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Full text of "The mutation theory; experiments and observations on the origin of species in the vegetable kingdom"

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ANTIRRHINUM MAJUS LUTEUM RUBRO-STRIATUM, 

With Bud Variation. 






VOL. II. 



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A-C. -CHRYSANTHEMUM SEGETUM PLENUM, 
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THE 



MUTATION THEORY 



EXPERIMENTS AND OBSERVATIONS 

ON THE 

ORIGIN OF SPECIES IN THE VEGETABLE 

KINGDOM 



BY 

HUGO DE VRIES 



PROFESSOR OF BOTANY AT AMSTERDAM 



TRANSLATED BY 

PROF. J. B. FARMER AND A. D. DARBISHIRE 



VOLUME II 

THE ORIGIN OF VARIETIES BY MUTATION 

WITH NUMEROUS ILLUSTRATIONS AND SIX COLORED PLATES 



CHICAGO 
THE OPEN COURT PUBLISHING COMPANY 

LONDON AGENTS 

KEGAN PAUL, TRENCH, TRUBNER & CO., LTD. 

1910 



. . . 

COPYRIGHT BY 

THE OPEN COURT PUBLISHING Co. 
1910 



3 



CONTENTS. 

PART I. 
THE ORIGIN OF HORTICULTURAL VARIETIES. 

PAGE 

I. THE SIGNIFICANCE OF HORTICULTURAL VARIETIES IN THE 

THEORY OF SELECTION 3 

1. Variability in Garden Plants 3 

2. The Doctrine of the Increase in Variability in One 

Direction Brought About by Selection 9 

II. LATENT AND SEMI-LATENT CHARACTERS 18 

3. Eversporting Varieties 18 

4. Half Races and Half Curves 26 

5. Trifolinm Pratense Quinquefolium, An Eversporting 

Race 36 

III. THE DIFFERENT MODES OF ORIGIN OF NEW SPECIES 56 

6. Horticultural and Systematic Varieties and Elementary 

Species 56 

7. Progressive, Retrogressive and Degressive Formation 

of Species 65 

IV. THE SUDDEN APPEARANCE AND THE CONSTANCY OF NEW 

VARIETIES 76 

8. Examples of Constant Races 76 

9. Sterile Varieties 88 

10. Instances of Races which Have Arisen Suddenly in 

Nature 95 

11. Horticultural Varieties which Have Arisen Suddenly. 99 

V. ATAVISM 104 

12. Atavism by Seeds and Buds * 104 

13. Vilmorin's Suggestion as to the Origin of Striped 

Flowers 113 

14. Antirrhinum Majus Striatnm 120 



iv Contents, 

PAGE 

15. Hesperis Matronalis 136 

16. Clarkia Pulchella ; . . . 144 

17. Plantago Lanceolata Ramosa 148 

VI. EXPERIMENTAL OBSERVATION OF THE ORIGIN OF VARIETIES. . 161 

18. The Origin of Chrysanthemum Segetum Plenum .... 161 

19. Double Flowers and Flowerheads 194 

20. The Origin of Linaria Vulgaris Peloria 201 

21. Heritable Pelorias 220 

VII. NON-ISOLABLE RACES 227 

22. Trifolitim Incarnatum Quadrifolium 227 

23. Ranunculus Bulbosus Semi-Plenus 243 

24. Variegated Leaves 265 

25. Alternating Annual and Biennial Habit 291 

VIII. NUTRITION AND SELECTION OF SEMI-LATENT CHARACTERS. 307 

26. Increased Nutrition Favors the Development of the 

Anomaly 307 

27. The Influence of External Conditions and of Manur- 

ing 315 

28. The Periodicity of Semi-Latent Characters 323 

29. The Choice of Seeds in Selection 332 

PART II. 

THE ORIGIN OF EVERSPORTING VARIETIES. 
I. TRICOTYLOUS RACES 343 

1. The Occurrence of Tricotyls as Half Races and Inter- 

mediate Races 343 

2. Tricotyls, Hemi-Tricotyls and Tetracotyls 356 

3. The Influence of Tricotyly on the Arrangement of 

Leaves 365 

4. Tricotylous Half Races 3/9 

5. Tricotylous Intermediate Races Do Not Arise by Se- 

lection 393 

6. The Isolation of Tricotylous Intermediate Races .... 417 

7. Partial Variability of Tricotyly 444 

8. The Influence of External Conditions on Tricotyly . . 450 

II. SYNCOTYLOUS RACES 457 

9. Hemi-Syncotyly, Syncotyly, Amphi-Syncotyly 457 

10. Helianthus Annuus Syncotyleus 466 

11. Improvement of a Hemi-Syncotylous Race 476 

12. Atavistic Races 481 



Contents. v 

PAGE 

13. The Influence of External Conditions on Hereditary 

Values 485 

III. THE INCONSTANCY OF FASCIATED RACES 488 

14. The Inheritance of Fasciations 488 

15. Half Races with Heritable Fasciation 502 

16. Eversporting Varieties with Heritable Fasciation . . . 508 

17. The Significance of the Atavists 514 

IV. HERITABLE SPIRAL TORSIONS 527 

18. Spiral Disposition of the Leaves 527 

19. Rare Spiral Torsions 537 

20. Spirally Twisted Races 543 

21. The Significance of the Atavists 554 

PART III. 

THE RELATIONS OF THE MUTATION THEORY TO 
OTHER BRANCHES OF INQUIRY. 

I. THE CONCEPTION OF SPECIES ACCORDING TO THE THEORY 

OF MUTATION 567 

1. Systematic Biology and the Theory of Mutation 567 

2. Progressive, Retrogressive and Degressive Mutations. 569 

3. The Theoretical Distinction Between Species and Va- 

rieties 578 

4. The Practical Conception of Species 589 

5. The Parallel Between Systematic and Sexual Relation- 

ship 592 

II. THE RANGE OF VALIDITY OF THE DOCTRINE OF MUTATION. . 599 

6. The Significance of the Available Evidence 599 

7. The Explanation of Adaptations 606 

8. Vegetative Mutations 614 

III. THE MATERIAL VEHICLES OF THE HEREDITARY CHARACTERS 631 

9. Darwin's Pangenesis 631 

10. Intracellular Pangenesis 639 

11. The Pangenes as Bearers of the Hereditary Char- 

acters 643 

IV. GEOLOGICAL PERIODS OF MUTATION 651 

12. The Periodicity of Progressive Mutations 651 

13. Iterative Formation of Species 661 

14. The Biochronic Equation , 663 

INDEX 675 



LITERATURE. 

LIST OF THE AUTHOR'S PAPERS BEARING ON THE THEORY OF 

MUTATION. 

(See the List at the Beginning of the First Volume.) 

a. Tntracellular Pangenesis. Translated from the German by 

Prof. C. Stuart Gager. Chicago : The Open Court Pub- 
lishing Co., 1910. 

b. Fluctuating Variability and Mutability. 

Eine zweigipfelige Yariationscurve. Roux' Archiv fur Entwicklungsmechanik 

der Organismen, 1895, II, Heft I. Archiv. Neerl., 1895. 
Sur les courbes Galtoniennes des monstruosites. Bull, scient. France et Bel- 

gique, 1898, T. XXVII, p. 395. 
Over het omkeeren van halve Galton-curven. Botanisch Jaarboek, Gent, 1898, X, 

p. 27. 
Ueber Curvenselection bei Chrysanthemum segetum. Ber. d. d. bot. Ges., 1899, 

Bd. XVII, Heft 3. 

De zaadkweekeryen te Erfurt. Het Nederlandsch Tuinbouwblad, 1891, p. 327. 
Gladiolus nanceianus, ibid., VIII, Jan. 1892. Tulipa Greigi, ibid., May 1892. 
Caladium, ibid., July 1892. Caladium's van ALFRED BLEU, ibid., July 1892. 
Dubbele Seringen, ibid., Sept. 1892. Grootbloemige Canna's I and II, 
ibid., Dec. 1892. Amaryllis, ibid., IX, Sept. 1893. 

c. Spiral Torsions. 

Ueber die Erblichkeit der Zwangsdrehung. Ber. d. d. bot. Ges., 1889, VIII, p. 7. 
Eenige gevallen van Klemdraai by de Meekrap. Bot. Jaarboek, Gent, 1891, 
III, p. 74- 

Monographic der Zwangsdrehungen. Jahrb. f. wiss. Bot., 1891, XXIII, pp. 13- 
206, Plates II-XI. 

Bydragen tot de leer van den Klemdraai. Bot. Jaarboek, 1892, IV, p. 145. 

Eine Methode, Zwangsdrehungen aufzusuchen. Ber. d. d. bot. Ges., 1894, Bd. 
XII, Heft 2. 

On Biastrepsis in Its Relation to Cultivation. Annals of Botany, 1899, XIII, 
P- 395- 

d. Fasciations and Other Anomalies. 

Sur un spadice tubuleux du Peperomia maculosa. Archiv. Neerl., 1891, T, 
XXIV, p. 258. 



viii Literature. 

Over de erfelykheid der fasciatien. Bot. Jaarboek, Gent, 1894, VI, p. 72. 

Over de erfelykheid van synfisen. Bot. Jaarboek, 1895, VII, p. 129. 

Krfelyke monstrositeiten in den ruilhandel der Bot. Tuinen. Bot. Jaarboek, 
1897, IX, p. 66. 

Een epidemic van vergroeningen. Bot. Jaarboek. 1896, VIII, p. 66. 

Sur la culture des monstruosites. Cps. rs. de 1'Acad. des Sc.. Paris, 1899. 

Sur la culture des fasciations des especes annuelles et bisannuelles. Revue gene- 
rale de botanique, 1899, T. XI, p. 136. 

Ueber die Abhangigkeit der Fasciation vom Alter bei zvveijahrigen Pflanzen. 
Bot. Centralblatt, 1899, LXXVII. 

Ueber die Periodicitat partieller Variationen. Ber. d. d. bot. Ges., 1899, XVII, 
Heft 2, p. 45. 

Over het periodisch ontreden van anomalien op monstreuze planten. Bot. Jaar- 
boek, 1899, XI, p. 46. 

Sur !a periodicite des anomalies dans les plantes monstrueuses. Archiv Xeerl., 
Serie II, T. III. 

Over verdubbeling van Phyllopodien. Bot. Jaarboek, 1893, V, p. 108. 

Ueber tricotyle Rassen. Ber. d. d. bot. Ges., 1902, Bd. XX, Heft 2. 

e. Unit-Characters. 

ADAM'S Gotiden regen (Cytisus Adami). Album der Natuur, 1894. 
Hybridizing of Monstrosities. Journ. Roy. Hortic. Soc., 1899. 

Sur la fecondation hybride de 1'albumen. Cps. rs. de 1'Acad. de Paris, 1899 
and Ref. Biol. Centralbl., 1900. 

Sur la fecondation hybride de rendosperme chez le Mais. Revue generale de 
botanique, 1900, T. XII, p. 129. 

Sur la loi de disjonction des hybrides. Cps. rs. de 1'Acad. de Paris, 1900. 
Das Spaltungsgesetz der Bastarde. Ber. d. d. bot. Ges., 1900, Bd. XVIII, 

Heft" 3- 
Ueber erbungleiche Kreuzungen. Ber. d. d. bot. Ges., 1900. Bd. XVIII. 

Heft 9. 

Sur les unites des caracteres specifiques. Revue generale de botanique, 1900, 
T. XII, p. 257. 

The Law of Separation of Characters in Crosses. Journ. Roy. Hortic. Soc., 
1901, XXV. Part 3. 

On Artificial Atavism. Proceed. Americ. Hortic. Soc., 1902. 

La loi de MENDEL et les caracteres constants des hybrides. Cps. rs. de 1'Acad. 
de Paris, 1903. 

Anwendung der Mutationslehre auf die Bastardirungsgesetze. Ber. d. d. bot. 
Ges., 1903, Bd. XXI. p. 45. 

Befruchtung und Bastardirung; ein Vortrag, 1903. Leipsic, Veit & Co. 



PART I. 
THE ORIGIN OF HORTICULTURAL VARIETIES. 



I. THE SIGNIFICANCE OF HORTICULTURAL 

VARIETIES IN THE THEORY OF 

SELECTION. 

i. VARIABILITY IN GARDEN PLANTS. 

DARWIN based his theory of selection, in great part, 
on the well-known horticultural principle that new varie- 
ties are obtained by seeking for small deviations with 
subsequent isolation and selection. Variations which at 
their first appearance almost escape observation can be 
worked up by the skill of the gardener ; in doing so varia- 
bility is seen to increase, and in favorable cases, very 
rapidly. In this way a new form arises, which answers 
the purposes and rewards the labors of the breeder. 

We have all heard how beautiful double varieties 
have resulted from the appearance of single flowers in 
which only one stamen and this often only partially was 
transformed into a petal. 

In the first volume we dealt with this practice more 
than once, and pointed out how liable it is to give rise 
to misunderstanding when applied to the elucidation of 
the problem of specific differentiation (Vol. I, 23, pp. 
176-185). The object of the present Part is to collate 
the relevant data and to show what light they throw on 
this all-important problem. Of course we can only go 
.^o far as the incomplete and scanty character of the 
material will allow. 



4 The Significance of Horticultural Varieties. 

The development of the statistical treatment of varia- 
tion which took place after DARWIN'S time, allows of an 
altogether different conception of the phenomena than 
was possible some fifty years ago. It was shown that 
the fluctuation of characters is due to their development 
to a greater or less degree. But the character in ques- 
tion does not vary in any other than these two directions. 
The variation is linear (Vol. I, p. 118). It increases 
or diminishes but creates nothing new. New characters 
can arise, so to speak, alongside of it, but they arise 
independently of the fluctuation of the old ones. 

This applies to the case before us. The variations 
which the horticulturist looks for and then works up 
are not variations of the old characters', such may indeed 
give rise, by selection, to improved races, but not to 
new types (Vol. I, p. 82). The required deviations are 
anomalies, as in the example of the origin of double 
flowers, just cited. When such an anomaly arises we may 
be sure that the new character already existed in the 
internal organization of the plant. Where it springs 
from and how it arose is a matter of indifference to the 
breeder : he has got it and can work it up. In other 
words : ' 'The first condition necessary for raising a nov- 
elty is to possess it" (Vol. I. p. 185). , 

In this connection two cases are distinguished in prac- 
tice according as one is dealing with apparently invariable 
forms, or with forms exhibiting a high degree of fluctu- 
ating variability. In the former case all that has to be 
done is to isolate the novelty and to free it of possible 
impurities introduced by crossing. If this can be done 
without much difficulty the variety is perfect and con- 
stant from the beginning and needs only a few years of 
multiplication before it can be put on the market (Vol. 



Variability in Garden Plants. 5 

I, pp. 77-80). Many white flowered varieties afford 
good examples of this kind of novelty. 

But it is very different with the second case. A nov- 
elty which exhibits fluctuating variability in a high de- 
gree seldom makes its first appearance in a full state of 
development. As a rule it is very slightly developed at 
first. The novelty is betrayed, as the expression is, by 
a quite small trace or indication. From the scientific 
standpoint we have to regard this as a minus-variant, 
i. e., as an extreme variant in the minus direction of the 
new character (Vol. I, p. 51). And it is plain that the 
seeds of such a variant of the new variety will, when 
sown in the garden, soon give the mean value of the 
character in question. 

This process is, as we can easily see, fundamentally 
a phenomenon of regression (Vol. I, Figs. 18 and 19, pp. 
73 and 84) ; but to the breeder it is a progressive change, 
and by no means an inconsiderable one, since on it the 
success of his operations largely depends. This apparent 
paradox, however, has been a great obstacle to the under- 
standing of these phenomena. But, to us, it explains in 
a very clear way the initial and rapid increase in varia- 
bility; for it is obvious that an approximation to the 
mean value will take place much more easily and rapidly 
than a departure from it. 

The breeder can now either rest content with this 
"regressive advance"; or he can endeavor to raise the 
new form above its mean value by choosing plus-variants 
as seed-parents. But in the latter case the value of the 
new form remains dependent on the continuance of se- 
lection (Vol. I, p. 80). 

Note's dealing with this process of breeding are not 
rare in horticultural literature, but they are generally 



6 The Significance of Horticultural Varieties. 

short and lack precision being much inferior in this re- 
spect to the accurate accounts that are given of artificial 
crossings. I shall bring together the most important 
facts that I have been able to find, in the following sec- 
tion (2). 

In order to penetrate more deeply into these phenom- 
ena I have endeavored to apply this method to a series 
of cases. With the help of control experiments, and by 
keeping detailed records, I succeeded in finding out how 
such novelties usually develop themselves. Just as hap- 
pens in practice, I was successful with some cases but not 
with others. And the correspondence between my results 
and the experience of breeders seems to me to be so com- 
plete that my experiments may simply be taken as in- 
stances of the method under discussion. 

I propose to distinguish, therefore, between highly 
variable and only slightly variable novelties. The lat- 
*ter are generally assumed to be instances of single var- 
iations which arise suddenly. In the case of these I 
shall, therefore, only have to discuss their origin and the 
question of their constancy. (Chapter IV of this Part.) 
Much more important from the critical standpoint are the 
varieties with a high degree of fluctuating variability, i. e., 
those very cases which passed for instances of the origin 
of new characters by artificial selection (Chapters II and 
VIII). As examples of this I refer to variegated leaves 
and to double and striped flowers. 

If we now compare, from a theoretical standpoint, 
this high variability with the normal examples which we 
dealt with before (Vol. I, pp. 47-52 etc.) we shall see 
that the two are not exactly the same. In variegated 
leaves the yellow alternates with the green, in semi-double 
flowers the petaloid stamens alternate with normal ones 



Variability in Garden Plants. 7 

and so forth. Therefore we are not here dealing with the 
variable development of a single quality, but with the 
simultaneous operation, or rather with the conflict, of 
two qualities. For in proportion as the one or the other 
of them prevails the plant will be more or less variegated, 
double and so forth. One of the characters is the old, 
normal one, pertaining to the original species. The other 
is the new, abnormal one pertaining to the variety in pro- 
cess of formation, in fact the anomaly. And the conflict 
of these two antagonistic types affords at least a partial 
explanation of this extraordinary variability. 

The green color itself is only very slightly variable, 
and the pure yellow or golden varieties, in which the 
green is entirely absent, are equally uniform (varietates 
anreae, for example Pyrcthnim Partlicniuin aureum). 
Of "double" forms there are two types ; the ordinary 
highly variable more or less double sorts, and on the 
other hand the sterile varieties which exhibit this peculiar- 
ity to its full extent in all their flowers (see Ranunculus 
acris petalomana, Vol. I, Fig. 40, p. 194). In this case 
the types with a high degree of fluctuating variability 
might be considered as a connecting link between two 
almost invariable forms, the normal single and the pet- 
alomanous types. 

If we regard this principle as an explanation of the 
case in point we arrive at the conception of intermediate 
forms with two antagonistic characters strking for the 
mastery, and possessing a remarkably high degree of vari- 
ability as a result of this struggle. The extent of this 
variability differs from case to case : in the most extreme 
examples whole organs or even whole individuals can 
come exactly to resemble one of the types between which 
they oscillate. Pure green or, on the other hand, pure 



8 The Significance of Horticultural Varieties. 

yellow or even white leaves or seedlings are by no means 
rare in variegated varieties. But the resemblance is only 
superficial. The green minus variant of the variegated 
type does not belong to the original species, nor the yel- 
low plus variant to the golden variety; as may often be 
seen by sowing the seeds of such extreme types. 

I propose to call such varieties intermediate races, and 
if neither of the two antagonistic characters preponder- 
ates too much over the other, balanced races or ever- 
sporting varieties 1 (see 3). 

If we attempt to make a statistical study and graph- 
ical description of the variability in such intermediate 
forms we must obviously not expect such simple and 
straightforward curves as those which describe the var- 
iability of normal characters (Vol. I, p. 48). In prin- 
ciple we may expect to obtain figures which simultane- 
ously exhibit the two magnitudes that is to say com- 
pound curves such as have been studied by LUDWIG, 
BATESON, PEARSON, DAVENPORT and others. It is evi- 
dent that they will present very different forms according 
to the mutual proportion of the two characters (see be- 
low 3-5). At the same time it is clear that in such 
cases selection may lead to special results which will often 
be due to the impossibility of transgressing the characters 
of the two limiting types (see 5 and Fig. 3). 

The two following generalizations may be derived 
from the facts we have been discussing. 

1. Some horticultural varieties owe their existence to 
a single nezv character. These are usually not more vari- 
able than the original species and as a rule just as con- 
stant from seed. Very frequently the novelty consists 
in the loss or latency of a character of the parent spe- 

1 See Species and Varieties, Their Origin by Mutation, p. 309. 



Increase in Variability in One Direction. 9 

cies. In cases where the origin of such a novelty is satis- 
factorily known it always happened suddenly. For the 
combination of several characters in the same variety 
see Vol. I, p. 197. 

2. On the other hand some horticultural varieties are 
compound types which owe their existence to the associa- 
tion of two (or more) antagonistic characters. The two 
characters tend to exclude one another more or less com- 
pletely and struggle for the upper hand; from this there 
results a very high degree of variability in their mani- 
festation (as in variegation, stripes, doubleness and so 
forth). These forms usually first appear as minus var- 
iants, i. e., with a slight degree of development of the 
abnormality in which condition they are sought for and 
isolated and subsequently improved by selection. The 
artificial production, therefore, of such a form is not a 
sudden one but a process of gradual improvement Their 
first origin however remains unknown. 

2. THE DOCTRINE OF THE INCREASE IN VARIABILITY 

IN ONE DIRECTION BROUGHT ABOUT 

BY SELECTION. 

One of the most attractive parts of the doctrine of 
selection is that according to which variability may be 
increased by selection. Many observations, especially in 
horticulture, seem to support this view ; which, if it were 
true would afford an almost irrefutable argument in favor 
of the prevailing belief in the omnipotence of natural 
selection ("Vol. I, p. 119). 

Varieties are said to be incipient species. By selecting 
the individuals which deviate most from the type of the 
species it is believed to be possible to attain first to varia- 
tions and then to varieties. To these is ascribed the 



10 The Significance of Horticultural Varieties. 

tendency to become fixed and so to become races : in the 
same way these races would later be transformed into 
species. This is the generally accepted view. 

This view is based, as I attempted to show in the first 
part of the first volume, on an unwarranted extension 
of DARWIN'S theory of selection. DARWIN argued from 
the results obtained in horticulture ; but these, at least as 
described in the works of the best authorities, do not 
seem to me to justify such an extension. 

According to the prevailing view, man has the power 
to produce any desired amelioration in any species ready 
to hand. All characters vary and all that need be done 
would be to isolate the extreme variants and to breed 
further from them. The process takes some time of 
course but in many species the experiment is already 
lasting about half a century. But the advances which 
have been made, and which are of the very greatest prac- 
tical importance, do not tally with this assumption. On 
the contrary we learn from them that for much that has 
been attained much has proved unattainable. 

The comparative studies of systematists show us that 
almost everywhere there exist imperceptible transitional 
stages between the smallest differences and perfectly dis- 
tinct species. This forms a weighty argument for, but 
no proof of, the prevalent view. For we have to reckon 
here with transgressive variability (Vol. I, Part II, 25, 
p. 430), which tends to blur the boundaries of related 
groups. 

I have indicated in the foregoing section (1) the 
principles on which in my opinion an elucidation of the 
process in question must be based. If a small anomaly 
is found in a wild or cultivated species, and a new and 
constant form is raised from this by selection, the whole 



Increase in Variability in One Direction. 11 

sequence of events may have the appearance of having 
been gradually brought about by the free will of the ex- 
perimenter ; whereas as a matter of fact the result was 
attained mainly by good luck. 

If we look through the literature of horticulture we 
shall soon see that this illusion has not taken in the really 
efficient breeder. He knows perfectly well that neither 
the beginning nor the end of such an experiment is under 
his control. It is only between these two limits that 
everything depends on his skill. 

The first indication of an anomaly in a pure species 
appears by chance ; and it is a well-known rule in horti- 
culture that the breeder should always be on the lookout 
for such chance occurrences. It does not matter how 
small the deviation is so long as it is an anomaly (p. 4). 
When such a deviation has once been found it lies with 
the breeder to perfect it and bring it to its full develop- 
ment. But the ever present, more or less considerable, 
fluctuating variations of normal characters are of no use 
for this purpose; by their means many varieties may be 
made better and prettier, but they can give rise to nothing 
really new. 

The best horticultural authorities are in agreement 
on this point. CARRIERE for example says : "Uhorticul- 
tenr ne pent faire naitre les varietes" and in greater de- 
tail in reference to double flowers: "Le point de depart 
des fleurs donbles est en dehors de notre puissance coin me 
de nos calcnls; nons ne ponvons rien, on a pen pres rien, 
sur le fait initiatif; nons ne ponrons qnc le saisir lorsqn'il 
se presente; nons ne pouvons pas le provoqner; c'est nn 
effct, dont la canse nous est inconnnc." 1 A well-known 

1 E. A. CARRIERE, Production et fixation dcs rarictcs dans les 
vegctaux, 1865, p. 64 and p. 15. 



12 The Significance of Horticultural Varieties. 

English breeder, WILLIAM PAUL, says : l 'He who is 
seeking to improve any class of plants, should watch 
narrowly and seize with alacrity any deviation from the 

fixed character However unpromising in appearance 

at the outset, he knows not what issues may lie concealed 
in a variation." SALTER also said that the greatest diffi- 
culty lies in finding a small initial deviation ; but when this 
has once been found all the rest lies within our power, 
however small the variation may be. And DARWIN, who 
cites this, 2 always emphasized its great importance when- 
ever he had occasion to refer to it. 

In other words, which we have already often quoted : 
The main condition necessary to produce a novelty is to 
be in possession of its first step. 

And yet as is well known the attempt is not by any 
means always successful. Sometimes the variation dis- 
appears without leaving a trace behind ; in which case of 
course all further efforts to deal with it are in vain. 

Unfixable deviations of this kind are, according to 
my experience, the occasional manifestation of latent 
characters. What the breeder wants to find are those 
cases in which the chance anomaly has already become 
a heritable although hidden race. If this has happened 
the anomaly will, in the first place, easily manifest itself, 
if the conditions of life are not quite unfavorable and in 
the second can rapidly be developed to the level of a good 
horticultural variety. 

So far as the available data enable -us to judge, breed- 
ing experiments of this kind always follow the same 
course. Hosts of examples can be found. Extensive 

1 Contributions to Horticultural Literature, 1892. Nature, Vol. 46, 
P- 583- 

2 Variations of Animals and Plants, II, p. 249. See also Part I, 
p. 267 et seq. 



Increase in Variability in One Direction. 13 

sowings repeated year after year avail nothing if chance 
does not play its part. Anemone coronaria plena arose 
in the nurseries of WILLIAMSON in England as a single 
plant, which exhibited a slight petaloid broadening of one 
of the stamens. 1 From the seed of this specimen a race 
has been started, the flowers of which became fully 
double in the course of a few generations. The double 
varieties of roses, Campanulas, and many other garden 
plants have arisen in the same way. I saw a bed of 
mignonette (Reseda odorata) some of which had double 
spikes, in a nursery at Erfurt. The spikes were fasciated, 
the flowers were broader and the whole plant fuller, more 
compact and handsomer than the species. The plants of 
this bed had been produced from the seed of two fasciated 
specimens which had accidentally appeared the year be- 
fore. The normal were weeded out and the abnormal 
saved and allowed to set seed with a view to putting a 
new r variety on the market. 

In cases such as this, selection has a twofold object. 
In the first place the variety must be isolated, that is 
purged of the impurities resulting from free crossing. 
It must also be actually improved by selection. The first 
indications of doubling are, as we have seen, single super- 
numerary petals, or in composites single supernumerary 
ray florets on the disc ; the first indication of a new color 
is often very pale : slit leaves and petals are indicated by 
quite small imaginations, combs (Vol. I, p. 191) appear 
as small outgrowths. All these qualities had to be im- 
proved by selection up to the level of the mean of the 
character and then even perhaps beyond. 

An improvement of this kind, when once started, is 
effected not only rapidly but with increasing swiftness. 

DARWIN, he. cit., TT, p. 269. 



14 The Significance of Horticultural 1 \irietics. 

Hence the illusion of an increase in variability. The ex- 
planation is simply this that, as shown in the preceding 
section ( 1), we first find a minus variant of the new 
character, which, in accordance with the law of regres- 
sion, approaches not the character of the old species but 
the mean value of the new variety, as soon as it is iso- 
lated. And this takes place easily and swiftly since the 
new variety in this case behaves like an improved race 
on the cessation of selection or under reversed selection 
(Vol. 1, 14, p. 122). 

The progress made by this improvement and through 
the purification from the results of crossing is often so 
rapid that it can be expressed in terms of a geometrical 
series. This generalization does not attain to the rank 
of a law, but my meaning will become clearer by citing 
an example. HOFMEISTER sowed the seeds of plants of 
Papaver somniferum polycepJialiim, 1 which he had found 
growing between normal examples of the species. By 
selecting the fruits which were richest in supernumerary 
carpels, but without isolation, he effected the following 
increase in the number of abnormal examples in the suc- 
ceeding generations : 

Year: 1863 1864 1865 1866 1867 

Percentage of abnormal plants: 6% 17% 27% 69% 97% 
Geometric series: 8 16 32 64 (100) 

These figures, as we see, do not differ considerably 
from a geometric series. I do not lay much stress on 
the fact, but I have myself more than once obtained 
similar series of figures in breeding experiments. 

The limits that can be reached are as little under the 
control of the breeder as the starting-points that had to 

1 Allgememe Morphologic, p. 565. See our Fig. 27 on p. 138 of 
the first volume; also HOFFMANN, Bot. Zcitg., 1881, p. 397, and VER- 
LOT, Production et fixation des varietes, p. 88. 



Increase in Variability in One Direction. 15 

be waited for. This is most forcibly brought out by the 
fact that numerous horticultural varieties are still at 
exactly the same level as they were at the time of their 
introduction. The most vigorous selection continued over 
long periods of time has only rarely succeeded in effecting 
a further improvement in the same direction. We are 
familiar with hosts of variegated plants, but Aurea vari- 
eties are very rare. Flowers with petalomany are sterile, 
and the plants can only be multiplied by vegetative meth- 
ods. But it is quite clear that this difficulty is by no means 
the cause of their rarity. Amongst composites we occa- 
sionally find isolated heads without tongue florets, but 
how small is the number of discoid varieties. I once 
found an example of Coreopsis tinctoria in my cultures, 
which exhibited only some spare ray florets, but although 
I isolated the plant, the abnormality did not reappear 
from its seed. Catacorolla (an outward doubling of the 
corolla so as to form lappets) occurs almost only as a 
commercial race in Gloxinia superba. Fistulous compo- 
sites are rare ; there is room on the market for monoph- 
yllous and laciniate varieties of many species, if only we 
could make them. But so long as chance does not put 
them into our hands, all our labor is in vain. 

Nevertheless, all plants no doubt possess numerous 
latent characters. Any culture carried out on a sufficiently 
large scale, or continued for several years, will give con- 
vincing proof. In fact it is often very difficult to keep 
races free from anomalies. Agrostemnia Githago, Raph- 
anus Rhaphanistnun and many other species contain an 
almost inconceivable number. Amongst garden plants 
desirable novelties must obviously be rare now because 
thev must have been already found and put on the market ; 



16 The Significance of Horticultural Varieties. 

useless and indifferent anomalies are common enough, 
especially in extensive cultures. 

When a new horticultural variety has been isolated 
and "fixed," that is to say improved and rid of impuri- 
ties by a few years' cultivation no considerable further 
improvement in the same direction is to be expected. 
Only two ways of progress are still at hand. These are 
to wait for the chance appearance of a new abnormality 
in the same strain, or to combine the new character with 
others by crossing. The former method is dependent 
on chance and therefore often unsatisfactory. The sec- 
ond is almost sure to succeed, and thus it is always chosen. 
Each new character is immediately transferred to nu- 
merous other varieties of the species and a corresponding 
number of novelties obtained in this way. Thus LE- 
MOINE transferred the double flowers of a single double 
lilac to several dozen varieties, and the Cactus Dahlia 
was, very soon after its introduction, obtainable in almost 
every shade of color and doubleness. Ordinarily this 
process is described in the opposite way that is to say, 
it is claimed that the properties of the old varieties are 
transferred to the new type. In this way there appears 
a vast series of varieties forming a new group co-exten- 
sive with the older forms of the original species. Thus 
a single new character can double the number of varieties. 
Petunias, Zinnias and Fuchsias are familiar examples of 
the application of this method in former times, Gladiolus, 
Begonia and many others of its recent application. The 
ostrich-feather Chrysanthemum (with ciliated petals) 
arose about thirty years ago in a single variety (Alph. 
Hardy), but can now be obtained in large numbers of 
forms. 

The doctrine of the onesided increase of variability 



Increase in Variability in One Direction. 17 

selection is based, therefore, as far as the available 
data enable us to decide, on the existence of strains with 
heritable but hitherto latent characters. Such races are 
highly variable, and their existence is betrayed when they 
first are met with, by trifling anomalies which however 
can easily be worked up by selection. As a result they 
rapidly depart from tlie type of the species but only be- 
cause they approach their neiv type: and as soon as this 
has been reached bv isolation or exceeded bv selection 

j *f 

it is just as difficult to effect any further improvement 
as in ordinary improved races. These varieties cannot 
be evoked at will; we have to wait till they chance to ap- 
pear. Nor when once fully developed can we improve 
them further. Nothing but chance that is to say some 
unknown factor can as yet overstep these two limits; 
selection can effect no more than the most transparent 
illusion of any thing approaching complete control. 



II. LATENT AND SEMI-LATENT CHARACTERS. 

3. EVERSPORTING VARIETIES. 

Before I proceed to deal with the results which have 
been obtained, in horticulture, with these highly variable 
varieties it is desirable, in order to clear up the concep- 
tions involved, to fix our attention on the various stages 
which may be interpolated between a species and a simple 
and constant variety derived from it. 

We will start from the fact that the chance appear- 
ance of an anomaly by no means always opens up the 
way to the acquisition of a novelty. One example out of 
many will suffice. Pitchers (Figs. 16, 106, and 109, Vol. 
I, pp. 61, 470, 484) are usually found as quite rare and 
isolated variations, 1 but in some species of plants, such 
as Magnolia and Tilia, tolerably frequently. But a vari- 
ety as rich in these structures as, for example, Tri folium 
pratensc quinquc folium is in 4- and 5-merous leaves does 
not exist, although it would obviously attract attention 
and pay the trouble of breeding experiments. 2 

This shows that an anomaly discovered by chance 
may be the expression of a latent character which cannot 
be brought to its full state of development. Besides this 

1 Over de erfelykheid van synfisen, Knildkundig Jaarbock, Gent, 
1895, P- 129- 

2 A variety of Ficus religiosa, with all its leaves changed into 
pitchers, has since been introduced into Europe by Mr. PRAIN, the 
Director of Kew-gardens. (Note of 1910.) 



Ever sporting Varieties. 19 

extreme but very common mode of appearance two other 
cases are possible, according to my experience : 

1. When the seeds of an abnormal individual are 
sown the anomaly is repeated from time to time in a few 
or more individuals, remaining rare or only appearing 
in a feeble state of development. Selection may improve 
it, but only to a very inconsiderable extent. 

2. Under favorable circumstances the anomaly may 
increase rapidly both in the degree of its development and 
in the number of individuals which present it. A so-called 
constant race is formed in the course of a few genera- 
tions. It is subject to a high degree of fluctuating vari- 
ability in respect to the character in question and is 
largely dependent on cultivation. 

I propose to term the first type of characters scini- 
latcnt and to distinguish amongst latent characters be- 
tween the genuine completely latent ones and those which 
occasionally come to light or the semi-latent ones. This 
term refers to the behavior of the character in the race as 
a whole; a semi-latent character may remain latent in 
many individuals and organs and be active in others. 
A true latent character on the other hand only very 
rarely becomes active. 

If we study these three cases statistically, trying to 
plot the variation of the anomaly in the form of a curve 
(p. 8) we generally obtain the following results: 

First cose. The genuine latent characters appear so 
rarely that they do not afford sufficient material for a 
curve. 

Second case. Semi-latent characters must be studied 
in combination with their antagonistic active characters, 
and are expressed by half curves (Fig. 1, p. 28), from 
which a two-sided curve mav be derived bv selection 



20 Latent and Semi-Latent Characters. 

(Fig. 2, p. 34), the apex of which however does not 
become very distant from that of the half-curve. 

Third case. The characters are first expressible by 
half curves because they are minus variants; but after 
isolation the curve very soon becomes a two-sided one 
with a new apex. The new variety reaches its full de- 
velopment and is maintained without further selection. 

A schematic presentation of the conflict between two 
antagonistic characters is given below : 

The normal character is: The anomaly is: 

I. active latent. 

II. active semi-latent. 

III. An equilibrium is maintained. 

IV. semi-latent active. 
V. latent active. 

I do not of course suppose that no further cases are 
possible, that there may not for example be various stages 
of semilatency. The facts at our disposal do not admit of 
any such definite statement. On the other hand it must 
be stated that the scheme I have given covers the cases 
which have been so far collected ; we shall soon see large 
numbers of examples of the main cases, whereas of others 
I have not yet found any. 

In the above table I obviously represents the normal, 
original species, and V the slightly variable and constant 
variety derived from it. The three other numbers repre- 
sent the three intermediate forms of which the two first 
(II and III) correspond to actuality whilst the fourth 
merely follows from the scheme. I am rather doubtful 
as to its occurrence in nature. 

It is necessary to introduce special names for the 
first two intermediate forms. I shall therefore call them 
both intermediate races, one of which- No. II I shall 



Eversporting Varieties. 21 

call a half race, and No. Ill a middle race. The word 
race is obviously not used here in the sense of an im- 
proved rare (Vol. I, p. 80) but simply means a heritable 
form. Instead of middle race I shall usually employ 
the more convenient term of eversporting variety. 1 

Two examples to which reference has already been 
made will serve to illuminate the foregoing discussion. 

EXAMPLES. 

VARIEGATED LEAVES. DOUBLE FLOWERS. 

I. Original species. Green. Simple. 

II. Half -race. Rarely variegated. Occasional petaloid 

stamens. 

III. Eversporting variety. Var. variegata. Var. plena. 

V. Constant variety. Var. aurea. Var. petalomana. 

The parallelism of these two groups rests on the 
assumption that the same character appearing in a state 
of full development would give rise to the constant golden 
and to the fully double varieties; 2 and that it is by their 
mixture with the antagonistic character that variegated 
and half-double varieties arise. The object of this as- 
sumption is solely to present the matter more clearly ; 
for in cases of segregation the characters behave slightly 
differently (see p. 124). 

There are many examples of half races and ever- 
sporting varieties; the former constitute a very con- 
siderable part of the material of teratology and afford 
suitable material for the experimental study of monstros- 
ities. The same holds good for many eversporting vari- 
eties, and I shall have to recur to this point in the second 
part of this volume with especial reference to twisted 
stems and fasciations. Half races as a rule exhibit their 

1 See Species and Varieties, Their Origin by Mutation, Chapters 
XI-XV, pp. 309-459- 

2 See 19 and especially 24 (on variegation). 



22 Latent and Semi-Latent Characters. 

abnormality too seldom to be of any use, or at any rate 
to be of more than of secondary value, in horticulture. 
On the other hand the eversporting varieties highly con- 
tribute to the diversity among horticultural plants. Nu- 
merous varieties with variegated leaves, with striped or 
double flowers, with double heads amongst the compo- 
sites, belong to this group. The Formae cristatae of many 
ferns, the combs in the flowers of Primula sinensis, Cyc- 
lamen persicum, Begonia etc., the polycephaly of Rapaver, 
the catacorolla of Gloxinia superba, and a series of other 
more or less rare instances may also be adduced. 

It is, obviously, not necessary that all the forms named 
should exist for every pair of antagonistic characters. 
In many cases the intermediate races are absent and in 

J 

others one or two of them. It is, likewise, not necessary 
that the pure type corresponding to a certain intermediate 
race should exist. We can, in such cases, very often 
reconstruct it by the help of analogy. The following 
are instances which will be described more fully later on 
in this part, in which the corresponding constant vari- 
ety is still failing. 



SPKC.BS. HA LF - RACE . 

Tri folium pratense wild four-leaved T. p. guinque folium. 

clover 

Trifolium incarnatum T. i. quadrifolium unknown. 

Ranunculus bulbosus R. b. semiplenus unknown. 

Chrysanthemum inodcrum unknown C. i. plenissimum. 

Chrysanthemum segetum C. s . grandiflorum C. s. plenum. 

Caltha palustris furnishes another instance; it ex- 
hibits in nature a half race with supernumerary petals 
and is represented on the market by a uniformly double 
sterile variety exhibiting petalomany. Camellia japonica 
presents the two types of doubling in different varieties. 



Eversporting I 'arietics. 23 

The remarkable fistulous and monophyllous varieties, so 
well known as examples of partial atavism, are further 
instances of eversporting types (Vol. I, Fig. 38, p. 193, 
and Fig. 15 of this volume), together with the viviparous 
grasses (Poa alpina liuipara, Poa bnlbosa livipara, etc.) 
and a number of other viviparous forms such as Agave 
vk'ipara and so forth. 1 If the constant variety corre- 
sponding to a certain intermediate race does not exist, 
this latter is usually classed as a variety in the case of 
middle races, but as a heritable anomaly in the case of 
half races. 

It is, further, very probable that many natural spe- 
cies which attract attention by the high degree of vari- 
ability of some particular character are really in a way 
intermediate races, i. e., that they owe their multiformity 
to the co-existence of two antagonistic characters. In- 
stead of entering further into this very attractive subject 
I shall content myself with citing the case of Acacia 
dk'ersi folia which owes its name and its nature to the 
conflict between the two characters of bipinnate leaves 
and flattened petioles without leaflets (phyllody of the 
stalks). 

The question of the constancy of these intermediate 
races is a very important one. I propose to deal with 
it when referring to individual cases in detail; and the 
only general statement I shall make now is that both con- 
stant and inconstant intermediate races exist. On the 
one hand there are those cases in which an overstepping 
of the limits between these two races is apparently as 
rare as the mutations by which new species arise, and 

1 See GOEBEL, Organografihie, I, pp. 153-159; E. H. HUNGER, 
Ueber einige vivipare Pflamen. Diss. Rostock, 1887. Bot. Jahresber., 
1888, T. XVI, I, p. 421, and also, especially, CLOS, in Actcs du congrcs 
international dc botaniquc, Paris, Sept., 1900, p. 7. 



24 Latent and Semi-Latent Characters. 

in which at least, in spite of every precaution and care, 
I have not yet succeeded in obtaining the one race from 
the other. (Trifolium incarnatum qnadrij oliiim , T. pra- 
tensc qiiinqucfolium, Ranunculus bulbosus scmiplcnus.) 
On the other hand are those races which when cultivated 
on a sufficiently large scale give rise every year to indi- 
viduals which seems to overstep the otherwise fixed lim- 
its of the race. These are therefore inconstant inter- 
mediate races. I regard this phenomenon as one of 
atavism, at any rate in those cases where, as in my own 
observations, they revert from an eversporting variety 
to the type of the parent species without however ac- 
quiring the constancy of the latter. Atavistic phenom- 
ena of this kind are well known in striped flowers and 
variegated leaves ; and I have also found very striking 
examples of it in Linaria vulgaris pcloria and Plantago 
lance olata ramosa (20 and 17). 

Besides the cases which fall into the two categories 
just discussed, I succeeded in finding a third in which one 
intermediate race arose from the other very rarely and 
only in isolated cases. I have seen two cases of this so 
far. One was the origin of Linaria vulgaris pcloria from 
L. v. hemi'peloria ( 20); the other was the formation 
of the double Chrysanthemum segetum plenum (Plate 
II), from C. s. grandiflorum with 21 instead of 13 
tongue-florets ( 18). Linaria vulg. peloria is probably 
an intermediate race, on account of its inconstancy; 
whereas L. vulg. hcniipeloria (with stray peloric flowers) 
is obviously a half race. The origin of the former from 
the latter presumably occurs in nature from time to time. 
My Chrysanthemum segetnm plenum is a novelty in the 
horticultural sense of the term, being just as double as 
the double varieties of other composites; so far as I 



Eversporting Varieties. 25 

know it has not as yet arisen anywhere else. It consti- 
tutes an eversporting variety like a number of other 
double composites which are analogous to it; and arose 
in my experimental garden, not from the original species, 
but from a variety known in the trade as C. s. grandi- 
flonun, which forms a first step towards it in respect of 
the number of its tongue florets, and is therefore to be 
regarded as a half race. 1 

Let us now briefly summarize the foregoing dis- 
cussion : 

1. There exist both in the cultivated state and in 
nature a series of forms which are either not constant 
or highly variable, a state of affairs which is probably 
due to the interaction of two antagonistic characters. 

2. Of these two characters one is to be regarded as 
normal, that is to say, as belonging to the parent species ; 
the other as the abnormal. 

3. Where the former preponderates, teratological half 
races with their half curves are the result. 

4. If the two maintain an equilibrium, there are 
formed what I have called middle races, intermediate 
races, or eversporting varieties, of which many examples 
are to be found amongst garden varieties and "heritable" 
teratological races. 

5. The high degree of fluctuating variability of the 
eversporting variety, its occasional discovery in nature 
and in cultivation, and the possibility which it affords 
of the working up of striking novelties by means of iso- 
lation and selection, afford an explanation of the major- 

1 The numerous apices of the curves describing variation in the 
number of rays in composites, which have received no explanation 
so far, tend however to make the application of this conception diffi- 
cult 

See also the origin of Dahlia variabilis fistulosa in my cultures 
( ii, p. 100. 



26 Latent and Semi-Latent Characters. 

ity of the phenomena which led DARWIN to his theory of 
the slow transformation of species. For at that time it 
was believed that the inception of this process was to 
be sought in the variation of a character already exist- 
ing, whereas as a matter of fact the variation in question 
is independent of the fluctuation of the existing char- 
acters. 

6. The origin of a constant variety or a new species 
could be easily imagined to occur in this way: First a 
half race would arise from a pure race, then from this 
half race a middle race and lastly, from this latter, a new 
constant form. But this would be pure fancy, since it 
is without any basis of fact. Besides in many cases the 
intermediate stages are entirely wanting. 

4. HALF RACES AND HALF CURVES. 

The study of anomalies must be based on the theory 
that external factors can only be efficient in altering the 
form of the plant if the power to react to them (or the 
potentiality for the change) is already present. 1 'The 
induction of malformations by external causes is no more 
than the manifestation of latent potentialities," says GOE- 

BEL. 2 

Every plant possesses a whole host of such latenV 
potentialities. A single plant of Plantago lanceolata may 
be ramosa, stipitata, and bracteata\ it may have splil 
leaves and pitchers composed of one or two leaves; and 
it may exhibit abnormal twisting and forked ears, or 
present a whole series of other anomalies. The seeds of 
a single self-fertilized plant will very often give rise to 

1 See Intracellulare Pangcnesis, p. 194. 
2 GoEBEL, Organo graphic, p. 158. 



Half Races and Half Curves. 27 

a whole series of malformations. Many cultivated plants, 
such as Cyclamen, Pelargonium and Fuchsia, are particu- 
larly productive of such abnormalities. 

The internal factors may either be latent or semi- 
latent. In the former case the characters are either not 
manifested, or only exceptionally, as in the pinnate leaves 
of the red clover (Fig. 46) and as in the numerous 
cases of pitchers which have been found once, or only 
at long intervals, in the same species. In the second case 
they appear more or less regularly, often yearly, and in 
many specimens. For example I have observed the for- 
mation of pitchers on Magnolia obovata in the various 
botanical gardens which I have visited ; and this species 
as well as its near allies bears pitchers with us every 
year. 1 

In both cases these potentialities are heritable. This 
is proved by their frequence in the case of the semi-latent 
characters and rendered extremely probable in that of 
the latent ones by their occasional reappearance. 

Latent arid semi-latent characters constitute what we 
may call the outer range of the forms of a species. The 
inner range of forms consists of the normal characters 
of a species which are exhibited during its normal life 
or are only induced by such common stimuli as w r ounds, 
mutilations, darkness, or the uncovering of subterranean 
organs and so forth. They are part of the innermost 
essence of the species. But the countless latent charac- 
ters belong just as much to the essence of the species, 
especially when they have formed part of the inner range 
in some remote ancestor and are therefore atavistic. And 
it is just this outer range which presents the best indica- 

1 Over de erfelykheid van Synfisen, Bot. Jaarb. d. Gesellsch. Do- 
donaea, Gent, 1895, P- I2 9- In the course of ten years I have observed 
about 100 pitchers on Magnolia. 



28 



Latent and Semi-Latent Characters. 



tions of descent and therefore of systematic relationship. 
It fully deserves and repays the attention given to it, as 
CELAKOWSKY'S admirable papers show. It is to be hoped 
that others will, following the lines laid down by HEIN- 
RICHER, undertake the task of rendering these characters 
more amenable to study by cultivation, and so bring an 
increased number of them to light. 

The manifestations of latent characters are so rare 

that they scarcely ever lend 
themselves to statistical study 
(p. 19). When they recur 
from time to time they are 
seen to be extremely vari- 
able, since as a rule even the 
B I rarest anomalies are not 

quite the same each time 
they appear. It is easily seen 
in such cases that the varia- 
bility is a unilateral one; but 
the construction of curves 
usually fails owing to the 
sparsity of the material. 

The half races are much 
more favorable in this re- 
spect. Here the deviations 
are by no means so very rare. 
As a rule the normal character still preponderates, but 
material sufficient for statistical study can often be found 
without difficulty. It shows clearly that the variation 
is a unilateral one. The apex of the curve is the mean 
of the normal character, and the deviations all lie on the 
same side. And in ordinary cases they are less numerous 
1 Ber. d. d. hot. Ges., Vol. XTT, 1894, P- IQ7. Plate X. 




5678345 

Fig. i. Half Curves. A, Caltha 
palustris. Curve of the num- 
ber of petals in 416 flowers. 
B, Weigelia amabilis, Curve 
of the slips of the corolla in 
1145 flowers. 1 



Half Races and Half Curves. 29 

the further they deviate from the type of the species. 
Fig. I gives a couple of examples at A and B. A gives 
the number of petals of Caltha palustris in a locality not 
far from Hilversum; the flowers, where the species is 
pure, are pentamerous. But in this place there occurred 
flowers with 5-8 petals in the following proportions : 

Flowers with 5678 Petals. 

Relative number 72% 21% 6% 1% 

Weigelia amabilis, also, has normally pentamerous 
flowers ; but it often varies in a minus direction. I found 
in 1145 flowers on three bushes in our garden (Fig. IB): 

Number of slips in the corolla 345 
Number of flowers 61 196 888 

Half curves differ from the half of a normal curve 
because the height of the mean, i. e., the number of nor- 
mal cases, is too great. Such curves do not display the 
variability of the character given by the highest ordinate, 
but that of another character which is concealed in the 
normal flowers. 1 

Half- or unilateral curves are widely distributed in 
nature. Where they occur they point to the existence 
of half races. Nevertheless middle races can, under cer- 
tain circumstances, as we have already pointed out (p. 20) 
exhibit half curves; just as, on the other hand, the half 

1 Half curves are therefore compound curves. Their apex cor- 
responds to the mean value of the normal character ; their flank is the 
expression of the semi-latent character. If the normal character, in 
the material at our disposal, does not vary it has no curve of its own, 
which accounts for the absence of a flank on the other side. This 
for example is the case for curves based on numbers, when the nor- 
mal number is constant or practically constant as in the case of the 
three-leaved clover or pentamerous flowers. If the normal character 
is distinctly, though slightly, variable, as in the case of data based on 
measurements, the half curve has a flank on the other side, but it is 
very steep. I do not propose to pursue this point any further here, 
since it is merely my object to show that half curves are only a 
special case of asymmetrical curves. 



30 Latent and Semi-Latent Characters. 

curve of a half race can be tran formed into a bilateral 
curve by selection and high nutrition. I shall recur to 
this point shortly. 

The well-known researches of FRITZ MULLER with 
Abutilon give instances of half curves. 1 MULLER ob- 
tained the following figures from a culture with seeds 
from flowers with six petals: 145 with 5 petals, 103 with 
6, and 13 with 7. Of more recent investigations we may 
mention those of BATESON and PERTZ with Veronica 
BiiA'bannin according to which the normal cases always 
composed 70-90% of the culture in spite of the selection 
of the extreme variants in petal-number as seed-parents, 
the remaining 30-10% being composed of abnormal cases 
in a rapidly diminishing series. 2 The fruits of Aqmlegia 
are pentamerous, but 6-, and still more rarely 7-merous, 
ones occur. The fruit of the cotton is also pentamerous, 
but I have found several tetramerous and occasional 
trimerous ones. Papavcr Argenwne has tetramerous 
flowers, but specimens with 5, and less often with 6 
petals, also occur ; by sowing seeds from the latter I was 
not able to obtain any increase in the number. 

Duplications of leaves, concrescence of umbel-rays in 
UmbclUferae, of the fruit stalks of Cruciferae, of the 
fruits themselves in the Compositac and so forth, the 
adnation of an axial bud with its axillary branch and a 
number of other anomalies behave as half races. The 
abnormal cases, which are of course infinitely rarer than 
the normal ones, become rarer in proportion as they de- 
part from the normal. It is unnecessary to give a longer 
list here, I may just mention the catacorolla on the outer 

1 HERMANN MULLER, Die Befruchlung dcr Bhimen, p. 450. 

2 W. BATESON and Miss D. F. M. PERTZ, Notes on the Inheritance 
of Variation in the Corolla of Veronica Bu.vbaumii. Proceed. Cam- 
bridge Phil. Soc., Vol. X, Pt. II, p. 78. 



Half Races and Half Curves. 31 

side of the corolla in a half race of Linaria vulgaris 
which I have studied for a few generations, and for 
which the half curves have recently been plotted and in- 
vestigated by GARJEANNE. 1 

It is w r ell known that every species has a tendency, 
as the expression is, to vary in certain definite directions ; 
in these the deviations occur fairly frequently, in others 
either not at all or very seldom. The number of anom- 
alies is by no means an unlimited one for a given species, 
hut strictly limited. One expression of this phenomenon 
is the fact that one species tends to produce and repeat 
one particular abnormality, and another species, another. 
This general fact, with which we are familiar in vague 
expressions of this kind, can be made the starting point 
of valuable experimental investigations. For what are 
we to understand by "tendency" in these cases? In my 
opinion simply the existence of a half race or sometimes 
even of an eversporting variety. These two types of 
races are, so far as my experience reaches, perfectly dis- 
tinct, and in numerous cases amenable to experimental 
study; they are things with nothing intrinsically vague 
about them although they are sometimes blurred in their 
manifestation, under a superficial examination, on ac- 
count of the high degree of fluctuating variability which 
they exhibit. 

> 

If we take a plant which presents this tendency to a 
particular anomaly and cultivate its progeny, isolating it 
with an eye to this tendency, we shall usually find that we 
are dealing with an intermediate race of the kind of which 
we have spoken. I shall refer to an instance in the fol- 
lowing section ( 5) ; but this will be only one out of 

1 A. J. M. GARJEANNE, Beobachtungen und Culturversuche ilber 
clue Bluthenanomalie von Linaria vulgaris. Flora, 1901, Vol. 88, p. 
78; with Plates IX and X. 



32 Latent and Semi-Latent Characters, 

many. It is frequently uncertain, at first at any rate, 
whether besides the half race, the "species" itself exists 
in pure condition, that is to say, a race in which the char- 
acter in question is not semi-latent but latent. But when, 
as is so often the case, the species is widely distributed 
but the half race is only observed locally, we are evi- 
dently fairly safe in assuming the separate existence of 
both. 

Anomalies which are very common in nature point 
to the existence of eversporting varieties ; those which 
are rare, to half races. In the former case they are often 
reckoned among the characters proper to the species, as 
for instance the remarkable lateral fruitlets on the fruits 
of Tetragonia expansa, which were included by DE CAN- 
DOLLE in his diagnosis of the species, in his Prodromus. 1 
Other well-known instances are the incomplete apetaly 
of Ranunculus auriconius, 2 as well as the branched ears 
of Lolium perenne ramosum which seem to be relatively 
common everywhere in my own country. LENECEK S 
records lime-trees with 20-30% of their leaves trans- 
formed into pitchers; and with us trees with single 
pitchers, and others which produce large numbers of 
them every year are met with from time to time (Vol. I, 
Fig. 106, p. 470). 

In many cases we know both the half race and the 
middle race of the same, or of closely related, species. 
For example, there grows very commonly here a form 
of Plantago major (/. bractcata] which bears more or 

A. DE CANDOLLE, Prodromus Regni Vegetabilis. See also EICH- 
LER, Bli'tthendiagramme, II, p. 120. 



z 



WINTER, Journ. of Bot., Vol. 35, 1897, P- 406. This form also 
grows in our garden and in our country in the wild condition. 

3 O. LENECEK, Mitth. d. naturw. Vercins, Vienna, 1893. Found 
not far from Leitmeritz. 



Half Races and Half Curves. 33 

less numerous green bracts on the lower parts of the 
spikes. The well-known Plantago major rosea of our 
gardens, all of the bracts of which are green and fairly 
large, constitutes the complementary, and constant, ever- 
sporting variety. Besides Papavcr somniferum polyceph- 
alum (Vol. I, Figs. 27-28, pp. 138-139) which is to be 
regarded as an eversporting variety, there are polyceph- 
alous half races of P. commntatnm and several other spe- 
cies which in my cultures behave in quite a different man- 
ner from the former, in response to selection. Besides 
the favorite Varietates cristatae of our cultivated ferns 
we occasionally find, in nature, wild species with a split 
leaf. Cclosia cristata, the cockscomb, is an exceedingly 
interesting eversporting variety, 1 besides which fasciated 
half races in numerous other genera are known. 2 But 
I must refrain from the citation of further instances. 

Just as a species can as a rule be distinguished from 
its nearest allies by two or several characters, so a half 
race can manifest as semi-latent anomalies two or more 
characters which are latent in the species in question. 
Nor is this by any means rare. In the case of characters 
which deviate in the opposite direction from the type of 
the species, "double half-curves" may be formed which 
have two unequal flanks. The number of petals of 
Hypcricum perforatum varies in this way, in this neigh- 
borhood, round a mean of 5 ; on the one side going fre- 
quently to 4 and rarely to 3, and on the other side rarely 
to 6. The corolla of Campanula rotundifolia often varies 
from 5 to 6 and 7, and rarely from 5 to 4 and 3. 3 

1 See the second part of this volume. 
" Botanisch Jaarbock, Gent, 1894, p. 72. 

3 See also Ber. d. d. hot. Ges., Vol. XII, 1894, P- 2 2 , where further 
examples will be found. 



34 



Latent and Semi-Latent Characters. 



Selection and nutrition have as usual a great effect 
on half races. I shall not deal exhaustively with this 
point until the end of this part, but will give here a brief 
discussion of the general principles underlying it in order 
to prepare a proper understanding of the question. 

Our discussion of the phenomena of fluctuating vari- 
ability in the third part of the first volume led us to the 
conclusion that selection and nutrition usually operate 
in the same manner on the individual characters of plants. 




Fig. 2. Influence of selection and nutrition on the half 
race Ranunculus bulbosus scmiplcnus. A, Half Curve 
after several years of culture. B, Curve of the 12 best 
individuals (i. e., those richest in petals). C, Curve of 
the best plant. 1 

Positive selection and plenty of food enhance the devel- 
opment of a character, whilst selection in a minus direc- 
tion or defective nutriment operate in the opposite direc- 
tion. 

Polycephaly in Papaver soinniferum behaves in this 
way, 2 and, as we shall see later on, all the other anomalies 
which have been tested do so, as well. Half curves can 
thereby be transformed into unilateral ones (Fig. 2) , either 

1 Ber. d. d. bot. Ges., Vol. XII, 1894, Plate X, Fig. 4. 
8 Vol. I, Part I, pp. I35-M3. 



Half Races and Half Curve. 35 

by making r. special curve from plants which exhibit the 
largest number of abnormalities, or by making a curve 
from a race bred from such plants. But an improved 
race of this kind remains dependent on selection and high 
nutrition, and is soon lost if these are withheld. 1 One 
instance will suffice. Achillea Millcfoliinn has white 
flowers, but occasional specimens have red ones. From 
this I have bred a race with red flowers, which some- 
times even attain the deep red of dark wine. After four 
years of stringent selection, all the plants in successful 
cultures were more or less red. But if the plants were 
grown too close or were on poor land, more than half 
were white, and when I made further sowings without 
selection the proportion of reds rapidly reverted to its 
original small amount. On the other hand there is on 
the market the well-known Begonia semperfiorens atro- 
pnrpurea Vcrnon as a constant dark brownish red vari- 
ety. 

Eversporting varieties revert rapidly under minus- 
selection, but it is seldom possible to eradicate their char- 
acter altogether as I experienced when working with the 
adnation of the lateral branches to their main stems in 
Aster Tripolium and Bidcns grandiflora, and as I shall 
describe later in greater detail in the case of Celosia cris- 
tata. (See Part II of this volume.) 

In conclusion, we see that in nature as well as in 
cultivation (especially in the case of horticultural vari- 
eties and other anomalies) intermediate forms between 
the original species and its constant variety are often 
met with. The two commonest are the half race and the 
middle race or eversporting variety. The former has 
a half curve, the latter a bilateral one. Both occur in 

1 Vol. I, Part I, 14, p. 122. 



36 



Latent and Semi-Latent Characters. 



numerous species and genera, either together, or sepa- 
rately. Both are easily influenced by high nutrition and 
selection, but are usually quite distinct and only appar- 
ently connected bv transitional forms. 



5. TRIFOLIUM PRATENSE QUINQUEFOLIUM, AN EVER- 
SPORTING RACE. 

Four-leaved clovers are notoriously rare in nature, 
but it is perfectly easy to have many hundreds of them, 
provided a hereditary race can be obtained. Isolated ex- 




Fig. 3. Tri folium pratense quinquc folium, five-leaved and 
seven-leaved leaves of clover. The left leaf, A, shows 
a transition towards the 6-merotis leaf in the splitting of 
one of its leaflets. 

amples of this race seem to occur sporadically in nature ; 
all that has to be done is to find, to isolate, and to multiply 
them. (Fig. 3.) 

In the following section I shall describe the history 
of a particular race. I shall do so largely with a view to 
emphasizing the contrast between a middle race and a 



Trifolium Pratcnsc Quinque folium. 37 

half race. In a half race the latent or semi-latent character 
is very seldom visible, perhaps in one leaf or on one plant 
amongst many thousands, and after several years of se- 
lection it is only on isolated individuals that two or three 
specimens of the anomaly may be found. 

In the middle race, or eversporting variety as I call 
it in contradistinction to the half race, the anomaly is by 
no means so rare. Most of the leaves consist of from 
4-7 leaflets, and plants without such scarcely occur at all 
even in the absence of any selection. Trifoliate leaves 
are not wanting; indeed no plant is without them, par- 
ticularly in its early stages and on weak branches. 

On the other hand pure five-leaved or pure seven- 
leaved races do not as yet exist : I mean forms which 
do not revert. 1 There is no ground for supposing that 
we may not succeed, some time, in obtaining at least a 
constant seven-leaved variety. But for this to happen 
the right combination of unknown causes must chance 
to offer itself (see 2) ; and this has not yet occurred 
in the case before us. 

When a variable race has been found in nature the 
next step is to isolate it. And if, as is the case with red 
clover, isolated individuals of the species are sterile, two 
or three of them must be cultivated together, or if this 
is not possible one or several generations must be grown 
as a rule in order to purify the race of the effects of cross- 
ing. But this is easily effected. Further, the character 
can be improved by selection within the limits of varia- 
bility in the new race, just as in the case of pure specific 
characters. When once the furthest point in this direc- 
tion has been reached, and this usually occurs after a 

1 Or at least revert as rarely as four-leaved individuals occur in 
the ordinary clover, which are in reality also partially atavistic. 



38 Latent and Semi-Latent Characters. 

few generations, further improvements are only to be 
expected from a corresponding amelioration of the con- 
ditions of cultivation. In this way I succeeded in the 
beginning in improving my four-leaved clover, but after 
1895, in spite of continuous and stringent selection, no 
further improvement has been observed. I shall there- 
fore confine myself to a description of the first seven 
generations. 
These were : 

1st Generation. 1886-89. Two plants from Loosdrecht , 

2nd 1890. Four plants with some four- and five-leaved 

leaves. 

3rd " 1891. 36 % abnormal leaves per plant. 

( S With isolated abnormal seedlings. 

4th 1 " 1892. ] C With 60% seedlings of which the first. 

second or third leaf was tetramerous. 

5th " 1893. C With 55% seedlings with compound pri- 

mary leaf. 

6th " 1894. C With 96-98% seedlings with compound 

primary leaf. 

7th " 1895. C With 95-97% seedlings with compound 

primary leaf. 

To proceed to a more detailed account I begin with 
the examples collected in the field. 2 I found them near 
Loosdrecht on the edge of a road which was covered with 
grass. They bore several tetramerous and one pentam- 
erous leaf and seemed therefore to afford better oppor- 
tunities than the usual find which often is only a single 
four-leaved clover leaf in a meadow. I transplanted 
them to my garden, where they lived for another three 
years. Here the anomaly not only reappeared but in- 

'The result for this year is a double one. vS" (spring) refers to 
the crop of 1892 itself. C (crop) to the record of the seedparents in 
terms of the seedlings raised from their seeds (see p. 40) : Similarly 
with the subsequent years. 

2 Over het omkcercn van halve Galton-curven, Kruidkundig Jaar- 
boek, Gent, Vol. X, 1898, pp. 27-54 with Plate I. 



Trifoliiun Pratcnsc Quinque folium. 39 

creased, on account, doubtless, of the improved conditions 
of life. In July and September, 1889, I counted 46 
tetramerous and 19 pentamerous leaves amongst a large 
number of normal ones. But there was no sign of a 6- 
or 7-foliate leaf on these two parent plants of my race. 

I saved seed from them in the autumn of 1889 and 
sowed it next spring on a bed in my experimental garden. 
I obtained something over one hundred plants of which 
about one-half showed at least one four-leaved leaf. The 
rest were removed either in July before they flowered, 
or whilst they were in flower. On September 1, I selected 
the four plants which bore the largest number of ab- 
normal leaves, and destroyed the rest. These four bore 
64 tetramerous and 44 pentamerous leaves. Of the de- 
stroyed plants the best had only an average of about 5 
abnormal leaves per plant. This year again there were 
no instances of 6- or 7-foliate leaves. 

In 1891 I obtained the third generation from the 
seeds of these four selected plants, sowing in the garden 
as before. It consisted of 300 plants on which I exam- 
ined 8366 leaves when they were beginning to flower. Of 
these 1117 or 14% were tetra- or pentamerous. Leaves 
with 6 or 7 leaflets were not observed ; they were first 
seen in August and September of that year. The number 
of plants with at least one quadri foliate leaf also ex- 
hibited an advance. There were about 50% of them in 
1890, but now there were nearly 80%. These plants 
had on an average about four tetramerous and as many 
pentamerous leaves. At the beginning of August I chose 
the twenty best individuals and destroyed all the rest. 
I only harvested seed from the nine best plants among 
them and in the following spring only sowed the seeds 
of a single seed-parent which seemed to me to be the 



40 Latent and Semi-Latent Characters. 

very best of all, 36% of its leaves being composed of more 
than 3 leaflets. 

In the spring of 1892 I sowed the seed in pans in the 
greenhouse attached to my laboratory instead of in the 
beds as before. The advantages of this were (1) that 
more seeds germinated and (2) that the examination of 
the seedlings was greatly facilitated. They stayed in the 
pans until the unfolding of the third leaf, were then 
looked through, and the best ones transplanted into pots 
with manured garden soil. Amongst the several hundred 
seedlings there were 18 in which the quadruplicity was 
already manifest among the first leaves. Only these 
specimens were planted out; during the summer they 
bore a large number of tetra- and pentamerous leaves ; 
and some 6- and 7-foliate ones, which appeared now for 
the first time in considerable numbers. 

With this, the isolation of the five-leaved race of clo- 
ver was brought to an end. The elaboration of the ordi- 
narily latent or semi-latent character had been fully ac- 
complished. The race could, like any other, be improved 
by selection but it could not be expected to change its 
character any further in the process. 

Of course I did not omit to effect this further im- 
provement. But there was no point in paying further 
attention to the characters of the adult plants, since dif- 
ferences could now only be found in them by a statistical 
examination of all their leaves. And it was found to be 
practically impossible to carry out this scrutiny with the 
necessary detail, for the plants soon become too big to 
be grown in pots. Therefore in order to make curves 
it is necessary to defoliate the plants, and this can not 
be done until after the choice of the seed-parents, whose 



Trifolium Pratense Quinquefolium. 41 

leaves must obviously neither be removed nor even dam- 
aged. 

For these reasons it is desirable to effect the selection 
in the seedling stage, or at any rate before transplanting. 
This process had already been begun in the spring of 
1892 and needed therefore only to be perfected by con- 
tinued selection. And the result justified my expecta- 
tions. 

In the spring of 1893 I sowed the seed of the 18 plants 
of the year before, already referred to, separately for 
each seedparent. I recorded the seedlings when the 
third leaf had unfolded. If all the leaves were normal, 
I straightway weeded out the plant; but if one or more 
of its leaves had a supernumerary leaflet I preserved it. 
Of the 3409 seedlings which I examined 2471 were normal 
and 938 were not, i. e., about 30 %. 1 Of course the re- 
maining 70% must also be abnormal, but the anomaly 
was not yet recognizable in the seedlings. Some of them 
which I transplanted produced, as adult plants, leaves 
with from 4 to 7 leaflets in large numbers. 

I determined the percentage production of abnormal 
seedlings in this manner for 16 of the 18 seed-parents; 
the values were distributed over them as follows : 

10-20% 21-30% 31-40% 41-50% 51-60% 61-70% 
Seed-parents^ 173221 

I further chose from this series a seed-parent pro- 
ducing 60% abnormal seedlings. It had itself had in its 
early stages a compound primordial leaf, which fact also 
marked it out for the continuation of the race. It will 
be found in the table on p. 38 under 1892 C. 

Amongst the seedlings from the seeds of this parent 

1 Botan. Jaarbock, Gent, Vol. X, p. 37, where the two figures 
have been transposed by an oversight. 



42 



Latent and S end-Latent Characters. 



several occurred with trifoliate (instead of single) pri- 
mordial leaves (Fig. 4). I only selected these as seed-bear- 
ers, for transplanting, and I effected a considerable simpli- 
fication in my cultures by adopting this mark as a cri- 
terion for all further selection of stock plants. For the 
definitive selection could now be made 2-3 weeks after 
sowing, and it was not necessary to pay any further 
attention to the development of the character; this was 
fully insured. Nevertheless I took care by means of 

further experiments to sat- 
isfy myself that there exists 
a fairly close relation be- 
tween a large number of 4-7- 
merous leaves on a plant and 
a high percentage of abnor- 
mal seedings produced by it. 
In July 1893 I only saved 
the 12 best plants raised 
from the seed of the plant 
of 1892 with 60% abnormal 
offspring. With the excep- 
tion of two plants they all 
bore not only 4-6-foliate 
leaves, but even some 7- 
merous ones. The four best had 27, 30, 33 and 34 of 
this latter type. There were no leaves with more than 
seven leaflets. 

The plant with 34 7-merous leaves also produced the 
highest percentage of abnormal seedlings, as shown by 
the result of the sowing in the following spring. Of 209 
seedlings produced, 51 had a bimerous, and 61 a trimer- 
ous, primordial leaf, i. e., 55% of abnormalities. It was 
therefore chosen as seed-parent (see p. 38). It should 




Fig. 4. Tri folium pratense quin- 
quefoliuni. A, Seedling with 
a trifoliate primordial leaf. 
B, C, Seedlings with single 
and bimerous primordial 
leaves ; these two latter types 
were regarded in my race as 
atavistic. 



Trifoliimi Pralcnsc Omnque folium. 43 

be remarked that in previous years seedlings with a com- 
pound primordial leaf had either been entirely absent or 
at any rate very rare. 1 

In the summer of 1894 I only bred offspring from 
the plant with 55% of abnormalities in its seedlings, and 
of these only the twenty best, with compound primordial 
leaf and the next leaf tetra-pentamerous. These only 
did I allow to flower and to bear seed. The result was 
recorded by means of the same characters in the following 
spring. For eleven plants it was 70-90%, for five others 
91-96%, and for the two best 98-99% seedlings with 
compound primary leaf. And the higher the number the 
greater was the percentage of trifoliate, as opposed to 
bimerous, primordial leaves. 

The same high percentage was obtained in the culture 
of the next year, 1895, in the seventh generation of my 
experiment. Since then the race has remained constant 
under the same conditions of selection. 

I have employed this constant and highly abnormal 
race for a series of observations and experiments, to the 
more important of which I shall now refer, 2 for they are 
well qualified to afford us some insight into the nature 
of such a race. This race exhibits a high degree of var- 
iability, which is due to the possession of a semi-latent 
character besides that which it has obviously inherited 
from the parent species. The extent to which this paren- 
tal heritage, the normal trifoliate leaf, is developed de- 
pends on the conditions of life of the plant. And, speak- 

1 See the remarks in 22 relating to the size of the seed in Tri- 
foliuin incarnatum. In the five-leaved clover, especially in later 
years, practically all the seedlings had compound primordial leaves, 
so that this character had nothing to do with the size of the seed. 

2 For a detailed account see the oft-cited paper in Kniidkundig 
Jaarboek, Vol. X. 



44 Latent and Semi-Latent Characters. 

ing generally, favorable conditions favor the characters 

O O J ' 

of the race, and unfavorable ones those of the species (see 
below, 26). 

This is only a special case of the well-known prin- 
ciple : Every injury increases the tendency to atavism . l 

In the first place let us consider the periodicity. The 
number of multipartite leaves increases with the indi- 
vidual strength both on the whole plant and on the sep- 
arate branches. And if, at the end of growth, weakness 
supervenes this number again decreases. 

Let us examine Fig. 5. It is a photograph of a strong 
young branch which was removed on August 1, 1900. 
The lowest leaf was nearly withered ; it was small and 
had the inversely egg-shaped form of the leaflets which 
is characteristic of the leaves of the young red clover, 
It consisted of only 3 leaflets. The two following leaves 
were markedly larger and stronger, of a more elliptical 
form and tetramerous. Then follows a 6- and then a 
7-merous leaf, after which the leaves again return to the 
simpler types. 

The branch photographed was chosen for its regu- 
larity; and yet a pentamerous leaf is absent from the 
ascending series. Most of the branches, even on the best 
plants, were less regular : indeed it often happened that 
tetramerous leaves were succeeded by some trimerous 
ones, and so forth. 2 

What has been stated concerning the lateral branches 
is also true of the rosette of radical leaves whose axis 



1 That is, reversion of the race to its parent species, for the char- 
acter of the race is itself, morphologically speaking, a reversion to 
a more remote ancestor. 

2 For exact figures the reader is referred to : Ueber die Periodici- 
tat der partiellen Variationen, in Ber. d. d. bot. Ges., 1899, Vol. XVII, 
p. 48. 



Trifolinin Pratcnsc Quinquefolium. 



45 



is, of course, the main stem of the whole plant. Here 
also the number of leaflets per leaf first increases, on the 
average, and then decreases, with many fluctuations how- 
ever. The branches themselves exhibit a certain periodic- 
ity since the lower ones contain a smaller quantity of 




Fig. 5. Tri folium pratcnse quinquefolium, 1900, showing 
the periodicity of the anomaly on a branch. Beginning 
from below the leaves have 3 4 4 6 7 5 leaflets. 

abnormal leaves than those next above them, whilst the 
highest of all are poorer again. 

If therefore the conditions are favorable to a branch 
in its earliest stages it will develop more 4-7-merous 



46 Latent and S end-Latent Characters. 

leaves. And it is obvious that such leaves will extend 
both above and below the maximum of the period in 
direct proportion to their number. \Yhence it again fol- 
lows that the better nourished the plant is, the earlier 
will the abnormality appear. And this is true both of 
the individual L ranches and of the rosette of radical 
leaves, and therefore of the whole plant. 

From these conclusions the converse rule may be de- 
duced that the earlier a seedling produces its first tetram- 
erous leaf, the greater will probably be the number of ab- 
normal leaves on the adult plant. The most abnormal 
plants will probably be those which in the seedling stage 
had a compound primary leaf. Experience has proved 
the truth of this rule throughout my experiments. 

If we now take another glance at the table on page 38 
we see that the character recorded has gradually shifted 
in the course of generations and as a result of selection. 
The more the improvement advanced the earlier could 
selection be effected. In the third generation I kept 300 
plants in the beds to be selected from; since the fourth 
generation I have carried out the selection in the seed- 
pans and only planted out the few best (e. g., 10-20) to 
act as seed-parents. 

It is possible, therefore, within the limits of such a 
race, on the one hand to effect an increase in the number 
of multipartite leaves, and on the other to reduce it In- 
reversed selection. In both cases we go as far as pos- 
sible from the mean of the race, without, however, suc- 
ceeding in overstepping its definite boundaries. Let us 
see what selection is able to effect in the two cases, and 
let us begin with the former. It is the question of in- 
tensifying the anomaly to its extreme limit. 

/ o J 

A striking peculiarity of my race is the fact that leaves 



Trifolium Prafcusc Quinque folium. 47 

with more than seven leaflets have never, or only ex- 
tremely rarely, been produced. As a matter of fact a 
duplication of the leaves by splitting, which is so common 
among other plants, 1 occurs in my race also, and if it 
affects a pentamerous leaf, makes a 10-merous one of it. 
But that is the expression of another latent character 
which we are not concerned with here. Apart from 
these I have not yet found in my cultures, in spite of the 
most careful search, a single instance of a leaf with 
more than 7 leaflets. 

The character of my race is the quinquefoliate leaf 
which is usually in the majority ; the remaining types are 
grouped round it in accordance with OUETELET'S law, so 
far as the tendency to symmetry permits this. For it is 
clear that this tendency does not favor the regularity of 
the curve of variation. The increase in the number of 
leaflets from 3 to 4 takes place by the lateral splitting 
of one of the lateral leaflets (see Fig. 3 A), one of the 
lateral veins becoming the primary vein of the new leaflet. 
Transitions such as that figured are certainly fairly rare, 
but all degrees of them, down to a splitting of the small 
partial stalk of the leaflet, occur from time to time. If 
only one leaflet is split, the leaf becomes asymmetrical ; 
but if the two lateral leaflets split, the whole may remain 
symmetrical. The duplication can extend to the terminal 
leaflet and turn a vein of this, either on one side or on 
both sides, into the primary vein of a new leaflet. In this 
way the 6- and 7-merous leaves arise ; the former are 
asymmetrical, the latter symmetrical. 

The statistical examination of large numbers proves 
that the symmetrical leaves predominate over the asym- 
metrical ones. The plant seems to prefer to retain its 

1 DELPTNO, Teoria general? dclla FiJlotassi, 1883, p. 197. 



48 



Latent and Semi-Latent Characters. 



symmetry even in the anomalies. This is brought out 
in the curves by the relative shortness of the ordinates 
corresponding to 4 and 6 (Fig. 6). 

Let us return to the processes of selection. The mean 
of the race is a pentamerous leaf, which varies within 
fairly narrow limits, never (or hardly ever) less than 




Fig. 6. Trifolium pratcnse quinque folium. A, Normal 
curve of the number of leaflets in the leaf. B, Curve of 
an atavistic individual. C, Curve of the maximum de- 
gree of abnormality, 1894. 



three or more than seven leaflets being produced. Selec- 
tion can therefore be either in the direction of the 7 or 
the 3. In both cases the original symmetrical curve be- 
comes unilateral. But in the former case the improve- 
ment of the race is pushed on as strongly as possible, in 
the latter the reverse happens until it can hardly be dis- 



Trifolinm Pratcnsc Quinque folium. 49 

tingiiished from the ordinary instances of the rare four- 



leaved clover. 

A glance at the table on page 38 will show that my 
race was only very slightly developed at first, and had to 
be brought to its normal type by isolation and selection. 
But in spite of this selection it is not so constant that it 
does not occasionally give rise to atavistic individuals. 
On the other hand individuals with a maximum develop- 
ment of the character of the race are from time to time 
produced. And these extremes are sometimes both found 
within the limits of a single culture. 

I observed this in 1894 with plants which had been 
raised from the seeds of a single individual in the third 
generation (1891, p. 38). The seed-parent in question 
had survived the winter and did not ripen its seed until 
the second year. In July, 1894, there was a large num- 
ber of strong plants of the same age, of which I chose 
the seven best for a detailed examination of their leaves. 
Some of the oldest leaves were already withered, the 
youngest not yet unfolded ; these were not recorded. Each 
of these seven plants was plotted in the form of a curve, 
one (Fig. 6 A) gave the normal curve of the race, an- 
other (B) was atavistic, whilst all the rest had their 
highest ordinate at 7. I have only given the mean value 
for these five (C). 

These three groups gave the following percentage 
of leaves with the number of leaflets written above them : 

Number of leaflets: 34567 Number of leaves counted 

A. Normal example: 17 16 37 14 16 172 

B. Atavistic example: 75 19 5 1 216 

C. Extreme variants: 12 9 22 17 40 97 1 

1 Mean number per plant. 



50 Latent and Scnii-Latcnt Characters. 

These figures are presented graphically in Fig. 6. 
It Will be seen that the normal curve is a symmetrical 
one slightly depressed, however, over the ordinates of 
the even numbers as a result of that symmetry which we 
discussed above. The two other lines form half curves; 
in both of them the apex coincides with one extreme. 
The curve B, of the atavistic individual, is almost the 
same as the curve which was the dominant one in the first 
years of my experiment when there were, as yet, no 6-7- 
foliate leaves (p. 38). It is an ordinary half curve of 
variation, which is characteristic of the half races of 
semi-latent anomalies. The curve C is, however, re- 
versed; it displays the predominance of the racial char- 
acter over the antagonistic one which is that of the 
original species. It also shows the preference for sym- 
metrical leaves. 

If atavistic individuals are used as seed-parents the 
character of the race can be observed to vanish more or 
less completely in a short time. I carried out an experi- 
ment of this kind in the years 1896-1898, after the race 
had reached its maximum development in 1894-1895 as 
described on page 38. Within the space of three gen- 
erations this race has retrogressed so far that the plants 
could no longer be recognized as belonging to it. For the 
purposes of this reversed selection I chose, from the 
plants which had borne a large number of 5-7-merous 
leaves in 1895, those seedlings of which the primary 
leaves were single and the first leaves trifoliate. With 
a few exceptions they had all developed occasional tetra- 
pentamerous leaves by the middle of June. Three of the 
exceptional ones were isolated before flowering, they sub- 
sequently developed a few multipartite leaves. But when 
their seeds o- e rrnmated it was seen that they were not 



Trifolinm Pratcnsc Quinque folium. 51 

only not poorer in seedlings with compound leaves but 
even slightly richer; they were therefore not chosen for 
the continuation of the experiment. I chose the seeds of 
three plants of 1896 which had given rise to no more 
than 2-3% seedlings with compound primary leaves. 
Atavistic seedlings only were transplanted, but in the 
following summer (1897) even those bore some tetra- 
pentamerous leaves, almost without exception. On the 
other hand 6-7-merous leaves were almost entirely ab- 
sent, and the race had thus returned to the condition 
described by the unilateral curve of the first year of the 
experiment (1891-1892). Some plants produced noth- 
ing but trifoliate leaves during the whole of the summer 
and the following spring. 

In 1898 I made another culture of atavists from the 
seeds harvested in 1897. This was therefore the third 
atavistic generation. But two thirds of the generation 
raised still consisted of plants with some tetra-pentam- 
erons leaves, and therefore possessed this character in 
a far higher degree of development than ordinary red 
clover. This stringent, thrice occurring reversed selec- 
tion had therefore considerably reduced the development 
of the anomaly but had not succeeded in destroying or 
even in concealing the fact that the culture belonged to 
the pentamerous race. 

I also made an experiment on the influence of ex- 
ternal conditions on the development of multipartite 
leaves. There are two ways of dealing with experiments 
of this kind ; we may either subject the different parts of 
the same plant to diverse conditions of life or similar 
samples of seed to diverse treatments from germination 
onwards. In the former case we determine the effect 
on the grown plant. This is however seldom great, inas- 



52 Latent and Semi-Latent Characters. 

much as the plant is most sensitive in its early stages. 
In this form of the experiment we can, so to speak, only 
investigate the last vestiges of its former susceptibility. 
Far more striking results are to be expected from experi- 
ments with seedlings; but here a great uniformity in the 
samples of the seeds is necessary for the results to be 
reliable. It is not sufficient to mix the seed, but it is 
advisable to harvest seed from two or three or still better 
from a single seed-parent of known and pure ancestry. 
It is even better to allow the influences that are to be 
investigated to operate during the development of the 
seed on the parent plant. 

In accordance with these considerations, therefore, 
I cut one of my plants into two parts, one of which I 
transplanted into poor sandy soil but the other into 
good garden soil, and allowed them to set seed. I was 
thus able to study both the direct effect on the plant and 
also the indirect effects on the succeeding generation. 
(See Vol. I, Part III, pp. 521-522.) 

The experiment, which was carried out during the 
years 1892-1894, was made with a single individual which 
arose from the stock plant for 1891, mentioned on page 
38 and marked S. This plant had, when it germinated 
in 1892, a bimerous primordial leaf, and in the same 
year bore seeds which, when sown in the spring of 1893, 
gave rise to about 40% seedlings with a tetramerous 
leaf. As soon as this was visible in the seeclpan the 
choice was made and the parent plant, which I had kept 
through the winter in a bed, was cut in two and trans- 
planted into the above mentioned kinds of soil. Both 
halves grew well, although not with equal luxuriance; 
they flowered in July, were pollinated from the various 
plants around them composing the main culture of that 



Trifolium Pratcnsc Quinquc folium. 53 

year, and set seed in August. At this time I examined 
an equal number of leaves on the two halves and ob- 
tained the following result : 

Number of leaflets: 34567 
On garden soil: 12 25 34 20 18 
On sandy soil: 18 19 35 19 17 

The behavior of the two halves was identical ; the 
difference in the soil exerted no visible effect. Moreover 
the seeds on the two halves were of about the same size 
and produced in roughly equal numbers. The two sets 
were harvested separately and sown in the following 
spring (1894) in pans. When the young plants had about 
3 leaves they were examined. Calling a plant with a 
tetra- or a pentamerous leaf "abnormal" the result was : 

Seeds from garden soil 30% abnormal 
" sandy soil 24% 

The experiment involved 150 and 200 seedlings. The 
abnormal ones were further sorted according to the 
composition of their primary leaves. 

Leaflets 123 Totals 

Seeds from sandy soil 24 10 13 47 

41 garden soil 16 12 13 41 

Both counts therefore gave a difference in favor of 
the better nourished seeds. For further investigation 
I selected those which appeared most abnormal from 
both series, i. e., the seedlings with a trimerous primordial 
leaf, and planted them out under similar conditions. In 
July when each plant had twenty or more stems, I pulled 
them up, selecting for examination the ten best plants 
from each group; i. e., those ten, the leaves of which 
numbered about 100 per plant. The leaves were recorded 
separately for each individual, and as there happened to 



54 Latent and Semi-Latent Characters, 

be practically no difference between the several individuals 
in each group, I calculated the mean for the two sets in 
percentages. 

Number of leaflets per leaf 34567 

From seeds from garden soil 14 13 25 16 32 

" sandv soil 39 13 23 10 15 



Difference 25 +2 +6 +17 

The effect of the treatment in the previous year is now 
perfectly plain. The curves for both groups have become 
unilateral but in the case of the better nourished ones 
the apex is at seven, and for the others at three leaflets 
per leaf. 

Conversely we may conclude that, in the experiment 
described on page 47 and graphically exhibited in Fig. 6, 
the atavists were produced by poorly nourished and the 
maximal variants by highly nourished seeds. And the 
following generalization about anomalies seems to be 
justified: that the nutrition of the seed on the parent 
plant is the most important factor influencing the devel- 
opment of the anomaly (Vol. I, pp. 521-522). 

Let us now briefly summarize the results of this 
experiment. I began by finding in the field two plants 
belonging to a five-leaved race, which however as the 
result of indifferent nutrition for several generations 
only developed tetra-pentamerous and no 6-7-foliate 
leaves. By better cultivation and by the continued selec- 
tion of the most abnormal individuals, no doubt those 
which happened to have been best fed, a race was evolved 
in the course of a few generations with a number of leaf- 
lets per leaf varying between 4 and 7 round a mean of 
five. After this selection had been repeated four or five 
times maximal variants were produced the majority of 



Trifolinm Pratcnsc Quinque folium. 55 

the leaves of which were 7-foliate. At the same time 
there were still "atavists" in the seventh generation the 
apex of whose curve was over 3 leaflets. The atavists 
however really belong to their race as is shown by the 
fact that even after repeated selection in an atavistic 
direction they produce far more quadri foliate leaves than 
the normal red clover (or more exactly, the corresponding- 
wild half race of the red clover). 

The better the seeds are fed on the parent plant the 
greater is the development of the anomaly on the indi- 
viduals produced by them. Poor seeds give rise to ata- 
vists, good ones to extreme variants. 

My experiment extends over ten generations. It 
gives no support to the view that the five-leaved race 
was, so to speak, caught in the act of developing its 
character, or that it could give rise to a higher type with- 
out further mutation. It is a highly variable, but constant 
variety. 



III. THE DIFFERENT MODES OF ORIGIN OF 

NEW SPECIES, 

6. HORTICULTURAL AND SYSTEMATIC VARIETIES 
AND ELEMENTARY SPECIES. 

The opinion has of late been often expressed, by VON 
WETTSTEIN in particular, that there is no ground for the 
assumption that all species have arisen in the same way. 1 
There is no difficulty in applying this view to the theory 
of mutation, although one of the chief objects of this 
book is to show that ordinary or fluctuating variability 
does not provide material for the origin of new species. 
But this does not exclude the possibility of different 
modes of origin of new species. The simultaneous origin 
of species in groups, in definite periods, such as I have 
described in the case of Ocnothcra Lainarckiana, must 
constitute for me the main type of this process, until the 
origin of species has been experimentally studied in other 
cases. Such experiments would have to study the phe- 
nomenon before and during the first appearance of the 
new type. Inferences drawn from data obtained after its 
appearance can hardly be considered as decisive. 

This essential type explains in my opinion in the first 

1 R. v. WETTSTEIN, Der Saison-Dimorpliismus ah Ausgangspunkt 
fiir die Bildung neuer Artcn im Pflanzenrcich, Ber. d. cl. hot. Ges., 
Vol. XIII, 1895, P- 3O3 ; and particularly the same author's Desccn- 
denztheoretische Untersuc/ningcii; I. Untersuchungen iibcr den Sai- 
son-Dimorphismus im Pflanzenrcich; Denkschr. d. Mat. Naturw. 
Classe d. k. Akad. d. Wiss., Vienna, 1900. 



Horticultural and Systematic Varieties. 57 

place the progressive origin of species, that formation of 
new characters to which in the main the evolution of the 
plant kingdom is due. On the other hand there is a 
whole series of other types which are now, so far as it 
is possible to judge, mainly confined to the lateral branches 
of the phyletic tree. With regard to these however we 
must content ourselves at present with indirect methods 
of investigation. 

DARWIN'S statement that varieties are incipient spe- 
cies is well known. So also are the words of one of the 
most famous authorities 1 on horticulture, VERLOT : Toute 
varicte a d'abord existe a I'ctat de variation. These two 
generalizations are evidently based on phenomena en- 
tirely different from those with which we have become 
familiar in Ocnothera. They constitute, so to speak, 
the other extreme of the series. 

I propose therefore now to investigate the manner in 
which "variations" in the sense of so-called structural 
abnormalities or anomalies (and not the individuals which 
exhibit variation in accordance with QUETELET'S law) 
arise, and how they result in the origin of "species." 
But here we come across an obstacle on the very threshold 
of the inquiry in the manifold meanings of the word 
variety. 2 It will soon become clear that horticultural 
and systematic varieties are to be considered as categories 
of entirely different values. But both DARWIN'S and 
VERLOT'S sentences just quoted are based on data ob- 
tained from horticultural varieties ; and we must now 

1 B. VERLOT, Production ct fixation dcs varictcs, 1865, p. 100. 

5 The general conception of this term is that formulated by CAR- 
RIERE in the following words: "On nomine varictc tout individu qui, 
par quclque caractcrc quc ce soit, se distingue d'un on de plusicurs 
autres avec Icsqucls on le compare ct quon considere comme apparte- 
nant a un meme type specifique (Production et fixation dcs varietes, 
1865, p. 6). 



58 The Different Modes of Origin of new Species. 

inquire how far their transference to systematic varie- 
ties is justified. 1 

The origin of horticultural varieties will therefore 
be submitted to a critical and experimental examination. 
But before we do this I think it advisable to consider 
first the meaning which is attached to the term variety 
in systematic works, and secondly the various ways in 
which species can arise. And we shall find that whilst 
there is no question that the mode of origin of horti- 
cultural varieties is often analogous to that of so-called 
"good" species, this parallel is by no means so common 
as the present form of the doctrine of descent would lead 
one to believe. 

To begin with systematic varieties : Here we find we 
can draw a pretty natural line between what we called ele- 
mentary species on the one hand, and real systematic 
varieties on the other. 

In connection with this antithesis I think it desirable, 
after what has already been said on this topic in the first 
volume, 2 to lay especial stress on the fundamental dif- 
ference between these two conceptions. LINNAEUS and 
his pupils describe the elementary species as varieties ; 
JORDAN, DE BARY, and others who argue from experi- 
mental data, refer to all forms as species. 

The terms "species" and "variety" have become so 
familiar that it is no longer possible to effect any radical 
change in their definition. For their exact meaning we 
have to refer to the works of LINNAEUS himself. His 

1 For some interesting observations relating to the origin of new 
forms, see the papers by F. KRASAN in ENGLER'S Botanischc Jalir- 
biichcr. Vol. XIII, Pts. 3-4; Vol. XXVIII, Pts. i, 2. and 5, and also 
his Mittheilungen ilbcr Cultiirvcrsuchc mit Potcntilla arcnaria, Graz, 
1900. 

2 See Vol. I, 7, "Species, Subspecies and Varieties," especially 
pp. 169-172. 



Horticultural and Systematic Varieties. 59 

conception of them is now common property, and in 
my opinion our best course is to interfere with that con- 
ception as little as possible. 

There can be little question that the difference between 
variants and variations is becoming more and more widely 
recognized. Variants are what we call individual devia- 
tions ; they are instances of fluctuating variability. The 
characters which distinguish them disappear under suit- 
able cultivation and are therefore to be regarded as in- 
constant. In systematic works they are not as a rule 
gi ven a place, or merely briefly mentioned, or, lastly, 
treated as a Forma, which is the lowest subdivision of 
the system; e. g., Forma alpestris, Forma aquatica. But 
this can only be done when the relationship of the form 
is sufficiently known ; lack of material in the case of 
exotic plants, or incomplete investigation of indigenous 
species of course would make this impossible, and such 
forms have therefore often first been described as vari- 
eties or even as species. 1 In many cases of course the 
true relationship is still unknown and the systematic 
grouping, therefore, to be considered as provisional: as 
for instance in the case of Anthyllis Vnlneraria alpcstris, 
Limosclla aquatica caulesccns, Carlina acaulis caulcsccns, 
and so forth. 

BONNIER'S researches on Alpine plants, discussed in 
detail above (Vol. I, p. 146), have demonstrated that 
some of these differences are not even instances of indi- 
vidual but of partial variability. From the two halves 
of a single individual can be grown the form character- 
istics of the plains and the Forma montana. 

1 For example Ranunculus aconitifolius L. in alpibus minor, caule 
3-5 floro ; R. aconitifolius altior KOCH, caule multifloro, fol. laciniis 
longius acuminatis, in montibus humilioribus = R. platanifolius L. 
mant. 79 (Keen, Synopsis, p. 12). 



60 The Different Modes of Origin of new Species. 

But the large number of cases of forms preliminarily 
described as varieties but which possibly may be only 
variants, is one of the most considerable obstacles in this 
inquiry. 

LINNAEUS himself followed two distinct rules in sub- 
dividing his species. According to the one the species 
was regarded as the type from which the varieties were 
derived ; according to the other, however, the species was 
regarded as a collective group which embraced a certain 
number of units of equal value. The separation is sharp 
and definite and LINNAEUS was obviously perfectly con- 
scious of its reality. In the derived varieties the series 
begins with /? followed by y, 3, e etc. ; it is taken for 
granted that the type or Forma geniiina represents the a. 
In a homonomous series there is no such Forma gcnuina, 
and the series of varieties therefore begins with a. 

Let us consider the two cases separately and let us 
begin with the second. 

LINNAEUS'S homonomous varieties, a, /?, y etc., are 
sometimes arranged in groups, and sometimes not (as in 
Teucrium Poliiiin, Lavandula Spica, etc.). In the former 
case the species falls into two or several subspecies, each 
of which again may include one or several varieties. For 
instance Euphorbia e.rigua has two subspecies acuta and 
retusa, the first of which consists of one and the second 
of two varieties. Beta mdgaris has the well-known sub- 
species mbra and Cicla; the first of these embraces five, 
the second two varieties. In these species there is no 
Forma typica or Forma gcnuina. The variety which is 
named first has no other priority over the others. 

In such cases the species is a group of similar com- 
position to that of a genus and of a family ; since in these 
no particular species or genus is regarded as the proto- 



Horticultural and Systematic Varieties. 61 

type from which the rest would be merely derived forms. 
Species of this kind are therefore obviously and avowedly 
collective species. 

LlNDLEY, A. P. DE CANDOLLE, ALPHONSE DE CAN- 

DOLLE and other eminent systematists consider the col- 
lective species without Forma typica to be the only really 
existing type. Species must be subdivided in exactly the 
same way as genera, says the last named of these authors 
in his Phy to graphic. 1 LINDLEY splits up his species of 
roses on the same principle; Rosa rubiginosa into 8, R. 
spinosissima into 9 varieties, etc. DE CANDOLLE deals 
with the difficult and numerous subgenera and elementary 
forms of Brassica in the same way in the second volume 
of his Systema Vegctabiliwn. 

DE CANDOLLE calls the units, which in such cases are 
treated as varieties, "Ics elements de I'espece"; 2 they are 
related to the species as these are to the genera and as the 
genera to the families. 

But the majority of botanists regard varieties as 
forms which have been derived from the species. For 
them the species is the type, the real entity, from which 
the varieties have arisen by small changes. They follow 
the course taken by LINNAEUS who based his diagnoses, 
in the vast majority of cases, on one of the forms of a 
species and arranged the rest in a lower grade under 
this. The origin of the varieties from the species was 
simply inferred from a priori premises as I have already 
shown in the first volume, this origin having only been 
directly observed in isolated cases of horticultural prod- 
ucts; for the majority and certainly the most important 

1 ALPH. DE CANDOLLE, La Phytographie on I'art de decrire les 
vegetaux, 1880, pp. 74-82. Much of the argument set forth in the 
text is due to this excellent work. 

z Loc. cit., p. 80. 



62 The Different Modes of Origin of new Species. 

cultivated varieties are as old or even older than cultiva- 
tion itself. 

If we examine a number of such derived forms in any 
systematic work or flora, it immediately becomes evident 
that the same kind of differences recur in the most widely 

j 

separated families, genera and species. Everywhere vari- 
eties present series of parallel forms. The recurrence 
of white flowered varieties in numerous species with blue 
or red flowers is so familiar a phenomenon, that often 
all reference to them is omitted. LINNAEUS himself knew 
that nearly all such species had a white variety. If the 
color of a flower is compound, and if one of the compo- 
nents is lacking, a white flower with a dark center often 
results and is known as a ]\ir. bicolor (for example Cyno- 
(llossmn offieinale bicolor, Agrostenuua coronaria bicolor} ; 
or the dark patches are absent as in Geutiana piinctata 
concolor, which case is exactly analogous to that of Arum 
niacitlatuni iiiimacnlatinu. 

Often too, the clothing of hair is lacking either on 
the whole plant or, when only certain parts are densely 
hirsute in the "species," on these. The nomenclature of 
the series of parallel forms, under this heading, is par- 
ticularly rich in terms which all indicate the same prop- 
erty, as for example : Papaver dubium ylabrum, Biscn- 
tella laevigata glabra, Arabis ciliata ylabrata, Arabis hir- 
suta ylabcrrima, Veronica spicata nitens, Amyydalus Per- 
sica laciis, Eritrichium namun leiospermum, Paeonia 
corallina (pcrcyrina) leiocarpa, etc. 

Thornless forms are usually termed incnnis; they oc- 
cur in Ranunculus arvensis, Genista ycrmanica, Robinia 
Pseud-Acacia and many others. The ] T arietas ciliata 
occurs in Cytisus prostratus and in C. spinescens, also in 
Lotus corniculatus, etc. A dense clothing of hair is the 



Horticultural and Systematic Varieties. 63 

distinguishing feature of Solatium Dulcamara tomcnto- 
sum, Veronica scntcllata pubescens, Melissa officiualis vil- 
losa, Galeopsis Ladanum canescens, Vicia lutca hirta, 
Lotus corniculatus hirsutus, etc. 

The patches of color at the base of the petals are often 
absent in Papavcr orientate, in Erodiitm cicutarium and 
many other plants. Such names as ochrolcuca, purpuras- 
cens, intcgrifolia, serratifolia, angustifolia, latifolia de- 
note varieties each one of which may recur in several 
unrelated species. Finally I may mention the red berries 
which occur as a varietal character in Empetum nigrum 
and characterize the red variety of the gooseberry; and 
the yellow berries of Atropa Belladonna lutca and Daphne 
Mezereum album which are only selected examples from 
a long series of such varieties. 

All these forms differ from their species in the fact 
that a particular one of their characters is either devel- 
oped to a greater extent (hirsuta, ciliata, purpurascens,) 
or on the other hand very slightly developed or entirely 
absent. 

The absence of a character may also be a case of ex- 
treme rarity in the vegetable kingdom such as the straw- 
berries without runners, and the peculiar Finns Abies 
aclada, with its tall absolutely unbranched stem, which 
has been figured by ScHROTER. 1 Fragaria t'csca mono- 
phylla (Vol. I, Fig. 38, p. 193), Robinia Pseud-Acacia 
monophylla, Fra.rinus Ornus monophylla,- and a mo- 
nophyllous form of Melilotus cocrulea (Fig. 12 on page 
87) belong to the same category. 

The varietal names enumerated above almost always 
occur, in systematic works, in series which begin not with 

1 C. SCHROTER, Die Vielgestaltigkeit dcr Fichte, 1898, pp. 52-53. 

2 A. BRAUN, Verjiingung, 332. Here also the earlier literature 
will be found; and some facts concerning Rubus Idaeus monophyllus. 



64 The Different Modes of Origin of new Species. 



a. but with ft and are therefore considered as having been 
derived from a Forma typica or gcnuina and not as being 
of equal value with this. Evidently the principle on 
which they are classified is borrowed from a consideration 
of horticultural varieties. This proceeding, however, is 
only justified in the relatively rare cases in which horti- 
cultural varieties can be demonstrated to be younger than 
the species. Besides this the geographical distribution 
of the forms in question is often employed to decide 
which is the species, and which are the varieties. If one 
particular form is wide-spread and another only local 
or sporadic in its appearance it is obvious that the former 
will be regarded as the older and therefore as the species. 
Often this fits in conveniently with the fact that the 
species was discovered earlier than the variety, so that 
instead of disturbing the classification in the system all 
that had to be done was to range the variety under the 
species. 

The exigencies of space prevent me from going into 
further detail here. What I have already said may suffice 
to show that the systematic term "variety" means two 
fundamentally different things to LINNAEUS and the 
later systematists : 

1. Homonomous Forms, amongst which even LIN- 
NAEUS could not select one as a type for the others ; 
"Elements de 1'espece" (DE CANDOLLE) or ele- 
mentary species. 

2. Derived Forms, which are distinguished from the 
type of the species only by the decreased or in- 
creased development of a particular quality; or 
by its complete absence: True varieties. 1 

Amongst these, again, the simple invariable types are to be 
distinguished from the intermediate or eversporting races. (See 
3-4-) 



Progression, Retrogression and Degression. 65 

I think it undesirable that these two types of sub- 
divisions of the species should continue to be denoted 
by the same term. The simplest plan would be to refer 
to the former as elementary species and only to the latter 
as varieties, and I hope that this limitation of the terms 
will come into general use. 

The question, however, is a purely systematic one and 
belongs to the department of descriptive science. For as 
soon as it is treated from the experimental standpoint 
the whole difference disappears. Many of the best vari- 
eties prove, when tested by sowing, to be as constant as 
elementary species, so that a separation on the basis of 
constancy is out of the question. 

# * # 

On the basis of the foregoing discussion I treat the 
homonomous subdivisions of the LINNEAN species as 
elementary species and eventually denote them with bi- 
nary names. In the case of derivative varieties, however, 
I prefer to make no definite choice ; I regard for example 
Chelidonium laciniatmn Miller and Chelidonlum inajus 
laciniatnni as equally justifiable. And when for instance 
several species in the same genus have white flowered or 
glabrous varieties, a binary nomenclature would obviously 
be much too cumbrous. 1 



7. PROGRESSIVE, RETROGRESSIVE AND DEGRESSIVE 

FORMATION OF SPECIES. 

A glance at the phylogeny of the vegetable kingdom 
reveals the fact that all species cannot have arisen in the 
same way. Progressive development is due to the con- 
dor instance if specific names like that of Agrostemma nicae- 
cnsis for Agrostemma Githago pallida were generally used for white 
flowered varieties. 



66 The Different Modes of Origin of new Species. 

tinual formation of new characters, to increasing differ- 
entiation. Nevertheless the great multiformity of spe- 
cies within the orders and families is only in part due to 
this progressive process, but to a large extent to an in- 
finite variety of combinations of characters already exist- 
ing. This is combined in innumerable cases with in- 

o 

stances of regression ; that is, with the absence of 
characters which are otherwise proper to the group to 
which the species belongs. Sinm and Bcrula have, for 
example, simple pinnate leaves within the group of the 
Umbclli ferae with doubly pinnate leaves ; and the assump- 
tion is that they have arisen from the latter by a simple 
loss. Similarly Primula aeanlis stands in the middle of 
a group containing the Primulas, Androsace etc. with 
umbellate inflorescences, and the same inference is drawn 
as to its origin. The same is true of a host of other 
cases, and even for whole groups. For instance DELPINO 
holds, as is well known, that the Monocotyledons have 
arisen from the lower Dicotyledons by the loss of a whole 
series of characters. 

Cases such as these are spoken of as instances of 
retrogressive metamorphosis. And it is probably not 
too much to say that there are possibly more species on 
the face of the earth at present that have arisen on retro- 
gressive than on progressive lines. 

The question is often debated whether, in retrogres- 
sion, the characters absolutely disappear or only become 
invisible, or latent. There is much evidence for the 
latter view, derived largely from the great variety of 
atavistic structures (youth forms, subvariations on the 
lower internodes of lateral branches, the form of the leaf 
in suckers, the effects of parasites, anomalies, reversions 
to the ancestral form by bud-variations, etc.). Latency 



Progression, Retrogression and Degression. 67 

is without doubt the general rule. That an actual internal 
loss may also occur is probable on general grounds, but 
very difficult to demonstrate in a given case. For every 
positive result points to latency, and nothing but a nega- 
tive result after exhaustive investigation could warrant 
the conclusion that a character had absolutely disap- 
peared. 

The multiformity of species within the larger groups 
is also due to a phenomenon which DARWIN calls parallel 
variation. I refer to the repeated appearance of the 
same new character in related or remote groups. 1 Climb- 
ing and tendril-bearing plants, parasites, saprophytes 
and insectivorous plants, decussate phyllotaxy, are a few 
names from a vast number of instances. One of the 
greatest difficulties for the systematist, the question as to 
the mono- or polyphyletic origin of many characters is 
a problem of a similar nature. For example, are the 
siliqua and silicula in the Cruci ferae, or is the position 
of their embryo to be regarded as an indication of mono- 
or polyphyletic origin? Do the Sympetalae with an in- 
ferior ovary originate from other Sympetalae or from 
epigynous Choripetalae ? Have the Gymnosperms arisen 
once or oftener from the vascular Cryptogams? We do 
not know, because, on such points, the highest authorities 
are not in agreement. And so long as these differences 
of opinion exist it will be difficult to approach the question 
as to the cause of the parallel formation of specific char- 
acters whether they arise from a common latent source, 
or afresh each time with any hope of success. 

The origin of svstematic and horticultural varieties 



1 On this point see also my Intracellulare Pangenesis, English 
translation by Prof. C. Stuart Gager (Chicago, The Open Court 
Publishing Co., 1910). 



68 The Different Modes of Origin of new Species. 

is evidently clue, in the vast majority of cases, to retro- 
gressive development or latency, as I have already at- 
tempted to show. 

There is a close analogy between the formation of 
these varieties and that of certain species. The origin 
of varieties (such as Var. hirsutissinia, spinosissima and 
ciliata) as the result of the intensification of characters 
is a much rarer phenomenon. This form of variety, 
which seems to be of very little importance in the evolu- 
tion of the vegetable kingdom, may be called subprogres- 
sive, and the phenomenon of its origin subprogressive 
formation of species. 

The parallel, retrogressive, and subprogressive modes 
of origin have this in common that they only provide new 
combinations and do not contribute new units or any es- 
sentially new elements to the progressive evolution of the 
vegetable kingdom. In this respect they stand in sharp 
contrast to progressive formation of species. 

There is another series of phenomena to be mentioned 
here, of still less significance in the phylogeny of plants. 
The first of these is the manifestation of old, latent char- 
acters. A whole series of anomalies are so widely dis- 
tributed in the vegetable kingdom, or at least among 
flowering plants, that it is almost impossible not to as- 
sume a common cause for them. This cause must be 
a latent character that has arisen in some common ances- 
tor and therefore must be of great antiquity. The com- 
monest and best known example of a widely distributed 
anomaly of this kind is that of fasciation, instances of 
which in almost any desirable number of species can be 
collected in the course of a few years. It appears that 
almost every species amongst Coni ferae and Monocotyl- 
edons, but especially among Dicotyledons, can exhibit 



Progression, Retrogression and Degression. 69 

fasciations. 1 As a constant horticultural variety it occurs 
in Celosia cristata; but as a specific character, so far as 
I know, it does not occur. This is, however, true of the 
almost equally widely distributed split leaves (as in Boeh- 
incria biloba), of adherences (Solatium), of flowers on 
leaves (Hclwinyia rusciflora and others) and of numer- 
ous other anomalies of which CASIMIR DE CANDOLLE has 
given a valuable general account. 2 He calls them "Varia- 
tions taxinomiques" ', whereas anomalies which do not 
occur as specific characters such as fasciation, twisting, 
virescence and sterile varieties, are designated by him as 
ataxinomous. I take the following further instances 
from his list : Connation of opposites leaves, which oc- 
curs normally in Dipsacus, Lonicera and others, or of the 
cotyledons (amphisyncotyly, normal in Sicyos) ; Pitch- 
ers, normal in Sarracenia etc., and in the peltate leaves, 
as for instance Eucalyptus citriodora; foliacious excres- 
cences on the leaves, normal in Senecio sagittifolins from 
Uruguay, and on petals, normal in Petaquia saniculae- 
folia and as a sport in Clarkia clcgans\ Synanthy in 
Lonicera, and so on. 

For our purposes, however, the question is not which 
anomalies can also occur as specific characters, but con- 
versely which specific characters can also occur as anom- 
alies in other species. For our task is to deal with the 
problem of species and especially to provide an answer 
to the question how far their characters can be derived 
from more or less widely distributed latent qualities 
which have existed for a long time in the vegetable king- 
dom or in particular groups of it. With this end in view 



5-6- 



1 See Vol. I, Figs. 34 and 35 on pp. 182-183. 

2 C. DE CANDOLLE, Rcmarqucs sur la tcralologie vegctale, 1896, pp. 



70 The Different Modes of Origin of new Species. 

I shall supplement the examples named with a few more ; 
they serve to show how general this parallelism between 
anomalies and specific characters is. Thus, for example, 
Polygonum viviparum and Agave vivipara bear adven- 
titious buds or bulbils normally in the inflorescences ; 
but I found them also as an anomaly in Aloe vcrrncosa 
and Sa.vifraga nmbrosa. A spiral involution is normally 
exhibited by the flowerstalks of Vallisneria and Cyclamen, 
and it occurs as a variety in the stalks of Juncus spiralis, 
and as an anomaly in Scirpns lacnstris of which latter 
a beautiful instance came under my notice. Hypocotyl- 
ous buds are, for example, normally present in Linaria 
and Limiin ; they occur as an anomaly in Siegesbeckia 1 
according to BRAUN, and I have also observed them in 
Phaseolns multiflorus. The numerous flowerbuds on the 
leaf stalk of Cucumis sath'iis as described by CASPARY 2 
are analogous to the buds scattered on the internodes of 
Begonia phyllonianiaca. The bulbs of Gladiolus carry 
their lateral conns on stalks; I observed the same mode 
of connection as an anomaly in Hyacinthus oriental is. 
MASTERS has collected a series of teratological cases 3 of 
buds on leaves, which may be regarded as parallel to the 
normal instance of the same phenomenon furnished by 
Bryophyllum. 

We see therefore that a large number of specific 
characters are analogous to taxinomous anomalies. The 
latter recur in related forms, but much more frequently 
in more or less remote groups. In so far as they are 
due to a common cause, they point to the widespread 

1 A. RRAUN, Verh. d. hot. Vcreins Brandcnb., XII, 1870, p. 151. 

2 CASPARY, Ueber Bliithensprosse auf Slattern, Schriften d. phys 
Gesellsch., Konigsberg, 1874, p. 99 and Table II. 

3 MASTERS, Vegetable Teratology, p. 170. 



Progression, Retrogression and Degression. 71 

existence of latent characters. I shall refer to this mode 
of formation of species as degressive. In it, that which 
arises is always something new, and often something 
strikingly new, but usually without any clear relation to 
the progressive development on the main lines of evolu- 
tion. They form, rather, lateral improvements of types 
already existing. 

Degressive formation of species is therefore due to 
the activation of long established latent characters. Of 
these, as GOEBEL has shown in his Organographie, there 
are two types to be distinguished. 1 Either the character 
in question was active in the earlier ancestors, or it was 
not. In the former case we have an instance of reversion 
or atavism, and moreover a genuine systematic reversion, 
at least inasmuch as the ancestral relation can be demon- 
strated. In the other case we have only the development 
of a specific character from a taxinomous anomaly. 

It is perhaps hardly necessary to state that the appli- 
cation of this criterion of grouping can only be effected 
at the present moment in a relatively small number of 
cases. The information at our disposal does not as yet 
meet the demands of such a system. On the physiolog- 
ical side, however, the question of prime importance is 
only the distinction between the chief groups; so that we 
will only lay stress on that point here . 

Bearing this limitation in mind we can summarize 
what we have already said, as follows : 

THE ORIGIN OF NEW SPECIES. 

A. By the formation of new characters: Progressive 
specific differentiation. 

B. Without the formation of new characters. 

1 K. GOEBEL, Organographie, Vol. I, p. 170. 



72 The Different Modes of Origin of new Species. 

B\, By characters already existing becoming la- 
tent: Retrogressive specific differentiation, 
cases of atavism. 

82- By the activation of latent characters : De- 
gressive specific differentiation. 

a. From taxinomous (latent) anomalies. 

b. As genuine atavism. 
#3. From hybrids. 



This list does not of course claim to be complete. 
There is no doubt a whole series of further types which 
can be more or less easily ranged under or parallel to 
these subdivisions. On the other hand it is at once clear 
that the distinction between A and B is, in the present 
state of our knowledge, the important thing, and more- 
over that it will suffice as a basis for experimental in- 
quiry. But before I proceed to illustrate this antithesis 
I will offer some remarks on the last section (3). 

New species can arise from hybrids but specific char- 
acters cannot arise by means of hybridization ; or, we may 
say that with regard to the production of mutations, hy- 
brids behave just like ordinary species, except that ac- 
cording to the prevalent view they are slightly more 
prone to it. The existence of a vast number of species, 
however, is due to the various combinations of characters 
which also exist in closely allied or in remote species. 
And it is evident that, by crossing, characters can be com- 
bined which have not appeared in the same genealogical 
line but in distinct though allied species. Thus for ex- 
ample by crossing Oenothera nibrinervis with O. nanella 
I obtained an O. rubrinervis-nanella which has remained 
constant for many generations without segregation and 



Progression, Retrogression and Degression. 73 

without reversion. And a host of new species have 
doubtless arisen on similar lines. 

Coming now to the discussion of the difference be- 
tween our two groups A and B, we draw a distinction 
between progressive specific differentiations or the origin 
of new specific characters on the one hand, and rctro- 
and degressive specific differentiation, which consists in 
the activation or latency of potentialities already in ex- 
istence. 

It is obvious that a premutation is necessary for pro- 
gressive but not for retro- and degressive differentiation. 
For in the case of the former the new potentialities must 
first arise before they can become visible externally, whilst 
in the case of the two latter we are only dealing with 
potentialities already existing. I propose therefore to 
apply the results obtained with Oenothera Laniarckiana 
and the conclusions regarding the premutation period to 
which we arrived, to the further elucidation of this ques- 
tion. 1 It is of course a purely speculative discussion 
that we are embarking on, but one which will, in my 
opinion, materially help in clearing the ground. And I 
may therefore say, in anticipation, that this theory is 
supported by the experiments to be recorded in this sec- 
tion and most strikingly by the history of my Linaria 
z'lilc/aris peloria (see 20). 

I have already stated, in Vol. I, Part II, that I regard 
the mutational period in Oenothera Laniarckiana as a 
type of the mode of origin of species in general; that is 
to say, of the essential form of that process, the pro- 
gressive type. 2 We often find in the vegetable kingdom 
analogous groups of closely related species which are 

1 See Vol. I, Part II and especially 31, p. 490. 

2 Vol. I, p. 259- 



74 The Different Modes of Origin of nciv Species. 

usually ranged as elementary species of larger species, 
but sometimes regarded by the best authorities as "good" 
species. The group most closely related to our experi- 
mental series is that of Oenothera bicnnis or the subgenus 
Onagra; 1 more remotely connected are the groups of 
Hicracium, Rosa, etc., or of Draba vcrnci, Viola tricolor 
etc. Such groups appear to us as the relics of past periods 
of mutation. The new forms which arise from such 
periodical mutations are to be regarded as homonomous 
subdivisions of the older species or as elementary species. 

It is natural in such periods not only that new specific 
characters should arise, but that old established latent 
ones should reappear more easily than at other times ; 
and among the mutations of Oenothera Lamarckiana our 
O. nanclla is undoubtedly analogous to typical horticul- 
tural dwarf varieties, and 0. laei'i folia to those systematic 
varieties which arise by the loss of a character. 

These latter, however, and similar retro- and degres- 
sive changes are an entirely different matter. The essen- 
tial condition for their production is always present, and 
all that is needed is the external stimulus to induce the 
mutation. This, it appears, need not occur periodically, 
nor affect several characters at the same time. New horti- 
cultural varieties appear at irregular intervals of time, 
and here and there in the area of cultivation of the spe- 
cies. But it is equally certain that we have to do in such 
such cases exclusively, or almost exclusively, with retro- 
gressive and degressive changes. 2 Analogy and paral- 
lelism are universal, and their effects sometimes go so 
far that the characters of the species fall into the back- 
ground. Double flowers look so much alike that one 

'See Vol. I, p. 439; and 31, p. 490. 

2 1 am excluding from this consideraton the effects of crossing. 



Progression, Retrogression and Degression. 75 

often cannot tell, even from the best illustrations, to 
which genus or family a given instance belongs. 

I shall therefore throughout this Part attempt to 
describe the origin of horticultural varieties as exhaus- 
tively as possible. In the present state of our knowledge 
they form in my opinion the pattern of retrogressive and 
degressive formation of species ; just as the mutations 
of Oenothera were the pattern of progressive changes. 
Together they give us some idea of the main lines along 
which specific differentiation takes place in nature, at the 
present time as well as in the past. 

In conclusion : Progress on the main lines of descent 
results from the production of new characters ; but the 
extraordinary variety of forms results from the occa- 
sional disappearance of characters already existing, or 
from the activation of latent ones (retrogression, de- 
gression, atavism). 



IV. THE SUDDEN APPEARANCE AND THE 
CONSTANCY OF NEW VARIETIES. 

8. EXAMPLES OF CONSTANT RACES. 

Horticultural varieties are generally constant ; excep- 
tions to this rule are usually noted expressly in the text- 
books. Most varieties are not only constant from seed 
but also pure. By constant is meant that in ordinary 
cultivation they produce no more impurities than are un- 
avoidable (that is to say, at most 3%). Absolute purity 
means that when isolated under experimental conditions 
the seeds reproduce their own variety without exception. 
Constancy in this case is complete, but it is seldom of 
practical interest to bring either the old established sorts 
or the novelties to this pitch of purity, or even to find 
out how closely they approach it. 

This has, however, been repeatedly done by scientific 
investigators and especially by DAR\VIN and HOFFMANN. 1 
Insufficient familiarity with the danger of chance cross- 
ings robbed the results of the older investigators of much 
of their value as evidence, except of course in those cases 
where the race proved constant. The large number of 
observations of instances of complete constancy were ob- 

1 See the Riickblick auf meinc Culturvcrsuchc of the latter author 
in the Botanischc Zeitung, 1881, and the literature cited there. IHNE 
and SCHROTER have given a complete list of HOFFMANN'S papers in 
the obituary of him in Bcrichte d. d. bot. Gescllsch., Vol. X, 1892, p. 
18 of the last part. 



Examples of Constant Races. 77 

viously made under conditions which excluded the effects 
of crossing. 

In spite of the existence of these experimental data, 
it is still the general view that varieties are inconstant 
forms. That which distinguishes them from true spe- 
cies is supposed to be their faculty of giving rise to 
occasional and not even rare reversions to the type of 
the species. This, moreover, is supposed to be a proof 
of their assumed relation to their species. 

Every one of course is free to choose his own defi- 
nition of a variety. But he who makes inconstancy an 
essential part of the definition will have to exclude a very 
large number and perhaps the most important of our 
horticultural varieties, and regard them as elementary 
species. 

I have spent much time in the endeavor to test the 
constancy of horticultural and also of wild varieties with 
a view partly of directly satisfying myself as to their 
purity and partly of finding inconstant forms for sub- 
sequent experiments. I have usually started from seed 
but sometimes, in the case of perennial varieties, from 
bought plants. Whenever possible the visits of insects 
were excluded and the plants artificially pollinated. But 
in the great majority of cases pollination has to be left 
to bumblebees and moths, and we must be content in 
providing complete isolation. 

The most important point is the extent of the experi- 
ment. Absolute constancy can obviously never be di- 
rectly demonstrated. The space and time needed for 
other experiments seldom permit the bringing to flower 
of more than a few thousands of plants of one sort. 
And even if this is continued for several years the possi- 
bility of the occurrence of rare cases of atavism (e. g., 



78 



Sudden Appearance and Constancy. 



once in a million) can not be excluded. The object of 
experimentation cannot therefore be to demonstrate ab- 
solute constancy. The best plan usually is to be content 
with a few hundred individuals; it is even often impos- 
sible to get sufficient seed for more. Experiments on a 
smaller scale should only serve to confirm the results ob- 
tained in other cases; but even if they only do this they 
are, in my opinion, by no means without value. 




Fig. /. Bidcns tripartita. Type without ray florets. 

The nearest that we can get to demonstration of ab- 
solute constancy is to make observations on races which 
grow in vast quantities in certain districts and are never- 
theless true to their type. In these cases the constancy 
is so striking as to induce many systematists to regard 
the form as a species. Amongst the better known ex- 



Examples of Constant Races. 



79 



amples of this are the Discoidca forms of many com- 
posites. 

MOOUIN TANDON regarded the Discoid 'ea, i. e., the 

*** fj 

form without tongue-florets, as the Peloria of the Com- 
posites. 1 They are generally regarded as having arisen 
from the Radiata forms. Sometimes the discoid form is 




Fig. 8. Senecio Jacobaea L. (/. radiata}. 

commoner than that with rays, and then the Discoidea 
form may be found described in systematic works as a 
species and the Radiata as the variety ; as for instance in 
Bldcns tripartita (Fig. 7), and B. cernua, 2 although B. 

1 Teratohgie vegctale, p. 179. 

2 KOCH, Synopsis Florae Gcrmanicae, p. 309. 



80 



Sudden Appearance and Constancy. 



grandiflora, B. bipinnata, and B. atropurpurea are well- 
known species with ray florets. B. trlpartlta and B. 
cermta are very common in Holland and I have often 
tried to find or to obtain examples with ligulate florets, 




Fig. g. Senecio Jacobaea discoidcus, KOCH. 

but as yet in vain. By this fact both forms are proved 
to be constant as thoroughly as a proof can be. In other 
countries, however, the varietates radiatae are known to 



Examples of Constant Races. 81 

occur. Similarly Scnccio Jacobaca has a Forma radiata 
and a F. discoidea 1 (Figs. 8 and 9) both of which grow 
in this country and are absolutely constant. The Discoi- 
deus grows in thousands of specimens in the dunes in 
the province of North Holland; but the Forma radiata 
grows equally abundantly in South Holland; both are 
amongst the commonest and most widely distributed spe- 
cies of our flora. For twenty and more years I have had 
them under observation, and never saw any trace of ad- 
mixture or reversion ; the two varieties were always ab- 
solutely pure in the respective localities. Of late, how- 
ever, there have been some cases of intermingling near 
the limits of their areas, probably as the result of seed 
transportation. The two sorts can therefore be regarded 
as absolutely constant. 2 Matricaria Chamomilla discoi- 
dea 3 has proved equally constant in my experimental 
garden, but MURR mentions the occasional occurrence of 
heads with ravs. 4 In 1897 I raised from the seeds of a 

j 

single plant of M. discoidea 575 plants, all of which were 
without ligulate florets. On these I only harvested the 
seeds of the weakest branches of the higher orders and 
raised 460 plants in 1898, all of which again were with- 

1 See Vol. I, p. 196. 

2 A valuable summary dealing with this point is given by. J . 
MURR, Strahllosc Bliltlien bei heimischen Kompositen, Deutsche Bot. 
Monatsschr., Vol. 14, 1896, pp. 161-164. See also Botan. Jahrcsber., 
T. 24, 2, p. n, where rare instances of forms with rays belonging 
to normally discoid species and rayless flowers on normally radiata 
forms, are given. I cite Senecio Jacobaea as an instance of the latter, 
in opposition to the observations given in the text. An attempt to 
discriminate half races amongst these forms (See 3, p. 18) would 
probably lead to valuable results. 

3 For an account of the rapid spread of this form in Norway see 
JENS HOLMBOE, Nogle Ugraesplanters Invandring i Norge, 1900. 
Nyt Magaz. f. Natitrv., Vol. XXXVIII, p. 187 (with map). The 
variety is there also fully constant. 

4 J. MURR, loc. at., pp. 161-164. 



82 Sudden Appearance and Constancy. 

out ligulate florets. From these plants I only harvested 
the poorest possible seed on the latest branches after 
cutting away the main stem and the stronger branches; 
but from this seed, as before, I obtained nothing but 
Discoidea (750 plants in 1899). 

Flowerheads without, or almost without, rays also 
occasionally occur in races usually normal in this respect. 
Examples of this have occurred in my experimental gar- 
den in Chrysanthemum coronarimn, Coreopsis tinctoria, 
Dahlia striata nana and others. 1 

In the first volume I cited numerous examples of 
constant varieties 2 and showed 3 that many of them were 
certainly one or two centuries old ; in fact as old, or 
probably even older than, the cultivation of their species 
itself. The varieties are generally as constant as the 
wild elementary species, of which Draba vcrna and Viola 
tricolor* w^ere cited as examples. Belonging to the same 
group are the two remarkable types, which HERMANN 
MULLER has distinguished in Iris Pseudacorus, of which 
the one with narrow openings to the flower is adapted 
for pollination by Rhingia, whilst the other is adapted 
for pollination by bumble bees ; 5 IRWIN LYNCH has re- 
cently compiled a very complete and valuable list of 

1 Further examples are given by MURR, loc. cit. 

~ See p. 196. Examples are afforded by GMLLON-strawberries 
(Vol. I, Fig. 7, p. 34) and by Chelidonium laciniotnin (Vol. I, Fig. 
36, p. 190). 

3 On page 183 of the first volume will be found a list of the vari- 
eties known to MUNTING (1671) and still cultivated. 

4 See Vol. I, Figs. 3 and 4, pp. 22 and 23. For the constancy of 
the elementary species of Viola tricolor see also V. B. WITTROCK, 
Viola Studicr in Acta Horti Bergiani, Vol. II, No. I, 1897 (Cultures 
extending over three years). 

H. MULLER, Die Bcfruchtung der Blumen, p. 68. 



Examples of Constant Races. 83 

constant varieties, based on data given by gardeners and 
botanists as well as on his own observations. 1 

It is a common opinion amongst gardeners that white 
flowered varieties are among the most constant. They 
are very plentiful and easy to control. From the cases 
as yet investigated it may be assumed that hybrids be- 
tween them and the colored species will be colored also, 
and therefore soon and easily discovered ; so that in the 
purification or fixation of these varieties the hybrids 
are usually removed soon and altogether, which is a 
very important thing for approaching constancy. Sev- 
eral investigators have tested the purity of white vari- 
eties. For instance HiLDEBRAND 2 worked with white 
Hyacinths, Delphinium Consolida, Matthiola incana and 
Lathyrus odoratus', HOFFMANN with Linnm usitatissi- 
11111111 album ; 3 HOFMEISTER for thirty years with Digitalis 
parviflora alba ; 4 PREHN with Scabiosa alba? etc. 

I myself have made similar observations. I started 
by buying a few plants of each of some varieties of 
perennial species, allowing them to flower on isolated 
spots and then saving and sowing their seed. Wherever 
the isolation was complete all the offspring, with a single 
exception (Aquilegia chrysantha), were white flowered. 
The following were the species tested in this way (I give 
in parentheses after each one the number of plants which 
were raised from their seed and observed in flower) : Cam- 
pan ula pyram idalis alba (26), C. persicifolia alba ( 1 044 ) , 

1 IRWIN LYNCH, The Evolution of Plants, Journ. Roy. Hort. Soc., 
Vol. XXV, Pt. i, pp. 34-37, Nov. 1900. 

2 HILDEBRAND, Die Farbcn der Bliitlicn, p. 7p. 

3 HOFFMANN, Botan. Zeitung, 1876, p. 566. See also the very 
complete list of constant white varieties given by CARRIERE, pp. 12-13, 
and the literature cited there. 

4 HOFMEISTER, Allgemeine Morphologic, p. 556. 

5 J. PREHN, Schr. Naturw. Vereins Hoist ein, Vol. X, 1895, p. 259. 



84 Sudden Appearance and Constancy. 

Catananche cocntlca alba (5), Hyssopus officinalis albus 
(198), Lobelia syphilitica alba (537), Lychnis chalcedo- 
nica alba (401), Polemonium dissectum album (126), 
Sak'ia sylvestris alba (296). The following white vari- 
eties of annual species I also found to be perfectly con- 
stant : Chrysanthemum coronariiim album (400), Godetia 
amocna, white Pearl (15), Linum usitatissimum album 
(779), Phlox Drummondi alba (50), Silene Armeriaalba 
(617). Among wild species I subjected especially Ero- 
dium ciciitarium album, which is common in Holland, 
to a severe test. In this form the pigment characteristic 
of the species is lacking both in the leaves and in the 
flowers. I found the variety constant through five gen- 
erations in my experimental garden, not a single red 
plant appearing although the sowings were conducted on 
a very large scale. Later I collected seeds of the "car. 
alba from another locality and found it also to be con- 
stant (43 specimens). 

Other color varieties usually prove equally pure if 
the seeds of plants that have been isolated are sown. In 
some cases this fact is so generally known that they have, 
on this ground, been raised to the rank of species, as, 
for instance, Anagallis (arvensis} coendca. In 1897 I 
had 25 examples of this variety flowering on an isolated 
spot, and from these in 1898 I had 866 plants which were 
without exception blue. Tetragonla e.rpansa, whose leaves 
and flowers are normally reddish brown, has given rise 
to a pure green form which has been raised to the rank 
of a species under the name of T. crystalline,. This I 
also found perfectly constant. In 1898 I sowed about 
600 fruits obtained from a culture of 1897. Each fruit 
contains from 6 to 10 and often more seeds, which ger- 
minate sooner or later, some of them not until after a 



Examples of Constant Races. 85 

few years have elapsed. In the course of the first sum- 
mer 3975 seeds germinated, during the second 1082, 
during the third 88, and during the fourth 90. All the 
5235 seedlings thus raised were green without a trace of 
the red pigment, and belonged therefore to the T. crys- 
tal Una. In this case, therefore, the seeds which germinate 
late are just as constant as those which germinate early. 1 
In other cases where the constancy is just as complete 
but happens to be less well known, the sorts in question 
are "only" regarded as varieties. Some of these forms 
even seem to be wholly unknown in botanical circles, 2 as 
for instance, Silcnc Armcria rosca whose color is inter- 
mediate between that of the species and that of the white 
variety and which is not a hybrid but an old established 
perfectly constant sort and just as "good" as the other 
two. In 1898 I had about 4000 plants raised from the 
seed of isolated plants of 1897 of the Var. fiorc roseo in 
flower; they were all of the same color as the parent 
plants. The same result was obtained on a smaller scale 
in subsequent years. Clarkia pulchella carnca behaved 
in the same way (50 specimens). I also found the pale 
flowered Agrostemma Githago nicaccnsis constant (for 
10 years), and Hyoscyamus (niger) pallid us (40 spec.) 
and Agrostemma coronaria bicolor (349 spec.). Further 
examples of the same phenomenon are afforded by the 
yellow Chrysanthemum coronarium, the varieties of the 
flax with white and with yellow seeds, many varieties 
without the dark patches at the base of the petals, which 
are characteristic of the species, as in Papaver soinni- 
fermn Danebrog, Papaver conimutatuni, Madia elegans 
(Fig. 10) and others. 

1 This is not the case with Trifolium incarnatum quadrifolium 
(See 22). 

2 See Bot. Zeitung, 1900, p. 234. 



86 



Sudden Appearance and Constancy. 



Another interesting constant variety is Chelidonium 
majus latipetalum. (Fig. 11), for the possession of which 
I am indebted to Prof. J. W. MOLL in Groningen. It 
differs from C. majus in its petals which are so broad 
that their edges overlap so that they form an unbroken 





Fig. 10. Madia elegans. 



Fig. ii. A, B, Chelidonium majus 
latipetalum. C, D, Chelidonium 
ma jus. 



crown instead of an open cross. I found it to be con- 
stant through several generations. 

The constancy of the fasciated variety of Myosotis 
alpestris; Victoria with its broad, many-petalled central 
flowers, is likewise well known, as is also that of Linaria 



Examples of Constant Races. 



87 



vulgaris tricalcarea, 1 of many glabrous forms like Lych- 
nis vespertina glabra, of thornless types like Datura Stra- 
monium incnnis, 2 etc., all of which I have tested per- 
sonally. Space does not permit of the compilation here 
of anything like a complete list of constant varieties. 




mm 

Fig. 12. Melilotus coendca monophylla. Each leaf consists 
of a single blade but is more or less deeply incised. One 
of the lateral leaflets in the middle leaf on the right of 
the figure appears to be quite free. A, a bract from the 
inflorescence; here the leaves are least incised. 

1 J. H. WAKKER, Linaria rulgaris, Nederl. Kruidk. Archief, 1889, 
with plate X. 

2 See Fig. 5 on page 31 of Vol. I. 



88 Sudden Appearance and Constancy. 

I shall conclude by referring to a race of Mclilotus 
coerulca, the possession of which I owe to the kindness 
of Prof. M. W. BEYERINCK (p. 63). Its leaflets 1 are 
fused to a single blade in which the three main nerves 
still diverge from the base. The blade moreover has 
three distinct tips, the depth of the indentations between 
these being subject to considerable fluctuating variability. 
Not rarely the three parts are only united from the base 
to halfway up or less, and sometimes they are separated 
almost to the base and in rare cases even entirely so. 
All these forms may occur on the same plant. But there 
was no reversion in my experimental sowings ; every 
plant exhibited this monophylly to a greater or less ex- 
tent. 

9. STERILE VARIETIES. 

One of the greatest difficulties presented by the cur- 
rent doctrine of selection lies, as I have pointed out more 
than once in the first volume of this work, in the fact 
that the gradual origin of species, which is presupposed 
by it, has never been observed. In every case in which 
observations have been made sufficiently close to the 
origin of a new form, they indicate a sudden change. 
We do not find those gradual transitions which the doc- 
trine of selection would lead us to expect. The new form 
may be highly variable, and in that way the limits be- 
tween it and the parent species may sometimes overlap; 
but, as I have already shown (Vol. I, 25, p. 430) trans- 
gressive variability of this kind only provides a morpho- 
logical transitional series and not a genetic one. 

My object in the present chapter is to bring together 

1 This form has been described by WYDLER, Flora, 1860, p. 56, 
and occasionally since. 



Sterile Varieties. 



89 



a list of further instances partly from the literature and 
partly from my own observations in order to place my 
conclusions on a broader basis 
of facts. 

The difficulty of this task is 
increased by the fact that it often 
seems impossible to show how 
those cases, in which other in- 
vestigators believed that they had 
detected transitional series, are 
to be explained on the theory of 
mutation. This is especially so 
where the authors have simply 
relied on comparative investiga- 
tions. The results of these can 
usually be explained, no doubt, 
by the supposition of transgres- 
sive variability, but a proof can 
only be given if the phenomena 
in question are investigated by 
statistical methods. 

In strong contrast to these 
doubtful cases, however, there is 
a long series of observations in 
which the absence of transitions 
is practically certain. Perhaps 
the most striking of these are 
the sterile varieties which consti- 
tute one of the most serious ob- 
stacles to the current doctrine of 
selection, at any rate as regards its exclusive application. 
DARWIN himself repeatedly cited them as objections and 
examined them minutely. 




Fig. 13. A flower of Li- 
Hum candidum plenum. 
The thalamus is changed 
into a long stalk on 
which the narrow per- 
fectly white petals are 
spirally arranged. 



90 Sudden Appearance and Constancy. 

In the case of the vast majority of sterile varieties 
we know neither how, when nor where they arose. They 
are propagated by vegetative methods and have been 
from time immemorial. But they differ from their sup- 
posed parent species so markedly that they take rank 
with the best varieties. Nobody supposes that they have 
arisen gradually. 

The first instance that I give is Lilium candidum 
plenum, a form which is on the market. It is a well- 
known variety, the bulbs of which are offered every year 
by dealers in bulbs, in their catalogues. Instead of 
flowers it has long stalks clothed with petals (Fig. 13). 
The stalk is the elongated thalamus ; the petals are nar- 
row and dead white, and of the color and structure of the 
petals of other white lilies. In each flower they continue 
to appear for several weeks ; the lowest may be brown and 
withered before the uppermost have unfolded. Figure 
13 shows a fairly short flower; they are often twice as 
long. Stamens and carpels are never formed ; the apex 
consists of a compact bud of the youngest petals. 

We do not know how the variety first arose. It was 
first described by G. VROLIK in 1827, after he had al- 
ready seen it flowering for 20 years in the Botanical 
Garden in Amsterdam. 1 It is therefore nearly a century 
old. In horticultural literature it is not referred to until 
much later, about 1840. 2 

Another well-known sterile garden plant is the green 

Dahlia (Dahlia varidbilis viridiflora). The flowerheads 



1 G. VROLIK, Over ccn rankroruiige ontwikkeling van wittc Iclic- 
blocnicn. Verhandelingen der eerste klasse v. h. k. Nederl. Instituut 
van Wet. te Amsterdam, Part I, 1827, pp. 295-301, with one table. 
The spike with five flowers figured there, is still preserved in our 
collection. 

2 See MERAT, Ann. Soc. d'hortic. dc Paris, 1841-1845, and VERLOT, 
loc. cit.j 1865, p. 91. 



Sterile Varieties. 91 

are destitute of flowers; and the thin, transparent bracts 
are transformed into small green leaves. The variety 
is much cultivated in gardens, partly as a curiosity and 
partly because their green "flowers" do not wither but 
remain fresh on the plant ; which renders it of a decora- 
tive effect until far into the autumn. 1 The variety arose 
in a crop of seedlings about the middle of the last cen- 
tury in Boskoop in Holland, and since then has been 
grown from tubers. It occasionally bears isolated red 
ray florets but, so far as I know, never sets seed. 

Some years ago I obtained what seems to be a new 
and hitherto undescribed form of green Dahlia through 
the kindness of Messrs. ZOCHER & Co. in Haarlem. It 
is not known whence this form came because it was at 
first taken for the type of green Dahlia we have just 
been considering. It differs from this however in the 
fact that the green heads are not of the normal form 
and size but transformed into long green leaf -bearing 
spikes like that figured in Fig. 14 with the exception of 
the clump at the top. 

This form produced elongated flowers of this kind in 
great numbers in the nursery garden ; but it could never, 
so to speak, bring its growth to a conclusion. They grow 
until the autumn and often longer, and frequently attain 
a length of 30 centimeters and more. They behaved in 
exactly the same way in my garden until last year when 
I manured them heavily. Then there appeared from a 
few of the green "flowers" in late autumn a little head 
at the uppermost end (Fig. 14). This unfolded, but 
consisted of green bracts only; it contained neither flow- 
ers nor seeds. The plant is therefore perfectly sterile. 

Another variety closely analogous with this is the 

1 See the literature in PENZIG'S Teratologic, IT, p. 71. 



92 



Sudden Appearance and Constancy. 



wheat ear carnation (Dianthns Ca- 
ryophyllns spicatus). In this case 
we find instead of the flowers small 
green ears which are formed of green 
bracts arranged crosswise. This 
sterile form does not appear to be 
in general cultivation, although it is 
perennial ; nevertheless it turns up 
here and there in crops of seedlings 
especially of mixed varieties. I cul- 
tivated a plant arisen in this way ; 
most of the ears were sterile as 
usual, but some of them produced a 
flower at their top. From these I 
obtained several germinative seeds. 1 

The green rose has been known 
from time immemorial, but the green 
Pelargonium Donalds a modern prod- 
uct. In both cases the petals and 
stamens are transformed into green 
leaves. They are said to be perfectly 
sterile, and are only propagated by 
cuttings. 

Many double flowers never pro- 
duce seed, and this is especially true 
of those forms which do not develop 
structures intermediate between sta- 
mens and petals, but are described 
as instances of Petalomania. 2 Ra- 

1 After having been sown these seeds 
have repeated the wheat-ear variety (Note 
of 1909). 

2 K. GOEBEL, Beit rage zur Kcnntniss gc- 
Fig. 14. Elongated Green fi'illtcr Blilthen, Jahrb. f. iciss. Bot., Vol. 
Dahlia, a new variety. XVII, pp. 217-219, and elsewhere. 



Sterile Varieties. 93 

nuncidus acris (Vol. I, Fig. 40, p. 194), Caltha palustris, 
Anemone nemorosa, Hepatica triloba, Tropaeolum ma jus 
florc plena, Clematis recta, Barbarea vulgar is floribus 
plenis and many others are alleged in horticultural litera- 
ture to be perfectly sterile. Double varieties of compo- 
sites also afford instances such as Achillea P tar mica, 
Ageratum mexicanum (some varieties), Pyrethriim ro- 
seum, etc. Others, such as Anthemis nobilis, are known 
to bear seed from time to time and so do not belong here. 

Viburnum Opulus, Hydrangea hortensea, Muscari co- 
mosum plumosum and others have become sterile by the 
transformation of their reproductive flowers into sterile 
ornamental ones. Bananas and other seedless fruits 
have already been dealt with in the first volume (p. 195). 

Many varieties of the sugar-cane never set seed, such 
as the Cheribon cane which is the richest in sugar. This 
variety, which extends over vast regions, consists of a 
single individual ; that is to say, it is derived from one 
single unknown stock plant and has always been propa- 
gated by cuttings or so-called Bibits only. 

Robinia Pseud-Acacia inermis 1 is also said never to 
flower; and is only propagated by grafting. 

If this sterility affects annual species or such as 
cannot be permanently reproduced by vegetative means, 
the sterile form must vanish sooner or later. Such forms 
hardly deserve the name of variety, and are usually 
spoken of as monstrosities. But, in regard to their ori- 
gin, they are perfectly analogous with the sterile forms 
of which we have already treated. In the first volume 
(p. 195, Fig. 41), I gave the sterile maize as such an 
instance. More remarkable still is the unbranched Fir 
(Pinus excelsa aclada or monocaulis) which SCHROTER 

1 DE CANDOLLE, Physiologic, II, p. 735. 



94 Sudden Appearance and Constancy, 

has described in his excellent monograph. The whole 
plant consists of a single branchless stem, which is merely 
slightly swollen at the limits of every year's growth ; the 
needles remain adherent for a long time. 1 This form 
has appeared in diverse localities. SCHROTER records 4 
examples from Italy, one from Baden, several from 
Westphalia, Mittelfranken and Bohemia, and some from 
Mariabrunn near Vienna. The majority of these plants 
reached a height of 1-2 meters, a few of them as much 
as 5-6 meters; some of them are still alive 

RIMPAU has described an instance of sterile rye. 2 
Ears of this rye appeared almost every year during a 
period of more than ten years; they were often much 
and sometimes excessively branched, especially in years 
and localities where the rye was very thin. But as ears 
of this kind occurred on plants which also bore normal 
ones, the repeated appearance of the anomaly may per- 
haps be due to inheritance. 

And lastly, instead of giving a further record of the 
numerous existing sterile varieties, let me refer to Nitella 
syncarpa, which has recently been described by A. ERNST, 
and which bears, instead of oogonia, incompletely devel- 
oped antheridia which never produce spermatozoids. 3 
The examples in question were observed near Zurich, 
and were completely sterile. 

1 See p. 63 and C. SCHROTER, Ucbcr die Fichtc (Picca cxcclsa 
Link) Vierteljahrsschr. d. nat. Ges. in Zurich, Jahrg. XLIII, 1898, 
Parts 2 and 3, pp. 50-53, Fig. 18. This valuable work contains a 
very full review of the varieties, forms, and monstrosities of this 
highly "variable" tree. 

2 Deutsche landivirthschaftliche Presse, Berlin, October 4, 1899, 
where photographs of monstrous ears of rye are given. 

3 ALFRED ERNST, Ueber Pscudo-Hcrmaphroditismus bci Nitella 
syncarpa. Flora, 1901, Vol. 88, Part I, with Plates I-III. 



Races which Have Arisen Suddenly in Nature. 95 



10. INSTANCES OF RACES WHICH HAVE ARISEN 

SUDDENLY IN NATURE. 

In nature, elementary species are, as is well known, 
not connected with their closest allies by transitional 
forms. Nevertheless fluctuating and transgressive varia- 
bility frequently bring about the appearance of contin- 
uous series, which however on closer examination espe- 
cially by statistical methods dissolve into perfectly dis- 
tinct component units. 1 In very many cases these tran- 
sitional forms are absolutely lacking, and the separation 
of a particular form as variety, subspecies, elementary 
species, or even species, is mainly founded on their ab- 
sence. 

The absence of transitional stages in the case of forms 
which have been long familiar and are widely distributed 
obviously tells little concerning their mode of origin. 
Results are more likely to follow from the investigation 
of those cases in which the types in question are local 
in occurrence and in which, therefore, if transitional 
stages should occur, one would expect to find them in the 
locality inhabited by the plant. In some instances an 
exhaustive and minute study of the geographical distribu- 
tion of certain varieties has led to the discovery of the 
center from which distribution took place. ASCHERSON 
and MAGNUS obtained a result of this kind with the 
pale fruited varieties of the European species of Vac- 
ci nil tin and some related Ericaceae. 2 In inquiries of this 
kind, the absence of transitions at the present time points 
to the conclusion that they may never have existed. 

'See Vol. I, Part II, 25, p. 430. 

2 P. ASCHERSON and P. MAGNUS, I'crhandl. d. k. k. zool.-botau. 
Gesellschaft in iricn, 1891, p. 677. 



96 Sudden Appearance and Constancy. 

In contradistinction to these more or less distributed 
varieties, there is a whole series of records scattered 
through the literature of cases in which a new form has 
been found on a particular spot under circumstances 
which warrant the conclusion that it has arisen exactly 
there and fairly recently. In such cases transitional forms 
are always lacking, a fact which proves pretty conclu- 
sively that such have not been produced in the origination 
of the form. In Part II of the first volume two cases 
afforded by Oenothcra Lamarckiana were described in 
detail : I refer to the appearance of O. brevistylis and O. 
lacvi folia on the original locality at Hilversum. Both 
species proved, when tested, to be perfectly constant from 
seed, without any atavism; and transitional forms were 
not seen in the field. If these species had arisen where 
I found them, their origin must have taken place between 
the year of the introduction of the species and the first 
year in which I discovered them; that is, between 1870 
and 1886 (See Vol. I, p. 266). 

The most important and accurate observation of such 
an occurrence is that which has recently been recorded 
by SOLMS-LAUBACH, and deals with a species newly 
arisen from Capsella Bursa Pasioris. 1 This was found 
by Professor HEEGER in the market place near Landau 
amongst the ordinary Shepherd's purse and called C. 
Hccgcri after him, by SOLMS. It occurred in 1897 and 
1898 in very small numbers and only on this one spot. 
In its vegetative parts it is exactly like C. Bursa pastoris, 
from which it only differs in the form of its fruits. But 
the differentiating characters are of the rank of some of 

1 H. GRAF zu SOLMS-LAUBACH, Crucifcrcn-Stiidicn, Botanische 
Zeitung, 1900, Heft X, Oct., i, 1900, pp. 167-190, Plate VIII. 



Races which Have Arisen Suddenly in Nature. 97 

those which serve to separate genera amongst the Cru- 
ci ferae. 

The fruits of Capsella Heegeri are oval, and about 
as thick as they are broad. The seeds are notorrhizous. 
The valves lack the firm anatomical structure, character- 
istic of the normal valve, but are soft and full of sap, 
a condition which may be considered as due to arrested 
development. On the weaker branches in the autumn, 
deviations from this type occur which revert more or less 
to that of C. Bursa ; moreover the flowers and young 
fruits may develop into malformations, as the result of 
the attacks of Cystopus candidus, which closely resemble 
those of C. Bursa pastoris. 

The seeds of isolated plants of C. Heegeri gave rise 
solely to the parent type (382 examples) without rever- 
sion to C. Bursa. 

There can therefore be scarcely any doubt that C. 
Heegeri is a good elementary species which arose from 
C. Bursa in 1897, or a few years previously, somewhere 
near Landau. It is moreover a species which is dis- 
tinguished from its nearest allies by characters of far 
greater systematic importance than those which separate 
many species of known origin. 

I myself found a Stcllaria Holostea apetala not far 
from Wageningen in Holland under similar circum- 
stances (1889), and also in the same year the well-known 
Capsella Bursa Pastoris a petal a 1 near Horn in Lippe. 
But I did not succeed in obtaining seed from either of 
them. In 1888 I collected some seed of Lychnis I'csper- 
tiua not far from Hilversum and obtained some per- 
fectly glabrous plants by sowing it. The new variety 
L. v. glabra proved fully constant as soon as I was able 

1 See PENZIG, Tcratologic, I, p. 267. 



98 Sudden Appearance and Constancy. 

to isolate it, and has maintained itself up to the present 
day without ever reverting. 

So far as published data go, forms which have sud- 
denly appeared in nature, or have not previously been 
noticed, prove constant, provided that cross-pollination 
is guarded against. In the opposite case they will prove 
themselves pure as soon as they can be isolated. One 
of the oldest cases in point is the constancy of Ranun- 
culus art'cnsis incnnis which was established by HOFF- 
MANN. 1 The majority of records refer to trees of which 
the larger number of varieties, if not all, according to 
DARWIN himself, have arisen suddenly, 2 such as the 
weeping oak, the weeping white hawthorn, etc. 3 A single 
specimen 4 of Fagns sylvatica aspleniifolia was found in a 
wood in Lippe-Detmolcl and could be multiplied from 
seed. According to LOUDON, Ta.rus baccata fastigiata 
was found in 1780 growing wild in Ireland; 5 but no pure 
seedlings of it have been obtained since only one speci- 
men was observed (a female one). 

The above list of cases is not a rich one ; but it makes 
no claim to completeness. The observations in point are, 
with few exceptions, relatively incomplete inasmuch as 
there is always the possibility that the first discovery of 
the new species or variety may have been preceded by 
a long period of evolution. If we assume this to be true, 
the absence of transitional forms and the constancy of the 

1 HOFFMANN, Bot. Zeitung, 1878, p. 273, where several other 
examples will be found. 

2 DARWIN, Variations, I, pp. 461-463. 

3 Further examples are given by BRAUN, Vcrjungung, p. 333 
(the sudden origin of red-leaved varieties of Quercus, Corylus, etc.). 

4 RATZEBURG, cited by BRAUN in Abh. d. k. Akad. Berlin, 1859, 
p. 217. 

5 L. BEISSNER, Handbuch der Nadclhohkundc, 1891, p. 169. A 
great number of further examples is given in this work. 



Horticultural \\irieties Arisen Suddenly. 99 

new form are the only arguments for its sudden appear- 
ance. 

11. HORTICULTURAL VARIETIES WHICH HAVE ARISEN 

SUDDENLY. 

It is a matter of common knowledge that horticultural 
varieties have very often arisen by sports. But opinions 
differ on two points. One is an empirical one and relates 
to the question of constancy; the other relates to the 
meaning of the word variety. The two points are nar- 
rowly bound up with one another. If the new form is 
not constant and pure from seed but frequently reverts 
to the parent species it is usually supposed to be derived 
from that species and is treated as a subdivision of it. 
But if the new form is as constant as the parent species, 
the empirical means of demonstrating its relationship 
are lacking, and the conclusions are drawn from his- 
torical data and based on analogy; a proceeding which, 
as we all know, often leads to differences of opinion. 

Besides the historical records the main point in such 
cases is always the proof of the constancy from seed. 
But inasmuch as the interest of the practical man only 
extends to the question whether the variety can be con- 
veniently multiplied by seed and is not concerned with 
the possibility of occasional reversions, such information, 
especially in older cases, can only be accepted with cau- 
tion. 

\Yith this reservation, I propose to give a brief review 
of some of the better known instances. But before I 
do this I will call attention to a very beautiful variety 
which I have not yet found described nor seen in trade- 
catalogues, but which has appeared in my own cultures. 



100 Sudden Appearance and Constancy. 

Fig. 15 represents a single Dahlia, whose ray florets 
are all transformed into long and broad tubes which are 
open above. The same thing occurs in many other com- 
posites, for instance in Chrysanthemum segetum fistu- 
losum, Coreopsis tinctoria fistulosa, etc. On the analogy 
of these cases I propose to call this new Dahlia, DaJilia 
variabilis fistulosa. This variety arose from a crop raised 




Fig. 15. Dahlia variabilis fistulosa , a new variety which 
has appeared in my cultures. 

from the seeds of D. far. Jul. Chretien, a dwarf single 
Dahlia with red flowers of the color of red lead, the 
tubers of which I had bought in 1892 in Lyons. From 
the seeds which I saved in that year from this variety, 
I raised in 1893 several plants of which one had a white 
flower. I only sowed seeds of this in 1894. 1 It was 

I have unfortunately not yet succeeded in fertilizing Dahlias 
artificially by their own pollen. 



Horticultural Varieties Arisen Suddenly. 101 

in the crop thus raised that the plant which bore the 
flower head shown in Fig. 15 appeared. The color was 
dark carmine red, not that of red lead. The flower heads 
were all fistulous from the beginning of June until well 
into October; but the later flowers manifested the ab- 
normality in varying degrees. Either the base only of 
the tube was closed; or only some of the ray florets had 
the form of a tube. The plant had to be left to free 
crossing with its neighbors so that no observations of 
real value as to its constancy could be made. Neverthe- 
less this was pretty considerable, for, from the seeds of 
my fistulosa I raised 43 plants in 1895 of which 25, that 
is to say more than half, had the characters of the new 
variety. 

The origin of Chclidoniuni laciniatum from C. ma/us 
was described in detail in the first volume (p. 189, Figs. 
36 and 37) ; where a series of other cases will also be 
found. VERLOT (loc. tit., p. 34) describes Ageratmn 
cocruleuin nanuin as a novelty which is sometimes sterile, 
but sometimes occurs as a fertile and constant variety. 
Verbena hybrida, "a fleur couronnee" arose about 1889 
from the variety "a fleur d'auricule," it immediately 
proved constant and after only two years was put on the 
market by E. FOURGEOT of Paris. 1 Robinia Pseud-Acacia 
rosea was found by DECAISNE in a crop of ordinary 
Acacias; and Glcditschia sinensis incruiis arose in the 
same way, as also did Sophora japonica pendula which 
appeared in M. JOLY'S nursery garden in Paris about 
1S00. 2 In 1860 a new strawberry "Rcus van Zuidwyk" 
appeared in Boskoop. Its leaves and fruits were larger 

1 See his Catalogue for 1891. 

2 VERLOT, loc. cit., pp. 59, 92, 93. 



102 Sudden Appearance and Constancy. 

and altogether better than any varieties then known; it 
was constant from the first and spread rapidly. 

I shall conclude this summary with a reference to the 
new species of Tomatoes which BAILEY has recently 
described. 1 He describes the origin of two new forms 
which he has called Upright and Mikado and which arose 
in his cultures. They differ from one another and from 
the parent species by more definite and more numerous 
characters than many among the older forms which are 
recognized as good species in the genus Lycopersicum. 
They arose suddenly as usual and were propagated by 
seed. 

The observations recorded in this and the two preced- 
ing sections, which are far from constituting complete 
lists, show that the origin of varieties and of elementary 
species both in the garden and in the field is amenable to 
experimental investigation, for the phenomenon is by no 
means so rare as is generally believed. The botanist 
will investigate the indifferent and useless forms with 
just the same result as the profitable ones, to which alone, 
of course, the practical man pays attention. The cultures 
need not be very extensive to afford novelties from time 
to time, though these must not be expected the first or 
every year. Once obtained, all that there is to be done 
is to isolate them as soon as they appear and pollinate 
them artificially. But it is far more important to go 
back to their ancestors, partly not to lose the historical 
evidence, but mainly in order to sow the seeds of these 
ancestors again and to find out if the novelty will be again 
produced, and if possible to discover the conditions which 
determine its appearance. Unfortunately there are many 
plants which do not lend themselves to such experiments, 

*L. H. BAILEY, Survival of the Unlike. 



Horticultural yaricties Arisen Suddenly. 103 

either because they produce no seed or yield too small 
a harvest when self -fertilized or because they cannot be 
artificially fertilized on a sufficiently large scale or be- 
cause the number of seeds produced, even under normal 
conditions, is too small. Moreover one is almost abso- 
lutely confined to annual or biennial species or to such 
perennial ones as flower freely in the first year. 

But in spite of these difficulties and of the incom- 
pleteness of the observations made hitherto, we may 
safely conclude from them the possibility of an experi- 
mental study of the origin of horticultural varieties. 1 

1 1 shall describe an experiment of this kind with Linaria vul- 
gar is pcloria in 20. 



V. ATAVISM. 

12. ATAVISM BY SEEDS AND BUDS. 

HOFMEISTER in his Allgemeine Morphologic defines 
atavism in these words : "The occurrence of reversions, 
the offspring of a variety of known origin resembling 
the parent type" (p. 559). 

According to the meaning of the word "known" in 
the above definition the term atavism may embrace quite 
a series of phenomena of the most diverse importance. 
It may mean either that this origin must have been actu- 
ally observed, or that it can be inferred with sufficient 
certainty from comparative and systematic studies. If 
we are merely dealing with morphological questions this 
distinction may appear unessential, but as soon as our 
object is to test by experiment the results obtained, it 
becomes of the highest importance. For to obtain true 
experimental proof of atavism it is obvious that the 
origin of the forms should be known directly by observa- 
tion. 

The origin of a whole series of varieties and ele- 
mentary species from their parent forms, however, is 
sufficiently established by the historical evidence relating 
to their first appearance. It seems therefore feasible to 
confine our attention to such cases and to draw a distinc- 
tion between physiological and phylogenetic atavism. The 
former is reversion to actually known ancestors, the latter 
to systematic ancestors. 



Atavism by Seeds and Buds. 105 

But before I proceed to examine these two forms of 
atavism more closely, I think it desirable to state that I 
here use the word "atavism" in its narrower sense, for 
in its wider sense it embraces so large a group of phe- 
nomena that it would not be possible to deal with them 
all within the limits at my disposal. It seems worth while 
to indicate the more important of these types because they 
are often confused with one another and because results 
obtained with one form are often taken to apply to an- 
other, simply because they both go by the same name. 

We must first of all draw a sharp distinction between 
atavism as applied to variability and as applied to muta- 
bility. In the first case we are dealing with the phenom- 
ena presented by a single heritable character ; in the latter, 
with the conflict of two or more. In the improvement 
of races the offspring do not resemble the selected pa- 
rents, they always revert partly towards the mean of 
their ancestors. We are of course dealing in such cases 
with the phenomenon of regression which was fully dis- 
cussed in the first volume (pp. 82 and 120) ; and it 
would be better to refer to all those individuals of less 
value which are eliminated in selection as regressive and 
those which exceed the level attained by their parents as 
progressive. But it is customary to call the former atav- 
ists ; and, as a matter of fact, they exhibit the degree of 
development of the characters in question as it was mani- 
fested by their grandparents and more remote ancestors, 
and not as in their parents. They could perhaps be 
called "curve atavists," since this term does not suggest 
a reversion beyond the curves in question. 1 

The most fascinating section of the subject of atav- 
ism is that which deals with so-called "youth" forms 

1 See the pedigree of the many-rowed maize, Vol. I, p. 73, Fig. 18. 



106 Atavism. 

and with related phenomena. GOEBEL'S admirable in- 
vestigations have demonstrated the wide distribution of 
these phenomena and their great importance to the theory 
of descent. 1 It is now a matter of common knowledge 
that many plants, and indeed whole groups of species, 
exhibit characters when young which they either lack in 
the adult state, or which in later life appear only under 
definite circumstances. BEISSNER'S discovery 2 that whole 
genera of cultivated Coniferae, such as Rctinospora, are 
only youth-forms of other known types such as Thuya; 
and REINKE'S investigations 3 into the earlier stages of 
Leguminosae, as well as the work of many others, have 
resulted in the accumulation of a mass of information 
relating to this subject. Sium and Bcrnla in their early 
stages have the doubly pinnate and finely slit leaves of their 
close allies ; the thorns of Berberis on the so-called suck- 
ers revert to the foliate form. These phenomena, how- 
ever, fall mostly within the sphere of systematic botany, 
and only concern the study of variability in so far as they 
are dependent on external influences. 

We must further exclude from our considerations 
the effects of crossing. The so-called reversions of the 
horticulturists which are brought about either by acci- 
dental crosses with the parent or by unconsciously using 
hybrid seed, certainly occupy a very prominent place 
in the practice of horticultural selection, but they should 
be rigidly excluded from scientific speculations. And 

1 K. GOEBEL, Ucbcr Jugcndformen von Pflanzen und dercn kilnst- 
Viche Wiederhervorrufung. Sitzungsber. d. k. bayr. Akad. d. Wiss., 
Vol. 26, 1896, Part III. For further references see GOEBEI/S Organo- 
graphie dcr Pftanzcn, Part I, 1898. 

2 L. BEISSNER, Handbuch der Nadelhohkunde, 1891. 

3 J. REINKE, Untcrsiichungen fiber die Assimilationsorgane dcr 
Leguminoscn, I-III and IV-VII. Jahrbiicher fiir wissensch. Botan., 
Vol. XXX, Parts i and 4, pp. I and 71, 1897. 



Atavism by Seeds and Buds. 107 

this is true not only of those cases in which the cause 
of the reversion is perfectly plain, but still more of those 
in which the facts observed may lead us to suspect a cross 
either in the previous generation or in more remote years. 
By excluding such cases, however, the apparent abun- 
dance of data relating to experimental atavism is very 
much reduced ; but it is obviously better to build on a few 
reliable facts than on the highly insecure basis formed 
by the numerous data which have hitherto been collected. 

With these reservations I shall now turn to the dis- 
tinction between physiological and phylogenetic atavism. 
Each has its own sphere. The object of the study of 
the former is to discover the laws to which this form 
of variation conforms. That of the latter is to discover 
the ancestors of the species in question either by the ob- 
servation of chance deviations, or by cultures and selec- 
tion. 

HEINRICHER'S extensive studies in the genus Iris 
show how fruitful may be the application of selection 
in the study of phylogenetic atavism. 1 The cultivated 
plants of this group are well known to be highly variable, 
and the favorite Iris Kaempferi with its large flowers 
affords numerous opportunities for the study of tetram- 
erous and pentamerous flowers and of other variations. 
HEINRICHFR, starting from occasional anomalies pre- 
sented by Iris pallida, and working on a methodical sys- 
tem of selection, has raised an atavistic race which he 
calls Iris pallida abavia. 2 The individual anomalies could 
not, it is true, be fixed although they were selected for 
three generations, but a series of new types gradually 

1 CARRIERE, Production et fixation des varictcs, 1865, p. 65. 

2 E. HEINRICHER, Versuche ilber die Vererbung von Riickschlags- 
erscheinungen. Jahrb. f. wiss. Bot, Vol. 24, Part I, 1892, and Iris 
pallida abavia in Biolog. Centralbl., Vol. XVI, No. i, p. 13, 1896. 



108 Atavism. 

appeared and threw a definite light on the probable na- 
ture of their common ancestor. This is regarded as being 
an extinct form, with an hexamerous perigon of equal 
petals, and six stamens. A still living form, Iris falci- 
folia, possesses such a perigon but has only three stamens. 

The reader who is interested in this branch of in- 
quiry and in the highly important results which it has 
afforded, is referred to the works of this author for 
further information. 

I now return to the main question, viz., that of phys- 
iological atavism. Here we are concerned not with the 
production of new forms but with an inquiry into the 
processes which underlie the reappearance of preexisting 
characters. The character in question is, therefore, one 
that is still retained in that species from which the one 
under investigation is descended. Atavism is in this 
case to be regarded as an oscillation between two empir- 
ically known extremes. The field of oscillation can ob- 
viously not be very considerable, for only in cases of very 
close relationship is the common origin of two forms 
historically known to us. 

In this restricted province also, atavism may be 
brought about by fluctuating variation as well as by muta- 
tion. In the case of the former it is merely a transitory 
phenomenon and dependent on external conditions; but 
in the second case it leads to the origin of a race which 
externally resembles the ancestors of its parent form. 
Variational atavism seems to be a phenomenon which 
plays a large part in the sphere of semi-latent characters. 
As an example of this I cite the case, described above, 
of the five leaved clover ( 5, p. 36) which always bears 
a certain number of trifoliate leaves especially under 
unfavorable conditions. These trifoliate leaves obviously 



Atavism by Seeds and Buds. 



109 



constitute a reversion to the normal clover leaf but, on 
the other hand, they are merely the extreme variants in 
the curve of the five-leaved 
race (Fig. 6, p. 48). A 
similar state of affairs pre- 
vails in numerous cases of 
semilatency where the range 
of variation of a character 
is occasioned by the antag- 
onism of two characters. 

Mutational atavism must 
obviously be as rare as mu- 
tation itself. The reversion 
of striped flowers to self- 
colored ones, the heritable 
atavism of Plantago lanceo- 
lata ramosa, and the incon- 
stancy of the peloric Lina- 
ria, are facts which we shall 
have to consider below. 

Physiological atavism 
can be manifested by plants 
propagated by seeds or by 
buds. In the case of the 
former definite proof is 
only possible under excep- 
tionally favorable circum- 
stances; in the case of the Fi f } 6 - .Cephalotaxus pedunculata 

fastigiata. The mam stem bears 

latter it is at once evident the upright branches with leaves 
/T-" 1^- A \ '-ni 1 inserted on all sides, character- 

ing. 16 at A). ihe pub- istic O f the var iety; but has pro- 

lished records of atavism uced at A, where a branch has 

been cut off close, several 

in crops of seedlings are branches with flat spreading bi- 

1 i 1 serial leaves such as are char- 

always subject to the StlS- acte ristic of the parent species. 




110 Atarisni. 

picions indicated above. I mean that they occur so rarely 
and in so few individuals that the possibility of a previous 
cross, by means of insects, with the pollen of allied forms, 
even if growing a long way off, can never be quite ex- 
cluded. It is only in cases in which, as in that of Ociw- 
tlicra sciutiUaiis (Vol. I, pp. 245 and 377), a species pro- 
duces a large number of atavistic individuals every year, 
that the phenomenon easily lends itself to experimental 
study. 

On account of the circumstances indicated, it is not 
possible to say whether atavism in plants propagated by 
seed is a common or a rare phenomenon. It is certainly 
much rarer than the practical gardener usually imagines. 
I have observed in my cultures a number of cases which 
might have been called atavistic with more or less cer- 
tainty, but only the cases of regularly inconstant races, 
such as those of Plantago and Linaria, and the phenom- 
ena presented by striped flowers, to be described shortly, 
seem to me to be sufficiently well established to be ad- 
duced as instances of atavism. 

Atavism by bud-variation, on the other hand, is a 
well-known phenomenon. One of the best instances is 
shown in Fig. 16. It represents a vertical branch of a 
bush of Ccphalota.rus pedunculata fastigiata (Podocarpus 
Koraiana Hort}. Below the middle of the figure can 
be seen the place where a branch has been cut off, and 
from the side of its base some lateral branches have arisen 
with flat spreading leaves (Fig. 16 A). 1 The variety 
Fastigiata has erect branches only and their leaves are 
inserted on all sides ; but the branches at A have the 
structure of the parent species, C. pedunculata ; their 

1 For a series of interesting experiments relating to this subject 
see Mutations ct traumatismcs by L. BLARINGHEM (Note of 1909). 



Atavism by Seeds and Buds. Ill 

leaves project to right and left, and their side branches 
are horizontal, making the whole shoot flat with definite 
dorsal and ventral surfaces. The bush which grows in 
our garden and bears several branches with similar bud- 
variations, I owe to the kindness of MESSRS. ZOCHER & 
Co., nurserymen in Haarlem. The variety can only be 
propagated by cuttings, as it never flowers, 1 and these 
produce reversions of this kind pretty regularly, both in 
the nursery of Messrs. ZOCHER & Co. and elsewhere. It 
appears to have been first observed in 1863 by CARRIERS 
in Paris, 2 and since that time by many others. This re- 
markable case is well worthy of a closer study. The 
perfectly analogous Ta.rus baccata fastigiata never ex- 
hibits atavism by bud-variations, so far as I know. 3 

The phenomena of bud-variation have hitherto not 
received from botanists the attention they deserve. In 
a few cases we know that the phenomenon is preceded by 
a s-ectorial segregation, as for instance in striped flowers 
(13) and variegated leaves ( 24) ; but as a rule there 
is no available information even on this point. Another 
point which awaits investigation is the nature of the 
offspring of self -pollinated bud-variants. 4 It seems cer- 
tain that new types sometimes arise in this way, but much 
of the proof in favor of this will not bear scrutiny. Under 
these circumstances it seems desirable to direct more gen- 
eral attention to this phenomenon 5 by means of some 

'BEISSNER, Handbuch, loc. cit., p. 181. 

2 CARRIERE, loc. cit., p. 44, with Figs, i and 2; see also CARRIERS, 
Traitc general dcs Conifcres, p. 717; and JAMES VEITCH & SONS, 
A Manual of the Conifcrae, iSSi, p. 308. 

3 See CARRIERE, loc. cit., and BEISSNER, Hand-buck, loc. cit., p. 169. 

4 In the older records attention is seldom paid to pollination ; 
see the literature in CARRIERE, loc. cit., p. 59, and DARWIN, Animals 
and Plants, I, 525; II, 442, etc. 

5 CARRIERE gives a very complete list ; he. cit., pp. 42-56 ; see also 



112 Atavism. 

further examples. They are taken mainly from woody 
plants because herbaceous and especially annual plants, 
with the exception of the instances named and of hybrids, 
very seldom exhibit bud-variations. 

Green branches on red-leaved bushes and trees are 
not rare and are for instance often seen in the variety 
atropurpiirca of Corylus Avellana, C. tiibulosa, Betula 
alba, and in the copper beech. The red bananas with their 
red fruits have given rise to a green variety with yellow 
fruit in spite of the fact that they are sterile. 1 BRAUN 
mentions an example of Kerria japonica plena which pro- 
duced some branches with single flowers. 2 On a garden 
Hortensia producing only large sterile flowers, FOCKE 
observed a branch bearing inflorescences with little fertile 
flowers in the middle of a circle of large ornamental ones 
as in the wild form. 3 

Trees with laciniate leaves habitually give rise to re- 
versions on solitary branches, as for instance Fagus syl- 
vatica aspleniifolia, Carpinus Betulns hetcrophylla, Sam- 
bucus nigra laciniata, Cytisus Laburnum quercifolia, Vitis 
and others. (BRAUN, loc. cit.) The same is true of 
Sali.r babylonica crispa, of the parsley grape, of nec- 
tarines, and especially of roses and bulbs (Hyacinthus, 
Gladiolus, etc.) although the possibility of previous crosses 
makes the latter cases still doubtful. 

In conclusion, this list shows that the series of cases 
which are amenable to experimental study is by no means 
small. On the other hand the number of examples is 
sufficient to demonstrate the pretty general occurrence 

HOFFMANN, Bot. Zeitung, 1881, p. 395; DARWIN, loc. cit., I, pp. 476- 
530; HOFMEISTER, Allgemcine Morphologic, p. 560, etc. 

1 FR. MULLER, Flora, Vol. 84, 1897, pp. 96-99. 

*Abh. d. k. Akad. Berlin, 1859, p. 219. 

3 Abh. d. Naturf. Vere'ms Bremen, Vol. 14, 1897, p. 276. 



The Oriyin of Striped Flozvcrs. 



113 



of reversion of varieties to their parent species, and there- 
fore to suggest that the characters of the latter were not 
lost when the variety originated, but only became latent. 

13. VILMORIN'S SUGGESTION AS TO THE ORIGIN OF 

STRIPED FLOWERS. 

One of the oldest and best-known instances both of 
bud - variations and of 
sectorial splitting is af- 
forded by certain so- 
called variegated garden 
flowers and particularly 
by the annual Larkspurs, 
Delphinium Ajacis and 
D. Consolida. All phases 
of the phenomenon can 
be followed in this case 
with great ease, for from 
time immemorial these 
varieties have borne 
flowers which show the 
most varied striping on 
a background of a dif- 
ferent color; and they 
also produce flowers a 
half or a third or some 
other fraction of which 
uniformly bears the color 
which commonly only 
appears in stripes (Fig. 

19). Flowers of this Fig. 17. Delphinium Consolida stria- 
i i , turn plenum. A plant in flower. 

kind may be scattered 

over the whole plant, but are oftener distributed in such 




114 



Atavism. 



a way that those on one side of a spike are uniform and 
those on the other striped. 1 Flowers which are inserted 
at the boundaries of the two regions exhibit on one side 
the color of one sector and on the other half, the stripes 
of the other. A diagram of such a branch is shown in 
Fig. 18 in which the flowers Nos. 1, 4, 6, 9, and 11 are 
dark blue, Nos. 2, 5, 7, 10, 12, and 13 pale red with scat- 





Fig. 18. Delphinium Consolida stria- 
turn plenum. Diagram of a branch 
of which the left half was blue, 
and of which the right bore flowers 
with fine blue stripes on a pale red 
background. 1899. 



Fig. 19. A sectorial flower 
of the same variety. The 
whole right half was dark 
blue ; the left, pale red 
with scattered blue stripes. 



tered blue stripes, and Nos. 3 and 8 half blue and half 
striped. I obtained this branch in my culture of 1899; 
similar cases are not at all rare. Branches with nothing 
but blue flowers also occur, but the seeds obtained from 
the self-fertilization of such flowers gave rise in my gar- 
den to the striped variety and not to a pure blue progeny. 

1 Exactly the same phenomenon is seen in the seedcoats of Pi sum. 
The minute purple spotting characteristic of some green-skinned 
varieties sometimes takes the form of a deep uniform purple. These 
uniformly purple seeds produce the ordinary form with small purple 
spots and no more full purples than are usually produced. (Trans- 
lator's Note.") 



The Oriyin of Striped Flowers. 115 

On the other hand a certain percentage (often 6% and 
more) of the plants raised from the seeds of striped 
flowers and especially of sectorial branches are usually 
uniform blues. 1 

The phenomena of segregation which we have been 
describing are quite common in striped flowers, and any 
one can observe them in Dahlia varidbilis striata (Vol. 
I, Fig. 14, p. 54), Mirabilis Jala pa, Verbena and many 
other favorite garden flowers. Sectorially colored flow- 
ers appear to manifest a tendency towards a simple pro- 
portion between the two parts. Frequently exactly half 
of the flower is atavistic, sometimes a quarter or three 
quarters. I observed the proportion % in white and red 
striped tulips and in partially dark blue and partially pale 
blue flowers of Iris xiphioides, etc. In these cases the 
various types frequently occur on the same plant, or in 
the case of plants grown from bulbs, on examples raised 
through vegetative propagation from a single original 
bulb; for instance on the tulips and Iris just mentioned 
there were also flowers of which one-half of each was 
atavistic. 

Sectorial variability often occurred in my cultures, 
as for instance in the flowerheads of Helichr\suin brac- 
teatiun and the flowers of Papaver nudicaide (Fig. 20), 
in both of which cases stripes or sectors of the color 
belonging to the parent species were superimposed on 
the paler background of the variety. A common balsam 
(Impatiens Balsam ina') whose flowers were usually white 
with fine red stripes bore a branch with red flowers only 
in my garden. The whole breadth of the fasciated stem 

1 A point of great interest to investigate would be the relation 
between sectorial variability and cell division in the vegetation cone ; 
clues which might lead to the solution of many important questions 
would probably be afforded by such an inquiry. 



116 



Atavism. 



of the striped cockscomb or Celosia variegata cristata, 
is traversed by longitudinal stripes of different colors, 
yellow and red according to the variety. Dahlias how- 
ever exhibit the most prodigal wealth of color of all 
variegated flowers, especially those varieties known as 
Fancy-flowers. 1 In this case the color is in some way 
connected with the amount of doubling, which often ex- 
hibits sectorial variations and bud-variations at the same 

time. 2 Striped Dahlias 
give rise to these partial 
variants sometimes very 
rarely, but sometimes in 
such abundance that a 
good variety is often ex- 
posed to the danger of 
being lost thereby. In 
most of the cases we have 
to do with two types which 
are manifested in various 
degrees of association and 
separation. Cases in which 
more than two forms are 
combined and which there- 
fore may produce by bud- 




Fig. 20. Papaver nudicaule. Yel- 
low variety with dark orange 
stripes. 



variation two or more 
types on the same plant, 
besides the normal one, 
have been described; but they were probably hybrids. 
Central dissociation seems to be a very rare phenomenon, 
but of Mad. H. Vonrchy, a variety which usually has 

1 See GROOMBRIDGE'S Treatises on Florist's Flowers; The Dahlia, 
1853, and the extensive literature which has appeared since. 

2 VILMORIN-ANDRIEUX, Les fteurs de pleine terre, first edition, p. 
340. 



The Origin of Striped Flowers. 117 

white flowers with red stripes, I have seen a head whose 
outer ray florets were dark red whilst the inner ones 
formed a disc of pure white with only very occasional 
red stripes. In the center the unmodified fertile yellow 
disc florets were seen. I have observed the same phe- 
nomenon in a few other 'cases. 

The striped varieties of Cyclamen persicum are said 
to bear in some instances only variegated flowers one 
year and from the same bulb uniformly colored atavistic 
flowers the next year. 

Centaurea Cyanns, the blue corn flower or blue bottle, 
has a brown variety with double flowerheads which is 

/ 

highly variable in color; it is far from being fixed yet, 
as a plantbreeder in Erfurt expressed it to me. I culti- 
vated it for five years, always selecting the purest and 
darkest brown specimens in small numbers as seed- 
parents. The race produced reversions to the blue form 
every year. Some plants bore blue flowers exclusively, in 
others the blue color appeared in segments or in stripes 
on some of the heads. No advance was brought about 
by this selection. 

The examples given must suffice to show the impor- 
tance of the striped flowers of horticulture. A Var. 
striata of a number of species is advertised in the cata- 
logues ; it is open to any one, therefore, to cultivate them. 
The Var. alba of many other species often reveals on 
closer inspection scattered stripes of the color of the 
parent species; these stripes can easily be intensified by 
isolation and selection as I shall show in one of the 
following sections ( 16). 

Str-iped flowers 1 are also of great importance in the 

1 Spotted flowers may possibly behave differently ; but up to the 
present time I have not grown them. 



118 Atai'isjn. 

science of variability and mutability, and especially in that 
of atavism of which they perhaps afford the most beauti- 
ful examples. As such they have been dealt with espe- 
cially by Louis VILMORIN whose theory we will now pro- 
ceed to examine. 1 

VILMORIN starts from the observation that striped 
flowers only occur on those species which are themselves 
colored, but which also possess a white variety; or if the 
color of the flower is composed of red and yellow the 
uniform yellow variety may behave like the white (Mira- 
bil'iSf Antirrhinum). The first variety to arise is the 
white (or yellow) from which later on the striped form 
originates and VILMORIN explains this as a partial re- 
version to the parent species. 

White varieties of a large number of decorative plants 
have arisen in cultivation, and in fact many favorite ones 
in M. VILMORIN'S own nurseries. They can usually be 
easily "fixed" in the course of a few years ; that is to 
say, they are generally constant from the very beginning 
but have to be purged of the consequences of unavoidable 
crosses, and this takes a few years, as a rule. The striped 
sorts do not appear in this period, the hybrids resulting 
from the crosses are like the parent species and segregate 
into this and the pure white variety. The striping is not 
the result of crossing therefore ; moreover in such cases 
deliberate crossing has only resulted in the production 
of self-colored and not of variegated flowers. Also, 
when such hybrids exhibit sectorial variation, the color 
is in large patches and not in fine stripes. 

It is not until the white varieties have attained com- 
plete purity and have proved constant for a considerable 

1 Societe Pliilomatiqiic dc Paris, Seance du 17 Janvier, 1852, Pro- 
ccs-verbaux, p. 9; Notices sur I' amelioration des plantes par le semis, 
1886, p. 39; and B. VERLOT, Sur la fixation des varietes, 1865, pp. 62-66. 



The Origin of Striped Flowers. 



119 



number of generations that the striping appears. It af- 
fects almost necessarily, so it seems, every cultivated 
white or yellow variety. Some are worth putting on the 
market ; others are not. Amongst the latter VILMORIN 
( 1852) has mentioned as an example Clarkia pnlchella, 
from bought seeds of the white variety of which the 
striped form has also appeared in my cultures (see 16). 
The same thing happened with Browallia erecta and Coiu- 
melina tuberosa. Geranium pratense is only to be bought 
in two forms, white and blue. I ob- 
tained seeds from two plants which 
were bought as Var. alba and raised 
from them, besides pure whites, 
plants with all grades of color ar- 
rangement from striping and secto- 
rial variations to complete blue (Fig. 
21). 

If it is thought desirable to put 
the striped variety on the market it 
must be purified by selection. The 

striping first appears as single fine 

i -in TC Fig- 21. Geranium fira- 

streaks on occasional flowers. It tc ,i sc cl!bum with pie _ 

these plants are isolated and their 

seeds sown separately the majority 

of the plants raised are pure white, 

but occasional ones are produced 

with broader and more numerous stripes. The seeds of 

these are saved, and so on. The object is to isolate the 

striped race from the white, and this can be attained in 

the course of a few years. On the other hand the breeder 

has to fight against the tendency of the striped form to 

return to the full blue either by buds or through seeds. 

It is to guard against this that VILMORIN recommends 




bald bine and white 
flowers. The dark 
parts of the petals 
were blue ; the others 
white. 



120 Atavism. 

the selection of seeds from the palest examples of the 
striped forms. 

Convolvulus tricolor was the first species in which 
this mode of origin of the striped form was observed 
(1840). It was followed by Gomphrena globosa, Antir- 
rhinum ma jus album and luteum, Ncmophila insignis, Por- 
tulacca grandiflora, and others. Of recent years a large 
number of blotched varieties have been obtained in vari- 
ous nurseries; and always, so far as is known, in the 
same way, by so-called partial reversion of a white or 
yellow variety to the red or blue color of the parent 
species. 

In the following sections we will therefore examine 
in detail some cases of striped flowers as instances of 
physiological atavism. 

14. ANTIRRHINUM MAJUS STRIATUM. 
(With Plate I.) 

Amongst the numerous cultivated varieties of the 
Snapdragon one group is distinguished by the possession 
of striped flowers. A bed of these produces a fine and 
varied show of color. On the other hand the horticul- 
turist's handbooks state that, whilst the remaining sorts 
are practically constant, the striped ones leave much to be 
desired in this respect. 1 Such a statement naturally in- 
vites the investigator to inquire into the mode of inheri- 
tance of this character. 

The striped varieties owe their character to the fact 
that the normal red color of the wild snapdragon is con- 
fined to broader or narrower longitudinal stripes. Where 
the red is absent the pure color of the background be- 
comes visible. This may be either white, rose, yellow 

^ILMORIN'S Blumengartnerei, 3d Ger. ed., Vol. I, 1896, p. 756. 



Antirrhinum Ma jus Striatum. 121 

or sulphur as in the corresponding self-colored varieties. 1 
It must further be mentioned that each of these types 
may exist in a tall, medium or dwarf form. In the ex- 
periment to be described the form I have used was 
Antirrhinum majns lutcum rubro-striatum of medium 

height. 

The richness of types of marking in these striped 
varieties is very great. The stripes may be sparse and 
very fine so that the flowers appear at first glance to be 
pure yellow or white; or the stripes may be bold and 
broad and very numerous in such a way that the yellow 
(or the white) appears in about equal parts with the red. 
Often half of a flower is entirely red whilst the other 
half is striped, and so on. 2 

If we buy seeds of the striped sorts and sow them, 
the crop raised is considerably less true than is usual in 
sowings of bought seeds. In 1899 I sowed samples of 
different varieties of Antirrhinum ma jus and obtained 
26% unstriped individuals from A. in. album rubro- 
striatnm, and \9% from A. m. tut cum rubro-striatum. 
In other cases a far higher degree of purity is usually 
obtained, e. g., in A. m. hit cum I found only 2% im- 
purities. 

The admixtures in the striped varieties were in the 
vast majority of cases uniform reds and therefore closely 
allied to them. Other deviations were not more numer- 
ous in the striped forms than in any other variety. The 
reason for the abundance of the red flowered individuals 
has been disclosed by subsequent culture ; it is to be 
sought in the incomplete inheritance of the striped char- 

1 A. m. album rubro-striatum, A. m. sulphureum rubro-venosum, 
A. m. pumilum roscum rubro-striatum, etc. 

2 ViLMORiN, Flcurs dc plclnc tcrrc, p. 723. 



122 Atavism. 

acter. For if the seeds of striped individuals which have 
been artificially self-fertilized are harvested and sown, 
we usually obtain some plants with uniformly red flowers. 

The striped varieties therefore give rise to red plants 
from time to time, and in my cultures, which extend over 
about eight years, A. m. Intciim rubro-striatum has done 
so almost every year in spite of being self-fertilized. 
As the original wild form is uniformly colored (that is, 
not striped, for the color itself is composed of white, 
red and yellow) the loss of the striping may be regarded 
as a case of atavism. 

Moreover this phenomenon of atavism was exhibited 
by my cultures in two other forms (Plate I) : on the one 
hand as a bud-variation in which whole branches of a 
plant with striped flowers revert to the red type; on the 
other hand as a lateral or sectorial variation, to adopt 
HEINSIUS'S term, 1 in which one side of the spike bears 
uniform flowers, whilst the other bears striped ones. 
Let us examine these two cases more closely. 

In the case of bud-variation a striped plant bears a 
branch all of whose flowers are red, without striping. 
If, as is usually the case, the plant flowers on 6-8 or 
more lateral branches the abnormality is very striking. 
A single plant very seldom bears two branches with red 
flowers, and it scarcely ever happens, if indeed it ever 
does, that the terminal portion of the main stem has red, 
and the branches striped flowers. As a rule it is one of 
the lower stronger branches which is atavistic and seldom 
one of the higher weaker ones. I occasionally found a 
tertiary branch with red flowers, i. e., a lateral twig of 
a striped branch. As might be expected, the coarsely 

1 H, W. HEINSIUS, Over bonte bladercn, Genootschap v. Natmir-, 
Genees- en Heelkunde, Biologische Sectie, May, 7, 1898, p. 2. 



Antirrhinum Mo jus Striatum. 123 

striped plants exhibit a stronger tendency to produce 
bud-variations than the finely striped ones. 

Sectorial variation is very diverse in the manner of 
its manifestation. I found it as a rule on the main stem, 
but also on the branches. If the inflorescence is looked 
at from above, i. e., in projection, one sector is red whilst 
the rest is white. This red sector often consists of a 
narrow red stripe only, or of one-half or three-quarters 
of the whole. As a rule the abnormality extends from 
the base to the top of the spike ; but it may also be con- 
fined to part of it, especially when it consists of a narrow 
line only. A single red flower on an otherwise striped 
spike is by no means a rare occurrence. On the borders 
of the two sectors the flowers are often striped on one 
side and red on the other. As in the case of bud-varia- 
tions it is the coarsely striped individuals which are most 
prone to the sectorial dissociation of color. 

The red color occurs not only on the corolla but also 
on the stamens. In finely striped flowers the stamens 
are, as a rule, yellow ; in flowers with broad stripes they 
are striped or red. The individual stamens in the same 
flower are usually dissimilar in respect to this character; 
yet it is difficult to find a strong contrast within a single 
flower, e. g., a single stamen which is almost red, and 
another nearly yellow. I have spent much trouble in 
the attempt to find such flowers, especially in those that 
had one longitudinal half almost or entirely without 
stripes. But I did not discover any definite relation 
between the striping on the stamens and that on the 
corresponding parts of the corolla. 

As a matter of fact pure yellow flowers never occur in 
this race. To a superficial observer it may seem as if 
they were not rare and even that the red stripes may 



124 Atavism. 

be lacking on whole spikes and sometimes on entire 
plants. But such absence is only apparent; closer in- 
spection will reveal the existence of very fine red stripes. 
I never found a branch on which they were quite lacking, 
nor a plant, nor even a twig which had reverted to the 
variety, A. m. hit cum. On inflorescences on which the 
striping is very meager it may sometimes occur that on 
a single flower no stripes can be found ; but this is merely 
an extreme case of that partial variability which all 
organisms exhibit. 

This negative result based on eight years' experience 
is important because it shows us that we are not dealing 
here with a segregation into two components, e. g., A. 
ma jus rubrum and A. ma jus hit cum. If we want to speak 
of a segregation the two units would be the red striped 
and the uniformly red form. 

A glance at a bed of these plants is sufficient to re- 
veal the fact that the breadth of the red stripes exhibits 
individual variability; moreover that, as might be ex- 
pected, plants with very fine and those with very coarse 
red stripes are the rarest. In 1897 I tried to find out if 
it were possible to express this variability in the form of 
a curve. At first it seemed impossible to obtain an ac- 
curate measure of the striping, for it seemed practically 
unfeasible to determine the sum of the breadths of all the 
stripes in a flower and to express this sum in proportion 
to the circumference of the corolla. I succeeded, how- 
ever, in attaining my object in the following way : I had 
the average flower on the main stem of every plant in a 
bed picked by an assistant, and then I endeavored to ar- 
range these in a series according to their color, ascending 
from the almost yellow to the completely red. With a 
group of between one and two hundred flowers this sue- 



Antirrhinum Ma jus Striatnm. 



125 



ceeded better than I had anticipated ; for at the end there 
turned up a certain number of groups which corresponded 
sufficiently closely to equal subdivisions of a scale to 
warrant their selection as ordinates. I admit of course 
that this method is not free from the personal factor; 
but for the case under consideration it sufficed, since, 
when the same group of flowers was sorted again, the 
result agreed sufficiently well with the first trial. 

I plotted three curves in this way in 1897; each was 
based on one typical flower of the terminal spikes of all 
the plants flowering on a bed. The three beds contained 
the offspring of three individual striped plants of the 
1894 harvest, seeds of which had been saved and sown 
separately; but whose flowers had been left to be polli- 
nated by insects in the midst of a larger culture. More- 
over the seed-parents were selected without reference 
to the degree of their striping, and so the curves give an 
idea of the average composition of the commercial race, 

I thus obtained the following table : 



STRIPES 


COLOR-EFFECT 


A 


B 


C 


Almost absent 


Lemon yellow (g) 





6 


4 


Very fine 


Yellow 





9 


18 


Narrow 


Dark yellow 


2 


12 


30 


1-2 mm broad 


Reddish yellow 


5 


15 


53 


1-3 mm broad 


Narrowly striped (s) 


18 


22 


84 


1-5 mm broad 


Coarsely striped 


28 


22 


31 


1-6 mm broad 


Broadly striped (b) 


42 


21 


16 


Broad fields 


Half yellow, half red 


26 


12 


10 


Uniform red 


Red (R) 


37 


9 


15 




Number of individuals 


158 


128 


261 



These figures are exhibited in the form of a curve in 
Fig. 22; in the case of the figures under C the scale or 
unit of the ordinates is half of that selected for A and B. 



126 Atavism. 

The result of this inquiry shows that the first eight 
groups merge continuously into one another ; but that 
between the striped and red flowers a broad gulf is fixed. 
The red are not connected with the striped by a series 
of transitional forms as the lemon yellow are with the 
broad striped ; red flowers with small yellow patches may 
occur, but they are at most very rare. 

The shape of the curves is far more regular than I 
had anticipated; but the reds obviously have no place 
in it; I mean, they are far too numerous in proportion. 
They are therefore obviously not the extreme variants 
of the series but constitute a group which is perfectly 
distinct from the striped although the size of this group 
varies directly with the amount of striping in the other. 

After the composition of the commercial race had 
been determined in this way, my next task was to dis- 
cover the nature of the offspring resulting from the self- 
fertilization of the individual components of this diverse 
assemblage. I have confined the solution of this problem 
to the three chief types : finely striped, coarsely striped, 
and uniformly red. Let us begin with the two former 
groups. 

The offspring of the parent plant A (Fig. 22 and table 
on page 125) contained many coarsely striped individ- 
uals (Fig. 22b} ; when they were in flower I transplanted 
some very coarsely striped ones to a special bed, picked 
off all their flowers and young fruits and enclosed all 
the buds which subsequently opened to insure self-fertili- 
zation. In the same way I treated some plants from the 
bed B (Fig. 22B) with almost yellow flowers. I har- 
vested and sowed the seeds of each plant separately. 

In August, 1898, when the beds were in full flower, 
T determined the amount of striping by the method al- 



Antirrhinum Majus Striatum. 



127 



ready employed, taking care that the boundaries between 
the individual groups corresponded as closely as pos- 
sible with those of the previous year. I succeeded in 




c 

I 

.'/. ft. b. 

Fig. 22. Antirrhinum inajus hiteum rubro-striatum. A, B, 
C, curves showing the degree of striping amongst the 
offspring of three insect-fertilized plants, 1897. g< lemon 
yellow, almost without red stripes; s, narrowly striped; 
b, broadly striped; R, uniform red. See table, page 125. 

recording the rather scanty offspring of four coarsely 
striped parents. The result is given below. (The indi- 
vidual seed-parents of 1897 are denoted as Ai--A4.) 

OFFSPRING OF THE COARSELY STRIPED SEED-PARENTS. 

Stripes 

Less than 4 mm broad 
1-5 mm broad 
1-6 mm broad 
Broad fields 
Uniform red 



AI 


A z 


A 3 


A* 


Totals 

















3 


2 


6 


8 


19 


5 


4 


6 


9 


24 


7 


8 


5 


6 


26 


2 





2 


5 


9 



Totals 17 



14 



19 



28 



78 



These figures are exhibited graphically in Fig. 23B. 

As the extent of this experiment was relatively small 
and especially as the proportion of self-colored plants 
appeared to me very small, I repeated it in the following 
year. I chose from the broad striped bed of this culture 



128 Atavism. 

a beautiful typical plant with broad stripes but without 
any broad patches on the corolla, and fertilized it with 
its own pollen in a bag. In 1899 I raised from its seeds 
about 250 plants, which covered a bed of about four 
square meters, and nearly all of which flowered on the 
main stem and on several lateral branches. There were 
only a few finely striped individuals amongst them, 
whereas the majority were very coarsely marked. But 
the proportion of uniformly red plants was considerable: 

Striped individuals 160 64% 
Red individuals 91 36% 



Total 251 

That is to say, about one-third of the olants had re- 
verted to a uniform red color. 

The offspring of the almost yellow parents showed 
the following distribution of the various types of colora- 
tion (Bi--B4 refer to the individual seed-parents and to 
the groups of offspring arising from them) : 

OFFSPRING OF THE YELLOW PARENTS. 



Stripes 


BI 


B 2 


B* 


4 


Totals 


Nearly absent 


6 


5 


12 


1 


24 


Very fine 


3 


7 


18 


2 


30 


Narrow 


3 


6 


12 


2 


23 


1-2 mm broad 


9 


7 


18 


3 


37 


1-3 mm broad 


7 


4 


22 


2 


35 


1-5 mm broad 








3 


1 


4 


1-6 mm broad 

















Broad fields 

















Uniform red 

















Totals 


28 


29 


85 


11 


153 



See Fig. 23A. 

These tables, and Fig. 23 which has been constructed 
from them, show that two races have been produced by 
the selection and self-fertilization of the extreme variants. 



Antirrhinum Majns Striatitin. 



129 



One of them, A, consists almost solely of finely striped 
individuals and contains no red ones. The other, B, 
consists almost entirely of broadly striped ones together 
with 11-36% of uniformly red ones. But the separation 
is not nearly so sharp as between the striped on the one 
hand and the red on the other, inasmuch as the two 
curves overlap. 




Fig. 23. Antirrhinum majus hitcum rubro-striatum. Curves 
to illustrate the distribution of color amongst the off- 
spring of self-fertilized individuals from the culture on 
which Fig. 22 is based. Experiment in selection with 
broadly and narrowly striped flowers. Curves represent- 
ing the offspring: A, of the finely striped seed-parents 
Bi_B 4 ; B, of the broadly striped seed-parents Ai_A 4 . 
See tables on pp. 127 and 128. For the signification of 
g, Sj b, R, see previous figure. 

We now come to the most important part of the ex- 
periment, the question of the inheritance of the red 
character. On account of this greater importance I had 
already given it previously much attention. 

Here we are concerned not merely with the inheri- 
tance of the red flowers in general, but with the study 
of the special cases already distinguished. First we have 
to consider the red seed variants, then the bud-variants 
and lastly the single red flowers on striped racemes. 
Finally it should be possible to test the red stamens of 



130 Atavism. 

striped flowers but I have not yet come across suitable 
material for the investigation of this point. 

In 1892 I had raised from bought seed of A. ma jus 
liiteum rubro-striatiun a large bed of plants the flowers 
of which were all striped. I gathered the seed of one 
individual for the next year's crop (1893). I obtained 
about 40 flowering plants in this way; the majority bore 
flowers with fine stripes, and here and there flowers 
occurred of which one-half was a uniform red. There 
were four plants which only bore pure red flowers. Of 
these I selected the strongest, enclosed their spikes in 
bags and fertilized their flowers with their own pollen. 
Besides these I dealt in the same way with two striped 
plants, with few and fine stripes. 

As soon as the seeds germinated in the following 
spring a difference became visible : the seedlings from the 
seed of striped plants had green foliage, those from the 
red, however, were reddish brown. This difference was 
particularly striking on the under surface of the later 
leaves of the young plants. On the former bed 152 plants 
flowered, on the latter 71. Both groups consisted of 
plants with striped flowers and plants with red ones, but 
as I had expected, in very different proportions. The 
proportions in the offspring from the two types of parents 
were as follows : 

STRIPED RED 

Finely striped parents 98% 2% 

Red flowered parents 24% 76% 

Most of the striped flowerr were finely striped 
coarsely striped plants only occurred in the proportions 
of 6 and 7%. 

The characters of both races are therefore heritable 
but, so to speak, incompletely so. We may describe the 



Antirrhinum Majus Striatum. 131 

production of individuals of the opposite race in both 
cases as atavism. The striped offspring of the red parents 
resemble their grandparents. The red offspring of the 
striped parents resemble the wild species, that is, their 
very remote ancestors. Thus the difference in the in- 
tensity of inheritance could be expressed in the state- 
ment that the influence of the nearer ancestors is greater 
than that of the remoter ones. But this is merely a re- 
statement of the facts in conventional terminology. It 
affords no clue to the solution of the problem. 

Amongst the finely striped individuals in the culture 
under consideration there were thirteen plants which had, 
besides the striped terminal portion of the main stem 
and the several striped lateral branches, one or two twigs 
with red flowers exclusively. A good opportunity was 
thus offered of studying inheritance in bud-variants. I 
owed it to the fact that the seeds had been sown early, 
the plants had been grown far apart and the ground 
well manured ; circumstances which together brought 
about a profuse branching in all the plants. I trans- 
planted these individuals to a separate spot, picked off 
all the open flowers and young fruits and superfluous 
twigs, and enclosed 1-2 striped and 1-2 red spikes in 
bags to insure pure self-fertilization. 

PERCENTAGES 

Plant No. Red Striped Totals Red Striped 

From the red } 
spikes I 



1 


73 


27 


100 


73 


27 


2 


21 


12 


33 


63 


37 


3 


25 


5 


30 


77 


23 


1 


3 


93 


96 


4 


96 


2 





75 


75 





100 


3 


1 


36 


37 


3 


97 



From the striped 
spikes I 

I obtained a sufficient harvest of the striped and red 
spikes of the same plant from three individuals only. 



132 



Atavism. 



These produced in the summer of 1895 the result shown 
in the table on page 131. 

In other words, the average intensity of inheritance 
for striped spikes was 98% and for red ones 71%. 

If we compare these figures with those derived from 
the previous generation we do not observe any appre- 
ciable difference between them. In other words, the in- 
tensity of inheritance exhibited by the red bud-variants 
is essentially the same as that of the red seed-variants. 

In the following year I continued this experiment 
through one more generation by self-fertilizing some 
striped and some red individuals amongst the offspring 
of the bud-variants. The seeds of three striped parents 
gave rise to 67 offspring that flowered, only 5% of which 
were red ; the seeds of the five red seed-parents, however, 
gave rise to 127 offspring of which 84% were red. (The 
percentages in the five individual groups were 71-78-84- 
88 and 100.) Thus the proportions were similar to 
those of the previous year. 

ANTIRRHINUM MAJUS LUTEUM RUBRO-STRIATUM. 

SEED- AND BUD-VARIATION (ANNUAL CULTURES). 



Year 
1896 

(1895) 



95% Striped 
Striped plant 



84% Red. 

I 
Red plants 



1895 98% Striped 
(1894) Striped twigs 



71% Red. 

I 
Red twigs. 



1894 
1893 

1892 



98% Striped 
90 % Striped plants 



76% Red. 

I 
10% Red plants 



f 
Striped plant 



Antirrhinum Ma jus Striatiun. 133 

I have exhibited on the opposite page the whole ex- 
periment in the form of a pedigree. 

The result of our experiment can be given in yet 
another form. The intensity of inheritance in the finely 
striped spikes in successive generations produced by self- 
fertilization was always about 95-98%. The intensity 
of the inheritance of the red character in the various 
subdivisions of the experiment was as follows : 

1. For seed variants 76% 

2. For bud variants 71% 

3. For the offspring of bud variants . .84% 



Average 77 % 

Finally I have endeavored to investigate the mode 
of inheritance in the case of sectorial variation ; that is, 
of spikes which on one lateral part bear striped flowers 
and on the others red ones. It is obvious that this phe- 
nomenon may be due to two entirely different causes. 
First the red flowers may be genuine bud- variants and, 
in such cases, they will presumably exhibit an intensity 
of inheritance which corresponds with that found for 
the bud-variants dealt with above. But it may also hap- 
pen that on a very coarsely striped spike some of the 
flowers may possess this striping in so extreme a degree 
that they appear uniformly red. In this case their mode 
of inheritance will presumably not differ from that of the 
remaining flowers on the same spike. 

The latter was the case in the only experiment which 
I have so far had the opportunity of making. In the 
summer of 1898 I employed for this purpose a broadly 
striped plant from the crop referred to on page 128. One 
side of its terminal spike bore red and the other striped 
flowers. There were 8 of the former and 7 of the latter. 

I enclosed the whole branch, before it flowered, in 



134 Atavism. 

a bag, fertilized each flower with its own pollen, and 
gathered the seeds separately. Five fruits of each color 
ripened, though some of them contained little seed. I 
sowed the seed in 1899 on ten separate beds; they flow- 
ered in July. On each bed one saw at a glance that about 
half the plants bore exclusively red whereas the other, 
slightly larger half, bore striped flowers. I recorded the 
numbers separately for the ten groups ; but do not con- 
sider it necessary to give the separate numbers. There 
flowered : 

From the seeds of: Plants Reds Average 

1. Red flowers 67 33 %} 

2. Striped flowers 137 46% f 

* * * 

The result of all the experiments described above may 
be summarized in the following theses : 

1. Antirrhinum inajiis Intcnm rubro-striatum (Plate I) 
is an inconstant race consisting of striped and of red 
flowered plants. 

2. The striping of the commercial race varies con- 
tinuously, but the continuity does not include the red 
ones; these are separated by a gulf from the striped 
(Fig. 22). _ 

3. The intensity of inheritance of the finely striped 
plants is about 95-98%. They pass into the red type 
either when propagated by seeds or by buds. 

4. In the same way the broadly striped individuals 
produce many more reds ; the mean of three experiments 
(11-36-42) was about 30%. 

5. The red plants resemble the wild ancestral form 
externally but are not constant as this is. The intensity 
of inheritance of their character is only about 70-85% : 
and the remainder of their offspring revert to the striped 



Antirrhinum Ma jus Striatum. 135 

type. I have not yet observed this to happen by means 
of bud-variation. 

6. Antirrhinum ma/its lutciim does not arise from 
these striped and red races. 

7. If we compare the forms which we have been 
considering, 1 with the half races and middle races which 
we distinguished in 3, p. 18, we find that between the 
two constant elementary species (the systematic species, 
A. iiiajus and the systematic variety, A. majns luteum) 
there exist two intermediate forms which are perfectly 
distinct from these two, but not from one another. We 
can distinguish, 

o. The eversporting variety, A. ma jus luteum striatum, 
with striped flowers and a high degree of fluctuating 
variability, from which a faintly striped and a broadly 
striped race can be raised by selection. These three races 
however merge continuously into one another. 

b. The atavistic type in this race is uniformly red, but 
with incomplete inheritance and gives rise, when self- 
fertilized, in each generation to about 25% striped indi- 
viduals besides the red ones. 

In contrast with the previously described cases, the 
transition from the atavistic type to the eversporting 
variety and the reverse process here occur every year 
but always with a slight gap. The red type arises from 
the striped race by seeds and by buds, but the striped 
race has, hitherto, arisen from the atavistic type only by 

1 The mode of inheritance in the coarsely striped individuals will 
have to be more closely investigated ; so also must sectorial varia- 
tion. Moreover the experiment should be repeated with other striped 
varieties, and the spotted forms investigated to see if they behave in 
the same way. But it is most important that pure cultures of the 
various types should be made by breeding for several generations. 
For this purpose the tall varieties should be chosen preferably, since 
they promise a much better harvest than the half-dwarf ones which 
I employed in my experiment. 



136 



Atavism. 



seeds. The transition from the red to the striped oscil- 
lates round 25%, the transition from the striped to the 
red is largely dependent on the degree of striping, which 
points to the existence of factors as yet incompletely 
understood. 

It may perhaps be mentioned here in anticipation that 
the varieties of Hesperis and Clarkia (15 and 16) 
with striped flowers behave in the same way , whilst both 
in Plantago ( 17) and Linaria vulgar is peloria (20) 
the eversporting variety is inconstant and reverts more 
or less easily to the atavistic type. 



15. HESPERIS MATRONALIS. 

The flowers of the dame's violet are violet as the 
name indicates. There are three varieties on the market : 

a white flowered, a double, and a 
dwarf variety, all of which are con- 
stant so far as I know. A Forma 
lUacina and a "mixed" sort are of- 
fered in the catalogues. The plants 
are perennial; if the seed is sown in 
the spring, the majority of the plants 
will not flower until the following 
year; but if the seed is sown as soon 
as it ripens, or is allowed to fall on 
the ground instead of being harvested, 
the plants generally flower the next 
year. I have employed both of these methods at different 
times. 

I obtained my seeds in 1890 from a mixed group 
of white and violet flowered plants which were growing 
in our Botanical Garden. I grew them for two genera- 




Fig. 24. Hesperis 
matronalis. A flow- 
er of the pale finely 
striped form, with 
half of one of its 
petals dark violet. 



Hcsperis matronalis. 



137 



tions and found that the "white" were not pure white 
but pale lilac. Then I kept only plants of this variety 
through the winter, and first examined them in 1894, 
when they were in full flower. They flowered in isola- 
tion and partly pollinated themselves with their own 
pollen, partly were fertilized by insects. In later years 
also I have not enclosed this species in bags but have 
either grown them in an isolated position and left them to 
be pollinated by insects, or have had them flowering in 
a little greenhouse entirely built of fine metal gauze, 
where they fertilized themselves. 

My object was to test the degree of inheritance of the 
pale, the lilac, and the violet types separately. I shall 
first give a summary of my experiment. In this table, W 
denotes whitish, L lilac, and V violet (that is, the color 
of the wild species). The numbers in each case are per- 
centages of the particular culture ; where the culture was 
too small I have omitted the numbers. 

HESPERIS MATRONALIS. 
(WHITISH, LILAC, AND VIOLET IN PERCENTAGES.) 



1900, 1899 
annual and biennial 

1898 
annual 

1897 
annual 


38 W. 30 L. 32 V. 50 W. 28 L. 22 V. 

^ i i i 


92 
U 


W. 6 L. 2 V. 

j 


V. 


7 

' . 


1895 
annual and biennial 

1894 


29 

v 


W. 57 


L. 14 V 


I 


^ 



Before I come to the description of this experiment 
it is necessary to give some more details as to the varia- 
bility of the color of the flower. 



138 Atavism. 

Plants with pure white flowers such as those belong- 
ing to the variety Alba did not occur in my cultures. I 
have compared the Alba and also the Alba plena directly 
with my plants. Certainly the difference is sometimes 
very slight, especially as the petals of Alba acquire a pale 
lilac color when they fade. They are all gradations 
between the whitest examples and those with the full 
lilac color; the variability in this case is perfectly con- 
tinuous. But between the lilacs and the violets there is 
always a gap; the darkest lilacs seem to be about half as 
dark as the violets ; intermediate stages do not occur. 

The vast majority of the plants have all their petals 
of the same color, but mixed conditions also occur. As 
in other cases there are striped flowers, sectorial and bud- 
variations. Examples of these three groups appeared in 
various years in my cultures but only sparingly. On the 
striped petals the stripes were fine and rare, but they ex- 
hibited the dark violet hue of the original species. The 
instances of sectorial variation have so far been occa- 
sional dark flowers on pale clusters, and on the other 
hand flowers of which one-half of a petal was whitish and 
the other violet (Fig. 24). Bud-/variations occurred on 
plants with very pale flowers, especially when they were 
richly branched and flowered on into the autumn. They 
were always stray twigs on the lower part of the main 
stems ; their flowers were all of the normal violet color. 
But so far I have not been able to obtain seed from them. 

A glance at a large bed reveals the general distribu- 
tion of color. At once the pale flowers are seen to be 
in the majority, whereas the whitish on the one hand 
and the lilac on the other are obviously rarer. The violet 
stand out conspicuously because they are not connected 
with the rest by any gradations. Except for this the varia- 



is Matronalis. 139 



tion is so continuous that it is almost impossible to ex- 
press it in numbers. I have tried to arrange the plants in 
groups and to count the numbers of each group. And 
I give the numbers obtained in this way, only with the 
object of conveying to the reader the general impression 
which a bed makes on the observer, for it is inevitable 
that the limits between the groups should be somewhat 
arbitrary. Nevertheless I trust that I have succeeded 
in keeping fairly well the same limits between the groups 
during the successive years of my experiment, and this is 
the most important point. 

For the purposes of these color valuations I picked a 
flowering cluster, if possible the terminal one, from each 
of the plants on a bed, brought them to my house and 
sorted them there. I made out the following more or 
less clearly defined groups : 

W. Whitish, always without stripes. 

W\. Almost white; buds and withering petals 

almost white. 
77 7 2. White suffused with lilac, not darker when 

withering. 
JI 7 s- Very pale lilac; buds lilac; only slightly 

darker when withered. 
L. Lilac, sometimes striped or spotted. 

LI. Definitely lilac, although pale; darker than 

Ws. 

Lo. Lilac; half as dark as V. 
V. Violet, the color of the typical species. 

I shall now give the composition of the culture of 
1898 which was raised from the seeds of plants with 
whitish flowers. On July 14, I sorted 250 individuals 
by the method described and found : 



140 Atavism. 

HESPERIS FROM THE SEED OF WHITISH FLOWERED PLANTS. 

W 5% 



IV 2 


57% 


\ 92% W. 


W^ 


30% 


} 


LI 


4% 
2% 


I 6% L. 


V 


2% 


2% V. 



I determined the composition of the cultures of the 
next year, 1 899, in the same way ; they were both raised 
from the seeds of lilac plants. One of them (5th gen- 
eration) flowered partly in 1899 and partly in 1900; 
but the other only in 1899. The result was as follows: 

HESPERIS FROM THE SEEDS OF LILAC FLOWERED PLANTS. 

Color 1st Experiment (5th Gen.) 2d Experiment (3d Gen.) 
W^ 3% \ 4% \ 

W 2 15% 38% W 22% - 50% W. 

W 3 20% > 24% J 

L L \ II \ . L 2 ll \ - 

V 32% = 32% V 22% = 22% V. 

The first list is based on 155 flowering plants, and the 
second on 219. 

The seeds of the whitish Hespcris, therefore, in this 
experiment, produce their like with a small percentage 
of lilacs and violets. The seeds of lilacs, on the other 
hand, give rise to the three types in about equal numbers, 
though it must be remembered that the limit between 
/T.3 and LI is to a certain extent arbitrary. 

I have not yet made a sufficient number of observa- 
tions on the inheritance of the violet color in this race. 
In the only experiment which I have carried out, only 
five plants flowered and they had the same color as their 
parents. 

Let us now pass on to a detailed description of the 



Hcspcris Matronalis. 141 

experiment. It began in 1894 with seven plants which 
had already flowered in 1893 and had been noted as 
lilac flowered. Many of their flowers were more or less 
striped, some of them produced in August the violet bud- 
variations mentioned above, when the rest of the flowers 
had been through blooming for a long time. Seed was 
only saved from the lilac flowered branches; a part of 
it was sowed in August, the rest as soon as it was ripe. 
Most of it germinated in the following February and 
March; more than half of these plants produced stems 
and flowered in August. I obtained altogether 234 plants 
in flower of which 29% were pale, 57% were lilac and 
14% normal violet. I selected the strongest plants from 
among the most typical of each group and transplanted 
them in the autumn to three as isolated spots as I could 
find in my garden. Here they grew freely, branched 
abundantly and flowered in the following year (1895) 
for a second time. 

There were three violet plants which however set 
very little seed. This was sown and the offspring flow- 
ered in the summer of 1897 in a conservatory. I took 
precautions to prevent their being visited by insects in 
order to render impossible the transference of their 
pollen to the other plants. As soon as the color of the 
flowers could be determined with certainty for any plant, 
this was pulled up. There were, as I have already stated, 
only five plants and their flo\vers were violet. 

I did not allow the lilac flowered plants to flower in 
this year but kept them for the next. Of the plants with 
pale flowers w r hich had been planted out separately in the 
autumn of 1895, only one plant flowered in 1896. Its 
seeds \vere sown immediately and gave rise to 12 plants 
which flowered in the summer of 1897; they were all 



142 Atavism. 

pale with no more than the faintest indication of the 
lilac color. The seeds were sown in pans in the autumn, 
the seedlings were pricked out in November and planted 
out in April 1898 on a large bed. In June 250 individ- 
uals flowered, and the percentage composition of the 
color, as given above, was determined. Then the four 
lilac individuals falling into the group Lo were taken 
up and transplanted with all possible care to the metal 
gauze greenhouse. Before doing so all open flowers 
and young fruits were of course removed. It may be 
noted that in this experiment the lilac flowered individ- 
uals began to flower conspicuously later than the pale 
and violet ones. 

The seeds of these four plants were sown partly in 
October and partly in November, separately for each 
parent. Only one of the four resultant groups flowered 
in the following year (1899) ; the rest remained in the 
rosette stage and flowered in 1900. The proportions 
of the various colors were very much the same in the 
four groups. I recorded them separately but did not 
find any significant differences. The numbers in the 
first column (1st Experiment, 5th Gen.) on the table 
on page 140 give the composition of the whole culture. 

I transplanted some lilac plants of the first crop 
(1895), but only kept one of them which caught my eye 
with its beautifully striped flowers. It grew up into a 
sturdy plant, flowered in 1898 in an isolated spot and 
set an abundance of seed. From this 219 flowering 

o 

plants were raised in 1899, and their colors are recorded 
in the last column of the table on page 140 (2d Experi- 
ment, 3d Gen.). 

If we consider the results of these experiments, ex- 



Hcspcris Matronalis. 143 

tending over seven years, in their relation to other known 
facts we find that we can distinguish the following races : 

1. Hcspcris matronalis alba, the constant commercial 
variety. 

2a. A whitish, pale lilac, seldom or never striped 
sort (Wi-Ws), which can reproduce the violet color by 
sectorial, bud- and seed-variation ; violet seed-variation 
about 2 r /c ; lilac offspring about 6 C ' ( . 

2b. A lilac, often striped or spotted, race which gives 
rise to an inconstant but mostly considerable number of 

/ 

whitish and violet offspring. Its color merges contin- 
uously into that of No. 2a. but is sharply separated from 
No. 3. 

3. A violet variety which has arisen from 2a and 2b 

j 

and is presumably inconstant, on the analogy of Antirrhi- 
num majus. 

4. Hcspcris matronalis, the original, constant, violet 
species. 

The analogy with the corresponding races of An- 
tirrhinum majus seems to me to be obvious and can be 
expressed as follows : 

1. The systematic variety which is perfectly con- 

f -1 v 

stant (H. in. alba, A. maj. Intcnm). 

2. The eversporting variety with lilac or striped 
flowers (H. m. lilacina, A. maj. lutcnm striatum). It 
can be split by selection in a plus and in a minus direction ; 
into a pale lilac, or finely striped race on the one hand, 
and on the other into the dark lilac and frequently striped 
dame's violet and the broadly striped snapdragon. 

3. The self-colored but inconstant atavistic type which 
has the color but not the constancy of the original species. 

4. The original violet, or red, perfectly constant spe- 
cies (Hcspcris matronalis. Antirrhinum majus). 



144 



16. CLARKIA PULCHELLA. 

A white variety of this pretty red species is offered 
by seedsmen. 1 Besides this a striped race sometimes oc- 
curs which has more or less numerous red bands of vary- 
ing breadth on the petals. 2 The red in these cases has 
the same intensity as that of the species. Moreover the 
white flowers are not pure white ; a very delicate but 
distinctly visible red flush can be seen on any bed of 

them in full flower. Sometimes 
occasional plants or individual 
flowers are somewhat richer in 
pigment, so that it is at once 
obvious that they are not pure 
white. 

I have only made an in- 
complete series of experiments 
with this plant because it does 
not lend itself easily to artificial 
fertilization and, as a rule, does 
not stand transplanting while 
in flower. But the results ob- 
tained suffice to demonstrate 
their essential correspondence 
with those obtained with Antirrhinum and Hes peris. 

We can distinguish in this as in the other two cases 
between a pale race poor in stripes and a richly striped 
one ; moreover these two races possess the characters of 
the corresponding ones in the two species named. But 
in Clarkia the broad stripes appear chiefly as sectors, as 

There is also a variety, Carnea, which is constant so far as my 
experience goes. 

2 See p. 119. It was referred to by VILMORIN and by B. VERLOT, 
Production et fixation dcs varictes, 1865, p. 64. 




Fig. 25. Clarkia pulchella. 
A white flower of which 
one petal and a half are 
dark red, while there are 
dark red stripes here and 
there on the other two 
petals. 



Clarkia I'ulchclla. 145 

for instance, whole or half petals; I shall therefore call 
such flowers and plants sectorial. 

In 1896 I had a bed of about 50 plants all of the 
flowers of which were whitish. The majority bore no 
red stripes, or only such fine ones and so rarely that they 
were oyerlooked, which is always possible since the plants 
produce very many and rapidly fading flowers. Only 
one plant stood out amongst the rest ; at the end of July 
it bore a flower with two red petals and at the beginning 
of August a petal the middle third of which was also 
colored red. Otherwise, the bed was practically white 
throughout the summer. Some of the seed of the whites 
was saved. 

From the seeds of a white flowered specimen I ob- 
tained in 1897 a culture of about 100 plants. Amongst 
these again there was only one sectorial example ; I saved 
its seeds separately although it had been fertilized by 
insects in the midst of the others. In the majority of 
these others I had not seen red stripes, but on a few of 
them there had been some insignificant ones. 

The seeds of the pale flowered plants gave rise to a 
generation equally poor in stripes ; in 1898 I only saw one 
striped one amongst 30. This race therefore remained 
poor in red sectors as a result of a continued selection 
of almost white plants. 

From the seeds of the sectorial plant I at once ob- 
tained a race which was rich in red petals and red sec- 
tions of petals, and often produced whole red flowers 
and twigs with red flowers only (Bud-variation). I 
grew it for two generations (1898 and 1899). The seeds 
for the first were gathered in 1897 from a seed-parent 
which had not been isolated; in 1898, however, I pulled 
up all of the non-sectorial plants whilst they were in 



146 



flower and on the remaining seed-parents only harvested 
the seeds from those flowers which opened after tHat 
operation. 

The single sectorial plant of 1897 bore one flower 
with one, and another with two red petals. Their seeds 
were harvested separately and sown. The other flowers 
were pale; I also harvested their seed separately. The 
first named seeds, naturally few in number, gave rise 
in 1898 to about 40 plants which flowered; the latter to 
200. In both groups the red stripes and sectors were 
remarkably numerous in comparison with the previous 
year. At the end of July I found amongst the former 
about 25%, and amongst the latter 23^ sectorial plants. 
Besides these, a plant bearing red flowers exclusively, 
occurred in the former group. If I had repeated these 
observations from time to time the two percentages would 
of course have been considerably increased. But in order 
to isolate the sectorial plants I pulled up all those which 
up to that time had exhibited only few and narrow 
stripes. As already mentioned, I harvested seed only 
from the fruits of those flowers which had opened after 
this operation. I saved two kinds of seed : one was from 
a number of sectorial flowers which I had marked on a 
large group of individuals ; the other was from a par- 
ticularly striking plant which I had also marked, and 
which had a fair number of sectorial and occasional per- 
fectly red flowers, exhibiting also red bud-variations on 
its lower branches. I harvested seeds only from the 
narrow striped flowers of this plant. 

I have one more case of sectorial variation to men- 
tion before I proceed to give the results obtained from 
this harvest. A green lateral branch in an inflorescence 
on an otherwise white or finely striped plant had a 



Clarkia Pnlchclki. 147 

narrow red longitudinal line on it which was not much 
broader than a flower stalk and extended over four inter- 
nodes. The upper, lower, and middle flowers of the 
tract stood on this line ; the two former were completely 
red, the middle one only partly so. The two flowers oc- 
cupying intermediate positions but on the green side of 
the branch were almost white. 

The culture of 1899 was richer in sectorial plants 
than that of 1898, as the isolation of the seed-parents 
would have led us to expect. From the mixed seeds 
referred to above, I had about 300 plants of which five 
were wholly red whilst the proportion of sectorial ones 
was 40%. The single selected seed-parent, however, 
gave rise to only 50 offspring which flowered, of which 
one was red, whilst the proportion of sector ials mounted 
to 70% . The average number of reds in the two cultures 
was 1-2% ; and that of sectorial plants 45%. 

These experiments show that the pale flowered plants, 
selected as seed-parents, give rise to a fairly constant 
progeny amongst which the proportion of sectorial plants 
is quite small. 

The progeny of sectorial plants, on the other hand, 
consists of about 45% broadly striped and 1-2% red 
plants, the remainder being pale tinged with red, or at 
any rate very poor in stripes. 

The cultures of the pale flowered plants are ordinarily 
in flower some weeks before the first stripes appear; but 
in the beds of sectorial plants the red may be seen among 
the very first flowers. Here also the white flowered ones 
are always in a large majority ; among a thousand flowers 
of this race I counted 34 striped and 8 sectorial ones, 
that is to say only 4% altogether. 



148 Atavism. 



17. PLANTAGO LANCEOLATA RAMOSA. 

Plantago lanccolata is one of of those plants which 
are remarkably rich in anomalies. PENZIG mentions a 
considerable number of them such as leafy stalks, ears 
the tops of which bear tufts of foliage leaves, 1 forked 
spikes with two or more tips, torsions etc. These and 
many other malformations such as split leaves, pitchers 
consisting of one or more leaves, occur commonly in this 

o - 

neighborhood and also in my cultures. It is worth men- 
tioning that all or nearly all of these abnormalities can 
occur in the same race, and sometimes indeed in a single 
stout individual. Evidently every plant must contain a 
number of latent or semi-latent characters which lie out- 
side its proper range of form ; these characters consti- 
tute, as I have already said, the outer range of the forms 
of the species (p. 27). 

A form also frequently mentioned 2 in the literature 
of the subject is one with branched ears (Plantago lan- 
ccolata rainosa). 3 In this variety sessile secondary spikes 
are produced in the axils of the bracts at the base of 
the main ear. They are often small, but sometimes 
nearly attain the size of the central ear. Their number 
is highly variable. Under good conditions of cultivation 
each head may have from 2-7 lateral ears, but on single 
ears the number may rise to 20 and more (Figs. 26, 27). 

I have been carrying out experiments on the inheri- 
tance of this ramosa-character since 1887. It proved to 

I 1 have often picked these tufts and made cuttings of them ; 
they take most quickly and grow to strong rosettes of radical leaves, 
the ears arising from which may repeat the phenomenon of the 
tufting to a certain extent (Plantago lanceolata coronata). 

~ PENZIG, Teratologie, II, p. 252. 

"Kruidkundig Jaarboek, Gent, 1897, pp. 76 and 91. 



Plantayo Lanceolata Ranwsa. 149 

be only partial. In spite of the most careful selection 
and isolation during the time of flowering this race every 
year produces plants not one of whose spikes, even when 
there are a hundred to the plant, exhibits the smallest 
trace of branching. They are obviously to be regarded 
as atavists. 

The proportion in which these atavists occur seems 
to be fairly constant, fluctuating however from year to 
year. It can be slightly increased or diminished by the 
choice of favorable or unfavorable seed-parents; but it 
does not seem possible to effect an essential and per- 
manent improvement by continued selection, at least not 
to a degree that would open a chance of altogether elim- 
inating the atavism. 

In the first years of my cultures I did not pay partic- 
ular attention to this phenomenon ;" moreover my experi- 
ments were on too small a scale to afford numerical data 
of any value. But I found atavists as well as ramosa- 
plants every year, although I always collected my seeds 
from the former. I did not determine the proportion 
until the fifth generation (1892) was reached. I should 
state that I have isolated my seed-parents every year, 
cutting off as many as possible of their unbranched ears 
before they flowered. Pollination which had to be left 
to the wind was therefore confined to the group of se- 
lected seed-parents, whose number scarcely ever ex- 
ceeded 10. It was as pure as it was possible to have it. 

I obtained the following figures : 

GENERATION PERCENTAGE OF ATAVISTS 

5. 1892 46% 

6. 1894 50 %, 58%, 59% 

7. 1897 47% 

8. 1898 45%, 56%, 59% 

8. 1900 52% 



150 



Atavism. 



Plantago lanccolata rainosa, therefore, produces a pro- 
portion of about one-half atavistic individuals every year. 

The variability in the fig- 
ures given is at least in part 
dependent on external in- 
fluences (nutrition and selec- 
tion). Closer examination 
of the individual years proves 
the truth of this. In 1892 I 
had 48 plants in flower ; nine 
of these plants produced split 
leaves and pitchers at the 
time when they were being 
transplanted, about three 
weeks after the seed had 
been sown, and seemed espe- 
cially desirable on this ac- 
count. In the summer they 
turned out to be all rainosa- 
plants with richly branched 
spikes. They were cultivated 
the following year also ; and 
the sixth generation was 
raised partly from their seed 
and partly from the seed har- 
vested in 1892 from two 
other seed-parents. From 
the latter were raised 103 

plants which flowered, of 

Fig. 26. Plantago lanceolata which 50 c/ c , atavists, 

ramosa. A whole plant. 

this proportion being nearly 

the same for the two seed-parents. In order to investi- 
gate this, the seeds of the individual seed-parents were, 




Plantayo Lanccolata Ramosa. 151 

as usual, sown separately. The higher figures 58 % and 
59% were derived from the offspring of a plant which 
had been divided into two in 1893, after which one-half 
of it was grown on sand and the other on ordinary 
garden soil. I shall have to revert to the effect of this 
treatment on the plant itself; but it will be observed that 
the differential treatment had no visible effect on the 
offspring of the two halves. (The numbers of indi- 
viduals dealt with in the two cultures were 57 and 60 
respectively. ) 

The seeds of the typical individuals of my race of 
1894 I sowed in 1897 under normal conditions, as usual 
(seed sown in the greenhouse; seedlings pricked out into 
pots, and afterwards transplanted to the beds). The 
seed had been saved from two plants with richly branched 
ears. It produced a culture of 70 plants which flowered 
and contained 47% atavists. Whilst flowering was pro- 
ceeding I transplanted all the ramosa-plants whose ears 
were only slightly branched, and marked among the re- 
mainder a specimen which seemed to be the most pro- 
fusely branched. I harvested seed from those flowers 
only which protruded their stigma after this separation 
had taken place and after the atavists had been weeded 
out. Seed was harvested separately from each plant. In 
the following summer (1898, 8th generation) it was 
seen that the seed of the best seed-parent had only pro- 
duced 45% atavists (among 100 plants that flowered). 
The seeds of the average seed-parents gave 56%, and 
those of the worst, 59%. Selection had therefore a dis- 
tinct, although not a very great effect. It should be re- 
marked that the number of average seed-parents was 8, 
and that of the worst ones 10. The composition of the 
progeny was determined separately for each seed-parent, 



152 



Atavism. 



but the differences were not greater than the extent of 
the experiment would lead us to expect. There were 
1033 offspring from the average seed-parents and 732 
from the ten worst plants. The two separate cultures 
which deviated most from the mean contained 37 % and 
65% atavists respectively. The value of 52% given 




Fig. 27. Plantago lanceolata ramosa. A, B, C, three 

branched ears. 

above for the same generation but grown in 1900, will 
be dealt with below. 

Bud-variations occur in this as in the inconstant races 
of other species, although very rarely. In such cases it 
is one or several lateral rosettes which varv. The struc- 

ff 

ture of our plant is a very simple one. The stem of the 



Plantayo Lanceolata Ramosa. 153 

seedling grows out into a short, somewhat oblique, rhi- 
zom which produces a rosette of radical leaves. Ears 
are formed in the axils of the higher leaves but rosettes 
of the second order groxv out from the axils of the lower 
ones. In the second summer the primary and secondary 
rosettes behave in the same way, again producing ears 
above and secondary rosettes below. If the plant grows 
very robustly it may consist of as many as 10-20 single 
rosettes ; if it is a raiuosa every rosette produces branched 
ears, at least on some stalks. Sometimes all the ears 
of the whole plant are branched, in which case it is per- 
fectly easy to see that there is no bud-variation. In its 
second year a single plant may often produce more than 
50 branched ears. 

The culture of 1897 contained a plant which exhibited 
a bud-variation. The seeds of its branched ears, har- 
vested in the first year, had produced 89 individuals that 
flo\vered, of which 36 (40%) were atavists. The plant 
in question consisted, in the autumn of its second year, 
of more than 25 single rosettes which were carefully 
isolated, and planted separately. Only the seven strong- 
est ones survived this operation. I kept them all in their 
pots until a sufficient number of ears were visible and 
then planted them out on two distant beds. On the one 
I planted four rosettes with unbranched ears, on the 
other, three with branched ears. The four former pro- 
duced, together, over 200 strong ears, all unbranched 
with the exception of a single one which bore a small 
lateral branch at its base. The three latter formed both 
unbranched and more or less richly branched inflores- 
cences, but during the whole summer the unbranched 
ears were all cut off before they flowered. The harvest 
from the two beds, gathered and sown separately, gave 



154 Atai'isjn. 

rise to two cultures in 1900. They had the following 
composition : 

Ears of seed-parent Extent of culture Atavists With branched ears 
Branched 44 individuals 52 % 48 % 

Unbranched 206 individuals 92 % 8 % 

The rosettes with branched ears gave rise to rather 
more atavists than the seed of the branched inflorescences 
of the same plant in the first year (52% as against 40% ) , 
which was probably due to the fact that it had a less 
sunny position in 1899 than in 1897. But the rosettes 
with unbranched ears, although they were in a good po- 
sition in 1899 and grew very healthily, gave a progeny 
dissimilar to that hitherto produced by any of the branched 
plants of this race (see Table on page 149 which gives 
the results of more than 25 individual sowings from 
separate seed-parents). 

The four lateral rosettes with unbranched ears, there- 
fore, formed in this case a clear instance of bud-variation, 
producing a race poor in branched ears. 

The question of the constancy of the atavists in my 
race is a point of considerable interest. Hitherto I have 
found them completely constant. With a view to test- 
ing this I did not weed out the atavists in the fifth gen- 
eration in 1894, but simply cut off all their ears before 
the branched plants flowered, and repeated this opera- 
tion from time to time when new ears appeared before 
they could protrude their stamens. After the harvest 
I weeded out all the branched individuals ; most of the 
atavists survived the winter and flowered luxuriantly 

J 

in 1895 in isolation. The majority of them produced 
over one hundred ears per individual. I harvested the 
seeds separately for each seed-parent. 

The sowings took place in 1896 and in 1897. They 



Plantago Lanccolata Ramosa. 155 

gave rise respectively to three and six cultures derived 
from the nine seed-parents. Each culture consisted of 
from 35 to 100 plants, making together 600 flowering 
individuals bearing 4000 inflorescences. These were un- 
branched without exception. 

The question suggests itself, whether the seed-atavists 
and the bud-atavists belong to the same type. On the 
one hand it is possible that the constancy of the former 
is not always so absolute as it appeared in my experiment. 
On the other hand, branched bud-variants might occa- 
sionally appear in the race derived from the atavistic 
bud-variants, and such might have been the cause of the 
occurrence of branched individuals (8%) in my culture 
of 1900. But further investigations are necessary to 
provide a satisfactory answer to this question. 

Plantago lanccolata ramosa, therefore, gives rise to 
atavistic individuals, cither by seed (about 50%) or by 
buds (very seldom) which are either absolutely, or at 
least in a high degree, constant from seed. 

It still remains to describe briefly the fluctuating vari- 
ability of our race of plantains. This is considerable, 
and conforms to the common laws; especially is it de- 
pendent to a large extent on external conditions and, 
within certain limits, capable of being altered by selec- 
tion. The observations, which I now shall give, refer 
to true ramosa-plants, and not to atavists and bud-varia- 
tions. 

The variability of this race corresponds with that 
of other monstrous races inasmuch as the curve describ- 
ing it is dimorphic. 1 During July and August 1893 I 



1 Sur Ics courbes galtoniennes dc.: monstruosites, Bull. Scientif. 
de la France et de la Belgiqne, public par A. GIARD, XXVII, 1896, 
P- 397- 



156 Atavism. 

picked all the ears of a small group of plants, and ob- 
tained the following figures: 

Ears without any branching . . . 191 

Ears with one lateral ear 80 

Ears with two lateral ears .... 136 

Ears with three lateral ears .... 93 

Ears with four lateral ears .... 33 

Ears with five lateral ears .... 12 

Sum of ears 545 

The degree of branching in this group was fairly 
low; nevertheless the apex of the curve of the atavistic 
ears is distinct from that of the branched ones. This 
phenomenon could indeed be easily observed, even with- 
out any counting, on account of the relative scarcity of 
heads bearing a single lateral ear, a fact which I have 
also observed repeatedly since. This is a character of 
the eversporting variety and suggests the possibility that 
the one-branched ears which are so common in nature 
(where the rauwsa-form, as is well known, is not at all 
rare) presumably constitute the half race; but I have 
not investigated this point. 

The number of compound ears per plant, and the 
degree of branching in each, are to a great extent de- 
pendent on the conditions of life. The stronger the 
growth of the whole plant, and the richer the foliage, 
the more pronounced will the anomaly be. Therefore, 
a more profuse branching of the individual ears usually 
goes hand in hand with a richness of branched inflores- 
cences. The branching also manifests a certain periodic- 
ity. The young plants almost always begin with un- 
branched ears; it is not until later that the monstrosity 
appears, gradually increasing in strength. Then towards 
the end of the summer I often observed a diminution in 
the amount of branching and often the formation of 



Plantago Lanccolata Rcunosa. 157 

more numerous unbranched ears. In the second summer 
often almost all the ears on healthy individuals are 
branched even when their number reaches 50-60 per 
plant. In the first year I found that as a rule there were 
10-20 branched ears, and sometimes as many as 30 or 
even more occurred on each plant. In fact we may 
assume that, on the average, and with ordinary methods 
of cultivation, about one-third of the ears will be branched 
during the first summer; for instance, in 1898 I found 
amongst 439 ears on 30 individuals 136 or 31% which 
were branched. It goes without saying that the atavistic 
individuals were excluded from these countings. 

I have also made some direct experiments to deter- 
mine the influence of individual vigor on the develop- 
ment of the anomaly. In the first place I have grown 
very weak plants and have then got them to grow stronger 
gradually. For this purpose I made use of the plantain's 
well-known property of producing buds from its roots. 
As the roots are all very thin, the plantlets obtained in 
this way are very weak at first, nor do they grow up 
as quickly as seedlings. 

For the purpose of this experiment I selected (March 
1893) ten plants which had had 10-25 branched ears 
each in the previous year. I pulled them out of the 
ground, cut off the mass of their roots and planted these, 
throwing away the rosettes and any leaf-buds that might 
be present. I put the roots of each individual straight 
into the ground without separating them. Radical buds 
were produced in hundreds, often so many from one 
bundle of roots that there was not room for all of them 
to develop. In the middle of June, that is, after about 
three months, they began to flower. At first there were 
only 40% branched ears, with only one or two lateral 



158 Atavism. 

ears (on the 46 first flowerstalks). In the next 100 the 
proportion mounted to 60%, and 3-4 partite inflores- 
cences also occurred. Later on, about the middle of 
July, the first stalks with five lateral ears appeared, and 
the number of branched ears gradually increased to 70%, 
and in August the strongest rosette had 67 ears of which 
52 were branched, i. e., about 78%. 

A question at one time much discussed was whether 
adventitious buds had the power to reproduce the varia- 
tions and anomalies of the parent plant. At that time 
malformations were not regarded as heritable, but since 
the inheritance of monstrosities has become generally 
recognized, 1 it must be considered evident that adven- 

o 

titious buds will behave like normal ones; and the only 
question that can arise is whether they are more liable 
to produce bud-variations or not. If they are weak the 
abnormal character will be less pronounced; but if their 
strength is equal to that of ordinary buds the abnormal 
character must be developed to the same extent. It is 
therefore almost superfluous to lay much stress on the 
reproduction of the branched ears from the radical shoots 
of our plantain. 

The rest of my experiments deal with divided plants. 
In the spring of 1893 I selected for this purpose two fine 
rosettes that had survived the winter and which had 
proved to be particularly rich in branched ears in the 
previous year. Both plants were divided as equally as 
possible into halves. Of the first plants one-half was 
planted in sand and of the other one-half was put in the 
shadow of a tree, the control halves of both plants being 
cultivated under ordinary conditions for the purpose of 

l Erfelyke Monstrositeiten, Kruidkundig Jaarboek, Gent, 1897, 
p. 62. 



Plantago Lanccolata Raniosa. 159 

comparison. At the beginning of the period of flowering 
no difference was discernible in either experiment be- 
tween the two halves, but it gradually became visible 
during the course of the summer. I picked off all the 
ears from the culture in sand at the end of July and at 
the end of August; here is a record of them: 

Number of lateral ears per primary ear Totals 
012345 

July 28th -! Sand 3 3 4 6 J i 20 

< Control 9 7 9 6 31 

A , ( Sand 14 10 12 8 3 1 48 

'( Control 12 2 10 7 6 2 39 

The difference though slight is distinct. It is more 
clearly brought out if the mean number of lateral ears 

j o 

per primary ear is calculated. In August in the plants 
on sand this was 1.5, in the control half 2. 

A similar effect was produced by shade which exerted 
a most deleterious effect on the whole growth of my 
experimental plants as will be seen from the small number 
of ears produced. I obtained the following figures in 
the same way as in the previous experiment. 

Number of lateral ears per primary ear Totals 
0123456 

Tnlv 28th * Shade 7627520 29 

[uly M Control 1 1 2 8 19 20 1 52 

. 1 \ Shade 15 1 1 2 19 

( Control 21 9 20 16 10 3 79 

The mean number of subsidiary ears per primary 
ear in August in the shadow half was 0.5 and in the 
control half 2.0. 

In conclusion, the results of the whole series of ex- 
periments which has lasted over more than ten years 
may be summarized as follows : The Plantago lanccolata 
rainosa of ;//v experiment constitutes an "inconstant" 



160 Atavism. 

middle race or eversporting variety ; that is to say, a race 
which produces in every generation a fairly constant 
proportion of atavists. This proportion is about 50</e . 

The segregation of atavists occurs regularly in gen- 
erations grown from seed, but sometimes also in those 
grown by means of bud-variation. The atavists are per- 
fectly, or at least very nearly, constant. 

The true representatives of the race (i. e., all other 
than atavists) produce both unbranched and more or less 
profusely branched ears, and are largely dependent, in 
regard to this character, on their environment and their 
individual vigor (fluctuating variability). The stronger 
the plant and the more favorable the conditions the more 
pronounced is the anomaly. 1 

1 Compare the behavior of Paparer somnifcrum polycephalum in 
Vol. I, Part I, 16, p. 138; and also the end of this part. 



VI. EXPERIMENTAL OBSERVATION OF THE 
ORIGIN OF VARIETIES. 

18. THE ORIGIN OF CHRYSANTHEMUM SEGETUM. 

PLENUM. 
(See Plate II.) 

The double corn marigold constitutes a new variety 
which has recently arisen in my cultures. It has never 
occurred before. Chrysanthemum scgctmn is, of course, 
a favorite annual garden plant, and so is a variety of it 
called C. scgctiun grandiflorum. A form called C. scge- 
tiHn Gloria is announced amongst this year's novelties i 1 
its flowers are said to attain a diameter of 10 centimeters, 
but it is not double. If a double form ever had appeared, 
it would without any doubt have been put on the market 
as a noteworthy improvement, even as the double vari- 
eties of Chrysanthemum inodonun and other composites 
are so widely grown. 

My "conquest," as the breeders of hyacinths in Haar- 
lem call their novelties, is the counterpart of the well- 
known Chrysanthemum inodonun plcnissinnun. It is 
inferior to it in the matter of color, inasmuch as white 
flowers are always in greater favor than yellow ones. 
The doubling of the heads of composites is never so 
perfect that tubular florets are completely absent from 
all inflorescences. Nevertheless it frequently looks as if 
this were so (Fig. 28) ; but if we look a little closer we 

1 Seed-catalogue of HAAGE and SCHMIDT in Erfurt, 1900. 



162 Observation of the Origin of J 7 arictics. 

will always find between the tongue florets, more or less 
numerous tubular florets which are hidden from view by 
the others. Moreover, the degree of doubling is to a 
considerable extent subject to fluctuating variability; one 
plant has more and another fewer, transformed florets. 




Fig. 28. Chrysanthemum inodoruui plenissimum. A plant 
with a high degree of doubling in the inflorescences, and, 
consequently, perfectly sterile. 

This is an important point, for the white tongue florets 
of C. inodoruui plenissimum are female and inflorescences 
such as those shown in Fig. 28 and Fig. 34C on page 184 
set absolutely no seed. The variety is therefore main- 



The Oric/in of Chrysanthemum Seyctinn Plenum. 163 

tained by saving seed from plants such as those figured 
in Fig. 34 A and B, p. 184. 

These remarks also apply to my new Chrysanthemum 
scgctnm plenum. Many specimens set absolutely no seed 
because the doubling has gone too far. For the same 
reason others afford only a meagre harvest. Too drastic 
a selection at the beginning of the flowering period would 
destroy any prospect of a harvest and might even result 
in the extinction of the variety. 

Moreover plants with a high degree of "doubling" 
produce no pollen for the fertilization of the others, 
because they are almost exclusively female ; so that they 
can take no part in the perpetuation of the race in this 
way either. 

My novelty is probably the first horticultural variety 
which has arisen in an experimental culture. By this 
I mean that pure fertilization has been insured since the 
beginning of the culture and that exact and detailed 
records of the course of the experiment have been kept 
every year. Moreover the selection of the seed-parents 
has constantly been carried out from the very beginning, 
with a view to the same ideal. Selection began in 1897, 
the "double" race was obtained in 1900. The selection 
occupied, therefore, a period of three years. 

The corn marigold, being a composite, is admirably 
adapted to form the material for a statistical investi- 
gation of its variability. The number of ray florets 
fluctuate in accordance with the well-known law of LUD- 
WIG based on BRAUN and SCHIMPER'S series. By this 
means the exact composition of a culture can be ex- 
pressed in figures and plotted graphically by recording 
a sufficient number of inflorescences. The course of the 
selective process can in this way be displayed in all its 



164 Observation of the Ov'ujln of Varieties. 



details. Although an explanation of BRAUN-SCHIMPER'S 
series is. still wanting, each of the numbers in it (e. g., 
13, 21, etc.) may figure as a specific character; that is, 
it may be the constant mean for a particular species. On 
the other hand they may constitute stages of variation 
or characterize races whose nature is still unknown to 
us. We must therefore limit ourselves to a purely em- 
pirical description. 

It seems desirable to 
give a general outline of 
the significance of my ex- 
periment before I proceed 
to describe the details. 

The corn marigold is 
very common in cornfields 
over the greater part of 
Europe, as also its German 
names "Saatwucherblume" 
and "gelbc Kornbluinc" im- 
ply. It has thirteen ray 
florets in the inflorescence 
and fluctuates around this 
number according toQuE- 

Fig 29. Chrysanthemum scgctum TELET ' S law A commercial 
plenum. An almost completely 

double inflorescence. See also variety, called Chrysanthe- 
Plate II. 

mum segetum grandiflo- 

nun, whose origin is not known, is distinguished by the 
possession of larger and more numerous tongue florets. 1 
So far as my experience goes, bought seeds of this vari- 
ety give rise to a mixture of this and of ordinary C. 
segetum, no doubt on account of the fact that in the 
nurseries both are grown close together, for practical 

1 RUMPLER, Vilmorin's Blumengartnerei, 1896, II, p. 507. 




The Origin of Chrysanthemum Scgctnm Plenum. 165 

reasons. In botanical gardens, too, both sorts are often 
grown together; and, frequently, simply under the name 
of C. segetum. 

This mixed assemblage gives rise to a dimorphic 
curve; 1 but the two groups of individuals which com- 
pose it can easily be isolated by selection. Then the 
C. segetum grandiflorum proves to have a mean of 21 
ligulate florets, around which variation practically takes 
place in the same way as in the 13-rayed race (i. e., the 
wild species), except that it has a tendency to multiply 
the number of rays beyond the limits of a normal OUETE- 
LET'S curve ; a fact which indicates discontinuous varia- 
tion. 2 

This slight indication was the starting point for my 
experiment. In 1897 I chose a seed-parent with 34 rays 
for the 1898 crop, and reached 49 rays. 3 Proceeding 
in the same way I reached 67 in 1899 and about 90 in 
1900 in the best inflorescences. Up till 1899 the ligulate 
florets only appeared in the circumference, the disc con- 
sisting solely of tubular florets. In this year, however, 
there appeared 2 or 3 ligulate florets in the midst of the 
disc of a few flowerheads on a single plant. This was 
the first indication of the double race. Therefore I only 
sowed the seeds of this one plant in 1900, and from that 
the race was fully developed (Plate II). Apart of course 
from eliminating the possible effects of crossing, it needed 
no further selection ; a too rigid selection was moreover 

1 Eine zwcigipfelige Variationscurve, Archiv fiir Entwickelungs- 
mechanik der Organismen, Leipsic, 1895, p. 52. 

~ Compare the half curves (p. 26) and the note on p&ge 29. See 
also Ucber halbc Galton-Curven als Zeichen discontinuirlicher Varia- 
tion. Berichte d. deutschen bot. Gesellschaft, Vol. XII, p. 197. 

3 Ucber Curvcnsclcction bei Chrysanthemum scgetuui. Same jour- 
nal, 1899, Vol. XVII, p. 84. 



166 Observation of the Oriyin of J'arieties. 

to be avoided on account of the sterility of the most 
highly modified individuals. 

My cultures embraced, as a rule, a hundred individ- 
uals each, but sometimes a few hundreds. There can 
hardly be a doubt that if I had carried out more extensive 
sowings I should have attained my object at least one 
year earlier. But the more stringent the selection is, the 
smaller are both the harvest and consequently the next 
year's crop. 

Of course the reader will ask, has this transition been 
a gradual or a sudden one ? I consider it sudden ; but 
much depends on the meaning that we attach to the 
words. At any rate the change did not occupy centuries, 
as is commonly supposed by the current theory of selec- 
tion ; it did not even require one decade. Three years 
were sufficient in a culture of no more than a few square 
meters in extent. 

I now come to the details of the experiment and shall 
first give a short description of the original wild species. 

The species does not grow around Amsterdam. The 
herbarium material collected by me in various parts of 
the Netherlands points to the general occurrence of a 
mean number of 13 rays. HEINSIUS plotted curves from 
plants from two localities in the province of North Bra- 
bant, and obtained the following numbers. The first row 
relates to plants which were collected near Vucht, the 
second to a collection from Hintham. 1 

NUMBER OF LIGULATE FLORETS (L. F.) IN THE NETHERLANDS. 

I- F. 6789 10 11 12 13 14 15 16 17 18 19 20 21 

Vucht 1 13 5 3 8 18 78 37 22 11 17 2 33 
Hintham 10 99 8 15 14 33 9 4 1 1 00 

1 Be r. d. d. bot. Gcs., Vol. XVII, p. 87. I have already exhibited 
the variation in both localities united into a single curve in Vol. I 
(See p. 152, Fig. 32). 



The Oricjin of Chrysanthemum Scyetnm Plenum. 167 

In all 221 and 104 flowers were examined. The 
curves are monomorphic and symmetrical. 

The same is true of this species in Thuringia. LUDWIG 
gives the following data derived from 1000 plants col- 
lected at Brotterode. 1 

DATA FROM THURINGIA. 

L. F. 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 

Inflorescences 1 6 3 25 46 141 529 129 47 30 15 12 8 6 2 

We may therefore assume that the mean number of 
rays for the wild corn-marigold is 13. 

I investigated the mixed race occurring in botanical 
gardens for the first time in 1892. The result proved to 




I! 12 13 14 15 16 17 18 19 20 21 22 23 
I 14 13 4 6 9 7 10 12 20 I 

Fig. 30. Chrysanthemum segetum. Mixed crop. Curve of 
the ray-florets in the primary inflorescences of 97 indi- 
viduals in 1892. The upper series of figures gives the 
number of rays, the lower series the number of those in- 
dividuals possessing the scale character written above it. 2 

be a dimorphic curve (Fig. 30), which at the time was 
the first compound curve to appear in botanical literature. 3 
I had obtained the seed for the experiment by exchange 
from a number of botanical gardens. I mixed it thor- 
oughly and sowed it on a single bed, where 97 plants 

1 F. LUDWIG, Ueber Variationscurven und Variationsft'dchen, Bot. 
Centralbl., Vol. LXIV, 1895, P- 5- Also F. LUDWIG, Die pftanslichen 
Variatiojiscuri'cn und die Gauss'sche WahrscheinUchkcitscurve; same 
journal, Vol. LXXIII, 1898, p. 71 (p. 16 of the offprint). 

2 From the Archiv f. Entwickelungsmechanik, loc. cit., p. 58. 

3 Archrc fiir Entwickelungsmechanik, 1895, he. cit. See also 
LUDWIG in Botan. Centralbl., Vol. LXIV, 1895, p. 71. 



168 Observation of the Origin of Varieties. 

flowered altogether. I picked off and recorded a head 
from each of these during the course of the summer. 
On every plant I selected the terminal inflorescence of 
the main stem as soon as it opened ; plants in which this 
failed were pulled up before they flowered. Only pri- 
mary inflorescences were, therefore, employed, and the 
curve obtained was an index of individual variability, 
that is to say each unit in it represented a whole plant. 
The figures obtained are represented in the following 
series. The upper row gives the number of ligulate 
florets (L. F.) per inflorescence; the lower, the number 
of individuals which possessed these numbers. 

VARIATION IN NUMBER OF RAYS IN C. SEGETUM,, 1892. 

L. F. 12 13 14 15 16 17 18 19 20 21 22 
Individuals 1 14 13 4 6 9 7 10 12 20 1 

The curve based on this series of figures is given in 
Fig. 30. One of its two apices corresponds to that of 
the wild species, the other to that of the curve for Chry- 
santhemum Leucanthemum and C. inodorum. 

My next task was to separate the components from 
this mixture and to do this in such a way as to place their 
existence in the mixture beyond doubt. On account of the 
inevitable interference of insects in pollination it seemed 
to me impossible to do this for both supposed races at 
the same time, so I determined to isolate the 13-rayed 
form first, and the 21 -rayed later on from a new mixed 
crop. I devoted the two years 1893 and 1894 to the 
former inquiry. 

With this object in view, I eradicated every indi- 
vidual of the mixed crop of 1892 which had more than 
13 rays, as soon as I had counted the rays on its terminal 
flowerhead. In this way only 15 plants were saved, of 
which one had 12 and the rest 13 ligulate florets; the rest 



The Origin of Chrysanthemum Segetum Plenum. 169 

were removed so early that there was no clanger of these 
15 being fertilized by them. These plants flowered abun- 
dantly from their lateral shoots but exhibited no tendency 
to form a curve with an apex at 21. They were there- 
fore sufficiently pure representatives of the supposed 
race. 

In September I harvested the seeds of the 13-rayed 
plants which I had spared, and sowed half of them in the 




789 10 II 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 

A B 

Fig. 31. A. Chrysanthemum segetum. B. Chrysanthemum 
segetum grandiflorum (after purification). Curves of 
the races after isolation. A, Curve of the 13-rayed race 
in 1894. B, Curve of the 2i-rayed race in 1897. The 
ordinates give the number of individuals with like 
number of ray-florets in the primary inflorescences of 
the individual plants. The numbers of ray-florets them- 
selves are given below the abscissa. 

following spring (1893). I raised 162 flowering indi- 
viduals, and recorded the numbers of rays on their ter- 
minal heads. The curve representing this generation 
was steep, monomorphic and symmetrical (see Fig. 31 A 
for 1894), and agrees satisfactorily with the curves, 
given above, for the plants from the wild locality (p. 167 
and Fig. 32, Vol. I, p. 152). Therefore there can be no 



170 Observation of the Origin of Varieties. 

doubt that the wild form exists in the mixtures grown 
in botanical gardens. But in order to strengthen this 
proof I have cultivated the isolated race for one more 
generation. For this purpose I selected three vigorous 
plants from amongst the 1893 crop whose terminal in- 
florescences had 12 ray-florets, and left them to be fer- 
tilized by themselves and by their like after all plants 
with 13 or more rays had been eradicated. From these 

ff 

three seed-parents I harvested the seed separately and 
raised three families, in 1894, on different beds. The 
rays of the terminal inflorescences were recorded, and the 
experiment brought to an end. 

I shall now give the results of these three counts 
made in 1894 together with that of 1893. It will be 
seen that the series of figures correspond with one an- 
other exactly ; at any rate as nearly as is necessary for 
the object of this experiment. The composition of the 
four cultures in the two generations was as much the 
same as we should expect four samples of an ordinary 
species to be. 

THE 13-RAYED RACE. 

VARIATION IX NUMBER OF RAYS, IN TWO GENERATIONS. 

Ray-florets 8 9 10 11 12 13 14 15 16 17 18] 19 20 21 

1893 2 1 7 13 94 25 7 7 1 2 3 

1894. First family 00 01 10 59 18 2341021 

Second (< 00 14 11 89 11 5002 100 

Third " 01 2 3 10 73 21 1200000 

Total, 1894 1 3 8 31 221 50 8 5 4 3 1 2 1 

The total for 1894 is given in the form of a curve 
in Fig. 31 A. The whole number of individuals dealt 
with in this year was 338. 1 

In order to isolate the 21 -rayed race out of the same 

1 For a detailed comparison of the curves of the two years see 
hh' fiir Entzvlckelungsmcch., II, 1895, toe. cit., p. 62. 



The Origin of Chrysanthemum Segetwn Plenum. 171 

mixture, I had to provide more seed because the previous 
stock had been completely exhausted. I procured it in 
the same way, by exchange from botanical gardens, and 
from a similar number of them (about 20). It was not 
to be expected that the identical form of curve would be 
obtained again, because the relative height of the two 
apices obviously depends on the proportion in which the 
two constituent races are mixed; and this must be 
left to chance. I was therefore curious to find out 
whether the 13-rayed race alone was cultivated in some 
gardens and the 21 -rayed exclusively in others. With this 
object I sowed the various samples separately, and on 
a sufficient space to bring as many specimens to flower 
as possible. I then recorded the terminal inflorescence 
of each plant. From no single garden had a pure race 
been sent, neither of the 13-rayed nor of the 21 -rayed 
form. In every case both forms were found mixed and 
in the most diverse proportions. The mixed race was 
therefore the only one generally cultivated at that time. 
The variation in the number of ray-florets in the ter- 
minal inflorescences of the 589 individuals of the whole 
culture of this mixed race from the botanical gardens in 
1895 was as follows: 

L. F. 89 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 

Individuals 73 3 5 14 153 77 60 55 31 33 39 41 56 10 1 1 

That is to say, the same apices as in 1892; but in this 
series the 13-rayed race is obviously more strongly rep- 
resented than the other. 

With a view to discovering also the character of the 
race which is sold as Chrysanthemum segetnm grandi- 
flonun, I sowed a quantity of its seed. When the plants 
flowered in July an extraordinary variety of forms was 
exhibited by the ligulate florets. These were in some 



172 Observation of the Origin of Varieties. 

cases very short, in others very long; in some cases so 
narrow that they did not touch one another, in others 
more than twice as broad as those of the wild form. 
The color varied between golden and straw yellow, the 
tips of the florets were entire or indented, and so forth. 
This was sufficient to indicate the presence of several 
races. With regard to the number of ray-florets the 
differences were not so great, as in the mixtures we have 
already dealt with. There was only one perfectly dis- 
tinct apex, that at 21. The other at 13 was more or 
less obscured. It was obvious that the commercial race 
was the 21 -rayed one, and that it had been adulterated 
by admixture with the other only as much as is unavoid- 
able and therefore admitted in all cultivation on a large 
scale. 

The terminal inflorescences of the 282 plants of this 
culture of C. scgetuin grandiflonnn were recorded with 
the following result : 

L. F. 89 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 

Individuals 10 1 1 27 27 24 31 30 21 29 24 58 7 1 

These figures confirm what I have said and show that 
the 21 -rayed race of C. s. grandiflonnn contains an ad- 
mixture of a relatively small number (which probably 
fluctuates from year to year) of the 13-rayed race. 

My next task was to isolate from this mixture the 
21 -rayed race, whose existence had so far been merely 
inferred. I devoted the two following years to this in- 
quiry, and in the summer of 1895 selected the necessary 
seed-parents from the mixed crop. 

We here encounter an obstacle in the shape of trans- 
gressive variability, to which we have already referred, 1 
and which has often raised difficulties in the earlier in- 

1 See Vol. I, Part I, p. 56; and Part II, 25, p. 430. 



The Origin of Chrysanthemum Seyctum Plenum. 173 

vestigations. In order to bring this phenomenon into 
bolder relief let us imagine that the isolation has already 
taken place and the new race isolated. In other words 
let us examine Fig. 31 (p. 169) and the data from which 
this is derived (pp. 170 and 176). Let us first fix our 
attention on the ordinate at 21. It contains only indi- 
viduals of the 21 -rayed race. But in 1894 a single ex- 
treme variant appeared, which, although it belonged to 
the 13-rayecl race, nevertheless had as many as 21 rays 
(p. 170). If the cultures of 1893 and 1894 had been 
more extensive the number of these extreme variants 
would obviously have been greater. For the ordinates 
20, 19, 18, etc., it is still more evident that individuals 
of both races can occur. 

If we choose plants which have 21 or more ligulate 
florets in their terminal inflorescences we cannot at all 
be certain that they all belong to the race which is be- 
ing sought. And if they are left to pollinate one an- 
other, or if their seeds are mixed in the harvest, there 
is small likelihood of the strain being pure. Amongst 
the majority of pure seed-parents a number of individ- 
uals of inferior value may exist and it is necessary to 
remove these as soon as possible, at any rate before the 
harvest. 

The possibility of doing this is afforded by the 
later flowers. By means of them a curve can be de- 
termined for each plant, and in this way values can 
be obtained which are independent of the chances in- 
separably connected with small numbers. The curves 
describing the separate parts of one individual are called 
its "part-curves.* 3 I have therefore plotted such curves of 
all the individuals selected at the beginning of the flow- 
ering period as having 21 and more rays in their ter- 



174 Observation of the Origin of \\uicties. 

minal inflorescences. The result proved my view to be 
correct and showed the necessity of the correction which 
it had suggested. For there were 22 plants which, al- 
though their terminal inflorescences were 21 -rayed, had 
a part-curve with an apex at 13-14. The following 
are the data as obtained at the end of August : 

L. F. 12 13 14 15 16 17 18 19 20 21 

Lateral flowerheads of 22 indiv. 2 54 58 51 28 19 19 12 2 2 

These plants therefore belonged to the 13-rayed race, 
and were consequently eradicated. 

Besides these, there were five plants with doubtful 
curves; they were also not retained. All that was left 
was a group of 6 individuals whose curves seemed to me 
sufficiently distinct and certain to justify the harvesting 
of their seed. The following line gives the sum of their 
data : 

L. F. 12 13 14 15 16 17 18 19 20 21 22 

Lateral flowerheads of 6 indiv. 1 3 5 4 6 11 21 30 29 1 

All in all there were 111 inflorescences. 1 If the 
terminal inflorescences of these plants (5 with 21, 1 with 
26 rays ) had been included, the maximum would have 
been exactly at 21. Seed was saved only from these 
six plants for the 1896 crop. It was harvested separately 
from each parent. 

The fertilization of these plants had not been wholly 
pure, because the rejected plants referred to above could 
not be recognized nor removed before the latter part 
of August, and because flowers which bloom in Sep- 
tember set hardly any seed with us. Each of the six 
crops actually gave a curve which had a distinct maxi- 
mum at 21, but only one of them (No. 1) wholly lacked 

1 The curve is figured in Bcr. d. d. bot. Gcs..Vol XVII. Plate VTI. 
. 2R. 



The Origin of Chrysanthemum Scgctum Plenum. 175 

the other maximum, without however being symmetrical. 
Even in this group the race was therefore still far from 
being pure. Below I give the curve for the offspring 
of the single best seed-parent together with the sum of 
the curves representing the offspring of the five remain- 
ing seed-parents (Nos. 2-6). These curves therefore 
refer to the initial culture of the 21-rayed race (1896). 

L. F. 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 

No. 1 1 3 9 15 15 22 30 33 36 64 123 15 5 

Nos. 2-6 1 5 11 12 70 84 69 92 79 77 114 150 416 46 3 1 

All in all 370 plants were recorded for No. 1 and 
1220 for Nos. 2-6. 

Only the first named group, that is to say the off- 
spring of the plant numbered 1 in 1895, was used for 
the continuation of the experiment, and from it the best 
seed-parents for the purification of the race were selected 
on the basis of an examination of their lateral branches. 

* 

These were two plants the lateral flowerheads of which 
gave the following curves (1896) : 

L. F. 12 13 14 15 16 17 18 19 20 21 22 
No. la 01143220330 
No. I b 000000203 14 

Of the two, No. \b most obviously belongs to the 
race I was looking for. 

I harvested only the seeds of these two plants, and 
sowed them separately in the following year. In har- 
vesting this seed I confined myself to flowers which had 
bloomed after the other plants had been removed and 
had therefore been pollinated with their own or similar 
pollen. The result corresponded with my expectation, 
for in the following summer the race was pure on both 
beds. 



176 Observation of the Origin of Varieties. 

This is seen at a glance from the two series that fol- 
low and from Fig. 31 B which relates to the second group. 
The data were obtained in the same way as in previous 
years, only the terminal inflorescence of the main stem of 
each plant being recorded. The character of the second 
generation of the 21 -rayed race in 1897 was, therefore, 
as follows : 

L. F. 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 32 
No. la 0012023 41 41200000 
No. 1 b 1 3 3 7 14 43 142 43 21 11 5 3 1 1 

Both groups are very symmetrical, a fact which can 
be immediately seen in Fig. 31 B which is even more 
regular than the corresponding figure of the 13-rayed 
race (Fig. 31 A). There were only 56 flowering off- 
spring of No. la but 298 of No. Ib. 

If I had not limited myself in the previous year to 
such a small number of seeds, I should have had to sow 
the seed either of less suitable individuals or from flowers 
on the same plants which had opened earlier, i. e., which 
had been pollinated with inferior pollen. In that case 
my race would have been just as incompletely pure in 
1897 as it had been in 1896. I have convinced myself, 
by special experiments with such seed, of the correctness 
of this view, but do not consider the details worth print- 



ing. 1 



By this result the isolation of the races supposed to 
exist in the mixture, was accomplished. Let us therefore 
once more examine Fig. 30 on page 167 and Fig. 31 on 
page 169. The first thing that we see is that the maxima 
are the same in both figures; they lie at 13 and 21. The 

1 Races differing in their number of ray-florets can be mixed by 
crossing (Ber. d. deutschen hot. Ges., Vol. XVII, p. 92). This mix- 
ture is an extremely interesting phenomenon in many respects, but 
needs a closer investigation. 



The Origin of Chrysanthemum Segctwn Plenum. 177 

explanation suggested by the double curve has thus been 
fully substantiated by the result of selection. On the 
other hand it is perfectly plain that the dimorphic curve 
is not simply the sum of the two monomorphic ones. 
The mixed assemblage does not simply contain the two 
mixed races, either in equal parts or in any other pro- 
portion. It cannot be synthesized from its components. 
This is proved by two circumstances : on the one hand 
by those parts of the curve that lie outside the maximum 
ordinates, on the other by the middle part. The two 
component curves begin at 7 and end at 28 (32) and 
their sum should do so too. But the curve of the mixed 
race is limited by 11 and 23. This is seen more clearly 
by looking at the ordinates 12 and 22, since there are 
far too few individuals in these in Fig. 30. Thus we 
see that the limits of the curves are, so to speak, "drawn 
in" in the mixture. On the contrary the individuals are 
heaped up between the two apices. Moreover in this 
part there is a secondary maximum. This is seen at 17, 
but in the commercial mixture of 1895 falls on 16 1 ac- 
cording to the figures given above (see p. 172). 

We come now to the double race. It is a well-known 
saying amongst horticulturists, that any one who wishes 
to obtain novelties must be eagerly on the lookout for 
small differences (See Vol. I. Part I, p. 185, and this 
volume, 2, p. 9). If these deviations are not cases of 
fluctuating- variabilitv but strike the eve by the fact that 

fJ * m ^ 

they are much rarer than these, it is probable that they 
are the external manifestations of semi-latent characters. 
If this is actually the case it is further probable that the 
character can be brought by isolation and selection to 

1 16 (= 3 -f- 5 -j- 8) is one of the subsidiary numbers in LUD- 
WIG'S law. The question arises whether by the crossing- of two pure 
races these subsidiary numbers may arise elsewhere also. 



178 Observation of the Origin of I'ariehcs. 

partial if not to complete predominance. The success 
of the experiment of course depends on factors still 
unknown to us, for it is by no means always successful. 
My belief in these principles, which DARWIN himself 
often refers to, led me to pay special attention, from the 
very outset of my experiment, to part-curves, i. e., to 
curves derived from the lateral flowers of the single 
plants (seep. 173). It is useless to give the numerous cases 
which afforded no indication of a latent character, and 
so I will proceed at once to that plant which was the 
first to do so. It was a specimen of the 21 -rayed race 
of 1896, which had 21 ray-florets in its terminal in- 
florescences and gave the following part-curve on the 
12th of August : 

L. F. 14 15 16 17 18 19 20 21 22 
No. Ic 1 1 2 2 2 3 3 4 

I refer to this plant as No. Ic 1 in order to indicate 
that it belonged to the same culture as Nos. la and Ib 
whose part-curves were given on page 175. It agrees 
with those two plants in the fact that there is not a trace 
of a maximum at 13; but it differs from them and from 
all the other plants that were examined on the same bed, 
by the possession of four flowers with 22 rays. On no 
other plant was there a single lateral flower with more 
than 21 rays. 

This indication was no doubt pretty small. It would 
not have been discovered but for the counting of the 
ligulate florets. Without this statistical method of in- 
vestigation it would certainly never have been grasped, 
for the plant If grew in a culture of about 1500 speci- 
mens. It was noted first, along with 500 others, as hav- 

1 Berichte d. d. lot. Ges., Vol. XVII, p. 91, where No ir is given 
as No. 12 in the series. 



The Origin of Chrysanthemum Scyctnm Plenum. 179 

ing 21 rays in the terminal inflorescence, and as thus 
complying with the main condition for the new race. By 
means of the grouping of the figures for the offspring, 
that of one seed-parent (1895, No. 1 of page 175) was 
first proved to be far better than that of the five other 
parents. Then amongst this chosen group the individuals 
with the largest number of florets in their terminal heads 
were selected and amongst the best of these was found 
the one which gave the faint indication already described. 

CHRYSANTHEMUM SEGETUM GRANDIFLORUM. 

ANCESTORS OF THE DOUBLE RACE. 



1895 No. 1 21 

1896 No. Ic 21 

1897 34 13 

1898 48 14 

1899 66 f8 

1900 Maximum 101 35 

But small though this indication was, it sufficed to 
bring the latent character to light. All that was still ne- 
cessary \vas to carry the process of selection on through 
three years in the same direction and on similar prin- 
ciples. 

I chose only one seed-parent each year for the 
continuation of the experiment, isolated it together with 
some of the next best as early as possible, and harvested 
its seeds separately from those of its neighbors. Com- 
pletely isolated plants of Chrysanthemum segetnm usually 
set so little seed that it is impossible to rely on them, and 
therefore fertilization has to be effected to a certain ex- 
tent by inferior individuals. If this were not the case 
my object would most certainly have been reached earlier. 



180 Observation of the Origin of Varieties. 

CHRYSANTHEMUM SEGETUM PLENUM. 
(See page 182.) 

CURVES OF RAYS IN THE ANCESTRAL GENERATIONS. 1 

(Only the terminal inflorescence of each individual was employed in 

plotting these curves.) 



T.F. 


14 


15 


16 


17 


18 


19 


20 


21 


22 


23 24 


25 26 


27 


28.29 


30 


1896 2 


15 


15 


22 


30 


33 


36 


64 


123 


15 


5 

















1897 


2 


1 


2 


1 





12 


10 


169 


102 


45 


30 


19 


21 


3 


1 


2 


1 


1898 












1 


2 


10 


17 


17 


20 


21 


30 


17 


13 


10 


11 


1899 












1 


1 


1 








3 


2 


9 


6 


6 


7 


3 



(CONTINUED.) 



T.F. 


31 


32 


33 


34 


35 


36 


37 


38 


39 


40 41 


42 


43 


44 


45 


46 


1897 


1 








1 


























1898 


6 


9 


13 


21 


6 


3 


5 


3 


1 


2 

















2 


1899 


8 


12 


13 


12 


14 


10 


10 


8 


6 


7 


4 


8 


6 


1 


10 


6 


1900 






1 








1 


1 


1 








1 





1 


2 


1 






(CONTINUED.) 



T.F. 


47 


48 


49 


50 


51 


52 


53 


54 


55 


56 


57 


58 


59 


60 


61 


62 


1898 
1899 
1900 



4 
4 


1 
4 



2 




2 
2 


2 





1 


2 
1 



2 


1 





1 


2 





2 














1 
1 



(CONTINUED.) 



T.F. 


63 


64 


65 


66 


67 


68 


69 


70 


71 


72 


73 


74 


75 


99 


101 


1899 











1 


1 






















1900 


1 





1 








1 











1 


1 


1 


1 


1 


1 



1 These series of figures, with the exception of those for 1896 
are exhibited in the form of curves in Fig. 32. 

2 For the complete curve of 1896 see page 175. The individuals 
with 10-13 ra ys are left out here. 



The Origin of Chrysanthemum Scyctiun Plenum. 181 



Chance may also be unfavorable in another respect. 
It often happens that the best plant is not sufficiently 
vigorous to be chosen as seed-parent, but fortunately this 

12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60 63 66 69 72 75 78 8< 84 87 90 93 96 99 1 02 




1897. 



21 




1898. 



AJL 



26 



48 




7599. 



26 




7900. 



AAAAA 



12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 5 7 60 63 66 69 12 75 78 81 84 87 90 93 96 99 102 



Fig. 32. Ancestral generations of Chrysanthemum scgctum 
plenum. Curves of the number of rays in the terminal 
inflorescences in the several individuals of the genera- 
tions of 1897-1900. For the numbers themselves see 
page 180. The seed-parent of 1896 was 2i-rayed (X at 
the top of the 1897 curve) ; the other chosen seed-parents 
are indicated in the various curves by a X over the appro- 
priate ordinate. The original plant, from which the 
culture was derived, was the individual grown in 1895 
as No. i (p. 175) from which No. ic arose in 1896, and 
from the seeds of this came the culture of 1897. 

difficulty did not present itself in the experiment under 
consideration, partly because of the favorable conditions 
of culture. 



182 Observation of the Origin of Varieties. 

The progress was uniform and regular and the sim- 
plest index of it is the series of successive seed-parents. 
The number of ray-florets in the terminal inflorescences 
of my selected plants in successive years was as shown 
in the table on page 179. 

The progress can be seen still better from the curves 
which I have plotted of the terminal inflorescences in the 
various generations. The reader is referred to the table 
on page 180 and Fig. 32 on page 181. The original plant 
of 1895 referred to as No. 1 arose from a seed which, 
as already stated, was obtained by exchange from a 
botanical garden. Indeed this particular lot of seed came 
from Groningen but produced a mixture the curve of 
which would obviously not have any special interest. The 
cultures of the subsequent years were every time the 
offspring of a single individual whose fertilization by its 
like had been insured as much as possible. 

The following considerations arise out of an inspec- 
tion of Fig. 32. 

The curve of 1897 was monomorphic like that of the 
typical examples of the 21-rayed race (Fig. 31 B, p. 169) ; 
but it was markedly asymmetrical, a fact which afforded 
a pretty strong indication that the race could be improved 
by selection in the plus direction. It confirmed the expec- 
tation based on the part-curve of the parent of this 
culture. 

The curve of 1898 relates to the offspring of the 34- 
rayed plant of 1897. In it new maxima appear. These 
conform with LUDWIG'S law, for they lie on the figures 
of the well-known BRAUN-SCHIMPER or FIBONACCI se- 
ries. One of them is at 34 (= 13 + 21) which belongs 
to the primary series ; the other is at 26 (= 5 + 8+ 13) 
which is one of the subsidiary numbers. The maximum 



The Oriyin of Chrysanthemum Scyctmn I'lcmun. 183 




in this year was offered by a plant with 48 rays which 
\vas healthy enough to be chosen as a seed-parent. But 
this figure lies very close to the next figure in the series 
(13 + 34: =47). The maximum at 21 has disappeared, 
but the form of the curve clearly indicates its participa- 
tion in the composition of the 
whole. 

In the following year the 
advance was much less consid- 
erable. The maxima at 26 and 
34 and that near 47 became 
more distinct, but the maxi- 
mum number of rays increased 
to 67. At the same time an- 
other still more important dif- 
ference appeared since now for 
the first time ligulate florets 
appeared between the tubular 
florets of the disc. This only 
occurred on a single plant and 
not till the beginning of Sep- 
tember. This plant had 66 
rays in its terminal inflores- 
cence, and was one of those 
which had been selected as seed- 
parents, and accordingly isolated at the beginning of the 
flowering period. On account of its possession of this 
first sign of real doubling it was chosen for the continua- 
tion of the experiment in 1900, to the exclusion of all 
the rest. 

It is well known that in other species of this genus 
( e. g.. Chrysanthemum indicuui and C. inodonun) the 
doubling consists in exactly the same phenomenon. In 



Fig- 33- Chrysanthemum se- 

gctiun plenum. One of 
the six inflorescences 
which in 1899 first exhib- 
ited true "doubling." The 
figure represents the par- 
ent plant of the "double" 
variety. 



184 Observation of the Oriyin of Varieties. 

the midst of the tubular florets (Fig. 34A) ligulate florets 
are developed (Fig. 34B). If the "doubling" is carried 
very far the former are completely covered by the latter 
(Fig. 34C), and can only be seen by pulling out the 
ligulate florets or by turning them aside. If this is done 
a large number (and not merely a few scattered ones, as 
might perhaps be expected) of tubular yellow corollas 




Fig. 34. Chrysanthemum inodorum plenissimum. A, in- 
florescence with central disc of tube florets (fertile) ; 
B, with scattered tongue-florets in the disc (half fer- 
tile) ; C, highest degree of "doubling" (sterile). 

are ordinarily found; and the less the amount of doubling 
the more conspicuous they are. Moreover we often find, 
in both species, inflorescences with a broad yellow disc 
over which occasional white ligulate florets are scattered 
(Fig. 34 B). Such flowerheads look like anomalies, 
though, as a matter of fact, they are less anomalous 
than the apparently completely "double" forms. 



The Origin of Chrysanthemum Scyctum Plenum. 185 

This 66-rayed plant was the first of my race to betray 
the fact that it contained the much desired double char- 
acter. From this moment the attainment of my object 
was assured. 

The six first "double" inflorescences referred to, had 
about 40-50 ray-florets around their circumference and 
moreover one to three in the disc. But as they flowered 
too late to ripen seeds, I have photographed and pre- 
served them (Fig. 33). 

Unfortunately this plant gave but a poor harvest, 
producing only 31 plants with terminal flowerheads. A 
curve representing these heads is given in Fig. 32 under 
1900. The number of observations is of course much 
too small to furnish a proper curve or to justify the draw- 
ing of conclusions as to its maxima. On the whole, 
however, the figure indicates a definite advance over the 
earlier years, and this advance is especially expressed in 
the fact that amongst this small number there were two 
plants which far outstripped all previous ones in the 
number of their ray-florets. Their terminal inflorescences 
contained respectively 99 and 101 rays, whereas the next 
maximum expected would be 34 -f- 55 = 89. 

"Doubling" now appeared quite suddenly in full de- 
velopment in this culture (Plate II). For convenience 
of reference I shall call the white ligulate florets situated 
amongst the little yellow tube florets, "disc-tongues." 
These disc-tongues were now quite common. From no 
single plant were they completely absent if attention was 
paid to both the terminal and lateral flowerheads. But 
their number was subject to a high degree of fluctu- 
ating variability. As a rule flowers with less than 40 
rays had no disc-tongues, and the number of these in- 
creased with the total number of the outer rays. For 



186 Observation of the Origin of Varieties. 

instance, a terminal flowerhead with 56 rays had 53 on 
the periphery and 3 inside ; while one with 74 rays had 
58 on the circumference and 16 in the disc. In the 
records on which were based the table on page 180 and 
Fig. 32, both kinds of ligulate florets were counted to- 
gether. The two flowers with 99 and 101 ligulate flo- 
rets respectively were to all appearance almost entirely 
double. 

The "doubling" was also exhibited on the lateral 
branches. When these were in full flower, I selected the 
twelve best "double" plants and pulled up the rest. The 
lateral inflorescences of the rejected plants gave a curve 
whose maximum was at 47 (=13 + 34) in accordance 
with the indications referred to above and apparent in 
Fig. 32. The worst flower had only 28, the best one 
94 rays. The average of the whole lot was 47; but the 
curve, in spite of the coincidence of the mean and the 
maximum was not symmetrical. Altogether the rays of 
378 inflorescences were counted. 

As was to be expected, the selected seed-parents ex- 
hibited great differences in the degree of "doubling" in 
the lateral inflorescences. On some this was inconsider- 
able. On others the mean was from 2-5 disc-tongues 
per inflorescence whilst on two a mean of 1 1 was counted. 
One plant bore nothing but wholly double flowers. It 
had seven flowers on which 279 disc-tongues were 
counted, giving an average of 40. In consequence of 
this the plant was absolutely sterile; it bloomed well 
afterwards, but in spite of every care I could not get 
a single seed from it. But the finest specimens of C . in- 
odoritm plenissimum are also known to set no seed. Like- 
wise the two plants whose lateral flowers had on the 
average 11 disc-tongues, set no seed. 



The Origin of Chrysanthemum Segctiun Plenum. 187 

We thus see that the limit has been reached. Any 
further improvement of the race will only increase the 
number of doubles and consequently of sterile individ- 
uals. Seed-parents therefore must always be chosen 
amongst the plants with the same degree of "doubling" 
as in this year (1900). In this respect my new race be- 
haved, immediately after its origin, exactly like the old- 
established Chrysanthemum inodorum plenissimum. 1 

It still remains to give some account of the general 
conditions of fertilization of the seed-parents in the vari- 
ous years. No doubt the experiment would have been 
purer and more demonstrative if the corn marigold were 
capable of self-fertilization. But this either does not 
occur at all, or only to a totally inadequate extent. Each 
year I have therefore left a group of a few selected plants 
to flower together after the eradication of the rest; and 
have been obliged to content myself with collecting the 
seed of each in a separate package. Future experiments 
will have to determine what the effect of this crossing 

o 

may have been on the progress of the race. Meanwhile 
it may be of interest to place on record the number of 
plants which have flowered together each year, showing 
the stringency of selection to which they were subjected. 
In the summer of 1895 the original parent of the 
whole race, which was raised from seeds obtained by ex- 
change (1895, No. 1), could not be isolated until late 
and then incompletely, but as the plants flowering at the 
same time also belonged to the 21 -rayed race the curve 
of the offspring was very "pure" in this respect (p. 176). 
In the next year the number of seed-bearers was reduced, 
about the middle of August, to three very vigorous incli- 

1 The Matricaria ftore _ toto albo plenissinw, described by MUN- 
TING in 1871, the best specimens of which also set no seed, was prob- 
ably the same variety (Waare Oeffeningc der Planten, p. 527). 



188 Observation of the Origin of Varieties. 

victuals which had 21, 21, and 22 rays respectively, in their 
terminal inflorescences. One of those with 21 served 
for the continuation of the experiment but all three had 
exhibited correspondingly high numbers in their lateral 
flowers. The fertilization in this year was therefore 
sufficiently pure. 

This was not the case in 1897. The 34-rayed seed- 
parent of that year was pollinated at first amongst all the 
other plants, and later amongst the rest of the selected 
ones which were however as many as 25 in number. It 
set so little seed that it was impossible to rely solely on 
the seed due to the later pollinations (i. e., the purest 
seed) for next year's crop. The two maxima of the 
curve of 1898 are therefore, at least to some extent, due 
to mixed pollination (Fig. 32 under 1898). 

In 1898 I selected the seeds for the continuance of 
the race in two periods on the chosen seed-parent after 
having marked the flowers separately for them. The 
first harvest was from flowers which had bloomed be- 
fore the removal of the rest, the second from those which 
had bloomed later. The latter must therefore have been 
fertilized by the seven remaining seed-parents whose ter- 
minal inflorescences, however, all had had more than 34 
rays (the numbers were 35-36-37-38-39-40 and 46). 
The two specimens were sown separately and their curves 
determined ; but no essential difference between them 
could be detected, either in their limits, or in their means, 
or in their general shape. The seed-parent of 1899 with 
66 rays and with the first 1-3 ligulate florets on its discs 
(Fig. 33), belonged to the first series, the 67-rayed plant 
shown in the table on page 180 for 1899, however, to 
the second. 

In the summer of 1899, towards the end of July, I 



The Origin of Chrysanthemum Scgctiun Plenum. 189 

saved 17 seed-parents with 48-67 rays in their terminal 
inflorescence. From these I collected the seed from the 
flowers which bloomed in July separately from those 
whose flowers had opened after the selection had taken 
place. But from the former specimen I raised only 
three plants that flowered (with 41-44-47 rays in their 
terminal head), which evidently could have no effect on 
the shape of the curve and were soon removed. Fertili- 
zation in 1899 therefore was again very pure. 

Having arrived at the end of the account of our ex- 
periment, all that remains is to compare the course of 
the selective process in this case with the ordinary pro- 
cess of selection carried out in the improvement of agri- 
cultural plants. I refer the reader to FRITZ MUELLER'S 
experiment with the many-rowed maize already de- 
scribed. 1 

That the difference is essential will be clear from the 
description given. In the case of the maize the object 
was to intensify the racial character (12-14 rows) as 
much as possible by selection; in the case of the Chry- 
santhemum the object was to uncover a latent character 
and to bring this to its full development. In the first 
case a visible character that had been known for ages 

o 

had to be increased as much as possible ; in the second, 
according to current conceptions at least, a new char- 
acter had to be called forth. The 26-28 rowed ears fall 
within the range of fluctuation of the 12-14 rowed race; 
and they would without doubt have appeared within it 
without any selection, if cultures of sufficient extent, 
which could be calculated beforehand, had been grown 
(Vol. I, p. 162). 

Without any doubt my crop of 1897 would have 

1 See the pedigree in Vol. I, Fig. 18, p. 73. 



190 Observation of the Origin of Varieties. 

given rise immediately to flowerheads with central ligu- 
late florets if it had been on a sufficiently large scale. 
But it would not have produced them in a proportion 
which could be predicted by QUETELET'S law, but accord- 
ing to the principles of discontinuous variation which 
are still unknown to us. 

The course of the improvement is different in the 
two cases. The results obtained with the maize conform 
to the law of regression, the increase in the number of 
rows in the ears becoming slower and more difficult to 
secure, the further we get from the starting-point. Ex- 
actly the reverse is the case in the Chrysanthemum. The 
progress was continuous and did not materially change 
until 1899, when the first central ligulate florets appeared. 
Then it took a leap, all the offspring of this plant having 
more or less double flowers. More strictly speaking, 
the leap had already taken place, the plant with the first 
central ligulate florets (Fig. 33) having already crossed 
the threshold. Its offspring behaved like the offspring 
of a pure race, such as for instance C '. inodonun plenis- 
simum. 

A break therefore occurred, and obviously before 
1899; either in the origin of the seeds of 1898 from 
which the plant in question arose, or even earlier. 

And since C. Inodornm plenissimum has maintained 
itself for many years without selection, it is probable 
that the new C. segetnm plenum will do the same. But 
the reverse was the case with the maize which reverted 
to the old form within a few years after the cessation 
of selection (Vol. I, p. 125). 

Hitherto I have taken the number of ray-florets in the 
terminal inflorescence -almost exclusively as a character 
of the whole plant, and the curves have been plotted 



The Origin of Chrysanthemum Seyetuin Plenum. 

from the figures obtained in this way. But there is, as 
\ve have already seen, another method of estimating the 
individual value of a plant, namely that based on a de- 
termination of the mean character of as many flowers 
as possible on a single individual. This raises two points 
for consideration : first the mode of branching of the 
corn marigold, and secondly the influence of the devia- 
tion of the individual from the mean of its race. 

The mode of branching in Chrysanthemum secjctinn 
is as follows. The main stem which arises from the 
plumule bears two groups of branches ; strong ones at its 
base from the axils of the radical leaves ; and, higher up, 
weaker ones whose vigor first gradually increases and 
then decreases, as they succeed one another from below 
upwards. This applies both to their length and to the 
number and strength of their secondary branches. These 
secondary branches are, therefore, of the third order: 
they often bear branchlets of the fourth and even of 
the fifth order. The flowers that bloom in July, with us, 
are mostly of the second order, those blooming in August 

- o o 

and September of the third and fourth. 

In the course of the summer, and with the flowers 
on the successively higher orders of branches variability 
is seen to manifest a general decrease. The sides of the 
curve are, so to speak, drawn in; the curve itself be- 
comes narrower. The amount of deviation of the various 
individuals from the mean of the race decreases, and 
the mean consequently comes to stand out more boldly. 
This is of especial importance in cases in which a curve 
has been shifted laterally by stringent selection (such 
as Fig. 32, p. 181) where it might remain doubtful what 
the shape of the curves would have been if selection had 



192 Observation of the Origin of Varieties. 

effected nothing more than the isolation of the individ- 
uals of the new race. 

We have therefore to examine the "late summer" 
curves of the 13-rayed, 21 -rayed and double races. Let 
us begin with the first. 

The extreme limits of the curve of this race at the 
beginning of August were 11 and 21 ray-florets. These 
numbers gradually decreased until September, when only 
heads with 13 and 14 rays were formed. In the next 
year at the end of July the limits were 10-19, but in 
August 12-14. 

I examined the 21 -rayed race, with reference to this 
character, in the summer of 1898, dealing with the indi- 
viduals which had been saved for seed. The data for 
three of the plants 1 are summarized in the following 
table : 

PLANT FLOWERS NUMBER MIN. MED. MAX. 

A. Terminal 1 48 
September 1st 32 29 33 45 
October 10th 42 18 27 36 
November 1st 28 19 26 31 

B. Terminal 1 35 
September 1st 36 24 28 36 
October 10th 33 16 22 27 
November 1st 23 15 21 25 

C. Terminal 1 46 
September 1st 14 26 28 35 
October 10th 18 18 26 30 
November 1st 8 21 23 28 

We see that the numbers gradually shift in the direc- 
tion of the maximum at 21 (in the case of one plant 
actually reaching it), without any indication of the max- 
imum at 13 of the other race. The plants dealt with, 
therefore, clearly belonged to the 21 -rayed race. 

1 Over het periodisch optreden dcr anomallen op monstreuze 
planten. Kruidkundig Jaarboek, Gent, XI, 1899, pp. 57-58. 



MIN. 


MED. 


MAX. 


33 


39 


50 


31 


42 


50 


37 


47 


54 


33 


51 


60 


33 


40 


51 


33 


47 


62 


32 


43 


52 



The Origin of Chrysanthemum Segetnm Plenum. 193 

This was apparently no longer the case in the follow- 
ing summer. The following are the records of five 
plants taken in late summer : 

TERMINAL INFL. 

A 67 

B 55 

C 51 

D 50 

D 

E 66 

E 

D' and E' were counted 6 weeks later on the same 
plants as D and E. The plant E is the seed-parent in 
Fig. 32, p. 181, under 1899, marked with a X- The 
figures may be regarded as the expression of a tendency 
to fall back on the secondary maximum at 47 (= 13 + 
34), and the same result was reached by the other count- 
ings, which it is not worth while to reproduce here. 

In the following year (1900) the maximum of the 
lateral inflorescences was still higher. I give the data 
derived from three plants which were "double" and con- 
sequently sterile, and of the four next best which were 
chosen as seedparents. 

Sterile I. 

II. 

III. 

Seed-parent I. 

II. 

III. 

IV. 

The curve of the "double" race thus seems to have 
its maximum at about 55 (=21+34). The possi- 
bility of attaining higher mean numbers seems to be 



MIN. 


MED. 


MAX. 


72 


87 


100 


48 


62 


94 


46 


56 


79 


47 


63 


76 


51 


62 


91 


44 


60 


94 


46 


56 


86 



194 Observation of the Origin of 1 \irieties. 

excluded by the sterility of the more perfectly double 
plants. 

Let us now briefly summarize the results of this ex- 
periment. There is, on the market, a 21 -rayed race of 
the normally 13-rayed Chrysanthemum segetnm. It is 
not strictly pure, but can easily be made so; it bears the 
name C. segetnin grand iflonmi. From a plant which, 
in 1895, caught my attention by a few 22-rayed lateral 
flowers, I succeeded in raising, by a process of selection, 
a hitherto unknown race with double flowerheads, the 
new C. segctwn plenum (Plate II). The course of this 
process is exhibited in Fig. 32, p. 181, in which the 
X X X X indicate the individuals selected as seed- 
parents for each succeeding generation. C. segetuin 
plenum behaves with regard to its double character, 
exactly like the double commercial varieties of other 
species of the same genus (C. inodonun, C. indiciun etc.). 

The new variety was therefore obtained by bringing 
to light a character latent in C. segetnin grandiflorum. 

19. DOUBLE FLOWERS AND FLOWERHEADS. 

The experiment described in the foregoing section 
( 18) justifies an attempt to form some conception of 
the manner in which this phenomenon of "doubling," 
which is widely distributed among cultivated composites, 
may have arisen in other cases. If we examine the facts 
closely we shall discover in the majority of cases an 
extraordinarily close agreement with our own specimen, 
at least so far as the absence of scientific observations 
admits the possibility of a comparison. 

There are, it is true, certain abnormal types of "doub- 
ling." such as the development of secondary flowerheads 



Double r lowers and Flowerheads. 195 

(Cineraria), the transformation of the little yellow disc- 
florets into long white tubes (Pyrethrum, see Fig. 36) 
etc. We shall however leave such cases out of considera- 
tion ; they may be regarded provisionally as cases of 
spurious doubling. 

The genuine "doubling," on the other hand, as ex- 
hibited by the most diverse species, presents a very 
marked agreement with the conditions found in Chry- 
santhemum segetuni. Indications of a tendency to "doub- 
ling" occur both in forms of which a double variety is 
not offered by seedsmen and in those of which such 
are already on the market. For instance in 1892 I ob- 
served occasional tube-florets more or less completely 
transformed into ligulate florets in a culture of Bidens 
grandifiora in my garden. In other cases the variation 
is only seen when curves are plotted. For example I 
obtained the following very asymmetrical curve from 
a culture of the single variety of Chrysanthemum eoro- 
narium, a favorite garden plant whose double form 
has long been known (Fig. 35). 130 flowers on 25 
plants of a single crop were recorded, the flower at the 
top of the main stem and those on the primary branches 
alone being taken into account. I found : 

Ligulate florets 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 
Inflorescences 101 2 2 12 25 19 21 15 14 6 7 2 3 

That is to say, 18 on one side of the mean and 87 on the 
other, with a faint indication of a second maximum at 
the next figure in the BRAUN-SCHIMPER series, 21. It is 
clear that the double variety of this species could prob- 
ably be obtained from these plants, exactly in the same 
way as in C. segetuni. 

These considerations evidently lead to the hypothesis 
that the secondary maxima on the positive side of LUD- 



196 Observation of the Origin of Varieties. 

WIG'S ray-curves 1 may also indicate the existence of a 
latent character, which, if it could be made active, might 
perhaps give rise to the double variety of the species. 

If we now examine the double varieties of the com- 
posites, we see that the structure of their inflorescences 
corresponds in every detail with that of Chrysanthemum 
segetnm plenum. The amount of doubling is always 




Fig- 35- Chrysanthemum coronarium. 

highly variable. The best cases reveal no tube florets 
as in the case of Chrysanthemum inodoniin in Fig. 34, 
p. 184. But if one looks between the ligulate florets 
small yellow tubes will be found in no inconsiderable 
quantity. This is true of Calendula officinalis and many 
other species. Such flowerheads are usually sterile, for 

1 May not the secondary maxima on the negative side similarly 
indicate the variety without ray-florets, the Var. discoidca (See 8, 
pp. 78-79 and Fig. 9, p. 80). 



Double Flowers and Flowcrheads. 197 

the ligulate florets are female, and inasmuch as very 
often all the flowerheads on a single plant attain to this 
degree of doubling the best variants cannot serve as 
seed-parents. But two further types are always found 
with yellow discs which are either uniform (Fig. 34A) 
or contain scattered ligulate florets amongst the tubular 
ones, as is so often seen in Chrysanthemum indiciun and 
Zinnia clcgans. The double Bcllis perennis also, if grown 
from seeds, is highly variable in this respect. These 
two types are fertile and therefore constitute the seed- 
parents of the variety; if the plants with central ligulate 
florets (see p. 185) furnish sufficient seed the harvest 
is saved exclusively from them ; but they often set little 
or hardly any seed. 

This unavoidable restriction in the choice of the seed- 
parents and the frequent difficulties of selection depen- 
dent on it account for the fact that bought samples of 
the seed of double composites often give rise to only 
a relatively small proportion of the desired type, as has 
long been known 1 to be, and still is, the case (Chrysan- 
themum coronanum sometimes only 50%, Ccntaurca 
Cyanns 40-50%, Tagctcs africana with rare exceptions 
double etc.). 2 

Many double varieties of composites seem to be al- 
most as old as horticulture itself (See Vol. I, p. 183). 
According to the oldest accounts the degree of doubling 
and the range of its variation were formerly the same as 
now. 

Finally I have to mention the fact that bud- and sec- 
torial variations are found in this case as well as in others. 

*E. g., Pyrethrum roseum, Dahlia, Chrysanthemum indicum, ac- 
cording to VERLOT, Production ct fixation des varictcs, 1865, P- 83. 

2 See the catalogues of BENARY, and HAAG-E-& SCHMIDT of Er- 
furt, VEITCH & SONS of London and SUTTON & Co. 



198 Observation of the Qjrigin of I 'arieties. 

I refer to a very beautiful instance of the latter (Fig. 36) 
which I owe to the kindness of MR. ERNST H. KRELAGE 
in Haarlem. 

The origin of double flowers in other groups of flow- 
ering plants has probably occurred on similar lines with 
that of double inflorescences. I restrict myself to a con- 
sideration of doubling by the transformation of stamens 
into petals, that is, the petalocly of the stamens, referring 
the reader for an account of the other types of doubling 
to GOEBEL'S well-known monograph. 1 

Occasional petaloid stamens occur fairly commonly 
both in culture and in nature ; they are so well known 
that it is not necessary to cite special instances. The 
curve which represents this variation is unilateral, indi- 
cating thereby the existence of a latent or semi-latent 
character. 2 The attempt to render this active may be 
made, and if it succeeds 3 the origin of a double variety 
may be expected. 

Double varieties of this kind tend to vary in the same 
way as those of composites. If, for instance, the com- 
mercial Varictatcs plcnac of Clarkia pulchclla, Clarkia 
clcyans. Phlox Drummondi and others are examined, 
almost all the intermediate stages between nearly hemi- 
spherical double flowers and flowers with normal sta- 
mens are met with. In such cases it is usually obvious 
that favorable conditions tend to increase "doubling," 
a fact which has been known for a long time in the 
case of Anthemls nobilis, of some species of Narcissus, 

1 K. GOEBEL, Bcitragc zur Kcnnhu'ss gcfiilltcr Bliithcn, in PRINGS- 
HEIM'S Jahrb. f. wiss. Bot, Vol. 17, 1886, p. 207. 

2 Ucbcr halbc Galton-Curvcn ah Zeichcn discontimurlichcr l r aria- 
tion. Ber. d. d. hot. Ges., Vol. XII, 1894, p. 197. 

3 Which is, however, by no means always the case. See the ex- 
periment with Ranunculus bulbosus in 23 of this part. 



Double Flowers and Flowerheads. 



199 



and other bulbous plants. 1 There is a certain periodicity 
in this case too ; for sometimes the first, but more usually 
the later, flowers are less double than those which bloom 
in the height of the flowering period. This fact is well 
known to breeders,- especially in the case of certain 
double varieties of Begonia in which seeds can only be 
saved from the autumn flowers. 





Fig. 36. Pyrethrum roscuin, from the nursery of Messrs. 
KRELAGE & SON in Haarlem (1899). In one half (the 
rear half in A, the left in B) the inflorescence is made 
"double" by the elongation of the tube-florets ; in the 
other half it is "single." A, oblique view; B, section. 

The majority of double varieties are constant from 
seed, even in the case of trees and shrubs (varieties of 
the peach and the apple for instance), 3 others appear to 
be only slightly so, and others not at all (Pmnns spi- 

1 LiNDLE\^ Theory of Horticulture, p. 333. 

2 CARRIERE, Production ct fixation dcs varietcs, 1865, pp. 66 and 
67 (Camellia alba plena, incarnata, Fuchsia, etc.). 

S VERLOT, loc. cit., p. 83. 



200 Observation of the Origin of Varieties. 



nosa). 1 For instance, 80% is the figure given for Dian- 
thus Caryophyllus, 2 and double varieties of Campanula 
are said always to produce a certain number of single 
plants. In the case of double stocks one may reckon on 
between 50-60% double offspring according to the treat- 
ment and selection of the seed. Pot culture favors "doub- 
ling." 3 

The transformation of stamens into petals often goes 

so far that no pollen is 
formed. When this oc- 
curs the stigma of the 
double flower must be 
fertilized with the pol- 
len of a single flower 
or left to be pollinated 
by insects. The result 
is that the race gives 
rise to both forms every 
year. For instance Pa- 
paver nudicanle auran- 
tiacum plenum, the seeds 
of which give rise to 
between 40 and 60% of 
double -flowered speci- 
mens every year. It is 
the other way round 
with the double Petunia whose capsules are usually mal- 
formed ; but they develop a few stamens, with the pollen 
from which the stigmas of single flowers are dusted, 
'Ibid, 

" Seed catalogue of D. SACHS, Quedlinburg, 1890-91. (Dianthus 
Caryophyllus c. H. Margaritae, novelty 1889). 

3 CHATE, Culture pratique des Giroflecs. NOBBE, Botan. Central- 
blatt, Vol. XXXII, 1887, p. 253. 




Fig. 37. Anemone coronaria, "The 
Bride." Double on one side, single 
on the other. From the cultures of 
Messrs. E. H. KRELAGE & SON of 
Haarlem. 



The Origin of Linaria Vulgaris Peloria. 201 

preferably after castration. The seeds collected after 
this operation are said to give from 25 to 40 % double 
plants the number varying directly with the care with 
which the castration was carried out. 

Double flowers are also subject to sectorial and bud- 
variation. A chestnut tree (Acsculits Hippocastaniun] 
at Geneva, a single branch of which has borne double 
flowers for many years, 1 is perhaps the best known ex- 
ample of the latter, whilst our Fig. 37 gives an interest- 
ing case of the former. It is a flower of the pure white 
Anemone coronaria, ''The Bride," which, like the Py- 
rcthrum, I owe to the kindness of MR. KRELAGE. It grew 
in a bed of the single variety; the plant which bore it 
had exclusively single flowers with the exception of 
this one. On the one half there were stamens only, as 
is shown by the figure; in the other half, however, the 
vast majority of stamens were transformed into narrow 
petals, just as happens all round the stigma in the double 
form. The single variety frequently exhibits more or 
less definite traces of doubling, and from these MESSRS. 
KRELAGE have succeeded in producing a double sort and 
putting it on the market. But a sectorial variation like 
that figured has only been observed once in the course 
of many years. 

20. THE ORIGIN OF LINARIA VULGARIS PELORIA. 

About ten years after the appearance of the first 
edition of DARWIN'S Origin of Species (1859) HOF- 

1 A. P. DE CANDOLLE, Physiologie vegetale, 1832, II, p. 479, and 
ALPH. DE CANDOLLE, Geographic botanique, 1855, H> P- 1080. This 
tree stood in the garden of M. SALADIN DE BUDE near Geneva. Many 
cuttings made from the double-flowered branch have been distrib- 
uted. 



202 Observation of the Origin of Varieties. 

MEISTER wrote the following words at the end of his 
account of pelorias. 1 

"One of the most remarkable features of the varia- 
tions of plants is, without question, the sharpness and 
suddenness of the origin of profound deviations from the 
normal form of structures such as we see it in the phe- 
nomena just considered, in many analogous cases, and 
especially in the formation of monstrosities. The new 
form does not come into existence bv the gradual sum- 

*> O 

mation of small deviations in one direction, during suc- 
ceeding generations; it appears all at once, perfectly 
distinct from the original form." 

This highly important and perfectly correct state- 
ment rests even now simply on the absence of transi- 
tional forms, and does not rest on direct observation. 
If the peloria had originated by a gradual process it 
would be reasonable to suppose that at least in some of 
the relatively numerous instances the intermediate steps 
would have been found ; but as this was not the case it 
was concluded that they did not exist and therefore that 
the origin of the variety had been immediate. 2 

But it is hardly necessary to point out that nothing 
short of direct observation can furnish the final proof. 
Direct observation will moreover inaugurate a new stage 
in the study of this remarkable phenomenon, by making 

1 W. HOFMEISTER, Allgcmc'me Morphologic dcr Gcivachsc, 1868, 
p. 564. 

2 On the pelorias of Linaria, especially of L. spuria, see H. 
VOCHTING, Ueber Bluthcnanomalien, Jahrb. fur wiss. Botan., Vol. 
XXXI, No. 3, 1893, and L. Josx, Bliithenanomalien bei Linaria spuria, 
Biolog. Centralblatt, Vol. XIX, 1899, p. 145. Also J. H. WAKKER, 
Over pelorien, Ned. Kruidk. Archief, Vol. V, p. i, July 1889, with 
Plate X. P. VUILLEMIN, Monstruosites chez le Linaria vulgar is, 
Bull. Soc. Sc., Nancy, Dec. 1893, with one plate (Vol. XIII, 1894, 
P- 33)- W. and A BATESON, On Variations in the Floral Symmetry, 
Journ. Linn. Soc. Bot., Vol. 28, 1871, p. 381. 





The Origin of Linaria J^ul (juris Pcloria. 203 

accessible to investigation the mode of its appearance 
and the external causes to which it is due. 

For these reasons I have endeavored to induce the 
occurrence of the Pcloria from the ordinary form in my 
experimental garden. It is obvious that the success of 
such an experiment, at least at first, is dependent on 
chance. This chance however can be favored by making 
the cultures as extensive as possible, and by widely vari- 
able conditions of life. Fortune has favored me, and 
after seven years' work my 
object has been attained. 
ThePeloria appeared quite 
suddenly in the fifth and 
sixth generation of my 
culture. 

The signification of 
my observations will be 
more properly understood 
if I premise my account 
of them with a short gen- 
eral and historical account 
of the subject, referring Fi s- 38. A B Linaria vulgaris. 

J . C, D, Pelonc flowers. 

the reader for the litera- 
ture to the following section (21) and to PENZIG'S 
TeratologieS 

Peloric flowers in Linaria I'ulgaris' 2 were first dis- 
covered, as is well known, in 1742 by ZIOBERG on an 
island near Upsala and described by LINN^US in the 

1 O. PENZIG, PHanzciv-Teratologic, Vol. II, p. 195. 

! The Pelorias have five spurs: Pcloria ncctaria. But there is 
also a Peloria ancctaria in which the flowers are regular but without 
spurs. See PENZIG, loc. cit., and VERLOT, Production des varictcs, 
p. 90. This variety is nearly sterile, setting very little seed, but it 
breeds true. 





204 Observation of the Origin of Varieties. 

Amoenitates academicae. 1 The plant grew there together 
with the ordinary Linaria and formed a "constant" race 




Fig. 39. Linaria vulgaris pelorla. A richly branched stem 
of a plant of the second generation. Raised in 1898 from 
seed of the first generation of 1897 and photographed in 
August 1900. All flowers are peloric. 

through propagation by the buds on its roots. All the 
flowers of this plant were peloric (as in Fig. 39). LIN- 

1 Amoen. acad., I, p. 55, p. 280 (1744). See MOQUIN-TANDON, 
Pfiansen-Teratologie, 1842, p. 170, and HOFMEISTER, loc. cit., p. 563. 



The Origin of Linaria Vulgaris Pcloria. 205 



described this form, which was new then, under 
the name of Pcloria, derived from the Greek WA<op, a 
monster. 

It was not till later that the occasional occurrence of 
isolated peloric flowers on the ordinary Linaria vulgaris 
was noticed. Moreover in the 
course of time further speci- 
mens of the true Peloria were 
found scattered over most of 
Europe. 

Such plants have been 
brought into cultivation by 
many investigators. They 
have remained constant and 
could be propagated by means 
of their numerous radical 
buds. In the occasional cases 
in which the plants apparently 
reverted to the one-spurred 
form it is possible that some 
roots of the ordinary L. vul- 
garis were accidentally trans- 
planted amongst the roots of 
the peloric specimen. So many 
descriptions of the flowers ex- 
ist that I think it is hardly 
necessary to repeat them. In 
Fig. 39, however, will be seen 
a freely branched specimen of our plant. I have also 
given a figure of a spike of the ordinary Linaria vulgaris 
in Fig. 40, for the sake of comparison. 

The common opinion of those who have worked with 
the Pcloria is that it is in a high degree sterile. The 




Fig. 40. Linaria vulgaris. A 
normal flowering stem. 



206 Observation of the Origin of J'arietics. 

pollen is poorly developed and the capsule is practically 
atrophied ; but not to such an extent that fertile seeds 
are never produced, as some investigators seem to think, 1 
for some attempts to harvest seed have been successful. 
\VILLDENOW records an experiment in which such seed 
has given rise almost exclusively to peloric plants. 2 

The Pcloria, or Linaria vulgaris peloria is character- 
ized by the fact that all its flowers are peloric. This 
character is, it is true, subject to considerable fluctuating 
variability, especially in the number and degree of devel- 
opment of the spurs. But I never found normal one- 
spurred flowers amongst them, although since 1894 I 
was able to observe in my cultures several hundreds of 
peloric flowers every year, and in favorable years even 
many thousands of them. 

Besides this Pcloria, as already stated, there are some- 
times found on the ordinary Linaria vulgaris isolated 
peloric structures, which are subject to a high degree of 
fluctuating variability (Fig. 41). The most usual case 
is a single flower on a plant which does not bear another 
afterwards during the whole course of the summer. 
Sometimes I found 2 or even 3 peloric flowers on the 
same plant, both in the wild and in the cultivated state, 
but seldom a larger number. It often happens that an 
individual which has produced the abnormality in its first 
year will not produce a single one in the second, although 
it branches more freely and bears many more flowers ; 
on the other hand the abnormality sometimes reappears. 
Such isolated pelorias are not limited to any particular 
position r although in my garden they usually occurred 

1 VERLOT, Production et fixation des varictcs, p. 90. 

' DE CANDOLLE, Physiologic vcgctale, II, p. 692. My experience is 
in full agreement with that of WILLDENOW. (See p. 216.) 

3 See PENZIG, loc. cit., p. 195 



The Origin of Li mm a rulyaris Pcloria. 207 



on the highest lateral twig below the main flower- 
spike. 

The question suggests itself, Is the power of pro- 
ducing isolated peloric flowers inherent in all plants of 
Linaria vulgaris? Or are there two races, one with and 
one without this faculty? This question seems not to 
have been investigated as yet. 
From the observations already 
described it must be concluded 
that this point can never be de- 
termined in the field, for the 
absence of the abnormality on 
particular days, or even in par- 
ticular years proves nothing in 
itself. Personally I think it 
likelv that both kinds exist and 

J 

that there are localities for Li- 
naria vulgaris in which these ab- 
normalities are never found. 

Holland however is not one 
of these. By paying attention 
to them when out on an expe- 
dition, one will find isolated pe- 
loric specimens fairly frequently 
and in the most diverse localities. 
When I wanted a specimen to 
photograph for an illustration (Fig. 41), I asked my 
wife to look for one in the neighborhood, and it was 
not long before I had one. The power to produce them 
is, therefore, widely distributed in this country; and 
also obviously heritable although in a latent state as a 
rule. Whether or no there are localities in which this 
character does not occur, I cannot tell. 




Fig. 41. Linaria vulgaris 
licinipcloria. Branch of 
a normal flowered plant 
with a single peloric 
flower. Zandpoort, Aug. 
1900. a, normal one- 
spurred flower, b, a Pe- 
loria. 



208 Observation of the Origin of Varieties. 

So long as it is not certain whether a Linaria vulgaris 
apcloria exists, I propose to call the plants with this power 
provisionally L. vulgaris hemipeloria (Fig. 41). This 
name of course refers both to those plants on which iso- 
lated peloric flowers have been observed, and to their 
offspring. 

Cases of true Pcloria (Fig. 39) are also occasionally 
seen in this country in the wild condition. A few local- 
ities for it are recorded in the Floras. I myself had 
some plants from a spot near Zandvoort in 1874, but 
since then it has not been found there again. Only one 
new locality has since become known to me, and this 
was near Oldenzaal (1896). It is of course not known 
whether the Pcloria occurred spontaneously in these var- 
ious localities and had not been introduced from else- 
where, but its high degree of infertility makes the likeli- 
hood of such an introduction very remote. 

For the purposes of my experiment I transplanted 
some plants from the country into my garden in the 
summer of 1886. I selected plants with occasional pel- 
oric flowers and freed their roots as carefully as possible 
of fragments of roots whose connection with the hemi- 
peloric plants was not absolutely certain. The plants came 
from Gooiland. I also collected, at the same time, the 
Linaria vulgaris with Catacorolla, 1 and obtained the 
three-spurred variety (see 8, p. 87) from DR. WAKKER. 
These three forms flowered together in the following 
summer in my garden. 

In 1888 I sowed the seeds which I had collected in 
1887, to produce the second generation, but the plants 
did not flower till 1889 and again in 1890. In the first 
year a single peloric flower was produced amongst in- 

1 See Chapter IT of this part, 4, p. 31. 



The Origin of Linaria Vulgaris Pcloria. 209 

numerable flowers with a single spur ; in the second year, 
however, two appeared. I collected the seeds of these 
plants in 1889. 

From this I raised the third generation in 1890. Here 
again the plants did not flower till the second year, and 
again there was one case of a Pcloria amongst thousands 
of normal flowers. I harvested the fruits of this peloric 
plant separately and it furnished me with sufficient seed 
for the culture of 1892. 

This year I adopted the plan of sowing the seeds in 
pans, containing good garden soil, in the greenhouse of 
my laboratory. Hitherto I had simply sown the seed in 
the bed, for which method, however, a much larger 
quantity of seed is required. The seedlings were planted 
out singly in pots containing richly manured soil as soon 
as they began to develop a hypocotylous bud ; then they 
were kept under glass, and were not transferred to the 
open bed until June. The result was that they not only 
flowered in the first year, but did so very luxuriantly. 
There were about twenty individuals in all. On one 
of these I saw a single peloric flower at the end of 
August. In the autumn I pulled up all the plants except 
two, one of which had exhibited the peloria. These two 
plants flowered in the following year in complete isola- 
tion, a profusion of flowers being borne on the freely 
branched stems, but they did not then develop a single 
peloric flower. They produced 13cc of seeds, an abun- 
dant harvest. I sowed a small proportion of this in the 
following year, and as it gave rise to the Linaria inil- 
garis peloria I was looking for, I sowed the rest in 1896, 
and some again in 1899. 

Before we proceed to give an account of this main 
section of the experiment let us briefly summarize the 



210 Observation of the Origin of Varieties. 

results obtained in the years 1886-1893. They com- 
prise four generations, each of which produced only 
one or two peloric flowers amongst thousands of normal 
ones. The anomaly, therefore, seems to recur every 
year and is obviously due to the existence of some her- 
itable semi-latent potentiality which only very seldom 
becomes active. 

This result of the experiment supports the conclu- 
sion based on the repeated occurrence of isolated peloric 
flowers in nature. Linaria vulgaris hemipeloria is thereby 
shown to be a heritable form. The question whether 
it is identical with Linaria vulgaris itself, or constitutes 
a variety or a race of this, cannot be answered for the 
present. From it my L. vulgaris peloria arose, as I shall 
now show. 

In order to make this part of my experiment more 
easily intelligible I shall first describe it in the form of a 
pedigree. This contains the four generations already 
dealt with, and two further ones of the Hemipeloria 
(1-6), together with the first, second, and third genera- 
tions of wholly peloric plants (I-III). The meanings 
of the abbreviations are : 

h and H: Linaria vulgaris hemipeloria. 

p: peloria, 1st generation. 

P: " " 2d and 3d generations. 

Wherever necessary the number of plants is prefixed 
to these letters either in absolute numbers or in percent- 
ages. For the fifth and sixth generation I have, as will 
be seen, made repeated sowings in various years. The 
sign ( 2 ) means that the examples in question were the 
same as in the previous year, and bore seed a second 
time. Finally I have denoted by H the two plants of 
1893 which in their second year produced the seed from 



The Origin of Linaria Vulgaris Peloria. 211 



which the L. vulgaris pcloria first arose. These H plants 
were therefore the parents of the peloric race. 

PEDIGREE OF THE ORIGIN OF LINARIA VULGARIS PELORIA. 



GENERATION 


H and h = Hemipeloria ; p and P Peloria. 


III 
II 
I-II 

6 
5 

4 
3 

2 

1 


1899 
annual 

1898 
annual 

1897 
annual and 
biennial 

1895, 1897 
annual 

1894, 1896, 
1899 
annual 

1892-93 
biennial 

1890-91 
biennial 

1888-89 
biennial 

1886-87 
biennial 


28 P -f 4 h 


75 P + 4 // 
3 P -f 5 h (2) 


i 

s 


15 // + 2 /> 6 h + 1 p 


1895 1897 
57 h -f 1 p h -f 1% p h + 1% / 


1894 1896 1899 

V 


H 

h 
h 
h 



We will begin the further account of the experiment 
with the parent plants (H) of the peloric race (1893). 
As I had not of course observed anything extraordinary 
up to that time I only sowed a little of its seed. This 
was done in pans in the greenhouse; the young plants 
were transferred into pots with manured soil until they 
were planted out in June. As a result of this treatment 



212 Observation of the Origin of Varieties. 

they all flowered in the first year, 58 plants in all, of 
which 45 were clicotylous and 13 tricotylous. Amongst 
the dicotyls there were eleven plants, each of which bore 
one, two, or three peloric flowers, while in one case a 
peloric flower replaced a whole raceme. Amongst the 
tricotyls I did not find any such flowers, partly because 
the majority of these \vere removed by the middle of 
August; but there appeared amongst them one plant 
which bore peloric flowers exclusively on all of its stems 
and their branches. It bore no seed in spite of repeated 
careful pollination, partly with pollen from the neigh- 
boring plants ; it survived the winter and flowered freely 
in the following year, again producing exclusively peloric 
flowers. 

This experiment seemed to suggest that the Peloria 
arose from the hemipeloric parent in a proportion of 
about 1-2%. So in order to obtain closer knowledge of 
this proportion, I made a larger sowing in 1896 from 
the same lot of seed, and was able to plant out about 
1850 seedlings in pots. By the middle of July some 
wholly peloric individuals had appeared, which were 
promptly taken up and transferred to a remote part of 
the garden. The further examples of Peloria which 
appeared from time to time, were planted beside them. 
By the middle of August all healthy plants were in 
flower and were recorded. There were altogether 16 
totally peloric plants and 1759 with ordinary flowers, 
and here and there occasional peloric structures. This 
gives a total of 1775 plants which flowered, of which 1% 
(strictly speaking 0.9%) belonged to the new peloric 
variety. 

For the harvest the flowers of the best peloric plants 
were enclosed in parchment bags and each fertilized with 



The Origin of Linaria Vulgaris Pcloriu. 213 

the pollen of another peloric plant. I also selected a 
beautiful hemipeloric plant which bore a profusion of 
flowers, one of the earlier of which was peloric. It set 
a quantity of seed after self-pollination. 1 

I repeated the experiment in 1899 with the rest of the 
seed of the parent plant H, and obtained the same result, 
as was to be expected. I raised slightly over 300 flower- 
ing plants, of which 3 were wholly peloric; that is to 
say, a proportion of \% again. I observed on the rest 
a certain number of stray peloric flowers during the 
course of about two months. 

These three cultures constituted the fifth generation 
of my experiment. The sixth generation therefore could 
be raised from the seeds of the hemipeloric plants in it. 
I did this partly in 1895 from the plants of 1894, and 
partly in 1897 from those of 1896. The plants which 
bore the seed had flowered in bags and had been fertilized 
partly by their own pollen and partly by pollen which 
I had transferred from one seed-parent to the other. 

In both cases the mutation was repeated. Wholly 
peloric individuals again arose from hemipeloric ances- 
tors, in spite of the smallness of the crops occasioned by 
the poorness of the harvest. 

In 1895 I raised 17 flowering individuals from seeds 
of the dicotylous plants mentioned on page 559; two of 
them were wholly peloric, all their flowers being of this 
type. In 1897 I sowed the seed of the fine hemipeloric 
plant of 1896 referred to above, but obtained only 7 
flowering individuals, one of which again, ho\vever, was 
wholly peloric. 

I come now to the consideration of the question as 

[ This frequently fails in Linaria vulgaris, but sometimes succeeds 
more or less completely on very vigorous plants. 



214 Observation of tlic Origin of Varieties. 

to whether the mutants are immediately constant from 
seed. An almost insurmountable obstacle in the way of 
providing an answer to this question is the low fertility, 
or rather the almost complete sterility, of the peloric 
flowers. Practically no results can be obtained with 
self-pollination, and when artificially fertilized with one 
another's pollen the majority of the flowers set no seed. 
I have pollinated thousands of flowers in the course of 
several years, only to obtain a little over one hundred 
fertile seeds. Under these circumstances it is obviously 
difficult to avoid mistakes ; stray pollen grains may happen 
to reach the stigma from distant groups of normal plants, 
by the agency of insects, or in the operation of artificial 
pollination. 1 These circumstances evidently tend to in- 
validate the conclusion in cases in which the abnormality 
would seem to be incompletely inherited. 

Only three of the wholly peloric plants of 1896 set 
seed in that year. From this seed only 8 plants were 
raised ; five of them had one-spurred flowers and 3 were 
wholly peloric. I kept the peloric plants of 1896 through 
the winter, and took much trouble in 1897 in the attempt 
to fertilize their flowers. Every other day I pollinated 
all the open flowers with pollen from two other seed- 
parents. I obtained a very small quantity of seed most 
of which was empty (0.2 cc). About 100 seeds ger- 
minated, but some of the young plants were so weak 
that they soon died. 79 plants flowered most of which 
were very vigorous and branched freely ; 75 were wholly 
peloric, and 4 normal, the latter being removed as soon 
as possible. The former exhibited great variability in 
the structure of their flowers, but did not produce a 
single one-spurred corolla. During July and August they 

1 Such crosses give normal one-spurred individuals. 



The Origin of Linaria Vulgaris Pcloria, 215 

filled an entire bed of over 3 square meters in extent, 
with hundreds of vigorous spikes which bore exclusively 
peloric flowers. 

I again obtained only a very small harvest from this 
bed (0.3 cc) ; it was the result partly of artificial and 
partly of insect pollination, the plants flowering in suffi- 
cient isolation. Very few of the seeds germinated (1899) 
and only 32 plants flowered ; 28 of them were peloric 
but 4 were normal. 

The progeny of the peloric race was therefore a mixed 
one, in the three experiments which were continued over 
two generations. It consisted altogether of 3 -\- 75 -p- 28 
= 106 peloric and 5 + 4-(-4 13 normal (including 



hemipeloric) individuals, a total of 119 with about 
atavists. WILLDENOW (see p. 206) also found the peloria 
character inherited, though incompletely. As already 
stated, however, insufficient isolation may have played 
some part in bringing about this result, but hardly to 
such a degree that we might infer from our experiments 
that the peloria comes true. 

If we now look back over this experiment, which 
occupied 13 years, its result may be summarized as fol- 
lows : 

1. Linaria vulgaris hemipelona is a race with an in- 
herited semi-latent character, which manifests it- 
self from time to time among thousands of flow- 
ers, but seldom in more than one instance on a 
plant. It is widely distributed in the wild state. 

2. From it the Linaria vulgaris peloria may arise 
but the conditions under which this happens are 
not yet understood. 

3. This origin is a mutation ; it takes place suddenly, 
and without any visible preparation. Especially 



216 Observation of the Origin of Varieties. 

in those individuals from the seeds of which the 
mutation arises the latent character is not more 
highly or more often developed than in the rest 
of the race. 

4. The mutation is repeated in successive genera- 
tions. I observed it for two years, but did not 
follow it further. 

5. The mutation occurred in about \ c /c of the indi- 
viduals. 

6. The new character was exhibited by the mutants, 
in a full state of development, in all their flowers ; 
although it was subject to considerable fluctuating 
variability. 

7. The mutants are to a large extent, perhaps even 
perfectly, constant from seed. The intensity of 
inheritance observed was about 90%, but it is 

probably more. 

* * * 

Let us next see how these results can be applied to 
the explanation of the occurrence of the Peloria in the 
free state. Wholly peloric plants have been found wild 
by numerous botanists and in the most diverse localities ; 
but, so far as the published information extends, always 
as rarities. They maintained themselves during a larger 
or shorter period of years by means of their radical buds, 
perhaps produced some scanty seed but could not spread 
nor reach new localities by this means. They must there- 
fore have originated in each case in the spot where they 
were found. 

I imagine that this origin is determined everywhere 
by the same general laws, and thence conclude that it 
occurs in the wild state in the same manner as in the 
particular case observed by me, i. e., from Linaria i'itl- 



The Origin of Linaria Vulgaris Pcloria. 217 

garis hemipeloria, and always suddenly. The very gen- 
eral occurrence of this race and the fact that intermediate 
forms between it and the fully developed Pcloria have 
never been mentioned by botanists, give support to this 
hypothesis 

If this view is correct we have here a mutation which 
is not limited to a period but continues to appear from 
time to time during the course of the ages. Its appear- 
ance in every single case is independent of the others, at 
least so far as external conditions are concerned. In 
this sense it is polyphyletic. 

A point which favors this view is the fact that it is 
not a member of a definite group of mutations as are the 
subspecies of Draba vcrna, Viola tricolor and others. 
Linaria vulgaris, it is true, frequently gives rise to other 
kinds of variations such as the Pcloria ancctaria and the 
Catacorolla, both of which have occasionally appeared 
in my own cultures, but nothing is on record concerning 
the relation between these and the Pcloria ncctaria which 
I have studied. 

If we compare these results with those which we have 
described above for Antirrhinum inajits striatuin ( 14, 
p. 134), we see that Linaria I'nlg. hemipeloria is obviously 
a half race; and that L. vulg. peloria, whose partial con- 
stancy seems analogous to that of the striped snapdragon, 
may perhaps be regarded as parallel to this. These two 
races fluctuate so as to approach one another, so to speak, 
occasionally overstepping the common boundary either in 
single flowers (L. vulg. hemipeloria) or in whole plants 
(L. vulg. pel o Ha). 

^ 5JJ JJC 

We now come to the most important point to which 
our results and conclusions lead us namely the com- 



218 Observation of the Origin of Varieties. 

parison of this mutation with those of Ocnothera La- 
marckiana. The two processes have several features in 
common, but possess others which are more or less 
strongly opposed. 

The points of similarity are : the sudden and imme- 
diate origin, the repeated appearance, the mutation- 
coefficient of about 1% (see Vol I, Part II, 14, p. 337), 
the completeness of the new type, and its high degree 
of heritability. 

These common characters justify the description of 
the origin of Linaria mdgaris peloria as a mutation. 1 

But it is a mutation of a special kind. The structural 
change does not extend to all parts of the plant, but is 
confined to the flowers; in their youth the two types 
cannot be distinguished. In the mutations of Oenothera 
Lamarckiana the new characters are analogous to the 
specific characters of related species already existing; 
in the case of Linaria no such analogy exists. On the 
contrary the new character in Linaria occurs as a variety 
in numerous other species, and even in distantly related 

1 LINNAEUS, as is well known, expressed the view that the Peloria 
is a hybrid between the common Linaria vulgaris and some other un- 
known plant. Its comparative sterility favored this view, but as the 
second^of the two parents could not be found this view has since 
been given up. Here, however, I might discuss the possibility that 
L. vulg. hemipcloria might be a cross between L. vulgaris (apeloria) 
and L. vulg. peloria. If this were so the appearance of the latter 
from the former would perhaps have to be regarded not as a muta- 
tion, but as a segregative process in a hybrid race. If this view 
were true the Peloria should first have arisen from the Apeloria, 
without the mediation of the Hemipcloria, a process which has still 
to be observed. It is, however, no more than a pure assumption 
that the hybrid Apeloria 'X Peloria would be a Hemipcloria; in fact 
our knowledge of other cases would lead us to suppose that it would 
be like one of the parents, in this case the Apeloria, and so long as 
there is no direct information on any of these points a further dis- 
cussion of this view seems barren. Moreover it is by no means cer- 
tain that Linaria vulgaris apeloria exists at all, or ever has existed ; 
the variety, in this genus particularly, may well be older than the 
species. 



The Origin of Linaria Vulgaris Pcloria. 219 

plants. Lastly the mutation in Linaria does not appeal- 
along with others in space and time, but occasionally, 
and scattered perhaps over the whole area of the parent 
form and probably over the whole period of the life of 
this race. 

The mutations of Ocnotlicra Lamarckiana necessi- 
tated the assumption of a definite premutation, but the 
origin of the Pcloria is obviously a phenomenon of a 
different kind. 

Pcloria is often regarded as an instance of atavism. 1 
The correctness of this interpretation obviously depends 
primarily on whether this term is used in a narrow or a 
broad sense. Atavism is a reversion to ancestral char- 
acters ; in the narrow sense to the complete type of par- 
ticular ancestors, in the wider it refers only to single 
characters. But it is clear that the spurs which form 
a distinctive character of the genus Linaria must be older 
than the species L. vulgaris, which cannot therefore have 
had ancestors without the spur but with the other char- 
acters of the species ; so that L. vulgaris ancctaria can 
occupy no place in the series of ancestors. The sym- 
metry is ever so much older and L. vulgaris with regular 
flowers has certainly never existed amongst the ancestors 
of the common toadflax. Moreover the sterilitv of the 



peloric plants does not favor such a view. 

If the Pcloria must be regarded as atavistic, this view 
can mean no more than the assertion that it has arisen 
by the loss or latency of a character of the common 
Linaria. Therefore we are concerned here with a retro- 
gressive mutation, and the question arises, how far the 
differences between this case and the progressive muta- 
tions with which we have become familiar in Oenothera 

1 See L. JOST, Biolog. CentralbL, 1899. p. 149. 



220 Observation of the Origin of Varieties. 

are thus to be explained. The explanation is so simple 
that it follows directly from the preceding discussion. 
It is merely necessary to point out that the most impor- 
tant condition for a character to become latent is its pres- 
ence ; and this explains how it is possible that the Peloria 
so often appears over the whole area of distribution of 
the species. Neither a premutation nor a period of muta- 
tion is necessary for such an occurrence. 

If the loss or latency (for the inner potentiality is ob- 
viously not lost but only becomes inactive) affects single 
flowers we have a partial atavism, but if it affects the 
whole plant we have the complete and heritable Peloria. 

It is on this basis that the atavistic phenomena of the 
striped flowers, of the many-spiked Plantago (17, p. 
148) and of the peloric Linaria fall in line. They are 
retrogressive phenomena, reversions to ancient charac- 
ters which have externally become lost but are still pres- 
ent in a latent state. Their agreement with one another 
on the one hand, and their contrast with the progressive 
mutations of Oenothera Lamarckiana, on the other, thus 
receive a satisfactory explanation. 

21. HERITABLE PELORIAS. 

Pelorias are very rarely met with in nature as a 
specific character. As an instance I may quote Mentha 
aquatica, the apical flowers of which according to SCHIM- 
PER'S discovery are always regular and consequently 
peloric, 1 and the orchid Uropedium Lindenii, which is 
regarded as the peloric form of Cypripedmm caudatnin.- 

*A. BRAUN, Abh. d. Berliner Akad., 1859, p. 112; and DELPINO, 
Mem. R. Instit. di Sci., Bologna, 5 Ser., Vol. I, 1890, p. 269. 

2 A. BROGNIART, Ann. Sc. nat., 3 Ser.l, Vol. XIII, p. 113 (Plate 
2) ; and J. M. JANSE, Maandblad voor Natuurwetenschappen, Vol. 
XIV, No. 3, 1887, p. 29. Uropedium Lindenii appears to be by no 



Heritable Pelorias. 221 

In a state of cultivation peloric races are also very rare, 
and the common Gloxinia superba erecta with its numer- 
ous color varieties and hybrids is the best generally 
known cultivated example. 1 

Our present knowledge of the origin of Linaria vul- 
yaris pcloria as described in the foregoing pages, justifies 
us in attempting to form some idea concerning the origin 
of such forms in these perfectly analogous cases and 
also to sketch the details of this idea on a basis, or back- 
ground of facts. 

But there are still difficulties in the way. The low 
fertility and the incomplete constancy of the Peloria 
distinguish it from true species. 2 Most systematists 
would evidently not consider L. vulgaris pcloria to be 
a true species unless the common L. vulgaris were ex- 
tinct. 

Besides the examples named, there is a whole series 
of heritable cases of peloria, which either appear as rare 
anomalies, or are familiar cultivated races, and repeat 
the abnormality regularly and in a fairly large number 
of individuals every year. 3 In both cases, however, the 
development of the anomaly is, as usual, in a high degree 
dependent on external conditions. 

There are, as we have stated in the foregoing section 

means rare in Colombia (South America) ; it was discovered there 
by LINDEN in 1843 (LINDEN, Pescatorea, Iconographie des Orchi- 
dees, 1860, Plate II. 

l The spurless varieties of certain species of Viola and Tropae- 
olum may also be regarded as pelorias : see the following page. 

2 From this point of view it would be very important to know 
whether the Mentha and Uropedium cited are perfectly constant, 
that is, never produce atavists without pelorias. 

3 It is extremely doubtful whether, besides these, there are 
pelorias, the origin of which is solely due to external influences 
and does not need the existence of a corresponding internal poten- 
tiality. 



222 Observation of the Origin of Variety. 

(20), various kinds of pelorias according as one or 
another form of the petals of the parent species has be- 
come the one which prevails in the subspecies. In spur- 
bearing species they are distinguished as Peloria nee- 
tana and anectaria. Both possess a very low degree of 
fertility but are, so far as is known, heritable. Peloric 
flowers without spurs are well known in Linaria, 1 An- 
tirrhinum, 2 Viola? Tropaeolum, 4 etc/' 

There are few heritable peloric races beyond those 
which have been named. The best known are Cor yd alls 
solida peloria which in GODRON'S experiments 6 was found 
to transmit the abnormality through a series of genera- 
tions, and Digitalis pnrpurca monstrosa (Fig. 42). This 
latter, the peloric foxglove, has been a favorite garden 
plant for a long time, and has often been the subject of 
morphological investigations. The oldest descriptions 
and figures are due to my predecessor G. VROLIK, whose 
preparations are still to be seen in the collection at Amster- 
dam. 7 Since his time the variety has been cultivated in 
our botanical garden more or less regularly, and is still 
growing there. 8 It is very constant; its peloric flowers 

*C. BILLOT, Annotations a la Flore de France et d'AUcmagnc, 
quoted in Bot. Zeitung, 1872, p. 278. 

2 J. T. C. RATZEBURG, Animadversiones ad peloriarum indolcm, 
1825, Plate I, Figs. 64-76. 

3 J. C. COSTERUS, P clones du Viola tricolor, Archiv. Neerl., Vol. 
XXIV, p. 142, Table II ; DE CANDOLLE, Organo graphic, PI. 45. 

4 E. VON FREYHOLD, Ueber Pelorienbildung bei Tropaeohim adun- 
cum, Botan. Zeitung, 1872, p. 725 and Plate IX. 

5 D. A. GODRON, Mem. Acad. Stanislas, 1865 and 1868 (Delphi- 
nium chinense, etc). 

8 GODRON, loc. cit., 1868, pp. 3-8, Cultures from 1862-68, with more 
than fifty peloric plants. 

7 G. VROLIK, Ueber cine sonderbare Wucherung der Bhnnen bci 
Digitalis purpurea, Flora, 1844,?. i, Plates I and II; also Fortge- 
setzte Beobachtungcn iiber die Prolification von Digitalis purpurea, 
Flore, 1846, p. 97, Plates I and II. 

8 The following selection of references may be of use : W. F. R. 



Heritable Pclorias. 



223 



are, however, highly variable and only too frequently 
accompanied by other malformations. The commonest 
of these are an increase in the number of organs, the 
formation of catacorollas and the production of a secon- 
dary raceme from the axis of the flower. These are the 
cases which are most 
commonly described and 
figured in literature. In 
order to find more regu- 
lar and even perfectly 
pentamerous flowers we 
must look to the tops of 
the weak lateral branches 
of vigorous plants (Fig. 
42) ; these hardly ever 
proliferate, are often still 
pleiomerous, but there 
will also occur amongst 
them flowers with a per- 
fectly regular corolla 
with five lips and five 
erect stamens. 

The peloric flowers 
of Digitalis purpurca are 
always terminal, whether they occur on the main stem 
or on branches. The same is true of most other Scrophu- 

SURINGAR, Plantaardige Monstruositcitcn, K. Akad. v. Wetensch., 
Amsterdam, 1873, 2d. R., Vol. VII, Plates I-II 

P. MAGNUS, Digitalis pur pur ea, Sitzungsber. Prov. Brandenb., 
Vol. XXII, 1880, p. 

J. C. COSTERUS, Teratologische Verschynsclcn by Digitalis pur- 
purca, Ned. Kruidk. Archief, 1885, Plate VII. 

ANGEL GALLARDO, Fasciacion, Proliferation y Sinantia, Ann. 
Miis. Nacion., Buenos Aires, Vol. VI, p. 37, PI. 3; also Sobre algunas 
onomalias de Digitalis purpurca (with complete bibliography), same 
journal, Vol. VII, pp. 37-72. 




Fig. 42. Digitalis purpurca mon- 
strosa. A lateral branch with a 
terminal pentamerous peloria. 



224 Observation of the Origin of Varieties. 



lariaccac, 1 and of many other families, especially or- 
chids. 2 The relation between this position and the reg- 
ular form of the flower is still without a proper explana- 
tion; and the question whether the anomaly is due to 
high nutrition or to the absence of the factor which 
determines the bilateral symmetry or both, still awaits a 
definitive answer. Laterally situated peloric flowers are 
very rare but sometimes occur as we have seen in Linaria 





Fig. 43. Antirrhinum ma jus. A, Peloric flower from the 
middle of an otherwise normal raceme, August 1899. 
Two slips of the corolla stand erect ; the other three are 
bent downward. B, Normal flower of the same spike. 



vulgaris hemipcloria (Fig. 41, p. 207), and as is shown 
by Antirrhinum majus (Fig. 43), etc. Of great impor- 
tance, also, is the hitherto little noticed fact that in Digi- 
talis and one or two other cases, the peloric terminal 
flower opens first of all, whilst the order of opening of 
all the other flowers on the stem is normal, i. e., aero- 
petal. 

1 EICHLER, Bliithendiagramme , I, p. 208. 

2 PFITZER, in ENGLER and PRANTL'S Naturl. Pfiansen-Familien : 
Orchid., p. 61. For further information on pelorias of Orchids see 
PENZIG, Mem. Soc. nat. Sc. Cherbourg, Vol| XXIX,, 1894, pp. 79-104. 



Heritable Pelorias. 225 

Peloric flowers occur as chance anomalies in a large 
number of plants. A specimen! of Scroplmlaria nodosa 
which I have had growing for the last ten years pro- 
duced them abundantly. On the other hand my cul- 
tures of Antirrhinum majiis although of twelve years 
duration and carefully guarded gave rise to no more 
than two peloric flowers, one of which is shown in Fig. 
43A. Both sprang from the middle of the racemes, that 
is, they were lateral. I have also observed occasional 
cases, of peloria on Acsculus Hippocastamim, Melam- 
pyrnm pratensc, Orobanche Galii, 1 Cytisus Laburnum , 
etc. In my cultures of 1892 a peloric flower occurred 
on a plant of Lupinus luteus. The tube-shaped peloric 
flowers of the cultivated Calceolarias are also well known. 
In these and similar cases the mode of inheritance has 
still to be investigated. In this respect the observations 
of PEYRITSCH are of great importance He has shown 
that in the case of peloria in Lconiinis Cardiaca, an an- 
nual Labiate, the anomaly can be reproduced from seed 
whether this originates from the peloric or the normal 
flowers of the same plant. 

PEYRITSCH'S memoir is one of the most valuable of 
those which deal with peloria, and is indeed an almost 
complete monograph so far as the Labiates are con- 
cerned. 2 He has also investigated the influence of the 
environment on the anomaly as occurring in a series 
of Labiates. 3 I select the following observations for 
notice here : 

1 See also W. F. R. SURINGAR, Orobanche Galii, Ned. Kruidk. 
Archief, 1874, Vol. I, p. 330, Plate 18. 

2 T. PEYRITSCH, Ueber Pelorien bci Lobiotcn, Sitzber. d. k. Akad. 
d. Wiss., Vienna, Vol. XL, Part I, 1869, p. 343, Plates I- VI; and 
Vol. XLII, ist section, 1870, p. 497, Plates I-VIII. 

s J. PEYRITSCH, Untcrsuch. fiber die Aetiologie pelorischer Bliiten- 



226 Observation of the Origin of Varieties. 

Lamiwn inacnlatuin and Galeobdolon luteiun commonly 
produce peloric flowers in the neighborhood of Vienna. 
They often bear them every year on the same plant, but 
one or more years are sometimes skipped. A sunny 
position increases the number of anomalous flowers whilst 
dense shade diminishes it ; consequently one locality often 
furnishes instances of peloria in several species of Lab- 
iates (e. g., Calainintha and others), whilst the same 
species growing together in another locality will not pro- 
duce a single symmetrical flower or only very few. When- 
ever the conditions affecting a plant were improved by 
cutting down timber, peloria occurred in profusion, and 
the transference of a plant to a sunny spot in a garden 
often resulted in its appearance. Other authors, and 
particularly VUILLEMIN/ also assert that the conditions 
of life play an important part in inducing the anomaly, 
provided that the inherited potentiality for it is present. 

bildungen, Denkschr. d. k. Akad., Vienna, Vol. XXXVIII, Part II, 
1877, with Plates I- VIII. See also GOEBEL, Organo graphic, I, p. 163. 

1 Loc. cit., 1894, P- 33- 



VII. NON-ISOLABLE RACES. 

22. TRIFOLIUM INCARNATUM QUADRIFOLIUM. 

Few experiences are so well fitted for enabling us to 
obtain an insight into the nature of specific characters as 
the failure of an experiment in selection. I am not speak- 
ing of practical experiments because in such cases the 
breeder is often disappointed by the fact that the result 
is not superior to what he has already, or is not suitable 
for cultivation on a large scale from other causes. This 
kind of failure only concerns the practical breeder and 
does not affect the scientific investigator. The object of 
the latter is simply to find out whether a race specified 
beforehand can be obtained or not. 

According to the theory of selection almost anything 
ought to be obtainable. Almost all characters manifest 
fluctuating variability to the extent requisite for selection. 
If the range of variation is considerable, selection should 
proceed rapidly; if it is within narrower limits it should 
merely require longer series of generations; and if, more- 
over, the familiar but undemonstrated opinion is assumed 
that fluctuating variability increases as the result of the 
selective process, there is no reason why in any given 
case the attempt to breed a desired race should not suc- 
ceed. 

But this discussion, in my opinion, only applies to 
ordinary fluctuating variability, and if thus limited, I 



228 Non-Isolable Races. 

willingly agree with the prevailing view. In the sphere 
of mutability, on the other hand, matters are entirely 
different. Here species, subspecies, varieties, races, etc. 
arise by mutations which are induced by rendering active 
a hitherto latent or semi-latent character. The first con- 
dition for a desired mutation therefore is the existence 
of the character in question in a latent or semi-latent 
state. Without this nothing can be achieved, at least in 
the present state of science, and it is only in the case of 
semi-latency that we can have any sort of evidence that 
the desired character is present. Horticultural breeders 
are well known to be continually on the lookout for any 
such indication. 1 

But the presence of a latent character is not of itself 
sufficient, according to my experience, to insure the suc- 
cess of an experiment in selection. For many an experi- 
ment has failed in spite of years of labor. 

This proves nothing in itself, because it is often due 
to lack of sufficient experience, and this experience can 
only be acquired by carrying out a successful experiment 
in an analogous case ; in other words, by making exactly 
the same experiment with a related plant, preferably 
with another species of the same genus. 

For this reason I have more than once endeavored 
to breed a race analogous to one already existing in a 
closely related species of the same group, which is either 
on the market, or has appeared in my own cultures. Ex- 
perience has taught me that the end may often be attained 
with greater or less ease according to circumstances ; but 
that in many other cases, so it appears, insurmountable 
obstacles bar the way. 

A very definite and simple case is afforded by the 

1 See Vol. I, Part I, 25, p. 188; and this volume, Part I, 2, p. o. 



Tri folium Incarnatum Quadrifoliiun. 



229 



attempt to breed a five-leafed race of the crimson clover 
(Trifolium incarnatum) analog- 
ous to the five-leafed race of the 
red clover (Trifolium pratense) 
which has already been described 
( 5, p. 36). I started the ex- 
periment in 1894; since then I 
have devoted a great amount of 
trouble to the task without any 
result, until in 1900 I gave it up. 
The attempt simply does not suc- 
ceed, with my material at any 
rate. 

The object was worth a great 
effort. At first I believed that 
I had artificially made the five- 
leaved red clover, or as it is 
often expressed, that I had cre- 
ated it. The gradual develop- 
ment of my theory, however, led 
me to doubt the correctness of 
this opinion. It seemed possible 
that I had merely found the race 
already existing in nature, but 
in a condition in which it was 
not recognizable as such. Eight 
years however had gone by since 
the beginning of that culture, 
and it was practically out of the 
question to go back to it. I re- Tig-. 44. Trifolium incar- 

1 i ,1 f . natum. A flowering 

solved therefore to endeavor to branch w ith a single 4 - 
raise a new five-leafed clover and fo r liate leaf; . the . result 

. of an experiment in se- 

selected the crimson clover. This lection lasting six years. 




230 Non-Isolable Races. 

choice was largely determined by the fact that there 
were no published records of 4- or 5-foliate leaves of this 
clover, 1 which means that the character, if present in a 
latent state, is much rarer than in the red clover. 

I take this opportunity of calling attention to the 
inestimable value of PENZIG'S "Teratology," This lies per- 
haps rather on the negative than on the positive side, 
for it is of course possible to collect the main literature 
relating to a given question oneself, although not with- 
out the expenditure of a great amount of time; but if 
one is not a teratologist by profession, it seems hardly 
possible without some such help, to satisfy oneself that 






Fig. 45. Tri folium incarnatum, 4-foliate leaves, the middle 
one with incomplete segregation of a lateral leaflet. 

absolutely no records relating to a particular phenomenon 
exist. 

The first step in a purely scientific breeding experi- 
ment evidently is to find out whether the deviation in 
question has occurred before, and if so, whether it is rare 
or common. My belief is that the commoner anomalies 
are heritable characters with a high index of inheritance 
(often about 30-40% or more), but that the rarer ones 
are the occasional expressions of latent or semi-latent 
characters. These are also inherited in their latent state, 
and if they turn up here and there this latent condition 
must probably be widely distributed. 



1 0. PENZIG, Pflanzcnteratologie, Vol. I, 1890, p. 385, where 
incarnatum is not even mentioned. 



T. 



Trifolium Iiicanialum Quadrifolium. 231 

If Trifolium incarnatum with 4-foliate leaves had 
often been mentioned it would therefore seem probable 
that a five-leaved race of it occurs in nature, although 
just as little separated from the ordinary crimson clover 
as the five-leaved race of the ordinary clover is from 
this. 

Latent characters, in my opinion, are often older than 
the species which bear them. I regard the division of the 
leaf into four blades in this case as an atavistic phenom- 
enon, and I believe that this latent potentiality is as old 
as the whole group of clovers 
with trifoliate leaves (Trifolium, 
Mcdicago, Mclilotns etc.), that 
is, older than the individual gen- 
era of this group. In many spe- 
cies this power of reproducing 
quadri foliate leaves may have 
been completely lost, for it is 
mentioned in PENZIG'S book only 
for a relatively small number of 

them. In others, however, it has Fl > ^. Trifolium 

An atavistic pinnate leat. 

persisted to the present day. If 

the trifoliate leaves of the clovers are derived from 
Papilionaceae with pinnate ones, the multi foliate leaves 
which they occasionally produce must evidently be re- 
garded as atavistic phenomena. The correctness of this 
view is proved by those very rare cases in which, in 
the races in question, pinnate leaves appear instead of the 
ordinary multi foliate ones. I have observed this from 

/ 

time to time in my Trifolium pratcnse quinqne folium 
(Fig. 46) and the same thing has been found by other 
authors in Trifolium minus and Trifolium re pens. 

I have myself found 4- and 5-foliate leaves in Medi- 




232 Non-Isolable Races. 

cago lupnlina, whilst BRAUN has observed them in M. 
saliva. They are well known in T. pratense and T. 
rcpcnSj and WYDLER has recorded 4-foliate leaves in 
Lotus major and Tetragonolobus biflorns. In some suc- 
cessive sowings which I made with Medicago lupnlina I 
found the character to be inherited although in a mod- 
erate degree only, but I have not continued the experi- 
ment. 

But let us return to the crimson clover. The question 
is, what prospects were present at the beginning of the 
experiment, and what may be expected from such ex- 
periments in general ? There are three main possibilities 
to be considered. \Ye may find at the beginning of the 
experiment (See 3 p. 20) : 

1. A race which often exhibits the anomaly in ques- 
tion, and bears it as a heritable character, i. e., an ever- 
sporting variety ; 

2. A half-race with a semi-latent anomaly which is 
only occasionally manifested; 

3. An ordinary plant of the species with the character 
in question in a latent condition. 

In the first case the race already exists and all that 
is necessary is to isolate it ; in the second it may possibly 
be obtained ; in the last there is little prospect of doing so. 

In order to present a clearer idea of the mutual rela- 
tions of these three cases let us examine Tri folium repens 
and T. pratense. That the anomaly is by no means very 
rare is testified in both cases by the popular belief in the 
so-called lucky four-leaved clover as well as by common 
experience. If looked for in a field of clover, or in a 
meadow, or along the roadside, a four-leaved clover will 
be found from time to time. If repeated attempts are 
made to find them they will certainly prove to be rare 



Tnfolium Incarnatum Quadrifoliuin. 233 

but not so rare as we might have imagined. I have found 
them almost every year, and often quite soon after I 
had been asked for one. On the other hand there is on 
the market the 5-foliate T. repcns air o pur pur cum which 
is often cultivated in gardens for its dark brown leaves, 
and for T. pratense I have described the five-leaved form 
in detail in 5. 

Plants of T. pratense are sometimes found in the field 
with two or more 4- or multi foliate leaves. I found one 
in 1866 in the Cronesteyn estate near Leyden, and an- 
other in 1886 near Loosdrecht. The first had several 
4-foliate leaves, and also some 5-6-foliate ones. I se- 
cured the former but did not cultivate it; the latter 
formed the starting point of my race. In view of my 
present knowledge I must assume that in both cases the 
plants already belonged to the race when I found them ; 
and I also consider it as probable that this race had arisen 
on these very spots, or at least not far from them. 1 

Whether the same race can also be produced from the 
occasional stray four-leaved clovers I do not, of course, 
know ; but I anticipate that the attempt would sometimes 
succeed and at other times fail. If this view is confirmed 
by future experiments we shall have proof of the exist- 
ence of the two races, the eversporting variety and the 
half-race, existing simultaneously within the limits of a 
single species. For the present we must be satisfied with 
the knowledge that there exists a race rich in anomalous 
leaves in the red and in the white clover, and one in the 
crimson clover which bears the character only in the 
semi-latent state. 

I shall now proceed to the description of the latter. 

In the winter of 1894-95 I bought a kilo of the seed 

1 A polyphyletic origin, therefore, as in Linaria vulgaris peloria. 



234 Non-I salable Races. 

of the ordinary crimson clover and sowed part of it on a 
bed of about five square meters. Two of the seedlings 
were tricotylous and one was tetracotylous, and these 
were transplanted to a special bed as soon as possible 
in the hope that tkey would exhibit the desired abnor- 
mality. This hope was based on the principle of the 
correlation between different kinds of anomalies. 1 If a 
plant exhibits an anomaly in its early stages it will, ac- 
cording to this principle, be more likely than any other 
individual in the same culture to give rise to other devia- 
tions later on. In this particular case my expectation 
was fulfilled, for the tetracotylous plant produced one 
4-foliate and one 5-foliate leaf in the course of the sum- 
mer. Such were not found on any other plant, either 
during the course of the experiment or at the end of 
July when the plants were in full bloom and were pulled 
up and minutely examined. There were about a thousand 
plants. 

I left the three selected specimens to flower together 
and sowed their seeds in April 1896. Over 600 seedlings 
came up, all of them with only two cotyledons. In all 
of them the first leaf was single, which is the general 
rule in clovers (Fig. 47 A). The second and third leaves 
developed in May; they were quite normally trifoliate, 
with the exception of one, of which one of the three 
leaflets was" split laterally, although not completely di- 
vided. The form of this blade was similar to that figured 
in Fig. 45 B. About 250 individuals of the whole group 
were planted out. The seed had been sown in pans; the 
young plants were transplanted into pots and were planted 
in the beds ir the middle of May. At the end of June, 

1 Eine Methode, Zwangsdrehungen aufzusuchcn, Ber. cl. d. hot. 
Ges., Vol. XII, 1894, p. 25. 



Trifoliiun Incarnatum Qiiadrifolinm. 235 

at the beginning of the flowering period, several indi- 
viduals exhibited one or more 4-foliate leaves ; the anom- 
aly was therefore a heritable one. 

Moreover the multiplication of the blades had also 
increased considerably as the result of selection, as the 
following figures prove. These refer to the offspring of 
that seed-parent which had already exhibited the anomaly 
in the previous year. There were 90 of them; among 
the offspring of the tricotylous parents "4-leaves" were 
not entirely absent, but they were relatively scarce, and 





Fig. 47. Trifolium Incarnatum. A, a seedling with 
normal primary leaf. B D, seedlings with 2- 
and 3-foliate leaves. The former arise from the 
larger; the latter from the smallest seeds. 

the whole group was consequently pulled up at the be- 
ginning of the following period. About % (58 out of 
90) of the rest were perfectly normal without any in- 
crease of the number of leaflets. On the average they 
had about 10 stems and 100 leaves per plant. The re- 
maining plants formed a half-curve 1 of the following 
composition. The first row gives the number of 4- or 
5-foliate leaves per plant, and the second the number of 



1 4, p. 26 ; and Ueber halbe Galton-Curven, Ber. d. d. hot. Ges., 
1894, Vol. XII, p. 197- 



236 Non-Isolable Races. 

individuals on which these numbers were observed (cul- 
ture of 1896) : 

Abnormal leaves 1 23456789 
Individuals 58 10 12 4 2 2 1 1 

The 58 normal plants were pulled up. Of the rest 
four were weak and died; there remained 28 which all 
flowered together. Their seed was harvested separately 
after the number of 4- and 5-foliate leaves on each parent 
had been recorded. 

In March 1897 I sowed a part of this seed in pans, 
separately for each seed-parent. The object of this was 
to find out whether there was any difference between the 
individual seed-parents with regard to the number of 
anomalous offspring which they produced. From an 
examination of the pans it was easily seen that the ab- 
normality had already appeared in the primary leaves of 
some of the seedlings. In the great majority of cases 
these were perfectly normal, consisting of one leaflet as 
in the whole of the previous generation. In some cases 
however this primary leaf consisted of two or three 
leaflets (Fig. 47 B-C). Such occurred in the crops raised 
from 6 of the 21 plants whose seeds had been sown. 
Each seed-parent had given a crop of about 300 seed- 
lings. Five of the crops contained not more than 2 ab- 
normal seedlings, but the remaining one had a very large 
number, namely 14 amongst 335 seedlings or about 4%. 
It is worthy of notice that the parent of this crop had only 
had two 4-foliate leaves itself and thus had not given 
the least sign that it would produce offspring with so 
much higher a degree of the abnormality. Moreover I 
could not find any relation between the number of ab- 
normal leaves on the other seed-parents and the pro- 
portion of abnormal offspring raised from their seeds. 



Trifolium Incarnatum Quadrifolium. 237 

The plant with nine 4- or 5-foliate leaves did not give 
rise to a single anomaly amongst 300 seedlings. 

Amongst breeders of animals it is generally recog- 
nized that the visible characters of an animal are of very 
little use as an indication of its value for breeding. The 
offspring which the animal has already produced afford 
a much more reliable indication. 

On the basis of the choice of the seedlings, the 14 
abnormal offspring of the seed-parent with 4% were 
planted out in the beds in June 1897, together with the 
seven next best plants. The latter produced very few 
4- to 5-foliate leaves per plant, the first and 1 in eleven 
cases, but 9, 9 and 4 in three cases. There was there- 
fore no marked advance on the previous year in this 
respect. 

The progress was just as inconsiderable in the harvest 
of that year. The percentage of abnormal individuals 
amongst the seedlings ranged in 1898 between 1 and 4% 
and in one case reached 6%. On the other hand all the 
(19) seed-parents investigated had at least one and usu- 
ally two or more seedlings with a divided primary leaf. 
But here again no relation was manifested between the 
number of abnormal seedlings and the number of 4- 
or 5-foliate leaves on the seed-parents which produced 
them. 

227 seedlings were planted out, most of which were 
perfectly normal at the time of flowering. I obtained 
the following half -curve (1898) : 

Number of multifoliate leaves per plant: 12345 
Individuals: 188 29 7 1 1 1 

That is to say, about 20% of individuals with the 
inherited anomaly in from 1 to 5 of the whole number 



238 Non-Isolable Races. 

of leaves counted on the plant (about 100). The numbers 
were therefore smaller in this than in the previous year. 
For this culture I had planted out the normal and ab- 
normal seedlings of the most abnormal seed-parents and 
some abnormal seedlings of the remaining seed-parents. 
No essential difference between these three groups could 
be detected when they were recorded at the time of flow- 

/ 

ering. 

Pitcher formation was observed both amongst the 
seedlings and during the later stages ; this is another 
indication of correlation amongst the various characters. 

In the summer of 1898, 41 of the selected plants fur- 
nished a sufficient quantity of seed. In the following 
spring I determined the proportions of seedlings with 
compound primary leaves in the crops from each of these 
parents and reckoned them in percentages. The compo- 
sition of the 1898 harvest with respect to this character 
was : 

Percentage of abnormal offspring 1 2 3 4 5 8 11 15 16 20 24 27 
Parents 3 12 75421211111 

That is to say, a considerable advance which at once 
becomes evident if this series of figures is compared with 
that given above for the 1897 harvest (1-4 and 6%). 
This advance has moreover taken place in spite of the 
falling off in the number of 4-foliate leaves in the seed- 
parents. 

In the spring of 1899 I only selected seedlings with 
trifoliate primary leaves for transplanting (see Fig. 47C), 
and only from amongst the offspring of the four seed- 
parents with from 15-24% abnormal offspring. At the 
time of flowering, however, my hopes were disappointed. 
In the middle of July there were amongst 120 richly 
branched flowering plants 45% without the anomaly, 



Trifolium Incarnatum Quadrifolium. 239 

27% with a single abnormal leaf each, and 28% with two 
to four 4- to 5-foliate leaves each. That is to say, 55% 
abnormals as against 20% in the previous year which 
indicated a marked advance. 

But my hope of obtaining a leaf with more than five 
leaflets was not fulfilled. In spite of repeated search 
I never found one. Nor did I obtain plants rich in four- 
bladecl leaves ; for there were none with more than four 
of them. 

Therefore I have since abandoned the hope of breed- 
ing a race of four-leaved clover, corresponding to my 
Trifolium pratcnse quinque folium, from this material. 

A striking feature of this experiment is the apparent 
absence of a relation between the degree of abnormality 
of the adult plants and that of the seedlings. For the 
paucity of four-bladed leaves in the grown plants seems 
incompatible with the abundance of multi foliate primary 
leaves in the seedlings from which they grew. 

The failing of this relation has led me to the dis- 
covery of a most remarkable connection between this 
variability and the size of the seeds, for the smallest 
seeds are those which give rise in the largest number to 
compound primary leaves. 

Small seeds germinate somewhat later than larger 
ones and also give rise to weaker plants. It had often 
struck me that the selection of the most abnormal of the 
seedlings was frustrated by the fact that many of the 
individuals with compound primary leaves were too weak 
to be planted out, or died soon after the process. It also 
struck me that all the seedlings in a pan could not be 
recorded at the same time. At first view the plants ap- 
pear to germinate very regularly, and hundreds in the 
same pan seem to unfold their leaves at the same moment. 



240 Non-I salable Races. 

At this point they were recorded and, if the first leaf 
was single, were usually pulled up. Those which were 
saved were usually weaker, more stunted and backward 
in growth. Several had not yet unfolded their first 
leaves, and amongst them a great number of the anom- 
alies were found when the examination was repeated a 
few days afterwards. 

I then convinced myself by a very simple experiment 
of the correctness of these conclusions. All that was 
necessary was to isolate the large and the small seeds in 
a sample and to sow them separately. But as there is 
no absolute limit between the two it was necessary to 
know how many seeds should be separated out, as the 
smallest. And this can only be done by the number of 
anomalies, i. e., compound primary leaves, they produce. 
I therefore selected a sample of seed whose capacity for 
producing anomalies I already knew. This was 15%; 
the sample was derived from a single seed-parent. I 
separated the seeds into three categories, small, inter- 
mediate and large. All in all there were 217 seeds of 
which 17 did not germinate. The characters of those 
which did are as follows: 

Number of divisions in the primary leaf. 

123 2-3 

Small seeds 31 9 16 12.5 % 

Intermediate seeds 50 2 1 1.5 % 

Large seeds 88 2 1 1.5% 

169 13 18 15.5 % 

It will be seen that almost all the abnormal seedlings 
are derived from the smallest seeds. The seedlings from 
the large seeds had, with a single exception which was an 
abnormal one, unfolded their primary leaves in May, and 
fourteen days after the seed had been sown ; the same 



Trifolium Incarnatum Quadrifoliiun. 



241 



is true of the intermediate seeds with the exception of 
four, two of which were abnormal. 22 normal plantlets 
developed from the smallest seeds in the same time ; the 
9 other normal and the 25 abnormal ones did not unfold 
their first leaf until the third week. 1 

These facts show further that the number of seed- 
lings with abnormal primary leaves does not depend 
simply on the degree of fixation of the variety. It de- 
pends mainly on the proportion of small seeds. This, 
however, in its turn, depends on the size of the harvest. 




Fig. 48. Trifolium incarnatum. Monstrous seedlings 
from the smaller seeds. A, B, D, with two to four 
primary leaves ; C, with a double leaf with broad 
flat peduncle. 



In the 41 samples which composed the harvest of 1898 
there were 8 with 8-27% abnormals; these samples con- 
sisted of from 0.3 to 1.5 cc. of seed. The remaining 
samples consisted of from 2 to 5 cc. of seed and the 
number of abnormals produced ranged between and 
5%. From these facts we see that the weaker individ- 

1 In stocks also the seeds which produce plants with double 
flowers and those which give rise to "singles" have different rates 
of germination, as is well known. An investigation of the seeds of 
inconstant varieties, or, as they are usually described, varieties which 
have not "yet" been fixed, would be certain to reward the inquirer 
with many interesting discoveries. 



242 Non-Isolablc Races. 

uals, which gave a poorer harvest, gave rise to the larg- 
est number of abnormals amongst their offspring. 

I have repeated the same experiment with the harvest 
of 1899, with the seeds of four separate seed-parents, but 
as I did not know their capacity for producing abnormals 
in advance, the difference was not so striking. The large 
seeds gave rise to 2-4%, the small ones to 3-13% abnor- 
mals. Altogether seedlings from 2758 large and from 
617 small seeds were examined. 

Two questions present themselves in connection with 
the interpretation of these experiments: (1) Can the 
position in which the small seeds are chiefly produced 
on the plant, be determined? 1 (2) Are the germs of the 
small seeds perhaps the better nourished ones ; is there, 
for instance, just as much nutriment brought to them 
as to the large seeds, but must they, for want of room 
or for other reasons, utilize it in some other way? 

I recommend these problems for further study, and 
may perhaps in the mean time record a few facts bear- 
ing on them which I have observed. In the crimson 
clover, monstrosities occur much more frequently among 
the seedlings from small than among those from large 
seeds. The latter are almost all perfectly normal. The 
small seeds often produce plants with supernumerary 
cotyledons, or with two or more primary leaves (instead 
of one) or with divided peduncles, symphyses in the 
leaves and other malformations (Fig. 48). Unfortunately 
it is often difficult to keep these individuals alive and to 
bring them to flower. 

Let us now cast a final glance over the whole course 
of the experiment. 

1 In stocks, according to CHATE, Culture des Giro-flees , the seeds 
which produce double-flowered plants arise chiefly from the lower 
half of the pods of the strongest racemes of the plant. 



Ranunculus Bnlbosus Semiplenus. 243 

A crimson clover plant with some quadri foliate leaves 
was obtained by the selection of tricotylous and tetra- 
cotylous seedlings in conformity with previously studied 
laws of correlation. The anomaly proved to be heritable 
and has maintained itself until now, during six genera- 
tions (1895-1900). It was improved by selection but 
only within very narrow limits. Plants with more than 
five leaflets per leaf have not as yet arisen, nor have 
plants bearing ten or more 4- to 5-foliate leaves, and it 
is nearly always the "small" seeds which give rise to 
seedlings with compound primary leaves. 

But the chief result is that the desired race, rich in 
4- foliate leaves, T. incarnatum quinqucfoUuni' anal- 
ogous with Trifolium pratcnse quinquefolium, did not 



arise. 1 



23. RANUNCULUS BULBOSUS SEMIPLENUS. 

Double flowers are common phenomena amongst the 
buttercups. 2 They occur not only in the cultivated Ra- 
nunculi (R. asiaticus} but also in several wild species. 
The doubling may be either complete and brought about 
by petalomania as in the Ranunculus acris shown in Fig. 
40, Vol. I, p. 194; or it may be more or less incomplete 
when caused by the transformation of a varying number 
of stamens into petals (R. acris, R. auricoinus, R. Phih- 
notis, R. r opens etc.). 

In Ranunculus bulbosus, the bulbous buttercup, the 

1 The same thing no doubt occurs also in other cases. The at- 
tempt to breed from occasional anomalies a constant race endowed 
with the particular variation, in some cases succeeds, but in others 
does not. For instance I have for many years endeavored to raise 
from the occasional polycephaly in Papaver cotnmutatuni a race with 
as beautiful crowns as those which characterize the familiar Papai'er 
somnifcrum polycephalum (see Vol. I, p. 138, Fig. 27), but in vain. 

- See PENZIG, Pfianzenteratologie, Vol. I, pp. 181-189. 



244 



Non-holable Races. 



stamens are often (either all, or only some of them) 
transformed into petals with the result that dense double 
flowers are produced. 1 These have been described by 




Fig. 49. Ranunculus bulbosus semiplenus. A , the bulb ; 
A' and A", its leaves from the axils of which the flower- 
ing stems S arise ; E, terminal flower of the main stem ; 
S, secondary flowers partly broken off; T, tertiary flow- 
ers. (See p. 256). 

various authors. 2 In the neighborhood of Amsterdam 
this variety does not occur, so far as I know. On the 

1 Loc. cit., p. 185. Fasciated stems with broadened terminal flow- 
ers are also met with occasionally in the Ranunculus bulbosus in 
Holland. 

2 Compare the Ranunculus bulbosus Alcae of Naples, described by 
TERRACCIANO, Nov. Atti d. R. Instit. Napoli, 1895, Vol. VIII, No. 7. 



Ranunculus Bulbosus Semiplenus. 



245 



other hand on plants growing as they often do in sandy 
localities, the flowers often possess a slightly increased 
number of petals. 

In these abnormal flowers there are usually six or, 
rarely, seven petals, very seldom more than 10-12. They 
are as a rule ordinary petals, but there sometimes occur 
some that are much smaller and narrower and are ob- 
viously metamorphosed stamens. This metamorphosis 
is often only partial, and the famil- 
iar intermediate stages are exhib- 
ited. The abortive stamens are 
usually to be found among the most 
peripheral ones ; but they are not 
necessarily the outermost ones, di- 
rectly adjoining the corolla. 1 

The potentiality of this doubling 
is therefore present in a semi-latent 
condition in the wild plants of this 
species growing in this neighbor- 
hood. I regard this race, therefore, 
as a half race in contradistinction 
to the normal double race which is 
only known to me from the pub- 
lished records. Obviouslv the two 

J 

possess the same character; which 




Fig. 50. Ranunculus bul- 
bosus semiplenus. A 
flower with 31 petals 
(partly petalodic sta- 
mens) ; the only one 
amongst 4425 flowers. 
It occurred on a qua- 
ternary branch in my 
culture of October, 
1892. See the series 
of figures on page 252. 



is, however, active in the one case 
but latent or semi-latent in the other. 

It seemed to me important to discover whether it was 
possible to obtain the double from the half race by selec- 
tion. According to the views advanced in this work 
this should be possible, but not every attempt need neces- 
sarily be successful. But if it does succeed the change 

1 See GOEBEL, Jahrb. f. wiss. Bot., Vol. XVII, pp. 217-219. 



246 Non-Isolablc Races. 

must be brought about suddenly, and, under ordinary 
conditions of culture, be effected in the course of a few 
years. In this way the double variety may have arisen 
from time to time in the wild state; and in the same 
manner the present half race may perhaps, in the course 
of time, undergo this change. 

This transformation, however, cannot be simply the 
result of careful selection. A mutation is needed; and 
we know as little about the causes of mutations as about 
the method of inducing them artificially. Mutations are 
known to occur with moderate frequency both in breed- 
ing experiments and in nature, but, up to the present, 
their occurrence has been a matter of chance (10 and 
11, pp. 95-103). 

In my experiment such a mutation did not occur, 
although it extended over five generations. 1 The half 
race was distinctly improved by repeated and very strin- 
gent selection. It became at the end very rich in extreme 
or almost extreme variants, but it was just in these that 
it proved to be so remarkably constant. In its five gen- 
erations it reached a point which did not seem to me 
likely to be exceeded by further selection. It produced 
occasional flowers with more than 1 5 petals, and a single 
one with 31, but the mean number of the petals in its 
selected individuals did not exceed 9-10. 

The double variety did not arise from it, in spite of 
every effort. 



1 The fluctuating variability of the semi-latent character in Ranun- 
culus bulbosus scmiplctnis seems to cover a much wider range of 
forms than in Trifolium. There the extremes are 3 and 7 leaflets; 
in the buttercup they are 5 and 31 and perhaps more petals. From 
this it does not, however, follow that the variation is greater in the 
one case than in the other, but only that the variation is expressed 
by a larger number of divisions in the latter case, i. e., that there are 
more scale characters in the curve. 



Ranunculus Bulbosus Semiplenus. 247 

I conclude, therefore, that in this case the half race 
cannot be transformed into the double race by simple 
selection, but only by an internal change a mutation 
the external causes of which are still unknown to us. 

Proceeding now to the detailed description of my 
experiment, I begin with the half race in the conditions 
in which I originally found it in nature. 

I found the half race growing in 1886 and 1887 in a 
sunny and sandy spot not far from Hilversum, where I 
have often seen it since. The bulbous buttercup grew 
there in abundance ; most of the flowers were normal, 
but a considerable number had more than five petals. 
I shall refer to these latter for convenience of expression 
as pleiopetalous. 

For several years I have recorded the flowers in that 
locality. I give the records of 1886 and 1887, each of 
which relate to 300-400 flowers. The data are given as 
percentages. 

Number of petals 5 6 7 8 9 10 11 12 13 14 
Flowers in 1886 91.5 5.5 1.2 0.6 0.6 0.3 0.3 
Flowers in 1887 90 7 2 0.5 0.5 

The two series 1 agree as closely as could be expected 
and the records for the other years also fall in line. The 
maximum of the curve (see Fig. 51 H) is over the 
normal number of petals ; and from it the curve falls 
rapidly. It is a so-called half GALTON-curve. Flowers 
with less than five petals do not occur in this locality. 

The great steepness of this curve is due to the fact 
that on many of the plants no pleiopetalous flowers were 
found on the days when the observations were made. 
But this does not mean that the half race is mixed with 

1 Ueber halbe Galton-Curven ah Zeichen discontinuirlicher Varia- 
tion. Ber. d. d. bot. Gesellschaft, Vol. XII, 1894, p. 197, where some 
of the series of figures given below can also be found. 



248 Non-holable Races. 

a pure race with five petals only. For the plants in ques- 
tion were either weaklings, or exhibited pleiopetalous 
flowers on other days. I was often able to observe that 
on many plants six-petalled flowers occur on one day but 
not on another. The 6-7-petalled flowers are found 
from the beginning of the flowering period, but the 
higher figures do not occur till later, as is also known to 
be the case in other instances of double flowers. 

In 1887 I moved some plants in which the abnormal- 
ity was well developed, to my garden, where they flowered 
again in the following summer and set eed. These plants 
constitute the first generation of my experiment. Since 
then I have sown seed every year, but only part of the 
plants, sometimes one-half, sometimes two-thirds, pro- 
duced flowering stems in the first year, and I have always 
confined my attention to these, throwing away those 
which did not bloom during the summer. I have some- 
times kept some of the best examples of the half race 
through the winter for secondary experiments, but I shall 
return to these later on. 

During the period 1889-1892 the second to the fifth 
generation of the half race were grown in this manner, 
the extent of the cultures being gradually increased. 
I always harvested my seed from the most abnormal in- 
dividuals, which I selected by simply cutting off the 
flowers with five petals from all the plants. The numbers 
of these on the individual plants were recorded in some 
years but not in others. Pollination was left to the 
bees, but no definite effects of cross-fertilization have 
been traceable in the results of the experiments. 

The first two years of the experiment (1889 and 
1890) need only a brief reference. Plants without pleio- 
petalous flowers or with only very few, were removed 



Ranunculus Bulbosus Semiplenus. 



249 



as soon as possible, or were deprived of their flowers: 
of the rest, only the seeds of flowers with six and more 

f> 

petals were saved. But this process is not one of selec- 
tion, as will be shown by means of some special experi- 
ments which were instituted later. 

The result of selection could be seen in 1891 in the 
best examples of the half race, but in 1892 (the fifth 
generation of the culture) in nearly all the plants. The 
number of petals increased in every respect, The apex 

>H7887. 




Fig. 51. Ranunculus bulbosus semiplenus. Experiments in 
selection during the period 1887-1892. H 1887, curve of 
the wild form; E 1891, curve of the abnormal plants in 
1891 ; A 1891, curve of the selected seed-parents in 1891. 
1892, curve of the whole crop in August 1892. The num- 
bers at the base refer to the number of petals per flower. 



of the curve shifted to 9 and 10 petals and even further; 
that is to say, the mean of the half race (9-10 petals) 
was separated by selection from that of the pure species 
(5 petals), a point which is rather striking because this 
was not effected in my experiment with Trifoliuin in- 
carnatmn. The course of the whole experiment is ex- 
hibited graphically in Fig. 51 which is composed of four 
curves. The first (H 1887) exhibits the countings given 



250 Non-Isolable Races. 

above, which were made in the original locality. Then 
there are two curves for 1891. In this year I had a 
culture of about four square meters from which I re- 
moved, about the beginning of August all plants which 
had not produced any pleiopetalous flowers as well as 
those which had not yet bloomed. For two weeks I 
counted every flower which appeared on the remaining 
specimens. They amounted to 128 and the various de- 
grees of the anomaly were distributed over them as 
follows : 

Number of petals 5 6 7 8 9 10 11 12 13 
Number of flowers 45 24 28 17 8 4 1 1 

The curve E 1891 in Fig. 51 is based on these figures. 
It is a half curve like the previous one, but without the 
steep apex. The disappearance of this is due partly to 
cultivation and to the repeated selection, but partly also 
to the fact that the individuals with the smallest number 
of pleiopetalous flowers had been removed before the 
counting took place. 

After these data had been determined I carried out 
a still further selection. Several plants had not produced 
a single flower with more than seven petals. These were 
removed in the middle of August and observations on 
the rest were continued. There were 18 plants, all of 
which were selected for seed-parents as being the best 
representatives of the race. I counted all the flowers 
which bloomed from August 15 to 31, and obtained the 
following numbers: 1 

Number of petals 5 6 7 8 9 10 11 12 13 14 
Number of flowers 9 17 39 64 45 37 15 9 6 2 

1 In the preliminary account of this experiment, mentioned 
above, this series is given separately in two curves, one of which 
refers to the most abnormal plant, the other to the rest. 



Ranunculus Bulbosus Semiplenus. 251 

Total 243. The curve (Fig. 51, A 1891) has be- 
come two-sided. It has no maximum at 5 but a very 
definitely pronounced one at 8. It is composed of ob- 
servations made on 18 plants which differ little from one 
another. Individuals with these characters occurred 
neither in the original locality nor at the beginning of 
my experiment. 

The sowing, in 1892, of the seeds of these selected 
individuals gave rise to above 300 plants which were 
coming into flower from July 21 to August 31. The 
curve for 1892 in Fig. 51 refers to these. Those which 
flowered later were examined separately and will be de- 
scribed afterwards. On all the flowers which opened 
between the dates named the petals were counted, and the 
numbers entered in my notebook separately for each 
plant. I give the totals, which relate to 4425 flowers. 
The numbers of petals were distributed over these as 
follows : 

Petals 5 6 7 8 9 10 11 12 13 14 15 16-31 
Flowers 409 532 638 690 764 599 414 212 80 29 18 20 

The curve which is now an index of the degree of de- 
velopment of the whole race, agrees fairly closely with 
that of the selected seed-parents of the previous year 
( 1891), as can be seen from a comparison of the curves 
A 1891 and 1892 in Fig. 51. The apex of the curve, 
however, has advanced a whole petal. There has been 
no regression as is the case in the selection of active char- 
acters, but a progression such as is usually characteristic 
of the selection of semi-latent characters. 

The change in the right half of the curve is also im- 
portant although not given in Fig. 51. It consists in the 
occurrence of more extreme variants. In the previous 



252 



Non-Isolable Races. 



generation there were no flowers with more than 14 

o 

petals. Now there are 38, distributed as follows : 

Petals 15 16 17 18 19 20 21 22 23 31 

Number of flowers 18 852111011 

It should be noted, however, that they were found 
amongst a group of 4425, and therefore only amount to 
about \% (0.86%). But as not a single one was found 
in 1891 amongst 243 flowers, a genuine, although only 
a slight, advance has taken place. 

The great majority of the 295 plants which were 
flowering in August and formed the 1892 culture, had 



F. 




Fg. 52. Ranunculus bulbosus semiplenus. Composition of 
the fifth generation in 1892. A, the curve of some "ata- 
vists" ; M, the curve of intermediate individuals ; V, the 
group of extreme variants. The figures refer to the 
number of petals per flower. 

individual curves whose maximum was at 9. But amongst 
their number were variants and extreme variants also. 
On the one hand there were "atavists" with a maximum 
on the ordinate of five petals, i. e,, with a one-sided curve, 
as in those from the original locality ; on the other hand 
there were variants on the plus side which bore on the 
average eleven petals per flower. In one case even a mean 
of 13 petals was reached. These curves were two-sided, 
and not, as in the five-leaved race of the red clover, in- 



Ranunculus Bulbosus Semiplenus. 253 

versely one-sided. But we are dealing here merely with 
a cumulative effect within a half race and not with an 
isolated, fully developed race. I have chosen a number 
of variants from the two categories, have added up the 
number of their petals, and obtained the following data : 

Petals: 5 6 7 8 9 10 11 12 13 14 15 16 17 18 23 

Number of flowers /$. 66 34 21 18 15 11 720010000 

" M: 13 14 22 28 51 26 16 12 6 4 2 1 1 

V: 9 11 26 39 62 79 148 84 30 8 4 3 2 1 1 

These data are exhibited graphically in Fig. 52. They 
relate to three small groups of individuals, chosen in 
such a way that the curves of the individual plants did not 
exhibit any considerable deviations from the mean of the 
group. A is the curve of the twelve atavists extracted 
from the whole series of observations ; the maxima of 
all their curves were at 5 petals. M is a curve represent- 
ing ten plants grown from the seeds of a single seed- 
parent. V is the curve composed of all the plants the 
apex of whose individual curves lay above 10. There 
were 22 of them altogether; the apices of their curves 
were at 11, with three exceptions which were at 12 and 
13, but these curves did not exercise any marked effect 
on the shape of the average curve of the whole group. 

If Fig. 51 and Fig. 52 are compared a most remark- 
able similarity will be observed. The latter figure gives 
the composition of my race at the end of a process of 
selection extending over five generations, the former re- 
lates to the separate stages in this process. This mutual 
resemblance lies in the fact that the original half curve 
(Fig. 51, H 1887) continues to appear throughout the 
process, although it is a little flattened; it occurs in 1891 
(Fig. 51, E 1891) and also in 1892 (Fig. 52 A). Ata- 
vistic fluctuation therefore is still exhibited by my race 



254 Xon-Isolable Races. 

in spite of the repeated selection. 1 The curve M has a 
more normal shape than the corresponding curve "1892" 
in Fig. 51; which is obviously due to the fact that the 
former represents a homogeneous group whilst the latter 
is a composite curve embracing all the groups of this 
culture. Curve V is related to curve M as it would be if 
we were dealing with ordinary fluctuating variability ; it 
is simply shifted to one side. 2 

It seems obvious that the race could still be improved 
by sowing the seeds of those seed-parents the apices of 
whose curves are at 11, i. e., that these curves could be 
shifted still further to the right. I have made some such 
sowings since 1892, but only on a small scale and not 
without interruption. They were not intended as a con- 
tinuation of the experiment. The number of petals per 
flower increased slightly, but the type itself was not es- 
sentially altered. I especially never saw a trace of any- 
thing like the origin of a double flower. 

In order to find out whether there was any likelihood 
that the type of my race would in the near future mani- 
fest an improvement I made the following calculation. 
The 295 plants of which the culture of 1892 consisted, 
arose from the seeds of 21 seed-parents. I selected the 
ten best of these parental groups and plotted the curves 
for all the offspring of each seed-parent. The curves 
proved to differ very little from one another. Their 
apices all fell over nine petals, with one exception, which 
was over ten. I should say that in making the calcula- 
tion I have left the groups which contained less than 300 



1 Whereas as a result of the selection of active characters the 
whole curve is shifted; see Vol. T, p. 73, Fig. 18, and the third part 
of the first volume. 

' Sec Vol. T. Fig. 116. on page 536. 



Ranunculus Bulbosus Semiplenus. 255 

flowers out of consideration. But even these did not 
manifest any notable differences. I then compared these 
ten curves with the part-curves determined from the 
parents themselves (i e., with the number of flowers 
counted on the seed-parents) and found no correlation. 
As a matter of fact the seed-parent with the smallest 
number of pleiopetalous flowers had the offspring with 
the largest number. The following four curves of the 
offspring of four seed-parents are extracted from my 
records. Under M are given the numbers of petals in the 
seed-parents of 1891. 

M NUMBER OF PETALS PER FLOWER 

5678 9 10 11 12 13 14 IS 16 17 18-23 Totals 

C 510 37 47 81 81 85 102 47 31 63410 525 

C 610 25 67 80 75 117 77 75 45 30 10 6 1 2 3 613 

C 611 54 53 62 78 87 60 59 37 10 4 4 1 1 1 511 

C 711 52 57 76 77 95 64 26 13 460 

Another fact which points in the same direction is 
that the plant which seemed to be far the best in the 
summer of 1891, inasmuch as the apex of its curve was 
over 11-12 petals, had offspring whose character cor- 
r^sponded exactly with that of the whole culture of 1892. 
The improvement on the seed-parent therefore did not 
justify the expectation of a real advance. 

For these reasons I then discontinued the experiment. 
It seemed to me that the impossibility of raising the 
double race from my half race by simple selection was 
placed beyond all doubt. This result could only be ex- 
pected from a further mutation. 

The extensive material afforded by these cultures 
has been utilized to find out how far the number of petals 
per flower in the half race is determined, apart from 
selection, bv internal causes, and how far bv external. 



256 Non-Isolable Races. 

I found it to be dependent only to a very slight degree on 
the former but in a high degree on the latter. 

The first question that presented itself was : To what 
principles of distribution does the number of petals on 
the individual plants correspond. Is this number de- 
termined by the situation of the flower or by external 
factors or by both? With regard to the position of the 
flower BRAUN in his Verjilngung distinguishes between 
a strengthening and a weakening system of branching. 
In the former the branches increase in strength, though 
often but slightly, with each new degree of division; in 
the latter each secondary branch is weaker than the 
branch on which it is borne. Ranunculus bulbosus be- 
longs to the former category (see Fig. 49 on page 244). 
The main stem (E) is surpassed by the vigorous lateral 
shoots (S), which arise directly from the tuber, and 
these in their turn are excelled by their own (tertiary) 
branches (T in the figure). The same thing continues 
with further growth until ultimately the process is re- 
versed and weaker branchlets are produced. The more 
vigorous a branch is, the larger and stronger, as a rule, 
will be its flower. 

If we now compare the number of petals on the 
flowers of this half race, with their position on the 
branches of the various orders, we are often struck by 
an apparently definite correlation. But this is only due to 
the fact that such cases produce a more vivid impression 
than the opposite ones. When a detailed record is made 
the latter are found to be just as numerous as the former. 
In September 1892 I determined the number of petals, 
and the position on the plant, of 1197 flowers on 82 
plants ; and plotted a curve for each position. Here how- 
ever I only give the means of the curves. 



Ranunculus Bulbosus Semiplemts. 257 

NUMBER OF 
FLOWERS PETALS PER FLOWER 

A. On the ma:'n stem: 

1. Terminal flower 75 697 9.3 

2. Secondary flowers 221 2005 9.1 

3. Tertiary " 134 1237 9.3 

B. From the tuber: 

4. Secondary flowers 259 2419 9.3 

5. Tertiary 397 3716 9.4 

6. Quaternary 111 1014 9.1 

1197 11088 9.3 

It is evident that the number of petals in the various 
groups is practically the same. 1 

Even the seeds of pleiopetalous flowers are by no 
means better. In gathering the harvest of 1891 I col- 
lected the seed on each plant in a separate bag with ref- 
erence to the number of petals of the flowers. The flow- 
ers were labelled for this purpose at the time of flowering. 
In the culture of 1892, therefore, the plants were arranged 
in groups, first according to their seed-parents, and sec- 
ondly according to the petal-number of the flowers from 
which the seed had been gathered. I then grouped all of 
the figures by the latter character and obtained the fol- 
lowing result : 

NUMBER OF PETALS IN THE MEAN NUMBER NUMBER 

FLOWERS WHICH OF PETALS OF FLOWERS 

FURNISHED THE SEED OF THE OFFSPRING 1 COUNTED 

C5-7 
C 8 
C 9 

C 10-11 
C 12-14 

Average 8.6 Total 5560 

1 In the weakening system of branching on the other hand the 
contrary seems to be the rule ; so for instance in my cultures of Sapo- 
naria officinalis with 5-10 petals, in Chrysanthemum scgetiini ( 18) etc. 

! The mean is slightly lower here than in the previous table be- 
cause that only refers to countings made in September. (See later.) 



8.3 


932 


8.7 


1072 


8.5 


1217 


8.6 


1420 


8.7 


919 



258 Non-Isolable Races. 

Here again there is no discernible correlation. I have 
obtained the same result in other years. From this we 
see that in this case at least selection must not be founded 
on the different flowers of a plant but on the individual 
plants. However, the possible influence of the various 
grades of branching independently of the number of 
petals remains to be investigated. 

But whereas no internal causes were found which 
determined the pleiopetaly in the individual flowers, the 
external causes could be discovered the more readily. 
This character follows the general rule ; for the higher 
the nutrition and the more favorable the environment 
the more petals are produced per flower. The following 
experiments and observations will prove this. 

I shall first refer to an observation for which un- 
fortunately I can give no numerical corroboration, but 
which may throw some light on the independence of the 
character of the flowers, of the order of branching. In 
the summer of 1892 when I examined all the flowers of 
my culture, and recorded the number of their petals twice 
a week, I was struck by the fact that the high numbers 
fell on particular days whilst on other days only low or 
intermediate numbers were observed. This would seem 
to indicate that during the development of the flowers 
in May and June pleiopetaly is influenced by weather 
conditions, in such a way that flowers which are in the 
susceptible period of their development during fine 
weather will produce more petals, quite independently 
of the order of the branch which bears them. 

This conclusion is supported by another set of obser- 
vations. In September 1892 the flowers, on the whole, 
produced more petals than they did in August of the 
same year. Or, to be more accurate, the number was greater 



Ranunculus Biilbosus Seniiplenns. 



259 



on those plants which opened their first flower in Sep- 
tember, than on those which had already begun to flower 
in July and August. The number of individuals of the 
former group was 77; they produced 1134 flowers du- 
ring the period ending with the beginning of November, 
when I stopped recording. In the other group there were 
295 plants which flowered, and they produced 4425 flow- 
ers. The distribution was as follows: 1 

Petals: 5 6 7 8 9 10 11 12 13 14 15 16-31 

Oldest plants. 409 532 638 690 764 599 414 212 80 29 18 20 
September plants: 40 52 126 165 204 215 177 104 35 8 4 




Fig. 53. Ranunculus bulbosus sctniplcinis. A, curve of the 
plants flowering in August ; S, curve of those flowering 
in Septemher. The figures at the base refer to the num- 
ber of petals per flower. 



These figures are exhibited graphically in Fig. 53 ; 
they have been reduced for convenience of comparison 
so that the numbers in the two groups are about the same. 
The apex of the curve of the early flowering plants is 
over the 9 ; it is the same curve which has already been 
given in Fig. 51 on page 249 for the year 1892. The 
other curve has its apex over the 10, and also remains 
above the other curve in the right half of its course. 

The cause of this difference can only lie in the re- 
tarded germination. Either the seeds which germinate 
later are intrinsically more productive of pleiopetalous 

1 See above, p. 250 ywd Fig. 5: v 1892). 



260 Non-1 'salable Races. 

flowers 1 (like the small, late-germinating seeds of the 
crimson clover), or germination in the height of the 
summer in better and particularly in warmer weather 
favors development in such a way that the flowers are 
richer in petals; for the plants which flowered in July 
and August, germinated for the largest part during the 
cold and unfavorable weather experienced in May shortly 
after they had been sown. 

I first made an experiment to determine the influence 
of nutrition on pleiopetaly in 1890. I had wintered the 
selected plants of 1889, and in March transplanted half 
of them on a bed of pure sand, and the other half on a 
bed of ordinary garden soil. Only two-thirds (i. e., 12) 
of the plants of the former lot flowered, whilst all of the 
latter did. On the sandy bed I counted the petals of all 
the flowers and about twice their number on the control 
bed by simply picking off all the open flowers on alternate 
days. I examined in all 75 and 147 flowers respectively. 
The following is the result reckoned in percentages for 
convenience of comparison : 

Number of petals: 5 6 7 8 9 10 

On the bed of sand- 73 23 400 
On garden soil: 53 26 14 5 1 1 

The plants on the better soil produce distinctly fewer 
five-petalled and more 7-10 petalled flowers. It is per- 
haps permissible to conclude from this that the steep drop 
of the curve from the wild locality, where the soil was 
sandy is, to a large extent at any rate, due to low nutri- 
tion. For presumably the same plants would exhibit a 
higher degree of pleiopetaly if grown on better soil and 

1 With regard to this, it would be of great interest to find out in 
this and other plants the degree of development of the anomaly in 
such individuals which do not germinate until two or three years 
after the sowing of the seed 



Ranunculus Bulbosus Semiplenus. 261 

so give rise to a less steep curve, just as in the experiment 
under consideration. 

I made a corresponding experiment in the summer of 
1891, on the effect of manured and unmanured garden 
soil, with the race which was by that time considerably 
improved (Fig. 51 and page 250). The manuring was 
done with guano ; the two beds lay next to one another 
and were of the same size. On each was sown half of 
the harvest of several plants which had been very pro- 
ductive of pleiopetalous flowers in 1890. In the course 
of the summer 1 59 flowers on the unmanured bed opened 
and were recorded and 376 on the manured. The rela- 
tion between these two numbers is the best measure of the 
effect of the manure. The results, reckoned in percent- 
ages, are as follows: 

Petals: 5 6 7 8 9 10 11 12 13 14 

Without manure: 12 15 25 21 12 10 3 1 1 
With guano: 14 15 17 21 14 9 4 3 2 1 

Without manure the apex of the curve was over the 
7 and there were very few flowers with more than eleven 
petals : with manure the apex was over the 8, and there 
were distinctly more pleiopetalous flowers. 

In both the above experiments the control material 
consisted of other individuals than those used for the 
experiment itself. It is possible, however, to subject the 
same plant alternately to favorable and unfavorable in- 
fluences, and when this is done the same result is ob- 
tained as in the previous cases. With this object I trans- 
planted a series of the best plants of 1892 to a very dry 
bed in the spring of 1893. I left them there, and did 
not water them although the weather was continually 
dry. They suffered visibly under this treatment and 
some of them even produced fewer flowers than in the 





1892 


1893 


1892 


1893 


No. 1 


25 


14 


11 


9 


No. 2 


43 


19 


9 


5 


No. 3 


9 


14 


10 


6 


No. 4 


44 


5 


8 


5 


No. 5 


12 


18 


10 


8 


No. 6 


16 


21 


9 


8 



262 Non-Isolablc Races. 

previous summer. I have a record, which has been al- 
ready alluded to, of the number of petals of all the 
flowers of each of the plants of 1892 ; these were recorded 
in the same way in 1893. But I only give here the mean 
numbers of petals per flower. 

PLANTS NUMBER OF MEAN NUMBER OF nwwKVKCV* 

FLOWERS PETALS PER FLOWER 

2 
4 
4 
3 

2 

1 

The anomaly was thus diminished on every single 
plant as the result of transplanting to dry earth. 

The results of all these experiments prove that the 
production of more than five petals in a flower is inde- 
pendent of the position of this flower on the plant, but 
on the other hand is dependent in a high degree on the 
external conditions under which the particular flower 
passes its early stages, i. e., the most susceptible period 
of its existence. The number of petals varies directly 
with the vigor of the plant, the moisture and richness 
of the soil, the warmness of the weather and even the 
amount of sunshine during this susceptible period. 

Cultivation in the garden is therefore bound to con- 
vert the steep half curve of the wild locality (Fig. 51 
for 1887) into a flatter one which will gradually extend 
to higher numbers of petals and will ultimately develop 
a new apex. 

This process, however, takes place more conveniently 
and more certainly, if the cultivation is combined with 
selection (see the same figure). The latter process picks 



Ranunculus Bnlbosus Serniplenus. 263 

out the plants which manifest the anomaly most abun- 
dantly and most strongly ; these must, however, according 
to the facts given, as a rule, be the best nourished ones, 
i. e., the most favored by their environment. l ; '>r on 
the same bed, even if it has been uniformly prepared with 
the greatest care, the conditions under which neighboring 
plants grow are often very different. One seed may 
germinate in a place in which moisture is better retained ; 
another may germinate in almost dry soil. Some germi- 
nate on warm and fine days and are in consequence ahead 
of their less favored brothers for their whole lives; and 
so on. 1 And so it is that the several plants from seeds 
of the same seed-parent sown on the same day and on 
the same bed, are necessarily exposed to diverse condi- 
tions of life. Amongst them selection picks out the best 
and therefore, at least as a general rule, the most highly 
nourished ones. Selection, so to speak, only precipitates 
the operation of these external factors ; as w r e have pointed 
out before in connection with Papa e'er somniferum poly- 
cephalum. 2 

Selection and cultivation have, therefore, worked in 
the same direction in my experiment for four genera- 
tions. They have about doubled the mean number of 
petals per flower, having brought it, in fact, to 9-10; 
they have produced, amongst several hundred plants and 
several thousand flowers, no more than three flowers with 
more than twenty petals (C 21, C 23 and C 31), i. e., 
not essentially more than would be expected according to 
OUETELET'S law from the actual mean and the amplitude 
of variation. These flowers occurred perfectly fortui- 
tously on plants which were not particularly favored oth- 
erwise, the means of the curves being only 10 for each 

1 See Vol. I, p. 138. 2 See Vol. I, p. 140. 



264 Non-I salable Races. 

of the three plants. We are thus justified in concluding 
that by the selection of these plants as seed-parents the 
mean of the race might further be slightly improved 
during the course of some years, but that these extreme 
variants afforded no more hope than did the others, of 
the attainment of the double race. 

Cultivation and selection cooperate in the direction of 
the desired end; they lead the half race measurably fur- 
ther on this line, but it is not through them that the 
object can be attained. The half race remains a half 
race, in spite of every effort and care, the semi-latent 
character expresses itself oftener and oftener, but it does 
not succeed in becoming the equal of the normal active 
characters, i. e., in constituting the mean character of a 
new race, independent of the continuance of selection 
and favorable cultural conditions. 

To arrive at this result a process of an entirely differ- 
ent nature is evidently required. According to the cur- 
rent theory of selection the goal would be reached if the 
experiment could be continued for tens or hundreds of 
years. But the course of the experiment we have de- 
scribed does not support this view ; it shows, on the con- 
trary, that all that can ever be gained by nutrition and 
selection has already been secured in these five genera- 
tions. The actual result is the production of an elite 
race which has a mean number of 9 petals in the flowers, 
under the favorable conditions of culture which obtained ; 
and gives rise, according to environmental conditions, on 
the one hand, to better variants (with a mean of about 
11-13, or perhaps a few more, petals) while, on the other, 
it throws off atavists with a half GALTON curve (see 
Fig. 52 on page 252). 

It is my opinion, howeve r , that if the culture of the 



Varie gated Leaves. 265 

half race were still continued, the double race would 
some day appear quite suddenly, and that it would then, 
after a short but sufficient isolation, persist as a constant, 
though highly variable, race. 1 

24. VARIEGATED LEAVES. 

Variegated plants have long been great favorites in 
the garden, and their great instability has contributed 
largely to the development of the horticultural concep- 
tion of a variety, for the variations in their color pattern 
are practically unlimited. Hardly any two leaves are 
alike, and many species have a whole series of dappled 
and flecked varieties. They also possess the striking 
property of continually and conspicuously reverting to 
the species to which they belong. Such reversions occur 
either amongst seedlings or as bud-variations, and since 
on shrubs and trees these latter often remain for many 
vears and not rarely in more than one instance on the 

* / 

same plant, they can be seen by every one. In this way 
these bud-variations have come to be regarded as a suf- 
ficient proof of the idea that varieties are derivative and 
unstable structures, which always tend to revert to their 
parent species. 

Especially in the first half of the eighteenth century 
were plants with speckled and striped leaves very much 
sought after. 2 About that time the well-known English 
gardener THOMAS FAIRCHILD possessed more than one 
hundred varieties of them in his garden, and afterwards 
SCHLECHTENDAHL published a list from which it can 
be seen that variegation is distributed over the whole 

*!. e., as an eversporting variety with a wide amplitude of varia- 
tion which however would not alter in the course of the generations. 

"MEYEN, Pfiansen-Pathologie, 1841, p 282. 



266 Non-Isolable Races. 

vegetable kingdom and occurs in all the larger groups 
and especially in most families of flowering plants. 1 

At that time some of the most widely cultivated forms 
were the ribbon grass, Phraguiitcs arundinacca I'aricgata, 
and the variegated holly, Ilex Aquifoliiiin. Both are 
still much grown in gardens, the ribbon grass being rela- 
tively uniform, the holly highly variable. Of the latter 
there is a variety with white-edged leaves, besides the 
ordinary one with flecked leaves. Phragmites is differ- 
ent in many respects from genuine variegated plants and 
is much less variable in its character. The Ilc.r, however, 
is highly variable and often bears green shoots which 
may soon supersede the others on account of the greater 
facility with which they can obtain nourishment. A fine 
variegated bush of this species, or of any other, may be- 
come entirely green, whenever the green branches are 
not cut away every year. Thus it is probable that many 
specimens of the holly, which are now quite green, were 
originally variegated and were bought and planted as 
such. On closer examination we often find on them an 
occasional variegated twig which proves the correctness 
of this supposition. This is also the case with the horse 
chestnut, of which many older trees still living were 
planted at a time when the variegated variety was in 
special favor. Since then their foliage has become green 
and their original character is no longer seen. But an 
occasional checkered branch, or even the numerous small 
twigs with white leaves along the main stem, betrays the 
original variegated condition of the specimen. In the 
same way many cases of single variegated twigs on 
green bushes and trees are not to be regarded as the indi- 

1 SCHLECHTENDAHL, Liiuiaea, 1830, V, p. 494. Very little seems to 
be known about variegated mosses and thallophytes. 



Variegated Leaves. 267 

cation of something new but as a reminiscence of times 
long past when these varieties were in general favor. 

Variegation is classified under several headings. In 
the first place there are the yellow and the white varieties. 
In the former the chlorophyll is only insufficiently pro- 
duced, but in the latter even the xanthophyll or carotin 
is lacking; 1 and a more or less abortive development of 
the chloroplasts is usually correlated with the absence 
of these pigments. 2 

Further we distinguish marginate, flecked and striped 
sorts. The former seem to constitute a variety for them- 
selves and are much rarer than the latter; they appear to 
be good races, that is, to be as constant as any ordinary 
garden variety, but I shall have little to say about them 
in this part. The most characteristic and best known 
example of them is the white bordered holly to which 
we have alreadv referred. 3 

/ 

Whether a plant is flecked or striped depends as a 
rule on the mode of venation of the leaves. Many varie- 
gated monocotyledons have striped leaves (Agave, Con- 
vaUaria majalis, Phormium tenax, Tradescantia repens, 
etc.) whereas the dicotyledons are usually flecked or 
streaked. 

The incomplete development of the chlorophyll ob- 

1 See T. TAMMES, Ueber Carotin, Flora, 1900. 

2 For further information on this point see the elaborate ana- 
tomical studies of A. ZIMMERMANN, Ucber die Chromatophoren in 
panachirten Slattern, in Beitrage zur Morphologic und Physiologic 
der Pflanzenzelle, Heft II, 1891, pp. 81-111, and Ber. d. d. hot. Ges. 
VIII, 1890, p. 95. Also H. TIMPE, Beitrage zur Kenntniss der 
Panachirung, Inaug.-Diss., Gottingen, 1900. 

5 Marginate forms are commonly supposed by gardeners to be 
more stable than flecked ones. This fact was noted by MORREN in 1865. 
(Heredite de la panachure, Bull. Acad. roy. Belg., T. XIX. 2d series, 
p. 225). VERLOT however maintains the opposite opinion (Des Varie- 
tes, 1865, p. 74). For information relating to variegated varieties of 
Ilex see FOCKE, Abh. d. Naturw. Ver. zu Bremen, Vol. V, pp. 401-404. 



268 Non-Isolable Races. 

viously results in an insufficient assimilation of carbonic 
acid gas. Thus the variegated parts grow less vigor- 
ously and are less resistant than the corresponding green 
ones. The Cy perns alter nifolius of our greenhouses, the 
Aspidistra elatior and a number of other favorite varie- 
ties show this clearly. Arundo do mix often attains a 
height of three or more meters whereas its striped vari- 
ety is scarcely half that height. Leaves of the variegated 
Aspidistra very often have one of their longitudinal 
halves green, but the other colorless. In such cases the 
leaf is distorted owing to the insufficient growth of the 
colorless half. The same thing happens in many other 
cases. 

The yellow leaves and parts of leaves, however, are 
not entirely without the green coloring matter, nor wholly 
without the power of assimilation. Most of them give 
a green extract when put into alcohol, and if examined 
under the microscope patches of green tissue can be found 
here and there, especially near the veins. The power to 
sustain life, however, is often lacking and the leaves die 
shortly after their growth is completed. Therefore, a 
high degree of the anomaly is not in favor, because the 
plants which possess it often become disfigured by the 
edges of their leaves turning brown. Many plants in 
which the variegation has gone too far die in their very 
early stages, while others have not sufficient strength to 
flower and bear seed. This latter circumstance is of 
special interest because it follows that plants with a high 
degree of variegation as a rule can have no part in the 
propagation of the variety. 1 In the opinion of some 

1 It is perhaps scarcely necessary to state that these remarks do 
not apply to brown and purple leaves or those with red spots. For 
information on this point see STAHL'S excellent article Ueber bunte 
Laubbldttcr, Ann. Jard. Bot. Buitenzorg., Vol. XIII, Pt. 2, 1896, p. 137. 



Variegated Leaves. 269 

authors another fact is connected with this, viz., that 
varieties which have both variegated leaves and double 
flowers are much rarer than would have been expected 
from the prevalence of these two anomalies in horti- 
culture. 1 

In variegated plants, as is well known, not only the 
leaves are flecked. Their stems and calices are also often 
variegated, and the same is true of the fruits (pears, 
grapes, the siliquae of cabbage, Barbarea vulgaris, Chei- 
ranthus Chciri, Alyssum maritinium, Acer, Ilex, Aego- 
podiuin, Ligusticum, etc.). 2 I have also sometimes found 
galls on variegated oaks to be variegated, especially in 
the case of the beautiful orbicular galls of Cynips Kollari. 

I shall now proceed to the important question of the 
inheritance of this abnormality or the degree of fixing as 
it is usually called. As already stated I shall exclude 
from consideration the white-flecked 3 and the marginate 
forms of variegation, and shall confine myself to the 
ordinary cases of yellow variegated leaves. I shall give 
the numerical proofs of my conclusions later, and shall 
now proceed to deal with the question whether variegated 
sorts are half races or intermediate races (see Chapter 
II of this part). 

In my opinion the great majority of the variegated 
garden varieties are intermediate races, as for instance 
Barbarea vulgaris: whereas wild plants which occasion- 
ally present this character represent half races. Their 

1 B. VERLOT, Sur la production et la fixation des varictes dans Ics 
Mantes d'ornement, 1865, p. 75. Also MORREN, Hercditc dc la pana- 
chure, loc. cit., p. 226. 

2 MORREN, loc. cit., p. 233. 

3 1 have not myself made any observations on this phenomenon 
(Albicatio, Albinismus} and the published records of it are very 
scanty. The fine white-variegated Humulus japonicus variegatus 
would be well worth experimenting with. 



2/0 Non-Isolable Races. 



multiformity and instability corroborate this view. It 
is only the commonness of variegated sorts and the great 
interest which attaches to them which brings them to be 
regarded as analogous to the best constant varieties. 

o o 

Moreover this view is supported by the general opinion 
that a complete development of the yellow color would 
characterise the supposed constant variety, but that it 
would at the same time of necessity lead to the destruc- 
tion of the plants. In this conception variegation is re- 
garded as an incomplete anomaly whose complete con- 
dition would involve its own destruction ; but this view 
is incorrect. 1 Complete yellow varieties are not only pos- 
sible and capable of existence but actually well known in 
horticulture, although the number of such forms is small. 
Instances can be found in seedsmen's catalogues; e. g., 
Sainbucus uiyra aurca and Fra.vinus c.rcclsior aurea, also 
the aurca varieties of Chrysanthemum carinatum, Mira- 
bilis Jala pa, Scabiosa atropurpurca, Hiunulus japomcus 
(liitcsccns) etc. These plants, so far as I know, are all 
either yellowish-green or golden-yellow. 2 They also ap- 
pear to be very constant and never or very seldom to 
revert to the green type. I have made a number of ex- 
perimental sowings on a large scale of the seeds of the 
ordinary golden-yellow variety of Chrysanthemum Par- 

/ <j / . 

thenium? (Matncaria c.viiiria nana coinpacta foliis aurcls 
Hoj't.) and did not find amongst the many hundred ex- 
amples a single atavist ; neither green nor variegated seed- 
lings occurred. But amongst other commercial seeds I 

o o 

have not found so great a degree of purity, the admixture 

1 See 3 of this part (pp. 18-26). 

2 T have not grown all the above forms myself; and it should be 
noticed that the name an r ens does not always relate to uniformly 
colored sorts, e. g., Agave striaia aurca. 

3 ViLMORiN, B lumen gartnereij Vol. IT, p. 509. 



] \irieyated Leaves. 



271 



of green plants, however, not being larger than might 
as a rule be expected from commercial seeds. For in- 
stance, Stellaria graininca aurca gave only 28% and Myo- 
sotis alpcstris coinpacta foliis anrcis only 3% of green 
seedlings. But even in these cultures there were no 
variegated plants. 

The fact that the aurca varieties give a green extract 
in alcohol and contain sufficient chlorophyll for their 
nutrition does not need special mention. 




Fig. 54. Thyinus Scrpylluni. The ordinary Thyme; a 
plant with a variegated branch B. 

The anrea varieties and the yellow variegated sorts 
owe their character to the masking of the green pigment 
by the yellow which is developed in the former case all 
over the leaf, and in the latter onlv in certain tracts. 

* 

The majority of variegated plants are analogous to those 
numerous half races which manifest their anomaly ( which 
may be doubling, pitcher formation, the production of 



272 Non-Isolable Races. 

quaclri foliate leaves, etc.) only in isolated organs and 
parts of organs. Some sorts I regard as analogous to the 
double varieties, whilst the aurca varieties are probably 
just as constant as the Varietatcs discoidcac and as the 
best elementary species. 

The very general occurrence of variegated plants 
points to the conclusion that the latent capacity for varie- 
gation is widely distributed throughout the vegetable 
kingdom. Moreover the fact that branches and whole 
plants with this character are met with every year in 
new species both in the garden and the field points in the 
same direction. In this connection I may mention the 
fact that forms with white variegated or white- or yellow- 
edged leaves occur only rarely. I observed an instance 
of the latter in a wild specimen of Oenothera Lamarck- 
iana (1887, see. Vol. I, p. 480) and of the former I 
found specimens in Spiraea Uhnaria, Callnna I'ulgaris, 
Tri folium pra tense, Lye Jin is dinrna in 1886 and 1887 in 
the neighborhood of Hilversum. In the above mentioned 
years I found yellow variegated plants of Plantago major, 
Phalaris arundinacea, Rhinanthus major, Erica TetralLv, 
Urtica nrens, Hypericum perforatum, Tri folium pra- 
tcnse, Hleraciuni Pilosella, Rnbns fmticosus, Polygomun 
Convolvulus and Genm nrbanum. In 1869 I found a 
beautiful variegated specimen of Arnica montana in the 
Thuringian Forest and later one of Plantago lanceolata 
in Saxon Switzerland, and one of Thyinus Serpyllum 
near Wyk aan Zee in Holland (Fig. 54), and I have 
since frequently found occasional variegated specimens 
of other wild species. In the same way they appeared 
in my own cultures where there can be no question but 
that they have been preceded by many generations of 
purely green ancestors; so for instance in Chrysanthe- 



Variegated Leaves. 273 

mum sccjctinn, Antirrhinum majus, Polygonwn Fayo- 
p\nim. Linaria I'ulgaris, Silcnc nocti flora etc. 

Hie large scale on which I have conducted my ex- 
periments with Ocnothcra Lamarckiana has enabled me 
to watch the origin of variegated forms in that species 
more closely. Here they appear almost every year from 
green ancestors, and in the most widely different experi- 
mental families and elementary species. 1 Instances of 
it I found in the main Lamarckiana families, first in the 
original wild locality, then in 1889, 1890, 1892, 1895, 
1898 and 1899 in my cultures, arising from series of 
seed-parents which were in every case green plants ; 
also in 0. rubrinervis in 1891, 1893 and 1894; in O. 
laevifolia in 1891, 1894 and 1899; in 0. snbliucaris in 
1896; in O. lata in 1890 and 1899; in O. nanclla in 1890, 
1896 and 1899; in 0. scintillans in 1898 and so on; also 
from the crosses 0. lata X O. cniciata and O. Lamarck- 
iana X 0. Lamarckiana cniciata and others. In 1899 
only eight variegated plants arose in my whole cultures 
which consisted of over five thousand plants of Ocno- 
thcra, that is, between 0.1 and 0.2%. But in the field 
the anomaly was evidently much rarer. 

One of the most striking phenomena presented by 
variegated plants is the so-called twig or bud-variation. 
From a bud a branch arises which is unlike the whole 
of the rest of the plant in the character of its variegation, 
and in this case both variegated plants bearing green 
twigs occur and conversely plants which have hitherto 
been green may bear stray variegated branches. In both 
cases a latent potentiality is manifested. 

The appearance of green branches on variegated 
plants is generally regarded as a case of atavism, that is 

1 See also Vol. I, p. 480. 



274 Non-Isolablc Races. 

reversion to the parental form. It is especially common 
on woody species and in shrubs. Evonymus japonica, 
Quercus pedunculate,, Weigelia amabilis, Cornus san- 
g nine a and many others afford well-known examples. 
Others are found amongst perennials and perhaps best 
of all in Arabis alpina. I may cite as further instances 
partly from the literature on the subject and partly from 
my own observations : Castanea vcsca, Kcrria japonica, 
Aesculus Hippocastanum, Yucca pcndula aiirca, Ulinns 
campestris, Zea Mays, Rub us fruticosus and so on. 

The green branches can obtain nutrition better than 
the variegated ones. Therefore they grow more vig- 
orously and become stronger during the course of 
years, and very often overgrow the others. As a rule 
all their leaves and branches are pure green, and they 
look as if they had entirely lost the capacity for varie- 
gation. But this is not the case, for sometimes we see 
single variegated twigs on these green branches. Arabis 
alpina is especially instructive in this connection, for it 
often gives rise to variations from its buds, and since 

o 

it is easy to separate these and cultivate them further. 
Analogous cases of this double reversion, as it may be 
called, were observed by me in 1893 in Castanea vcsca 
variegata and Kcrria japonica variegata which bore a 
little variegated twig on a green branch; and the same 
has been observed in other cases. 

The deficient nutrition frequently makes the varie- 
gated leaves smaller than the green ones. If the pigment 
is mainly absent in the margin of the leaves this becomes 
too small for the middle area and the whole leaf becomes 
crumpled. A unilateral checking of the growth leads 
to a corresponding bending. It is due to these circum- 
stances that the habitus of variegated plants is often so 



Variegated Leaves. 275 

different from that of the typical form, but as soon as 
reversion occurs through bud-variation all these second- 
ary characters are dispersed at once, the green leaves be- 
coming flattened out, assuming the normal form, and 
often attaining twice the size of the variegated ones. In 
this way the reverted branch easily strikes the eye. I ob- 
served this most beautifully in Castanea vesca and Ulmus 
campestris, but Kerria japonica and many other species 
show it as well. 

The question which buds are most likely to give rise 
to atavistic branches has been much discussed, and the 
general opinion seems to be that the rhizome and the 
adventitious buds on the roots are most prone to rever- 
sion. Thus Glechoma hederaceuin variegatum often pro- 
duces green runners 1 whereas the variegated Tussilago 
Farfara breeds true from its runners. For the last ten 
years I have had a variegated plant of Rub us fruticosus 
which has produced both green and variegated plants 
from its radical buds in proportions which vary according 
to conditions, and to the year. It seems to me probable 
that the weaker buds are most likely to give rise to ata- 
vists ; but since this results in the production of green 
branches which grow much more vigorously than the 
neighboring variegated ones, it is not easy to decide this 
point. 2 

Variegated branches on green plants are almost as 
common. It is the general idea amongst gardeners that 
the numerous variegated varieties of woody plants have, 
with few exceptions, arisen in this way. One of these 

'VERLOT, loc. tit., p. 78. 

2 In papers on this subject we often come across an expression 
of the opinion that it is the strongest branches which become green; 
but this view, no doubt, is largely due to a misapprehension of the 
relation between the cause and its effect, as explained in the text. 



276 Non-Isolable Races. 

exceptions is Wcicjclia amabilis varicgata which was 
raised by VAN HouTTE 1 from the seed of the green 
variety; another is the variegated grape raised by 
KNIGHT. 2 In many cases a record of the original dis- 
covery has been preserved. Thus WOLFF 3 states that 
he found a variegated branch on a bush of Spiraea opuli- 
folia ; the leaves were whitish green with a sulphur yel- 
low margin, marked here and there with dark green 
flecks. The new form was easily multiplied by cuttings 
and appeared on the market as Spiraea opiili folia hetero- 
phylla fol. aur. marg. 

In nature bud-variations of this kind are also occa- 
sionally found, and it seems that this is almost the only 
bud-variation which is met with amongst wild plants, 
for usually this phenomenon is observed as a case of re- 
version on cultivated varieties or on hybrids. I myself 
have found very beautiful and large variegated twigs in 
Qiiercus pedunculata, Betula alba and Fagns sylvatica 
in the forests near Hilversum; in each case there was 
one large variegated branch on an otherwise green tree 
amongst hundreds or even thousands of perfectly green 
individuals. 

On the variegated branches the variegation often ap- 
pears unilaterally. The anomaly is developed laterally 
or unilaterally, or to use a more accurate expression, 
sectorially. For in the vertical projection of the branch 
there is usually only one sector which is variegated ; some- 
times one-half, sometimes one-third, and often even a 
smaller section of the circumference of the stem being 
affected. 4 The sectorial variation behaves in the same 

^ERLOT, IOC. Clt., p. 74. 

2 DE CANDOLLE, Physiologic, II, p. 734. 

s Gartenflora, Vol. XXXIX, 1890, p. 9. 

4 A study of sectorial variation in relation to the divisions in the 



Variegated Leaves. 277 

way in this case as in that of the striped flowers. The 
buds in the axils of the leaves on the variegated sectors 
usually produce variegated branches, but those of the 
green sectors preen ones. Breeders take this fact into 

o o 

consideration in the choice of buds for use in the multi- 
plication of variegated forms, as we have already seen. 1 
It seems that the bud-variations, that is to say both the 
progressive (producing variegation) and the retrogres- 
sive or atavistic ones, are generally the result of a pre- 
ceding sectorial variation. But in most cases all traces 
of the latter are soon lost. In Quercus pcdunculata I ob- 
served, as I have already mentioned, a variegated twig 
on a green bush. In this case the variegation extended 
on to the bark and the color of the branches of the pre- 
ceding years could thus still be recognized. The main 
branch proved to be unilaterally variegated and the varie- 
gated twig arose from this side. The branches at the 
other side were green (Hilversum 1886). AYhen the 
leaves are arranged in two rows as in Castanea vcsca, 
Ulmns campestris etc. the leaves on one side of the 
branch may be variegated and on the other, green. In 
such cases I found the lateral twigs on the older parts 
on the green side to be entirely green and those on the 
variegated side entirely variegated ; but I might repeat 
here that there is still a tendency in the green branches, 
even if only a slight one, to produce variegated leaves. 
The contrast between green and variegated is therefore 
not nearly so great as would appear at first sight. 

We have no\v to consider the question of the in- 
fluence of external conditions on the degree of variega- 

apical cells would be of great interest, especially in the Conifers and 
vascular Cryptogams (e. ., funiperus, Adianthum, Selag'mella etc.). 

1 See SALTER'S method, Vol. I, Part I, p. 147. 



278 Non-Isolablc Races. 



tion. 1 On this point the literature is rich in contradictory 
information. This contradiction is probably mainly due 
to the fact already mentioned that the green parts are 
so very much stronger than the variegated ones. This 
strikes the eye so forcibly that the idea easily arises that 
the strongest parts of the variegated plants are most liable 
to become green and the weakest branches of green 
plants most likely to become variegated. In my opinion, 
however, this conclusion is incorrect. The relative vigor 
is determined by the anomaly, but from this it by no 
means follows that the anomaly, in its turn, is determined 
by it. So far as my experience goes -the reverse is the 
case, and variegation forms no exception to the general 
rule for semi-latent characters, that favorable conditions 
increase the intensity of the anomaly. 

The best instance that I know is furnished by the 
variegated horse-radish (Cochlearia Arnwracea varie- 
gata), which with unfavorable treatment is almost green, 
but under glass or in'a cold frame may even become en- 
tirely white. Plants growing in the open in a sunny posi- 
tion are often beautifully variegated, whereas in shady 
positions they are a much darker green. The same is 
true according to SCHLECHTENDAHL of Plectog\nc I'aric- 
yata on the leaves of which a greater or lesser number 
of white stripes can be induced at will by merely trans- 
planting it. 2 Fragaria indica variegata is a favorite 
plant for hanging-baskets. If one wishes it to be nicely 
variegated it must be planted in good dry soil, not too 
loamy or calcareous. 3 The same is true of the striped 
sorts of the ordinary strawberries, in which, as VER- 

1 E. LAURENT, Sur 1'origine des varictes panacliccs. Bull. Soc. 
R. Bot. Belgique, Vol. XXXIX, 1900, pp. 6-9. 

-Bot. Zcituug, 1855, P- 558. 

3 VILMORIN-ANDRIEUX, Flcitrs dc plcinc Icrrc, p. 408. 



Variegated Leaves. 279 

LOT 1 says, "La panachure pent s'obtenir pour ainsi dire 
a -culunte" by merely growing them in a dry position. 
A dry position is however at the same time as a rule a 
sunny one, whereas a damp one, as a rule, is shaded. 
Experiments which I have conducted with these and 
several other variegated sorts of various species, in order 
to determine the influence of daily and profuse watering 
in full sunlight on variegation, have been without any 
positive result. On the other hand I succeeded with 
Tradescantia repcns in controlling the proportion of yel- 
low and green stripes. In this experiment I cultivated 
the plants in pots and simply removed the pots to better 
or less well-lighted parts of the greenhouse without alter- 
ing the soil or the amount of water I gave them. The 
more intense the light the more variegated were the new 
leaves that were formed. 2 

On variegated shrubs we often see that in the better 
lighted parts variegation is more intense and in the shadec 
ones less pronounced. Even variegated conifers such as 
the Juniperus, may show this, and it is well known to be 
the case with Sambuciis nlgra. The variegation in myr- 
tles with striped leaves is also dependent on nutrition ; :: 
and various authors and gardeners hold that the soil and 
position exert a more or less important influence on the 
degree of variegation. 4 Pelargonium zonale, Conral- 
laria majalis, Mentha aquatlca, Phalaris arundinacea, 
Phlox decussata and others are given as instances. 5 Such 

1 VERLOT, loc. cit., p. 76. 

2 For facts relating- to the influence of galls on variegation in 
Eupatorinm cannabmum see Vol. I, p. 407. 

" MEYEN, Pftaiizen-Pathologie, p. 287. 

4 As for instance SALTER, quoted in DARWIN, Variations, II, pp. 
263-264. 

n DARWIN, loc. cit., I, p, 390; II, p. 263. 



280 Non-Isolable Races. 

plants are often entirely green during years of improper 
treatment, but with due care can be restored to the varie- 
gated condition. 1 

The degree of variegation is not only dependent upon 
the conditions of growth but also on the time of the year. 
If we look closely at variegated plants in green-houses 
we shall see that the branches which arise in summer are 
beautifully flecked, whereas those which arise in winter, 
when they get less light, are much greener and sometimes 
even quite green. This at least is true in our climate; 
but one must remember that the leaves formed in sum- 
mer remain on the shrubs through the winter, and 
undergo no further change in their variegation. There- 
fore it is not the general appearance which is dependent 
on the time of the year. Quercus pedunculata argcntco- 
picta is green in spring, but becomes white or variegated 
later on. 2 Young plants are often still green in spring 
even though later they may become variegated, as for 
instance, Symphytum, Barbarea vulgaris, etc. 3 I have 
observed in a culture of Geum urbanum, which I have 
kept up during several years, that the variegated speci- 
mens gradually develop green leaves in the autumn and 
lose the variegated ones. In winter they were almost 
completely green, but as soon as life awoke in the spring 
they began to develop flecked leaves again, and through- 
out the whole summer they were fully variegated. They 
behaved in this way throughout every winter of their 
life. On the other hand a variety of the ornamental 
curly cale with yellow-veined leaves is beautifully varie- 

1 VERLOT, loc. cit., p. 75. 

2 L. BEISSNER, Knospenvariation, Mitth. d. deutsch. Dendrolog. 
Gesellsch., No. 4, 1895. 

3 VERLOT, loc. cit., p. 76. 



Variegated Leaves. 281 

gated in late autumn and winter but becomes completely 
green in summer. 1 

In all these observations there was no question of bud- 
variation. Of the causes of this phenomenon little is 
known. On the other hand it is generally recognized that 
if resting buds on variegated plants are allowed to grow 
vigorously they often develop into completely white or 
yellow so-called chlorotic branches;--! mean those buds 
which on green sorts would develop into strong succu- 
lent shoots under similar inducements, but the chlorosis 
soon puts an end to this development. Adventitious buds 
which arise from the stem a little above the soil fre- 
quently give rise to chlorotic branches, either after the 
stems have been cut down or when the leaves have been 
eaten by snails, or from some other cause. Aesculus 
Hippocastamun is the best known example, so also are 
Evonymus japonicus, Pelargonium zonale, Azalea ja- 
ponica, Aucitba japonica, Ilex Aquifolium; also Spiraea 
eallosa, Kerria japonica, Vlnca major, 2 Hydrangea Jwr- 
tensis, 3 Fagus syh'atica, 4 Ulmus campestrisf Cornus son- 
guinea , r ^ Sambuciis nigra? Myrtus communis tarantina, 
Zea Mays etc. 

The inheritance of variegation through seeds is one 
of the most interesting phenomena presented by this 

1 H. MOLISCH, Ucbcr die Panachilrc des Kohls. Ber. d. d. bot. 
Gesellsch., Vol. XIX, 1901, p. 32. 

2 VERLOT, loc. cit., p. 75. Here also will be found information 
relating to Glechoma hederacea. 

3 MORREN, Hercditc, loc. cit., p. 230. Here also Pelargonium in- 
quinans. 

4 According to SCHLEIDEN, after being damaged by snails, cited 
by MORREN, loc. cit., p. 227. 

5 Ulmus, Cornus and Sambucus according to my own observa- 
tions. Moreover I have seen such branches on almost all the above 
named varieties. 

6 G. ARCANGELI, Bull. Soc. Bot. Ital, 1895, PP- 16-18. 



282 Non-I salable Races. 

whole set of facts. The variegated sorts are nearly all 
more or less constant; sometimes to a very small and 
sometimes to a very large extent. This character has 
been subjected to what we may call an automatic selec- 
tion, for every gardener naturally plants out only varie- 
gated specimens neglecting the green ones; also it is 
customary to cut away the green twigs which arise by 
bud-variation. Here we have a sort of unconscious se- 
lection which has however been exercised in the same 
direction for many years, and in many cases through 
some centuries. 

And what has been effected by this continued selec- 
tion? Absolutely nothing. At least, so far as we know, 
nothing more than maintaining the variegated varieties 
and keeping them in a fairly pure condition. But nothing 
like fixation has resulted ; that is to say, the varieties 
continue to produce atavists when grown from seed, and 
moreover, the pure and constant varieties which corre- 
spond to them have not been obtained. For in this case 
these varieties, as we stated above, would have to be the 
pure yellow ones, such as are known to gardeners under 
the name of aurea forms. 

All in all there are in our gardens, perhaps twenty 
or thirty, or even a few more of these anrca forms; and 
this number is as nothing compared with the almost un- 
limited series of variegated forms. Moreover exactly 
those variegated forms which have been cultivated most 
carefully and for the longest time have not given rise to 
aurea varieties. 1 

From this discussion I draw the conclusion that con- 
tinued selection with variegated plants will not of itself 
lead to the production of constant forms. For this, 

1 See the list on page 270. 



Variegated Leaves. 283 

something else is necessary, and this something chance 
alone can provide. What we want is the transition from 
one race to another, a transition, which according to my 
opinion, cannot he effected gradually, hut takes place 
suddenly from as yet unknown causes; we have, in fact, 
to wait for a mutation. 

The longer a variegated plant has been in cultiva- 
tion the more strongly does the fact that it has not pro- 
gressed support this conclusion. The best instance is 
afforded by the familiar Rocket 1 which is one of the 
oldest, favorite and most widely distributed variegated 
plants in cultivation, and which is often seen to escape 
from gardens (Barbarea vidgans variegata). The plant 
is cultivated almost solely for its variegated leaves, al- 
though it is a kind of cress. It is biennial and sufficiently 
constant ; it is usually grown from seed, although it can 
also be propagated by division. Only a small percentage 
of the seedlings are found to be variegated. Amongst 
a thousand grown from seeds which I had harvested 
myself from isolated variegated plants, I found only 
one per cent variegated and ninety-nine per cent plants 
whose cotyledons and first leaves were pure green. No 
white or yellow seedlings occurred. Of the greens a large 
proportion developed later into variegated plants, as was 
to he expected. 2 But the variety can by no means be 
regarded as fully fixed. 

Very many variegated varieties, especially of annual 
and biennial plants, come true to seed. MORREN, CAR- 
RiERE 3 and other authors have drawn up lists, and much 
information relating to the subject can be gathered from 

1 VILMORIN-ANDRIEUX, Fleurs de pJcine terre, p. 387. 

2 According to MORREN, Hercditc, he. cit.. p. 229, from 70-99% 
of the seedlings become variegated in later life. 

3 E. A. CARRIERE, Production et fixation des varictcs, 1865. p. 14. 



284 Non-Isolable Races. 

seedsmen's catalog-ties. Such statements relate, of course, 
only to practical and not to absolute constancy. It suf- 
fices that the harvests justify a reasonable hope that 
a certain number of variegated individuals will occur 
amongst the seedlings. Information as to the magni- 
tude of this proportion is rarely given. GODRON found 
Acer striatum variegatum to repeat the anomaly in only 
one-third of its seedlings. 1 VIVIAND-MOREL found only 
occasional variegated specimens amongst five hundred 
seedlings of Hedera Helix varicgata and only one 
amongst fifty of variegated Yucca, the majority being 
green. 2 PEPIN states that the seeds of Sophora japonic a 
foliis varlegatis always give rise to more variegated than 
green plants; 3 but in the case of these and similar data 
we know nothing, as a rule, as to whether the seeds have 
been derived from individuals which had been isolated. 
POLLOCK sowed the seeds of a variegated plant of Ballota 
nigra which he had found wild and obtained thirty per 
cent variegated seedlings. In the next generation the 
seeds of these, however, gave 60% of variegated indi- 
viduals. 4 The plant is now on the market and from the 
commercial seed I raised 25% variegated and 75% green 
plants. The seeds of a variegated specimen of Chrysan- 
themum inodorum found near Amsterdam produced 65 
plants in my garden, of which 5% were variegated whilst 
17 produced spotted leaves during the course of the 
summer, and the rest were green (1893). From the 
seeds of a variegated Lunaria biennis I raised green 
plants only, (1893) and I obtained the same result in 



. Acad. Stanislas, 1873. 
* Lyon horticolc, 1893, p. 144. 

3 VERLOT, loc. cit., p. 75. 

4 DARWIN, Variations of Animals and Plants, T, p. 409. 



Variegated Leaves. 285 

1896 from some self-fertilized variegated Ocnothcra La- 
uuirckiana, although these two sorts are ordinarily con- 
stant from seed. Variegated Oenothera rubrinervis gave 
rise to 20% variegated seedlings (1892), but on a repe- 
tition of the experiment with another plant (1893) all the 
offspring were green. 

In sectorial variegation we might expect the seeds of 
the variegated sectors to give rise to more variegated 
plants than those of the green ones. The only informa- 
tion relating to this question as far as I know is due to 
HEiNSius. 1 He found a stem of Dianthus barbatns, one 
of the longitudinal halves of which was variegated, whilst 
the other was colored in the ordinary w r ay. During the 
flowering period the plant was protected from insects by 
gauze and artificially fertilized, each flower being polli- 
nated with pollen from another in the same longitudinal 
half. On the one half the capsules were white, on the 
other green ; both produced ripe seed. The seeds of the 
white fruits produced seedlings without chlorophyll but 
the seedlings from green capsules were the normal green. 
In 1888 I myself collected the green and the variegated 
fruits of a sectorial main stem of Oenothera Lamarckiana 
separately. The seeds of the former gave rise almost 
exclusively to green plants, those of the latter to a large 
proportion of variegated ones. In the summer of 1895 
I saved the fruits from a green and from a variegated 
branch of the same plant of this species, but both sets of 
seeds gave about the same very small proportion of varie- 
gated specimens, viz., 2%. 

In the summer of 1898 I conducted a more exhaustive 
research with sectorial variegation in Oenothera La- 

1 H. W. HEINSIUS in the Proceedings of the Gcnootschap ter 
bevordering der Natunr- Genees- en Heelkunde te Amsterdam. Meet- 
ing of May 7, 1898. 



286 Xou-Isolable Races 

marckiana. In the normal families of my cultures some 
specimens that happened to be variegated had, after arti- 
ficial self-fertilization, given rise to no more than two 
per cent of variegated offspring and in the next genera- 
tion the same proportion was repeated, the conditions be- 
ing the same. From these I selected in 1898 the four 
finest young plants, planted them out a meter apart, and 
thereby obtained strong, richly-branched individuals, of 
which some were slightly, and others strongly, variegated. 
On all of them the flowers from which I intended to save 
seed were artificially and purely fertilized with their own 
pollen. On each of the four plants I first fertilized 
flowers on the pure green and afterwards some on the 
variegated lateral branches. Amongst 675 seedlings of 
the former and 1300 of the latter group the seeds pro- 
duced the following percentages of yellow and variegated 
seedlings : 

PL\NTS PERCENTAGE IN VARIEGATED SEEDLINGS 

GREEN BRANCHES VARIEGATED BRANCHES 

No. 1 0-0 % 1 % 

No. 2 3 

No. 3 0-0 4-12-18 

No. 4 0-0 6-9-45-100 

Each number refers to a separate branch The six 
greens gave rise, as we see, to green seedlings only, but 
the variegated ones to a larger or smaller number of 
seedlings with this character. The figures 1, 3, 4, and 
45 in the last column relate to the slightly variegated 
branches ; the rest to those with this character more 
strongly developed. The latter therefore gave a higher 
percentage of variegated offspring. The variegated seed- 
lings had either vellow or flecked cotvledous, or o-reen 

f C5 

cotyledons and flecked leaves, and of these three groups 
there were 68% of the first, 12% of the second and 20% 



Variegated Leaves. 287 

of the third group. The more yellow seedlings there 
were in a group the more variegated specimens did it, 
as a rule, also contain. I collected the seeds of a yellow 
fruit separately; only eleven of these germinated but 
these had all pure yellow cotyledons. On the other hand 
striped fruits had percentages of variegated seedlings 
which varied greatly, and this was also true of the striped 
parts of capsules when their seeds were harvested sepa- 
rately. Lastly the seeds of green capsules produced only 
green seedlings. 

The color of the seedlings is therefore to a large ex- 
tent determined by the color of that part of the mother 
plant which produced the seed (and also the pollen). 

I made a further investigation of the seedlings from 
seeds of green and variegated branches of individual 
plants in various other species, after artificial isolation 
had been secured, either by means of parchment bags, or 
by planting the plants some distance apart, or by making 
them flower at different times. 1 I obtained the following 
percentages of variegated and yellow seedlings : 

SEEDS OF 

GREEN VARIEGATED 

BRANCHES BRANCHES 

A. Commercial variegated races: 

Arabis alpina 2-10 % 90 % 

Helianthits annuns " 100" 

B. Occasional finds: 

Lamium album '' 3 " 

Gemn urbanum 0.3 " 4 " 

Silene noctiflora (5 ") (34") 

The high percentage of green plants in Arabis alpina 
corresponds presumably to the readiness with which this 
species produces bud-variations, variegated branches be- 

1 In Silcne iwctiflnra only was fertilization left to the free agency 
of insects. 



288 Non-Isolable Races. 

ing easily produced by green plants and green branches 
by variegated ones. 

Now let us consider the yellow seedlings of variegated 
plants. They appear, it is true, to be mutants, but, as a 
matter of fact, they are the extreme variants which, how- 
ever, do not attain to their goal but perish in the attempt, 
for they are too poor in chlorophyll and are thereby des- 
tined to die early. Nearly all of them die without so 
much as having unfolded their first leaves, or sometimes 
even their cotyledons. They constitute the extreme limit 
of a long series of variegated forms, but have, so to 
speak, followed a wrong direction. They are by no 
means rare ; for instance they are well known in the 
holly, Ilex Aquifolimn, and they often result in a very 
considerable loss amongst the seedlings raised from the 
seed of variegated plants. 

It is not, however, variegated plants only which pro- 
duce such seedlings ; green plants do so only too often, 
and this even occurs in families cultivated for experi- 
mental purposes when the cultures are pure green and 
have been so for many years or did not produce more 
than an occasional variegated leaf or twig. If in such 
cases the seeds of the single seed-parents are sown sepa- 
rately the proportions in which variegated seedlings oc- 
cur in the various groups are found to vary greatly. 

Some species appear never to produce them, for in- 
stance the tricotylous races of Cannabis sativa, Mcrcu- 
rialis anmia, and Phacclia tanacctifolia which I have 
cultivated, although I have sown the seeds of several 
hundreds of individual plants separately in the course of 
some years. In other species they are very rare ; in some, 
however, the percentage of yellow seedlings is so con- 
siderable as to become a real nuisance. Thus, for in- 



Variegated Leaves. 



289 



stance, the highest numbers (not to mention the numer- 
ous smaller ones) that I found amongst the seedlings of 
individual seed-parents were as folows : 



Antirrhinum majits 
Clarkia pulchella 
Papaver Rhoeas 
Polygonum Fagopyrum 
Scrophularia nodosa 
Tri folium incarnatum 
Ch rysa n th em u m segetu in 
Linaria vulgaris 
Trifolium pratense 
Oenothera Lamarckiana 



YELLOW OR WHITE SEEDLINGS 

5-6 % 

9-13 " 

15-30 " 

8-12 " 

10-15 " 

4-6 " 

13 " 

25 " 

13 " 

20 " 



In many other species I have, as yet, found not more 
than one or two per cent of yellow seedlings from the 
seeds of individual parents. Therefore I presume that 
this extreme variation is 
brought about, besides by 
the heritable potentiality, 
by causes similar to those 
in operation amongst the 
variants in the small 
seeds of Trifolium incar- 
natum (p. 239). 

In some cases, as for 
instance Pol\gonuui Fa- 
go py nun and Tri folium 
incarnatum it struck me 
that the higher numbers 





O.I. 3 6 9 12 15 18 21 24 

Fig. 55. Papaver rupifragum. Pro- 
portion of yellow seedlings among 
the seeds of 54 green plants. These 
plants themselves were the off- 
spring of a single green parent 
plant. The two first ordinates 
are slightly reduced. The figures 
3, 6, 9, etc., signify 2-4, 5-7, 8-10% 
yellow seedlings and so forth. 



were more frequent than 

some of the lower ones. 

This was especially the 

case in Papai'cr rupifragum, amongst the offspring of a 

single parent plant. This plant was selected as being a 



290 Non-Isolable Races. 

tricotylous specimen and had been raised from seed ob- 
tained in exchange; it flowered in 1893 in complete iso- 
lation and produced 6% yellow seedlings amongst its off- 
spring. I planted out about 60 of the green plants which 
grew to healthy individuals in 1899. I left the pollina- 
tion to insects but saved the seeds of each plant separately 
and then counted the number of yellow seedlings for each 
in a lot of 300. 

Y. S. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 22 24 27 30 
Ex. 27 611100011231 12403 1001 

Or 27 63 4 5 6 31001 

'Y. S." signifies the yellow seedlings in each lot of 
seed and 'Ex." the number of plants which exhibited 
this proportion amongst their seedlings. In the lower 
line from 2% onwards these are arranged in groups of 
3 in order to emphasize the general result. The num- 
bers of this last row are plotted in Fig. 55. This curve 
is similar to the curves of monstrosities which have been 
subjected to a selection extending over many years. 1 
Even as these, it consists of a half curve and of a bilateral 
curve. It indicates therefore the selection of a latent 
character which in this particular case started with the 
choice of a tricotylous plant which happened to be a 
particularly suitable one. 2 

The observations and experiments which we have 
described or passed in review show that variegated plants 
constitute a group of forms which in spite of being se- 
lected for years or even for a century have manifested 
no further improvement in the quality and constancy of 

1 See the second section and Sur les courbes galtoniennes des 
monstniositcs. Bull. sc. de la France et de la Belgique, published by 
A. GIARD, Vol. XXVII, April 1896, p. 396. 

2 See Uebcr cine Mcthode, Zivangsdrchun^cn aufznsuchcn, Ber. 
d. d. hot. Ges., Vol. XII, 1894, p. 25. 



Alternating Annual and Biennial Habit. 291 

their peculiar character than many of the most recently 
arisen variegated sorts. They are highly variable and 
give rise in many cases almost every year to green des- 
cendants, on the one hand, and to pure yellow, on the 
other. The former are regarded as atavists, the latter, 
however, are only variants and not mutants, since so far 
as the observations extend they give no hope that they 
will ever form the basis of a pure yellow race. These, 
the true aurca varieties, have only arisen in relatively very 
rare cases ; possibly from variegated types but without 
showing any evidence to support this supposition. 

The capacity for producing variegated leaves or yel- 
low seedlings is more widely distributed in the vegetable 
kingdom in a latent and semi-latent condition than per- 
haps any other character. 

25. ALTERNATING ANNUAL AND BIENNIAL HABIT. 

One of the strongest pieces of evidence for the doc- 
trine of mutation is the phenomenon in beets which is 
called bolting or shooting. It can be observed in almost 
every field of beets. Occasional plants are seen to de- 
velop a stem in the first year, to flower and to bear seed. 
They store no sugar or other food-stuffs or at any rate 
only to a very slight extent in their roots which become 
correspondingly woody. They are useless for practical 
purposes. On good fields about 1 % of the plants ordi- 
narily behave like this, and more rarely a smaller per- 
centage of the whole crop. Under unfavorable circum- 
stances, however, their number often increases consider- 
ably ; reaching for instance from ten to twenty per cent 
and sometimes still more. 

No farmer uses the seeds of such annual plants for 



292 Non-Isolablc Races. 

sowing. They obviously offer too great a prospect of 
a repetition of the evil. Moreover the seeds of these 
bolters cannot, either by chance or carelessness, get mixed 
up with those of the biennial beets because they ripen 
a year earlier. Thus in every generation an absolutely 
rigid selection of biennial examples as seed-parents takes 
place, and must have taken place as long as the culture 
of beets has proceeded on rational lines. 

Nevertheless these bolters have not disappeared. 
Stringent selection has failed to eliminate them. More- 
over as far as historical data enable us to decide, the 
proportion of bolters remains about the same. In ref- 
erence to this case at any rate we are therefore fully 
justified in stating that selection cannot effect in the 
course of a long period of time what it fails to bring 
about within a few years. 

This belief is widely and firmly held by beet-farmers. 
They are always in search of new means of combating 
this evil ; but the mere selection of biennial beets is con- 
sidered to be without prospect of success. RIMPAU has 
endeavored to attain this end by raising a triennial race, 
by selecting the so-called laggers, i. e., plants which have 
not flowered in the second year ;* but most agriculturists 
content themselves with making the conditions of culture 
as unfavorable as possible to this evil. 2 

These laggers are in a sense analogous to the bolters, 
inasmuch as they have been eliminated by the normal 
process of selection since the time when beets were first 

1 W. RIMPAU, Das Attfschiessen der Runkclrilbcn, Landwirtsch. 
Jahrbiicher, Vol. V, 1876, p. 31, and Vol. IX, 1880, p. 191. By the 
same author, Das Samenschiesscn dcr Ruben, Deutsche Landw. Presse, 
Jahrg. XXI, No. 102, Dec. 22, 1894, P- 94- 

2 A list of the most important papers on the subject is given by 
RUMKER, Die Zuckerrubenzuchtung der Gcgemvart, Blatter fiir 
Zuckerriibenbau, 1894, PP- 22-23. 



Alternating Annual and Biennial Habit. 293 

cultivated and have nevertheless not been extirpated. 

The general opinion of botanists is that the represen- 
tatives of the main line of the evolution of plants have 
been for the most part perennials. From these the an- 
nual and biennial forms must have arisen independently 
in the various families and groups; and it is further 
natural to suppose that the biennials arose first and that 
the annuals arose from them. If this is true the pro- 
duction of a biennial from an annual or of a perennial 
by one of these two would have to be regarded as a 
phenomenon of reversion. 1 Instances of such atavism 
seem to occur very generally in the vegetable kingdom, 
but progressive transitions, that is to say, those that take 
place in the opposite direction, are also by no means 
rare. 2 

From the abundant literature on this point I select 
two cases which seem to me the most important. Pha- 
scolits imdtifloms (Ph. coccinens L.) is, with us, an 
annual plant, producing occasionally, however, a bulbous 
root which can be wintered and by means of which the 
plant can be perpetuated. VON WETTSTEIN, S to whom 
we owe our knowledge of this phenomenon, has obtained 
plants which lived four years, and in my own experi- 
mental garden I have succeeded in wintering several 
such Phaseohis tubers. VON WETTSTEIN'S view is that 
we are dealing here with the transformation of a peren- 

1 Many, however, hold the opposite view. See DARWIN, Varia- 
tions, II, p. 5 ; and RIMPAU, loc. tit. 

2 See the works relating to this subject by IRMISCH and WARMING. 
Also HILDEBRAND in ENGLER'S Botan. Jahrb., II, 1882, pp. 51-135; 
with regard to different sorts of beets : F. SCHINDLER in Bot. Ccntral- 
blatt, 1891, Nos. 14 and 15, and the literature cited there. 

3 R. VON WETTSTEIN, Die Innovationsverhaltnisse von Phaseohis 
coccincus L. (= Ph. multifiorus IVilld.}, Oesterr. bot. Zeitschrift, 
1897, No. 12, 1898, No. i. 



294 Non-lsolable Races. 

nial species into an annual one. 1 The careful experiments 
of BRIEM lead to the same conclusion ; for he succeeded 
in wintering the sugar beet after it had borne seed and 
in inducing in this way the same plant to bear seed a 
second and sometimes even a third time. 2 All that was 
necessary to bring this about was that the beet in question 
should continue to increase in thickness 3 and accumulate, 
in its new rings of tissue, the necessary quantity of sugar 
and other food-stuffs. 

It is known that summer wheat can be changed into 
winter wheat 4 by a selective process, and that the con- 
verse process may also take place; also that a perennial 
sort of rye is occasionally raised in Russia besides the 
ordinary annual rye. G Numerous annual species also give 
rise to biennial and perennial forms such as Arabis dcn- 
tota and Delphinium Consolida: 7 and as a general rule 
interferences of various kinds with the normal vital pro- 
cesses of the plant are considered to be the causes of these 
changes. 8 

1 Loc. cit., p. ii. 

2 F. STROHMER, H. BRIEM and A. STIFT, Ucbcr uiehrjahn'ge 
Zuckerruben und dercn Nachzucht, Oesterr.-Ungar. Zeitschr. fiir 
Zuckerindustrie, Pt. 4, 1900, with Plate XV. 

3 For facts relating to this growth in thickness see Die abnonnale 
Entsteliung sccundarer Geivebe in PRINGSH. Jahrb. fiir wissensch. 
Bot, Vol. XXII, 1890, p. 35; and Plate III, Fig. 14. 

4 Numerous illustrations of the question dealt with in the text 
are furnished from agricultural experience by C. FRUWIRTH, Die 
Zuchtung der landwirtschaftlichen Culturpftanzen, 1901, p. 146. 

5 DARWIN, Animals and Plants, I, p. 333. 

A. BATALIN, Das Perenuiren dcs Roggcns. A very important 
paper dealing with these questions is H. C. SCHELLENBERG'S Grau- 
bilndens Getreidevariet'dtcn, Ber. d. Schweiz. bot. Gesellschaft, Part 
X, 1900. 

? THEOD. HOLM, On the Vitality of Some Annual Plants, Amer. 
Journal of Science, Vol. XLII, 1891, p. 304. 

s W. BARTOS, Zeitschrift f. Zuckerindustrie in Bohnicn, Vol. XII, 
1898, p. 456. 



Alternating Annual and Biennial Habit. 295 

Conversely many perennial plants which under nor- 
mal conditions flower the second year after germination 
for the first time, can be induced by favorable cultiva- 
tion to flower in the first summer, though this does not 
always succeed with every individual. In this way many 
perennial species are treated in horticultural practice as 
annuals, and I myself have cultivated a whole series of 
plants more or less regularly as such ; for instance, 
Achillca Millefolium, Hesperis matronalis, Lychnis i'cs- 
pcrtina ylabra, Picris hieracioidcs, Trifoliuni pratcnse 
quinquefolium and others. 

Let us proceed now to our more immediate subject, 
the phenomenon of the occurrence of many species partly 
in annual and partly in biennial specimens. Such plants 
are regarded by descriptive systematists as biennials, as, 
for instance, the name Oenothera bicnnis indicates; for, 
under the less favorable conditions which usually obtain 
in the field the great majority of the specimens will be 
biennials. 

In my opinion this view is quite correct, but the bien- 
nial species in question must possess the capacity of grow- 
ing as annuals, in a semi-latent condition. Moreover 
this capacity does not seem to be universal, but to be con- 
fined to particular races. For instance, KOCH'S Synopsis 
Florae. Gennanicae et Helveticae (3d eel. 1857) and GRE- 
NIER and GODRON in the Flore de France (1852) give 
Dipsacus sylvestris as an annual, whilst I myself have 
hitherto only been able to raise biennial races of it from 
seeds derived from numerous different sources, and in 
spite of the fact that I modified the culture in every con- 
ceivable direction in the hope of making them annual. 
It is highly probable that many species exist in certain 



296 Non-Isolablc Races. 

regions as pure biennials, in others as annuals, and in 
still others in a mixture of these two forms. 1 

Inasmuch therefore as the biennial habit is to be re- 
garded as the character of the species and the annual 
habit as the anomaly, the latter is likely to follow the 
general rule according to which the development of the 
anomaly is favored by improved conditions of life. And 
the experiments which I propose to describe in this sec- 
tion prove the correctness of this view. 

However, there is an apparent contradiction, for, as 
is well known, RIMPAU has shown in the case of the 
beet that every retardation or interruption of the growth, 
whether it occurs during germination or just after the 
seed comes up or at a later stage of the development of 
the plant, favors the production of the seed in the first 
year of the plant's life. 2 

But in this case it only appears that we are dealing 
with conditions favorable to the production of the anom- 
aly whereas in reality we are concerned with the stimulus 
necessary for the manifestation of this bolting. As it 
is not very easy to make this difference clear I shall select 
an instance of a pure biennial race 3 which lacks the power 
of giving rise to annual specimens. I refer to my cul- 
tures of Dipsacus sylvestris. This race can be sown at 
any period of the year, and the plants will always remain 
rosettes until the end of the next winter and develop a 
stem in the spring of their second year. According to 
whether the sowing was made in the spring or in the 
summer or not till autumn are the rosettes vigorous or 

1 Instances of this are given by J COSTANTIN, Les vcgctanx ct 
Ics milieux cosmiques, Paris, 1898, pp. 28 f. 

2 Landw. Jahrbilcher, passim, 1880, p. 194. 

3 On Biastrepsis and Its Relation to Cultivation^ Annals of Bot- 
any, Vol. XIII, No. LI, Sept. 1899, p. 395. 



Alternating Annual and Biennial Habit. 297 

weak, but this treatment has no effect on the period at 
which the stem will be developed. If the seeds are sown 
in March in the greenhouse and the seedlings are picked 
out early into pots and planted out in May or June, we 
get vigorous rosettes with abundant leaves, but not a 
single stem in the first year. If the seeds are sown in 
September in the greenhouse, soon after harvesting, the 
rosettes remain weak until winter, but nevertheless de- 
velop a stem in the following spring. By sowing the 
seed in late autumn in the open ground, however, the 
plants will develop only a single pair of leaves above the 
cotyledons and they can be induced to pass through the 
winter without producing their stems in the spring. In 
this case they pass through the whole of the summer 
as rosettes, become extraordinarily vigorous and do not 
develop a flowering stem until after the second winter. 
These experiments show that a definite stimulus is 
necessary for the production of a stem. Under the con- 
ditions of my own experiments it seems to be the winter 
which exerts the stimulus and that it can do so at any 

/ 

age of the plant except the very young stages when only 
the first two leaves are unfolded. But without this stim- 
ulus no stem is formed. 

The experience of beet cultivators goes to show that 
the chief cause of the bolting is the night frosts of the 
spring. Manifestly they exert an effect on the young 
plants similar to that produced by the winter. It is a 
fact generally known that the percentage of bolters is 
high in direct proportion as the seed was sown early; 
crops which have been sown late are sometimes perfectly 
free from this defect. RIMPAU showed that if a small 
section of a field which has been sown early is covered 
over with a sheet every night that threatens to be frosty, 



298 Non-Isolable Races. 

the occurrence of bolters is considerably diminished ; in 
one experiment for instance from 7 to 4 c /o. 1 Other 
results point in the same direction. 

HEUZE, in his valuable little book on the oil plants, 2 
says with regard to the rape (Brassica Napus oleifem), 
that in the north of France it should not be sown before 
the middle of July or after the middle of August, for in 
the latter case the plants will not be strong enough to sur- 
vive the winter, and in the former too large a proportion 
will set seed in the first year. The same thing is true of 
a whole series of other biennial plants both cultivated 
and wild ; those which germinate late become biennial ; 
of those which germinate early a greater portion become 
annual, the earlier the sowing or the germination took 
place. 

In these cases we are not concerned with the induction 
of bolting by night frosts, or by any other stimulus, but 
with a case of inherited variability. It is true that the 
beet possesses this variability also, but the general con- 
ditions in this species are much complicated thereby. 
That we have to deal with a phenomenon of inheritance 
is proved by the fact that the annual form can easily 
be fixed by selection, without, however, attaining a state 
of absolute purity. RIMPAU sowed the seed of bolters, 3 
and by always selecting seeds ripened in the first year, 
he obtained in the fourth generation a race whose seeds 
when sown on the 31st of March produced annual plants 
only and which in the fifth generation, when sown on 
the 5th of April, was as constant an annual as the normal 



RIMPAU, Das Aufschiessen dcr Rimkelrilben, Landwirtsch. 
Jahrbiicher, 1880, p. 192. 

2 L. HEUZE, Les plantes oleagineuses, Bibliotheque du cultivateur, 
Paris, 2d ed., p. 16. 

3 Loc. cit., p. 197. 



Alternating Annual and Biennial Habit. 299 

beet, sown at the same time, was biennial. The same 
is true with other species. Seeds of the wild Daucits 
Car ota saved from annual plants gave me a large pro- 
portion of annuals ; but seeds from plants which had 
come through the winter gave a predominant proportion 
of biennials. On the other hand selection does not seem 
to lead to the production of annual races which would 
be free from occasional atavism. It is my custom now 
to cultivate my Oe not her a Lamarckiana and its derivative 
species mostly as annuals. Many of these cultures have 
been continued for six or more generations by means of 
the seeds of annual specimens only. Nevertheless every 
year there occur occasional and sometimes several bien- 
nial plants amongst them. 

Aster Tripolinm 1 is usually given as an annual in 
the floras, but with us it is represented by specimens 
which pass through the winter as well as by plants which 
flower in the first summer. In experimental sowings in 
the garden I obtained roughly equal numbers of the two 
types; but if I sowed the seed in March or April in the 
greenhouse the plants developed stems in the first year 
almost without exception. They were, as a rule, covered 
with glass every night until June, and thus protected 
from night frosts, and they were well treated also in 
other respects, especially by transplanting them soon 
after germination into rich well-manured garden soil. 
For according to my experience one of the best means 
of inducing biennial plants to behave as annuals is to give 
them plenty of manure, provided of course that the 



1 KOCH, Synopsis Florae Germanlcae et Helve ticac, p. 361. GRE- 
NIER ET GODRON, Flore de France, Vol. II, p. 102; KARSCH, Vade- 
mecum botamcnm etc. 



300 Non-Isolable Races. 

capacity to do this is present in them in a semi-latent 
state. 1 

With Oenothera Lamarckiana I have made some more 
extensive experiments on accelerating the development of 
the stem by improving the conditions of growth. In the 
wild state this plant consists chiefly of biennials, but 
partly also of annual and of triennial individuals. Under 
experimental conditions, however, the duration of its 
life seems to depend more on external influences than 
on the choice of seeds. I have especially tested the 
distance between the plants, the sunniness of the position, 
and the richness of the soil. 

In 1888 I selected some seeds of my biennial stock 
plants of the Lamarckiana family of 1 886-1887, 2 in order 
to investigate the effect of the degree of separation of 
Jie plants in the bed. For this purpose I selected four 
adjacent beds of similar contents with regard to soil and 
manure, sowed the seeds in the middle of April fairly 
thickly in rows, and weeded them out during germina- 
tion in such a way that on two beds the plants stood at 
moderate distances, on one further apart, and on a 
third more closely. In the summer up to the middle of 
September I recorded the number of individuals with 
stems and the number of the rosettes. The sum of the 
two obviously affords a measure of the distances between 
the plants. The extent of each bed was 13 square meters. 
The figures are : 



* Sur la culture des monstruositcs, Comptes rendus de 1'Ac. d. 
Sc., Paris, January, 1899; Sur la culture des faseiations des especes 
arniuelles et bisannuelles, Revue generale de botanique, Vol. XI, 
1899, p. 136; and Ueber die Abhdngigkeit der Fasciation vom Alter 
bei sweij'dhrigen Pftanzen, Botanisches Centralblatt, Vol. LXXVII, 
1899. 

* See the pedigree in Vol. I, p. 224. 



Alternating Annual and Biennial Habit. 301 

PLANTS PER PERCENTAGE OF PLANTS 
SQUARE METER WITH STEMS 

No. 1 1350 100 23 % 

" 2 and 3 630 + 650 50 43 " 

" 4 380 30 58 " 

That is to say, the closer the plants are together, and 
the less room each one has, as a result of this, for the 
unfolding of its leaves, the smaller is the number of 
annual plants. 

In the following year I repeated this experiment, but 
this time with the seeds of annual plants. The result 
was, however, the same. There were 1188 plants on one 
bed of 13 square meters, that is, about 90 per square 
meter; of these 20% were annuals. On the other bed 
of the same size there were 348 plants (or 27 per square 
meter) and 54% developed stems. 

I repeated the same experiment once more, in 1890, 
with the seeds of an annual plant of 1889. On the one 
bed there were 40 plants per square meter, of which 
17% were annual. On the control bed there were only 
ten plants in the same area, and of these 72% produced 
stems in the first summer; the extent of the bed in both 
cases was 5 square meters. 

In 1891 I investigated the influence of the distance 
between the plants in an experiment with Oenothera 
laei'ifolia, raised from the seeds of an annual race which 
had been selected for three generations. 1 The two beds 
were of the same size, had the same aspect and the same 
soil, and both received a similar and liberal dressing of 
guano. They were sown in the middle of May on the 
same day, but at the end of July they contained 195 
and 638 plants respectively (per each 6.5 square meters). 
As a result of this, the bed in which the plants were far 

1 See the pedigree in Vol. I, p. 224. 



302 Non-IsolaUe Races. 

apart had 162 plants which developed stems, whilst on 
that in which they were close together there were 145. 
The difference between the two reckoned as a percentage 
of the whole culture is of course more striking, viz., 
83% as against 20%. More important, however, is the 
fact that per each square meter in absolute numbers 
more annual individuals are produced when the plants 
are grown far apart than when they are grown more 
densely and therefore in larger numbers. When viewed 
in this way the result points to the great importance of 
sowing seeds thinly in experimental cultures. 

Experiments with shading are met with the difficulty 
that the young plants cannot stand it very well, even 
when, as in my experiments, the shadow is that of trees. 
The experiment was conducted at the same time as that 
of 1890, referred to above, on a similar scale and by 
growing the plants far apart; it produced about 46% 
annuals as against 72% in the control experiment al- 
ready mentioned. 

By far the best means, however, of increasing the 
proportion of annual plants or even of securing their 
exclusive production, is to sow the seed and keep the 
young plants under glass. In doing so the seed can be 
sown in March or April in un-manured sterilized soil, 
and the seedlings may be pricked out singly into pots 
containing richly manured soil after the appearance of 
the third or fourth leaf. In this condition they remain 
under glass until the end of May, at least during the 
nights and on cloudy days, and can then be turned out 
of the pots without breaking the ball of earth round the 
roots and transplanted to the place where they are to 
grow. Treate 1 in this way almost all the plants behave 



Alternating Annual and Biennial Habit. 303 

as annuals, and of late I have grown all my cultures by 
this method or by some .slight modification of it. 

In order to determine the effect of the soil on the 
development of the stem I have compared the difference 
between plants grown on manured and unmanured beds, 
and also the difference between plants grown on barren 
sand and on fertile soil. The first of these two experi- 
ments I have made with the Oenothera laevi folia. I 
used seeds which I had saved in 1890 from the third 
annual generation of my culture (see Vol. I, p. 273). 
The seeds were sown in the middle of May on three 
beds of 3 l /4 square meters each. They were adjacent to 
one another, had the same soil, a similar exposure, and 
so forth. The seedlings were thinned out early, to 100 
per bed, in such a way that the distances between them 
were as uniform as possible. The sole difference lay 
in the kind of manure which they received, which in 
No. 1 was nothing, in No. 2 a quarter of a kilo of guano, 
and in No. 3 a quarter of a kilo of hornmeal. In the 
second bed, therefore, the manure was rich in phosphates 
and in the third in nitrogen. On the 30th of July 1 
recorded the plants with the following result : 

PLANTS ANNUALS 

No. 1. Without manure 100 17% 

No. 2. With guano 98 90% 

No. 3. With hornmeal 108 94% 

In spite, therefore, of the fact that the race had been 
selected for three years the proportion of annual plants 
on the bed without manure was only 77 per cent, whilst 
this proportion was considerably increased by the addi- 
tion of manure, and more by the addition of nitrogen 
than by that of phosphates. Further experiments with dif- 
ferent quantities of the same manure showed that the 



304 Non-Isoldble Races. 

amounts employed in this experiment (about 80 grams 
per square meter) should not be exceeded, that is to say, 
that the result cannot be improved by still heavier ma- 
nuring. 

For the experiment with sand I dug in my experi- 
mental garden a bed of 13 square meters in extent and 
one-half a meter deep, and filled it with ordinary fine 
sand. On this bed and on a neighboring one of the same 
size I sowed seed of Oenothera Lamarckiana in the sum- 
mer of 1899. The control bed was not manured but 
contained a very fertile soil ; the seed was sown in the 
middle of April. 

The sand of the bed bordered immediately on the 
rich soil of the path which surrounded it. 1 Therefore 
the plants at the margin could thrust their lateral roots 
into this, and thus obtain richer food than the more 
central rows. This circumstance showed very important 
results during the course of June, for while many flower- 
ing stems were produced towards the outside of the bed, 
hardly any occurred in the middle. It was not until the 
middle of July that the development of stems set in here 
also. Curiously enough this occurred in almost every 
instance at exactly the same time. In the middle of 
August among the 82 plants of the outer rows about 
60% had developed stems, whilst in the middle there 
were 133 rosettes amongst 203 plants, that is to say 
about 24% of annual specimens. We see that the dis- 
tances between the plants in this experiment were very 
considerable, for on 13 square meters there were only 
285 plants. Even at the end of the summer they hardly 
touched one another. In the control experiment in which 

1 In subsequent years I have separated the sand from the earth 
by bonrds. 



Alternating Annual and Biennial Habit. 305 

the distance between the plants was practically the same 
there were about the same number of plants that devel- 
oped stems as there were on the margin of the sand bed, 
in fact a little less, 53 % amongst 348 plants. 

Our main result therefore is that the proportion of 
plants which developed stems in the center of the sand 
bed is 34% as against the 53% and 60% amongst the 
plants on the margin of this bed and in the control bed 
respectively. Equally striking was the sudden change 
in the behavior of the central plants in July. This pointed 
to some special cause. I suspected that it was connected 
with the growth of the roots and that these about this 
time had penetrated the layer of sand and reached the 
fertile earth beneath it. When I dug up the roots at the 
conclusion of the experiment I found that these were, 
as a matter of fact, longer than half a meter and had 
branched freely below the level of the sand. 

In order to find out whether this was the real cause 
of the development of the stems I made an experiment 
in 1891 with a bed in which the layer of sand was much 
deeper (one meter). A part of the original sand bed 
which was only one-half meter deep, and a neighboring 
bed filled with ordinary good garden soil served as con- 
trol. This time the bed was surrounded by boards and, 
consequently, there was no difference in the behavior 
of the central and marginal plants. For this experiment 
I used the seeds of a culture of Oenothcra rubrinervis 
which had been cultivated as an annual for two genera- 
tions (seeds of 1890 of the pedigree of Vol. I, p. 273). 
The sowing took place in May 1891. At the end of July 
I recorded the plants on the three beds, each of which 
was 3 square meters in extent. 



306 Non-I salable Races. 

PLANTS ANNUALS 

Sand-bed, 1 meter deep 161 21 % 

\ " " 226 50 " 

Garden-soil 131 98 " 

On the control bed the distances between the plants 
were somewhat greater, but as practically they did not 
touch one another on the sand bed this fact does not 
signify. 

The seeds employed in this experiment gave a larger 
proportion of annual specimens than did those of the 
previous one. The main result is that the proportion 
of plants which produce stems in their first year can be 
reduced to about one-half by cultivation in a bed with 
half a meter of sand, and to less than a quarter by culti- 
vating in a meter of sand. 

The results of the foregoing experiments prove that 
biennial species which possess, in a semi-latent state, the 
capacity to produce annual specimens, can be induced to 
manifest this anomaly to a much greater extent by sup- 
plying them with more food. Crowding of plants, sha- 
ding, lack of manure, or cultivation on sand, favor the 
production of biennials; but the more space, light and 
nourishment in the soil there is at the disposal of the 
individual plants the greater will be the number of those 
which will produce stems, flower and ripen their seed 
in their first summer. The stimulus of the winter or 
spring frosts, which in other cases induces the young 
plants to develop stems, is without effect here ; for under 
the described conditions even seeds sown in the middle 
of May in the open ground may give rise almost exclu- 
sively to annual plants. 

Continued selection, however, fails either to fix the 
biennial races and to free them of annual specimens, or 
to free the annual races of biennial individuals. 



VIII. NUTRITION AND SELECTION OF SEMI- 
LATENT CHARACTERS. 

26. INCREASED NUTRITION FAVORS THE DEVELOP- 
MENT OF THE ANOMALY. 

Fluctuating variability is a phenomenon of nutrition, 
whereas mutability is the result of hitherto unknown 
causes (Vol. I, p. 575). This statement, which is per- 
haps the sharpest expression of the contrast between 
fluctuating or continuous variability on the one hand 
and occasional sudden transitions from one species into 
another on the other, has been discussed more than once 
in this work. It is equally true for the variability of 
semi-latent characters as for that of normal ones. This 
side of the statement has also been already alluded to, 
and I have cited many instances in order to prove its 
truth. Everywhere nutrition and variability are so in- 
timately connected that the physiology of the latter phe- 
nomenon can hardly be dealt with without discussing 
its relation to the former. 

Artificial selection is the choice of the better nour- 
ished individuals, except of course, when selection is 
carried out in the negative direction (Vol. I, p. 142). 
In the first volume I cited as a proof of this generaliza- 
tion an experiment with a semi-latent character. The 
number of accessory carpels of Papaver somniferum 
pol\ccphahun was shown to be dependent on selection 



308 Nutrition and Selection. 

and, to a no less extent, on nutrition. In the third part 
of the first volume, the curve representing the length of 
the fruits in Ocnothcra and the curves of the rays of cer- 
tain Umbelli ferae and Compositae also proved that these 
two factors operate in the same direction. Active and 
semi-latent characters are thus shown to behave in the 
same way with regard to these two factors. 

Since, however, the extraordinary variability of semi- 
latent characters (of which an account has been given 
in 2 of this part, p. 9), is one of the strongest supports 
of the doctrine of selection, it seems to me that it is worth 
while to attempt to make the relation between this phe- 
nomenon and nutrition specially clear. In this last chap- 
ter I will therefore deal with a series of facts gathered 
partly from the literature of the subject and partly from 
my own observations, which all point more or less defi- 
nitely to the conclusion that semi-latent characters are 
largely dependent on the external conditions of life. 

External influences exert their effect on the develop- 
ment of organs during their youth, that is to say during 
the so-called susceptible period. After the character of 
the organ has been definitely established in this period, 
the further development cannot affect it. The number 
of leaflets in a clover leaf, of the petals of Ranunculus 
bulbosus, of the accessory carpels of Papaver are finally 
determined in this period; but the conditions of life at 
the critical moment are not the only factor. The accu- 
mulated effects of previous influences have also com- 
bined to determine the individual strength of the organ 
or of the individual ; and the part which this latter factor 
plays in the determination of the degree of development 
of the deviating character is sometimes greater and some- 
times less than that of the immediate external conditions. 



Nutrition Favors the Anomaly. 



309 



The most susceptible stage seems to be that of the 
young embryo in the ripening seed, for external in- 
fluences show their greatest effect 
on seed-plants. But they also play 
a part in vegetative methods of 
propagation and operate in the 
same direction, though as a rule 
with less intensity. 

The gap between anomalies and 
normal active characters is bridged 
by a complete series of normal, la- 
tent characters. These too are de- 
pendent on external conditions in 
just the same way as the other two 
are. As a general rule we may 
state that, \vithin the specific range 
of its character, the form of an 
organ is determined by external 
physical influences. 1 

As an instance let me cite the 
result of some experiments with 
the germination of potato seeds. 2 
The first leaves of the seedlings are 
simple (Fig. 56), and the follow- 
ing ones gradually approach the 
peculiar pinnate form of those of 
the grown plant. If the germina- 
tion takes place in the garden, in 
full sunlight, the plant develops 
quickly and the various steps in 
the development of the leaf-form 




Fig. 56. Seedling of po- 
tato grown under un- 
favorable conditions 
of light. From i to 6 
the form of the leaf 
increases in complica- 
tion, but from 8 to 12 
it decreases again. 
Cultivated in a room 
in 1876. 



1 Keiv.mngsgeschichte der Kartoffchamcn in Landwirthsch. Tahr- 
biicher, VII. Jahrg., 1878, p. 35. 
2 Loc. cit., p. 35. 



310 Nutrition and Selection. 

follow rapidly on one another. But if the conditions are 
unfavorable, as in a room, differentiation proceeds more 
slowly. The internodes tend to become abnormally long, 
to produce too little wood, the leaves develop small pin- 
nules only, and in very unfavorable conditions I have 
sometimes observed an interruption in the series of leaf- 
forms on the stem. Above the lyrate leaves simple ones 
were again formed, the series turning backwards. 1 

These phenomena are much better illustrated in those 
cases in which the first leaves are more compound than 
the later ones; for instance in the species of Acacia which 
produces phyllodes in reference to which GOEBEL'S im- 
portant investigations have thrown so much light on the 
relation between embryonic forms and external condi- 
tions. 2 I have already referred to this above; but I 
might now mention a figure of a seedling of Acacia 
I'crticillata which, after it had already reached the stage 
of producing phyllodes, was induced to repeat the bi- 
pinnate form of the embryonic leaves by unfavorable 
conditions. In the same way the production of linear or 
arrow-shaped leaves of Sagittaria sagitti folia and that 
of the perforated leaves of Momtera deliciosa and others 
was shown to be dependent on external conditions. In- 
sufficient nutrition tends to bring about a recurrence of 
the embryonic form, and it seems to be a secondary 
question whether this is the simpler or the more com- 
plicated. The Campanula rotundifolia studied by GOE- 
BEL, the flowerstalk of which changed from the linear 
to the heart-shaped form of leaves, 3 is perhaps the best 

1 See also E. ROZE, La transmission des formes ancestralcs dans 
Ics vcgetaux, Journ. d. Bot, Annee X, Nos. I and 2, 1896. 

2 K. GOEBEL, Organogra>phie der Pftanzen, I, p. 150, Fig. 105. 

3 GOEBEL, Flora., 1896, Vol. LXII, Ft. I. 



Nutrition Favors the Anomaly. 311 

known example. In the case of the Conifers BEISSNER 
has also shown that insufficient nutrition, for instance 
by cultivation in pots, can lead to a protracted reten- 
tion of the embryonic form. 1 In Eucalyptus Globulits 
and Acacia coring era stems which have been cut down 
produce branches which repeat the embryonic form of 
leaves, which are sessile in the one species and thornless 
and destitute of the so-called ant-bread appendages in the 
other. 2 

Exactly the same general conditions obtain in the 
development of anomalies, that is to say of those char- 
acters which are only exceptionally or never developed 
in the normal life of the species. Here again their pre- 
cise nature seems to be a matter of indifference, that is 
to say, whether they are harmful or harmless; in either 
case they are under the influence of external conditions. 
Instances of deleterious characters are furnished by varie- 
gated leaves and by flowers and flowerheads which have 
become sterile by doubling (see 19 and 24). The 
same is also true of real monstrosities, such as fascia- 
tion and twisting, as we shall see in the next chapter ; 
and of new characters, reversionary phenomena, pro- 
gressive and retrogressive variations of which I shall 
give a series of instances in the following section ( 27). 
It is true both of half races and of middle races; in both 
it is the older or specific character which is intensified 
by unfavorable conditions, whilst the anomaly or the 
younger character is intensified by favorable ones. Ob- 
viously there is only a small step from these two races 
characterized by the semi-latency of the former or the 

*L. BEISSNER, Handbuch der Nadelholzkunde. See also Bot. 
Zeitung, 1890, p. 539. 

' F. HlLDEBRAND, Botail. Zd'tllUg, l8()2, p. 5. 



312 



Nutrition and Selection. 



latter character to the true elementary species in which 
the character of the parent species has become completely 
latent, for in this case the variation of the new character 
of course conforms to the general laws of variability. 

We have studied this relation of variability to nutri- 
tion from various points of view in our researches with 
the half races of Tri folium incarnatum quadrifolium and 
Ranunculus bulbosus semiplenus, but especially with the 
true middle races, Trifolium pratense quinque folium, and 
Chrysanthemum scgetum plenum as well as with anal- 
ogous groups. 





Fig. 57. Lysimachia vulgaris. Transverse sections of two 
buds which were to develop into upright stems in winter. 
A, quaternary, and B, trimerous symmetry. 

It should be remembered that in all these cases we 
are dealing with variability in the restricted sense and 
not with mutability. How one race is transformed into 
another, we do not know. The phenomenon is as yet 
far too rare and has not yet been adequately investigated. 
The variability of the eversporting races is of the trans- 
gressive kind ; but it does not lead, as a rule, to muta- 
bility. 

Finally I wish to illustrate by means of a scheme the 
relation between the variability of semi-latent characters 
and the external conditions of life, and I select as material 



Nutrition Favors the Anomaly. 



313 



for this the disposition of the leaves of Lysimachia i'iil- 
garis (Fig. 59). This species has opposite leaves as 
a rule, but often occurs with quaternary and ternary 
whorls. With regard to this character the species be- 
haves as a half race, in this neighborhood at any rate. 

If we examine the rhizome in the spring we find the 
vegetative buds growing vertically upwards under the 
top soil or moss and ready for sprouting. At this period 
it can easily be seen that all of the buds have their scales 




Fig. 58. Scheme to illustrate the relation 
between external conditions and anom- 
aly. Shifting of the apex of the curve. 
A, the effect of high nutrition; B, the 
effect of unfavorable conditions. The 
(a) and (b) curves illustrate the dis- 
position of the leaves of the stems of 
Lysimachia vulgaris', a, after high, b, 
after low nutrition. (See the figures on 
page 314.) 



'1 



ft 

L 



v' 4 /\ 

Y) 

B 

Fig. 59. Lysimachia vulga- 
ris. Rhizome buds which 
would develop into stems. 
A, thick, with quaternary 
bud ; B, thin, with ternary 
whorls in the interior of 
the bud. The visible 
scales show a decussate 
arrangement in both 
cases. (For diagram see 
Fig. 57-) 



in a decussate arrangement at the lower end (Fig. 59), 
but within the bud the disposition of the leaves is different. 
In this region the structure is that which will be mani- 
fested by the growing stem in the summer. 

The thickness of the future stem is correlated with 
that of the upright subterranean shoot, and on it depends 
the disposition of the leaves. The weakest shoots have 
the leaves arranged in opposite pairs, the stronger ones 
in trimerous and the strongest of all in tetramerous 



314 Nutrition and Selection. 

whorls. This character of the stem, which must be defi- 
nitely determined by microscopical examination, can, how- 
ever, be predicted with sufficient accuracy by the thick- 
ness of the shoot. Of course, the same relation obtains 
in the summer when the contrast strikes the eye far more 
forcibly, and then we see that the lateral branches of 
ternary and quaternary stems have almost without ex- 
ception decussate leaves, obviously because they are the 
weakest of all. 

If the plant is taken into cultivation it is easy to mod- 
ify the proportions of the various sorts of stems by suit- 
able treatment, although vegetative methods of propaga- 
tion alone are employed; but it must be remembered that 
the buds for the following year are already completely 
laid down in October, and that the disposition of their 
leaves is therefore finally decided at that time. The ac- 
tual disposition in any given year is therefore deter- 
mined by external conditions which prevailed in the pre- 
vious year. 

The curves in Fig. 58 are plotted from observations 
which gave the following results. In March 1890, 1 planted 
out a group of rhizomes in a favorable position in my 
garden, and in June I noted the two-, three- and four- 
whorled stems, which therefore had been laid down under 
the influence of the unfavorable conditions which ob- 
tained in 1899. In the following summer I repeated the 
observations and thus formed an estimate of the effect 
of growth under more favorable circumstances (better 
soil and more light). The results were: 

RECORDS FOR WHORLS 2- 3- 4-MEROUS TOTALS 

Summer, 1890 35 21 2 58 

1891 17 40 10 67 

The apex is seen to be shifted from stems with oppo- 



External Conditions and Manuring. 315 

site leaves to stems with trimerous whorls (Fig. 58 b 
and a). 

The arrow A in Fig. 58 indicates the result of im- 
proved conditions, the arrow B that of more unfavorable 
ones. 

The figure therefore not only illustrates a particular 
case but is a graphic representation of our thesis that 
high nutrition favors the production of the anomaly. 

This scheme can be applied to a long series of cases, 
both of anomalies that occur in the field and of highly 
variable horticultural varieties. The best known example 
is furnished by the tricolored pansy Viola tricolor ma- 
xima. Here, as every gardener knows, the spring and 
early summer flowers have larger, much broader and 
more intensely colored petals than those of late summer. 1 
The greater drought and the gradual exhaustion of ma- 
nure around the plants are the causes. The same general- 
ization applies to numerous cases to some of which we 
will refer in the following section. 



27. THE INFLUENCE OF EXTERNAL CONDITIONS AND 

OF MANURING. 

J. COSTANTIN has dealt with the relation between the 
plant and its environment in a book devoted to this ques- 
tion. 2 In it he treats of the influence of the environment 
both on the normal characters of the plant and also on 
varieties and anomalies. An immense range of facts and 
observations is thus made accessible to the student. 

1 V. B. WITTROCK, Viola-Studier, Acta Horti Bergiani, Vol. II. 
1897, Nos. i and 2. See also VERLOT, loc. cit., pp. 46-47. 

2 J. COSTANTIN, Lcs vcgctaux ct les milieux cosmiques. Bibl. 
scientif. Internationale, 1898. The earlier writings of this author 
have been dealt with in our first volume (p. 99). 



316 Nutrition and Selection. 

We shall here confine ourselves to true anomalies, 
that is, to semi-latent characters, 1 and will start with 
some instances of plants which are propagated vegeta- 
tively. First let us look at the continued growth at the 
top of the inflorescence of the white clover (Fig. 60), an 
anomaly which is fairly rare in this region, but which 
has been intensified considerably by favorable cultivation 
in my garden. Fig. 60 affords instances of this anomaly 
selected from a vast number of available cases. 2 Elonga- 
tion of an inflorescence into an ear-shaped peduncle, pro- 
liferation or formation of two inflorescences, one above 
the other, on the same stem, and the appearance of small 
clusters in the place of the individual flowers accompanied 
by an increase of the bracts are some of the more impor- 
tant instances. 

In the summer of 1890 I found near Hilversum a 
specimen which bore a single flower on the elongated 
axis of one of its inflorescences. I transplanted it to 
my garden, sowed the seeds in the following year and 
obtained a few "perumbellate" inflorescences. Again 
I collected the best seeds and sowed them in 1891. When 
the plants flowered about 2% of the several thousands 
of inflorescences had proliferated, most of them belonged 
to the type shown in Fig. 60 B, others to the rarer types 
A, C and D. I then selected the best plant, isolated it 
completely, and made certain that all the branches really 
belonged to it. After this I divided it, planted out the 
parts, and let them grow as strong as possible. In this 

L The methods of cultivation suitable for producing pure white 
flowers on colored varieties of Syringa in winter, and the well-known 
blue coloration in the Hortensias are widely different. (See VERLOT, 
loc. cit., pp. 60-61). 

! The anomalies in question have long since been dealt with in 
the literature of the subject, and have been collated by PENZIG, in 
Tcr atologie, I, p. 387. 



External Conditions and Manuring. 



317 



way I filled two beds of about two square meters each 
in the summer of 1892. They gave a very characteristic 
half curve when the inflorescences were plotted according 
to the number of flowers on that part of the axis which 
had proliferated. These numbers varied from to 10 
and were distributed as follows (August 1892) : 

NUMBER OF FLOWERS ON THE PROLONGATION 



OF THE AXIS 

Inflorescences 0123456789 10 

On the 1st bed 325 83 66 51 36 36 18 7 6 1 1 

" " 2nd bed 403 97 62 35 46 20 20 14 11 3 2 



11 Totals 

630 

1 721 




Fig. 60. Trifolium repens pernmbellatum. Four different 
inflorescences from the same culture, 1891. A, with thick 
continuation of the main axis ; B, the continuation thin 
and sparsely covered with flowers ; C and D, with three- 
fold continuation. 

We see that one-half of the inflorescences on this 
plant had proliferated this time, partly as the result of 
selection, partly on account of improved cultivation. Most 



318 Xiitrition and Selection. 

of the perumbellate inflorescences appeared in July. Be- 
fore July there were 21%, in July 47%, in August 38%, 
and this last record was made on over 500 inflorescences. 

I continued the experiment by planting out some of the 
creeping stems of this plant into two other beds, of which 
one consisted of good garden soil, the other of dry sandy 
soil. In this year under less favorable conditions of 
growth, the proportion of anomalies was less . Amongst 
about 300 inflorescences in each bed 6% had elongated 
on the sand bed and 12% on the control bed. On the 
former the plants were small, their leaves being smaller, 
and paler and less numerous than the normal. 

This experiment shows that the proportion of anom- 
alous inflorescences is to a very large extent determined 
by external conditions even when the method of propa- 
gation is purely vegetative. 

In the literature of this subject we sometimes come 
across the view that anomalies are favored by improved 
external conditions because more nutriment is necessary 
for their development, and the fasciations, and the multi- 
plication of the number of leaves, leaflets, etc., are given 
as instances. As a matter of fact even when the anom- 
aly consists in a reduction of parts the same relation ob- 
tains. This is shown by the second instance that I shall 
give. This is Potentilla anserina, of which I found some 
plants with occasional tetramerous flowers near Hilver- 
sum in 1889 among the ordinary pentamerous ones. I 
planted them out and divided them, and in the summer of 
1891 I selected the best specimens and made sure that 
all the runners were still organically connected. In 1892 
I planted out one-half of this on a manured bed and the 
other half on an unmanured bed adjacent to it. 

From the middle of July to the beginning of August, 



External Conditions and Manuring. 319 

I counted the sepals of all the flowers. There were about 
2500 on the manured bed, and about 1500 on the un- 
manured. Amongst them were many with live and four 
sepals, and about 20 with 3, but none with fewer than 3 
or more than 5. Here again, a pronounced half curve 
was the result. I have reckoned together the proportion 
of 3-4-merous flowers for the individual counts, and at 
each stage in the counting collected all the flowers which 
had opened since the preceding one. The counts were 
made when possible every fourth day, or, when the num- 
ber of flowers was too small, at greater intervals. The 
result was as follows : 

PROPORTION OF 3-4-MEROUS FLOWERS IN %. 

June July Augus. 



Day: 19 23 27 159 13 17 21 25 29 2 

Manured: 7 13 24 28 34 39 50 65 49 49 43 27 % 

Unmanured: 7 20 33 39 42 49 46 44 % 

We see that the proportion of anomalies increased 
on both beds gradually throughout the summer, reached 
its maximum in the second half of July, and then sank 
again. On the manured bed, how r ever, this proportion 
amounted to 65% of the whole and on the unmanured 
bed to 49% of the flowers counted (160 and 224 flowers 
in the two cases respectively). In this case, therefore, 
both the periodicity and the relation to the external con- 
ditions are in all essentials the same as in the case of the 
white clover. In this latter case a plant which I had 
raised from seed served as material ; but in that of 
Potentilla a specimen which I had collected in the field. 

I shall now deal as briefly as possible with a series 
of further instances, emphasizing as before that the ex- 
ternal influences have the results in question only when 
the particular characters are already present in the semi- 



320 Nutrition and Selection. 

latent condition. On completely latent characters no 
effect can be produced; we are dealing solely with half 
and intermediate races. 'In other specimens, however, 
this is obviously not the case," says GOEBEL, "they retain 
their normal form even when grown in rich soil ; the 
high nutrition operates on the malformation, not as a 
cause, but as a releasing factor." 1 

It is a familiar fact that many garden plants de- 
teriorate if they are allowed to remain for a long time 
in the same place. They exhaust the soil and must, 
therefore, be moved from time to time. This is true, 
for instance, of Pansies, Anemones, 2 Dahlias, Petunias, 3 
the crested forms of many ferns 4 and so on. MORREN 
planted out a specimen of Saxifraga decipiens which 
had hitherto borne normal flowers on stony ground, into 
good garden soil. In this it grew very vigorously, formed 
larger flowers than before, and manifested at first a 
slight transformation of its stamens into petals which, 
however, increased gradually during the course of the 
summer until ultimately the flowers became entirely 
double. In Hedychiwn coronarmm the structure of the 
flowers is also shown to be dependent on nutrition. 6 
Wild apples and medlars lose their thorns in a few years 
if they are transplanted to gardens, 7 and Carlina acaulis 
becomes the so-called Var. canlescens, in rich soil, a fact 
which has already been recorded by WOLFF in his Tlieo- 

1 K. GOEBEL, Or gano graphic, I, p. 159. Various instances are also 
given by BURKILL, Journ. Linn. Soc. Bot., Vol. XXXI, 1895, pp. 2i8ff. 

2 VILMORIN-ANDRIEUX, Les fleurs de pleine terre, p. 87. 

3 HILDEBRAND, Ber. d. d. hot. Ges., Vol. XIV, 1896, p. 327. 

4 LOWE, cited by GOEBEL, loc. cit. 

'"Bull. Acad. R. Belg., Vol. XVII, Pt. I, p. 424. 

6 FR. MULLER, Flora, 1889, Pt. Ill, pp. 348-352, PI. 16. 

7 DE CANFOLLE, Physiologic vcgctalc, II, p. 721. 



External Conditions and Manuring. 321 

ria generationis. The branching of the ears of Triticnm 
turgidum compositum (Vol. I, p. 125) and the carpello- 
mania of Papai'cr somniferum (Vol. I, p. 138) are to a 
very large extent dependent on external conditions. 
Double poppies become almost single under unfavorable 
conditions; I have observed this in Papaver somniferum 
nannin album in my own cultures. Again the double 
Saponaria officinalis plena seems to become single after 
transplantation, but subsequently to regain its double 
character. 1 The ordinary Saponaria officinalis often 
forms hexamerous flowers in this neighborhood. These 
were, however, more numerous in my cultures under 
good than under bad treatment. The studies of PEY- 
RITSCH on the influence of the cutting clown of wood- 
bands on peloric varieties has already been referred to 
( 21, p. 225). On a lime tree in the vicinity of Baarn 
pitchers are produced every year; but I always found 
them on the open sunny side and never in parts of the 
tree where the branches were shaded by neighboring 
trees. 

The color is also well known to be very dependent on 
external conditions. Achillea Mille folium rosea will only 
form its fine red inflorescences in a sunny position ; if 
this is shaded the color is pale or absent, as I have myself 
often observed. Inflorescences grown in the dark re- 
main quite white, even when they would otherwise have 
been red. The same is true of Begonia semperflorens 
atropurpurea Vernon, whose brown red foliage cannot, 
so to speak, stand the smallest amount of shadow. In 
this case I have succeeded in making some plants almost 
quite green by shading them during their youth. The 

1 MuNTiNG, Waarc Ocffcuhigcn dcr Plantm, 1671, p. 588. Also in 
my garden. 



322 Nutrition and Selection. 

color of Amarantus tricolor, the variety of whose color 
is its only claim to popularity, is dependent on external 
conditions. 1 

Zca Mays forms more bi-sexual panicles and ears 
when the seed has germinated at a high temperature. 
Ranunculus bulbosits semiplenus ( 23, p. 258) forms 
more petals if it germinates in the summer than if it 
germinates in spring. Summer wheat can, as is well 
known, be transformed into winter wheat by sowing it 
in autumn, although, as it appears, only in a small pro- 
portion of individuals. 2 

Amongst the cultivated Begonias we sometimes find 
bi-sexual flowers which are the result of the appearance 
of stamens in female flowers; in them the inferior fruits 
become more or less completely superior and other anom- 
alies make their appearance. 3 For the last 12 years I 
have grown such a specimen of Begonia Scdcni (B. boli- 
I'iensis X B. Pearcei) which I have gradually multiplied 
by dividing its tubers. In the summer of 1890 I marked 
the tubers which produced the smallest numbers of such 
transformed flowers and planted them out in 1891 into 
a bed which was more richly manured and better situated 
than the rest. As a result of this they produced a con- 
siderably larger number of anomalous flowers than the 
control specimens. Lupinus lutcus sometimes produces 
twisted inflorescences. 4 Seeds of such flowers collected 
in the field and sown in the garden did not repeat the 
anomaly; but in the next generation it reappeared as the 

1 VILMORIN-ANDRIEUX, Lcs fteurs de pleine terre, p. 64. 

2 MONNIER, cited by DARWIN, Variations, I, p. 333. 

3 P. MAGNUS, Sitzber. d. bot. Vcr. d. Prov. Brandenburg, XXVI, 
\, p. 72, Table II, and PENZIG, Tcratologie, I, p. 500. 



4 Monographic ' der Zwangsdrchnngcn, Jahrb. f. wiss. Bot., 1891, 
Vol. XXIII, p. 107, PI. IX. 



The Periodicity of Semi-Latent Characters. 323 

result of heavier manuring and better treatment (1890- 
1892). 

Of a kindred nature, probably, is the well-known 
fact that anomalies are more abundant in certain years 
than in others. HUNTING records this for Lilinm crucn- 
tnui plenum 1 and KICKX for pitchers, of which there was 
in the neighborhood of Gent, in Belgium, something like 
an epidemic in 1848 in the tobacco fields, and in 1851 
in Rosa Gallica and Rosa centifolia. 2 In the neighbor- 
hood of Freiburg there was an extraordinary abundance 
of floral malformations in the summer of 1866. 3 In 
France the hot and dry summer of 1893 brought out a 
large number of these, and GAGNEPAIN records a long 
series of anomalies which he observed at that time. 4 The 
year 1845 was a great year for peloric Calceolarias, 1862 
for central umbels in Auricula (in England). For ten 
years I have observed the formation of pitchers in Mag- 
nolia obovata and that of hermaphrodite flowers in Saliv 
aurita. In both these cases the frequency varied greatly 
with the year, although the specimens which were exam- 
ined closely every year, were growing in our garden. I 
shall not extend this list which the reader may easily 
complete either by personal observations or from the 
abundant literature on the subject. 

28. THE PERIODICITY OF SEMI-LATENT CHARACTERS. 

The immediate external conditions which obtain dur- 
ing the susceptible period of development do not consti- 
tute the sole factor which determines the greater or less 

1 MUNTING, loc. dt., p. 501. 

2 J. KICKX, Bull. Acad. Roy. Belgique, Vol. XVIII, Pt. I, p. 591. 

3 HlLDEBRAND, Bot. ZcitllHg, l866, p. 239. 

4 Bull. Soc. Bot. France, Vol. XL, 1893, PP- 309-312. 



324 Nutrition and Selection. 

visible development of semi-latent characters. Of almost 
equal importance is the individual strength of the young 
plant, which, however, is the result of the operation of 
external factors during preceding periods of time, which 
may be weeks or months or even years. The stronger 
a bud is, the more is it liable to produce anomalies. 

This phenomenon is most clearly seen in the periodic- 
ity of the manifestation of anomalies by the same plant, 
and in the parallel between this manifestation and the 
gradual increase and subsequent decline in strength, either 
of the whole individual or of the succeeding orders of 
its branches. 1 This periodicity has been exhaustively 
studied in the five-leaved clover, and we have become 
familiar with instances of it in several other species. 
It remains now therefore to examine the nature of this 
process from a more general point of view. 

For this let us select a concrete instance. 

In gardens a double form of Chelidonium inajns is 
often found in which, as a rule, the doubling is only slight, 
and seldom consists in the production of more than 
16-20 petals per flower (Fig. 61). On the plants in my 
cultures this doubling regularly increases from the spring 
until the summer, both on the main stems of plants in 
their first year and on the lateral stems of plants that 
have been wintered. For instance in May all the flow- 
ers were single, i. e., with four petals (Fig. 61 A). With 
June the number began to increase, and many flowers with 
6 and 7 and occasional ones with as many as 10 petals 
occurred : whilst in the second half of June the majority 
had 12 to 14 and some 15 and 16 petals. Every year 

1 Over lict pcriodisch optreden dcr anomalien oft monstreuse 
plantcn. Bot. Jaarb., Gent, Vol. XI, 1899, p. 46, and Ueber die Pen'o- 
dicitat dcr particllen Variationen, Ber. d. d. hot. Ges., Vol. XVII, 
1899, p. 45. 



The Periodicity of Semi-Latent Characters. 325 

the doubling was seen to increase in intensity in the same 
way. 

BRAUN, in his great work on the rejuvenescence of 
plants, has discussed the part played by periodicity in 
normal development with great thoroughness and clear- 
ness. 1 In the whole plant and also in the separate orders 
of branches the vigor of life goes up and down. The in- 




Fig. 61. Chclidonium inajus plenum. A, a normal flower 
with four petals ; B and C, flowers with five petals ; D, a 
flower with eight well-developed petals and two petaloid 
stamens. 1-5, the transition between stamens and petals. 

dividual strength of the plant is perpetually fluctuating, 
affecting the size of the leaves, the length and thickness 
of the internodes, the number of leaflets in compound 
leaves, the number of rays in the umbels, the ramifica- 
tions in the inflorescences, the number of florets in the 

1 A. BRAUN, Verjungung, pp. 23-55, 75-76, 90 etc. See further: 
HEINRICHER, Biolog. Ccntmlblatt, Vol. XVI, No. i, pp. 13-14. Po- 
KORNY, Sitzber. d. Acad. d. Wiss. } Vienna, 1875, Vol. 72, pp. 527-547. 



326 Nutrition and Selection. 

flowerheads of composites, and so forth. Every shoot 
has its cycle. It begins with simple or atavistic forms, 
then gradually manifests the characters which are pecu- 
liar to the species in their full development, and gradually 
reverts. From the primary shoot this cycle is transmitted 
to the secondary shoots and from these to the branches 
of still higher orders. In this process the latter may 
become stronger or weaker in comparison with the main 
shoot, or even of equal strength. As a rule the branches 
are weaker than the main shoot ; those which are not fall 
into two categories according to BRAUN, strengthened 
shoots and repeating shoots (Erstarkungssprosse and 
Wiederholungssprosse). 1 Spikes and racemes are the 
best known instances of weakened shoots ; their apical 
flowers, if such are present, are in advance of all the 
rest in their development as for instance in the peloric 
Digitalis. In the red clover the main shoot consists of 
a short upright rhizome, whereas the lateral branches 
gradually increase in strength and develop into flowering 
stems. In Tetragonia e.vpansa the main shoot is always 
short and erect, terminating with a flower. The secon- 
dary shoots often grow to more than a meter in length 
and are much stronger. Instances of strengthening 
shoots are the lateral branches which arise from the 
axils of the radical leaves of many plants (Ranunculus 
bulbosus}, or from the middle part of the stem (Chry- 
santhemum scgctum and Trifolium incarnatum) ; also 
the forked inflorescences as in Saponaria officinalis. Re- 
peating shoots are often runners, and then we have what 
BRAUN calls "repetitional generations," as in Valeriana 
officinalis, LysimacJiia vulgans, etc. 

See 23, p. 256. 



The Periodicity of Semi-Latent Characters. 327 

Space does not permit the extension of this list; 1 
moreover all I am concerned with here is to show that 
this scheme also holds good for the distribution of anom- 
alies on the plant. Unfortunately it often can not be 
exactly applied because it is complicated with the effect 
of external influences. Every shoot and system of 
branches has its susceptible period, during which the 
external factors which happen to prevail favor the pro- 
duction of the anomaly, or the type of the species, ac- 
cording to their nature. But apart from these numerous 
fluctuations the rule holds good where the material is 
sufficiently plentiful to justify the neglect of exceptions. 

In a culture of Specularia Speculum which I had in 
1892 I found the flowers to be partly tetramerous and 
partly pentamerous. The pentamerous ones occurred 
at the top of the stem and of the strongest branches of 
the second order, whilst all the remaining flowers were 
tetramerous. A similar difference between apical and 
lateral flowers is exhibited as a normal character by 
Ado.va Moscliatellina and by many other plants. The 
Finns sylvestris of this neighborhood often has its needles 

^ <j 

combined into groups of three instead of groups of two. 
Each such group of needles, as is well known, belongs 
to a single dwarf shoot or spur. I found that the tri- 
foliate spurs occurred almost exclusively on the stronger 
branches, and chiefly at their upper end; but where they 
did occur they were numerous and closely packed. As 
a rule it is the main stem itself which bears them, but 
sometimes the strongest branches do so as well. There 
occurred up to 15 trifoliate spurs on the same one year's 
growth of the stem, all close to the apex, mixed with 

1 On the question of periodicity in the branching of cereals see 
SCHRIBAUX in Journal d' Agriculture pratique, 1899, and RIMPAU in 
Landwirthsclt. Jalirbitcher, Vol. XXIX, p. 589. 



328 Nutrition and Selection. 

numerous bifoliate ones. Pinus Pinaster exhibits the 
same phenomenon. In different years the frequency of 
its occurrence varies greatly. 

Camellia japonica with striped flowers, is striped 
mainly in November and December; but if it flowers 
in April, it produces only self-colored ones. 1 A form 
of Trifolium repens produced pitchers in my garden al- 
most every year in no inconsiderable numbers and in 
great variety of forms. But they never occurred except 
in the spring; 2 just as the lime bears its pitchers chiefly 
on the first leaves of the branches and Saxijraga crassi- 
folia on the lower abbreviated and leafy part of the 
flower peduncle. 3 Ulinus campestris, on the other hand, 
forms its pitchers chiefly from the strongest leaves in the 
middle and upper part of the branches. 

It is in this middle region of the branches that anom- 
alies are most commonly found, either exclusively or 
chiefly. Thus FRITZ MULLER describes a Begonia from 
Brazil, of the height of a man, which bore little append- 
ages at the base of the leaf blade, 4 which were usually not 
more than 1-3, and sometimes from 5-50 mm. long. 
They were only found on the fourth to the tenth leaf, in 
one case from the second to the fifth leaf, of the upright 
stem; and occurred at the same height on every anom- 
alous stem, both in the garden and in the field. 

In May 1890 I observed a group of Epilobium hir- 
sutum, the numerous and still young stems of which 
were for the most part forked. These divisions occurred 
always about the same height and did not recur during 

'VERLOT, loc. dt., p. 67. 

2 J. C. COSTERUS, Bekertjes aan de eindblaadjes van Trifolium 
repens. Botan. Jaarboek, Gent, 1892, p. 13, PI. I. 

' T. TAMMES, Kon. Akad. d. Wetensch., Amsterdam, 1903. 
4 FR. MULLER, Ber. d. d, Ges., Vol. V, p. 44. 



The Periodicity of Semi-Latent Characters. 329 

the course of the summer. They were split fasciations, 
but the division had gone somewhat deeper, as was vis- 
ible by the individual leaves being torn from below up- 
wards with one half adhering to the one arm of the 
fork and the other half inserted on the other arm. Such 
leaves occurred on several shoots, but, as already stated, 
always at the same height on the plant. 

The lower end of many racemose inflorescences is 
a favorite place for anomalies. Thus slightly double 
varieties of Gladiolus bear double flowers almost always 
in this position only. The racemes of Primus Padus 
bear lateral racemes in this position almost exclusively; 
and, in other cases, it is also only in this position that 
tetramerous flowers are borne. Many double varieties 
are known to bear single flowers at the end of the flow- 
ering period, and sometimes also at the beginning. These 
flowers alone set seed, while the double ones are sterile. 



It is well known amongst horticulturists that in multi- 
plying perennials and bulbs by seed, the value of the 
plants cannot definitely be estimated in the first year in 
which they flower. It is not until the second or the 
third year of the flowering that their qualities are dis- 
played to their full advantage. Many specimens of 
Chrysanthemum indicum, which when raised from seed, 
are only half double in the first year, will develop double 
flowers in the second year if grown from cuttings. 1 The 
varieties with tricolored leaves of Pelargonium zonalc 
tricolor do not exhibit their full range of color until the 
second year after their seed is sown. 2 To breeders of 
tulips, hyacinths and other bulbous plants this rule is 
well known. 

I REID and BORNEMANN'S Catalogue, 1891, p. 20. 
SUTTOX'S Catalogue, 1891, p. 77. 



330 Nutrition and Selection. 

The rule for ordinary branching is that the anomaly 
diminishes with the higher orders of branching, omitting 
from consideration, of course, the strengthening and 
repetitional shoots. Every one knows the beautiful case 
of Myosotis azorica Victoria (M. alpestris var.}, which 
has been on the market for many years, and was de- 
scribed by MAGNUS. 1 This heritable anomaly has a very 
much extended flower at the top of its main axis, often 
consisting of more than 10 and sometimes over 20 petals 
in one row. The number of sepals and stamens has cor- 
respondingly increased. The subsequent flowers of the 
inflorescence have become much less compound and the 
number of petals gradually diminishes during the course 
of the flowering period, until finally only pentamerous 
and hexamerous flowers are produced. Chrysanthemum 
mo dor um plenissimum manifests a similar periodicity, 
and the number of petals in Ficaria ranunculoides and 
Centaurca Cyanns are in the same manner dependent on 
the order of branching. 2 Veronica Buxbaumii, according 
to BATESON and PERTZ, bears the largest number of 
anomalous flowers at the beginning of the flowering pe- 
riod, that is to say, just before it is at its height. 3 Myo- 
surus minimus bears the more single flowers the weaker 
these are. 4 A number of similar cases have alreadv been 

/ 

collected by HUNTING in the seventeenth century, and 
recently by BURKILL amongst others. 5 

1 Vcrhandl. d. Bot. Ver. d. Prov. Brandenburg, XXIV, 1882, p. 
119, PI IV. 

2 J. MAC LEOD, Botanisch Jaabock, Gent, 1899, Vol. XI. 

3 W. BATESON and Miss PERTZ, Notes on the Inheritance of Vari- 
ation in the Corolla of Veronica Buxbaumii, Proceed. Cambridge 
Phil. Soc., X, Part 2, p. 78 (1898). 

4 H. MULLER, Nature, Vol. XXVI, 1882, p. 81. 

5 A. MUNTING, Waare oeffcninge, 1671; J. H. BURKILL, Limiacan 
Soc. Journ. Bot., Vol. XXXI, 1895, p. 216. 



The Periodicity of Semi-Latent Characters. 331 

Tagetcs africana and T. signata often first exhibit 
single flowerheads only, but subsequently double ones in 
increasing numbers on the same plants. The same thing 
can be seen in Zinnia elegans, and in Althaea rosea the 
flowers are sometimes seen to become more double as 
we proceed up the stem. 

Weak lateral buds in variable races often exhibit a 
special tendency to atavistic variations. This is true of 
the branches of the highest orders, of the accessory 
shoots, which are formed in addition to the normal axil- 
lary bud, of resting buds, etc. But it should be remem- 
bered that it is just these buds which often develop into 
very strong branches and become the succulent shoots 
which tend to reproduce the anomaly rather than the 
specific type. I have already referred to this exception 
above. 

Capsella Hecgcri, the new species described by SOLMS/ 
produces reversions to C. Bnrsa pastoris on its weak lat- 
eral branches and, according to the same author, the 
same phenomenon is exhibited by those varieties of Nas- 
turtium pahistre which have been lumped together into 
the genus Tetrapoma. Papavcr somniferuni polyccpha- 
hnn produces flowers without any accessory carpel almost 
exclusively on the very weak branches which arise from 
the main stem towards the end of the year when the 
lateral branches have been cut away. The peloric flowers 
of Digitalis purpurea are monstrously developed at the 
apex of the stem and on the strongest lateral branches ; 
but on the weaker ones they are simple and very regular 
(Fig. 42, p. 223). 

Such buds can often be induced to develop by cutting 

3 H. GRAF zu SOLMS-LAUBACH, Crucifcrenstudicn, Botan. Zei- 
t n rig, 1900, Pt. X, p. 167. 



332 Nutrition and Selection. 

down the main stem; and by this means we can often 
obtain the desired variations, as GOEBEL has shown, 
unless the anomaly is too much favored by a very vig- 
orous growth. 

29. THE CHOICE OF SEEDS IN SELECTION. 

From the periodical changes in the tendency of the 
plant to produce anomalies, we might expect a corre- 
sponding periodicity in the seeds. 1 The seeds of flowers 
which have bloomed under favorable circumstances should 
produce more anomalous individuals, those of the weaker 
branches, on the other hand, more atavistic ones. This 
expectation, however, is only to a slight extent fulfilled, 
and the latent capacity of the seeds seems to be regulated 
much more by factors other than those determining the 
periodicity of the parent plant. Our knowledge of this 
subject is, however, still in its infancy. 

Nevertheless there is a whole series of facts which 
are worth collating because they are likely to serve as a 
stimulus to further investigation. In doing so, it should 
be emphasized that in the selection of seeds we are con- 
cerned with variability and not with mutability, and in 
most cases, in fact, with the extreme fluctuating varia- 
bility of semi-latent characters. 

It is only a strong, well-developed seed, furnished 
with a healthy germ and richly supplied with food mate- 
rial that can give rise to the very strongest plant in a 
healthy culture. Doubtless, of course, the differences 
between the individual seeds are to a large extent levelled 
down during the first weeks after sowing ; but this is not 
always the case. Obviously the most favorable condi- 

1 C. FRUWIRTH, Die Ziichtung der landwirthschafilichen Cultur- 
pflanzen, 1901, p. 102. 



The Choice of Seeds in Selection. 



333 



tions can only give the best possible result when they 
are combined with the highest germinal capacity. 

For this reason in agricultural practice and occasion- 
ally also in horticulture special attention is often paid 
to the individual seed. The points to which attention is 
paid are, on the one hand, the size and weight of the 
individual seeds and, on the other, the place of their 
origin on the parent plant. The practice of selection in 
cereals consists essentially in the choice of the largest and 
heaviest seeds, or more 
strictly, in the elimina- 
tion of the smaller ones by 
winnowing machines or 
other devices. 1 When the 
object is to produce small 
families to serve as the 
stocks of new races, meas- 
urement and weighing of 
the individual seeds is rec- 
ommended by the best 
authorities, and special 
trays for determiningtheir 
weight have been devised. 2 

An important advance 
in the method of selection 
has been made in recent years by VAN DE VELDE who 

1 See VON RUMKER, Getreidezuchtung, 1889, and VON RUMKER, 
Dcr idrthschaftliche Mehnverth guter CuUurvarietaten und ausge- 
lesenen Saatgutes, Arbeiten der D. Landw. Gesellsch., 1898, Pt. 36, 
p. 127. 

2 VON RUMKER, Journ. fiir Landzvirthschaft, 39. Jahrg., Pt. 2, 
p. 129. 

' The specimens from which this drawing was made I owe to 
the kindness of Messrs. KUHN & Co., beet seedsmen in Naarden, 
Holland. They were taken from selected beets of the very high 




Fig. 62. Clumps of fruits of the 
sugar beet ; half schematic. A, 
two ripe clumps on a stem ; B, one 
of these cut longitudinally snow- 
ing the three seeds in the three 
special fruits. 3 



334 Nutrition and Selection. 

has studied the relation between the size of the seeds 
and rapidity of germination. 1 As a rule the larger seeds 
germinate faster than the smaller ones; and thus their 
weight favors the production of strong plants in more 
than one way. Moreover, as has long been known, the 
seeds which germinate the first are the best and produce 
the finest plants. When harvesting of flower seeds has 
to be done in the field, the first seeds often fall out before 
the harvest; they germinate easily and usually do so at 
once ; and we all know that from such seeds the finest 
specimens may be produced. In fact for certain definite 
species the handbooks recommend the practice of allow- 
ing them to sow themselves, since this self-sowing leads 
to much better results than are obtained even from seed 
carefully harvested at the proper time. 

The question as to where the best seeds occur on the 
plant is one that has been much discussed. Let us con- 
sider the sugar beet as our first instance. In this species 
2-5 or more fruits are associated to form a so-called clump 
(Fig. 62), in which the upper flower produces the larg- 
est seed Fig. 62 b) ; whilst the lateral seeds of the same 
clump are less fine and markedly smaller and differ 
amongst themselves very much in size. 2 This phenom- 
enon has been recently subjected by BRIEM to an exhaus- 
tive investigation. 3 He sowed the clumps, and planted 
out their individual seedlings separately in a row. In 

percentage value of from 18.9 to 20.1% of sugar, and with roots 
weighing 900-1100 grams. 

*VAN DE VELDE, Invlocd van de grootte dcr zaden op de kicmiiig. 
Botanisch Jaarb. Gent, 1898, pp. 109-131. 

* Keimungsgeschichte dcr Znckcrrubc, Landw. Jahrb., VIII, 1879, 
P- M, 

3 H. BRIEM, Studien fiber Samenruben, cincin Riibcnknaucl ent- 
stammend. Oesterr.-Ungar. Zeitschr. f. Zuckerindustrie und Land- 
wirthsch.. 1900. Pts. IT, TV, and VI. 



The Choice of Seeds in Selection. 335 

this way the plantlets derived from a single clump could 
be compared with one another throughout the whole 
course of their development. The largest seed becomes 
the largest seedling which produces the finest beet, and 
lastly the most fertile seed-parent. The relative weights 
of the five seedlings of a clump at the end of germination 
were as follows: 100 74 67- -51 46. The heaviest 
seedling weighed 5.8 milligrams. The full-grown beets 
derived from a single clump weighed in one case 1156, 
859, 574, 344, 310 grams, and they furnished respectively 
241, 167, 202, 239, 104 grams of seed at the end of their 
second year. 

E. SCHAAF considers a very important advantage of 
the so-called "cutting"-culture in beets to be the exclusive 
development of the largest seed of each clump which is 
effected by the close proximity of the plants during the 
production of the clumps. 1 

Amongst cereals the matter has been most thoroughly 
investigated and I refer the reader to the literature on 
the subject which I have already cited. The heaviest 
grains are situated at the middle or somewhat below the 
middle of the ear. FRUWIRTH showed this to be true 
for barley, rye, wheat, spelt, and also for maize. 2 There 
proved to be certain subordinate differences characteristic 
of the various varieties and species. 3 BRUYNING found 
that in oats the lower grains of the lateral ears are far 

1 E. SCHAAF, Blatter fiir Zuckerrubenbau, Jahrg. VII, No. 24, 
Dec. 1900. 

~ C. FRUWIRTH, Ueber den Sits des sclnvcrstcn Kornes in den 
Fruchtstdnden beim Getreide, in WOLLNY'S Forschungen anf dem 
Gebiete der Agric.-Physik, XV, 1892, p. 49. 

3 E. NOTHWANG, Unters. iiber die Vcrtheilung d. Kornergeurichtes 
an Roggcnahrcn, Diss., Leipsic, 1893; Bot. Centralhlatt, 1895, II. p. 
263. 



336 Nutrition and Selection. 

better than the upper ones, 1 and the same is true of other 
species of cereals. 

Lastly some reference should be made to those cases 
in which individual seeds possess the peculiarity of 
germinating late, and of remaining one or more years in 
the soil, as for instance the small seeds of various species 
of clover. In Xanthium canadcnsc each fruit contains 
two seeds, one of which germinates after the first win- 
ter, the other not until after the second. 2 

When we are dealing with semi-latent or, in general, 
with highly variable characters, a selection of seeds either 
by their size and weight or by their place of origin on 
the plant is to be recommended in many cases, and the 
general rule seems to be that the place of origin of the 
best seeds will also be that of the desired variants. There 
are some cases in which this rule does not apply, such 
as we have seen in Trifolium incarnatum, where it is 
the smallest late germinating seeds which contain the 
best representatives of the four-leaved half race. 

In Chelidoniuui inajus plenum the single flowers 
bloom first, and the double ones later, as we have seen 
in the preceding section ( 28). I have harvested the 
seeds of both and sown them separately; but found no 
difference in respect of the doubling amongst the off- 
spring. BATESON and Miss PERxz 3 also failed to find 
any difference in respect of doubling amongst the off- 
spring of normal and abnormal flowers of the same 
plant with Veronica Biixbanniii. In Oenothera Lamarck- 
iana I found about the same percentage of annual and 

1 F. F. BRUYNING, Proefnemingen met havervarictcitcn, Wage- 
ningen, 1900. 

2 J. C. ARTHUR, Proceedings Ann. Meeting Soc. Agr'ic., Science, 
August, 1895. 

3 W. BATESON and Miss PERTZ, he. c\t., p. 79. 



The Choice of Seeds in Selection. 337 

biennial individuals from the upper and lower fruits of 
the same spike. In Viola tricolor maxima the small sum- 
mer Mowers furnish the main quantity of seed. It never 
occurs to a seed collector to regard them as of less value 
than the first seeds. In many double plants, especially 
in Begonia, it is practically only the flowers which bloom 
last that produce pollen and set seed. This seed is always 
sown without any detrimental result to the degree of 
doubling of the varietv. 

o * 

On the other hand it is generally regarded as desirable 
to harvest the lower seeds of the inflorescence in the cox- 
comb, Celosia cristata ; and in the case of the crested spe- 
cies of ferns (Varietates cristatae) the spores which are 
found on the dissected leaves, and still more on the tips 
of such leaves, are regarded as the best, although spores 
found on the other parts of the leaves will certainly re- 
peat the anomaly. 1 Another instance which has been 
studied by many investigators is furnished by the stocks, 
whose double varieties have been known for a very long 
time, for a century at least, to consist in each generation, 
of double and single plants in about equal numbers. 2 
The former are absolutely sterile, lacking pistils and 
pollen as a result of their petalomania (see Vol. I, p. 
194), so that only the latter can play a part in the con- 
tinuation of the race. There are certain differences be- 
tween the seeds which produce the single and the double 
specimens. The latter are heavier and germinate more 
quickly, 3 and the young plants can be sorted out in the 

1 See the long list of references given by GOEBEL, Organograplne, 
I, p. 158 ; VERLOT, loc. cit., p. 97 ; CARRIERE, loc. cit., p. 67 ; KENCELY 
BRIDGMAXN, Ann. Sc. not., 4 Serie, Vol. XVI, p. 367; C. T. DRUERY. 
fount. Roy. Hort. Soc., Vol. XII, III, 1890, p. 517, etc. 

2 E. CHATE FILS, Culture pratique des giro-flees, Paris, Biblioth. 
de 1'horticulteur praticien. 

3 NOBBE, Botan. Centralbhtt, Vol. XXXII, 1887, p. 253. 



338 Nutrition and Selection. 

beds long before they exhibit buds. 1 The lower pods 
on the main stem and on the principal branches as well 
as the lower two-thirds of each pod furnish on the 
average more double than single plants; the upper sec- 
tions of the pod and the pods of weaker branches yield 
more single ones. The proportion of double plants in 
the harvest can be increased to about 60% either by lim- 
iting the production of seed by means of culture in pots, 
or by pruning; and in the best nurseries the finer sorts 
are usually subjected to this treatment. If the seeds 
are kept through some years the proportion of double 
seedlings gradually increases, because the mortality is 
greater amongst seeds that were destined to produce 
singles. 

It is stated that in the case of the Balsam and many 
other double flowered varieties the seeds are rounder 
and fuller and also smoother than those of the corre- 
sponding single sorts. The "double" seeds of Petunia 
are said to germinate later than the single ones, so at 
least I have been told by nursery men at Erfurt. In the 
Composites the central seeds of the disc in double vari- 
eties are said to be more likely to repeat the anomaly 
than the marginal ones. All these statements should, 
however, be regarded critically, and many of them are 
in need of experimental confirmation. 2 

Nevertheless the general rule is that the various seeds 
of a plant may give rise to offspring of widely different 
degrees of individual vigor, according to the place of 
their origin on the parent plant, their size and their 

1 This process which is carried out by children is called esimplcr, 
in France. The matter stands in need of closer investigation. 

2 PEYRITSCH has collected references to the earlier literature re- 
lating to this point. Zur Aetiologie pclorisclier Bliithcnbildnngcn, 
Abhandl. k. k. Akad. Wien, 1877, pp. 135-136. 



The Choice of Seeds In Selection. 339 

weight ; and that, in accordance with the rules which we 
have already enunciated, a greater or less development 
of the varietal character is correlated with these degrees 
of strength. 



PART II. 
THE ORIGIN OF EVERSPORTING VARIETIES. 



I. TRICOTYLOUS RACES. 

i. THE OCCURRENCE OF TRICOTYLS AS HALF RACES 
AND INTERMEDIATE RACES. 

In the chapter on latent and semi-latent characters in 
the first part of this volume, I have discussed the differ- 
ence between half races and intermediate races. It is 
not in the possession of certain elementary characters 
that they differ one from another; in this respect they 
are identical. They possess exactly the same characters 
and in the same numbers. That feature, however, which 
constitutes the point of difference, is semi-latent in the 
half race, that is to say manifests itself only rarely and 
in occasional individuals, one in every thousand for in- 
stance. In the intermediate race, on the other hand, it 
is active and equivalent to the character to which in the 
half race it is, as it were, subordinate. Considered with 
regard to the features which distinguish them, both races, 
therefore, possess two elementary characters, which, how- 
ever, cannot be expressed simultaneously in the same 
organ but are mutually exclusive. 

In an ideal intermediate race, these two antagonistic 
characters would be of exactly equal value ; that is to 
say, half of the individuals would exhibit the one, and 
the other half the other character. Whether such ideal 
races actually exist in nature is an open question, since 
as a rule one of the two characters is more or less easilv 



344 Tricotylons Races. 

manifested than the other. Moreover those cases would 
have to be excluded in which either the conditions of 
life or some selection of the race could have exerted an 
influence in one direction or the other; for, as we have 
seen, intermediate races are very susceptible to both these 
groups of factors. 

Among the intermediate races known to me the tri- 
cotylous and syncotylous forms approach most closely 
this ideal picture. 1 For, in pure cultures, they furnish 
as a rule 50 % dicotylous and 50% tricotylous or syn- 
cotylous seedlings. By altering the conditions of growth 
as well as by selection this proportion can be easily and 
greatly modified in both directions, almost to the ex- 
clusion of one or other of the two types. But such treat- 
ment leaves the essential nature of the intermediate race 
untouched. It neither reverts to the half race when 
subjected to selection, nor is it possible to derive a con- 
stant and pure tricotylous variety from it. 2 

As far as I know, there are hardly any references 
to tricotylous races in botanical literature, and the possi- 
bility of the existence of tricotylous intermediate races 
seems never to have been discussed. In this part, how- 
ever, I shall describe some instances of such races in 
order to demonstrate their existence and to study their 
characters. In the period from 1892 to 1897 I succeeded 
in producing such races from half a dozen very different 
species. 

1 wanted also to include in this inquiry some pure 
tricotylous and pure dicotylous races, that is to say, 
races the seedlings of which were in the first case ex- 
clusively tricotylous and in the latter exclusively dicotyl- 

' See my preliminary note Ueber tricotyJe Rassen in Ber. d. d. 
bot. Ges., 1902, Vol. XX, p. 45. 

2 See the scheme on page 24. 



Tricotyls as Half Races and Intermediate Races. 345 



ous. But hitherto I have not discovered a single in- 
stance of the former, and have only obtained one in- 
stance of the latter. 1 

Before I proceed to a detailed description of my 
races and cultures it seems desirable to give a general 
account of the manner in which tricotylous seedlings 
are found, and how the desired half and intermediate 
races may be most easily derived from them. 

It is well known that amongst the seedlings of dicot- 
ylous species occasionally individuals are found with 
three seed leaves. It is only 
necessary to look over a 
seed-bed in the garden in 
spring in order to find in- 
stances of these. The more 
extensive the sowing and 
the more careful our search 
the greater will be the num- 
ber of tricotylous seedlings 
found. Some species pro- 
duce them in greater, oth- 






Fig. 63. Antirrhinum majus. A, 
C, D, seedlings with 2, 3, and 
4 cotyledons. B, with a deeply 
cleft cotyledon. 



ers in smaller proportions ; 
and they can often be found 
even in the smaller pot-cultures of the greenhouse, but 
in many cases I have had to sow 10,000 or 20,000 seeds 
of a species before finding a single individual which 
showed any variation in this direction. But numerous 
species seem to produce one or several tricotyls in every 
hundred or thousand seedlings. 

1 My Helianthus annuus syncotyleus has not produced a single 
tricotylous plant in the ten years during which I have often counted 
hundreds or even thousands of seedlings every year. On the other 
hand they occasionally occur in Helianthus animus varicgatus and 
some other varieties of the sunflower. 



346 Tricotylous Races. 

If the variants are rare, they are as a rule normal 
tricotyls; but if they are more numerous the type is 
usually seen to be variable both in the minus and in the 
pins direction. For convenience of expression we may 
regard a tricotylous seedling as having arisen by the 
doubling of one of the two cotyledons of a dicotyledon 
by splitting, just as is so frequently observed in foliage 
leaves. Smaller degrees of the splitting would lead to 
variations in the minus direction; but if the splitting 
affects both cotyledons there arise variations in the plus 
direction, which, if the doubling is complete, result in 
the origin of tetracotyls (Fig. 63 D). A seedling with 
one normal and one split seed-leaf is called a hemi- 
tricotyl; 1 one with two split seed-leaves, or with three 
of which one is split, is called a hemi-tetracotyl. In the 
same way hemi-pentacotyls, and so on, may be found ; 
but the deviations become rarer as they are more remote 
from the pure tricotylous type. 

If we make a collection of all these forms it is easv 

w> 

to construct a continuous series which extends from the 
pure type, on one side, through stages characterized by 
more or less deep fission, to the dicotyls ; and in the other 
direction in a similar manner to the tetracotyls and, if 
the material is extensive, even further, to the pentacotyls, 
and so on. Fig. 64 exhibits such a series derived from 
Ocnothcra hirtella, the unsplit seed-leaf of each plantlet 
being omitted. But obviously even here the forms fig- 
ured are only a selection from a. much more complete 
series. If we imagine those cotyledons which have been 
cut off in these figures to be split also, the series would 
represent the transition from the tricotyls to the tetra- 
cotvls. 

*> 

1 Beri'hte d. d. bot. Ges., 1894, Vol. XII, p. 26. 



Tricotyls as Half Races and Intermediate Races. 347 

A series of this kind is, however, a purely morpho- 
logical one and neither physiological nor statistical. If 
we wish to obtain this, we must not merely pay attention 
to the forms, but also to the frequency of their occur- 
rence. In doing so the first striking fact is that all the 
aberrant forms taken together, constitute only a very 
small percentage of the total number, even smaller some- 
times than the figures already given. Therefore, if we 
construct a frequency curve the dicotyls produce a high 
peak and the curve extends from this only in one direc- 
tion and is therefore a so-called half curve. 1 

Further, amongst the aberrant forms themselves, the 
various forms occur in widely different proportions. The 
hemi-tricotyls are far rarer than the tricotyls ; the num- 
ber of all the hemi-tricotylous types together often does 
not amount to as much as that of the pure tricotyls. 
Deep clefts are somewhat less rare than shallow ones; 
and we often see specimens which at first seem to be 
purely tricotylous but which, when the peduncles of the 
cotyledons gradually elongate, turn out to be deeply cleft. 
This is particularly evident in Amarantus speciosus and 
Antirrhinum majus (Fig. 63 B), in which the closer 
juxtaposition of two of the cotyledons betrays the fact 
that they arise from a common stalk. Hemi-tetracotyls 
are always much rarer than tricotyls in sowings from 
commercial seed as well as in selected races. Neverthe- 
less some species seem to be richer in them than others. 

If we plot such a frequency distribution we obtain 
a two-peaked curve which has a small secondary apex 
over the ordinate for the tricotyls, besides the main one 
for the dicotyls. Thus I found a crop of 800 seedlings 
of Cannabis sativa of 1894 to have the following com- 

1 See above, p. 26. 



348 



Tricotylous Races. 



position, the proportion of tricotyls (that is to say all 
the aberrant forms of the series) being about 10%. 



DICOTYLS HEMITRIC. TRICOT. 



Or in % 



726 
90.8 



24 
3.0 



46 
5.7 



HEMI-TETR ACOT Y LS 
AND TETRACOTYLS 
4 

0.5 



If we wish to make ordinates for the various degrees 
of cleavage we are met by the difficulty presented by the 
choice of the limits of such arbitrary groups. This diffi- 






Fig. 64. Oenothera hirtella. Intermediate forms between 
the dicotylous seedling (A) and a tricotylous one (G). 
The normal cotyledon has been cut away from each 
plant. Cultivated in 1900. 

culty is partly due to the fact that the stalks of the 
cotyledons continue to grow for some time after the 
cotyledons themselves have assumed their definitive form. 



Tricotyls as Half Races and Intermediate Races. 349 



But as a rule we find the general relations to be such as 
are exhibited in Figure 65. This curve has a form which 
is also commonly seen in other anomalies. 1 

Whilst clicotyly is a character without variation tri- 
cotyly is one which exhibits a very high degree of fluc- 
tuation. The limit between dicotyls and the extreme 
minus variants of the tricotyls can always be easily and 
certainly observed ; because 
the apex of the cotyledon is 
the first part of it to assume 
its definitive form, and a 
cleft in this apex, however 
small, can be clearly seen. 
There is therefore no fear 
that the rarity of such ex- 
tremes might be due to im- 
perfect observation. The 
limits between the remaining 
smaller groups are blurred 
and arbitrary. But this dif- 
ficulty disappears in the eval- 
uation of the degree of in- 
heritance, because all the 
seedlings which exhibit cleav- 
age in one or both cotyledons 
are united into a single 
group and treated as tri- 
cotyls in the larger sense. 

I shall denote the dicotyl- 
ous seedlings of these races as atavists. 2 In the sowings 

1 See Chapter IV of this part, and Sur les courbes galtoniennes 
dcs monstruositcs, in the Bull. Scientif. de la France et de la Bel- 
gique, published by A. GIARD, Vol. XXVII, 1896, p. 397. 

2 See above, p. 104. 




Die. 



Hemitricot. 



Trie. Tetracot. 



Fig. 65. Schematic representa- 
tion of the fluctuating varia- 
bility of tricotyly. The tri- 
cotyls and the dicotyls con- 
stitute the two apexes, the 
hemi-tricotyls and tetracotyls 
(together with the hemi- 
tetracotyls) constitute the re- 
maining ordinates. 



350 Tricotylous Races. 

of commercial seed the application of this term would 
not, of course, be justified; but in my cultures, which, 
almost without exception, were started by the selection 
of tricotylous individuals, this term is obviously fully 
justified. Moreover, in this way, the word dicotyl is 
left to its pure systematic signification. And, as in some 
other cases, atavism is here seen to be an oscillation be- 
tween two empirically known extremes. 1 

So far as my experience goes, tricotylous seedlings 
are much commoner amongst cultivated species than 
amongst wild ones, and even amongst the latter they 
usually occur from seeds saved in botanical gardens and 
very seldom from those collected in the field. Amongst 
cultivated plants, again, they are commoner amongst spe- 
cies which are grown on a large scale than on a small 
one. 

Thus I have obtained my intermediate races from 
amongst the former, partly from agricultural and partly 
from horticultural species. As an instance of the former 
I may mention the hemp and of the latter the snap-dragon 
and the wild poppy. But besides these I discovered a 
rich tricotylous race in my Ocnothcra hirtella, an entirely 
new species which was found quite by chance in my 
garden. It is not impossible that cultivation on a large 
scale favors the origin of new races. 

A profusion of instances of some anomaly in a species 
either in the field or in cultivation, suggests the presence 
of an intermediate race ; 2 a scarcity, however, that of a 
half race, as is especially well known to be true in the 
case of fasciations. Tricotyly conforms strictly to this 
rule. From seeds obtained from the trade or by exchange 

1 See page 108. 
* See page 32. 



Tricotyls as Half Races and Intermediate Races. 351 

we rarely get more than low percentages ; but it is obvious 
that we should not expect all the seed-parents in the field 
to furnish the same number of tricotylous seedlings. Com- 
mercial seed is almost certain to be a mixture and to 
yield a mean proportion, which may perhaps be much 
lower than the seed of those specimens would yield, 
which were the richest in tricotylous offspring. It fol- 
lows from this that we can only form a proper estimate 
if we select a group of plants among our first sowing 
and harvest their seeds separately, if possible after tak- 
ing the precaution of preventing too much cross-fertili- 
zation by insects. It is obvious that in such a culture a 
choice will have to be made, and as a rule the tricotyls, 
using this term in its widest sense, will be selected. From 
the separate harvest of these selected specimens, individ- 
ual hereditary coefficients may then be obtained. 

In spite of every precaution, the choice of the plants 
will depend mainly on chance, for, as we shall see later, 
tricotyls are by no means more likely to reproduce the 
anomaly than some of the dicotyls. On the contrary, 
plants much better in this respect sometimes occur among 
these ; but we have at present no other means of dis- 
covering them except by growing their seed. Experience 
however has shown that if we allow a fairly large group 
to ripen their seed we may become independent of chance 
in so far that we can be fairly sure that at least some 
seedparents will give a relatively high proportion, pro- 
vided of course that the original mixture contains such 
amongst its components. It will soon be seen that in 
spite of all apparent intermediate degrees, two main 
groups can be distinguished. In one of them we find 
onlv low individual values, from to 3%, or very little 

/ / 

over ; in the second, on the other hand, besides these 



352 Tricotylous Races. 

some higher ones which not rarely attain a value of 10% 
to 20 % and in rare cases even of 30% to 40 %. 

\Yhenever the cultivation in the garden gives no 
ground for the assumption of special influences the differ- 
ence between the values derived from the original com- 
mercial samples of seed and the self -harvested seed of 
the first year must be attributed almost exclusively to 
the fact that the commercial seed was a mixture whilst 
the self -harvested crops matured in isolation. But since 
mixtures of this kind have been the rule during the gen- 
erations which preceded the purchase of the commercial, 
horticultural or agricultural, seeds, it is evident that 
those species which contain a number of rich seed-parents 
every year, will give a higher percentage of tricotyls in 
the mixture than others. Thus the percentage compo- 
sition of commercial seed gives some idea of what may 
be expected from it by subsequent culture. 

In the following sections (2-8) I shall describe 
my experiments on these two groups in detail. Here, 
however, I will give the main result. It is this : 

By far the largest number of species contain only 
a half race in respect to tricotyly, but some few also con- 
tain, besides this, the intermediate race. If the latter is 
present in commercial seed or in seed obtained by ex- 
change, it can be easily and speedily isolated; but if it 
is not present years of selection cannot bring it out. The 
half race and the intermediate race are, here as else- 
where, perfectly distinct things, which do not merge into 
one another, or if they do, they do so only by chance. 

Sometimes, but on the whole very seldom, an indi- 
cation of the likelihood of obtaining tricotylous inter- 
mediate races may be afforded in nurseries and in agri- 
culture. This consists in species with a decussate ar- 



Tricotyls as Half Races and Intermediate Races. 353. 

rangement of the leaves in the exhibition of trimerous 
whorls on the stems in the later life of the plant. I paid 
great attention to this point at the beginning of my ex- 
periments when I visited the great nurseries at Erfurt. 
Here the ternary individuals of Antirrhinum majiis in 
the fields impressed me greatly. They were not con- 
sidered by the gardeners as worth any attention, but they 
formed the foundation for my first tricotylous inter- 
mediate race. 

The difference between tricotylous half and inter- 
mediate races lies in their percentage composition and 
not in the visible characters of the individuals. Neither 
the number nor the cleavage of the cotyledons on a single 
individual is decisive. As a rule tricotylous specimens 
of both races tend to produce a richer harvest of the 
tricotyls than the atavists of the same race; but expe- 
rience shows that the difference is only a small one ; and, 
further, that tricotyls, even those of a high productive ca- 
pacity, are often surpassed in this respect by some of their 
atavistic brethren. The chief point is, however, that both 
the half race and the intermediate race are composed of 
both types of individuals ; in the former the tricotyls are 
rare, whereas in the latter, under normal circumstances, 
both forms appear in about equal numbers. Moreover, 
both races contain all the stages of hemi-tricotyls, and, 
although these are rarer, of hemi-tetracotyls also. 

It is not possible, therefore, to tell from a single plant 
to which race it belongs. Only its ancestry can deter- 
mine this; and if this is unknown, we have to reach the 
decision by means of subsequent breeding. It is an ex- 
treme case of the transgressive variability which was 
discussed in the first volume. 1 The forms composing a 

'Vol. I, Part IT, 25, pp. 430 ff. 



354 



Tricotylous Races. 



half race occur in the intermediate race also, and as a 
rule all of them in every sowing, provided it is not too 
small. On the other hand, if the half race is cultivated 
on a sufficiently large scale, it will contain all the forms 
of the intermediate race. There is no morphological 
limit between the two, although the physiological one is 
perfectly definite, and in my experiments has never been 



\ 





15 ?0 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 
1 0121 1 6 9 10 7 16 13 13 15 3 1 0. 

Fig. 67. Oenothera hlrtella. Tricotylous 
intermediate race ; curve of hereditary 
capacities of plants of 1896, including 
both atavists and tricotyls. The ca- 
pacities oscillate between 15 and 95%. 
The meaning of the figures is the same 
as in Fig. 66. 



O.t 0.4 0.7 1.0 1.8 1.6 1.9 2.8 1.6 2.8 3.1 3.6 3.7 
26 15 14 10 9 8 5 8 00 Oil. 

Fig. 66. Oenothera rubri- 
nervis. Tricotylous half 
race. Curve of the he- 
reditary capacities of 
the plants of 1894. The 
highest of these was 
3.7%. The upper row 
of figures relates to the 
percentage composition 
in tricotyls, the lower 
to the numbers of 
seed-parents with this 
composition. The ordi- 
nates have the same 
signification as these 
latter figures. 1 

overstepped. The tricotyls of the half race do not lead 
on to the intermediate race, nor do the atavists of this 
race lead on to the half race. The two races are just 

l The percentage figures are calculated, in this experiment, from 
counts made on 300 seedlings from each plant ; but the number of 
ordinates is reduced to one-third. Therefore o.i means, o 0.2; 0.4, 
0.3 0.5 and so on. The tricotylous race-s of Dracocephalum molda- 
I'icum and Penstemon gentianoides gave similar curves. (Harvest 
of 1894). 



Tricotyls as Half Races and Intermediate Races. 355 

as sharply and unalterably separated as, in the first part 
of this volume, we saw was the case in numerous in- 
stances, and especially in the five-leaved race of the red 
clover. Nothing less than a mutation can effect the 
transition between the two, but I have not yet had the 
good fortune to observe such an occurrence. 

In these experiments therefore the differences be- 
tween individuals to which attention has to be paid are 
their hereditary values ; and whether they themselves 
have two, or three or cleft cotyledons is a matter of sec- 
ondary importance. In my cultures the selection of tri- 
cotyls as seed-parents has been the general rule, since 
this practice on the one hand increases the probability 
of excluding specimens with a low hereditary capacity, 
and on the other, of including those with the high ; but 
the increase of this chance is only a small one, as the 
frequent cultures I have made from atavists clearly show 
(see below, 6). 

For a half race the curve describing these values is 
a half curve. The vast majority of individuals have 
either nothing, or little else, but dicotylous offspring; 
and the numbers of individuals with the larger numbers 
of tricotylous offspring decrease rapidly (Fig. 66). These 
curves may be improved in the same way as those of 
other half races, viz., by the selection of individuals with 
the highest value, as we have seen in Ranunculus bul- 
bosiis semiplenus (see 23, of the first part of this 
volume, p. 249). 

Curves describing these values in intermediate races 
usually have their maximum ordinates at 50% ; they are, 
however, liable to be much altered by selection and ex- 
ternal conditions. Fig. 67 is a curve of this kind for 
Oenothera hirtella, whose apex is at about 65%. If 



356 Tricotylous Races. 

from a group like this the plants with the smallest values 
are selected for the continuation of the culture, values 
which are equal to or even smaller than the best ones of 
the half race can be obtained. Here also the variability 
is of the transgressive kind; but it does not result in the 
transition from one race to the other. 

Half races and intermediate races are, therefore, with 
regard both to the forms of their individuals and the 
magnitude of their hereditary capacities highly variable 
races. On the other hand they are perfectly constant 
inasmuch as neither race can be transformed into the 
other artificially. They behave like the majority of ever- 
sporting races of other anomalies. 1 

2. TRICOTYLS, HEMI-TRICOTYLS, AND TETRACOTYLS. 

The opinion, prevalent amongst gardeners, that hy- 
brids are intermediate in form between their parents, and 
that intermediate types, therefore, should be regarded 
as hybrids, might easily lead to the assumption that the 
hemi-tricotyls are hybrids between tricotyls and dicotyls. 
Intermediate they are without any doubt, especially when 
the cotyledons are cleft over half their length. But the 
occurrence of a continuous series of intermediate forms 
between di- and tricotylous plants proves the incorrect- 
ness of this view, or at least indicates that it does not 
cover all the facts. The question has to be decided by 
experiment. For this reason I have made a series of 
crosses between dicotyls of a half race, and tricotyls of 
the corresponding intermediate race. Although I always 
paid especial attention to the occurrence of hemi-tricot- 
ylous seedlings amongst their results, they were just as 

1 See above, p. 22. 



Tricotyls, Hemi-tricotyls, and Tetracotyls. 357 

rare amongst the hybrids as in other cultures. The hy- 
brids are almost without exception dicotylous, although 
of course occasional hemi-tricotyls and tricotyls occur 
amongst them, just as they do in the half races. There 
is therefore no ground for the supposition that seedlings 
with cleft leaves should be of a hybrid nature. 

They are simply variants of the tricotylous type. The 
occurrence of seedlings in which both the cotyledons are 
cleft or doubled, favors this view. They cannot possibly 
be regarded as hybrids ; they occur so regularly and abun- 




Fig. 68. Silene odontipetala. A, a hemi-tricotylous, B, 
a tricotylous, and C, a tetracotylous seedling, 1900. 

dantly in tricotylous intermediate races that they must 
be simply regarded as plus variants of the same character. 
Moreover the fact that one or the other of the seed leaves 
in a tetracotyl may be cleft also, supports this view. 
Such a cleavage results in the origin of pentacotyls and 
hexacotyls which, however, will be, obviously, very rare. 
True pentacotyls, arisen by such a cleavage, I have seen, 
for instance, in Scrophularia nodosa, Amarantns spcci- 
osus, Ocnothera Lamarckiana and Papaver Rhocas (Fig. 
69.) 



358 



Tricotylous Races. 



Hemi-tricotyls and tetracotyls are, as we have al- 
ready stated, as a rule rarer than tricotyls, even when we 
include all the minus and plus variants of these groups. 
This can be observed in bought samples of seed ; but 
better if we sow the seed of plants grown from such a 
sample separately. Thus, for instance, I found in 1892 
among the seeds of a plant of Asperula azurea setosa 
3 hemi-tricotyls, 15 tricotyls and 3 tetracotyls among 
1170 seedlings, and in the crop derived from another 
individual of the same culture 2 hemi-tricotvls and 5 




Fig. 69. Palaver R/wcas. Semi-double cultivated form. 
Dicotylous, hemi-tricotylous, tricotylotis, tetracotylous, 
and pentacotylous seedlings; from the seeds of 1899. 

tricotyls amongst 550 seedlings. Further, I found in 
1892, amongst 13,000 seedlings of Amarantus spcciosns 
202 hemi-tricotyls, 245 tricotyls, and 22 tetracotyls and 
hemi-tetracotyls. In the former group the cleavage was 
shallow in 47 cases, deep in 97 and intermediate in 58. 
The same general result was obtained in other plants. 

To obtain a further knowledge of tricotyls and hemi- 
tricotyls we must cultivate them further, allow them to 
flower separately, and compare the composition of their 
progeny with that of the tricotylous individuals from the 



Tricutyls, Ilcini-lricotyls, and 'J'ctraculyls. 359 

same culture. In doing so we find that they do not tend 
to reproduce their own type, but behave, as a rule, in the 
same way as tricotyls. Minor quantitative differences 
may occur, but of qualitative there are none. At any 
rate it seems impossible to isolate and fix these two sub- 
sidiary types and obtain pure hemi-tricotylous or tricotyl- 
ous races. 

I propose to deal first with the hemitricotyls. I have 
repeatedly isolated them and tested their hereditary capa- 
city, especially in Amarantus spcciosus and Cannabis 
satii'a. In Amarantus, if we plant out some hemi-tricotyls 
and some tricotyls, the highest values are sometimes ob- 
tained for the former, and sometimes for the latter; but 
only with slight differences. For instance, in the harvest 
of 1892 the value of 20,000 seedlings w^as a mean of 2% 
for the former, and 3.5% for the latter. Moreover 
there were slightly more hemi-tricotyls than tricotyls 
amongst the former, the difference, however, was only 
0.1% in 10,000 seedlings of each group, and in this 
figure the various degrees of cleavage were, moreover, 
lumped together. In 1892 to 1895 I then grew the 
hemi-tricotyls and the tricotyls separately for three fur- 
ther generations, always selecting the individuals with the 
highest hereditary capacities. In these four years the 
highest values obtained varied for the hemi-tricotyls from 
4.2 to 8.5% with a mean of 5.5%, and for the tricotyls 
from 3.6% to 7.4% with a mean of 5.7%. From these 
figures it seems to make practically no difference whether 
hemi-tricotyls or tricotyls are selected as seed-parents. 
Of Cannabis sativa I had in the summer of 1894 a bed 
of each of the two types. The hemi-tricotyls gave values 
varying from 1 to 26%, and the tricotyls from 4 to 14% : 
with means therefore of 11 and 9%. In Penstemon 



360 



Tricotylons Races. 



gcntianoides the cleft forms gave a mean of 2. 8%, but 
the tricotyls a mean of 2.9%. On the whole, therefore, 
there are no essential differences in hereditary capacity 
between the hemi-tricotylous and tricotylous examples 
of the same races. Moreover we shall see later that this 

rule must be true, when we 
shall find that even the 
atavists in the pure races 
do not differ essentially 
in these values from the 
tricotyls (see 6). 

We now come to the 
tetracotyls. Experiments 
here meet with the diffi- 
culty of distinguishing the 
true types from others. 
For, occasionally, double 
seedlings or twins occur. 
In these the axis is more 
or less deeply cleft; it 
looks as if two seedlings 
had fused together side 
by side. If the cleavage 
extends downwards into 
the hypocotylous region 
there are two separate 
groups of seed-leaves and 
these are frequently at 




Fig. 70. Acer Pseudo-Platanus. 
A tetracotylous seedling, the 
axis of which splits above the 
cotyledon. In the cleft two 
leaves are seen, the lower part 
of whose stalks are grown to- 
gether, back to back. (Spring, 
1887). 



different heights. There 
is obviously no danger of confusing such cases with 
tetracotyls, although the twin seedling does actually bear 
four seed leaves (Fig. 71). But if the division affects 
only the part of the axis above the seed-leaves, these 



Tricotyls, Hcuii-tricotyls, and Tctracotyls. 361 



stand in a whorl and the seedling cannot be distinguished 
from those in which the seed-leaves and not the axis have 
divided. Only after further growth its true nature can 
be decided. If, however, the doubling is continued with- 
out splitting of the stem, peculiar fasciated plants may 
be the result. In such cases the real state of affairs often 
remains hidden. 

In Amarantus spcciosiis especially, I have often ob- 
served such twins (Fig. 71), and also in Datura S tra- 
in onhun, Acer Pscudo-Platanus (Fig. 70) etc. 1 Fig. 72 
represents a section of a stem of a tetracotylous plant of 







Fig. 71. Seedlings of Amarantus speciosus. A, tetracotyl- 
ous ; B, twin, each of the split halves of the axis bearing 
two seed-leaves ; C, twin, one of whose halves is tricotyl- 
ous ; D, hemi-pentacotylous seedling, the sole instance of 
this case in a culture of over 20,000 seedlings ; E, Tri- 
syncotylous plant. Harvest of 1893. 



Ainarantns speciosus, which split at a considerable height 
above the insertion of the cotyledons and bore in the 
fork two leaves the midrib of which had grown together 
on the dorsal side up to within a short distance of the 
apex. In the axils of these leaves small branches were 
seen with a little terminal inflorescence and a small leaf 
inserted below this. Above this point the two branches 
of the fork were of normal growth. Fig. 70 represents 

1 See L. J. LEGER'S exhaustive work on the anomalies in the seed- 
lings of Acer Pseudo-Platanus. Bull. Soc. Linn. Normandie, 1889, p. 
199, with plate. 



362 



Tricotylows Races. 



a seedling of Acer Psciido-Platanits with four seed-leaves 
which I found in the spring of 1887 in a forest and trans- 
planted to my garden. Here it developed its stem. As 
soon as this had definitely split, and just before the cotyl- 
edons were about to fall away 
I dried this specimen in order 
to keep and photograph it. 

It is obvious that such twins 
do not belong to the tricotyl- 
ous race, that is to say, that 
their anomaly is due to some 
other elementary character. 
Therefore they should not be 
counted when recording the 
seedlings, nor be used as seed- 
parents. But as their nature 
can only be determined for cer- 
tain in some cases, it is not al- 
ways possible to take this pre- 
caution ; and the fact that the 
hereditary values obtained from 
tetracotylous individuals are 
sometimes worse than those 
from the corresponding trico- 
tyls may in part be due to this 
circumstance. 

For the rest tetracotyls do 
not in any essential respect be- 
have differently in inheritance 
from the tricotyls. From their 
seeds are produced, besides the atavists, mainly tricotyls, 
with hemi-tricotyls and tetracotyls in the usual dimin- 
ishing proportions. My tricotylous half race of Scrophu- 




Fig. 72. Amarantus specio- 
sus. Forking of a stem 
of a tetracotylous plant 
with two leaves in the 
fork which have grown 
together dorsally. The 
figure shows also their 
axillary twigs. 



Tricotyls, Hemi-tricotyls, and Tetracotyls. 363 

laria nodosa produced, in the harvest of 1894, a mean 
of 2% and a maximum of 5.5% tricotyls per seed-parent. 
I harvested the seeds from two tetracotyls and obtained 
0.5% and 3% tricotyls. Amongst the 2000 seedlings 
which these cultures contained, there were 30 tricotyls, 
3 hemi-tricotyls and only 2 tetracotyls. 

On the other hand a tetracotylous plant of Asperula 
azurca gave 7% and the corresponding tricotylous seed- 
parents only 2%, in 1892. Of this 7%, there were 5% 
tricotylous, 1% tetracotylous, and 1% hemi-tricotylous. 
I bred the tetracotyls of Amarantus spcciosus for two 
generations, in 1893 and 1894. In the summer of 1893, 
9 tetracotylous plants were left to flower ; 3 proved to be 
fasciated, but the rest gave values varying from 1 to 
7.5% with a mean of 5%. I counted for each seed- 
parent 500-1000 seedlings. The corresponding tricotyl- 
ous culture gave values from 2.5% to 7.5%, that is, a 
mean of 4.5%; from each of the 15 seed-parents from 
700 to 1000 seedlings being examined. We see there is 
practically no difference between the two cases. Together 
the tetracotylous parents produced only 6 tetracotylous 
offspring among 4000 seedlings, and the tricotyls 13 
among 10,000; that is to say, they behaved in regard 
to this character as variants of the same race. I then 
selected the tetracotylous offspring of the tetracotylous 
seed-parents for a continuation of the race in 1894, but 
observed no further progress, the percentage in tetra- 
cotyls being only 0.2%. 

The question suggests itself whether the proportion 
of tetracotylous seedlings, perhaps, simply obeys the laws 
of probability. The splitting of a cotyledon may be im- 
agined to be distributed at random over a group of say 
100 individuals, and we may ask, how many times a 



364 Tricotylous Races. 

seedling will have two such divisions and so become a 
tetracotyl or hemi-tetracotyl. If, for instance, 50 divi- 
sions are distributed over 100 seedlings, with 200 cotyl- 
edons, how often may we expect a single plant to present 
two such divisions? 

In the same way the expectation of pentacotyls may 
be calculated. Without going closely into this calcula- 
tion, it is obvious that the proportion of tetracotyls will, 
on the whole, increase with that of the tricotyls indepen- 
dently of course of the nature of the species in question. 
As a matter of fact we do not observe such an independ- 
ence. Some species are relatively rare in tetracotyls 
whilst others produce them more abundantly. Thus An- 
tirrhinum- ma jus never gave more than 1% to 2% of 
tetracotyls (Fig. 63 D, p. 345), although the proportion 
of tricotyls was as much as 79%. Ocnothera hirtclla, 
Scrophularia nodosa, and Cannabis sativa are also poor 
in tetracotyls. The latter produced only 1 to 3.5% of 
them, even when the whole value amounted to 63% (in 
20 individual records). On the other hand, other species, 
or at any rate the races of them which I observed, pro- 
duced tetracotyls abundantly. 

I have grouped together well over 100 separate rec- 
ords from my cultures of 1894-1896, in which the heini- 
tricotyls, tricotyls and tetracotyls were recorded sep- 
arately for each sowing, which almost always consisted 
of about 300 seeds. From these I have especially cal- 
culated, besides the percentage composition in split-leaved 
seedlings, the proportion of these to the tetracotyls ; and 
I give below the number of tetracotyls per 100 tricotyls 
in the wider sense of that term. This proportion varied 
in Amarantus speciosus, for 2-10% tricotyls, and in Can- 
nabis satira for 6-52%, between 1 and 7%. In Mcr- 



TricotylSj He mi-trie otyls, and Tetracotyls. 365 



ciirialis annuci for 8-86% tricotyls between 1 and 
in Silene inflata for 27-73%, in Clarkia pulchella for 
6-16% and in Helichrysum bracteatum for 3-41% tri- 
cotyls, from 2 to 28%. In the individual records this 
ratio is obviously subject to considerable fluctuation on 
account of the small number of tetracotyls in the indi- 
vidual crops, and for a proper estimation of this ratio 
cultures on a much larger scale and especially designed 
for this end would be necessary. Here I shall content 
myself with giving an experimental series obtained with 
Clarkia pulchclla, which shows roughly how the ratio 
of tetracotyls to tricotyls increases with the number of 
the latter. 

Percentage ratio of tricotyls 6 7 14 16 27 55 62 63 
Number of tetracotyls per 

every 100 tricotyls ... 15 5 26 5 10 18 22 20 

Similar figures were obtained with Phacelia tanaccti- 
folia, Pa paver Rhocas, Helichrysum bracteatum and 
Mcrcurialis annua. 



3. THE INFLUENCE OF TRICOTYLY ON THE ARRANGE- 
MENT OF LEAVES. 

Elementary characters are not as a rule betrayed by 
a single external characteristic, but by several. In most 
cases one of these can easily be recognized as the primary 
one, and the rest are then termed secondary. In other 
cases a doubt may arise as to which should be regarded 
as primary and which as secondary. White-flowered 
varieties of red or blue species often exhibit the absence 
of color in the fruits as well as in the leaves or the stem. 
Moreover they can frequently be recognized as early as 
in the seedling stage by their pure green color. My new 



366 Tricotylous Races. 

Oenotheras differ from the parent species in several char- 
acters ; nevertheless each arises suddenly with its char- 
acters complete. From this fact we conclude that all of 
them must be regarded as the expression of a single in- 
ternal change. A single new elementary character can 
thus affect more or less profoundly a whole group of 
older internal characters. 

We will regard tricotyly, for the present at any rate, 
as the primary expression of a definite internal factor 
which occurs in the latent state in large numbers of di 
cotyledons, though not necessarily in all. It also occurs, 
although as yet in a small group of cases, in the active 




c 



Fig. 73. Scrophularia nodosa. A tricotylous seedling with the 
first whorl of leaves which is ternary also; C, the cotyl- 
edons. From the harvest of 1899. 

state alongside dicotyly. On this point of view the ques- 
tion suggests itself whether this internal factor will per- 
haps also betray itself during the later life of the plant. 
Tricotyly results in an abnormal arrangement of the 
seed-leaves, and thus it is only natural to expect that its 
internal cause may lead to anomalies in the disposition 
of the foliage leaves as well. 

As a matter of fact, this is the case. In the first 
place, in species with decussate leaves, the arrangement 
of the leaves in whorls of three may continue upwards 
from the cotvlerlons (FiV. 73"). Tin's mav be limited to 



Tricotyly and the Arrantjeinenl of Lea-res. 367 



the lower whorls, or continue in all of them. In the first 
case the transition between the two arrangements is often 
effected by intermediate stages, such as cleft leaves. 1 
Other disturbances of the disposition of the leaves also 
can follow on tricotyly, amongst the most important of 
which are twisted and fasciated stems as well as the pro- 
duction of so-called terminal leaves. In the following 
paragraphs I shall describe some of the most important 
of these various phenomena which have occurred fre- 
quently, and in many cases almost regularly, in my ex- 
periments. 2 

It seems desirable to state beforehand that the anom- 
alies in question exhibit an obvious genetic connection 
with the splitting or duplication of the cotyledons, al- 
though this relation needs closer investigation. Other 
malformations of structure no doubt are also met with 
amongst tricotylous individuals (for instance, variegated 
leaves, prolification of flowers and flowerheads), but not 
more abundantly than elsewhere. Moreover it is by no 
means a rule that in all species the same anomalies should 
occur amongst tricotyls. It appears, on the contrary, 
that certain species, (or at any rate, certain commercial 
races of them), have a marked preference for definite ab- 
normalities, since both torsions and fasciations appear 
relatively abundantly amongst certain species, but rarely 
amongst others. In the same way subterminal leaves 
have hitherto been observed in quite a limited number of 
instances only. 

On this relation between tricotyly and abnormalities 
in the disposition of the subsequent leaves I have based 

1 DELPINO, Tcoria dclla FUlotassi. 

2 Further facts will be found in Eiue Mcthodc, Zzvangsdrehungen 
aufsusuchen, Ber. d. cl. hot. Ges., 1894, Vol. XIT, p. 25. 



368 Tricotylous Races. 

a simple method of searching for such anomalies. Fas- 
ciations are so common in nature and in the garden that 
special means for obtaining them are not required; but 
twisting is much rarer and ordinarily it is only by a lucky 
chance that we meet with an instance of it. 1 If we wish 
to become independent of this chance we must have re- 
course to the culture of variations of cotyledons, because 
such will offer a greater likelihood of furnishing the de- 
sired anomaly than other examples of the same species. 
In the first, or at least in the second, generation we may 
count on finding them, if the extent of the experiment 
is sufficiently great, and once obtained, they can easily 
be further improved by ordinary selection. A single in- 
stance will suffice. MORREN found a very fine specimen 
of twisting in Dracocephalum spcciosnm in a meadow not 
far from Liege, 2 and when I read his description I be- 
came extremely anxious to investigate such a case of 
torsion in this species, or at any rate in this genus. For 
this purpose I selected Dracocephalum moldavicum, 
which, being an annual, seemed more suitable. In the 
spring of 1892 I selected a single hemi-tricotylous seed- 
ling found in a sowing of commercial seed (a little less 
than 20,000 seedlings), and from this bred a race which 
in the first year exhibited nothing remarkable but pro- 
duced fasciations in the second year and traces of twist- 
ing in the third, and finally, in the fourth, some very 
fine instances of spiral torsion. One of these had the 
whole main stem transformed into a screw (Fig. 74). 
Fortunately in such experiments, the aim can be attained, 
as a rule, in a much smaller number of years. 

1 Monographic dcr Zwan^sdrehun^en. PUINGSHEIM'S Jahrb. f. 
wiss. Bot, Vol. XXIII, p. 116. 

z Bull. Acad. Roy. Bclg., Vol. XVIII, p. 37. 



Tricot yly and the Arrangement of Leaves. 369 

Tricotylous specimens of species with a decussate 
arrangement of their leaves very often produce the lower 
leaves of the stem in whorls of three. Sometimes this 
extends all the way up, or at least to the inflorescence, 




Fig. 74. Dracocephalwn moldavicum. Twisting of the 
main stem as the result of a breeding experiment ex- 
tending over four years. (Compare below Fig. 82.) 

sometimes, however, it reverts to the decussate arrange- 
ment sooner or later as we proceed upwards. Very often 
also the latter follows immediately on the seed-leaves 
(Fig. 76 B). All such cases can often be observed in 



370 



Tricotylous Races. 



the same culture from the seeds of a single seed-parent. 
This is especially the case in Antirrhinum majns and 
Scrophnlaria nodosa, in which species I have often pre- 
ferred as seed-parents, the tricotyls, whose first whorls 
were trimerous. Nevertheless they have not, as a rule, 
proved the better qualified to continue the character of 
the race. Further instances are afforded by Dipsacus 
sylvestris, Lychnis fulgens, Dracoccphalum moldavicwn, 

Dianthus barbatns and so 
on. In the spring of 1887 I 
had some tricotylous seed- 
lings of Acer Pscudo-Plata- 
nns ; two of them are now 
high trees, whose trunks bear 
their branches in trimerous 
whorls. 

The lateral branches of 
ternary main stems tend, as 

mi 

a rule, to revert to the de- 
cussate arrangement. Sub- 
terranean runners, (for in- 
stance in Valeriana officina- 
lis) and the secondary stems 
which are produced at the 
level of the ground (e. g., DiantJuis barbatus), afford, 
however, numerous exceptions. 

In tricotylous cultures, dicotylous individuals some- 
times become ternary later. Thus I possess a plant with 
ternary whorls of Aescithis Hippocastamnn (now 13 
years old), which only had two cotyledons, and from 
the same crop a plant which was tricotylous but has since 
produced leaves on the decussate plan only. In both 
specimens the change in the disposition of the leaves 




Fig. 75. Fagus syhatica. Tri- 
cotylous seedlings. A, with a 
ternary whorl of the first 
leaves ; B, with a leaf with 
two apices and a divided vein. 



Tricotyly and the Arrangement of Leaves. 371 

took place before the cotyledons were dead. In Dipsacus 
syhestris torsus, a race which is usually rich in ternary 
individuals, these are almost without exception decussate 
in early youth. 

On the boundary between the 2- and 3-merous whorls 
2 1 /i>-merous ones not infrequently occur. I mean whorls 
with one normal and one more or less deeply cleft leaf. 
All degrees of cleavage (or symphysis) may occur. In 
the tricotylous races of Antirrhinum ma jus and Scrophu- 
larla nodosa they are particularly abundant, and merge 




Fig. 76. Mercurialis annua. A, normal seedling; C, cotyl- 
edons, (i) the first, and (2) the second pair of leaves; 
B, a tricotylous seedling the first two leaves of which 
stand opposite one another (1900). 

into the decussate arrangement in the first or second or 
in some later whorl. In the choice of seed-parents I have 
always paid attention to this point, although it has only a 
secondary effect upon the result. Further instances of cleft 
leaves in the transition from tricotyly to the later normal 
arrangement were afforded me by Dianthns barbatus. 
Lychnis vespertlna, Polygonum Fagopynun, Collinsia hc- 
terophylla, Anagallis grandi flora and in large quantities 
by Fag-its sylvatica (Fig. 75) as well as by many other 
species. As the phenomenon is quite common when 
more extensive sowings are made and as, especially in 



372 



Tricotylous Races. 



perennial plants, the transition from one mode of ar- 
rangement to the other has been frequently observed 
on the same axis, as DELFINO has shown, I need not 
enter further into it now. Sometimes it happens also 
that the main stem of a tricotylous plant bears its leaves 
in quaternary whorls (Scabiosa atropurpurca). 

Fasciations are a frequent consequence of tricotyly, 

though they sometimes do not 
appear until late in the life 
of the plant. Mercurialis an- 
nua and Amarantus speeiosus 
furnished a series of instances 
nearly every year during sev- 
eral years of culture. In the 
former species they usually 
appear low on the stem; in 
the latter not below the in- 
florescence (See Fig. 83, p. 
399). My tricotylous race of 
Mercurialis anmia furnished 
almost all forms of fasciation. 
Fig. 77 represents a tricotylous 
plant whose stem was split 
from the first node after the 
cotyledons, and was therefore 
only fasciated in the epicotyl- 
ous internode. Between this condition and a flat stem 
one centimeter broad, and much contorted, all inter- 
mediate stages are presented by this species. In the 
spring of 1887 I collected a large group of hemi-tricotyl- 
ous, tricotylous and tetracotylous seedlings (See Fig. 
70) of Acer Pseudo-Platanus not far from Hilversum 
and grew them for several years. Most of them I threw 




Fig. 77. Mercurialis annua. 
A, tricotylous seedling with 
split stem ; B, a seedling the 
first whorl of leaves of 
which was ternary ; C, hemi- 
tricotylous plant (1900). 



Tricotyly and the Arrangement of Leaves. 373 

away as soon as they reverted to the decussate arrange- 
ment of their leaves, but seven of these trees are still 
alive, two with ternary stems (p. 370), two with a de- 
cussate arrangement of the leaves, and one with a much 
flattened main stem. This last one began with three 
cotyledons; it then became decussate, and in its second 
year (1889) became ternary again. In the autumn of 
the following year it began to flatten out, formed three 
five-leaved whorls and began to split when laying down 
the winter bud. I then broke off all the terminal buds 
except one, which in the spring of 1891, during sub- 
sequent growth, split into three flat twigs of which 
again two were removed. In the following summer the 
fasciation recurred, and also, after splitting in the win- 
ter, in the next year (1892), and again in 1893. Every 
time the forked branches were reduced to one. The 
divisions became much rarer, later on, and the older sec- 
tions of the stem which were at first flat gradually be- 
came cylindrical, as usually happens in fasciation when 
it affects trees. 1 

On tricotylous specimens I also observed flattened 
stems in Antirrhinum majus, Artemisia Absynthinm, Sca- 
biosa atropurpiirea, Dianthus plumarms, Collinsia hetero- 
phylla, C. grandi flora, C. violacea and Tetragonia e.v- 
pansa (Fig. 78) ; and amongst tetracotyls in Scrophn- 
larla nodosa and Collinisia violacea and other species. 2 

In many cultures I have observed that fasciations are 
more common amongst tricotylous plants than amongst 
dicotyloiis ones, but I shall only deal in detail with an 
experiment on Asperula azurea. In the spring of 1892 
I selected the hemi-tricotylous, tricotylous and tetra- 

*Kruidk. Jaarb. Gent, 1894, Plate XI, (Abies excelsa). 
*Ber. d. d. bot. Ges., Vol. XII, p. 38. 



374 



Tricotylous Races. 



cotylous seedlings from commercial seed of this pretty 
little annual (Fig. 79). I cultivated them and saved 
their seeds and in the following year planted out the 
variants and the atavists separately. There were 37 of 
the former group and 15 atavists. From the former 
there arose 28 flattened stems and branches ; from the 




Fig. 78. Tetragonia c.vpansa. A, branch split by forking; 
B, comb-like expanded terminal flower of a flattened 
main stem. 



latter only four, that is to say, a proportion of 75% and 
27% respectively. It should be mentioned that all the 
variants among the seedlings were planted out and that 
some of these gave rise to rather weak plants, whilst of 
the atavists I selected the strongest seedlings only. These, 
however, in spite of their greater individual strength and 



Tricot\l\ and the Arrangement of Leases. 375 



in spite of their origin from tricotylons parents, produced 
considerably fewer fasciations than the tricotyls. 

We come now to the spiral torsions. These occurred 
in several of my tricotylous races nearly every year since 
1893, and often in considerable numbers. As a rule they 





Fig. 79. Aspcrula azurca. 



Fig. 80. Melampyrum pratensc. 
Tetracotylous plant with spiral 
arrangement of leaves (1887). 



consisted of fairly long, much twisted sections of the 
main stem, or of the stronger lateral branches which 
abutted above and below on the normal or decussate 
sections. They bore their leaves sometimes in a very 
steep spiral and sometimes in an unbroken line on one 



376 



Tricotylous Races. 



side of the stem. 1 I found these torsions not only in 
my own races but also on tricotylous individuals raised 
from commercial seed of Anagallis grandi flora, Collinsia 
bicolor, C. heterophylla, C. violacea, Dianthus plurnarius, 
Fedia scorpioides, Scabiosa atropurpurea nana, Silene 
noctiflora and Zinnia elegans. Also in the second gen- 
eration of Asperula azurea setosa and Viscaria ocidata. 2 




Fig. 81. Antirrhinum majus. Seedlings with terminal leaves 
A, tricotylous ; the others are atavists from the same 
race. A, B, with a single terminal leaf ; C, the two 
leaves of the first whorl fused laterally and placed termi- 
nally; D, a terminal pitcher formed of two leaves. 

Lastly I wish to refer to a tetracotylous plant of 
Melampyrum prat ens e (Fig. 80), whose first leaves above 
the cotyledons, instead of being decussate, were arranged 
in a very irregular spiral. I found it in the summer of 
1887 growing wild not far from 'S Graveland. It is 
important, because it shows that even a splitting of both 

1 F-gured in Ber. d. d. bot. Ges., Vol. XII, PI. II, Figs. 9 and 10. 

2 Ber. d. d. bot. Ges., loc. cit., pp. 32-35 ; see the figures on Plate II 
of this article. 



Tricotyly and the Arrangement of Leaves. 377 

the cotyledons and especially a splitting equally deep on 
the two sides may involve an alteration in the disposition 
of the leaves. This, of course, is by no means a neces- 
sary consequence, but the present case indicates that the 
internal cause is not necessarily limited in its operation 
to the cotyledons. 

Terminal leaves have hitherto been regarded by tera- 
tologists as very rare occurrences, but my tricotylous 
races of Antirrhinum majns have afforded me the oppor- 
tunity of observing them repeatedly and in hundreds of 
specimens (Fig. 81). 

A well-known instance is the great terminal leaf of 
Gesncra Geroltiana described by MORREN and reproduced 
by MASTERS/ This specimen bears only one normal 
pair of leaves, and above these an erect leaf of double 
the normal size. In the figure we can see the node at which 
this is inserted; and the simplest explanation of this 
remarkable phenomenon is that, for some reason or other, 
the growth of the second leaf of the pair, as well as that 
of the terminal bud was impeded in early youth. BER- 
NOULLI mentions a similar apparently terminal leaf of 
Coffea arabica, and was able in this case to confirm the 
correctness of this supposition by microscopical obser- 
vation. 2 He also describes a shoot of Fuchsia macro- 
stem ma which bore a funnel-shaped leaf at the top. 

The races of the Snap-dragon, which we have already 
mentioned bear every variety of these structures. These 
may consist of single or of double leaves, or of leaves 
grown together in the shape of a funnel. All inter- 
mediate stages between these and the normal plants oc- 

J CH. MORREN, Bull Acad. Brig., Vol. XVII, Part II, p. 387; 
M. T. MASTERS, Vegetable Teratology, p. 88, Fig. 40. 

2 G. BERNOULLI, Ueber schcinbar terminate Blatter, Botan. Zei- 
tung, 1869, P- 19- 



378 Tricotylous Races. 

cur. These anomalies are found especially on the seed- 
lings and usually replace the first or second whorl of 
leaves and rarely the third or a higher one. In the 
spring of 1894 I had a large crop of the red flowered 
variety which produced about \% of these abnormali- 
ties amongst many hundred seedlings. In subsequent 
years I had even larger numbers. In the spring of 1897, 
for instance, I had about 10% in very extensive sowings 
of a tricotylous race with striped flowers. The most 
important cases are, of course, those in which the rudi- 
ments of the opposite leaf and of the terminal bud can 
be clearly seen with the naked eye alongside the terminal 
leaf. I have frequently planted out such plantlets in the 
hope of growing them for my experiments, but usually 
without success. Either they did not develop a main 
stem at all, or only a delicate one ; often there arose from 
the axil of one of the lower leaves or of one of the 
cotyledons a lateral branch which, however, remained 
weaklv. 

mt 

Sometimes the organ situated opposite the terminal 
leaf is somewhat better developed, but usually it cannot 
be seen without the help of a microscope. If the terminal 
structure has only one vein I regard it as a single leaf 
(Fig. 81 B). But if it has two points with a double or 
divided midrib (Fig. 81 C) it obviously represents the 
two leaves of a pair. Sometimes these are fused together 
laterally; the peduncle is, however, considerably broad- 
ened and its point of insertion clearly recognizable. Fre- 
quently, however, the peduncles are fused at their base, 
at both sides, and form a little tube which embraces the 
terminal bud. If the concrescence is of considerable 
extent terminal ascidiae are the result, which, in most 



Tricotylons Half Races. 379 

cases, can be clearly recognized as consisting of two 
leaves (Fig. 81 D). 

The fact that so rare a teratological phenomenon 
should occur so regularly in two well-known varieties of 
the same species, the one uniform red, and the other 
striped yellow and red means perhaps that the char- 



acter in question has existed for a long time in the Snap- 
dragon and will be found, after a close investigation, 
to exist in other cultivated varieties also and possibly 
even in the wild ancestral form. Of course the fact that 
I found them in a tricotylous race need not necessarily 
indicate a causal relation between this character and 
tricotyly, because, at the beginning of my cultures, I 
started by selecting the tricotyls and continued the race 
from their seeds alone. If such a relation did exist the 
fact that the anomaly occurs both on dicotylous and on 
tricotylous individuals would be very important, for it 
would show that it is not the visible tricotyly itself, but 
some corresponding internal character, which must be 
regarded as the cause. It is to be hoped that the abund- 
ance in which the anomaly can now be obtained will 
render possible a closer examination of this problem. 

4. TRICOTYLOUS HALF RACES. 

Occasional tricotylous seedlings will be found among 
samples of seed in very many species. All that is neces- 
sary, therefore, to start a culture is to buy a sufficient 
quantity of seed and to sow it. The seed will either 
give no aberrant forms, or very few, or a considerable 
number. In the first case the possibility of obtaining 
tricotyls still remains open if a larger quantity of seed 
is sown. In the second case the variants can be used as 



380 Tricotylous Races. 

the point of departure for the race ; they offer the prospect 
of providing a half race. In the third case we may ex- 
pect to obtain an intermediate race rich in tricotyls. 

Almost every year I have made experiments of this 
kind, but I was especially engaged with them in the 
spring of 1895. At that time I sowed about 20 grams of 
each of 40 species of annual plants, or in the case of 
very small seeds a somewhat smaller quantity, so as to 
investigate several thousand seedlings of each kind. I 
shall now give a list of the species falling into the third 
category, species, that is, which gave so large a number 
of aberrant forms as to justify the expectation of an 
intermediate race an expectation which has, as a rule, 
been fulfilled, as we shall see in the following section 
(5). 

TRICOTYLS FROM BOUGHT SEED. 
(Spring, 1895.) 

SPECIES DICOT- HEMI- TRICOT- TETRA- 

YLS TRICOTYLS YLS COTYLS 

Chrysanthemum inodoruin 

plenissimum .... 1000 3 32 

Silene orientalis alba . . 3000 3 70 

Papaver Rhoeas fl. pleno . 3000 1 15 1 

Clarkia pulchella alba . 4000 5 50 

Glaucium luteum . . . 16000 15 

Nigella hispanica alba . 10000 15 

Phacelia tanacetifolia . . 16000 8 18 

Helichrysum bracteatuni . 35000 9 16 3 

With the exception of Silene, Glaucium and Nigella, 
I have raised intermediate races from all these sowings. 
As I have already mentioned, hemi-tricotyls and tetra- 
cotyls are seen to be rarer than the typical tricotyls. A 
sample of seed of Lobelia Erinns, grown in the spring 
of 1902, had a very high proportion of tricotyls, viz., 
31 in 100 seedlings. 



Tricotylous Half Races. 381 

Very small proportions of tricotyls were yielded by 
Silene hirsuta, which only produced 3 in 80,000 seed- 
lings. The following species produced from 1-2 speci- 
mens in every 10,000 seedlings: Argemone grandiflora, 
Aster tenellus, Clarkia elegans, Godetia ainoena, Hyos- 
cyainus pictus, Silene Armeria, and others. I observed 
no tricotyls at all in sowings of the same extent of 
Argemone mexicana, Datura lacvis, Hyoscyamus albtis, 
Nigella damascena, Phacelia texana etc. I tested 800 
seeds of each of 8 species of Cerinthe, and only obtained 
a single tricotylous plant in C. bicolor, C. gymnandra 
and C. major. 

The seeds mentioned were all obtained from the 
nursery of Messrs. HAAGE & SCHMIDT in Erfurt. It is 
not unlikely that if the seeds were bought from other 
nurseries, different results could be obtained, especially 
from firms who do not exchange seed with the nurseries 
at Erfurt. 

Similarly the seeds of wild species occasionally pro- 
duce tricotyls, but, as it seems, only in very small quan- 
tities, and they have hitherto given no promise of yield- 
ing an intermediate race. As instances I mention Ra- 
phanus Raphanistrum and Epilobium hirsutum, of which 
species I found 1-2 tricotyls in large crops. If the seeds 
of wild species come from botanical gardens the pro- 
portion of tricotyls is sometimes greater; for instance 
in Silene noctiflora (1892) it was about 20 in 10,000 
seedlings. Amongst trees I have hitherto found tri- 
cotylous seedlings abundantlv in Acer Pseudo-Plat anus 
and Fagus sylvatica and also in Robinia Pseud-Acacia 
and Ulmus campestris. 

In order to test the hereditary capacity of the cotyle- 
don variants in such crops, I have frequently planted 



382 Tricotylons Races. 

them out and allowed them to flower in isolation. 
Higher proportions are thus obtained : for instance in 
cultivated species in Celosia cristata 2%, in Chrysan- 
themum Myconis 1-2%, in Oenothcra lone/if olia \%, 0. 
mollissima \%, 0. undnlata, 1%, Xylopleurum tetra- 
ptcrum 2%, Podolepis gracilis 2%, Tetragonia c.vpansa 
2%, Veronica longi folia 4% ; and amongst wild species 
in Chenopodmm album \%, Thrmcia hirta 1%, and so 
forth, the two latter having been grow for three genera- 
tions. Further instances will be afforded by the be- 
ginnings of my cultures to be mentioned below. 

If we compare the proportions just given, excluding 
those species which are so rich in tricotyls that they 
probably contain an intermediate race, we find from 
0-2 tricotyls in about every 10,000 seeds, from mate- 
rial which has been bought or obtained by exchange or 
collected in the field, whilst the harvest obtained after 
the isolation of the tricotyls, contains from 1-2%. The 
original mixtures, therefore, must have contained the 
seed of many individuals without tricotylous offspring. 

Besides the hereditary capacity of bought seed and 
of the tricotyls raised from it after artificial fertilization, 
we have to consider the question whether this capacity 
can be increased by a selection extending over several 
generations, or whether it maintains itself without chang- 
ing. As I have already stated, the conclusion derived 
from my experiments is that the answer may fall into 
one of two categories. In some species selection may 
soon lead to a proportion of 50% tricotyls and more; 
in others, this does not take place even if the selection 
is continued for many years. Obviously this depends 
on the question whether an intermediate race is present 
in the given sample of seed, or not. If it is there, it 



Tricotyloiis Half Races. 383 

can be isolated immediately; if it is not, no amount of 
selection will bring it about. The experiments in which 
isolation succeeded will be described in 6; but the ex- 
periments which failed fall into two groups, according 
to whether it could be decided immediately, or not until 
much later, that an intermediate race could not be raised. 
In the former group fall those cultures in which there 
was no progress at all, or so small a one that I had to 
give them up after three or four generations. For if, 
after this time, a proportion of no more than from 1 to 
2 or at most 4% is reached, or if in the case of higher 
proportions the ratio fluctuates greatly but does not ex- 
hibit a regular increase, how many years of work would 
it take before we can be certain that nothing can be at- 
tained? These briefer experiments will form the sub- 
ject of this section. 

In the second group fall two cultures which I have 
continued for a considerable time, namely Amarantus 
speciosus through nine generations and Scrophularia no- 
dosa through ten. Neither now leaves any hope of ever 
becoming successful (see 5) ; but, as I have already 
said in the first part of this volume (p. 227), it is just 
the experiments in selection that fail, which give us the 
deepest insight into the nature of elementary characters. 

I shall now proceed to the description of my ex- 
periments; and I shall confine myself to those which 
were instituted with the express hope of breeding a 
tricotylous intermediate race, and were continued for 3 
or 4 generations with this sole object in view, until it 
became evident that only a half race was present. The 
extent of the cultures varied greatly, according to the 
importance which I attached to them at the beginning. 
In the first place I shall deal with Ocnothcra rubrinervis. 



384 Tricotylous Races. 

Oenothera rubrinervis. In the pedigree of the Laevi- 
folia family on p. 273 of the first volume, the origin of 
two specimens of 0. rubrinervis is recorded for the year 
1889. In the generations which were raised from these 
two mutants, no tricotyls were at first observed (1890- 
1891). They first appeared in the spring of 1892, and 
with them the culture of the tricotylous half race began. 
I selected the tricotyls from amongst thousands of seed- 
lings and planted them out singly in pots with well 
manured soil. I obtained 22 strong plants which flowered 
freely in an isolated spot. The seeds were saved sep- 
arately from each parent, each of which was labelled 
according to its individual vigor. The five strongest 
plants gave respectively 1.5, 1.9, 2.3, 2.6, and 2.8% trico- 
tyls amongst from 700 to 900 seedlings. The remainder, 
the weaker plants, only 0-1% with an average of 0.7% 
amongst 8000 seedlings. The value 2.8% was obtained 
from a very vigorous plant ; in the three following gen- 
erations it has hardly been reached again, in spite of 
selection, and never was really exceeded. 

The offspring of only the five best plants were 
planted out and in all cases only tricotylous individuals. 
There were about 70 of them and they were potted singly 
and well manured (1893). In the middle of May they 
were planted out into the bed at distances of about 30 
centimeters apart, where they flowered in isolation in 
August, and could be mutually fertilized by insects. In 
the spring of 1894 the seed of each plant was sown sep- 
arately, and when the cotyledons had completely unfolded 
the seedlings were recorded, 300 for each parent but 
1000 or more in the 20 which appeared to be the best. 
Altogether 45,000 seedlings were recorded, and amongst 
these were 170 tricotyls, i. e., about 0.4%. Of these 



Tricotylous Half Races. 385 

12 were hemi-tricotyls and one was a tetracotylous speci- 
men. There were also some few syncotylous ones. The 
ratio from the best seed-parents was no more than from 
0.8% to 1.1%. The tricotylous offspring of these and 
of some with from 0.5 to 0.6% were planted out in the 
same way as in the previous year, provided they were 
strong little plants. This time the inflorescence of each 
plant was guarded against the visits of insects by means 
of a parchment bag and artificially fertilized in the hope 
of thus isolating individuals producing higher propor- 
tions. 

On page 354 I have plotted, in Fig. 66, a curve of the 
harvest of 1894, based on the records made in the spring 
of 1895. There were two seed-parents which manifested 
an advance on the previous year, inasmuch as their ratio 
was 3.5% and 3.7%, but the difference was only a 
very inconsiderable one. In all, there were 87 seed- 
parents. As I had planted the offspring of the individual 
grandparents of 1893 together in groups in 1894, I 
could now make a selection not only between the parents 
but also between the grandparents. The grandchildren 
of those grandparents only, whose offspring had pro- 
duced the highest mean proportion, were planted out. 
By means of such a selection of grandparents the pedi- 
gree becomes an individual one in spite of the size of the 
-ultures, embracing, in each generation the offspring of 
one selected individual only. The method, therefore, 
unites this principle with the greater certainty that can 
be obtained by extensive cultures and a double selection. 
I have also applied it to a number of other cases. 

From one grandparent with 1%, therefore, and from 
six of its offspring with from 0.9% to 2.1% 54 tricotyl- 
ous specimens in all were planted out (1895). From the 



386 Tricotylous Races. 

beginning of the flowering period all these were covered 
with fine gauze, guarded from the visits of insects and 
artificially fertilized every day or every other day. About 
300 seedlings of each plant were recorded. The ratios 
were from to 1.2% with an average of 0.8%. Two 
parents had 1.4% and one 2%, that is to say, that here 
again there was no progress. The offspring of the six 
parents fell into groups between which the differences 
were but slight (3 with 0.7%, and 3 with 0.8% on the 
average). 

In the list which follows I have collected the highest 
values that were obtained in the course of these genera- 
tions. 



-SPRING OF- 



1893 1894 1895 1896 

Highest values 2.8 % i.l % 3.7 % 2.0 % 

Selected seed-parents 2.8% 1.0% 2.1% 

These figures show a fluctuation within fairly nar- 
row limits, but no essential advance in the course of four 
generations. It seemed therefore to be useless to carry 
the experiment further. It is certainly probable that, 
in the course of time, further selection might have 
brought about some slight improvement; but obviously 
this would have been of little significance, and at any 
rate there was no prospect of ever obtaining a race with 
50% tricotyls. 

Chenopodiinn album. A tricotylous plant flowered in 
1889, in isolation in my garden, and produced 1% tri- 
cotyls in the spring of 1890 amongst about 1000 seed- 
lings. Four of these were cultivated further, but their 
seeds gave rise again to no more than 1%. The third 
generation was therefore not better than the second. 

Dracocephahnn nwldaiicuin (Fig. 82). In the spring 



Tricotylous Half Races. 



387 



of 1892 I obtained only a single hemi-tricotyl from about 
20,000 bought seeds. The seeds of this plant gave rise 
in 1893 to live tricotyls and two hemi-tricotyls among 
4000 seedlings, that is, about 02%. Their seeds were 
harvested separately, and as the expectation of tricotyls 
was a small one, great quantities of it were sown, 
recorded from 800 to 2900 from each, i. e., altogether 
about 15,000 seedlings, and 
found the ratio of tricotyls 
(and hemi-tricotyls) to be 
from 0.2 to 0.4%. It did not, 
therefore, seem justified to 
make a selection among the 
individual seed-parents. In 
1894, 12 tricotyls the stems of 
which had remained ternary, 
and twelve specimens with 
normal decussate stems were 
planted out. Several beauti- 
ful fasciations and occasional 
cases of spiral torsion oc- 
curred in this culture (p. 369) . 
The seeds were harvested sep- 
arately. In the spring of 1895 
they again produced only 
from 0.1 to 0.4% of tricotyls. 
Seventeen specimens from the 
seed pans with from 0.2 to 0.4% were planted out about 
a meter apart, but the seeds produced, in 1896, scarcely 
any tricotyls and only from five seed-parents, the pro- 
portion being from 0.3 to 0.7%. 

In the course of four generations selection had, there- 
fore, brought about practically no advance. 




Fig. 82. Dracocephalum rnol- 
davicum. A whole plant. 



388 Tricotylons Races. 

Lychnis fulgens. The tricotylous seedlings of this 
species are as a rule weakly; their culture, therefore, is 
difficult and their harvest poor. In 1892 I had a tri- 
cotylous plant whose seeds gave a proportion of 5%. 
From these I reached, in the spring of 1894, a ratio of 
13 % containing one tetracotylous plant; most of the 
tricotyls afterwards remained ternary. In 1895 they 
produced tricotyls in proportions varying from 3 to 1 1 % , 
with a mean of 6%. In the next, i. e., the fifth genera- 
tion (spring of 1896), I counted from 2 to 8% tricotyls 
per seed-parent, and from a particular individual 21 tri- 
cotyls amongst 110 seedlings, i. e., about 19%. But the 
number of seedlings in this case was too small to signify 
a real advance. 

Penstemon gentianoides. In 1892 I had raised four 
tricotylous plants from bought seed. They produced 
respectively 0.3, 1.0, 2.6 and 3% tricotyls in 1893. I 
planted out the tricotylous seedlings of the best seed- 
parent, but only six managed to flower. Their seeds gave 
ratios varying from 4% to 12% (March 1892), with a 
mean of 7%. The tricotylous seedlings of those seed- 
parents only which had ratios above 10% were planted 
out. Of these 8 tricotyls, 6 hemi-tricotyls and 2 tetra- 
cotyls have flowered. The seeds of the former gave 
ratios of tricotyls, ranging from to 3.3% with a mean 
of 2.8%; the hemi-tricotyls from 1.2% to 2.4% with a 
mean of 4.8% ; and the four tetracotyls 10% and 11%, 
amongst which, however, only a single seedling had four 
cotyledons. The offspring of both of these tetracotyls 
and of the best of the remaining seed-parents were 
planted out in 1895. Only in the case of eight plants, 
however, was the harvest a sufficient one and gave a 
ratio which as a rule was between and 12% and which 



Tricotylous Half Races. 389 

attained its maximum in lS f /c. The latter occurred 
amongst the 300 seedlings from the seeds of a daughter 
plant of one of the two tetracotylous grandparents. 

In the last three generations the maximum ratios 
were, therefore, 12, 11 and 15%, indicating no advance 
of any significance. 

Polygomim Convolvulus. A tricotylous plant flow- 
ered in 1888, in isolation, in my garden. Its seeds gave 
rise to normal seedlings only (1889). From their seeds, 
about 4000 in all, 1450 seedlings were raised, and 12 of 
them were tricotylous, i. e., \% (1890). I harvested the 
seeds of six tricotylous plants separately, and obtained 
ratios from 1% to 2.4% in sowings of about 1000 seeds 
each. Of these, 12 seed-parents produced only about 
1% in the next generation in the spring of 1892; two 
of them, however, produced 1.5 and 2%. Seventeen 
plants were planted out. In their crop (April 1893) the 
proportion of tricotyls varied from 0.5 to 2% in lots of 
200 and 400 seedlings, and twelve tricotyls succeeded in 
flowering. The next generation (April 1894) contained, 
in the best cases, 2.8% tricotyls; the next one, to 2% 
from 8 seed-parents (1895) ; and the last, or ninth, again 
2% only. 

Silcnc conica. In 1892 I had a few tricotyls in 
flower from seed received by exchange from another 
botanical garden. Their seed gave 3 tricotyls amongst 
1000 seedlings. I planted these out, together with some 
dicotylous seedlings, and in May 1894 I had from 0.2 
to 1% tricotyls in every lot of 350 to 800 seedlings. 
Eight tricotyls were planted out and in the spring of 
1895 their harvest gave a proportion of only 2% and 
less. From these I obtained in 1895 a fourth generation, 



390 Tricotylous Races. 

the seeds of four seed-parents producing no tricotyls 
and those of one, 2 amongst 500 atavists. 

Silcne conoidea, like the foregoing species, was ob- 
tained by exchange in 1892 and gave a single tricotylous 
seedling. In the following spring I had about as many 
tricotylous seedlings as in the previous species; and in 
the succeeding generation (1894) 3% tricotylous plants 
amongst 407 seedlings from seeds of a single tricotylous 
seed-parent. Only these 12 tricotyls were then planted 
out; and their seeds were harvested separately in late 
summer. In every lot I recorded from 300 to 900 seed- 
lings and only in two cases, where the harvest had been 
too small, so few as 200. The sowings contained, as a 
rule, from 0.5 to 1.5% and only in one case, amongst 
316 seedlings, 3% tricotyls. All the vigorous tricotylous 
seedlings were planted out in such a way that the off- 
spring of the individual seed-parents stood in groups. 
Their seed was harvested from each seed-parent and 
sown separately; and the proportion of tricotylous indi- 
viduals was determined for each among 300 seedlings. 
This proportion fluctuated, for the 26 seed-parents, be- 
tween and 4.2%. The separate groups manifested no 
relation to the hereditary index of their several seed- 
parents. The offspring of parents with 0.5% and also 
of those with 2% and 3%, had, as a rule, 0.6%. On 
the other hand the offspring of seed-parents with a mean 
of 1 % exhibited this mean ratio of 1 % again, and the 
highest figure obtained in this experiment, 4.2% oc- 
curred amongst them. 

The maximum values in the three succeeding genera- 
tions were therefore 3, 3 and 4%, i. e., they were fairly 
constant. 

In Silcne noctiflora. also, I have studied tricotyly 



Tricotylous Half Races. 391 

through the course of four generations (1891-1894), 
and found it heritable to the extent of from 1 to 2%, 
but I have not made any detailed records. 

Spinacia olcracca. The spinach also contains tri- 
cotylous seedlings. I employed the Dutch spinach with 
smooth round seeds without thorns, a fine and perfectly 
constant type. In 1892 I found a tricotylous specimen, 
and grew this amongst some normal plants, because the 
species is dioecious. When the harvest was first exam- 
ined there proved to be five tricotyls and one hemi-tricotyl 
amongst 1000 seedlings, i. e., 0.6%. Then the best tri- 
cotyls were selected from several thousand seedlings ; 
thirteen being met with. During the flowering period, 
several of them proved to be monoecious, a phenomenon 
which sometimes occurs in this species and has been ob- 
served also in Cannabis saliva, Mercurlalis anmia, and 
others. I harvested the seeds separately from 5 female 
or monoecious plants, and obtained ratios of 0, 0, 0, 1 and 
2% tricotyls amongst the seedlings, of which only 4 
managed to flower. They were one male and 3 female 
plants which latter set an abundance of seed. They gave 
ratios of 0, and 2%, the latter occurring amongst 430 
seedlings. In the summer of 1895 the tricotyls flowered, 
and I collected the harvests of the various female plants 
separately, and thus was able to determine the proportion 
of tricotyls for each parent in the spring of 1896. This 
fluctuated between and 3% and in one case reached 
4% (mean 1.5%). 

Summary: The results of the experiments described 
show that, in the cases dealt with, a stringent selection, 
extending over three years, failed to effect any definite 
and certainly any considerable advance. The individual 
instances fall into two categories ; as a rule the propor- 



392 



Tjricotylous Races. 



tion of tricotyls was 1 to 2% and reached 3 and 4% 
so rarely that these numbers must perhaps be regarded as 
the extreme results of the errors of observation which 
are bound to occur in such countings. In two species 
the ratio was about 10 to 15%, but these were both 
perennial forms which, in my annual cultures set but little 
seed. They were Lychnis fulgens, from 1892 to 1895, 
with 5- -13- -11 and 8 19% tricotyls and Penstemon 
gentianoides in the same years with 3 12- -11 and 15%. 
They should perhaps be excluded from further considera- 
tion. Summarizing my data therefore (with the omis- 
sion of these cases) we obtain a very uniform picture 
of the inheritance of tricotyly in half races under con- 
tinued selection. 

INHERITANCE OF TRICOTYLY IN HALF RACES UNDER 

CONTINUAL SELECTION. 





L 


MAXIMUM VALUES IN THE 




v W O 

>^ ^^ 


SPRINGS OF 




fe W ^ 


' 












s 




o 


1890 


1891 


1892 


1893 


1894 


1895 


1896 


Oenothera rubrinervis . 


1892 











2.8 


1.1 


3.7 


2 


Chenopodium album . 


1889 


1 


1 

















Dracocephalum moldavicum 


1892 











0.2 


0.4 


0.4 


0.7 


Polygomnn Convolvulus 


1888 


1 


2.4 


2 


2 


2.8 


2 





Silene conic a 


1892 


__ 








3 


1 


2 


4 


" conoidea .... 


1892 











3 


3 


4 




Spinacia oleracea .... 


1892 











0.6 


2 


2 


4 



Thus we see that tricotylous half races exist which 
even under the most stringent selection can produce only 
small percentages of this anomaly. So far as we can 
conclude from indirect data, half races of this kind ap- 
pear to be widely distributed in the vegetable kingdom. 
Samples of seed, whether they be bought or collected in 



Tricot ylous Races Do Not Arise by Selection. 393 

the garden or in the field, which give rise to no more than 
occasional aberrant forms amongst about 10,000 seed- 
lings, as a rule strongly suggest the existence of such 
half races. 

5. TRICOTYLOUS INTERMEDIATE RACES DO NOT 

ARISE BY SELECTION. 

In the first part of the first volume I brought to- 
gether a long series of facts from botanical and horti- 
cultural and, most important of all, from agricultural 
literature, which afforded sufficient proof that specific 
characters do not arise by selection. 

Applied to tricotyly, the truth of this generalization 
is demonstrated by the results of the experiments de- 
scribed in the foregoing section (4) and summarized 
in the table on the preceding page. This result is in com- 
plete agreement with my experience in regard to the 
origin of species and constant races in other cases. In 
contrast to these the so-called improved races of the 
agriculturists which have arisen by artificial and re- 
peated selection are constant only to a small extent (VoN 
RUMKER). On the other hand the so-called heritable 
or constant races do not arise by selection, with however 
much acumen and perseverance it may be prosecuted. 1 
The distinguishing terms are, I admit, not very practical 
and open to much criticism. The two kinds of races 
which they indicate are, however, absolutely distinct 
things, among wild plants as well as among cultivated 
species; but, unfortunately, if we only have a single in- 
dividual before us we cannot, as a rule, determine to 
which of the two types it belongs. Only its progeny can 
decide, and even this, often not until after the lapse of 

1 See Vol. I, p. 106. 



394 Tricotylous Races. 

several generations. But, at the beginning of our cen- 
tury, we stand only on the threshold on which systematic 
botany must be raised from a comparative to an experi- 
mental science. 

The experiments described in the foregoing section 
(4) cover four generations as a rule, i. e., a selection 
of tricotylous plants four times repeated, and thrice re- 
peated for those with apparently the highest values. It 
may, however, be allowable to suppose that stray un- 
favorable individuals occurred amongst the selected ones 
and that a selection of longer duration might possibly be 
crowned with success. 

In order to determine this point I have, as I have 
stated above on page 383, continued the experiment with 
two species, to which I have lately added a third, through 
about ten generations. I devoted every possible care to 
the selection and carried it out on as large a scale as 
could be desired. The result was a genuine progress 
which amounted in both cases from one or two per cent to 
a value which reached in the seeds of some rare seed- 
parents, even as much as 25%. But from the character 
of an intermediate race with a mean value of 50% the 
races are still far removed, and every circumstance points 
to the conclusion that it is simply impossible to reach 
this by the method (as yet the only available one) which 
was employed. 

The two plants used in these experiments were Aina- 
rantns speciosus and Scrophularia nodosa. The former 
is an annual garden plant, much in favor on account of 
its height and its red foliage (Fig. 83) ; the second is a 
wild perennial species which is very common in this 
neighborhood. It flowers in its first year and can be 
easily cultivated as an annual. In the previous section 



Tricotylous Races Do Not Arise by Selection. 395 

(4) these two species were omitted from consideration 
in order to describe the experiments here in their en- 
tirety. 

The hope which I cherished at the beginning of these 
experiments has not been fulfilled, it is true; but I think 
that a brief notice of it will serve a useful purpose. The 
present form of the theory of selection would justify 
the expectation that a continued selection of the tricotyl- 
ous individuals would result in a race which should, 
year after year, produce tricotyls in continually increas- 
ing quantities, until ultimately a new variety or sub- 
species would arise, composed solely of such individuals. 
This form of the theory is very accommodating. If we 
have regard to the law of regression (Vol. I, p. 83), the 
mean of the race always lags further behind the indi- 
viduals which have been and are to be selected ; so that, 
as a matter of fact we never attain to the type of a new 
and constant race. But if we neglect this law, as is now 
frequently done, we might expect that continual and 
uniform progress, which alone could account on the 
ground of the theory of selection for the origin of spe- 
cies in the vegetable and animal kingdom. And lastly 
we might assume an increase of variability in the chosen 
direction by means of selection, an hypothesis which, as 
I have shown in the first part (p. 9), is entirely unsup- 
ported by evidence. 

The first of these hypotheses would lead us to ex- 
pect a variable tricotylous race, never becoming perfectly 
constant, a thoroughbred race in the agricultural sense 
of the word. The second would lead us to expect a con- 
tinuous and uninterrupted increase in tricotylous indi- 
viduals resulting in a constant tricotylous subspecies. 
The third would point to a gradual acceleration of the 



396 Tricotylous Races. 

process. As a matter of fact neither one nor the other 
has occurred. If we would speak of a thoroughbred 
race I only obtained a thoroughbred half race with a 
mean value of no more than 10 to 15% which remains 
dependent on the selection of seed-parents with about 
25%, and is perhaps capable of some very small further 
improvement. The second hypothesis is so remote from 
facts that as yet it hardly admits of being tested ; my 
experiments at any rate, lend no support to it. Rather 
might they be taken to be in favor of the third view ; 
for the progress does actually seem to become gradually 
more rapid after the first few years. But then it should 
be remembered that selection is at first a very difficult 
matter, the tricotyls being still very rare, and for a large 
part delicate and unfit for further cultivation. In sub- 
sequent years there are hundreds of tricotyls from which 
the strongest may be selected ; and we can even limit 
ourselves to the best specimens produced by the best 
parents and grandparents, and thus carry out a much 
more stringent selection. In reality the acceleration of 
the progress is thus brought about by a practical im- 
provement in method and not by a biological increase in 
variability. 

At first I entertained the hope that even if these ex- 
pectations were not justified some relation between varia- 
bility and mutability might perhaps exist. 1 I imagined 
that the capacity for producing mutations might be con- 
ditioned by external influences and therefore might it- 
self be a variable character. The diversity amongst the 
mutation-coefficients of my Oenotheras seemed to sup- 
port this view. 2 Moreover the external conditions which 

1 See my Intraccllular Pangenesis. 

2 See Vol. I, p. 337. 



Tricotylons Races Do Not Arise by Selection. 397 

shift the variability in the half race in the phis direction 
might perhaps be the same as those which would lead 
to a mutation and thereby to the sudden origin of a 
rich intermediate race. This would, in fact, perhaps, 
constitute the smallest step amongst all the possible forms 
of mutation. 1 If a mutation were ultimately to be in- 
duced by an improvement in the external conditions and 
by the choice of individuals thus modified in the desired 
direction, 2 it should most easily occur on the limits be- 
tween the half race and the corresponding intermediate 
race. My hope was, therefore, that an intermediate race 
would suddenly arise from my improved half race and 
at first give about 50%, and then, by further culture, 
yield still higher numbers, perhaps even 80 to 90%. 
This hope was based on the analogous case of the origin 
of Chrysanthemum segctum plenum from C. segetum 
grandiflorum; for in this way tricotylous races behave 
when they happen to be found and are isolated (see 6). 
A step of this kind I have, however, not yet observed. 
In the case of both species I have determined the heredi- 
tary capacity of as many as 300 seed-parents in a single 
year, but without result. I have employed every device 
of culture and in Scrophidaria I sowed the seeds of the 
second and sometimes those of the third year of the life 
of the plant; but every advance was followed by a step 
in the reverse direction. I believe that I have tried every- 
thing that was possible to me at the time, and I have 
continued to make every conceivable effort in spite of the 

1 See p. 20 ; with regard to premntation. Vol. I, p. 490 ; and with 
regard to varieties and subspecies, p. 64 of this volume. 

2 Alimentation et selection. Volume jubilaire de la Societe de 
Biologie, 1899; and Vol. I, p. 142 of this work where the statement 
is made that "selection is the choice of the best nourished individ- 
uals." 



398 Tricotylous Races. 

fact that the goal became ever more obviously unattain- 
able; but nothing I did was of any avail. The half races 
remained half races, and the prospect of attaining an 
intermediate race is no greater now than it was at the 
beginning. 1 

I shall proceed now to the description of my two ex- 
periments. 

Amarantus spcciosiis (Fig. 83). In 1889 I had a 
tricotylous and a hemi-tricotylous specimen of this fine 
garden plant, which usually attains a height of from 
1 1 /2 to 2 meters. They flowered together, but far removed 
from any other specimens of the same genus. 2 I har- 
vested the seeds separately, but only sowed those of the 
hemi-tricotylous plant. This had a small comb-shaped 
extension of the summit of the raceme as is shown in 
Fig. 83, and as it afterwards often occurred in this race. 
Its seeds gave rise to four tricotyls and one hemi-tricotyl 
amongst 110 seedlings, that is, a proportion of about 
4.5%. The degree of inheritance therefore proved to 
be greater than in most of the other half races investi- 
gated (4). The culture was, however, unfavorable, 
since only one hemi-tricotylous plant could be brought 
to flower, and since therefore a number of atavists had 
to be cultivated with it as a precautionary measure ; but 
T only saved the seed of the hemi-tricotylous plant. This 
produced 6 tricotylous and 5 hemi-tricotylous seedlings 
amongst 250, that is, about 4.5% or the same amount 
as in the previous generation. This time, however, I 
could plant out the aberrant forms only and I managed 
to keep the majority of them alive. Only one, however, 

1 Mutations must, nevertheless, have external causes, and these 
must be found some day, but perhaps by some other means. 

2 Amarantus sficciosus is regarded by some authors as a sub- 
species of A. paniculatus. 



Tricot vlous Races Do \of .Irise by Selection. 399 

flowered. It was a richly branched compact tricotylous 
specimen, which was only a meter high. It set an 
abundance of seed, which produced a proportion of hemi- 
tricotyls and tricotyls, much greater than that attained 




Fig. 83. Ainaranius spcciosus. Top of a plant of two 
meters height from the tricotylous half race. 

in the previous generation. There were 89 aberrant 
forms amongst 700 seedlings, that is, about 13%. 
A very considerable advance had therefore been made 



400 Tricotylous Races. 

in the fourth generation (1892) and this has been main- 
tained since that time in spite of considerable fluctuation. 
Up till that time my selection had been limited by the 
fact that only hemi-tricotyls had survived to become seed- 
parents. From this point onwards I had both hemi- 
tricotyls and tricotyls in abundance. For the next four 
years I selected in these two directions, and maintained 
a tricotylous and hemi-tricotylous race simultaneously 
(1892-1896), but as no essential difference was mani- 
fested between the two I abandoned the hemi-tricotylous 

*> 

race, as stated in 2, and only went on with the tricotyl- 
ous one. The account which follows relates solely to this. 
But before I proceed with it I wish to call attention 
to some facts relating to the method of culture. The seed 
was sown in sterilized soil in pans ; the soil was not 
manured. As soon as the cotyledons had fully unfolded 
and before, the first leaf was visible, the seedlings were 
recorded. All, or nearly all, of the dicotylous ones were 
destroyed and only the aberrant forms saved. Of the 
latter I chose what I considered to be a sufficient number 
of the strongest specimens, and planted them singly in 
pots with heavily manured soil. The best manures for 
this purpose are nitrogenous ones. If the number per- 
mits it, two tricotyls are put in each pot, of which the 
weaker is subsequently killed out. This transplantation 
takes place in April or May ; the pots are kept under glass 
in the garden until June, during the nights at any rate. 
Then the plants are planted out into the bed at distances 
of from 20 to 30 centimeters, and the larger lateral 
branches are cut off in order that the plants may not 
interfere with one another. The plants are monoecious, 
the male and female flowers standing close together. 
Self-fertilization seems to be the rule; for isolated plants 



Tricot y Ions Races Do Xot Arise by Selection. 401 

set as much seed as those grown in groups. The seeds 
do not fall out and as soon as the desired quantity is ripe 
the whole raceme is cut off and rubbed between the hands. 
One cubic centimeter per plant, and often less, is suffi- 
cient for next year's seed ; as a rule I obtained about 
4 to 5 cubic centimeters from each individual. 

After the transplantation of the seedlings the length 
of the cotyledons, and of their stalks especially, increases 
considerably. In this way it may happen that specimens 
which, at their first examination, appeared to be pure 
tricotyls are found to have two of their cotyledons united 
at the base, and therefore to be deeply cleft hemi-tricotyls. 
I have as a rule removed such specimens when I discov- 
ered them, and not cultivated them further, although this 
is not actually necessary. 

In the summer of 1892 I had 11 tricotylous speci- 
mens which flowered in a group as far removed as pos- 
sible from the hemi-tricotylous culture already men- 
tioned. The harvest gave a maximum of 11.9% tricotyls, 
but on the average only 1 to 6.5% with a mean of 3.5%. 
In 1893 I planted out the purely tricotylous seedlings only 
of a seed-parent with a hereditary value of 6.3%. I saved 
the seeds of 15 plants, examined between 500 and 1000 
seedlings per seed-parent, and obtained values which fluc- 
tuated between 2.6% and 7.4%; mean 47% (1894). 
I selected the parent with 7.4% for the continuation of 
the race and only planted out the best tricotylous speci- 
mens from amongst its offspring. I had 44 tricotyls 
amongst 1000 seedlings to choose from; besides these 
there were 31 hemi-tricotyls and one tetracotyl. I re- 
peated the evaluation of the ratio with 4000 seedlings and 
found 7.2%, that is to say, about the same value. 

At the end of the summer of 1894 my culture con- 



402 Tricotylous Races. 

sisted of the 20 best tricotyls only, and 16 of these ripened 
their seeds. In this generation, however, there was a 
considerable step back, for the individual parents varied 
between 0.5% and 3.7% ; and one parent had not a single 
aberrant form amongst 200 seedlings. The mean was 
1.8%. The seeds of the five best plants were again sown 
and 1000 seedlings from each examined. The values 
were now 2.6 2.8 3.2 3.2 and 3.6%. In the following- 
years I endeavored to determine the cause of this re- 
turn by a series of collateral experiments, but without 
success. The variability of the hereditary value in such 
races obviously depends in great part on causes which 
we do not yet understand. 

I now planted out the tricotylous offspring of two 
plants with 3.2 and 3.6%, but in two separate groups 
in order to be able to confine the selection to the offspring 
of one of them later, if desired. These cultures consisted 
of 12 and 13 tricotyls, no essential difference between 
them being manifested. The values calculated from the 
batches of 300 seedlings from each seed-parent were : 

SEED- VALUES CALCULATED FROM THE OFFSPRING 

PARENT (Spring, 1896) 

with 3.2 % 1.3 1.7 1.7 2.0 2.3 2.3 2.7 2.7 2.7 3.0 4.0 5.5 
with 3. 6% 0.7 0.7 1.0 1.3 1.7 2.0 2.7 2.7 3.0 3.0 3.7 4.7 5.3 

The mean for both cases was therefore about 2.5% 
(actually 2.5% and 2.7% respectively). This experi- 
ment proves how little effect an enlargement of the ex- 
tent of the cultures has in such an experiment in selection, 
for if I had only dealt with the offspring of one of the 
two parents, the result would obviously not have been 
essentially different. 

In the summer of 1896 I did not go on with this cul- 
ture, but tried to find out whether by planting out a con- 



Tricotylous Races Do Not Arise by Selection. 403 

siderably larger number of individuals, I could yet im- 
prove the prospects of success. For this purpose I se- 
lected the two plants of 1895 which seemed to be the 
best, and for which I had found the highest values in 
the spring of 1896, viz., 5.3% and 5.5%. In order 
to have a large crop to select from, I sowed 15 cubic 
centimeters of seed, and raised from 15,000 to 20,000 
seedlings, of which the strongest tricotyls and hemi- 
tricotyls were planted out singly in pots, and later put 
out in the beds. Three sowings were made, at the end 
of March, at the end of April and in the middle of May, 
in the hope of possibly increasing thereby the variability 
and the prospect of a mutation. Furthermore, within the 
three groups, widely different positions, different degrees 
of remoteness of the individual plants, and different 
treatment in the matter of pruning, obtained. Many 
plants gave more than 30 cubic centimeters of seed each, 
but more than ten cubic centimeters was never saved. 

Altogether I saved the seeds of about 450 plants, 
and sowed them separately. For each seed-parent 300 
seedlings were recorded in 1898; and the proportion of 
tricotyls was calculated from these data. The result was, 
however, that a very great difference was seen to exist 
between the two grandparents of 1895 ; the one with the 
value of 5.3% proved to be a bad stock plant. Amongst 
its offspring, of which there were 30, the ratio was 
greater than 3% in ten cases only, and on the average 
it was 0.3 0.5%. And this in spite of the treatment, 
which, though varied, was the best that could be given, 
and in spite of the complete exclusion of atavists. 

The second grandparent, with the value of 5.5%, 
proved as fortunate in its progeny as the former had 
been unfortunate. Its offspring had all been sown to- 



404 Tricotylous Races. 

gether, and planted out under the same average treat- 
ment on the same bed and on the same day. About 140 
plants set seed abundantly. 

On the average, however, this culture was not better 
than those of the previous years, for it only yielded a 
ratio of 4.5%; but the range of variability was much 
greater. Eight plants occurred, the hereditary coefficients 
of which exceeded all previous ones. Of these, six were 
14 to 17%, one 21%, and one 25%. Here the possibility 
of a sudden advance seemed to open up. 

Before I give the whole series of figures, I wish to 
make one further observation. If in the year 1897 I 
had not cultivated 450 plants, but only, let us say, one- 
third, I would have limited myself to the offspring of 
the grandparent with 5.5%, although the value is only 
apparently greater than the other, because the difference 
lies within the limits of observational error. I would 
then have obtained precisely the same result with only 
one-third of the labor. In other words, neither the se- 
lection of tricotyls as seed-parents, nor the attention paid 
to the hereditary values, although this excludes the poor- 
est tricotyls in spite of the latitude of possible errors, 
can make the experiment independent of chance. Noth- 
ing less than carrying out the experiments on a much 
larger scale can effect this. But the results of the two 
following generations will show that even in the present 
very favorable case, no real or permanent advance was 
effected. 

The values obtained, in the spring of 1898, for the 
140 offspring of the best parent of 1895, which itself 
had a value of 5.5%, are distributed as follows: (P 
refers to the figures in percentages and A to the cor re- 



Tricotylous Races Do Not Arise by Selection. 405 

spending number of offspring which manifested these 
numbers amongst their seeds). 

P 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 21 25 
A 16 27 30 18 18 11 6 4 2 2 2 3 2 1 2 1 2 1 l 

This series only relates to the tricotyls selected for 
my experiment. If I had planted out the whole progeny 
of the parent in question without selection, the number 
of low values would most certainly have been somewhat 
larger; and the apex of the curve would perhaps have 
stood over the instead of over 3%. But the chief point 
in this series is that from 3% onwards the figures regu- 
larly and continually diminish in such a way that the 
two extreme variants with 21% and 25% round off the 
series continuously; i. e., in the ordinary manner pecu- 
liar to physiological curves. It is obvious that they do 
not stand in discontinuous relations to it. 

In the estimation of the higher individual values a 
latitude of 5% must be allowed, i. e., the figure 15 de- 
notes a real capacity of from 10 to 20%, the figure 25 
one of from 20 to 30%. In the case of extreme devia- 
tions it is always well to assume that these errors may 
have operated in the same direction. We may only state, 
therefore, that by means of a cultivation through eight 
generations, a ratio of 20% has been attained. But 
whether or not this is the limit, we do not know. Also, 
it is uncertain whether the parent with 25% was really 
better than those with 15 to 21%. But it is certain that 
the best seed-plant, as judged by its hereditarv value 
must be one of this group. 

Therefore, at this stage in the development of our 
race, the process of selection has become much more 
certain than before and less dependent on chance. It is 
only necessary not to limit our choice to those which 



406 Tricotylous Races. 

appear to be the very best, but to cultivate also some of 
the next best seed-parents for the continuation of the 
race. Of the culture of 1897 I selected five, viz., those 
with 16, 17, 17, 21 and 25%. In order to allow as many 
different external factors as possible to come into play, 
I sowed the following generation in two subsequent years 
(1898 and 1899), and in the first year in two separate 
lots, one in the middle of April and one in the middle of 
May. Altogether somewhat over 400 tricotylous plants 
were planted in this year, and the hereditary capacity was 
determined on 300 seedlings in each lot. 

But in spite of every care, the result was a return to 
previous values, and this in the case of every one of the 
five parents. The mean value for all of them was only 
2% ; the five highest values were 9.6--10.6 10 11- 
\\% mostly amongst the offspring of the same grand- 
parent (E in the following table). Below I give a short 
review of the values found separately for each individual 
grandparent of 1897. The countings were made in the 
spring of 1899. 

A. Grandparents in 1897 A B C D E 

Their values in spring 1898 ... 16 17 17 21 25 

B. Parents sown on April 21st, 1898: 
Their values in spring 1899: 

Maximum 5.3 2.6 3.0 3.3 11.0 

Mean 15 0.8 0.7 1.1 4.7 

C. Parents sown on May 7th, 1898: 
Their values in spring 1899: 

- Maximum 9.6 6.6 4.6 6.3 7.3 

Mean 4.1 2.2 2.1 2.5 2.5 

Mean of the two series . . .2.8 1.5 1.4 1.8 3.6 

The two grandparents with 16 and 25% must there- 
for be regarded as the best ; and it must be supposed that 
the five exceptionally high figures were brought about 






ricotylous Races Do \ot Arise by Selection. 407 



by peculiarly favorable circumstances which were not 
repeated in the following year. 

The repetition of the experiment in 1899 gave prac- 
tically the same result. 

All in all, in the ten generations of my experiment, 
there occurred neither a sudden nor a gradual transition 
to an intermediate race. 

And lastly let me summarize the whole culture in a 
simple table which gives only the mean and the highest 
value for each generation as well as the value for the 
seed-parent selected for the continuation of the race. 

VALUES FOUND IN THE FOLLOWING 
GENERA- YEAR OF gpRING 

TION FLOWERING 

MEAN MAXIMUM SEED-PARENT 

I. 1889 4.5 

II. 1890 4.5 

III. 1891 13 

IV. 1892 3.5 11.8 6.3 
V. 1893 4.7 7.4 7.4 

VI. 1894 1.8 3.6 3.6 

VII. 1895 2.5 5.5 5.5 

VIII. (450 Ex.) 1897 4 25 16-25 

IX. (400 Ex.) 1898 2 11 

The whole series, with the exception of the maximum 
figures for 1897 rather indicates a fluctuating around a 
constant mean value than a steady progress under the 
influence of selection. 

Scrophularia nodosa. Of this species a series of 
forms occurs. Their characters have been given in the 
Prodromus of DE CANDOLLE. The leaves are broadly 
cordate or only rounded at the base, with little teeth of 
almost uniform size, or very coarsely and irregularly 
indented, and the fruits are large or small. The form 
with cordate, uniformly toothed leaves is very common 
in this neighborhood, and, so far as I know, the only 



408 



Tricotylous Races. 



one that occurs. The form with coarsely dissected 

* 

leaves rounded at the base, and small flowers and fruits, 
is the one employed in my experiments (Fig. 84). In 
the summer of 1901 I planted out large numbers of both 
types in my garden, after a close examination of their 
characters. Both are, as far as my experience extends, 

quite constant for many gen- 
erations, i. e., they are good 
subspecies. 

My culture began in 1890 
with the seeds of a tricotylous 
plant from our botanical gar- 
den, which, in the following 
year, produced, besides a num- 
ber of atavists, four plants with 
three cotyledons and a main 
stem with ternary whorls up to 
the inflorescence (1891). From 
the seeds of one of these plants 
I again obtained in the summer 
of 1892 some tricotylous seed- 
lings, the majority of which, 
how r ever, became decussate af- 
terwards. Only two of them 
remained ternary throughout 
the summer, and these were the 
only ones which I allowed to 
flower. Among their seed I counted 780 and 1000 seed- 
lings respectively, and found the value in each case to 
be 1%. 

In 1893, 16 tricotylous plants flowered and constituted 
the fourth generation of my race. Their seeds were 
saved separately and produced a mean of from 1 to 2%, 




Fig. 84. Scrophularia nodosa. 
Main stem of the tricotyl- 
ons half race with ternary 
whorls of leaves. 



Tricotylous Races Do Not Arise by Selection. 409 

in the best cases 2.4 to 4.1 and 5.4%. The counts were 
made on 700, 800 and 2000 seedlings. These three plants 
had, however, decussate leaves on their main stems, and 
this shows that the disposition of leaves on the stem is 
of subordinate value in selection. In the later genera- 
tions I have always selected the ternary individuals where 
possible, but have not found that they are any better than 
the others. 

In the summer of 1894 tricotylous seedlings of the 
seed-parent with 5.4% were planted out. I saved the 
seeds of 25 plants separately, and in the following spring 
examined from 300 to 500 seedlings in each crop. The 
values were essentially the same as in the previous year, 
and varied between 0.5% and 5.5% with a mean of 2% ; 
and the five best gave 3.6 3.8 4.0 4.2 and 5.5%; 
the three last values are based on counts of 1000, 1500 and 
2000 seedlings. It was only the offspring of these parents 
that were planted out in 1895, and only those with three 
cotyledons and with a first whorl of three leaves (Fig. 
73, p. 366). 

By planting them out in three groups in the following 
spring, a selection was made possible which related to the 
grandparents. Those with 4.0 to 4.2% gave offspring 
with 1.3 to 5% with a mean of 3%; (from 12 parents 
and from counts of groups of 300 seedlings). The 
grandparent with 5.5% proved to be considerably better. 
Its twelve offspring had 2 to 8%, with a mean of 4.5%. 
Seedlings of this group only were planted out in 1896 
and only tricotylous specimens with ternary lower whorls, 
from parents with 6 6 and 8%. They were in all 72 
strong plants each of which gave a sufficient harvest for 
the calculation of their hereditary values in groups of 
300 seedlings. The parent with 8% gave 2 to 15%, with 



410 Tricotylous Races. 

a mean of 6%. The two other parents 2 to 10% and 
3 to 14%, with means of 6 and 7%. Obviously the 
difference was not sufficiently considerable to base a se- 
lection among the grandparents upon. On the other 
hand it was evident that the race had been improved by 
the process of selection which now extended over six 
generations ; and this improvement was afterwards main- 
tained. 

For the culture of 1897 I selected the tricotylous off- 
spring of three seed-parents with 11- -11 and 15% tri- 
cotylous offspring, and planted out 100 of them, which 
were all strong plants with a ternary first whorl of leaves. 
The harvest was recorded in the spring of 1898 in the 
usual way. The three parents, however, which were now 
grandparents, again showed no essential difference in 
their offspring. 

VALUE FOR VALUE FOR THE PARENTS NUMBER 

THE GRANDPARENTS MIN. MED. MAX. OF PARENTS 

11% 27 15 20 

11% 3 7.5 15 24 

15% 4 8.5 13 28 

Here again the figures were the same as in the pre- 
vious generation. 

Although, as we have seen, the selection of grand- 
parents, in this case, afforded no reliable ground from 
which an improvement of the race could be started, yet 
this must be the case whenever the hereditary capacity 
of the grandparent is much influenced by fortuitous cir- 
cumstances which affect the selection of the seeds. There- 
fore the special object of such selection is mainly to ex- 
clude such cases as much as possible from the main trunk 
of the pedigree, by simply not planting out their seed 
lings. 



Tricotylons Races Do Not Arise by Selection. 411 

But when the values of several parents do not differ 
so greatly from one another that the differences fall out- 
side the limits of probable error, individuals should be 
planted out every year from all of the best parents. This 
would, however, necessitate an increase of the cultures on 
too large a scale. Nevertheless I extended my culture 
as far as possible in the summer of 1898 on this principle, 
and saved the seeds of 300 plants separately. 

The result of the 300 counts which were made on 
these lots of seeds, embracing 300 seedlings for each 
lot, corresponded with my expectations to this extent 
that one of the grandparents proved to be by far the best. 
Its hereditary value was 14%, that of its offspring had 
a mean of 20%, and for two individuals even 25 to 27%. 
Moreover, outside the limits of this group, this race also 
showed an increase in hereditary capacity. 

The harvest of 1898 contained the seeds of 300 tri- 
cotylous plants, which in their turn had been raised from 
15 parents with values from 10 to 15%. The results 
were as follows (expressed in percentages) : 

Parents 10 10 10 10 10 10 11 11 12 12 13 13 14 15 15 

Offs rin ^ Mean ' 8 10 10 H 14 19 10 l5 U 16 10 13 20 14 14 
' < Max. . 8 11 20 20 27 26 19 25 20 24 21 21 27 21 22 

Number of offspring 1 2 19 28 11 6 8 9 27 6 36 32 12 64 39 

The mean of the whole series of counts was 12% and 
denoted a considerable increase in the character of the 
race. 

Let us now compare this series of figures with that 
given on page 405 for Amarantus speciosus. That series 
relates to the hereditary coefficients of 140, this to those 
.of 300 plants, which in the former case belong to the 
8th, and in this one to the 9th generation. Both series, 
therefore are the result of a selection which extended 



412 Tricotylous Races. 

over a sufficiently long period of time to justify the expec- 
tation that a definite result would be obtained. They 
exhibit, however, one striking difference. The mean of 
the figures for Amarantus is between 2 3%, and this 
renders it not improbable that, if the coefficients of the 
atavists could have been incorporated in the curve, its 
apex would have been at 0, that is to say, that a unilateral 
or so-called half curve would have been the result. But 
the apex of the Scrophularia curve is at 12% and varies 
amongst the individual families from 8 to 20%, indi- 
cating thereby the possibility of an isolation of a separate 
apex for the tricotylous specimens. 

In other words, the tricotylous half race of Amaran- 
tus behaves, during this long period of selection, in es- 
sentially the same way as at the beginning (table p. 407), 
whereas Scrophularia behaves like other half races im- 
proved by selection. The scheme representing the in- 
fluence of selection on the half race of Ranunculus bid- 
bosus semiplcnus (Fig. 52 on page 252 of this volume) 
would apply equally to this case. 

The explanation of this difference in behavior is per- 
haps to be sought in the assumption that in Scrophularia 
tricotyly has only been indirectly improved. I am re- 
ferring to the case of Trifolium Incarnatum quadrifolium 
which I described above on page 239. In that case the 
smallest seeds gave rise to the largest number of aberrant 
seedlings. If the production of small seeds could be 
increased by selection the number of seedlings with com- 
pound primordial leaves would also be increased. It 
seems possible that in Scrophularia similar factors were at 
work, since the character involved need not, of course, 
necessarily be the size of the seeds. The repeated selec- 
tion of tricotyls would not, on this assumption lead di- 



Tricotylous Races Do Not Arise by Selection. 413 

rectly to the increase of this character, but to a supposed 
change in the structure of the seeds which would favor 
the anomaly. Whether or no this supposition is correct 
I do not know, but it is a fact that the fruits and seeds 
of my race have gradually become smaller; and that it 
is the plants producing the largest number of tricotyls 
which bear the smallest fruits and seeds, I find repeatedly 
noted in my records. 

At any rate we are here in touch with a principle 
which may be applicable to other cases also. A selection 
may produce its effect on an unknown character which in 
its turn will affect the character actually dealt with. 

With regard to the extent of my culture of 1898 it 
is further worth remarking that it shows that, in general, 
the extent of the cultures is by no means so important a 
factor as is usually supposed. If I had confined myself to 
experimenting with three or five seed-parents, as for in- 
stance in Amarantus in 1897 (p. 406), I should have 
chosen the best ones according to their hereditary co- 
efficients ; and it was exactly amongst these that the best 
of all occurred as the series on page 41 1 shows. Increased 
extent of the experiment deepens one's insight into the 
processes involved, but does not hasten the improvement 
of the race ; although it is never advisable to confine one- 
self to experimenting with one single seed-parent, if this 
can be avoided. 

The next generation, the 10th and at present the last, 
has repeated the progress observed in the ninth. Here 
again the race of Scrophularia behaved differently from 
that of Amarantus. I confined myself to the progeny 
of the plants of 1897 which exhibited the value of 14%, 
and amongst the offspring of which the mean attained 
20%. From these I selected five specimens with 22 23 



414 Tricotylous Races. 

-23 25 and 27%. I planted out 165 tricotylous seed- 
lings from amongst their offspring in pots, as soon as 
they proved themselves also to be ternary in their first 
whorls of leaves. In the following whorls about half of 
them reverted to the decussate arrangement. These were 
thrown away, and only 72 plants which remained ternary 
were ultimately planted out. They were fairly uniformly 
distributed over the crops of the five parents. 

From these 72 plants, 72 values, in five groups, were 
calculated in the following spring (1900). The lowest 
values, arranged in a series corresponding with the in- 
creasing values of the five parents, now grandparents, 
were 9, 8, 13, 8 and 11%, the means 16, 17, 18, 17, and 
19%, and the maxima 19, 22, 26, 22 and 26%. As we 
see the five groups did not exhibit any essential differ- 
ence. The mean value of the previous generation, 12%, 
had now been exceeded, but the maximum remained the 
same. 

Let us now summarize the whole experiment in the 
following table : 



VALUES FOUND IN THE FOLLOWING 
TION FLOWERING 



GENERA- YEAR OF SPRING 



LOWEST MEAN HIGHEST 
I. 1890 
II. 1891 

III. 1892 1 

IV. 1893 0-0.3 1-2 5.4 
V. 1894 0.5 2 5.5 

VI. 1895 2 4.5 8 

VII. 1896 2-3 6-7 14-15 

VIII. 1897 2-3 7-8 15 

IX. 1898 2 12 25-27 

X. 1899 8 16-19 26 

Progress is, as we can see, a continual one, and the 

selection has been, although perhaps only indirectly, (p. 



Tricotylous Races Do Not Arise by Selection. 415 

412), successful throughout. Nevertheless an interme- 
diate race has not arisen, either gradually or by means 
of a sudden jump. The progress in the last two years was 
more rapid than before as the result of increased strin- 
gency of selection, without, however, affording any in- 
dication that the mean of 50 /t was likely soon to be 
reached. 

Oenothera Berteriana. Besides the two cultures men- 
tioned which were begun in the first years of my ex- 
periments in selection, I have cultivated yet a third race 
with the same object. This race was one in which the 
intercrossing of the various individuals could always be 
avoided. There is, however, no ground for fear that 
occasional unavoidable crosses in Amarantus and Scro- 
phularia had any considerable effect on the selection pro- 
cess ; for both species must be fertilized almost entirely 
with their own pollen on acount of the great number of 
their flowers which are open at the same time ; and they 
are, when thus fertilized, perfectly fertile as isolated in- 
dividuals show. Moreover what is spoiled by crossing 
is eliminated bv selection. 

ff 

But the evidence is more satisfactory if self-fertiliza- 
tion can be insured. This occurs in Oenothera Berteriana. 
Its flowers form perfectly normal fruits and seeds, when 
the visits of insects are excluded. I enclosed my plants 
in a cage of fine metal gauze. Some years I have fer- 
tilized them artificially in it ; but this is quite superfluous, 
because when the flower withers the stigma bends down- 
wards and thus reaches the pollen. In the two last sum- 
mers the cage was shut from the beginning of the flow- 
ering period until the seed began to ripen. Nevertheless 
they all produced fruits with scarcely an exception. These 
fruits contained an abundance of seed, and a few from 



416 Tricotylous Races. 

each plant are sufficient, and this is a great advantage 
as compared with the laborious process of harvesting in 
Scrophularia. 

My culture began in the summer of 1896. At that 
time the prospect of obtaining an intermediate race in 
the other two races had already become very remote. 
From some plants in our botanical garden I saved seeds 
which produced 13 tricotyls, 4 hemi-tricotyls and one 
tetracotyl amongst 300 seedlings, i. e., 6%. This figure 
was considerably higher than most of the values of my 
half races mentioned on page 392, and about as high 
as the value attained by Amarantus and Scrophularia at 
that time. At the same time six other species of Oeno- 
thcra were tested with reference to their production of 
tricotyls. I found from to 1 and 2% and therefore 
selected the 0. Berteriana. In the spring of 1897, tri- 
cotyls only were potted singly, and planted out in July 
in the beds. Their hereditary values were determined in 
the following year in the case of 1 5 plants. They fluctu- 
ated between 1 and 12% and exhibited a mean of 4%. 
In the following generation, 1898, I was able to plant out 
about 60 strong tricotyls, and since that time I have con- 
ducted the cultures on this scale with only slight modi- 
fications. 15 tricotyls from the plant with 12%, and 45 
from those with 6 to 7% were planted out. The former 
group, however, proved to be no better than the latter. 
The values of these plants varied from 2 to 16%, with 
a mean of 4%. The best of the five other groups, how- 
ever, had values varying from 6 to 16%, with a mean 
of 8% (from 10 separate crops). The remainder varied 
between 4 and 11, with a mean of 6%. I selected the 
three best parents whose values were 15, 16 and 16%, 
and I planted out the strongest tricotylous offspring of 



The Isolation of Tricotylous Intermediate Races. 417 

each (1899). This year 77 plants gave a sufficient har- 
vest, the figures for the three groups (each derived from 
a single grandparent) did not exhibit any differences 
worth mentioning. The minimum was 2%, the mean 
12, and the highest value 25%. Therefore a consider- 
able advance on the preceding generation had taken place. 
In 1900 I had only 31 plants, bearing seed, which were 
cultivated in the same way as in the previous year. They 
constituted three groups, each from a single grandparent, 
but without exhibiting any differences worth considera- 
tion. The hereditary values varied between 5 and 17% 
and their mean was 10 to 13%. The culture of the last 
year (1901) embraced 40 plants, the values of which 
varied between and 21 and had a mean of 10%. 

The result, like that of the two foregoing species, 
may now be summarized in tabular form. 

VALUES DETERMINED IN THE FOLLOWING 
GENERA- YEAR OF SPRING 

TION FLOWERING 

MEAN HIGHEST SEED-PARENTS 

1. 1896 6 

II. 1897 4 12 12 

III. 1898 4-8 16 15-16 

IV. 1899 12 25 23-25 
V. 1900 10-13 16-17 14 

VI. 1901 10 21 

The prospect of raising an intermediate race seems 
therefore in this experiment to be as small as in Ainaran- 
tus and Scrophnlaria. 

6. THE ISOLATION OF TRICOTYLOUS INTERMEDIATE 

RACES. 

It is just as easy to isolate an intermediate race from 
seed which has been bought or obtained from any other 
source if it happens to be already present in it, as it is 



418 Tricotylous Races. 

difficult to raise one if it is not. Isolation can be effected 
in two to three generations as a rule, in fact as soon 
as the hereditary values of the plants raised from the 
original mixture of seed have been determined. Very 
little care and no artificial fertilization at all is necessary 
for this purpose. It takes place as quickly in dioecious 
wind-fertilized flowers, such as the hemp, as in self- 
fertilizing species enclosed in bags or cages. 

In the choice of species and varieties one obviously 
has not a free hand. We must first search for cases in 
which the desired races happen to be present, and for this 
purpose sowings of considerable extent have to be made. 
If lots of ten to twenty grams of seed, according to the 
size of the individual grains, are sown, it can be seen 
soon after germination whether the species is likely to 
produce a tricotylous intermediate race or not. The oc- 
currence of 1 to 2 tricotyls amongst about 10,000 normal 
seedlings does not justify this expectation, but that of 
one or more per thousand does as a rule. 

The cultures of my half races mentioned in 4 (p. 
392) had begun in 1892 or earlier, and in the spring 
of 1895 there could be no doubt that I should not obtain 
any intermediate races from them. I resolved therefore 
to seek them elsewhere, and selected for this purpose 
about forty species and varieties of garden plants, which 
were chiefly annuals. The result of this sowing, which 
was conducted on a large scale, has already been given 
on page 380. Most of the sorts contained too few tri- 
cotylous seedlings. Only 8 offered the prospect of giving 
rise to an intermediate race, and of these I had to reject 
three for various reasons. The remaining five, however, 
fulfilled my expectations. 

Before I proceed to the description of my experiments 



The Isolation of Tricotylous Intermediate Races. 419 

it is desirable, in connection with what was said in the 
first part of this volume, to consider what we should 
expect to occur in the isolation of such intermediate races 
as may happen to be present. The intermediate race does 
not differ from the ordinaiy types or half races in any 
visible characters, but only in the frequency of tricotylous 
specimens. If the tricotylous individuals are selected for 
culture from crops raised from bought seed, it is by no 
means certain that these and these only belong to the 
intermediate race, if indeed such exists at all. For in 
addition to this, the half race is almost always present, 
and this, as we know, also contains some tricotyls. On 
the other hand the intermediate race always produces 
atavists and usually in considerable numbers. Provided 
therefore that the crop contains an intermediate race, 
some of the dicotyls and some of the tricotyls would be- 
long to it ; but the prospect of obtaining it from the latter 
will obviously be greater than from the former. For this 
reason I select, whenever possible, tricotyls only for trans- 
plantation. All that then remains to be done is to save 
their seeds separately from each plant and to determine 
their hereditary values in the harvest. If any of these 
are especially high they belong to the intermediate race, 
and all the res! are thrown away inasmuch as they in- 
clude the half race and the doubtful cases. Ordinarily 
the race is by this time perfectly pure and can be improved 
by selection on the ordinary lines. As a rule, the means 
of the curves describing my intermediate races, lie be- 
tween 50 and 60%, and can be brought as high as 80 to 
90% by selection in occasional individuals. 

In contradistinction to the unsuccessful experiments 
described in the previous section there can be no doubt 
in these successful cases that we are not dealing with the 



420 Tricotylous Races. 

selection of the extreme variants of ordinary fluctuating 
variability. Even the doctrine of unilateral increase in 
variability as a result of selection is of no help in this 
case (see 2, p. 9), for selection could hardly operate 
so rapidly as to produce its whole effect in a single gen- 
eration. The old saying of gardeners that the first con- 
dition necessary for the production of a novelty is to 
possess it already, also applies to these purely experi- 
mental races (Vol. I, p. 185 and elsewhere). If the tri- 
cotylous race does not already exist it cannot, at present 
at any rate, be either isolated or bred. 

A high percentage in tricotyls is seldom found in 
wild species. The highest value I have yet found oc- 
curred in Linaria vulgaris in the spring of 1894 in a sow- 
ing of the seed of a hemipeloric plant of the race that 
I was cultivating at that time (see p. 211). There were 
59 tricotyls amongst the 425 seedlings, i. e., 14%. Amongst 
commercial seed the prospect of obtaining intermediate 
races seems to me to be the greatest, as I have already 
stated, in those sorts which are cultivated on a large scale 
in the field or in the garden. It is much smaller in those 
varieties of flowers which are only grown on a small 
scale every year. Moreover it seems obvious that cul- 
tivation on a large scale should favor the origin of new 
races. 

If the intermediate race, which is being sought for, 
exists in some sample of seed, we may expect to find 
mean, bettei or inferior representatives of it. If the 
former is the case the mean character of the race, that 
is about 50 to 60% of tricotyly is attained at once, and 
this occurs in the majority of cases, as might be expected 
and as the table at the conclusion of this section will 
show (p. 439). Individuals with a higher productive 



The Isolation of Tricotylous Intermediate Races. 421 

capacity are rarely found at first. I came across an 
instance of one only once, at the beginning of my experi- 
ment with the syncotylous Helianthus animus (see the 
following chapter). If individuals with low hereditary ca- 
pacities are found, those with mean values can as a rule 
be easily raised from them, for they are to be regarded 
simply as minus variants of the race sought for; and 
will therefore, in conformity with the law of regression, 
revert to this value even if selection be only suspended 
( see above, p. 5 ) . Experience shows, and the table al- 
ready referred to will demonstrate, that one or two gen- 
erations are, as a rule, sufficient for the attainment of 
values of 50 to 60%. 

Before I proceed to a detailed description of my ex- 
periments I will give a few instances to show the course 
which these experiments in the isolation of tricotylous 
intermediate races follow. 

The attainment of the mean value. On page 380 I 
have given, in a small table, the numbers of tricotyls 
which I found in some samples of seed in the spring of 
1895. For some of these species these tricotyls were 
planted out and their seeds saved separately and sown. 
I obtained values from 12 to 19% in the best individuals 
(spring 1896). and on the rest, as a rule, much fewer. 
These were regarded as belonging to the half race or as 
of doubtful significance. The tricotyls from the best 
parents were now (1896) planted out, and the hereditary 
value for each was calculated in the following spring. 
Below I give a resume of these figures in groups of 2, 
3 7, 8--129f, with means of l--5--10% and so forth, 
for convenience of comparison, and indicate, for each 
such reduced value, the number of individuals which 
exhibited it. 



422 Tricotylous Races. 

ISOLATION OF TRICOTYLOUS RACES. 
HEREDITARY VALUES UF THE SECOND GENERATION. 
FIRST 

GENER- 1 5 10 15 20 25 30 35 40 45 50 55 60 65 

ATION 

Clarkia pulchella 16% 01171473421422 
rapaver R/weas 18% 002854 3 10001 

Papaver Rhoeas 19% 001 18214401 

Phacelia tanaceti folia 14^033113864222 

It is easily seen that in such cultures the choice of 
specimens which belong undoubtedly to the intermediate 
race is made possible. All plants with a low hereditary 
value are simply rejected, since the possibility exists that 
among them may be hidden hybrids between the two 
races. The high values are free from this doubt and 
indicate the pure race we are searching for. 

Thoroughbred races. Under this term those races 
are included in agriculture which have been considerably 
improved by stringent selection. In the first part of the 
first volume we have seen that they remain dependent 
on continued selection, and do not really become constant. 
For studying the features of such races, the tricotylous 
intermediate races afford most suitable material, for, 
after reaching the mean value of about 50%, we may 
select the extreme variants, and, by their culture, improve 
the race much farther. As instances I choose Mercurialis 
aiiuiia, a large agricultural crop, and Silene inflata, which 
I derived from seed introduced with cereals. Both cul- 
tures were started in 1892, and reached a hereditary 
value of 55% in the harvest of 1894. From plants with 
this value I raised a fourth generation, which offered me 
the following figures : 



The Isolation of Tricotylous Intermediate Knees. 423 



SELECTION OF THOROUGHBRED TRICOT YLol'S RACKS. 

HEREDITARY YAI.L'ES OF THE BEST TKICOTYI.oUS SEED-PARENTS OF Till: 

FOURTH GENERATION. 

THIRD 

GENER- 25 30 35 40 45 50 55 60 65 70 75 80 85 

ATION 

Merc -uriahs an nua 55% 122121231 

Silene inflata 55% 10234444711 

It will be seen that regression did not accompany this 
..election, because the parent plants deviated too little as 
yet from the mean of the new race. On the other hand 
the high values of 75-85% were immediately reached, 
and this obviously indicates a considerable advance. These 
instances, taken together with the table which will be 
given on page 439, are sufficient to indicate the method 
by which tricotylous intermediate races, if they are at 
all present, can be isolated and improved. They will 
facilitate the understanding of the detailed description 
of my experiments. These obviously present, according 
to the species investigated, greater or less deviations from 
the instances given, but as a rule they are not essential 
ones. Therefore I shall give these descriptions as briefly 
as possible. 

But before doing so I wish once more to lay emphasis 
on the fact that these cases are thoroughly distinct from 
those in which only half races are present, and from 
which, after several generations, often no more than 2 
to 4% and only very rarely as much as 20% was reached, 
as maximum figures (see table on page 392). 

Oenothera kirtclla. Under this name I cultivate a 
tricotylous race which I obtained by chance from bought 
seed. In 1895 I was growing some samples of seed of 
Oenothera Lciinarckiana and allied species which had 



424 Tricotylous Races. 

either been bought or obtained by exchange, in order to 
compare them with my own strains. In the autumn I 
saved the seed of a number of separate specimens and 
sowed it in the hope of finding a tricotylous intermediate 
race amongst them, inasmuch as my own races and vari- 
eties offered no pro3pect of producing them, as has al- 
ready been mentioned for a special case, that of Oeno- 
t/iera rubrinervis (p. 383). This hope was fulfilled by 
a single specimen, all the remaining lots of seed giving the 
usual very low values of from to 4%. This specimen 
was a plant which was noticed by some striking distinc- 
tive marks. It was taller and slenderer in growth than 
all the other species, more than 2 meters high, with a long 
raceme interrupted in places by the failure of some of the 
lower buds. Its flowers were of the size and structure 
of those of 0. biennis and, like this form, were self- 
fertilized within the buds before their opening. Its pro- 
geny have kept true to this type through a series of gen- 
erations. 

This stray plant produced from its seeds, in a lot 
of 300 seedlings, 7% tricotyls, and in another estimation, 
amongst 2430 seedlings, 8% tricotyls, of which 143 were 
tricotyls in the restricted sense, 59 were hemi-tricotyls, 
and 4 tetracotyls. Whether the parent itself had three 
cotyledons, I do not of course know. 

Of this crop the tricotylous seedlings only, and of 
these only the strongest, were planted out on the 2d of 
April, 1896. In the middle of July, some few clays be- 
fore they flowered, the whole bed was covered with a 
great cage of fine cloth. The cloth was removed at the 
beginning of September and at the same time all the 
open flowers and buds were removed from the plants. 
Seeds were saved separately from 54 individuals and 300 



The Isolation of Tricotylous Intermediate Races. 425 

seedlings were counted from each lot. The result was a 
very remarkable one. With a single exception the fig- 
ures formed a close series of which the mean was 7%, 
whilst the great majority of figures lay between 2 and 
12%. (Two parents with 0.5 and 1.0 and three with 
13, 14, and 17%. ) Besides these there was a single 
plant which stood far from the others in the series. It 
had produced 56% tricotyls, i. e., more than half of its 
seeds were tricotylous. For the sake of greater certainty 
this value was determined twice. The percentage value 
calculated from a lot of 768 seedlings was 58% ; from 
another of 657 seedlings 54% ; with a mean of 56% for 
1492 seedlings. 

This one plant, therefore, had a hereditary value 
which corresponded closely with the mean value which 
we should expect the intermediate race sought for to 
possess. Of course the experiment was continued from 
the seeds of this plant only. The seedlings of all the 
other parents, tricotyls as well as dicotyls, were thrown 
away. 

Two courses were now open to me, either simply to 
maintain the race, or to endeavor to improve it by further 
selection. In the former case, selection would have to 
be avoided as much as possible, and we should have to 
harvest and sow the seeds of all the specimens mixed 
together, and in planting out the seedlings be careful not 
to give preference to the tricotyls. I have not done this ; 
but as is my custom, I have harvested and recorded the 
seeds of each individual separately and only planted out 
the seedlings of the best parents, that is to say the parents 
with the highest hereditary values, for the continuation of 
the race. 

In the summer of 1897, 37 tricotylous offspring of the 



426 Tricotylous Races. 

parent with the value of 56% flowered in a cage of metal 
gauze. The values, calculated in the usual way from the 
harvest, gave a good curve, whose mean was 72 c /o. The 
lowest percentage of tricotyls was now 38%, the three 
highest 83 83 and 89%, that is to say, a very consider- 
able advance. 

Atavistic seedlings of the same parent were also 
planted out, but they naturally exhibited a somewhat 
smaller advance. 

In the following year, 1898, I did not sow the seeds of 
the plant with 89%, but from various considerations 
those of one with 66%. The reason for this choice was 
that the plant had flowered early and that the harvest 
had been increased thereby. The parents with the higher 
values had flowered too late or set too little seed, and it 
would have been very dangerous to have continued the 
experiment along this line. Moreover there was no 
longer any particular interest in improving the race fur- 
ther. The mean value has been lessened thereby to 
about 40%, and the maximum to 74%. 

Canuabis satii'a. I propose to deal now with two 
cultures of dioecious plants, Cannabis and Mercurialis. 
In these cases self-fertilization is impossible; neverthe- 
less the isolation of the intermediate races was effected 
as easily and almost as quickly as in Ocnothera. Without 
doubt self-fertilization has in such experiments, when- 
ever feasible, the high value which is usually assigned to 
it ; but the experiments now to be described show that it 
can often be dispensed with, as well. This result is very 
important, because it makes isolation and selection pos- 
sible in species in which an artificial fertilization of every 
single seed-parent would increase the labor bevond meas- 



The Isolation of Tricotylous Intermediate Races. 427 

ure. Such a task I have, therefore, only undertaken 
with a single species, Antirrhinum uiajus. 

Only some varieties of hemp seem to include tricotyl- 
ous intermediate races. Amongst those which I have 
tested I have found such a one in the giant hemp only. 
In the spring of 1893 I sowed a large quantity of seed of 
this species, but was only able to bring 7 tricotylous plants 
to maturity. Unfortunately the majority of them were 
male, and there was but a single female plant. This, how- 
ever, produced four tricotyls amongst 126 seedlings. In 
1894 two of these were female and two male. The seeds 
of the former were saved separately and yielded 15 and 
9% tricotyls amongst 400 and 600 seedlings respectively. 

For the continuation of the race, onlv the tricotylous 

./ . 

seedlings of the parent with 15% were planted out 
(1895). There were 29 plants, of which 10 bore seed. 
Their values were 1931384043474850 
52 and 63%. As we see they attained the mean value of 
the intermediate race and even exceeded it in one case, 
(63% amongst 316 seedlings). The tricotylous offspring 
of this individual alone were planted out (1896). Of 
these, 38 specimens set seed, and from this the values of 
the individual parents were calculated. I reduced them, 
as usual to groups with 40 45 and 50% etc., as a mean 
value, and found the 38 offspring of the parent with 63% 
to be distributed as folows : 

Proportion of tricotyls 40 45 50 55 60 65 ' 70 75 80 
Number of seed -parents 553 10 55221 

The mean of the series is at about 55%, and the 
series therefore constitutes a good instance of a young, 
isolated race which, however, has not yet been improved 
to anv considerable extent bv selection. 



428 Tricot \lous Races. 

In 1897 I continued the culture for the purpose of 
improving the race. I sowed the seeds of four plants 
which had 65 66 67 nd 70% tricotyls, and managed 
to bring 60 tricotylous plants to maturity, of which 26 
set seed. Their hereditary values varied between 35 and 
90%, their mean being 74%. This indicates a satisfac- 
tory advance. 

Mercunalis annua. In 1892 I possessed two tricotyl- 
ous plants, one a female, the other a male, which had 
been raised from species that had been obtained in ex- 
change from some botanical garden. The yield was very 
poor; only 14 seeds germinated and they had two cotyl- 
edons each (1893). In saving their seeds I did not 
isolate them and found 2% tricotyls amongst the 1100 
seedlings which were raised in the following spring 
(1894). Besides these several tricotyls had come up in 
the bed from seeds which had fallen out, so that I had 
altogether 18 female and a corresponding number of 
male tricotyls. This culture gave the expected result. 
The hereditary values calculated for the individual seed- 
parents were distributed regularly between 1 and 55%, 
the five highest being 3134 4152 and 55%. The 
intermediate race had therefore been isolated at least in 
these latter specimens. In 1895 I only planted out tri- 
cotylous seedlings from the one parent with 55%. Of 
course it was uncertain in this case whether the pollen 
had been produced by plants belonging to the intermediate 
race. But the values calculated in the spring of 1896 
suggested that the race was fairly pure. I have already 
given this series of figures above (p. 423). The mean 
was at 67, the maximum had increased to 86%. 

In 1896 the tricotyls of two parents, whose values 
were 78 and 81%, were planted out in lots of 25 and 20 



The Isolation of Tricotylous Intermediate Races. 429 

respectively. The values for the two groups did not 
differ essentially, and were distributed between 51 and 
92%, and the mean of the 25 plants (the rest had been 
male) was 73%. The race had, therefore, in compari- 
son with the previous year, undergone a further im- 
provement. 

It was continued one year more in the same way 
(1897). 12 female and several male tricotylous off- 
spring of the parent with 92% were planted out, and the 
values calculated from these were found to be distributed 
between 65 and 91%, with a mean of 78%. 

We see, therefore, that after the figure 55% had 
been reached in the harvest of 1894 the mean value rose 
in the three following years of the experiment to 67, 73 
and 78%. 

Clarkia pulchella, Fig. 85. It was in the spring of 
1895 that I made the extensive sowings of horticultural 
seeds to which I have already referred, for the purpose 
of isolating tricotylous intermediate races. The seeds 
of Clarkia pulchella alba produced about 1% tricotyls. 
30 of these flowered, but only 18 of them produced suf- 
ficient seed. Two of them had hereditary values of 14 
and 16%, the rest from to 7%, with a mean of 4%. 
In 1896 only the tricotyls of the parent with 16% were 
planted out. There were 39 of these, and for all of them 
a value could be calculated. These values have been given 
on page 422, and were above 50% for eight plants. The 
intermediate race, therefore, was already represented by 
several specimens. 

In 1897 I planted out only the tricotylous seedlings 
of the plant with 64%, and saved the seeds of 39 
of them. Their hereditary values were distributed be- 



430 



Tricotylous Races. 



tAveen 16 and 79% and gave a mean of 49%. The race 
could therefore be regarded now as perfectly pure. 

Helichrysum bracteatum cornposituin, Fig. 86. From 
the same set of sowings as that which contained Clarkia, 
I planted out some tricotylous seedlings of Helichrysum. 
There was a relatively large number of them, and alto- 
gether 19 set seed. For each one the value was calcu- 




Fig. 85. Clarkia pulchella alba. A flowering sprig. 

lated separately. In the case of 15 plants these were 
distributed between 2 and 8% and exhibited a mean of 
4% ; but there were higher figures besides, viz., 12 12 
16 and 41%. The latter plant was obviously a repre- 
sentative of the intermediate race sought for; the re- 
mainder were thrown away as doubtful, although if 
there had not happened to be such a favorable plant 



The Isolation of Tricotylous Intermediate Races. 431 



among them all, the plant with 16% would, no doubt, 
have offered me as good a prospect as the corresponding 
plant of Clarkia. The chosen plant was remarkable for 
the large proportion of tetracotyls and the low proportion 
of hemi-tricotyls which it produced. There were 1 1 % 
of the former, and only \% of the 
latter. This peculiarity has reappeared 
amongst its descendants, especially with 
regard to the tetracotyls. 

In 1895 I planted out on separate 
beds tricotyls and tetracotyls of the 
parent with 41% only. Among the 
tricotyls 32 plants set plenty of seed. 
Of these one produced only 6% tri- 
cotyls, amongst the rest the values 
were distributed between 13 and 43%, 
and their mean was at 26%. The 
tetracotyls gave similar numbers, em- 
bracing 19 plants with from 14 to 42% 
and a mean of 25% ; besides these there 
was one plant with as much as 51%. 
This latter fact must obviously be at- 
tributed to a fortunate chance, and we 
may conclude that the tetracotyls are 
not more likely, nor on the other hand 
less so, to produce tricotyls than the 
tricotyls themselves, but that they ob- 
viously belong to the same race, i. e., 
that their character is brought about by the same ele- 
mentary factor. The proportion of tetracotylous seed- 
lings in this culture was very high, but not higher than 
the ratio recorded for the first generation. 

For the continuation of the race onlv seedlings of the 




Fig. 86. Hclichry- 
suin bracteatum 
compositum. A 
flowering stem of 
a plant of the tri- 
cotylous interme- 
diate race. 



432 Tricotylous Races. 

tetracotylous parent with 51% were planted out. Here 
again both the tricotylous and tetracotylous plantlets were 
used, but this time not in separate lots. Seeds of 37 
plants were saved and sown, and they gave values which 
did not differ essentially from those obtained in the fore- 
going year. They were distributed fairly regularly be- 
tween 16 and 52% and had a mean of 35%, i. e., the 
mean value had undergone a considerable increase. 

Antirrhinum majus. It was with this plant that I 
made one of my first experiments in the production of 
tricotylous races, and the fact that the progress in this 
case was much slower than in later cultures, may well 
be ascribed to the less extensive experience which I had 
at that time. I am now inclined to regard the practice 
of selecting from an insufficient number of seed-parents, 
and also of inadequate manuring as some of the causes. 
Nevertheless I shall describe the experiment because it 
ultimately led to a genuine tricotylous race. On the other 
hand it may not be unimportant to show 7 that, if a repe- 
tition of my tricotylous cultures is made, the attainment 
of the end must not always be expected to be reached 
in two or three generations. 

I have attempted to isolate tricotylous races from two 
varieties of the Snap-dragon. First from the striped 
variety mentioned on page 120 of this volume, and figured 
in Plate I ; but as the success attained with this after 
four generations (1892-1896), was not so great as in 
the other case, and 45% had not been exceeded, I did 
not proceed further with it. Therefore I shall confine 
my description to the latter. It was a dark red half- 
dwarf variety. 

In 1892 I had four tricotylous plants from bought 
seed, and from their seeds obtained in the following 



The Isolation of Tricotylous Intermediate Races. 433 

spring (1893) the proportions 2 A 7 and 7% of tri- 
cotylous seedlings, counted in lots of from 300 to 500. 
I only planted out the seedlings of one of the plants with 
7%, but the experiment was not successful, and only 
three tricotylous plants gave a sufficient quantity of seed. 
Their hereditary values were 2 8 and 8%. The seed- 
lings of one of the best plants were planted out in 1894. 
In this year I had twelve tricotylous plants for which I 
could calculate the values. With two exceptions, they 
were distributed between 7 and 19%, but the exceptions 
attained 23 and 25%, the mean of the whole group being 
13%. In 1895 the tricotylous seedlings of the two best 
parents were planted out in separate groups. The mean 
numbers of these differed considerably ; but both attained 
a proportion of 41% as maximum. The parent with 
23% had produced offspring the values of which were 
distributed between 7 and 31% (18 plants with a mean 
of 17% and one plant with 41% tricotylous grand- 
children; whilst the parent with 25% gave values from 
15 to 31% amongst 12 offspring, with a mean of 26%, 
and two specimens with 41%. In conformity with the 
principles of selection of the grandparents, the three 
plants with 41% were not regarded as analogous, and 
only the offspring of the parent with 25% and with a 
mean, calculated from its grandchildren, of 26% were 
planted out. The progeny of the third plant with 41% 
were considered as of inferior value and thrown away. 
In the following spring, when the values were cal- 
culated, no essential difference could be detected between 
the two groups of my culture of 1896. In percentage 
calculated from lots of 300 seedlings these figures were 
as follows : 



434 Tricotylous Races. 

VALUES OF THE OFFSPRING NUMBER OF 

LOWEST MIDDLE HIGHEST SEED-PARENTS 

A 41% 31 45 67 16 

B 41% 22 50 79 22 

Since these two cultures may be regarded as typical 
of ordinary intermediate races, not subjected to improve- 
ment by selection, I will give the full series of figures 
for one of them (B). They are as follows: 



56 58 59 



71 


79 








60 


60 








50 


51 


55 


55 


55 


41 


42 


46 


47 


47 


35 


36 


39 






22 


25 









Written in this way the figures show, without any 
further treatment, a group in the form of a curve the 
apex of which was between 50 and 55%. 1 

I planted out the grandchildren of the plant B only, 
and selected for this purpose (1897) the two parents 
with 71 and 79%. The two cultures consisted of tri- 
cotylous plants only, flowered on separate beds, fertili- 
zation being left to the agency of insects, however, as in 
previous years. The result of the determination of the 
values in the spring of 1898 was as follows: 

_ HEREDITARY VALUES OF THE OFFSPRING NUMBER OF 

LOWEST MIDDLE HIGHEST SEED-PARENTS 

C 11% 34 62 74 23 

D 79% 48 64 79 24 

In comparison with the previous year, therefore, an 
advance had taken place in the mean values but not in the 
maximum. 

1 It is my custom to plot the harvest raised from each parent and 
from each grandparent in this way. When grouped in this manner 
the figures display the result very graphically; and immediately show 
whether it falls outside the limits of observational error ; and whether 
therefore the existence of differences between the individuals is 
shown beyond doubt. 



The Isolation of Tricotylous Intermediate Races. 435 

Let us now summarize the whole culture, which ex- 
tended over six years. We obtain the following series: 

VALUES IN THE HARVESTS OF 

1892 1893 1894 1895 1896 1897 

Highest value 7 8 25 41 79 79 

Mean " 5 6 13 26 50 64 

Lowest 22 7 15 22 48 

As already stated, the intermediate race had therefore, 
in this case been isolated only gradually from the mix- 
ture, chiefly as the result of the originally small extent 
of the cultures. 

Papai'cr Rhoeas. In 1895 I selected 21 tricotylous 
seedlings from a sowing of the double garden variety 
of this plant with mixed colors. They yielded an abun- 
dance of seed, which gave the following percentage of 
tricotyls, counted in groups of 300 seedlings each: 



18 


19 


19 


20 




12 


12 








7 


7 


8 






4 


4 


4 


4 


6 


0.5 


1 


1 


1 


1 



This group plainly exhibits two sections, a half curve 
with an apex at 1 % and 4 seed-parents with the proportion 
of 18 to 20%. Obviously these four belong to the inter- 
mediate race sought for, whilst the rest are partly hybrids 
between the two races. The best tricotylous seedlings of 
the two parents with 18 and 19% were planted out in 
1896. They flowered and set an abundance of seed. 
The determination of the hereditary values from lots 
of 300 seedlings each gave a result for one of the two 
parents, with 24 offspring, of 10 to 56% with a mean 
of 19%, and for the other from 10 to 53% with a mean 
of 26%. Seedlings were planted out from the two best 



436 Tricotylous Races. 

plants of these groups and the result in the following 
spring, 1898, was 23 to 65%, with a mean of 40% among 
17 seed-parents, and 26 to 75%, with a mean of 47 /r , 
amongst 13. 

Phacelia tanacetifolia, Fig. 87. My race arose from 
the same set of bought seed which included Clarkia, Hcli- 
chrysiun and Papaver. In the summer of 1895 I had 
20 tricotylous plants, raised from bought seed, in flower. 
Their values constituted a two-fold group like that which 
occurred in Papaver. Three seed-parents had 12- -12 
and 14%, but the rest had values between 1 and 10%; 
the three former were alone used as the basis of my 
race. The three cultures derived from them gave 30 6 
and 9 separate harvests, which were evaluated in the 
spring of 1897 in the usual way. The lowest, middle 
and highest values for the three groups were 5 26 58, 
212842, and 61-4 16%. Obviously the two first 
grand-parents had given better offspring than the last 
one. I selected the former group for the continuation 
of the race, employing the two best plants with 54 and 
58%. They gave two groups of tricotylous plants, the 
harvests from which exhibited a great advance on the 
average, but which did not differ essentially from one 
another. With the exception of the extremes these fig- 
ures constituted a closely circumscribed group of 35 val- 
ues distributed between 35 and 72%, with a mean of 
57%. 

The extremes were 20 and 22%, and on the other 
side 80 85 and 90%. The two former figures, which 
were probably the result of incomplete isolation, occurred 
in the same group. The higher figures, however, were 
distributed over the offspring of both grandparents. 

Obviously the mean value of 57% of the intermediate 



The Isolation of Tricotylous Intermediate Races. 437 

race had been attained, and therefore I did not continue 
the culture. 

Silene inflata, Fig. 88. I obtained this race by pure 
chance. The stock plant was one of that series of forms 
which I had taken into cultivation, during the course of 
many years, for the purpose of finding species in a mu- 




Fig. 87. Phacelia tanacetifolia. A 
flowering sprig. 



Fig. 88. Silene inflata, A 
whole plant. 



table state (Vol. I, p. 271). A single specimen which 
had come up from seed of weeds, accidentally imported 
with cereals into our harbor, was transplanted into my 
experimental garden. The seed from this plant produced 
a proportion of 3% tricotyls, and when it flowered again 
in 1893, one of 4%. The tricotyls of the first harvest 



438 Tricotylous Races. 

were planted out in the summer of 1893 and eight of 
them yielded an ample quantity of seed. In each lot, of 
from 200 to 1300 seedlings, I counted the percentage of 
tricotyls and found most of them to be distributed be- 
tween 2 and 15%, the highest numbers being 24 and 
32% (these latter amongst 1300 and 1060 seedlings re- 
spectively). The mean was 11%. 

Therefore the original plant obviously belonged to a 
tricotylous intermediate race, a fact which, however, was 
only proved by the behavior of its descendants. 

In the spring of 1894 I only planted out the tricotyl- 
ous offspring of a parent with 32%, and obtained 22 
plants which set seed. From these I obtained in the 
following year 22 hereditary values which were distrib- 
uted between 26 and 55% and reached a mean of 37%. 
There were three individuals with 54 55 and 55%. We 
see that the mean was higher than the corresponding 
value of the parent plant, and from this we conclude that 
regression did not take place in the direction of 0, but 
towards the other side; and this is exactly what should 
happen in the isolation of new races from their mix- 
tures. 

In the summer of 1895 I planted out tricotylous off- 
spring from the two parents with 55% ; I kept them in 
two groups and determined their values from the har- 
vests of 31 individuals. There was no essential differ- 
ence between the two groups ; the numbers were dis- 
tributed between 26 and 73 and their mean was 53%. 
The mean had, therefore, reached the value of the parent, 
and the race could be regarded as an intermediate race, 
isolated but not yet subjected to selection. 

For the next generation I selected the tricotylous 
offspring of three plants with 66 68 and 73%. Of 



The Isolation of Tricotylous Intermediate f\accs. 439 



these plants 25 set seed, but the culture was unsuccess- 
ful in this year, owing to adverse circumstances, and 
only a few of the plants produced more than 200 fertile 
seeds. The values, therefore, were not very exact, but 
formed a close group ranging between 18 and 56%, 
with a mean of 32%. It will be seen that in spite of the 
selection a general retrogression had taken place. 

Sun unary. If we look at the results of the experi- 
ments which have been described, we are struck by the 
fact that a certain group of hereditary values appears 
much more commonly than others. These are the fig- 
ures ranging round 55%, and this value is usually 
reached at the conclusion of the second generation or, 
in less favorable experiments, at the conclusion of the 
third or fourth. AYith a view to emphasizing this fact 
I have grouped the whole series of experiments in such 
a way that the figures round 55% are brought together 
in one column : 

ISOLATION OF TRICOTYLOUS INTERMEDIATE RACES. 

HIGHEST HEREDITARY VALUES EXPRESSED IN PERCENTAGES FOR THE 

SUCCESSIVE GENERATIONS. 





FIRST GEN- 
ERATION 


1-50 c r 


ABOUT 
55% 


60-95 % 


Antirrhinum inajus . 


1892 


1 


8 


25 


41 


79 


79 





Mercurialis annua . 


1892 


I 





2 


55 


86 


92 


91 


Silcne inflata .... 


1892 


I 


3 


32 


55 


73 


56 





Cannabis sativa . 


1893 


I 


3 


15 


52-63 


80 


90 





Clarkia pulchella . 


1895 





I 


16 


64 


79 








Helich rysu in bracteatum 


1895 





I 


41 


51 


52 








Pa paver Rhoeas . 


1895 





I 20 


56 


75 








Phacelia tanacetifolia, . 


1895 





I 14 


58 


90 








Oenothera hi rt el la 


1895 





I 


8 


56 


89 









In this table the first column gives the year in which 
the experiments began, either with the selection of tri- 



440 Tricotylous Races. 

cotylous seedlings from seed which had been bought or 
obtained from some other source, or with plants which 
had been found by chance (Oenothera, Silenc). Where 
necessary, this year is denoted in the table by I (first 
generation). The numbers which succeed each other in 
the row to the right of it refer to the first and the follow- 
ing generations. Thus for instance in Clarkia there were 
as many as 16% tricotyls in the harvest of the first gen- 
eration, 64 in those of the second and 79 in the third. 

The point which this table is intended to illustrate 
is best brought out by a comparison with the series of 
figures given on page 392 for the half races. In that 
case, a selection continued from four to six years, did 
not bring this value, as a rule, further than 2 to 4%, and 
only in exceptional cases attained 15 to 20%. In this 
case, on the other hand, 55% is attained in two or three 
generations. In the half race a continuation of the 
selection would presumably not have led to any con- 
siderable increase, a fact which is demonstrated by the 
experiments with Amarantus and Scrophularia which 
were continued over a longer period of time. In this 
case, however, selection is as a rule very effective, inas- 
much as it can increase the best representatives of the 
race, in a very short time, to a hereditary capacity of 
80 to 90%. 

Therefore there can be no doubt that entirely differ- 

ft 

ent factors are at work in these two cases. In the former 
there occurred only races with half curves on which se- 
lection has little effect. In this case, however, there oc- 
curred, besides these, the highly variable intermediate 
races which are extraordinarily susceptible to selection 
and to external conditions of life. They were easily 
isolated, either because one or more examples of them 



The Isolation of Tricotylous Intermediate Races. 441 

were already present in the original sample of seed, or 
because between the intermediate and the half races hy- 
brids were met with, by the subsequent segregation of 
which the race was produced. 

In the first experiments the isolation of the tricotyl- 
ous intermediate race took from three to four genera- 
tions. Later when I started the experiments on a larger 
scale, the number was reduced to two years. Further 
selection brought it up, in one year as a rule, to 70- 
80% and sometimes even to 90%, either immediately 
in the course of another year, or after two generations. 
Unfavorable conditions of life led to exceptions, or even 
to retrogression; but only Helichrysum and Silene ex- 
hibited this feature. Cannabis, Mercurialis and Antir- 
rhinum maintained a value of 80 90% under continued 
selection, and it is quite probable that even 100% might 
have been attained in occasional individuals. The mean 
figures of the whole group correspond, as a rule, to these 
maximum values. They maintained themselves at about 
55%, but are liable to be increased by selection or dimin- 
ished by unfavorable conditions. 

Lastly, it should be noted that the ngures for these 
intermediate races are so far removed from those of the 
half races (p. 392), that all suspicion as to the possible 
effect of occasional errors in the choice of the samples 
is excluded; in other words, that hereditary values from 
1 to 5% or even of 5 to 20%, if they are maintained in 
sf>itc of selection, may be regarded as characteristic of 
half races, whilst values of 40 to 60%, when found in 
separate crops, may be taken to indicate the presence of 
intermediate races. 

When an intermediate race is isolated from an orig- 
inal sample of seed, it is separated from the half race 



442 Tricotylons Races, 

which is also present, for hardly ever is the intermediate 
race found pure by itself. As far as I know, at least, 
there is no species of plants which has so much as half 
of its seedlings showing three cotyledons, without being 
selected. If we study the process of separation by the 
statistical method, w T e find that two curves, a half curve 
with an apex at 0, and a bilateral curve with an apex at 
50 55%, can be distinguished from one another. Some- 
times in one or other of the transitional generations 
both curves can be more or less clearly seen side by side, 
constituting a so-called dimorphic curve. I have fre- 
quently observed this in these experiments, and have, in 
some cases referred to it. 

Dimorphic curves of this kind are best obtained in the 
transitional generations by planting out dicotylous as well 
as tricotylous seedlings ; for, as was mentioned before, 
it is very likely that many dicotyls will belong to the 
half race and most of the tricotyls to the intermediate 
race. But if the latter is once isolated, all the individuals 
belong to it, independently of the question whether they 
have two or three or cleft cotyledons. In this stage a 
dimorphism of this kind is no longer to be expected, un- 
less selection is continued in two different directions. 1 

As an instance of this let me cite the case of my cul- 
ture of Mercurialis annua in 1895 (see the table on page 
439), inasmuch as this species, being dioecious, would 
be expected to exhibit a levelling of the differential char- 
acters. The plant with a value of 55% in 1894 could 
obviously have been partly cross-fertilized. Its offspring 
had in their seeds the following hereditary values : 

1 With regard to this question compare the analogous experi- 
ments with H "licnitliits annuns syncotylcus (II. n). 



The Isolation of Tricotylous Intermediate Races. 443 

81 82 86 

. , . 72 74 76 78 

A. Tricotylous offspring 

bo b/ 

44 48 50 

34 35 36 40 



B. Dicotylous offspring 24 25 25 

18 20 

The group is therefore dimorphic, the intermediate 
race is not yet pure. I found the same conditions to 
obtain in other cases. 

In Clark ia pulcliella also, the atavists reverted when 
sown in 1897 alongside the tricotylous culture already 
mentioned and from seed of the same parent. This 
parent already had a hereditary value of 64 %, but was 
the first in this race with a high figure, and therefore 
still belonged to the transitional period. The values are 
arranged in groups of 5 to 15, 15 to 25 etc., and the 
number of individuals which fall into each group are 
given under the mean percentage number, i. e., 10, 20 etc. 

Proportion of tricotyls in percentage 10 20 30 40 50 60 70 80 
Number of tricotylous individuals 02588 12 31 
Number of atavistic individuals 4 13 911 2 

The mean for the tricotylous individuals is 49%, for 
the atavists 30%. 

The race once isolated, the atavists obviously still 
have smaller values than the tricotyls; but the difference 
is never more than a small one, and the curve for the 
two races together will have only one apex. In Oeuo- 
thcra hirtella I examined a series of values of the atavistic 
offspring as well as the tricotylous offspring of the same 
parent of 1896 which had a value of 56%. This parent 
had been self-fertilized, the visits of insects having been 
excluded ; and so were all its offspring. I shall group the 
values in the same wav as above. 



444 Tricotylous Races. 

Proportion of tricotyls in percentages 10 20 30 40 50 60 70 80 90 

Number of tricotylous individuals 1 611 14 10 1 

Number of atavistic individuals 1 4 3 10 11 11 6 

Calculated for the whole progeny 1 4 4 19 27 32 21 1 

The average value for the tricotyls is 72% and of the 
atavists 60%, which latter figure is of itself high enough 
for an intermediate race. The last row was obtained 
by means of a correction of the values of the tricotyls, 
since too small a number of these had been cultivated in 
comparison with the atavists. The whole curve is ob- 
viously monomorphic although much flattened. 

A curve with such a great amplitude indicates a cor- 
responding high variability and therefore also a consider- 
able susceptibility to external influences, as we have found 
in several instances to be the case with intermediate races. 

To this great amplitude also the fact is due that se- 
lection, however stringent, never quite eliminates the 
lower values. Even when the apex of the curve is be- 
tween 60 and 70%, values as low as 25% may still 
occur. In such cases the curve has a "sweep" to the 
atavistic side, and thus differs most conspicuously from 
the curves of the half race, the shape of which might be 
considered as its mirrored image ; but as I shall come 
back to this point when I deal with syncotylous races, 
I shall not give any instances now. 

7. PARTIAL VARIABILITY OF TRICOTYLY. 

In experiments with tricotylous races the hereditary 
capacity or value is, as we have seen, the main character 
subjected to selection. This term indicates the number 
of tricotylous seedlings in the harvest. The seeds of 
each individual are saved and sown separately, and then 
recorded after germination. Whether the individual it- 



Partial Variability of Tricotyly. 445 

self has two or three or merely cleft seed-leaves is a 
question of minor importance, and does no more than 
furnish a suggestion in starting the experiment. On 
the average, atavists and hemi-tricotyls are, without 
doubt, of less value in this respect than tricotyls and 
tetracotyls; but the differences are too small to warrant 
a choice of seed-parents on this ground. 

The determination of the hereditary value depends, 
therefore, largely on the extent of the crops. The larger 
this is for any one individual, the more closely will the 
value found correspond to that which would be derived 
from an imaginary harvest, consisting of an infinite num- 
ber of seeds. Therefore, the best plan would be to make 
the plants grow as vigorously as possible, and to save 
the seeds of all fruits from as many branches and sprigs 
as possible. In practice, however, this cannot be done, 
since it is far more important to grow as many indi- 
viduals as possible in a given space. The more numerous 
the individuals are, the more stringent the selection be- 
comes ; and, what is far more interesting, at least in 
working with mixtures, the greater is the prospect of 
finding any desired particular sort. Unbranched, or al- 
most unbranched, plants with terminal inflorescences only, 
obviously need much less room than much branched in- 
dividuals ; and larger harvests require relatively too much 
time to gather. The best plan, therefore, would be to 
collect only just so much seed from each individual as is 
necessary for sowing in the following year. 

These considerations suggest the question whether 
different groups of fruits are alike in regard to hereditary 
capacity or whether they exhibit, perhaps, considerable 
differences. Shall we find this capacity to be different on 
the branches from what it is on the main stem? Will 



446 Tricotylous Races. 

the earlier seeds give different values from those given 
by the later ones? Has the character of the year in 
which the harvest is made any such influence amongst 
perennial plants ? Obviously these questions must be 
answered if the individual harvests are to be limited in 
the interest of the experiment. 

In the last two sections of the first part of this vol- 
ume we have seen that semi-latent characters manifest 
a certain periodicity in their distribution over the plant, 
and also that the choice of seeds on the plant plays some 
part in the process of selection. The question is, how 
do the tricotylous races behave in this respect? 

The general rule seems to be that a bud, whether of 
a branch or of a flower, is more likely to reproduce an 
anomaly, the more vigorous it is (p. 324). Therefore 
with an increase in the degree of branching the expecta- 
tion of the occurrence of anomalies decreases (p. 329). 
The first or lower fruits of an inflorescence will be 
stronger than the higher ones, and the fruits on the 
weak lateral sprigs of the primary and secondary branches 
may as well be thrown away. 

There is no ground for supposing that the flower buds 
behave differently from the vegetative parts. The best 
instance of the phenomena in question is afforded by 
profusely branched specimens of the twisted race. Dip- 
saciis sylvestris forsus. The torsion affects the middle 
portion of the main stem, but neither its upper nor lower 
extremity. Tt is repeated on the strongest branches situ- 
ated on the middle of the stem, and on these only in 
their middle parts, and excluding the weaker ones. The 
stronger a stem or a branch is, the greater is the extent 
of the twisted part. Tn the branches it is always con- 
fined to sinHe internodes, whereas the stem may fre- 



Partial Variability of Tricolyly. 447 

quently be entirely transformed. tranches of the second 
order exhibit no more than traces of the anomaly. 

If we apply this instance to the distribution of tri- 
cotylous seeds on a plant, we should conclude that the 
lower part of the terminal inflorescence of the main stem 
would produce the highest proportion of tricotylous seed- 
lings ; but the flowers and fruits themselves are lateral 
branches, and so the question arises, how far we are 
justified in expecting this. 

In species like Ocnothcra and Antirrhinum, which 
have a primary inflorescence rich in flowers and in seeds, 
I have usually limited myself to this and, where possible, 
to its lower and middle parts. In Helichrysum to the 
flowerheads which open first, in Clarkia and Phacclia to 
as many of the earlier flowering branches as would pro- 
vide a sufficient quantity of seed, and so on. The question 
is w r hether these first fruits possess the same hereditary 
capacity as would be found from the largest number of 
fruits that could be gathered on the plant. 

With a view to determining this point I have insti- 
tuted a number of subsidiary experiments. The answer 
has been in the affirmative throughout. Certainly there 
are small differences ; these, however, seldom fall out- 
side the latitude of S c /c which is the limit of observational 
error. I shall now present the results of these experi- 
ments in a condensed form. 

A first experiment was conducted with Oenotliera 
hirtclla, which fertilizes itself in parchment bags with- 
out artificial aid. In the summer of 1898 I planted out 
seven tricotylous seedlings of one parent with a heredi- 
tary value of 66 c /r at distances of about a meter apart, 
allowed them to branch freely and to develop into vig- 
orous plants, enclosed the flowers in parchment bags and 



448 Tricotylous Races. 

harvested and examined the seeds for each individual 
branch separately. Only slight differences were pre- 
sented by the values obtained, and I shall therefore only 
give the means. I determined the values of the inflores- 
cences of the main stem and found the average to be 
38% ; for the strong lateral stems produced from the 
axils of the rosette (see Fig. 55, Vol. I, p. 302) I found 
it to be 45% ; for the upper branches of the stem (see 
Fig. 49, Vol. I, p. 282), however, 47% (calculated from 
24 determinations), and for the lower branches of the 
stem, which in iihis species tend to be very much weaker, 
52% (in eight counts). The distribution of the differ- 
ences, therefore, was different from what would have 
been expected. They show that in this case, the harvest 
from the primary inflorescence gives a somewhat lower 
value than the whole harvest of the plant in question 
would have given. In Dracocephalum moldavicum, where 
the values are always small, I collected, in the summer of 
1895, the seeds of all specimens from the main stem and 
lateral branches separately, but found no difference (0.4% 
for both). In Amaranhis spcciosus the seeds from the 
terminal panicle regularly gave somewhat higher values 
than those from the lower branches, but with very slight 
differences only (1892). The average calculated from 
20 plants was 2.8% for the former and 1.7% for the 
latter. 

In many of my experiments I have saved the seeds 
which ripened first, separately from those which ripened 
later: e. g., Amarantus speciosus, Scrophularia nodosa, 
Mercurialis annua, Antirrhinum majns, Silene inflata, 
and others. No differences of any importance were 
found in this way. Deviations are sometimes found in 
larger series, but only such as can be attributed to the 



Partial Variability of Tricotyly. 449 

unavoidable errors in the samples of seed. In Mcrcit- 
rialis annua I have for several years recorded the seed- 
lings which came up from the first seeds that fell out 
on the bed. In this species, as is well known, the fruits 
open suddenly and scatter their seeds about. These counts 
gave essentially the same results as those obtained later 
from seeds harvested and sown by hand. I often made 
use of them to obtain a preliminary idea concerning the 
extent of the improvement to be expected. 

My custom is to limit the separate harvests to the 
desired quantity of seed, by cutting back during the 
period of growth, and by stopping the saving of seed as 
soon as a sufficient quantity has been secured. For this 
purpose I have estimated this amount from the result 
obtained in the first generation, in the case of each species. 
Moreover I have frequently compared such gatherings 
with much more extensive ones, obtained either by not 
cutting the plants back or by not ceasing to save the seed 
before all of it was ripe. In this way Amarantus spc- 
ciosus often gave higher values from a smaller harvest, 
but the differences were slight and the exceptions many. 
Caunabis sativa gave the same values from large plants 
bearing more than 100 cubic centimeters of seed each, 
as from average or weaker individuals. In such large 
crops, saved without limitation and amounting to 80- 
110 cc. of seed the average was 11%, but in crops of 
20 35 cc. it was 14%. The cultures were made in 1894 
and the same happened in other years. In Ooiothcra 
rubrinerzis the value was seen to decrease as the size 
of the harvest increased, but only in degrees of one-tenth 
per cent, on the average, amongst numerous individual 
trials. The same occurred in Scropliularia nodosa. 

This latter species, as well as Silcnc inflata, is a per- 



450 Tricotylous Races. 

ennial form ; and therefore both of them afford material 
for comparing the harvest of the same plant as produced 
in successive years. Here again I failed to find differences 
of any significance. I have given above the values de- 
rived in 1892 and 1893 from a single plant of Silene, 
which flowered in isolation; they were 3 and 4% for 
these two years. In Scrophularia I made a series of ob- 
servations at the beginning of my cultures when the hered- 
itary values were still small, and repeated them in the 
period of 1896-1899, when they had become higher (15% 
and more). In these years, 1897, 1898 and 1899 six 
plants gave the following values, the bracketed number 
referring to the second year: A 22 (25), B 25 (17), 
C 22 (17), D 23 (25), E 27 (25), F 23 (22). Ob- 
viously these figures do not justify a conclusion as to any 
diminution or increase in the ratio in which tricotyls are 
produced. 

The result of all of these experiments is such as to 
justify my practice of limiting the individual harvest to 
the quantity of seed necessary for sowing. 



8. THE INFLUENCE OF EXTERNAL CONDITIONS ON 

TRICOTYLY. 

Which seeds in a fruit produce aberrant seedlings? 
This question is at once one of the most simple and one 
of the most difficult presented by experimental breeding. 
If some day we could succeed in solving it and thereby 
make a control of this process possible, much light would 
be thrown on a whole series of phenomena connected 
with the origin of races. 

In dealing with this question we are thrown back 
on egg cells and pollen grains and the problem at once 



Influence of External Conditions on Tricotyly. 451 

becomes a double one. To these is added a third factor, 
namely the union of the two germ cells, which may itself 
be influenced by outward conditions in different ways. 

I have gone into the questions only so far as was 
necessary for the choice of the conditions of my experi- 
ments. The course of these has, as a rule, been very 
regular. The results of selection seldom have been dis- 
turbed, to any great extent, by other influences. Some- 
times, however, this did obviously occur ; and it is exactly 
experiments of this kind which justify us in ascribing 
an important part to external conditions in the determi- 
nation of the proportion of tricotylous seedlings. But 
when, from these facts, we proceed to analyze this in- 
fluence, we do not succeed in making experiments in 
which the same influences have the same results. 

Two instances will suffice. Under very peculiar con- 
ditions which affected the whole growth of the plant, 
the hereditary capacity of my race of Amarantus spe- 
ciosus suddenly rose, in 1891, from 4.5 to 13%, with- 
out, however, maintaining that proportion even under 
selection (p. 407). On the other hand, in the summer 
of 1896 the whole culture of Silcnc inflata underwent 
considerable deterioration as the result of unfavorable 
conditions, the mean of all values falling from 53 to 
32%. One year may obviously affect the plants quite 
differently from another, even when the treatment to 
which they are subjected is as uniform as posoible. The 
effect is perhaps produced in the early stages of the plant, 
perhaps also in the development of the sexual cells and 
at the time of fertilization. Abundant starting-points 
for further investigations may here be found. 

As a rule the likelihood of obtaining anomalies in- 
creases with the vigor of the seeds which produce them 



452 Tricotylous Races. 

(p. 332). It is natural to inquire, therefore, whether this 
vigor of the seeds can be increased by improved nutri- 
tion of the plant. Unfortunately we must, in such cases, 
be content with averages, and these obviously give much 
smaller differences than the single extreme cases. Some- 
times I found that the external conditions exerted a con- 
siderable influence, but, as a rule, I could not detect any 
difference. 

In the first place I shall refer to the effects of manu- 
ring. The prevailing opinion is that manuring with ni- 
trates favors the development of leaves, but that phos- 
phates favor flowers and fruits. As a nitrate manure 
I employed horn-meal combined with dried guano and 
as phosphate manure the ordinary superphosphate ; but 
I find that the former usually produces more abundant 
flowering and a larger harvest of seed than the latter. 
In 1899 I instituted a comparative experiment with Ocno- 
thcra hirtella by planting out the seedlings of a single 
self-fertilized plant. During the period of flowering each 
inflorescence was guarded from the visits of insects by 
a parchment bag. The nitrate plants grew more rapidly 
and luxuriantly at first than those on the phosphate bed. 
Moreover they began to flower somewhat earlier, and 
consequently set more seed ; for fertilization must be 
stopped before all the flowerbuds have opened, since in 
our climate flowers which open in September have not 
time enough left to ripen their seed. 

The harvest for each individual plant was examined 
separately, and from this was calculated, in the way we 
have so frequently described, the percentage value for 
each plant. In the following summary these are associ- 
ated in groups of from 15-25, 26-35, 36-45; the means 
of the groups being 20, 30, 40 etc. 



Influence of External Conditions on Tricotyly. 453 

HEREDITARY VALUES IN OENOTHERA HIRTELLA IN 1899. 

Percentage values 10 20 30 40 50 60 70 80 90 

After manuring with nitrates 08 17 12 95221 
After manuring with phosphates 129 14 78511 

The number of individuals in the first experiment is 
56, in the second 48; average harvest per plant, 3.5 and 
2.5 cc. The seed was collected from the terminal spike 
only. The mean value for the nitrate plants was 37%, 
for those manured with phosphates, 44%. The parent 
of all these plants had had a value of 66%. 

Manuring with superphosphate has therefore, in this 
case, in an otherwise uniform culture, been more favor- 
able to the production of tricotylous seedlings than ma- 
nuring with hornmeal. 

I found exactly the same result in the same year with 
Helichrysum bracteatuni. I planted out tricotylous seed- 
lings only of a single parent with 11%. I determined and 
arranged the values as before and found : 

HEREDITARY VALUES IN HELICHRYSUM BRACTEATUM IX 1899. 

Percentage values 10 20 30 40 50 Mean 

After manuring Avith nitrates 2 22 18 5 1 26% 

After manuring with phosphates 1 5 20 11 2 32% 

Number of individuals 48 and 39. The growth on 
the nitrate bed was very luxuriant ; the leaves were dark- 
green, and the flowers abundant. On the phosphate bed 
the plants were yellowish-green, very little branched, and 
with fewer ripe flowerheads. Indeed, only 39 of the 
50 plants which had been set out set sufficient seed. 

Results as definite as these are not, however, always 

J 

obtained, especially when a comparison is instituted not 
between individual plants raised from seed, but between 
the various parts of a single individual obtained by di- 
viding it. I conducted such an experiment with Ocno- 



454 Tricotylons Races. 

thera (Knciffia) ylauca in 1899, but counted 5% tri- 
cotyls, both on the phosphate and on the nitrate half. 
I obtained the same result in Scrophularia nodosa by 
growing one half in ordinary garden soil and the other 
in sand, both yielding \% (1894). 

The two first experiments on the influence of manure 
show that an increase in the number of tricotyls is as- 
sociated with a diminution of the yield. The same result 
can also be obtained if the harvest of the individual plants 
is reduced in other ways. In Oenotlicra hirtclla I adopted 
two methods of doing this, late sowing and culture in 
pots throughout the whole summer. Tricotylous seed- 
lings of a single parent (with 66%) were planted out. 
In one of the two groups the sowing had taken place in 
March, in the other at the beginning of May (1898). 
Some plants of the former sowing were kept in pots of 
15 centimeters filled with well-manured garden soil 
throughout the whole summer. Fertilization took place 
in parchment bags and the individual crops, recorded and 
evaluated in the usual way, gave the following result : 

HEREDITARY VALUES IN OENOTHERA HIRTELLA IN 1898. 

Percentage values 10 20 30 40 50 60 70 Mean 

Normal culture 1 4 4 3 5 1 37 '; 

After sowing in May 10 14 11 1 41'; 

After culture in pots 3 5 7 4 047% 

Number of plants experimented with 18, 36 and 1'). 

We see therefore in this case a definite though small 
increase in the number of tricotyls. The mean of the 
harvest for the normal culture was 3.5 cc., for the late 
culture 2.5, for the pot-culture 4.5 cc. This latter had 
therefore not had the expected result of making the 
yield smaller, and as, nevertheless, the proportion of 



Influence of External Conditions on Tricotyly. 455 

tricotyls has increased, it is plain that the factors under- 
lying these differences are by no means simple. 

This is further shown by the fact that a repetition of 
the experiments does not always produce the same result. 
Thus in Amarantns spcciosns (1897), and Scrophularia 
nodosa (1898), I was not able to observe any influence 
exerted by the various external conditions on the propor- 
tion of tricotyls, although the experiments were carried 
out on a large scale. I also found that if I sowed sam- 
ples from the same lot of seed in two successive years, 
the mean ratio of tricotyls in the harvest of the two 
cultures was the same, (e. g., Oenothera hirtella, 1898 
and 1899). 

Moreover, unfavorable conditions can sometimes, by 
diminishing the yield, lead to an increase in the per- 
centage values. This is shown by an experiment which 
I made in 1898 with Antirrhinum majits. I covered half 
of my culture with a cage made of fine metal gauze 
painted black, after the plants had developed a stem of 
10 centimeters above the cotyledons. Within the cage 
it was considerably darker than outside, and the plants 
grew very weakly, produced only few branches, and de- 
veloped but a small number of flowers and fruits on the 
terminal spikes. Fertilization was artificial, and all the 
plants were guarded from the visits of insects. The 
yield in the cage was 0.5 cc. per plant, and outside 1 cc. 
per plant. In the former case as many fruits as possible 
were gathered but in the latter the upper flowers of the 
spike were not fertilized. The material used in this 
experiment consisted exclusively of the offspring of a 
single parent of 1897 which had had a value of 14%, 
but tricotylous and dicotylous seedlings were both used, 
each group being planted half within the cage and half 



Tricotylous Races. 456 

outside. I collected the seeds and determined the values 
in the same way as usual, and obtained the figures which 
appear in the following summary : 

HEREDITARY VALUES IN ANTIRRHINUM MAJUS. 

Percentage values 1-4 10 20 30 40 Mean 

Dicotyls in the shade 4 2 2 2 20% 

Dicotyls in the sun 5 8 4 1 4 14% 

Tricotyls in the shade 3 2 3 4 35 % 

Tricotyls in the sun 1 14 9 14% 

Number of seed-parents 10, 21, 12 and 24. 

We see that in both cases the proportion of tricotyls 
was considerably increased by cultivation in the shade. 

The experiments which we have passed in review in 
this section prove that the proportion of tricotyls in the 
offspring may be considerably modified by external in- 
fluences, especially in eversporting varieties, but within 
certain limits. The differences are such as cannot be 
neglected in comparative experiments and cultures, and 
show the importance of carrying out the latter under as 
constant conditions as possible. In general it must be 
assumed that a treatment, favorable to the individual 
flowers and seeds, will increase the production of tri- 
cotylous seedlings, but the question as to the nature of 
this relation in the individual cases must, for the present, 
remain unanswered. 



II. SYNCOTYLOUS RACES. 

9. HEMI-SYNCOTYLY, SYNCOTYLY, AMPHI-SYNCOTYLY. 

Alongside seedlings with split or double cotyledons 
there occur others, the seed-leaves of which have fused 
so as to form one single organ. They are, however, much 
rarer, but not so rare that they cannot be found every 
year, at least in some sowing or other. Tricotyls may 
be found in the proportion say, of one in a thousand, 
but syncotyls, as a rule, only one in tens of thousands 
of seedlings. 

In the sowings of 1895 which we have already men- 
tioned (p. 380), I found, amongst more than 250,000 
seedlings of 40 species, only 10 syncotyls as against 150 
tricotyls. Where they occur more abundantly this is due 
to inheritance, for as soon as the syncotyls are allowed 
to flower in isolation and their seeds are saved separately, 
it is found that they inherit their character in almost the 
same degree as do tricotyls. 

Instances of syncotyls were afforded me by Aster 
tenellus, Clarkia elegans, C. pulchella, Cerlnthe g\m- 
nandra, Chrysanthemum Myconis, Helichrysum bractea- 
tuin, Phaceliatanacetifolia, Silenehirsuta, Anagallis gran- 
diflora, Epilobium hirsutum, Hesperis niatronalis, Pent- 
stem on gentianoides, Robinia Pseud-Acacia, and many 
other forms; 1 but always in small proportions. A few 

1 Further instances are given by H. B. GRUPPY, Irregularity of 
Sonic Cotyledons, Science Gossip, N. S., Vol. II, 1895, p. 171. 



458 Syncotylous Races. 

species, however, produced them more abundantly. Among 
these were the following which produced the proportions 
of syncotyls from the seeds of single individuals, indi- 
cated by the attached figures: Oenothera (Kneiffia) 
glauca 16% (Figs. 89 and 90), Picris hieracioides 8%, 
Valeriana alba 3%. Dahlia variabilis and Sycios angu- 
lata were also found to be rich in syncotylous seedlings, 




Fig. 89. Oenothera glauca. A plant which produces an 
abundance of syncotylous seedlings. 

and in Centranthus macrosiphon I found 37% of them 
amongst the seeds of a single syncotylous plant. 1 

By syncotyls we mean, in the strict sense of the term, 
those individuals whose seed-leaves are completely, or 
almost completely, fused together along one side. Smaller 
degrees of fusion are called hemi-syncotyls, and they 
constitute an uninterrupted series between normal di- 

1 Eine Methode, Zwangsdrehungen aufzusuchen, Ber. d. d. bot. 
Ges., Vol. XII, 1894, P- 25. 



Hemi-Syncotyly, Syncotyly, Amphi-Syncotyly. 459 



cotyls and types in which the fusion has extended to the 
very tip. The lesser degrees of fusion are usually rarer 
than the greater, and, therefore, in order to get a fairly 
complete series of transitional forms, cultures from the 
seeds of selected individuals are required. It is often 
very difficult, especially in forms with stalked cotyledons, 
to distinguish between the lowest grades of fusion and 
pure dicotyls. If the crops are recorded before the 
cotyledons and their peduncles have grown to their full 
extent, it may easily happen that occasional seedlings, 






Fig. 90. Ocnothera glanca. Syncotylous seedlings. A and 
B, ordinary syncotyls ; C and D, pitcher-shaped syncotyls 
or amphi-syncotyls. 

which, after further growth, will prove to b hemi-syn- 
cotylous, are mistaken for dicotyls. 

The hemi-syncotyls constitute the minus variants of 
the series, the corresponding plus variants being the 
amphi-syncotyls of double or two-sided syncotyls (amphi- 
cotyls). In these latter cases the cotyledons are fused 
on both sides, often more on one side than the other, 
sometimes equally high on both sides. The cotyledons 
constitute a pitcher (Fig. 90 C and D, and Fig. 91) 
which is either cylindrical or urn-shaped or disc-shaped, 



460 



Syncotylous Races 



according to the breadth of the cotyledons on the normal 
plant. I found instances of these remarkable and pretty 
structures almost every year in Helianthus animus syn- 
cotyleus and in larger numbers in Mercurialis annua and 
Centranthus macrosiphon* and also occasionally in An- 
tirrhinum majns, Sinapis alba, etc. 

The fusion of these cotyledons sometimes results in 
a pressure being exerted on the plumule and interfering 
with its growth, and we often find that syncotyls grow 
slower than normal seedlings, at least at first, and that 





Fig. 91. Raphanus Raphanistrum. A cotyl pitcher ex- 
panded in the form of a disc. A, from the side ; B, the 
same, seen obliquely from above and showing the plumule. 

amphi-syncotyls are especially backward. The extent of 
this influence cannot, as yet, be measured ; but the fact 
that syncotyls are so much rarer than tricotyls may per- 
haps be explained by this check on their growth. Some- 
times the plumule breaks sideways through the cotyl- 
pitcher by splitting its lower part (Centranthus macrosi- 
phon, Mercurialis annua). Sometimes it succeeds, although 
very late, in elongating in the normal direction. In 
Helianthus annuus I have sometimes operated upon such 
1 Figured in Bcr. d. d. bot. Ges., Vol. XII, PI. IT, Figs. 3 and 4. 



Hcmi-Syncotyly, Syncotyly, Ainphi-Syncotyly. 461 



pitchers by splitting them up along one side with a sharp 
knife, as soon as I saw that the plant would not grow 
without this help. By this means I succeeded in bringing 
the plants to flower, but they were weak, thin-stemmed 
individuals. 

The growth of the plumule is often entirely sus- 
pended, both in ordinary unilateral syncotyls and in 
pitcher-like structures. In such cases the seedlings live 
much longer than usual, the cotyledons grow to a great 
size, often twice the normal, but finally the plant dies 
without producing a stem. This occurred frequently 
in Helianthus annnus and Dahlia variabilis, and less often 







Fig. 92. Polygomim Convolvulus. Instances of tri-syn- 
cotylous seedlings with various degrees of splitting and 
fusion. 

in Penstemon gcntianoidcs and Cannabis sativa. In the 
two latter species one or two leaves were sometimes de- 
veloped, but after that the terminal bud ceased to grow, 
whilst those leaves attained an abnormal size and thick- 
ness (Fig. 93). In such cases the question arises whether 
the inhibition of the growth may not, both here and 
elsewhere, have some other cause also. 

Syncotyly may be combined with tricotyly, and since, 
as we have seen, the fluctuating variability of both pre- 
sents a long series of forms, the multiformity will be 
much greater still in the series of the so-called tri-syn- 
cotyls. Thus, for instance, in Polygomim Convolvulus 



462 



Syncotylous Races. 



(Fig. 92), and also in Chenopodium album, Thrincia 

hirta, etc. 

Between syncotyly and disturbances in the normal 
arrangement of leaves in the later life of a plant, there 




Fig. 93. Cannabis sat'rca. A, a seed- 
ling which unfolded its cotyledons 
in April, but up till June had formed 
no plumule ; B, another with two 
abnormally large and thick first 
leaves, the terminal bud of which 
underwent no further growth. Both 
are from a culture, in the remain- 
ing seedlings of which the length 
of the stem had become 10-20 centi- 
meters during the same time (1894). 



Fig. 94. Fagus sylvatica. 
Syncotylous seedling with 
much elongated epicotylous 
internode and abnormal 
development of the plu- 
mule. 



is a close connection, as there was in the case of tricotyly. 
Frequently this disturbance is only a small one (Fig. 94) ; 
but in species with a decussate arrangement of the leaves 
or at anv rate of the first leaves, there often follows on 



Hemi-Syncotyly, Syncotyly, Amphi-Syncotyly. 463 

the syncotylous organ a node with only one leaf, which 
then usually stands opposite to this structure. I have 
frequently observed such cases in Mercurialis annua 
(Fig. 95) and Helianthus annuus. 1 Further disturbances 
ma / then follow, such as unequal size of the two leaves 




Fig. 95. Mercurialis annua. Syncotylous seedlings. A and 
B, hemi-syncotyls with normal arrangement of leaves ; 
C and D, completely syncotylous; the first leaf is single 
and opposite the cotyledon. 

of a pair, leaves with two apexes, and in the same cul- 
tures such even occur not infrequently immediately above 
the cotyledons. 

Not infrequently spiral torsion and fasciation occur 

1 Over dc erfelykheid van Synfiscn. Bot. Taarboek, Gent, 
Plate TV. 



464 



Syncotylons Races. 



after syncotyly. 1 I found the former case, for instance, 
in Anagallis grandi flora, Collinsia hctcrophylla, C. grandi- 
flora, C. bicolor, Scabiosa atropurpurea, Centranthus 
macrosiphon, and very abundantly in Mercurialis annua 




Fig. 96. Mercurialis annua. A lateral branch with spiral 
torsion. All the leaves of the twisted region are situated 
on one side of the stem. 

(Fig. 96). Fasciations also occurred in the latter and 
several other species, especially in Helianthus annuus. 
Moreover, pitcher formation seems often to be associated 
with syncotyly, either on the same individuals or amongst 
l Ber. d. d. hot. Gcs., Vol. XII, he. cit., 



Hemi-Syncotyly, Syncotyly, Amplii-Syncotyly. 465 

other individuals of the same culture (Fig. 97). As in- 
stances I mention Mercurial is annmi, Anagallis yrundi- 
flora, Antirrhinum niajus, Fagns sylvatica, Polygonuin 
Fagopynnn, Spiuacia olcracea and Raphanus Raphanis- 
trum. 1 

Syncotyly is a heritable anomaly; if we isolate the 
stray syncotyls we will find the phenomenon repeated 




Fig. 97. Coriandrum sativum. A, a flowering sprig; B, a 
hemi-syncotylous seedling; C, a dicotylous seedling from 
the same culture, whose first leaf is transformed into a 
pitcher (189.1). 

amongst their offspring; as for instance in Valeriana alba 
(1892, 3%; 1893, 6%). Moreover the seeds of non- 
syncotylous individuals from the same crop may repro- 
duce the syncotyly; as for instance in Amarantus spccio- 
sits, Polygonuin Coni'ok'iilus, Scrophularia nodosa, etc. 2 

1 Kruidkundig Jaarbock, loc. clt. } pp. 172-177. 
2 Kruidkundig Jaarboek, loc. cit., p. 159. 



466 Syncotylous Races. 

In the spring of 1894 I planted out into separate beds 
some syncotyls and amphi-syncotyls from my tricotylous 
intermediate race of Mercurialis annna, which produces a 
large number of syncotyls every year. There were three 
female plants and some male ones. Saved separately, their 
seeds produced 4, 19 and 24% syncotyls, amongst which 
hemi-syncotyls and amphicotyls appeared in considerable 
numbers. There is little doubt that I would have suc- 
ceeded in isolating the syncotylous intermediate races 
from Mercurialis (with 24%) as well as from Ccntran- 
thns (with 37%), and also perhaps from Picris (8%) 
and Valcriana (6%) ; but the difficulties, due mainly to 
the retarded growth of the plumule, have led me to limit 
my experiments in this direction to a single species, 
Helianthus animus. 

10. HELIANTHUS ANNUUS SYNCOTYLEUS.l 

As early as 1887 I found a syncotylous race of the 
ordinary sun-flower and isolated it immediately. Since 
then I have grown this race for ten generations. It has 
always been extremely variable, both in the extent of 
the fusion of the cotyledons and in the percentage num- 
ber of syncotylous seedlings. On the other hand it has 
proved perfectly constant and immutable. 

For instance, every effort to bring it to a uniform 
condition, free from atavists, or, on the other hand, to 
reduce it to the corresponding half race, has failed, in 
spite of the most stringent selection. Therefore we have 
here as good an instance of a constant type, which, in 
its visible properties merges into other races, i. e., is 
transgressively variable, as was furnished by the best 

1 Over de erfelykhcid van Synfisen. Kruidkundig Jaarboek, 1895. 
pp. 136-142 and Plate IV. See also the same journal, 1894. 



Helianthus Annuus Syncotylcns. 467 

tricotylous strains. Whether from this a pure, almost 
tin variable syncotylous race can be raised, which would 
no longer be an intermediate race, but show to this the 
same relation as that between the aurea varieties and 
variegated plants (see p. 21), is a point on which we 
are at present completely in the dark. 

As already stated, I found my race in the year 1887. 
At that time I had sowed a large quantity of seed of 
Helianthus annuus, obtained in exchange from different 
botanical gardens, and found 18 syncotyls amongst 500 
seedlings. I planted out these only. They flowered to- 
gether, but the seeds of each individual were saved, sown 

o 

and examined separately. In 17 lots the proportions of 
syncotylous seedlings were distributed between 1 and 
15%, and in the case of only one of them it was 19%. 
The latter plant had had its cotyledons fused up to their 
upper margin and was selected as the basis of my race. 
The offspring of the other plants were not grown, and 
moreover from this selected individual only syncotylous 
seedlines were chosen for further cultivation. 

o 

These flowered together and were left to be pollinated 
by insects. This is apparently necessary in this species, 
or at any rate in my race of it, because isolated indi- 
viduals fertilized with their own pollen, either artificially 
or by humble bees, set no seed. In the later generations 
the seed has always been collected separately from each 
plant, and in the following spring sown with a label 
bearing the number of the parent, and examined. In 
this way I obtained hereditary values for each single 
plant. 1 The seeds are large and few plants produce as 
many as 300 seedlings, so that the values are not so 

1 This rule holds without exception, and therefore I shall not 
mention it in the description of the experiments which are to follow. 



468 Syncotylous Races. 

accurate as those calculated from more extensive crops. 
Nevertheless they fall into definite groups, so that this 
source of error may be neglected. 

In the harvest of 1888 it was at once evident that 
the race had been obtained in its pure state by the selec- 
tion carried out in the foregoing year. Twelve plants 
set an abundance of seed; 9 of them had from 30 to 55% 
syncotyls, whilst the remaining three parents had 76, 81 
and 89%, in samples of 121, 275 and 128 seedlings. 
Of course the plant with 89% was chosen for the con- 
tinuation of the race. 

It was important to find out whether, if these three 
high values had not been found, the remaining parents 
would have given the same result. For this purpose I 
made a subsidiary culture in 1890, and chose for this 
purpose the syncotylous seedlings of a parent with 51% 
They produced 23 seed-parents of which the values were 
distributed evenly between 24 and 91% with a mean of 

^ * 

55%. The four highest numbers were 77, 79, 84 and 
91%. The result can therefore be reached also by an 
indirect way, as the following scheme shows at the first 
glance. 

ORIGIN OF THE SYNCOTYLOUS EVERSPORTING VARIETY OF 

HELIANTHUS ANNUUS 

HARVEST OF 1887 1888 1889 

Hereditary values of the best parents jg j 89 81 

in percentages ( 51 91 

111 order to consider this fact in combination with the 
figures found for the tricotylous races, we must compare 
it with the table on page 439. Into this table the experi- 
ment with Helianthus could be inserted straight away. 
On the one hand it confirms the expectation, which that 
table justified, of finding a value of 55% in the second 



Helianthus Annuus Syncotylcus. 469 

generation ; on the other it shows that this can sometimes 
be passed over, inasmuch as in a fortunate case the high 
value of 80-90% may be directly attained; notwithstand- 
ing that this never appeared until after the 55% stage 
had been reached in the species dealt with in that table. 
When I repeated the experiment described for my tri- 
cotylous race of Helichrysum bracteatum, I had to pass 
through several generations before reaching the hereditary 
value of about 50%, and this also shows that in different 
cases the same value may be reached by means of dif- 
ferent numbers of generations. We may therefore con- 
clude that the isolation of a syncotylous race takes place 
according to the same scheme as that which has been 
found for the tricotylous intermediate races. 

The general statements on page 17 of this volume 
and elsewhere relating to the isolation of eversporting 
varieties, and the apparent increase in variability, by 
which we explained the isolation of the five-leaved red 
clover, find an experimental confirmation in the present 
instance. The new race departs rapidly from the type 
of its species, but only because it is approaching its own 
new type. 

Into the group of figures given on the preceding 
page I have inserted a value for 1889 relating to the 
first-mentioned line of my race. It would take me too 
long to describe the subsequent generations singly, but, 
as is very important in the culture of such forms, they 
were treated in the same way ever year. I shall there- 
fore give the pedigree of the whole culture on the fol- 
lowing page. 

In this summary I have written at the top the per- 
centage number of syncotyls in the crops in such a way 
that the single numbers have been associated into small 



470 



Syncotylous Races. 



groups; thus 48 signifies the values from 46 to 50%; 
53 the values from 51 to 55%, etc. The numbers which 
occur in a vertical line below these figures give the 
number of individuals for each generation with the hered- 
itary value indicated by the upper figures. The barb 
in the bracket, below one of the values for a generation, 
denotes the character of the parent plant, that is to say, 
that plant whose offspring alone constituted this gen- 
eration. 

HELIANTHUS ANNUUS SYNCOTYLEUS. 
PEDIGREE OF THE SYNCOTYLOUS EVERSPORTING VARIETY. 

Under Selection of the Individuals \\ith the Highest Hereditary Value. 





HEREDITARY VALUES IN PERCENTAGES. 


19 25-40 48 53 58 63 68 74 78 


83 88 


93 98 


9th generation 
1896 

8th generation 
1895 

7th generation 
1894 

6th generation 
1892 

5th generation 
1891 

4th generation 
1890 


113841 

y 


2 


j 


1252 


4 7 


3 


110111 




1 2 


1 


1 2 

, 


3 8 


9 5 


1 


2 2 


11 6 


1012 


4 8 


15 1 








3d generation 
1889 

2d generation 
1888 

1st generation 
1887 



100110021 



250000111 



The pedigree shows that from an original plant with 



Helianthus A unit us Syncotylcus. 471 

a value of 19% a race with values ranging between 50 c /o 
and 89/c arose immediately, and that this value was 
fairly constantly maintained under continued selection. 
Some low values (25-50% ) still occurred in the first 
two generations which followed the original plant of 
1887, but they have not occurred since. The highest 
values attained in the various years deviate but little ; 
the deviations lying well within the probable error of 
observation, or due to occasional differences between the 
climates of the succeeding years. The hereditary values 
of the parents selected each year were as follows : 

HARVEST OF 1887 1888 1889 1890 1891 1892 1894 1895 1896 

Values of the parent ig gg gl 94 g? gg SQ Q3 82 
plants in percentages 

In some years the parent was not the individual which 
possessed the highest value. This was due to the fact 
that when the differences in the values are small it mav 

tf 

be necessary to pay attention to other circumstances also 
and especially to reject weak individuals, or such as 
flower too late, or set little seed, or happen to be fas- 
ciated. 

The choice of a parent must further be left to chance 
in groups of equally good plants with practically the 
same hereditary values ; because sunflowers are too large 
to permit of diminishing the elements of chance by dou- 
bling the principle of the selection by the application of 
the method of selection by grandparents (see p. 385); 
but, as it happened, I was mostly fortunate in my choice, 
with the exception of the last year in which the mean 
sank from SS% to about 68%. 

My race is not to be regarded as a normal eversport- 
ing variety but as an improved breed within it. Instead 
of selecting parents with SQ-90 c /r and over I could have 



472 Syncotylous Races. 

used the plants with a mean value (say 50-55%) for the 
continuation of the culture. But then I would have ob- 
tained a non-selected strain, and the figures for the first 
two generations following on the original plant, clearly 
indicate that this mean would have been about 50-55%, 
which is also, as we know, the mean value for tricotylous 
intermediate races. 

The figures given in the pedigree do not present a 
complete picture of the whole improved race, for in each 
year the hereditary value of the best offspring alone was 
determined. Dicotylous seedlings and those with a low 
degree of fusion in the seed-leaves were excluded from 
further cultivation, as were also weak plants. If I had 
not applied this selection, the mean values would ob- 
viously have turned out somewhat lower; but the differ- 
ence would not have been a very considerable one, as the 
next two sections will show. 

The chance of obtaining a pure syncotylous progeny, 
i. e., a crop without dicotylous seedlings, may appear 
to be very great in this experiment. In 13 individual 
crops 96% and over was reached. But appearances 
are deceptive. Only once did I have a perfectly pure 
crop (100%) and that even at the outset of my experi- 
ment, in 1890; but this plant had produced only 105 fer- 
tile seeds ; and of course we must acknowledge the possi- 
bility of some stray atavistic seedlings occurring amongst 
them if the harvest had been larger. In other words, 
selection leads the race as close as possible to the highest 
degree of purity, without, however, enabling it to reach 
it. Moreover, the table shows at a glance, that the pro- 
geny of the plant with 100% would probably have fallen 
back from this high value, in the case of many of its 
offspring at any rate. 



Helianthus Annuus Syncotyleus. 473 

If all the seeds of a single head are planted out in 
groups according to their degree of syncotyly, very little 
differences will be seen in the results. Atavists and seed- 
lings, in which the fusion extends less than half way up, 
give a progeny the value of which is, on the average, 
somewhat lo\ver, but only if we fix our attention on the 
mean values, and not if we compare the single individ- 
uals. Many an atavist or hemi-syncotyl has a higher value 
than most of the average syncotyls, and amongst these 
latter, the question whether the fusion is so complete 
that the apex of the double leaf exhibits no invagination, 
has no effect on the hereditary values of its offspring, so 
far as I have been able to determine. In the same way 
the disturbances in the disposition of the leaves, which 
so often follow on syncotyly, are of no value as selective 
characters ( 9) ; but it is not necessary to describe the 
experiments which prove this point. 

Hemi-syncotylous seedlings are always rarer, and 
often much rarer than the true syncotyls ; amongst these 
latter on the other hand, the highest degrees of symphysis 
are more abundant than the lower ones, which have an 
obvious invagination of the apex. I have often recorded 
separately the various degrees of syncotyly in my seed- 
lings. In this way figures are obtained which give curves 
with two peaks, such as have been found for other anom- 
alies, especially for fasciation. 1 The atavists constitute 
one peak and the most complete syncotyls the other. From 
the former the curve drops rapidly to mount again grad- 
ually with the increasing degrees of symphysis ; whilst 
on the other side of the apex of the syncotyls there is 
another rapid drop to the very rare cases of amphicotyly, 

* Sur les courbes galtoniennes des monstruosites, Bull. Scientif. 
de la France et de la Belgique. Public par A. GIARD, Vol. XXVII, 
p. 396, April, 1896. See especially the curve on page 397. 



474 



Syncotylous Races. 



in which the seed-leaves are fused together on both sides 
(Fig. 90, C and D). Fig. 98 represents such a curve 
from the harvest of 1889, which includes 2439 seedlings. 
The absolute numbers of the seedlings which possess the 
various degrees of symphysis are given below the figure. 
The groups are obviously arbitrary, but it is not likely 
that a grouping according to a different scheme would 
have any essential effect on the form of the curve, for 
the seedlings with fused peduncles only would always 
constitute a minimum between the two peaks. 

If we examine the se- 
ries of figures of our pedi- 
gree statistically, we see 
that they are, as a rule, 
asymmetrical, i. e., the 
highest values are closer 
to the one end than to the 
other. In all the years 
with the exception of the 
first and the last, the high- 
est peak is shifted in the 
direction of selection. In 
order to examine this ef- 
fect more closely I insti- 
tuted an experiment in the 
summer of 1890 on a 




At. ^ 
233 20 



I S. 
23 



Y\ K. % K. H K. g AoKA K. B. 
5? 7.0 .175 226 634 



Fig. 98. Helianthus annuus syn- 
cotylens. Curve representing the 
degree of syncotyly in the seed- 
lings of the harvest of 1889. At, 
atavists ; Y 2 S, iS, peduncles 
fused along half their extent or 
entirely; %K, Y 2 K, y 4 K, 9 />K, 
i K, seed-leaves fused over % of 
their extent and so forth ; B, 
pitcher-cotyls or amphicotyls. 



larger scale alongside the 
one dealt with on page 470. For this purpose I planted 
out about 60 syncotyls from a parent with a value of 
81% ; 55 of these gave a sufficient harvest. The values 
have been arranged in groups in the same way as in the 
pedigree on page 470, and the sizes of the groups thus 
obtained, are graphically displayed in Fig. 99 and Hven 



Helianthus Ann it us Syncotyleus. 



475 



in a lower row of numbers. The asymmetrical form of 
the curve is seen at a glance, although the selection which 
preceded this generation was limited to two years only. 
If we compare this curve with the groups of figures 
representing the tricotylous half races, w r e see that it 
is not simply its mirror-image. It is true that both have 
their highest point over or close to the end of the base 
line. But in the case of the half race the longer side of 




98 p Ct 
3 Ind. 

Fig. 99. Helianthus annuus syncotyleus. Curve of the 
hereditary values of 55 syncotylous offspring of a parent 
with 81% (Culture 1890). Given as a type of a curve 
resulting from selection. 

the curve extends seldom so far as 25%, (Scrophularia} 
and ordinarily much less, and this in spite of the selection 
in the plus direction (see the table on p. 392). In the case 
of Helianthus, however, the longer side extends almost 
to the middle or about 60%, and this in spite of the selec- 
tion of the best syncotyls with the highest values. If the 
selection, in this case as in the other, had been directed 



476 Syncotylous Races. 

towards the middle of the base line, the sweep of the 
curve would obviously have been a still more gradual 
one. We see, therefore, here as elsewhere, that the inter- 
mediate race or eversporting variety is far more suscep- 
tible to selection than the half race. 

ii. IMPROVEMENT OF A HEMI-SYNCOTYLOUS RACE. 

Like tricotyly, I regard syncotyly as a single ele- 
mentary character the external manifestation of which 
is subject to fluctuating variability. Completely fused 
cotyledons, which are the type occurring most abundantly 
(see Fig. 98), constitute the normal or typical structure, 
whilst the lower degrees of fusion and the bilateral unions 
are the minus and plus variants of the same series. 

One of the most important problems in the theory 
of mutation is to bring together the various expressions 
of the same elementary character in each particular case. 
The delimitation of such groups is often clear at once, 
but often it can only be reached by the actual observa- 
tion of the process of mutation. Still, the question is 
obviously a fundamental one, for our whole conception 
of affinities must rest on it, both in the question of species 
and in that of hybridization. We must therefore seek for 
methods which will lead to a solution of this problem. 

With regard to the present case we may start from 
the following discussion. If the hemi-syncotyls and 
amphi-syncotyls were representatives of distinct elemen- 
tary characters, we should expect to be able to isolate 
the corresponding races. The amphicotyls are too rare 
and too difficult to cultivate, on account of the disturb- 
ance in the growth of the plumule, to offer much prospect 
of success. Hemi-syncotyls, on the other hand, are well 



Improvement of a hemi-Syncotylous Rat\. t/ / 

adapted to such an experiment in isolation. Our expe- 
rience with the tricotylous races teaches us what to ex- 
pect; for, obviously, either a half race or an intermediate 
race must arise, if hemi-syncotyly is at all capable of 
separate existence. 

But if such an isolation cannot be effected, i. e., if the 
hemi-syncotyls are only minus variants of the syncotylous 
intermediate race, the selection of hemi-syncotyls will 
obviously do no more than maintain this latter race, and 
only modify it slightly in the mi Hits direction. We should 
then expect to obtain a strain which should not differ 
essentially from a true syncotylous intermediate race, 
except by a slight shifting of its mean value. In this 
case the number of the hemi-syncotyls will be somewhat 
increased by selection, but not, however, to the exclusion 
of the syncotyls. 

From this discussion it is clear that we can furnish 
the experimental proof that the hemi-syncotyls are minus 
variants of the syncotvls by an appropriate experiment 
in selection. For this purpose I started in 1890 with a 
lateral branch of the pedigree on page 470, by selecting 
every year only hemi-syncotylous plants as seed-parents. 
I have continued this experiment in the same way for 
seven generations, and the result was, as we shall see, 
a confirmation of the above conclusion. 

This experiment was conducted in another garden 
from that in which I cultivated the syncotylous race, but 
otherwise carried out in exactly the same way. In the 
crops the hemi-syncotyls and the true syncotyls were 
always recorded separately, so that for each seed-parent 
two values were obtained. The individuals to be planted 
out were at first chosen from two parents, but later only 
from one ; the selection being made according to the pro- 



478 



Syncotylous Races. 



portion of hemi-syncotyls among the seedlings, i. e., that 
parent was chosen which produced the highest percentage 
of hemi-syncotyls, no regard being paid to the number of 
syncotyls produced. 

I shall now give the values of these selected parents 
for several generations in tabular form : 

HEMI-SYNCOTYLOUS RACE. 

HEREDITARY VALUE OF THE SEED-PARENTS SELECTED FOR THE CONTINUA- 
TION OF THIS RACE. 



From the 
harvest of 


Proportion in percentages of 


Degree of symphysis 
of cotyledons 


Hemi-syncotyls 


Syncotyls 


Totals 


1880 


5 


76 


81 


i 


1890 


40 


36 


76 


i 


1891 


15 


15 


30 


\ 


1892 


20 


20 


40 


\ 


1893 


28 


27 


55 


~2 


1894 


31 


55 


86 


2 


1895 


34 


35 


69 


1 


1896 


37 


30 


67 






In this table the degree of symphysis in the cotyledons 
is given for each parent selected. This was, where pos- 
sible one-half, i. e., the cotyledons were fused along half 
the distance between the upper end of their petioles and 
their tips. In the earlier years this was more or less a 
matter of chance, and in the harvest of 1890 it was by 
no means the plant with the highest degree of fusion that 
gave the best hereditary value. Later, I could limit my- 
self to planting out those seedlings in which the fusion 
had only extended half-way and so I only determined 
the values from these. 

The first row of the table (1889) refers to that indi- 
vidual of the syncotylous race (p. 470), whose offspring 
constituted the basis for this special culture. The selec- 



Improvement of a Hemi-Syncotylous Race. 479 

tion and the planting out of hemi-syncotylous seedlings 
suddenly increased the proportion of the latter and cor- 
respondingly diminished that of the syncotyls ; but only 
for a time. In the harvest of 1891 both have become 
low, and from that time onwards selection has gradually 
increased, with but slight deviations, both the number 
of hemi-syncotyls and that of syncotyls. In the last 
harvest (1896) the numbers are given for the plant with 
the largest proportion of hemi-syncotyls. The average 
number of the hemi-syncotyls of the whole crop was, 
however, 29%, and that of the syncotyls 31%. 

The result of this experiment of seven years was, 
therefore, that by the double selection of seed-parents, 
which produced the largest number of hemi-syncotyls, 
and of hemi-syncotylous individuals for seed-parents, 
we do not even approach a pure hemi-syncotylous race. 
In spite of the inevitable fluctuation of the numbers, the 
syncotyls remain in about the same proportion as the 
half type. If we think how many degrees of symphysis 
this latter embraces as opposed to the uniform group of 
the true syncotyls, the number of the latter actually found 

J ^ 

assumes even greater importance. 

In the pedigree on page 480 I have given a summary 
of the whole course of this culture. In this I have en- 
tered only the totals of hemi-syncotyls and svncotvls ; but 

~ J ~ V 

as half of these values belonged to hemi-syncotyls, the 
pedigree would not have been different if these alone 
had been entered, except of course that the percentage 
figures at the top of the table would have to be halved. 
As usual, these figures relate to means of small groups, 
which in this case embrace values between 1 and 9, 10 
and 19, 30 and 39, etc. The figures which are given for 
the several generations indicate the number of individuals 



480 



Syncotylous Races. 



whose hereditary value is represented vertically above 
them. The barbs in the bracket show the parents of the 
previous generation which had been selected and cor- 
respond therefore to the totals in the table on page 478. 
The chief point which this pedigree brings out, is that 
the selection of the hemi-syncotyls does not modify the 

HEMI-SYNCOTYLOUS RACE. 

PEDIGREE OF THE TOTALS OF HEMI-SYNCOTYLOUS AND SYNCOTYLOUS 

SEEDLINGS. 





5 15 25 35 45 55 65 75 85 95 


7th generation 
1896 

6th generation 
1895 

5th generation 
1894 

4th generation 
1893 

3d generation 
1892 

2d generation 
1891 

1st generation 
1890 

Syncotylous 
race, 1889 


1 3 2 10 3 

^ 


1673 


343133 

V. J 


152322 

V _J 


34352 

V p : J 


3545451 

^ j 


11784 

t j 


1 



race either in one direction or in the other. If we omit 
the crop of 1890 the several generations fluctuate round 
a mean value which does not deviate greatly from 55% 
and thereby agrees sufficiently closely with the average 
of tricotylous individuals in tricotylous intermediate races. 
In other words, the selection of hemi-syncotyls gives a 
syncotylous race of average value; and if we compare 



Atavistic Races. 481 

the several generations of this race with a true syncotyl- 
ous race (see the, table on page 470), we only find in most 
of them an oscillation within much wider limits. 

The hemi-syncotyls are, therefore, only variants of 
the syncotylous race. 

12. ATAVISTIC RACES. 

Although the atavistic specimens of Helianthus an- 
nuus syncotyleus are exactly similar to the normal seed- 
lings of the ordinary sunflower, they nevertheless belong 
to the syncotylous race and do not depart from it. With 
regard to their visible characters they are aberrant forms; 
with regard to their progeny, however, simply extreme 
minus variants ; but the latter is true only on the average, 
and not for the particular atavists whose values often 
approach those of the best syncotyls, and not infrequently 
exceed the mean of the race. 

If the intermediate race were not pure we should, of 
course, still be able to select the corresponding half race 
from it. But after it has once been purified by selection, 
this is no longer possible. A syncotylous intermediate 
race can no more give rise to a half race than a tricotylous 
half race can be transformed by selection into an inter- 
mediate race (see Amarantus and Scrophularia, pp. 398 
and 407). In the years 1890, 1891, 1892 and 1894, I 
made extensive cultures of atavists derived from my 
syncotylous race and also from my hemi-syncotylous 
race, and determined their hereditary values for one or 
two generations. In these experiments curves were ob- 
tained which were not asymmetrical, with a peak at one 
end, but were flattened curves, extending over the whole 
length of the base line. Thus, for instance, I obtained 
from a dozen atavists from the seeds of the seed-parent 



482 Syncotylons Races. 

of 1890, selected for the syncotylous race, the following- 
percentage numbers of syncotyls : 

19 48 54 56 62 68 69 73 80 84 88 96 

If we compare this series with the pedigree on page 
470 and especially with the figures given there for 1890 
and later years, it will be seen that it is almost only the 

J * 

first two figures 19 and 48% which fall outside the group 
of values of the syncotylous offspring of the selected 
seed-parents. 

A selection of atavists as seed-parents continued 
through several generations, and a selection amongst 
these of specimens which produce the smallest percentage 
of syncotyls, will obviously reduce the mean value of 
such a race, but not to such an extent as to justify the 
expectation that a continuation of the process will lead 
to the origin of a half race. I started such an experiment 
in the summer of 1894, from the seeds of the harvest of 
1892. I selected a specimen from my syncotylous race, 
(p. 470), which had produced 92% syncotyls and only 
8% atavists, and planted out the latter only. Since that 
time I have cultivated the race continuously and on an 
isolated spot and have planted out every year only the 
seedlings from those parents which had produced the 
largest number of atavists amongst their offspring. From 
these I always selected the pure dicotylous seedlings only. 

I determined the hereditary value for each example 
and combined these in small groups in the usual way. At 
the top of the pedigree on page 483 will be found the 
mean values of these groups (5 = 1 9, 15 = 10 19 
etc.), and, vertically below these figures the corresponding 
number of individuals. The figures at the top give the 
percentage numbers of syncotyls. The pedigree can, 



Atavistic Races. 



483 



therefore, be directly compared with those on pages 470 
and 480. The brackets in each case indicate the selected 
seed-parent. 

HELIANTHUS ANNUUS SYNCOTYLEUS. 

ATAVISTIC RACE. 





5 15 25 35 45 55 65 75 8 


5 95 


4th generation 
1897 

3d generation 
1896 

2d generation 
1895 

1st generation 
1894 

Syncotylous 
race, 1892 


01234792 




75812 

v ' 


1 5 12 

t j 


\ 

2 1 3 

V ^ 


| 



We see that the minus selection has actually had its 
effect in that direction. The extremes and the mean have 
regularly decreased. The experiments correspond exactly 







Fig. lop. Helianthus anmms syncotyleus. Hemi-syncotylous 
seedlings with various degrees of fusion of the cotyledons. 
A and B small, C and D larger degrees of symphysis. 



with that with maize, which was represented in Fig. 18 
on page 73 of the first volume, except that in this case 
the change took place in the reverse direction. On the 



484 



Syncotylous Races. 



other hand, the signification of the pedigree is, in this 
case, quite different from that of the main syncotylous 
race (p. 470). In that case we found a sudden transi- 
tion from 19% to about 98% in the first generation, and 
since then only fluctuation around the obtained value. In 
this instance, however, there was a regular retrogression 
which has reduced the mean value from 90% to about 
50 to 55%. This value corresponds to that of an inter- 




Fig. 101. Helianthus annuus syncotyleus. 1-7, fused cotyl- 
edons, each figure of a single plant; At, atavistic normal 
seed-leaf ; I and 2, simple opposed syncotyls of which 
la represents a transverse section ; 3-4, doubly folded 
syncotyls with 3 peaks; their transverse section in ^a ; 
5. with very slight imagination of the apex ; 6 and 7, 
without imagination ; 6, with one vein and 7, with two. 



mediate race without selection, especially of tricotyls. and 
is about the same as that which was reached by the hemi- 
syncotylous culture (p. 480). There can, however, be 
no doubt that a further selection in the minus direction 
would have reduced the proportion of syncotyls in my 
race to a figure much below this mean. 

We thus see that after a minus selection extending 
over -four Generations, the race still contains individuals 



External Conditions and Hereditary Values. 485 

with 65 to 75% syncotylons offspring, and coulcl there- 
fore be brought back in one or two generations to the 
highest point attained by the original race. It is there- 
fore far removed even from the slightest semblance of 
a half race. 

How far, in the case before us, selection could lead 
in the course of years can, of course, only be surmised. 
But the sunflower is not a suitable species for the con- 
tinuation of these experiments, on account of the risk 
of occasional pollen grains of the ordinary sort being 
brought by insects from distant gardens ; for under these 
conditions selection would promptly extract a half race 
which would be the result of hybridization and not of 
selection, and artificial fertilization in the sunflower is 
beset with very great difficulties. 



13. THE INFLUENCE OF EXTERNAL CONDITIONS ON 

HEREDITARY VALUES. 

In these cultures my practice has been, first to record 
the seedlings in the pans and then to plant them out into 
pots with well manured soil, from which they were trans- 
planted to the beds in June. Here the plants stood at 
distances of over half a meter apart. As soon as axillary 
buds became visible they were removed, and only the 
terminal head was allowed to flower. Fertilization was 
left to insects, for my sunflowers do not set seed without 
crossing. As soon as the seed is ripe, I cut off the whole 
head in order to collect and clean the seed. 

The question presents itself, does this method of cul- 
ture exert any considerable influence on the proportions 
of syncotyls? In order to provide an answer I have in- 
stituted a number of subsidiary cultures in different vears, 

mr * 



486 



Syncotylous Races. 



preferably with seedlings which did not differ much from 
those of the main culture. These have, however, prac- 
tically always exhibited no more than slight deviations; 
and where these happened to be exceptionally large, the 
cause of the deviations has remained obscure. As a rule, 
we may assume that favorable conditions increase the 




Fig. 102. Hclianthus annnus syncotyleus. The first leaves 
of syncotylous seedlings. A, a leaf of the first pair with 
three peaks and inserted above the syncotyl ; B, a leaf 
with two peaks placed opposite the syncotyl ; C, a leaf 
with two peaks above the first pair of leaves. 

hereditary values ; but only to an inconsiderable extent, 
and especially so within the relatively narrow limits of 
the scale on which our plant can be cultivated in the 
garden. 

In 1892, and at other times, I also collected the seeds 
from the flowers on lateral branches ; both the flower- 
heads and their fruits are smaller here than at the top of 



External Conditions and Hereditary / 'allies. 487 



the main stem, and they produce a correspondingly smaller 
number of synootyls, but only in the proportion of 87 to 
80%, on an average for 12 plants. If the seeds of single 
inflorescences are harvested in three lots in such a way 
that the outer, inner and middle areas are separated, the 
former generally contain slight- 
ly more syncotyls, for the fruits 
in the middle of the head tend 
to be somewhat weaker. From 
each of these three groups I 
have allowed the best seedlings 
to flower and bear fruit, but 
I found no essential difference 
in their hereditary values. It 
appears that improved condi- 
tions during the early stages of 
the plant, have some small in- 
fluence in a positive direction, 
but crowding in later life and 
partial removal of the leaves 
during the flowering period had 
little noticeable effect (1891). 
Furthermore a culture on good 




Fig. 103. Helianthus annuus 
syncotyleus. A and B, seed- 
lings whose plumule has 
not developed during the 
course of several weeks ; the 
syncotyl is abnormally en- 
larged. C, Amphi-syncotyl- 
pus plant, also with inhib- 
ited development of the 
stem. 



sandy soil, instead of garden 

soil, made no difference in the values (1892). 

Striking exceptions, however, sometimes occurred, for 
instance in the year 1891, when three plants in my main 
culture became affected with Peziza a short time after 
flowering, and died, not however without ripening some 
of their seed. These three produced the smallest values 
of the whole group. (76, 84 and 85% as against 86 to 
99% V But perhaps they were the weakest individuals 
and contracted the disease for this reason. 



III. THE INCONSTANCY OF FASCIATED 

RACES. 

14. THE INHERITANCE OF FASCIATIONS. 

Fasciations are amongst the commonest anomalies 
which occur in the vegetable kingdom. 1 Until about ten 
years ago the prevailing opinion concerning them, as in- 
deed in regard to monstrosities in general, was that they 
were not heritable but owed their origin to external in- 
fluences only. The coxcomb, Cclosia cristata, was con- 
sidered an exception to this rule. It was, however, well 
known that the phenomenon occurred more frequently 
among certain species than among others ; but the con- 
ception that some plants possessed a greater tendency 
to the production of such anomalies than others was 
taken for a sufficient explanation of this fact. 

But since I have succeeded, in the case of a series of 
apparently fortuitous fasciations, in establishing, by iso- 
lation and selection, races in which the deviation is re- 
peated regularly and in a considerable number of indi- 
viduals, it has become evident that we are concerned here 
with heritable qualities which are handed on from one 
generation to another in certain strains of individuals, 
and which really differ from the characters of ordinary 
varieties only in the fact that they are always accom- 
panied by reversions. It never happens that every branch 

1 See A. GALLARDO, Fasciacion, Proliferation y Sinantia. Anales 
del Museo Nacional de Buenos Aires, Vol. VI, pp. 37-45. 



The Inheritance of Fasciations. 



489 



on a sufficiently branched individual is fasciated, any more 
than that all the individuals in a large crop produce the 
anomaly without exception. The Celosia cristata, which 
comes closest to perfection in this respect, is only an ap- 
parent exception to the rule. 

Fasciations, therefore, afford valuable material for 
the study of inconstant characters. Moreover they are 




Fig. 104. Ears of rye with two and three tops, such as are 
sometimes found in mowing the fields (1891). 

known everywhere, can be procured by everybody, and 
are fairly easy to cultivate; and the successful cultures 
give rise to beautiful instances of fasciation in a third 
or even in a greater proportion of the individuals. There 
is a complete series of transitional forms between the 
atavists and the most abnormal specimens, inasmuch as 
the broadening of the axis can be either very slight or 



490 The Inconstancy of Fas dated Races. 

very considerable, and all the intermediate stages can 
often be observed on the lateral branches of a single plant. 
The most important result which can be deduced from 
the experiments which follow is the discovery that the 
atai'ists or non-fasciated individuals of the race can only 
be regarded as reversions in the morphological sense; 
but that physiologically considered, that is, as transmitters 




Fig. 105. Ranunculus bulbosus. A fasciated stem which 
has grown up from a broadened rosette of radical leaves. 
The terminal flower is also broadened and split. Hilver- 
sum, 1894. 

of fasciations, they are scarcely inferior to the best fas- 
ciated specimens of the race. The character in question 
is only latent in them, or rather only temporarily invisible ; 
perhaps simply not developed by reason of the absence 
of some necessary external factors. 

The atavists do not, so to speak, depart from the 
race, as do those of Oenothera scintillans; the race con- 



The Inheritance of Fasciations. 



491 



stitutes a uniform group of individuals and only differs 
from constant races or true varieties by the extraordi- 
narily high degree of variability of its distinguishing 
character. 

This degree of variability relates not only to the 
degree of expansion of the axis, but also to the manner 
in which the anomaly is manifested. First we have to 




Fig. 106. 1'iola tricolor maxima, the garden pansy. A 
forked flower stalk arising from the axil of a double 
leaf (a, a) ; ^and^, the outer stipules; s , the inner un- 
split stipules of this leaf. The continuation of the main 
axis has been bent down laterally, 



distinguish between the split branches and the fasciated 
branches scnsu stricto. Split ears of the rye are some- 
times found in the fields (Fig. 104) and then preserved 
by the country folk. The axis of these ears may be 
divided once or oftener, the parts above the division 
being perfectly normal themselves. Or again the haulm 



492 The Inconstancy of Fascia ted Races. 

below the ear may be split and produce two ordinary 
ears side by side. Amongst other plants also forkings 
of this kind are by no means rare, but as a rule they 
occur associated with typical fasciations. 

The latter are of the same breadth from below, that 
is to say in the strict sense ribbon-shaped, or they begin 
with a cylindrical form below, and gradually flatten out 
towards the top. The latter case is the normal one ; from 
it the former has been derived. This may occur either on 
an axis of two or more years of age, or on the lateral 
branches of stems which are themselves fasciated. Axes 
of two or more years of age begin by being circular in 
transverse section, and can, in the same summer, obtain 
a maximum breadth which they then retain in later years. 
This is observed especially in stems which arise from a 
rosette of radical leaves developed in the preceding year 
(Crepis bicnnis, Aster Tripoliuni, Picris hicracioidcs, Pri- 
mula japomca, Ranunculus bulbosus [Fig. 105] etc.). 
In trees and shrubs and especially in nrs (Abies excclsa) 
a fasciation that has once appeared, frequently reappears 
for several years in succession. 1 The lateral branches 
of fasciated axes often have an expanded base and then 
grow on without further increase in breadth. 

Like the base of a lateral twig, a leaf on a fasciation 
can undergo expansion in its youth. In this way there 
arise broader, more or less deeply split, leaves, not infre- 
quently even with similarly expanded or split axillary 
twigs (Fig. 106) ; or again the germs may be split and 
parted quite early, and two or more leaves arise in this 
way instead of a single one. Especially when the leaves 

1 C. DE CANDOLLE, Fasciation chez un Sapin, Archiv. Sc. phys. et 
nat, 1889, Vol. XXI, p. 95, PI. TI ; and Over dc erfelykhcid der 
fasciaticn, Botan. Jaarboek, 1894, PI. XI. 



The Inheritance of Fasciations. 



493 



are arranged in whorls, this kind of multiplication looks 
very striking (Fig. 107). 

If we examine the growing point of a fasciated shoot, 
the abnormal conformation can already be distinguished. 




Fig. 107. The Madder, Rubia tinctorum. Fasciated stems 
with an increased number of leaves in the whorls, found 
in a madder field near Ouwerkerk and broken off at the 
rhizome (1890). 

Where the fasciations are very broad this was to be ex- 
pected, as for instance in the case of Scdiun reflexuui 
cristatnm figured in the first volume (Figs. 34-35, pp. 



494 



The Inconstancy of Fasciated Races. 



182-183). Expanded combs of this kind are often seen 
at the top of inflorescences, especially in Veronica longi- 




Fig. 108. Veronica longifolia. Inflorescence with the tip 
expanded in the form of a comb. 

folia (Fig. 108), Amarantus speciosus (Fig. 83, p. 399), 
Oenothera Laniarckiana and 0. brevistylis, etc. 









Tlic Inheritance of Fasciations. 495 

These phenomena have been more closely investigated 
by NESTLER who regularly found inside the terminal bud 
of a fasciated branch a line of fasciation instead of a 
point, in other words a growing comb instead of a grow- 
ing cone. 1 The leaves arising from this latter are pro- 
duced in very large numbers and in an abnormal arrange- 
ment, and in consequence of this, the disposition of the 
leaves on fasciated stems tends to be extremely irresfular ; 

mf O 

but although this subject is obviously very important in 
its bearing on the whole question of phyllotaxy, it still 
awaits a thorough investigation. In this respect it would 
be particularly valuable to make a study of fasciations in 
conifers, for our knowledge of the normal structure of 
their cone of vegetation is much more extensive than it 
is in regard to that of angiosperms. 2 Moreover there 
is no lack of material, for Cryptomeria japonica mon- 
strosa and the fasciated varieties of several other species 
are on the market (Fig. 109). 

Besides the cases of ordinary fasciation, and of those 
in which the surface may be bent by unequal secondary 
growth, there are some cases of most peculiar conforma- 
tion which hitherto have been very little investigated. It 
is not known whether these are the expressions of the 
same internal character or whether they must be referred 
to special factors. Their morphological structure is in 
favor of the latter view ; but the former is supported by 
the fact that they have hitherto always been observed in 
conjunction with ordinary fasciations, i. e., in species 
which are particularly liable to them. Examples are af- 
forded by the multi-radiate and annulate fasciations. 

1 A. NESTLER, Untersuchungen iibcr Fasciat'wncn, Oesterr. botan. 
Zeitschrift, 1894. No. 9 ff., with 2 plates. 

H. DINGLER, Ziim Scheitelwachsthwn dcr Gymnospermen, Ber. 
d. d. bot. Ges., Vol. IV, 1886, p. 18. 



496 



The Inconstancy of Fasciated Races. 



In the ring fasciations the vegetative cone is trans- 
formed into an annular wall which ultimately develops 

into a smaller or larger 
funnel. I found these 
remarkable structures re- 
peatedly in my cultures 
of Veronica longi folia, 
where they remained 
quite small, scarcely 
reaching a centimeter. 1 
On the other hand I have 
observed a funnel - like 
structure in Peperomia 
maciilosa of more than 
a decimeter in length. 2 
Some of the best known 
instances of ring fascia- 
tions occur in Taraxa- 
cum officinal 'e ; these have 
frequently been described 
and I have myself often 
had the opportunity of in- 
vestigating them. 3 With- 
a thick, tube - like 




a 



Fig. 109. Crytomeria faponica mon- 
strosa. A commercial variety very 
rich in fasciations. a, laterally ex- 
panded tip of a branch producing 
a normal twig at d by means of 
splitting; b and c, further fascia- 
tions of this branch. 



in 



flower - stalk, often as 
many as 10 to 20 slender 
stalks arise, each in the 
axil of a leaf and each 



1 A. NESTLER, Ucber Ringfasciation, Sitzungsber. d. k. Acad. d. 
Wiss., Wien, Vol. CIII, Part I, 1894, Plates I-II. 

2 Sur un spadice tubuleux du Peperomia inaculosa. Archives Neer- 
landaises d. sc. ex. et nat, Vol. XXIV, p. 258, PI. XII. Afterwards 
the anomaly occurred again on the same plant (1892). 

3 MiCHELis, Botnn. Zcitung, 1873, p. 334; 1885, p. 440. Further 
literature will be found in NESTLER'S paper already cited. For Hclian- 



The Inheritance of Fasciations. 



497 



bearing a more or less normal inflorescence. From the 
seeds of such an individual, I have for many years culti- 
vated a large bed containing over 100 plants which, how- 
ever, only produced ordinary fasciations, but no ring- 
fasciations. 

Sometimes I have found radiate fasciations in my 
cultures of Amarantus speciosus alongside of the more 





/ ^ :' r ^ - 

Fig. no. Amarantus speciosus. Tri-radiate peaks of 

inflorescences. 

common, ordinary fasciations. 1 The tip of the inflores- 
cence was not flattened, but tri- or sometimes quadri- 
radiate (Fig. 110). In Digitalis lutea I have observed 
a similar case, and in Celosia cristata I found a good 

thus anmtus, see PAUL RICHTER, Bcr d. d. hot. Ges., 1890, Vol. VIII, 
p. 231, PI. XVI. 

1 Over de erfelykheld van fasciatien, Botanisch Jaarboek, Gent, 
1894, p. 90. 



498 The Inconstancy of Fasciated Races. 

instance of a quadri-radiate apex on a branched indi- 
vidual (1893). Tri-radiate fasciated heads have often 
been found in Composites ; for instance in Chrysanthe- 
mum Leucanthemum, Helianthus annuus and Erigeron 
bcUldiflorus. In the latter species these have occurred 
with tolerable frequency in my garden. All these cases 
are greatly in need of a closer investigation. 

For the production of a fasciation the presence of the 
internal factor is not of itself sufficient. Favorable con- 
ditions of life are also quite necessary. The stronger a 
plant or a branch is, the more liable is it to expand and 
flatten out. This is best seen in those biennial or peren- 
nial plants which occasionally have the power of flower- 
ing in the first year. If they do this, either only small 
fasciations, or none at all, are developed, whilst it is 
amongst the specimens which remain in the rosette stage 
during the first year and do not develop their stem till 
the second, i. e., after they have undergone considerable 
increase in strength, that the most numerous and finest 
fasciations will be found. Thus, for instance, I obtained 
through the kindness of PROFESSOR LAGERHEIM from 
Stockholm seeds of a fasciated plant of Hieracium uin- 
bellatum, and in the summer of 1901 I had from these 
a bed with nearly a hundred plants without a trace of 
fasciation. Some plants, however, did not make a stem 
that year but, after they had survived the winter, pro- 
duced in the following spring some beautiful expanded 
stems with comb-shaped inflorescences at the top. The 
same occurred in my cultures of Aster Tripolinni, Picris 
Irieracioides, Oenothera Lamarckiana and others. The 
first species, when grown as an annual, developed tall 
stems which remained fairly cylindrical in the lower part, 
and then began to flatten, without, however, attaining 






The Inheritance of Fasciations. 499 

a greater breadth than about 2.5 centimeters; but in large 
cultures there were sometimes as many as 60 or 70 c /c of 
such broadened shoots. When grown as a biennial, how- 
ever, the hearts of the rosettes gradually expand in the 
first autumn or during the winter, and from these, stems 
are produced which sometimes attain a very considerable 
breadth. Thus, for instance, in the summer of 1895 I 
measured some of from 3-6 centimeters. Picris hiera- 
cioides seldom produces fasciations in the first year, and 
when it does they are not broad ; whilst the stems pro- 
duced in the second year from the broadened rosettes of 

m> 

radical leaves ordinarily afford some of the finest in- 

* 

stances of this anomaly. 1 

Just as the age of the various individuals of a culture 
has a great effect on the production and development 
of the fasciations, so also has the time of the year at which 
the seed is sown. Many biennial or perennial plants 
which quickly manifest the character of the race when 
sown early, remain apparently normal if the sowing was 
made late, and they cannot grow out to sufficient strength 
before winter. My fasciated races of Crcpis bicnnis and 
Taraxacum officlnale are very instructive in this connec- 
tion. Sowings of Crepis, made in April and May, gave 
from 30-40% of fasciated individuals. Sowings made 
at the end of July produced 20% only, and those made in 
September none at all. Similarly, Taraxacum officlnale, 
when sown in spring, produced 13 to 27% of fasciations, 
whilst a sowing made in August did not produce even 
so much as a single flattened flower-stalk. 

1 Sur la culture dcs monstruo sites, Compt. rend., Paris, Jan. 1899; 
Sur la culture dcs fasciations dcs especcs annuelles et bisanuuclles, 
Revue gen. d. Bot, 1899, Vol. XI, p. 136; and Ucbcr die Abhdngig- 
kcit dcr Fasciation vom Alter bci zweij'dhrigen Pflanzen, Botanisches 
Centralblatt, 1899, Vol. LXXVII. 



500 



The Inconstancy of Fasciated Races. 



In races of this kind all conditions of the environ- 
ment are of importance. By crowding, the proportion 
of fasciated individuals can be reduced, for instance, from 




Fig. in. Agrostemma Githago. 
A plant the main axis of which 
had been cut off at o. The cotyl- 
edons have dropped off at C and 
C'. Their axial twigs are fasciated, 
and instead of producing decussate 
leaves, bear multiple whorls. They 
split occasionally at the nodes, 
forming forks with branches at 
a, b, c, d } e and f. Just above f the 
calyx of the flower is spiral (kk), 
and fused with the uppermost fo- 
liage leaf (fr), by which the flower 
stalk is seen to be twisted. (1892.) 



40 to 5%. Even if the number of fasciations is calcu- 
lated per area of the bed, a small number of specimens 
give a prospect of obtaining more fasciations than a 



The Inheritance of Fasciations. 501 

larger number planted on the same area, but too close to- 
gether. The number of fasciations can be diminished 
by cultivation on sterile sand and increased by the addi- 
tion of manure. The most numerous and the finest in- 
stances of the anomaly are produced by cultivation in 
pots with heavy manuring and by subsequent transplan- 
tation to the beds; and so forth. 1 

Further, a considerable effect can be exerted on the 
production of fasciations, as upon that of monstrosities 
in general, by pruning and by the selection of buds which 
accompanies this process. Thus, GOEBEL says in his Or- 
gaiwgraphie 2 that fasciations can be artificially produced 
by diverting the "sap" with great intensity into a lateral 
bud which would otherwise have obtained only a small 
quantity of it. It is for this reason that fasciations are 
particularly abundant on adventitious branches and shoots 
from cut stems. Even in annual plants such as Phaseolus 
multiflorus and Vicia Faba, fasciation can be induced by 
cutting off the plant above the cotyledons. A plant which 
is peculiarly suitable for the demonstration of this method 
is Agrostemuia Git ha go, which in my cultures always 
produced an abundance of anomalies, but did so with 
greater certainty when I had removed the main stem, 
just above the cotyledons or the first pair of leaves. The 
axillary buds, which, as a rule, do not develop, grew out 
under this treatment and frequently became fasciated 
(Fig. 111). 

The phenomena of periodicity are also associated with 
the effects of nutrition. Lateral branches of fasciated 
shoots are usually of normal structure ; but broadened 
ones not infrequently occur amongst them. If they do, 

1 Botan. Centralblatt, 1899, loc. cit. 
* Vol. I, p. 234- 



502 The Inconstancy of Fascia ted Races. 

they manifest a certain order in their disposition since 
they are usually found in that region where other normal 
and abnormal characters also attain the maximum of 
their development. 1 This phenomenon which can easily 
be demonstrated in the fasciated race of Tetragonia ex- 
pansa, is, however, in need of more thorough investi- 
gation. 

But the chief point seems to me to be, as GOEBEL 
pointed out in his work to which we have already re- 
ferred, that the latent factor for the production of anom- 
alies must be present in all those parts of the plant in 
which external influences are able to induce fasciations 
or anomalies. If this is absent no amount of manipula- 
tion is of any avail. It seems, however, that the factor 
for the production of fasciations is pretty generally dis- 
tributed throughout the vegetable kingdom; though it 
is not so general but that there are certain groups in 
which it does not occur. It is a curious fact that fascia- 
tions are much commoner amongst dicotyledons than 
amongst monocotyledons, although some very well-known 
instances are presented by the latter (Asparagus, Liliuui, 
Frit ilia ria , O rch is ) . 



15. HALF RACES WITH HERITABLE FASCIATION. 

It is only by conducting special breeding experiments 
that we can discover for certain whether fasciation is 
heritable in a given species, and to what extent. If, 
however, such cultures are made, we shall soon find that 
these anomalies fall into two categories which are per- 
fectly analogous to the half races and eversporting vari- 

1 See T. TAMMES, Ucber die Periodicit'dt morphologischer Er- 
schcinungen bci den Pflanzcn Kon. Acad. v. Wet., Amsterdam, 1903. 



Half Races ivith Heritable Fasciation. 503 

eties distinguished in the first part of this volume (p. 18). 
In the former case the anomalies are rare and their fre- 
quency can not be increased by selection to any consider- 
able extent. In the second case the f asciations occur even 
in the field in obviously larger numbers ; and it is only 
necessary to isolate the examples in question in order to 
be in immediate possession of a race producing f asciations 
abundantly. These experiments are perfectly analogous 
to those which we have described in the case of other 
anomalies and especially to those relating to tricotylous 
and syncotylous cultures (see page 343). Nevertheless, 
in the case of f asciations, we have by no means so strin- 
gent a character to select by, as is presented by the per- 
centage hereditary values, calculated from the seedlings 
of tricotylous races, and therefore the subsequent devel- 
opment of the race after the initial isolation is a matter 
of much greater difficulty. 

Postponing the consideration of the eversporting vari- 
eties or intermediate races to the next section, let us here 
attempt to obtain some insight into the races in which the 
anomaly occurs more rarely. Unfortunately, in many 
instances the available data are not yet sufficient to enable 
us to decide with perfect certainty to which of the two 
types a given case belongs. 

Fasciations occur in so many commercial varieties that 
they are accessible to everybody; sometimes even the 
variety owes its name to the frequency of this character, 
as, for instance, the Sword-elder (Sambucus nigra fas- 
cia fa} ; or it may be an almost constant attribute of the 
cultivated sorts, as in the Japanese spindle-tree (E-ron\- 
iiuis japonica. Fig. 112). When the varieties are either 
largely or exclusively multiplied in the vegetative way, 
it is possible that the anomaly, although only heritable 



504 The Inconstancy of Fasciated Races. 

to a slight degree, may be manifested frequently; as, 
for instance, in Liliuni speciosum album corymbiflorum 



and in the so-called sword-shaped variety of Fritillaria 
imperialis. The well-known monstrous species of Cactus 
should also be referred to here (C. peruvianus mon- 
strosus). Experimental estimations of the constancy 




Fig. 112. Evonymus japonica. A fasciated much-split twig 
of this common garden plant. A, B, growth in 1898; 
C, D, in 1900. Photographed, Aug. 1900, from life. 

of these abnormalities from seed do not yet seem to have 
been made. 

The same general conditions obtain amongst many 
species of trees and shrubs, of which any collector can 
easily obtain a fasciated sprig. As instances from my 
own collection I mention Fraxinus excelsior, A I nits gluti- 
nosa, Crataegus nigra, Azalea indica, Robinia Pseud- 



Half Races with Heritable Fasciation. 



505 



Acacia, SalLv purpurea, SalLv alba, Spiraea callosa afro- 
pur pur ca. Moreover I have obtained, by the kindness 
of Prof. W. JOHANNSEN of Copenhagen, beautiful broad 




Fig. 113. Helianthus tubcrosns. A fasciated stem which is 
split into two almost equal fork-branches b and c, at the 
node marked a. From the fork there arise two leaves d 
the mid-ribs of which have fused along their dorsal side. 1 

fasciations of the underground stems or runners of Spi- 
raea sorbifolia from the nursery of Mr. ZEINER LASSEN 
in Helsingor. Instances of the same fasciations have 

1 1 have also observed this remarkable occurrence of fusing by 
the backs in leaves in the forks of split twigs, in Robinia Pseud- 
Acacia and Evonymus japonica (PRINGSHEIM, Jahrb. f. wiss. Bpt., 
XXIII, p. 81) and also in Collinsia heterophylla (1892), Epilobium 
hirsutum (1892), Echium vulgare (1892), Chrysanthemum segetum 
(1892), AgrostenimaGithago (1892 and 1894), Acer Pseudo-Platanus 
(1891), Crepis biennis (1893), Amarantus speciosus (1894), Mercu- 
rialis annua (1894) and Lamiuui purpureum (1895). 



506 The Inconstancy of Fasciated Races. 



been described and figured by CASPARY and therefore 
appear to be fairly abundant in this species. 1 

In perennial weeds fasciations also occur freely, and 
here we may often observe that the phenomenon is re- 
peated more or less regularly in successive years on the 
same specimens or groups of specimens. For instance, 
we have in the botanical gardens at Amsterdam a plant 
of Sonchus palustrls on which I first observed a splendid 

tall broadened stem in 1890. 
Since then the plant has pro- 
duced almost every year one 
or several such structures, 
sometimes 2 meters in height, 
sometimes not more than 1 
meter,and attaining a breadth 
of 6 centimeters by a thick- 
ness of 1. These stems are 
cylindrical at the level of the 
ground, but flatten out grad- 
ually upwards. 

Similar instances were 
afforded by Aconitum Xa- 

mf 

pellns, and Helianthus tnbc- 
rosns (Fig. 113) in our gar- 



Fig. 114. Plantago lanceolata. 
Ears which have split one, 
two or three times. Cultures 
of 1894 and 1895. 



den, by Justitia snpcrba in 
the greenhouse, and byAgri~ 
nionia Eupatorium and Chrysanthemum Leucanthemwn 
in the field. I frequently observed fasciations in annual 
and biennial species, and usually in the course of several 
years in the same locality; for instance in Raphanus 

1 R. CASPARY, Eine gebdnderte Wurzel von Spiraea sorbifolia L., 
Schriften d. Physik. Oec. Ges. Konigsberg, 1878, XIX, p. 149, Plate 
IV. As a matter of fact, however, it was not a root ; see PEXZIG, 
Tcratologie, I, p. 421. 



Half Races u'ith Heritable Fasciation. 



507 



RaphanistruiHj Pedicularis palustris and Oenothcra bi- 
cnnis. In my cultures of Amarantus speciosus, Helian- 
'tlius animus and Oenothcra Lamarckiana, the anomaly 
was reproduced almost every year through the course of 
ten years. 1 

One of the best known 
instances is afforded by the 
sugar-beet, fasciated speci- 
mens of which can be found 
almost every year in the 
fields. We frequently find 
amongst them quite long, 
broad and wholly flat stems. 
In spite of the obvious fact 
that they are not selected 
as seed-parents they recur 
regularly, and this fact is 
sufficient to demonstrate 
the heritability of the anom- 
aly. 

I have further to men- 
tion Plantago lanceolata, 
the variety raniosa of which 
I have described in detail 
in the first part of this vol- 
ume (page 148) and which 
I have cultivated every year 
since 1889. It sometimes 
produces split ears (Fig. 
114), especially amongst the inflorescences which are not 
branched at their base, i. e., the atavistic ones. In this 

1 Further details relating to this subject and more instances of 
the phenomenon will be found in Over de erfelykheid der fasciatien, 
Botanisch Jaarboek Gent, 1894, p. 72. 




Fig. 115. Artemisia Absynthium. 
A fasciated branch which has 
been heavily bent in conse- 
quence. 



508 The Inconstancy of Fasciated Races. 

race the anomaly is obviously in the latent condition and 
only to a slight extent heritable. 

N. MEZZANA records an instance of a fasciated stem 
of Cucurbita Pcpo, the upper part of which gradually be- 
came broader over about a meter of its length, and was 
thickly set with leaves and flowers. The phenomenon 
was observed on a number of specimens which had been 
raised from seed of the same fruit and MEZZANA con- 
cludes from this fact that the anomaly is inherited. 1 The 
fact that I have frequently observed such fasciations in 
my own cultures of Cucurbita supports this conclusion. 
In Artemisia Absynthium also, fasciations are sometimes 
very common as I observed in 1883 (Fig. 115), 1887, 
1888, 1889 and 1890, and the phenomenon was repeated 
from seed in 1889 and 1891. 2 The remarkable forms 
which the fasciated branches of this species so frequently 
assume offer a profitable subject for future inquiry. 

16. EVERSPORTING VARIETIES WITH HERITABLE 

FASCIATION. 

Some wild species produce, in certain districts at least, 
a much higher proportion of fasciated examples than 
others do. According to my experience, such cases sug- 
gest the occurrence of heritable races, the individuals 
of which are mixed with those of the normal species or 
occasionally occur by themselves alone. So far as I am 
aware, such races do not consist exclusively of fasciated 
plants, but partly of these and partly of normal ones. 
Without cultivation the latter cannot be distinguished 
from the normal plants of the species in question, and 

1 N. MEZZANA, Sopra un caso di fasciasione ncl ftisto di Cucur- 
Pepo, Bull. d. Soc. Bot. Italiana, Florence, 1899, pp. 268-273. 

2 Botan. faarb. Gent, 1894, p. 97- 



Ever sporting Varieties with Heritable F (isolation. 509 

therefore we can not directly see whether both races or 
only the first grow in the particular locality; but their 
great rarity points to the mixed condition. 

The heritable races which have hitherto been found 
and isolated in this way, behave like eversporting vari- 
eties inasmuch as each generation consists both of fasci- 
ated individuals and of atavists, even under conditions 
of the most stringent selection. Moreover the proportion 
of these two types appears to be pretty constant, at least 
under similar conditions of life. As a rule, there are 
about 40% fasciated individuals and 60% atavists. Higher 
percentages of the former occur only under favorable 
circumstances, whilst the proportion of the latter very 
easily increases under unsuitable conditions of culture, in 
spite of selection. 

The first instance that I shall describe was afforded 
by C re f>is bicnnis, an exclusively biennial plant, fasciated 
stems of which have been frequently observed in various 
localities in Holland. The starting point of my culture 
consisted in two fasciations, which I found in May 1886, 
in a meadow near Hilversum, amongst hundreds of 
normal plants of Crepis. The broadening of their stems 
was small and limited to the top. I collected ripe seed in 
this meadow in June, but from normal plants only. 
Whether all or only some of these belonged to the ever- 
sporting race I was in search of could, of course, not be 
determined then. 

This seed furnished in the following year about one 
hundred plants, of which three were already fasciated 
in the rosette stage, whilst in the following year nine 
more of them developed more or less flattened stems or 
branches. The total proportion, therefore, was 12%. 
In order to make perfectly sure, I retained only the first 



510 The Inconstancy of Fasriated Races. 

mentioned specimens as seed-parents and destroyed the 
rest before they flowered. 

These three plants therefore formed the beginning of 
my race. Denoting the wild specimens of 1886 as the 
first generation, the second grew in 1887 and 1888, the 
third in 1889 and 1890, and so on. This third one con- 
sisted of 120 plants, of which 48 or about 40% already 
exhibited a comb-shaped linear growing point in the 
heart of their rosettes in the winter. This comb was in 
some specimens as much as six centimeters long. I se- 
lected the three finest fasciations as seed-parents and re- 
moved the rest before flowering. The fourth generation 
raised from this seed produced a slightly lower propor- 
tion of fasciations, containing, as it did, only 30% of 
them. In the fifth generation a further reduction took 
place, viz., to 24% - 1 The sixth generation (1895-1896) 
was very rich in fasciations, and in ten plants out of the 
40, produced a growing comb of from 4 to 7 centimeters. 
Unfortunately the remaining fasciations of less degree 
mostly died in the winter before they were recorded, so 
that an exact percentage value can not be given, Never- 
theless it was obvious that the character of the race had 
been displayed oftener than in the previous generation. 
In the following, viz.. the seventh generation, I also re- 
corded only the expanded rosettes before the winter, and 
found ten of them amongst 49 plants, that is about 20%. 
The eighth generation was not sown till 1902, and only 
on a very small scale. The combs became visible during 
the winter 1902-3. 

If we summarize the results which we have described, 
we see that the seed collected in the field, without selec- 
tion, gave about 12% fasciatecl offspring, whilst the seeds 

1 Botaiiisch faarbaek, Gent, 1894, p. 80, and 1897, p. 66. 



Eversporting Varieties with Heritable Fasciatiou. 511 

of the best cultivated individuals gave values between 
10 and 20%, in the course of the five generations which 
followed. These would probably have been higher if 
the cultures had been larger and the external conditions 
more favorable, and especially if a closer search had 
been made for smaller fasciations on the lateral branches. 
We may therefore regard the constitution of this race as 
fairly constant under normal conditions, and put it on the 
average about 30-40%. 

No doubt, this figure is somewhat lower than the 
normal value of tricotylous intermediate races which we 
described in the second chapter of this part. In that 
case the value was about 55%; but this difference does 
not seem to be of great significance, especially when we 
remember that tricotyly is already determined in the seed- 
lings, whilst a long period of time elapses between the 
ripening of the seed of the fasciated plants and the mani- 
festation of its character, during which period all sorts 
of external influences may be affecting the result. 

A second difference between tricotylous and fasciated 
races also demands brief notice. In the former, selection 
soon led to a transgression of the original normal value ; 
and values of 70 to 90% were often reached or even sur- 
passed without much trouble. In the fasciated races, 
on the other hand, it is very difficult to raise the value 
above about 40%. The explanation of this seems to me 
to be as follows : In my tricotylous races a twofold se- 
lection took place, inasmuch as, first, the tricotylous in- 
dividuals were selected for subsequent cultivation, and, 
secondly, a selection was based -on the proportion of tri- 
cotylous individuals amongst their seeds. By the selec- 
tion of the parents with the highest hereditary values, 
this value itself was seen to increase in the following 

o 



512 The Inconstancy of Fasciatcd Races. 

generation. In the fasciated races, on the other hand, 
we are obliged to limit our selection to the best represen- 
tatives of the anomaly; but there is no further reason 
to suppose that these also possess the highest hereditary 
values. Thus, an essential part of the selective process 
as applied to the tricotyls is omitted in this case. This 
is mainly due to the impossibility of calculating the hered- 
itary values in the seed pans, and the fact that these 
would need cultivation on a very large scale in the gar- 
den. In order to calculate the hereditary values for only 
20 seed-parents from lots of only 100 offspring each 
and even this would hardly give reliable results 80 
square meters of the garden would have to be devoted 
to Crcpis, and this can scarcely be done in an ordinary 
garden. It is to be hoped that institutions will .soon 
be erected where such determinations can be carried out. 1 
Besides Crcpis bicnnis I discovered one or two other 
species behaving in the same way and succeeded in rais- 
ing eversporting varieties from them. 2 The first to be 
mentioned is Aster Tripolium, of which I obtained a 
splendid fasciated example with ripe fruits in the autumn 
of 1900, from this neighborhood. At first I grew the 
plant as an annual and reached only a low proportion of 
fasciated individuals as a result of this. The figure was 
7% for the fourth generation. In the fifth generation, 
however, in the summer of 1894, the plants were sub- 
jected to better treatment, and more than half of them 
produced fasciated stems, amongst which many were 
more than 3-4 centimeters broad. I shall deal with 

My experimental garden contains 75 beds of about 4 square 
meters each. 

2 Botanisch Jaarbock, Gent, 1894, an d Bull. Scicntifiqtie de la- 
France ct de la Bclgiqnc, public par A. GIARD, XXVIT, 1896. p. 402. 



Eversporting Varieties with Heritable Fasciation. 513 

Geranium molle fasciatuin in the next section. Of this 
race, one-third consists, as a rule, of individuals with 
fasciated branches. In 1895 I was growing its sixth 
generation. I have also cultivated six generations of 
Taraxacum officinale fasciatnm. This species, as a rule, 
produces 30%, and sometimes more, of fasciated individ- 
uals. Beautiful instances of fasciation have been fur- 
nished almost every year, since 1885, by Tetragonia ex- 
pansa in the botanical garden in Amsterdam, and the 
proportion of these was, in the fourth and fifth genera- 
tions after isolation, slightly over 50%. 

The same general behavior was observed in my fas- 
ciated races of Thrincia lurta, Veronica longifolia, Hes- 
peris matronalis, Picris hieracioides etc. 

From these data we may draw the general conclu- 
sion that such races, after having been isolated and sub- 
jected to good treatment, and by the selection of the 
finest instances of fasciations as seed-parents, consist of 
a little less than one-half of fasciated individuals, and of 
a little more of apparently normal, atavistic, plants. This 
proportion, ho\vever, depends to a large extent on ex- 
ternal conditions. Bv means of suitable cultivation it 

/ 

can be considerably increased, but on cessation of this 
care it soon sinks to quite low values. 

Many of the known instances of fasciations probably 
behave in the same way. For instance KORNICKE has 
grown for many years a perfectly constant race of a 
fasciated pea (Pisitm sativum) in Poppelsdorf, and RIM- 
PAU has informed me that he cultivated this fasciated 
race from seeds during several years in good garden soil 
and found it constant. The result of sowing the seed 
of Sednni refiexinn cristahun (Vol. I, p. 183), in this 
garden, was the reappearance of the abnormality in large 



514 The Inconstancy of Fasciatcd Races. 

numbers. To this group, also Asparagus officinalis and 
several other species seem to belong. 



17. THE SIGNIFICANCE OF THE ATAVISTS. 

As we have seen in the first section of this chapter 
(page 490) a proper understanding of what is meant by 
atavism is a necessary basis for the discussion of our 
appreciation of the inheritance of fasciations, and of 
anomalies in general. Here, the atavists are not indi- 
viduals which step out of the race ; on the contrary, they 
are to be regarded merely as specimens in which, from 
some external cause or other, the anomaly is not mani- 
fested during their lifetime. In the selection for the 
continuation of the race they are, of course, not usually 
preferred, but as a matter of fact they may serve just as 
well for this purpose as the fasciated individuals them- 
selves. 

Extensive investigations are still to be carried out 
before a complete and proper understanding of the prin- 
ciples which underlie these phenomena can be attained. 
The knowledge however, which we already possess, ap- 
pears to me to be sufficient to demonstrate the correctness 
of the generalization just enunciated. In the first place 
I mentioned the remarkable fact that the anomaly can re- 
main latent during a whole generation without disap- 
pearing forever or even becoming noticeably diminished. 
Sometimes indeed two or several generations can be 
skipped in this way. Let me give some instances as proof 
of this. 1 In the fall of 1887 I collected some seed of 
Tetragoma e.vpansa from fruits on very broad stems and 
obtained, in the following years. 1888-1890, three further 

o / 

1 Botanisch Jaarboek, Gent, 1894. 



The Significance of the ^Ikii'ists. 515 

generations which produced a greater or les> number of 
fasciations. The seeds of the finest fasciations of 1890, 
however, produced nothing but normal plants in 1891 
which did not exhibit the anomaly, even on a single 
lateral branch. They were weak plants and it looked 
as if the anomaly were lost once and for all; but seeds 
of these plants produced in the following year, 1892, 
fourteen plants, of which seven were fasciated. Six 
of them had 1 1 2 2 3 3 broadened stems, and 
one plant had as much as four large fasciations. More- 
over the lateral branches were so much affected by the 
anomaly that I found about one-third of them to be 
modified in this way. Since that time the anomalv has 

j * 

remained constant in this strain. In the third generation 
of my race of Amarantus speciosus (1891) the fascia- 
tions were also absent, but returned in the fourth and 
fifth generations in 30 and 50% of the individuals. In 
Helianthus annuus they were also absent from the third 
generation (1889), whilst the fourth contained about 
20% of fasciated individuals, and the anomaly has since 
remained constant. In the maize I observed fasciated 
ears in 3 cultivated race in the years 1888, 1889, 1892 
and 1893, but not in the generation of 1891, between 
these. From the seed of a very broad stem of Picris 
lueracioides (188?) I raised three generations under 
unfavorable conditions, and they did not produce a trace 
of the anomalv on manv hundreds of branches and stems. 

*> * 

It was not until the fourth generation that the anomaly 
reappeared, although only to a slight extent. Besides 
this strain. I have cultivated a race of biennial individuals, 
and these have presented fine instances of fasciations in 
greater or less abundance in every generation. 1 

iie generate d^ hotanigue, 1899, Vol. XL D. 136. 



516 The Inconstancy of Fasciated Races. 

In the summer of 1895 I isolated some of the atavists 
of my race of Crcpis bicnnis described above, before they 
flowered. 1 The seeds were sown in the following year 
and produced over 350 plants. About 20% of these ex- 
hibited the comb-like structure in the center of the ro- 
settes, and this line sometimes reached a length of five 
centimeters. Thus we see that the seeds of the atavists 
may produce fasciations in about the same quantities as 
do the selected fasciated individuals. Inasmuch as the 
monstrosity frequently lowers the strength of the plant, 
it might perhaps even be advisable to choose the seeds 
of the atavists or of individuals which are only fasciated 
on their lateral branches. 

A further proof of the view that the atavists are only 
fasciated individuals with their character in a latent con- 
dition is afforded by experiments on the effect of thor- 
ough manuring. For the individuals which under normal 
favorable circumstances behave as atavists can be in- 
duced by it to a relatively considerable development of 
fasciations. In 1895 I made such an experiment with 
my strain of Crcpis biennis fasciata which then contained 
some 20 to 40 % of fasciated individuals every year. I 
manured a group of 41 plants with an abundance of horn- 
meal. At the time of ripening only six of these lacked 
the anomaly, i. e., 85% instead of 40% were fasciated. 
The plants stood fairly close together, at distances of 
about 20 centimeters apart. If I had given them enough 
room I should probably have succeeded in inducing the 
anomaly in every one of them. 2 

The fasciated commercial race of Celosia cristata, 

1 Botanisch Jaorbock, Gent, 1897, p. 66. 

2 Botanisch Jaarbock, 1897, p. 66; and Bull. Scicntif., loc. cit., 
Vol. XXVTT, p. 413. 



The Significance of the Atavists. 



517 



generally known as the coxcomb, is peculiarly well suited 
for an investigation of atavism. The great combs pro- 
duced by this favorite garden plant are merely the se- 
lected well treated and highly nourished individuals, i e., 
the extreme phis variants of the race. 1 All the rest are 
thrown away in their early stages by the gardener; but 
if we wish to know how the race really behaves, we must 




Fig. 116. Celosia cristata. An almost entire plant under 
poor treatment. Top comb-shaped but small ; most of 
the lateral branches were also broadened at their tips. 

make sowings ourselves and plant out all the individuals 
without selection, and cultivate them further. It is well 
known that in this way we obtain numerous plants with 
branched stems and with a much lower degree of the 
anomaly (Figs. 116 and 117). By the selection of these 
minus variants for further cultivation one might expect, 

1 For the mode of cultivation suitable for this variety see MOL- 
LER'S Deutsche Gartenzeitung, 1892, p. 200. 



518 The Inconstancy of Fasciatcd Races. 



as SOLMS-LAUBACH suggests, to ultimately obtain the un- 
fasciated original form of this highly modified plant. 1 
But according to the view laid down in this book, a mu- 
tation would be necessary for this ; 
and, so far as we know, these ap- 
pear only very seldom and fortui- 
tously, unless we happen to meet 
with a plant in a mutational period. 
During the years 1893-1897 I 
endeavored to obtain a race devoid 
of fasciations, but in vain ; and in- 
asmuch as the general rule is that 
favorable circumstances increase 
the production of the anomalies, 
and as correspondingly the worst 
nourished and weakest individuals 
have always borne the smallest fas- 

*/ 

ciations, I was ultimately obliged 
to give up the experiment, because 
my strain gradually became very 
much debilitated without, however, 
producing the desired result. 

In 1893 I raised about fifty 
plants from bought seed, but did 
not make any detailed record of 
them. Most of them produced 
combs in every degree of devel- 
shaped but mostly with opment, 2 but usually of small size. 




Fig. 117. Cclosia cris- 
tata. Top of a plant 
about V-2 meter high ; 
the stem was much 
branched and its in- 
florescences were ear- 



comb-shaped 



5 10 centimeters broad or less. 



1 H. SOLMS-LAUBACH, Bot. Zcitung, 1900, p. 42. 

'' The plane of the fasciation is the median plane of the cotyle- 
dons ; and this is also the case in Crcpis bicunis. This fact might 
be used as a starting point for an inquiry into the ontogeny of fas- 
ciations. 



The Significance of llic Atavists. 519 

Six plants had a terminal spike at the top of the main 
stem with a small comb; in six others this comb was ab- 
sent, although small fasciations occurred here and there 
amongst the lateral branches. These six plants were 
selected as seed-parents, and from their seeds I obtained 
the second generation (1894), in which about half the 
individuals bore terminal spikes without a comb. There 
were 41 of these. The remaining 53 had combs ranging 
from 1-3 centimeters broad and were thrown away. Of 
the selected atavists, several produced lateral combs later, 
and each one of these plants was destroyed as soon as 
I discovered the anomalv, until at the end of the harvest 

J * 

period there were left only five plants which, though 
profusely branched, manifested no trace of fasciation. 
In the following year there were 29 plants with small 
combs and 6 without any at all ; these latter were again 
isolated as seed-parents. In 1896 I had 38 individuals, 
all of which, without exception, produced combs, the 
length of which ranged between 2 and 8.5 centimeters 
with a mean of 4.5. Only one plant had no comb at the 
apex of the stem ; but had a much flattened lateral branch 
instead. This, and the plants with the smallest terminal 
combs, were selected as seed-parents. Again, in the 
following year (1897), no progress was made, inasmuch 
as only a single weakly individual failed to produce a 
comb. Therefore I gave up the experiment and I con- 
clude that complete atavists are very rare in Celosia 
cristata and that even under repeated selection in the 
minus direction they will only be obtained in very small 
quantities. At present at least there seems not to be any 
prospect of obtaining a pure atavistic strain. 

The experiments I have described show that, as a rule, 
there is no sharp limit between the fasciated individuals 



520 The Inconstancy of Fasciated Races. 

and the atavists. This fact can be illustrated by statistical 
examination of the material, provided it can be made 
sufficiently large by cultivation. As an example of this 
I may again cite my race of Crepis biennis fasciata. 1 

In order to obtain a pure curve, I sowed the seeds 
of a single broadly fasciated individual of the third gene- 
ration of my race (1890) in March 1894. The plant 
had flowered together with two other fasciated individ- 
uals of the same ancestry, but this little group had been 
completely isolated. The seeds were sown in pans in the 
greenhouse and afterwards planted out at suitable dis- 
tances in the bed. Whilst still in the rosette stage many 
of them produced in the first year a comb-shaped heart. 
Others did not exhibit fasciation until the stem began to 
develop in the second year. Still others had not produced 
a single comb at the time when all their branches were 
fully developed. The external conditions had been as 
favorable as possible, so that I obtained a relatively high 
proportion of fasciated individuals. When I examined 
the plants in June of the second year, I obtained the fol- 
lowing result : 

Stems without fasciation 33 

with slight fasciation at the top . 9 
fasciated along their whole length 108 

Total 150 

The breadths of the stems of these latter 108 plants 
were distributed as follows : 

Cm. 2 3 4 5 6 7 8 9 10 11 12 13 14 19 
Ind. 9 9 4 11 11 11 13 15 11 6 3 3 1 1 

The numbers are plotted in Fig. 118 in the form of 
a curve. In this curve indicates the group of 33 ata- 

1 Sur les courbes Galtoniennes des monstruosites, Bull. Scientif., 
publie par A. GIARD, XXVII, 1896, p. 396. 



The Significance of the Atavists. 



521 



vists, 1 the nine plants with cylindrical stems and slight 
broadening at the top; whilst 2-20 denote the breadth 
of the stems in centimeters. 

The curve is seen to have two peaks, one of which is 
formed by the atavists (a), the other by the fasciations 
of mean breadth, i. e., of about nine centimeters. Ex- 
pressed in words, the result is that transitions between 



10 11 12 13 14 15 16 17 18 19 20 




Fig. 118. Crepis biennis fasciata. A curve representing the 
breadth of the main stems of all the individuals of my 
culture of 1895. The numbers under the base line indi- 
cate the breadth of the stems in centimeters, o, stem 
round; I, stems only flattened at the upper end; 2-20, 
stems flattened along their whole length. The height of 
the ordinates gives the number of individuals. Total 
number of individuals 150. a, the peak of the atavists; 
b, that of the fasciated individuals. 1 

the fasciated individuals and the atavists do occur, but are 
relatively rare. The race produces by preference the 
two pure types, and the same thing is seen to happen in 
chance fasciations and in many other monstrosities. I 
call to mind the relative rarity of hemi-tncotyls and hemi- 
syncotyls, both in the wild state and in the tricotylous 

1 Bull Sdcntif., loc. dt., Vol. XXVII, p. 397. 



The Inconstancy of Fasciated Races. 



and syncotylous races described in the first two chapters 
of this part. 

Similar results may be obtained with other fasciated 




Fig. 119. Geranium molle fasciatum. Fasciated branches 
with broadened and split fruits, a, b, c. 

races. Thus I obtained in the fifth generation of my fas- 
ciated race of Aster Tripolium, under biennial culture : 



WITHOUT FASCIATION 

Cm. 1 

Individuals 16 2 



WITH FASCIATION 

23456 
68111 



The Significance of the Atavists. 



523 



The curve representing these 35 plants would have 
a distinct peak representing the atavists and another cor- 
responding to the fasciated individuals of the average 
breadth of 3 centimeters. 1 

In Geranium inolle fasciatum the variation of this 
character proved, after a statistical examination of the 
material to be represented by a many-peaked curve. This 




Fig. 120. Geranium mollc fasciatum. a, fruit containing 
6 single fruits ; b, split into one group of 4 and one of 
5 ; c, split into three groups containing 5 7 and 5 single 
fruits ; d, one group has 16 and the other 5 divisions of 
fruit and stigmas; c, fruit \vith 33 divisions and stigmas 
(1895). 

race 2 is remarkable from the fact that the stems have, 
as is well known, a sympodial structure (Fig. 119), 
Therefore the anomaly affects, as a rule, one member of 
the sympodium only ; but sometimes it extends to two 
or more adjacent ones. These are again succeeded by 
atavistic members. Each part terminates in a flower. 

1 Revue gcncrale de botaniquc, 1899, Vol. XI, p. 143. 
s Botanisch Jaarb. Gent, 1894, P- 81 ; and 1897, p. 67. 



524 The Inconstancy of Fasciatcd Races. 

In the fasciated parts these flowers are broadened and 
usually more or less divided, the fruit sometimes form- 
ing a flat structure (Fig. 120 e), with or without one or 
two lateral fruits in the same flower (Fig. 120 c and d). 
Often these latter are pentamerous. Lastly the whole 
fruit can be split into two or three nearly equal parts 




Fig. 121 Geranium molle fasciatum. Curve representing 
the number of sections of the fruit in the individual 
flowers of the sixth generation, June 1895 ; a, number of 
normal flowers far above 100; number of flowers with 6 
to 23 stigmas, 120. 

(Fig 120 b). In these various types of splitting there 
seems to be a tendency to the production of whorls of five, 
and the lateral flowers nearly always present this number. 
My race began with a specimen found wild in 1888 
and in the third and fourth generations produced 25 to 



The Significance of the Atavists. 525 

30% individuals with fasciations. In the two following 
generations they were much more abundant. In the sixth 
there were 65% fasciated specimens, in a culture of 220 
plants, and these afforded me sufficient material for a 
statistical examination. For this purpose I collected, 
shortly before the ripening of the seed, all the aberrant 
flowers from a certain number of plants, and counted the 
number of the divisions of the fruit or that of the stig- 
mas of 120 individual flowers taken at random. The 
figures which I obtained were as follows : 

NUMBER OF 

Stigmas 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 
Flowers 13 945 10 15 2 2 10 15 63 7593 1 1 

I did not count the normal flowers, but their number 
far exceeded that of the whole group of the fasciated 
ones. In the curve in Fig. 121, in which the above series 
of figures is graphically displayed, the apex representing 
the atavists is therefore only formally indicated. The 
secondary peaks fall at 11 (10), 15 and 20 pistils, and 
the normal pentamery of the flowers is thus clearly re- 
peated in these multiple figures. 1 

Besides illustrating this curious fact, the curve shows 
that low grades of fasciation are relatively rare and that 
atavistic and normal flowers constitute two distinct 
groups, although connected by intermediate stages. 

Let us now summarize the conclusions we have come 
to in regard to fasciated eversporting varieties. 

1. The races always consist of fasciated individuals 
and atavists. 

2. The proportion of the former varies greatly, of- 
ten amounting to only 40% or less, but not infrequently 

1 A further inquiry into this point is, in my opinion, urgently 
called for. 



526 The Inconstancy of Fasciated Races. 

to more (Geranium and Crcpis with 65% and 85% ; 
Celosia cristata). 

3. The fasciated individuals and the atavists are con- 
nected by transitional forms, which are, however, rare; 
and the statistical curves representing them have there- 
fore two apices. 

4. These proportions are to a large extent dependent 
on external conditions of life, which can transform ata- 
vists into fasciated plants and vice versa. This trans- 
formation obviously takes place during the plastic period 
in youth, before the character in question is actually de- 
veloped. 

5. The atavists, as well as the selected individuals, 
produce fasciated offspring, and often in proportions very 
little lower than those in which the selected individuals 
produce them. They may therefore be used for the per- 
petuation of the race. 

6. Between the broadened specimens and the atavists 
there is no essential or fundamental difference, in spite 
of the great difference in their external forms. 



IV. HERITABLE SPIRAL TORSIONS. 

(Plate VI.) 

18. THE SPIRAL DISPOSITION OF THE LEAVES. 

In the case of spiral torsion the difference between 
normal and abnormal individuals is far more striking 
than in that of fasciations. Valeriana officinalis is one of 
the best known and the most frequently figured instances 
(Fig. 122). Here the whole stem, instead of growing 
to a height of more than a meter, can be reduced to about 
a decimeter, and becomes more or less funnel-shaped. 
Low down the leaves are disposed spirally, but higher up, 
the spiral gradually becomes steeper, until, in the ex- 
panded upper part of the funnel all the leaves are directed 
to one side like a fan. The terminal inflorescence sur- 
passes the highest lateral flowering branches very little 
or not at all. 

By no means every stem of the spirally twisted plant 
manifests the anomaly. On the contrary, very few of 
them do as a rule. Since 1889, I have had a specimen 
which has gradually increased by runners and now covers 
an area of several square meters in the botanical garden 
of Amsterdam. It produces spiral torsions every year, 
but they are rare, and, as a rule, there are not more than 
two or three among several hundreds of normal stems. 

The same rarity is seen in the inheritance of the 
anomaly, both in Valeriana and other species ; as a rule, 



528 



Heritable Spiral Torsions. 



only a small proportion of the plants repeat the anomaly, 
even when the seeds have been saved on the most highly 
modified stems. Races which produce the anomaly abun- 
dantly have been very rare hitherto. They will be de- 
scribed in the following section ( 19). 




Fig. 122. Valeriana ofKcinalis. An entire plant the stem of 
which attained the height of 10 centimeters only. Photo- 
graphed from life in June 1900. Disposition of the leaves 
spiral below, unilateral above. 

In consequence of this rarity the belief prevailed, 
up till about 10 years ago, that these torsions were not 
heritable. The general view was that they were induced 
by special external influences which operated immediately 
upon the individual every time the anomaly arose. At that 
time the experiments which I had made with a twisted 



The Spiral Disposition of the Leaves. 529 






Fig. 123. Dipsacus sylvestris torsus. Two spirally twisted 
main stems, w, root ; r, stem with the scars of the radical 
leaves and at I 5 the windings of the spiral ; g, stalk of 
the terminal inflorescence ; A, leaf-spiral left hand, stem 
right hand; B, leaf spiral right hand, stem left. Stems 
thickened and hollow. 



530 Heritable Spiral Torsion. 

race of Dipsacus sylvestris torsus, during over thirteen 
years, together with a long series of further observations 
on the inheritance of this anomaly in other plants, have 
proved that this character is as heritable as other anomalies 
are. Plate VI gives a view of a culture of this race, re- 
produced from a photograph of one of my beds. 

Real spiral torsion only occurs in those species which 
normally have a decussate or whorled disposition of the 
leaves. It consists in the substitution of a spiral arrange- 
ment for this. The leaves arise from an unbroken spiral, 
along which they are attached to one another more or 
less closely to their bases (Fig. 123). This close spiral 
is sometimes interrupted and normal internodes are inter- 
calated in the twisted part. Not infrequently the torsion 
is limited to a greater or a lesser part of the stem (com- 
pare, e. g., below Dianthus, Fig. 129). Indeed no sin- 
gle stem is completely abnormal from the very beginning. 

As might be expected the fusion of the base of the 
peduncles into a continuous band results in an inhibition 
of the longitudinal growth of the stem. The internodes 
cannot elongate normally, and as they strive to extend, 
they partly unwind the leaf spirals. In consequence the 
spiral becomes steeper and not infrequently unwinds so 
much in the upper parts of the stem, i. e., those parts 
which normally grow in length, as to become a straight 
line. When this occurs the leaves and their axillary buds 
arise in a longitudinal series on one side of the stem 
(Fig. 122). Obviously this can only be reached by the 
stem twisting itself in the opposite direction to that of 
the leaf-spiral (Fig. 123). Inside the twisted stem, 
if it is hollow, the diaphragms which normally occur at 
the nodes, do not exist as such, but are united together 



The Spiral Disposition of the Leaves. 531 

to a continuous screw-like band which corresponds ex- 
actly to the leaf-spiral on the outer side. 

Twisted stems look as if they were inflated (Figs. 
122 and 123), and are much thicker than the normal 
stems of the same species. Longitudinal growth has, 
so to speak, been changed into a tangential growth, as 
the course of the otherwise vertical ribs clearly shows 
in our figures. The longer the particular internodes on 
the normal individuals are, the broader are the correspond- 
ing parts on the twisted ones. In this way the funnel 
shape of the twisted Valerian, as well as other specific 
and local differences, are easily explained. 

From this we see that a right-hand torsion of the 
stem (mounting in the direction of the movement of the 
hands of a clock) must be associated with a left-hand 
leaf-spiral and vice versa (Fig. 123). 

The explanation here given was first suggested by 
BRAUN, and later demonstrated by KLEBAHN, by the 
microscopical examination of the top of the stem of a 
twisted Galium. 1 It can now easily be confirmed by 
every one on the material afforded by my heritable races. 2 

In Dipsacus sylvestris torsns the spiral arrangement 
of the leaves can be detected towards the end of the first 
summer in the heart of the rosette of radical leaves, with 
the naked eye, and without any damage to the plant. 
After germination and in the earlier stages the leaves 
are decussate (Fig. 124 A) in all the plants with very 
rare exceptions ; it is not until later that this arrangement 

*AL. BRAUN, Monatsber. d. k. Akad. d. Wiss., Berlin, 1854, p 
440. See Bot. Zeitung, 1873, p. 31 ; H. KLEBAHN, Ber. d. d. hot. Ges., 
Vol. VI, p. 346. See also Ueber die Erblichkeit der Zivangsdrehungen, 
same journal, Vol. VII, p. 291. 

2 For the literature of the subject see Monographic dcr Zwangs- 
drehungen, Jahrb. f. wiss. Bot., Vol. XXIII, 1891. 



532 



Heritable Spiral Torsions. 



is changed into the spiral one, and in different individuals 
this occurs at varying ages. If a transverse section of 
the plant is then examined under high power, at the 
level of the growing point, the spiral arrangement of the 
leaves can easily be seen. Taken later, i. e., during the 
elongation of the stem, such transverse sections have still 
more or less the same appearance (Fig. 124B). The 
outer leaves of this figure have been cut through their 
lower parts where they are fused laterally with one 
another; their left-hand spiral can easily be followed 




Fig. 124. Dipsacus syhestris tarsus. A, a transverse sec- 
tion through a seedling a little above the growing point 
showing the normal decussate arrangement of the 
leaves ; c, c , the cotyledons ; B, a transverse section 
through the still young point of the stem of a twisted 
individual with spiral arrangement of leaves. 

in the figure. The subsequent leaves were still very 
young and were therefore cut across their upper free 
parts, but are nevertheless obviously arranged in a spiral. 
The three youngest leaves do not seem to form part of 
the spiral, but a trimerous whorl, such as very often 
occurs in the upper part of the stem of twisted speci- 
mens of Dipsacus If the angle of divergence of the 
leaves is measured it usually corresponds pretty closely 



The Spiral Disposition of the Leaves. 533 
to one of the ordinary types of leaf arrangement, (e. g., 



In the rosettes of radical leaves, where the internodes 
do not lengthen, the spiral disposition of the leaves does 
not involve any further disturbance. The leaves simply 
grow out and retain their original position. But when, 
in the second year, the young internodes begin to elon- 
gate, this cannot happen equally on all sides of the stem, 
because the line of attachment of the leaves acts as a 
check. In consequence of this the stem must twist and 
unwind the leaf-spiral, the angle of divergence between 
successive leaves becoming gradually smaller. The num- 
ber of windings decreases, and on the other hand, the 
numbers of leaves on a single section of the spiral (i. e., 
from a given point on the stem to another vertically 
above it) increases, as our Fig. 123 clearly shows. 

Spiral torsion is, therefore, a mechanical result of the 
loss of a single character, the decussate arrangement of 
the leaves. Once this is lost, the ancestral spiral dispo- 
sition steps in, but now accompanied by peculiarities in 
the structure of the basal parts of the leaves, which on 
normal plants never occur independent of an arrangement 
in whorls, since they can only, so to speak, agree with the 
normal structure of plants with this arrangement. There- 
fore, in my opinion spiral torsion is due to a retrogressive 
transformation of the decussate arrangement of leaves. 

That it is a mechanical result can be proved by ex- 
periment; all that is necessary is to remove the cause of 
the twisting at an early stage, by cutting through the 
leaf spiral. If this is done carefully, the general growth 
of the plant is not interfered with, but the torsion will 
be locally inhibited, or, more strictly speaking, does not 
appear at the place operated on. Thus a straight inter- 



534 



Heritable Spiral Torsions. 



node will become intercalated in the middle of an other- 
wise twisted stem. This can easily be seen in Fig. 125 
at a, in the gaping wound and in the vertically ascending 
longitudinal ribs. Sometimes nature itself makes a simi- 




Fig. 125. Dipsacus sylvestris torsus. 
The two leaves a and b of the twisted 
stem have been separated from one 
another in earliest youth by a cut : 
between them is seen the gaping split. 
The one leaf, b, is situated now about 
2 centimeters higher than the other, a. 
Above a the stem has remained straight 
for more than 2 centimeters. Some of 
the lower leaves were removed before 
photographing in order to show the 
important parts more clearly. 



lar experiment, and longitudinal growth tears the leaf- 
spiral in one or two places, without, however, making 
so deep a wound as results from an experiment. The 
result of such a natural experiment is a straight internode 



The Spiral Disposition of the Leaves. 535 

of normal length, for instance of a decimeter or more, 
in the middle of a twisted stem. 

Like other anomalies spiral torsions are to a very 
large extent dependent on external conditions. Under 
unfavorable treatment the anomaly may be almost en- 
tirely absent, even from cultures from seeds which other- 
wise would give rise to a third or more of individuals 
with fine spiral torsions. The experiments which I have 
made on this point with Dipsacus sylvestris torsus and 
which have been confirmed by the results of my experi- 
ments with other species, seem to justify the following 
conclusion. 1 

The more favorable the conditions of life and the 
more vigorous therefore the growth, the greater will be 
the proportion of beautifully twisted plants in a given 
culture, and the more complete will be the torsions which 
are produced. 

The most important of these conditions is the space 
given to the individual plants. They ought not to be 
shaded by one another nor touch one another. More 
than 20-25 plants should never be grown on a square 
meter. Grown thus they nevertheless stand in close con- 
tact in autumn, and it is obviously still better that no 
more than 10-15 plants should occupy a square meter. 

Fewer torsions are produced on a given area when 
the plants are crowded than when the distances between 
them are greater. No useful purpose is therefore served 
by increasing the number of plants on the same bed. If 
nevertheless this is done the twisted individuals will be 
found almost exclusively along the edges of the bed. 

The time of sowing the seed is a point of considerable 

1 On Biastrepsis in Its Relation to Cultivation, Annals of Botany, 
Vol. XIII, 1899, p. 395- 



536 Heritable Spiral Torsions. 

importance, inasmuch as it determines the length of the 
life of the plant up to the moment of the production of 
the stem. The longer this period continues under favor- 
able circumstances the greater is the likelihood of the 
leaves becoming spirally arranged. 

Sowings, made in summer or early autumn, which 
gave rise to stems in the next year, reduced the prospect 
of obtaining torsions almost to nil. On the other hand, 
autumn sowings which do not give rise to stems until 
the summer after the next, contain very large numbers 
of twisted specimens; so that if the seeds are sown late 
in the autumn the proportion of plants with a spiral ar- 
rangement of their leaves is even greater than amongst 
plants raised from seeds sown in ths spring. 

Little effect is produced upon the result of a culture 
by sowing in March or in April or even in the begin- 
ning of May. Also it does not matter much whether 
the sowing is carried out in the greenhouse in pans and 
the seedlings planted out later into the beds, or whether 
the seeds are sown where they are to grow. For various 
reasons I have for many years preferred the former 
method, as it is more convenient and safer, especially in 
dry springs. 

A good loose soil with a strong manure rich in nitrates 
seems to be an essential condition. On unmanured sandy 
soil even the best seeds do not produce twisted individuals, 
and on hard or barren soil the proportion is considerably 
diminished. 

It is possible to confine the cycle of life of Dipsacus 
sylvestris torsus within the limits of a year by sowing 
the seeds under favorable circumstances immediately 
after they are ripe. In this way a generation can be 
grown every year, and an annual twisted race might pos- 



Rare Spiral Torsions. 537 

sibly be raised by selection. At present, however, the 
annual habit and the torsion are mutually exclusive, the 
anomaly being represented on the stems of such plants 
either not at all or as faint indications only. 



19. RARE SPIRAL TORSIONS. 

From time to time spiral torsions are also found on 
wild and cultivated plants under conditions which make 
it impossible to make any other observations on the in- 
heritance of the anomaly than that they occur relatively 
frequently on the several branches of the same plant or 
in more or less numerous examples in the same locality ; 
or recur during the course of several years. They may 
be found in dozens in Weigelia amabilis, and are also 
well known in several species of Galium. In Galium 
verum and G. Atoarine I have collected them in this 

A. 

neighborhood. Equisetum is also a well-known example, 
which deserves special mention as belonging to the vas- 
cular cryptograms as well as on account of its peculiar 
leaf-whorls. Our figure 126 is photographed from a 
stern which Dr. TH. WEEVERS found near Nymegen in 
the summer of 1900. Here it grew among several other 
instances of torsion in the same species. Casuarina also 
sometimes forms such anomalies on its branches ; for 
instance, several occurred in 1897 in the botanical garden 
of Amsterdam (Fig. 127 a). 

In the first chapter of this part we have seen how, 
as a result of the correlation between various abnormal 
types of leaf arrangement, the selection of tricotylous 
seedlings often leads to the discovery of spiral torsions 
in species from which otherwise they can be obtained 
only very rarely. As instances of such species I may 



538 



Heritable Spiral Torsions. 



recall Dracocephalum moldavicum (Fig. 74, p. 369), 
Aspernla azurca, Centranthus macrosiphon and especially 
Mercurialis annua. In the latter species these malforma- 
tions appeared almost every year and often in consider- 




Fig. 126. Eqnisetiun Tclmatcja. Spiral torsion of an 

erect stem. 

able numbers, in mv tricotvlous and svncotvlons races 

* ^ > *> 

(Fig. 96, p. 464 J. 

Unless direct experiments in isolation have been made 
it is impossible in the majority of cases to be certain 



Rare Spiral Torsions. 



539 



whether the race we are dealing with is a half or an inter- 
mediate race. Nevertheless the rarity of the anomaly 
in repeated sowings strongly indicates the former alter- 
native. This was certainly the case in Lupinus lutcus, 

u 




Fig. 127. Casitarina qitadrivalvis. A branch with a lateral 
torsion, a. From the botanical garden in Amsterdam, 
1897- 

Silcnc noctiflora and other species which occasionally 
produced spiral torsions in my cultures. In Valeriana 
officinalis (Fig. 122, p. 528), which has already been 
mentioned, the proportion of anomalous individuals raised 



540 



Heritable Spiral Torsions. 



from seeds gathered from twisted stems was very small, 
and in Rubia tinctorum, of which I have had several 
beautiful instances of spiral torsions from the fields in 
Holland, they are never by any means common, although 




Fig. 128. Agrostemma Githago. The calyx is open at one 
side and fused with the uppermost pair of leaves and 
transformed into a spiral. Culture of 1896. 

they occur nearly every year. 1 In Agrostemma Githago 
I have often observed torsions in a race which I have 
cultivated during ten generations since 1888, but always 

1 Ecnigc gcvallcn van Klemdraai by de Meekrap (Rubia tinc- 
torum}. Botan. Jaarb. Gent, 1891, p. 74 and Plate IV. 



Rare Spiral Torsions. 541 

in small numbers. Sometimes these were confined to the 
vegetative parts, but sometimes the calyx, together with 
the upper pair of leaves, was transformed into an open 
spiral (Fig. 128). 

In order to determine the intensity of inheritance of 
this anomaly in such cases, I have conducted an experi- 
ment with Dipsacus laciniatus. This plant was of pecu- 
liar interest to me because it belonged to a genus which 
has been known for a long time to produce fine spiral 
torsions and to which also the Dipsacus syhestris be- 
longs, from which I have been able to isolate an ever- 
sporting variety which produces this anomaly in abun- 
dance. In Dipsacus laciniatus, on the other hand, the 
attempt to effect a similar isolation was unsuccessful. In 
this case an intermediate race was not present, but only 
a half race; for in spite of extensive cultures for two 
generations no more than slight local torsions were ob- 
tained. 

A plant of Dipsacus laciniatus which I had seen in 
full bloom in the botanical garden at Groningen formed 
the starting point of this experiment. It was over two 
meters high with a perfectly straight stem which, how- 
ever, had a little group of spirally arranged leaves at 
one of the upper nodes and here exhibited local twisting. 
Prof. J. W. MOLL kindly sent me seeds of this plant. 
From these I grew in the two following years 400 plants 
on a bed of about 16 square meters, that is about 25 per 
square meter, which may be regarded as giving ample 
room. The sowing took place in the beginning of April. 
In the summer of 1897 all the stems became straight; 
not a single one was twisted, as in Dipsacus syhestris 
(Fig. 123, p. 529). Moreover, the arrangement of the 
leaves was decussate in all of them. Slight abnormal- 



542 Heritable Spiral Torsions. 

ities in this arrangement certainly occurred, such as 
split leaves, trifoliate upper whorls, fusion of two pairs 
of leaves by a so-called line of tearing extending over 
the internode, a phenomenon which shows that the leaves 
in their early stages were fused in a spiral manner instead 
of in whorls. Besides these, there were eight plants, i. e., 
about 2%, which had a distinct local torsion at one of 
the upper nodes of the same development as in the parent 
plant. Their leaf spiral involved from 3-6 leaves. Only 
these plants were allowed to flower, and there was no 
other Dipsacns laciniatits in the garden. Five of them 
produced a sufficient quantity of seed. 

The second generation of this culture occupied the 
years 1888 and 1889 and consisted of 435 plants which 
produced stems and were allowed considerably more 
space than their predecessors, 12 specimens being grown 
to each square meter. Nevertheless the result was the 
same as in the foregoing generation. All the plants 
formed erect and tall but straight stems, from 2-2% 
meters high. Amongst them there were five specimens 
which had a somewhat larger local twisted part than 
occurred in the preceding generation, inasmuch as in 
these cases from 7-12 leaves were combined into an un- 
interrupted spiral. They arose from three of the five 
parents. Less pronounced torsions (at the nodes) which 
affected from 2-3 or rarely from 4-6 leaves, occurred 
fairly commonly in this year. I counted the percentages 
of 5, 5, 13, 13, and 28% of such individuals per parent. 

A general advance had therefore taken place, brought 
about partly by selection and partly by the ample room 
given to the plants ; but whilst the isolation of twisted 
specimens of Dipsacns syhestris torsns resulted imme- 
diately in a proportion of 34% of fine, almost complete 



Spirally Twisted Races. 543 

malformations, as soon as the culture was given sufficient 
room, nothing but small local twistings occurred in this 
case, in spite of highly favorable conditions of growth. 
From this I concluded that an eversporting variety anal- 
ogous to my Dipsacus syk'cstris torsus cannot be raised 
from these seeds. 



20. SPIRALLY TWISTED RACES. 

The often mentioned race of Dipsacus sylrestris tor- 
sus (Figs. 123-125, pp. 529-534, and Plate VI) has now 
completed its ninth generation. It consists of about 40' , 
of individuals with fine torsions and about 60% of ata- 
vists with, as a rule, decussate, but occasionally ternary, 
arrangement of the leaves. The acavists and the twisted 
plants with incomplete or interrupted spirals have always 
been destroyed before flowering. The completely twisted 
individuals, however, were left to be, fertilized by one 
another through the agency of insects. 

This I'cry stringent process of selection has had the 
result of maintaining the race at a fairl\ constant level. 
During the first two generations I did not know the proper 
conditions and sowed the seed much too thick, and con- 
sequently only obtained twisted individuals at the edges 
of the beds, and even here in small numbers. But with 
the improvement of these conditions the proportion of 
twisted stems at once mounted to 34%, and the heredi- 
tary value has since remained about the same, although 
subject to fluctuation due to the greater or less favorable 
climatic conditions obtaining in successive years. But 
no advance could be discovered. 

In order to exhibit graphically the result of this cul- 



544 Heritable Spiral Torsions. 

ture, which extended over 18 years, I shall give here a 
brief summary of the nine successive generations. 

NUMBER OF PLANTS PER PROPORTION OF 

IjH,^ iSrv.A 1 IvJ^ 

PLANTS SQUARE METER TWISTED MAIN STEMS 

1st. 1884-1885 

2d. 1886-1887 1643 50 0.1 

3d. 1888-1889 1616 35 4 

4th. 1891-1892 107 25 34 

5th. 1893-1894 45 22 10 20 1 

6th. 1895-1896 33 8 42 

7th. 1897-1898 70 16 46 

8th. 1899-1900 1295 22 32 

9th. 1901-1902 492 22 41 

The mean of the six generations was therefore about 
35%. 

We see from this table that the continued isolation 
and selection of the finest torsions maintained the race 
at its level, but did not improve it to any considerable 
extent. 

Two points about this result should be noted. In the 
first place the percentage figures given do not denote the 
proportion of twisted individuals, but relate solely to 
those with torsions on the main stem. In some experi- 
ments, however, instead of pulling up the atavists, I only 
removed all their inflorescences before the flowers opened, 
and by this means I found that several, and often many of 
them, had the power of developing more or less fine local 
torsions on their lateral branches. In 1902 I made as 
accurate an account of these as possible, and found 71 
of them or 14%. Of twisted individuals there were, 
therefore, 41 -j- 14=5 5% altogether, i. e., somewhat more 
than half the individuals produced torsions. It seems 
of some interest to note that this percentage is the same 

1 The percentage figures for the 5th, 6th and 7th generations are 
hardly decisive on account of the small size of the cultures. 



Spirally Twisted Races. 545 

as has been observed elsewhere in intermediate races, 
and especially in the tricotyls (see page 439). 

Secondly, I call the attention of the reader to the 
remark which I made in the previous chapter ( 16, p. 
511) with regard to selection. Even as in the case of 
fasciation, a double selection, by the visible characters 
of the seed-parents and by their hereditary value, cannot 
here be carried out under the ordinary conditions of the 
experiments. The most valuable character to select by, 
the hereditary coefficient, fails, and in consequence of this 
the improvement of the race, which in the case of the 
tricotyls so soon resulted in a proportion of from 70- 
90%, obviously cannot be carried to its full height here. 
Nothing less than a lucky chance or the conducting of 
the experiment on a much larger scale can bring this 
about. In the eighth generation I compared the heredi- 
tary coefficients of ten parents. They ranged between 
10 and 55% ; but as only from 100-140 offspring of each 
parent could be compared, the percentage numbers did not 
seem to me to be of much importance from the point of 
view of selection. In the 9th generation I saved the 
seeds from over 100 very finely twisted individuals, in 
the hope of still being able to carry out an experiment in 
selection by hereditary coefficients. 

I shall now give a detailed description of the whole 
experiment. 1 The starting point of my race was formed 
by two individuals with a twisted main stem which flow- 
ered in 1885 in a culture sown in 1884 in my garden. 
All the remaining plants were destroyed before they 
flowered. 

In 1886 I obtained a second generation from their 
seeds. As I have already mentioned, I was not at that 

1 Annals of Botany, Vol. XIII, No. LI, Sept. 1899, P- 401. 



546 Heritable Spiral Torsions. 

time familiar with the most favorable conditions of this 
culture, and obtained only two twisted individuals amongst 
nearly 1650, probably for this reason alone. These two 
flowered in isolation and set an abundance of seed. The 
third generation (1888-1889) raised from seeds of the 
second, produced 67 twisted stems in a culture of about 
the same extent, i. e., about 4%. Here again the seed- 
parents flowered in isolation. 

The fourth generation was sown partly in 1890, and 
produced as many as 10% twisted individuals which 
however could not be used for the continuation of the 
race. The rest of the seed was sown in 1891 with a 
better knowledge of the conditions, whereby the propor- 
tion of twisted individuals rose to 34%, a value which 
the later generations on the average maintained, without 
surpassing it to any considerable extent. 

The improvement in the method of culture consisted 
essentially in providing the young plants from their very 
earliest stages with more room. In the two previous 
generations about 50 specimens were grown per square 
meter In this generation, however, the number was 
reduced to about 25 by the removal of the superfluous 
ones in June, as soon as the plants began to touch one 
another. 

The seed had been sown in May in the beds. At the 
beginning of October I noticed, amongst about 100 indi- 
viduals, 6 with a spiral arrangement of leaves in the 
heart of a rosette. In the beginning of November I was 
able to remove more than half of the plants as undoubted 
atavists, and when, towards the end of May 1892, the 
stems grew up vigorously, they were finally examined 
and recorded. The result, together with that obtained in 
November, i. e., for the whole culture, is as follows: 



Spirally Twisted Races. 547 

Twisted stems 37 =34% 

Stems with ternary whorls J2 = 11% 

Atavists with decussate arrangement of eaves 58 =55% 

Total 107 

It is very important to notice that the number of 
twisted stems increased as the result of the greater dis- 
tances between the plants, not only relatively (i e., per 
100 individuals), but absolutely (i. e., per square meter). 
In the third generation there were 50 plants per square 
meter, of which 4% (1-7%, from 1-4 specimens) were 
spirally twisted. In the fourth generation, however, 
there were 37 twisted individuals on 4 square meters or 
9 per square meter. 

I selected the seven plants with the finest torsions 
on this bed as seed-parents. They all, moreover, pre- 
sented local torsions on several branches. I isolated 
them before they flowered. 

The fifth generation (1893-1894) was not so success- 
ful. Only 25% with twisted stems were produced. The 
seed to produce this generation had not as hitherto been 
so\vn on the beds but in seed-pans in the greenhouse 
attached to my laboratory. This method has since proved 
more convenient and safer, and has been employed in the 
two generations which follow. 

The seed saved in September 1892 was sown in the 
middle of March 1893. In the middle of May the best 
seedlings were planted separately in 10 centimeter pots 
with good, richly manured garden soil, and planted in 
the bed in the middle of May, at the same distance apart 
as were the plants in the preceding generation (22 plants 
per square meter). In the following year (1894), all 
the stems developed and were recorded. The result was 
as follows : 



548 Heritable Spiral Torsions. 

A B %A %B 

Twisted main stems . . 5 2 20 10 

Ternary main stems 1 1 4 5 

Decussate mam stems 19 17 76 85 



Total 25 20 

A and B are two groups which had been produced 
from seeds separately harvested from two seed-parents 
of 1892. 

The extent of the culture is, as we see, too small to 
allow of an exact determination of percentage values. 

Seed was saved in the autumn of 1894 from the four 
best plants which had been isolated from the rest before 
they flowered. 

The sixth generation (1895-1896) again produced 
a better result, viz., 42% twisted main stems, a result 
due in part at least to the increase in the distance between 
the plants in the culture, which was in other respects the 
same as in the previous year. The seed of 1894 was 
sown in the middle of March in pans in the greenhouse. 
The seedlings were transplanted to pots in April and into 
the bed in May Altogether there were only 33 plants 
on 4 square meters, that is about 8 per square meter. 
In October I found 14 rosettes with a spiral arrangement 
of their inner leaves, whilst seven were ternary and 12 
decussate, that is 42% spiral, 21</c ternary, and 36% 
decussate. This result was confirmed in May and the 
decussate and ternary individuals were thrown awav. The 

* m 

six individuals with the finest torsions were selected as 
seed-parents and isolated before flowering. 

The seventh generation (1897-1898) was grown in 
practically the same way. Seeds of 1896 were sown in 
the greenhouse in May 1897, were transferred to pots 
later, and to the beds at the beginning of July at the rate 



Spirally Twisted Races. 549 

of 16 individuals per square meter. Altogether there 
were 70 plants. 

A record made at the end of May 1898 gave the fol- 



lowing result : 



Twisted stems . . . . 32 =46% 
Ternary stems .... 21 =30% 
Decussate stems . 17 =24% 



Total 70 

In the eighth generation the plants were treated in 
exactly the same way as in the preceding one. As already 
mentioned, the offspring of 10 distinct parents were 
compared. Moreover for each parent the seeds of the 
terminal inflorescence were compared with those of the 
inflorescences on the main branches. For the latter de- 
termination I selected from each parent 4-8 of the strong- 
est branches which arose from that part of the middle 
of the stem which had undergone most torsion. They 
corresponded, therefore, with the period of maximum 
activity of the stem, 1 and confirmed this by the fact that 
small local torsions appeared on them. From the seed of 
the primary inflorescences I raised 645 plants with 31%, 
from those of the secondary inflorescences 650 individ- 
uals with 34% cwisted main stems. There was therefore 
no difference of any significance. 

The ninth generation was composed partly of off- 
spring of twisted individuals and partly of those of ata- 
vists. The method of culture employed was the same as 
before ; but I shall revert to the result of it in the next 
section. 

Besides Dipsacus sylvestris I have grown two other con- 
stant races with an abundance of fine torsions which must 

1 See T. TAMMES, Die Perlodicitat morphologischer Erschci- 
nungen bei den Pflanzen, Kon. Akad. v. Wet., Amsterdam, 1903. 



550 



Heritable Spiral Torsions. 



be regarded as intermediate races. The first is Dianthus 
barbatus torsus. I obtained a fine twisted branch of this 
form in the autumn of 1894 from Air. J. ENSINK in 
Rtuirlo. The torsion was similar to that represented in 
Fig. 129, but the fruits were ripe and full of seed. I 

could not, however, sow the 
seed until the spring of 1897. 
This species does not 
flower till the second year, 
10-20 shoots being produced 
on each individual. I made 
a culture of about 300 indi- 
viduals, which were planted 
out at distances of 20 centi- 
meters apart. Plants began 
to flower in June of the sec- 
ond year (1898) ; the great 
majority of their stems were 
normally decussate ; whilst 
several had ternary whorls 
along the whole length, or in 
other cases, only in the up- 
per parts of the stems. Oth- 
ers again were twisted and 
manifested a spiral arrange- 
ment of the leaves. The 
twisting, too, seemed to pre- 
fer the upper half of the 

stem, just underneath the inflorescence. Sometimes how- 
ever the whole stem, or a great part of it, was twisted 
or the torsion extended into the inflorescence. The maxi- 
mum development of the anomaly largely corresponded, 
so far as I could determine, with the period of maximum 




Fig. 129. Dianthus barbatus 
torsus. Twisted Sweet Wil- 
liam The stem has a de- 
cussate arrangement of leaves 
below and spiral above. June 
1900. 



Spirally '/'misled Races. 



551 



growth, as in Dipsacus. Altogether I counted amongst 
somewhat over 4600 normal stems, 53 more or less dis- 
tinctly twisted ones in all degrees of development, 33 
torsions extending over a greater part of the shoot and 




Fig. 130. The dark-eyed Viscaria (Viscaria oculata) with 
spiral torsion of the main stem, a, the terminal flower 
of this main stem ; the flowerstalk, first bent downwards 
by the torsion, has subsequently turned upwards again. 
b, c, the normal straight portion below the twist ; d, a 
local interruption of the torsion (1900). 



552 Heritable Spiral Torsions. 

20 over smaller portions. This means a proportion of 
about \% of the total number of the stems. The 33 
best torsions occurred on ten plants of which five had 12, 
6, 5, 3 and 2 twisted shoots, and the remaining five, one 
such anomaly each. The 20 smaller abnormalities were 
distributed at random over the plants in such a way that 
about 10% of the individuals had developed the anomaly. 
It is worth remarking that the most abnormal individuals 
occurred chiefly on the most sunny edge of the bed. 

The selected individuals mentioned were not allowed 
to flower before all the remaining plants had been re- 
moved. In the spring of 1899 I only sowed the seeds of 
the plant with 12 torsions. I planted out 180 individ- 
uals, at the same distances apart and also in other respects 
under exactly similar conditions as those which obtained 

f 

in the preceding generation. They flowered in the sum- 
mer of 1900. At the beginning of the flowering period 
I had 2246 stems, in 1246 of which the arrangement of 
the leaves was decussate, whilst in 414 it was ternary. 
Further, there were 227 stems which were twisted over 
more than half their length and 359 which were twisted 
in the upper part only, i. e.,26% twisted shoots as against 
1 % in the preceding generation, on the average 3 torsions 
per plant. According to a rough estimate well over half 
the individuals had produced one or more twisted stems. 

Two generations, therefore, had sufficed for the iso- 
lation of a genuine intermediate race from an original 
insect-fertilized sample of seed. 

The other race referred to above occurred in Vise aria 
oculata (Lychnis Coeli-rosa), a favorite garden plant. 
The plant is annual and its culture easy. In twisting, 
its stems become much shortened, and the plants become 
low, but they flowered freely (Fig. 130). In 1897 in a 



Spirally Twisted Races. 553 

culture grown for another purpose, I found a twisted 
plant like the one figured and saved its seed separately; 
its flowers had not been protected. 

From this seed I raised in 1898 a culture of 300 plants 
of which 259 were normal, whilst 40 exhibited torsions 
in the main stem and 28 others in one or several of the 
lateral branches, i. e., a proportion of 21% twisted indi- 
viduals. I only allowed the 21 finest specimens of these 
to flower and set seed ; and of these I only sowed the seeds 
of the one finest twisted plant. In the following year, 
1899, I raised from it 385 individuals of which 137 or 
about 35% showed torsions. Here also, as in the case 
of Dipsacus and Dianthus, many individuals exhibited a 
ternary arrangement in the whorls. I counted about 100 
of these, which therefore constituted about one-quarter 
of the whole culture. 

In 1900 I grew the fourth generation, but on a smaller 
scale. Torsions were as abundant as before, and amongst 
their number was the plant represented in Fig. 130. 

There is little doubt that similar intermediate races 
could be raised by an isolation of the spirally twisted 
individuals of several other species. And the best chance 
would obviously be given by those which frequently give 
rise to this anomalv without selection. Thus, for in- 

/ 

stance, Gypsophila paniculata, Urtica urens (of which 
I have already cultivated two generations with success), 
and perhaps also Scabiosa atropurpurea. On the other 
hand, as stated in the previous section, my sowings of the 
seeds of spirally twisted examples of Valeriana officinalis, 
Saponaria officinalis, Galiuin Aparine 1 and others, have 
offered no such prospects. 

1 Bydragen tot de leer van den klemdraai. Botanisch Jaarboek, 
Gent, IV, 1892, p. 154, PI. XV. 



554 Heritable Spiral Torsions. 

The existence of constant intermediate races or ever- 
sporting varieties exhibiting spiral torsion seems to me 
to be conclusively demonstrated by the experiments de- 
scribed. They were found by chance and then easily 
extracted by isolation, and induced to produce a pro- 
portion of 30-40% twisted individuals. This result could 
be made permanent by subsequent cultivation, but could 
not be increased by a continuation of the selection. 

% 

21. THE SIGNIFICANCE OF THE ATAV1STS. 

In spite of every attention and in spite of repeated 
and careful selection spirally twisted races will continue 
to produce numerous atavists. These are either decussate 
individuals of the normal structure of the species, or 
they have ternary leaf whorls, as is also often seen in 
twisted individuals above the torsions. 

I propose now to examine more closely the nature 
of, and especially the mode of, inheritance in these ata- 
vists, as I have done in the case of the fasciations. The 
essential point about them is that the atavists do not, as 
we may express it, depart from the twisted race ; but can 
be used almost as safely for its continuation, as the 
twisted individuals. 1 

A fact of the highest importance is that there is no 
sharp limit between the atavists and the twisted individ- 
uals. Of course the difference between the tall erect 
stems and the short stunted anomalous ones is most 
striking, as our Plate VI shows. It is quite clear that 
this is not a case of the fluctuating variation of a single 

1 In Stocks the double specimens are sterile, as is well known, 
and the variety has to be propagated by means of the seeds of the 
single ones. Under cultivation in the field as a rule about 50% of 
"single" atavists are produced. 



The Significance of the Atavists. 555 

character, but that two antagonistic factors are at work, 
the one excluding the other, although never completely. 
Even the stems with the most pronounced torsions pro- 
duce branches, most of which revert to the decussate 
arrangement of leaves. It never occurs that this char- 
acter is completely excluded from the whole plant. Con- 
versely, as we have already seen, atavistic individuals 
with perfectly erect main stems and with a decussate or 
ternary arrangement of the leaves frequently exhibit 
torsions in their lateral branches. In 1887 I cut half the 
atavists of my culture of Dipsacus sylvestris torsus close 
clown to the ground ; they shot out from the base of the 
stem. In this way I obtained about 2000 branches of the 
second and third order. Amongst them 235 had a slight 
but quite definite torsion and 26 had a small many-leaved 
spiral. In the third generation I repeated the experiment 
with the same result ; and moreover observed torsions 
on the lateral branches of some atavists which had been 
allowed to remain on the beds until they were just about 
to flower. 

Other abnormalities in the arrangement of leaves also 
betray the real nature of the atavists. First, there are the 
individuals with ternary whorls. Such whorls do not 
occur in the early stages of the plant, and tricotylous 
seedlings are even very rare. At first the arrangement 
of the leaves is always decussate, and it is not until late 
summer or autumn, at the time when other specimens 
begin to produce their leaves in a spiral, that the decussate 
arrangement gives place to a ternary one. But when 
this has once appeared it usually remains on the stem 
up to the terminal flowerhead. Such plants look quite 
normal, and especially their leaves do not produce those 
forkings of the mid-rib which are so common in the 



556 



Heritable Spiral Torsions. 







W 



Fig. 131. Dipsacus syhestris torsus. Split leaves from the 
decussate atavists of the eighth generation. A-D, in- 
creasing degrees of splitting. 



The Significance of the Atavists. 557 

decussate individuals. On the lateral branches of these 
whorled stems, on the other hand, these splittings, as 
well as local torsions and other anomalies are by no means 
rare. 

The relation of the ternary whorl to the spiral ar- 
rangement demands closer investigation. Perhaps the 
former is to be regarded as a lower stage of the anomaly ; 
and this view is supported by the fact that highly twisted 
individuals which have one or more straight internodes 
above the torsion, usually exhibit ternary whorls between 
them. 

The decussate individuals often produce leaves with 
split midribs (Fig. 131 A B), and in all degrees of split- 
ting from leaves with two tips to leaves split down to 
the base. 1 Sometimes they even produce one or two 
ternary whorls in the upper parts of the plant. The 
range of variation in these splittings has been dealt with 
by DELPiNO, 2 and material for a complete demonstration 
of these forms may be furnished by every generation of 
my race. 

In the third generation I left three atavists on the bed 
until shortly before they flowered. They all bore some 
split leaves in the upper part of their stem; in the ninth 
generation I observed the same anomaly on the main 
stems of 172 of the 200 decussate atavists, that is to say, 
in about 80% of the whole group. Several of the re- 
mainder exhibited the anomaly on the lateral branches. 

From the axil of a split leaf there usually arises, ac- 
cording to my observations, a single shoot ; but sometimes 
two of them, or a single broad flattened one with two 

1 Bcr. d. d. hot. Gcs., Vol. VII, 1889, p. 296. 

2 F. DELPINO, Teoria gcneralc dclla Fillotassi, Atti della R. Uni- 
versita di Geneva, IV, Parte II, 1883. 



558 Heritable Spiral Torsions. 

inflorescences at the top. In this respect also, my results 
confirm those of DELPINO. 

External conditions exert a great influence on these 
secondary anomalies just as they do on the main torsions. 
The more favorable the conditions, the rarer are the in- 
dividuals, all of whose branches and leaves are normal. 
Obviously this fact suggests that the factor for the mal- 
formation must be present in all of them, 

Brief mention should also be made of the so-called 
local torsions. They occur occasionally in all twisted 
races. Fig. 132 represents an instance of them in J \ilc- 
rlana officinalis. It flowered in the same year and on the 
same bed as the completely twisted stem shown in Fig. 
122 (p. 528). 

In Dipsacus laciniatus the malformation was confined 
to these, and in Dipsacus syk'estris torsus I observed 
them, under very special conditions of culture, on erect 
and otherwise decussate stems ; but on the lateral branches 
of twisted individuals, especially on the strongest ones, 
such as those which arise from the axils of the radical 
leaves or from the middle of the twisted stems, they are 
always seen to be most profusely produced. 

As in the case of fasciations, forms intermediate be- 
tween these local torsions and the normal arrangement 
of the leaves, are relatively rare. This is not true, how- 
ever, if the ternary whorls, split leaves, and the local 
torsions on the lateral branches are included, but only if 
we confine our attention to the torsions on the main 
stems. Unfortunately the exact measurement of the 
part bearing leaves in a spiral is a matter of considerable 
difficulty : inasmuch as the spiral begins inside the ro- 
sette at a time when the oldest leaves have already rotted 
off and disappeared. Nevertheless I have recorded the be- 



The Significance of the Alarists. 



559 



ginning of the spiral accurately in some cases by mark- 
ing and counting the pairs of leaves, as they made their 
appearance, from the moment of germination. But I 
have not yet plotted a curve from data collected in this 
extremely laborious way. On the other hand the number 
of straight internodes above the torsion can easilv be 

o j 




Fig 132. Valcriana officinalis. A stem with a local tor- 
sion, from the same culture as Fig. 122. (June 1900.) 

counted ; and their number obviously varies inversely 
with the extent of the twisted part. 

In 1900, when my eighth generation consisted of 
1295 flowering plants, I recorded the number of straight 
internodes above the torsion in everv twisted stem. Omit- 



560 Heritable Spiral Torsions. 

ting the long stalk of the terminal inflorescence, which 
is always present, I obtained the following series. 

PLANTS WITHOUT WITH 0~6 STRAIGHT INTER- 
TORSION NODES ABOVE THE TORSION 

Straight internodes 65432 1 

Individuals 900 2 3 1 2 40 200 148 

The curve constructed from these figures is obviously 
one with two peaks, and essentially the same as the cor- 
responding curve for fasciations seen in Fig. 118 (p. 521). 
Torsions with two, with one, and without any straight 
internodes above the torsions are far the commonest. 
Smaller torsions only occurred in nine cases among 1295, 
that is less than 1 % of all the individuals, or in about 
2% of the twisted individuals. I repeated the same ex- 
aminations in 1902; the intermediate forms were some- 
what more numerous and reached a proportion of about 
7% in 492 individuals. The form of the curve, was, 
however, not essentially modified. 

In order to determine the hereditary coefficients of 
the atavists I instituted an experiment in the eighth and 
ninth generation of my race. In July 1900, I had some 
highly twisted plants, some completely decussate ones, 
and some with ternary whorls only, on the same bed. 
Before the flowering period I reduced the inflorescences 
to the required number and afterwards insured pure fer- 
tilization in the following way. All the inflorescences 
were enclosed in parchment bags, and the bags were 
taken off the individuals falling into one group, for sev- 
eral hours one day out of three for each group. The 
humble bees flvmg about could thus fertilize only twisted 

* *> 

individuals on some days, on others only decussate, and 
on still others only ternary ones. This practice was 
continued until all the flowers were gone. The seeds 



The Significance of the Atavists. 561 

were saved separately from each plant. In the spring of 
1901 I sowed the seeds of two decussate, three ternary 
and four twisted seed-parents and recorded the main 
stems produced by each parent in 1902, just before the 
flowering period; but since the numbers from the indi- 
vidual seed-parents of each group did not differ to any 
considerable extent amongst themselves, I shall give the 
total result only. 

OFFSPRING, IN PERCENTAGES. 

SEED-PARENTS NUMBER 

DECUSSATE TERNARY TWISTED 

Decussate 48 8 44 201 

Ternary 39 24 37 136 

Twisted 45 14 41 155 

Total 492 

We see that the offspring of the atavists produced 
just as large a proportion of twisted stems as the offspring 
of the twisted individuals. On the other hand the choice 
of decussate or of ternary atavists seems to have exerted 
some influence in the direction of ternary offspring. 

The twisted stems of Dipsacus are partly right-hand 
and partly left-hand spirals; and about equal numbers 
of the two sorts are always found. 1 

A very curious question thus presents itself, viz., 
whether this equilibrium can be disturbed by selection 
and whether the balance can be upset in a given direc- 
tion. 2 According to the view laid down in this book, 
that it is not true that with selection all things are pos- 
sible, we might expect that this would not be a fixable 
character and that selection would have no influence on 

1 Annals of Botany, loc. cit., p. 404. 

2 R. M. YERKES, Variation in the Fiddler Crab, Gelasimus pugi- 
lator, Proceed. Amer. Ac. of Arts and Sciences, 1901, Vol. XXXVI, 
No. 24, p. 417. On page 441 this author states that right- and left- 
handed animals occur in approximately equal numbers. 



562 Heritable Spiral '/'orsions. 

it. For this reason I allowed plants with a right-hand 
spiral only to flower in the seventh generation ; and in the 
following one also, the spiral of all the chosen seed- 
parents was right-handed. The result was as follows : 

LEAF-SPIRAL 
RIGHT-HAND LEFT-HAND 

8th generation 205 215 individuals 

9th generation 40 24 individuals 

These constant but eversporting twisted varieties offer 
favorable material for attempting to transfer the mal- 
formation to related species by means of hybridization. 
At present, however, only a single attempt of this kind 
lias been made, viz., one which was communicated to me 
by Prof. LE MONNIER of Nancy. 1 . 

He sent me two twisted stems of Dipsacus fullonum 
which exhibited a torsion as pronounced and as complete 
as the best instances of my race (Fig. 123 a and b, p. 
529) ; and which owed this malformation to a cross be- 
tween the species in question and my Dipsacus syk'cstris 
torsus, which Mr. LE MONNIER had cultivated on a large 
scale for many years. 

In 1896 my race flowered at the same time as the 
normal D. fullonum in the botanical garden at Nancy, 
at a distance of 100 meters apart but in great quantities 
of individuals. Pollen could easily be transferred by 
insects from one bed to the other. From the seeds of 
these Dipsacus -fullonum there arose besides numerous 
normal plants three with twisted stems ; one of them 
had upwardly directed bracts in the involucre, a char- 
acter of D. syhcstris which distinguishes it from D. ful- 
lonuin. The investigation of this important question has, 
however, not been continued. 

*Iniirn. Roy. Hortic. Soc., 1900. Vol. XXIV, p. 69. 



The Significance of the Atavists. 563 

The facts described in this and the preceding sections 
seem to me to furnish sufficient proof that the twisted 
eversporting varieties behave in exactly the same way 
as the corresponding fasciated races; and that, in both 
cases, atavism is merely a morphological phenomenon 
and not a real deviation from the race. 



PART III. 

THE RELATIONS OF THE MUTATION THEORY TO 
OTHER BRANCHES OF INQUIRY. 



I. THE CONCEPTION OF SPECIES ACCORDING 
TO THE THEORY OF MUTATION. 

i. SYSTEMATIC BIOLOGY AND THE THEORY OF 

MUTATION. 

In every case in which we were able to obtain a deeper 
insight into the nature of the hereditary character of an 
organism by direct observation or experiment we have 
found this character to be of a compound nature. No 
plant transmits its peculiarities to its offspring as an in- 
separable whole, as has been the general view until now. 
On the contrary we have described a long series of phe- 
nomena in which a single character or a smaller or larger 
group of them can be separated from the rest and behave 
in an entirely different way. When new species or vari- 
eties originate, it is not the whole nature of the organism 
that is changed ; on the contrary everything remains in 
a state of rest except at one or two points, and it is only 
to the changes of these points that all the improvement 
is due. In hybridization the two types which sexually 
unite are always alike in the vast majority of their char- 
acters, and the differences between them are limited to 
a few definite units, which, in the simplest cases, can be 
dealt with numericallv. 

j 

The analysis of organisms, therefore, leads us to the 
hypothesis of units, which are in many respects analogous 
to the molecules of the chemist. They are, however, of 



568 Species According to the Theory of Mutation. 

a much more complicated structure and have arisen in 
a historical way. They cannot be isolated and then sub- 
jected to experiment like chemical bodies; we can only 
investigate them by studying the relation of closely allied 
species and varieties, i. e., forms in which a definite unit, 
or several of them, are present in one plant and absent in 
the other. For this reason our investigations are, for 
the present at any rate, confined to the units which have 
arisen most recently. 

But even as it is the business of comparative science 
in general, first, to apply the conclusions derived directly 
from the facts, to cases that have not been themselves 
observed and then to extend them gradually further and 
further, it is our duty and our right to test the applica- 
bility of our conclusions as thoroughly and as widely as 
possible. 

Therefore we have now to face the question whether 
the theory of the origin of species by mutation and the 
theory that hereditary characters are composed of ele- 
mentary units are in harmony with the theoretical concep- 
tions to which systematic science on the one hand and 
embryology on the other have given rise. If it can be 
shown that the mutation theory satisfies the demands of 
these sciences better than the present form of the theory 
of selection, its justification as a theory of the nature 
of inheritance will, in my opinion, be placed on a sure 
foundation. 

For this reason I shall devote the last part of this 
work to general considerations of this kind. In doing 
so I leave the safe ground of facts and venture into a 
region in which I can no longer mainly depend on my 
own experience. But experimental inquiry must derive 
its problems from this more general aspect of the ques- 



Progressive, Retrogressive, Degressive Mutations. 569 

tions; and it does not by any means seem superfluous to 
ask ourselves from time to time what has already been 
achieved and what is to be done in the immediate future. 
In doing so I shall have to keep a close rein on myself 
and, whenever possible, conform to the opinions of rec- 
ognized authorities, limiting my own views to such points 
as may throw light on the relation between those opinions 
and the theory of mutation. I shall try to avoid ques- 
tions of minor importance or concerning uncertain or 
subordinate points; the literature of the subject has long 
since grown so prodigiously that it is no longer possible 
to keep pace with it. 

My only object is to demonstrate the applicability of 
the theory of mutation to the main conclusions of the 
doctrine of evolution; and only to do this briefly and 
sometimes no more than in outline. New theories and 
new hypotheses I shall not have to introduce, the more 
so, as I am convinced that the doctrine of mutation will 
lead everywhere to a simplification and a clearer concep- 
tion of the problems. The prospect of recognition of a 
theory rests on the one hand on its empirical foundation, 
and on the other on its suggestiveness and the number of 
facts which it explains. Therefore the consideration of 
this latter point will now be my task. I shall devote the 
several chapters of this part to the various problems 
involved. 



2. PROGRESSIVE, RETROGRESSIVE AND DEGRESSIVE 

MUTATIONS. 

Progress in organic nature consists essentially in in- 
crease of differentiation. The peculiarities which go to 
make up the individual character of the species become 



570 Species According to the Theory of Mutation. 

more numerous. Every more highly organized being has, 
as a rule, more of them than its ancestors of long ago had. 
In applying this principle to the doctrine of elementary 
characters we see at once that the number of these units 
must increase with increasing differentiation; or, con- 
versely, that the degree of differentiation is ultimately 
determined by the number of elementary characters. 
Whenever a new unit is added to those already existing, 
differentiation advances a step forward. If it were pos- 
sible to count the units we should have a measure of the 
degree of differentiation of all organisms. 

Obviously the individual steps are only small ones, 
at the present time at least ; and any single one of them 
can hardly effect a noticeable increase in differentiation. 
At any rate we have at present no means of so exactly 
measuring the degree of differentiation, since we cannot 
estimate the possible influence of a single unit on a com- 
plex built up of thousands of them. Only groups of units 
produce clear and obvious differences in the degree of 
organization ; but within the limits of a small genus or 
of a multiform collective species the several types seem 
to us to be almost always equivalent. 

The individual steps into which, according to this 
view, the process of gradual differentiation can be ana- 
lyzed, we propose to call mutations ; and since they con- 
stitute an advance, progressive mutations. Each of them 
contributes a new character to the complex of hereditary 
qualities already present. 

Such a new character need not, however, become vis- 
ible as soon as it arises, since we are not dealing solely 
with external qualities but with the internal factors to 
which they owe their appearance. Even as the germ 
contains large numbers of qualities awaiting development, 



Progressive, Retrogressive, Degressive Mutations. 571 

so we can imagine that a new character remains latent 
for some time after its first origin, its phylogenetic birth, 
if I may so express it, and does not become active until 
after the lapse of a lesser or greater period of time. 

According to this view, every progressive mutation 
is fundamentally a double process, and consists in the 
production of a new internal factor and in its activation. 
Both may sometimes happen at the same time, but this- 
is not necessary. It is therefore desirable to apply sepa- 
rate names to the two processes ; the internal one I have 
called premutation, the externally visible one a mutation 
sensu strict o. 

The premutation is therefore of a hypothetical, the 
mutation, however, of an empirical nature. 

It further follows from this that an internal factor 
does not of itself lead to the origin of an external change. 
As in ontogeny so also in phylogeny an elementary char- 
acter can be sometimes active, but at other times latent 
or inactive. If a new character emerges from its original 
latent conditions and becomes active, we call the process 
a progressive mutation ; conversely we can denote its 
return from the active to the latent condition as a retro- 
gressive mutation. 

The experience of gardeners and of the systematists 
with the smaller species and varieties teaches that retro- 
gressive mutations of this kind are common phenomena. 
Almost any character may disappear. This applies not 
only to the superficial characters, such as color, hairs, or 
thorns, but also to those deeper ones which affect the 
inner organization of the plant, such as the decussate ar- 
rangement of leaves, and even the symmetry of the organ- 
ism. Spiral torsion and peloria show how profound an 
alteration in the appearance of a plant or in the structure 



572 Species According to the Theory of Mutation. 



of a flower may be brought about even by only one of 
these elementary characters becoming inactive. 

Retrogressive mutations give the impression of some- 
thing being lost ; some character or other disappears from 
the picture. But everything seems to point to the con- 





Fig. 133. Castanea vesca. Ab- 
normally leaved catkins. A, 
with two leaves ; B and C, with 
one leaf each. C has also a 
lateral twig, a male, b female 
flowers ; c normal leaf. Apel- 
doorn, 1896. Collected by Dr. 
P. F. ABBINK-SPAINK. 



Fig. 134. Mercunalis annita. A 
sprig of the male plant with 
stray fruits on the long thin 
ears. On the female plants the 
fruits are inserted on short 
stalks in the axils of the leaves. 



elusion that, in the vast majority of cases at least, this 
loss is only an external one ; and that the factor remains 
in the inner organization of the plant, in an inactive state. 
This view is especially supported by those cases in which 
a systematic character which has become latent is occa- 



Progressive, Retrogressive, Degressive Mutations. 573 

sionally manifested as an anomaly; as for instance the 
appearance of female flowers on male specimens of dioe- 
cious species (Fig. 134), or of leaves on normally leaf- 
less inflorescences (Fig. 133). 

Two races, which only differ in the latency or activity 
of a single factor, therefore possess the same number of 
elementary units in their internal organization. Ob- 
viously the relation between them is different from that 
between two races, of which one has arisen from the 
other by the formation of a new factor; in which case 
there is a difference of one, in the number of units, be- 
tween the two. 

But before we examine this relation more closely we 
must face the question whether the active and the in- 
active states are the only ones in which an internal factor 
can occur. Theoretically this is obviously not necessarily 
the case, for we can easily imagine various degrees of 
activity between the two extremes, and as a matter of 
fact, experience shows that these intermediate stages do 
actually occur. We have described them above (p. 20) 
as semi-latent; and have given the name of middle races 
to those which possess such semi-latent characters. Of 
these there are two types, which we frequently meet both 
in nature and in our cultures, half races and intermediate 
races, or eversporting varieties. In both of them the 
semi-latent quality is associated in such a way with some 
active character that the two cannot be manifested at the 
same time. They exclude one another, if we may so ex- 
press it, and so constitute a mutually vicarious pair. Tri- 
foliate and qtiinquefoliate leaves of clover, tricotylous 
seedlings or split cotyledons and dicotylous ones, normal 
and peloric flowers, cylindrical and fasciated stems, ordi- 
nary and petaloid stamens, constitute such pairs. The 



5/4 Species According to the Theory of Mutation. 

same leaf cannot be at once trifoliate and quinque foliate 
and so on ; in a word, an organ cannot be both normal and 
abnormal. 

These vicarious pairs of characters are the sources 
of a great variability inasmuch as the anomaly can ap- 
pear in all degrees of development. In such cases the 
individuals of a group are not ranged round a mean in 
respect of their external qualities, as with ordinary fluc- 
tuating or oscillating variability, but between two types 
which are often widely separated and more or less anti- 
thetic to one another. They have the appearance of being 
inconstant; and races and varieties of this kind are 
usually so described, but this is only true in the sense 
that the range of forms which they present is a very 
wide one; and, moreover, is ditypic or dimorphic. But 
it would not be true in the sense that any individual could 
transgress the boundaries of this range and found a new 
race. In this sense the so-called inconstant races are just 
as stable as the best constant species and varieties. 

The difference between half and middle races lies 
solely in the difference between the mutual relation of the 
members of the vicarious pair in the two cases. If, 
under ordinary conditions, and in the absence of selection, 
one of them predominates over the other to a very large 
extent, the race is, so to speak, unilateral and is called a 
half race (e. g., Fig. 135). But if, under similar cir- 
cumstances, neither of them predominates but an equilib- 
rium is maintained, we have an intermediate race (e. g.. 
Fig. 27 of the first volume, page 138). In the case of 
tricotyls and syncotyls the half race rarely contains more 
than a very few anomalous individuals, in the absence 
of selection ; whilst the intermediate race consists as a 
rule about half of normal, and the other half of tricotvl- 



Progressive, Retrogressive, Degressive Mutations. 575 



ous or syncotylous individuals. The seeds, however, of 
both types give the same proportion of tricotyls or syn- 
cotvls even when self-fertilization has been insured. 

> 

If we wish to elaborate terminologies still further, 
the term semi-latent may be limited to the anomalous 
character of the half race, and the character of the middle 
race may be described as semi-active (see p. 21). \Ye 
can then distinguish four conditions of one and the same 
factor; the active, the latent, the 
semi-active and the semi-latent. 
This classification may suffice for 
the time ; and at any rate it can 
be said that it is in accord, so far 
as my experience goes, with the 
facts known at present. 

Such a factor cannot be trans- 
ferred at will from one of these 
conditions to the other, either 
by selection or by any other 
means, at any rate in the present 
state of our knowledge. Such a 
transition is only effected by com- 
binations of causes of which we 
still know nothing, or as we say 
by chance. Moreover the tran- 
sitions, so far as we can observe them, are not slow or 
gradual, but take place suddenly. The new race appears 
on the scene at once and unexpectedly, as in the case of 
the peloric Linaria. Sudden transitions of this kind are 
exactly what we call mutations ; and to distinguish them 
from the progressive and retrogressive types, we may 
refer to them as degressive mutations. 

Every mutation therefore consists fundamentally in 




Fig. 135. Papaver com- 
uintatmn polycephalum. 
The same anomaly which 
occurs in P. somnifcruui 
as a middle race (Vol. I, 
Fig. 27, p. 138) occurs 
here as a half race, mani- 
festing the character very 
rarely and only to a small 
extent. 






576 Species According to the Theory of Mutation. 

the transposition of an internal character; from being 
latent it becomes active; from semi-latent, semi-active; 
and so on. If new factors are becoming active for the 
first time after having been latent through a shorter or 
longer series of ancestors, we speak of progressive muta- 
tions. If the active characters again become latent, the 
process is a retrogressive one. In all other cases it is 
degressive. 

The phenomena of hybridization find a ready ex- 
planation in the principles derived, in the first part of this 
volume, from our consideration of the origin of species 
and varieties. There are two main types of crosses, the 
bi-sexual or Mendelian and the uni-sexual. The former 
conform to the laws of segregation, they lead to various 
combinations of elementary characters, and thus can lead 
to the origin of as many new races as the number of pos- 
sible combinations indicates. These races are constant; 
the hybrids, however, always exhibit segregation in the 
formation of their sexual cells and sometimes even in the 
formation of buds. The hybrids of uni-sexual crosses 
on the other hand are constant ; so far as my experience 
goes, they do not segregate. If they are fertile they are, 
as a rule, as true from seed as their parents; but they 
may inherit the inconstancy of these (if, for instance, 
one of these belonged to an eversporting variety) and 
transmit it to their posterity. 

A strong body of facts, which have been given else- 
where lead to the conclusion that crosses follow MENDEI/S 
laws if one of the two parents stands in the relation to the 
other of having arisen from it by retrogressive or de- 
gressive mutation. This means that the two parents of 
the cross possess exactly the same internal elementary 
characters; but that one or more of these occur in dif- 



Progressive, Retrogressive, Degressive Mutations. 577 

ferent conditions in the two parents; as for instance in 
the union of latent characters with active, of semi-latent 
with semi-active, and so forth. The opposite visible qual- 
ities, determined by the two different conditions of the 
same internal factor, constitute a so-called pair of char- 
acters. Therefore, racial forms which differ from one 
another by such qualities only, constitute a group for 
themselves, in the theory both of hybridization and of the 
origin of species. 

Uni-sexual crosses are of an entirely different nature 
and lead to the direct production of constant hybrid 
races. They occur when at least one character is present 
in one parent, but is absent from the other. Hence MAC- 
FARLANE'S name uni-sexual. In more complicated cases 
one form may have a larger excess of factors; or again, 
each of the parents may possess factors which are absent 
from the other. The excess will be unilateral, if one of 
the forms has arisen directly from the other, but bi-lateral 
if both have arisen in diverging directions from the same 
ancestor. In these cases vicarious pairs of characters do 
not exist in the two forms crossed, although externally 
thev may seem to do so. 

r j 

Therefore uni-sexual crosses correspond to progres- 
sive mutations ; the Mendelian law, however, to the retro- 
gressive and degressive forms of differentiation. Con- 
versely we may infer that characters which, when crossed, 
behave in a Mendelian way, are in a latent or semi-latent 
condition, and that in the uni-sexual crosses an internal 
factor is entirely absent on one side. I willingly admit 
that the main purpose of this discussion is to make my 
principles clear, and to show how the two great branches 
of the theory of mutation may, in spite of the vast differ- 
ence in their points of departure, ultimately lead to the 



578 Species According to the Theory of Mutation. 

same theoretical conception of the nature of elementary 
characters. This conception may in the present state of 
our knowledge be most conveniently formulated as fol- 
lows : 

Forms which have arisen by retrogressive and de- 
gressive mutation follow MENDEL'S law, when crossed 

C3 

with their ancestors; whilst forms which have arisen by 
progressive mutation behave uni-sexually. 



3. THE THEORETICAL DISTINCTION BETWEEN SPE- 
CIES AND VARIETIES. 

The idea of a fundamental difference between ancient 
and recent characters runs like a scarlet thread through 
the whole history of systematic biology. The nature and 
limits of this assumed difference have often furnished 
problems which the greatest investigators in this field 
have attempted to solve ; and the answer has been a 
different one according to the information available at 
the time when it was attempted. From the transmuta- 
tionists up to NAGELI'S well-known distinction between 
organic and adaptive characters there has been a long 
series of attempts to deal with these questions. 

In ancient times the matter was easily settled by in- 
voking supernatural causes. The higher systematic char- 
acters were assumed to have arisen by creation ; the later 
ones by natural means ; but in practice even this view 
led to confusion, because some authors regarded the 
genera, others the collective species, and yet others the 
constant elementary forms as the units which had been 
created. 

Our discussions have led us also along several differ- 
ent lines, to the conviction that, as a matter of fact, there 



Distinction Between Species and Varieties. 579 

is a fundamental antithesis between ancient and recent 
characters, which finds its expression both in the phe- 
nomena of specific differentiation, and in those of arti- 
ficial hybridization; for on the one hand forms can arise 
from others without the production of new factors, simply 
by the transference of factors already present into another 
condition, as from latent to active; and on the other hand, 
by the genuine appearance of new elementary characters. 
Progress in organization is due to the latter process, 
whilst the former is to a large extent the cause of the di- 
versity of organic life. 

If we compare this experimental result with the above 
theoretical considerations, we may assume that the dis- 
tinction between older and younger characters consists 
in the difference between the formation of a new factor 
and the transposition of factors already present. On 
the basis of the doctrine of creation the origin of new 
units must be explained as being due to a supernatural 
cause, but no one has as yet applied this theory to the 
change in position of factors already present. Moreover 
in the light of the idea of evolution also the antithesis 
mentioned has its real and full significance. 

It would lead me too far to analyze here the concep- 
tions of other authors on these points, but such an anal- 
ysis has led me to the conviction that the difference be- 
tween the formation and the transposition of factors cor- 
responds closely to the difference which the best system- 
atists consider to exist between species and varieties. 1 
A form which owes its origin to the production of a new 
internal factor is to be regarded as a species ; a form 
which owes its peculiarity merely to the change in con- 
dition of a factor already present is to be regarded as a 

1 See also Vol. I, p. 185, and Vol. II, pp. 71-72. 



580 Species According to the Theory of Mutation. 

variety; 1 or, as we have already expressed it in the first 
part of this volume (pp. 64, 71. etc.). the origin of new 
characters leads to specific differentiation, whereas the 
true derivative varieties arise by so-called retrogressive 
and degressive mutations without the formation of new 
characters. In my opinion this is, at any rate, the sim- 
plest view of the matter. 

This, however, is purely theoretical, for in practice 
our definition can, at present, only rarely be applied. Here 
however the principles of hybridization come to our aid ; 
for, expressed in hybridological terminology, our gen- 
eralization runs : Forms, all of the characters of which 
follow MENDEL'S laws in crosses, are to be regarded as 
varieties of the same species. This form of our generali- 
zation obviously admits of an immediate application in 
every case where the material can be dealt with experi- 
mentally. 

Obviously this generalization is at present too sweep- 
ing; nevertheless the best investigators 2 have regarded 
the study of hybridization as an empirical foundation on 
which this distinction may be based. Moreover the diffi- 
culties are not really so great as they seem to be at first 
sight; for as soon as the body of evidence will have at- 
tained a certain extent, definite laws will be detected 
which will fit the majority of cases by judging from anal- 
ogy. 

The species, however, which I am here distinguishing 
from varieties are the smaller or elementary species ; the 
delimitation of the larger or collective species is, from the 
very nature of the case, a question not for the experi- 

1 It should not be forgotten that varieties have been called in- 
cipient species and that from seed they are just as constant as species. 

2 See NAGELI, Joe. cit.. p. 396; FCCKE. loc. cit., pp. 488, 502; NAU- 
DIN, he. cit. p. 164 : ABBADO, loc. cit., p. 9, etc. 



Distinction Between Species and Varieties. 581 

mental but for the comparative biologist. 1 The elemen- 
tary species are demonstrably the existing units of the 
system ; whilst the larger species are only aggregations 
of these. They will therefore be discussed in dealing 
with the question of the practical differences between spe- 
cies and varieties. 

But, before I proceed to this, reference must be made 
to the more complicated but more common case in which 
two closely related forms differ from one another, partly 
by progressive and partly by retrogressive or degressive 
characters. To judge by the former they should be re- 
garded as elementary species, by the latter however, as 
derivative varieties ; and as they are hardly allowed to be 
in our system both at the same time, we must make a 
decision one way or the other 

With a view to clearing up these difficulties let me 
deal with a particular instance, and select Lychnis vespcr- 
tina and L. diurna, which are regarded by several sys- 
tematists as belonging to one species, Lychnis dioica. If 
we regard these two forms as having been derived from 
a common original ancestor, and consider their individual 
characters, the difference in the color of the flowers 
stands out as the most striking distinguishing feature. 
The flowers of the original species must obviously have 
been red, and those of L. vcspcrtina must have become 
white in the same way as those of other white-flowered 
varieties of red species. This view is supported by the 
fact that the colors of the flowers in these two species 
behave in exactly the same way in crosses as they do in 
many varieties, inasmuch as they conform to MENDEL'S 
laws. Other differences between the two campions are 

1 1 do not propose to enter here into the question of the desirabil- 
ity of a ternary nomenclature (see p. 65) ; it is entirely a question of 
convention. 



582 Species According to the Theory of Mutation. 

the breadth of the leaves and the length of the flower 
stalks. But these characters do not segregate in the 
offspring of the hybrids. They are presumably to be 
regarded as results of progressive specific differentiation. 1 
L. vespcrtina is, perhaps, a white-flowered variety of a 
red-flowered species which has disappeared. At any 
rate I do not think we shall go far wrong if we conclude 
that L. vespertina and L. diurna differ from one another 
partly by typical specific, and partly by varietal char- 
acters. 

GARTNER has repeatedly expressed exactly the same 
view and has illustrated it by the same instance. 2 He 
says that any doubt as to the specific difference between 
closely related species, as for instance between Lychnis 
diurna and L. vespertina, can be most easily removed by 
crossing; for if such species give exactly similar hybrids 
with some other, i. e., with a third species, the difference 
between the two is of a varietal nature only. But if this 
does not occur we have proof that the essential nature 
of the species crossed, although they appear closely related 
with regard to their external features, is specifically dis- 
tinct. For instance the two species of Lychnis just men- 
tioned give wholly different hybrids with Cucnbalus vis- 
cosns. On the other hand GARTNER lays stress on the 
fact that these species behave as varieties in regard to 
the color of their flowers when they are mutually crossed. 
Moreover Lychnis vespertina behaves as a variety with 
regard to the bending over of the teeth of the capsule, 
that is to say as a retrogressive variety of a species with 
the character of L. diurna. 

1 For a historical and critical treatment of the point, see a paper 
by R. ALLEN ROLFE, Hybridization Viewed from the Standpoint of 
Systematic Botany, Journ. Roy. Hort. Soc., April 1900, p. 197. 

'GARTNER. Joe. cit., pp. 581-582. 



Distinction Bct-i^ccn Species and Varieties. 583 

We will now discuss the principle illustrated by this 
instance from a more general point of view. In the 
literature of the subject we frequently find the opinion 
that forms which are mutually fertile and produce a 
normal harvest of seed, giving fertile hybrids, are to be 
regarded as varieties of one and the same species. Forms, 
however, the union of which is followed by a diminution 
in fertility and the hybrids of which are less fertile than 
the species crossed, are regarded by the majority of the 
investigators as specifically distinct. These generaliza- 
tions have served as criteria of relationship from the 
time of KOLREUTER and GARTNER up to the present ; and 
DARWIN himself relies on them in considerations of this 
kind. 1 Based as they were on extensive experience and 
on a profound systematic knowledge, they constitute prin- 
ciples which bid fair to become universally recognized. 
For these reasons they deserve to be placed in the fore- 
ground as a convenient point of departure for our dis- 
cussion : and our object will be not to find out their weak 
points or to replace them by others, but rather to give 
them the more definite forms required by our present 
knowledge of hybridization. 

Therefore we will start from the oft-cited proposi- 
tion that varieties are only small species. 2 This means 
that the difference between species and varieties is not 
of a fundamental nature but rather of a gradual or even 
a conventional kind. Moreover we will start from the 
conception enunciated in the first part of this volume, 
according to which the forms which compose the collec- 
tive species are mainly of two kinds (p. 64) : Hoinonoin- 

See FOCKE, Die Pflarizeninisclilingc, pp. 436, 446-502, etc. 
2 See Vol. T, p. i/i and above p. 580. 



584 Species According to the Theory of Mutation. 

ous forms or elementary species and derived forms or 
true varieties. 

As we concluded in 7, Part I, p. 65, the origin of 
elementary species is due to the formation of new ele- 
mentary characters, i. e., to their actual numerical in- 
crease. True varieties differ from the species to which 
they belong by the latency of certain characters, which 
may either be active as in the type of the species, or latent 
as in the variety, or which may occur in a latent or semi- 
latent condition in the former, and become active or semi- 
active in the production of the variety. In other words, 
we may say that elementary species arise by progressive 
mutations, but derivative varieties by retrogressive and 
degressive ones (p. 71). 

If we now compare the principles derived from the 
study of hybrids with these conclusions, we see that the 
two main types of hybrids are in essential agreement 
with these two systematic groups. Mendelian hybrids 
correspond to retrogressive and degressive specific dif- 
ferentiation, and consequently to true varieties; uni- 
sexual hybridizations correspond to progressive specific 
differentiation and consequently to elementary species. 

There can hardly be any misconception as to the sig- 
nification of this important conclusion. But it only indi- 
cates the principle and not its application to particular 
cases; and, as a matter of fact, it is only another form 
of the generalization enunciated above relating to the 
fertility of crosses and hybrids. For Mendelian crosses 
have as a rule the same fertility as the pure parent forms, 
and fertility does not diminish in the subsequent hybrid 
generations. In uni-sexual crosses, however, fertility di- 
minishes and it does so in proportion as the relation be- 
tween the two forms crossed becomes more remote. 



Distinction Between Species and Varieties. 585 

The truth of this conclusion has become more obvious 
owing to the attention which has been paid to the subject 
since the re-discovery of MENDEL'S work. The paral- 
lelism between the two groups of hybridization and the 
two types of systematic subdivisions has been most ex- 
haustively dealt with by TSCHERMAK, who attempted to 
base upon it a principle of distinction between the spe- 
cific hybrids and varietal mongrels. 1 

We will, then, regard the principle in its new form 
as demonstrated, and examine the question why the cri- 
teria which it supplies are not sufficient for universal 
application. In doing so I shall, for various reasons, 
leave the mutation crosses, which TSCHERMAK also re- 
gards as specific hybrids, out of consideration ; and shall 
denote the Mendelian hybrids as bi-sexual in accordance 
with MACFARLANE'S terminology, employing also the 
term uni-sexual in the sense in which it is used by that 
author. Expressed very briefly, therefore, bi-se.\'nal 
crosses produce varietal hybrids, uni-sexual ones spe- 
cific hybrids. 

But some limitation is necessary ; and herein lies the 
difficulty of the question, which is felt by every one who 
endeavors to apply the conclusions drawn from the study 
of hybrids to taxinomic problems. This limitation is, that 
the criterion really applies only to monohybrids ; for di- 
poly hybrids, however, only in so far as they can be com- 
pared with these. 

We have given the name of monohybrids to those 
mongrels whose parents differ from one another in a 
single elementary character only. Obviously they occur 
both in uni-sexual and in bi-sexual crosses. But, of 

1 E. TSCHERMAK, in the third appendix to his edition of MEN- 
DEL'S Versuche ilber Pflanzenhybriden, p. 58. 



586 Species According to the Theory of Mutation. 

course, any given monohybridic cross can only belong 
to one of these two groups. If it is bi-sexual and be- 
haves in a Mendelian fashion we may immediately infer 
that the two parents are to be considered as varieties. 1 
If it is uni-sexual they are elementary species, of which 
the one must have been derived from the other. 

The di-polyhybrids are mongrels whose parents differ 
from one another in respect of two or more elementary 
characters. Two cases must be distinguished. Let us 
confine ourselves first to the dihybrids. In some cases 

/ 

the two points of difference may belong to the same 
category and therefore follow the same laws in the crosses 
and their products. If each of them, considered by itself, 
would lead to the conclusion that the parents were related 
as varieties, the same conclusion will obviously hold good 
for the combination. So, for instance, is Papaver soinni- 
ferum polycephalnm Danebrog to be regarded as a vari- 
ety ; so also, if it is allowed to judge by analogy, Calliopsis 
tinctoria piimila pur pur ea (Vol. I, p. 197). For the same 
reason the compound colors, which may be split into their 
components by means of crossing and can be recon- 
structed out of these, fall within the category of varietal 
characters. 

Similarly forms, of which one has arisen from the 
other by two successive mutations in the progressive di- 
rection, and whose crosses, therefore, conform to the laws 
of uni-sexual unions, would most certainly have to be re- 
garded as elementary species. 

2 And this independently of the nomenclature chosen. For in- 
stance according to the principles enunciated above, Chelidonium 
lachriatum Mill, will have to be regarded as a variety of C. inajus, 
even when this more convenient name is retained. See Part I, p. 65. 
And from a practical point of view it would be very desirable to drop 
the attempt to correlate the nomenclature with the ever-changing 
systematic conceotions. 



Distinction Between Species and Varieties. 

It may, however, also happen that in forms which 
differ from one another in two points only, one of these 
would give a bi-sexual union, whilst the other would lead 
to a uni-sexual cross. Such is the often cited instance of 
L\clinis I'cspertina X dinrna. One of the characters 
A'oulcl follow MENDEL'S law in crosses, whilst the other 
would tend to produce a constant intermediate form. 1 
In this case, according to the former character, one parent 
would be related to the other as a derivate variety, but ac- 
cording to the latter as a homonomous elementary species. 

Exactly the same, though to a greater extent, must 
be true of tri-polyhybrids. The points of difference be- 
tween their parents can be all uni-sexual or all bi-sexual, 
or some of them uni-sexual and others bi-sexual. In 
the first case the parents are to be considered as ele- 
mentary species, in the second as varieties; in the third, 
however, the principle affords no decision. 

It is just this case which appears to be the commonest 
in nature. In experiments in hybridization, we must, if 
we wish at all to elucidate the laws to which the results 
conform, confine our attention to certain points of differ- 
ence and leave all the rest out of consideration as of 
subordinate importance. MENDEL did this in his experi- 
ments with peas, and the same has to be done in crossing 
Maize, the races of which do not differ from one another 
exclusively in varietal characters ; so also in Lychnis ves- 
pertina and dinrna and in many other cases. 

It would take us too long to continue this discussion 
further, and to accumulate examples; my meaning will, 
I believe, be sufficiently clear. It may be expressed in 

*I call to mind the Oenothera Pohh'ana (O. Iatay,brevistylis} , one 
of my crosses, the /afa-character of which behaves as a mutational 
character in a cross ; whilst the shortness of the stamen behaves as 
a Mendelian character. 



588 Species According to the Theory of Mutation. 

its simplest terms, if we call those qualities which in cross- 
ing conform to MENDEL'S law, varietal characters, and 
those which give uni-sexual unions, specific characters. 
This would conduce to a more general form of the thesis 
based on the experiments with Lychnis (p. 582), viz., 
that two related forms can differ from one another simul- 
taneously in varietal and in specific characters. 

Are they therefore to be regarded as varieties or as 
species ? Here we arrive at the boundary which separates 
facts from conventional terminology. Here lies the point 
to which GOETHE refers in his well-known lines : 

"Dich im Unendlichen zu finden, 
Musst unterscheiden nnd dann verbinden." 

The process of distinguishing is an objective one, 
that of combining subjective. The former is the imme- 
diate result of inquiry ; in our case, of systematic studies 
on the one hand, and of experiments in hybridization on 
the other. The combination is partly a question of taste ; 
it has to serve special aims ; and above all it must facilitate 
general conceptions and mutual understanding. 

It is not my task to go more deeply into the question 
of systematic subdivisions or to make any definite pro- 
posals. 1 My sole object is to place the actual facts in as 
clear a light as possible. This attempt, however, again 
leads to the conclusion that here also this insight can 

o 

only be obtained on the basis of the theory of mutation. 
It is only by attempting to analyze the species into its 
component factors, the elementary characters, that we 

1 If two forms were found to differ from one another exclusively 
in varietal characters, but the number of these were very large, they 
would probably have to be separated as species. Here also the dis- 
tinction between species and variety is an arbitrary one, and as a 
matter of fact, many of the larger groups and sometimes even whole 
families have among their distinguishing marks some which do not 
really differ from "varietal characters." 



The Practical Conception of Species. 589 

can hope to arrive at a conception of species which shall 
be both in accord with the facts, and justified by experi- 
ment. 

Of course, I am well aware that the experiments 
which have been carried on up to the present are by no 
means sufficient and that much remains to be done. Nu- 
merous experiments in hybridization are necessary before 
they can serve as a foundation for systematic distinctions. 
But the leading principle in these researches must always 
be the attempt to determine the elementary characters. 



4. THE PRACTICAL CONCEPTION OF SPECIES. 

Both collective and elementary species are called spe- 
cies ; and this twofold significance of the word has thrust 
its roots so deeply into the history of descriptive biology, 
that it will probably never be wholly eradicated LIN- 
NAEUS himself confused the two ideas; and whilst some 
readers derive from the study of his works the conviction 
that in his mind the collective forms were the true spe- 
cies, 1 others come to a different view of his attitude, and 
believe that in formulating the conception of species, he 
was considering the real units of the system. 2 

The fundamental conception from which almost all 
investigators start, is that species are the only real enti- 
ties. 8 As to what these entities are, opinions differ. 
"On ne peut pas douter," says DE CANDOLLE, "que le 
groupe appele espece par 1'illustre Suedois ne fut, dans 

1 See Vol. I, p. 20. 

~ S. BELLI, Observations critiques sur la rcalitc dcs espcces en 
nature au point de vue de la systematique des vcgctaux, 1901. 

3 C NAGELI, Entstchung und Bcgriff der naturhistorischen Art, 
1865, p. 31. 



590 Species According to the Theory of Mutation. 

sa maniere de voir, tine association de formes voisines." 1 
On the other hand JORDAN, as is well known, based his 
conception of the smaller or elementary species as the 
real species on the same fundamental proposition. The 
wish to see in the species something real, has always 
played a prominent part ; but the reality as it appeared 
to the descriptive biologist has been very different from 
that in the mind of the experimental investigator. 

It would certainly be desirable to agree to call only 
one of the two groups species ; it is only the question 
which. The older view and the popular idea limit this 
term to the larger groups, and give the name of sub- 
species to the smaller ones. 2 But the term subspecies, 
as it is now in use does not signify a unit, but a group 
of units which is also compound and merely differs from 
the species itself in being smaller (Part I, p. 60). The 
modern tendency is to regard the smaller types as spe- 
cies, and wherever the criterion is of an experimental 
kind, like that employed by JORDAN, tin's view will pre- 
dominate. Its importance to descriptive biology has re- 
cently been demonstrated in a most clear and convincing 
manner by BELLI : 3 and there seems every prospect of its 
being recognized by the best systematists. 

It has been proposed to denote collective species by 
a special name, and the word "stirp" has been suggested. 
This term has been applied in this sense by several sys- 
tematists. 4 and BELLI has adduced a long series of histor- 

1 ALPH. DE CANDOLLE, Arch fa. dcs sc. dc la bib!, unfacrscllc, Ge- 
neva, Febr. 1878, Vol. LXI, p. 4. 

2 In what follows, I shall leave varieties, in the sense in which 
this term has been used in the foregoing sections, out of account. 

3 S. BELLI, he. at. 

4 For instance, H. LEVETLLE, Monographic dn genre Ocnothcra, 
1902. T, pp. 72, 106, etc. 



The Practical Conception of Species. 591 

ical and critical arguments for this practice. The word 
stirp would perhaps correspond most closely to the Ger- 
man word Sippe } 1 although this word has been employed 
by various authors in a different sense. 1 ' At any rate it is 
most desirable to make some distinction of this kind, and 
BELLI'S suggestion might well form the foundation of 
such. But questions of nomenclature have little interest 
in this discussion and I prefer to leave the task to others. 

\Ye may now proceed to the practical delimitation of 
the conception of species. 

Descriptive biology wants a definition, independent 
of the results of hybridization ; in its commonest form it 
is based on the absence or presence of transitional forms, 
as was explained in the first part of this volume. Groups 
of individuals which are connected together by transitions 
are considered to belong to the same species. The limits 
between species correspond to gaps in the series. 3 With- 
out some such convention the description of species oc- 
curring in collected material would be impossible ; and this 
method has been employed by the best systematists since 
the time of DECANDOLLE. It is only when direct experi- 
ments can be carried out that the problem can be dealt 
with in a different way. 

Two difficulties, however, present themselves, which 
T shall now briefly deal with. In the first place, exactly 

1 Die Mutatwncn nnd die Mutationsperioden bei dcr Entstehung 
dcr Art en. Leipsic, VEIT & Co., 1901, p. 14. 

2 C. CORRENS, Schcinbarc Ausnahmcn von dcr MendeVschen Spal- 
lungsrcgcl fiir Bastardc, Bcr. d. d. hot. Ges., 1902, Vol. XX, Part 3 ; 
p. 170. See also the same author in Ber. d. d. hot. Ges.. 1901. Vol. 
XIX, p. 77, note i, and his Monographic dcr Maisbastarde, p. i, and 
VON WETTSTETX. Grundziige dcr geographisch-morphologischen Mc- 
thodc dcr Pflanzcnsystcmatik , 1898, p. 3. 

3 See, for instance. Anncc biologiquc, IV. 1898, p. 470; V, 1899, 
p. 377 and elsewhere. Also BORRADAILLE, On Crustaeians, 1901, p. 193; 
GRISEBACH, Die 1 7 egetation dcr Erdc nach Hirer kh'niatisehen Anord- 
ining, 1872. p. 9. and so forth. 



592 Species According to the Theory of Mutation. 

the best varieties are, as a rule, not united by transitional 
forms with the parent species ; in the second place, trans- 
gressive variability tends to obscure boundaries where 
they really exist. These limits are often overlooked in 
the descriptive method, and the search for them can only 
be carried out on experimental and statistical lines. With 
good right DE CANDOLLE speaks in such cases of provi- 
sional species. 1 



5. THE PARALLEL BETWEEN SYSTEMATIC AND 
SEXUAL RELATIONSHIP. 

Since the doctrine of descent now commands general 
recognition, it is desirable that the systematic divisions 
should be an expression of the various degrees of rela- 
tionship. Even before the appearance of DARWIN^S 
works it was recognized that the task of systematic biol- 
ogy as a descriptive and classificatory science was differ- 
ent from the mere question of actual relationship. To in- 
vestigate this and, where possible, to bring the divisions 
of the natural system into harmony with it, these were 
the ends which the pioneers in the study of hybridization 
had continually in view. 

The result did not, however, correspond to this ex- 
pectation. We have not, as yet, succeeded in bringing 
into harmony the study of hybridization with that of 
systematic biology. NAGELI expressed this incompati- 
bility most clearly by introducing his conception of sex- 
ual affinity. The degree of this affinity between two 
types was judged first by the degree of their fertility 
when crossed with one another, and, then, by that of the 
fertility of the hybrids thus produced. 

1 ALPH. DE CANDOLLE, La Phy to graphic, pp. 98, 167. 



Systematic and Sexual Relationship. 593 

The simplest form to which it has been proposed to 
reduce the parallel between systematic and sexual rela- 
tionship, is the following: (1) Plants which produce 
offspring when crossed with one another, always belong- 
to the same genus; (2) Plants whose fertility is not 
diminished in crossing belong to the same systematic 
species (or collective species). Both generalizations are 
in great favor and are defended by prominent investi- 
gators. They have, however, a weak side, viz., that they 
cannot be reversed. 

Let us first examine the former proposition. It de- 
nies the existence of hybrids between distinct genera, 
or so-called generic hybrids. It originated amongst those 
philosophers who regarded the genera as having been 
created, the species, however, as having arisen from them 
by natural means. We have already dealt with the his- 
torical significance of these transmutationists in the first 
volume (p. 17). To them the view, stated above, is also 
due, that not only do species arise within the genera by 
a normal process of evolution, but that new forms may 
arise from these species by crossings. W. HERBERT is 
the most famous representative of this view. 1 which was 
later defended by GODRON. The latter investigator de- 
scribes all genera, the species of which are fertile with 
those of related genera as artificial, and has collected a 
mass of evidence in support of this view. 2 

No fundamental objection can be brought against this 
view, and its adoption would lead in relatively few cases 

1 W. HERBERT, Amaryttidaceae, With a Treatise Upon Cross-bred 
Vegetables, London 1837, PP- 337 et sec l- See also GARTNER, loc. cit., 
p. 152, and NAGELI, Sitzungsbcr. d. k. bayr. Akad. d. Wiss., Dec. 15. 
1865, p. 400. 

2 A. GODRON, De I'cs^ecc et des races dans les etres organises, 1859, 
Vol. I, pp. 225-236, and Mem. A cad. Stanislas a Nancy, 1862, pp. 296- 
298. 



594 Species According to the Theory of Mutation. 

to an enlargement of genera. On the other hand it would 
put a check on the splitting up of genera which has been 
so much in vogue of recent years, and not less to the 
elevation of subgenera to the rank of genera. In practice, 
however, the application of HERBERT'S suggestion has 
proved impossible. At that time there were only a few 
generic hybrids, but their number has undergone a con- 
siderable increase ; partly no doubt through the arbitrary 
splitting up of genera mentioned above, but partly also 
through the rapid accumulation of experimental data. 
Berber is and Mahonia (e. g. B. Neuberti) could well be 
united into one genus. The suggested union of rye and 
wheat, a hybrid between which has been raised by RIM- 
PAU, 1 into a single genus Frumentum, is not likely to 
win much favor; and the fact that BURBANK, in Cali- 
fornia, has raised a hybrid bet ween Nicotiana and Petunia 
which he calls Nicotunia, 2 will hardly be regarded as a 
sufficient ground for a systematic union of these two 
genera. There are now about 150 bi-generic hybrids 
amongst the Orchids, especially between the genera Lae- 
lia, Cattleya, Epidendrum and Sophronitis, as also be- 
tween Zygopctalum, Colax and Batemannia. 3 

The practical difficulties which stand in the way of 
HERBERT'S proposal are, on the one hand, the fact that 
the limits to possible hybrid combinations are by no means 
definite, and on the other hand, the objection, which has 
so often been raised, that crosses are exceptional phe- 
nomena and that it would therefore be impossible to 

1 W. RIMPAU, Kreuzungsprodukte landwirthschaftlicher Cultur- 
pHanzen. Landwirthsch. Jahrb., 1891, p. 20, and PI. VI, Fig. 58. 

2 LUTHER BURBANK, Neiv Creations in Fruits and Floivers (Bur- 
bank's Experiment Grounds, Santa Rosa, California), 1893, with a 
figure of the Nicotunia. 

3 C. C. HURST, Journ. Roy. Hort. Soc., Vol. XXIV, pp. 102, 125. 



Systematic and Sc. vital Relationship. 595 

apply the principle in those numerous cases in which they 
fail. With regard to the former point, it should be noted 
that there are numerous natural hybrids which cannot as 
yet be made artificially, as for instance Ribes Gordonia- 
num ; in other words that many possible hybridizations 
do not succeed within the narrow limits of an experiment. 
The impossibility of a successful cross can therefore 
hardly ever be proved experimentally. With regard to 
the second point it suffices to cite the fact that in the 
great majority of genera no specific hybrids exist at all ; 
and that therefore here the delimitation of genera accor- 
ding to this principle, would fail entirely. 

We come now to the species. KOLREUTER expressed 
the view that crosses within the limits of these are fertile 
and give fertile offspring; whereas crosses between spe- 
cies would either show a lessened fertility or at least 
would produce infertile hybrids. GARTNER and most of 
the more recent investigators have subscribed to this 
view, except that they regard diminished fertility, rather 
than the actual absence of it, as the index of the bound- 
aries of the species. 1 

But even to these generalizations the exceptions are 
so numerous that unanimity in their application has not 
yet been reached. The parallel between sexual affinity 
and systematic relationship holds good in general, but 
fails only too often in particular cases. 2 NAUDIN re- 
garded these deviations from the rule as exceptions, 3 and 
ABBADO and several other investigators have claimed the 
determining cause of these exceptions in individual cases 
to be the task of hybridological researches. 4 

PARTNER, loc. cit., pp. 163-164, 578-579, etc. 

2 See MURBECK, Botaniska Notiser, 1901, p. 214. 

3 CH. NAUDIN, L'Hybridite dans les vegctaiix, 1869, P- 145- 

4 ABBADO, L'ibridisino net vegetali, 1898, p. 48. 



596 Species According to the Theory of Mutation. 

These causes may fall into two entirely different cat- 
egories ; on the one hand, they may consist in insufficient 
systematic knowledge, on the other, in the insufficient num- 
ber of experimental crosses. With regard to the former 
point it should be remembered that, although the sys- 
tematist frequently takes latent characters into considera- 
tion, it is obviously by no means always possible to de- 
cide on systematic grounds whether a character which 
we do not see is really absent or exists only in a latent 
condition. Nevertheless, latency is often regarded as a 
retrogressive metamorphosis and therefore as the mark 
of a variety; whereas absence is considered as a phylo- 
genetically older step and therefore as a specific character 
(see above p. 71). 

From this discussion we see that we may cross a plant 
in which any given character is active either with one in 
which the internal factor for this character is absent, or 
with a species or variety in which it is present but in a 
latent or inactive state. Externally there is no difference 

w* 

between two such crosses, but fundamentally they are 
exactly opposite, and therefore it is to be expected that 
their results will differ. The cross, active X absent is a 
uni-sexual union and will presumably lead to a halving 
of the external characters of the parents in the hybrid, 
whereas the cross active X latent is a bi-sexual one, and 
follows MENDEL' s laws, at least in ordinary cases. Many 
paradoxes, which at present seem to negative the parallel 
between systematic and sexual affinity may perhaps be 
explained by more exact investigation on these lines. 
FOCKE gives the following cases as instances: 1 "Silenc 
vidgaris, and 5*. maritima, Capsella rubella and C. bursa 
pastoris, Phaseolus vidgaris and Ph. niultiflorus, or the 

1 FOCKE, loc. at., p. 448. 



Systematic and Sexual Relationship. 597 

species of Diplacus (Mimulus) do not seem to be mor- 
phologically more remote from one another than Tro- 
pacolnm ma jus and Tr. minus, Nicotiana latissima and 
N. Maryland-lea, N. rustica and N. Texana or Pisitm sa- 
tiviim and P. arvense. Nevertheless the results of cross- 
ing in the former cases exhibit all the characters of hy- 
brids, but in the latter those of mongrels." FOCKE sum- 
marizes his conclusions on this subject in the thesis that 
''systematically probable" crosses often miscarry, whilst 
improbable ones sometimes succeed (loc. cit., p. 457). 

Even regarded from this point of view the difference 
between Mendelian and uni-sexual crosses offers itself 
as a criterion for distinguishing between species and 
varieties. 

But sexual affinity does not always give reliable in- 
dications. In the first place GARTNER frequently found 
that fertility, as measured by the number of seeds ripen- 
ing in a capsule, is different in reciprocal crosses. This 
shows that it is not merely determined by the degree of 
relationship, but obviously by some other causes besides. 
The best known of these is the length of the style; and 
the recent investigations of BURCK on the concentration 
and stimulating properties of the fluid secreted by the 
stigma have thrown much valuable light on this subject. 1 
In extreme cases one of the crosses succeeds well, whilst 
the other does not at all, as for instance Mirabilis Jalapa 
X longiflora, Geum urbanum X rivale, Sophronitis X 
Cattleya, and so forth. In the second place some crosses 
do not succeed in spite of a very close apparent relation- 
shin, as for instance between Anagallis arvensis and coe- 
rulea (GARTNER). 

1 W. BURCK, Over de "bewcging der stempels by Mimidus en To- 
ren'ia. Sitzungsber. d. Kon. Akad. d. Wet., Amsterdam, 1901, and 
in previous articles. 



598 Species According to the Theory of Mutation. 

I do not propose to elaborate this theme further ; it 
has often been dealt with and especially in great detail 
by FOCKE, who has presented it in a masterly way in his 
textbook on plant hybrids. The main conclusion, how- 
ever, is that the majority of authors agree that systematic 
and sexual affinity, if properly understood, are essentially 
parallel ; indeed, that they are really no more than two 
manifestations of one and the same thing, but that we 
have not yet succeeded in explaining the apparent ex- 
ceptions to this parallel. 

For our purpose, however, the important question is, 
whether the diagnoses of species and varieties will grad- 
ually come to be based on elementary characters as units, 
and whether sexual relationship will come to be judged 
by the number of differentiating units. GARTNER has 
already pointed out that those genera in which the largest 
numbers of hybrids have been produced are exactly those 
in which the number of very closely related species is 
the greatest (he. cit., p. 168). NAGELI has elaborated 
this idea and SACHS has followed him in his Lchrbuch 
der Botanik. ABBADO, HURST, GILLOT and many others 
have also subscribed to this view. 

The opinion expressed by these writers on the paral- 
lel between systematic and sexual affinity, may be sum- 
marized in the following thesis, viz., that the fertility 
of crosses and of the hybrids resulting from them, di- 
minishes, on the average, as the number of points of 
difference (that is to say, that of the elementary char- 
acters, which constitute the differences) increases. But 
many more experiments are necessary before this sug- 
gestion can be examined critically or be regarded as 
resting on a sure foundation of experimental facts. 



II. THE RANGE OE VALIDITY OF THE DOC- 

TRIXE OF MUTATION. 

6. THE SIGNIFICANCE OF THE AVAILABLE EVIDENCE. 

L'nlike the prevailing form of the theory of selection, 
the doctrine of mutation lays stress on sudden or dis- 
continuous changes, and regards only these as active in 
the formation of species. The Darwinian form of the 
theory of selection regards both these and fluctuating 
variations as operative in the origin of new forms, whilst 
WALLACE favors the other extreme, according to which 
all formation of species goes by a slow and gradual 
process of change. 

The two schools of thought naturally adopt different 
attitudes towards the doctrine of mutation. It is at once 
rejected by WALLACE'S adherents, whilst those who in- 
cline to DARWIN'S own form of the theory are less un- 
reservedly inimical ; many of them have even greeted it 
with open arms. 

Inasmuch as these two lines of thought have been 
clearly manifested in the critiques which have been pub- 
lished of the first volume of this work, I propose to dis- 
cuss them briefly here, in order to point out the funda- 
mental questions which are involved in this controversy. 

The extreme opponents of my theory maintain that 
there are no mutations at all ; Natnra nou facit saltns, 
they say. What I have described as discontinuous changes, 



600 Validity of the Doctrine of Mutation. 

are, in their opinion, merely the extreme deviations 
brought about by ordinary variability; for the further 
these are from the mean, the rarer they are, and the 
greater are the intervals by which they are separated. 
The number of petals in Ranunculus bulbosus semiplenus 
oscillates around 9 or 10, frequently reaching 14, very 
seldom 20-23. Only in one case did I observe a larger 
number, which happened to be 31 (see p. 252). The 
gap between 23 and 31 is, however, not a discontinuous 
variation. It is perfectly normal, and quite a common 
occurrence in this part of QUETELET'S curves. In a 
general way, gaps of this kind in the curves of variation 
may be thus explained, and according to my opponents 
the so-called springs and jumps have to be explained in 
the same manner. They are assumed to be no more than 
the extreme variants of series which when investigated 
further, would prove to be continuous ones. 

This view is chiefly maintained against my opinion 
by morpholgists 1 and statisticians. 2 It is, as KOR- 
SCHINSKY has lately shown, directly contradicted by horti- 
cultural experience; 3 and the absence of transitions and 
the stability of my new species of Oenothera prove that, 
in this case at any rate, true mutations do occur. The 
greatest obstacle in the way of agreement on this point, 
however, lies in the phenomena of transgressive varia- 
bility, which to the morphological observer so often give 

1 Among my numerous critics I mention here CH. SCHRODER, 
Die Variabilitdt der Adalia bipimctata L., Allgem. Zeitschrift fur 
Entomologie, Vols. VT-VIT, 1901-1902. The view taken by SCHRODER 
has since been proved to be erroneous by the experiments of A. G. 
MAYER on the colors of butterflies. See Effects of Natural Selection 
and Race-Tendency Upon the Color-Patterns of Lepidoptera, Museum 
Brooklyn Inst. of Arts and Sc., 1902, Vol. I, No. 2, p. 31. 

2 See the journal Biometrika and especially the articles in it by 
WELDON. 

3 S. KORSCHINSKY, Mem. Acad. Imp. Petcrsbourg, 1899, IX. 



Significance of the Available Evidence. 601 

the appearance of transitional forms and only reveal 
their true nature when tested by breeding experiments. 

Several of the critics who have expressed themselves 
more or less favorably on my theory, have pointed out 
that the greatest danger for it lies in this very point. In 
a very clear and concise summary of the doctrine of muta- 
tion MAC DOUGAL has expressed himself as follows : "The 
greatest misunderstanding which may likely arise in the 
consideration of these results will be that founded on the 
error of confusing fluctuating variability and mutabil- 
ity/' 1 

The distinction between species-forming and fluctu- 
ating variability was first derived by DARWIN from his 
theory of pangenesis, and this may perhaps explain the 
antipathy which so many investigators bear towards it. 2 

The great majority of writers assume that fluctuating 
as well as discontinuous variability play a part in the 
formation of species. 3 This view of DARWIN, which 
under WALLACE'S influence gradually shifted into the 
background, has in latter years come again prominently 
to the front; and the various investigators concede here 
a less or there a greater share to discontinuous variations 
or mutations, according to their preconceptions and their 
experience in investigation. This long series of shades 
of opinion would seem to indicate that we are not con- 
cerned here with an independent principle, but with a 
gradual change of opinion from the prevailing theory 

1 D. T. MAcDoucAL, The Origin of Species by Mutation, Torreya, 
1902, Vol. II, p. 99. 

2 See Intraccllular Pangenesis, e.g., p. 214 (English ed.), and 
Ber. d. d. Ges., 1900, XVIII, p. 83. 

3 VON WETTSTEIN has published a useful summary of his views 
in the form of a lecture delivered to the Scientific and Medical Asso- 
ciation at Karlsbad, and entitled Dcr Neo-Lamarckisuius und seine 
Beziehungen sum Danvinismus, 1903. 



602 Validity of the Doctrine of Mutation. 

to some other one ; and especially amongst American in- 
vestigators the tendency has been in recent years to pro- 
ceed as far as possible in this direction. 

If we look for a fixed point among these oscillating 
opinions we may well choose the view repeatedly ex- 
pressed by DARWIN himself, that it is possible to imagine 
that characters may originate by a slow process, but may 
disappear all of a sudden. 1 In combining this with the 
distinction made in the first part of this volume between 
progressive, retrogressive and degressive formation of 
species, the proposition would run: Progressive forma- 
tion of species may occur slowly and gradually, whilst 
retrogressive and degressive specific differentiation is due 
to mutations. Progressive differentiation consists in the 
formation of a new character which was not previously 
present; whilst retrogressive and degressive differentia- 
tion consists in the transference of internal factors, al- 
ready present, from one condition to another. In the for- 
mer case the active unit becomes latent ; in the latter the 
latent becomes active, or the semi-latent semi-active ; but 
the material vehicles of these characters remain funda- 
mentally the same throughout ; nothing new arises in the 
idioplasma. 2 

In horticulture, as we have seen, mutations are largely 
of the retrogressive or degressive kind. Discontinuous 
formation of species on the progressive line is much 
rarer. Nevertheless I believe that my researches with 
Ocnoihera have contributed instances which may demon- 
strate the occurrence of progressive mutations in this 
species at any rate. Obviously there is a great need of 

1 With reference to this point see the valuable critique by L. 
PLATE, Ucbcr Bedcutung und Tragweite des Darwin' schen Selections- 
t>rinci[>s, 1900, p. 37 and elsewhere. 

~ See below, 9-11. 



Significance of the Available Evidence. 603 

further investigations on this point, and these should 
not merely be concerned with new phenomena, but with 
the testing of results already obtained ; for many instances 
of discontinuous origin stand in need of more convincing 
proof, and in other cases the progressive nature of a 
process which is interpreted as a mutation is often subject 
to doubt. In such investigations attention should be 
paid to the question whether the hypothetical premuta- 
tions may perhaps be prepared gradually, whilst the new 
character which has been so developed in secret, might 
unfold suddenly. But it will take manv vears to decide 

tf m * 

these points. 

Starting from general arguments KoLLiKER 1 was 
the first to insist on the importance of mutations against 
DARWIN, indicating the process, which was then a purely 
hypothetical one, by the name heterogenic development. 
Others have expressed themselves favorably with regard 
to this view ; especially K. E. VON BAER and BRONN, and 
also HAACKE, G. PFEFFER, DELAGE, CUNNINGHAM, 
WOLFF, DREYER, DRIESCH, EMERY 2 and many others. 
This doctrine has of recent years found its strongest 
champion in BATESON, whose views I have already dealt 
with above. Those authors too, who have made mono- 
graphic studies of special genera and species have wel- 
comed it ; for instance WITTROCK, in his study of Viola, 
inclined to the view that species have originated discon- 
tinuously. Further, this doctrine is defended on purely 
speculative grounds by many prominent biologists, among 
whom I need only mention VON HARTMANN and also 
HAMANN and KERSTEN. S On the zoological side Hu- 

1 KOLLIKER, Abhandl. Scuckcnb. Gescllsch., 1864, pp. 223-229. 

2 EMERY, Biolog. Centralblatt, 1893, No, 13, p. 723. 

3 See the careful and critical exposition in H. KERSTEN'S Die 



604 Validity of the Doctrine of Mutation. 

BRECHT and MORGAN have expressed themselves in favor 
of the new view, 1 the latter on the ground of his studies 
in the regeneration of injured organs. 2 

Amongst practical agriculturists my views have been 
well received by EM. VON PROSKOWETZ and HJALMAR 
NILSSON. The former has conducted a long series of in- 
vestigations on the transformation of the wild Beta patula 
into the sugar beet; and it was found that the changes 
do not by any means take place by imperceptible tran- 
sitions but suddenly. 3 Each new character is brought to 
light at one stroke ; it is not the product of selection but 
of internal processes, the nature of which we do not as 
yet know. Even such secondary characters as color, 
change in the same way. HJALMAR NILSSON, the direc- 
tor of the practical and experimental station for the im- 
provement of seed at Svalof in Sweden, has for many 
years been collecting a valuable mass of evidence, which 
promises to throw great light on the doctrine of muta- 
tion, but has not as yet, been grouped for that purpose. 
Judging from the oral and other communications which 
I have received from time to time from this investigator, 
I may state here that his results are in perfect harmony 
with the doctrine of mutation. 4 

ideallstische Richtung in der modernen Entivlckelungslehre, Zeitschr. 
f. Naturw., 1901, Vol. 73, p. 321. 

1 A. A. W. HUBRECHT, De cvolutie in nleuwe bancn, Utrecht, 1902. 

2 Tn. HUNT MORGAN, Darwinism in the Light of Modern Criti- 
cism, Harpers Monthly Magazine, Feb. 1903, and in many other 
papers. 

3 EM. v. PROSKOWETZ JR., CuUiirversuche mit Beta, 1892-1901 in 
Oesterr.-Ungar. Zeitschrift f. Zuckerindustrie und Landwirthschaft 
des Centralvereins f. Riibenznckerindustrie in d. Oest.-Ung. Mo- 
narchic, 1892-1902. The experiments of a given year will be found 
in the number for the following year, and in the number for 1892 will 
be found an account of the earlier experiments and the literature of 
the subject. For the mutations which occurred see especially the 
number for 1902. 

4 See the various numbers of the journal issued by the experi- 



Significance of the Available Evidence. 605 

To the important observations already mentioned, 
made by HEINRICHER on Iris pallida abavia, by SOLMS- 
LAUBACH on Capsella, by WITTROCK on Viola, by BAILEY 
and WHITE on Tomatoes, and by many others, I have 
here to add the following. NOLL has described the sud- 
den origin of a regular tendril in Tropaeolum, and draws 
conclusions from this in favor of the possibility of dis- 
continuous changes and their significance for the theory 
of descent. 1 TRACY has observed the sudden origin of 
a dwarf variety of Phaseohis lunatus, 2 MACFARLANE has 
investigated the variability in the genus Primus, 3 CARUEL 
has collected a number of cases in which direct transitions 
can be demonstrated and calls them "Euthymorphoses." 4 
CARLSON has investigated the mutations of the forms of 
Succisa occurring in Sweden, 5 and LAURENT expresses 
himself in the same way with regard to several species 
of fruit trees. 6 Dr. J. W. HARSHBERGER sent me mate- 
rial of Hibiscus moscheutos and Euphorbia ipecacuanha 
from Pennsylvania, the extraordinary abundance of forms 
in which seems to indicate the occurrence of a period of 
mutation in these species; and Mr. L. COCKAYNE has 
given me information on some transformations of Saro- 
thamnus scoparius and Lupinus arboreus observed by 
him in New Zealand. It may further be mentioned that 

mental station at Svalof, Sveriges Utsddefdrenings Tidskrift, and 
particularly the Arsberdttelse under ar 1901, in Vol. XII, 1902, No. i, 
page 3. 

1 F. NOLL, Das Auftreten einer typischen Ranke an einer sonst 
rankcnlosen Pflansenart, Sitznngsber. d. Niederrhein. Ges. f. Naturk., 
Bonn, Jan. 14, 1895. 

2 W. W. TRACY, American Naturalist, 1895, XXIX, p. 485. 

3 J. M. MACFARLANE, Publications of the University of Pennsyl- 
vania, 1901, p. 216. 

4 T. CARUEL, Bull. Soc. Bot. Ital., Florence, 1896, p. 84. 

5 Bot. Not., 1901, p. 224. 

6 E. LAURENT, De I' experimentation en horticulture, 1902, p. 12. 



606 / \ilidily of the Doctrine of Alutation. 

BORRADAILLE, working with decapods, came to the con- 
clusion that great difficulty stands in the way of the ex- 
planation of specific differentiation by means of ordinary 
natural selection. 1 Mr. R. LAUTERBORN was so kind as 
to draw my attention to the appearance of the yellow 
Atropa Belladonna lutca, and to the evidence given on 
this variety by Dr. Scnuz. 2 Dr. RAATZ was also kind 
enough to send me some seeds of a most remarkable 
shiny brown variety of the sugar-beet which suddenly 
arose in the cultures of Klein- Wanzleben, and from which 
I obtained fine instances of the new character in my 
garden. 

I have only given a selection from the long list at 
my disposal. My object was simply to show that the 
doctrine of mutation already finds adherents everywhere 
and is supported by a broad foundation of facts. This 
justifies the expectation that the difficulties which still 
stand in its way will ultimately be overcome. 

7. THE EXPLANATION OF ADAPTATIONS. 

Ever since the belief in the common origin of organ- 
isms has been recognized as a basis for investigation and 
speculation, one aspect of the problem has aroused the 
special interest both of the author and of the student, viz., 
the explanation of adaptations. As a matter of fact this 
problem lies outside the scope of the present book, which 
is only concerned with the empirical foundations of the 
theory of descent. Nevertheless it seems to me that it 

1 L. A. BORRADAILLE, Marine Crustaceans, The Fauna and Ge- 
ography of the Maldive and Laccadive Archipelagoes, Vol. I. Pt. 2, 
page 197. 

2 Aintl. Bcricht iibcr die 33. Versamml. d. Natttrf. und Acrztc. 
Bonn, Sept., 1854 (Bonn, 1859), p. 139. A single specimen of the 
plant had been found a few years previously in the Black Forest. 



The Explanation of Adaptations. 607 

may be of interest to show that the prevailing view, ac- 
cording to which WALLACE'S form of the theory of selec- 
tion is the only one which will account for adaptations, 
is erroneous. 

The view that all the characters of organisms vary 
in every desired direction, and that the slightest deviation 
may be subjected to the struggle for existence, and can 
be accentuated to, and finally fixed at, the necessary de- 
gree of development, is certainly an extremely convenient 
one. I willingly admit that almost anything can be 
squared with this theory in a very plausible way, and 
that explanations of this kind are very attractive to the 
student ; but this is not science. The contradictions in 
such a system must be satisfactorily explained before it 
is accepted ; and if we attempt to do this, we soon come to 
the conclusion that the hypothesis itself is not in harmony 
with the available evidence. 

The limits of the applicability of the theory of selec- 
tion, as applied to this question, are known to everybody ; 
and without doubt they are extremely wide. How much 
the theory of mutation has to offer in this respect we 
do not know, because no attempt to estimate this has as 
yet been made, but everything points to the conclusion 
that this theory will explain adaptations just as com- 
pletely, or rather just as incompletely, as the present 
view. It will, however, always have the special feature 
of emphasizing the hypothetical parts of the argument, 
rather than of dismissing them into the background. 

At the present time the theory of selection has still 
the larger number of adherents ; but amongst the younger 
investigators a train of thought is developing which, as 
we have seen above, ascribes a greater importance to 
discontinuous changes. For them fluctuating variability 



608 Validity of the Doctrine of Mutation. 

consists merely in an oscillation around a given point of 
equilibrium ; whilst the formation of new species necessi- 
tates the attainment of a new equilibrium. Especially in 
America has this view made great progress, as has been 
described by CONN in an admirable exposition in his new 
work on evolution. 1 

Of the numerous writings which \ve owe to WAL- 
LACE'S school, I shall only mention here that on Natural 
Selection and Tropical Nature, of this author (1895), 
and PLATE'S critical exposition of WALLACE'S theory. 2 
Although PLATE, at the conclusion of his clear and per- 
ceptive critique of the questions which pertain to this 
point, declares in favor of the theory of selection, his 
work, of all those of which I have made use, gives me the 
impression of the greatest objectivity; and I am con- 
vinced that the gulf between his views and those I hold 
will surely be bridged over some day. Therefore I refer 
the reader to his book for a closer study of these ques- 
tions, and shall confine myself here to a few points which 
stand in the closest relation to those discussed above. 

1. The significance of fluctuating variability is very 
limited, whereas the explanation of adaptations demands 
almost unlimited variability. In earlier days when the 
law of QUETELET was only known to apply to anthro- 
pology, almost all the changes of plants and animals 
were considered to be the consequences of ordinary varia- 
bility, but now this is shown to be governed by laws which 
largely curtail its importance. In the first part of the 
first volume this theme has been discussed in detail, and 
I may here simply refer the reader to those chapters. 

1 H. W. CONN, The Method of Evolution, New York, 1900, p. 132. 

2 L. PLATE, Ueber Bedcutung and Tragzvcite des Danvin'schcn 
Selectionsprincips, Leipsic, 1900. A very complete bibliographical 
list will be found on pp. 145-153 of this book. 



The Explanation of Adaptations. 609 

A strong argument for my view was put forward by 
ROSA and CATTANEO. 1 According to these authors the 
extinction of large groups of species proves that the 
variability resident in them was powerless to adapt them 
to the changing conditions of life; and from this con- 
clusion they infer that the ordinary variability, as it is 
always manifested, is not sufficient for this purpose. Ob- 
viously some other process is necessary. 

II. Fluctuating variability is linear] it oscillates only 
in a phis and a minus direction, whilst adaptations demand 
a variability which will produce variations in all direc- 
tions. 2 On this point also I have expressed my opinion 
in the first volume (p. 118). It constitutes, in my opin- 
ion, one of the strongest objections to the prevailing 
view ; and it also shows more clearly than anything else 
how far DARWIN'S adherents have departed from the 
views actually expressed by him. To DARWIN'S mind 
the essential point was that the struggle for existence 
should have to select from material supplied by an in- 
determinate variability. Natural selection is a sieve. It 
creates nothing, as is so often assumed; it only sifts. 
It retains only what variability puts into the sieve. 
Whence the material comes that is put into it, should be 
kept separate from the theory of its selection. How the 
struggle for existence sifts is one question; how that 
which is sifted arose is another. In both respects, DAR- 
WIN'S original view is still the best, but the point at issue 
has been often obscured by later writers. The meshes 
of the sieve are not such as to separate only the very best ; 
on the contrary natural selection only throws out some 
part of the individuals, and amongst them the worst, i. e., 

1 See below in 12. 

2 GusT,\v WOLFF, Dcr gegenwdrtige Stand dcs Dari^'inisinns, 1896. 



610 Validity of the Doctrine of Mutation. 

those the least adapted to the immediate external condi- 
tions. Selection is the elimination of the inferior, whilst 
the choice of the superior individuals should be called 
"election," and this leads to the stock-races (elite races) 
as in the selection of beets and cereals (Vol. I, pp. 99- 
118) ; or, as an admirable critic, A. KUYPER, says, "se- 
lection aims at the maintenance of species ; election is the 
choice of persons." 1 The doctrine of the direct influence 
of the environment on organisms, as entertained bv LA- 

o ^ 

MARCK, is that against which DARWIN directed his hy- 
pothesis of indeterminate variability as being more in 
harmony with the demands of pure science. This old 
doctrine is repeatedly met with in modern times, 2 and this 
shows at least, in my opinion, that the prevailing form 
of fhe theory of selection does not find favor in those 
quarters. 3 

Thus the sieve of natural selection perpetually elim- 
inates numerous individuals of inferior value; but how 
the differences between the individuals arise is another 
question. Linear variability provides differences only in 
two directions, by means of which selection can either 
increase or diminish, strengthen or weaken the various 
characters. It cannot effect more, unless material of an- 
other kind is provided by variation. The hypothesis of 
mutation meets this demand; for it necessarily assumes 
a variability in almost all directions, as I have shown 

1 A. KUYPER, Evolutie, Amsterdam 1899, p. n. 

2 G. HENSLOW, Does Natural Selection Play any Part in the Ori- 
gin of Species, Nat. Sc., XT, 1897, p. 166. WARMING, Lehrbnch d. 
Oekologie, p. 382. VON WETTSTEIN, Ber. d. d. bot. Ges., 1900, Vol. 
XVIII, Generalversammlungsber. p. 184. STRASBURGER, Ceratophyl- 
hnn submersum, Jahrb. f. wiss. Bot., Vol. XXXVII, p. 518, where a 
list of references to papers, dealing with the direct effect of the en- 
vironment, will be found. 

3 R. v. WETTSTEIN, Haudbuch der systcmatischcn Botanik, 1901, 
p. 32. 



The Explanation of Adaptations. 611 

in the first part of the first volume (p. 198), and our 
consideration of those species which are rich in subordi- 
nate forms, as well as the results obtained with Oenothcra 
Lamarckiana have justified this claim. Thus we see that 
the current form of the theory of selection cannot supply 
the kind of variability which the theory demands, whilst 
the doctrine of mutation can supply it, as we know from 
actual observation. 

III. The first insignificant beginnings of new charac- 
ters do not come under the operation of natural selection 
since they are of no significance in the struggle for ex- 
istence. This is the best known objection against the 
prevailing form of the theory of selection. It has been 
elaborated by many authors and admirably expressed by 
CONN in his work cited above, so that we need not deal 
with it further here. It ultimately leads every thoughtful 
investigator to the view 7 that every organ must have its 
origin in a discontinuous variation. 1 The doctrine of mu- 
tation alone can overcome these difficulties although we 
must not forget that the objection is directed only against 
the present form of the theory of selection and not against 
DARWIN'S own conception of it ; for if the sieve of selec- 
tion does no more than eliminate those of less fitness, and 
if its function is merely to increase the mean of those 
that remain, even the very slightest average progress 
must have a result, as DARWIN so frequently insisted. 

In the doctrine of mutation, however, these slow tran- 
sitions and these slight advantages have no place. Spe- 
cies-forming variability simply omits these, both in ex- 
periment and in horticultural experience, so that they 
constitute no obstacle to the theory. 2 

1 CONN, loc. tit., p. 134. 

i- Tt is in the explanation of instinct that the current form of the 



612 Validity of the Doctrine of Mutation. 

IV. The theory of selection explains the existence of 
useful characters, but does not explain that of useless or 
actually harmful ones. 1 Whereas the doctrine of muta- 
tion assumes that specific differentiation does not take 
place in any definite direction, that mutations are pro- 
duced independently of their adaptive value, and that they 
may survive, provided that they do not prejudice the 
existence or annul the fertility of the individual, the 
theory of selection cannot account for the origin of sterile 
forms of which, nevertheless, there are many. I have 
already mentioned instances of these in the first part of 
this volume, and will here only add a reference to a most 
remarkable sterile form of oats, recently described and 
figured by NOLL ; 2 to the dates 3 and grapes 4 without pips, 
and to the highly branched and absolutely sterile variety 
of our gardens, called Muscari comosum plninoswii, 
which belongs to a species characterized by a tuft of 
sterile flowers at the tip of the normal spike (Fig. 136). 

Instead of giving a further discussion I shall content 
myself with referring to the curious case of Mimulus 
and Torenia, which BURCK has described, and which this 

theory of selection is most evident!}' insufficient. See WASMANN, 
Biol. Ccntralblatt, Vol. XXI, Nos. 22, 23; also EMERY, Gcdankcn zur 
Descendenz- und Vererbungstheorie, Biol. Centralblatt, 1893, Vol. 
XIII, Nos. 13 and 14, p. 397; further W. WAGNER, V Industrie dcs 
Arandna, Mem. Acad. Imp. St. Petersbourg, Vllth Ser., Vol. XLII, 
No. n, 1894; and N. CHOLODKOVSKY, Die Conifer enlduse, Hor. Soc. 
Ent. Ross., XXXI, p. 43. 

1 For a list of these I refer the reader to DEMOOR, MASSART and 
VAX DER VELDE, L' evolution regressive, Paris, 1897, especially pp. 
286-289. 

2 F. NOLL, Sitsungsber. d. Nicdcrrliein. Ges. f. Naturk., Bonn, 
March 4, 1901. 

3 CH. RIVIERE, Societe nat. d'acclimatation, Paris, La Nature, 
1901, No. 1477, p. 247. The tree in question grows near Hamma in 
Algeria. 

4 H. MULLER-THURGAU has given an exhaustive list of wholly 
or partially sterile varieties of grapes in Experiment Station Record, 
XI, p. 16, 1902. 



The Explanation of Adaptations. 



613 



investigator claims to be of itself sufficient to disprove 
the doctrine of selection. 1 These plants contain four 
stamens in each flower, two large normal ones, and two 




Fig. 136. Muscari comosum plumosiun. 

small abnormal ones. The latter contain fertile pollen, 
but never dehisce. The pollen is therefore absolutely 

1 W. BURCK, Kon. Akad. v. Wet., Amsterdam, 1901 ; Album d. 
Natuur, 1902. See also the earlier writings of this author on facts 
which cannot be explained by the theory of selection. 



614 Validity of the Doctrine of Mutation. 

useless, although if applied to the pistil, it is capable of 
producing an abundance of good seed. It is evident 
that this condition cannot have arisen either by gradual 
modifications or under the influence of the ordinary se- 
lection of useful characters. 

All the difficulties which we have mentioned as be- 
setting the current view, disappear if we substitute muta- 
bility for fluctuating variability, as the source of the 
origin of species ; and there is no doubt that adaptations 
can be explained by mutability just as satisfactorily as 
by fluctuating variability. 



8. VEGETATIVE MUTATIONS. 

In order to conduct an experimental investigation 
into the manner in which mutations arise, it is necessary 
to know when they occur. According to the prevailing 
opinion this moment is assumed to be that of fertilization. 
GALLESIO clearly expressed this view at the beginning 
of the last century, and advocated it against the belief 
in the direct influence of the environment which was 
common amongst breeders at that time. 1 Some associa- 
tion of species-forming variability with fertilization is 
generally regarded as being clearly demonstrated both 
in the animal and vegetable kingdoms, and especially for 
annual plants and those which are ordinarily multiplied 
by seed. 

On the other hand we have the bud variations, or 
vegetative mutations as they should rather be called. They 
were well known to the older scientists, but DARWIN was 
the first to insist on their importance by collecting all 



1 G. GALLESTO, Traitc dn Citrus; Tcorici dclla riproduzione rcgc- 
tabile, Pisa, 1816; DE CANPOLT.E, Physiologic regctalc, IT. p. 720. 



Vegetative Mutations. 615 

the evidence bearing on them. Most of the later writers 
have agreed with him. DELAGE opposes the view that 
fertilization is the sole cause of variability, partly on 
the ground of the existence of bud- variations, partly 
because nothing new is produced in fertilization, in which 
nothing more occurs than a recombination of heritable 
characters already present. 1 SAVASTANO gives many rea- 
sons, derived chiefly from the study of woody plants, in 
support of the view that varieties usually arise from seeds 
and more rarely from buds. 2 BAILEY, on the other hand, 
lays greater stress on bud-variations. According to him 
bi-sexual reproduction is not a condition of variability, 
since many new varieties have arisen by vegetative means, 
such as several sorts of pine-apples, bananas, strawberries, 
apples, weeping willows, etc. 3 

KASSOWITZ goes furthest in this direction when he 
says: 4 "Even if there had never been any sexual repro- 
duction, our earth would be peopled by beings differing 
widely from one another in their characters and in their 
functions ; and there is no ground for the assumption that 
the differences between the most widely separated forms 
would have been any less without this (i. e., sexual re- 
production) than it actually is." 

The conclusion from this all too brief historical sur- 
vey is that the importance of vegetative mutations is 
gradually obtaining wider recognition, whilst the attempt 
to associate species-forming variability with fertilization 
is coming to be regarded with less and less favor. 

1 Y. DELAGE, L'heredite, 1895, P- 283. 

2 L. SAVASTANO, La Varicta in arboricultura, Annali d. R. Scuola 
Sup. d'Agricoltura in Portici, 1899, I 2 - P- 63 and elsewhere. 

' L. H. BAILEY, The Plant Individual in the Light of Evolution, 
Science, 1897. 

4 MAX. KASSOWITZ, AUgemcinc Biologic, II, 1899, p. 247. 



616 Validity of the Doctrine of Mutation. 

Before we proceed to a consideration of the facts 
let us first examine the question itself more closely. We 
may ask in which periods in the life of a plant the con- 
ditions for the appearance of mutation may be different. 
The life of a plant may be divided into the vegetative and 
the reproductive period, and there are therefore four 
possibilities to be taken into consideration. First we 
have the two periods themselves, then the two transi- 
tions from the one to the other, viz., the origin of the 
germ cells (the moment of the so-called numerical re- 
duction of the chromosomes of the nucleus) and the 
fertilization, which latter is the beginning of the vege- 
tative life. Confining ourselves first to general considera- 
tions, the processes involved in the origin of the sexual 
cells are obviously of a much more complicated nature 
than those involved in fertilization. On the other hand 
the sexual cells are usually regarded as more susceptible 
than the vegetative organs. For these reasons therefore, 
we might be inclined to assume for the moment of muta- 
tion not that of fertilization but some previous point of 
time. How much earlier, then becomes a further ques- 
tion. 

In bi-sexual or Mendelian crosses segregation occurs 
during the maturation of the egg- and pollen-cells, and 
it is complete when these elements are being formed. 
For the egg- and pollen-cells of the monohybrids are no 
more of a hybrid nature, but entirely assume the one or 
the other of the two parental types. The same thing 
must hapen in mutation, for all the evidence seems to 
indicate that the egg- and pollen-cells have already mu- 
tated before they unite in fertilization. 

Of course, as a rule the mutation will not find external 
expression until the germ develops, and thus the new 



Vegetative Mutations. 617 

character is only displayed after fertilization; but that 
the process should be its result, by no means follows from 
this. The moment of appearance evidently tells us noth- 
ing about the preparation which may have preceded it. 
This may have occurred during the sexual life, or may 
even have extended back into the vegetative stage. 

The phenomena of sector ial variation, which are best 
known amongst striped flowers and variegated leaves 
(see page 114), but which have also been observed else- 
where, and especially in the sectorial segregation of hy- 
brids support, the latter view. I refer to the instance de- 
scribed above (page 276), of a variegated bud-variation 
in an oak. A variegated twig occurred on a bush whose 
leaves were otherwise quite green. But the point of 
insertion of the twig occurred on a variegated longitu- 
dinal stripe on the branch which produced it. The change 
therefore had not taken place in the actual origin of the 
bud, but long before. The term bud-variation is there- 
fore, in such cases, not strictly applicable. 

We can apply this instance to the appearance of mu- 
tations in general and say that the moment of the actual 
appearance of the character is preceded by a shorter or 
a longer period in which the change, although complete, 
was still in a latent condition. If, for instance, we are 
dealing with a transformation in flowers, a sectorial and 
a bud-mutation could occur without becoming externally 
visible. In the first part of this volume (page 123) I 
drew attention to the stamens with red stripes in striped 
flowers and dealt with the question whether the pollen 
grains themselves might not differ with regard to this 
mark, some of them possessing this character and others 
not. Obviously this question may be applied just as well 
to those characters which can not be seen in the stamens. 



618 Validity of the Doctrine of Mutation. 

I shall not pursue this train of thought further; but 
this much seems to be clear, that germinal variations may 
be the results of changes which have already taken place 




Fig. 137. Green Dahlia. A branch whose terminal inflores- 
cence b as well as the lateral one b' have become green, 
as in the remaining parts of the plant, whilst a branch 
has arisen at a from an axillary bud, bearing double red 
inflorescences of normal structure and without a trace of 
virescence. a', flowering and a", a bud. See above, p. 
92, Fig. 14 (1902). See also pp. 628-629. 

in the pollen- and egg-cells ; and that these changes them- 
selves may have had their origin before the development 



Vegetative Mutations. 



619 



of the sexual cells, and perhaps even before the origin 
of the flower itself. In other words : 

Germinal variations may be regarded as a special case 
of vegetative mutations; and this possibility always re- 
mains open where the contrary cannot be proved. 

Concluding these discussions I propose now to adduce 
a series of facts in which mutations have occurred vege- 
tatively, that is to say, such facts as have hitherto been 
dealt with as bud-variations. It will be necessary to 




Fig. 138. Cryptomeria japonica spiraliter falcata, with an 
atavistic branch (see page 628). 

consider three groups of phenomena separately: first, 
vegetative segregation in hybrids; secondly, vegetative 
atavism in eversporting varieties, especially as exhibited 
by striped flowers (Part I, Plate I), and thirdly, the 
true vegetative mutations which are usually of an atavis- 
tic nature (Figs. 137, 138), but sometimes may happen to 
be of a progressive kind. 

Vegetative segregations in hybrids are rare phenom- 
ena ; but this may perhaps be due to the fact that in many 



620 Validity of the Doctrine of Mutation. 

instances of bud-variations the possibility of the plant 
in question being a hybrid has not been considered. A 
single case has fallen within my own experience ; this is 
a hybrid between Veronica longifolia and its variety V . 
I. alba. The flowers of this hybrid are blue, and it may 
easily be kept in cultivation for many years by means of 
vegetative propagation. Ever since 1889, when I ob- 
tained the first specimen, I have had many thousands of 
stems in flower, ariongst which I observed several cases 
of sectorial and of bud-variation, the last of them in the 
summer of 1902. The bud-variation sometimes occurred 
in the rhizome (1902) ; the whole shoot above the earth 
lacked the red pigment, both in its bark and its flowers, 
and so was easily recognizable before it bloomed. All the 
flowers were white, whilst those of the remaining shoots 
from the same rhizome were blue. Occasionally I found 
a raceme with white flowers arising as a lateral branch 
from a stem on which the rest of the flowers were blue 
(1894). The sectorial segregation is manifested in this 
hybrid in such a way that one side of the raceme had blue 
flowers, whilst those on the other were white. 1 The 
breadth of the longitudinal strip bearing white flowers 
is subject to variation ; it may be either a half of the whole 
raceme (as in 1891), or a quarter (1898), or even less 
(1894, 1895). The seeds of flowers which have thus 
become white by vegetative mutation produce white- 
flowered offspring, so far as I am able to judge from 
some preliminary experiments. 

As is well known, NAUDIN has crossed Datura Stra- 
monium with D. laeiis, and found amongst many hybrids 
with exclusively thorny fruits, three individuals which 
gave instances of vegetative segregation. These belonged 

1 Ber. d. d. bot. Ges., 1900, XVIII, p. 86. 



Vegetative Mutations. 621 

to the first generation and bore numerous fruits, the sur- 
face of which was partly thorny and partly smooth as 
in D. laevis. Sometimes one-half was smooth, but usually 
only a quarter or a smaller part. The valves without 
thorns had also reverted to the character of D. laevis in 
the fact that they were shorter than the thorned ones, 
and so did not fit into them properly. Fertilization had 
been left to insects, so that the results obtained by sowing 
the seeds would have been of no value. Such vegetative 
segregations appear, however, to be very rare in Datura. 
Other investigators do not seem to have obtained them; 
and I have myself frequently made extensive cultures of 
this hybrid in the hope of obtaining some, but as yet 
without success. 

The records of instances of hybrid segregation are 
scattered through the literature of this subject, so that 
it may be worth while to give the following selection. 
SAGERET obtained a hybrid between Brassica and Ra- 

/ 

phamis with two types of pods. 1 DOUNET-ADANSON ob- 
served on an intermediate hybrid between Abies Pinsapo 
X pectinata a branch with the characters of A. Pinsapo. 2 
FOCKE mentions a case of the cross Anagallis phoe- 
nicea X coerulea which had red flowers but exhibited 
half a petal with the blue color of the latter species. 3 
Vegetative segregations in the fruits of Citrus hybrids 
have frequently been described. 4 Flowers of different 
colors have been found occurring together on the same 

1 SAGERET, Ann. Sc. Nat., 1826. 

2 Bull. Soc. hot. Fr., 1899; ABBADO, L'ibridismo, loc. cit., p. 26. 

3 W. O. FOCKE, Nat. Ver. Bremen, 1887, p. 422. See also GART- 
NER, Die Bastarderzeugung, p. 309, and FOCKE, Pflansenmischlinge, 
p. 450. 

4 VERLOT, La variabilite, p. 14; KERNER, PAanzcnkben, II, pp. 559- 
560, etc. 



622 Validity of the Doctrine of Mutation. 

stock in hybrids of Helianthemum. 1 Hybrid peas may 
be partly green and partly yellow 2 and similar segrega- 
tions have been found by CORRENS and WEBBER on grains 
of hybrid maize. 

But the best known instance of a vegetative segrega- 
tion is furnished by Cytisus Adami (C. Laburnum X 
purpureus), which any one can observe in his garden 
or in parks. The hybrid is absolutely sterile, and all 
the specimens of it are grown from cuttings from one 
single individual. Whether the extraordinary tendency 
to segregate is peculiar to this hybrid as such, or to this 
particular individual, we cannot know. 3 The fact is, 
that this hybrid is intermediate between its two parents 
and besides this produces from time to time buds, of 
which some become strong branches of C. Laburnum 
with its large leaves and long racemes (Fig. 139L), 
whilst from others the delicate, slender and bushy 
branches of C. purpureus arise, bearing their fruits and 
flowers either singly or in small groups (Fig. 140 PV 

The current view is that C. Ad ami is a graft hybrid. 4 
There is, however, neither an historical nor a physiolog- 
ical justification for this view. 5 The original raiser of 
the plant, the Parisian gardener ADAM, seems himself 
to have thought that this form which he put on the 

1 FOCKE, Die Pftansenmischlinge, p. 473. where further instances 
will be found. See also BRAUX, Ver/iingung, p. 336; DARWIN, Ani- 
mals and Plants Under Domestication, etc. Similar facts are afforded 
by Hieracium, O.ralis. Chamacdorea etc. ; see F. HILDEBRAND, Jen. 
Zcitsehrift, Vol. XXIII, 1889, Plate XXV. 

2 F. WELDON, Biomctrika. I, 2, 1902. 

3 See the remarks relating to Datura on the foregoing pages. 

* Intracellulare Pangenesls (Ger. eel.), p. 206. 

5 T have given an historical account of Cytisus Adanii, in Dutch, 
in the Album der Natuur, 1894, Part 7, under the title Adam's Gouden 
Regen. The original source of the historical data is found in Annales 
de h Soeietc horticole de Paris, Vol. VTT, 1830. 



Vegetative Mutations. 



623 



market only as a variety of C. purpurcus, had arisen as 
a result of the grafting of C. purpurcus on C. Laburnum] 
but his contemporaries did not agree with this, and CA- 
MUZET maintains that he has seen the tree from which 




Fig. 139. Cytisus Adami. A, A', A"; B, a branch of C. 
Laburnum, L, L', L", with numerous racemes bearing 
ripe pods. 

ADAM had taken his buds for the purpose of making 
the grafts, and that this tree possessed all the characters 
of Cytisus Adami. The hypothesis that this form is a 
graft hybrid, originated with CASPARY (1865). No case 



624 Validity of the Doctrine of Mutation. 

of an undoubted graft hybrid has, however, as yet been 
produced experimentally and, consequently, the charac- 




Fig. 140. Cytisus Adaini. A, A', bearing at I a bunch of 
twigs of C. pur pur cits \ P, H, and I. 

ters which such hybrids would have if they existed are 
not known and can even hardly be guessed at. Therefore 



Vegetative Mutations. 



625 



no conclusion concerning this question can be drawn 
from the characters of C. Adanii. 

The view that it is an ordinary hybrid which was 
afterwards grafted on C. Laburnum seems to be much 
more probable. 1 

In other data relating to graft hybrids this view has 
long been proved to be incorrect, as in LINDEMUTH'S ex- 




Fig. 141. Ulmus campestris variegata with atavism by 
bud variation. A branch with larger green leaves has 
arisen at A. 

perfments with potatoes ; or the grafts may have been 
made on hybrid stems, as LAURENT suspects to be the 
case in the Ne flier de Bronvaux? or again, a graft of 

1 The same view is adopted by E. LAURENT, DC I* experimentation 

en horticulture, Brussels, 1902, p. 16. The literature dealing with 
Cytisus Adauii has been given so often that I need not go into further 
detail here. 

2 See the papers on this supposed hybrid between Mcspihis and 
Crataegus in Le Jar din and Journ. Roy. Hort. Soc., 1900, Vol. 24, 



626 Validity of the Doctrine of Mutation. 

a hybrid may have been made on a normal plant, as 
WILLE has told me he suspects to be the case in the sup- 
posed graft hybrid consisting of a pear worked on a 
white thorn stock. 1 

The reader who is interested in the direct influence 
of the stock on the grafted bud is referred to the recent 
exhaustive studies by L. DANIEL. 2 

By pruning Cytisus Ad ami, BEYERINCK obtained very 
important results on the vegetative segregation of hy- 
brids. He found that buds which, as a rule, are resting, 
but which can be made to develop by cutting off the 
higher branches, tend to produce the characters of C. 
Laburnum or of C. purpurcus, so that we have it in our 
power to multiply the number of such segregations at 
will. More than one hundred instances were obtained 
by him on some few trees. Sectorial segregations of 
buds also occurred, sometimes transforming a longitu- 
dinal half of a shoot into C. Laburnum, whilst the other 
half remained C. Adaiui." It is to be expected that the 
application of this principle to other cases will lead to the 
discovery of important facts. 

Of the numerous instances of bud-variations de- 
scribed in the literature of this subject, many are, with- 

p. 237. Also LAURENT, loc. cit., p. 16. For a general review *of graft 
hybrids see FRUWIRTH, Zi'ichtimg landwirthschaftlicher KulturpUan- 
zcn, p. 72 ff. 

1 N. WILLE, Mittheilungen d. biolog. Gesellschaft in Christiania, 
Biol. Centralblatt, 1896, Vol. XVI, No. 3, p. 126. Perhaps this may 
be Pyrus auricula ris (P. coinmunis X Sorbus Aria} or a related hy- 
brid. See DIPPEL, Handbuch dcr Laubholzkundc, III, p. 359. 

2 LuciEN DANIEL, La variation dans la grcffe ct Vhcrcditc dcs 
caracteres acquis, Ann. sc. nat. bot, 1899, VITIth ser., Vol. VTTT. 
pp. 1-226 and Plates I-X, and the subsequent publications of the 
same author. 

3 M. W. BEYERINCK, Kon. Akad. v. Wetensch., Amsterdam, Nov. 
1900. 



Vegetative Mutations. 



627 



Dut doubt, cases of such hybrid segregation, and therefore 
have no immediate bearing on the question of vegetative 
mutations. The same is true of the bud-variations of 
eversporting varieties (see Plate I, Antirrhinum) which 




Fig. 142. Rhus typhma. A leaf of an otherwise green bush 
which was almost yellow from a to b ; these leaflets have 
grown much smaller (on one side at a), Doom (1886) ; 
collected bv MRS. WEBER. 



have already been dealt with at sufficient length. More- 
over the graded differences between the various branches 
of a plant belonging to an eversporting variety are not 
instances of mutations, and, as a rule, do not affect the 



628 Validity of the Doctrine of Mutation. 

hereditary properties of the seeds which they produce; 
as, for instance, in Chclidoniuin inajus flore plcno (p. 
336). 

In the majority of cases a more detailed examina- 
tion is urgently needed, before the true nature of even 
the commonest bud-variations can be properly under- 
stood. This is particularly the case in variegated plants, 
amongst which every one is familiar with the phenom- 
enon, on shrubs and trees at any rate ; but even here the 
process has not yet been exhaustively studied. On the 
one hand, some of these cases consist of 'bud-atavism, 
whole branches of a variegated variety reverting to the 
normal type of the species in their color as well as in 
their secondary characters (Fig. 141). 1 On the other 
hand, sometimes halves of leaves become green, or occa- 
sional branches with usually slightly, but sometimes 
finely, variegated leaves arise on green individuals (Figs. 
142 and 143). On a large tree of Morns nigra in our gar- 
den the latter phenomenon occurs almost every year. 

It is not until all these and similar cases have been 
excluded that bud-variations may be regarded as true 
cases of A r egetative mutations. Even then we should 
require the proof that the deviating branches will re- 
produce their type from their seeds, after pure self-fer- 
tilization. In many cases, however, this is not possible 
because the bud-variations in 'question often bear no 
seeds, even when they occur regularly, as in Cephalo- 
ta.vus pcdnncnlata fasti giata (p. 109, Fig. 16) and in 
numerous other conifers, the bud-variations of which 
have been described by BEISSNER; as, for instance, in 
Cryptonieria japomca spiraliter falcata (Fig. 138, p. 619). 
Even from the green Dahlia I was, unfortunately, unable 

1 See above p. in and pp. 272-277. 



Vegetative Mutations. 



629 



to obtain any seed (Fig. 137, p. 618), because it flow- 
ered too late in the year. I have cultivated this plant, 
which was described and figured in the first section of 
this volume (p. 92), for many years by vegetative meth- 
ods, because it is perfectly sterile. In the summer of 
1902, however, it suddenly began to produce bud-varia- 




Fig. 143. Cat'pinus Betulus. At a, a partly variegated leaf 
on a tree which had otherwise only green leaves, Hilver- 
sura (1887). 

tions, distributed in considerable numbers over the various 
main stems ; they were apparently independent of one 
another, but seemed to arise in response to the same un- 
known external influences. The flowerheads of the ata- 
vistic branches were of the normal structure of the ordi- 
nary Dahlias, double, and with carmine red florets, at the 
tip of each of which \vas a white spot. From this we 



630 Validity of the Doctrine of Mutation. 

may conclude that this green Dahlia had arisen from the 
corresponding double-flowered variety. 

I do not propose to adduce any further instances; 
those which I have given show that varietal characters 
may disappear in a vegetative way, the original char- 
acters becoming active again. For such a mutation 
neither the formation of sexual cells nor fertilization 
is necessary. Therefore the possibility that seed-varia- 
tions may ultimately be derived from bud-variations can- 
not be denied ; but many more experimental data will have 
to be collected before a final judgment based on a suffi- 
cient foundation of facts can be given. One of the best 
methods is that which T have already mentioned, as 
adopted by BEYERINCK, of artificially inducing bud-varia- 
tions by pruning. 



III. THE MATERIAL VEHICLES OF THE 
HEREDITARY CHARACTERS. 

9. DARWIN'S PANGENESIS. 

The real meaning of the title of DARWIN'S book, 
On the Origin of Species by Means of Natural Selection, 
has often been largely misapprehended. In DARWIN'S 
mind the emphasis lay on the word "natural." He pleaded 
a natural origin of species against the accepted super- 
natural one. The whole object of his work was to show 
that the genetic relationships of animals and plants may 
be explained without invoking supernatural causes, and 
that their explanation by natural means is far more satis- 
factory and simple. For this conviction he succeeded 
in obtaining general credence, and thus laid a broad foun- 
dation for all future investigation in this sphere. 

The modern tendency, however, is to shift the em- 
phasis on the word selection and on the analogy between 
selection in nature and the artificial production of races 
in agriculture. In doing so it is often overlooked that 
half a century ago the science of the various forms of 
variability, and consequently of selection, was still in its 
infancy, and that we must not apply our present knowl- 
edge to the state of opinions which prevailed then. Xo 
distinction was drawn at that time, for instance, between 
mutability and variability; and it was DARWIN who first 



632 Vehicles of the Hereditary Characters. 

attempted in various cases to distinguish between these 
two types of variation. 

Even now this contrast does not yet find so clear an 
expression in th