal>le IV 
are not strictly comparable. Table VI has therefore been prepared to 
show all breeds calculated to common ages. 

If the live weights of animals exhibited in the "Carcase Classes" 
given in Table VI are compared with those shown in Table III for the 
"Live Classes" of the same age it will be seen that, as has been pointed 
out by Long (30), the live class animals are much heavier. With Berk- 
sliires the difference at 3 months is 12 lbs., while at 11 months it is 
154 lbs. and again with Large Whites at 3 months the difference is 19 lbs., 
while at 11 months it is 156 lbs. The reason for this is probably that the 
"Live Class" animals are more heavily fattened. Evidence, which it is 
hoped to pubhsh shortly, has been accumulated on this point in sheep 
and it shows that the difference in weight and composition of the body 
of animals from the Live and Carcase Classes is one of fat alone. It would 
seem probable that this result would also apply to pigs and that the 
difference in weight between the two classes is due to extra fat in the 
Live Classes, wliich from the butchers" point of view is superfluous. It is 
worthy of note that the Tamworth, a breed which does not put on 
superfluous fat easily, has only a difference of 45 lbs. between "Carcase" 



398 Groivth and Development of Breerh and Crosses oj Plys 



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400 Growth and Development of Breeds and Crosses of Plcjs 

and " Live " Classes at 1 1 months old as compared with 154 lbs. and 156 lbs. 
for Berkshire and Large Whites respectively. At ') months old tlic Live 
Classes are only 16 per cent, heavier than the Carcase Clas.ses, yet at 
11 months old this difference is increased to 62 per cent., the young 
animal being much more diflicult to overfatten than the old one. 

The carcase percentage for the different breeds is shown in Table VII ; 
the variations at different ages are discussed below (see Age) as also are 
the relative orders of the breeds at the younger ages (see Early Maturity). 

The Middle White has the highest carcase percentage and is followed 
by the Berkshire, Large White, Tamworth and Large Black in the order 
named. The proportion of pluck is in inverse proportion to the carcase 
percentage and so the order of breeds as regards this part is reversed. 

The carcase percentages are on the whole less than those of pigs 
exhibited at the International Live Stock Show at Chicago (3i) which 
vary from 83 to 88 per cent, but there a different type of pig — the lard 
pig — is required. 

Table VII. Proporlioii.s of or(jans in different bree(U of pigs — 
as percentage of the live weight. 

3 months 5 month.s 7 months !t rnoiUhs 11 months 



t3 T3 Ts -a -0 

^ ^ <^ CJ 9 



S .5 c S 3 ^ c 



9 



a 



Breed Q S 5^ O S &£ O S t)>2 O S D£ O S D^ 

Aliddle White ... 74-3 6-0 19-7 76-8 5-2 180 82-4 4-5 131 840 40 12-0 85-2 30 10-9 

Berkshire ... 770 5-5 175 78-7 S-S lo-S 811 4-7 14-2 82-5 4-5 130 83-1 4-4 12-5 

Large White ... 730 5-9 211 76-9 5-4 17-7 80-9 4-7 14-4 81-3 4-5 14-2 83-5 40 12-5 

Tamworth ...— — — 70-1 6-1 23-H 76-3 5-2 18-5 80-4 4-7 14-9 84-8 4-0 11-2 

Large Bhiek ... 72-9 5-8 21-3 73-9 GO 201 79-7 4-8 ir,-5 80-3 4-8 14-9 SO-7 51 14-2 

Lincohishire Curly SO-9 4-3 14-8 — — — ^ __ ____ ___ 

Coated 

Average (4 breeds) 74-3 5-8 199 70(i 5 5 17-9 810 4-7 14-3 820 4-4 13(> 831 4-3 12i; 

Age. The effect of age on the rate of growth iu live weiglit in the 
different breeds, calculated as increase in lbs. per day since birth, is seen 
in Table II and V. The rates of growth of two breeds (Berkshire and 
Middle White) of which sufficient numbers have been available at all 
ages, have been averaged and are shown in Fig. 1 . 

The rate of growth in these two breeds falls from 3 to 5 months and 
then rises till it reaches a maximum at 9 months old when it falls again. 
The reason for the first drop between 3 and 5 months is to a very small 
extent caused by neglecting the birth weight which would naturally play 



John Hammond 



401 



a greater part m pii;i;s of smaller weight; this is not the main reason 
however which is probably due to the fact that the 3 mouths old pigs 
have not been weaned early but forced through, whereas the 5 months 
ones have often been weaned early and some may possibly have had a 
short store period. 

lOr 



» 7 - 




Fig. 1 



5 7 9. n 

Jlonths old 
Rate of Growth — Live Weight — lbs. per week since birth. 
Average of i! breeds (Berkshire and Middle White). 



The maximum rate of growth in these two breeds appear to be made 
at 9 months old but if reference is made to Table II for the Live Classes 
and Table V for the Carcase Classes it will be seen that breeds vary 
greatly at which the maximum rate is attained: the Large White and 
Large Black attaining their maximum at 7 months. It is notable that 
although the pork type of pig (Middle White, Berkshire) appears to reach 
the maximum growth later than the bacon type (Large White and Large 
Black) yet the decline in rate of growth of the latter is not so great 
between the ages of 9-11 months as it is in the former. 

Since Uve weight growth is the sum of the growth of various organs 
and tissues in the body it does not necessarily follow that the rate of 
increase of meat is most at this time. The differences in rate of increase 
between the Carcase and Live Classes (shown in Fig. 1) which become 
greater as the pigs get older lead one to believe that the growth at this 
stage (9 montks) consists mainly of fat. 



402 Gi'oirth and Dcrelopment of Breeds and Crosses of Pigs 

Till' variations in rate of growth in different breeds have yet to be 
analysed in terms of the components of the body ; the various systems 
of the body reach thoir maximum rate of growth at different stages and 
thus breed variations in the rate of growth may be explained. 

The figures given above for rate of growth may be criticized however 
because they show the rate from birth to that particular age ; thus they 
give the total result of growth to tlie particular age and not the rate at 
which growth is proceeding at the time. The rate of growth between 
certain ages has been calculated in another way — by subtraisting the 
weight at x months from the weight at // months and the age at x months 
from the age at // months and from this finding the rate of growth per 
week. This has been done for four breeds and the results are sjiown in 
Fig. 2 and in Table Vlll. From these it will be seen that, as before, the 
rate of growth falls between 3 and 5 months but attains its maximum 
(of approximately 1"2 lbs. per week) between 5 and 7 months and then 
falls again until between '.) and 11 months it is only about 3 lbs. per week. 

Data collected from various authorities for the growth in live weight 
of the pig are given in the following table : 

Groiolh in lbs. per week gain. 

Months old ... 1 2 3 4 5 G 7 

Biicklcy(32) ... 
HarpciMiS) 

0.stertag iintl Ziintz(35) 2-8 — — — — — — — — — — — 

The economy of gain in live weight however cannot altogether be 
measured by the rate of increase per week. J 1 enry and Morrison (36) found 
from data collected from the U.S. Experimental Stations that pigs of 
78 lbs. (corresponding to 3 months old) put on 100 lbs. live weight from 
400 lbs. food whereas pigs of 320 lbs. (corresponding to 9 months old) 
put on 100 lbs. live weight from .535 lbs. food; the composition of this 
gain in live weight as shown in Table Vlll however is very different. 

Morgan (37) has pointed out that man is larger than the rabbit because 
he grows for a longer period but the daily i