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SPECIES AND VARIETIES
Their Origin by Mutation

Species and Varieties

Their Origin by
Mutation

Lectures Delivered at the University of

California

by

Hugo DeVries

Professor of Botany in the University of Amsterdam

Edited by
Daniel Trembly MacDougal

Director Department of Botanical Research, Carnegie Institution

of Washington

Second Edition,
Corrected and Revised

CHICAGO
The Open Court Publishing Company

LONDON
Kegan Paul, Trench, Trubner & Co., Ltd.

1906

Copyright 1904

BY

The Open Court Pub. Co.
Chicago

THE ORIGIN OF SPECIES

The origin of species is a natural phenomenon,

Lamarck.

The origin of species is an ohject of inquiry.

Darwin.

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

PREFACE BY THE AUTHOR

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

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

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

• •

Vll

viii Preface by the Author

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

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

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

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

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

Preface by the Author ix

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

Hugo de Vries.
Amsterdam, Octoher, 190 J^.

PREFACE BY THE EDITOE

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

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

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

xii Preface by the Editor

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

D. T. MacDougal.

New York Botanical Garden, Octoher, 190J^,

PREFACE TO THE SECOND EDITION.

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

The portrait which forms the frontispiece is a repro-
duction of a photograph taken by Professor F. E. Lloyd
and Dr. W. A. Cannon during the visit of Professor de
Vries at the Desert Botanical Laboratory of the Carnegie
Institution, at Tucson, Arizona, in June, 1904.

D. T. MacDougal.

December 15, 1905,

CONTENTS

A. Introduction.
Lecture Page

I. Descent : theories of evolution and methods

of investigation 1

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

B. Elementary Species.

II. Elementary species in nature ... 32
Viola tricolor, Draba verna. Primula
acaulis, and other examples. Euphorbia
Ipecacuanha. Prunus maritima. Taraxa-
cum and Hieracium.

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

IV. Selection of elementary species ... 92

Cereals. Le Couteur. Running out of
varieties. Rimpau and Risler, Aveiia fa-
tua. Meadows. Old Egyptian cereals.
Selection by the Romans. Shirreff. Hays.

C. Retrograde Varieties.

V. Characters of retrograde varieties . . 121
Seed varieties of pure, not hybrid origin.
Differences from elementary species.
Latent characters. Ray-florets of com-
xiii

XIV Contents

Lecture Page

posites. Progressive red varieties. Ap-
parent losses. Xanthium canadense.
Correlative variability. Laciniate leaves
and petals. Compound characters.

VI. Stability and real atavism .... 154
Constancy of retrograde varieties. Atav-
ism in Ribes sanguineum albidum, in
conifers, in Iris pallida. Seedlings of
Acacia. Eeversion by buds.

VII. Ordinary or false atavism .... 185
Vicinism or variation under the influence
of pollination by neighboring individ-
uals. Vicinism in nurseries. Purify-
ing new and old varieties. A case of
running out of corn in Germany.

VIII. Latent characters 216

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

IX. Crossing of species and varieties . . 247
Balanced and unbalanced, or species and
variety crosses. Constant hybrids of
Oenothera muricata and 0. biennis.
Aegilops, Medicago, brambles and other
instances.

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

Contents

XV

Lecture Page

erum Mephisto Danebrog. Mendel's laws.
Unit-characters.

D. EVERSPORTING VARIETIES.

XI. Striped flowers 309

Antirrhinum majus luteum rubro-striatum
with pedigree. Striped flowers, fruits
and radishes. Double stocks.
XII. " Five leaved " clover 340

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

Xm. Polycephalic poppies 369

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

XIV. Monstrosities 400

Inheritance of monstrosities. Half races
and middle races. Hereditary value of
atavists. Twisted stems and fascia-
tions. Middle races of trieotyls and
syncotyls. Selection by the hereditary
percentage among the offspring.

XV. Double adaptations 430

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

E. Mutations.

XVI. Origin of the peloric toad-flax . . . 459
Sudden and frequent origin in the wild
state. Origin in the experiment-garden.
Law of repeated mutations. Probable
origin of other pelories.

xvi Contents

Lecture Page

XVII. The production of double flowers . . 488
Sudden appearance of double flowers in
horticulture. Historical evidence. Ex-
perimental origin of Chrysanthemum
segetum plenum. Dependency upon
nourishment. Petalody of stamens.

XVIII. New species of Oenothera .... 516
Mutations of Oenothera lamarckiana in
the wild state near Hilversum. New
varieties of 0. laevifolia, O. brevistylis,
and O. nanella. New elementary species,
O. gigas, O. rubrinervis, albida, and ob-
longa. O. lata a pistillate form. In-
constancy of O. scintillans.

XIX. Experimental pedigree-cultures . . . 547
Pedigree of the mutative products of
Oenothera lamarckiana in the Botan-
ical Garden at Amsterdam. Laws of
mutability. Sudden and repeated leaps
from an unchanging main strain. Con-
stancy of the new forms. Mutations in
all directions.

XX. Origin of wild species and varieties . . 576
Problems to solve. Capsella heegeri.
Oenothera biennis cruciata. Epilobium
hirsutum cruciatum. Hibiscus Mos-
cheutos. Purple beech. Monophyllous
strawberries. Chances of success with
new mutations.

XXI. Mutations in horticulture .... 604
Chelidonium majus lacinatum. Dwarf and
spineless varieties. Laciniate leaves.
Monophyllous and broom-like varieties.

Contents

xvii

Lecture

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

XXII.

Systematic atavism
Reappearance of

Primula acaulis

crucifers. Zea

Equisetum, Dipsacus sylvestris

Tomatoes.

630

ancestral characters.

umbellata. Bracts of

Mays cryptosperma.

torsus.

XXIII.

Taxonomic anomalies 658

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

XXIV. Hypothesis of periodical mutations . . 686
Discovering mutable strains. Periods of
mutability and constancy. Periods of
mutations. Genealogical trees. Limited
life-time of the organic kingdom,

F. Fluctuations.

XXV. General laws of fluctuations .... 715
Fluctuating variability. Quetelet's law.
Individual and partial fluctuations.
Linear variability. Influence of nutri-
tion. Periodicity-curves.

XXVI. Asexual multiplication of extremes . . 742
Selection between species and intra-spe-
cific selection. Excluding individual

xviii Contents

Lecture Page

and embryonic variability. Sugar-canes.
Flowering cannas. Double lilacs. Other
instances. Burbank's method of selec-
tion.

XXVII. Inconstancy of improved races . . . 770
Larger variability in the case of propaga-
tion by seed. Progression and regres-
sion after a single selection, and after
repeated selections. Selection experi-
ments with corn. Advantages and effect
of repeated selection.

XXVIII. Artificial and natural selection . , . 798
Conclusions. Specific and intra-specific
selection. Natural selection in the field.
Acclimatization. Improvement-selection
of sugar-beets by various methods. Rye.
Hereditary percentage and centgener
power as marks by which intra-specific
selection may be guided.

Index 827

A. INTRODUCTION
Lecture I

DESCENT : THEORIES OF EVOLUTIOIT, AND METHODS

OF INVESTIGATION

Newton convinced his contemporaries that
natural laws rule the whole universe. Lyell
showed, by his principle of slow and gradual
evolution, that natural laws have reigned since
the beginning of time. To Darwin we owe the
almost universal acceptance of the theory of
descent.

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

Lamarck proposed the hypothesis of a com-
mon origin of all living beings and this ingenious
and thoroughly philosophical conception was
warmly welcomed by his partisans, but was not
widely accepted owing to lack of supporting evi-
dence. To Darwin was reserved the task of

1

frnPERTT imiuRr
N. C. State College

2 Descent

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

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

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

Darwin tried to show that the links which
bind species to genera are of the same nature
as those which determine the relationship of

Theories of Evolution 3

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

The origin of subspecies and varieties as
found in nature was not proved, but only gen-
erally recognized as evident. A broader
knowledge has brought about the same state of
opinion for greater groups of relationships.
Systematic affinities find their one possible ex-
planation by the aid of this principle; without
it, all similarity is only apparent and accidental.
Geographic and paleontologic facts, brought to-
gether by Darwin and others on a previously
unequalled scale, point clearly in the same di-
rection. The vast amount of evidence of all

4 Descent

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

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

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

Physiologic facts concerning the origin of

Theories of Evolution 5

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

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

6 Descent

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

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

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

Theories of Evolution 7

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

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

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

8 Descent

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

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

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

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

Theories of Evolution 9

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

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

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

10 Descent

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

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

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

In order to observe directly the birth of new
forms it is necessary, in the first i3lace, to be
fully clear concerning the question as to what
forms are to be expected to arise from others,
and before proceeding to a demonstration of the
origin of species, it is pertinent to raise the
question as to what constitutes a species.

Species is a word, which always has had a

Theories of Evolution 11

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

12 Descent

In order to meet this difficulty we must recog-
nize two sorts of species. The systematic spe-
cies are the practical units of the systematists
and florists, and all friends of wild nature
should do their utmost to preserve them as
Linnaeus has proposed them. These units how-
ever, are not really existing entities; they
have as little claim to be regarded as such
as genera and families. The real units are
the elementary si3ecies; their limits often ap-
parently overlap and can only in rare cases be
determined on the sole ground of field-obser-
vations. Pedigree-culture is the method re-
quired and any form which remains constant
and distinct from its allies in the garden is to
be considered as an elementary species.

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

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

Theories of Evolution 13

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

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

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

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

14 Descent

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

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

Theories of Evolution 15

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

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

16 Descent

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

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

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

Theories of Evolution 17

mentary species are far more rare, but I have
discovered in the great evening-primrose, or
Oenothera lamarckiana a strain which is pro-
ducing them yearly in the wild state as well as
in my garden. These observations and pedi-
gree-experiments will be dealt with at due
length in subsequent lectures.
'^^ Having proved the existence and importance
of mutations, it remains to inquire how far the
improvements may go which are due only to
fluctuating variability. As the term indicates,
this variability is fluctuating to and fro, oscil-
lating around an average type. It never fails
nor does it, under ordinary circumstances, de-
part far from the fixed average.

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

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

18 Descent

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

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

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

Theories of Evolution 19

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

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

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

20 Descent

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

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

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

Theories of Evolution 21

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

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

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

22 Descent

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

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

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

Theories of Evolution 23

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

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

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

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

24 . Descent

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

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

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

fmrmrf mutf

Theories of Evolution 25

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

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

26 Descent

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

Of course, crosses may lie in the proposed
line of work, and this is the third point to be
alluded to. They must be surrounded with the
same careful isolation and protection against
bees, as any other fertilizations. And not only
the seed-parent, but also the pollen must be
kept pure from all possible foreign admixtures.
A pure and accurately recorded ancestry is
thus to be considered as the most important
condition of success in experimental plant-
breeding. Next to this comes the gathering of
the seeds of each individual separately. Fifty
or sixty, and often more, bags of seeds are by no
means uncommon for a single experiment, and
in ordinary years the harvest of my garden is
preserved in over a thousand separate lots.

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

Theories of Evolution 27

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

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

28 Descent

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

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

Theories of Evolution 29

defined and as pure of type as might be ex-
j)ected of any species.

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

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

30 Descent

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

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

Theories of Evolution 31

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

B. ELEMENTARY SPECIES
Lecture II

ELEMENTARY SPECIES IN NATURE

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

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

32

Elementary Species in Nature 33

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

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

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

Based on the idea of a direct creation of all

34 Elementary Species

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

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

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

Elementary Species in Nature 35

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

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

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

36 Elementary Species

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

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

Elementary Species in Nature 37

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

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

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

38 Elementary Species

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

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

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

Elementary Species in Nature 39

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

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

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

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

40 Elementary Species

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

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

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

Elementary Species in Nature 41

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

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

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

42 Elementary Species

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

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

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

Elementary Species in Nature 43

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

44 Elementary Species

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

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

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

There seem to be very many local subspecies

Elementary Species in Nature 45

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

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

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

46 Elementary Species

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

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

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

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

Elementary Species in Nature 47

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

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

48 Elementary Species

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

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

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

J

Elementary Species in Nature 49

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

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

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

50 Elementary Species

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

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

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

Elementary Species in Nature 51

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

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

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

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

52 Elementary Species

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

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

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

Elementary Species in Nature 53

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

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

54 Elementary Species

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

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

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

Elementary Species in Nature 55

can only be recognized by comparative experi-
mental studies.

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

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

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

56 Elementary Species

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

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

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

Elementary Species in Nature 57

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

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

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

58 Elementary Species

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

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

Elementary Species in Nature 59

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

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

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

60 Elementary Species

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

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

Elementary Species in Nature 61

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

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

62 Elementary Species

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

Lecture III

ELEMENTARY SPECIES OF CULTIVATED PLANTS

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

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

63

64 Elementary Species

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

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

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

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

Cultivated Elementary Species 65

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

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

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

66 Elementary Species

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

Some authors assume that cultivation itself
might have been the principal cause of variabil-
ity, but it is not proved, nor even ]3robable, that
cultivated plants are intrinsically more variable
than their wild prototypes. Appearances in
this case are very deceptive. Of course widely
distributed plants are as a rule richer in subspe-
cies than forms with limited distribution, and
the former must have had a better chance to be
taken into cultivation than the latter. In many
cases, especially with the more recent cultivated
species, man has deliberately chosen variable
forms, because of their greater promise.
Thirdly, wide variability is the most efficient
means of acclimatization, and only species with
many elementary units would have offered
the adequate material for introduction into new
countries.

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

Cultivated Elementary Species 67

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

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

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

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

68 Elementary Species

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

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

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

Cultivated Elementary Species 69

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

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

70 Elementary Species

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

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

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

The varieties of the cultivated beets are com-

Cultivated Elementary Species 71

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

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

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

72 Elementary Species

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

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

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

Cultivated Elementary Species 73

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

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

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

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

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

74 Elementary Species

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

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

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

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

Cultivated Elementary Species 75

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

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

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

76 Elementary Species

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

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

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

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

Cultivated Elementary Species 77

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

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

78 Elementary Species

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

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

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

Cultivated Elementary Species 79

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

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

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

80 Elementary Species

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

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

Cultivated Elementary Species 81

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

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

82 Elementary Species

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

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

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

Cultivated Elementary Species 83

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

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

84 Elementary Species

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

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

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

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

Cultivated Elementarti Species 85

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

86 Elementary Species

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

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

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

Cultivated Elementary Species 87

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

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

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

We now have to inquire into the main ques-

88 Elementary Species

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

I

Cultivated Elementary Species 89

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

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

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

90 Elementary Species

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

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

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

Cultivated Elementary Species 91

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

f

Lecture IV

SELECTION OF ELEMENTARY SPECIES

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

92

Selection of Elementary Species 93

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

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

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

94 Elementary Species

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

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

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

Selection of Elementary Species 95

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

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

96 Elementary Species

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

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

Selection of Elementary Species 97

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

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

The discoverv of Lagasca and Le Couteur was

98 Elementary Species

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

Selection of Elementary Species 99

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

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

100 Elementary Species

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

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

The wild oat, Avena fatua, is very common in

JL

Selection of Elementary Species 101

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

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

102 Elementary Species

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

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

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

Selection of Elementary Species 103

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

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

104 Elementary Species

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

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

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

Selection of Elementary Species 105

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

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

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

106 Elementary Species

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

Vidi lecta diu, et multo spectata labore
Degenerare tamen, ni vis humana quotannis
Maxima quaeque manu legeret.
(The chosen seed, through years and labor

improved,
Was seen to run back, unless yearly
Man selected by hand the largest and fullest
of ears.)

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

Selection of Elementary Species 107

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

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

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

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

108 Elementary Species

*

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

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

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

Selection of Elementary Species 109

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

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

110 Elementary Species

appeared some years later at the International |

Exhibition of London in 1862. Hence, when-
ever Darwin speaks of selection, Shirreif 's use i
of the word mav as well be meant as that of
Vilmorin.

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

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

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

Selection of Elementary Species 111

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

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

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

112 Elementary Species

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

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

Selection of Elementary Species 113

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

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

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

114 Elementary Species

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

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

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

Selection of Elementary Species 115

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

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

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

116 Elementary Species

Some years later Patrick Sliirreff described his
experiments and results in a paper entitled,
^^ On the improvement of cereals," but the de-
scriptions are very short, and give few details
of systematic value. The leading principle,
however, is clearly indicated, and anyone who
studies with care his method of working, may
confidently attempt to improve the varieties of
his own locality in the same way.

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

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

Selection of Elementary Species 117

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

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

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

118 Elementary Species

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

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

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

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

Selection of Elementary Species 119

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

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

120 Elementary Species

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

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

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

C. RETROGRADE VARIETIES
Lecture V

CHARACTERS OF RETROGRADE VARIETIES

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

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

121

122 Retrograde Varieties

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

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

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

Retrograde Varieties 123

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

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

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

124 Retrograde Varieties

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

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

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

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

Retrograde Varieties 125

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

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

126 Retrograde Varieties

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

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

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

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

Retrograde Varieties 127

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

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

128 Retrograde Varieties

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

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

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

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

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

Retrograde Varieties 129

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

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

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

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

130 Retrograde Varieties

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

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

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

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

Retrograde Varieties 131

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

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

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

132 Retrograde Varieties

In systematic works the positive ones are as a
rule called '* radiate," and the negative ones
** discoid." Discoid forms of the ordinarj^
camomile, of the daisy, of some asters {Aster
Tripolmm), and of some centauries have been
described. Radiate forms have been observed
in the tansy {Tanacetum vulgar e), the common
horse-weed or Canada fleabane {Erigeron cana-
densis) and the common groundsel (Senecio
vidgaris). Taken broadly the negative varie-
ties seem to be somewhat more numerous than
the positive ones, but it is very difficult to come
to a definite conclusion on this point. .

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

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

Retrograde Varieties 133

from time to time in sunny and sandy localities.
I have isolated it and cultivated it during a
series of years and during many generations.
It is quite true to its character, but the degree
of its coloring fluctuates between pink and white
and is extremely variable. Perhaps it can be
considered as an inconstant variety. A red-
flowered form of the common Begonia semper-
florens is cultivated under the name of ^' Ver-
non," the white hawthorn (Crataegus Oxya-
cantha) is often seen with red flowers, and a
pink-flowered variety of the '^ Silverchain " or
'' Bastard acacia " (Robinia Pseud-Acacia) is
not rarely cultivated. The '* Crown " variety
of the yellow wall-flower and the black varieties,
are also to be considered as positive color-
variations, the black being due in the latter
cases to a very great amount of the red pigment.
Among fruits there are also some positive
red varieties of greenish or yellowish species, as
for instance the red gooseberry (Ribes Grossu-
laria) and the red oranges. The red hue is far
more common in leaves, as seen among herbs, in
cultivated varieties of Coleus and in the brown-
leaved form of the ordinary white clover, among
trees and shrubs in the hazelnut (Corylus), the
beach '(Fagus), the birch (Bettda), the barberry
(Berberis) and many others. But though most
of these forms are very ornamental and abun-

134 Retrograde Varieties

dant in parks and gardens, little is as yet known
concerning the origin of their varietal attributes
and their constancy, when propagated by seeds.
Besides the ray-florets and the colors, there are
of course a great many other characters in
which varieties may differ from their species.
In most of the cases it is easy to discern
whether the new character is a positive or a
negative one. And it is not at all necessary to
scrutinize very narrowly the list of forms to be-
come convinced that the negative form is the
one which prevails nearly everywhere, and that
positive aberrations are in a general sense so
rare that they might even be taken for exce]3-
tions to the rule.

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

Retrograde Varieties 135

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

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

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

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

136 Retrograde Varieties

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

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

Retrograde Varieties 137

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

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

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

138 Retrograde Varieties

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

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

Retrograde Varieties 139

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

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

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

140 Retrograde Varieties

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

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

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

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

Retrograde Varieties 141

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

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

142 Retrograde Varieties

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

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

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

f

Retrograde Varieties 143

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

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

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

144 Retrograde Varieties

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

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

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

This conception of a physiologic unit as the

Retrograde Varieties 145

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

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

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

146 Retrograde Varieties

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

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

Retrograde Varieties 147

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

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

148 Retrograde Varieties

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

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

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

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

Retrograde Varieties 149

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

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

150 Retrograde Varieties

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

Retrograde Varieties 151

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

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

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

152 Retrograde Varieties

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

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

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

Retrograde Varieties 153

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

Lecture VI

STABILITY AND REAL ATAVISM

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

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

154

stability and Real Atavism 155

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

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

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

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

156 Retrograde Varieties

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

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

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

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

stability and Real Atavism 157

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

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

158 Retrograde Varieties

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

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

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

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

stability and Real Atavism 159

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

160 Retrograde Varieties

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

stability and Real Atavism 161

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

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

162 Retrograde Varieties

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

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

stability and Real Atavism 163

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

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

164 Retrograde Varieties

known as " peloria/' or regular form of a
normally symmetric type ; they are large and ir-
regular on the stems and the vigorous branches
but slender and quinate on the weaker twigs.
Their beauty and highly interesting anomalous
character has been the cause of their being de-
scribed many times, and nearly always as a
novelty; they have been recently re-introduced
into horticulture as such, though they were al-
ready cultivated before the middle of the last
century. About that time very good descrip-
tions with plates were published in the journal
^' Flora '' by Vrolik, but afterwards they seem
to have been forgotten. The peloric variety
of the foxglove always comes true from seed,
though in the strict sense of the word which
we have chosen for our discussion, it does not
seem to be a constant and pure variety.

It is very interesting to compare old botani-
cal books, or even old drawings and engravings
containing figures of anomalous plants. The
celebrated Pinacothec of Munich contains an
old picture by Holbein (1495-1543) representing
St. Sebastian in a flower-garden. Of the plants
many are clearly recognizable, and among
others there is one of the *^ one-leaved " variety
of the strawberry, which may still be met
with in botanical gardens. In the year
1671 a Dutch botanist, Abraham Hunting pub-

Stability and Real Atavism 165

lished a large volume on garden-plants, con-
taining a great number of very good engrav-
ings. Most of them of course show normal
plants, but intermixed with these are varieties,
that are still in cultivation and therefore must
be at least two centuries old. Others, though
not figured, are easily recognized by their names
and descriptions. The cockscomb is the most
widely known, but many white or double flow-
ered varieties were already cultivated at that
time. The striped Jalappa, the crested Sedum^
the fasciated crown-imperial, white strawber-
ries, red gooseberries and many others were
known to Hunting.

Some varieties are as old as culture itself,
and it is generally known that the Eomans cul-
tivated the white form of the opium-poppy and
used the foliage of the red variety of the sugar-
beet as a vegetable.

In our time flowers and fruits are changing
nearly as rapidly as the fancies and tastes of
men. Every year new forms are introduced
and usurp the place of older ones. Many are
soon forgotten. But if we look at old country
gardens, a goodly number of fine and valued old
sorts are still to be found. It would be worth
while to make special collections of living plants
of old varieties, which surely would be a good
and interesting work and bring about a convic-

166 Retrograde Varieties

tion of the stability of pure strainis. Coming
now to the other side of the question, we may
consider those cases of reversion which have
been recorded from time to time, and which al-
ways have been considered as direct proofs of
the varietal character of the reverting form.
Reversion means the falling back or returning
to another type, and the word itself expresses
the idea that this latter type is the form from
which the variety has arisen.

Some instances of atavism of this kind are
well known, as they are often repeated by in-
dividuals that are multii^lied by buds or by
grafting. Before looking attentively into the
different features of the many cases of rare
reversions it will be advisable to quote a few
examples.

The flowering-currant of the Pacific Coast
or North American scarlet ribes {Ribes san-
giiineum), a very popular ornamental shrub,
will serve as a good example. It is prized be-
cause of its brilliant red racemes of flowers
which blossom early in the spring, before the ap-
pearance of the leaves. From this species a
white form has arisen, which is an old and wide-
ly cultivated one, but not so highly prized be-
cause of its pale flowers. These are not of a
pure white, but have retained a faint reddish
hue. The young twigs and the stalks of the

Stahility and^ Real Atavism 167

leaves afford an instance of correlated variabil-
ity since in the species the red color shows it-
self clearly mixed with the green, while in the
variety this tinge is wholly wanting.

Occasionally this white-flowered currant re-
verts back to the original red type and the re-
version takes place in the bud. One or two
buds on a shrub bearing perhaps a thousand
bunches of white flowers produce twigs and
leaves in which the red pigment is noticeable
and the flowers of which become brightly col-
ored. If such a twig is left on the shrub, it may
grow further, ramify and evolve into a larger
group of branches. All of them keep true to
the old type. Once reverted, the branches re-
main forever atavistic. It is a very curious
sight, these small groups of red branches among
the many white ones. And for this reason at-
tention is often called to it, and more than once
I myself have had the opportunity of noting its
peculiarities. It seems quite certain that by
planting such shrubs in a garden, we may rely
upon seeing sooner or later some new buds re-
verting to the prototype.

Very little attention seems hitherto to have
been given to this curious phenomenon, though
in many respects it deserves a closer investiga-
tion. The variety is said to have originated
from seed in Scotland, many years ago, and

168 Retrograde Varieties

seems to be propagated only by cuttings or by
grafting. If this is true, all specimens must be
considered as constituting together only one
individual, notwithstanding their wide distribu-
tion in the gardens and parks of so many coun-
tries. This induces me to suppose, that the
tendency to reversion is not a character of the
variety as such, but rather a peculiarity of this
one individual. In other words it seems prob-
able that when the whitish variety arises a sec-
ond time from the red species, it is not at all
necessary that it should exhibit this same tend-
ency to revert. Or to put it still in another
way, I think that we may suppose that a variety,
which might be produced repeatedly from the
same original stock, would only in rare indi-
viduals have a tendency to revert, and in most
cases would be as absolutely constant as the
species itself.

Such a conception would give us a distinct
insight into the cause of the rarity of these
reversions. Many varieties of shrubs and trees
have originated but once or twice. Most of
them must therefore, if our supposition is cor-
rect, be expected to be stable and only a few
may be expected to be liable to reversions.

Among the conifers many very good cases of
reversions by buds are to be found in gardens
and glasshouses. They behave exactly like the
whitish currant. But as the varietal characters

Stability and Real Atavism 169

are chiefly found in the foliage and in the
branches, these aberrations are to be seen on
the plants during the whole year. Moreover
they are in some cases much more numerous
than in the first instance. The Cryptomeria of
Japan has a variety with twigs resembling
ropes. This is not caused by a twisting, but
only by a curvature of the needles in such a way
that they seem to grow in spiral lines around
the twigs. This variety often reverts to the
type with widely spread, straight needles. And
on many a specimen four, five, or more reverted
branches may be seen on different parts of the
same shrub. Still more widely cultivated is the
shrub called Cephalotaxus pedunculata fasti-
giata, and more commonly known under its old
name of Podocarpus koraiana. It is the broom-
like variety of a species, nearly allied to the
common American and European species of
yew, (Taxus minor and T. haccata). It is a low
shrub, with broadly linear leaves of a clear
green. In the species the leaves are arranged in
two rows, one to the left and one to the right
of the horizontally growing and widely spread-
ing branches. In the variety the branches are
erect and the leaves inserted on all sides.
When sporting, it returns to the bilateral pro-
totype and flat wings of fan-shaped twigs are
produced laterally on its dense broom-like tufts.

170 Retrograde Varieties

Wherever this variety is cultivated the same re-
version may be seen; it is produced abundant-
ly, and even under seemingly normal circum-
stances. But as in the case of the Ribes all the
specimens are derived by buds from a single
original jDlant. The variety was introduced
from Japan about the year 1860, but is prob-
ably much older. Nothing is known as to its
real origin. It never bears flowers or fruits.
It is curious to note that the analogous variety
of the European yew, Taxus baccata fastigiata,
though much more commonly cultivated than
the Ceplialotaxus, never reverts, at least as far
as I have been able to ascertain. This clearly
corroborates the explanation given above.

After considering these rare instances of
more widely known reversions, we may now ex-
amine the question of atavism from a broader
point of view. But in doing so it should once
more be remembered, that all cases of hybrid-
ism and also all varieties sporting annually or
frequently, are to be wholly excluded. Only the
very rare occurrence of instances of atavism in
varieties that are for the rest known to be ab-
solutely constant, is to be considered.

Atavism or reversion is the falling back to a
prototype. But what is a prototype? We may
take the word in a physiologic or in a systematic
sense. Physiologically the signification is a

stability and Real Atavism 171

very narrowly restricted one, and includes only
those ancestors from which a form is known to
have been derived. But such evidence is of
course historic. If a variety has been observed
to spring from a definite species, and if the cir-
cumstances have been sufficiently ascertained
not to leave the slightest doubt as to its pure
origin, and if moreover all the evidence has
been duly recorded, we may say that the origin
of the variety is historically known. In most
cases we must be content with the testimony,
given somewhat later, and recorded after the
new variety had the opportunity of showing
its greater merits.

If it now happens that such a variety of re-
corded origin should occasionally revert to its
parent-species, we have all we can wish for, in
the way of a thoroughly proved case of atavism.
But such instances are very rare, as the birth
of most varieties has only been very imper-
fectly controlled.

Next to this comes the systematic relation of
a variety to its species. The historic origin of
the variety may be obscure, or may simply be
forgotten. But the distinguishing marks are
of the order described in our last lecture, either
in the positive or in the negative direction, and
on this ground the rarer form is considered to
be a variety of the more wide-spread one. If

172 Retrograde Varieties

now the presumed variety sports and runs over
to the presumed type, the probability of the
supposed relation is evidently enhanced. But
it is manifest that the explanation rests upon
the results of comparative studies, and not
upon direct observations of the phenomena
themselves.

The nearer the relations between the two
types in question, the less exposed to doubt and
criticism are the conclusions. But the domain
of atavism is not restricted to the cases de-
scribed. Quite on the contrary the facts that
strike us most forcibly as being reversions are
those that are apt to give us an insight into the
systematic affinity of a higher degree. We are
disposed to make use of them in our attempts
to perfect the natural system and to remould
it in such a way as to become a pedigree of the
related groups. Such cases of atavism no
doubt occur, but the anomalies referred to them
must be interpreted merely on the ground of our
assumptions as to the relative places in the sys-
tem to be assigned to the different forms.

Though such instances cannot be considered
as belonging strictly to the subject we are deal-
ing with, I think it may be as well to give an ex-
ample, especially as it affords an occasion for
referring to the highly important researches of
Heinricher on the variability and atavistic

stability and Real Atavism 173

tendencies of the pale blue flag or Iris pallida.
The flowers of the blue flags have a perianth
of six segments united below into a tube. The
three outer parts are dilated and spreading, or
reflexed, while the three inner usually stand
erect, but in most species are broad and colored
like the outer ones. Corresponding to the outer
perianth-segments are the three stamens and
the three petal-like divisions of the style, each
bearing a transverse stigma immediately above
the anther. They are pollinated by humble-bees,
and in some instances by flies of the genus
Rhingia, which search for the honey, brush the
pollen out of the anthers and afterwards de-
posit it on the stigma. According to systematic
views of the monocotyledons the original proto-
type of the genus Iris must have had a whorl of
six equal, or nearly equal perianth-segments
and six stamens, such as are now seen in the
more primitive types of the family of the lilies,
as for instance in the lilies themselves, the
tulips, hyacinths and others. As to the
perianth this view is supported by the
existence of one species, the Iris falcifolia,
the perianth of which consists of six equal
parts. But species with six stamens are
wholly lacking. Heinricher however, in culti-
vating some anomalous forms of Iris pallida,
succeeded in filling out this gap and in produc-

174 Retrograde Varieties

ing flowers with a uniform perianth and six
stamens, recalling thereby the supposed ances-
tral type. The way in which he got these was
as follows: he started from some slight devia-
tions observed in the flowers of the pale spe-
cies, sowed the seeds in large numbers and se-
lected from the seedlings only those, which
clearly showed anomalies in the expected
atavistic direction. By repeating this during
several generations he at last reached his goal
and was able to give reality to the prototype,
which formerly was only a hypothetical one.
The Iris kaempferi, a large-flowered Japanese
species much cultivated in gardens, is very vari-
able in the number of the different parts of its
flowers, and may in some instances be seen even
with six stamens. If studied in the same way as
Heinricher's iris, it no doubt will yield highly
interesting and confirmatory results.

Many other instances of such systematic atav-
ism could be given, and every botanist can easily
add some from memory. Many anomalies, oc-
curring spontaneously, are evidently due to the
same principle, but it would take too long to
describe them.

Reversion may occur either by buds or by
seeds. It is highly probable that it occurs more
readily by sexual than by asexual propagation.
But if we restrict the discussion to the limits

stability and Real Atavism 175

hitherto observed, seed-reversions must be said
to be extremely rare. Or rather cases which
are sufficiently certain to be relied upon, are
very rare, and perhaps wholly lacking. Most
of the instances, recorded by various writers,
are open to question. Doubts exist as to the
purity of the seeds and the possibility of some
unobserved cross disturbing the results.

In the next lecture we shall deal in general
with the ordinary causes and results of such
crosses. We shall then see that they are so
common and occur so regularly under ordinary
circumstances that we can never relv on the
absolute purity of any seeds, if the impossibility
of an occasional cross has not been wholly ex-
cluded, either by the circumstances themselves,
or by experimental precautions taken during
the flowering period.

For these reasons cases of atavism given
without recording the circumstances, or the pre-
cautions that guarantee the purity of the fertili-
zation, should always be disregarded. And
moreover another proof should always be de-
manded. The parent which yielded the seeds
might be itself a hybrid and liable to reversions
by the ordinary laws of the splitting up of hy-
brids. Such cases should likewise be discarded,
since they bring in confusing elements. If we
review the long list of recorded cases by these

176 Retrograde Varieties

strict methods of criticism very few instances
will be found that satisfy legitimate demands.
On this ground it is by far safer in the present
state of our knowledge, to accept bud-variations
only as direct proofs of true atavism. And
even these may not always be relied on, as some
hybrids are liable to split up in a vegetative
way, and in doing so to give rise to bud-varia-
tions that are in many respects apparently sim-
ilar to cases of atavism. But fortunately such
instances are as yet very rare.

After this discussion it would be bold indeed
to give instances of seed-atavism, and I believe
that it will be better to refrain wholly from do-
ing so.

Many instances of so-called atavism are of
purely morphologic nature. The most interest-
ing cases are those furnished by the forms
which some plants bear only while young, and
which evidently connect them with allied species,
in which the same features may be seen in the
adult state. Some species of the genus Acacia
bear bipinnate leaves, while others have no
leaves at all, but bear broadened and flattened
petioles instead. The second type is presumed
to be descended from the first by the loss
of the leaflets and the modification of the stalks
into flat and simple phyllodes. But many of
them are liable to recall this primitive form

Stability and Real Atavism 111

when very young, in the first two or three, or
sometimes in eight or ten primary leaves.
These leaves are small because of the weakness
of the young plant and therefore often more or
less reduced in structure. But they are usually
strictly bipinnate and thereby give testimony
as to their descent from species which bear such
leaves throughout their life.

Other similar cases could be given, but this
will suffice. They once more show how neces-
sary it is to separate the different cases, thrown
together until now, under this general name of
atavism. It would be far better to give them
all special names, and as long as these are not
available we must be cautious not to be mis-
guided by the name, and especially not to con-
fuse different phenomena with one another, be-
cause at the present time they bear the same
names.

Taking into consideration the relatively nu-
merous restrictions resulting from this discus-
sion, we will now make a hasty survey of some
of the more notable and generally acknowledged
cases of atavism by bud-propagation. But it
should be repeated once more that most of the
highly cultivated plants, grown as vegetables or
for their fruit or flowers, have so many crosses
in their ancestry, that it seems better to exclude
them from all considerations, in which purity of

1^8 Retrograde Varieties

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

stability and Real Atavism 179

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

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

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

180 Retrograde Varieties

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

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

stability and Real Atavism 181

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

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

182 Retrograde Varieties

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

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

stability and Real Atavism 183

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

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

Many questions in scientific research can only

184 Retrograde Varieties

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

Lecture VII

FALSE ATAVISM OR VICINISM

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

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

185

186 Retrograde Varieties

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

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

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

False Atavism 187

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

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

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

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

188 Retrograde Varieties

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

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

False Atavism 189

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

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

190 Retrograde Varieties

yielding new, and very often, valuable varieties.
But it is manifest that this form of variation
is of quite another nature from the variations
of pure races. Many hybrid varieties are quite
constant, and remain true to their type if no
further crosses are made ; many others are arti-
ficially propagated only in a vegetative way,
and for this reason are always found true.
Hybrid varieties as a rule were formerly con-
fused with pure varieties, and in many in-
stances our knowledge as to their origin is quite
insufficient for sharp distinctions. To every
student of nature it is obvious, that crossing
and pure variability are wholly distinct groups
of phenomena, which should never be treated
under the same head, or under the same name.
Leaving aside polymorphy, we may now dis-
cuss those cases of variability, in which the
changes themselves, and not only their final
results play a part. Of such changes two types
exist. First, the ever-recurring variability,
never absent in any large group of individuals,
and determining the differences which are al-
ways to be seen between parents and their
children, or between the children themselves.
This type is commonly called '^ individual
variabilitv " and since this term also has still
other meanings, it has of late become customary
to use instead the term ^' fluctuating varia-

False Atavism 191

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

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

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

192 Retrograde Varieties

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

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

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

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

False Atavism 193

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

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

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

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

194 Retrograde Varieties

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

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

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

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

False Atavism 195

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

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

196 Retrograde Varieties

taining as much as 20^ of red-flowered speci-
mens.

Many fine varieties are recorded to come true
from seed, as in the case of the holly with
yellow fruits, tested by Darwin. Others have
been found untrue to a relatively high degree,
as is notorious in the case of the purple beech.
Seeds of the laciniated beech gave only 10^
of laciniated plants in experiments made by
Strasburger; seeds of the monophyllous aca-
cia, Rohinia Pseud-Acacia monopJiylla, were
found to be true in only 30^ of the seedlings.
Weeping ashes often revert to the upright type,
red May-thorns (Crataegus) sometimes revert
nearly entirely to the white species and the
yellow cornel berry is recorded to have reverted
in the same way to the red berries of the Cor-
nus Mas,

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

False Atavism 197

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

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

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

198 Retrograde Varieties

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

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

False Atavism 199

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

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

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

200 Retrograde Varieties

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

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

False Atavism 201

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

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

True hybrids between species may arise in

202 Retrograde Varieties

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

False Atavism 203

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

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

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

204 Retrograde Varieties

at its base. The two lateral lobes are narrower,
sometimes linear, and are often prolonged into
an awn, which is generally turned away from
the center of the spike. The central lobe some-
times bears two florets at its base, although but
one is usually present and it may be incomplete.
I might give one more instance from my own
experience. A variety of the evening -primrose
with small linear petals was once found by one
of my sons growing wild near Amsterdam. It
was represented by only one individual, flower-
ing among a great many of the ordinary type
with broad petals. But the evening-primroses
open their anthers in the morning, fertilize
themselves during the day, and only display
their beautiful flowers in the evening, after the
pollination has been accomplished. They then
allure evening moths, such as Agrotis and
Plusia, by their bright color, their sweet honey-
smell and their nectar. Since the fertiliza-
tion is accomplished many hours before opening,
crosses are effected only in rare instances, and
the seeds commonly remain true to the parent-
type. The seeds of this one plant, when sown
separately in my garden, produced exclusively
flowers with the small linear petals of their
parent. Although I had a hundred individuals
bearing many thousands of flowers, there was
not an instance of reversion. And such would

False Atavism 205

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

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

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

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

206 Retrograde Varieties

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

False Atavism 207

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

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

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

208 Retrograde Varieties

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

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

False Atavism 209

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

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

210 Retrograde Varieties

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

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

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

False Atavism 211

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

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

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

212 Retrograde Varieties

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

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

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

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

False Atavism 213

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

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

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

214 Retrograde Varieties

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

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

False Atavism 215

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

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

Lecture VIII

LATENT CHAEACTERS

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

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

216

Latent Characters 217

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

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

218 Retrograde Varieties

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

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

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

Latent Characters 219

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

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

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

220 Retrograde Varieties

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

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

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

For this purpose we must take a somewhat

Latent Characters 221

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

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

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

222 Retrograde Varieties

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

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

Latent Characters 223

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

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

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

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

224 Retrograde Varieties

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

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

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

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

Latent Characters 225

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

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

226 Retrograde Varieties

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

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

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

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

Latent Characters 227

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

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

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

228 Retrograde Varieties

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

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

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

Latent Characters 229

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

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

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

230 Retrograde Varieties

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

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

Latent Characters 231

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

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

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

Our second point was the incomplete loss of

232 Retrograde Varieties

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

Latent Characters 233

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

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

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

234 Retrograde Varieties

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

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

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

Latent Characters 235

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

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

236 Retrograde Varieties

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

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

Latent Characters 237

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

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

238 Retrograde Varieties

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

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

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

Latent Characters 239

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

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

240 Retrograde Varieties

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

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

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

Latent Characters 241

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

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

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

The yellow fails in many highly developed

242 Retrograde Varieties

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

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

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

«

tant families. Each of them is quite evident
and easily understood on the principle of
latency.

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

Latent Characters 243

ferent countries from the same species. The
repetition obviously indicates a common inter-
nal cause. The white varieties of blue- and red-
flowered plants occur in the wild state so often,
and in most of the instances in so few in-
dividuals that a common pedigree is absolutely
improbable. In horticulture this tendency is
widely and vexatiously known, since the repeti-
tion of an old variety does not bring any ad-
vantage to the breeder. The old name of
^^ conquests/' given by the breeders of hya-
cinths, tulips and other flower-bulbs to any
novelty, in disregard of the common occurrence
of repetitions, is an indication of the same ex-
perience in the repeated appearance of certain
varieties.

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

244 Retrograde Varieties

brambles and some garden-varieties of the tur-
nip {Br as sic a).

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

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

The last of the four rules above mentioned is

Latent Characters 245

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

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

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

246 Retrograde Varieties

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

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

•"> ?;"'4'Jfi '■?/

Lecture IX

CROSSES OF SPECIES AND VARIETIES

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

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

247

248 Retrograde Varieties

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

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

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

Unbalanced Crosses 249

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

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

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

250 Retrograde Varieties

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

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

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

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

Unbalanced Crosses 251

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

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

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

We must alwa5^s distinguish the qualities,
which are the same in both parents, from those
that constitute the differentiating marks in
every single cross. In respect to the first

252 Retrograde Varieties

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

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

Unbalanced Crosses 253

quirement of some new character. The deriva-
tive species has one unit more than the parent.
All other qualities are the same as in the par-
ent. Whenever such a derivative is combined
with its parent the result for these qualities
will be exactlv as in a normal fertilization. I71
such ordinary cases it is obvious that each char-
acter of the pollen-parent is combined with the
same character of the pistil-parent. There may
be slight individual differences, but each unit-
character will become opposed to, and united
with, the same unit-character in the other par-
ent. In the offspring the units will thus
be paired, each pair consisting of two equivalent
units. As to their character the units of each
single pair are the same, only they may exhibit
slight differences as to the degree of develop-
ment of this character.

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

254 Retrograde Varieties

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

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

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

Unbalanced Crosses 255

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

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

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

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

256 Retrograde Varieties

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

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

Unbalanced Crosses 257

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

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

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

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

258 Retrograde Varieties

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

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

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

Unbalanced Crosses 259

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

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

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

260 Retrograde Varieties

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

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

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

Unbalanced Crosses 261

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

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

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

262 Retrograde Varieties

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

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

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

I )/••"»

Unbalanced Crosses 26

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

264 Retrograde Varieties

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

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

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

Unbalanced Crosses 265

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

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

266

Retrograde Varieties

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

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

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

Unbalanced Crosses 267

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

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

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

268

Retrograde Varieties

is a hybrid sundew between D. anglica and D,
rotundifolia. Primula variabilis is a hybrid
between the two common primroses, P. offici-
nalis and P. grandiflora. The willow-herb
(Epilobium)j the self-heal (Brunella) and the
yellow pond-lilies (Nuphar) afford other in-
stances of constant wild hybrids.

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

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

Unbalanced Crosses 269

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

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

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

270

Retrograde Varieties

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

Among the species of Ribes or currant, which
are cultivated in our gardens, the most beauti-
ful are without doubt the Californian and the
Missouri currant, or Ribes sanguineum and R.
aureum. A third form, often met with, is ^' Gor-
don's currant," which is considered to be a
hybrid between the two. It has some peculiar-
ities of both i3arents. The leaves have the gen-
eral form of the Californian parent, but are as
smooth as the Missouri species. The racemes
or flower-spikes are densely flowered as in the
red species, but the flowers themselves are of a
yellow tinge, with only a flesh-red hue on the
outer side of the calyx. It grows vigorously
and is easily multiplied by cuttings, but it never
bears any fruit. Whether it would be constant,
if fertile, is therefore impossible to decide.

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

Unhalanced Crosses 271

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

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

272 Retrograde Varieties

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

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

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

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

Unbalanced Crosses 273

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

274 Retrograde Varieties

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

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

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

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

Unbalanced Crosses 275

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

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

Lecture X

MENDEL ^S LAW OF BALANCED CROSSES

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

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

In a former lecture we have dealt with the
qualities which must be considered as being due
to the acquisition of new characters. If we

276

Balanced Crosses 277

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

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

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

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

278

Retrograde Varieties

built up of one active and one dormant unit.

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

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

Balanced Crosses 27[)

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

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

<

ists, such as Koelreuter and Gaertner affords
numerous instances.

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

280

Retrograde Varieties

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

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

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

Balanced Crosses 281

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

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

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

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

282

Retrograde Varieties

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

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

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

Balanced Crosses 283

for instance, the dark " Mephisto " with the
white-hearted '' Danehrog/' the hybrid shows
the active character of the dark pattern.

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

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

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

284 Retrograde Varieties

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

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

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

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

Balanced Crosses 285

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

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

286 Retrograde Varieties

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

Segregation seems to be a very difficult pro-
cess in the vegetative way, but it must be very
easy in sexual reproduction, indeed so easy as
to show itself in nearly every single instance.

Leaving this first generation, the original
hybrids, we now come to a discussion of their
offspring. Hybrids should be fertilized either
by their own pollen, or by that of other individ-
uals born from the same cross. Only in this
case can the offspring be considered as a means
of arriving at a decision as to the internal na-
ture of the hybrids themselves. Breeders gen-
erally prefer to fertilize hybrids with the pollen
of their parents. But this operation is to be
considered as a new cross, and consequently is
wholly excluded from our present discussion.
Hence it follows that a clear insight into the
heredity of hybrids may be expected only from
scientific experiments. Furthermore some of
the diversity observed as a result of ordinary
crosses, may be due to the instability of the par-
ents themselves or at least of one of them, since
breeders ordinarily choose for their crosses
some already very variable strain. Combining
such a strain with the desirable qualities of
some newly imported species, a new strain may

Balanced Crosses 287

result, having the new attribute in addition to
all the variability of the old types. In scientific
experiments made for the purpose of investi-
gating the general laws of hybridity, such com-
plex cases are therefore to be wholly excluded.
The hereditary purity of the parents must be
considered as one of the first conditions of
success.

Moreover the progeny must be numerous,
since neither constancy, nor the exact propor-
tions in the case of instability, can be deter-
mined with a small lot of plants.

Finally, and in order to come to a definite
choice of research material, we should keep in
mind that the chief object is to ascertain the
relation of the offspring to their parents. Now
in nearly all cases the seeds are separated from
the fruits and from one another, before it be-
comes possible to judge of their qualities. One
may open a fruit and count the seeds, but ordi-
narily nothing is noted as to their characters.
In this respect no other plant equals the com
or maize, as the kernels remain together on the
spike, and as it has more than one variety
characterized by the color, or constitution, or
other qualities of the grains. A corn-grain,
however, is not a seed, but a fruit containing a
seed. Hence the outer parts pertain to the par-
ent plant and only the innermost ones to the

288 Retrograde Varieties

seedling and therefore to the following genera-
tion. Fruit-characters thus do not offer the
qualities we need, only the qualities resulting
from fertilizations are characteristic of the new
generation. Such attributes are afforded in
some cases by the color, in others by the chem-
ical constitution.

We will choose the latter, and take the sugar-
corn in comparison with the ordinary or starch-
producing forms for our starting point. Both
sugar- and starch-corns have smooth fruits when
ripening. No difference is to be seen in the
young ripe spikes. Only the taste, or a direct
chemical analysis might reveal the dissimilar-
ity. But as soon as the spikes are dried, a
diversity is apparent. The starchy grains re-
main smooth, but the sugary kernels lose so
much water that they become wrinkled. The
former becomes opaque, the latter more or less
transparent. Every single kernel may in-
stantly be recognized as belonging to either of
the types in question, even if but a single grain
of the opposite quality might be met with on a
spike. Kernels can be counted on the spike,
and since ordinary spikes may bear from 300-
500 grains and often more, the numerical rela-
tion of the different types may be deduced with
great accuracy.

Coming now to our experiment, both starchy

Balanced Crosses 289

and sugary varieties are in this respect wholly
constant, when cultivated separately. No
change is to be seen in the spikes. Further-
more it is very easy to make the crosses. The
best way is to cultivate both types in alternate
rows and to cut off the staminate panicles a few
days before they open their first flowers. If
this operation is done on all the individuals of
one variety, sparing all the panicles of the
other, it is manifest that all the plants will be-
come fertilized by the latter, and hence that the
castrated plants will only bear hybrid seeds.

The experiment may be made in two ways ; by
castrating the sugary or the starchy variety.
In both cases the hybrid kernels are the same.
As to their composition they repeat the active
character of the starchy variety. The sugar is
only accumulated as a result of an incapacity
of changing it into starch, and the lack of this
capacity is to be considered as a retrogressive
varietal mark. The starch-producing unit-
character, which is active in the ordinary sorts
of corns, is therefore latent in sugar-corn.

In order to obtain the second generation, the
hybrid grains are sown under ordinary condi-
tions, but sufficiently distant from any other
variety of com to insure pure fertilization.
The several individuals may be left to pollinate

290 Retrograde Varieties

eacli other, or they may be artificially pollinated
with their own pollen.

The outcome of the experiments is shown by
the spikes, as soon as they dry. Each spike
bears two sorts of kernels irregularly dispersed
over its surface. In this point all the spikes
are alike. On each of them one mav see on the
first inspection that the majority of the kernels
are starch-containing seeds, while a minor part
becomes wrinkled and transparent according to
the rule for sugary seeds. This fact shows at
once that the hvbrid race is not stable, but has
differentiated the parental characters, bringing
those of the varietal parent to perfect purity
and isolation. Whether the same holds good
for the starchy parent, it is impossible to judge
from the inspection of the spikes, since it has
been seen in the first generation that the hybrid
kernels are not visibly distinguished from those
of the pure starch-producing grains.

It is verv easv to count the number of both
sorts of grains in the spike of such a hybrid.
In doing so we find, that the proportion is
nearly the same on all the spikes, and only
slight variations would be found in hundreds
of them. One-fourth of the seeds are wrinkled
and three-fourths are always smooth. The
number may vary in single instances and be a
little more or a little less than 25^, ranging, for

Balanced Crosses 291

instance, from 20 to 27;^ , but as a rule, the aver-
age is found nearly equal to 25^.

The sugary kernels, when separated, from the
hybrid spikes and sown separately, give rise to
a pure sugary race, in no degree inferior in
purity to the original variety. But the starchy
kernels are of different types, some of them
being internally like the hybrids of the first
generation and others like the original parent.
To decide between these two possibilities, it is
necessary to examine their progeny.

For the study of this third hybrid generation
we will now take another example, the opium-
poppies. They usually have a dark center in
the flowers, the inferior parts of the four petals
being stained a deep purple, or often nearly
black. Many varieties exhibit this mark as a
large black cross in the center of the flower. In
other varieties the pigment is wanting, the cross
being of a pure white. Obviously it is only re-
duced to a latent condition, as in so many other
cases of loss of color, since it reappears in a
hybrid with the parent-species.

For mv crosses I have taken the dark-centered
'' Mephisto " and the '' Danebrog," or Danish
flag, with a white cross on a red field. The sec-
ond year the hybrids were all true to the type of
^* Mephisto." From the seeds of each artifi-
cially self- fertilized capsule, one-fourth (22.5^^ )

292 Retrograde Varieties

in each instance reverted to the varietal mark
of the white cross, and three-fourths {11. b^)
retained the dark heart. Once more the flowers
were self-pollinated and the visits of insects ex-
cluded. The recessives now gave only reces-
sives, and hence we may conclude that the varie-
tal marks had returned to stability. The dark-
hearted or dominants behaved in two different
ways. Some of them remained true to their
type, all their offspring being dark-hearted.
Evidently they had returned to the parent
with the active mark, and had reassumed this
type as purely as the recessives had reached
theirs. But others kept true to the hybrid char-
acter of the former generation, repeating in
their progeny exactly the same mixture as their
parents, the hybrids of the first generation, had
given.

This third generation therefore gives evi-
dence, that the second though apparently show-
ing only two types, really consists of three dif-
ferent groups. Two of them have reassumed
the stability of their original grandparents, and
the third has retained the instability of the hy-
brid parents.

The question now arises as to the numerical
relation of these groups. Our experiments
gave the following results :

Balanced Crosses

293

Cross

Mephisto

1. Generation 2. (jreneration 3. Generation

/4- 100% Mephisto

Danebrog

77.5% Dom

All Mephisto^

{

9- all hybrids with
83-68% domi-
nants and 17-
32% recessives.

22.5% Recess.

100%
brog.

Dane

Examining these figures we find one-fourth of
constant recessives, as has already been said,
further one-fourth of constant dominants, and
the rest or one half as unstable hybrids. Both
of the pure groups have therefore reappeared
in the same numbers. Calling A the specimens
with the pure active mark, L those with the la-
tent mark, and H the hybrids, these proportions
may be expressed as follows:

lA-|-2H-hlL.

This simple law for the constitution of the sec-
ond generation of varietal hybrids with a single
differentiating mark in their parents is called
the law of Mendel. Mendel published it in
1865, but his paper remained nearly unknown
to scientific hybridists. It is only of late years
that it has assumed a high place in scientific
literature, and attained the first rank as an in-
vestigation on fundamental questions of hered-

294 Retrograde Varieties

ity. Read in the light of modern ideas on unit-
characters it is now one of the most important
works on heredity and has already widespread
and abiding influence on the philosophy of hy-
bridism in general.

But from its very nature and from the choice
of the material made by Mendel, it is restricted
to balanced or varietal crosses. It assumes
pairs of characters and calls the active unit of
the pair dominant, and the latent recessive,
without further investigations of the question
of latency. It was worked out by Mendel for a
large group of varieties of peas, but it holds
good, with only apparent exceptions, for a wide
range of cases of crosses of varietal characters.
Recently many instances have been tested, and
even in many cases third and later generations
have been counted, and whenever the evidence
was complete enough to be trusted, Mendel's
prophecy has been found to be right.

According to this law of Mendel's the pairs
of antagonistic characters in the hybrid split up
in their progeny, some individuals reverting to
the pure parental types, some crossing with
each other anew, and so giving rise to a new
generation of hybrids. Mendel has given a
very suggestive and simple explanation of his
formula. Putting this in the terminology^ of
to-day, and limiting it to the occurrence of only

Balanced Crosses 295

one differential unit in the parents, we may
give it in the following manner. In fertiliza-
tion, the characters of both parents are not uni-
formly mixed, but remain separated though
most intimately combined in the hybrid
throughout life. They are so combined as to
work together nearly always, and to have nearly
equal influence on all the processes of the whole
individual evolution. But when the time ar-
rives to produce progeny, or rather to produce
the sexual cells through the combination of
which the offspring arises, the two parental
characters leave each other, and enter sepa-
rately into the sexual cells. From this it may be
seen that one-half of the pollen-cells will have
the quality of one parent, and the other the qual-
ity of the other. And the same holds good for
the egg-cells. Obviously the qualities lie latent
in the pollen and in the egg, but ready to be
evolved after fertilization has taken place.

Granting these premises, we may now ask as
to the results of the fertilization of hybrids,
when this is brought about by their own pollen.
We assume that numerous pollen grains fer-
tilize numerous egg cells. This assumption at
once allows of applying the law of probability,
and to infer that of each kind of pollen grains
one-half will reach egg-cells with the same qual-

296 Retrograde Varieties

ity and the other half ovules with the opposite
character.

Calling P pollen and 0 ovules, and represent-
ing the active mark by P and 0, the latent qual-
ities by P' and 0', they would combine as fol-
lows :

P + O giving uniform pairs with the active mark,

P + O' giving unequal pairs,

P' + O giving unequal pairs,

P' + O' giving uniform pairs with the latent mark.

In this combination the four groups are ob-
viously of the same size, each containing one-
fourth of the offs]3ring. Manifestly they corre-
spond exactly to the direct results of the
experiments, P -|- O representing the indi-
viduals which reverted to the specific mark,
P'-fO' those who reassumed the varietal
quality and P+0' and P+0' those who hybrid-
ized for the second time. These considerations
lead us to the following form of MendePs
formula :

P -h O = l/4-Active or 1 A,

P 4-0')

P' + O I "= 1/2-Hybrid or 2 H,

P' + O' =l/4-Latent or 1 L,

Which is evidently the same as Mendel's
empirical law given above.

To give the proof of these assumptions Men-
del has devised a very simple crossing experi-

Balanced Crosses 297

ment, which he has effected with his varieties of
peas. I have repeated it with the sugar-corn,
which gives far better material for demonstra-
tion. It starts from the inference that if dissim-
ilarity among the pollen grains is excluded, the
diversity of the ovules must at once become
manifest and vice versa. In other terms, if a
hybrid of the first generation is not allowed to
fertilize itself, but is pollinated by one of its
parents, the result will be in accordance with the
Mendelian formula.

In order to see an effect on the spikes pro-
duced in this way, it is of course necessary to
fertilize them with the pollen of the variety,
and not with that of the specific type. The
latter would give partly pure starchy grains
and partly hybrid kernels, but these would
assume the same type. But if we pollinate the
hybrid with pollen of a pure sugar-corn, we
may predict the result as follows.

If the spike of the hybrid contains dormant
paternal marks in one-half of its flowers and in
the other half maternal latent qualities, the
sugar-corn pollen will combine with one-half of
the ovules to give hybrids, and with the other
half so as to give pure sugar-grains. Hence
we see that it will be possible to count out direct-
. ly the two groups of ovules on inspecting the
ripe and dry spikes. Experience teaches us

298 Retrograde Varieties

that both are present, and in nearly equal num-
bers ; one-half of the grains remaining smooth,
and the other half becoming wrinkled.

The corresponding experiment could be made
with plants of a pure sugar-race by pollination
with hybrid pollen. The spikes would show ex-
actly tlie same mixture as in the above case, but
now this may be considered as conclusive proof
that half the pollen-grains represent the quality
of one parent and the other half the quality of
the other.

Another corollary of MendePs law is the fol-
lowing. In each generation two groups return
to purity, and one-half remains hybrid. These
last will repeat the same phenomenon of split-
ting in their progeny, and it is easily seen
that the same rule will hold good for all succeed-
ing generations. According to Mendel's prin-
ciple, in each year there is a new hybridization,
differing in no respect from the first and
original one. If the hybrids only are propa-
gated, each year will show one-fourth of the
offspring returning to the specific character,
one-fourth assuming the type of the variety and
one-half remaining hybrid. T have tested this
with a hybrid between the ordinary nightshade
with black berries, and its variety, Solamim
nigrum cUorocarpum, with pale yellow fruits.

Eight generations of the hybrids were culti-

Balanced Crosses 299

vated, disregarding always the reverting off-
spring. At the end I counted the progeny of
the sixth and seventh generations and found
figures for their three groups of descendants,
which exactly correspond to Mendel's formula.

Until now we have limited ourselves to the
consideration of single differentiating units.
This discussion gives a clear insight into the
fundamental phenomena of hybrid fertilization.
It at once shows the correctness of the assump-
tion of unit-characters, and of their pairing in
the sexual combinations.

But MendePs law is not at all restricted to
these simple cases. Quite on the contrary, it
explains the most intricate questions of hybrid-
ization, providing they do not transgress the
limits of symmetrical unions. But in this realm
nearly all results may be calculated beforehand,
on the ground of the principle of probability.
Only one more assumption need be discussed.
The several pairs of antagonistic characters
must be independent from, and uninfluenced by,
one another. This premise seems to hold good
in the vast majority of cases, though rare excep-
tions seem to be not entirely wanting. Hence
the necessity of taking all predictions from Men-
del's law only as probabilities, which will prove
true in most, but not necessarilv in all cases.

300 Retrograde Varieties

But here we will limit ourselves to normal
cases.

The first example to be considered is obvious-
ly the assumption that the parents of a cross
differ from each other in respect to two charac-
ters. A good illustrative example is afforded
by the thorn-apple. I have crossed the blue-
flowered thorny form, usually known as Datura
Tatula, with the white thornless type, desig-
nated as D. Stramonium inermis. Thorns and
blue pigment are obviously active qualities, as
they are dominant in the hybrids. In the
second generation both pairs of characters are
resolved into their constituents and paired anew
according to Mendel ^s law. After isolating my
hybrids during the period of flowering, I counted
among their progeny :

128 individuals with blue flowers and thorns
47 " " " " without "

54 " " white " and "

21 " " " " without "

250

The significance of these numbers may easily
be seen, when we calculate what was to be ex-
pected on the assumption that both characters
follow MendePs law, and that both are inde-
pendent from each other. Then we would have
three-fourths blue offspring and one-fourth in-
dividuals with white flowers. Each of these

Balanced Crosses 301

two groups would consist of thorn-bearing and
thornless plants, in the same numerical relation.
Thus, we come to the four groups observed in
our experiment, and are able to calculate their
relative size in the following way :

Proportion

Blue with thorns 3/4X3/4=: 9/16 = 56.25% 9

Blue, unarmed 3/4X1/4 = 3/16 = 18.75% 3

White with thorns 1/4X3/4 = 3/16 = 18.75% 3

White, unarmed 1/4X1/4= 1/16 = 6.25% 1

In order to compare this inference from Men-
dePs law and the assumption of independency,
with the results of our experiments, we must cal-
culate the figures of the latter in percentages.
In this way we find :

Found. Calculated.

Blue with thorns 128 = 51% 56.25%

Blue unarmed 47 = 19% 18.75%

White with thorns. .. . 54 = 22% 18.75%

White unarmed 21= 8% 6.25%

The agreement of the experimental and the
theoretical figures is as close as might be
expected.

This experiment is to be considered only as
an illustrative example of a rule of wide appli-
cation. The rule obviously will hold good in
all such cases as comply with the two conditions
already premised, viz.: that each character
agrees with Mendel's law, and that both are
wholly independent of each other. It is
clear that our figures show the numerical com-

302 Retrograde Varieties

position of the hybrid offspring for any single
instance, irrespective of the morphological
nature of the qualities involved.

Mendel has proved the correctness of these
deductions by his experiments with peas, and
by combining their color (yellow or green) with
the chemical composition (starch or sugar) and
other pairs of characters. I will now give two
further illustrations afforded bv crosses of the
ordinary campion. I used the red-flowered or
day-campion, which is a perennial herb, and a
smooth variety" of the white evening-campion,
which flowers as a rule in the first summer.
The combination of flower-color and pubescence
gave the following composition for the second
hybrid generation:

Number % Calculation

Hairy and red 70 44 56.25%

Hairy and white 23 14 18.75%

Smooth and red 46 23 18.75%

Smooth and white 19 12 6.25%

For the combination of pubescence and the
capacity of flowering in the first year I found :

Xumber % Calculated

Hairy, flowering 286 52 56.25%

Hairy, without stem . . 128 23 18.75%

Smooth, flowering 96 17 18.75%

Smooth, without stem 42 8 6.25%

Many other cases have been tested by dif-
ferent writers and the general result is the

Balanced Crosses 303

applicability of Mendel's formula to all cases
complying with the given conditions.

Intentionally I have chosen for the last ex-
ample two pairs of antagonisms, relating to
the same pair of plants, and which may be
tested in one experiment and combined in one
calculation.

For the latter we need only assume the same
conditions as mentioned before, but now for
three different qualities. It is easily seen that
the third quality would split each of our four
groups into two smaller ones in the proportion

of 3/4 :!/,,

We would then get eight groups of the follow-
ing composition:

9/16 X 3/4 = 27/64 or 42.2%
9/16 X 1/4= 9/64 " 14.1%

3/16 X 3/4 —

9/64 "

14.1%

3/16 X 1/4

3/64 "

4.7%

3/16 X 3/4

9/64 "

14.1%

3/16 X 1/4

3/64 "

4.7%

1/16 X 3/4

3/64 "

4.7%

1/16 X 1/4

1/64 '•'

1.6%

The characters chosen for our experiment in-
clude the absence of stem and flowers in the
first year, and therefore would require a second
year to determine the flower-color on the per-
ennial specimens. Instead of doing so I have
taken another character, shown by the teeth of
the capsules when opening. These curve out-

304 Retrograde Varieties

wards in the red campion, but lack this capacity
in the evening-campion, diverging only until an
upright position is reached. The combination
of hairs, colors and teeth gives eight groups,
and the counting of their respective numbers of
individuals gave the following result:

Teeth

Hairs

Flowers

of capsules

Number

%

Calculated

Hairy

red

curved

91

47

42.2%

Hairy

red

straight

15

7.5

14.1%

Hairy

white

curved

23

12

14.1%

Hairy

white

straight

17

8.5

4.7%

Smooth

red

curved

23

12

14.1%

Smooth

red

straight

9

4.5

4.7%

Smooth

white

curved

5

2.5

4.7%

Smooth

white

straight

12

6

1.6%

The agreement is as comprehensive as might
be expected from an experiment with about 200
plants, and there can be no doubt that a repeti-
tion on a larger scale would give still closer
agreement.

In the same way we might proceed to crosses
with four or more differentiating characters.
But each new character will double the number
of the groups. Four characters will combine
into 16 groups, five into 32, six into 64, seven
into 128, etc. Hence it is easily seen that the
size of the experiments must be made larger
and larger in the same ratio, if we intend to
expect numbers equally trustworthy. For

Balanced Crosses 305

seven differentiating marks 16,384 individuals
are required for a complete series. And in
this set the group with the seven attributes all
in a latent condition would contain only a
single individual.

Unfortunately the practical value of these
calculations is not very great. They indicate
the size of the cultures required to get all the
possible combinations, and show that in ordi-
nary cases many thousands of individuals have
to be cultivated, in order to exhaust the whole
range of possibilities. They further show that
among all these thousands, only very few are
constant in all their characters ; in fact, it may
easily be seen that with seven differentiating
points among the 16,384 named above, only one
individual will have all the seven qualities in
pure active, and only one will have them all in a
purely dormant condition. Then there will be
some with some attributes active and others
latent, but their numbers will also be very small.
All others will split up in the succeeding genera-
tion in regard to one or more of their appar-
ently active marks. And since only in very
rare cases the stable hvbrids can be distin-
guished by external characters from the un-
stable ones, the stability of each individual
bearing a desired combination of characters
would have to be established by experiment

306 Retrograde Varieties

after pure fertilization. Menders law teaches
ns to predict the difficulties, but hardly shows
any way to avoid them. It lays great stress on
the old prescript of isolation and pure fertiliza-
tion, but it will have to be worked out and ap-
plied to a large number of practical cases before
it will gain a preeminent influence in horticul-
tural practice.

Or, as Bailey states it, we are only beginning
to find a pathway through the bewildering maze
of hybridization.

This pathwaj^ is to be laid out with regard to
the following considerations. We are not to
cross species or varieties, or even accidental
plants. We must cross unit-characters, and
consider the plants only as the bearers of these
units. We may assume that these units are
represented in the hereditary substance of the
cell-nucleus by definite bodies of too small a size
to be seen, but constituting together the chromo-
somes. We may call these innermost repre-
sentatives of the unit-characters pangenes, in
accordance with Darwin's hypothesis of pan-
genesis, or give them any other name, or we may
even wholly abstain from such theoretical dis-
cussion, and limit ourselves to the conception of
the visible character-units. These units then
may be present, or lacking and in the first case
active, or latent.

Balanced Crosses 807

True elementary species differ from each
other in a number of unit-characters, which do
not contrast. They have arisen by progressive
mutation. One species has one kind of unit,
another species has another kind. On com-
bining these, there can be no interchange.
Mendelism assumes such an interchange be-
tween units of the same character, but in a
different condition. Activity and latency are
such conditions, and therefore Mendel's law
obviously applies to them. They require pairs
of antagonistic qualities, and have no connec-
tion whatever with those qualities which do not
find an opponent in the other parent. Now,
only pure varieties afford such pure conditions.
When undergoing further modifications, some
of them may be in the progressive line and
others in the retrogressive. Progressive modi-
fications give new units, which are not in con-
trast with any other, retrograde changes turn
active units into the latent condition and so give
rise to pairs. Ordinary species generally
originate in this way, and hence differ from
each other partly in specific, partly in varietal
characters. As to the first, they give in their
hybrids stable peculiarities, while as to the
latter, they split up according to Mendel's law.

Unpaired or unbalanced characters lie side by
side with paired or balanced qualities, and they

308 Retrograde Varieties

do so in nearly all the crosses made for prac-
tical purposes, and in very many scientific ex-
periments. Even Mendel's peas were not pure
in this respect, much less do the campions noted
above differ only in Mendelian characters.

Comparative and systematic studies must be
made to ascertain the true nature of every unit
in every single plant, and crossing experiments
must be based on these distinctions in order to
decide what laws are applicable in any case.

D. EVER-SPORTING VARIETIES

Lecture XI

STRIPED FLOWERS

Terminology is an awkward thing. It is as
disagreeable to be compelled to make new
names, as to be constrained to use the old
faulty ones. Different readers may associate
different ideas with the same terms, and unfor-
tunately this is the case with much of the
terminology of the science of heredity and
variability. What are species and what are
varieties? How many different conceptions
are conveyed by the terms constancy and varia-
bility? We are compelled to use them, but we
are not at all sure that we are rightly under-
stood when we do so.

Gradually new terms arise and make their
way. They have a more limited applicability
than the old ones, and are more narrowly cir-
cumscribed. They are not to supplant the older
terms, but permit their use in a more general
way.

309

310 Ever-sporting Varieties

One of these doubtful terms is the word sport.
It often means bud-variation, while in other
cases it conveys the same idea as the old botan-
ical term of mutation. But then all sorts of
seemingly sudden variations are occasionally
designated by the same term by one writer or
another, and even accidental anomalies, such as
teratological ascidia, are often said to arise by
sports.

If we compare all these different conceptions,
we will find that their most general feature is
the suddenness and the rarity of the phenom-
enon. They convey the idea of something un-
expected, something not always or not regularly
occurring. But even this demarcation is not
universal, and there are processes that are reg-
ularly repeated and nevertheless are called
sports. These at least should be designated by
another name.

In order to avoid confusion as far as possible,
with the least change in existing terminology,
I shall use the term '' ever-sporting varieties "
for such forms as are regularly propagated by
seed, and of pure and not hybrid origin, but
which sport in nearly every generation. The
term is a new one, but the facts are for the most
part new, and require to be considered in
a new light. Its meaning will become clearer
at once when the illustrations afforded by

striped Flowers 311

striped flowers are introduced. In the follow-
ing discussion it will be found most convenient
to give a summary of what is known concerning
them, and follow this by a consideration of the
detailed evidence obtained experimentally,
which supports the usage cited.

The striped variety of the larkspur of our
gardens is known to produce monochromatic
flowers, in addition to striped ones. They may
be borne by the same racemes, or on different
branches, or some seedlings from the same
parent-plant may bear monochromatic flow-
ers while others may be striped. Such devia-
tions are usually called sports. But they occur
yearly and regularly and may be observed in-
variably when the cultures are large enough.
Such a variety I shall call '' ever-sporting."

The striped larkspur is one of the oldest gar-
den varieties. It has kept its capacity of
sporting through centuries, and therefore may
in some sense be said to be quite stable. Its
changes are limited to a rather narrow circle,
and this circle is as constant as the peculiari-
ties of any other constant species or variety.
But within this circle it is always changing
from small stripes to broad streaks, and from
them to pure colors. Here the variability is a
thing of absolute constancy, while the constancy
consists in eternal changes! Such apparent

312 Ever-sporting Varieties

contradictions are unavoidable, when we ap-
ply the old term to such unusual though not
at all new cases. Combining the stability and
the qualities of sports in one word, we may evi-
dently best express it by the new term of ever-
sporting variety.

We will now discuss the exact nature of such
varieties, and of the laws of heredity which
govern them. But before doing so, I might
point out, that this new type is a wery common
one. It embraces most of the so-called variable
types in horticulture, and besides these a wide
range of anomalies.

Every ever-sporting variety has at least two
different types, around and between which it
varies in numerous grades, but to which it is
absolutely limited. Variegated leaves fluctuate
between green and white, or green and yellow,
and display these colors in nearly all possible
patterns. But there variability ends, and even
the patterns are ordinarily narrowly prescribed
in the single varieties. Double flowers afford
a similar instance. On one side the single type,
on the other the nearly wholly double model are
the extreme limits, between which the variabil-
ity is confined. So it is also with monstrosities.
The race consists of anomalous and normal in-
dividuals, and displays between them all possi-
ble combinations of normal and monstrous

striped Flowers 313

parts. But its variability is restricted to this
group. And large as the group may seem on
first inspection, it is in reality very narrow.
Many monstrosities, such as fasciated branch-
es, pitchers, split leaves, peloric flowers, and
others constitute such ever-sporting varieties,
repeating their anomalies year by year and gen-
eration after generation, changing as much as
possible, but remaining absolutely true within
their limits as long as the variety exists.

It must be a very curious combination of the
unit-characters which causes such a state of
continuous variability. The pure quality of the
species must be combined with the peculiarity
of the variety in such a way, that the one ex-
cludes the other, or modifies it to some extent,
although both never fully display themselves
in the same part of the same plant. A corolla
cannot be at once monochromatic and striped,
nor can the same part of a stem be twisted and
straight. But neighboring organs may show
the opposite attributes side by side.

In order to look closer into the real mechan-
ism of this form of variabilitv, and of this con-
stant tendency to occasional reversions, it will
be best to limit ourselves first to a single case,
and to try to gather all the evidence, which
can be obtained bv an examination of the he-
reditary relations of its sundry constituents.

314: Ever-sporting Varieties

This may best be done by determining the de-
gree of inheritance for the various constituents
of the race during a series of years. It is only
necessary to apply the two precautions of ex-
cluding all cross-fertilization, and of gathering
the seeds of each individual separately. We do
not need to ascertain whether the variety as
such is permanent; this is already clear from
the simple fact of its antiquity in so many
cases. We wish to learn what part each in-
dividual, or each group of individuals with
similar characters, play in the common line
of inheritance. In other words, we must
build up a genealogical tree, embracing several
generations and a complete set of the single
cases occurring within the variety, in order to
allow of its being considered as a part of the
genealogy of the whole. It should convey to us
an idea of the hereditary relations during the
life-time of the variety.

It is manifest that the construction of such
a genealogical tree requires a number of sepa-
rate experiments. These should be extended
over a series of vears. Each should include a
number of individuals large enough to allow
the determination of the proportion of the dif-
ferent types among the offspring of a single
plant. A species which is easily fertilized by
its own pollen, and which bears capsules with

striped Flowers 315

large quantities of seeds, obviously affords the
best opportunities. As such, I have chosen the
common snapdragon of the gardens, Antirrhi-
num majus. It has many striped varieties,
some tall, others of middle height, or of dwarfed
stature. In some the ground-color of the flow-
ers is yellow, in others it is white, the yellow
disappearing, with the exception of a large
mark in the throat. On these ground-colors the
red pigment is seen lying in streaks of pure car-
mine, with white intervals where the yellow
fails, but combined with yellow to make a fiery
red, and with yellow intervals when that color
is present. This yellow color is quite constant
and does not vary in any marked degree, not-
withstanding the fact that it seems to make
narrower and broader stripes, according to the
parts of the corolla left free by the red pig-
ment. But it is easily seen that this appearance
is only a fallacious one.

The variety of snapdragon chosen was of me-
dium height and with the yellow ground-color,
and is known by horticulturists as A. majus
luteum rubro-striatum. As the yellow tinge
showed itself to be invariable, I may limit my
description to the red stripes.

Some flowers of this race are striped, others
are not. On a hasty survey there seem to be
three types, pure yellow, pure red, and stripe?

316 Ever-sporting Varieties

with all their intermediate links of narrower
and broader, fewer and more numerous streaks.
But on a close inspection one does not succeed
in finding pure yellow racemes. Little lines of
red may be found on nearly every flower. They
are the extreme type on this side of the range
of variability. From them an almost endless
range of patterns passes over to the broadest
stripes and even to whole sections of a pure red.
But then, between these and the wholly red
flowers we observe a gap, which may be narrow-
er by the choice of numerous broad striped in-
dividuals, but which is never wholly filled up.
Hence we see that the red flowers are a separate
type within the striped variety.

This red type springs yearly from the striped
form, and yearly reverts to it. This is what in
the usual descriptions of this snapdragon, is
called its sporting. The breadth of the streaks
is considered to be an ordinary case of varia-
bility, but the red flowers appear suddenly, with-
out the expected links. Therefore they are to
be considered as sports. Similarly the red
forms may suddenly produce striped ones, and
this too is to be taken as a sport, according to
the usual conception of the word.

Such sports may occur in different ways.
Either by seeds, or by buds, or even within
the single spikes. Both opposite reversions,

Striped Flowers 317

from striped to red and from red to stripes, oc-
cur by seed, even by the strictest exclusion of
cross-fertilization. As far as my experiments
go, they are the rule, and parent-plants that
do not give such reversions, at least in some of
their offspring, are very rare, if not wholly
wanting. Bud-variations and variations within
the spike I have as yet only observed on the
striped individuals, and never on the red ones,
though I am confident that they might appear in
larger series of experiments. Both cases are
more common on individuals with broad stripes
than on plants bearing only the narrower red
lines, as might be expected, but even on the al-
most purely yellow individuals they may be seen
from time to time. Bud-variations produce
branches with spikes of uniform red flowers.
Every bud of the plant seems to have equal
chances to be transformed in this way. Some
striped racemes bear a few red flowers, which
ordinarily are inserted on one side of the spike
only. As they often cover a sharply defined
section of the raceme, this circumstance has
given rise to the term of sectional variability to
cover such cases. Sometimes the section is
demarcated on the axis of the flower-spike by a
brownish or reddish color, sharply contrasting
with the green hue of the remaining parts.
Sectional variation mav be looked at as a

318 Ever-sporting Varieties

special type of bud-variation, and from this
point of view we may simplify our inquiry and
limit ourselves to the inheritance of three types,
the striped plants, the red plants and the red
asexual variants of the striped individuals. In
each case the heredity should be observed not
only for one, but at least for two successive
generations.

Leaving these introductory remarks I now
come at once to the genealogical tree, as it may
be deduced from my experiments :

Year.

1896
1895

95% Str. 84% Red
Striped Indiv. Red Indiv.

1895
1894

98% Str. 71% Red.
Striped branches. Red branches.

1894
1893

98% Str. 76% Red.
90% Striped Indiv. 10% Red Indiv.

1892

T

Striped Individual.

This experiment was begun in the year 1892
with one individual out of a large lot of striped
plants grown from seeds which I had purchased
from a firm in Erfurt. The capsules were gath-
ered separately from this individual and about
40 flowering plants were obtained from the
seeds in the following year. Most of them had
neatly striped flowers, some displayed broader
stripes and spare flowers were seen with one-

striped Flowers 319

half wholly red. Four individuals were found
with only uniform red flowers. These were iso-
lated and artificially pollinated, and the same
was done with some of the best striped indi-
viduals. The seeds from every parent were
sown separately, so as to allow the determina-
tion of the proportion of uniform red individ-
uals in the progeny.

Neither group was constant in its off-
spring. But as might be expected, the type
of the parent plant prevailed in both groups,
and more strongly so in the instances with
the striped, than with the red ones. Or, in
other words seed-reversions were more numer-
ous among the already reverted reds than
among the striped ij^e itself. I counted 2%
reversion in the latter case, but 24% from the
red parents.

Among the striped plants from the striped
parents, I found some that produced bud-
variations. I succeeded in isolating these red
flowering branches in paper bags and in polli-
nating them with their own pollen, and subjected
the striped spikes of the same individuals to a
similar treatment. Three individuals gave a
sufficient harvest from both types, and these
six lots of seeds were sown separately. The
striped flowers repeated their character in 98^
of their offspring, the red twigs in only 71^, the

320 Ever-sporting Varieties

remaining individuals sporting into the oppo-
site group.

In the following year I continued the experi-
ment with the seeds of the offspring of the red
bud-variations. The striped individuals gave
95^, but in the red ones only 84^ of the progeny
remained true to the parent type.

From these figures it is manifest that the
red and striped types differ from one another
not only in their visible attributes, but also in
the degree of their heredity. The striped in-
dividuals repeat their peculiarity in 90 - 98^ of
their progeny, 2 - 10^ sporting into the uniform
red color. On the other hand the red individ-
uals are constant in 71 - 84^ of their offspring,
while 16-29% go over to the striped type. Or,
briefly, both types are inherited to a high degree,
but the striped type is more strictly inherited
than the red one.

Moreover the figures show that the degree of
inheritance is not contingent upon the question
as to how the sport may have arisen. Bud-
sports show the same degree of inheritance as
seed-sports. Sexual and asexual variability
therefore seem to be one and the same process
in this instance. But the deeper meaning of
this and other special features of our genealog-
ical tree are still awaiting further investigation.
It seems that much important evidence might

striped Flowers 321

come from an extension of this line of work.
Perhaps it might even throw some light on
the intimate nature of the bud-variations of
ever-sporting varieties in general. Sectional
variations remain to be tested as to the degree
of inheritance exhibited, and the different occur-
rences as to the breadth of the streaks require
similar treatment.

In ordinary horticultural practice it is desir-
able to give some guarantee as to what may be
expected to come from the seeds of brightly
striped flowers. Neither the pure red type,
nor the nearly yellow racemes are the object
of the culture, as both of them may be had pure
from their own separate varieties. In order
to insure proper striping, both extremes are
usually rejected and should be rooted out as
soon as the flowering period begins. Simi-
larly the broad-striped ones should be re-
jected, as they give a too large amount of uni-
form red flowers. Clearly, but not broadly
striped individuals always yield the most reli-
able seed.

Summing up once more the results of our ped-
igree-experiment, we may assert that the striped
variety of the snapdragon is wholly permanent,
including the two opposite types of uniform
color and of stripes. It must have been so since
it first originated from the invariable uniform

322 Ever-sporting Varieties

varieties, about the middle of the last century,
in the nursery of Messrs. Vilmorin, and prob-
ably it will remain so as long as popular taste
supports its cultivation. It has never been ob-
served to trangress its limits or to sport into
varieties without reversions or sports. It fluc-
tuates from one extreme to the other yearly, al-
ways recurring in the following year, or even in
the same summer by single buds. Highly va-
riable within its limits, it is absolutely constant
or permanent, when considered as a definite
group.

Similar cases occur not rarely among culti-
vated plants. In the wild state they seem to
be wholly wanting. Neither are they met with
as occasional anomalies nor as distinct varie-
ties. On the contrary, many garden-flowers
that are colored in the species, and besides this
have a white or yellow variety, have also
striped sorts. The oldest instance is probably
the marvel of Peru, Mirahilis Jalappa, which
already had more than one striped variety at
the time of its introduction from Peru into the
European gardens, about the beginning of the
seventeenth century. Stocks, liver-leaf (He-
patica), dame's violet (Hesperis), Sweet Wil-
liam (Dianthus harhatus), and periwinkles
{Vinca minor) seem to be in the same condition,
as their striped varieties were already quoted

striped Flower's 32

o

by the writers of the same century. Tulips, hy-
acinths, Cyclamen, Azalea, Camellia, and even
such types of garden-plants as the meadow
crane's-bill {Geranium pratense) have striped
varieties. It is always the red or blue color
which occurs in stripes, the underlying ground
being white or yellow, according to the presence
or absence of the yellow in the original color-
mixture.

All these varieties are known to be perma-
nent, coming true during long series of
successive generations. But very little is known
concerning the more minute details of their he-
reditary qualities. They come from seed, when
this is taken from striped individuals, and
thence revert from time to time to the corre-
sponding monochromatic type. But whether
they would do so when self-fertilized, and
whether the reversionary individuals are al-
ways bound to return towards the center of the
group or towards the opposite limit, remains to
be investigated. Presumably there is nowhere
a real transgression of the limits, and never or
only very rarely and at long intervals of time a
true production of another race with other he-
reditary qualities.

In order to satisfy myself on these points, I
made some pedigree-cultures with the striped
forms of dame's violet (Hesperis matronalis)

324 Ever-sporting Varieties

and of Clarkia pulchella. Both of them are
ever-sporting varieties. The experiments were
conducted during five generations with the vi-
olet, and during four with the striped Clarkia,
including the progeny of the striped and of the
monochromatic red offspring of a primitive
striped plant. I need not give the figures here
for the numerical relations between the differ-
ent types of each group, and shall limit myself
to the statement that they behaved in exactly
the same manner as the snapdragon.

It is worth while to dwell a moment on the
capacity of the individuals with red flowers to
reproduce the striped type among their off-
spring. For it is manifest that this latter qual-
ity must have lain dormant in them during their
whole life. Darwin has already pointed out
that when a character of a grandparent, which
is wanting in the progeny, reappears in the sec-
ond generation, this quality must always be
assumed to have been present though latent in
the intermediate generation. To the many in-
stances given by him of such alternative inher-
itance, the monochromatic reversionists of the
striped varieties are to be added as a new type.
It is moreover, a very suggestive type, since the
latency is manifestly of quite another character
than for instance in the case of Mendelian hv-

«

brids, and probably more allied to those in-

striped Flowers 325

stances, where secondary sexual marks, which
are as a rule only evolved by one sex, are trans-
ferred to the offspring through the other.

Stripes are by no means limited to flowers.
They may affect the whole foliage, or the fruits
and the seeds, and even the roots. But all such
cases occur much more rarely than the striped
flowers. An interesting instance of striped
roots is afforded by radishes. White and red
varieties of different shapes are cultivated.
Besides them sometimes a curious motley sort
may be seen in the markets, which is white with
red spots, which are few and narrow in some
samples, and more numerous and broader in
others. But what is very peculiar and striking
is the circumstance, that these stripes do not
extend in a longitudinal, but in a transverse
direction. Obviously this must be the effect of
the very notable growth in thickness. Assum-
ing that the colored regions were small in
the beginning, they must have been drawn out
during the process of thickening of the root, and
changed into transverse lines. Rarely a streak
may have had its greatest extension in a trans-
verse direction from the beginning, in which
case it would only be broadened and not defi-
nitely changed in its direction.

This variety being a very fine one, and more
agreeable to the eye than the uniform colors, is

326 Ever-sporting Varieties

being more largely cultivated in some countries.
It has one great drawback: it never comes
wholly true from seed. It may be grovm in
full isolation, and carefully selected, all red or
nearly monochromatic samples being rooted out
long before blooming, but nevertheless the seed
will always produce some red roots. The most
careful selection, pursued through a number
of years, has not been sufficient to get rid of
this regular occurrence of reversionary individ-
uals. Seed-growers receive many complaints
from their clients on this account, but they are
not able to remove the difficulty. This experi-
ence is in full agreement with the experimental
evidence given by the snapdragon, and it would
certainly be very interesting to make a complete*
pedigree-culture with the radishes to test
definitely their compliance with the rules ob-
served for striped flowers.

Horticulturists in such cases are in the habit
of limiting themselves to the sale of so-called
mixed seeds. From these no client expects pu-
rity, and the normal and hereditary diversity
of types is here in some sense concealed under
the impurities included in the mixture from
lack of selection. Such cases invite scrutiny,
and would, no doubt, with the methods of isola-
tion, artificial pollination, and the sowing of
the seeds separately from each parent, yield

striped Flowers 327

results of great scientific value. Any one who
has a garden, and sufficient perseverance to
make pure cultures during a series of years
might make important contributions to scien-
tific knowledge in this way.

Choice might be made from among a wide
range of different types. A variety of corn
called ^^ Harlequin '' shows stripes on its ker-
nels, and one ear may oifer nearly white and
nearly red seeds and all the possible interme-
diate steps between them. From these seeds
the next generation will repeat the motley ears,
but some specimens will produce ears of uniform
kernels of a dark purple, showing thus the or-
dinary way of reversion. Some varieties of
beans have spotted seeds, and among a lot of
them one may be sure to find some purely red
ones. It remains to be investigated what will
be their offspring, and whether they are due to
partial or to individual variation.

The cockscomb (Celosia cristata) has varie-
ties of nearly all colors from white and yellow
to red and orange, and besides them some
striped varieties occur in our gardens, with the
stripes going from the lower parts of the stem
up to the very crest of the comb. They are
on sale as constant varieties, but nothing has
as yet been recorded concerning their peculiar
behavior in the inheritance of the stripes.

328 Ever-sporting Varieties

Striped grapes, apples and other fruits might
be mentioned in this connection.

Before leaving the striped varieties, atten-
tion is called to an interesting deduction, which
probably gives an explanation of one of the
most widely known instances of ever-sporting
garden plants. Striped races always include
two types. Both of them are fertile, and each
of them reproduces in its offspring both its
own and the alternate type. It is like a game
of ball, in which the opposing parties always
return the ball. But now suppose that only
one of the types were fertile and the other for
some reason wholly sterile, and assume the
reversionary, or primitive monochromatic indi-
viduals to be fertile, and the derivative striped
specimens to bloom without seed. If this were
the case, knowledge concerning the hereditary
qualities would be greatly limited. In fact the
whole pedigree would be reduced to a mono-
chromatic strain, which would in each genera-
tion sport in some individuals into the striped
variety. But, being sterile, they would not be
able to propagate themselves.

Such seems to be the case with the double
flowered stocks. Their double flowers produce
neither stamens nor pistils, and as each indi-
vidual is either double or single in all its flow-
ers, the doubles are wholly destitute of seed.

striped Flowers 329

Nevertheless, they are only reproduced by seed
frora single flowers, being an annual or bien-
nial species.

Stocks are a large family, and include a won-
derful variety of colors, ranging from white
and yellow to purple and red, and with some
variations toward blue. They exhibit also di-
versity in the habit of growth. Some are an-
nuals, including the ten-week and pyramidal
forms ; others are intermediates and are suitable
for pot-culture ; and the biennial sorts include
the well-known " Brompton " and '^ Queen '^
varieties. Some are large and others are small
or dwarf. For their brightness, durability and
fragrance, they are deservedly popular. There
are even some striped varieties. Horticultur-
ists and amateurs generally know that seed can
be obtained from single stocks only, and that
the double flowers never produce any. It is
not difficult to choose single plants that will
produce a large percentage of double blossoms
in the following generation. But only a per-
centage, for the experiments of the most skilled
growers have never enabled them to save seed,
which would result entirely in double flower-
ing plants. Each generation in its turn is a
motley assembly of singles and doubles.

Before looking closer into the hereditary pe-
culiarities of this old and interesting ever sport-

330 Ever-a pot tiny Varieties

ing variety, it may be as well to give a short
description of the plants with double flowers.
Generally speaking there are two principal
types of doubles. One is by the conversion of
stamens into petals, and the other is an anomaly,
known under the name of petalomany.

The change of stamens into petals is a grad-
ual modification. All intermediate steps are
easily to be found. In some flowers all sta-
mens may be enlarged, in others only part of
them. Often the broadened filaments bear one
or two fertile anthers. The fertility is no doubt
diminished, but not wholly destroyed. Individ-
ual specimens may occur, which cannot produce
any seed, but then others of the same lot may
be as fertile as can be desired. As a whole,
such double varieties are regularly propagated
by seed.

Petalomany is the tendenc}^ of the axis of
some flowers never to make any stamens or pis-
tils, not even in altered or rudimentary form.
Instead of these, they simply continue produc-
ing petals, going on with this production with-
out any other limit than the supply of available
food. Numerous petals fill the entire space
within the outer rays, and in the heart of the
flower innumerable young ones are developed
half-way, not obtaining food enough to attain

striped Flowers 331

full size. Absolute sterility is the natural con-
sequence of this state of things.

Hence it is impossible to have races of petal-
omanous types. If the abnormality happens to
show itself in a species, which normally prop-
agates itself in an asexual way, the type may
become a vegetative variety, and be multiplied
by bulbs, buds or cuttings, etc. Some cultivated
anemones and crowfoots (Ranunculus) are of
this character, and even the marsh-marigold
(Caltha palustris) has a petalomanous variety.
I once found in a meadow such a form of the
meadow-buttercup (Ranunculus acris), and suc-
ceeded in keeping it in my garden for several
years, but it did not make seeds and finally
died. Camellias are known to have both types
of double flowers. The petalomanous type is
highly regular in structure, so much so as to be
too uniform in all its parts to be pleasing, while
the conversion of stamens into petals in the al-
ternative varieties gives to these flowers a more
lively diversity of structure. Lilies have a va-
riety called Lilium candidum fore plena , in
which the flowers seem to be converted into
a long spike of bright, white narrow bracts,
crowded on an axis which never seems to cease
their production.

It is manifestly impossible to decide how all
such sterile double flowers have originated.

332 Ever-sporting Varieties

Perhaps each of them originally had a congru-
ent single-flowered form, from which it was pro-
duced by seed in the same way as the double
stocks now are yearly. If this assumption is
right, the corresponding fertile line is now lost ;
it has perhaps died out, or been masked. But
it is not absolutely impossible that such strains
might one day be discovered for one or another
of these now sterile varieties.

Returning to the stocks we are led to the con-
ception that some varieties are absolutely sin-
gle, while others consist of both single-flowered
and double-flowered individuals. The single
varieties are in respect to this character true
to the original wild type. They never give seed
which results in doubles, providing all inter-
crossing is excluded. The other varieties are
ever-sporting, in the sense of this term pre-
viously assumed, but with the restriction that
the sports are exclusively one-sided, and never
return, owing to their absolute sterility.

The oldest double varieties of stocks have at-
tained an age of a century and more. During
all this time they have had a continuous pedi-
gree of fertile and single-flowered individuals,
throwing off in each generation a definite num-
ber of doubles. This ratio is not at all depend-
ent on chance or accident, nor is it even variable
to a remarkable degree. Quite on the contrary

striped Floivers 33

o

it is always the same, or nearly the same, and
it is to be considered as an inherent quality of
the race. If left to themselves, the single indi-
viduals always produce singles and doubles in
the same quantity ; if cultivated after some spe-
cial method, the proportion may be slightly
changed, bringing the proportion of doubles
up to 60;^ or even more.

Ordinarily the single and double members of
such a race are quite equal in the remainder of
their attributes, especially in the color of their
flowers. But this is not always the case. The
colors of such a race may repeat for themselves
the peculiarities of the ever-sporting characters.
It often happens that one color is more or less
strictly allied to the doubles, and another to
the singles. This sometimes makes it difficult
to keep the various colors true. There are cer-
tain sorts, which invariably exhibit a difference
in color between the single and the double flow-
ers. The sulphur-yellow varieties may be ad-
duced as illustrative examples, because in them
the single flowers always come white. Hence in
saving seed, it is impossible so to select the
plant, that an occasional white does not also
appear among the double flowers, agreeing in
this deviation with the general rule of the ever-
sporting varieties.

I commend all the above instancoR to those

334 Ever-sporting Varieties

who wish to make pedigree-cultures. The co-
operation of many is needed to bring about any
notable advancement, since the best way to se-
cure isolation is to restrict one's self to the
culture of one strain, so as to avoid the inter-
mixture of others. So many facts remain doubt-
ful and open to investigation, that almost any
lot of purchased seed may become the starting-
point for interesting researches. Among these
the sulphur-yellow varieties should be consid-
ered in the first place.

In respect to the great questions of heredity,
the stocks offer many points of interest. Some
of these features I will now trv to describe, in
order to show what still remains to be done,
and in what manner tlie stocks mav clear the
way for the study of the ever-sporting varieties.

The first point, is the question, which seeds
become double-flowered and which single-flow-
ered plants! Beyond all doubt, the determi-
nation has taken place before the ripening of the
seed. But though the color of the seed is often
indicative of the color of the flowers, as in some
red or purple varieties, and though in balsams
and some other instances the most ^^ highly
doubled " flowers are to be obtained from the
biggest and plumpest seeds, no such rule seems
to exist respecting the double stocks. Now
if one half of the seeds gives doubles, and

striped Floivers 335

the other half singles, the question arises,
where are the singles and the doubles to be
found on the parent-plant?

The answer is partly given by the following
experiment. Starting from the general rule of
the great influence of nutrition on variability,
it may be assumed that those seeds will give
most doubles, that are best fed. Now it is man-
ifest that the stem and larger branches are in
a better condition than the smaller twigs, and
that likewise the first fruits have better chances
than the ones formed later. Even in the same
pod the uppermost seeds will be in a compara-
tively disadvantageous position. This concep-
tion leads to an experiment which is the basis
of a practical method much used in France in
order to get a higher percentage of seeds of
double-flowering plants.

This method consists in cutting off, in the first
place the upper parts of all the larger spikes, in
the second place, the upper third part of each
pod, and lastly all the small and weak twigs.
In doing so the percentage is claimed to go up
to 67 - 70^, and in some instances even higher.
This operation is to be performed as soon as the
required number of flowers have ceased blos-
soming. All the nutrient materials, destined
for the seeds, are now forced to flow into these
relativelv few embrvos, and it is clear that

336 Ever-sporting Varieties

they will be far better nourished than if no
operation were made.

In order to control this experiment some
breeders have made the operation on the fruits
when ripe, instead of on the young pods, and
have saved the seeds from the upper parts sep-
arately. This seed, produced in abundance,
was found to be very poor in double flowers,
containing only some 20-30^. On the con-
trary the percentage of doubles in the seed of
the lower parts was somewhat augmented, and
the average of both would have given the normal
proportion of 50%.

Opposed to the French method is the German
practice of cultivating stocks, as I have seen it
used on a very large scale at Erfurt and at other
places. The stocks are grown in pots on small
scaffolds, and not put on or into the earth.
The obvious aim of this practice is to keep the
earth in the pots dry, and accordingly they are
only scantily watered. In consequence they
cannot develop as fully as they would have done
when planted directly in the beds, and they pro-
duce only small racemes and no weak twigs,
eliminating thereb}^ without further operation
the weaker seeds as by the French method.
The effect is increased by planting from 6-10
separate plants in each pot.

It would be very interesting to make compar-

Striped Flowers 337

ative trials of both methods, in order to discover
the true relation between the practice and the
results reached. Both should also be compared
with cultures on open plots, which are said to
give only 50;j^ of doubles. This last method of
culture is practiced wherever it is desired to
produce great quantities of seeds at a low cost.
Such trials would no doubt give an insight into
the relations of hereditary characters to the
distribution of the food within the plant.

A second point is the proportional increase of
the double-flowering seeds with age. If seed
is kept for two or three years, the greater part
of the grains will gradually die, and among the
remainder there is found on sowing, a higher
percentage of double ones. Hence we may in-
fer that the single-flowered seeds are shorter-
lived than the doubles, and this obviously points
to a greater weakness of the first. It is quite
evident that there is some common cause for
these facts and for the above cited experience,
that the first and best pods give more doubles.
Much, however, remains to be investigated be-
fore a satisfactory answer can be made to these
questions.

A third point is the curious practice, called
b}^ the French ^^ esimpler," and which consists
in pulling out the singles when very young. It
seems to be done at an age when the flower-buds

338 Ever-sporting Varieties

are not yet visible, or at least are not far
enough developed to show the real distinctive
marks. Children may be employed to choose
and destroy the singles. There are some slight
differences in the fullness and roundness of the
buds and the pubescence of the young leaves.
Moreover the buds of the doubles are said to
be sweeter to the taste than those of the singles.
But as yet I have not been able to ascertain,
whether any scientific investigation of this proc-
ess has ever been made, though according to
some communications made to me bv the late
Mr. Cornu, the practice seems to be very gen-
eral in the environs of Paris. In summer large
fields may be seen, bearing exclusively double
flowers, owing to the weeding out of the singles
long before flowering.

Bud- variation is the last point to be taken up.
It seems to be verv rare with stocks, but some
instances have been recorded in literature.
Darwin mentions a double stock with a branch
bearing single flowers, and other cases are
known to have occurred. But in no instance
does the seed of such a bud-variant seem to
have been saved. Occasionally other rever-
sions also occur. From time to time speci-
mens appear with more luxurious growth
and with divergent instead of erect pods.
They are called, in Erfurt, ^' generals " on ac-

striped Flowers 339

count of their stiff and erect appearance,
and they are marked by more divergent horns
crowning the pods. They are said to produce
only a relatively small number of doubles from
their seeds, and even this small number might
be due to fertilization with pollen of their
neighbors. I saw some of these reversionary
types, when inspecting the nurseries of Erfurt,
but as they are, as a rule, thrown out before
ripening their seed, nothing is exactly known
about their real hereditary qualities.

Much remains to be cleared up, but it seems
that one of the best means to find a way through
the bewildering maze of the phenomena of in-
heritance, is to make groups of related forms
and to draw conclusions from a comparison of
the members of such groups. Such comparisons
must obviously give rise to questions, which in
their turn will directly lead to experimental in-
vestigation.

Lecture XII

FIVE-LEAVED CLOVER

Every one knows the ^' four-leaved " clover.
It is occasionally found on lawns, in pastures
and by the roadsides. Specimens with five leaf-
lets may be found now and then in the same
place, or on the same plant, but these are rarer.
I have often seen isolated plants with quater-
nate leaves, but only rarely have I observed in-
dividuals with more than one such leaf.

The two cases are essentially dissimilar.
They may appear to differ but little morpholog-
ically, but from the point of view of heredity
they are quite different. Isolated quaternate
leaves are of but little interest, while the occur-
rence of many on the same individual indicates a
distinct variety. In making experiments upon
this point it is necessary to transplant the di-
vergent individuals to a garden in order to
furnish them proper cultural conditions and
to keep them under constant observation. When
a plant bearing a quaternate leaf is thus
transplanted however, it rarely repeats the

340

Five-leaved Clover 341

anomaly. But when plants with two or more
quaternate leaves on the same individual are
chosen it indicates that it belongs to a definite
race, which under suitable conditions may
prove to become very rich in the anomalies in
question.

Obviously it is not always easy to decide
definitely whether a given individual belongs to
such a race or not. Many trials may be neces-
sary to secure the special race. I had the good
fortune to find two plants of clover, bearing one
quinate and several quaternate leaves, on an
excursion in the neighborhood of Loosdrecht in
Holland. After transplanting them into my
garden, I cultivated them during three years
and observed a slowly increasing number of
anomalous leaves. This number in one summer
amounted to 46 quaternate and 16 quinate
leaves, and it was evident that I had secured an
instance of the rare ^' five-leaved " race which
I am about to describe.

Before doing so it seems desirable to look
somewhat closer into the morphological fea-
tures of the problem. Pinnate and palmate
leaves often vary in the number of their parts.
This variability is generally of the nature of a
common fluctuation, the deviations grouping
themselves around an average type in the ordi-
nary way. Ash leaves bear ^lyq pairs, and

342 Ever-sporting Varieties

the mountain-ash (Sorbus Aucuparia) has six
pairs of leaflets in addition to the terminal one.
But this number varies slightly, the weaker
leaves having less, the stronger more pairs than
the average. Such however, is not the case
with ternate leaves, which seem to be quite con-
stant. Four leaflets occur so very rarely that
one seems justified in regarding them rather as
an anomaly than as a fluctuation. And this is
confirmed by the almost universal absence of
two-bladed clover-leaves.

Considering the deviation as an anomaly, we
may look into its nature. Such an inquiry
shows that the supernumerary leaflets owe their
origin to a splitting of one or more of the nor-
mal ones. This splitting is not terminal, as is
often the case with other species, and as it may
be seen sometimes in the clover. It is for
the most part lateral. One of the lateral nerves
grows out becoming a median nerve of the new
leaflet. Intermediate steps are not wanting,
though rare, and they show a gradual separa-
tion of some lateral part of a leaflet, until this
division reaches the base and divides the leaflet
into two almost equal parts. If this splitting
occurs in one leaflet we get the *^ four-leaved "
clover, if it occurs in two there will be five leaf-
lets. And if, besides this, the terminal leaflet
produces a derivative on one or both of its sides,

Five-leaved Clover 343

we obtain a crown of six or seven leaflets on one
stalk. Such were often met with in the race I
had under cultivation, but as a rule it did not ex-
ceed this limit.

The same phenomenon of a lateral doubling
of leaflets may of course be met with in other
instances. The common laburnum has a va-
riety which often produces quaternate and
quinate leaves, and in strawberries I have also
seen instances of this abnormality. It occurs
also in pinnate leaves, and complete sets of all
the intermediate links may often be found on
the false or bastard-acacia (Robinia Pseud-
Acacia).

Opposed to this increase of the number of
leaflets, and still more rare and more curious is
the occurrence of ^^ single-leaved '' varieties
among trees and herbs with pinnate or temate
leaves. Only very few instances have been de-
scribed, and are cultivated in gardens. The
ashes and the bastard-acacia may be quoted
among trees, and the ^^ one-leaved " strawberry
among herbs. Here it seems that several leaf-
lets have been combined into one, since this one
is, as a rule, much larger than the terminal leaf-
let of an ordinary Teaf of the same species.
These monophyllous varieties are interesting
also on account of their continuous but often in-
complete reversion to the normal type.

344 Ever-sporting Varieties

Pinnate and palmate leaves are no doubt
derivative types. They must have originated
from the ordinary simple leaf. The monophyl-
ly may therefore be considered as a reversion to
a more primitive state and the monophyllous
varieties may be called atavistic.

On the other hand we have seen that these
atavistic varieties may revert to their nearest
progenitors, and this leads to the curious con-
ception of positive and negative atavism. For
if the change of compound leaves into single
ones is a retrograde or negative step, the con-
version of single or ternate leaves into pinnate
and palmate ones must evidently be considered
in this case as positive atavism.

This discussion seems to throw some light on
the increase of leaflets in the clover. The pea-
family, or the group of papilionaceous plants,
has pinnate leaves ordinarily, which, according
to our premises, must be considered as a deriva-
tive type. In the clovers and their allies this
type reverts halfway to the single form, pro-
ducing only three leaflets on each stalk. If now
the clover increases its number of leaflets, this
may be considered as a reversion to its nearest
progenitors, the papilionaceous plants with pin-
nate leaves. Hence a halfway returning and
therefore positive atavism. And as I have al-
ready mentioned in a former lecture, pinnate

Five-leaved Clover 345

leaves are also sometimes produced by my new
race of clover.

Returning to the original plants of this race,
it is evidently impossible to decide whether they
were really the beginning of a new strain, and
had originated themselves by some sudden
change from the common type, or whether
they belonged to an old variety, which had
propagated itself perhaps during centuries,
unobserved by man. But the same diffi-
culty generally arises when new varieties are
discovered. Even the behavior of the plants
themselves or of their progeny does not afford
any means of deciding the question. The sim-
plest way of stating the matter therefore, is to
say that I accidentally found two individuals of
the ^ ^ five-leaved ' ' race. By transplanting them
into my garden, I have isolated them and kept
them free from cross-fertilization with the ordi-
nary type. Moreover, I have brought them un-
der such conditions as are necessary for the full
development of their characters. And last but
not least, I have tried to improve this character
as far as possible by a very rigid and careful
selection.

The result of all this effort has been a rapid
improvement of my strain. I saved the seed
of the original plants in 1889 and cultivated the
second generation in the following year. It

346 Ever-sporting Varieties

showed some increase of the anomaly, but not to
a very remarkable degree. In the flowering pe-
riod I selected four plants with the largest num-
ber of quaternate and quinate leaves and de-
stroyed all the others. I counted in the average
25 anomalous organs on each of them. From
their seed I raised the third generation of my
culture in the year 1891.

This generation included some 300 plants, on
which above 8000 leaves were counted. More
than 1000 were quaternate or quinate, the ter-
nate leaves being still in the majority. But the
experiment clearly showed that ' ^ four-leaved ' '
clovers may be produced in any desired quan-
tity, provided that the seed of the variety is
available. In the summer only three, four and
five leaflets on one stalk were seen, but towards
the fall, and after the selection of the best in-
dividuals, this number increased and came up
to six and seven in some rare instances.

The selection in this year was by no means
easy. Nearly all the individuals produced at
least some quaternate leaves, and thereby
showed the variety to be quite pure. I counted
the abnormal organs on a large group of the
best plants, and selected 20 excellent speci-
mens from them, with more than one-third of
all their leaves changed in the desired manner.

Having brought my race up to this point, I

Five-leaved Clover 347

was able to introduce a new and far more easy-
mark, afforded by the seedlings, for my selec-
tions. This mark has since remained constant,
and has brought about a rapid continuance of
the improvement, without necessitating such
large cultures.

This seedling in the various species of
clover usually begins with a first leaf above
the cotyledons of a different structure from
those that follow. It has only one blade
instead of three. But in my variety the in-
crease of the number of the leaflets may extend
to these primary organs, and make them binate
or even temate. Now it is obvious that an indi-
vidual, which begins with a divided primary
leaf, will have a greater tendency to produce a
large number of supernumerary leaflets than a
plant which commences in the ordinary way.
Or in other words, the primary leaves afford a
sure criterion for the selection, and this selec-
tion may be made in the seed-pans. In conse-
quence, no young individual with an undivided
primary leaf was planted out. Choosing the
20 or 30 best specimens in the seed-pan, no
further selection was required, and the whole
lot could be left to cross-fertilization by insects.
The observation of this distinguishing mark
in the young seedlings has led to the discover}^
of another quality as a starting-point for fur-

348 Ever-sporting Varieties

tlier selection. According to the general rule
of pedigree-culture, the seeds of each individual
plant are always saved and sowed separately.
This is done even with such species as the
clover, which are infertile when self-pollinated,
and which are incapable of artificial pollina-
tion on the required scale, since each flower pro-
duces only one seed. My clover was always
left free to be pollinated by insects. Obviously
this must have led to a diminution of the differ-
entiating characters of the individual plants.
But this does not go far enough to obliterate
the differences, and the selection made among
the seedlings will always throw out at least
a large part of those that have suffered from
the cross.

Leaving this discussion, we may inquire
closer into the nature of the new criterion af-
forded by the seedlings. Two methods present
themselves. First, the choice of the best seed-
lings. In the second place it becomes possible
to compare the parent-plants by counting the
number of deviating seedlings. This leads to
the establishment of a percentage for every
single parent, and gives data for comparisons.
Two or three hundreds of seeds from a parent
may easily be grown in one pan, and in this
way a sufficiently high degTee of accuracy
may be reached. Only those parents that give

Five-leaved Clover 349

the highest percentage are chosen, and among
their progeny only the seedlings with trif oliolate
primary leaves are planted out. The whole
procedure of the selection is by this means con-
fined to the glasshouse during the spring, and
the beds need not be large, nor do they require
any special care during the summer.

By this method I brought my strain within
two years up to an average of nearly 90 ^ of the
seedlings with a divided primary leaf. Around
this average the real numbers fluctuated be-
tween the maximum of 99;^ and the minimum
of 70^ or thereabouts. This condition was
reached by the sixth generation in the year 189-I-,
and has since proved to be the limit, the group
of figures remaining practically the same during
all the succeeding generations.

Such selected plants are very rich in leaves
with four, fi\e and six blades. Excluding the
small leaves at the tops of the branches, and
those on the numerous weaker side-branches,
these three groups include the large majority
of all the stronger leaves. In summer the
range is wider, and besides many trifoliolate
leaves the curiously shaped seven-bladed ones
are not at all rare. In the fall and in the win-
ter the range of variability is narrowed, and
at first sight the plants often seem to bear only
quinquefoliolate leaves.

350 Ever-sporting Varieties

I have cultivated a new generation of this
race nearly every year since 1894, using always
the strictest selection. This has led to a uni-
form type, but has not been adequate to produce
any further improvement. Obviously the ex-
treme limit, under the conditions of climate and
soil, has been reached. This extreme type is
always dependent upon repeated selection. No
constant variety, in the older sense, has been
obtained, nor was any indication afforded that
such a type might ever be produced. On the
contrary, it is manifest that the new form be-
longs to the group of ever-sporting varieties.
It is never quite free from the old atavistic
type of the trifoliolate leaves, and invariably,
when external conditions become less favorable,
this atavistic form is apt to gain dominion over
the more refined varietal character. Rever-
sions always occur, both partial and individual.

Some instances of these reversions may now
be given. They are not of such a striking char-
acter as tliose of the snapdragon. Intermediate
steps are always occurring, both in the leaves
themselves, and in the percentages of deviating
seedlings of the several parent plants.

On normal plants of my variety the quinque-
foliolate leaves usually compose the majority,
when there are no weak lateral branches, or
when they are left out of consideration. Next

Five-leaved Clover 351

r

to these come the fours and the sixes, while the
trifoliolate and seven-bladed types are nearly
equal in number. But out of a lot of plants,
grown from seed of the same parent, it is often
possible to choose some in which one extreme
prevails, and others with a preponderating
number of leaves with the other extreme num-
ber of leaflets. If seed from these extremes are
saved separately, one strain, that with numer-
ous seven-bladed leaves will remain true to the
type, but the other will diverge more or less,
producing leaves with a. varying number of sub-
divisions.

Very few generations of such opposite selec-
tion are required to reduce the race to an
utterly poor one. In three years I was able to
nearly obliterate the type of my variety. I
chose the seedlings with an undivided primary
leaf, cultivated them and counted their off-
spring separately after the sowing. I found
some parents with only 2 - 3^ of seedlings with
divided primary leaves. And by a repeated
selection in this retrograde direction I suc-
ceeded in getting a great number of plants,
which during the whole summer made only
very few leaves with more than three blades.
But an absolute reversion could no more be
reached in this direction than in the normal
one. Any sowing without selection would be

352 Ever-sporting Varieties

liable to reduce the strain to an average condi-
tion.

The production of varietal and of atavistic
leaves is dependent to a high degree on
external conditions. It agrees with the gen-
eral rule, that favorable circumstances
strengthen the varietal peculiarities, while un-
favorable conditions increase the number of the
parts with the atavistic attribute. These in-
fluences may be seen to have their effect on the
single individuals, as well as on the generations
growing from their seed. I cannot cite here all
the experimental material, but a single illustra-
tive example may be given. I divided a strong
individual into two parts, planted one in rich
soil and the other in poor sand, and had both
pollinated by bees with the pollen of some nor-
mal individuals of my variety growing between
them. The seeds of both were saved and sown
separately, and the two lots of offspring culti-
vated close to each other under the same ex-
ternal conditions. In the beginning no differ-
ence was seen, but as soon as the young plants
had unfolded three or four leaves, the progeny
of the better nourished half of the parent-plant
showed a manifest advance. This difference
increased rapidly and was easily seen in the
beds, even before the flowering period.

This experience j^robably gives an explana-

Five-leaved Clover 35

o

tion why the quinquefoliolate variety is so
seldom met with in the wild state. For even if
it did occur more often, the plants would hardly
find circumstances favorable enough for the
full development of their varietal character.
They must often be so poor in anomalous leaves
as to be overlooked, or to be taken for instances
of the commonly occurring quadrifoliolate
leaves and therefore as not indicating the true
variety.

In the beginning of my discussion I have as-
serted the existence of two different races of
** four-leaved " clovers, a poor one and a rich
one, and have insisted on a sharp distinction be-
tween them. This distinction partly depends
on experiments with clover, but in great part
on tests with other plants. The previously
mentioned circumstance, that clover cannot be
pollinated on a sufficiently large scale otherwise
than by insects, prevents trials in more than one
direction at the same time and in the same
garden. For this reason I have chosen another
species of clover to be able to give proof or dis-
proof of the assertion quoted.

This species is the Italian, or crimson clover,
which is sometimes also called scarlet clover
{Trifolium incarnatum). It is commonly used
in Europe as a crop on less fertile soils than
are required by the red clover. It is annual

354 Ever-sporting Varieties

and erect and more or less hairy, and has
stouter leaves than other kinds of clover. It
has oblong or cylindrical heads with bright
crimson flowers, and may be considered as one
of the most showy types. As an annual it has
some manifest advantages over the perennial
species, especially in giving its harvest of hay
at other seasons of the vear.

I found some stray quaternate leaves of this
plant some years ago, and tried to win from
them, through culture and selection, a race that
would be as rich in these anomalies as the red
clover. But the utmost care and the most rigid
selection, and all the attention I could afford,
failed to produce any result. It is now ten
years since I commenced this experiment, and
more than once I have been willing to give it
up. Last year (1903) I cultivated some hun-
dreds of selected plants, but though they yielded
a few more instances of the desired anomaly
than in the beginning, no trace of a truly rich
race could be discovered. The experimental
evidence of this failure shows at least that strav
^' four-leaves '' may occur, which do not indi-
cate the existence of a true " four-" or '' five-
leaved " variety.

This conception seems destined to become of
great value in the appreciation of anomalies, as
they are usually found, either in the wild state

Five-leaved Clover 355

or in gardens. And before describing the de-
tails of my unsuccessful pedigree-culture, it may
be as well to give some more instances of what
occurs in nature.

Stray anomalies are of course rare, but not
so rare that they might not be found in large
numbers when perseveringly sought for.
Pitcher-like leaves may be found on many trees
and shrubs and herbs, but ordinarily one or
only two of them are seen in the course of many
years on the same plant, or in the same strain.
In some few instances they occur annually or
nearly so, as in some individuals of the Euro-
pean lime-tree {Tilia parvifolia) and of the
common magnolia (Magnolia ohovata). Many
of our older cultivated plants are very rich in
anomalies of all kinds, and Cyclamen, Fuchsia,
Pelargonium and some others are notorious
sources of teratologic phenomena. Deviations
in flowers may often be seen, consisting of
changes in the normal number of the several or-
gans, or alterations in their shape and color.
Leaves may have two tips, instead of one, the
mid-vein being split near the apex, and the fis-
sure extending more or less towards the base.
Rays of the umbels of umbelliferous plants may
grow together and become united in groups of
two or more, and in the same way the fruits of

356 Ever-sporting Varieties

the composites may be united into groups.
Many other instances could easily be given.

If we select some of these anomalies for
breeding-experiments, our results will not agree
throughout, but will tend to group themselves
under two heads. In some cases the isolation
of the deviating individuals will at once show
the existence of a distinct variety, which is
capable of producing the anomaly in any de-
sired number of instances, only dependent on
a favorable treatment and a judicious selection.
In other cases no treatment and no selection
are adequate to give a similar result, and the
anomaly remains refractory despite all our en-
deavors to breed it. The cockscomb and the
peloric fox-glove are widely known instances of
permanent anomalies, and others will be dealt
with in future lectures. On the other hand
I have often tried in vain to win an anomalous
race from an accidental deviation, or to isolate
a teratologic. variety out of more common aber-
rations. Two illustrative examples may be
quoted. In our next lecture we shall deal with
a curious phenomenon in poppies, consisting in
the change of the stamens into pistils and giving
rise to a bright crown of secondary capsules
around the central one. Similar anomalies may
be occasionally met with in other species of the
same genus. But they are rare, and may show

Five-leaved Clover 357

the conversion of only a single stamen in the
described manner. I observed this anomaly in
a poppy called Papaver commutatum, and sub-
jected it during several years to a rigid selec-
tion of the richest individuals. No ameliora-
tion was to be gained and the culture had to be
given up. In the same way I found on the bul-
bous buttercup (Ranunculus hulbosus) a strain
varying largely in the number of the petals,
amounting often to Q-S^ and in some flowers
even yet to higher figures. During five succeed-
ing years I cultivated five generations, often in
large numbers, selecting always those which
had the highest number of petals, throwing out
the remainder and saving the seed only from
the very best plants. I got a strain of selected
plants with an average number of nine petals
in every flower, and found among 4000 flowers
four having 20 petals or more, coming up even
to 31 in one instance. But such rare instances
had no influence whatever on the selection,
since thev were not indicative of individual
qualities, but occurred quite accidentally on
flowers of plants having only the average num-
ber of petals. Now double flowers are widely
known to occur in other species of the butter-
cups, both in the cultivated varieties and in
some wild forms. For this reason it might be
expected that through a continuous selection of

358 Ever-sporting Varieties

the individuals with the largest numbers a
tendency to become double would be evolved.
Such, however, was not the case. No propen-
sity to vary in any definite direction could be
observed. Quite on the contrary, an average
condition was quickly reached, and then re-
mained constant, strongly counteracting all
selection.

Such experiences clearly show that the same
anomaly may occur in different species, and no
doubt in strains of the same species from dif-
ferent localities, according to at least two dif-
ferent standards. The one is to be called the
poor, and the other the rich variety. The first
always produces relatively few instances of the
deviation, the last is apt to give as many of them
as desired. The first is only half-way a variety,
and therefore would deserve the name of a half-
race ; the second is not yet a full constant vari-
ety, but always fluctuates to and fro between the
varietal and the specific mark, ever-sporting in
both directions. It holds a middle position be-
tween a half-race and a variety, and there-
fore might be called a " middle-race." But
the term ever-sporting variety seems more ade-
quate to convey a right idea of the nature of
this curious type of inheritance.

From this discussion it will be seen that the
behavior of the crimson clover is not to be con-

Five-leaved Clover 359

sidered as an exception, but as a widely occur-
ring type of phenomenon, occurring perhai)s in
all sorts of teratologic deviations, and in wide
ranges of species and genera. Hence it may be
considered worth while to give some more de-
tails of this extended experiment.

Ten years ago (1894-5) I bought and sowed
about a pound of seed of the crimson clover.
x\mong many thousands of normal seedlings I
found two with three and one with four cotyle-
dons. Trusting to the empirical rules of corre-
lation, I transplanted these three individuals in
order to isolate them in the flowering period.
One of them produced during the ensuing sum-
mer one four-bladed and one five-bladed leaf.
The seeds were saved separately and sown the
following spring and the expected result could
soon be seen. Among some 250 individual
plants I counted 22 with one or two deviations,
and 10 with from three to nine four- or five-
bladed leaves. Proportions nearly similar have
been observed repeatedly. Better nourished in-
dividuals have produced more deviating leaves
on one plant, partly owing to the larger number
of stems and branches, and poor or average
specimens have mostly been without any aber-
ration or with only one or two abnormal leaves.
No further improvement could be attained.
Quadrifoliolate leaves were always rare, never

360 Ever-sporting Varieties

attaining a number that would put its stamp on
a whole bed. I have endeavored to get some
six- and seven-bladed crimson clover leaves, but
in vain ; selection, culture of many hundreds of
individuals, manure, and the best possible treat-
ment has not been adequate to produce them.
Of course I am quite convinced that a repetition
of my experiment on a far larger scale would
jdeld the desired types, but then only in such
rare instances that they would have no influence
whatever on the average, or on the improve-
ment of the race. The eighth generation in the
year 1903 has not been noticeably better than
the second and third generations after the first
selection.

In comparing this statement with the results
gained in the experiment with the red clover,
the difference is at once striking. In one case
a rich variety was isolated, and, by better
treatment and sharp methods of selection, was
brought up in a few years to its highest
pitch of development. In the other case a very
weak race was shown to exist, and no amount
of work and perseverance was adequate to im-
prove it to any noticeable degree.

I wish to point out that the decision of what
is to be expected from deviating specimens may
become manifest within one or two generations.
Even the generation grown from the seeds of

Five-leaved Clover 361

the first observed aberrant individuals, if gath-
ered after sufficient isolation during the period
of blossoming, may show which type Oi in-
heritance is present, whether it is an unpromis-
ing half-race, or a richly endowed sporting
variety. I have kept such strains repeatedly
after the first isolation, and a special case, that
of cotyledoneous aberrations, will be dealt with
later. The first generation always gave a final
decision, provided that a suitable method of
cultivation for the species under observation
was found at the beginning. This however,
is a condition, which it is not at all easy to
comply with, when new sorts are introduced
into a garden. Especially so when they had
been collected in the wild state. Often one or
two years, sometimes more, are necessary to
find the proper method of sowing, manuring,
transplanting and other cultural methods satis-
factory to the plants. Many wild species re-
quire more care and more manure in gardens
than the finest garden flowers. And a large
number are known to be dependent on very
particular conditions of soil.

One of the most curious features of anom-
alies, which has been learned from accumulated
instances, is the fact that they obey definite
laws as to their occurrence on the different
parts of the plant. Obviously such laws are

362 Ever-sporting Varieties

not apparent as long as each plant produces
only one or two, or, at most, a few instances of
the same deviation. On the contrary, any ex-
isting regularity must betray itself, as soon as
a larger number of instances is produced. A
rule of periodicity becomes most clearly mani-
fest in such cases.

This rule is shown by no other race in a more
undoubted and evident manner than by the
*^ five-leaved " clover. Evidently the several
degrees of deviation, going from three to seven
leaflets, may be regarded as responses to differ-
ent degrees of variation, and their distribution
over the stems and branches, or over the whole
plant, may be considered as the manifestation of
the ever-changing internal tendency to vary.

Considered from this point of view, my plants
always showed a definite periodicity in this dis-
tribution, which is the same for the whole plant.
Each of them, and each of the larger branches,
begin with atavistic leaves or with slight devia-
tions. These are succeeded by greater devia-
tions, but only the strongest axes show as many
as seven leaflets on a stalk. This ordinarily
does not occur before the height of development
is reached, and often only towards its close-
Then the deviation diminishes rapidly, return-
ing often to atavistic leaves at the summit of the
stem or branch. I give the numbers of the

Five-leaved Clover 363

leaves of a branch, in their order from the base
to the top. They were as follows :

3. 4. 5. 6. 7. 5. 5. 4.

But this is a selected case, and such regular
examples of the expected periodicity are rarely
found. Often one or more of the various steps
are lacking, or even leaves with smaller num-
bers may be interspersed among those with
larger numbers of leaflets. But while the regu-
larity of the periodicity is in some degree
diminished by such occurrences, yet the rule
always holds good, when taken broadly. It
may be expressed by stating that the bases and
apices have on the average fewer leaflets on each
leaf than the middle parts of the stem and
branches, and that the number of leaflets grad-
ually^ increases from the base toward a maxi-
mum, which is reached in organs on the middle
or upper part of the axis, and then diminishes
from this toward the apex.

This periodicity is not limited to the stems
and branches, considered singly, but also holds
good in a comparison made between the
branches of a single stem, in regard to their rel-
ative places on that stem. So it is also for the
whole plant. The first stems, produced by the
subterranean axis, ordinarily show only a low
maximum deviation: the next succeeding being

364: Ever-sporting Varieties

more divergent and the last ones returning to
less differentiated forms.

It is evident that on a given stem the group
of deviating leaves will be extended upward and
downward, with the increase of the number of
these organs. This shows that a stem, or even
a plant, promises a higher degree of differentia-
tion if it commences with its aberration earlier.
Hence it becomes possible to discern the most
promising individuals in early youth, and this
conclusion leads to a very easy and reliable
method of selection, which may be expressed
simply as follows: the seedlings which com-
mence earliest with the production of four- and
five-foliolate leaves are the best and should be
selected for the continuance of the race. And
it is easily seen that this rule agrees with that
given above, and which was followed in my
pedigree-culture.

Furthermore it is seen that there is a com-
plete agreement between the law of periodicity
and the responses of the deviations to nourish-
ment and other conditions of life. Weak plants
only produce low degrees of deviation, the
stronger the individual becomes, the higher it
reaches in the scale of differentiation, and the
more often it develops leaves with five or more
blades. Whether weakness or strength are de-
rived from outer causes, or from the internal

Five-leaved Clover 365

succession of the periods of life, is evidently of
no consequence, and in this way the law of
periodicity may be regarded as a special in-
stance of the more general law of response to
external conditions.

The validity of this law of periodicity is of
course not limited to our ^^ five-leaved " clover.
Quite on the contrary it is universal in ever-
sporting varieties. Moreover it may be ascer-
tained and studied in connection with the most
widely different morphologic abnormalities, and
therefore affords easily accessible material for
statistical inquiry. I will now give some fur-
ther instances, but wish to insist first upon the
necessity of an inquiry on a far larger scale,
as the evidence as yet is very scanty.

The great celandine (Chelidonium ma jus)
has a very curious double variety. Its flowers
are simpler and much more variable than in
ordinary garden-varieties. The process of
doubling consists mainly in a change of stamens
into petals. This change is dependent on the
season. On each stem the earliest flowers are
single. These are succeeded by blossoms with
one or two converted stamens, and towards the
summer this number increases gradually, attain-
ing 10 - 11 and in some instances even more
altered filaments. Each vear the same succes-
sion may be seen repeating itself on the stems of

366 Ever-sporting Varieties

the old roots. Double tuberous begonias are or-
dinarily absolutely sterile throughout the sum-
mer, but towards autumn the new flowers be-
come less and less altered, producing some nor-
mal stamens and pistils among the majority of
metamorphosed organs. From these flowers the
seeds are saved. Sometimes similar flowers
occur at the beginning of the flowering-period.
Double garden-camomiles (CJirysanthemnm in-
odorum plenissimum) and many other double
varieties of garden-plants among the great
family of the composites are very sensitive to
external agencies, and their flower-heads are
fuller the more favorable the external condi-
tions. Towards the autumn many of them pro-
duce fewer and fewer converted heads and often
only these are fertile and yield seeds.

Ascidia afford another instance of this
periodicity, though ordinarily they are by far
too rare to show any regularity in their distri-
bution. However, it is easy to observe that on
lime-trees they prefer the lower parts of each
twig, while on magnolias the terminal leaves
of the branches are often pitcher-bearing.
Ascidia of the white clover have been found
in numbers, in my own experiment-garden,
but always in the springtime. The thick-
leaved saxifrage (Saxifraga crassifolia) is
often very productive of ascidia, especially in

Five-leaved Clover 367

the latter part of the season, and as these organs
may be developed to very different degrees,
they afford fine material for the study of the
law of periodicity. On a garden-cytisus
(Cytisus candicans attleyanus) I once had the
good fortune to observe a branch with ascidia,
which ordinarily are very rare in this species.
It had produced seven ascidia in all, each
formed by the conversion of one leaflet on the
trifoliolate leaves. The first six leaves were
destitute of this malformation and were quite
normal. Then followed a group of fL\e leaves,
constituting the maximum of the period. The
first bore one small pitcher-like blade, the sec-
ond and third, each one highly modified organ,
the fourth, two ascidia, and the last, one leaflet
with slightly connate margins. The whole
upper part of the branch was normal, with the
exception of the seventeenth leaf, which showed
a slight change in the same direction. All in
all, the tendency to produce ascidia increased
from the beginning to the tenth leaf, and de-
creased from this upward.

The European Venus' looking-glass was ob-
served in my garden to produce some quater-
nate and some quinate flowers on the same spec-
imens. The quinate were placed at the end of
the branches, those with four petals and sepals
lower down. The peloric fox-glove shows the

368 Ever-sporting Varieties

highest degree of metamorphy in the terminal
flowers of the stem itself, the weaker branches
having but little tendency towards the forma-
tion of the anomaly. The European pine or
Pinus sylvestris ordinarily has two needles in
each sheath, but trifoliolate sheaths occur on the
stems and stronger branches, where they prefer,
as a rule, the upper parts of the single annual
shoots. Camellia japonica is often striped in
the fall and during the winter, but when flower-
ing in the spring it returns to the monochro-
matic type.

Peloric flowers are terminal in some cases,
but occur in the lower parts of the flower-spikes
in others. Some varieties of gladiolus com-
mence on each spike with more or less double
flowers, which, higher up, are replaced by single
ones. A wide range of bulbs and perennial gar-
den-plants develop their varietal characters
only partly when grown from seed and flower-
ing for the first time. The annual garden-for-
get-me-not of the Azores {Myosotis azorica)
has a variety with curiously enlarged flowers,
often producing 20 or more corolla-segments in
one flower. But this number gradually dimin-
ishes as the season advances. It would be quite
superfluous to give further proof of the general
validity of the law of periodicity in ever-sport-
ing varieties.

Lecture XIII

PISTILLODY IN POPPIES

One of the most curious anomalies that may
be met with in ornamental garden-plants is the
conversion of stamens into pistils. It is neither
cormnon nor rare, but in most cases the change
is so slight comparatively that it is ordinarily
overlooked. In the opium-poppy, on the con-
trary, it is very showy, and heightens the orna-
mental effect of the young fruits after the fad-
ing of the flowers. Here the central capsule is
surrounded by a large crown of metamorphosed
stamens.

This peculiarity has attracted the attention
both of horticulturists and of botanists. As a
rule not all the stamens are changed in this way
but only those of the innermost rows. The
outer stamens remain normal and fertile, and
the flowers, when pollinated with their own pol-
len, bear as rich a harvest of seeds as other
opium-poppies. The change affects both the
filament and the anther, the former of which is
dilated into a sheath. Within this sheath per-

369

370 Ever-sporting Varieties

feet and more or less numerous ovules may be
produced. The anthers become rudhnentary
and in their place broad leafy flaps are de-
veloped, which protrude laterally from the tip
and constitute the stigmas. Ordinarily these
altered organs are sterile, but in some instances
a very small quantity of seed is produced, and
when testing their viability I succeeded in
raising a few plants from them.

The same anomaly occurs in other plants.
The common wall-flower (Cheircmthus Cheiri)
and the houseleek (Sempervivum tectorum) are
the best known instances. Both have repeated-
ly been described by various investigators. In
compiling the literature of this subject it is
very interesting to observe the two contrasting
views respecting the nature of this anomaly.
Some writers, and among them Masters in his
^' Vegetable Teratology " consider the devia-
tions to be merely accidental. According to them
some species are more subject to this anomaly
than others, and the houseleek is said to be very
prone to this change. Goeppert, Hofmeister
and others occasionally found the pistilloid pop-
pies in fields or gardens, and sowed their seeds
in order to ascertain whether the accidental
peculiarity was inheritable or not. On the
other hand De Candolle in his '' Prodromus '^
mentions the pistilloid wall-flowers as a distinct

Polycephalic Poppies 371

variety, under the name of Cheiranthus Cheiri
gynantherus, and the analogous form of the
opium-poppy is not at all an accidental anomaly,
but an old true horticultural variety, which
can be bought everywhere under the names of
Papaver somniferum monstruosum or polyce-
phalum. Since it is an annual plant, only the
seeds are for sale, and this at once gives a suffi-
cient proof of its heredity. In all cases, where
it was met with accidentally by botanists, it is to
be assumed that stray seeds had been casually
mixed with those of other varieties, or that the
habit had been transmitted by a spontaneous
cross.

Wherever opportunity led to experiments on
heredity, distinct races were found to be in pos-
session of this quality, while others were not.
It is of no use to cultivate large numbers
of wall-flowers in the hope of one day seeing the
anomaly arise ; the only means is to secure the
strain from those who have got it. With pop-
pies the various varieties are so often inter-
crossed by bees, that the appearance of an acci-
dental change may sometimes be produced, and
in the houseleek the pistilloid variety seems to
be the ordinary one, the normal strain being
very rare or perhaps wholly wanting.

Our three illustrative examples are good and
permanent races, producing their peculiar quali-

372 Ever-sporting Varieties

ties regularly and abundantly. In this respect
they are however very variable and dependent
on external circumstances. Such a regularity
is not met with in other instances. Often pedi-
gree-experiments lead to poor races, betraying
their tendency to deviate only from time to time
and in rare cases. Such instances constitute
what we have called in a former lecture, ^ ^ half-
races," and their occurrence indicates that the
casual observation of an anomaly is not in itself
adequate to give an opinion as to the chance of
repetition in sowing experiments. A large
number of species seem to belong to this case,
and their names may be found in the above
mentioned work by Masters and elsewhere.
But no effort has yet been made to separate
thoroughly the pistilloid half-races from the
corresponding ever-sporting varieties. Some
plants are recorded as being more liable to this
peculiarity than others.

Stamens are sometimes replaced by open
carpels with naked ovules arising from their
edges and even from their whole inner sur-
faces. This may be seen in distinct strains of
the cultivated bulbous Begonia, and more rarely
in primroses. Here the apex of the carpellary
leaf is sometimes drawn out into a long style,
terminated by a flattened spatulate stigma.

The pistillody of the stamens is frequently

Polycephalic Poppies 373

combined with another deviation in the poppies.
This is the growing together of some of the
altered stamens so as to constitute smaller or
larger connate groups. Often two are united,
sometimes three, four or more. Flowers with
numerous altered stamens are seldom wholly
free from this most undesirable secondary
anomaly. I call it undesirable with respect
to experiments on the variability of the
character. For it may easily be seen that
while it is feasible to count the stamens
even when converted into pistils, it is not
possible when groups of them are more or
less intimately united into single bodies. This
combination makes all enumeration difficult and
inaccurate and often wholly unreliable. In
such cases the observation is limited to a compu-
tation of the degree of the change, rather than
to a strict numerical inquiry. Happily the re-
sponses to the experimental influences are so
marked and distinct that even this method of de-
scribing them has proved to be wholly sufficient.

In extreme instances I have seen all the
changed stamens of a flower of the opium-poppy
united into a single body, so as to form a close
sheath all around the central ovary. Lesser
sheaths, surrounding one-half or one-third of
the capsule are of course less rarely met with.

Leaving this description of the outer appear-

374 Ever-sporting Varieties

ance of our anomaly, we may now consider it
from the double point of view of inheritance
and variability.

The fact of inheritance is shown by the ex-
perience of many authors, and by the circum-
stance already quoted, that the variety has been
propagated from seed for more than half a cen-
tury, and may be obtained from various seed-
merchants. In respect to the variability, the
variety belongs to the ever-sporting group, con-
stituting a type which is more closely related to
the ''five-leaved '' clover than to the striped
flowers or even the double stocks.

It fluctuates around an average type with half
filled crowns, going as far as possible in both
directions, but never transgressing either limit.
It is even doubtful whether the presumable
limits are, under ordinary circumstances, ever
reached. , Obviously one extreme would be the
conversion of all the stamens, and the other the
absolute deficiency of any marked tendency to
such a change. Both may occur, and will prob-
ably be met with from time to time. But they
must be extremely rare, since in my own exten-
sive experiments, which were strictly controlled,
I never was able to find a single instance of
either of them. Some of the outer stamens
have always remained unchanged, yielding
enough pollen for the artificial pollination of

Polycephalic Poppies 375

the central ovary, and on the other hand some
rudmients of hardened filaments were always
left, even if they were reduced to small pro-
tuberances on the thalamus of the flower.

Between these extremes all grades occur.
From single, partially or wholly changed
stamens upwards to 150 and over, all steps may
be seen. It is a true fluctuating variability.
There is an average of between 50 and 100, con-
stituting a nearly filled crown around the cen-
tral capsule. Around this average the smaller
deviations are most numerous and the larger
ones more rare. The inspection of any bed of
the variety suffices to show that, taken broadly,
the ordinary laws of fluctuating variability are
applicable. No counting of the single individ-
uals is required to dispel all doubts on this
point.

Moreover all intermediate steps respecting
the conversion of the single stamens may nearly
always be seen. Rarely all are changed into
normal secondary ovaries with a stigma and
with a cavity filled with ovules. Often the
stigma is incomplete or even almost wanting, in
other instances the ovules are lacking or the
cavity itself is only partially developed. Not
rarely some stamens are reduced and converted
into thin hard stalks, without any appearance of
an ovary at their tip. But then the demar-

376 Ever-sporting Varieties

cation between them and the thalamus fails, so
that they cannot be thrown off when the flower
fades away, but remain as small stumps around
the base of the more fully converted filaments.
This fact would frequently render the enumera-
tion of the altered organs quite unreliable.

For these reasons I have chosen a group of
arbitrary stages in order to express the degree
of deviation for a given lot of plants. The
limits were chosen so as to be sufficiently trust-
worthy and easy to ascertain. In each group
the members could be counted, and a series of
figures was reached by this means which al-
lowed of a further comparison of the competing
sets of plants.

It should be stated that in such experiments
and especially in the case of such a showy crite-
rion as the pistilloid heads afford after the time
of flowering is over, the inspection of the con-
trolling beds at once indicates the result of the
experiment. Even a hasty survey is in most
cases sufficient to get a definite conclusion.
Where this is not the case, the counting of the
individuals of the various groups often does not
add to the evidence, and the result remains un-
certain. On the other hand, the impression
made by the groups of plants on the experi-
menter and on his casual visitors, cannot well
be conveyed to the readers of his account by

Poly cephalic Poppies 317

other means than by figures. For this reason
the result of the experhnents is expressed in
this way.

I made six groups. The first includes tlie
cases where the whole circle is reduced to
small rudiments. The second shows 1-10 sec-
ondary capsules. The two following consti-
tute half a crown around the central fruit, the
third going up to this limit, the fourth going
from this limit to a nearly filled circle. Wholly
filled circles of secondary capsules without gaps
give the two last degrees, the fifth requiring
only continuity of the circle, the sixth display-
ing a large and bright crown all around the
central head. The fifth group ordinarily in-
cludes from 90 - 100 altered stamens, while the
sixth has from 100 - 150 of these deviating
parts.

In ordinary cultures the third and fourth
group, with their interrupted crowns, predomi-
nate. Large crowns are rare and flowers which
at first sight seem to be wholly normal, occur
only under circumstances definitely known to be
unfavorable to growth, and to the development
of the anomalv.

Having reached by this means a very simple
and easy method of stating the facts shown by
equal lots under contrasting influences, we will
now make use of it to inquire into the relation

378 Ever-sporting Varieties

of this exceptionally high degree of variability
to the inner and outer conditions of life.

As a rule, all experiments show the existence
of such a relation. Unfavorable conditions re-
duce the numbers of altered stamens, favorable
circumstances raise it to its highest point. This
holds true for lots including hundreds of speci-
mens, but also for the sundry heads of one bed,
and often for one single plant.

We may compare the terminal flower with
those of the lateral branches on a plant, and
when no special influences disturb the experi-
ment, the terminal head ordinarily bears the
richest crown. If the first has more than
100 metamorphosed parts, the latter have
often less than 50 on the same plant. In poor
soil, terminal heads are often reduced to 10 - 20
monstrous organs, and in such cases I found the
lateral flowers of the same plants ordinarily
with less than 10 altered stamens. In some
cases I allowed the branches of the third and
fourth degree, in other words, the side twigs of
the first branches of my selected plants to grow
out and produce flowers in the fall. They were
ordinarily weak, sometimes very small, having
only 5-9 stigmas on their central fruit. Sec-
ondary capsules were not seen on such flowers,
even when the experiment was repeated on a

Polycephalic Poppies 379

somewhat larger scale and during a series of
years.

Among the same lot of plants individual dif-
ferences almost always occur. They are partly
due to inequalities already existing in the seeds,
and partly to the diversity of the various parts
of the same bed. Some of the plants become
stout and have large terminal heads. Others
remain very weak, with a slender stem, small
leaves and undersized flowers. The height and
thickness of the stem, the growth of the foliage
and of the axillary buds are the most obvious
measures of the individual strength of the
plant. The development of the terminal flower
and the size of its ovary manifestly depends
largely on this individual strength, as may be
seen at once by the inspection of any bed of
opium-poppies. Now this size of the head can
easily be measured, either by its height or cir-
cumference, or by its weight. Moreover we can
arrange them into a series according to their
size. If we do this with the polycephalous vari-
ety, the relation between individual strength
and degree of metamorphosis at once becomes
manifest. The largest heads have the brightest
crowns, and the number of supernumerary car-
pels diminishes in nearly exact proportion to the
size of the fruits. Fruits with less than 50 al-
tered stamens weighed on an average 5 grams,

380 Ever-sporting Varieties

those with 50 - 100 such organs 7 grams and
those with a bright crown 10 grams, the appen-
dices being removed before the weighing. Cor-
responding results have been reached by the
comparison of the height of the capsules with
their abnormal surroundings. The degree of
development of the monstrosity is shown by this
observation to be directly dependent on, and in
a sense proportionate to the individual strength
of the plant.

The differences between the specimens grown
from a single lot of seeds, for instance from
the seeds of one self-fertilized capsule are, as I
have said, partly due to the divergences which
are always present in a bed, even if the utmost
care has been taken to make it as uniform as
possible. These local differences are ordinarily
underrated and overlooked, and it is often con-
sidered to be sufficient to cultivate small lots of
plants under apparently similar conditions on
neighboring beds, to be justified in imputing all
the observed deviations of the plants to heredi-
tary inequalities. This of course is true for
large lots, whenever the averages only are com-
pared. In smaller experiments the external con-
ditions of the single individuals should always
be considered carefully. Lots of one or two
square meters suffice for such comparisons, but
smaller lots are always subject to chances and

PolycephaUc Poppies 381

possibilities, which should never be left out of
consideration.

Therefore I will now point out some circum-
stances, which are ordinarily different on va-
rious parts of one and the same bed.

In the first place comes the inequality of the
seeds themselves. Some of them will germi-
nate earlier and others later. Those that dis-
play their cotyledons on a sunny day will be
able to begin at once with the production of
organic food. Others appear in bad weather,
and will thus be retarded in their development.
These effects are of a cumulative nature as
the young plants must profit by every hour of
sunshine, according to the size of the cotyledons.
Any inequality between two young seedlings is
apt to be increased by this cumulative effect.

The same holds good for the soil of the bed.
It is simply impossible to mix the manure so
equally that all individuals receive the same
amount of it from the very beginning. I am in
the habit of using manures in a dry and pulver-
ized condition, of giving definite quantities to
each square meter, and of taking the utmost
care to get equal distribution and mixture with
the soil, always being present myself during this
most important operation. Nevertheless it is
impossible to make the nourishment exactly
equal for all the plants of even a small bed.

382 Ever-sporting Varieties

Any inequality from this cause will increase
the difference in the size of the young leaves,
augment the inequality of their production of
organic matter and for this reason go on in an
ever increasing rate.

Rain and spraying, or on the other hand dry-
ness of the soil, have still greater consequences.
The slightest unevenness of the surface will
cause some spots to dry rapidly and others to
retain moisture during hours and even some-
times during days.

Seeds, germinating in such little moist de-
pressions grow regularly and rapidly, while
those on the dryer elevations may be retarded
for hours and days, before fully unfurling their
seed-leaves. After heavy rains these differ-
ences may be observed to increase continu-
ally, and in some instances I found that plants
were produced only on the wet spots, while the
dry places remained perfectly bare. From this
the wet spots seem to be the most favorable, but
on the other hand, seeds may come to germinate
there too numerously and so closely that the
young plants will be crowded together and find
neither space nor light enough, for a free and
perfect development. The advantage may
change to disadvantage in this way unless the
superfluous individuals are weeded out in due
time.

Polycephalic Poppies 383

From all these and other reasons some plants
will be favored by the external conditions from
the beginning, while others will be retarded, and
the effects will gradually increase until at last
they become sufficient to account for a consider-
able amount of individual variability. There
is no doubt that the difference in the strength of
the plant and in the size of the capsules, going
from 5-10 grams for a single fruit, are for the
most part due to these unavoidable circum-
stances. I have tried all conceivable means to
find remedies for these difficulties, but only by
sowing my seeds in pans in a glass-house have
I been able to reach more constant and equal
conditions. But unfortunately such a method
requires the planting out of the young seed-
lings in the beginning of the summer, and this
operation is not without danger for opium-pop-
pies, and especially not without important influ-
ence on the monstrosity of the pisiilloid variety.
Consequently my sowings of this plant have
nearly always been made in the beds.

In order to show how great the influence of all
these little things may become, we only have to
make two sowings on neighboring beds and un-
der conditions which have carefully been made
as equal as possible. If we use for these con-
trolling experiments seeds from one and the
same capsule, it will soon become evident that

384 Ever-sporting Varieties

no exact similarity between the two lots may be
expected. Such differences as may be seen in
these cases are therefore never to be considered
of value when comparing two lots of seeds of
different origin, or under varying conditions.
No amount of accuracy in the estimation of the
results of a trial, or in the counting out of the
several degrees of the anomaly, is adequate to
overcome the inaccuracy resulting from these
differences.

It is certainly of great importance to have a
correct conception in regard to the influence of
the surrounding conditions on the growth of a
plant and on the development of the attribute we
are to deal with. No less important is the ques-
tion of the sensibility of the plants to these fac-
tors. Obviously this sensibility must not be
expected to remain the same during the entire
life-period, and periods of stronger and of
weaker responses may be discerned.

In the first place it is evident that external or
inner influences are able to change the direction
of the development of an organ only so long as
this development is not yet hiMj finished. In
the young flower-bud of the pistilloid poppy
there must evidently be some moment in which
it is definitely decided whether the young
stamens will grow out normally or become meta-
morphosed into secondary pistils. From this

Polycephalic Poppies 385

moment no further change of external condi-
tions is able to produce a corresponding change
in the degree of the anomaly. The indi-
vidual strength of the whole plant may still be
affected in a more or less manifest degree, but
the number of converted stamens of the flower
has been definitely fixed. The sensitive period
has terminated.

In order to determine the exact moment of
this termination of the period of sensibility, I
have followed the development of the flower-
buds during the first weeks of the life of the
young plants. The terminal flower may al-
ready be seen in young plants only seven weeks
old, with a stem not exceeding 5-6 cm. in
height and a flower-bud with a diameter of
nearly 1mm., in which the stamens and sec-
ondary pistils are already discernible, but still
in the condition of small rounded protuberances
on the thalamus. Though it is not possible at
that time to observe any difference between the
future normal and converted stamens, it does
not seem doubtful that the development is so far
advanced, that in the inner tissues the decision
has already definitely been taken. In the next
few days this decision rapidly becomes vis-
ible, and the different parts of the normal
stamens and the metamorphosed carpels soon
become apparent. From this observation it

386 Ever-sporting Varieties

can be inferred that the sensitive period of the
anomaly is limited for the terminal flower-head,
to the first few weeks of the life of the young
plants. The secondary heads manifestly leave
this period at a somewhat later stage.

In order to prove the accuracy of this con-
clusion I have tried to injure the anomalies
after the expiration of the first six or seven
weeks. I deprived them of their leaves, and
damaged them in different ways. I succeeded
in making them very weak and slender, without
being able to diminish the number of the super-
numerary carpels. The proportionality of the
size of the central fruit and the development of
the surrounding crown can often be modified or
even destroj^ed by this means, and the apparent
exceptions from this rule, which are often ob-
served, may find their explanation in this way.

In the second place I have tried to change the
development of the anomaly during the period
of sensibility, and even in the last part of it.
This experiment succeeded fully when carried
out within the fifth or sixth week after the be-
ginning of the germination. As means of in-
jury I transplanted the young plants. To this
end I sowed my seeds in pans in unmanured soil,
planted them out in little pots with richly pre-
pared earth, grew them in these during a few
weeks and afterwards transferred them to the

Polycephalic Poppies 387

beds, taking care that the pots were removed,
but the balls of earth not broken.

In consequence of this treatment the plants
became very large and strong, with luxuriant
foliage and relatively numerous large flowers
and fruits. But almost without exception they
were poor in anomalous stamens, at least so on
the terminal heads. On a lot of some 70 plants
more than 50 had less than half a crown of sec-
ondary capsules, while from the same packet of
seed the control-plants gave in an equal number
more than half of filled crowns on all plants with
the exception of ^we weak specimens.

It is curious to compare such artificially in-
jured plants with the ordinary cultures.
Strong stems and heavy fruits, which otherwise
are always indicative of showy crowns, now
bear fruits wholly or nearly destitute of any
anomalous change. The commonly prevailing
rule seems to be reversed, showing thereby the
possibility of abolishing the correlation between
individual strength and anomaly by an artificial
encroachment upon the normal conditions.

Aside from these considerations the experi-
ments clearly give proof of the existence of a
period of sensibility limited to the first weeks of
the life of the plant for the terminal flower.
This knowledge enables us to explain many ap-

388 Ever-sporting Varieties

parent abnormalities, which may occur in the
experiments.

We now may take a broader view of the pe-
riod of sensibility. Evidently the response to
external influences will be greater the younger
the organ. Sensibility will gradually diminish,
and the phenomena observed in the last part
of this period may be considered as the last re-
mainder of a reaction which previously must
have been much stronger and much readier, pro-
viding that it would be possible to isolate them
from, and contrast them with, the other re-
sponses of the same plant.

With the light thus cast upon the question,
we may conclude that the sensitive period com-
mences not only at the beginning of the germi-
nation, but must also be considered to include
the life of the seed itself. From the moment
of fertilization and the formation of the
young embryo the development must be sub-
jected to the influence of external agencies
which determine the direction it will take and
the degree of development it will finally be able
to acquire. Probably the time of growth of
the embryo and of the ripening of the seed
correspond exactly to the period of highest
sensibility. This period is only interrupted
during the resting stage of the seed, to be re-
peated in germination. Afterwards the sensi-

Poly cephalic Poppies 389

bility slowly and gradually decreases, to end
with the definite decision of all further growth
sometime before the outer form of the organ be-
comes visible under the microscope. The last
period of life includes only an expansion of the
tissues, which may still have some influence on
their final size, but not on their form. This
has been definitely arrested before the end of
the sensitive period, and ordinarily before the
com,mencement of that rapid development,
which is usually designated by the name of
growth, as contrasted with evolution.

Within the seed the evolution of the young
plant manifestly depends upon the qualities
and life-conditions of the parent-plant. The
stronger this is, and the more favorable circum-
stances it is placed under, the more food will be
available for the seed, and the healthier will be
the development of the embryo. Only well-
nourished plants give well-nourished seeds, and
the qualities of each plant are for this reason
at least, partly dependent on the properties of
its parents and even of its grandparents.

From these considerations the inference is
forced upon us that the apparently hereditary
differences, which are observed to exist among
the seeds of a species or a variety and even of a
single strain or a single parent-plant, may for
a large part, and perhaps wholly, be the result

odiJ Ever-sporting Varieties

of the life-conditions of their parents and
grandparents. Within the race all variability
would in this way be reduced to the effects
of external circumstances. Among these nour-
ishment is no doubt the most momentous,
and this to such a degree that older writers
designated the external conditions by the term
nourishment. According to Knight nutrition
reigns supreme in the whole realm of vari-
ability, the kind of food and the method of nour-
ishment coming into consideration only in a sec-
ondary way. The amount of useful nutrition
is the all-important factor.

If this is so, and if nutrition decides the de-
gree of deviation of any given character, the
widest deviating individuals are the best nour-
ished ones. The best nourished not only dur-
ing the period of sensibility of the attribute un-
der consideration, but also in the broadest sense
of the word.

This discussion casts a curious light upon the
whole question of selection. Not of course
upon the choice of elementary species or varie-
ties out of the original motley assembly which
nature and old cultures offer us, but upon the
selection of the best individuals for isolation and
for the improvement of the race. These are,
according to my views, only the best nourished
ones. Their external conditions have been the

Poly cephalic Poppies 391

most favorable, not only from the beginning of
their own life in the field, but also during their
embryonic stages, and even during the prepara-
tion of these latter in the life of their parents
and perhaps even their grandparents. Selec-
tion then, would only be the choice of the best
nourished individuals.

In connection with the foregoing arguments
I have tried to separate the choicest of the pop-
pies with the largest crown of pistilloid stamens,
from the most vigorous individuals. As we
have already seen, these two attributes are
as a rule proportional to one another. Excep-
tions occur, but they may be explained by some
later changes in the external circumstances, as
I have also pointed out. As a rule, these ex-
ceptions are large fruits with comparatively too
few converted stamens; they are exactly the
contrary from what is required for a selection.
Or plants, which from the beginning were
robust, may have become crowded together by
further growth, and for these reasons become
weaker than their congeners, though retaining
the full development of the staminodal crown,
which was fixed during the sensitive period and
before the crowding. I have searched my beds
yearly for several years in vain to find individ-
uals which might recommend themselves for se-
lection without having the stamp of permanent.

392 Ever-sporting Varieties

or at least temporarily better, nourishment. No
starting-point for such an independent selection
has ever been met with.

Summing up the consequences of this some-
what extended discussion, we may state it as a
rule that a general proportion between the in-
dividual strength and the degree of develop-
ment of the anomaly exists. And from this
point of view it is easy to see that all external
causes which are known to affect the one, must
be expected to influence the other also.

It will therefore hardly be necessary to give
a full description of all my experiments on the
relations of the monstrosity to external condi-
tions. A hasty survey will suffice.

This survey is not only intended to convey an
idea of the relations of pistilloid poppies to
their environment, but may serve as an ex-
ample of the principle involved. According
to my experience with a large range of other
anomalies, the same rule prevails everywhere.
And this rule is so simple that exact knowledge
of one instance may be considered as sufficient
to enable us to calculate from analogy what is
to be expected from a given treatment of any
other anomaly. Our appreciation of observed
facts and the conditions to be chosen for
intended cultures are largely dependent on such
calculations. What I am now going to describe

Polycephalic Poppies 393

is to be considered therefore as an experimental
basis for such expectations.

First of all comes the question how many in-
dividuals are to be grown in a given place.
When sowing plants for experimental purposes
it is always best to sow in rows, and to give as
few seeds to each row as possible, so as to in-
sure all necessary space to the young plants.
On the other hand the seeds do not all germi-
nate, and after sowing too thinly, gaps may ap-
pear in the rows. This would cause not only a
loss of space, but an inequality between the
plants in later life, as those nearest the gaps
would have more space and more light, and a
larger area for their roots than those growing
in the unbroken rows. Hence the necessity of
using large quantities of seed and of weeding
out a majority of young plants on the spots
where the greatest numbers germinate.

Crowded cultures as a rule, will give weak
plants with thin stems, mostly unbranched and
bearing only small capsules. According to the
rule, these will produce imperfect crowns of sec-
ondary pistils. The result of any culture will
thus be dependent to a high degree on the num-
ber of individuals per square meter. I have
sown two similar and neighboring beds with
the thoroughly mixed seeds of parent-plants of
the same strain and culture, using as much

o94 Ever-sporting Varieties

as 2.5 cub. cm. per square meter. On one of the
beds I left all the germinating plants untouched
and nearly 500 of them flowered, but among
them 360 were almost without pistillody, and
only 10 had full crowns. In the other bed 1
weeded away more than half of the young
plants, leaving only some 150 individuals and got
32 with a full crown, nearly 100 with half crowns
and only 25 apparently without monstrosity.

These figures are very striking. From the
same quantity of seed, in equal spaces, by sim-
ilar exposure and treatment I got 10 fully de-
veloped instances in one and 32 in the other
case. The weeding out of supernumerary indi-
viduals had not only increased the percentage
of bright crowns, but also their absolute num-
ber per square meter. So the greatest number
of anomalies upon a given space may be ob-
tained by taking care that not too many plants
are grown upon it : any increase of the number
beyond a certain limit will diminish the prob-
ability of obtaining these structures. The most
successful cultures may be made after the max-
imum number of individuals per unit of area
has been determined. A control-experiment
was made under the same conditions and with
the same seed, but allowing much less for
the same space. I sowed only 1 cu. cm. on my
bed of 2 square meters, and thereby avoided

Poli/cephalic Popples 395

nearly all weeding out. I got 120 plants, and
among them 30 with full crowns of converted
stamens, practically the same number as after
the weeding out in the first experiment. This
shows that smaller quantities of seed give an
equal chance for a greater number of large
crowns, and should therefore always be pre-
ferred, as it saves both seed and labor.

Weeding out is a somewhat dangerous oper-
ation in a comparative trial. Any one who has
done it often, knows that there is a strong
propensity to root out the weaker plants and to
spare the stronger ones. Obviously this is the
best way for ordinary purposes, but for com-
parisons evidently one should not discriminate.
This rule is very difficult in practice, and for
this reason one should never sow more than is
absolutely required to meet all requirements.

Our second point is the manuring of the soil.
This is always of the highest importance, both
for normal and for anomalous attributes. The
conversion of the stamens into pistils is in a
large measure dependent upon the conditions of
the soil. I made a trial with some 800 flowering
plants, using one sample of seed, but sowing
one-third on richly manured soil, one-third on
an unprepared bed of my garden, and one-third
on nearly pure sand. In all other respects the
three groups were treated in the same way. Of

396 Ever-sporting Varieties

the manured plants one-half gave full crowns,
of the non-manured only one-fifth, and on the
sandy soil a still smaller proportion. Other
trials led to the same results. I have often made
use of steamed and ground horn, which is a ma-
nure very rich in nitrogenous substances. One-
eighth of a kilo per square meter is an ample
amount. And its effect was to increase the
nmnber of full crowns to an exceptional degree.

In the controlling trial and under ordinary
circumstances this figure reached some 50^,
but with ground horn it came up as high
as 90^. We may state this result by the
very striking assertion that the number of large
crowns in a given culture may be nearly doubled
by rich manure.

All other external conditions act in a similar
manner. The best treatment is required to at-
tain the best result. A sunny exposure is one
of the most essential requisites, and in some at-
tempts to cultivate my poppies in the shade, I
found the pistillody strongly reduced, not a
single full crown being found in the whole lot.
Often the weather may be hurtful, especially
during the earlier stages of the plants. I pro-
tected my beds during several trials by covering
them with glass for a few weeks, until the young
plants reached the glass covering. I got a nor-
mal number of full crowns, some 55%, at a time

Polycephalic Poppies 397

when the weather was so bad as to reduce the
number in the control experiments to 10%.

It would be quite superfluous to give more de-
tails or to describe additional experiments.
Suffice to say, that the results all point in the
same direction, and that pistillody of the pop-
pies always clearly responds to the treatment,
especially to external conditions during the first
few weeks, that is, during the period of sensi-
tiveness. The healthier and the stronger the
plants the more fully they will develop their
anomaly.

In conclusion something is to be said about
the choice of the seed. Obviously it is possible
to compare seeds of different origin by sowing
and treating them in the same way, giving at-
tention to all the points above mentioned. In
doing so the first question will be, whether there
is a difference between the seeds of strong
plants with a bright crown around the head and
those of weaker individuals with lesser develop-
ment of the anomaly. It is evident that such a
difference must be expected, since the nutrition
of the seed takes place during the period of the
greatest sensitiveness.

But the experiments will show whether this
effect holds good against the influences which
tend to change the direction of the development
of the anomaly during the time of germination.

398 Ever-sporting Varieties

The result of my attempt has shown that the
choice of the seeds has a manifest influence upon
the ultimate development of the monstrosity, but
that this influence is not strong enough to over-
whelm all other factors.

The choice of the fullest or smallest crowns
may be repeated during succeeding generations,
and each time compared with a culture under
average conditions. By this means we come to
true selection-experiments, and these result in
a notable and rapid change of the whole strain.
By selecting the brightest crowns I have come
up in three years from 40 to 90 and ultimately
to 120 converted stamens in the best flower of
my culture, and in selecting the smallest crowns
I was able in three j'ears to exclude nearly all
good crowns, and to make cultures in which
heads with less than half-filled crowns consti-
tuted the majority. But such selected strains
always remain very sensitive to treatment, and
by changing the conditions the effect may be
wholly lost in a single year, or even turned
in the contrary direction. In other words, the
anomaly is more dependent on external condi-
tions during the germinating period than on the
choice of the seeds, providing these belong to
the pistilloid variety and have not deteriorated
by some crossing with other sorts.

At the beginning of this lecture I stated that

Polycephalic Poppies 399

no selection is adequate to produce either a pure
strain of brightly crowned flower-heads without
atavism, or to conduce to an absolute and per-
manent loss of the anomaly. During a series of
years I have tested my plants in both directions,
but without the least effect. Limits are soon
reached on both sides, and to transgress these
seems quite impossible.

Taking these limits as the marks of the
variety, and considering all fluctuations between
them as responses to external influences work-
ing during the life of the individual or govern-
ing the ripening of the seeds, we get a clear pic-
ture of a permanent ever-sporting type. The
limits are absolutely permanent during the
whole existence of this already old variety.
They never change. But they include so wide a
range of variability that the extremes may be
said to sport into one another, so much the more
so as one of the extremes is to be considered
morphologically as the type of the variation,
while the other extreme can hardly be distin-
guished from the normal form of the species.

Lecture XIV

MONSTROSITIES

I have previously dealt with the question of
the hereditary tendencies that cause monstros-
ities. These tendencies are not always ident-
ical for the same anomaly. Two different
types may, generally, be distinguished. One of
them constitutes a poor variety, the other a rich
one. But this latter is abundant and the first
one is poor in instances of exactly the same con-
formation. Therefore the difference only lies
in the frequency of the anomaly, and not in its
visible features. In discovering an instance of
any anomaly it is therefore impossible to tell
whether it belongs to a poor or to a rich race.
This important question can only be answered
by direct sowing-experiments to determine the
degree of heredity.

Monstrosities are often considered as acci-
dents, and rightfully so, at least as long as they
are considered from a morphological point of
view. Physiology of course excludes all acci-
dentality. And in our present case it shows

400

Monstrosities 401

that some internal hereditary quality is pres-
ent, though often latent, and that the observed
anomalies are to be regarded as responses
of this innate tendency to external con-
ditions. Our two types differ in the frequency
of these responses. Eare in the poor race, they
are numerous in the rich variety. The external
conditions being the same for both, the heredi-
tary factor must be different. The tendency is
weak in the one and strong in the other. In
both cases, according to my experience, it may
be weakened or strengthened by selection and
by treatment. Often to a very remarkable de-
gree, but not so far as to transgress the limits
between the two races. Such transgression
may apparently be met with from time to time,
but then the next generation generally shows
the fallacy of the conclusion, as it returns more
or less directly to the type from which the strain
had been derived.

Monstrosities should always be studied by
physiologists from this point of view. Poor
and rich strains of the same anomaly seem at
first sight to be so nearly allied that it might be
thought to be very easy to change the one into
the other. Nevertheless such changes are not
on record, and although I have made several at-
tempts in this line, I never succeeded in passing
the limit. I am quite convinced that sometime

402 Ever-sporting Varieties

a method will be discovered of arbitrarily pro-
ducing such conversions, and perhaps the easi-
est way to attain artificial mutations may lie
concealed here. But as yet not the slightest in-
dication of this possibility is to be found, save
the fallacious conclusions drawn from too
superficial observations.

Unfortunately the poor strains are not very
interesting. Their chance of producing beauti-
ful instances of the anomaly for which they are
cultivated is too small. Exceptions to this rule
are only afforded by those curious and rare
anomalies, which command general attention,
and of which, therefore, instances are always
welcome. In such cases they are searched for
with perseverance, and the fact of their rarity
impresses itself strongly on our mind.

Twisted stems are selected as a first example.
This monstrosity, called biastrepsis^ consists of
strongly marked torsions as are seen in many
species with decussate leaves, though as a rule
it is very rare. Two instances are the most
generally known, those of the wild valerian
(Valeriana officinalis) and those of cultivated
and wild sorts of teasels (Dipsacus fiillonum, D.
sylvestris, and others). Both of these I have
cultivated during upwards of fifteen years, but
with contradictorv results. The valerian is a
perennial herb, multipljang itself yearly by

Monstrosities 403

slender rootstocks or runners producing at their
tips new rosettes of leaves and in the center of
these the flowering stem. My original plant
has since been propagated in this manner, and
during several years I preserved large beds
with hundreds of stems, in others I was com-
pelled to keep my culture within more restricted
limits. This plant has produced twisted stems
of the curious shape, with a nearly straight
flag of leaves on one side, described by De Can-
dolle and other observers, nearly every year.
But only one or two instances of abnormal
stems occurred in each year, and no treatment
has been found that proved adequate to increase
this number in any appreciable manner. I have
sown the seeds of this plant repeatedly, either
from normal or from twisted stems, but without
better results. It was highly desirable to be
able to offer instances of this rare and interest-
ing peculiarity to other universities and mxU-
seums, but no improvement of the race could be
reached and I have been constrained to give it
up. My twisted valerian is a poor race, and
hardly anything can be done with it. Perhaps,
in other countries the corresponding rich race
may be hidden somewhere, but I have never had
the good fortune of finding it.

This good fortune however, I did have with
the wild teasel or Bipsacus sylvestris. Twisted

404 Ever-sporting Varieties

stems of this and of allied species are often met
with and have been described by several writers,
but they were always considered as acci-
dents and nobody had ever tried to cultivate
them. In the summer of 1885 I saw among a
lot of normal wild teasels, two nicely twisted
stems in the botanical garden of Amsterdam.
I at once proposed to ascertain whether they
would yield a hereditary race and had all the
normal individuals thrown away before the
flowering time. My two plants flowered in this
isolated condition and were richly pollinated by
insects. Of course, at that time, I knew nothing
of the dependency of monstrosities on external
conditions, and made the mistake of sowing the
seeds and cultivating the next generation in
too great numbers on a small space. But
nevertheless the anomaly was repeated, and the
aberrant individuals were once more isolated
before flowering. The third generation re-
peated the second, but produced sixty twisted
stems on some 1600 individuals. The result
was very striking and quite sufficient for all fur-
ther researches, but the normal condition of the
race was not reached. This was the case only
after I had discovered the bad effects of grow-
ing too many plants in a limited space. In the
fourth generation I restricted my whole culture
to about 100 individuals, and by this simple

Monstrosities 405

means at once got up to 34^ of twisted stems.
This proportion has since remained practically
the same. I have selected and isolated my
plants during ^ye succeeding generations, but
without any further result, the percentage of
twisted stems fluctuating between 30 and
about 45 according to the size of the cultures
and the favorableness or unfavorableness of the
weather.

It is very interesting to note that all depends
on the question whether one has the good for-
tune of finding a rich race or not, as this pedi-
gree-culture shows. Afterwards everything de-
pends on treatment and very little on selection.
As soon as the treatment becomes adequate, the
full strength of the race at once displays itself,
but afterwards no selection is able to improve
it to any appreciable amount. Of course, in
the long run, the responses will be the same as
those of the pistilloid poppies on the average,
and some influence of selection will show itself
on closer scrutiny.

Compared with the polycephalous poppies my
race of twisted teasels is much richer in atav-
ists. They are never absent, and always con-
stitute a large part of each generation and each
bed, comprising somewhat more than half of the
individuals. Intermediate stages between them
and the wholly twisted stems are not wanting,

406 Ever-sporting Varieties

and a whole series of steps may easily be ob-
served from sufficiently large cultures. But
they are always relatively rare, and any lot of
plants conveys the idea of a dimorphous race,
the small twisted stems contrasting strongly
with the tall straight ones.

A sharper contrast between good representa-
tives of a race and their atavists is perhaps to
be seen in no other instance. All the details
contribute to the differentiation in appearance.
The whole stature of the plants is affected by
the varietal mark. The atavists are not, as
in the case of the poppies, obviously allied with
the type by a full range of intermediate steps,
but quite distant from it by their rarity. There
seems to be a gap in the same way as between
the striped flowers of the snapdragon and their
uniform red atavists, while with the poppies
the atavists may be viewed as being only the
extremes of a series of variations fluctuating
around some average type.

From this reason it is as interesting to appre-
ciate the hereditary position of the atavists of
twisted varieties as it was for the red-flowered
descendants of the striped flowers. In order to
ascertain this relation it is only necessary to iso-
late some of them during the blooming-period.
I made this experiment in the summer of 1900
with the eighth generation of my race, and con-

Monstrosities 407

trived to isolate three groups of plants by the
use of parchment bags, covering them alter-
nately, so the flowers of only one group were
accessible to insects at a time. I made three
groups, because the atavists show two different
types. Some specimens have decussate stems,
others bear all their leaves in whorls of three,
but in respect to the hereditary tendency of the
twisting character this difference does not seem
to be of any importance.

In this way I got three lots of seeds and sowed
enough of them to have three groups of plants
each containing about 150 - 200 well developed
stems. Among these I counted the twisted indi-
viduals, and found nearly the same numbers for
all three. The twisted parents gave as many
as 4rlfc twisted children, but the decussate ata-
vists gave even somewhat more, viz., 44;^, while
the ternate specimens gave 37;^. Obviously the
divergencies between these figures are too slight
to be dwelt upon, but the fact that the atavists
are as true or nearly as true inheritors of the
twisted race as the best selected individuals is
clearly proved by this experience.

It is evident that here we have a double race,
including two types, which may be combined in
different degrees. These combinations deter-
mine a wide range of changes in the stature of
the plants, and it seems hardly right to use the

408 Ever-sporting Varieties

same term for such changes as for common
variations. It is more a contention of opposite
characters than a true phenomenon of simple
variability. Or perhaps we might say that it
is the effect of the cooperation of a very vari-
able mark, the twisting, with a scarcely varying
attribute of the normal structure of the stem.
Between the two types an endless diversity pre-
vails, but outwardly there are limits which are
never transgressed. The double race is as per-
manent, and in this sense as constant, as any
ordinary simple variety, both in external form,
and in its intimate hereditary qualities.

I have succeeded in discovering some other
rich races of twisted plants. One of them
is the Sweet William {Dianthus harhatus),
which yielded, after isolation, in the second
generation, 25^ of individuals with twisted
stems, and as each individual produces often
10 and more stems, I had a harvest of
more than half a thousand of instances of this
curious, and ordinarily very rare anomaly. My
other race is a twisted variety of Viscaria ocula-
ta, which is still in cultivation, as it has the very
consistent quality of being an annual. It yield-
ed last summer (1903) as high a percentage as
65 of twisted individuals, many of them repeat-
ing the monstrosity on several branches. After
some occasional observations Gypsophila pani-

Monstrosities 409

culata seems to promise similar results. On
the other hand I have sowed in vain the seeds of
twisted specimens of the soapwort and the
cleavewort (Saponaria officinalis and Galium
Aparine). These and some others seems to be-
long to the same group as the valerian and to
constitute only poor or so-called half -races.

Next to the torsions come the fasciated
stems. This is one of the most common of all
malformations, and consists, in its ordinary
form, of a flat ribbon-like expansion of the stems
or branches. Below they are cylindrical, but
they gradually lose this form and assume a flat-
tened condition. Sometimes the rate of growth
is unequal on different portions or on the op-
posite sides of the ribbon, and curvatures are
produced and these often give to the fasciation
a form that might be compared with a shep-
herd's crook. It is a common thing for fas-
ciated branches and stems to divide at the
summit into a number of subdivisions, and ordi-
narily this splitting occurs in the lower part,
sometimes dividing the entire fasciated portion.
In biennial species the rosette of the root-leaves
of the first year may become changed by the
monstrosity, the heart stretching in a transverse
direction so as to become linear. In the next
year this line becomes the base from which the
stem grows. In such cases the fasciated stems

410 Ever-sporting Varieties

are broadened and flattened from the very be-
ginning, and often retain the incipient breadth
throughout their further development. Species
of primroses {Primula japonica and others), of
buttercups {Ranunculus bulbosus), the rough
hawksbeard {Crepis biennis), the Aster Tripo-
lium and many others could be given as in-
stances.

Some of these are so rare as to be considered
as poor races, and in cultural trials do not pro-
duce the anomaly except in a very few in-
stances. Heads of rye are found in a cleft
condition from time to time, single at their base
and double at the top, but this anomaly is only
exceptionally repeated from seed. Flattened
stems of Rubia tinctorum are not unfrequently
met with on the fields, but they seem to have as
little hereditary tendency as the split rye
{Secale Cereale). Many other instances could
be given. Both in the native localities and in
pedigree-cultures such ribboned stems are only
seen from time to time, in successive years, in
annual and biennial as well as in perennial
species. The purple pedicularis {Pedicularis
palustris) in the wild state, and the sunflower
among cultivated plants, may be cited instead of
giving a long list of analogous instances.

On the other hand rich races of flattened
stems are not entirely lacking. They easily be-

Monstrosities 411

tray themselves by the frequency of the anom-
aly, and therefore may be found, and tried in
the garden. Under adequate cultivation they
are here as rich in aberrant individuals as the
twisted races quoted above, producing in good
years from 30 - 4:0^ and often more instances. I
have cultivated such rich races of the dandelion
(Taraxacum officinale) ^ of Thrincia hirta, of the
dame's violet (Hesperis matronalis), of the
hawkweed (Picris hieracioides) , of the rough
hawksbeard (Crepis biennis), and others.

Respecting the hereditary tendencies these
rich varieties with flattened stems may be put in
the same category with the twisted races. Two
points however, seem to be of especial interest
and to deserve a separate treatment.

The common cockscomb or Celosia cristata,
one of the oldest and most widely cultivated
fasciated varieties may be used to illustrate
the first point. In beds it is often to be;
seen in quite uniform lots of large and beau-
tiful crests, but this uniformity is only se-
cured by careful culture and selection of the
best individuals. In experimental trials
such selection must be avoided, and in doing
so a wide range of variability at once shows
itself. Tall, branched stems with fan-
shaped tops arise, constituting a series of
steps towards complete atavism. This last

412 Ever-sporting Varieties

however, is not to be reached easily. It often
requires several successive generations grown
from seed collected from the most atavistic spec-
imens. And even such selected strains are al-
ways reverting to the crested type. There is
no transgression, no springing over into a
purely atavistic form, such as may be supposed
to have once been the ancestor of the present
cockscomb. The variety includes crests and
atavists, and may be perpetuated from both.
Obviously every gardener would select the seeds
of the brightest crests, but with care the full
crests may be recovered, even from the worst
reversionists in two or three generations. It is
a double race of quite the same constitution as
the twisted teasels.

My second point is a direct proof of this as-
sertion, but made with a fasciated variety of a
wild species. I took for my experiment the
rough hawksbeard. In the summer of 1895 I
isolated some atavists of the fifth generation of
my race, which, by ordinary selection, gave in
the average from 20-40^ of fasciated stems.
My isolated atavists bore abundant fruit, and
from these I had the next year a set of some 350
plants, out of which about 20^ had broadened
and linear rosettes. This proportion corre-
sponds with the degree of inheritance which is
shown in many years by the largest and strong-

Monstrosities 413

est fasciated stems. It strengthens our conclu-
sion as to the innermost constitution of the
double races or ever-sporting varieties.

Twisted stems and fasciations are very strik-
ing monstrosities. But they are not very good
for further investigation. They require too
much space and too much care. The calculation
of a single percentage requires the counting of
some hundreds of individuals, taking many
square meters for their cultivation, and this, as
my best races are biennial, during two years.
For this reason the countings must always be
very limited, and selection is restrained to the
most perfect specimens.

Now the question arises, whether this mark
is the best upon which to found selection. This
seems to be quite doubtful. In the experiments
on the heredity of the atavists, we have seen
that they are, at least often, in no manner
inferior to even the best inheritors of the race.
This suggests the idea that it is not at all certain
that the visible characters of a given individual
are a trustworthy measure of its value as to the
transmission of the same character to the off-
spring. In other words, we are confronted with
the existence of two widely different groups of
characters in estimating the hereditary tend-
ency. One is the visible quality of the indi-
viduals and the other is the direct observation

414 Ever-sporting Varieties

of the degree in which the attribute is trans-
mitted. These are by no means parallel, and
seem in some sense to be nearly independent
of each other. The fact that the worst atavists
may have the highest percentage of varietal
units seems to leave no room for another ex-
planation.

Developing this line of thought, we gradually
arrive at the conclusion that the visible attribute
of a varying individual is perhaps the most un-
trustworthy and the most unreliable character
for selection, even if it seems in many cases
practically to be the only available one. The di-
rect determination of the degree of heredity it-
self is obviously preferable by far. This degree
is expressed by the proportion of its inheritors
among the offspring, and this figure therefore
should be elevated to the highest rank, as a
measure of the hereditary qualities. Hence-
forward we will designate it by the name of
hereditary percentage.

In scientific experiments this figure must be
determined for every plant of a pedigree-culture
singly, and the selection should be founded ex-
clusively or at least mainly on it. It is easily
seen that this method requires large numbers
of individuals to be grown and counted. Some
two or three hundred progeny of one plant are
needed to give the decisive figure for this one

Monstrosities 415

individual, and selection requires the compari-
son of at least fifty or more individuals. This
brings the total amount of specimens to be
counted up to some tens of thousands. In prac-
tice, where important interests depend upon the
experiments, such numbers are usually em-
ployed and often exceeded, but for the culture
of monstrosities, other methods are to be sought
in order to avoid these difficulties.

The idea suggests itself here that the younger
the plants are, when showing their distinguish-
ing marks, the more of them may be grown on a
small space. Hence the best way is to choose
such attributes, as may already be seen in the
young seedlings, in the very first few weeks of
their lives. Fortunately the seed-leaves them-
selves afford such distinctive marks, and by this
means the plants may be counted in the
pans, requiring no culture at all in the gar-
den. Only the selected individuals need be
grown to ripen their seeds, and the whole selec-
tion may be made in the spring, in the glass-
house. Instead of being very troublesome, the
determination of the hereditary percentages
becomes a definite reduction of the size of the
experiments. Moreover it may easily be effect-
ed by any one who cares for experimental
studies, but has not the means required for cul-
tures on a larger scale. i\nd lastly, there are

416 Ever-sporting Varieties

a number of questions about heredity, period-
icity, dependency on nourishment and other life-
conditions, and even about hybridizing, which
may be answered by this new method.

Seed-leaves show many deviations from the
ordinary shape, especially in dicotyledonous
plants. A very common aberration is the multi-
plication of their number, and three seed-leaves
in a whorl are not rarely met with. The whorl
may even consist of four, and in rare cases of
five or more cotyledons. Cleft cotyledons are
also to be met with, and the fissure may extend
varying distances from the tips. Often all these
deviations may be seen among the seedlings
of one lot, and then it is obvious that together
they constitute a scale of cleavages, the ternate
and quaternate whorls being only cases where
the cleaving has reached its greatest develop-
ment. All in all it is manifest that here we are
met by one type of monstrosity, but that this
type allows of a wide range of fluctuating varia-
bility. For brevity's sake all these cleft and
ternate, double cleft and quaternate cotyledons
and even the higher grades are combined under
one common name and indicated as tricotyls.

A second aberration of young seed-plants is
exactly opposite to this. It consists of the
union of the two seed-leaves into a single
organ. This ordinarily betrays its origin by

Monstrosities 417

having two separate apices, but not always,
Such seedlings are called syncotyledonous or
syncotyls. Other monstrosities have been ob-
served from time to time, but need not be men-
tioned here.

It is evident that the determination of the
hereditary percentage is very easy in tricotyl-
ous or syncotylous cultures. The parent-
plants must be carefully isolated while bloom-
ing. Many species pollinate themselves in the
absence of bees; from these the insects are
to be excluded. Others have the stamens and
stigmas widely separated and have to be polli-
nated artificially. Still others do not lend them-
selves to such operations, but have to be left free
to the visits of bees and of humble-bees, this be-
ing the only means of securing seed from every
plant. At the time of the harvest the seeds
should be gathered separately from each plant,
and this precaution should also be observed m
studies of the hereditary percentage at large,
and in all scientific pedigree-cultures. Every lot
of seeds is to be sown in a separate pan, and care
must be taken to sow such quantities that three
to four hundred seedlings will arise from each.
As soon as they display their cotyledons, they
are counted, and the number is the criterion of
the parent-plant. Only parent-plants with the
highest percentages are selected, and out of

418 Ever-sporting Varieties

their seedlings some fifty or a hundred of the
best ones are chosen to furnish the seeds for the
next generation.

This description of the method shows that
the selection is a double one. The first feature
is the hereditary percentage. But then not all
the seedlings of the selected parents can be
planted out, and a choice has to be made. This
second selection may favor the finest tricotyls,
or the strongest individuals, or rely on some
other character, but is unavoidable.

We now come to the description of the cul-
tures. Starting points are the stray tricotyls
which are occasionally found in ordinary
sowings. In order to increase the chance of
finding them, thousands of seeds of the same
species must be inspected, and the range of
species must be widened as much as possible.

Material for beginning such experiments is
very easily obtained, and almost any large
sample of seeds will be found suitable. Some
tricotyls may be found among every thousand
seedlings in many species, while in others ten or
a hundred times as many plants must be exam-
ined to secure them, but species with absolutely
pure dicotylous seeds are very rare.

The second phase of the experiment how-
ever, is not so promising. Some species are rich,
and others are poor in this anomaly. This dif-

Monstrosities 419

ference often indicates what may be expected
from further culture. Stray tricotyls point to
poor or half-races, while more frequent devia-
tions suggest rich or double-races. In both
cases however, the trial must be made, and this
requires the isolation of the aberrant individ-
uals and the determination of their hereditary
percentage.

In some instances the degree of their in-
heritance is only a very small one. The iso-
lated tricotyls yield 1 or 2fo of inheritors, in some
cases even less, or upwards to 3 or 4^. If the
experiment is repeated, no amelioration is ob-
served, and this result remains the same during
a series of successive generations. In the case
of Polygonum Convolvulus, the black bindweed,
I have tried as many as six generations without
ever obtaining more than 3^. With other
species I have limited myself to four successive
years with the same negative result, as with
spinage, the Moldavian dragon-head {Dracoce-
phalum moldavicum), and two species of corn
catch-fly (Silene conica and 8. conoidea).

Such poor races hardly afford a desirable ma-
terial for further inquiries. Happily the rich
races, though rare, may be discovered also from
time to time. They seem to be more common
among cultivated plants and horticultural as
well as agricultural species may be used. Henq)

420 Ever-sporting Varieties

and mercury (Mercurialis annua) among the
first, snapdragon, poppies, Phacelia, Helich-
rysuyn, and Clarkia among garden-flowers may
be given as instances of species containing the
rich tricotylous double races.

It is very interesting to note how strong the
difference is between such cases and those which
only yield poor races. The rich type at once
betrays itself. No repeated selection is re-
quired. The stray tricotyls themselves, that
are sought out from among the original samples,
give hereditary percentages of a much higher
type after isolation than those quoted above.
They come up to 10 - 20^ and in some cases even
to 40^. As may be expected, individual differ-
ences occur, and it must even be supposed that
some of the original tricotyls may not be pure,
but hybrids between tricotylous and dicotyl-
ous parents. These are at once eliminated
by selection, and if only the tricotyls which
have the highest percentages are chosen for the
continuance of the new race, the second genera-
tion comes up with equal numbers of dicotyls
and tricotyls among the seedlings. The figures
have been observed to range from 51 - 58^ in the
majority of the cases, and average 55^, rarely
diverging somewhat more from this average.

Here we have the true type of an ever-sport-
ing variety. Every year it produces in the

Monstrosities 421

same way heirs and atavists. Every plant, if
fertilized with its own pollen, gives rise to
both types. The parent itself may be tricotyl-
ous or dicotylous, or show any amount of
multiplication and cleavage in its seed-leaves,
but it always gives the entire range among its
progeny of the variation. One may even select
the atavists, pollinate them purely and repeat
this in a succeeding generation without any
chance of changing the result. On an average
the atavists may give lower hereditary figures,
but the difference will be only slight.

Such tricotylous double races offer highly
interesting material for inquiries into questions
of heredity, as they have such a wide range of
variability. There is little danger in asserting
that they go upwards to nearly 100^, and down-
wards to Ofo^ diverging symmetrically on both
sides of their average (50-55;'^). These limits
they obviously cannot transgress, and are not
even able to reach them. Samples of seed con-
sisting only of tricotyls are very rare, and when
they are met with the presumption is that they
are too few to betray the rare aberrants they
might otherwise contain. Experimental evi-
dence can only be reached by the culture of a
succeeding generation, and this always discloses
the hidden qualities, showing that the double

422 Ever-sporting Varieties

type was only temporarily lost, but bound to
return as soon as new trials are made.

This wide range of variability between def-
inite limits is coupled with a high degree of
sensibility and adequateness to the most di-
verging experiments. Our tricotylous double
races are perhaps more sensitive to selection
than any other variety, and equally dependent
on outer circumstances. Here, however, I will
limit myself to a discussion of the former point.

In the second generation after the isolation of
stray tricotylous seedlings the average con-
dition of the race is usually reached, but only
by some of the strongest individuals, and if we
continue the race, sowing or planting only from
their offspring, the next generation will show
the ordinary type of variability, going upwards
in some and downwards in other instances.
With the Phacelia and the mercury and some
others I had the good luck in this one generation
to reach as high as nearly 90;^ of tricotyl-
ous seedlings, a figure indicating that the
normal dicotylous type had already become
rare in the race. In other cases 80^ or
nearly 80^ was easily attained. Any further
divergence from the average would have re-
quired very much larger sowings, the effect of
selection between a limited number of parents
being only to retain the high degree once

Monstrosities 423

reached ; so for instance with the mercury, I had
three succeeding generations of selection after
reaching the average of 55;^, but their extremes
gave no increasing advance, remaining at 86, 92
and 91^.

If we compare these results with the effects
of selection in twisted and fasciated races, we
observe a marked contrast. Here they reached
their height at 30-40%, and no number of gen-
erations had the power of making any further
improvement. The tricotyls come up in two
generations to a proportion of about 54;^, which
shows itself to correspond to the average
type. And as soon as this is reached, only one
generation is required to obtain a very consid-
erable improvement, going up to 80 or even 90;?^.

It is evident that the cause of this difference
does not lie in the nature of the monstrosity, but
is due to the criterion upon which the selection
is made. Selection of the apparently best in-
dividuals is one method, and it gives admirable
results. Selection on the ground of the hered-
itary percentages is another method and gives
results which are far more advantageous than
the former.

In the lecture on the pistillody of the poppies
we limited ourselves to the selection of the finest
individuals and showed that there is always a
manifest correlation between the individual

424 Ever-sporting Varieties

strength of the plant and the degree of develop-
ment of its anomaly. The same holds good with
other monstrosities, and badly nourished speci-
mens of rich races with twisted or fasciated
stems always tend to reversion. This rever-
sion, however, is not necessarily correlated with
the hereditary percentage and therefore does
not always indicate a lessening of the degree of
inheritance. This shows that even in those
cases an improvement may be expected, if only
the means can be found to subject the twisted
and the fasciated races to the same sharp test
as the tricotylous varieties.

Much remains to be done, and the principle of
the selection of parents according to the average
constitution of their progeny seems to be one of
the most promising in the whole realm of varia-
bility.

Besides tricotylous, the syncotylous seed-
lings may be used in the same way. They
are more rarely met with, ind in most instances
seem to belong only to the unpromising half-
races. The black bindweed {Polygonum Con-
volvulus), the jointed charlock {Raplianus Uap-
hanistrum), the glaucous evpniug-prir irose
{Oenothera glauca) and many other plants seem
to contain such half-rac^s. On the other hand
I found a plant of Centrantlms macrosiphon
yielding as much as 55;^ of syncotylous chil-

Monstrosities 425

dren and thereby evidently betraying the na-
ture of a rich or double race. Likewise the mer-
cury was rich in such deviations. But the best
of all was the Russian sunflower, and this was
chosen for closer experiments.

In the year of 1888 I had the good luck to
isolate some syncotylous seedlings and of find-
ing among them one with 19^ of inheritors
among its seeds. The following generation at
once surpassed the ordinary average and came
up in three individuals to 76, 81 and even 89^.
My race was at once isolated and ameliorated by
selection. I have tried to improve it further
and selected the parents with the highest per-
centages during seven more generations; but
without any remarkable result. I got figures of
90^ and above, coming even in one instance up
to the apparent purity of 100^. These, how-
ever, always remained extremes, the averages
fluctuating yearly between 80-90,*^ or there-
abouts, and the other extremes going nearly
every year downwards to 50^, the value which
would be attained, if no selection were made.

Contra-selection is as easily made as normal
selection. According to our present principle it
means the choice of the parents with the smallest
hereditary percentage. One might easily im-
agine that by this means the dicotylous seed-
lings could be rendered pure. This, how-

426 Ever-sporting ]^arieties

ever, is not at all the case. It is easy to re-
turn from so highly selected figures as for in-
stance 9^^ to the average about of 50^, as
regression to mediocrity is always an easy mat-
ter. But to transgress this average on the
lower side seems to be as difficult as it is on the
upper side. I continued the experiment during
four succeeding generations, but was not able to
go lower than about 10/^, and could not even ex-
clude the high figures from my strain. Parents
with 65 - 75^ of syncotylous seedlings returned
in each generation, notwithstanding the most
careful contra-selection. The attribute is in-
herent in the race, and is not to be eliminated by
so simple a means as selection, nor even by a se-
lection on the ground of hereditary percentages.

We have dealt with torsions and fasciations
and with seedling variations at some length, in
order to point out the phases needing investiga-
tion according to recent views. It would be
quite superfluous to consider other anomalies in
a similar manner, as they all obey the same laws.
A hasty survey may suffice to show what pros-
pects they offer to the student of nature.

First of all come the variegated leaves. They
are perhaps the most variable of all variations.
They are evidently dependent on external cir-
cumstances, and by adequate nutrition the
leaves may even become absolutely white or

Monstrosities 427

yellowish, with only scarcely perceptible traces
of green along the veins. Some are very old
cultivated varieties, as the wintercress, or Bar-
barea vulgaris. They continuously sport into
green, or return from this normal color, both by
seeds and by buds. Sports of this kind are
very often seen on shrubs or low trees, and
they may remain there and develop during a
long series of years. Bud-sports of variegated
holly, elms, chestnuts, beeches and others might
be cited. One-sided variegation on leaves or
twigs with the opposite side wholly green are
by no means rare. It is very curious to note
that variegation is perhaps the most universally
known anomalv, while its hereditarv tendencies
are least known.

Cristate and plumose ferns are another in-
stance. Half races or rare accidental cleavages
seem to be as common with ferns as cultivated
double races, which are very rich in beautiful
crests. But much depends on cultivation. It
seems that the spores of crested leaves are more
apt to reproduce the variety than those of nor-
mal leaves, or even of normal parts of the same
leaves. But the experiments on which
this assertion is made are old and should
be repeated. Other cases of cleft leaves should
also be tested. Ascidia are far more common
than is usually believed. Rare instances point

428 Ever-sporting Varieties

to poor races, but the magnolias and lime-trees
are often so productive of ascidia as to suggest
the idea of ever-sporting varieties. I have
seen many hundred ascidia on one lime-tree, and
far above a hundred on the magnolia. They dif-
fer widely in size and shape, including in some
cases two leaves instead of one, or are composed
of only half a leaf or of even still a smaller part
of the summit. Kich ascidia-bearing varieties
seem to offer notable opportunities for scientific
pedigree-cultures.

Union of the neighboring fruits and flowers on
flower-heads, of the rays of the umbellifers or
of the successive flowers of the racemes of cab-
bages and allied genera, seem to be rare.
The same holds good for the adhesion of foliar
to axial organs, of branches to stems and
other cases of union. Many of these cases re-
turn regularly in each generation, or may at
least be seen from time to time in the same
strains. Proliferation of the inflorescence is
very common and changes in the position of
staminate and pistillate flowers are not rare.
We find starting points for new investigations
in almost any teratological structure. Half-
races and double-races are to be distinguished
and isolated in all cases, and their hereditary
qualities, the periodicity of the recurrence of
the anomaly, the dependency on external circum-

Monstrosities 429

stances and many other questions have to be an-
swered.

Here is a wide field for garden experiments
easily made, which might ultimately yield much
valuable information on many questions of he-
redity of universal interest.

Lecture XV

DOUBLE ADAPTATIONS

The chief object of all experimentation is to
obtain explanations of natural phenomena.
Experiments are a repetition of things occur-
ring in nature with the conditions so guarded
and so closely followed that it is possible to
make a clear analysis of facts and their
causes, it being rightfully assumed that the laws
are the same in both cases.

Experiments on heredity and the experience
of the breeder find their analogy in the succes-
sion of generations in the wild state. The sta-
bility of elementary species and of retrograde
varieties is quite the same under both condi-
tions. Progression and retrogression are nar-
rowly linked everywhere, and the same laws
govern the abundance of forms in cultivated
and in wild plants.

Elementary species and retrograde varieties
are easily recognizable. Ever-sporting varie-
ties on the contrary are far less obvious, and
in many cases their hereditary relations have

430

Double Adaptations 431

had to be studied anew. A clear analogy be-
tween them and corresponding types of wild
plants has yet to be pointed out. There can be
no doubt that such .analogy exists ; the concep-
tion that they should be limited to cultivated
plants is not probable. Striped flowers and va-
riegated leaves, changes of stamens into carpels
or into petals may be extremely rare in the wild
state, but the "" five-leaved '' clover and a large
number of monstrosities cannot be said to be
typical of the cultivated condition. These, how-
ever, are of rare occurrence, and do not play
any important part in the economy of nature.
In order to attain a better solution of the
problem we must take a broader view of
the facts. The wide range of variability of
ever-sporting varieties is due to the presence of
two antagonistic characters which cannot be
evolved at the same time and in the same or-
gan, because they exclude on^ another. AAHien-
ever one is active, the other must be latent. But
latency is not absolute inactivity and may often
only operate to encumber the evolution of the
antagonistic character, and to produce large
numbers of lesser grades of its development.
The antagonism however, is not such in the ex-
act meaning of the word ; it is rather a mutual
exclusion, because one of the opponents simply
takes the place of the other when absent, or sup-

432 Ever-sporting Varieties

plements it to the extent that it may be only im-
perfectly developed. This completion ordinar-
ily occurs in all possible degrees and thus
causes the wide range of the variability. Nev-
ertheless it may be wanting, and in the case of
the double stocks only the two extremes are
present.

It is rather difficult to get a clear conception
of the substitution, and it seems necessary to
designate the peculiar relationship between the
two characters forming such a pair by a simple
name. They might be termed alternating, if
only it were clearly understood that the alterna-
tion may be complete, or incomplete in all de-
grees. Complete alternation would result in
the extremes, the incomplete condition in the
intermediate states. In some cases as with the
stocks, the first prevails, while in other cases, as
with the poppies, the very extremes are only
rarely met with.

Taking such an alternation as a real char-
acter of the ever-sporting varieties, a wide
range of analogous cases is at once revealed
among the normal qualities of wild plants. Al-
ternation is here almost universal. It is the ca-
pacity of young organs to develop in two diverg-
ing directions. The definitive choice must be
made in extreme youth, or often at a relatively
late period of development. Once made, this

Double Adaptations 433

choice is final, and a further change does not oc-
cur in the normal course of things.

The most curious and most suggestive in-
stance of such an alternation is the case of the
water-persicaria or Polygonum amphibium. It
is known to occur in two forms, one aquatic and
the other terrestrial. These are recorded in
systematic works as varieties, and are described
under the names of P. amphibium var. natans
Moench, and P. amphibium var. terrestre Leers
or P, amphibium var. terrestris Moench. Such
authorities as Koch in his German flora, and
Grenier and Godron in their French flora agree
in the conception of the two forms as varieties.

Notwithstanding this, the two varieties may
often be observed to sport into one another.
They are only branches of the same plant,
grown under different conditions. The aquatic
form has floating or submerged stems with ob-
long or elliptic leaves, which are glabrous and
have long petioles. The terrestrial plants are
erect, nearly simple, more or less hispid
throughout, with lanceolate leaves and short pe-
tioles, often nearly sessile. The aquatic form
flowers regularly, producing its peduncle at
right angles from the floating stems, but the
terrestrial specimens are ordinarily seen with-
out flower-spikes, which are but rarely met with,
at least as far as my own experience goes. In-

434 Ever-sporting Varieties

termediate forms are very rare, perhaps wholly
wanting, though in swamps the terrestrial
plants may often vary widely in the direction of
the floating type.

That both types sport into each other has
long been recognized in field-observations, and
has been the ground for the specific name of
amphibium, though in this respect herbarium-
material seems usually to be scant. The mat-
ter has recently been subjected to critical and
experimental studies by the Belgian botanist
Massart, who has shown that by transplanting
the forms into the alternate conditions, the
change may always be brought about arti-
ficially. If floating plants are established on
the shore they make ascending hairy stems, and
if the terrestrial shoots are submerged, their
buds grow into long and slack, aquatic stems.
Even in such experiments, intermediates are
rare, both types agreeing completely with the
corresponding models in the wild state.

Among all the previously described cases of
horticultural plants and monstrosities there is
no clearer case of an ever-sporting variety than
this one of the water-persicaria. The var.
terrestris sports into the var. natans, and
as often as the changing life conditions may
require it. It is true that ordinary sports oc-
cur without our discerning the cause and with-

Double Adaptations 435

out any relation to adaptation. This however
is partly due to our lack of knowledge,
and partly to the general rule that in nature
only such sports as are useful are spared by
natural selection, and what is useful we ordi-
narily term adaptive.

Another side of the question remains to be
considered. The word variety, as is now be-
coming generally recognized, has no special
meaning whatever. But here it is assumed in
the clearly defined sense of a systematic va-
riety, which includes all subdivisions of spe-
cies. Such subdivisions may be, from a
biological point of view, elementary species and
also be eversporting varieties. They may be
retrograde varieties, and the two alternating
types may be described as separate varieties.

It is readily granted that many writers
would not willingly accept this conclusion. But
it is simply impossible to avoid it. The two
forms of the water-persicaria must remain
varieties, though they are only types of the dif-
ferent branches of a single plant.

If not, hundreds and perhaps thousands of
analogous cases are at once exposed to doubt,
and the whole conception of systematic varie-
ties would have to be thrown over. Biologists
of course would have no objection to this, but
the student of the flora of any given country

436 Ever-sporting Varieties

or region requires the systematic subdivisions
and should always use his utmost efforts to
keep them as they are. There is no intrinsic
difficulty in the statement that different parts of
the same plant should constitute different va-
rieties.

In some cases different branches of the same
plant have been described as species. So for
instance with the climbing forms of figs. Un-
der the name of Ficus repens a fine little plant is
quite commonly cultivated as a climber in flower
baskets. It is never seen bearing figs. On the
other hand a shrub of our hothouses called
Ficus stipulata, is cultivated in pots and makes
a small tree which produces quite large, though
non-edible figs. Now these two species are sim-
ply branches of the same plant. If the repens is
allowed to climb up high along the walls of the
hothouses, it will at last produce stipulata-
branches with the corresponding fruits. Ficus
radicans is another climbing form, correspond-
ing to the shrub Ficus ulmifolia of our glass-
houses. And quite the same thing occurs with
ivy, the climbing stems of which never flower,
but always first produce erect and free branches
with rhombic leaves. These branches have
often been used as cuttings and yield little erect
and richly flowering shrubs, which are known in

Double Adaptations 437

horticulture under tlie varietal name of Uede-
ra Helix arborea.

Manifestly this classification is as nearly
right as that of the two varieties of the water-
persicaria. Going one step further, we meet
with the very interesting case of alpine plants.
The vegetation of the higher regions of moun-
tains is commonly called alpine, and the plants
show a large number of common features, dif-
ferentiating them from the flora of lower sta-
tions. The mountain plants have small and
dense foliage, with large and brightly-colored
flowers. The corresponding forms of the low-
lands have longer and weaker stems, bearing
their leaves at greater distances, the leaves
themselves being more numerous. The alpine
forms, if perennial, have thick, strongly de-
veloped and densely branched rootstocks with
heavy roots, in which a large amount of food-
material is stored up during the short summer,
and is available during the long winter months
of the year.

Some species are peculiar to such high al-
titudes, while many forms from the lowlands
have no corresponding type on the mountains.
But a large number of species are common to
both regions, and here the difference of course is
most striking. Lotus cornicidatus and Cala-
mintJia Acinos, Calluna vidgaris and Campa-

438 Ever-sporting Varieties

7iula rotundifolia may be quoted as instances,
and every botanist who bas visited alpine re-
gions may add other examples. Even the edel-
weiss of the Swiss Alps, Gnaphalium Leonto-
podium, loses its alpine characters, if cultivated
in lowland gardens. Between such lowland and
alpine forms intermediates regularly occur.
They may be met with whenever the range of the
species extends from the plains upward to the
limit of eternal snow.

In this case the systematists formerly enu-
merated the alpine plants as forma alpestris, but
whenever the intermediate is lacking the term
varietas alpestris was often made use of.

It is simply imjoossible to decide concerning
the real relation between the alpine and low-
land types without experiments. About the
middle of the last century it was quite a com-
mon thing to collect plants not only for her-
barium-material, but also for the purpose of
planting them in gardens and thus to observe
their behavior under new conditions. This
was done with the acknowledged purpose
of investigating the systematic significance of
observed divergencies. Whenever these held
good in the garden they were considered to be
reliable, but if they disappeared they were re-
garded as the results of climatic conditions,
or of the influence of soil or nourishment. Be-

Double Adaptations 431)

tween these two alternatives, many writers
have tried to decide, by transplanting their
specimens after some time in the garden, into
arid or sandy soil, in order to see whether they
would resume their alpine character.

Among the systematists who tested plants in
this way, Nageli especially, directed his atten-
tion to the hawkweeds or Hieracium. On
the Swiss Alps they are very small and ex-
hibit all the characters of the pure alpine type.
Thousands of single plants were cultivated by
him in the botanical garden of Munich, partly
from seed and partly from introduced root-
stocks. Here they at once assumed the
tall stature of lowland forms. The identical
individual, which formerly bore small rosettes
of basal leaves, with short and unbranched
flower-stalks, became richly leaved and often
produced quite a profusion of flower-heads on
branched stems. If then they were trans-
planted to arid sand, though remaining in the
same garden and also under the same climatic
conditions they resumed their alpine charac-
ters. This proved nutrition to be the cause
of the change and not the climate.

The latest and most exact researches on this
subject are due to Bonnier, who has gone into
all the details of the morphologic as well as
of the physiologic side of the problem.

440 Ever-sporting Varieties

His purpose was the study of partial variabil-
ity under the influence of climate and soil. In
every experiment he started from a single indi-
vidual, divided it into two parts and planted
one half on a mountain and the other half on
the plain. The garden cultures were made
chiefly at Paris and Fontainebleau, the alpine
cultures partly in the Alps, partly in the Py-
renees. From time to time the halved plants
were compared with each other, and the cul-
tures lasted, as a rule, during the lifetime of the
individual, often covering many years.

The common European frostweed or Helian-
themum vulgare will serve to illustrate his re-
sults. A large plant growing in the Pyrenees in
an altitude of 2400 meters was divided. One half
was replanted on the same spot, and the other
near Cadeac, at the base of the mountain range
(740 M.). In order to exclude the etfect of a
change of soil, a quantity of the earth from the
original locality was brought into the garden
and the plant put therein. Further control-
experiments were made at Paris. As soon as
the two halved individuals commenced to grow
and produced new shoots, the influence of tlie
ditferent climates made itself felt. On the
mountain, the underground portions remained
strong and dense, the leaves and internodes
small and hairy, the flowering stems nearly

Double Adaptations 441

procumbent, the flowers being large and of a
deep yellow. At Cadeac and at Paris the whole
plant changed at once, the shoots becoming
elongated and loose, with broad and flattened,
rather smooth leaves and numerous pale-hued
flowers. The anatomical structure exhibited cor-
responding differences, the intercellular spaces
being small in the alpine plant and large in the
one grown in the lowlands, the wood-tissues
strong in the first and weak in the second case.

The milfoil {Achillea Millefolium) served
as a second example, and the experiments were
carried on in the same localities. The long and
thick rootstocks of the alpine plant bearing
short stems only with a few dense corymbs
contrasted markedly with the slender stems,
loose foliage and rich groups of flowerheads of
the lowland plant. The same differences in in-
ner and outer structures were observed in nu-
merous instances, showing that the alpine type
in these cases is dependent on the climate, and
that the capacity for assuming the antagonistic
characters is present in every individual of the
species. The external conditions decide which
of them becomes active and which remains in-
active, and the case seems to be exactly paral-
lel to that of the water-persicaria.

In the experiments of Bonnier the influence
of the soil was, as a rule, excluded by trans-

442 Ever-sporting Varieties

planting part of the original earth with tlie
transplanted half of the plant. From this he
concluded that the observed changes were due
to the inequality of the climate. This involved
three main factors, light, moisture and tem-
perature. On the mountains the light is more
intense, the air drier and cooler. Control-ex-
periments were made on the mountains, de-
priving the plants of part of the light. In va-
rious ways they were more or less shaded, and
as a rule responded to this treatment in the
same way as to transplantation to the plain
below. Bonnier concluded that, though more
than one factor takes part in inciting the
morphologic changes, light is to be consid-
ered as the chief agency. The response is to
be considered as a useful one, as the whole
structure of the alpine varieties is fitted to pro-
duce a large amount of organic material in a
short time, which enables the plants to thrive
during the short summers and long winters of
their elevated stations.

In connection with these studies on the in-
fluences of alpine climates. Bonnier has inves-
tigated the internal structure of arctic plants,
and made a series of experiments on growth
in continuous electric light. The arctic climate
is cold, but wet, and the structure of the leaves
is correspondingly loose, though the plants be-

Double Adaptations 443

come as small as on the Alps. Continuous elec-
tric light had very curious effects; the plants
became etiolated, as if growing in darkness,
with the exception that they assumed a deep
green tinge. They showed more analogy with
the arctic than with the alpine type.

The influence of the soil often produces
changes similar to that of climate. This was
shown by the above cited experiments of Na-
geli with the hawkweeds, and may easily be
controlled in other cases. The ground-honey-
•suckle or Lotus corniculatus grows in Holland
partly on the dry and sandy soil of the dunes,
and occasionally in meadows. It is small and
dense in the first case, with orange and often
very darkly colored petals, while it is loose and
green in the meadows, with yellower flowers.
Numerous analogous cases might be given. On
mountain slopes in South Africa, and especial-
ly in Natal, a species of composite is found,
which has been introduced into culture and is
used as a hanging plant. It is called Othonna
crassifolia and has fleshy, nearly cylindrical
leaves, and exactlv mimics some of the crassu-
laceous species. On dry soil the leaves become
shorter and thicker and assume a reddisli
tinge, the stems remain short and woody and
bear their leaves in dense rosettes. On moist
and rich garden-soil this aspect becomes

444 Ever-sporting Varieties

changed at once, the stems grow longer and
of a deeper green. Intermediates occur, but
notwithstanding this the two extremes consti-
tute clearly antagonistic types.

The flora of the deserts is known to exhibit
a similar divergent type. Or rather two types,
'one adapted to paucity of water, and the other
to a storage of fluid at one season in order to
make use of it at other times, as is the case with
the cactuses. Limiting ourselves to the alter-
nate group, we observe a rich and dense branch-
ing, small and compact leaves and extraordi-
narily long roots. Here the analogy with the
alpine varieties is manifest, and the dryness
of the soil evidently affects the plants in a sim-
ilar way, as do the conditions of life in alpine
regions. The question at once comes up as to
whether here too we have only instances of
partial variability, and whether many of the
typical desert-species would lose their pecu-
liar character by cultivation under ordinary
conditions. The varieties of Monardella ma-
crantha, described by Hall, from the San Ja-
cinto Mountain, Cal., are suggestive of such
an intimate analogy with the cases studied by
Bonnier, that it seems probable that they might
yield similar results, if tested by the same
method.

Leaving now the description of these special

Double Adaptations 445

cases, we may resume our theoretical discus-
sion of the subject, and try to get a clearer in-
sight into the analogy of ever-sporting varie-
ties and the wild species quoted. All of them
may be characterized by the general term of
dimorphism. Two types are always present,
though not in the same individual or in the same
organ. They exclude one another, and dur-
ing their juvenile stage a decision is taken in
one direction or in the other. Now, according
to the theory of natural selection, wild species
can only retain useful or at least innocuous
qualities, since all mutations in a wrong direc-
tion must perish sooner or later. Cultivated
species on the other hand are known to be
largely endowed with qualities, which would
be detrimental in the wild condition. Mon-
strosities are equally injurious and could not
hold their own if left to themselves.

These same principles may be applied to
ever-sporting or antagonistic pairs of charac-
ters. According to the theory of mutations
such pairs may be either useful or useless. But
only the useful will stand further test, and if
they find suitable conditions will become spe-
cific or varietal characters. On this conclusion
it becomes at once clear, why natural di-
morphism is, as a rule, a very useful quality,
while the cultivated dimorphous varieties

446 Ever-sporting Varieties

strike us as something unnatural. The rela-
tion between cause and effect, is in truth other
than it might seem to be at first view, but nev-
ertheless it exists, and is of the highest impor-
tance.

From this same conclusion we may further
deduce some explanation of the hereditary
races characterized bv monstrosities. It is
quite evident that the twisted teasels are in-
adequate for the struggle with their tall con-
geners, or with the surrounding plants. Hence
the conclusion that a pure and exclusively
twisted race would soon die out. The fact that
such races are not in existence finds its expla-
nation in this circumstance, and therefore it
does not prove the impossibility or even the im-
probability that some time a pure twisted race
might arise. If chance should put such an ac-
cidental race in the hands of an experimenter,
it could be protected and preserved, and hav-
ing no straight atavistic branches, but being
twisted in all its organs, might yield the most
curious conceivable monstrosity, surpassing
even the celebrated dwarf twisted shrubs of
Japanese horticulturists.

Such varieties however, do not exist at pres-
ent. The ordinary twisted races on the other
hand, are found in the wild state and have only
to be isolated and cultivated to yield large num-

Double Adaptations 447

bers of twisted individuals. In nature they are
able to maintain themselves during long cen-
turies, quite as well as normal species and va-
rieties. But they owe this quality entirely to
their dimorphous character. A twisted race of
teasels might consist of successive generations
of tall atavistic individuals, and produce year-
ly some twisted specimens, which might be de-
stroyed every time before ripening their seeds.
Reasoning from the evidence available, and
from analogous cases, the variety would, even
under such extreme circumstances, be able to
last as long as any other good variety or ele-
mentary species. And it seems to me that this
explanation makes clear how it is possible that
varieties, which are potentially rich in their pe-
culiar monstrosity, are discovered from time to
time among plants when tested by experimental
methods.

Granting these conclusions, monstrosities on
the one side, and dimorphous wild species on
the other, constitute the most striking examples
of the inheritance of latent characters.

The bearing of the phenomena of dimorphism
upon the principles of evolution formulated by
Lamarck, and modified by his followers to con-
stitute Neo-Lamarckianism, remains to be con-
sidered. Lamarck assumed that the external
conditions directly affected the organisms in

448 Ever-sporting Varieties

such a way as to make them better adapted to
life, under prevailing circumstances. Nageli
gave to this conception the name "" Theory
of direct causation " (Theorie der direc-
ten Bewirkung), and it has received the ap-
proval of Von Wettstein, Strasburger and other
German investigators. According to this con-
ception a plant, when migrating from lowlands
into the mountains would slowly be changed
and gradually assume alpine habits. Once ac-
quired this habit would become fixed and attain
the rank of specific characters. In testing this
theory by field-observations and culture-exper-
iments, the defenders of the Nagelian principle
could easily produce evidence upon the first
point. The change of lowland-plants into al-
pine varieties can be brought about in numer-
ous cases, and corresponding changes under
the influence of soil, or climate, or life-condi-
tions are on record for the most various charac-
ters and qualities.

The second point, however, is as difficult to
prove as the first is of easy treatment. If after
hundreds and thousands of years of exposure to
alpine or other extreme conditions a fixed
change is proved to have taken place, the ques-
tion remains unanswered, whether the change
has been a gradual or a sudden one. Darwin
pointed out that long periods of life afford a

Double Adaptations 449

chance for a sudden change in the desired di-
rection, as well as for the slow accumulation of
slight deviations. Any mutations in a wrong
direction would at once be destroyed, but an
accidental change in a useful way would be
preserved, and multiply itself. If in the course
of centuries this occurred, they woukl be near-
ly sure to become established, however rare at
the outset. Hence the positive assertion is
scarcely capable of direct proof.

On' the other hand the negative assertion
must be granted full significance. If the al-
pine climate has done no more than produce a
transitory change, it is clear that thousands
of years do not, necessarily, cause constant
and specific alterations. This requirement is
one of the indispensable supports of the La-
marckian theory. The matter is capable of
disproof however, and such disproof seems to
be afforded by the direct evidence of the pres-
ent condition of the alpine varieties at large,
and by many other similar cases.

Among these the observations of Holter-
mann on some desert-plants of Ceylon are of
the highest value. Moreover they touch ques-
tions which are of wide importance for the
study of the biology of American deserts. For
this reason I mav be allowed to introduce them

ft''

here at some length.

450 Ever-sporting Varieties

The desert of Kaits, in Northern Ceylon,
nourishes on its dry and torrid sands some
species, represented by a large number of in-
dividuals, together with some rarer plants.
The commonest forms are Erigeron asteroides,
Vernonia cinerea^ Laurea pinnatifida, Vicoa au-
riculata^ Heylandia latehrosa and Chrysopo-
gon montanus. In direct contrast with the or-
dinary desert-types they have a thin epidermis,
with exposed stomata, features that ordinarily
were characteristic of species of moister re-
gions. They are annuals, growing rapidly,
blooming and ripening their seeds before the
height of the dry season. Evidently they are
to be considered as the remainder of the flora
of a previous period, when the soil had not yet
become arid. They might be called relics. Of
course they are small and dwarf-like, when com-
pared with allied forms.

These curious little desert-plants disprove
the Nagelian views in two important points.
First, they show that extreme conditions do not
necessarily change the organisms subjected to
them, in a desirable direction. During the
many centuries that these plants must have ex-
isted in the desert in annual generations, no
single feature in the anatomical structure has
become changed. Hence the conclusion that
small leaves, abundant rootstocks and short

Double Adaptations 451

stems, a dense foliage, a strongly cuticularized
epidermis, few and narrow air-cavities in the
tissues and all the long range of characteris-
tics of typical desert-plants are not a simple
result of the influence of climate and soil.
There is no direct influence in this sense.

The second point, in Avhich Nageli's idea is
broken down by Holtermann's observations, re-
sults from the behavior of the plants of the
Kaits desert when grown or sown on garden-
soil. When treated in this way they at once
lose the only peculiarity which might be con-
sidered as a consequence of the desert-life of
their ancestors, their dwarf stature. They be-
have exactly like the alpine plants in Bonnier's
experiments, and with even more striking dif-
ferences. In the desert they attain a height
of a few centimeters, but in the garden they
attain half a meter and more in height. Noth-
ing in the way of stability has resulted from the
action of the dry soil, not even in such a minor
point as the height of the stems.

From these facts and discussions we may
conclude that double adaptation is not induced
by external influences, at least not in any way
in which it might be of use to the plant. Tt
may arise by some unknown cause, or may
not be incited at all. In the first case the plant
becomes capable of living under the altemat-

452 Ever-sporting Varieties

ing circumstances, and if growing near the
limits of such regions it will overlap and get
into the new area. All other species, which did
not acquire the double habit, are of course ex-
cluded, with such curious exceptions as those
of Kaits. The typical vegetation under such
extreme conditions however, finds explanation
quite as well by the one as by the other view.

Leaving these obvious cases of double adap-
tation, there still remains one point to be con-
sidered. It is the dwarf stature of so many
desert and alpine plants. Are these dwarfs
only the extremes of the normal fluctuating va-
riability, or is their stature to be regarded as
the expression of some peculiar adaptive but
latent quality? It is as yet difficult to decide
this question, because statistical studies of this
form of variability are still wanting. The ca-
pacity of ripening the seed on individuals of
dwarf stature however, is not at all a uni-
versal accompaniment of a variable height.
Hence it cannot be considered as a necessary
consequence of it. On the other hand the dwarf
varieties of numerous garden-plants, as for in-
stance: of larkspurs, snapdragon, opium-pop-
pies and others are quite stable and thence are
obviously due to peculiar characteristics. Such
characteristics, if combined with tall stature
into a pair of antagonists, would yield a double

Double Adaptations 453

adaptation, and on such a base a hypothetical
explanation could no doubt be rested.

Instead of discussing this problem from the
theoretical side, I prefer to compare those spe-
cies which are capable of assuming a dwarf
stature under less uncommon conditions than
those of alpine and desert-plants. Many weeds
of our gardens and many wild species have this
capacity. They become very tall, with large
leaves, richly branched stems and numerous
flowers in moist and rich soil. On bad soil, or
if germinating too late, when the season is
drier, they remain very small, producing only
a few leaves and often limiting themselves to
one flower-head. This is often seen with thorn-
apples and amaranths, and even with oats and
rye, and is notoriously the case with buck-
wheat. G-auchery has observed that the ex-
tremes differ often as much from one another
as 1 :10. In the case of the Canadian horse-
weed or Erigeron canadensis, which is widely
naturalized in Europe, the tallest specimens
are often twenty-five times as tall as the small-
est, the difference increasing to greater ex-
tremes, if besides the main stem, the length of
the numerous branches of the tall plants are
taken into consideration. Other instances
studied by the French investigator are Ery-
thraea pulchella and Calamintha Acinos.

454 Ever-sporthig Varieties

Dimorphism is of universal occurrence in the
whole vegetable kingdom. In some cases it is
typical, and may easily be discerned from ex-
treme flutuating variability. In others the con-
trast is not at all obvious, and a closer
investigation is needed to decide between the
two possibilities. Sometimes the adaptive qual-
ity is evident, in other cases it is not. A large
number of plants bear two kinds of leaves linked
with one another by intermediate forms. Often
the first leaves of a shoot, or those of accident-
ally strong shoots, exhibit deviating shapes,
and the usefulness of such occurrences seems to
be quite doubtful. The elongation of stems and
linear leaves, and the reduction of lateral or-
gans in darkness, is manifestly an adaptation.
Many plants have stolons with double adapta-
tions which enable them to retain their char-
acter of underground stems with bracts or to
exchange it for the characteristics of erect
stems with green leaves according to the outer
circumstances. In some shrubs and trees the
capacity of a number of buds to produce either
flowers or shoots with leaves seems to be in
the same condition. The capacity of producing
spines is also a double adaptation, active on
dry and arid soil and latent in a moist climate
or under cultivation, as with the wild and cul-
tivated apple, and in the experiments of Lo-

Double Adaptations 455

tlielier with Berheris, Lycium and other species,
which lose their spines in damp air.

In some conifers the evolution of horizontal
branches may be modified by simply turning
the buds upside down. Or the lateral branches
can be induced to become erect stems by
cutting off the normal summit of a tree. Nu-
merous organs and functions lie dormant un-
til aroused by external agencies, and many
other cases could be cited, showing the wide
occurrence of double adaptation.

There are, however, two points, which should
not be passed over without some mention. One
of them is the influence of sun and shade on
leaves, and the other the atavistic forms, often
exhibited during the juvenile period.

The leaves of many plants, and especially
those of some shrubs and trees, have the ca-
pacity of adapting themselves either to intense
or to diffuse light. On the circumference of the
crown of a tree the light is stronger and the
leaves are small and thick, with a dense tissue.
In the inner parts of the crown the light is
weak and the leaves are broader in order to
get as much of it as possible. They become
larger but thinner, consisting often of a small
number of cell layers. The definitive forma-
tion is made in extreme youth, often even
during the previous summer, at the time of the

456 Ever-sporting Varieties

very first evolution of the young organs within
the buds. Iris, and Lactuca Scariola or the
prickly lettuce, and many other plants afford
similar instances. As the definitive decision
must be made in these cases long before the di-
rect influence of the conditions which would
make the change useful is felt, it is hardly con-
ceivable how they could be ascribed to this
cause.

It is universally known that many plants
show deviating features when very young, and
that these often remind us of the characters of
their probable ancestors. Many plants that
must have been derived from their nearest sys-
tematic relatives, chiefly by reductions, are
constantly betraying this relation by a repeti-
tion of the ancestral marks during their
youth.

There can be hardly a doubt that the general
law of natural selection prevails in such cases
as it does in others. Or stated otherwise, it is
very probable, that in most cases the atavistic
characters have been retained during youth
because of their temporary usefulness. Un-
fortunately, our knowledge of utility of quali-
ties is as yet very incomplete. Here we must
assume that what is ordinarily spared by nat-
ural selection is to be considered as useful,

Double Adaptations 457

until direct experimental investigations have
been made.

So it is for instance with the submerged leaves
of water-plants. As a rule they are linear, or
if compound, are reduced to densely branching
filiform threads. Hence we may conclude that
this structure is of some use to them. Now
two European and some corresponding Amer-
ican species of water-parsnip, the Slum lati-
folium and Berula angustifolia with their al-
lies, are umbellifers, which bear pinnate instead
of bi- or tri-pinnate leaves. But the young
plants and even the young shoots when devel-
oping from the rootstocks under water comply
with the above rule, producing very compound,
finely and pectinately dissected leaves. From a
systematic point of view these leaves indicate
the origin of the water-parsnips from ordinary
umbellifers, which generally have bi- and tri-
pinnate leaves.

Similar cases of double adaptation, depend-
ent on external conditions at different periods
of the evolution of the plant are very numerous.
They are most marked among leguminous
plants, as shown by the trifoliolate leaves of the
thorn-broom and allies, which in the adult state
have green twigs destitute of leaves.

As an additional instance of dimorphism and
probable double adaptation to unrecognized ex-

458 Ever-sporting Varieties

ternal conditions I might point to the genns
Acacia. As we have seen in a previous
lecture some of the numerous species of this
genus bear bi-pinnate leaves, while others
have only flattened leaf-stalks. According to
the prevailing systematic conceptions, the
last must have been derived from the first by
the loss of the blades and the corresponding
increase of size and superficial extension of the
stalk. In proof of this view they exhibit, as we
have described, the ancestral characters in the
young plantlets, and this production of bi-pin-
nate leaves has probably been retained at the pe-
riod of the corresponding negative mutations,
because of some distinct, though still unknown
use.

Summarizing the results of this discussion,
we may state that useful dimorphism, or dou-
ble adaptation, is a substitution of characters
quite analogous to the useless dimorphism of
cultivated ever-sporting varieties and the stray
occurrence of hereditary monstrosities. The
same laws and conditions prevail in both cases.

E. MUTATIONS
Lecture XVI

THE ORIGIN OF THE PELORIC TOAD-FLAX

I have tried to show previously that species, in
the ordinary sense of the word, consist of dis-
tinct groups of units. In systematic works
these groups are all designated by the name of
varieties, but it is usually granted that the
units of the system are not always of the same
value. Hence we have distinguished between
elementary species and varieties proper. The
first are combined into species whose common
original type is now lost or unknown, and from
their characters is derived an hypothetical im-
age of what the common ancestor is supposed
to have been. The varieties proper are derived
in most cases from still existing types, and
therefore are subjoined to them. A closer in-
vestigation has shown that this derivation is
ordinarily produced by the loss of some definite
attribute, or by the re-acquisition of an appar-

459

460 Mutations

ently lost character. The elenientary species,
on the other hand, must have arisen by the pro-
duction of new qualities, each new acquisition
constituting the origin of a new elementary
form.

Moreover we have seen, that such improve-
ments and such losses constitute sharp limits
between the single unit-forms. Every type, of
course, varies around an average, and the ex-
tremes of one form may sometimes reach or
even overlap those of the nearest allies, but
the offspring of the extremes always return to
the type. The transgression is only temporary
and a real transition of one form to another
does not come within ordinary features of fluc-
tuating variability. Even in the cases of ever-
sporting varieties, where two opposite types
are united within one race, and where the suc-
ceeding individuals are continually swinging
from one extreme to the other, passing through
a wide range of intermediate steps, the limits
of the variety are as sharply defined and as free
from real transgression as in any other form.

In a complete systematic enumeration of the
real units of nature, the elementary species and
varieties are thus observed to be discontinous
and separated by definite gaps. Every unit
may have its youth, may lead a long life in the
adult state and may finally die. But through

Origin of Peloric Toadflax 461

the whole period of its existence it remains the
same, at the end as sharply defined from its
nearest allies as in the beginning. Should
some of the units die out, the gaps between the
neighboring ones will become wider, as must
often have been the case. Such segregations,
however important and useful for systematic
distinctions, are evidently only of secondary
value, when considering the real nature of the
units themselves.

We may now take up the other side of the
problem. The question arises as to how species
and varieties have originated. According to
the Darwinian theory they have been produced
from one another, the more highly differenti-
ated ones from the simpler, in a graduated
series from the most simple forms to the most
complicated and most highly organized exist-
ing types. This evolution of course must have
been regular and continuous, diverging from
time to time into new directions, and linking
all organisms together into one common pedi-
gree. All lacunae in our present system are ex-
plained by Darwin as due to the extinction of
the forms, which previously filled them.

Since Lamarck first propounded the concep-
tion of a common origin for all living beings,
much has been done to clear up our ideas as to
the real nature of this process. The broader

-1:62 Mutations

aspect of the subject, including the general pedi-
gree of the ammal and vegetable kingdom, may
be said to have been outlined by Darwin and his
followers, but this phase of the subject lies be-
yond the limits of our present discussion.

The other phase of the problem is concerned
with the manner in which the single elementary
species and varieties have sprung from one an-
other. There is no reason to suppose that the
world is reaching the end of its development,
and so we are to infer that the production of
new species and varieties is still going on. In
reality, new forms are observed to originate
from time to time, both wild and in cultivation,
and such facts do not leave any doubt as to their
origin from other allied types, and according to
natural and general laws.

In the wild state however, and even with cul-
tivated plants of the field and garden, the condi-
tions, though allowing of the immediate obser-
vation of the origination of new forms, are by no
means favorable for a closer inquiry into the
real nature of the process. Therefore I shall
postpone the discussion of the facts till an-
other lecture, as their bearing will be more
easily understood after having dealt with more
complete cases.

These can only be obtained by direct experi-
mentation. Comparative studies, of course,

Origin of Peloric Toadflax 463

are valuable for the elucidation of general prob-
lems and broad features of the whole pedigree,
but the narrower and more practical question as
to the genetic relation of the single foi-ms to one
another must be studied in another way, by
direct experiment. The exact methods of the
laboratory must be used, and in this case the
garden is the laboratory. The cultures must
be guarded with the strictest care and every
precaution taken to exclude opportunities for
error. The parents and grandparents and their
offspring must be kept pure and under control,
and all facts bearing upon the birth or origin of
the new types should be carefully recorded.

Two great difficulties have of late stood in
the way of such experimental investigation.
One of them is of a theoretical, the other of a
practical nature. One is the general belief in
the supposed slowness of the process, the other
is the choice of adequate material for experi-
mental purposes. Darwin's hypothesis of nat-
ural selection as the means by which new types
arise, is now being generally interpreted as
stating the slow transformation of ordinary
fluctuating divergencies from the average type
into specific differences. But in doing so it is
overlooked that Quetelet's law of fluctuating
variability was not yet discovered at the time,
when Darwin propounded his theory. So there

464: Mutations

is no real and intimate connection between these
two great conceptions. Darwin frequently
pointed out that a long period of time might be
needed for slow improvements, and was also a
condition for the occurrence of rare sports. In
any case those writers have been in error, ac-
cording to my opinion, who have refrained from
experimental work on the origin of species, on
account of this narrow interpretation of Dar-
win's views. The choice of the material is
quite another question, and obviously all de-
pends upon this choice. Promising instances
must be sought for, but as a rule the best way
is to test as many plants as possible. Many of
them may show nothing of interest, but some
might lead to the desired end.

For to-day's lecture I have chosen an in-
stance, in which the grounds upon which the
choice was based are very evident. It is the
origin of the peloric toad-flax (Lmaria vulgaris
peloria).

The ground for this choice lies simply in the
fact that the peloric toad-flax is known to have
originated from the ordinary type at different
times and in different countries, under more or
less divergent conditions. It had arisen from
time to time, and hence I presumed that there
was a chance to see it arise again. If this
should happen under experimental circum-

Origin of Peloric Toadflax 465

stances the desired evidence might easily be
gathered. Or, to put it in other words, we must
try to arrange things so as to be present at the
time when nature produces another of these
rare changes.

There was still another reason for choosing
this plant for observational work. The step from
the ordinary toad-flax to the peloric form is
short, and it appears as if it might be produced
by slow conversion. The ordinary species pro-
duces from time to time stray peloric flowers.
These occur at the base of the raceme, or rarely
in the midst of it. In other species they are
often seen at the summit. Terminal pelories
are usually regular, having five equal spurs.
Lateral pelories are generally of zygomorphic
structure, though of course in a less degree than
the normal bilabiate flowers, but they have un-
equal spurs, the middle one being of the ordi-
nary length, the two neighboring being shorter,
and those standing next to the opposite side of
the flower being the shortest of all. This curi-
ous remainder of the original symmetrical
structure of the flower seems to have been over-
looked hitherto by the investigators of peloric
toad-flaxes.

The peloric variety of this plant is character-
ized by its producing only peloric flowers. No
single bilabiate or one-spurred flower remains.

466 Mutations

I once had a lot of nearly a hundred spedmens
of this fine variety, and it was a most curious
and beautiful sight to observe the many thou-
sands of nearly regular flowers blooming at the
same time. Some degree of variability was of
course present, even in a large measure. The
number of the spurs varied between four and six,
transgressing these limits in some instances, but
never so far as to produce really one-spurred
flowers. Comparing this variety with the ordi-
nary type, two ways of passing over from the
one to the other might be imagined. One would
entail a slow increase of the number of the
peloric flowers on each plant, combined with a
decrease of the number of the normal ones, the
other a sudden leap from one extreme to the
other without any intermediate steps. The
latter might easily be overlooked in field obser-
vations and their failure may not have the value
of direct proof. They could never be over-
looked, on the other hand, in experimental cul-
ture.

The first record of the peloric toad-flax is that
of Zioberg, a student of Linnaeus, who found it
in the neighborhood of Upsala. This curious
discovery was described by Kudberg in his dis-
sertation in the year 1744. Soon afterwards
other localities were discovered by Link near
Gottingen in Germany about 1791 and after-

Origin of Peloric Toadflax 467

wards in the vicinity of Berlin, as stated by
Ratzeburg, 1825. Many other localities have
since been indicated for it in Europe, and in my
own country some have been noted of late, as
for instance near Zandvoort in 1874 and near
Oldenzaal in 1896. In both these last named
cases the peloric form arose spontaneously in
places which had often been visited by botanists
before the recorded appearance, and therefore,
without any doubt, they must have been pro-
duced directly and independently by the ordi-
nary species which grows in the locality. The
same holds good for other occurrences of it.

In many instances the variety has been re-
corded to disappear after a certain lapse of
time, the original specimens dying out and no
new ones being produced. Linaria is a peren-
nial herb, multiplying itself easily bj^ buds grow-
ing on the roots, but even with this means of
propagation its duration seems to have definite
limits.

There is one other important point arguing
strongly for the independent appearance of the
peloric form in its several localities. It is the
difficulty of fertilization and the high degree of
sterility, even if artificially pollinated. Bees and
hmnble-bees are unable to crawl into the nar-
row tubular flowers, and to bring the fertilizing
pollen to the stigma. Ripe capsules with seeds

468 Mutations

have never been seen in the wild state. The
only writer who sueceeded in sowing seeds of
the peloric variety was Wildenow and he got
only very few seedlings. But even in artificial
pollination the result is the same, the anthers
seeming to be seriously affected by the change.
I tried both self-fertilization and cross-pollina-
tion, and only with utmost care did I succeed
in saving barely a hundred seeds. In order
to obtain them I was compelled to operate on
more than a thousand flowers on about a dozen
peloric plants.

The variety being wholly barren in nature,
the assumption that the plants in the different
recorded localities might have a common origin
is at once excluded. There must have been at
least nearly as many mutations as localities.
This strengthens the hope of seeing such a mu-
tation happen in one's own garden. It should
also be remembered that peloric flowers are
known to have originated in quite a number
of different species of Linaria, and also with
many of the allied species within the range of
the Lahiatiflorae.

I will now give the description of my own ex-
periment. Of course this did not give the ex-
pected result in the first year. On the contrary,
it was only after eight years' work that I had
the good fortune of observing the mutation.

Origin of Peloric Toadflax 469

But as the whole life-history of the preceding
generations had been carefully observed and
recorded, the exact interpretation of the fact
was readily made.

My culture commenced in the year 1886. I
chose some plants of the normal type with one
or two peloric flowers besides the bilabiate ma-
jority which I found on a locality in the neigh-
borhood of Hilversum in Holland. I planted
the roots in my garden and from them had the
first flowering generation in the following sum-
mer. From their seeds I grew the second gen-
eration in three following years. They flow-
ered profusely and produced in 1889 only one,
and in 1890 only two peloric structures. I saved
the seeds in 1889 and had in 1890-1891 the third
generation. These plants likewise flowered
only in the second year, and gave among some
thousands of symmetrical blossoms, only one
five-spurred flower. I pollinated this flower
myself, and it produced abundant fruit with
enough seeds for the entire culture in 1892, and
they only were sown.

Until this year my generations required two
years each, owing to the perennial habit of the
plants. In this way the prospects of the cul-
ture began to decrease, and I proposed to try to
heighten my chances by having a new genera-
tion yearly. With this intention I sowed the

470 Mutations

selected seeds in a pan in the glasshouse of my
laboratory and planted them out as soon as the
young stems had reached a length of some few
centimeters. Each seedling was put in a sepa-
rate pot, in heavily manured soil. The pots
were kept under glass until the beginning of
June, and the young plants produced during
this period a number of secondary stems from
the curious hypocotylous buds which are so
characteristic of the species. These stems
grew rapidly and as soon as they were
strong enough, the plants were put into
the beds. They all, at least nearly all,
some twenty specimens, flowered in the follow-
ing month.

I observed only one peloric flower among the
large number present. I took the plant bearing
this flower and one more for the culture of the
following year, and destroyed all others. These
two plants grew on the same spot, and were al-
lowed to fertilize each other by the agency of
the bees, but were kept isolated from any other
congener. They flowered abundantly, but pro-
duced only one-spurred bilabiate flowers during
the whole summer. They matured more than
10 cu. cm. of seeds.

It is from this pair of plants that my peloric
race has sprung. And as they are the ancestors
of the first closely observed case of peloric mu-

Origin of Peloric Toadflax 471

tation, it seems worth while to give some details
regarding their fertilization.

Isolated plants of Linaria vulgaris do not
produce seed, even if freely pollinated by bees.
Pollen from other plants is required. This re-
quirement is not at all restricted to the genus
Linaria, as many instances are known to occur
in different families. It is generally assumed
that the pollen of any other individual of the
same species is capable of producing fertiliza-
tion, although it is to be said that a critical
examination has been made in but few instances.

This, however, is not the case, at least not in
the present instance. I have pollinated a num-
ber of plants, grown from seed of the same
strain and combined them in pairs, and ex-
cluded the visits of insects, and pollen other
than that of the plant itself and that of the spec-
imen with which it was paired. The result was
that some pairs were fertile and others barren.
Counting these two groups of pairs, I found
them nearly equal in number, indicating there-
by that for any given individual the pollen of
half of the others is potent, but that of the other
half impotent. From these facts we may con-
clude the presence of a curious case of dimor-
phy, analogous to that proposed for the prim-
roses, but without visible differentiating marks
in the flowers. At least such opposite charac-

472 Mutations

ters have as yet not been ascertained in the case
of our toad-flax.

In order to save seed from isolated plants it is
necessary, for this reason, to have at least two
individuals, and these must belong to the two
physiologically different types. Now in the
year 1892, as in other years, my plants, though
separated at the outset by distances of about 20
cm. from each other, threw out roots of far
greater length, growing in such a way as to
abolish the strict isolation of the individuals.
Any plot may produce several stems from such
roots, and it is manifestly impossible to decide
whether they all belong to one original plant or
to the mixed roots of several individuals. No
other strains were grown on the same bed with
my plants however, and so I considered all the
stems of the little group as belonging to one
plant. But their perfect fertility showed, ac-
cording to the experience described, that there
must have been at least two specimens mingled
together.

Returning now to the seeds of this pair of
plants, I had, of course, not the least occasion
to ascribe to it any higher value than the har-
vest of former years. The consequence was
that I had no reason to make large sowings, and
grew only enough young plants to have about
50 in bloom in the summer of 1894. Among

Origin of Peloric Toadflax 473

these, stray peloric flowers were observed in
somewhat larger number than in the previous
generations, 11 plants bearing one or two,
or even three such abnormalities. This how-
ever, could not be considered as a real advance,
since such plants may occur in varying, though
ordinarily small numbers in every generation.

Besides them a single plant was seen to bear
only peloric flowers ; it produced racemes on sev-
eral stems and their branches. All were peloric
without exception. I kept it through the winter,
taking care to preserve a complete isolation of
its roots. The other plants were wholly de-
stroyed. Such annihilation must include both
the stems and roots and the latter of course re-
quires considerable labor. The following year,
however, gave proof of the success of the opera-
tion, since my plant bloomed luxuriously for the
second time and remained true to the type of
the first year, producing peloric flowers ex-
clusively.

Here we have the first experimental mutation
of a normal into a peloric race. Two facts were
clear and simple. The ancestry was known for
over a period of four generations, living under
the ordinary care and conditions of an experi-
mental garden, isolated from other toad-flaxes,
but freely fertilized by bees or at times by my-
self. This ancestry was quite constant as to

474 Mutations

the peloric peculiarity, remaining true to the
wild type as it occurs everywhere in my country,
and showing in no respect any tendency to the
production of a new variety.

The mutation took place at once. It was a
sudden leap from the normal plants with very
rare peloric flowers to a type exclusively
peloric. No intermediate steps were observed.
The parents themselves had borne thousands of
flowers during two summers, and these were
inspected nearly every day, in the hope of find-
ing some pelories and of saving their seed sep-
arately. Only one such flower was seen. If
there had been more, say a few in every hun-
dred flowers, it might be allowable to consider
them as previous stages, showing a preparation
of the impending change. But nothing of this
kind was observed. There was simply no vis-
ible preparation for the sudden leap.

This leap, on the other hand, was full and
complete. No reminiscence of the former con-
dition remained. Not a single flower on the
mutated plant reverted to the previous type.
All were thoroughly affected by the new attri-
bute, and showed the abnormally augmented
number of spurs, the tubular structure of the
corolla and the round and narrow entrance of
its throat. The whole plant departed absolute-
ly from the old type of its progenitors.

Origin of Pelorlc Toadflax 475

Three ways were open to continue my exper-
iment. The first was indicated by the abundant
harvest from the parent-plants of the mutation.
It seemed possible to compare the numerical
proportion of the mutated seeds with those
of normal plants. In order to ascertain
this proportion I sowed the greatest part of
my 10 cu. cm. of seed and planted some 2000
young plants in little pots with well-manured
soil. I got some 1750 flowering plants and ob-
served among them 16 wholly peloric individ-
uals. The numerical proportion of the muta-
tion was therefore in this instance to be
calculated equal to about 1^ of the whole crop.

This figure is of some importance. For it
shows that the chance of finding mutations
requires the cultivation of large groups of indi-
viduals. One plant in each hundred may mu-
tate, and cultures of less than a hundred speci-
mens must therefore be entirely dependent on
chance for the appearance of new forms, even
if such should accidentally have been produced
and lay dormant in the seed. In other cases
mutations may be more numerous, or on the
contrary, more rare. But the chance of muta-
tive changes in larger numbers is manifestly
much reduced by this experiment, and they may
be expected to form a very small proportion of
the culture.

476 Mutations

The second question which arose from the
above result was this. Could the mutation be
repeated? Was it to be ascribed to some latent
cause which might be operative more than
once? Was there some hidden tendency to muta-
tion, which, ordinarily weak, was strengthened
in my cultures by some unknown influence?
Was the observed mutation to be explained by
a common cause with the other cases recorded
by field-observations? To answer this question
I had only to continue my expermient, exclud-
ing the mutated individuals from any inter-
crossing with their brethren. To this end I
saved the seeds from duly isolated groups
in different years and sowed them at dif-
ferent times. For various causes I was not
prepared to have large cultures from these
seeds, but notwithstanding this, the mutation
repeated itself. In one instance I obtained
two, in another, one peloric plant with exclusive-
ly many-spurred flowers. As is easily under-
stood, these were related as ^' nieces " to the
first observed mutants. They originated in
quite the same way, by a sudden leap, without
any preparation and without any intermediate
steps.

Mutation is proved by this experience to be
of an iterative nature. It is the expression of
some concealed condition, or as it is generally

Origin of Peloric Toadflax 477

called, of some liidden tendency. The real
nature of this state of the hereditary qualities
is as yet wholly unknown. It would not be safe
to formulate further conclusions before the evi-
dence offered by the evening-primroses is
considered.

Thirdly, the question arises, whether the
mutation is complete, not only as to the mor-
phologic character, but also as to the hered-
itary constitution of the mutated individuals.
But here unfortunately the high degree of ster-
ility of the peloric plants, as previously noted,
makes the experimental evidence a thing of
great difficulty. During the course of several
years I isolated and planted together the
peloric individuals already mentioned, all in all
some twenty plants. Each individual was nearly
absolutely sterile when treated with its own
pollen, and the aid of insects was of no avail.
I intercrossed my plants artificially, and
pollinated more than a thousand flowers. Not
a single one gave a normal fruit, but some small
and nearly rudimentary capsules were pro-
duced, bearing a few seeds. From these I had
119 flowering plants, out of which 106 were
peloric and 13 one-spurred. The great major-
ity, some 90^, were thus shown to be true to
their new type. Whether the 10;^ reverting
ones were trulv atavists, or whether thev were

478 Mutations

only vicinists, caused by stray pollen grains
from another culture, cannot of course be de-
cided with sufficient certitude.

Here I might refer to the observations con-
cerning the invisible dimorj)hous state of the
flowers of the normal toad-flax. Individuals of
the same type, when fertilized with each other,
are nearly, but not absolutely, sterile. The
yield of seeds of my peloric plants agrees fairly
well with the harvest which I have obtained
from some of the nearly sterile pairs of indi-
viduals in my former trial. Hence the sugges-
tion is forced upon us that perhaps, owing to
some unknown cause, all the peloric individuals
of my experiment belonged to one and the same
type, and were sterile for this reason only. If
this is true, then it is to be presumed that all
previous investigators have met the same con-
dition, each having at hand only one of the two
required types. And this discussion has
the further advantage of showing the way,
in which perhaps a full and constant race of
peloric toad-flaxes may be obtained. Two indi-
viduals of different type are required to start
from. They seem as yet never to have arisen
from one group of mutations. But if it were
possible to combine the products of two muta-
tions obtained in different countries and under
different conditions, there would be a chance

Origin of Peloric Toadflax 479

that they might belong to the supposed opposite
types, and thus be fertile with one another.

My peloric plants are still available, and the
occurrence of this form elsewhere would give
material for a successful experiment. The
probability thereof is enhanced by the experi-
ence that my peloric plants bear large capsules
and a rich harvest of seeds when fertilized from
plants of the normal one-spurred race, while
they remain nearly wholly barren by artificial
fertilization with others. I suppose that they
are infertile with the normal toad-flaxes of their
own sexual disposition, but fertile with those of
the opposite constitution. At all events the
fact that they may bear abundant seed when
properly pollinated is an indication of success-
ful experiments on the possibility of gaining a
hereditary race with exclusively peloric flowers.
And such a race would be a distinct gain for
sundry physiologic inquiries, and perhaps not
wholly destitute of value from an horticultural
point of view.

Returning now to the often recorded occur-
rence of peloric toad-flaxes in the wild state and
recalling our discussion about the improb-
ability of a dispersion from one locality to
another by seed, and the probability of inde-
pendent origin for most of these cases, we are
confronted with the conception that a latent

480 Mutations

tendency to mutation must be universally
present in the whole species. Another observa-
tion, although it is of a negative character,
gains in importance from this point of view.
I refer to the total lack of intermediate steps
between normal and peloric individuals. If
such links had ordinarily been produced pre-
vious to the purely peloric state they would no
doubt have been observed from time to time.
This is so much the more probable as Linaria
is a perennial herb, and the ancestors of a
mutation might still be in a flowering condi-
tion together with their divergent offspring.
But no such intermediates are on record. The
peloric toad-flaxes are, as a rule, found sur-
rounded by the normal type, but without inter-
grading forms. This discontinuity has already
been insisted upon by Hofmeister and others,
even at the time when the theory of descent was
most under discussion, and any link would
surely have been produced as a proof of a slow
and continuous change. But no such proof has
been found, and the conclusion seems admissible
that the mutation of toad-flaxes ordinarily, if
not universally, takes place by a sudden step.
Our experiment may simply be considered as a
thoroughly controlled instance of an often re-
curring phenomenon. It teaches us how, in the

Origin of Peloric Toadflax 481

main, the peloric mutations must be assumed to
proceed.

This conception may still be broadened. We
may include in it all similar occurrences, in
allied and other species. There is hardly a
limit to the possibilities which are opened up by
this experience. But it will be well to refrain
from hazardous theorizing, and consider only
those cases which may be regarded as exact
repetitions of the same phenomenon and of
which our culture is one of the most recent in-
stances on record. We will limit ourselves to
the probable origin of peloric variations at
large, of which little is known, but some evi-
dence may be derived from the recorded facts.
Only one case can be said to be directly analo-
gous to our observations.

This refers to the peloric race of the coromon
snapdragon, or Antirrhinum majus of our gar-
dens. It is known to produce peloric races from
time to time in the same way as does the toad-
flax. But the snapdragon is self-fertile and so
is its peloric variety. Some cases are rela-
tively old, and some of them have been recorded
and in part observed by Darwin. Whence they
have sprung and in what manner they were
produced, seems never to have been noted.
Others are of later origin, and among these one
or two varieties have been accidentally pro-

482 Mutations

duced in the nursery of Mr. Clir. Lorenz in
Erfurt, and are now for sale, the seeds being
guaranteed to yield a large proportion of
peloric individuals. The peloric form in this
case appeared at once, but was not isolated, and
was left free to visiting insects, which of course
crossed it with the surrounding varieties.
Without doubt the existence of two color-varie-
ties of the peloric type, one of a very dark red,
indicating the ^' Black prince " variety as the
pollen-parent, and the other with a white tube
of the corolla, recalling the form known as
' ' Delila, ' ' is due to these crossings. I had last
year (1903) a large lot of plants, partly normal
and partly peloric, but evidently of hybrid
origin, from seeds from this nursery, showing
moreover all intermediate steps between nearly
wholly peloric individuals and apparently nor-
mal ones. I have saved the seeds of the iso-
lated types and before seeing the flowers of
their offspring, nothing can be said about the
purity and constancy of the type, when freed
from hybrid admixtures. The peloric snap-
dragon has five small unequal spurs at the base
of its long tube, and in this respect agrees with
the peloric toad-flax.

Other pelories are terminal and quite regular,
and occur in some species of Linaria, where I
observed them in Linaria dalmatica. The

Origin of Peloric Toadflax 483

terminal flowers of many branches were large
and beautifully peloric, bearing five long and
equal spurs. About their origin and inher-
itance nothing is known.

A most curious terminal pelory is that of the
common foxglove or Digitalis purpurea. As we
have seen in a previous lecture, it is an old
variety. It was described and figured for the
first time by Vrolik of Amsterdam, and the
original specimens of his plates are still to be
seen in the collections of the botanic garden of
that university. Since his time it has been
propagated by seed as a commercial variety,
and may be easily obtained. The terminal
flower of the central stem and those of the
branches only are affected, all other flowers
being wholly normal. Almost always it is ac-
companied by other deviations, among which a
marked increase of the number of the parts of
the corolla and other whorls is the most strik-
ing. Likewise supernumerary petals on the
outer side of the corolla, and a production of a
bud in the center of the capsule may be often
met with. This bud as a rule grows out after
the fading away of the flower, bursting through
the green carpels of the unripe fruit, and pro-
ducing ordinarily a secondary raceme of flow-
ers. This raceme is a weak but exact repetition
of the first, bearing symmetrical foxgloves all

484 Mutations

along and terminating in a peloric structure.

On the branches these anomalies are more or
less reduced, according to the strengi:h of the
branch, and conforming to the rule of perio-
dicity, given in our lecture on the ' ' five-leaved ' '
clover. Through all this diminution the peloric
type remains unchanged and therefore becomes
so much the purer, the weaker the branches on
which it stands.

I am not sure whether such peloric flowers
have ever been purely pollinated and their seed
saved separately, but I have often observed
that the race comes pure from the seed of the
zygomorjDhic flowers. It is as yet doubtful
whether it is a half race or a double race, and
whether it might be purified and strengthened
by artificial selection. Perhaps the determina-
tion of the hereditary percentage de-
scribed when dealing with the tricotyls might
give the clue to the acquisition of a higher
specialized race. The variety is old and widely
disseminated, but must be subjected to quite a
number of additional experiments before it can
be said to be sufficiently understood.

The most widespread peloric variety is that
of gloxinia. It has erect instead of drooping
flowers; and with the changed position the
structure is also changed. Like other pelories
it has five equal stamens instead of four un-

Origin of Peloric Toadflax 485

equal ones, and a corolla with five equal seg-
ments instead of an upper and a lower lip. It
shows the peloric condition in all of its flowers
and is often combined with a small increase
of the number of the parts of the whorls.
It is for sale under the name of erecta, and
may be had in a wide range of color-types. It
seems to be quite constant from seed.

Many other instances of peloric flowers are
on record. Indian cress or Tropaeolum majus
loses the spur in some double varieties and
with it most of its symmetrical structure; it
seems to be considered justly as a peloric mal-
formation. Other species produce such anom-
alies only from time to time and nothing is
known about their hereditary tendency. One
of the most curious instances is the terminal
flower of the raceme of the common laburnum,
which loses its whole papilionaceous character
and becomes as regularly quinate as a common
buttercup.

Some families are more liable to pelorism
than others. Obviously all the groups, the
flowers of which are not symmetrical, are to be
excluded. But then we find that labiates and
their allies among the dicotyledonous plants,
and orchids among the monocotyledonous ones
are especially subjected to this alteration. In
both groups many genera and a long list of spe-

486 Mutations

cies could be quoted as proof. The family of the
labiates seems to be essentially rich in terminal
pelories, as for instance in the wild sage or
Salvia and the dead-nettle or Lamium. Here
the pelories have long and straight corolla-
tubes, which are terminated by a whorl of four
or ^VQ segments. Such forms often occur in
the wild state and seem to have a geographic
distribution as narrowlv circumscribed as in
the case of many small species. Those of the
labiates chiefly belong to southern Europe and
are unknown at least in some parts of the other
countries. On the contrary terminal pelories
of Scropliularia nodosa are met with from time
to time in Holland. Such facts clearly point
to a common origin, and as only the terminal
flowers are affected by the malformation, the
fertility of the whole plant is evidently not seri-
ously infringed upon.

Before leaving the labiates, we may cite
a curious instance of pelorism in the toad-flax,
which is quite different from the ordinary
peloric variety. This latter may be considered
from a morphologic standpoint to be owing to
a five-fold repetition of the middle part of the
underlip. This conception would at once ex-
plain the occurrence of ^ve spurs and of the
orange border all around the corolla-tube. We
might readily imagine that any other of the five

Origin of Pelortc Toadflax 487

parts of the corolla could be repeated five-fold,
in which case there would be no spur, and no
orange hue on the upper corolla-ring. Such
forms really occur, though they seem to be more
rare than the five-spurred pelories. Very little
is known about their frequency and hereditary
qualities.

Orchids include a large number of peloric
monstrosities and moreover a wild pelory
which is systematically described not only as a
separate species but even as a new genus. It
bears the name of Uropedium lindenii, and is
so closely related to Ci/pripedium caudatum
that many authors take it for the peloric variety
of this plant. It occurs in the wild state in
som-e parts of Mexico, where the Cypripedium
also grows. Its claims to be a separate genus
are lessened by the somewhat monstrous con-
dition of the sexual organs, which are described
as quite abnormal. But here also, interme-
diates are lacking, and this fact points to a
sudden origin.

Many cases of pelorism afford promising ma-
terial for further studies of experimental muta-
tions. The peloric toad-flax is only the proto-
type of what may be expected in other cases.
No opportunity should be lost to increase the as
yet too scanty evidence on this point.

Lectuke XVII

THE PRODUCTION OF DOUBLE FLOWERS

Mutations occur as often among cultivated
plants as among those in the wild state. Gar-
den flowers are known to vary markedly.
Much of their variability, however, is due to
hybridism, and the combination of characters
previously separate has a value for the breeder
nearly equal the production of really new qual-
ities. Nevertheless there is no doubt that some
new characters appear from time to time.

In a previous lecture we have seen that
varietal characters have many features in com-
mon. One of them is their frequent recur-
rence both in the same and in other, often very
distantly related, species. This recurrence is an
important factor in the choice of the material
for an experimental investigation of the nature
of mutations.

Some varieties are reputed to occur more
often and more readily than others. White-col-
ored varieties, though so very common, seem for
the most part to be of ancient date, but only few

488

Production of Double Flowers 489

have a known origin, however. Without any
doubt many of them have been found in a wild
state and were introduced into culture. On the
other hand double flowers are exceedingly rare
in the wild state, and even a slight indication of
a tendency towards doubling, the stray petaloid
stamens, are only rarely observed growing wild.
In cultivation, however, double flowers are of
frequent occurrence ; hence the conclusion that
they have been produced in gardens and nur-
series more frequently than perhaps any other
type of variety.

In the beginning of my experimental work I
cherished the hope of being able to produce a
white variety. My experiments, however, have
not been successful, and so I have given them
up temporarily. Much better chances for a
new double variety seemed to exist, and my en-
deavors in this direction have finally been
crowned with success.

For this reason I jDropose to deal now with
the production of double flowers, to inquire
what is on record about them in horticultural
literature, and to give a full description of the
origin thereof in an instance which it was my
good fortune to observe in my garden.

Of course the historical part is only a hasty
survey of the question and will only give such
evidence as may enable us to get an idea of the

492 Mutations

of a later period. A long list could easily be
made, to show that during the whole history of
horticulture double varieties have arisen
from time to time. As far as we can judge,
such appearances have been isolated and sud-
den. Sometimes they sprang into existence in
the full display of their beauty, but most com-
monly they showed themselves for the first time,
exhibiting only spare supernumerary petals.
Whenever such sports were worked up, a few
years sufficed to reach the entire development
of the new varietal attribute.

From this superficial survey of historical
facts, the inference is forced upon us that the
chance of producing a new double variety is
good enough to justify the attempt. It has fre-
quently succeeded for practical purposes, why
should it not succeed as well for purely scien-
tific investigation? At all events the type rec-
ommends itself to the student of nature, both
on account of its frequency, and of the apparent
insignificance of the first step, combined with
the possibility of rapidly working up from this
small beginning of one superfluous petal to-
wards the highest degree of duplication.

Compared with the tedious experimental pro-
duction of the peloric toad-flax, the attempt to
produce a double flower has a distinct attrac-
tion. The peloric toad-flax is nothing new ; the

Production of Double Flowers 493

experiment was only a repetition of what pre-
sumably takes place often within the same
species. To attempt to produce a double
variety we may choose any species, and of
course should select one which as yet has not
been known to produce double flowers. By
doing so we will, if we succeed, produce some-
thing new. Of course, it does not matter
whether the new variety has an horticultural in-
terest or not, and it seems preferable to choose
a wild or little cultivated species, to be quite
sure that the variety in question is not already
in existence. Finally the prospect of success
seems to be enhanced if a species is chosen, the
nearest allies of which are known to have pro-
duced double flowers.

For these reasons and others I chose for my
experiment the corn-marigold, or Chrysanthe-
mum segetum. It is also called the golden corn-
flower. In the wheat and rye fields of central
Europe it associates with the blue-bottle or blue
corn-flower. It is sometimes cultivated and the
seeds are offered for sale by many nursery-
men. It has a cultivated variety, called grandi-
iiorum, which is esteemed for its brilliancy and
long succession of golden bloom. This variety
has larger flower-heads, surrounded with a
fuller border of ray-florets the species belongs
to a genus many species of which have pro-

"494 Mutations

duced double varieties. One of them is
the Japanese marigold, others are the cari-
natum and the imhricatimi species. Nearly
allied are quite a number of garden-plants with
double flower-heads, among which are the
double camomiles.

My attention was first drawn to the structure
of the heads and especially to the number of the
ray-florets of the corn-marigold. The species
appertains to that group of composites which
have a head of small tubular florets surrounded
by a broad border of rays. These rays, when
counted, are observed to occur in definite num-
bers, which are connected with each other by a
formula, known as ** the series " of Braun and
Schimper. In this formula, which commences
with 1 and 2, each number is equal to the sum
of the two foregoing figures. Thus 5, 8 and 13
are very frequent occurrences, and the following
number, 21, is a most general one for apparent-
ly full rays, such as in daisies, camomiles, ^rmca
and many other wild and cultivated species.

These numbers are not at all constant. Thev
are only the averages, around which the real
numbers fluctuate. There mav even be an over-
lapping of the extremes, since the fluctuation
around 13 may even go beyond 8 and
21, and so on. But such extremes are only
found in stray flowers, occurring on the same

Production of Double Floivcrs 495

individuals with tiie lesser degrees of deviation.
Now the marigold averages 13, and the
grandiflorum 21 rays. The wild speeies is pure
in this respect, but the garden-variety is not.
The seeds which are offered for sale usually
contain a mixture of both forms and theii*
hybrids. So I had to isolate the pure types
from this mixture and to ascertain their con-
stancy and mutual independency. To this end
I isolated from the mixture first the 13-rayed,
and afterwards the 21-rayed types. As the
marigolds are not sufficiently self-fertile, and
are not easily pollinated artificially, it seemed
impossible to carry on these two experiments at
the same time and in the same garden. I de-
voted the first three vears to the lower form,
isolated some individuals with 12 - 13 rays out of
the mixture of 1892 and counted the ray-florets
on the terminal head of every plant of the en-
suing generation next year. I cultivated and
counted in this way above 150 individuals and
found an average of exactly 13 with compara-
tively few individuals displaying 14 or only 12
rays, and with the remainder of the plants
grouped symmetrically around this average. T
continued the experiment for still another year
and found the same group of figures. T was
then satisfied as to the purity of the isolated
strain. Next year T sowed a new mixture in

496 Mutations

order to isolate the reputed pure grandiflorum
type. During the beginning of the flowering-
period I ruthlessly threw away all plants dis-
playing less than 21 rays in the first or terminal
head. But this selection was not to be consid-
ered as complete, because the 13-rayed race may
eventually transgress its boundary and come
over to the 21 and more. This made a second
selection necessary. On the selected plants
all the secondary heads were inspected and
their ray-florets counted. Some individuals
showed an average of about 13 and were de-
stroyed. Others gave doubtful figures and
were likewise eliminated, and only 6 out of a
lot of nearly 300 flowering plants reached an
average of 21 for all of the flowers.

Our summer is a short one, compared with the
long and beautiful summer of California, and it
was too late to cut off the faded and the open
flowers, and await new ones, which might be
purely fertilized after the destruction of
all minor plants. So I had to gather the seed
from flowers, which might have been partially
fertilized by the wrong pollen. This however,
is not so great a drawback in selection experi-
ments as might be supposed at first sight. The
selection of the following year is sure to elim-
inate the offspring of such impure parentage.

Production of Double Flowers 497

A far more important principle is that of the
hereditary percentage, already discussed in our
lecture on the selection of monstrosities. In
our present case it had to be applied only to the
six selected plants of 1895. To this end the seeds
of each of them were sown separately, the ray-
florets of the terminal heads of each of the
new generation were counted, and curves and
averages were made up for the six groups.
Five of them gave proof of still being mixtures
and were wholly rejected. The children of the
sixth parent, however, formed a group of uni-
form constitution, all fluctuating around the de-
sired average of 21. All in all the terminal
heads of over 1500 plants have been subjected
to the somewhat tedious work of counting their
ray-florets. And this not in the laboratory, but
in the garden, without cutting them off. Other-
wise it would obviously have been impossible to
recognize the best plants for preservation. I
chose only two plants which in addition recom-
mended themselves by the average number of
rays on their secondary heads, sowed their
seeds next year separately and compared the
numerical constitution of their offspring.
Both groups averaged 21 and were distributed
very symmetrically around this mean. This re-

498 Mutations

suit showed that no further selection could be
of any avail, and that I had succeeded in purify-
ing the 21-rayed grandiflorum variety.

It is from this grandiflorum that I have finally
produced my double variety. In the year 1896
I selected from among the above quoted 1500
plants, 500 with terminal heads bearing 21 or
more rays. On these I counted the rays of all
the secondary heads about the middle of August
(1896) and found that they had, as a rule,
retrograded to lower figures. On many thou-
sands of heads only two were found having 22
rays. All others had the average number of 21
or even less. I isolated the individual which
bore these two heads, allowed them to be fertil-
ized by insects with the pollen of some of the
best plants of the same group, but destroyed the
remainder.

This single exceptional plant has been the
starting point of my double variety. It was not
remarkable for its terminal head, which exhib-
ited the average number of rays of the 21-rayed
race. Nor was it distinguished by the average
figure for all its heads. It was only selected
because it was the one plant which had some
secondary heads with one ray more than all the
others. This indication was very slight, and
could not have been detected save by the
counting of the rays of thousands of heads.

Production of Double Flowers 499

But the rarity of the anomaly was exactly the
indication wanted, and the same deviation
would have had no signification whatever, had it
occurred in a group fluctuating symmetrically
around the average figure. On the other hand,
the observed anomaly was only an indication,
and no guarantee of future developments.

Here it should be remarked that the indica-
tion alluded to was not the appearance of the
expected character of doubling in ever so slight
a measure. It was only a guide to be followed
in further work. The real character of double
flower-heads among composites lies in the pro-
duction of rays on the disk. No increase of the
number of the outer rays can have the same sig-
nificance. A hasty inspection of double flower-
heads may convey the idea that all rays are ar-
ranged around a little central cluster of disk-
florets, the remainder of the original disk. But
a closer investigation will always reveal the
fallacy of this conclusion. Hidden between
the inner rays, and covered by them, lie the
little tubular and fertile florets everywhere
on the disk. Thev mav not be easilv seen, but
if the supernumerary raj^s are pulled out, the
disk may be seen to bear numerous small
florets at intervals. But these intervals
are not at all numerous, showing thereby that
only a relatively small number of tubes has been

500 Mutations

converted into rays. This conversion is ob-
viously the true mark of the doubling, and be-
fore traces of it are found, no assertion what-
ever can be given as to the issue of the pedigree-
experiment.

Three more years were required before this
first, but decisive trace was discovered. During
these years I subjected my strain to the same
sharp selection as has already been described.
The chosen ancestor of the race had flowered in
1896, and the next year I sowed its seeds only.
From this generation I chose the one plant with
the largest number of rays in its terminal head,
and repeated this in the following year.

The consequence was that the average num-
ber of rays increased rapidly, and with it the
absolute maximum of the whole strain. The
average came up from 21 to 34. Brighter and
brighter crowns of the yellow rays improved
my race, until it became difficult and very time-
consuming to count all the large rays of the bor-
ders. The largest numbers determined in the
succeeding generations increased by leaps from
21 to 34 in the first year, and thence to 48 and 66
in the two succeeding summers. Every year I
was able to save enough seed from the very best
plant and to use it only for the continuance of
the race. Before the selected plants were al-
lowed to open the flowers from which the seed

Production of Double Flowers 501

was to be gathered, nearly the whole remaining
culture was exterminated, excepting only some
of the best examples, in order to have the re-
quired material for cross-pollination by insects.
Each new generation was thereby as sharply
selected as possible with regard to both parents.
All flower-heads were of course closely in-
spected. Not the slightest indication of real
doubling was discovered, even in the summer of
1899 in the fourth generation of my selected
race. But among the best the new character
suddenh^ made its appearance. It was at the
commencement of September (1899), too late
to admit of the seeds ripening before win-
ter. An inspection of the younger heads
was made, which revealed three heads
with some few rays in the midst of the disk on
one plant, the result of the efforts of four years.
Had the germ of the mutation lain hidden
through all this time! Had it been pres-
ent, though dormant in the original sample
of seed? Or had an entirely new creation taken
place during my continuous endeavors? Per-
haps as their more or less immediate re-
sult? It is obviously impossible to answer these
questions, before further and similar experi-
ments shall have been performed, bringing to
light other details that will enable us to reach a
more definite conclusion.

502 Mutations

The fact that the origination of such forms
is accessible to direct investigation is proven
quite independently of all further considera-
tions. The new variety came into existence at
once. The leap may have been made by the
ancestor of the year 1895, or by the plant of
1899, which showed the first central rays, or
the sport may have been gradually built up dur-
ing those four years. In each case there was a
leap, contrasting with the view which claims a
very long succession of years for the develop-
ment of every new character.

Having discovered this first trace of doubling,
it was to be expected that the new variety would
be at once as pure and as rich as other double
composites usually are. Some effect of the
crossing with the other seed-bearing individuals
might still disturb this uniformity in the follow-
ing year, but another year's work would elim-
inate even this source of impurity.

These two years have given the expected re-
sult. The average number of the rays, which
had already arisen from 13 to 34 now at once
came up to 47 and 55, the last figure being the
sum of 21 and 34 and therefore the probable
uttermost limit to be reached before absolute
doubling. The maximum numbers came as high
as 100 in 1900, and reached even 200 in 1901.
Such heads are as completely double as are the

Production of Double Flowers 5Uo

brightest heads of the most beautiful double
commercial varieties of composites. Even the
best white camomiles {Chrysanthemum ino-
dorum) and the gold-flowers or garden-mari-
golds {Calendida officinalis) do not come nearer
to purity since they always have scores of little
tubular florets between the rays on their disks.

Real atavists or real reversionists were seen
no more after the first purification of the race.
I have continued my culture and secured last
summer (1903) as many and as completely
doubled heads as previously. The race has at
once become permanent and constant. It has of
course a wide range of fluctuating variability,
but the lower limit has been worked up to about
34 rays, a figure never reached by the grandi-
florum parent, from which my new variety is
thus sharply separated.

Unfortunately the best flowers and even the
best individuals of my race are wholly barren.
Selection has reached its practical limit. Seeds
must be saved from less dense heads, and no
way has been found of avoiding it. The ray-
florets are sterile, even in the wild species, and
when growing in somewhat large numbers on
the disk, they conceal the fertile flowers from
the visiting insects, and cause them also to be
sterile. The same is the case with the best cul-
tivated forms. Their showiest individuals are

504 Mutations

barren, and incapable of the reproduction of tlie
race.

This last is therefore, of necessity, always
continued by means of individuals whose devia-
tion from the mean average is the least. But
in many cases the varieties are so highly dif-
ferentiated that selection has become quite su-
perfluous for practical purposes. I have al-
ready discussed the question as to the actual
moment, in which the change of the grandiflor-
um variety into the new plenum form must be
assumed to have taken place. In this respect
some stress is to be laid on the fact that the im-
provement through selection has been gradual
and continuous, though very rapid from the first
moment. But with the appearance of the first
stray rays within the disk, this continuity sud-
denly changed. All the children of this original
mutated plant showed the new character, the
rays within the disk, without exception. Not
on all the heads, nor even on the majority of the
heads on some individuals, but on some heads all
gave clear proof of the possession of the new
attribute. This was present in all the repre-
sentatives of the new race, and had never been
seen in any of their parents and grandparents.
Here there was evidently a sudden leap, at
least in the external form of the plants. And it
seems to me to be the most simple conception,

Production of Double Flowers 505

that this visible leap directly corresponded to
that inner change, which brought about the com-
plete inheritability of the new peculiarity. It
is very interesting to observe how completely
my experience agrees with the results of the
observations of breeders at large. No doubt
a comparison is difficult, and the circumstances
are not adequate to a close study.

Isolation and selection have been applied com-
monly only so far as was consistent with the re-
quirements of practical horticulture, and of
course a determination of the hereditary per-
centage was never made. The disregard of this
feature made necessary a greater length of time
and a larger number of generations to bring
about the desired changes. Notwithstanding
this, however, it has been seen that double va-
rieties are produced suddenly. This may have
occurred unexpectedly or after a few years' ef-
fort toward the end desired. Whether this
sudden appearance is the consequence of a
single internal differentiating step, or of the
rapid succession of lesser changes, cannot yet
be made out. The extreme variability of dou-
ble flowers and the chance of their appearance
with only slight indications of the previous pet-
aloid alterations of a few stamens mav often re-
suit in their origin being overlooked, while
subsequent generations may come in for full no-

506 Mutations

tice. In the greater number of cases recorded
it remains doubtful whether the work said to be
done to obtain a new double variety was done
before the appearance of these preliminary indi-
cations or afterward.

In the first case, it would correspond with
our selection of large numbers of florets in the
outer rays, in the second however, with the or-
dinary purification of new races from hybrid
mixtures.

In scientific selection-experiments such cross-
es are of course avoided, and the process of
purification is unnecessary, even as in the
Chrysanthemum culture. The first generation
succeeding the original plant with disk-rays was
in this respect wholly uniform and true to the
new type.

In practice the work does not start from such
slight indications, and is done with no other
purpose in view than to produce double flowers
in species in which they did not already exist.
Therefore it is of the highest importance to
know the methods used and the chances of suc-
cess. Unfortunately the evidence is very scanty
on both points.

Lindlev and other writers on horticultural
theory and practice assert that a large amount
of nourishment tends to produce double flow-
ers, while a culture under normal conditions.

Production of Double Flowers 507

even if the plants are very strong and healthy,
has no such effect. But even here it remains
doubtful whether it applies to the period before
or after the internal mutation. On the other
hand success is not at all to be relied upon, nor
is the work to be regarded as easy. The in-
stances of double flowers said to be obtainable
at will, are too rare in comparison with the
number of cases, where the first indication of
them was found accidentallv.

Leaving all these doubtful points, which will
have to be cleared up by further scientific in-
vestigation, the high degree of variability re-
quires further discussion. It may be considered
from three different points of view according
to the limit of the deviation from the average,
to the dependency on external conditions and to
periodicity. It seems best to take up the last
two points first.

On a visit to a nurserv at Erfurt I once in-
spected an experiment with a new double varie-
ty of the common blue-bottle or blue corn-flow-
er. The plants were dependent on the weather
to a high degree. Bad weather increased the
number of poorly filled flower-heads, while
warm and sunny days were productive of beau-
tiful double flowers. The heads that are borne
by strong branches have a greater tendency to
become double than those of the weaker ones.

508 Mutations

and towards the autumn, when all those of the
first group are faded away, and only a weak
though large section of the heads is still flower-
ing, the whole aspect of the variety gradually
retrogrades. The same law of dependency and
periodicity is prevalent everywhere. In my
own cultures of the improved field-marigold I
have observed it frequently. The number of the
ray-florets may be considered as a direct re-
sponse to nourishment, both when this is deter-
mined by external circumstances, and when it
depends on the particular strength of the
branch, which bears the head in question. It is
a case exactly similar to that of the supernumer-
ary carpels of the pistilloid poppy, and the de-
ductions arrived at with that variety may be
applied directly to double flowers.

This dependency upon nourishment is of high
practical importance in combination with the
usual effect of the doubling which makes
the flowers sterile. It is a general rule that the
most perfect flowers do not produce seed. At
the height of the flowering period the external
circumstances are the most favorable, and the
flowering branches still constitute the stronger
axes of the plants. Hence we may infer that
sterility will prevail precisely in this period.
Many varieties are known to yield only seeds
from the very last flowers, as for instance some

Production of Double Flowers 509

double begonias. Others bear only seed on their
weaker lateral branches, as the double camomile,
or become fertile only towards the fall, as is
often the case with the above quoted Erfurt va-
riety of the blue-bottle. As far as I have been
able to ascertain, such seeds are quite adequate
for the reproduction and perpetuation of the
double varieties, but the question whether there
are differences between the seeds of the more
or less double flowers of the same plants still
remains open. It is very probable, from a the-
oretical point of view, that such differences ex-
ist, but perhaps they are so slight, as to have
practically no bearing on the question.

On the ground of their wide range of varia-
bility, the double varieties must be regarded as
pertaining to the group of ever-sporting forms.
On one side thev fluctuate in the direction to-
wards such petalomanous flowers as are borne
by the stocks and others, which we have pre-
viously discussed. Here no trace of the fertile
organs is left. But this extreme is never reach-
ed by petaloid double flowers. A gap remains
which, often overlooked, always exists, and
which sharply separates the two types. On the
other hand the alteration of the stamens grad-
ually relapses to perfectly single flowers. Here
the analogy with the pistillody of the poppies
and with the '' five-leaved " clover is obvious.

510 Mutations

This conception of the inner nature of double
flowers explains the fact that the varietal mark
is seldom seen to be complete throughout larger
groups of individuals, providing these have not
been already selected by this character.
Tagetes africana is liable to produce some
poorly filled specimens, and some double va-
rieties of carnations are offered for sale with the
note that the seed yields only 80% of doubles.
With Chrysanthemum coronarium and blue-bot-
tles this figure is often announced to be only
about 50^. No doubt it is partly due to im-
purities, caused by vicinism, but it is obviously
improbable that the effect of these impurities
should be so large.

Some cases of partial reversion may be inter-
preted in the same way. Among the garden
anemones, Anemone coronaria, there is a va-
riety called the ^ * Bride, ' ' on account of its pure
white flowers. It is for sale with single and
with double flowers, and these two forms are
known to sport into one another, although they
are multiplied in the vegetative way. Such cases
are known to be of quite ordinary occurrence.
Of course such sports must be considered as
partial, and the same stem may bear both types
of flowers. It even happens that some partic-
ular flower is partly double and partly single.
Mr. Krelage, of Haarlem, had the kindness to

Production of Double Flowers 511

send me such a curious flower. One half of it
was completely double, while the other half was
entirely single, bearing normal and fertile sta-
mens in the ordinary number.

The same halfway doubling is recorded to
occur among composites sometimes, and from
the same source I possess in my collection a
head of Pyrethrum roseum, bearing on half of
its disk elongated corolla tubes, and on the
other half the small disk-florets of the typical
species.

It is a current belief, that varieties are im-
proved by continued culture. I have never been
able to ascertain the grounds on which this con-
viction rests. It may be referred either to the
purity of the race or to the complete develop-
ment of the varietal character. In the first case
it is a question of hybrid mixtures from which
many young varieties must be freed before be-
ing placed on the market. But as we have al-
ready seen in a former lecture, this requires
only three or four years, and afterwards the
degree of purit}^ is kept up to the point which
proves to be the most suitable for practical
purposes. The complete development of the
varietal character is a question restricted to
ever-sporting varieties, since in white flowers
and other constant varieties this degree is va-
riable in a very small and unimportant meas-

512 Mutations

lire. Hence the double flowers seem to afford
a very good example for this discussion.

It can be decided by two facts. First by a
consideration of the oldest double varieties, and
secondly by that of the very youngest. Are the
older ones now in a better condition than at the
outset! Have they really been gradually im-
proved during the centuries of their existence?
Obviously this can only be answered by a com-
parison of the figures given by older writers,
with the varieties as they are now in culture.
Munting's drawings and descriptions are now
nearly two centuries and a half old, but I do not
find any real difference between his double va-
rieties and their present representatives. So
it is in other cases in which improvements by
crossing or the introduction of new forms does
not vitiate the evidence. Double varieties, as
a rule, are exactly the same now, as they were
at the time of their first introduction.

If this were otherwise one would expect that
young double varieties should in the main dis-
play only slight grades of the anomaly, and
that they would require centuries to reach their
full development. Nothing of the kind is on
record. On the contrary the newest double
sorts are said to be not only equal to their prede-
cessors, but to excel them. As a rule such claims
may be exaggerated, but not to any great extent.

Production of Double Floivers 513

This is proven in the simplest way by the re-
sult of our own experiment.

In the double field-marigold we have the very
first generation of a variety of pure and not
hybrid origin. It shows the new attribute in
its full development. It has flower-heads near-
ly as completely filled as the best double varie-
ties of allied cultivated composites. In the sec-
ond generation it reached heads with 200 rays
each, and much larger numbers will seldom be
seen in older species on heads of equal size. I
have compared my novelty with the choicest
double camomiles and others, but failed to dis-
cover any real difference. Improvement of the
variety developed in the experiments carried on
by myself seems to be excluded by the fact
that it comes into conflict with the same difficul-
ty that confronts the older cultivated species,
viz. : the increasing sterility of the race.

It is perfectly evident that this double mari-
gold is now quite constant. Continuously va-
rying about a fixed average it may live through
centuries, but the mean and the limits will al-
ways remain the same, as in the case of the
ever-sporting varieties.

Throughout this lecture I have spoken of
double flowers and double flower-heads of com-
posites as of one single group. They are as
nearly related from the hereditary point of

514 Mutations

view, as they are divergent in other respects.
It would be superfluous to dwell any longer
upon the difference between heads and flowers.
But it is as well to point out, that the term dou-
ble flowers indicates a motley assemblage of dif-
ferent phenomena. The hen-and-chicken daisy,
and the corresponding variety of the garden-
cineraria (Cineraria cruenta), are extremes on
one side. The hen-and-chicken type occurs
even in other families and is known to produce
most curious anomalies, as with Scabiosa, the
supernumerary heads of which may be pro-
duced on long stalks and become branched
themselves in the same manner.

Petalody of the stamens is well known to be
the ordinary type of doubling. But it is often
accompanied by a multiplication of the organs,
both of the altered stamens and of the petals
themselves. This proliferation may consist in
median or in lateral cleavages, and in both
cases the process may be repeated one or more
times. It would be quite superfluous to give
more details, which may be gathered from any
morphologic treatise on double flowers. But
from the physiologic point of view all these
cases are to be considered as one large group,
complying with previously given definitions of
the ever-sporting varieties. They are very va-
riable and wholly permanent. Obviously this

Production of Double Flowers 515

permanency agrees perfectly with the concep-
tion of their sudden origin.

Lecture XVIII

NEW SPECIES OF OENOTHERA

In our experiments on the origin of peloric
varieties and double flowers we were guided in
the choice of our material by a survey of the
evidence already at hand. We chose the types
known to be most commonly produced anew,
either in the wild state or under the conditions
of cultivation. In both instances our novelty
was a variety in the ordinary sense of the word.
Our pedigree-culture was mainly an experi-
mental demonstration of the validity of conclu-
sions, which had previously been deduced from
such observations as can be made after the ac-
cidental birth of new forms.

From these facts, and even from these pedi-
gree-experiments, it is scarcely allowable to
draw conclusions as to the origin of real spe-
cies. If we want to know how species originate,
it is obviously necessary to have recourse to
direct observation. The question is of the high-
est importance, both for the theory of descent,
and for our conception of the real nature of

516

Neiv Species of Oenothera 517

systematic affinities at large. Many authors
have tried to solve it on the ground of compara-
tive studies and of speculations upon the bio-
logic relations of plants and animals. But in
vain. Contradiction and doubt still reign su-
preme. All our hopes now rest on the result of
experiments.

Unfortunately such experiments seemed sim-
ply impossible a few years ago. What is to
guide us in the choice of the material? The
answer may only be expected from a consid-
eration of elementary species. For it is obvious
that they only can be observed to originate, and
that the systematic species, because they are
only artificial groups of lower unities, can never
becom.e the subject of successful experimental
inquiry.

In previous lectures we tried to clear up the
differences existing between nearly related ele-
mentary species. We have seen that they af-
fect all of the attributes of the plants, each of
them changing in some measure all of the or-
gans. Nevertheless they were due to distinct
unities and of the lowest possible degree. Such
unit-steps may therefore be expected to become
visible some time or other by artificial means.
On the other hand, mutations as a rule make
their appearance in groups, and there are many
systematic species which on close inspection

518 Mutations

have been shown to be in reality composite as-
semblages. Roses and brambles, hawkweeds
and willows are the best known examples. Vio-
lets and Drab a verna, dandelions and helian-
themums and many other instances were dealt
with in previous lectures. Even wheat and bar-
ley and corn afford instances of large groups
of elementary species. Formerly mixed in
the fields, they became separated during the
last century, and now constitute constant races,
which, for brevity's sake, are dealt with under
the name of varieties.

In such groups of nearly allied forms the sin-
gle members must evidently be of common or-
igin. It is not necessary for them to have orig-
inated all in the same place or at the same time.
In some cases, as with Drab a verna, the present
geographic distribution points to a common
birthplace, from whence the various forms may
about the same period have radiated in all direc-
tions. The violets on the other hand seem to
include widely diffused original forms, from
which branches have started at different times
and in different localities.

The origin of such groups of allied forms
must therefore be the object of our research.
Perhaps we might find a whole group, perhaps
only part of it. In my opinion we have the
right to assume that if Draba and violets and

New Species of Oenothera 519

others have formerly mutated in this way, oth-
er species must at present be in the same
changeable condition. And if mutations in
groups, or such periodic mutations should be
the rule, it is to be premised that these periods
recur from time to time, and that many species
must even now be in mutating condition, while
others are not.

It is readily granted that the constant condi-
tion of species is the normal one, and that mu-
tating periods must be the exception. This fact
does not tend to increase our prospect of dis-
covering a species in a state of mutability.
Many species will have to be tested before find-
ing an instance. On the other hand, a direct trial
seems to be the only way to reach the goal. No
such special guides as those that led us to the
choice of pelories and double flowers are avail-
able. The only indication of value is the pre-
sumption that a condition of mutability might
be combined with a general state of variability
at large, and that groups of plants of very uni-
form features might be supposed to be constant
in this respect too. On the contrary, anomalies
and deviations if existent in the members of
one strain, or found together in one native lo-
cality of a species, might be considered as an
indication in the desired direction.

Few plants vary in the wild state in such a

520 Mutations

measure as to give distinct indications. All have
to be given a trial in the garden under conditions
as similar as possible to their natural environ-
ments. Cultivated plants are of course to be
excluded. Practically they have already under-
gone the experience in question and can not be
expected to change their habits soon enough.
Moreover they are often of hybrid origin. The
best way is to experiment with the native plants
of one's own country.

I have made such experiments with some hun-
dred species that grow wild in Holland. Some
were very variable, as for instance, the jointed
charlock (Raphanus RapJianistrum) and the
narrow-leaved plantain (Plantago lanceolata) ,
Others seemed more uniform, but many species,
collected without showing any malformation,
subsequently produced them in my garden,
either on the introduced plants themselves or
among their offspring. From this initial ma-
terial I have procured a long series of heredi-
tary races, each with some peculiar anomaly for
its special character. But this result was only
a secondary gain, a meager consolation for the
negative fact that no real mutability could be
discovered.

My plants were mostly annuals or biennials,
or such perennials as under adequate treatment
might produce flowers and seeds during their

New Species of Oenothera 521

first summer. It would be of no special use to
enumerate them. The negative result does not
apply to the species as such, but only to the in-
dividual strain, which I collected and cultivated.
Many species, which are quite constant with us,
may be expected to be mutable in other parts
of their range.

Only one of all my tests met my expectations.
This species proved to be in a state of mutation,
producing new elementary forms continually,
and it soon became the chief member of my ex-
perimental garden. It was one of the evening-
primroses.

Several evening-primroses have at different
times been introduced into European gardens
from America. From thence they have spread
into the vicinity, becoming common and exhibit-
ing the behavior of indigenous types. Oenoth-
era biennis was introduced about 1614 from
Virginia, or nearly three centuries ago. 0.
muricata, with small corollas and narrow
leaves, was introduced in the year 1789 by
John Hunneman, and 0. suaveolens, or sweet-
scented primrose, a form very similar to the
biennis, about the same time, in 1778, by
John Fothergill. This form is met with in dif-
ferent parts of France, while the biennis and
muricata are very common in the sandy regions
of Holland, where I have observed them for

522 Mutations

more than 40 years. They are very constant
and have proven so in my experiments. Be-
sides these three species, the large-flowered
evening-primrose, or Oenothera lamarckiana,
is found in some localities in Holland
and elsewhere. We know little concerning
its origin. It is supposed to have come
from America in the same way as its con-
geners, but as yet I have not been able to
ascertain on what grounds this supposition
rests. As far as I know, it has not been seen
growing wild in this country, though it may
have been overlooked. The fact that the
species of this group are subject to many sys-
tematic controversies and are combined by dif-
ferent writers into systematic species in differ-
ent ways, being often considered as varieties
of one or two types, easily accounts for it
having been overlooked. However, it would be
of great interest to ascertain whether 0. la-
marckiana yet grows in America, and whether
it is in the same state of mutability here as it
is in Holland.

The large-flowered evening-primrose was also
cultivated about the beginning of the last cen-
tury in the gardens of the Museum d'Histoire
Naturelle, at Paris, where it was noticed by
Lamarck, who at once distinguished it as an un-
described species. He wrote a complete descrip-

New Species of Oenothera 523

tion of it and his type sjjecimens are still pre-
served in the herbarium of the Museum, where
I have compared them with the plants of my
own culture. Shortly afterwards it was re-
named by Seringe, in honor of its eminent dis-
coverer, whose name it now bears. So Lamarck
unconsciously discovered and described himself
the plant, which after a century, was to become
the means of an empirical demonstration of his
far-reaching views on the common origin of all
living beings.

Oenothera lamarckiana is considered in
Europe as a garden-plant, much prized for
parks and ornamental planting. It is cultivated
by seed-merchants and offered for sale. It has
escaped from gardens, and having abundant
means for rapid multiplication, has become wild
in many places. As far as I know its known
localities are small, and it is to be presumed
that in each of them the plant has escaped sep-
arately from culture. It was in this state that
I first met with this beautiful species.

Lamarck's evening-primrose is a stately
plant, with a stout stem, attaining often a height
of 1.6 meters and more. When not crowded the
main stem is surrounded by a large circle of
smaller branches, growing upwards from its
base so as often to form a dense bush. These
branches in their turn have numerous lateral

524 Mutations

branches. Most of them are crowned with
flowers in summer, which regularly succeed each
other, leaving behind them long spikes of young
fruits. The flowers are large and of a bright
yellow color, attracting immediate attention,
even from a distance. They open towards
evening, as the name indicates, and are pollin-
ated by humble-bees and moths. On bright days
their duration is confined to one evening, but
during cloudy weather they may still be found
open on the following morning. Contrary to
their congeners they are dependent on visiting
insects for pollination. 0. biennis and 0.
muricata have their stigmas in immediate con-
tact with the anthers within the flower-buds, and
as the anthers ojDen in the morning preceding
the evening of the display of the petals, fecun-
dation is usually accomplished before the in-
sects are let in. But in 0. lamarckiana no
such self-fertilization takes place. The stigmas
are above the anthers in the bud, and as the
style increases in length at the time of the
opening of the corolla, they are elevated above
the anthers and do not receive the pollen. Or-
dinarily the flowers remained sterile if not vis-
ited by insects or pollinated by myself, although
rare instances of self-fertilization were seen.

In falling off, the flowers leave behind them
a stout ovary with four cells and a large number

'New Species of Oenothera 525

of young seeds. The capsule, when ripe, opens
at its summit with four valves, and contains
often from two to three hundred seeds. A hun-
dred capsules on the main stem is an average
estimate, and the lateral branches may ripen
even still more fruits, b}^ which a very rapid dis-
semination is ensured.

This striking species was found in a locality
near Hilversum, in the vicinity of Amsterdam,
where it grew in some thousands of individuals.
Ordinarily biennial, it produces rosettes in the
first, and stems in the second year. Both the
stems and the rosettes were at once seen to be
highly variable, and soon distinct varieties
could be distinguished among them.

The first discovery of this locality was made
in 1886. Afterwards I visited it many times,
often weekly or even daily during the first few
years, and always at least once a year up to
the present time. This stately plant showed the
long-sought peculiarity of producing a number
of new species everv vear. Some of them were
observed directly on the field, either as stems
or as rosettes. The latter could be transplanted
into my garden for further observation, and
the stems vielded seeds to be sown under like
control. Others were too weak to live a suffi-
ciently long time in the field. They were dis-
covered by sowing seed from indifferent plants

526 Mutations

of the wild locality in tlie garden. A third
and last method of getting still more new spe-
cies from the original strain, was the repetition
of the sowing process, by saving and sowing
the seed which ripened on the introduced
plants. These various methods have led to the
discovery of over a dozen new types, never pre-
viously observed or described.

Leaving the physiologic side of the rela-
tions of these new forms for the next lecture,
it would be profitable to give a short descrip-
tion of the several novelties. To this end they
may be combined under five different heads, ac-
cording to their systematic value. The first
head includes those which are evidently to be
considered as varieties, in the narrower sense
of the word, as previously given. The second
and third heads indicate the real progressive
elementary species, first those which are as
strong as the parent-species, and secondly a
group of weaker types, apparently not destined
to be successful. Under the fourth head I shall
include some inconstant forms, and under the
last, head those that are organically incomplete.

Of varieties with a negative attribute, or real
retrograde varieties, I have found three, all of
them in a flowering condition in the field. I
have given them the names of laevi folia, brevi-
stylis and nanella.

New Species of Oenothera 527

The laevifolia, or smooth-leaved variety, was
one of the very first deviating types found in
the original field. This was in the summer of
1887, seventeen years ago. It formed a little
group of plants growing at some distance from
the main body, in the same field. I found some
rosettes and some flowering stems and sowed
some seed in the fall. The variety has been
quite constant in the field, neither increasing
in number of individual plants nor changing
its place, though now closely surrounded by oth-
er Lamarckianas. In my garden it has proved
to be constant from seed, never reverting to the
original lamarckiana, provided intercrossing
was excluded.

It is chiefly distinguished from Lamarck's
evening-primrose by its smooth leaves, as the
name indicates. The leaves of the original form
show numerous sinuosities in their blades, not
at the edge, but anywhere between the veins.
The blade shows numbers of convexities on
either surface, the whole surface being undu-
lated in this manner; it lacks also the bright-
ness of the ordinary evening-primrose or
Oenothera biennis.

These undulations are lacking or at least very
rare on the leaves of the new laevifolia. Or-
dinarily they are wholly wanting, but at times
single leaves with slight manifestations of this

528 Mutations

character may make their appearance. They
warn us that the capacity for such sinuosities
is not wholly lost, but only lies dormant in the
new variety. It is reduced to a latent state, ex-
actly as are the apparently lost characters of
so many ordinary horticultural varieties.

Lacking the undulations, the laevifolia-lesiYes
are smooth and bright. They are a little nar-
rower and more slender than those of the La-
marckiana. The convexities and concavities of
leaves are said to be useful in drv seasons,
but during wet summers, such as those of the
last few years, they must be considered as very
harmful, as they retain some of the water which
falls on the plants, prolonging the action of the
water on the leaves. This is considered by some
writers to be of some utility after slight show-
ers, but was observed to be a source of weak-
ness during wet weather in my garden, pre-
venting the leaves from drying. Whether the
laevifolia would do better under such circum-
stances, remains to be tested.

The flowers of the laevifolia are also in a
slight degree different from those of LamarcJc-
iana. The yellow color is paler and the petals
are smoother. Later, in the fall, on the weaker
side branches these differences increase. The
laevifolia petals become smaller and are often
not emarginated at the apex, becoming ovate

Neiv Species of Oenothera 529

instead of obcordate. This shape is often the
most easily recognized and most striking mark
of the variety. In respect to the reproductive
organs, the fertility and abundance of good seed,
the laevifolia is by no means inferior or superior
to the original species.

0. brevistylis, or the short-styled evening-
primrose, is the most curious of all my new
forms. It has very short styles, which bring
the stigmas only up to the throat of the calyx-
tube, instead of upwards of the anthers. The
stigmas themselves are of a different shape,
more flattened and not cylindrical. The pollen
falls from the anthers abundantly on them, and
germinates in the ordinary manner.

The ovary which in lamarckiana and in
all other new forms is wholly underneath the
calyx-tube, is here only partially so. This
tube is inserted at some distance under its
summit. The insertion divides the ovary into
two parts : an upper and a lower one. The up-
per part is much reduced in breadth and some-
what attenuated, simulating a prolongation of
the base of the style. The lower part is also
reduced, but in another manner. At the time
of flowering it is like the ovary of lamarckiana,
neither smaller nor larger. But it is reached
by only a very few pollen-tubes, and is there-
fore always incompletely fertilized. It does

530 Mutations

not fall off after the fading away of the
flower, as unfertilized ovaries usually do;
neither does it grow out, nor assume the upright
position of normal capsules. It is checked in its
development, and at the time of ripening it is
nearly of the same length as in the beginning.
Many of them contain no good seeds at all ; from
others I have succeeded in saving only a hun-
dred seeds from thousands of capsules.

These seeds, if purely pollinated, and with
the exclusion of the visits of insects, reproduce
the variety entirely and without any reversion
to the lamarckiana type.

Correlated with the detailed structures is the
form of the flower-buds. They lack the high
stigma placed above the anthers, which in the
lamarckiana, by the vigorous growth of the
, style, extends the calyx and renders the flower-
bud thinner and more slender. Those of the
hrevistylis are therefore broader and more
swollen. It is quite easy to distinguish the in-
dividuals by this striking character alone, al-
though it differs from the parent in other par-
ticulars.

The leaves of the 0. hrevistylis are more
rounded at the tip, but the difference is only pro-
nounced at times, slightly in the adult rosettes,
but more clearly on the growing summits of the
stems and branches. By this character, the plants

New Species of Oenothera 531

may be discerned among the others, some weeks
before the flowers begin to show themselves.

But the character by which the plants may
be most easily recognized from a distance in the
field is the failure of the fruits. They were
found there nearly every year in varying, but
always small numbers.

Leaving the short-styled primrose, we come
now to the last of our group of retrograde va-
rieties. This is the 0. nanella, or the dwarf, and
is a most attractive little plant. It is very short
of stature, reaching often a height of only 20-
30 cm., or less than one-fourth of that of the par-
ent. It commences flowering at a height of 10-
15 cm., while the parent-form often measures
nearly a meter at this stage of its development.
Being so very dwarfed the large flowers are all
the more striking. They are hardly inferior
to those of the lamarckiana, and agree with
them in structure. When they fade away
the spike is rapidly lengthened, and often be-
comes much longer than the lower or vegetative
part of the stem.

The dwarfs are one of the most common mu-
tations in my garden, and were observed in the
native locality and also grown from seeds saved
there. Once produced they are absolutely con-
stant. I have tried manv thousands of seeds
from various dwarf mutants, and never ob-

532 Mutations

served any trace of reversion to the lamarcJc-
iana type. I have also cultivated them in suc-
cessive generations with the same result. In
a former lecture we have seen that contrary to
the general run of horticultural belief, varieties
are as constant as the best species, if kept free
from hybrid admixtures. This is a general rule,
and the exceptions, or cases of atavism are ex-
tremely rare. In this respect it is of great inter-
est to observe that this constancy is not an ac-
quired quality, but is to be considered as innate,
because it is already fully developed at the very
moment when the original mutation takes place.
From its first leaves to the rosette period,
and through this to the lengthening of the stem,
the dwarfs are easily distinguished from any
other of their congeners. The most remarkable
feature is the shape of the leaves. They are
broader and shorter, and especially at the base
they are broadened in such a way as to become
apparently sessile. The stalk is very brittle,
and any rough treatment may cause the leaves
to break off. The young seedlings are
recognizable by the shape of the first two or
three leaves, and when more of them are pro-
duced, the rosettes become dense and strikingly
different from others. Later leaves are more
nearly like the parent-type, but the petioles re-
main short. The bases of the blades are fre-

New Species of Oenothera 533

quently almost cordate, the laminae themselves
varying from oblong-ovate to ovate in outline.

The stems are often quite unbranched, or
branched only at the base of the spike. Strong
secondary stems are a striking attribute of the
lamarchiana parent, but they are lacking, or
almost so in the dwarfs. The stem is straight
and short, and this, combined with the large
crown of bright flowers, makes the dwarfs emi-
nently suitable for bed or border plants. Un-
fortunately they are very sensitive, especially
to wet weather.

Oenothera gigas and 0. rubrinervis, or the
giant, and the red-veined evening-primroses, are
the names given to two robust and stout spe-
cies, which seem to be equal in vigor to the
parent-plant, while diverging from it in strik-
ing characters. Both are true elementary
species, differentiated from lamarckiana in
nearly all their organs and qualities, but not
showing any preponderating character of a
retrograde nature. Their differences may
be compared with those of the elementary
species of other genera, as for instance, of
Draba, or of violets, as will be seen by their
description.

The giant evening-primrose, though not taller
in stature than 0. lamarclxiana, deserves
its name because it is so much stouter in all re-

534 Mutations

spects. The stems are robust, often with twice
the diameter of lamarckiana throughout. The
internodes are shorter, and the leaves more
numerous, covering the stems with a denser
foliage. This shortness of the internodes ex-
tends itself to the spike, and for this reason the
flowers and fruits grow closer together than on
the parent-plant. Hence the crown of bright
flowers, opening each evening, is more dense
and more strikingly brilliant, so much the more
so as the individual flowers are markedly larger
than those of the parents. In connection with
these characters, the flower-buds are seen to be
much stouter than those of lamarckiana. The
fruits attain only half the normal size, but are
broader and contain fewer, but larger seeds.

The rubrinervis is in many respects a coun-
terpart to the gigaSj but its stature is more
slender. The spikes and flowers are those of
the lamarckiana, but the bracts are narrower.
Red veins and red streaks on the fruits afford
a striking differentiating mark, though they are
not absolutely lacking in the parent-species.
A red hue may be seen on the calyx, and even
the yellow color of the petals is somewhat deep-
ened in the same way. Young plants are often
marked by the pale red tinge of the mid-veins,
but in adult rosettes, or from lack of sunshine,
this hue is often very faint.

'New Species of Oenothera 535

The leaves are narrow, and a curious feature
of this species is the great brittleness of the
leaves and stems, especially in annual individ-
uals, especially in those that make their stem
and flowers in the first year. High turgid-
ity and weak development of the mechanical
and supporting tissues are the anatomical cause
of this deficiency, the bast-fibers showing thin-
ner walls than those of the parent-type under
the microscope. Young stems of ruhrinervis
may be broken off by a sharp stroke, and
show a smooth rupture across all the tissues,
while those of lamarckiana are very tough and
strong.

Both the giant and the red-veined species are
easily recognized in the rosette-stage. Even the
very young seedlings of the latter are clearly
differentiated from the lamarckiana, but often
a dozen leaves are required, before the dif-
ference may be seen. Under such circumstances
the young plants must reach an age of
about two months before it is possible to
discern their characters, or at least before
these characters have become reliable enough
to enable us to judge of each individual
without doubt. But the divergencies rapidly
become greater. The leaves of 0. gigas are
broader, of a deeper green, the blade more
sharply set off against the stalk, all the ro-

536 Mutations

settes becoming stout and crowded with leaves.
Those of 0. rubrinervis on the contrary are
thin, of a paler green and with a silvery white
surface; the blades are elliptic, often being
only 2 cm. or less in width. They are acute
at the apex and gradually narrowed into the
petiole.

It is quite evident that such pale narrow
leaves must produce smaller quantities of or-
ganic food than the darker green and broad
organs of the gigas. Perhaps this fact is ac-
countable partly, at least, for the more robust
growth of the giant in the second year. Per-
haps also some relation exists between this dif-
ference in chemical activity and the tendency
to become annual or biennial. The gigas, as a
rule, produces far more, and the riihrinervis
far less biennial plants than the lamarckiana.
Annual culture for the one is as unreliable as
biennial culture for the other. Rubrinervis
may be annual in apparently all specimens, in
sunny seasons, but gigas will ordinarily remain
in the state of rosettes during the entire
first summer. It would be very interesting
to obtain a fuller insight into the relation
of the length of life to other qualities, but
as yet the facts can only be detailed as
they stand.

Both of these stout species have been found

New Species of Oenothera 537

quite constant from the very first moment of
their appearance. I have cultivated them from
seed in large numbers, and they have never re-
verted to the lamarckiana. From this they
have inherited the mutability or the capacity of
producing at their turn new mutants. But they
seem to have done so incompletely, changing in
the direction of more absolute constancv. This
was especially observed in the case of rubri-
nervis, which is not of such rare occurrence as
0. gigas, and which it has been possible to study
in large numbers of individuals. So for in-
stance, '^ the red-veins '' have never produced
any dwarfs, notwithstanding they are produced
very often by the parent-tj^pe. And in crossing-
experiments also the red- veins gave proof of the
absence of a mutative capacity for their produc-
tion.

Leaving the robust novelties, we may now
take up a couple of forms, which are equally
constant, and differentiated from the parent-
species in exactly the same manner, though by
other characters, but which are so obviously
weak as to have no manifest chance of self-
maintenance in the wild state. These are the
whitish and the oblong-leaved evening-prim-
roses or the Oenothera alhicla and ohlonga.

Oenothera albida is a very weak species, with
whitish, narrow leaves, which are evidently in-

538 Mutations

capable of producing sufficient quantities of or-
ganic food. The young seedling-plants are soon
seen to lag behind, and if no care is taken of
them they are overgrown by their neighbors.
It is necessary to take them out, to transplant
them into pots with richly manured soil, and
to give them all the care that should be given
to weak and sickly plants. If this is done fully
grown rosettes may be produced, which are
strong enough to keep through the winter. In
this case the individual leaves become stronger
and broader, with oblong blades and long
stalks, but retain their characteristic whitish
color.

In the second year the stems become relative-
ly stout. Not that they become equal to those
of lamarckiana, but they become taller than
might have been expected from the weakness of
the plants in the previous stages. The flowers
and racemes are nearly as large as those of the
parent-form, the fruits only a little thinner and
containing a smaller quantity of seed. From
these seeds I have grown a second and a third
generation, and observed that the plants remain
true to their type.

0. ohlonga may be grown either as an annual,
or as a biennial. In the first case it is very
slender and weak, bearing only small fruits and
few seeds. In the alternative case however, it

New Species of Oenothera 539

becomes densely branched, bearing flowers on
quite a number of racemes and yielding a full
harvest of seeds. But it always remains a small
plant, reaching about half the height of that of
lamarckiana.

When very young it has broader leaves, but
in the adult rosettes the leaves become very nar-
row, but fleshy and of a bright green color.
They are so crowded as to leave no space be-
tween them unoccupied. The flowering spikes
of the second year bear long leaf-like bracts
under the first few flowers, but those arising
later are much shorter. Numerous little cap-
sules cover the axis of the spike after the fading
away of the petals, constituting a very striking
differentiating mark. This species also was
found to be quite constant, if grown from pure
seed.

We have now given the descriptions of seven
new forms, which diverge in different ways from
the parent-type. All were absolutely constant
from seed. Hundreds or thousands of seedlings
may have arisen, but they always come true
and never revert to the original 0. lamarckiana
type. From this they have inherited the condi-
tion of mutability, either completely or partly,
and according to this they may be able to pro-
duce new forms themselves. But this occurs
only rarely, and combinations of more than one

540 Mutations

type in one single plant seem to be limited to the
admixture of the dwarf stature with the charac-
ters of the other new species.

These seven novelties do not comprise the
whole range of the new productions of my 0.
lamarckiana. But they are the most interest-
ing ones. Others, as the 0. semilata and the 0.
leptocarpa are quite as constant and quite as
distinct, but have no special claims for a closer
description. Others again were sterile, or too
weak to reach the adult stage and to yield seeds,
and no reliable description or appreciation can
be given on the ground of the appearance of
a single individual.

Contrasted with these groups of constant
forms are three inconstant types which we now
take up. They belong to two different groups,
according to the cause of their inconstancy. In
one species which I call 0. lata, the question
of stability or instability must remain wholly
unsolved, as only pistillate flowers are produced,
and no seed can be fertilized save by the use of
the pollen of another form, and therefore by
hybridization. The other head comprises two
fertile forms, 0. scintillans and 0. elliptica,
which may easily be fertilized with their own
pollen, but which gave a progeny only partly
sunilar to the parents.

The Oenothera lata is a very distinct form

New Species of Oenothera 541

which was found more than once in the field, and
recently (1902) in a luxuriant flowering speci-
men. It has likewise been raised from seeds
collected in different years at the original sta-
tion. It is also wholly pistillate. Apparently the
anthers are robust, but they are dry, wrinkled
and nearly devoid of contents. The inner wall
of cells around the groups of pollen grow out
instead of being resorbed, partly filling the
cavity which is left free by the miscarriage of
the pollen-grains. This miscarriage does not
affect all the grains in the same degree, and
under the microscope a few of them with an ap-
parently normal structure may be seen. But the
contents are not normally developed, and I have
tried in vain to obtain fertilization with a large
number of flowers. Only by cross-fertilization
does 0. lata produce seeds, and then as freely as
the other species when self-fertilized. Of course
its chance of ever founding a wild type is pre-
cluded by this defect.

0. lata is a low plant, with a limp stem, bent
tips and branches, all very brittle, but with
dense foliage and luxuriant growth. It has
bright yellow flowers and thick flower-buds.
But for an unknown reason the petals are apt to
unfold only partially and to remain wrinkled
throughout the flowering time. The stigmas
are slightly divergent from the normal type,

542 Mutations

also being partly united with one another, and
laterally with the summit of the style, but with-
out detriment to their function.

Young seedlings of lata may be recognized by
the very first leaves. They have a nearly or-
bicular shape and are very sharply set olf
against their stalk. The surface is very un-
even, with convexities and concavities on both
sides. This difference is lessened in the later
leaves, but remains visible throughout the whole
life of the plant, even during the flowering sea-
son. Broad, sinuate leaves with rounded tips
are a sure mark of 0. lata. On the smnmits of
the stems and branches they are crowded so as
to form rosettes.

Concerning inheritance of these characteris-
tics nothing can be directly asserted because of
the lack of pollen. The new type can only.be
perpetuated by crosses, either with the parent-
form or some other mutant. I have fertilized
it, as a rule, with lamarckiana pollen, but have
often also used that from nanella and others. In
doing so, the lata repeats its character in part of
its offspring. This part seems to be independ-
ent of the nature of the pollen used, but is very
variable according to external circumstances.
On the average one-fourth of the offspring be-
come lata^ the others assuming the type of the
pollen-parent, if this was a lamarckiana or

New Species of Oenothera 543

partly this ij^Q and partly that of any other of
the new species derived from lamarckiana, that
might have been used as the pollen-parent. This
average seems to be a general rule, recurring
in all experiments, and remaining unchanged
through a long series of successive generations.
The fluctuations around this mean go up to near-
ly 50;^ and down nearly to 1^, but, as in other
cases, such extreme deviations from the aver-
age are met with only exceptionally.

The second category includes the inconstant
but perfectly fertile species. I have already
given the names of the only two forms, which
deserve to be mentioned here.

One of them is called scintillans or the shiny
evening-primrose, because its leaves are of a
deep green color with smooth surfaces, glistening
in the sunshine. On the young rosettes these
leaves are somewhat broader, and afterwards
somewhat narrower than those of 0. lamarck-
iana at the corresponding ages. The plants
themselves always remain small, never reaching
the stature of the ancestral type. They are
likewise much less branched. Thev can easilv
be cultivated in annual generations, but then
do not become as fully developed and as fertile
as when flowering in the second year. The
flowers have the same structure as those of the
lamarckiana, but are of a smaller size.

544 Mutations

Fertilizing the flowers artificially witli tlieir
own pollen, excluding the visiting insects by
means of paper bags, and saving and sowing
the seed of each individual separately, fur-
nishes all the requisites for the estimation of the
degree of stability of this species. In the first
few weeks the seed-pans do not show any un-
equality, and often the young plants must be re-
planted at wider intervals, before anything
can be made out with certainty. But as soon
as the rosettes begin to fill it becomes mani-
fest that some of them are more backward than
others in size. Soon the smaller ones show
their deeper green and broader leaves, and
thereby display the attributes of the scintillans.
The other grow faster and stronger and exhibit
all the characteristics of ordinary lamarcki-
anas.

The numerical proportion of these two groups
has been found different on different occasions.
Some plants give about one-third scintillans
and two-thirds lama^^cJciana, while the progeny
of individuals of another strain show exactly
the reverse proportion.

Two points deserve to be noticed. First the
progeny of the scintillans appears to be mutable
in a large degree, exceeding even the lamarcki-
ana. The same forms that are produced most
often by the parent-family are also most ordi-

New Species of Oenothera 545

narily met with among the offspring of the
shiny evening - primrose. They are oblonga,
lata and nanella. Oblonga was observed at
times to constitute as much as 1% or more of
the sowings of scintillans, while lata and
nanella were commonly seen only in a few
scattering individuals, although seldom lacking
in experiments of a sufficient size.

Secondly the instability seems to be a con-
stant quality, although the words themselves are
at first sight, contradictory. I mean to con-
vey the conception that the degree of instability
remains unchanged during successive genera-
tions. This is a very curious fact, and strongly
reminds us of the hereditary conditions of
striped-flower varieties. But, on the contrary,
the atavists, which are here the individuals
with the stature and the characteristics of the
lamarckiana, have become lamarckianas in
their hereditary qualities, too. If their seed is
saved and sown, their progeny does not contain
any scintillans^ or at least no more than might
arise by ordinary mutations.

One other inconstant new species is to be
noted, but as it was very rare both in the field
and in my cultures, and as it was difficult of cul-
tivation, little can as yet be said about it. It is
the Oenothera elliptica, with narrow elliptical
leaves and also with elliptical petals. It re-

546 Mutations

peats its type only in a very small proportion
of its seed.

All in all we thus have a group of a dozen new
types, springing from an original form in one
restricted locality, and seen to grow there,
or arising in the garden from seeds collected
from the original locality. Without any doubt
the germs of the new types are fully developed
within the seed, ready to be evolved at the time
of germination. More favorable conditions in
the field would no doubt allow all of the de-
scribed new species to unfold their attributes
there, and to come into competition with each
other and with the common parents. But ob-
viously this is only of secondary importance,
and has no influence on the fact that a number
of new types, analogous to the older swarms of
Braha, Viola and of many other poljnnorphous
species, have been seen to arise directly in the
wild state.

Lecture XIX

EXPERIMENTAL PEDIGREE-CULTURES

The observation of the production of mutants
in the field at Hilversum, and the subsequent
cultivation of the new types in the garden at
Amsterdam, gives ample proof of the mutability
of plants. Furthermore it furnishes an analogy
with the hypothetical origin of the swarms of
species of Draba and Viola. Last but not least
important it affords material for a complete
systematic and morphologic study of the new-
ly arisen group of forms.

The physiologic laws, however, which gov-
ern this process are only very imperfectly re-
vealed by such a study. The instances are too
few. Moreover the seeds from which the mu-
tants spring, escape observation. It is simply
impossible to tell from which individual plants
they have been derived. The laevifoUa and the
brevistylis have been found almost every year,
the first always recurring on the same spot, the
second on various parts of the original field. It
is therefore allowable to assume a common

547

548 Mutations

origin for all the observed individuals of either
strain. But whether, besides this, similar
strains are produced anew by the old lamarcki-
ana group, it is impossible to decide on the sole
ground of these field-observations.

The same holds good with the other novelties.
Even if one of them should germinate repeated-
ly, without ever opening its flowers, the possi-
bility could not be excluded that the seeds might
have come originally from the same capsule but
lain dormant in the earth during periods of un-
equal length.

Other objections might be cited that can only
be met by direct and fully controlled experi-
ments. Next to the native locality comes the ex-
perimental garden. Here the rule prevails that
every plant must be fertilized with pollen of its
own, or with pollen of other individuals of
known and recorded origin. The visits of in-
sects must be guarded against, and no seeds
should be saved from flowers which have been
allowed to open without this precaution. Then
the seeds of each individual must be saved and
sown separately, so as to admit of an apprecia-
tion, and if necessary, a numerical determina-
tion of the nature of its progeny. And last but
not least the experiments should be conducted
in a similar manner during a series of successive
years.

Experimental Pedigree-Cultures 549

I have made four such experiments, each com-
prising the handling of many thousands of in-
dividual plants, and lasting through ^ve to nine
generations. At the beginning the plants were
biennial, as in the native locality, but later I
learned to cultivate them in annual genera-
tions. They have been started from different
plants and seeds, introduced from the original
field into my garden at Amsterdam.

It seems sufficient to describe here one of
these pedigree-cultures, as the results of all four
were similar. In the fall of 1886 I took nine
large rosettes from the field, planted them to-
gether on an isolated spot in the garden, and
harvested their seeds the next year. These nine
original plants are therefore to be considered
as constituting the first generation of my race.
The second generation was sown in 1888 and
flowered in 1889. It at once yielded the ex-
pected result. 15000 seedlings were tested
and examined, and among them 10 showed
diverging characters. They were properly
protected, and proved to belong to two new
types. 5 of them were lata and 5 nanella.
They flowered next year and displayed all the
characters as described in our preceding lec-
ture. Intermediates between them and the gen-
eral type were not found, and no indication of
their appearance was noted in their parents.

550 Mutations

They came into existence at once, fully equipped,
without preparation or intermediate steps. No
series of generations, no selection, no struggle
for existence was needed. It was a sudden leap
into another type, a sport in the best acceptation
of the word. It fulfilled my hopes, and at once
gave proof of the possibility of the direct obser-
vation of the origin of species, and of the ex-
perimental control thereof.

The third generation was in the main a repeti-
tion of the second. I tried some 10000 seed-
lings and found three lata and three nanella, or
nearly the same proportion as in the first in-
stance. But besides these a rubrinervis made
its appearance and flowered the following year.
This fact at once revealed the possibility that the
instability of lamarckiana might not be re-
stricted to the three new types now under obser-
vation. Hence the question arose how it would
be possible to obtain other types or to find them
if they were present. It was necessary to
have better methods of cultivation and examina-
tion of the young plants. Accordingly I de-
voted the three succeeding years to working on
this problem.

I found that it was not at all necessary to
sow any larger quantities of seed, but that the
young plants must have room enough to develop
into full and free rosettes. Moreover I ob-

Experimental Pedigree-Cultures 551

served that the attributes of lata and nanella,
which I now studied in the offspring of my first
mutants, were clearly discernible in extreme
youth, while those of rubrinervis remained con-
cealed some weeks longer. Hence I con-
cluded that*the young plants should be examined
from time to time until they proved clearly to be
onlv normal lamarckiana. Individuals ex-
hibiting any deviation from the type, or even
giving only a slight indication of it, were forth-
with taken out of the beds and planted separate-
ly, under circumstances as favorable as possible.
They were established in pots with well-manured
soil and kept under glass, but fully exposed to
sunshine. As a rule they grew very fast, and
could be planted out early in June. Some of
them, of course, proved to have been erroneous-
ly taken for mutants, but many exhibited new
characters.

All in all I had 334 young plants which did
not agree with the parental tjipe. As I exam-
ined some 14000 seedlings altogether, the result
was estimated at about 2.5^. This proportion
is much larger than in the yields of the two first
generations and illustrates the value of im-
proved methods. No doubt many good muta-
tions had been overlooked in the earlier observa-
tions.

As was to be expected, lata and nanella

552 Mutations

were repeated in this third generation (1895).
I was sure to get nearly all of them, without any
important exceptions, as I now knew how to de-
tect them at almost any age. In fact, I found
many of them; as many as 60 nanella and 73
lata, or nearly .5^ of each. Rubrinervis also
recurred, and was seen in 8 specimens. It
was much more rare than the two first-named
types.

But the most curious fact in that year was
the appearance of ohlonga. No doubt I had
often seen it in former years, but had not at-
tached any value to the very slight differences
from the type, as they then seemed to me. I
knew now that any divergence was to be es-
teemed as important, and should be isolated for
further observation. This showed that among
the selected specimens not less than 176, or more
than 1% belonged to the ohlonga type. This
type was at that time quite new to me, and it had
to be kept through the winter, to obtain stems
and flowers. It proved to be as uniform as its
three predecessors, and especially as sharply
contrasted with lamarchiana. The opportuni-
ty for the discovery of any intermediates was as
favorable as could be, because the distinguish-
ing marks were hardly beyond doubt at the time
of the selection and removal of the young plants.
But no connecting links were found.

Experimental Pedigree-Cultures 553

The same holds good for albida, which ap-
peared in 15 specunens, or in O.W, of the whole
culture. By careful cultivation these plants
proved not to be sickly, but to belong to a new,
though weak type. It was evident that I had
already seen them in former years, but having
failed to recognize them had allowed them to be
destroyed at an early age, not knowing how to
protect them against adverse circumstances.
Even this time I did not succeed in getting them
strong enough to keep through the winter.

Besides these, two new types were observed,
completing the range of all that have since been
recorded to regularly occur in this family.
They were scintillans and gig as. The first
was obtained in the way just described. The
other hardly escaped being destroyed, not hav-
ing showed itself early enough, and being left in
the bed after the end of the selection. But as
it was necessary to keep some rosettes through
the winter in order to have biennial flowering
plants to furnish seeds, I selected in August
about 30 of the most vigorous plants, planted
them on another bed and gave them sufficient
room for their stems and branches in the follow-
ing summer. Most of tliem sent up robust
shoots, but no difference was noted till the first
flowers opened. One plant had a much larger
crown of bright blossoms than any of the others.

554 Mutations

As soon as these flowers faded away, and the
young fruits grew out, it became clear that a
new type was showing itself. On that indica-
tion I removed all the already fertilized flowers
and young fruits, and protected the buds from
the visits of insects. Thus the isolated flowers
were fertilized with their own pollen only, and
I could rely ujDon the purity of the seed saved.
This lot of seeds was sown in the spring of 1897
and yielded a uniform crop of nearly 300 young
gigas plants.

Having found how much depends upon the
treatment, I could gradually decrease the size of
my cultures. Evidently the chance of discover-
ing new types would be lessened thereby, but the
question as to the repeated production of the
same new forms could more easily and more
clearly be answered in this way. In the follow-
ing year (1896) I sowed half as many seeds as
formerly, and the result proved quite the same.
With the exception of gigas all the described
forms sprang anew from the purely fertilized
ancestry of normal Lamarckianas. It was now
the fifth generation of my pedigree, and thus I
was absolutely sure that the descendants of the
mutants of this year had been pure and without
deviation for at least four successive genera-
tions.

Owing partly to improved methods of selec-

Experimental Pedigree-Cultures 555

tion, partly no doubt to chance, even more mu-
tants were found this year than in the former.
Out of some 8000 seedlings I counted 377 deviat-
ing ones, or nearly 5^, which is a high propor-
tion. Most of them were ohlonga and lata^ the
same types that had constituted the majority in
the former year.

Alhida, nanella and ruhrinervis appeared in
large numbers, and even scintillanSj of which
I had but a single plant in the previous genera-
tion, was repeated sixfold.

New forms did not arise, and the capacity of
my strain seemed exhausted. This conclusion
was strengthened by the results of the next
three generations, which were made on a much
smaller scale and yielded the same, or at least
the mutants most commonly seen in previous
years.

Instead of giving the fignires for these last
two years separately, I will now summarize my
whole experiment in the form of a pedigree. In
this the normal lamarckiana was the main line,
and seeds were only sown from plants after suf-
ficient isolation either of the plants themselves,
or in the latter years by means of paper bags
enclosing the inflorescences. I have given the
number of seedlings of lamarckiana which were
examined each year in the table below. Of
course by far the largest number of them were

556 Mutations

thrown away as soon as they showed their dif-
ferentiating characters in order to make room
for the remaining ones. At last only a few
plants were left to blossom in order to perpet-
uate the race. I have indicated for each genera-
tion the number of mutants of each of the ob-
served forms, placing them in vertical columns
underneath their respective heads. The three
first generations were biennial, but the five last
annual.

PEDIGREE OF A MUTATING FAMILY OF OENOTHERA LAMARCKIANA
IN THE EXPERIMENTAL GARDEN AT AMSTERDAM.

Gener:

O.gig.

albida

obi.

rubrin.

Lam.

nanella

lata.

scint,

VIII.

5

1

0

1700

21

1

VII.

9

0

3000

11

VI.

11

29

3

1800

9

5

1

V.

25

135

20

8000

49

142

6

IV.

1

15

176

8

14000

60

73

1

III.

1

10000

3

3

II.

15000

5

5

I.

9

It is most striking that the various mutations
of the evening-primrose display a great degree
of regularity. There is no chaos of forms, no
indefinite varying in all degrees and in all direc-
tions. Quite on the contrary, it is at once evi-
dent that very simple rules govern the whole
phenomenon.

I shall now attempt to deduce these laws from

Experimental Pedigree-Cultures 557

my experiment. Obviously they apply not only
to our evening-primroses, but may be expected
to be of general validity. This is at once
manifest, if we compare the group of new mu-
tants with the swarms of elementary forms
which compose some of the youngest systematic
species, and which, as we have seen before, are
to be considered as the results of previous mu-
tations. The difference lies in the fact that the
evening-primroses have been seen to spring
from their ancestors and that the drabas
have not. Hence the conclusion that in com-
paring the two we must leave out the pedigree of
the evening-primroses and consider only the
group of forms as they finally show themselves.
If in doing so we find sufficient similarity, we are
justified in the conclusion that the drabas and
others have probably originated in the same way
as the evening-primroses. Minor points of
course will differ, but the main lines cannot have
complied with wholly different laws. All so-
called swarms of elementary species obviously
pertain to a single type, and this type includes
our evening-primroses as the only controlled
case.

Formulating the laws of mutability for the
evening-primroses we therefore assume that
they hold good for numerous other correspond-
ing cases.

558 Mutations

I. The first law is, that new elementary spe-
cies appear suddenly, without intermediate
steps.

This is a striking point, and the one that is in
the most immediate contradiction to current
scientific belief. The ordinary conception as-
sumes very slow changes, in fact so slow that
centuries are supposed to be required to make
the differences appreciable. If this were true,
all chance of ever seeing a new species arise
would be hopelessly small. Fortunately the
evening-primroses exhibit contrary tendencies.
One of the great points of pedigree-culture is the
fact that the ancestors of every mutant have
been controlled and recorded. Those of the last
year have seven generations of known lamarck-
iana parents preceding them. If there had been
any visible preparation towards the coming mu-
tation, it could not have escaped observation.
Moreover, if visible preparation were the rule,
it could hardly go on at the same time and in the
same individuals in five or six diverging direc-
tions, producing from one parent, gigas and na-
nella, lata and rubrinervis, ohlonga and albida
and even scintillans.

On the other hand the mutants, that constitute
the first representatives of their race, exhibit
all the attributes of the new type in full display
at once. No series of generations, no selection,

Experimental Pedigree-Cultures 559

no struggle for existence are needed to reach
this end. In previous lectures I have mentioned
that I have saved the seeds of the mutants
whenever possible, and have always obtained
repetitions of the prototype only. Reversions
are as absolutely lacking as is also a further de-
velopment of the new type. Even in the case of
the inconstant f oinns, where part of the progeny
yearly return to the stature of lamarckiana, in-
termediates are not found. So it is also with
lata, which is pistillate and can only be prop-
agated by cross-fertilization. But though the
current belief would expect intermediates at
least in this case, thev do not occur. I made a
pedigree-culture of lata during eight successive
generations, pollinating them in different ways,
and always obtained cultures which were partly
constituted of lata and partly of lamarckiana
specimens. But the latas remained lata in all
the various and most noticeable characters,
never showing any tendency to gradually revert
into the original form.

Intermediate forms, if not occurring in the
direct line from one species to another, might be
expected to appear perhaps on lateral branches.
In this case the mutants of one type, appearing
in the same year, would not be a pure type, but
would exhibit different degrees of deviation
from the parent. The best would then have to

560 Mutations

be chosen in order to get the new type in its pure
condition. Nothing of the kind, however, was
observed. All the oblong a-m\xtsints were pure
oblongas. The pedigree shows hundreds of
them in the succeeding years, but no difference
was seen and no material for selection was af-
forded. All were as nearly equal as the in-
dividuals of old elementary species.

II. New fonns spring laterally from the
main stem.

The current conception concerning the origin
of species assumes that species are slowly con-
verted into others. The conversion is assumed
to affect all the individuals in the same direction
and in the same degree. The whole group
changes its character, acquiring new attributes.
By inter-crossing they maintain a common line
of progress, one individual never being able to
proceed much ahead of the others.

The birth of the new species necessarily
seemed to involve the death of the old one. This
last conclusion, however, is hard to understand.
It may be justifiable to assume that all the in-
dividuals of one locality are ordinarily inter-
crossed, and are moreover subjected to the same
external conditions. They might be supposed
to vary in the same direction if these conditions
were changed slowly. But this could of course
have no possible influence on the plants of the

Experimental Pedigree-Cultures 561

same species growing in distant localities, and
it would be improbable they should be affected
in the same way. Hence we should conclude
that when a species is converted into a new type
in one locality this is only to be considered as
one of numerous possible ones, and its alteration
would not in the least change the aspect of the
remainder of the species.

But even with this restriction the general be-
lief is not supported by the evidence of the even-
ing-primroses. There is neither a slow nor a
sudden change of all the individuals. On the
contrary, the vast majority remain unchanged;
thousands are seen exactly repeating the orig-
inal prototype yearly, both in the native field
and in my garden. There is no danger that
lamarckiana might die out from the act of mu-
tating, nor that the mutating strain itself would
be exposed to ultimate destruction from this
cause.

In older swarms, such as Draha or Helianthe-
mum, no such center, around which the various
forms are grouped, is known. Are we to con-
clude therefore that the main strain has died
out? Or is it perhaps concealed among the
throng, being distinguished by no peculiar char-
acter 1 If our gig as and rubrinervis were grow-
ing in equal numbers with the lamarckiana in
the native field, would it be possible to decide

562 Mutations

which of them was the progenitor of the others?
Of course this could be done by long and tedious
crossing-experiments, showing atavism in the
progeny, and thereby indicating the common
ancestor. But even this capacity seems to be
doubtful and connected only with the state of
mutability and to be lost afterwards. Therefore
if this period of mutation were ended, probably
there would be no way to decide concerning the
mutual relationship of the single species.

Hence the lack of a recognizable main stem in
swarms of elementary species makes it impossi-
ble to answer the question concerning their com-
mon origin.

Another phase of the ojDposition between the
prevailing view and my own results seems far
more important. According to the current be-
lief the conversion of a group of plants growing
in any locality and flowering simultaneously
would be restricted to one type. In my own ex-
periments several new species arose from the
parental form at once, giving a wide range of
new forms at the same time and under the same
conditions.

III. Neiv elementary species attain their full
constancy at once.

Constancy is not the result of selection or of
improvement. It is a quality of its own. It can
neither be constrained bv selection if it is absent

Experimental Pedigree-Cultures 563

from the beginning, nor does it need any natural
or artificial aid if it is present. - Most of my
new species have proved constant from the first.
Whenever possible, the original mutants have
been isolated during the flowering period and
artificially self-fertilized. Such plants have al-
ways given a uniform progeny, all children ex-
hibiting the type of the parent. No atavism
was observed and therefore no selection was
needed or even practicable.

Briefly considering the different forms, we
may state that the full experimental proof has
been given for the origin of gig as and rubriner-
visj for alhida and oblong a, and even for na-
nella, which is to be considered as of a varietal
nature ; with lata the decisive experiment is ex-
cluded by its unisexuality. Laevifolia and
brevistylis were found originally in the field,
and never appeared in my cultures. No obser-
vations were made as to their origin, and seeds
have only been sown from later generations.
But these have yielded uniform crops, thereby
showing that there is no ground for the assump-
tion that these two older varieties might behave
otherwise than the more recent derivatives.

Scintillans and elliptica constitute exceptions
to the rule given. They repeat their character,
from pure seed, only in part of the offspring. I
have tried to deliver the scintillans from this

564 Mutations

incompleteness of heredity, but in vain. The
succeeding generations, if produced from true
representatives of the new type, and with pure
fertilization, have repeated the splitting in the
same numerical proportions. The instability
seems to be here as permanent a quality as the
stability in other instances. Even here no se-
lection has been adequate to change the original
form.

IV. So7ne of the new strains are evidently ele-
mentary species, ivhile others are to he consid-
ered as retrograde varieties.

It is often difficult to decide whether a given
form belongs to one or another of these two
groups. I have tried to show that the best
and strictest conception of varieties limits
them to those forms that have probably
originated by retrograde or degressive steps.
Elementary species are assumed to have been
produced in a progressive way, adding one
new element to the store. Varieties differ from
their species clearly in one point, and this is
either a distinct loss, or the assumption of a
character, which may be met with in other
species and genera. Laevifolia is distin-
guished by the loss of the crinkling of the
leaves, hrevistylis by the partial loss of the
epigj-nous qualities of the flowers, and nanella is
a dwarf. These three new forms are therefore

Experimental Pedigree-Cultures 565

considered to constitute only retrograde steps,
and no advance. This conclusion has been fully
justified by some crossing experiments with
brevistylis, which wholly complies with Men-
del's law, and in one instance with nanella,
which behaves in the same manner, if crossed
with ruhrinervis.

On the other hand, gigas and ruhrinervis, oh-
longa and alhida obviously bear the characters
of progressive elementary species. They are
not differentiated from lamarchiana by one or
two main features. They diverge from it in
nearly all organs, and in all in a definite though
small degree. They may be recognized as soon
as they have developed their first leaves and re-
main discernible throughout life. Their char-
acters refer chiefly to the foliage, but no less to
the stature, and even the seeds have peculiari-
ties. There can be little doubt but that all the
attributes of every new species are derived from
one principal change. But why this should af-
fect the foliage in one manner, the flowers in
another and the fruits in a third direction, re-
mains obscure. To gain ever so little an insight
into the nature of these changes, we may best
compare the differences of our evening-prim-
roses with those between the two hundred ele-
mentary species of Draba and other similar
instances. In doing so we find the same main

566 Mutations

feature, the minute differences in nearly all
points.

V. The ^ame new species are produced in a
large number of individuals.

This is a very curious fact. It embraces two
minor points, viz : the multitude of similar mu-
tants in the same year, and the repetition there-
of in succeeding generations. Obviously there
must be some common cause. This cause must
be assumed to lie dormant in the Lamarckianas
of my strain, and probably in all of them, as no
single parent-plant proved ever to be wholly
destitute of mutability. Furthermore the dif-
ferent causes for the sundry mutations must lie
latent together in the same parent-plant. They
obey the same general laws, become active under
similar conditions, some of them being more
easily awakened than others. The germs of the
ohlonga, lata and nanella are especially ir-
ritable, and are ready to spring into activity at
the least summons, while those of gig as ^ ruhri-
nervis and scintillans are far more difficult to
arouse.

These germs must be assumed to lie dormant
during many successive generations. This is
especially evident in the case of lata and nanella,
which appeared in the first year of the pedigree-
culture and which since have been repeated
yearly, and have been seen to arise by mutation

Experimental Pedigree-Cultures 567

also during the last season (1903). Only gigas
appeared but once, but then there is every rea-
son to assume that in larger sowings or by a pro-
longation of the experiments it might have made
a second appearance.

Is the number of such germs to be supposed
to be limited or unlimited? My experiment has
produced about a dozen new forms. Without
doubt I could easily have succeeded in getting
more, if I had had any definite reason to search
for them. But such figures are far from favor-
ing the assumption of indefinite mutability.
The group of possible new forms is no doubt
sharply circumscribed. Partly so by the mor-
phologic peculiarities of lamarckiana, which
seem to exclude red flowers, composite leaves,
etc. No doubt there are more direct rea-
sons for these limits, some changes having taken
place initially and others later, while the present
mutations are only repetitions of previous ones,
and do not contribute new lines of development
to those already existing. This leads us to the
supposition of some common original cause,
which produced a number of changes, but which
itself is no longer at work, but has left the af-
fected qualities, and only these, in the state of
mutability.

In nature, repeated mutations must be of far
greater significance than isolated ones. How

568 Mutations

great is the chance for a single individual to be
destroyed in the struggle for life! Hundreds
of thousands of seeds are produced by la-
marckiana annually in the field, and only
some slow increase of the number of specimens
can be observed. Many seeds do not find the
proper circumstances for germination, or the
young seedlings are destroyed by lack of water,
of air, or of space. Thousands of them are so
crowded when becoming rosettes that only a few
succeed in producing stems. Any weakness
would have destroyed them. As a matter of
fact they are much oftener produced in the seed
than seen in the field with the usual unfavorable
conditions ; the careful sowing of collected seeds
has given proof of this fact many times.

The experimental proof of this frequency in
the origin of new types,'Seems to overcome many
difficulties offered by the current theories on the
probable origin of species at large.

VI. The relation hetiveen mutability and fluc-
tuating variability has always been one of the
chief difficulties of the followers of Darwin. The
majority assumed that species arise by the slow
accumulation of slight fluctuating deviations,
and the mutations were only to be considered as
extreme fluctuations, obtained, in the main, by a
continuous selection of small differences in a
constant direction.

Experimental Pedigree-Cultures 569

My cultures show that quite the opposite is
to be regarded as fact. All organs and all quali-
ties of lamarckiana fluctuate and vary in a
more or less evident manner, and those which I
had the opportunity of examining more closely
were found to comply with the general laws of
fluctuation. But such oscillating changes have
nothing in common with the mutations. Their
essential character is the heaping up of slight
deviations around a mean, and the occurrence of
continuous lines of increasing deviations, link-
ing the extremes with this group. Nothing of
the kind is observed in the case of mutations.
There is no mean for them to be grouped around
and the extreme only is to be seen, and it is
wholly unconnected with the original type. It
might be supposed that on closer inspection each
mutation might be brought into connection with
some feature of the fluctuating variability. But
this is not the case. The dwarfs are not at all
the extreme variants of structure, as the fluctua-
tion of the height of the lamarckiGna never de-
creases or even approaches that of the dwarfs.
There is always a gap. The smallest specimens
of the tall type are commonly the weakest, ac-
cording to the general rule of the relationship
between nourishment and variation, but the
tallest dwarfs are of course the most robust
specimens of their group.

570 Mutations

Fluctuating variability, as a rule, is subject to
reversion. The seeds of the extremes do not
produce an offspring which fluctuates around
their parents as a center, but around some point
on the line which combines their attributes with
the corresponding characteristic of their ances-
tors, as Vilmorin has put it. No reversion ac-
companies mutation, and this fact is perhaps the
completest contrast in which these two great
types of variability are opposed to each other.

The offspring of my mutants are, of course,
subject to the general laws of fluctuating varia-
bility. They vary, however, around their own
mean, and this mean is simply the type of the
new elementary species.

VII. The mutations take place in nearly all
directions.

Many authors assume that the origin of spe-
cies is directed by unknown causes. These
causes are assumed to work in each single case
for the improvement of the animals and plants,
changing them in a manner corresponding
in a useful way to the changes that take
place in their environment. It is not easy to
imagine the nature of these influences nor how
they would bring about the desired effect.

This difficulty was strongly felt by Darwin,
and one of the chief purposes of his selection-
theory may be said to have been the at-

Experiniental Pedigree-Cultures 571

tempt to surmount it. Darwin tried to re-
place the unknown cause by natural agencies,
which lie under our immediate observation.
On this point Darwin was superior to his
predecessors, and it is chiefly due to the clear
conception of this point that his theory has
gained its deserved general acceptance. Accord-
ing to Darwin, changes occur in all directions,
quite independently of the prevailing circum-
stances. Some may be favorable, others detri-
mental, many of them without significance,
neither useful nor injurious. Some of them
will sooner or later be destroyed, while others
will survive, but which of them will survive,
is obviously dependent upon whether their
particular changes agree with the existing
environic conditions or not. This is what
Darwin has called the struggle for life.
It is a large sieve, and it only acts as
such. Some fall through and are annihilated,
others remain above and are selected, as the
phrase goes. Many are selected, but more are
destroyed ; daily observation does not leave any
doubt upon this point.

How the differences originate is quite another
question. It has nothing to do with the theory
of natural selection nor with the struggle for
life. These have an active part only in the ac-
cumulation of useful qualities, and only in so

572 Mutations

far as they protect the bearers of such charac-
ters against being crowded out by their more
poorly constituted competitors.

However, the differentiating characteristics
of elementary species are only very small. How
widely distant they are from the beautiful adap-
tative organizations of orchids, of insectivorous
plants and of so many others ! Here the differ-
ence lies in the accumulation of numerous ele-
mentary characters, which all contribute to the
same end. Chance must have produced them,
and this would seem absolutely improbable, even
impossible, were it not for Darwin's ingenious
theory. Chance there is, but no more than any-
where else. It is not by mere chance that the
variations move in the required direction. They
do go, according to Darwin's view, in all direc-
tions, or at least in many. If these include the
useful ones, and if this is repeated a number of
times, cumulation is possible; if not, there is
simply no progression, and the type remains
stable through the ages. Natural selection is
continually acting as a sieve, throwing out the
useless changes and retaining the real improve-
ments. Hence the accumulation in apparent-
ly predisposed directions, and hence the
increasing adaptations to the more specialized
conditions of life. It must be obvious to any
one who can free himself from the current ideas.

Experimental Pedigree-Cultures 573

that this theory of natural selection leaves the
question as to how the changes themselves are
brought about, quite undecided. There are two
possibilities, and both have been propounded by
Darwin. One is the accumulation of the slight
deviations of fluctuating variability, the other
consists of successive sports or leaps taking
place in the same direction.

In further lectures a critical comparison of
the two views will be given. To-day I have only
to show that the mutations of the evening-prim-
roses, though sudden, comply with the demands
made by Darwin as to the form of variability
which is to be accepted as the cause of evolution
and as the origin of species.

Some of my new types are stouter and others
weaker than their parents, as shown by gigas
and alhida. Some have broader leaves and
some narrower, lata and ohlonga. Some have
larger flowers {gigas) or deeper yellow ones
(ruhrinervis) J or smaller blossoms (scintillans) y
or of a paler hue (alhida). In some the cap-
sules are longer (nihrinervis), or thicker
(gigas), or more rounded (lata), or small (ob-
longa), and nearly destitute of seeds (brevi-
stylis). The unevenness of the surface of the
leaves may increase as in lata^ or decrease as in
laevifolia. The tendency to become annual pre-
vails in riibrinervis, but gigas tends to become

574 Mutations

biennial. Some are rich in pollen, while scin-
tillans is poor. Some have large seeds, others
small. Lata has become pistillate, while
brevistylis has nearly lost the faculty to pro-
duce seeds. Some undescribed forms were
quite sterile, and some I observed which pro-
duced no flowers at all. From this statement it
may be seen that nearly all qualities vary in op-
posite directions and that our group of mutants
affords wide material for the sifting process of
natural selection. On the original field the
laevi folia and brevistylis have held their own
during sixteen years and probably more, with-
out, however, being able to increase their num-
bers to any noticeable extent. Others perish
as soon as they make their appearance, or a
few individuals are allowed to bloom, but prob-
ably leave no progeny.

But perhaps the circumstances may change,
or the whole strain may be dispersed and spread
to new localities with different conditions. Some
of the latter might be found to be favorable to
the robust gig as, or to riihrinervis, which re-
quires a drier air, with rainfall in the spring-
time and sunshine during the summer. It would
be worth while to see whether the climate
of California, where neither 0. lamarckiana
nor 0. hieMfiis are found wild, would not exactly

Experimental Pedigree-Cultures 575

suit the requirements of the new species ruhri-
nervis and gigas.

Note. — Oenotheras are native to America and all
of the species growing in Europe have escaped from
gardens directly, or may have arisen by mutation, or
by hybridization of introduced species. A fixed
hybrid between 0. cruciata and 0. biennis constituting
a species has been in cultivation for many years.
The form known as 0. biennis in Europe, and used
by de Vries in all of the experiments described in these
lectures, has not yet been found growing wild in
America and is not identical with the species bearing
that name among American botanists. Concerning
this matter Professor de Vries writes under date of
Sept. 12, 1905: "The 'biennis' which I collected in
America has proved to be a motley collection of forms,
which at that time I had no means of distinguishing.
No one of them, so far as they are now growing in
my garden is identical with our biennis of the sand
dunes." The same appears to be the case with
0. muricata. Plants from the Northeastern American
seaboard, identifiable with the species do not entirely
agree with those raised from seed received from
Holland.

0. Lamarckiana has not been found growing wild
in America in recent years although the evidence at
hand seems to favor the conclusion that it was seen
and collected in the southern states in the last century.
(See MacDougal, Vail, Shull, and Small. Mutants
and Hybrids of the Oenotheras. Publication 24.
Carnegie Institution. Washington, D. C, 1905.)

Editor.

Lecture XX

THE ORIGIN OF WILD SPECIES AND VARIETIES

New species and varieties occur from time to
time in the wild state. Setting aside all theo-
retical conceptions as to the common origin of
species at large, the undoubted fact remains that
new forms are sometimes met with. In the case
of the peloric toad-flax the mutations are so
numerous that they seem to be quite regular.
The production of new species of evening-prim-
roses was observed on the field and afterwards
duplicated in the garden. There is no reason
to think that these cases are isolated instances.
Quite on the contrary they seem to be the pro-
totypes of repeated occurrences in nature.

If this conception is granted, the question at
once arises, how are we to deal with analogous
cases, when fortune offers them, and what can
we expect to learn from them?

A critical study of the existing evidence seems
to be of great importance in order to ascertain
the best way of dealing with new facts, and of
estimating the value of the factors concerned.

576

Origin of Wild Species 577

It is manifest that we must be very careful and
conservative in dealing with new facts that are
brought to our attention, and every effort should
be made to bring additional evidence to light.
Many vegetable anomalies are so rare that
they are met with only by the purest
chance, and are then believed to be wholly
new. When a white variety of some common
plant is met with for the first time we generally
assume that it originated on that very spot
and only a short time previously. The discov-
ery of a second locality for the same variety at
once raises the question as to a common origin
in the two instances. Could not the plants of
the second locality have arisen from seeds
transported from the first!

White varieties of many species of blue-bells
and gentians are found not rarely, white-flower-
ing plants of heather, both of Erica Tetralix and
Calluna vulgaris occur on European heaths;
white flowers of Brunella vulgaris, Ononis re-
pens, Thymus vulgaris and others may be seen
in many localities in the habitats of the colored
species. Pelories of labiates seem to occur
often in Austria, but are rare in Holland ; white
bilberries {Vaccinium Myrtillus) have many
known localities throughout Europe, and nearly
all the berry-bearing species in the large heath-
family are recorded as having white varieties.

578 Mutations

Are we to assume a single origin for all the
representatives of such a variety, as we have
done customarily for all the representatives of
a wild species 1 Or can the same mutation have
been repeated at different times and in distant
localities? If a distinct mutation from a given
species is once possible, why should it not occur
twice or thrice?

A variety which seems to be new to us may
only appear so, because the spot where it grows
had hitherto escaped observation. Lychnis
preslii is a smooth variety of Lychnis diurna
and was observed for the first time in the year
1842 by Sekera. It grew abundantly in a grove
near Miinchengratz in southern Hungary. It
was accompanied by the ordinary hairy type of
the species. Since then it has been observed to
be quite constant in the same locality, and some
specimens have been collected for me there late-
ly by Dr. Nemec, of Prague. No other native
localities of this variety have been discovered,
and there can be no doubt that it must have
arisen from the ordinary campion near the spot
where it still grows. But this change may have
taken place some years before the first discov-
ery, or perhaps one or more centuries ago.
This could only be known if it could be proved
that the locality had been satisfactorily investi-
gated previously, and that the variety had not

Origin of Wild Species 579

been met with. Even in this case only some-
thing would be discovered about the time of the
change, but nothing about its real nature.

So it is in many cases. If a variety is ob-
served in a number of specimens at the time
of its first discovery, and at a locality not
studied previously, it takes the aspect of an old
form of limited distribution, and little can be
learned as to the circumstances under which it
arose. If on the contrary it occurs in very
small numbers or perhaps even in a single in-
dividual, and if the spot where it is found is
located so that it could hardly have escaped pre-
vious observation, then the presumption of a re-
cent origin seems justified.

What has to be ascertained on such occasions
to give them scientific value? Three points
strike me as being of the highest importance.
First, the constancy of the new type; secondly,
the occurrence or lack of intermediates, and last,
but not least, the direct observation of a re-
peated production.

The first two points are easily ascertained.
Whether the new type is linked with its more
common supposed ancestor by intermediate
steps is a query which at once strikes the bota-
nist. It is usually recorded in such cases, and
we may state at once that the general result is,
that such intermediates do not occur. This is

580 Mutations

of the highest importance and admits of only
two explanations. One is that intermediates
may be assumed to have preceded the existent
developed form, and to have died out after-
wards. But why should they have done so,
especially in cases of recent changes? On the
other hand the intermediates may be lacking
because they have never existed, the change
having taken place by a sudden leap, such as the
mutations described in our former lectures. It
is manifest that the assumption of hypothetical
intermediates could only gain some probability
if they had been found in some instance. Since
they do not occur, the hypothesis seems wholly
unsupported.

The second point is the constancy of the new
type. Seeds should be saved and sown. If the
plant fertilizes itself without the aid of insects,
as do some evening-primroses, the seed saved
from the native locality may prove wholly pure,
and if it does give rise to a uniform progeny the
constancy of the race may be assumed to be
proved, provided that repeated trials do not
bring to light any exceptions. If the offspring
shows more than one type, cross-fertilization is
always to be looked to as the most probable
cause, and should be excluded, in order to sow
pure seeds. Garden-experiments of this kind,
and repeated trials, should always be combined

Origin of Wild Species 581

with the discovery of a presumed mutation. In
many instances the authors have realized the
importance of this point, and new types have
been found constant from the very beginning.
Many cases are known which show no rever-
sions and even no partial reversions. This fact
throws a distinct light on our first point, as it
makes the hypothesis of a slow and gradual de-
velopment still more improbable.

My third point is of quite another nature and
has not as yet been dealt with. But as it ap-
peals to me as the very soul of the problem,
it seems necessary to describe it in some detail.
It does not refer to the new type itself, nor to
any of its morphologic or hereditary attributes,
but directly concerns the presumed ancestors
themselves.

The peloric toad-flax in my experiment was
seen to arise thrice from the same strain. Three
different individuals of my original race showed
a tendency to produce peloric mutations, and
they did so in a number of their seeds, exactly
as the mutations of the evening-primroses were
repeated nearly every year. Hence the infer-
ence, that whenever we find a novelty which is
really of very recent date, the parent-strain
which has produced it might still be in existence
on the same spot. In the case of shrubs or
perennials the very parents might yet be found.

582 Mutations

But it seems probable, and is especially proved
in the case of the evening-primroses, that all
or the majority of the representatives of the
whole strain have the same tendency to mutate.
If this were a general rule, it would suffice to
take some pure seeds from specimens of the
presumed parents and to sow and multiply the
individuals to such an extent that the mutation
might have a chance to be repeated.

Unfortunately, this has not as yet been done,
but in my opinion it should be the first effort of
any one who has the good luck to discover a new
wild mutation. Specimens of the parents
should be transplanted into a garden and fertil-
ized under isolated conditions. Seeds saved
from the wild plant would have little worth, as
they might have been partly fertilized by the
new type itself.

After this somewhat lengthy discussion of the
value of observations surrounding the discovery
of new wild mutations, we now come to the de-
scription of some of the more interesting cases.
As a first example, I will take the globular-
fruited shepherd's purse, described by Solms-
Laubach as Capsella heegeri. Professor
Heeger discovered one plant with deviating
fruits, in a group of common shepherd's purses
in the market-place near Landau in Germany,
in the fall of 1897. They were nearly spher-

Origin of Wild Species 58

Q

ical, instead of fiat and purse-shaped. Their
valves were thick and fleshy, while those of the
ordinary form are membranaceous and dry.
The capsules hardly opened and therefore dif-
fered in this point from the shepherd's purse,
which readily loosens both its valves as soon as
it is ripe.

Only one plant was observed ; whence it came
could not be determined, nor whether it had
arisen from the neighboring stock of Capsella
or not. The discoverer took some seed to his
garden and sent some to the botanical garden
at Strassburg, of which Solms-Laubach is the
director. The majority of the seeds of course
were sowed naturally on the original spot. The
following year some of the seeds germinated
and repeated the novelty. The leaves, stems and
flowers were those of the common shepherd's
purse, but no decision could be reached concern-
ing the type of this generation before the first
flowers had faded and the rounded capsules had
developed. Then it was seen that the heegeri
came true from seed. It did so both in the
gardens and on the market-place, where it was
observed to have multiplied and spread in some
small measure. The same was noted the fol-
lowing year, but then the place was covered with
gravel and all the plants destroyed. It is not
recorded to have been seen wild since.

584 Mutations

Intermediate forms have not been met with.
Some slight reversions may occur in the autumn
on the smallest and weakest lateral branches.
Such reversions, however, seem to be very rare,
as I have tried in vain to produce them on large
and richly branched individuals, by applying all
possible inducements in the form of manure
and of cutting, to stimulate the production of
successive generations of weaker side branches.
This constancy was proved by the experi-
ments of Solms-Laubach, which I have repeated
in my own garden during several years with
seed received from him. No atavists or deviat-
ing specimens have been found among many
hundreds of flowering plants.

It is important to note that within the family
of the crucifers the form of the capsule and the
attributes of the valves and seeds are usually
considered to furnish the characteristics of
genera, and this point has been elucidated at
some length by Solms-Laubach. There is, how-
ever, no sufficient reason to construe a new
genus on the ground of Heeger's globular-
fruited shepherd's purse; but as a true elemen-
tary species, and even as a good systematic
species it has proved itself, and as such it is de-
scribed by Solms-Laubach, who named it in
honor of its discoverer.

Exactly analogous discoveries have been

Origin of Wild Species 585

made from time to time with other plants by
different writers. Near Wageningen, in Hol-
land, I found Stellaria Holostea apetala in the
year 1889, and near Horn in Lippe (Germany)
Capsella Biirsa-pastoris apetala, both in a very
few specimens on a single spot. Whether these
were mutations or introductions remains of
course uncertain. About the same time I dis-
covered near Hilversum in Holland a smooth
variety of the evening campion, Lychnis vesper-
Una, forming a very small group of individuals
in a field, where the hairy type was common.
It was sown in my garden and proved pure and
constant, without intermediates. As the local-
ity had been repeatedly and carefully investi-
gated by me, I trust to be justified in the asser-
tion that I gathered the very first individuals of
the variety. The stock soon was overgrown by
surrounding shrubs and died out, and now only
the cultivated offspring are available, as in the
case of Heeger's shepherd's purse.

A very curious instance of spontaneous muta-
tions is afforded by a peculiarity of some even-
ing-primroses and their allies. This peculiarity
is shown by the petals remaining minute and
assuming a linear shape. The character is de-
veloped as a specific one in Oenothera cruciata.
This plant owes its name to the shape of the
petals, which form a slender cross in the flower,

586 Mutations

instead of displaying a bright yellow cup.
0, cruciata grows in the Adirondack Mountains,
in the states of New York and Vermont, and
seems to be abundant there. It has been intro-
duced into botanical gardens and yielded a num-
ber of hybrids, especially with 0. biennis and 0.
lamarchiana, and the narrow petals of the
parent-species may be met with in combination
with the stature and vegetative characteristics
of these last named species. 0. cruciata has a
purple foliage, while biennis and lamarckiana
are green, and many of the hybrids may in-
stantly be recognized by their purple color.

The curious attribute of the petals is not to be
considered simply as a reduction in size. On
anatomical inquiry it has been found that these
narrow petals bear some characteristics which,
on the normal plants, are limited to the calyx.
Stomata and hairs, and the whole structure of
the surface and inner tissues on some parts of
these petals are exactly similar to those of the
calyx, while on others they have retained the
characteristics of petals. Sometimes there
may even be seen by the naked eye green longi-
tudinal stripes of calyx-like structure alter-
nating with bright yellow petaloid parts. For
these reasons the cruciata character may be con-
sidered as a case of sepalody of the petals, or of
the petals being partly converted into sepals.

Origin of Wild Species 587

It is worth while to note that as a monstrosity
this occurrence is extremely rare throughout the
whole vegetable kingdom, and only very few
instances have been recorded.

Two cases of sudden mutations have come to
my knowledge, producing this same anomaly in
allied species. One has been already alluded to ;
it pertains to the common evening-primrose or
Oenothera biennis, and one is a species belong-
ing to another genus of the same family, the
great hairy willow-herb or Epilohium hirsutum.
I propose to designate both new forms by the
varietal name of cruciata, or cruciatum.

Oenothera biennis cruciata was found in a
native locality of the 0. biennis itself. It con-
sisted, of only one plant, showing in all its flow-
ers the cruciata marks. In all other respects it
resembled wholly the biennis, especially in the
pure green color of its foliage, which at once
excluded all suspicion of hybrid origin with the
purple 0. cruciata. Moreover in our country
this last occurs onlv in the cultivated state in
botanical gardens.

Intermediates were not seen, and as the plant
bore some pods, it was possible to test its con-
stancy. I raised about 500 plants from its seeds,
out of which more than 100 flowered in the first
year. The others were partly kept through tho
winter and flowered next year. Seeds saved in

588 Mutations

both seasons were sown on a large scale. Both
the first and the succeeding generations of
the offspring of the original plant came true
without any exception. Intermediates are
often found in hybrid cultures, and in them the
character is a very variable one, but as yet they
were not met with in progeny of this mutant.
All these plants were exactly like 0. biennis,
with the single exception of their petals.

Epilobium Mrsutum cruciatum was discov-
ered by John Rasor near Woolpit, Bury St. Ed-
munds, in England. It flowered in one spot,
producing about a dozen stems, among large
quantities of the parent-species, which is very
common there, as it is elsewhere in Europe.
This species is a perennial, multiplying itself by
underground runners, and the stems of the
new variety were observed to stand so close to
each other that they might be considered as the
shoots of one individual. In this case this spec-
imen might probably be the original mutant, as
the variety had not been seen on that spot in
previous years, even as it has not been found
elsewhere in the vicinity.

Intermediates were not observed, though the
difference is a very striking one. In the cru-
ciate flowers the broad and bright purple petals
seem at first sight to be wholly wanting. They
are too weak to expand and to reflex the calyx

Origin of Wild Species 589

as in the normal flowers of the species. The
sepals adhere to one another, and are only
opened at their summit by the protruding pis-
tils. Even the stamens hardly come to light.
At the period of full bloom the flowers convey
only the idea of closed buds crowned by the con-
spicuous white cross of the stigma. Any inter-
mediate form would have at once betrayed itself
by larger colored petals, coming out of the
calyx-sheath. The cruciate petals are small
and linear and greenish, recalling thereby the
color of the sepals.

Mr. Rasor having sent me some flowers and
some ripe capsules of his novelty, I sowed the
latter in my experimental garden, where the
plant flowered in large numbers and with many
thousands of flowers both in 1902 and 1903.
All of these plants and all of these flowers re-
peated the cruciate type exactly, and not the
slighest impurity or tendency to partial rever-
sion has been observed.

Thus true and constant cruciate varieties
have been produced from accidentally observed
initial plants, and because of their very curious
characters they will no doubt be kept in
botanical gardens, even if they should event-
ually become lost in their native localities.

At this point I might note another observation
made on the wild species of Oenothera cruciata

590 Mutations

from the Adirondacks. Through the kindness
of Dr. MacDougal, of the New York Botanical
Garden, I received seeds from Sandy Hill near
Lake George. When the plants, grown from
these seeds, flowered, they were not a uniform
lot, but exhibited two distinct types. Some had
linear petals and thin flower-buds, and in
others the petals were a little broader and the
buds more swollen. The difference was small,
but constant on all the flowers, each single plant
clearly belonging to one or the other of the two
types. Probably two elementary species were
intermixed here, but whether one is the sys-
tematic type and the other a mutation, remains
to be seen.

Nor seem these two types to exhaust the range
of variability of Oenothera cruciata. Dr. B. L.
Eobinson of Cambridge, Mass., had the kind-
ness to send me seeds from another locality in
the same region. The seeds were collected in
New Hampshire and in my garden produced a
true and constant cruciata, but with quite differ-
ent secondarv characters from both the afore-
said varieties. The stems and flower-spikes and
even the whole foliage were much more slender,
and the calyx-tubes of the flowers were notice-
ably more elongated. It seems not improbable
that Oenothera cruciata includes a group of
lesser unities, and may prove to comprise a

Origin of Wild Species 591

swarm of elementary species, while the original
strain might even now be still in a condition of
mutability. A close scrutiny in the native re-
gion is likely to reveal many unexpected
features.

A very interesting novelty has already been
described in a former lecture. It is the Xan-
thium wootoni, discovered in the region about
Las Vegas, New Mexico, by T. D. A. Cockerell.
It is similar in all respects to X. commune^ but
the burrs are more slender and the prickles
much less numerous, and mostlv stouter at their
base. It grows in the same localities as the
X. commune, and is not recorded to occur else-
where. Whether it is an old variety or a recent
mutation it is of course impossible to decide.
In a culture made in my garden from the seed
sent me by Mr. Cockerell, I observed (1903) that
both forms had a subvariety with brownish
foliage, and, besides this, one of a pure green.
Possibly this species, too, is still in a mutable
condition.

Perhaps the same may be asserted concerning
the beautiful shrub. Hibiscus Moscheutos, ob-
served in quite a number of divergent types by
John W. Harshberger. They grew in a small
meadow at Seaside Park, New Jersey, in a
locality which had been undisturbed for years.
They differed from each other in nearlv all the

592 Mutations

organs, in size, in the diameter of the stems,
which were woody in some and more fleshy in
others, in the shape of the foliage and in the
flowers. More than twenty types could be dis-
tinguished and seeds were saved from a num-
ber of them, in order to ascertain whether they
are constant, or whether perhaps a main stem in
a mutating condition might be found among
them. If this should prove to be the case, the
relations between the observed forms would
probably be analogous to those between the 0.
lamarcMana and its derivatives.

Many other varieties have sprung from the
type-species under similar conditions from time
to time. A fern-leaved mercury, Mercurialis
annua laciniata, was discovered in the year 1719
by Merchant The type was quite new at the
time and mamtained itself during a series of
years. The yellow^ deadly nightshade or Atropa
Belladonna lutea wa^s found about 1850 in the
Black Forest in Germciny in a single spot, and
has since been multiplied by seeds. It is now
dispersed in botanical gardens, and seems to be
quite constant. A dwarf variety of a bean,
Phaseolus lunatus, was obsei-ved to spring from
the ordinary type by a sudden leap about 1895
by W. W. Tracy, and many similar cases could
be given.

The annual habit is not very favorable for

Origin of Wild Species 593

the discovery of new forms in the wild state.
New varieties may appear, but may be crowded
out the first year. The chances are much
greater with perennials, and still greater with
shrubs or trees. A single aberrant specimen
may live for years and even for centuries, and
under such conditions is pretty sure to be dis-
covered sooner or later. Hence it is no won-
der that many such cases are on record. They
have this in common that the original plant
of the variety has been found among a vast
majority of representatives of the correspond-
ing species. Nothing of course is directly
known about its origin. Intermediate links
have as a rule been wanting, and the seeds,
which have often been sown, have not yielded
reliable results, as no care was taken to pre-
serve the blossoms from intercrossing with their
parent-forms.

Stress should be laid upon one feature of
these curious occurrences. Eelatively often
the same novelty has been found twice or thrice,
or even more frequently, and under conditions
which make it very improbable that any relation
between such occurrences might exist. The
same mutation must have taken place more than
once from the same main stem.

The most interesting of these facts are con-
nected with the origin of the purple beech, which

594 Mutations

is now so universally cultivated. I take the fol-
lowing statements from an interesting historical
essay of Prof. Jaggi. He describes three orig-
inal localities. One is near the Swiss village,
Buch am Irchel, and is located on the Stamm-
berg. During the 17th century five purple
beeches are recorded to have grown on this spot.
Four of them have died, but one is still alive.
Seedlings have germinated around this little
group, and have been mostly dug up and trans-
planted into neighboring gardens. Nothing is
known about the real origin of these plants, but
according to an old document, it seems that
about the year 1190 the purple beeches of Buch
were already enjoying some renown, and at-
tracting large numbers of pilgrims, owing to
some old legend. The church of Embrach is said
to have been built in connection with this legend,
and was a goal for pilgrimages during many
centuries.

A second native locality of the purple beech
is found in a forest near Sondershausen in
Thiiringen, Germany, where a fine group of
these trees is to be seen. They were mentioned
for the first time in the latter half of the
eighteenth century, but must have been old spec-
imens long before that time. The third locality
seems to be of much later origin. It is a forest
near Roveredo in South Tyrol, where a new

Origin of Wild Species 595

university is being erected. It is only a century
ago that the first specimens of the purple beech
were discovered there.

As it is very improbable that the two last
named localities should have received their pur-
ple beeches from the first named forest, it seems
reasonable to assume that the variety must have
been produced at least thrice.

The purple beech is now exceedingly common
in cultivation. But Jaggi succeeded in showing
that all the plants owe their origin to the orig-
inal trees mentioned above, and are, including
nearly all cultivated specimens with the sole ex-
ception of the vicinity of Buch, probably derived
from the trees in Thiiringen. They are easily
multiplied by grafting, and come true from
seed, at least often, and in a high proportion.
Wiether the original trees would yield a
pure progeny if fertilized hj their own pol-
len has. as yet not been tested. The young seed-
lings have purple seed-leaves, and may easily be
selected by this character, but they seem to
be always subjected in a large measure to
vicinism.

Many other instances of trees and shrubs,
found in accidental specimens constituting a
new variety in the wild state, might be given.
The oak-leaved beech has been found in a forest
of Lippe-Detmold in Germany and near Ver-

596 Mutations

sailles, whence it was introduced into horticul-
ture by Carriere. Similarly divided and cleft
leaves seem to have occurred more often in the
wild state, and cut-leaved hazels are recorded
from Kouen in France, birches and alders from
Sweden and Lapland, where both are said to
have been met with in several forests. The
purple barberry was found about 1830 by Ber-
tin, near Versailles. Weeping varieties of
ashes were found wild in England and in Ger-
many, and broom-like oaks, Qiiercus pedun-
culata fastigiata, are recorded from Hessen-
Darmstadt, Calabria, the Pyrenees and other
localities. About the real origin of all these
varieties nothing is definitely known.

The '^ single-leaved " strawberry is a variety
often seen in botanical gardens, as it is easily
propagated by its runners. It was discovered
wild in Lapland at the time of Linnaeus, and
appeared afterwards unexpectedly in a nursery
near Versailles. This happened about the year
1760 and Duchesne tested it from seeds and
found it constant. This strain, however, seems
to have died out before the end of the 18th cen-
tury. In a picture painted by Holbein (1495-
1543), strawberry leaves can be seen agreeing
exactly with the monophyllous type. The va-
riety may thus be assumed to have arisen inde-

Origin of Wild Species 597

pendently at least thrice, at dilt'erent periods
and in distant localities.

From all these statements and a good many
others which can be found in horticultural and
botanical literature, it may be inferred that
mutations are not so very rare in nature as is
often supposed. Moreover we may conclude
that it is a general rule that they are neither
preceded nor accompanied by intermediate
steps, and that they are ordinarily constant
from seed from the first.

Why then are they not met with more often?
In my opinion it is the struggle for life which is
the cause of this apparent rarity ; which is noth-
ing else than the premature death of all the in-
dividuals that so vary from the common type of
their species as to be incapable of development
under prevailing circumstances. It is obvious-
ly without consequence whether these deviations
are of a fluctuating or of a mutating nature.
Hence we may conclude that useless mutations
will soon die out and will disappear without
leaving any progeny. Even if they are pro-
duced again and again by the same strain, but
under the same unfavorable conditions, there
will be no appreciable result.

Thousands of mutations may perhaps take
place yearly among the plants of our immediate
vicinity without any chance of being discovered.

598 Mutations

We are trained to the appreciation of the dif-
ferentiating marks of systematic species. When
we have succeeded in discerning these as given
by our local flora lists, we rest content. Meet-
ing them again we are in the habit of greeting
them with their proper names. Such is the
satisfaction ensuing from this knowledge that
we do not feel any inclination for further in-
quiry. Striking deviations, such as many
varietal characters, may be remarked, but then
they are considered as being of only secondary
interest. Our minds are turned from the deli-
cately shaded features which differentiate ele-
mentary species.

Even in the native field of the evening-prim-
roses, no botanist would have discovered the
rosettes with smaller or paler leaves, constitut-
ing the first signs of the new species. Only by
the guidance of a distinct theoretical idea were
they discovered, and having once been pointed
out a closer inspection soon disclosed their
number.

Variability seems to us to be very general, but
very limited. The limits however, are distinct-
ly drawn by the struggle for existence. Of
course the chance for useful mutations is a very
small one. We have seen that the same muta-
tions are as a rule repeated from time to time
by the same species. Now, if a useful mutation,

Origin of Wild Species 599

or even a wholly indifferent one, might easily be
produced, it would have been so, long ago, and
would at the present time simply exist as a sys-
tematic variety. If produced anew somewhere
the botanist would take it for the old variety
and would omit to make any inquiry as to its
local origin.

Thousands of seeds with perhaps wide circles
of variability are ripened each year, but only
those that belong to the existing old narrow
circles survive. How different would Nature
appear to us if she were free to evolve all her
potentialities !

Darwin himself was struck with this lack of
harmony between common observations and the
probable real state of things. He discussed
it in connection with the cranesbill of the
Pyrenees {Geranium pyrenaicum). He de-
scribed how this fine little plant, which has never
been extensively cultivated, had escaped from a
garden in Staffordshire and had succeeded in
multiplying itself so as to occupy a large area.
In doing so it had evidently found place for an
uncommonly large number of plantlets from its
seeds and correspondingly it had commenced to
vary in almost all organs and qualities and
nearly in all imaginable directions. It dis-
played under these exceptional circumstances a
capacity which never had been exceeded and

600 Mutations

which of course would have remained concealed
if its multiplication had been checked in the or-
dinary way.

Many species have had occasion to invade new
regions and cover them with hundreds of thou-
sands of individuals. First are to be cited
those species which have been introduced from
America into Europe since the time of Colum-
bus, or from Europe into this country. Some of
them have become very common. In my own
country the evening-primroses and Canada flea-
bane or Erigeron canadensis are examples, and
many others could be given. They should be
expected to vary under these circumstances in
a larger degree. Have they done so? Mani-
festly they have not struck out useful new char-
acters that would enable their bearers to found
new elementary species. At least none have
been observed. But poor types might have
been produced, and periods of mutability might
have been gone through similar to that which is
now under observation for Lamarck's evening-
primrose in Holland.

From this discussion we may infer that the
chances of discovering new mutating species are
great enough to justify the utmost efforts to
secure them. It is only necessary to observe
large numbers of plants, grown under circum-
stances which allow the best opportunities for

Origin of Wild Species 601

all the seeds. And as nature affords such op-
portunities only at rare intervals, we should
make use of artificial methods. Large quan-
tities of seed should be gathered from wild
plants and sowed under very favorable condi-
tions, giving all the nourishment and space re-
quired to the young seedlings. It is recom-
mended that they be sown under glass, either in
a glass-house or protected against cold and rain
by glass-frames. The same lot of seed will be
seen to yield twice or thrice as many seedlings
if thus protected, compared with what it would
have produced when sown in the field or in the
garden. I have nearly wholly given up sowing
seeds in my garden, as circumstances can be
controlled and determined with greater ex-
actitude when the sowing is done in a glass-
house.

The best proof perhaps, of the unfavorable
influence of external conditions for slightly de-
teriorated deviations is afforded by variegated
leaves. Many beautiful varieties are seen in
our gardens and parks, and even corn has a
variety with striped leaves. They are easily re-
produced, both by buds and by seeds, and they
are the most ordinarv of all varietal deviations.
They may be expected to occur wild also. But
no real variegated species, nor even good
varieties with this attribute occurs in nature.

602 Mutations

On the other hand occasional specimens with a
single variegated leaf, or with some few of them,
are actually met with, and if attention is once
drawn to this question, perhaps a dozen or so
instances might be brought together in a sum-
mer. But they never seem to be capable of
further evolution, or of reproducing themselves
sufficiently and of repeating their peculiarity in
their progeny. They make their appearance,
are seen during a season, and then disappear.
Even this slight incompleteness of some spots
on one or two leaves may be enough to be their
doom.

It is a common belief that new varieties owe
their origin to the direct action of external
conditions and moreover it is often assumed that
similar deviations must have similar causes, and
that these causes may act repeatedly in the same
species, or in allied, or even systematically dis-
tant genera. No doubt in the end all things
must have their causes, and the same causes
will lead under the same circumstances to the
same results. But we are not justified in deduc-
ing a direct relation between the external con-
ditions and the internal changes of plants.
These relations may be of so remote a nature
that they cannot as yet be guessed at. There-
fore only direct experience may be our guide.

Summing up the result of our facts and dis-

Origin of Wild Species 603

cussions we may state that wild new elementary
species and varieties are recorded to have
appeared from time to time. Invariably this
happened by sudden leaps and without interme-
diates. The mutants are constant when prop-
agated by seed, and at once constitute a new
race. In rare instances this may be of sufficient
superiority to win a place for itself in nature,
but more often it has qualities which have led to
its introduction into gardens as an ornamental
plant or into botanical gardens by reason of the
interest afforded by their novelty, or by their
anomaly.

Many more mutations may be supposed to be
taking place all around us, but artificial sowings
on a large scale, combined with a close exam-
ination of the seedlings and a keen appreciation
of the slightest indications of deviation seem
required to bring them to light.

Lecture XXI

MUTATIONS IN HORTICULTURE

It is well known that Darwin based his theory
of natural selection to a large extent upon the
experience of breeders. Natural and artificial
selection exhibit the same general features, yet
it was impossible in Darwin's time to make a
critical and comparative analysis of the two
processes.

In accordance with our present conception
there is selection of species and selection within
the species. The struggle for life determines
which of a group of elementary species shall sur-
vive and which shall disappear. In agricultural
practice the corresponding process is usually
designated by the name of variety-testing.
Within the species, or within the variety, the
sieve of natural selection is constantly eliminat-
ing poor specimens and preserving those that
are best adapted to live under the given condi-
tions. Some amelioration and some local races
are the result, but this does not appear to be of
much importance. On the contrary, the selec-

604

Mutations in Horticulture 605

tion within the race holds a prominent place in
agriculture, where it is known by the imposing
term, race-breeding.

Experience and methods in horticulture differ
from those in agriculture in many points.
Garden-varieties have been tested and separated
for a long time, but neither vegetables nor
flowers are known to exhibit such motley groups
of types as may be seen in large forage crops.

New varieties which appear from time to time
may be ornamental or otherwise in flowers, and
more or less profitable than their parents in
vegetables and fruits. In either case the dif-
ference is usually striking, or if not, its culture
would be unprofitable.

The recognition of useful new varieties being
thus made easy, the whole attention of the
breeder is reduced to isolating the seeds of the
mutants that are to be saved and sown separate-
ly, and this process must be repeated during
a few years, in order to produce the quantity of
seed that is needed for a profitable introduction
of the variety into commerce. In proportion to
the abundance of the harvest of each year this
period is shorter for some and longer for other
species.

Isolation in practice is not so simple nor so
easy an affair as it is in the experimental gar-
den. Hence we have constant and nearly un-

606 Mutations

avoidable cross-fertilizations with the parent-
form, or with neighboring varieties, and conse-
quent impurity of the new strain. This impurity
we have called vicinism, and in a previous lec-
ture have shown its effects upon the horticul-
tural races on one hand, and on the other, on the
scientific value that can be ascribed to the ex-
perience of the breeder. We have established
the general rule that stability is seldom met
with, but that the observed instability is always
open to the objection of being the result of vicin-
ism. Often this last agency is its sole cause;
or it may be complicated with other factors
>\^ithout our being able to discern them.

Though our assertion that the practice of the
horticulturist in producing new varieties is lim-
ited to isolation, whenever chance affords them,
is theoretically valid, it is not always so. We
may discern between the two chief groups of
varieties. The retrograde varieties are con-
stant, the indi\dduals not differing more from
one another than those of any ordinary species.
The highly variable varieties play an important
part in horticulture. Double flowers, striped
flowers, variegated leaves and some others yield
the most striking instances. Such forms have
been included in previous lectures among the
ever-sporting varieties, because their peculiar
characters oscillate between two extremes, viz.:

Mutations in Horticulture GOT

the new one of the variety and the correspond-
ing character of the original species.

In such cases isolation is usuall}^ accompanied
by selection: rarely has the first of a double,
striped or variegated race well filled or richly
striped flowers or highly spotted leaves.
Usually minor degrees of the anomaly are seen
first, and the breeder expects the novelty to de-
velop its features more completely and more
beautifully in subsequent generations. Some
varieties need selection only in the beginning,
in others the most perfect specimens must
be chosen every year as seed-bearers. For
striped flowers, it has been prescribed by Vil-
morin, that seeds should be taken only from
those with the smallest stripes, because there is
always reversion. Mixed seed or seed from
medium types would soon yield plants with too
broad stripes, and therefore less diversified
flowers.

In horticulture, new varieties, both retrograde
and ever-sporting, are known to occur almost
yearly. Nevertheless, not every novelty of the
gardener is to be considered as a mutation in
the scientific sense of the word. First of all,
the novelties of perennial and woody species are
to be excluded. Any extreme case of fluctuat-
ing variability may be preserved and multiplied
in the vegetative way. Such types are desig-

608 Mutations

nated in horticulture as varieties, though ob-
viously they are of quite another nature than
the varieties reproduced by seed. Secondly, a
large number, no doubt the greater number
of novelties, are of hybrid origin. Here we
may discern two cases. Hybrids may be
produced by the crossing of old types, either
of two old cultivated forms or newlv intro-
duced species, or ordinarily between an old
and an introduced variety. Such novelties are
excluded from our present discussion. Sec-
ondly, hybrids may be produced between a true,
new mutation and some of the already existing
varieties of the same species. Examples of this
obvious and usual practice will be given further
on, but it must be pointed out now that by such
crosses a single mutation may produce as many
novelties as there are available varieties of the
same species.

Summarizing these introductory remarks we
must lay stress on the fact that only a small part
of the horticultural novelties are real mutations,
although they do occur from time to time. If
useful, they are as a rule isolated and multiplied,
and if necessary, improved by selection. They
are in many instances, as constant from seed as
the unavoidable influence of vicinism allows
them to be. Exact observations on the origin,
or on the degree of constancy, are usually lack-

Mutations in Horticulture 609

ing, the notes being ordinarily made for com-
mercial purposes, and often only at the date of
introduction into trade, when the preceding
stages of the novelty may have been partly for-
gotten.

With this necessary prelude I will now give a
condensed survey of the historical facts relat-
ing to the origin of new horticultural varieties.
An ample description has been given recently
by Korshinsky, a Russian writer, who has
brought together considerable historical mate-
rial as evidence of the sudden appearance of
novelties throughout the whole realm of garden-
plants.

The oldest known, and at the same time one
of the most accurately described mutations is
the origin of the cut-leaved variety of the
greater celandine or Chelidonium majus. This
variety has been described either as such, or as
a distinct species, called Chelidonium laciniatum
Miller.

It is distinguished from the ordinary species,
by the leaves being cut into narrow lobes, with
almost linear tips, a character which is, as we
have seen on a previous occasion, repeated in
the petals. It is at present nearly as commonly
cultivated in botanical gardens as the C. majus,
and has escaped in many localities and is ob-
served to thrive as readily as the native wild

610 Mutations

plants. It was not known until a few years be-
fore the close of the 16th century. Its history
has been described by the French botanist, Rose.

It was seen for the first time in the garden of
Sprenger, an apothecary of Heidelberg, where
the C. majus had been cultivated for many
years. Sprenger discovered it in the year 1590,
and was struck by its peculiar and sharply de-
viating characters. He was anxious to know
whether it was a new plant and sent specimens
to Clusius and to Plater, the last of whom
transmitted them to Caspar Bauhin. These
botanists recognized the type as quite new and
Bauhin described it some years afterwards in
his Phytopinax under the name of Chelidonium
ma jus foliis qtiernis, or oak-leaved celandine.
The new variety soon provoked general interest
and was introduced into most of the botanical
gardens of Europe. It was recognized as quite
new, and repeated search has been made for it
in a wild state, but in vain. No other origin
has been discovered than that of Sprenger 's
garden. Afterwards it became naturalized in
England and elsewhere, but there is not the
least doubt as to its derivation in all the ob-
served cases.

Hence its origin at Heidelberg is to be con-
sidered as historically proven, and it is of course
only legitimate to assume that it originated in

Mutations in Horticulture 611

the year 1590 from the seeds of the C. majus.
Nevertheless, this was not ascertained by
Sprenger, and some doubt as to a possible intro-
duction from elsewhere might arise. If not,
then the mutation must have been sudden, oc-
curring without visible preparation and without
the appearance of intermediates.

From the very first, the cut-leaved celandine
has been constant from seed. Or at least it has
been propagated by seed largely and without
difficulty. Nothing, however, is known about it
in the first few years of its existence. Later
careful tests were made by Miller, Rose and
others and later by myself, which have shown
its stability to be absolute and without rever-
sion, and it has probably been so from the begin-
ning. The fact of its constancy has led to its
specific distinction by Miller, as varieties
were in his time universally, and up to the pres-
ent time not rarely, though erroneously, be-
lieved to be less stable than true species.

Before leaving the laciniate celandine it is to
be noted that in crosses with C. majus it follows
the law of Mendel, and for this reason should
be considered as a retrograde variety, the more
so, as it is also treated as such from a mor-
phological point of view by Stahl and others.

We now come to an enumeration of those
cases in which the date of the first appearance

612 Mutations

of a new horticultural variety has been record-
ed, and I must apologize for the necessity of
again quoting many variations, which have pre-
viously been dealt with from another point of
view. In such cases I shall limit myself as
closely as possible to historical facts. They have
been recorded chiefly by Verlot and Carriere,
who wrote in Paris shortly after the middle of
the past century, and afterwards by Darwin,
Korshinsky, and others. It is from their writ-
ings and from horticultural literature at large
that the following evidence is brought together.
A very well-known instance is that of the
dwarf variety of Tagetes signat a, which arose in
the nursery of Vilmorin in the year 1860. It
was observed for the first time in a single indi-
vidual among a lot of the ordinary Tagetes sig-
nata. It was found impossible to isolate it, but
the seeds were saved separately. The majority
of the offspring returned to the parental type,
but two plants were true dwarfs. From these
the requisite degree of purity for commercial
purposes was reached, the vicinists not being
more numerous than 10^ of the entire number.
The same mutation had been observed a year
earlier in the same nursery in a lot of Saponaria
calahrica. The seeds of this dwarf repeated the
variety in the next generation, but in the third
none were observed. Then the variety was

Mutations in Horticulture 613

thought to be lost, and the culture was given up,
as the Mendelian law of the splitting of varietal
hybrids was not known. According to our pres-
ent knowledge we might expect the atavistic de-
scendants of the first dwarf to be hybrids, and
to be liable to split in their progeny into one-
fourth dwarfs and three-fourths normal speci-
mens. From this it is obvious that the dwarfs
would have appeared a second time if the strain
had been continued by means of the seeds of the
vicinistic progeny.

In order to avoid a return to this phase of the
question, another use of the vicinists should at
once be pointed out. It is the possibility of in-
creasing the yield of the new variety. If space
admits of sowing the seeds of the vicinists, a
quarter of the progeny may be expected to come
true to the new type, and if they were partly
pollinated by the dwarfs, even a larger number
would do so. Hence it should be made a rule to
sow these seeds also, at least when those of the
true representatives of the novelty do not give
seed enough for a rapid multiplication.

Other dwarfs are recorded to have sprung
from species in the same sudden and unexpected
manner, as for instance Ageratum coeruleum of
the same nursery, further Clematis Viticella
nana and Acer campestre nanum. Primus Ma-
haleb nana was discovered in 1828 in one

614 Mutations

specimen near Orleans by Mme LeBrun in a
large culture of Mahaleb. Lonicera tatar-
ica nana appeared in 1825 at Fontenay-aux-
Roses. A tall variety of the strawberry is
called " Giant of Zuidwijk " and originated at
Boskoop in Holland in the nursery of Mr. van
de Water, in a lot of seedlings of the ordinary
strawberry. It was very large, but produced
few runners, and was propagated with much dif-
ficulty, for after six years only 15 plants were
available. It proved to be a late variety with
abundant large fruit, and was sold at a high
price. For a long time it was prominent in
cultures in Holland only.

Varieties without prickles are known to have
originated all of a sudden in sundry cases.
Gleditschia sinensis, introduced in 1774 from
China, gave two seedlings without spines in the
year 1823, in the nursery of Caumzet. It is
curious in being one of the rare instances where
a simultaneous mutation in two specimens is
acknowledged, because as a rule, such records
comply with the prevailing, though inexact, be-
lief that horticultural mutations always appear
in single individuals.

Prom Korshinsky's survey of varieties with
cut leaves or laciniate forms the following cases
may be quoted. In the year 1830 a nurseryman
named Jacques had sown a large lot of elms.

Mutations in Horticulture 615

Ulmus pedunculata. One of the seedlings had
cut leaves. He multiplied it by grafting and
gave it to the trade under the name of U.
pedunculata urticaefolia. It has since been
lost.

Laciniate alders seem to have been produced
by mutation at sundry times. Mirbel says that
the Alnus glutinosa laciniata is found wild in
Normandy and in the forests of Montmorency
near Paris. A similar variety has been met
with in a nursery near Orleans in the year 1855.
In connection with this discovery some discus-
sion has arisen concerning the question whether
it was probable that the Orleans strain was a
new mutation, or derived in some way from the
trees cited by Mirbel. Of course, as always in
such cases, any doubt, once pronounced, affects
the importance of the observation for all time,
since it is impossible to gather sufficient his-
torical evidence to fully decide the point. The
same variety had appeared under similar cir-
cumstances in a nursery at Lyons previously
(1812).

Laciniated maples are said to be of relatively
frequent occurrence in nurseries, among seed-
lings of the typical species. Loudon says that
once 100 laciniated seedlings were seen to orig-
inate from seed of some normal trees. But in
this case it is rather probable that the presumed

616 Mutations ^

normal parents were in reality hybrids between
the type and the laciniated form, and simply
split according to Mendel's law. This hy-
pothesis is partly founded on general consider-
ations and partly on experiments made by my-
self with the cut-leaved celandine, previously
alluded to, which I crossed with the type. The
hybrids repeated the features of the species and
showed no signs of their internal hybrid con-
stitution. But the following year one-fourth
of their progeny returned to the cut-leaved
form. If the same thing has taken place in the
case of Loudon's maples, but without their
hybrid origin being known, the result would
have been precisely what he observed.

Broussonetia papyrifera dissecta originated
about 1830 at Lyons, and a second time in 1866
at Fontenay-aux-Eoses. The cut-leaved hazel-
nuts, birches, beeches and others have mostly
been found in the wild state, as I have already
pointed out in a previous lecture. A similar
variety of the elder, Samhucus nigra laciniata,
and its near ally, Samhucus racemosa laciniata,
are often to be seen in our gardens. They have
been on record since 1886 and come true from
seed, but their exact origin seems to have been
forgotten. Cut-leaved walnuts have been known
since 1812; they come true from seed, but are
extremely liable to vicinism, a nuisance which is

Mutations in Horticulture 617

ascribed by some authors to the fact that often
on the same tree the male catkins flower and fall
otf several weeks before the ripening of the
pistils of the other form of flowers.

Weeping varieties afford similar instances.
Sophora japonica pendula originated about
1850, and Gleditschia triacanthos pendula some
time later in a nursery at Chateau-Thierry
(Ai^ne, France). In the year 1821 the bird's
cherry, or Prunus Padus, produced a weeping
variety, and in 1847 the same mutation was ob-
served for the allied Primus Mahaleh. Numer-
ous other instances of the sudden origin of
weeping trees, both of conifers and of others,
have been brought together in Korshinsky's
paper. This striking type of variation includes
perhaps the best examples of the whole his-
torical evidence. As a rule they appear in large
sowings, only one, or only a few at a time. Many
of them have not been observed during their
youth, but only after having been planted out
in parks and forests, since the weeping charac-
ters show only after several years.

The monophyllous bastard-acacia originated
in the same way. Its peculiarities will be dealt
with on another occasion, but the circumstances
of its birth may as well be given here. In 1855
in the nursery of Deniau, at Brain-sur-PAu-
thion (Maine et Loire), it appeared in a lot of

618 Mutations

seedlings of the typical species in a single in-
dividual. This was transplanted into the Jar-
din des Plantes at Paris, where it flowered and
bore seeds in 1865. It must have been partly
pollinated by the surrounding normal repre-
sentatives of the species, since the seeds yielded
only one-fourth of true offspring. This propor-
tion, however, has varied in succeeding years.
Briot remarks that the monophyllous bastard-
acacia is liable to petaloid alterations of its
stamens, which deficiency may encroach upon
its fertility and accordingly upon the purity of
its offspring.

Broom-like varieties often occur among trees,
and some are known for their very striking re-
versions by buds, as we have seen on a previous
occasion. They are ordinarily called pyramidal
or fastigiate forms, and as far as their history
goes, they arise suddenly in large sowings
of the normal species. The fastigiate birch was
produced in this way by Baumann, the Abies
concolor fastigiata by Thibault and Keteleer at
Paris, the pyramidal cedar by Paillat, the analo-
gous form of W ellingtonia by Otin. Other in-
stances could easily be added, though of course
some of the most highly prized broom-like trees
are so old that nothing is known about their
origin. This, for instance, is the case with the
pyramidal yew-tree, Taxus haccata fastigiata.

Mutations in Horticulture 619

Others have been found wild, as already men-
tioned in a former lecture.

An analogous case is afforded by the purple-
leaved plums, of which the most known form is
Prunus Pissardi. It is said to be a purple va-
riety of Prunus cerasifera, and was introduced
at the close of the seventies from Persia, where
it is said to have been found in Tabris. A simi-
lar variety arose independently and unex-
pectedly in the nursery of Spath, near Berlin,
about 1880, but it seems to differ in some minor
points from the Persian prototype.

A white variety of Cyclamen vernum made its
appearance in the year 1836 in Holland. A sin-
gle individual was observed for the first time
among a large lot of seedlings, in a nursery near
Haarlem. It yielded a satisfactory amount of
seed, and the progeny was true to the new type.
Such plants propagate slowly, and it was only
twenty-seven years later (1863) that the bulbs
were offered for sale bv the Haarlem firm of
Krelage & Son. The price of each bulb was
$5.00 in that year, but soon afterwards was re-
duced to $1.00 each, which was about thrice the
ordinary price of the red variety.

The firm of Messrs. Krelage & Son has
brought into commerce a wide range of new
bulb-varieties, all due to occasional mutations,
some by seed and others by buds, or to the acci-

620 Mutations

dental transference of new qualities into the
already existing varieties by cross-pollination
through the agency of insects. Instead of giv-
ing long lists of these novelties, I may cite the
black tulips, which cost during the first few
years of their introduction about $25.00 apiece.

Horticultural mutations are as a rule very
rare, especially in genera or species which have
not yet been brought to a high degree of varia-
bility. In these the wide range of varieties and
the large scale in which they are multiplied of
course give a greater chance for new varieties.
But then the possibilities of crossing are like-
wise much larger, and apparent changes due to
this cause may easily be taken for original mu-
tations.

The rarity of the mutations is often proved
by the lapse of time between the introduction
of a species and its first sport. Some instances
may be given. They afford a proof of the length
of the period during which the species remained
unaltered, although some of these alterations
may be due to a cross with an allied form.
Erythrina Crista-galli was introduced about
1770, and produced its first sport in 1884, after
more than a century of cultivation. Begonia
semperflorens has been cultivated since 1829,
and for half a century before it commenced
sporting. The same length of time has elapsed

Mutations in Horticulture 621

between the first culture and the first variation
of Crambe maritima. Other cases are on rec-
ord in which the variability exhibited itself
much sooner, perhaps within a few years after
the original discovery of the species. But such
instances seem, as a rule, to be subject to doubt
as to the concurrence of hybridization. So for
instance the Iris lortetii, introduced in the year
1895 from the Lebanon, which produced a white
variety from its very first seeds. If by chance
the introduced plants were natural hybrids be-
tween the species and the white variety, this ap-
parent and rather improbable mutation would
find a very simple explanation. The length of
the period preceding the first signs of variability
is largely, of course, due to divergent methods
of culture. Such species as Erythrina, which
are perennial and only sown on a small scale,
should not be expected to show varieties very
soon. Annual species, which are cultivated
yearly in thousands or even hundreds of thou-
sands of individuals, have a much better chance.
Perhaps the observed differences are largely
due to this cause.

Monstrosities have, from time to time, given
rise to cultivated races. The cockscomb or
Celosia is one of the most notorious instances.
Cauliflowers, turnips and varieties of cabbages
are recorded by De Candolle to have arisen in

622 Mutations

culture, more than a century ago, as isolated
monstrous individuals. They come true from
seed, but show deviations from time to time
which seem to be intimately linked with their
abnormal characters. Apetalous flowers may
be considered as another form of monstrosity,
and in Salpiglossis sinuata such a variety with-
out a corolla made its appearance in the year
1892 in the nursery of Vilmorin. It appeared
suddenly, yielded a good crop of seed and
was constant from the outset, without any sign
of vicinism or impurity.

In several cases the origin of a variety is ob-
scure, while the subsequent historical evidence
is such as to make an original sudden appear-
ance quite probable. Although these instances
otfer but indirect evidence, and will sooner or
later lose their importance, it seems desirable
to lay some stress on them here, because most of
these cases are very obvious and more striking
than purely historical facts. Sterile varieties
belong to this heading. Sometimes they bear
fruit without kernels, sometimes flowers with-
out sexual organs, or even no flowers at all. In-
stances have been given in the lecture on
retrograde varieties; they are ordinarily as-
sumed to have originated by a leap, because it is
not quite clear how a loss of the capacity for the
formation of seeds could have been slowlv accu-

Mutations in Horticulture 623

mulated in preceding generations. An interest-
ing case is afforded by a sterile variety of corn,
which originated some time ago in my own pedi-
gree-cultures made for another purpose, and
which had begun with an ear of 1886. The first
generation from the original seeds showed noth-
ing particular, but the second at once produced
quite a number of sterile plants. The sterility
was caused by the total lack of branches, includ-
ing those bearing the pistillate flowers. The
terminal spikes themselves were reduced to
naked spindles, without branches, without flow-
ers and even almost without bracts.

In some individuals, however, this negative
character was seen to give way at the tip, show-
ing a few small naked branches. Of course it
was impossible to propagate this curious form,
but my observations showed that it sprang into
existence from known ancestors by a single step
or sudden leap. This leap, however, was not
confined to a single specimen; on the contrary
it affected 40 plants out of a culture of 340
individuals. The same phenomenon was re-
peated from the seeds of the normal plants in
the following year, but afterwards the mon-
strosity disappeared.

The Italian poplar affords another instance.
It is considered bv some authors as a distinct
species, Popidus italica, and by others as a

624 Mutations

broom-like variety of the Populus nigra, from
which it is distinguished by its erect branches
and other characters of minor importance. It
is often called the pyramidal or fastigiate
poplar. Its origin is absolutely unknown and
it occurs only in the cultivated state. In Italy
it seems to have been cultivated from the
earliest historical times, but it was not intro-
duced into other countries till the eighteenth
century. In 1749 it was brought into France,
and in 1758 into England, and to-day it
may be seen along roads throughout cen-
tral Europe and in a large part of Asia. But
the most curious fact is that it is only observed
in staminate specimens ; pistillate trees have not
been found, although often sought for. This
circumstance makes it very probable that the
origin of the broom-like poplar was a sudden
mutation, producing only one individual. This
being staminate, it has been propagated ex-
clusively by cuttings. It is to be admitted,
however, that no material evidence is at hand
to prove that it is not an original wild species,
the pistillate form of which has been lost by
vegetative multiplication. One form only of
many dioecious plants is to be found in cultiva-
tion, as for instance some South American
species of Ribes.

Total lack of historical evidence concerning

Mutations in Horticulture 625

the origin of a variety has sometimes been con-
sidered as sufficient proof of a sudden origin.
The best known instance is that of the renowned
cactus-dahlia with its recurved instead of in-
curved ray-florets. It was introduced from
Mexico into the Netherlands by Van den Berg of
Jutphaas, under the following remarkable cir-
cumstances. In the autumn of 1872 one of his
friends had sent him a small case, containing
seeds, bulbs and roots from Mexico. From
one of these roots a Dahlia shoot developed.
It was cultivated with great care and bloomed
next year. It surprised all who saw it by
the unexpected peculiarity of its large rich
crimson flowers, the rays of which were re-
versed tubular. The margins of the narrow
rays were curved backwards, showing the bright
color of the upper surface. It was a very
showy novelty, rapidly multiplied by cuttings,
and was soon introduced into commerce. It has
since been crossed with nearly all other avail-
able varieties of the Dahlia, giving a large and
rich group of forms, bound together by the
curious curling of the petals. It has never been
observed to grow in Mexico, either wild or in
gardens, and thus the introduced individual has
come to be considered as the first of its race.

I have already mentioned that the rapid pro-
duction of large numbers of new varieties, by

626 Mutations

means of the crossing of the offspring of a
single mutant with previously existing sorts, is
a very common feature in horticultural prac-
tice. It warns us that only a small part of the
novelties introduced yearly are due to real mu-
tations. Further instances of novelties with
such a common origin are the purple-leaved
dahlias, the gooseberries without prickles, the
double petunias, erect gloxinias and many
others. Accumulation of characters, acquired
in different races of a species, may easily be
effected in this way ; in fact it is one of the im-
portant factors in the breeding of horticultural
novelties.

I have alluded more than once in this lecture
to the question, whether it is probable that mu-
tations occur in one individual or in more.
The common belief among horticulturists is
that, as a rule, they appear in a single plant.
This belief is so widespread that whenever a
novelty is seen for the first time in two or more
specimens it is at once suggested that it might
have originated and been overlooked in a previ-
ous generation. Not caring to confess a lack
of close observation, the number of mutants
in such cases is usually kept secret. At least
this statement has been made to me by some of
the horticulturists at Erfurt, whom I visited
some years ago in order to learn as much as

Mutations in Horticulture 627

possible about the methods of production of
their novelties. Hence it is simply impossible
to decide the question on the basis of the ex-
perience of the breeders. Even in the case of the
same novelty arising in sundry varieties of the
same species, the question as to common origin,
by means of crossing, is often hard to decide,
as for instance in moss-roses and nectarines.
On the other hand, instances are on record
where the same novelty has appeared at differ-
ent times, often at long intervals. Such is the
case with the butterfly-cyclamen, a form with
wide-spreading petals which originated in
Martinis nursery in England. The first time it
was seen it was thought to be of no value, and
was thrown away, but when appearing for a
second time it was multiplied and eventually
placed on the market. Other varieties of Cycla-
men, as for instance the crested forms, are also
known to have originated repeatedly.

In concluding this series of examples of hor-
ticultural mutations, I might mention two
cases, which have occurred in my own experi-
mental garden. The first refers to a tubular
dahlia. It has ray-florets, the ligules of which
have their margins grown together so as to
form tubes, with the outer surface correspond-
ing to the pale under-surface of the corolla.

This novelty originated in a single plant in a

628 Mutations

culture from the seed of the dwarf variety
' ^ Jules Chretien. ' ' The seeds were taken from
introduced plants in my garden, and as the
sport has no ornamental value it is uncertain
whether this was the first instance or whether
it had previously occurred in the nursery at
Lyons, from whence the bulbs were secured.
Afterwards it proved true from seed, but was
very variable, exhibiting rather the features of
an ever-sporting variety.

Another novelty was seen the first time in
several individuals. It was a pink sport of the
European cranesbill. Geranium pratense. It
arose quite unexpectedly in the summer of 1902
from a striped variety of the blue species. It
was seen in seven specimens out of a lot of about
a hundred plants. This strain was introduced
into my garden in 1897, when I bought two
plants under the name of Geranium pratense
album, which however proved to belong to the
striped variety. From their seeds I sowed in
1898 a first generation, of which a hundred
plants flowered the next year, and from their
seeds I sowed in 1900 the lot which produced
the sport. Neither the introduced plants nor
their offspring had exhibited the least sign of a
color-variation, besides the blue and white
stripes. Hence it is very probable that my nov-
elty was a true first mutation, the more prob-

Mutations in Horticulture 629

ably so since a pink variety would without doubt
have a certain horticultural value and would
have been preserved if it had occurred. But as
far as I have been able to ascertain, it is as yet
unknown, nor has it been described until to-day.
Summing up the results of this long, though
very incomplete, list of horticultural novelties
with a more or less well-known origin, we see
that sudden appearances are the rule. Having
once sprung into existence the new varieties are
ordinarily constant, except as affected by
vicinism. Details concerning the process are
mostly unavailable or at least are of very doubt-
ful value. And to this it should be added that
really progressive mutations have hardly been
observed in horticulture. Hence the theoretical
value of the facts is far less than might have
been expected.

Lecture XXII

SYSTEMATIC ATAVISM

The steady cooperation of progression and re-
trogression is one of the important principles
of organic evolution. I have dwelt upon this
point more than once in previous lectures. I
have tried to show that both in the more im-
portant lines of the general pedigree of the
vegetable kingdom, and in the numerous lateral
branches ending in the genera and species with-
in the families, progression and retrogression
are nearly always at work together. Your at-
tention has been directed to the monocotyledons
as an example, where retrogression is every-
where so active that it can almost be said to be
the prevailing movement. Reduction in the veg-
etative and generative organs, in the anatomical
structure and growth of the stems, and in sun-
dry other ways is the method by which the
monocotyledons have originated as a group
from their supposed ancestors among the lower
dicotyledonous families. Retrogression is the
leading idea in the larger families of the group,

630

Systematic Atavism 631

as for instance in the aroids and the grasses.
Retrograde evolution is also typical in the high-
est and most highly differentiated family of the
monocotyledons, the orchids, which have but
one or two stamens. In the second place I have
had occasion more than once to assert that retro-
gression, though seemingly consisting in the
disappearance of some quality, need not, as a
rule, be considered as a complete loss. Quite on
the contrary, it is very probable that real losses
are extremely rare, if not wholly lacking. Ordi-
narily the loss is only apparent, the capacity
becomes inactive only, but is not destroyed. The
character has become latent, as it is commonly
stated, and therefore may return to activity and
to the full display of its peculiarity, whenever
occasion offers.

Such a return to activity was formerly called
atavism. But as we have seen, when dealing
with the phenomena of latency at large, sundry
eases of latency are to be distinguished, in order
to get a clear insight into these difficult proc-
esses.

So it is with atavism, too. If any plant re-
verts to a known ancestor, we have a positive
and simple case. But ancestors with alternate
specific marks are as a rule neither historically
nor experimentally manifest. They are only
reputed to be such, and the presumption rests

632 Mutations

upon the systematic affinity between the deriva-
tive species and its nearest probable allies.
Such reversions are now to be examined at some
length and may be adequately treated under the
head of systematic atavism. To this form of
atavism pertain, on the basis of our definition,
those phenomena by which species assume one
or more characters of allies, from which they
are understood to have descended by the loss of
the character under discussion. The phenom-
ena themselves consist in the production of
anomalies and varieties, and as the genetic
relation of the latter is often hardly beyond
doubt, the anomalies seem to afford the best in-
stances for the study of systematic atavism.
This study has for its chief aim the demonstra-
tion of the presence of the latent characters, and
to show that they return to activity suddenly
and not by a slow and gradual recovery of the
former features. It supports the assertion
that the visible elementary characters are es-
sentially an external display of qualities carried
by the bearers of heredity, and that these
bearers are separate entities, which may be
mingled together, but are not fused into a
chaotic primitive life-substance. Systematic
atavism by this means leads us to a closer ex-
amination of the internal and concealed causes,
which rule the affinities and divergencies of

Systematic Atavism 633

allied species. It brings before us, and empha-
sizes the importance of the conception of the
so-called unit-characters.

The primrose will serve as an example. In
the second lecture we have seen that the old
species of Linnaeus, the Prmiida veris, was
split up by Jacquin into three smaller ones,
which are called P. officinalis, P. elatior and P.
acaulis. From this systematic treatment we
can infer that these three forms are assumed to
be derived from a common ancestor. Now two
of them bear their flowers in bracted whorls,
condensed into umbels at the summits of a scape.
The scapes themselves are inserted in the axils
of the basal leaves, and produce the flowers
above them. In the third species. Primula
acaulis, this scape is lacking and the flowers are
inserted singly in the axils on long slender
stalks. For this reason the species is called
acaulescent, indicating that it has no other
stem than the subterranean rootstock. But on
closer inspection we observe that the flower-
stalks are combined into little groups, each
group occupying the axil of one of the basal
leaves. This fact at once points to an analogy
with the umbellate allies, and induces us to ex-
amine the insertion of the flowers more crit-
ically. In doing so we find that they are united
at their base so as to constitute a sessile umbel.

634 Mutations

The scapes are not absolutely lacking, but only
reduced to almost invisible rudiments.

Belying upon this conclusion we infer that all
of the three elementary species have umbels,
some pedunculate and the others not. On this
point they agree with the majority of the allied
species in the genus and in other genera, as for
instance in Androsace. Hence the conclusion
that the common ancestors were perennial
plants with a rootstock bearing their flowers
in umbels or whorls on scapes. Lacking in the
Primula veris, these scapes must obviously have
been lost at the time of the evolution of this
form.

Proceeding on this line of speculation we at
once see that a very adequate opportunity for
systematic atavism is offered here. According
to our general conception the apparent loss of a
scape is no proof of a corresponding internal
loss, but might as well be caused simply by
the reduction of the scape-growing capacity to
a latent or inactive state. It might be awak-
ened afterwards by some unknown agency, and
return to activity.

Now this is exactly what happens from time
to time. In Holland the acaulescent primrose
is quite a common plant, filling the woods in the
spring with thousands of clusters of bright yel-
low flowers. It is a very uniform type, but in

Systematic Atavism 635

some years it is seen to return to atavistic con-
ditions in some rare individuals. More than
once I have observed such cases myself, and
found that the variation is only a partial one,
producing one or rarely two umbels on the same
plant, and liable to fail of repetition when tlie
varying specimens are transplanted into the
garden for further observation. But the fact
remains that scapes occur. The scapes them-
selves are of varying length, often very short,
and seldom long, and their umbels display the
involucre of bracts in a manner quite analogous
to that of the Primula officinalis and P. elatior.
To my mind this curious anomaly strongly sup-
ports the view of the latent condition of the
scape in the acaulescent species, and that such a
dormant character must be due to a descent
from ancestors with active scapes, seems to be in
no need of further reiteration. Returning to.
activity the scapes at once show a full develop-
ment, in no way inferior to that of the allied
forms, and only unstable in respect to their
length.

A second example is afforded by the bracts
of the crucifers. This group is easily distin-
guished by its cruciform petals and the group-
ing of the flowers into long racemes. In other
families each flower of such an inflorescence
would be subtended by a bract, according to the

636 Mutations

general rule that in the higher plants side
branches are situated in the axils of leaves.
Bracts are reduced leaves, but the spikes of the
cruciferous plants are generally devoid of
them. The flower-stalks, with naked bases,
seem to arise from the common axis at indefinite
points.

Hence the inference that crucifers are an ex-
ception to a general rule, and that they must
have originated from other types which did
comply with this rule, and accordingly were in
the possession of floral bracts. Or, in other
words, that the bracts must have been lost dur-
ing the original evolution of the whole family.
This conclusion being accepted, the accidental
re-apparition of bracts within the family must
be considered as a case of systematic atavism,
quite analogous to the re-appearance of the
scapes in the acaulescent primrose. The sys-
tematic importance of this phenomenon, how-
ever, is far greater than in the first case, in
which we had only to deal with a specific char-
acter, while the abolition of the bracts has be-
come a feature of a whole family.

This reversion is observed to take place ac-
cording to two widely different principles. On
one hand, bracts may be met with in a few
stray species, assuming the rank of a specific
character. On the other hand they may be seen

Systematic Atavism 637

to occur as an anomaly, incompletely developed,
often very rare and with all the appearance of
an accidental variation, but sometimes so com-
mon as to seem nearly normal.

Coming now to particular instances, we may
turn our attention in the first place to the genus
Sisymbrium. This is a group of about 50 species,
of wide geographic distribution, among which
the hedge mustard (S. offlcinalis) is perhaps the
most common of weeds. Two species are re-
puted to have bracts, Sisymbrium hirsutum and
S. supiniim. Each flower-stalk of their long
racemes is situated in the axil of such a bract,
and the peculiaritj^ is quite a natural one, corre-
sponding exactly to what is seen in the inflor-
escence of other families. Besides the Sisym-
brium some six other genera afford similar
structures.

Erucastrum pollichii has been already allud-
ed to in a former lecture when dealing with the
same problem from another point of view. As
previously stated, it is one of the most manifest
and most easily accessible examples of a latent
character becoming active through systematic
atavism. In fact, its bracts are found so often
as to be considered by some authors as of quite
normal occurrence. Contrasted with those of
the above mentioned species of Sisymbrium,
they are not seen at the base of all the flower-

638 Mutations

stalks, but are limited to the lowermost part of
the raceme, adorning a few, often ten or twelve,
and rarely more flower-stalks. Moreover they
exhibit a feature which is indicative of the pres-
ence of an abnormality. They are not all of the
same size, but decrease in length from the base
of the raceme upward, and finally slowly dis-
appear.

Besides these rare cases there are quite a
number of cruciferous species on record, which
have been observed to bear bracts. Penzig
in his valuable work on teratology gives a
list of 33 such genera, many of them repeat-
ing the anomaly in more than one species.
Ordinary cabbages are perhaps the best known
instance, and any unusual abundance of nour-
ishment, or anomalous cause of growth seems
to be liable to incite the development of bracts.
The hedge garlic or garlic mustard (Alliaria),
the shepherd's purse, the wormseed or Erysi-
mum cheiranthoides and many others afford
instances. In my cultures of Heeger's shep-
herd's purse, the new species derived at Lan-
dau in Germany from the common shepherd's
purse, the anomaly was observed to occur more
than once, showing that the mutation, which
changed the fruits, had not in the least affected
this subordinate anomalous peculiarity. In all
these cases the bracts behave as with the Eru-

Systematic Atavisjn 639

castrum, being limited to the base of the spike,
and decreasing in size from the lower flowers
upward. Connected with these atavistic bracts
is a feature of minor importance, which how-
ever, by its almost universal accompaniment of
the bracts, deserves our attention, as it is indica-
tive of another latent character. As a rule, the
bracts are grown together with their axillary
flower-stalk. This cohesion is not complete, nor
is it always developed in the same degree.
Sometimes it extends over a large part of the
two organs, leaving only their tips free, but on
other occasions it is limited to a small part of
the base. But it is very interesting that this
same cohesion is to be seen in the shepherd's
purse, in the wormseed and in the cabbage, as
well as in the case of the Erucastrum and most
of the other observed cases of atavistic bracts.
This fact suggests the idea of a common origin
for these anomalies, and would lead to the
hypothesis that the original ancestors of the
whole family, before losing the bracts, exhibited
this peculiar mode of cohesion.

Bracts and analogous organs afford similar
cases of systematic atavism in quite a number
of other families. Aroids sometimes produce
long bracts from various places on their
spadix, as may be seen in the cultivated
greenhouse species, Atifhurium scherzerianum.

640 Mutations

Poppies have been recorded to bear bracts
analogous to the little scales on the flower-stalks
of the pansies, on the middle of their flower-
stalks. A similar case is shown by the yellow
foxglove or Digitalis parviflora. The foxgloves
as a rule have naked flower-stalks, without the
two little opposite leafy organs seen in so many
other instances. The yellow species, however,
has been seen to produce such scales from time
to time. The honeysuckle genus is, as a rule,
devoid of the stipules at the base of the petiole,
but Lonicera etrusca has been observed to
develop such organs, which were seen to be free
in some, but in other specimens were adnate
to the base of the leaf, and even connate with
those of the opposite leaf.

Other instances could be given proving that
bracts and stipules, when systematically lack-
ing, are liable to reappear as anomalies. In
doing so, they generally assume the peculiar
characters that would be expected of them by
comparison with allied genera in which they are
of normal occurrence. There can be no doubt
that their absence is due to an apparent loss,
resulting from the reduction of a formerly
active quality to inactivity. Resuming this ef-
fective state, the case attains the value and sig-
nificance accorded to systematic atavism.

A very curious instance of reduced bracts, de-

Systematic Atavism 641

veloping to unusual size, is afforded by a variety
of corn, which is called Zea Mays cryptosperma,
or Zea Mays tunicata. In ordinary cora the
kernels are surrounded by small and thin, incon-
spicuous and membranaceous scales. Invisible
on the integrate spikes, when ripe, they are
easily detected by pulling the kernels out. In
cryptosperma they are so strongly developed as
to completely hide the kernels. Obviously they
constitute a case of reversion to the characters
of some unknown ancestor, since the corn is the
only member of the grass-family with naked
kernels. The var. tunicata, for this same rea-
son, has been considered to be the original wild
form, from which the other varieties of corn
have originated. But as no historical evidence
on this point is at hand, we must leave it as it is,
notwithstanding the high degree of attractive-
ness attached to the suggestion.

The horsetail-family may be taken as a fur-
ther support of our assertion. Some species
have stems of two kinds, the fertile being
brownish and appearing in early spring before
the green or sterile ones. In others the stems
are all alike, green and crowned with a cone-
like spike of sporangia-bearing scales. Mani-
festly the dimorphous cases are to be considered
as the j^ounger ones, partly because they are
obvious exceptions to the common rule, and

642 Mutations

partly because the division of labor is indicative
of a higher degree of evolution. But sometunes
these dimorphic species are seen to revert to the
primary condition, developing a fertile cone at
the summit of the green summer-stem. I have
had the opportunity of collecting an instance of
this anomaly on the tall Equisetum telmateja
in Switzerland, and other cases are on record in
teratological literature. It is an obvious ex-
ample of systematic atavism, occurring sud-
denly and with the full development of all the
qualities needed for the normal production of
sporangia and spores. All of these must be
concealed in a latent condition within the young
tissues of the green stems.

More than once I have had occasion to deal
with the phenomenon of torsions, as exhibited
by the teasels and some other plants. This
anomaly has been shown to be analogous to the
cases described as double adaptations. The
capacity of evolving antagonistic characters is
prominent in both. The antagonists are as-
sumed to lie quietly together while inactive.
But as soon as evolution calls them into activity
they become mutually exclusive, because only
one of them can come to full display in the same
organ. External influences decide which of the
two becomes dominant and which remains dor-
mant. This decision must take place separately

Systematic Atavism 643

for each stem and each branch, but as a rule,
the stronger axes are more liable to furnish
anomalies than the weaker.

Exactly the same thing is true of double
adaptations. Every bud of the water-persi-
caria may develop either into an erect or into a
floating stem, according as it is surrounded by
water or by relatively dry soil. In other cases
utility is often less manifest, but some use may
either be proved, or shown to be very probable.
At all events the term adaptation includes the
idea of utility, and obviously useless contriv-
ances could hardly be brought under the same
head.

We have also dealt with the question of
heredity. It is obvious that from the flowers of
the floating and erect stems of the water-persi-
caria seeds will result, each capable of yielding
both forms. Quite the same thing was the case
with the teasels. Some 4(¥ of the progeny pro-
duce beautifully twisted stems, but whether the
seed was saved from the most completely
twisted specimens or from the straight plants
of the race was of no importance.

This phenomenon of twisting may now be
considered from quite another point of y'lew-
It is a case of svstematic atavism, or of the re-
acquirement of some ancient and long-lost qual-
ity. This quality is the alternate position of

644 Mutations

the leaves, which has been replaced in the teasel-
family by a grouping in pairs. In order to
prove the validity of this assertion, it will be
necessary to discuss two points separately, viz. :
relative positions of the leaves, and the manner
in which the alternate position causes the stems
to become twisted.

Leaves are affixed to their stems and branches
in various ways. Among them one is of
wide occurrence throughout the whole realm
of the higher plants, while all the others are
more rare. ' Moreover these subordinate ar-
rangements are, as a rule, confined to definite
systematic groups. Such groups may be large,
as for instance, the monocotyledons, that have
their leaves arranged in two opposite rows in
many families, or small, as genera or subdivi-
sions of genera. Apart from these special
cases the main stem and the greater part of the
branches of the pedigree of the higher plants
exhibit a spiral condition or a screw arrange-
ment, all leaves being inserted at different
points and on different sides of the stem. This
condition is assumed to be the original one,
from which the more specialized types have
been derived. As is usual with characters in
general, it is seen to vary around an average,
the spiral becoming narrower and looser. A
narrow spiral condenses the leaves, while a

Systematic Atavism 645

loose one disperses them. According to such
fluctuating deviations the number of leaves, in-
serted upon a given number of spiral circuits, is
different in different species. In a vast major-
ity of cases 13 leaves are found on 5 circuits,
and as we have only to deal with this propor-
tion in the teasels we will not consider others.

In the teasels this screw-arrangement has dis-
appeared, and has been replaced by a decussate
grouping. The leaves are combined into pairs,
each pair occupying the opposite sides of one
node. The succeeding pairs alternate with one
another, so as to place their leaves at right
angles. The leaves are thus arranged on the
whole stem in four equidistant rows.

On the normal stem of a teasel the two mem-
bers of a pair are tied to one another in a com-
paratively complicated way. The leaves are
broadly sessile and their bases are united so as
to constitute a sort of cup. The margins of
these cups are bent upward, thereby enabling
them to hold water, and after a rainfall they
may be seen filled to the brim. It is believed
that these little reservoirs are useful to the
plant during the flowering period, because they
keep the ants away from the honey. Consider-
ing the internal structure of the stem at the base
of these cups we find that the vascular bundles
of the two opposite leaves are strongly con-

64:6 Mutations

nected with one another, constituting a ring
which narrowly surrounds the stem, and which
would impede an increase in thickness, if such
were in the nature of the plant. But since the
stems end their existence during the summer of
their development, this structure is of no real
harm.

The grouping of the leaves in alternate pairs
may be seen within the bud as well as on the
adult stems. In order to do this, it is necessary
to make transverse sections through the heart
of the rosette of the leaves of the first year.
If cut through the base, the pair exhibit connate
wings, corresponding to the water-cups; if cut
above these, the leaves seem to be free from one
another.

In order to compare the position of leaves
of the twisted plants with this normal arrange-
ment, the best way is to make a corresponding
section through the heart of the rosette of the
first year. It is not necessary to make a micro-
scopic preparation. In the fall the changed dis-
position may at once be seen to affect the central
leaves of the group. All the rosettes of the
whole race commence with opposite leaves;
those that are to produce straight stems remain
in this condition, but the preparation for twist-
ing begins at the end of the first year as shown
by a special arrangement of the leaves. This

Systematic Atavism 647

disposition may then be seen to extend to the
very center of the rosette, by use of microscop-
ical sections. Examining sections made in the
spring, the original arrangement of the leaves
of the stem is observed to continue until
the beginning of the growth of the shoot.
It is easy to estimate the number of leaves cor-
responding to a given number of spiral circuits
in these sections and the proportion is found to
indicate 13 leaves on 5 turns. These figures
are the same as those given above for the ordi-
nary arrangement of alternate leaves in the
main lines of the pedigree of the vegetable king-
dom.

Leaving aside for the moment the subsequent
changes of this spiral arrangement, it becomes
at once clear that here we have a case of sys-
tematic atavism. The twisted teasels lose their
decussation, but in doing so the leaves are not
left in a disorderly dispersion, but a distinct new
arrangement takes its place, which is to be
assumed as the normal one for the ancestors
of the teasel family. The case is to be consid-
ered as one of atavism. Obviously no
other explanation is possible, than the sup-
position that the 5-13 spiral is still latent,
though not displayed by the teasels. But in
the very moment when the faculty of decussa-
tion disappears, it resumes its place, and be-

648 Mutations

comes as prominent as it must once have been in
the ancestors, and is still in that part of their
offspring, which has not become changed in this
respect. Thus the proof of our assertion of
systematic atavism is, in this case, not obtained
by the inspection of the adult, but by the investi-
gation of the conditions in an early stage.
It remains to be explained how the twisting may
finally be caused by this incipient grouping of
the leaves. Before doing so, it may be as well
to state that the case of the teasel is not an iso-
lated one, and that the same conclusions are
supported by the valerian, and a large num-
ber of other examples. In early spring some
rosettes show a special condition of the
leaves, indicating thereby at once their atavism
and their tendency to become twisted as soon
as they begin to expand. The Sweet William
or DiantJius barbatus affords another instance;
it is very interesting because a twisted race
is available, which may produce thousands of
instances developed in all imaginable degrees,
in a single lot of plants. Viscaria oculata
is another instance belonging to the same fam-

iiy.

The bedstraw (Galium) also includes many
species which from time to time produce twist-
ed stems. I have found them myself in Holland
on Galium verum and G. Aparine. Both seem

Systematic Atavism 649

to be of rare occurrence, as I have not suc-
ceeded in getting any repetition by prolonged
culture.

Species, which generally bear their leaves in
whorls, are also subjected to casual atavisms of
this kind, as for instance the tall European
horsetail, Equisetum Telmateja, which occasion-
ally bears cones on its green summer stems.
Its whorls are changed on the twisted parts into
clearly visible spirals. The ironwood or Cas-
uarina quadrivalvis is sometimes observed to
produce the same anomaly on its smaller lateral
branches.

Coming now to the discussion of the way in
which the twisting is the result of the spiral dis-
position of the leaves, we may consider this ar-
rangement on stems in the adult state. These
at once show the spiral line and it is easy to fol-
low this line from the base up to the apex. In
the most marked cases it continues without in-
terruption, not rarely however, ending in a
whorl of three leaves and a subsequent straight
internode, of which there may even be two or
three. The spiral exhibits the basal parts of the
leaves, with the axillary lateral branches. The
direction of the screw is opposed to that of the
twisting, and the spiral ribs are seen to cross the
line of insertion of the leaves at nearly right
angles. On this line the leaves are nearer

650 Mutations

to one another than would correspond to the
original proportion of 5 turns for 13 leaves.
In fact, 10 or even 13 leaves may not rarely
be counted on a single turn. Or the twist
may become so strong locally as to change the
spiral into a longitudinal line. On this line
all inserted leaves extend themselves in the
same direction, resembling an extended flag.

The spiral on the stem is simply the continua-
tion of the spiral line from within the rosettes
of the first year. Accordingly it is seen to be-
come gradually less steep at the base. For this
reason it must be one and the same with this
line, and in extreme youth it must have pro-
duced its leaves at the same mutual distances as
this line. Transverse sections of the growing
summits of the stems support this conclusion.

From these several facts we may infer that
the steepness of the spiral line increases on the
stem, as it is gradually changed into a screw.
Originally 5 turns were needed for 13 leaves,
but this number diminishes and 4 or 3 or even 2
turns may take the same number of foliar
organs, until the screw itself is changed into a
straight line.

This change consists in an unwinding of the
whole spiral, and in order to effect this the stem
must become wound up in the opposite direc-
tion. The winding of the foliar screw must

Systematic Atavism 651

curve the longitudinal ribs. The straighter
and steeper the screw becomes, the more the
ribs will become twisted. That this happens in
the opposite direction is obvious, without fur-
ther discussion. The twisting is the inevitable
consequence of the reversal of the screw.

Two points remain to be dealt with. One is
the direct proof of the reversal of the screw, the
other the discussion of its cause. The first may
be observed by a simple experiment. Of course
it proceeds only slowly, but all that is necessary
is to mark the position of one of the younger
leaves of a growing stem of a twisting indi-
vidual and to observe the change in its posi-
tion in a few hours. It will be seen to have
turned some way around the stem, and finally
may be seen to make a complete revolution in
the direction opposite to the screw, and there-
by demonstrating the fact of its uncurling.

The cause of this phenomenon is to be sought
in the intimate connection of the basal parts of
the leaves, which we have detailed above. The
fibrovascular strands constitute a strong rope,
which is twisted around the stem along the
line on which the leaves are inserted. The
strengthening of the internodes may stretch this
rope to some extent, but it is too strong to be
rent asunder. Hence it opposes the normal
growth, and the only manner in which the inter-

652 Mutations

nodes may adjust themselves to the forces which
tend to cause their expansion is by straighten-
ing the rope. In doing so they may find the re-
quired space, by growing out in an unusual
direction, bending their axes and twisting the
ribs.

To prove the validity of this explanation, a
simple experiment may be given. If the fibro-
vascular rope is the mechanical impedimeni
which hinders the normal growth, we may tr^
the effect of cutting through this rope. By this
means the hindrance may at least locally
be removed. Now, of course, the operatior
must be made in an early stage before
or at the beginning of the period of growth
in every case before the uncurling of th(
rope begins. Wounds made at this time are ap1
to give rise to malformations, but notwithstand
ing this difficulty I have succeeded in giving th(
necessary proof. Stems operated upon become
straight where the rope is cut through, thougl
above and under the wounded part they go oi
twisting in the usual way.

Sometimes the plants themselves succeed ii
tearing the rope asunder, and long straight in
ternodes divide the twisted stems in two or mor(
parts in a very striking manner. A line of ton
leaf-bases connects the two parts of the serev
and gives testimony of what has passed withii

Systematic Atavism 653

the tissues. At other times the straightening
may have taken place directly internal to a leaf,
and it is torn and may be seen to be attached to
the stem by two distinct bases.

Summing up this description of the heredi-
tary qualities of our twisted teasels arid of their
mechanical consequences, we may say that the
loss of the normal decussation is the cause of all
the observed changes. This special adaptation,
which places the leaves in alternating pairs, re-
placed and concealed the old and universal ar-
rangement on a screw line. In disappearing, it
leaves the latter free, and according to the rule
of systematic atavism, this now becomes active
and takes its place. If the fibrovascular con-
nection of the leaf-bases were lost at the same
time the stems would grow and become straight
and tall. This change however, does not occur,
and the bases of the leaves now constitute a con-
tinuous rope instead of separate rings, and
thereby impede the stretching of the intemodes.
These in their turn avoid the difficulty by twist-
ing themselves in a direction opposite to that
of the spiral of the leaves.

As a last example of systematic atavism I will
refer to the reversionary changes, afforded by
the tomatoes. Though the culture of this plant
is a recent one, it seems to be at present in a
state of mutability, producing new strains, or

654 Mutations

assuming the features of their presumable an-
cestors. In his work ^ ^ The Survival of the Un-
like," Bailey has given a detailed description of
these various types. Moreover, he has closely
studied the causes of the changes, and shown
the great tendency of the tomatoes to vicinism.
By far the larger part of the observed cases of
running out of varieties are caused by acciden-
tal crosses through the agency of insects. Even
improvements are not rarely due to this cause.
Besides these common and often unavoidable
changes, others of greater importance occur
from time to time. Two of them deserve to be
mentioned. They are called the '* Upright " and
the '^ Mikado '^ types, and differ as much or
even more from their parents than the latter do
from any one of their wild congeners. Their
characters come true from seed. The *^ Mika-
do ' ' race or the Lycopersicum grandifolium (L.
latifolium) has larger and fewer leaflets than
the slender and somewhat flimsy foliage of the
common form. Flat or plane blades with de-
current margins constitute another character.
This variety, however, does not concern our
present discussion. The upright type has stiff
and self-sustaining stems and branches, resem-
bling rather a potato-plant than a tomato.
Hence the name Lycopersicum solanopsis or L,
validum, under which it is usually described.

Systematic Atavism 655

The foliage of the plant is so distinct as to yield
botanical characters of sufficient importance to
justify this specific designation. The leaflets
are reduced in numbers and greatly modi-
fied, and the flowers in the inflorescence are re-
duced to two or three. This curious race came
in suddenly, without any premonition, and the
locality and date of its mutation are still on
record. Until some years ago it had not made
its appearance for a second time. Obviously it
is to be considered as a reversionary form.
The limp stems of the common tomatoes are in
all respects indicative of the cultivated condi-
tion. They cannot hold themselves erect, but
must be tied up to supports. The color of
the leaves is a paler green than should be ex-
pected from a wild plant. Considering other
species of the genus Solaniim, of which the
Lycopersicum is a subdivision, the stems are as
a rule erect and self-supporting, with some few
exceptions. These, however, are special adapta-
tions as shown by the winding stems of the
bitter-sweet.

From this discussion we seem justified in con-
cluding that the original appearance of the up-
right type was of the nature of systematic
atavism. It differs however, from the already
detailed cases in that it is not a monstrosity, nor
an ever-sporting race, but is as constant a form

656 Mutations

as the best variety or species. Even on this
ground it must be considered as a representa-
tive of a separate group of instances of the uni-
versal rule of systematic reversions.

Of late the same mutation has occurred in the
garden of C. A. White at Washington. The
parent form in this case was the ^* Acme," of
the ordinary weak and spreading habit of
growth. It is known as one of the best and most
stable of the varieties and was grown by Mr.
White for many years, and had not given any
sign of a tendency towards change. Seeds
from some of the best plants in 1899 were sown
the following spring, and the young seedlings
unexpectedly exhibited a marked difference
from their parents. From the very outset they
were more strong and erect, more compact and
of a darker green than the ^^ Acme." When
they reached the fruiting stage they had devel-
oped into typical representatives of the Lyco-
persicum solanopsis or upright division. The
whole lot of plants comprised only some 30
specimens, and this number, of course, is too
small to base far-reaching conclusions upon.
But all of the lot showed this type, no
true ** Acme " being seen among them. The
fruit differed in flavor, consistencv and color
from that of the parent, and it also ripened
earlier than the latter. No seed was saved from

Systematic Atavism 657

these plants, but the following year the
'* Acme " was sown again and found true to its
type. Seeds saved from this generation in 1900
have, however, repeated the mutation, giving
rise to exactly the same new upright form in
1901. This was called by its originator ^^ The
Washington." Seeds from this second muta-
tion were kindly sent to me by Mr. White, and
proved true to their type when sown in my
garden. ,

Obviously it is to be assumed in the case of
the tomatoes as well as in instances from
other genera cited, that characters of an-
cestors, which are not displayed in their
progeny, have not been entirely lost, but are still
present, though in a latent condition. They
may resume their activity unexpectedly, and at
once develop all the features which they for-
merly had borne.

Latency, from this point of view, must be one
of the most common things in nature. All or-
ganisms are to be considered as internally
formed of a host of units, partly active and
partly inactive. Extremely minute and almost
inconceivably numerous, these units must have
their material representatives within the most
intimate parts of the cells.

Lecture XXIII

TAXONOMIC ANOMALIES

The theory of descent is founded mainly
on comparative studies, which have the ad-
vantage of affording a broad base and the
convincing effect of concurrent evidence
brought together from widely different sources.
The theory of mutation on the other hand rests
directly upon experimental investigations, and
facts concerning the actual descent of one form
from another are as yet exceedingly rare. It is
always difficult to estimate the validity of con-
clusions drawn from isolated instances selected
from the whole range of contingent phenomena,
and this is especially true of the present case.
Systematic and physiologic facts seem to indi-
cate the existence of universal laws, and it is not
probable that the process of production of new
species would be different in the various parts
of the animal and vegetable kingdoms. More-
over the principle of unit-characters, the pre-
eminent significance of which has come to be
more fully recognized of late, is in full harmony

658

Taxonomic Anomalies 659

with the theory of sudden mutations. Together
these two conceptions go to strengthen the prob-
ability of the sudden origin of all specific char-
acters.

Experimental researches are limited in their
extent, and the number of cases of direct obser-
vation of the process of mutation will probably
never become large enough to cover the whole
field of the theory of descent. Therefore it will
always be necessary to show that the similarity
between observed and other cases is such as to
lift above all doubt the assertion of their result-
ing from the same causes.

Besides the direct comparison of the muta-
tions described in our former lectures, with the
analogous cases of the horticultural and natural
production of species and varieties at large, an-
other way is open to obtain the required proof.
It is the study of the phenomena, designated by
Casimir de Candolle by the name of taxo-
nomic anomalies. It is the assertion that char-
acters, which are specific in one case, may be
observed to arise as anomalies or as varieties in
other instances. If they can be shown to be
identical or nearly so in both, it is obviously
allowable to assume the same origin for the
specific character and for the anomaly. In
other terms, the specific marks may be consid-
ered as having originated according to the laws

660 Mutations

that govern the production of anomalieSj and
we may assume them to lie within reach of our
experiments. The experimental treatment of
the origin of species may also be looked upon as
a method within our grasp.

The validity and the significance of these
considerations will at once become clear, if we
choose a definite example. The broadest and
most convincing one appears to me to be af-
forded by the cohesion of the petals in gamo-
petalous flowers. According to the current
views the families with the petals of their
flowers united are regarded as one or two main
branches of the whole pedigree of the vege-
table kingdom. Eichler and others assume
them to constitute one branch, and therefore one
large subdivision of the system. Bessey, on the
other hand, has shown the probability of a sep-
arate origin for those groups which have in-
ferior ovaries. Apart from such divergencies
the connation of the petals is universally recog-
nized as one of the most important systematic
characters.

How may this character have originated?
The heath-family or the Ericaceae and their
nearest allies are usually considered to be the
lowest of the gamopetalous plants. In them the
cohesion of the petals is still subject to rever-
sionary exceptions. Such cases of atavism may

Taxonomic Anomalies 661

be observed either as specific marks, or in the
way of anomalies. Ledum, Monotropa and Py-
rola, or the Labrador tea, the Indian pipe and
wintergreen are instances of reversionary
gamopetalism with free petals. In heaths
{Erica Tetralix) and in rhododendrons the
same deviation is observed to occur from time
to time as an anomaly, and even the common
Rhododendron ponticum of our gardens has a
variety in which the corolla is more or less
split. Sometimes it exhibits five free petals,
while at other times only one or two are entirely
free, the remaining four being incompletely
loosened.

Such cases of atavism make it probable that
the coherence of the petals has originally arisen
by the same method, but by action in the op-
posite direction. The direct proof of this con-
clusion is afforded by a curious observation,
made by Vilmorin upon the bright and large-
flowered garden-poppy, Papaver hracteatum.
Like all poppies it has four petals, which are
free from one another. In the fields of Messrs.
Vilmorin, where it is largely cultivated for its
seeds, individuals occur from time to time which
are anomalous in this respect. They exhibit a
tendency to produce connate petals. Their
flowers become monopetalous, and the whole
strain is designated by the name of Papaver

662 Mutations

hracteatum monopetalum. Henry de Vilmorin
had the kindness to send me some of these
plants, and they have flowered in my garden
during several years. The anomaly is highly
variable. Some flowers are quite normal, ex-
hibiting no sign of connation ; others are wholly
gamopetalous, the four petals being united from
their base to the YO^ry margin of the cup formed.
In consequence of the broadness of the petals
however, this cup is so wide as to be very
shallow.

Intermediate states occur, and not infre-
quently. Sometimes only two or three petals
are united, or the connation does not extend the
entire length of the petals. These cases are
quite analogous to the imperfect splitting of
the corolla of the rhododendron. Giving free
rein to our imagination, we may for a moment
assume the possibility of a new subdivision of
the vegetable kingdom, arising from Vilmorin 's
poppy and having gamopetalous flowers for its
chief character. If the character became fixed,
so as to lose its present state of variability,
such a group of supposititious gamopetalous
plants might be quite analogous to the corre-
sponding real gamopetalous families. Hence
there can be no objection to the view, that the
heaths have arisen in an analogous manner from
their polypetalous ancestors. Other species of

Taxonomic Anomalies 663

the same genus have also been recorded to pro-
duce gamopetalous flowers, as for instance,
Papaver hybridum, by Hoffmann. Poppies are
not the sole example of accidental gamopetaly.
Linnaeus observed the same deviation long ago
for Saponaria officinalis, and since, it has been
seen in Clematis Vitalha by Jaeger, in Peltaria
alliacea by Schimper, in Silene annulata by Bo-
reau and in other instances. No doubt it is not
at all of rare occurrence, and the origin of the
present gamopetalous families is to be consid-
ered as nothing extraordinary. It is, as a mat-
ter of fact, remarkable that it has not taken
place in more numerous instances, and the mal-
lows show that such opportunities have been
available at least more than once.

Other instances of taxonomic anomalies are
afforded by leaves. Many genera, the species of
which mainly bear pinnate or palmate leaves,
have stray types with undivided leaves.
Among the brambles, Rubus odoratus and
E. flexuosus may be cited, among the aralias,
Aralia crassifolia and A. papyrifera, and
among the jasmines, the deliciously scented
sambac {Jasminum Sambac), But the most
curious instance is that of the telegraph-plant,
or Desmodium gyrans, each complete leaf of
which consists of a large terminal leaflet and
two little lateral ones. These latter keep up,

^Q4. Mutations

night and day, an irregular jerking movement,
which has been compared to the movements of
a semaphore. Desmodium is a papiliona-
ceous plant and closely allied to the genus
Hedysarum, which has pinnate leaves with
numerous pairs of leaflets. Its place in the
system leaves no doubt concerning its origin
from pinnate-leaved ancestors. At the time of
its origination its leaves must have become re-
duced as to the number of the blades, while the
size of the terminal leaflet was correspondingly
increased.

It might seem difficult to imagine this great
change taking place suddenly. However, we are
compelled to familiarize ourselves with such hy-
pothetical assumptions. Strange as they may
seem to those who are accustomed to the concep-
tion of continuous slow improvements, they are
nevertheless in complete agreement with what
really occurs. Fortunately the direct proof of
this assertion can be given, and in a case
which is narrowly related, and quite parallel to
that of the Des^nodiitm, since it affects a plant
of the same family. It is the case of the
monophyllous variety of the bastard-acacia or
Robinia Pseud-Acacia. In a previous lecture
we have seen that it originated suddenly in a
French nursery in the year 1855. It can be
propagated by seed, and exhibits a curious de-

Taxonomic Anomalies 665

gree of variability of its leaves. In some in-
stances these are one-bladed, the blade reaching
a length of 15 cm., and hardly resembling those
of the common bastard-acacia. Other leaves
produce one or two small leaflets at the base of
the large terminal one, and by this contrivance
are seen to be very similar to those of the Des-
modium, repeating its chief characters nearly
exactly, and only differing somewhat in the rela-
tive size of the various parts. Lastly real in-
termediates are seen between the monophyllous
and the pinnate types. As far as I have been
able to ascertain, these are produced on weak
twigs under unfavorable conditions; the
size of the terminal leaflet decreases and the
number of the lateral blades increases, showing
thereby the presence of the original pinnate
type in a latent condition.

The sudden origin of this ** one-leaved "
acacia in a nursery may be taken as a prototype
of the ancient origin of Desmodium. Of
course the comparison only relates to a single
character, and the movements of the leaflets are
not affected by it. But the monophylly, or rath-
er the size of the terminal blade and the reduc-
tion of the lateral ones, may be held to be suf-
ficiently illustrated by the bastard-acacia. It
is worth while to state, that analogous varieties
have also arisen in other genera. The *' one-

666 Mutations

leaved ^' strawberry has already been referred
to. It originated from the ordinary type in
Norway and at Paris. The walnut likewise, has
its monophyllous variety. It was mentioned
for the first time as a cultivated tree about 1864,
but its origin is unknown. A similar variety of
the walnut, with '^ one-bladed " leaves but of
varying shapes, was found wild in a forest near
Dieppe in France some years ago, and appeared
to be due to a sudden mutation.

Something more is known concerning the
** one-bladed " ashes, varieties of which are
often seen in our parks and gardens. The com-
mon form has broad and deeply serrate leaves,
which are far more rounded than the leaflets of
the ordinary ash. The majority of the leaves
are simple, but some produce one or two smaller
leaflets at their base, closely corresponding in
this respect to the variations of the '' one-
bladed " bastard-acacia, and evidently indicat-
ing the same latent and atavistic character. In
some instances this analogy goes still further,
and incompletely pinnate leaves are produced
with two or more pairs of leaflets. Besides
this variable type another has been described
by Willdenow. It has single leaves exclusive-
ly, never producing smaller lateral leaflets,
and it is said to be absolutely constant
from seed, while the more variable types

Taxonomic Anomalies 667

seem to be also more inconstant when propa-
gated sexually. The difference is so striking
and affords such a reliable feature that Koch
proposed to make two distinct varieties of them,
calling the pure type Fraxinus excelsior mono-
phylla, and the varying trees F. excel, exhetero-
phylla. Some writers, and among them Will-
denow, have preferred to separate the " one-
leaved '^ forms from the species, and to call
them Fraxinus simplicifolia.

According to Smith and to Loudon, the ^ ^ one-
leaved " ashes are found wild in different dis-
tricts in England. Intermediate forms have not
been recorded from these localities. This
mode of origin is that already detailed for the
laciniate varieties of alders and so many other
trees. Hence it may be assumed that the '^ one-
leaved " ashes have sprung suddenly but fre-
quently from the original pinnate species. The
pure type of Willdenow should, in this case,
be considered as due to a slightly different
mutation, perhaps as a pure retrograde variety,
while the varying strains may only be ever-
sporting forms. This would likewise explain
part of their observed inconstancy.

In this respect the historic dates, as collected
by Korshinsky, are not very convincing. Vi-
cinism has of course, almost never been exclud-
ed, and part of the multiformity of the offspring

668 Mutations

must obviously be due to this most universal
agency. Indirect vicinism also plays some part,
and probably affords the explanation of some
reputed mutative productions of the variety.
So, for instance, in the case of Sinning, who aft-
er sowing the seeds of the common ash, got as
large a proportion as 2^' of monophyllous trees
in a culture of some thousand plants. It is
probable that his seeds were taken partly from
normal plants, and partly from hybrids between
the normal and the '' one-bladed " ijve, assum-
ing that these hybrids have pinnate leaves like
their specific parent, and bear the characters of
the other parent only in a latent condition.

Our third example relates to peltate leaves.
They have the stalk inserted in the middle of
the blade, a contrivance produced by the conna-
tion of the two basal lobes. The water-lilies
are a well known instance, exhibiting sagit-
tate leaves in the juvenile stage and changing
in many species, into nearly circular pel-
tate forms, of which Victoria regia is a very
good example, although its younger stages do
not always excite all the interest they deserve.
The Indian cress (Tropaeolmn), the marsh-
pennywort or Hydrocotyle, and many other in-
stances could be quoted. Sometimes the peltate
leaves are not at all orbicular, but are elon-
gated, oblong or elliptic, and with only the lobes

Taxonomic Anomalies 669

at the base united. The lemon-scented Eucor
lyptus citriodora is one of the most widely
known cases. In other instances the peltate
leaves become more or less hollow, constituting
broad ascidia as in the case of the crassulaceous
genus Umbilicus.

This connation of the basal lobes is universal-
ly considered as a good and normal specific
character. Nevertheless it has its manifest
analogy in the realm of the anomalies. This is
the pitcher or ascidiiim. On some trees it is of
quite common occurrence, as on the lime-tree
{Tilia parvifolia) and the magnolia {Magnolia
obovata and its hybrids). It is probable that
both these forms have varieties with, and others
without, ascidia. Of the lime-tree, instances are
known of single trees which produce hundreds
of such anomalous leaves yearly, and one such a
tree is growing in the neighborhood of Amster-
dam at Lage Vuursche. I have alluded to these
cases more than once, but on this occasion a
closer inspection of the structure of the ascidium
is required. For this purpose we may take the
lime-tree as an example. Take the shape of the
normal leaves in the first place. These are cor-
date at their base and mainly inequilateral, but
the general shape varies to a considerable ex-
tent. This variation is closely related to the
position of the leaves on the twigs, and shows

670 Mutations

distinct indications of complying with the gen-
eral law of periodicity. The first leaves are
smaller, with more rounded lobes, the subse-
quent leaves attain a larger size, and their lobes
slightly change their forms. In the first leaves
the lobes are so broad as to touch one another
along a large part of their margins, but in or-
gans formed later this contact gradually dimin-
ishes and the typical leaves have the lobes wide-
ly separated. Now it is easily understood that
the contact or the separation of the lobes must
play a part in the construction of the ascidia,
as soon as the margins grow together. Leaves
which touch one another, may be affected by
the connation without any further malforma-
tion. They remain flat, become peltate and ex-
hibit a shape which in some way holds a mid-
dle position between the pennyworts and the
lemon-scented eucalyptus. Here we have
the repetition of the specific characters of these
plants by the anomaly of another. Whenever
the margins are not in contact, and become con-
nate, notwithstanding their separation, the blade
must be folded together in some slight degree,
in order to produce the required contact. This
is the origin of the ascidium. It is quite super-
fluous to insist upon the fact that their width
or narrowness must depend upon the corre-
sponding normal form. The more distant the

Taxonomic Anomalies 671

lobes, the deeper the ascidium will become. It
should be added that this explanation of the dif-
ferent shapes of ascidia is of general validity.

Ascidia of the snake-plantain or Plantago
lanceolata are narrow tubes, because the leaves
are oblong or lanceolate, while those of the
broad leaved species of arrowhead, as for in-
stance, the Sagittaria japonica, are of a conical
shape.

From the evidence of the lime-tree we may
conclude that normal peltate leaves may have
originated in the same way. And from the fact
that pitchers are one of the most frequent
anomalies, we may conclude that the chance of
producing peltate leaves must have been a very
great one, and wholly sufficient to account for
all observed cases. In every instance the pre-
viously existing shape of the leaf must have de-
cided whether peltate or pitcher-like leaves
would be formed. As far as we can judge pel-
tate anomalies are quite uninjurious, while as-
cidia are forms which must impede the effect of
the light on the leaf, as they conceal quite an
important part of the upper surface. In this
way it is easily conceivable that peltate leaves
are a frequent specific character, while ascidia
are not, as they only appear in the special cases
of limited adaptation, as in the instances of the
so called pitcher-plants. The genera Nepenthes,

672 Mutations

Sarracenia and some others are very well
known and perhaps even the bladderworts or
Utricularia might be included here.

The reproduction of specific characters by
anomalous ascidia is not at all limited to the
general case as described above. More minute
details may be seen to be duplicated in the same
way. Proofs are afforded on one side by in-
complete ascidia, and on the other by the double
cups.

Incomplete ascidia are those of the Nepenthes.
The leaf is divided into three parts, a blade, a
tendril and the pitcher. Or in other words, the
limb produces a tendril at its summit, by means
of which the plant is enabled to fasten itself to
surrounding shrubs and to climb between their
branches. But the end of this tendril bears a
well-formed urn, which however, is produced
only after the revolving and grasping move-
ments of the tendril have been made. Some
species have more rounded and some more
elongated ascidia and often the shape is seen to
change with the development of the stem. The
mouth of the urn is strengthened by a thick rim
and covered with a lid. Numerous curious con-
trivances in these structures to catch ants and
other insects have been described, but as they
have no relation to our present discussion, we
shall abstain from dealing with them.

Taxonomic Anomalies 673

Likewise we must refrain from a consid-
eration of the physiologic qualities of the ten-
dril, and confine our attention to the combina-
tion of a limb, a naked midvein and an ascidium.
This combination is to be the basis of our dis-
cussion. It is liable to be produced all of a sud-
den. This assertion is proved by its occurrence
as a varietal mark in one of our most ordinary
cultivated plants. It is the group known as
Croton, belonging to the genus Codiaeum,
A variety is called interruptum and another ap-
pendiculatiim^ and these names both relate to
the interruption of the leaves by a naked mid-
vein. The leaves are seen to be built up of three
parts. The lower half retains the aspect of a
limb; it is crowned by a vein without lateral
nerves or blade-like expansions, and this stalk
in its turn bears a short limb on its summit. The
base of this apical limb exhibits two connate
lobes, forming together a wide cup or ascidium.
It should be stated that these interruptum varie-
ties are highly variable, especially in the rela-
tive size of the three principal parts of the leaf.
Though it is of course conceded that the ascidium
of Nepenthes has many secondary devices
which are lacking in Croton, it seems hardly al-
lowable to deny the possibility of an analogous
origin for both. Those of the Croton, according
to our knowledge regarding similar cases, must

674 Mutations

have arisen at once, and hence the conclusion
that the ascidia of Nepenthes are also originally
due to a sudden mutation. Interrupted leaves,
with an ascidium on a naked prolongation of the
midvein, are by no means limited to the Croton
varieties. As stray anomalies they have often
been observed, and I myself had the oppor-
tunity of collecting them on magnolia, on clover
and on some other species. They are additional
evidence in support of the explanation given
above.

In the same way double ascidia may be made
use of to explain the foliar cups of the teasels
and some other plants, as for instance, some
European snakeroots {Eryngium maritimum
and E. campestre), or the floral leaves of the
honeysuckle. The leaves on the stems of the
teasels are disposed in pairs, and the bases of
the two leaves of each pair are connate so as
to constitute large cups. We have already men-
tioned these cups, and recall them in the present
connection to use them as a prototype of the
double ascidia. These are constituted of two op-
posite leaves, accidentally connated at their base
or along some part of their margins. If the
leaves are sessile, the analogy with the teasels
is complete, as shown, for instance, in a case
of Cotyledon, a crassulaceous plant which is

Taxonomic Anomalies 675

known to produce such cups from time to time.
They are narrower than those of the teasel, but
this depends, as we have seen for the *' one-
leaved '' ascidium, on the shape of the original
leaf. In other respects they exactly imitate the
teasel cups, showing thereby how these cups
may probably have originated.

In numerous cases of anomalies some acci-
dental structures are parallel to specific char-
acters, while others are not, being obviously in-
jurious to their bearers. So it is also with the
double ascidia. In the case of stalked leaves
the two opposite stalks must, of course, consti-
tute a long and very narrow tube, when growing
together. This tube must bear at its summit
the conical ascidium produced by the two con-
nate limbs. At its base however, it includes the
terminal bud of the stem, and frequently the
tube is so narrow as to impede its further de-
velopment. By this contrivance the double as-
cidium assumes a terminal position. Instances
have been observed on magnolia, in Boehmeria
and in other cases.

Flowers on leaves are of rare occurrence.
Notwithstanding this, they constitute specific
characters in some instances, accidental anoma-
lies in others. Helwingia rusciflora is the most
curious and best known instance. It is a
little shrub, belonging to the Cornaceae, and

676 Mutations

has broad elliptical undivided leaves. On
the middle of the midvein these leaves are seen
to bear small clusters of flowers; indeed this
is the only place where flowers are produced.
Each cluster has from 13 - 15 flowers, of which
some are staminate and borne on stalks, while
others are pistillate and nearly sessile. These
flowers are small and of a pale greenish color
and yield small stone-fruits, with a thin
coating of pulpy tissue. As the name indicates,
this mode of flowering is closely similar to that
of Ruscus, which however, does not bear its
flowers and berries on real leaves, but on leaf-
like expansions of the twigs. Phyllonoma nis-
cifolia, a saxifragaceous plant, bears the same
specific name, indicating a similar origin of the
flowers. Other instances have been collected by
Casimir de Candolle, but their number is very

small.

As a varietal mark, flowers on leaves like-
wise rarely occur. One instance however, is
very remarkable, and we have already dealt
with it, when treating of constant varieties, and
of the lack of vicinism in the case of species
with exclusive self-fertilization.

It is the '' Nepaul-barley " or Hordeum tri-
furcatum. The leaves, which in this case bear
the adventitious flowers, are the inner scales of
the spikelets, and not on green leaves as in the

Taxonomic Anomalies 677

cases already alluded to. But this of course
makes no real difference. The character is
variable to a high degree, and this fact indicates
its varietal nature, though it should be recalled
that at least with the Hehvingia, the majority of
the leaves are destitute of flowers, and that in
this way some degree of variability is present
in this normal case too.

All in all there are three sorts of ^' Nepaul-
barley.'' They have the same varietal mark,
but belong to different species of barley. These
are differentiated according to the number of
the rows in which the grains are seen on the
spikes. These numbers may be two, four or six,
giving rise to the specific names of Hordeum dis-
tichum, tetrastichum and hexastichum. Whether
these three varieties are of independent, but
parallel origin, or are to be considered as due to
a single mutation and subsequent crosses is not
known, all of them being of ancient origin.
Historic evidence concerning their birth is
wholly wanting. From analogy it would seem
probable that the character had arisen by a mu-
tation in one of the three named species, and
had been transferred to others by means of ac-
cidental crosses, even as it has been artificially
transmitted of late to quite a number of other
sorts. But however admissible this conception
may seem, there is of course no real objection

678 Mutations

to the assumption of independent and parallel
mutations.

For the purpose of a comparison with the
Helivingia type we are however, not at all con-
cerned with the species to which the trifurca-
tum variety belongs, but only with the varietal
mark itself. The spikelets may be one-, two- or
three-flowered, according to the species. If we
choose for further consideration the hexasti-
chum type, each spikelet produces three nor-
mal flowers and afterwards three normal grains.
Morphologically however, the spikelet is not
homologous to those parts of other grasses
which have the same name. It is constituted of
three real spikelets, and thus deserves the name
of a triple construction. Each of these three
little organs has its normal pair of outer scales
or glumae. These are linear and short, ending
in a long and narrow spine. Those of the mid-
dle-most spikelets stand on its outer side, while
those of the lateral part are placed transversely.
In this way they form a kind of involucre
around the central parts. The latter consist
of the inner and outer palets or scales, each two
of which include one of the flowers. The outer
palet is to be considered as the metamorphosed
leaf, in the axil of which the flower is produced.
In the common sorts of barley it bears a long
awn, giving thereby its typical aspect to the

Taxonomic Anomalies 679

whole spike. The axillary flower is protected on
the opposite side by a two-keeled inner palet.
Each flower exhibits three stamens and an
ovary. In the six-rowed barley all the three
flowers of a triple spikelet are fertile, and each
of them has a long awn on the top of the outer
palet. But in the two-rowed species only the
middle-most flower is normal and has an awn,
the two remaining being sterile and more or less
rudimentary and with only very short awns.
From this description it is easily seen that the
species of barley may be distinguished from one
another, even at a casual glance, by the number
of the rows of the awns, and therefore by the
shape of the entire spikes. This striking fea-
ture, however, does not exist in the ^^ Nepaul-
barley." The awns are replaced by curiously
shaped appendices, which are three-lobed. The
central lobe is oblong and hollow, and forms a
kind of hood, which covers a small supernumer-
ary floret. The two lateral lobes are narrower,
often linear and extended into a smaller or
longer awn. These awns are mostly turned
away from the center of the spike. The central
lobe may sometimes bear two small florets, but
ordinarily only one is to be found, and this is
often incomplete, having only one or two
stamens, or is different in some other way.

680 Mutations

These narrow lateral lobes heighten the abnor-
mal aspect of the whole spike.

They are only produced at a somewhat ad-
vanced stage of the development of the palet,
are united to one another and to the central
part by strong veins, which form transversal
anastomoses at their insertion. The length of
these awns is very variable, and this quality is
perhaps the most striking of the whole variety.
Often they reach only 1-2 mm., or the major-
ity may become longer and attain even 1 cm.,
while here and there, between them, longer ones
are inserted, extending in some instances even
as far as 3 cm. from the spike. Their trans-
verse position in such cases is strikingly con-
trasted with the ordinary erect type of the
awns.

These lateral lobes are to be regarded, from
the morphologic point of view, as differentiated
parts of the blade of the leaf. Before they are
formed, or coincidently with the beginning of
their development, the summit of the central
lobe becomes hollow, and the development of
the supernumerary flower commences. In dif-
ferent varieties, and especially in the most re-
cent crosses of them, this development is ex-
cessively variable.

The accidental flower arises at some distance
beneath the summit of the scale, on its middle

Taxonomic Anomalies 681

vein. The development begins with the protru-
sion of a little scale, and the flower itself is
situated beneath this scale, and is to be pro-
tected by it and by the primary scale, but is
turned upside down at the same time. Op-
posite to this organ, which represents the outer
palet of the adventitious flower, two little swol-
len bodies are evolved. In the normal flowers
of barley and other grains and grasses their
function is to open the flowers by swelling, and
afterwards collapse and allow them to close.

In the adventitious flowers of the '^ Nepaul-
barley,'' however, this function is quite super-
fluous. The stamens occur in varying numbers ;
typically there are three, but not rarely
less, or more, are seen. In some instances the
complete double whorl of six, corresponding to
the ancestral monocotyledonous type, has been
found. This is a very curious case of sys-
tematic atavism, quite analogous to the Iris
pallida ahavia, previously alluded to, which
likewise has six stamens, and to the cases given
in a previous lecture. But for our present dis-
cussion it is of no further interest. The ovary
is situated in the middle of the flower, and in
some instances two have been observed. This
is also to be considered as a case of atavism.

All these parts of the adventitious flower are
more or less subject to arrest of development

682 Mutations

in a later stage. They may even sometimes be-
come abnormal. Stamens may unite into pairs,
or carpels bear four stigmas. The pollen-sacs
are as a rule barren, the mother-cells under-
going atrophy, while normal grains are seen but
rarely. Likewise the ovaries are rudimentary,
but Wittmack has observed the occasional
production of ripe grains from these abnormal
florets.

The scale is seldom seen to extend any far-
ther upwards than the supernumerary flower.
But in the rare instances where it does pro-
long its growth, it may repeat the abnormality
and bear a second floret above the first. This of
course is generally much weaker, and more rudi-
mentary.

Raciborsky, who has lately given a full and
very accurate description of this anomaly, lays
great stress upon the fact that it is quite use-
less. It is perhaps the most obviously useless
structure in the whole vegetable kingdom. Not-
withstanding this, it has come to be as complete-
ly hereditary as any of the most beautiful adap-
tations in nature. Therefore it is one of the
most serious objections to the hypothesis of
slow and gradual improvements on the sole
ground of their usefulness. The struggle for
life and natural selection are manifestly in-
adequate to give even the slightest indication of

Taxonomic Anomalies 683

an explanation of this case. It is simply im-
possible to imagine the causes that might have
produced such a character. The only way out
of this difficulty is to assume that it has arisen
at once, in its present apparently differentiated
and very variable condition, and that, being
quite uninjurious and since it does not decrease
the fertility of the race, it has never been
subjected to natural selection, and so has saved
itself from destruction.

But if we once grant the probability of the
origin of the ' ' Nepaul-barley " by a sudden mu-
tation, we obviously must assume the same in
the case of the Helwingia and other normal in-
stances. In this way we gain a further support
for our assertion, that even the strangest
specific characters may have arisen suddenly.

After having detailed at some length those
proofs which seem to be the most striking, and
which had not been previously described with
sufficient detail, we may now take a hasty survey
of other contingent cases. In the first place the
cruciate flowers of some onagraceous plants
should be remembered. Small linear petals oc-
cur as a specific character in Oenothera cru-
ciata of the Adirondacks, but have been seen to
arise as sudden mutations in the common even-
ing-primrose (0. biennis) in Holland, and in the
willow-herb (Epilobium hirsutum) in England.

684

Mutations'

Leaves placed in whorls of three are very rare.
The oleander, jumper and some few other
plants have ternate whorls as a specific char-
acter. As an anomaly, ternate whorls are far
more common, and perhaps any plant with op-
posite leaves may from time to time produce
them. Races rich in this abnormality are
found in the wild state in the yellow loose-
strife or Lysimachia vulgaris, in which it is
a very variable specific character, the whorls
varying from two to four leaves. In the
cultivated state it is met with in the myrtle
or Myrtus communis, where it has come to be
of some importance in Israelitic ritual. Crisped
leaves are known in a mallow, Malva crispa, and
as a variety in cabbages, parsley, lettuce and
others. The orbicular fruits of Heeger's shep-
herd's purse (Capsella heegeri) recall similar
fruits of other cruciferous genera, as for in-
stance, Camelina. Screw-like stems with wide
spirals are specific in the flower-stalks of
Cyclamen and Vallisneria, varietal in Juncus
effusus spiralis and accidental in Scirpns lacus-
tris. Dormant buds or small bulbs in inflo-
rescences are normal for wild onions. Polygo-
num viviparum and others, varietal in Poa
alpina vivipara and perhaps in Agave vivi-
para, and accidental in plantains {Plant ago
lanceolata), Saxifraga umbrosa and others.

Taxonomic Anomalies 685

Cleft leaves, one of the most general anomalies,
are typical in Boehmeria hiloha. The adnation
of the peduncles of the inflorescences to the
stem is typical in Solanum and accidental in
many other cases.

It seems quite superfluous to add further
proof. It is a very general phenomenon that
specific characters occur in other genera as
anomalies, and under such circumstances that
the idea of a slow evolution on the ground of
utility is absolutely excluded. No other ex-
planation remains than that of a sudden muta-
tion, and once granted for the abnormal cases,
this explanation must obviously likewise be
granted for the analogous specific characters.

Our whole discussion shows that mutations,
once observed in definite instances, afford the
most probable basis for the explanation of spe-
cific characters at large.

Lectuke XXIV

THE HYPOTHESIS OF PERIODIC MUTATIONS

The prevailing belief that slow and gradual,
nearly invisible changes constitute the process
of evolution in the animal and vegetable king-
dom, did not offer a strong stimulus for experi-
mental research. No appreciable response to
any external agency was of course to be ex-
pected. Responses were supposed to be pro-
duced, but the corresponding outward changes
would be too small to betray themselves to the
investigator.

The direct observation of the mutations of
the evening-primrose has changed the whole
aspect of the problem at once. It is no longer
a matter dealing with purely hypothetical con-
ditions. Instead of the vague notions, uncer-
tain hopes, and a priori conceptions, that have
hitherto confused the investigator, methods of
observation have been formulated, suitable for
the attainment of definite results, the general
nature of which is already known.

To my mind the real value of the discovery

686

Periodic Mutations 687

of the mutability of the evening-primrose lies
in its usefulness as a guide for further work.
The view that it might be an isolated case, lying
outside of the usual procedure of nature, can
liardly be sustained. On such a supposition it
would be far too rare to be disclosed by the
investigation of a small number of plants from
a limited area. Its appearance within the lim-
ited field of inquiry of a single man would have
been almost a miracle.

The assumption seems justified that analo-
gous cases will be met with, perhaps even in
larger numbers, when similar methods of ob-
servation are used in the investigation of plants
of other regions. The mutable condition may <not
be predicated of the evening-primroses alone.
It must be a universal phenomenon, although
affecting a small proportion of the inhabitants
of any region at one time: perhaps not more
than one in a hundred species, or perhaps not
more than one in a thousand, or even fewer may
be expected to exhibit it. The exact proportion
is immaterial, because the number of mutable
instances among the many thousands of species
in existence must be far too large for all of
them to be submitted to close scrutiny.

It is evident from the above discussion that
next in importance to the discovery of the pro-
totype of mutation is the formulation of meth-

688 Mutations

ods for bringing additional instances to light.
These methods may direct effort toward two dif-
ferent modes of investigation. We may search
for mutable plants in nature, or we may hope
to induce species to become mutable by artificial
methods. The first promises to yield results
most quickly, but the scope of the second is
much greater and it may yield results of far
more importance. Indeed, if it should once be-
come possible to bring plants to mutate at our
will and perhaps even in arbitrarily chosen di-
rections, there is no limit to the power we may
finally hope to gain over nature.

What is to guide us in this new line of work?
Is it the minute inspection of the features of the
process in the case of the evening-primroses?
Or are we to base our hopes and our methods on
broader conceptions of nature 's laws ? Is it the
systematic study of species and varieties, and
the biologic inquiry into their real hereditary
units? Or is the theory of descent to be our
starting-point? Are we to rest our conceptions
on the experience of the breeder, or is perhaps
the geologic pedigree of all organic life to open
to us better prospects of success?

The answer to all such questions is a very
simple one. All possibilities must be considered,
and no line of investigation ignored. For my-
self I have based my field-researches and my

Periodic Mutations 689

testing of native plants on the hypothesis of
unit-characters as deduced from Darwin's
Pangenesis. This conception led to the expec-
tation of two different kinds of variability, one
slow and one sudden. The sudden ones known
at the time were considered as sports, and
seemed limited to retrograde changes, or to
cases of minor importance. The idea that
sudden steps might be taken as the principal
method of evolution could be derived from the
hypothesis of unit-characters, but the evidence
might be too remote for a starting point for ex-
perimental investigation.

The success of my test has given proof to the
contrary. Hence the assertion that no evidence
is to be considered as inadequate for the pur-
pose under discussion. Sometime a method of
discovering, or of producing, mutable plants
may be found, but until this is done, all facts of
whatever nature or direction must be made use
of. A very slight indication may change for-
ever the whole aspect of the problem.

The probabilities are now greatly in favor of
our finding out the causes of evolution by
a close scrutiny of what really happens in na-
ture. A persistent study of the physiologic
factors of this evolution is the chief condition
of success. To this study field-observations
may contribute as well as direct experiments.

690 Mutations

microscopical investigations as well as extended
pedigree-cultures. The cooperation of many
workers is required to cover the field. Some-
where no doubt the desired principle lies hid-
den, but until it is discovered, all methods must
be tried.

With this conception as the best starting-
point for further investigation, we may now
make a brief survey of the other phase of the
problem. We shall try to connect our observa-
tions on the evening-primroses with the theory
of descent at large.

We start with two main facts. One is the
mutability of Lamarck's primrose, and the sec-
ond is the immutable condition of quite a num-
ber of other species. Among them are some
of its near allies, the common and the small-
flowered evening-primrose, or Oenothera bien-
nis and 0. muricata.

From these facts, a very important question
arises in connection with the theory of descent.
Is the mutability of our evening-primroses tem-
porary, or is it a permanent condition? A dis-
cussion of this problem will give us the means of
reaching a definite idea as to the scope of our
inquiries.

Let us consider the present first. If mutabil-
ity is a permanent condition, it has of course no
bednninsr, and moreover is not due to the

Periodic Mutations 691

agency of external circumstances. Should this
be granted for the evening-primrose, it would
have to be predicated for other species found in
a mutable state. Then, of course, it would be
useless to investigate the causes of mutability
at large, and we should have to limit ourselves
to the testing of large numbers of plants in
order to ascertain which are mutable and
which not.

If, on the other hand, mutability is not a per-
manent feature, it must once have had a begin-
ning, and this beginning itself must have had an
external cause. The amount of mutability and its
possible directions may be assumed to be due to
internal causes. The determination of the mo-
ment at which they will become active can never
be the result of internal causes. It must be as-
signed to some external factor, and as soon as
this is discovered the way for experimental in-
vestigation is open.

In the second place we must consider the past.
On the supposition of permanency all the ances-
tors of the evening-primrose must have been
mutable. By the alternative view mutability
must have been a periodic phenomenon, produc-
ing at times new qualities, and at other times
leaving the plants unchanged during long suc-
cessions of generations. The present mutable
state must then have been preceded by an im-

692 Mutations

mutable condition, but of course thousands of
mutations must have been required to produce
the evening-primroses from their most remote
ancestors.

If we take the species into consideration
that are not mutable at present, we may ask
how we are to harmonize them with each of
the two theories proposed. If mutability is
permanent, it is manifest that the whole pedi-
gree of the animal and vegetable kingdom is to
be considered as built up of main mutable lines,
and. that the thousands of constant species can
only be taken to represent lateral branches of
the genealogic tree.

These lateral branches would have lost the
capacity of mutating, possessed by all their an-
cestors. And as the principle of the hypothesis
under discussion does not allow a resumption of
this habit, they would be doomed to eternal con-
stancy until they finally die out. Loss of muta-
bility, under this conception, means loss of the
capacity for all further development. Only
those lines of the main pedigree which have
retained this capacity would have a future ; all
others would die out without any chance of pro-
gression.

If, on the other hand, mutability is not perma-
nent, but a periodic condition, all lines of the
genealogic tree must be assumed to show alter-

Periodic Mutations 693

natively mutating and constant species. Some
lines may be mutating at the present moment;
others may momentarily be constant. The mu-
tating lines will probably sooner or later revert
to the inactive state, while the powers of de-
velopment now dormant may then become awak-
ened on other branches.

The view of permanency represents life as
being surrounded with unavoidable death, the
principle of periodicity, on the contrary, fol-
lows the idea of resurrection, granting the
possibility of future progression for all living
beings. At the same time it yields a more hope-
ful prospect for experimental inquiry.

Experience must decide between the two main
theories. It demonstrates the existence of poly-
morphous genera, such as Draba and Viola and
hundreds of others. They clearly indicate a
previous state of mutability. Their systematic
relation is exactly what would be expected, if
they were the result of such a period. Perhaps
mutability has not wholly ceased in them, but
might be found to survive in some of their mem-
bers. Such very rich genera however, are not
the rule, but are exceptional cases, indicating
the rarity of powerful mutative changes.

On the other hand, species may remain in a
state of constancy during long, apparently dur-
ing indefinite, ages.

694

Mutations

Many facts plead in favor of the constancy
of species. This principle has always been
recognized by systematists. Temporarily the
current form of the theory of natural selec-
tion has assumed species to be inconstant, ever
changing and continuously being improved and
adapted to the requirements of the life-condi-
tions. The followers of the theory of descent
believed that this conclusion was unavoidable,
and were induced to deny the manifest fact that
species are constant entities. The mutation
theory gives a clew to the final combination of
the two contending ideas. Reducing the change-
ability of the species to distinct and probably
short periods, it at once explains how the
stability of species perfectly agrees with the
principle of descent through modification.

On the other hand, the hypothesis of mutative
periods is by no means irreconcilable with the
observed facts of constancy. Such casual
changes can be proved by observations such as
those upon the evening-primrose, but it is ob-
vious that a disproof can never be given. The
principle grants the present constancy of the
vast majority of living forms, and only claims
the exceptional occurrence of definite changes.

Proofs of the constancy of species have been
given in different ways. The high degree of
similarity of the individuals of most of our

Periodic Mutations 695

species has never been denied. It is observed
throughout extended localities, and during long
series of years. Other proofs are afforded by
those plants which have been transported to dis-
tant localities some time since, but do not ex-
hibit any change as a result of this migration.
Widely dispersed plants remain the same
throughout their range, provided that they be-
long to a single elementary species. Many
species have been introduced from America into
Europe and have spread rapidly and widely.
The Canadian horsetail {Erigeron canadensis) ,
the evening-primrose and many other instances
could be given. They have not developed any
special European features after their introduc-
tion. Though exposed to other environmental
conditions and to competition with other spe-
cies, they have not succeeded in developing
a new character. Such species as proved ade-
quate to the new environment have succeeded,
while those which did not have succumbed.

Much farther back is the separation of the
species which now live both in arctic regions
and on the summits of our highest mountain-
tops. If we compare the alpine flora with the
arctic plants, a high degree of similarity at once
strikes us. Some forms are quite identical;
others are slightly different, manifestly repre-
senting elementary species of the same sys-

696 Mutations

tematic type. Still others are more distant or
even belong to different genera. The latter,
and even the diverging, though nearly allied,
elementary species, do not yield adequate evi-
dence in any direction.

They may as well have lived together in
the long ages before the separation of the now
widely distant floras, or have sprung from a
common ancestor living at that time, and subse-
quently have changed their habits. After ex-
cluding these unreliable instances, a good num-
ber of species remain, which are quite the same
in the arctic and alpine regions and on the sum-
mits of distant mountain-ranges. As no trans-
portation over such large distances can have
brought them from one locality to the other, no
other explanation is left than that they have
been wholly constant and unchanged ever since
the glacial period which separated them. Ob-
viously they must have been subjected to widely
changing conditions. The fact of their stability
through all these outward changes is the best
proof that the ordinary external conditions do
not necessarily have an influence on specific evo-
lution. They may have such a result in some
instances, in others they obviously have not.
Many arctic forms bearing the specific name of
alpinus justify this conclusion. Astragalus al-
pinus, Phleum alpinum, Hieracium alpinum and

Periodic Mutatio.ns 697

others from the northern parts of Norway may
be cited as examples.

Thus Primula imperialis has been found
in the Himalayas, and many other plants of the
high mountains of Java, Ceylon and north-
ern India are identical forms. Some species
from the Cameroons and from Abyssinia have
been found on the mountains of Madagascar.
Some peculiar Australian types are represented
on the summit of Kini Balu in Borneo. None of
these species, of course, are found in the inter-
vening lowlands, and the only possible explana-
tion of their identity is the conception of a com-
mon post-glacial origin, coupled with complete
stability. This stability is all the more remark-
able as nearly allied but slightly divergent
forms have also been reported from almost
all of these localities. Other evidence is
obtained by the comparison of ancient plants
with their living representatives. The re-
mains in tombs of ancient Egypt have al-
ways afforded strong support of the views of
the adherents of the theory of stability, and to
my mind they still do so. The cereals and fruits
and even the flowers and leaves in the funeral
wreaths of Rameses and Amen-Hotep are the
same that are still now cultivated in Egypt.
Nearly a hundred or more species have been
identified. Flowers of Acacia, leaves of Mimu-

698

Mutations

sops, petals of Nymphaea may be cited as in-
stances, and they are as perfectly preserved as
the best herbarium-specimens of the present
time. The petals and stamens retain their orig-
inal colors, displaying them as brightly as is
consistent with their dry state.

Paleontologic evidence points to the same
conclusion. Of course the remains are incom-
plete, and rarely adequate for a close compari-
son. The range of fluctuating variability should
be examined first, but the test of elementary
species given by their constancy from seed can-
not, of course, be applied. Apart from these
difficulties, paleontologists agree in recognizing
the very great age of large numbers of species.
It would require a too close survey of geologic
facts to go into details on this point. Suffice it
to say that in more recent Tertiary deposits
many species have been identified with living
forms. In the Miocene period especially, the
similarity of the types of phanerogamic plants
with their present offspring, becomes so striking
that in a large number of cases specific distinc-
tions rest in greater part on theoretical con-
ceptions rather than on real facts. For a long
time the idea prevailed that the same species
could not have existed through more than one
geologic period. Many distinctions founded
on this belief have since had to be abandoned.

Periodic Mutations 699

Species of algae belonging to the well-pre-
served group of the diatoms, are said to have
remained unchanged from the Carboniferous
period up to the present time.

Summing up the results of this very hasty
survey, we may assert that species remain un-
changed for indefinite periods, while at times
they are in the alternative condition. Then at
once they produce new forms often in large
numbers, giving rise to swarms of subspecies.
All facts point to the conclusion that these pe-
riods of stability and mutability alternate more
or less regularly with one another. Of course
a direct proof of this view cannot, as yet, be
given, but this conclusion is forced upon us by
a consideration. of known facts bearing on the
principle of constancy and evolution.

If we are right in this general conception, we
may ask further, what is to be the exact place
of our group of new evening-primroses in this
theory? In order to give an adequate answer,
we must consider the whole range of the obser-
vations from a broader point of view. First of
all it is evident that the real mutating period
must be assumed to be much longer than the
time covered by my observations. Neither the
beginning nor the end have been seen. It is
quite obvious that Oenothe^^a lamarchiana
was in a mutating condition when I first

700 Mutations

saw it, seventeen years ago. How long had
it been so! Had it commenced to mutate after
its introduction into Europe, some time ago, or
was it already previously in this state! It
is as yet impossible to decide this point. Per-
haps the mutable state is very old, and dates
from the time of the first importation of the
species into Europe.

Apart from all such considerations the period
of the direct observations, and the possible
duration of the mutability through even more
than a century, would constitute only a moment,
if compared with the whole geologic time.
Starting from this conception the pedigree of
our mutations must be considered as only one
small group. Instead of figuring a fan of mu-
tants for each year, we must condense all the
succeeding swarms into one single fan, as might
be done also for Draha verna and other poly-
morphous species. In Oenothera the main stem
is prolonged upwards beyond the fan; in the
others the main stem is lacking or at least
undiscernible, but this feature manifestly is only
of secondary importance. We might even pre-
fer the image of a fan, adjusted laterally to
a stem, which itself is not interrupted by this
branch.

On this principle two further considerations
are to be discussed. First the structure of the

Periodic Mutations 701

fan itself, and secondly the combination of suc-
ceeding fans into a common genealogic tree.

The composition of the fan as a whole in-
cludes more than is directly indicated by the
facts concerning the birth of new species. They
arise in considerable quantities, and each of
them in large numbers of individuals, either in
the same or in succeeding years. This multiple
origin must obviously have the effect of
strengthening the new types, and of heightening
their chances in the struggle for life. Arising
in a single specimen they would have little
chance of success, since in the field among thou-
sands of seeds perhaps one only survives and
attains complete development. Thousands or
at least hundreds of mutated seeds are thus re-
quired to produce one mutated individual, and
then, how small are its chances of surviving!
The mutations proceed in all directions, as I
have pointed out in a former lecture. Some are
useful, others might become so if the circum-
stances were accidentally changed in definite
directions, or if a migration from the original
locality might take place. Many others are
without any real worth, or even injurious.
Harmless or even slightly useless ones have
been seen to maintain themselves in the field
during the seventeen years of my research, as
proved by Oenothera laevifolia and Oeno-

702 Mutations

thera brevistylis. Most of the others quickly
disappear.

This failure of a large part of the productions
of nature deserves to be considered at some
length. It may be elevated to a principle, and
may be made use of to explain many diffi-
cult points of the theory of descent. If, in
order to secure one good novelty, nature must
produce ten or twenty or perhaps more bad
ones at the same time, the possibility of im-
provements coming by pure chance must be
granted at once. All hypotheses concerning the
direct causes of adaptation at once become su-
perfluous, and the great principle enunciated by
Darwin once more reigns supreme.

In this way too, the mutation-period of the
evening-primrose is to be considered as a proto-
type. Assuming it as such provisionally, it may
aid us in arranging the facts of descent so as to
allow of a deeper insight and a closer scrutiny.
All swarms of elementary species are the re-
mains of far larger initial groups. All species
containing only a few subspecies may be sup-
posed to have thrown off at the outset far more
numerous lateral branches, out of which how-
ever, the greater part have been lost, being
unfit for the surrounding conditions. It is
the principle of the struggle for life between ele-
mentary species, followed by the survival of the

Periodic Mutations 703

fittest, the law of the selection of species, which
we have already laid stress upon more than
once.

Our second consideration is also based upon
the frequent repetition of the several mutations.
Obviously a common cause must prevail. The
faculty of producing nanella or lata remains the
same through all the years. This faculty must
be one and the same for all the hundreds of mu-
tative productions of the same form. When
and how did it originate I At the outset it must
have been produced in a latent condition, and
even yet it must be assumed to be continuously
present in this state, and only to become active
at distant intervals. But it is manifest that
the original production of the characters of
Oenothera gigas was a phenomenon of far great-
er importance than the subsequent accidental
transition of this quality into the active state.
Hence the conclusion that at the beginning of
each series of analogous mutations there must
have been one greater and more intrinsic mu-
tation, which opened the possibility to all its
successors. This was the origination of the
new character itself, and it is easily seen that
this incipient change is to be considered as the
real one. All others are only its visible ex-
pressions.

Considering the mutative period of our even-

704 Mutations

ing-primrose as one unit-stride section in the
great genealogic tree, this period includes two
nearly related, but not identical changes. One
is the production of new specific characters in
the latent condition, and the other is the bring-
ing of them to light and putting them into active
existence. These two main factors are conse-
quently to be assumed in all hypothetic concep-
tions of iDrevious mutative periods.

Are all mutations to be considered as limited
to such periods? Of course not. Stray muta-
tions may occur as well. Our knowledge con-
cerning this point is inadequate for any definite
statement. Swarms of variable species are
easily recognized, if the remnants are not too
few. But if only one or two new species have
survived, how can we tell whether they have
originated alone or together with others. This
difficulty is still more pronounced in regard to
paleontologic facts, as the remains of geologic
swarms are often found, but the absence of
numerous mutations can hardly be proved in
anv case.

I have more than once found occasion to lay
stress on the importance of a distinction be-
tween progressive and retrograde mutations in
previous lectures. All improvement is, of
course, by the first of these modes of evolution,
but apparent losses of organs or qualities are

Periodic Mutations 705

perhaps of still more universal occurrence. Pro-
gression and regression are seen to go hand in
hand everywhere. No large group and proba-
bly even no genus or large species has been
evolved without the joint agency of these two
great principles. In the mutation-period of the
evening-primroses the observed facts give direct
support to this conclusion, since some of the
new species proved, on closer inspection, to be
retrograde varieties, while others manifestly
owe their origin to progressive steps. Such
steps may be small and in a wrong direction;
notwithstanding this they may be due to the
acquisition of a wholly new character and there-
fore belong to the process of progression at
large.

Between them however, there is a definite
contrast, which possibly is in intimate connec-
tion with the question of periodic and stray mu-
tations. Obviously each progressive change is
dependent upon the production of a new charac-
ter, for whenever this is lacking, no such muta-
tion is possible. Retrograde changes, on the
other hand, do not require such elaborate pre-
liminary work. Each character may be con-
verted into the latent condition, and for all we
know, a special preparation for this purpose is
not at all necessary. It is readily granted that
such special preparation may occur, because the

706 Mutations

great numbers in wliich onr dwarf variety of the
Oenothera are yearly produced are suggestive
of such a condition. On the other hand, the
laevifolia and hrevistylis mutations have not
been repeated, at least not in a visible way.

From this discussion we may infer that it is
quite possible that a large part of the progres-
sive changes, and a smaller part of the retro-
grade mutations, are combined into groups, ow-
ing their origin to common external agencies.
The periods in which such groups occur would
constitute the mutative periods. Besides them
the majority of the retrograde changes and
some progressive steps might occur separately,
each being due to some special cause. De-
gressive mutations, or those which arise by
the return of latent qualities to activity, would
of course belong with the latter group.

This assumption of a stray and isolated pro-
duction of varieties is to a large degree sup-
ported by experience in horticulture. Here
there are no real swarms of mutations. Sud-
den leaps in variability are not rare, but then
they are due to hybridization. Apart from this
mixture of characters, varieties as a rule appear
separately, often with intervals of dozens of
years, and without the least suggestion of a com-
mon cause. Tt is quite superfluous to go into
details, as we have dealt with the horticultural

Periodic Mutations 707

mutations at sufficient length on a previous oc-
casion. Only the instance of the peloric toad-
flax might be recalled here, because the historic
and geographic evidence, combined with the re-
sults of our pedigree-experiment, plainly show
that peloric mutations are quite independent of
any periodic condition. They may occur any-
where in the wide range of the toad-flax, and the
capacity of repeatedly producing them has
lasted some centuries at least, and is perhaps
even as old as the species itself.

Leaving aside such stray mutations, we may
now consider the probable constitution of the
great lines of the genealogic tree of the evening-
primroses, and of the whole vegetable and ani-
mal kingdom at large. The idea of drawing up
a pedigree for the chief groups of living organ-
isms is originally due to Haeckel, who used this
graphic method to support the Darwinian the-
ory of descent. Of course, HaeckePs genealogic
trees are of a purely hypothetic nature, and have
no other purpose than to convey a clear concep-
tion of the notion of descent, and of the great
lines of evolution at large. Obviously all de-
tails are subject to doubt, and many have ac-
cordingly been changed by his successors. These
changes may be considered as partial improve-
ments, and the somewhat picturesque form of
HaeckePs pedigree might well be replaced by

p

708 Mutations I

more simple plans. But the changes have by no
means removed the doubts, nor have they been
able to supplant the general impression of dis-
tinct groups, united by broad lines. This
feature is very essential, and it is easily seen to
correspond with the conception of swarms, as
we have deduced it from the study of the lesser
groups.

Genealogic trees are the result of comparative
studies ; they are far removed from the results
of experimental inquiry concerning the origin of
species. What are the links which bind them
together? Obviously they must be sought in
the mutative periods, which have immediately
preceded the present one. In the case of the
evening-primrose the systematic arrangement
of the allied species readily guides us in the de-
limitations of such periods. For manifestly
the species of the large genus of Oenothera are
grouped in swarms, the youngest or most recent
of which we have under observation. Its imme-
diate predecessor must have been the subgenus
Onagra, which is considered by some authors as
consisting of a single systematic species, Oenoth-
era biennis. Its multifarious forms point to a
common origin, not only morphologically but
also historically. Following this line backward
or downward we reach another apparent muta-
tion-period, which includes the origin of

Periodic Mutations 709

the group called Oenothera, with a large num-
ber of species of the same general type as the
Onagra-forms. Still farther downward comes
the old genus Oenothera itself, with numerous
subgenera diverging in sundry characters and
directions.

Proceeding still farther we might easily con-
struct a main stem with numerous succeeding
fans of lateral branches, and thus reach, from
our new empirical point of view, the theoretical
conclusion already formulated.

Paleontologic facts readily agree with this
conception. The swarms of species and va-
rieties are found to succeed one another like so
many stories. The same images are repeated,
and the single stories seem to be connected by
the main stems, which in each tier produce the
whole number of allied forms. Only a few pre-
vailing lines are prolonged through numerous
geologic periods; the vast majority of the lat-
eral branches are limited each to its own storey.
It is simply the extension of the pedigree of
the evening-primroses backward through ages,
with the same construction and the same lead-
ing features. There can be no doubt that we
are quite justified in assuming that evolution
has followed the same general laws through the
whole duration of life on earth. Only a mo-
ment of their lifetime is disclosed to us, but it

710 Mutations

is quite sufficient to enable us to discern the
laws and to conjecture the outlines of the whole
scheme of evolution.

A grave objection which has often, and
from the very outset, been urged against Dar-
win's conception of very slow and nearly im-
perceptible changes, is the enormously long time
required. If evolution does not proceed any
faster than what we can see at present, and if
the process must be assumed to have gone on
in the same slow manner always, thousands of
millions of years would have been needed to de-
velop the higher types of animals and plants
from their earliest ancestors.

Now it is not at all probable that the duration
of life on earth includes such an incredibly
long time. Quite on the contrsLYj the lifetime
of the earth seems to be limited to a few
millions of years. The researches of Lord Kel-
vin and other eminent physicists, seem to leave
no doubt on this point. Of course all esti-
mates of this kind are only vague and approx-
imate, but for our present purposes they may
be considered as sufficiently exact.

In a paper published in 1862 Sir William
Thomson (now Lord Kelvin) first endeavored to
show that great limitation had to be put upon
the enormous demand for time made bv Lvell,
Darwin and other biologists. From a consider-

Periodic Mutations 711

ation of the secular cooling of the earth, as de-
duced from the increasing temperature in deep
mines, he concluded that the entire age of the
earth must have been more than twenty and less
than forty millions of years, and probably much
nearer twenty than forty. His views have been
much criticised by other physicists, but in the
main they have gained an ever-increasing sup-
port in the way of evidence. New mines of
greater depth have been bored, and their tem-
peratures have proved that the figures of Lord
Kelvin are strikingly near the truth. George
Darwin has calculated that the separation of
the moon from the earth must have taken place
some fifty-six millions of years ago. Geikie has
estimated the existence of the solid crust of the
earth at the most as a hundred million years.
The first appearance of the crust must soon have
been succeeded by the formation of the seas,
and a long time does not seem to have been re-
quired to cool the seas to such a degree that life
became possible. It is very probable that life
originally commenced in the great seas, and that
the forms which are now usually included in the
plankton or floating-life included the very first
living beings. According to Brooks, life must
have existed in this floating condition during
long primeval epochs, and evolved nearly all the
main branches of the animal and vegetable king-

712 Mutations

dom before sinking to the bottom of the sea, and
later producing the vast number of diverse
forms which now adorn the sea and land.

All these evolutions, however, must have been
very rapid, especially at the beginning, and to-
gether cannot have taken more time than the
figures given above.

The agency of the larger streams, and the
deposits which they bring into the seas, afford
further evidence. The amount of dissolved
salts, especially of sodium chloride, has been
made the subject of a calculation by Joly, and
the amount of lime has been estimated by
Eugene Dubois. Joly found fifty-five and Du-
bois thirty-six millions of years as the probable
duration of the age of the rivers, and both fig-
ures correspond to the above dates as closely
as might be expected from the discussion of evi-
dence so very incomplete and limited.

All in all it seems evident that the duration of
life does not comply with the demands of the
conception of very slow and continuous evolu-
tion. Now it is easily seen, that the idea of
successive mutations is quite independent of
this difficulty. Even assuming that some thou-
sands of characters must have been acquired in
order to produce the higher animals and plants
of the present time, no valid objection is raised.
The demands of the biologists and the results of

Periodic Mutations 713

the physicists are harmonized on the ground of
the theory of mutation.

The steps may be surmised to have never been
essentially larger than in the mutations now
going on under our eyes, and some thousands of
them may be estimated as sufficient to account
for the entire organization of the higher forms.
Granting between twenty and forty millions
of years since the beginning of life, the intervals
between two successive mutations may have
been centuries and even thousands of years. As
yet there has been no objection cited against this
assumption, and hence we see that the lack of
harmony between the demands of biologists and
the results of the physicists disappears in the
light of the theory of mutation.

Summing up the results of this discussion, we
may justifiably assert that the conclusions de-
rived from the observations and experiments
made with evening-primroses and other plants
in the main agree satisfactorily with the in-
ferences drawn from paleontologic, geologic
and systematic evidence. Obviously these ex-
periments are wonderfully supported by the
whole of our knowledge concerning evolution.
For this reason the laws discovered in the ex-
perimental garden may be considered of great
importance, and they may guide us in our fur-
ther inquiries. Without doubt many minor

714 Mutations

points are in need of correction and elaboration,
but such improvements of our knowledge will
gradually increase our means of discovering
new instances and new proofs.

The conception of mutation periods produc-
ing swarms of species from time to time, among
which only a few have a chance of survival,
promises to become the basis for speculative
pedigree-diagrams, as well as for experimental
investigations.

F. FLUCTUATION
Lecture XXV

GENERAL LAWS OF FLUCTUATION

The principle of unit-characters and of ele-
mentary species leads at once to the recognition
of two kinds of variability. The changes of
wider amplitude consist of the acquisition of
new units, or the loss of already existing ones.
The lesser variations are due to the degree of
activity of the units themselves.

Facts illustrative of these distinctions were
almost wholly lacking at the time of the first
publication of Darwin's theories. It was a bold
conception to point out the necessity for such
distinction on purely theoretical grounds. Of
course some sports were well known and fluc-
tuations were evident, but no exact analysis of
the details was possible, a fact that was of great
importance in the demonstration of the theory
of descent. The lack of more definite knowl-
edge upon this matter was keenly felt by Dar-

715

716 Fluctuations

win, and exercised much influence upon his
views at various times.

Quetelet's famous discovery of the law of
fluctuating variability changed the entire situa-
tion and cleared up many difficulties. While a
clear conception of fluctuations was thus gained,
mutations were excluded from consideration,
being considered as very rare, or non-existent.
They seemed wholly superfluous for the theory
of descent, and very little importance was at-
tached to their study. Current scientific belief
in the matter has changed only in recent
years. Mendel's law of varietal hybrids is
based upon the principle of unit-characters, and
the validity of this conception has thus been
brought home to many investigators.

A study of fluctuating or individual variabil-
ity, as it was formerly called, is now carried on
chiefly by mathematical methods. It is not my
purpose to go into details, as it would re-
quire a separate course of lectures. I shall con-
sider the limits between fluctuation and muta-
tion only, and attempt to set forth an adequate
idea of the principles of the first as far as they
touch these limits. The mathematical treat-
ment of the facts is no doubt of very great value,
but the violent discussions now going on be-
tween mathematicians such as Pearson, Kap-
teyn and others should warn biologists to ab-

Laws of Fluctuations 111

stain from the use of methods which are not
necessary for the furtherance of experimental
work.

Fortunately, Quetelet's law is a very clear
and simple one, and quite sufficient for our con-
siderations. It claims that for biologic phe-
nomena the deviations from the average comply
with the same laws as the deviations from the
average in any other case, if ruled by chance
only. The meaning of this assertion will be-
come clear by a further discussion of the facts.

First of- all, fluctuating variability is an al-
most universal phenomenon. Every organ and
every quality may exhibit it. Some are very
variable, while others seem quite constant.
Shape and size vary almost indefinitely, and the
chemical composition is subject to the same law,
as is well known for the amount of sugar in
sugar-beets. Numbers are of course less liable
to changes, but the numbers of the rays of um-
bels, or ray-florets in the composites, of pairs of
blades in pinnate leaves, and even of stamens
and carpels are known to be often exceedingly
variable. The smaller numbers however, are
more constant, and deviations from the quinate
structure of flowers are rare. Complicated
structures are generally capable of only slight
deviations.

From a broad point of view, fluctuating varia-

718 Fluctuations

bility falls under two heads. They obey quite
the same laws and are therefore easily confused,
but with respect to questions of heredity they
should be carefully separated. They are des-
ignated by the terms individual and partial
fluctuation. Individual variability indicates
the differences between individuals, while
partial variability is limited to the devia-
tions shown by the parts of one organ-
ism from the average structure. The same
qualities in some cases vary individually and in
others partially. Even stature, which is as
markedly individual for annual and biennial
plants as it is for man, becomes partially variant
in the case of perennial herbs with numbers of
stems. Often a character is only developed once
in the whole course of evolution, as for instance,
the degree of connation of the seed-leaves in
tricotyls and in numerous cases it is impos-
sible to tell whether a character is individual or
partial. Consequently such minute details
are generally considered to have no real im-
portance for the hereditary transmission of the
character under discussion.

Fluctuations are observed to take place only
in two directions. The quality may increase or
decrease, but is not seen to vary in any other
way. This rule is now widely established by
numerous investigations, and is fundamental to

Laivs of Fluctuatioyis 719

the whole method of statistical investigation.
It is equally important for the discussion of the
contrast between fluctuations and mutations,
and for the appreciation of their part in the
general progress of organization. Mutations
are going on in all directions, producing, if they
are progressive, something quite new every
time. Fluctuations are limited to increase and
decrease of what is already available. They
may produce plants with higher stems, more
petals in the flowers, larger and more palatable
fruits, but obviously the first petal and the first
berry cannot have originated by the simple in-
crease of some older quality. Intermediates
may be found, and they may mark the limit, but
the demonstration of the absence of a limit is
quite another question. It would require the
two extremes to be shown to belong to one unit,
complying with the simple law of Quetelet.

Nourishment is the potent factor of fluctuat-
ing variability. Of course in thousands of cases
our knowledge is not sufficient to allow us to ana-
lyze this relation, and a number of phases of the
phenomenon have been discovered only quite
recently. But the fact itself is thoroughly mani-
fest, and its appreciation is as old as horticul-
tural science. Knight, who lived at the begin-
ning of the last century, has laid great stress
upon it, and it has since influenced practice in a

720 Fluctuations

large measure. Moreover, Knight pointed out
more than once that it is the amount of nourish-
ment, not the quality of the various factors, that
exercises the determinative influence. Nourish-
ment is to be taken in the widest sense of the
word, including all favorable and injurious ele-
ments. Light and temperature, soil and space,
water and salts are equally active, and it is the
harmonious cooperation of them all that rules
growth.

We treated this important question at some
length, when dealing with the anomalies of the
opium-poppies, consisting of the conversion of
stamens into supernumerary pistils. The de-
pendency upon external influences which this
change exhibited is quite the same as that shown
by fluctuating variability at large. We inquired
into the influence of good and bad soil, of sun-
light and moisture and of other concurrent fac-
tors. Especial emphasis was laid upon the
great differences to which the various individ-
uals of the same lot may be exposed, if moisture
and manure differ on different portions of the
same bed in a way unavoidable even by the most
careful preparation. Some seeds germinate on
moist and rich spots, while their neighbors are
impeded by local dryness, or by distance from
manure. Some come to light on a sunny day,
and increase their first leaves rapidly, while on

Laws of Fluctuations 721

the following day the weather may be unfavor-
able and greatly retard growth. The individual
differences seem to be due, at least in a very
great measure, to such apparent trifles.

On the other hand partial differences are
often manifestly due to similar causes. Con-
sidering the various stems of plants, which mul-
tiply themselves by runners or by buds on the
roots, the assertion is in no need of further
proof. The same holds good for all cases of
artificial multiplication by cuttings, or by other
vegetative methods. But even if we limit our-
selves to the leaves of a single tree, or the
branches of a shrub, or the flowers on a plant,
the same rule prevails. The development of
the leaves is dependent on their position, wheth-
er inserted on strong or weak branches, exposed
to more or less light, or nourished by strong or
weak roots. The vigor of the axillary buds
and of the branches which they may produce is
dependent upon the growth and activity of the
leaves to which the buds are axillary.

This dependency on local nutrition leads to
the general law of periodicity, which, broadly
speaking, governs the occurrence of the fluctuat-
ing deviations of the organs. This law of pe-
riodicity involves the general principle that
every axis, as a rule, increases in strength when

722 Fluctuations

growing, but sooner or later reaches a maximum
and may afterwards decrease.

This periodic augmentation and declination is
often boldly manifest, though in other cases it
may be hidden by the effect of alternate influ-
ences. Pinnate leaves generally have their
lower blades smaller than the upper ones, the
longest being seen sometimes near the apex
and sometimes at a distance from it. Branches
bearing their leaves in two rows often afford
quite as obvious examples, and shoots in gen-
eral comply with the same rule. Germinating
plants are very easy of observation on this
point. When they are very weak they produce
only small leaves. But their strength gradually
increases and the subsequent organs reach
fuller dimensions until the maximum is at-
tained. The phenomenon is so common that its
importance is usually overlooked. It should be
considered as only one instance of a rule, which
holds good for all stems and all branches, and
which is everywhere dependent on the relation
of growth to nutrition.

The rule of periodicity not only affects the
size of the organs, but also their number, when-
ever these are largely variable. Umbellate
plants have numerous rays on the umbels of
strong stems, but the number is seen to decrease
and to become very small on the weakest lateral

Laivs of Fluctuations 723

branches. The same holds good for the number
of ray-florets in the flower-heads of the com-
posites, even for the nmnber of stigmas on the
ovaries of the poppies, which on weak branches
may be reduced to as few as three or four.
Many other instances could be given.

One of the best authenticated cases is the de-
pendency of partial fluctuation on the season
and on the weather. Flowers decline when the
season comes to an end, become smaller and less
brightly colored. The number of ray-florets in
the flower-heads is seen to decrease towards the
fall. Extremes become rarer, and often the
deviations from the average seem nearly to dis-
appear. Double flowers comply with this rule
very closely, and many other cases will easily
occur to any student of nature.

Of course, the relation to nourishment is dif-
ferent for individual and partial fluctuations.
Concerning the first, the period of development
of the germ within the seed is decisive. Even
the sexual cells may be in widely different condi-
tions at the moment of fusion, and perhaps this
state of the sexual cells includes the whole mat-
ter of the decision for the average characters of
the new individual. Partial fluctuation com-
mences as soon as the leaves and buds begin to
form, and all later changes in nutrition can
only cause partial differences. All leaves,

724 Fluctuations

buds, branches, and flowers must come under
the influence of external conditions during the
juvenile period, and so are liable to attain a de-
velopment determined in part by the action of
these factors.

Before leaving these general considerations,
we must direct our attention to the question of
utility. Obviously, fluctuating variability is
a very useful contrivance, in many cases at
least. It appears all the more so, as its relation
to nutrition becomes manifest. Here two as-
pects are intimately combined. More nutrient
matter produces larger leaves and these are in
their turn more fit to profit by the abundance of
nourishment. So it is with the number of
flowers and flower-groups, and even with the
numbers of their constituent organs. Better
nourishment produces more of them, and there-
by makes the plant adequate to make a
fuller use of the available nutrient substances.
Without fluctuation such an adjustment would
hardly be possible, and from all our notions of
usefulness in nature, we therefore must recog-
nize the efficiency of this form of variability.

In other respects the fluctuations often strike
us as quite useless or even as injurious. The
numbers of stamens, or of carpels are dependent
on nutrition, but their fluctuation is not known
to have any attraction for the visiting insects.

Laws of Fluctuations 725

If the deviations become greater, they might
even become detrimental. The flowers of the
St. Johnswort, or Hypericum perforatum,
usually have five petals, but the number varies
from three to eight or more. Bees could hardly
be misled by such deviations. The carpels of
buttercups and columbines, the cells in the cap-
sules of cotton and many other plants are vari-
able in number. The number of seeds is there-
by regulated in accordance with the available
nourishment, but whether any other useful pur-
pose is served, remains an open question. Vari-
ations in the honey-guides or in the pattern of
color-designs might easily become injurious by
deceiving insects, and such instances as the
great variability of the spots on the corolla of
some cultivated species of monkey-flowers, for
instance, the Mimulus quinquevulnerus, could
hardly be expected to occur in wild plants. For
here the dark brown spots vary between nearly
complete deficiency up to such predominancy as
almost to hide the pale yellow ground-color.

After this hasty survey of the causes of fluc-
tuating variability, we now come to a discussion
of Quetelet's law. It asserts that the deviations
from the average obey the law of probability.
They behave as if they were dependent on
chance only.

Everyone knows that the law of Quetelet can

726 Fluctuations

be demonstrated the most readily by placing a
sufficient nmnber of adult men in a row, arrange
ing them according to their size. The line pass-
ing over their heads proves to be identical with
that given by the law of probability. Quite
in the same way, stems and branches, leaves and
petals and even fruits can be arranged, and
they will in the main exhibit the same line of
variability. Such groups are very striking, and
at the first glance show that the large majority
of the specimens deviate from the mean only to
a very small extent. Wider deviations are far
more rare, and their number lessens, the greater
the deviation, as is shown by the curvature
of the line. It is almost straight and horizontal
in the middle portion, while at the ends it
rapidly declines, going sharply downward at
one extreme and upward at the other.

It is obvious however, that in these groups
the leaves and other organs could conveniently
be replaced by simple lines, indicating their size.
The result would be quite the same, and the lines
could be placed at arbitrary, but equal dis-
tances. Or the sizes could be expressed by fig-
ures, the compliance of which with the general
law could be demonstrated by simple methods
of calculation. In this manner the variability
of different organs can easily be compared.

Another method of demonstration consists in

Laws of Fluctuations 727

grouping the deviations into previously fixed
divisions. For this purpose the variations
are measured by standard units, and all the in-
stances that fall between two limits are consid-
ered to constitute one group. Seeds and small
fruits, berries and many other organs may
conveniently be dealt with in this way. As an
example we take ordinary beans and select them
according to their size. This can be done in
different ways. On a small piece of board a
long wedge-shaped slit is made, into which seeds
are pushed as far as possible. The margin of
the wedge is calibrated in such a manner that the
figures indicate the width of the wedge at the
corresponding place. By this device the figure
up to which a bean is pushed at once shows its
length. Fractions of millimeters are neglected,
and the beans, after having been measured, are
thrown into cylindrical glasses of the same
width, each glass receiving only beans of equal
length. It is clear that by this method the
height to which beans fill the glasses is ap-
proximately a measure of their number. If now
the glasses are put in a row in the proper se-
quence, they at once exhibit the shape of a line
which corresponds to the law of chance. In this
case however, the line is drawn in a different
manner from the first. It is to be pointed out
that the glasses may be replaced by lines in-

728 Fluctuations

dicating the height of their contents, and that,
in order to reach a more easy and correct state-
ment, the length of the lines may simply be made
proportionate to the number of the beans in
each glass. If such lines are erected on a com-
mon base and at equal distances, the line which
unites their upper ends will be the expression of
the fluctuating variability of the character under
discussion.

The same inquiry may be made with other
seeds, with fruits, or other organs. It is quite
superfluous to arrange the objects themselves,
and it is sufficient to arrange the figures in-
dicating their value. In order to do this a
basal line is divided into equal parts, the de-
marcations corresponding to the standard-units
chosen for the test. The observed values are
then written above this line, each finding its
place between the two demarcations, which in-
clude its value. It is very interesting and
stimulating to construct such a group. The
first figures may fall here and there, but very
soon the vertical rows on the middle part of
the basal line begin to increase. Sometimes
ten or twenty measurements will suffice to make
the line of chance appear, but often indentations
will remain. With the increasing number of
the observations the irregularities gradually

Laws of Fluctuations 729

disappear, and the line becomes smoother and
more uniformly curved.

This method of arranging the figures directly
on a basal line is very convenient, whenever ob-
servations are made in the field or garden.
Very few instances need be recorded to obtain
an appreciation of the mean value, and to show
what may be expected from a continuance of
the test. The method is so simple and so
striking, and so wholly independent of any
mathematical development that it should be ap-
plied in all cases in which it is desired to ascer-
tain the average value of any organ, and the
measure of the attendant deviations.

I cite an instance, secured by counting the
ray-florets on the flower-heads of the corn-mari-
gold or Chrysanthemum segetum. It was that,
by which I was enabled to select the plant, which
afterwards showed the first signs of a double
head. I noted them in this way :

47

47 52

41 54 68

44 50 62 75

36 45 58 65 72 — 99

Of course the figures might be replaced in
this work by equidistant dots or by lines, but
experience teaches that the chance of making
mistakes is noticeably lessened by writing down

730 Fluctuations

the figures themselves. Whenever decimals are
made use of it is obviously the best plan to keep
the figures themselves. For afterwards it often
becomes necessary to arrange them according
to a somewhat different standard.

Uniting the heads of the vertical rows of fig-
ures by a line, the form corresponding to Que-
telet's law is easily seen. In the main it is
always the same as the line shown by the meas-
urements of beans and seeds. It proves a dense
crowding of the single instances around the
average, and on both sides of the mass of the
observations, a few wide deviations. These be-
come more rare in proportion to the amount of
their divergency. On both sides of the average
the line begins by falling very rapidly, but then
bends slowly so as to assume a nearly horizon-
tal direction. It reaches the basal line only be-
yond the extreme instances.

It is quite evident that all qualities, which
can be expressed by figures, may be treated in
this way. First of all the organs occurring in
varying numbers, as for instance the ray-florets
of composites, the rays of umbels, the blades of
pinnate and palmate leaves, the numbers of
veins, etc., are easily shown to comply with
the same general rule. Likewise the amount
of chemical substances can be expressed
in percentage numbers, as is done on a large

Laws of Fluctuations 731

scale with sugar in beets and sugar-cane, with
starch in potatoes and in other instances.
These figures are also found to follow the same
law.

All qualities which are seen to increase and
to decrease may be dealt with in the same man-
ner, if a standard unit for their measure-
ment can be fixed. Even the colors of flowers
may not escape our inquiry.

If we now compare the lines, compiled from
the most divergent cases, they will be found to
exhibit the same features in the main. Ordi-
narily the curve is symmetrical, the line sloping
down on botli sides after the same manner. But
it is not at all rare that the inclination is
steep on one side and gradual on the other. This
is noticeably the case if the observations relate
to numbers, the average of which is near zero.
Here of course the allowance for variation is on-
ly small on one side, while it may increase with-
out distinct limits on the alternate slope. So it
is for instance with the numbers of ray-florets
in the example given on p. 729. Such divergent
cases, however, are to be considered as excep-
tions to the rule, due to some unknown cause.

Heretofore we have discussed the empirical
side of the problem only. For the purpose
of experimental study of questions of hered-
ity this is ordinarily quite sufficient. The in-

732 Fluctuations

quiry into the phenomenon of regression, or of
the relation of the degree of deviation of the
progeny to that of their parents, and the selec-
tion of extreme instances for multiplication are
obviously independent of mathematical consid-
erations. On the other hand an important in-
quiry lies in the statistical treatment of these
phenomena, and such treatment requires the
use of mathematical methods.

Statistics however, are not included in the
object of these lectures, and therefore I shall
refrain from an explanation of the method of
their preparation and limit myself to a general
comparison of the observed lines with the law
of chance. Before going into the details, it
should be repeated once more that the empirical
result is quite the same for individual and for
partial fluctuations. As a rule, the latter occur
in far greater number, and are thus more easily
investigated, but individual or personal aver-
ages have also been studied.

Newton discovered that the law of chance can
be expressed by very simple mathematical cal-
culations. Without going into details, we may
at once state that these calculations are based
upon his binomium. If the fonn (a + b)° is cal-
culated for some value of the exponent, and if
the values of the coefficients after develop-
ment are alone considered, they yield the basis

Laivs of Fluctuations 733

for the construction of what is called the line or
curve of probability. For this construction the
coefficients are used as ordinates, the length of
which is to be made proportionate to their value.
If this is done, and the ordinates are arranged
at equal distances, the line which unites their
summits is the desired curve. At first glance it
exhibits a form quite analogous to the curves
of fluctuating variability, obtained by the meas-
urements of beans and in other instances. Both
lines are symmetrical and slope rapidly down in
the region of the average, while with increasing
distance they gradually lose their steep incli-
nation, becoming nearly parallel to the base at
their termination.

This similarity between such empirical and
theoretical lines is in itself an empirical fact.
The causes of chance are assumed to be innu-
merable, and the whole calculation is based on
this assumption. The causes of the fluctuations
of biological phenomena have not as yet been
critically examined to such an extent as to allow
of definite conceptions. The term nourishment
manifestly includes quite a number of separate
factors, as light, space, temperature, moisture,
the physical and chemical conditions of the soil
and the changes of the weather. Without doubt
the single factors are very numerous, but
whether thev are numerous enough to be treated

734 Fluctuations

as innumerable, and thereby to explain the laws
of fluctuations, remains uncertain. Of course
the easiest way is to assume that they combine
in the same manner as the causes of chance, and
that this is the ground of the similarity of the
curves. On the other hand, it is manifestly of
the highest importance to inquire into the part
the several factors play in the determination
of the curves. It is not at all improbable that
some of them have a larger influence on indi-
vidual, and others on partial, fluctuations. If
this were the case, their importance with respect
to questions of heredity might be widely differ-
ent. In the present state of our knowledge the
fluctuation-curves do not contribute in any
large measure to an elucidation of the causes.
Where these are obvious, they are so without
statistics, exactly as they were, previous to
Quetelet's discovery.

In behalf of a large number of questions con-
cerning heredity and selection, it is very desir-
able to have a somewhat closer knowledge of
these curves. Therefore I shall try to point out
their more essential features, as far as this can
be done without mathematical calculations.

At a first glance three points strike us, the
average or the summit of the cur\^e, and the ex-
tremes. If the general shape is once denoted by
the results of observations or by the coeffi-

Laws of Fluctuations 735

cients of the binomium, all further details seem
to depend upon them. In respect to the average
this is no doubt the case ; it is an empirical value
without need of any further discussion. The
more the number of the observations increases,
the more assured and the more correct is this
mean value, but generally it is the same for
smaller and for larger groups of observations.

This however, is not the case with the ex-
tremes. It is quite evident that small groups
have a chance of containing neither of them.
The more the number of the observations in-
creases, the larger is the chance of extremes. As
a rule, and excluding exceptional cases, the ex-
treme deviations will increase in proportion to
the number of cases examined. In a hundred
thousand beans the smallest one and the largest
one may be expected to differ more widely from
one another than in a few hundred beans of the
same sample. Hence the conclusion that ex-
tremes are not a safe criterion for the discus-
sion of the curves, and not at all adequate for
calculations, which must be based upon more
definite values.

A real standard is afforded by the steepness
of the slope. This may be unequal on the two
sides of one curve, and likewise it may differ for
different cases. This steepness is usually meas-
ured by means of a point on the half cur\^e and

736 Fluctuations

for this purpose a point is chosen which lies
exactly half way between the average and the
extreme. Not however half way with respect to
the amplitude of the extreme deviation, for on
this ground it would partake of the uncertainty
of the extreme itself. It is the point on the
curve which is surpassed by half the number,
and not reached by the other half of the num-
ber of the observations included in the half of
the curve. This point corresponds to the im-
portant value called the probable error, and
was designated by Galton as the quartile. For
it is evident that the average and the two quar-
tiles divide the whole of the observations into
four equal parts.

Choosing the quartiles as the basis for cal-
culations we are independent of all the second-
ary causes of error, which necessarily are in-
herent in the extremes. At a casual examina-
tion, or for demonstrative purposes, the ex-
tremes may be prominent, but for all further
considerations the quartiles are the real values
upon which to rest calculations.

Moreover if. the agreement with the law of
probability is once conceded, the whole curve is
defined by the average and the quartiles, and
the result of hundreds of measurements or
countings may be summed up in three, or, in

Laws of Fluctuations 1^1

the case of symmetrical curves, perhaps in two
figures.

Also in comparing different curves with one
another, the quartiles are of great importance.
Whenever an empirical fluctuation-curve is to be
compared with the theoretical form, or when
two or more cases of variability are to be con-
sidered under one head, the lines are to be
drawn on the same base. It is manifest that
the averages must be brought upon the same
ordinate, but as to the steepness of the line,
much depends on the manner of plotting. Here
we must remember that the mutual distance of
the ordinates has been a wholly arbitrary
one in all our previous considerations. And
so it is, as long as only one curve is considered
at a time. But as soon as two are to be com-
pared, it is obvious that free choice is no longer
allowed. The comparison must be made
on a common basis, and to this effect the quar-
tiles must be brought together. They are to lie
on the same ordinates. If this is done, each
division of the base corresponds to the same
proportionate number of individuals, and a
complete comparison is made possible.

On the ground of such a comparison we may
thus assert that fluctuations, however different
the organs or qualities observed, are the same
whenever their curves are seen to overlap one

738 Fluctuations

another. Furthermore, whenever an empirical
curve agrees in this manner with the theoretical
one, the fluctuation complies with Quetelet's law,
and may be ascribed to quite ordinary and uni-
versal causes. But if it seems to diverge from
this line, the cause of this divergence should be
inquired into.

Such abnormal curves occur from time to
time, but are rare. Unsymmetrical instances
have already been alluded to, and seem to be
quite frequent. Another deviation from the
rule is the presence of more than one summit.
This case falls under two headings. If the ray-
florets of a composite are counted, and the fig-
ures brought into a curve, a prominent summit
usually corresponds to the average. But next
to this, and on both sides, smaller summits are
to be seen. On a close inspection these summits
are observed to fall on the same ordinates, on
which, in the case of allied species, the main
apex lies. The specific character of one form
is thus repeated as a secondary character on an
allied species. Ludwig discovered that these
secondary summits comply with the rule discov-
ered by Braun and Schimper, stating the rela-
tion of the subsequent figures of the series.
This series gives the terms of the dis-
position of leaves in general, and of tlie
bracts and flowers on the composite flower-

Laws of Fluctuations 739

heads in our particular case. It is the
series to which we have already alluded
when dealing with the arrangement of the leaves
on the twisted teasels. It commences with
1 and 2 and each following figure is equal to
the sum of its two precedents. The most com-
mon figures are 3, 5, 8, 13, 18, 21, higher cases
seldom coming under observation. Now the
secondary summits of the ray-curves of the
composites are seen to agree, as a rule, with
these figures. Other instances could readily be
given.

Our second heading includes those cases
which exhibit two summits of equal or nearly
equal height. Such cases occur when dif-
ferent races are mixed, each retaining its own
average and its own curve-summit. We have al-
ready demonstrated such a case when dealing
with the origin of our double corn-chrysanthe-
mum. The wild species culminates with 13 rays,
and the grandiflorum variety with 21. Often
the latter is found to be impure, being mixed
with the typical species to a varying extent.
This is not easily ascertained by a casual in-
spection of the cultures, but the true condition
will promptly betray itself, if curves are con-
structed. In this way curves may in many in-
stances be made use of to discover mixed races.

Double curves may also result from the inves-

740 Fluctuations

tigation of true double races, or ever-sporting
varieties. The striped snapdragon shows a
curve of its stripes with two summits, one cor-
responding to the average striped flowers, and
the other to the pure red ones. Such cases may
be discovered by means of curves, but the con-
stituents cannot be separated by culture-exper-
iments.

A curious peculiarity is afforded by half-
curves. The number of petals is often seen
to vary only in one direction from what should
be expected to be the mean condition. With
buttercups and brambles and many others there
is only an increase above the typical five;
quaternate flowers are wanting or at least are
very rare. With weigelias and many others the
number of the tips of the corolla varies down-
wards, going from five to four and three. Hun-
dreds of flowers show the typical five, and de-
termine the summit of the curve. This drops
down on one side only, indicating unilateral
variability, which in many cases is due to a
very intimate connection of a concealed sec-
ondary summit and the main one. In the
case of the bulbous buttercup, Ranunculus hul-
hosus, I have succeeded in isolating this second-
ary summit, although not in a separate variety,
but only in a form corresponding to the type
of ever-sporting varieties.

Laws of Fluctuations 741

Recapitulating the results of this too con-
densed discussion, we may state that fluctua-
tions are linear, being limited to an increase and
to a decrease of the characters. These changes
are mainly due to differences in nourishment,
either of the whole organism or of its parts.
In the first case, the deviations from the mean
are called individual; they are of great impor-
tance for the hereditary characters of the
offspring. In the second case the deviations
are far more universal and far more striking,
but of lesser importance. They are called par-
tial fluctuations.

All these fluctuations comply, in the main,
with the law of probability, and behave as if
their causes were influenced only by chance.

Lecture XXVI

ASEXUAL MULTIPLICATION OF EXTREMES

Fluctuating variability may be regarded from
two different points of view. The multiformity
of a bed of flowers is often a desirable feature,
and all means which widen the range of fluctua-
tion are therefore used to enhance this feature,
and variability affords specimens, which sur-
pass the average, by yielding a better or larger
product.

In the case of fruits and other cultivated
forms, it is of course profitable to propagate
from the better specimens only, and if possible
only from the very best. Obviously the best are
the extremes of the whole range of diverging
forms, and moreover the extremes on one side of
the group. Almost always the best for practical
purposes is that in which some quality is
strengthened. Cases occur however, in which
it is desirable to diminish an injurious pecul-
iarity as far as possible, and in these instances
the opposite extreme is the most profitable one.

These considerations lead us to a discussion

742

Multiplication of Extremes 743

of the results of the choice of extremes, which it
may be easily seen is a matter of the greatest
practical importance. This choice is generally
designated as selection, but as with most of the
terms in the domain of variability, the word
selection has come to have more than one mean-
ing. Facts have accumulated enormously since
the time of Darwin, a more thorough knowl-
edge has brought about distinctions, and di-
visions at a rapidly increasing rate, with which
terminology has not kept pace. Selection in-
cludes all kinds of choice. Darwin distin-
guished between natural and artificial selection,
but pro]3er subdivisions of these conceptions are
needed.

In the fourth lecture we dealt with this same
question, and saw that selection must, in the first
place, make a choice between the elementary
species of the same systematic form. This
selection of species or species-selection was the
work of Le Couteur and Patrick Shirretf , and is
now in general use in practice where it has re-
ceived the name of variety-testing. This clear
and unequivocal term however, can hardly be
included under the head of natural selection.
The poetic terminology of selection by nature
has already brought about many difficulties that
should be avoided in the future. On the other
hand, the designation of the process as a natural

744 Fluctuations

selection of species complies as closely as possi-
ble with existing terminology, and does not
seem liable to any misunderstanding.

It is a selection between species. Opposed to
it is the selection ivithin the species. Manifest-
ly the first should precede the second, and if this
sequence is not conscientiously followed it will
result in confusion. This is evident when it
is considered that fluctuations can only appear
with their pure and normal type in pure strains^
and that each admixture of other units is liable
to be shown by the form of the curves. More-
over, selection chooses single individuals, and a
single plant, if it is not a hybrid, can scarcely
pertain to two different species. The first
choice therefore is apt to make the strain pure.

In contrasting selection between species with
that within the species, of course elementary
species are meant, including varieties. The
terms would be of no consequence if only right-
ly understood. For the sake of clearness we
might designate the last named process with
the term of intra- specific selection, and it is
obvious that this term is applicable both to
natural and to artificial selection.

Having previously dealt with species-selec-
tion at sufiicient length, we may now confine our-
selves to the consideration of the intra-specific

Multiplication of Extremes 745

selection-process. In practice it is of secondary
importance, and in nature it takes a very subor-
dinate position. For this reason it will be best
to confine further discussions to the experience
of the breeders.

Two different ways are open to make fluctuat-
ing variability profitable. Both consist in the
multiplication of the chosen extremes, and this
increase may be attained in a vegetative man-
ner, or by the use of seeds. Asexual and sexual
propagation are different in many respects, and
so they are also in the domain of variability.

In order to obtain a clear comprehension of
this difference, it is necessary to start from the
distinction between individual and partial fluc-
tuations, as given in the last lecture. This
distinction may be discussed more understand-
ingly if the causes of the variability are taken
into consideration. We have dealt with them
at some length, and are now aware that inner
conditions only, determine averages, while some
fluctuation around them is allowable, as influ-
enced by external conditions. These outward
influences act throughout life. At the very first
they impress their stamp on the whole organism,
and incite a lasting change in distinct directions.
This is the period of the development of the
germ within the seed ; it begins with the fusion
of the sexual cells, and each of them may be in-

746 Fluctuations

fluenced to a noticeable degree before this union.
This is the period of the determination of indi-
vidual variability. As soon as ramifications be-
gin, the external conditions act separately on
every part, influencing some to a greater and
others to a lesser degree. Here we have the
beginning of partial variability. At the outset
all parts may be affected in the same way and
in the same measure, but the chances of such an
agreement, of course, rapidly diminish. This is
partly due to differences in exposure, but main-
ly to alterations of the sensibility of the organs
themselves.

It is difficult to gain a clear conception of the
contrast between individual and partial varia-
bility, and neither is it easy to appreciate
their cooperation rightly. Perhaps the best
way is to consider their activity as a gradual
narrowing of possibilities. At the outset the
plant may develop its qualities in any measure,
nothing being as yet fixed. Gradually how-
ever, the development takes a definite direction,
for better or for worse. Is a direction once
taken, then it becomes the average, around
which the remaining possibilities are grouped.
The plant or the organ goes on in this way, un-
til finallv it reaches maturitv with one of the
thousands of degrees of development, between
which at the beginning it had a free choice.

Multiplication of Extremes 747

Putting this discussion in other terms, we find
every individual and every organ in the adult
state corresponding with a single ordinate of
the curve. The curve indicates the range of
possibilities, the ordinate shows the choice that
has been made. Now it is clear at once that
this choice has not been made suddenly but
gradually. Halfway of the development, the
choice is halfway determined, but the other half
is still undefined. The first half is the same for
all the organs of the plant, and is therefore
termed individual; the second differs in the
separate members, and consequently is known as
partial. Which of the two halves is the greater
and which the lesser, of course depends on the
cases considered.

Finally we may describe a single example, the
length of the capsules of the evening-primrose.
This is highly variable, the longest reaching
more than twice the length of the smallest.
Many capsules are borne on the same spike,
and they are easih^ seen to be of unequal size.
They vary according to their position, the
size diminishing in the main from the base up-
wards, especially on the higher parts. Like-
wise the fruits of weaker lateral branches are
smaller. Curves are easily made by measuring
a few hundred capsules from corresponding
parts of different plants, or even by limiting tlie

748 Fluctuations

inquiry to a single individual. These curves
give the partial variability, and are found to
comply with Quetelet ^s law.

Besides this limited study, we may compare
the numerous individuals of one locality or of
a large plot of cultivated plants with one an-
other. In doing so, we are struck with the fact
that some plants have large and others small
fruits. We now limit ourselves to the main
spike of each plant, and perhaps to its lower
parts, so as to avoid as far as possible the im-
pression made by the partial fluctuations. The
differences remain, and are sufficient to fur-
nish an easy comparison with the general law.
In order to do this, we take from each plant a
definite number of capsules and measure their
average length. In some experiments I took
the twenty lowermost capsules of the main
spikes. In this way one average was obtained
for each plant, and combining these into a curve,
it was found that these fluctuations also came
under Quetelet 's law. Thus the individual aver-
ages, and the fluctuations around each of them,
follow the same rule. The first are a measure
for the whole plant, the second only for its parts.

As a general resume we can assert that, as a
rule, a quality is determined in some degree
during the earlier stages of the organism, and
that this determination is valid throughout its

Multiplication of Extremes 749

life. Afterwards only the minor points remain
to be regulated. This makes it at once clear
that the range of individual and partial vari-
ability together must be wider than that of
either of them, taken alone. Partial fluctua-
tions cannot, of course, be excluded. Thus our
comparison is limited to individual and partial
variability on one side, and partial fluctuations
alone on the other side.

Intra-specific selection is thus seen to fall
under two heads: a selection between the in-
dividuals, and a choice within each of them.
The first affords a wider and the latter a nar-
rower field.

Individual variability, considered as the re-
sult of outward influences operative during ex-
treme youth, can be excluded in a very simple
manner. Obviously it suffices to exclude ex-
treme youth, in other words, to exclude the use
of seeds. Multiplication in a vegetative way,
by grafting and budding, by runners or roots,
or by simple division of rootstocks and bulbs is
the way in which to limit variability to the par-
tial half. This is all we may hope to attain, but
experience shows that it is a very efficient means
of limitation. Partial fluctuations are gener-
ally far smaller than individual and partial
fluctuations together.

Individual variability in the vegetable king-

750 Fluctuations

dom might be called seed-variation, as opposed
to partial or bud-fluctuation. And perhaps these
terms are more apt to convey a clear conception
of the distinction than any other. The germ
within the unripe seed is easily understood to
be far more sensitive to external conditions than
a bud.

Multiplication of extremes by seed is thus al-
ways counteracted by individual variability,
which at once reopens all, or nearly all, the ini-
tial possibilities. Multiplication by buds is ex-
empt from this danger and thus leads to a high
degree of uniformity. And this uniformity is in
many cases exactly what the breeder endeavors
to obtain.

We will treat of this reopening of previous
possibilities under the head of regression in the
next lecture. It is not at all absolute, at least
not in one generation. Part of the improve-
ment remains, and favors the next generation.
This part may be estimated approximately as
being about one-third or one-half of the im-
provement attained. Hence the conclusion that
vegetative multiplication gives rise to varieties
which are as a rule twice or thrice as good as
selected varieties of plants propagated by seeds.
Hence, likewise the inference that breeders gen-
erally prefer vegetative multiplication of im-
proved forms, and apply it in all possible cases.

Multiplication of Extremes 751

Of course the application is limited, and forage-
crops and the greater number of vegetables will
always necessarily be propagated by seed.

Nature ordinarily prefers the sexual way.
Asexual multiplications, although very common
with perennial plants, appear not to otfer im-
portant material for selection. Hence it fol-
lows that in comparing the work of nature
with that of man, the results of selection fol-
lowed by vegetative propagation should always
be carefully excluded. Our large bulb-flowers
and delicious fruits have nothing in common
with natural products, and do not yield a stand-
ard by which to judge nature's work.

It is very difficult for a botanist to give a sur-
vey of what practice has attained by the asexual
multiplication of extremes. Nearly all of the
large and more palatable fruits are due to such
efforts. Some flowers and garden-plants af-
ford further instances. By far the greatest
majority of improved asexual varieties, how-
ever, are not the result of pure intra-specific
selection. They are due largely to the choice
of the best existing elementary species, and to
some extent to crosses between them, or be-
tween distinct systematic species. In practice
selection and hybridization go hand in hand and
it is often difficult to ascertain what part of

752 Fluctuations

the result is due to the one, and what to the
other factor.

The scientist, on the contrary, has nothing to
do with the industrial product. His task is the
analysis of the methods, in order to reach a
clear appreciation of the influence of all the
competing factors. This study of the working
causes leads to a better understanding of the
practical processes, and may become the basis
of improvement in methods.

Starting from these considerations, we will
now give some illustrative examples, and for
the first, choose one in which hybridization is
almost completely excluded.

Sugar-canes have long been considered to be
plants without seed. Their numerous varieties
are propagated only in a vegetative way. The
stems are cut into pieces, each bearing one
or two or more nodes with their buds. An
entire variety, though it may be cultivated in
large districts and even in various countries, be-
haves with respect to variability as a single in-
dividual. Its individual fluctuability has been
limited to the earliest period of its life, when it
arose from an unknown seed. The personal
characters that have been stamped on this one
seed, partly by its descent, and partly in the de-
velopment of its germ during the period of
ripening, have become the indelible characters

Multiplication of Extremes 753

of the variety, and only the partial fluctuability,
due to the effect of later influences, can now be
studied statistically.

This study has for its main object the pro-
duction of sugar in the stems, and the curves,
which indicate the percentage of this important
substance in different stems of the same variety,
comply with Quetelet's law. Each variety has
its own average, and around this the data of the
majority of the stems are densely crowded,
while deviations on both sides are rare and be-
come the rarer the wider they are. The ' * Cher-
ibon '' cane is the richest variety cultivated in
Java, and has an average of 19^ sugar, while it
fluctuates between life and 28^. '' Chunnic ''
averages 14^, '' Black Manilla'' 13f and "White
Manilla ' ' 10^ ; their highest and lowest extremes
diverge in the same manner, being for the last
named variety If and 15^.

This partial variability is of high practical
interest, because on it a selection may be found-
ed. According to the conceptions described in
a previous lecture, fluctuating variability is the
result of those outward factors that determine
the strength of development of the plant or the
organ. The inconstancy of the degree of sensi-
bility, combined with the ever-varying weather-
conditions preclude any close proportionality,
but apart from this difficulty there is, in the

754 Fluctuations

main, a distinct relation between organic
strength and the development of single qual-
ities. This correlation has not escaped obser-
vation in the case of the sugar-cane, and it is
known that the best grown stocks are generally
the richest in sugar. Now it is evident that
the best grown and richest stems will have the
greater chance of transmitting these qualities
to the lateral-buds. This at once gives a
basis for vegetative selection, upon which it is
not necessary to choose a small number of very
excellent stems, but simply to avoid the plant-
ing of all those that are below the average. By
this means the yield of the cultures has often
noticeably been enhanced.

As far as experience goes, this sort of selec-
tion, however profitable, does not conduce to the
production of improved races. Only temporary
ameliorations are obtained, and the selection
must be made in the same manner every year.
Moreover the improvement is very limited and
does not give any promise of further increase.
In order to reach this, one has to recur to the in-
dividual fluctuability, and therefore to seed.

Nearly half a century ago, Parris discovered,
on the island of Barbados, that seeds might
occasionally be gathered from the canes. These,
however, yielded only grass-like plants of no
real value. The same observation was made

Multiplication of Extremes 755

shortly afterwards in Java and in other sugar-
producing countries. In the year 1885, Solt-
wedel, the director of one of the experiment sta-
tions for the culture of sugar-cane in Java,
conceived the idea of making use of seedlings
for the production of improved races. This
idea is a very practical one, precisely because of
the possibility of vegetative propagation. If
individuals would show the same range as that
of partial fluctuability, then the choice of the
extremes would at once bring the average up
to the richness of the best stocks. Once at-
tained, this average would be fixed, without fur-
ther efforts.

Unfortunately there is one great drawback.
This is the infertility of the best variety, that
of the ^* Cheribon '' cane. It flowers abun-
dantly in some years, but it has never been
known to produce ripe seeds. For this reason
Soltwedel had to start from the second best sort,
and chose the '* Hawaii " cane. This variety
usually yields about 14^ sugar, and Soltwedel
found among his seedlings one that showed
15,1 This fact was quite unexpected at that
time, and excited widespread interest in the
new method, and since then it has been ap-
plied to numerous varieties, and many thou-
sands of seedlings have been raised and
tested as to their sugar-production.

756 Fluctuations

From a scientific point of view the results are
quite striking. From the practical standpoint,
however, the question is, whether the '' Ha-
waii " and other fertile varieties are adequate
to yield seedlings, which will surpass the
infertile ** Cheribon '' cane. Now " Hawaii "
averages 14^ and '' Cheribon " W, and it
is easily understood that a ^ ' Hawaii ' ' seed-
ling with more than 19% can be expected
only from very large sowings. Hundreds of
thousands of seedlings must be cultivated, and
their juice tested, before this improvement can
be reached. Even then, it may have no signif-
icance for practical purposes. Next to the
amount of sugar comes the resistance to the
disease called ^* Sereli," and the new race
requires to be ameliorated in this important di-
rection, too. Other qualities must also be con-
sidered, and any casual deterioration in
other characters would make all progress
illusory. For these reasons much time is re-
quired to attain distinct improvements.

These great difficulties in the way of selecting
extremes for vegetative propagation are of
course met with everywhere. They impede the
work of the breeder to such a degree, that but
few men are able to surmount them. Breeding
new varieties necessitates the bending of every
effort to this purpose, and a clear conception of

Multiplication of Extremes 757

the manifold aspects of this intricate problem.
These fall under two heads, the exigencies of
practice, and the physiologic laws of varia-
bility. Of course, only the latter heading comes
within the limits of our discussion which in-
cludes two main points. First comes the gen-
eral law of fluctuation that, though slight
deviations from the average may be found
by thousands, or rather in nearly every in-
dividual, larger and therefore important de-
viations are very rare. Thousands of seedlings
must be examined carefully in order to find one
or two from which it might be profitable to
start a new race. This point is the same
for practical and for scientific investigation.
In the second place however, a digression
is met with. The practical man must take
into consideration all the varying qualities of
his improved strains. Some of them must be
increased and others be decreased, and their
common dependency on external conditions
often makes it very difficult to discover the de-
sired combinations. It is obvious, however,
that the neglect of one quality may make all im-
provement of other characters wholly useless.
No augmentation of sugar-percentage, of size
and flavor of fruits can counterbalance an in-
crease in sensitiveness to disease, and so it is
with other qualities also.

758 Fluctuations

Improved races for scientific investigation
can be kept free from infection, and protected
against numerous other injuries. In the exper-
imental garden they may find conditions which
cannot be realized elsewhere. They may show
a luxuriant growth, and prove to be excellent
material for research, but have features which,
having been overlooked at the period of selec-
tion, would at once condemn them if left to
ordinary conditions, or to the competition of
other species.

Considering all these obstacles, it is only nat-
ural that breeders should use every means to
reach their goal. Only in very rare instances
do they follow methods analogous to scientific
processes, which tend to simplify the questions
as much as possible. As a rule, the practical
way is the combination of as many causes of
variability as possible. Now the three great
sources of variability are, as has been pointed
out on several occasions, the original multi-
fomiity of the species, fluctuating variability,
and hybridization. Hence, in practical experi-
ments, all three are combined. Together they
yield results of the highest value, and Bur-
bank's improved fruits and flowers give testi-
mony to the practical significance of this com-
bination.

From a scientific point of view however, it is

Multiplication of Extremes 759

ordinarily difficult, if not impossible, to discern
the part which each of the three great branches
of variability has taken in the origination of the
product. A full analysis is rarely possible, and
the treatment of one of the three factors must
necessarily remain incomplete.

Notwithstanding these considerations, I will
now give some examples in order to show that
fluctuating variability plays a prominent part in
these improvements. Of course it is the third
in importance in the series. First comes the
choice of the material from the assemblage of
species, elementary species and varieties.
Hybridization comes next in importance. But
even the hybrids of the best parents may be im-
proved, because they are no less subject to
Quetelet's law than any other strain. Any
large number of hybrids of the same ancestry
will prove this, and often the excellency of a
hybrid variety depends chiefly, or at least defi-
nitely, on the selection of the best individuals.
Being propagated only in a vegetative way, they
retain their original good qualities through all
further culture and multiplication.

As an illustrative example I will take the
genus Canna. Originally cultivated for its
large and bright foliage only, it has since be-
come a flowering plant of value. Our garden
strains have originated by the crossing of

760 Fluctuations

a number of introduced wild species, among
which the Canna indica is the oldest, now giv-
ing its name to the whole group. It has tall
stems and spikes with rather inconspicuous
flowers with narrow petals. It has been crossed
with C. nepalensis and C. warczewiczii, and
the available historic evidence points to the
vear 1846 as that of the first cross. This was
made by Annee between the indica and the ne-
palensis; it took ten years to multiply them to
the required degree for introduction into com-
merce. These first hybrids had bright foliage
and were tall plants, but their flowers were by
no means remarkable.

Once begun, hybridization was widely prac-
ticed. About the year 1889 Crozy exhibited at
Paris the first beautifully flowering form, which
he named for his wife, '' Madame Crozy."
Since that time he and many others have im-
proved the flowers in the shape and size, as well
as in color and its patterns. In the main,
these ameliorations have been due to the discov-
ery and introduction of new wild species pos-
sessing the required characters. This is illus-
trated by the following incident. In the year
1892 I visited Mr. Crozv at Lvons. He showed
me his nursery and numerous acquisitions, those
of former years as well as those that were quite
new, and which were in the process of rapid

Multiplication of Extremes 761

multiplication, previous to being given to the
trade. I wondered, and asked, why no pure
white variety was present. His answer was:
^^ Because no white species had been found up
to the present time, and there is no other means
of producing white varieties than by crossing
the existing forms with a new white type. ' '

Comparing the varieties produced in succes-
sive periods, it is very easy to appreciate their
gradual improvement. On most points this is
not readily put into words, but the size of the
petals can be measured, and the figures may
convey at least some idea of the real state of
things. Leaving aside the types with small
flowers and cultivated exclusively for their
foliage, the oldest flowers of Canna had
petals of 45 mm. length and 13 mm. breadth.
The ordinary types at the time of my visit had
reached 61 by 21 mm., and the '' Madame
Crozy ' ' showed ^^ by 30 mm. It had however,
already been surpassed by a few commercial va-
rieties, which had the same length but a breadth
of 35 mm. And the latest production, which
required some years of propagation before be-
ing put on the market, measured 83 by 43 mm.
Thus in the lapse of some thirty years the length
had been doubled and the breadth tripled, giv-
ing flowers with broad corollas and with petals

762 Fluctuations

joined all around, resembling the best types of
lilies and amarvllis.

%■'

Striking as this result unquestionably is, it
remains doubtful as to what part of it is due to
the discovery and introduction of new large
flowered species, and what to the selection of
the extremes of fluctuating variability. As far
as I have been able to ascertain however, and
according to the evidence given to me by Mr.
Crozy, selection has had the largest part in re-
gard to the size, while the color-patterns are
introduced qualities.

The scientific analysis of other intricate ex-
amples is still more difficult. To the practical
breeder they often seem very simple, but the
student of hereditv, who wishes to discern the
different factors, is often quite puzzled by this
apparent simplicity. So it is in the case of
the double lilacs, a large number of varieties of
which have recently been originated and intro-
duced into commerce by Lemoine of Nancy. In
the main they owe their origin to the crossing
and recrossing of a single plant of the old
double variety with the numerous existing
single-flowered sorts.

This double variety seems to be as old as the
culture of the lilacs. It was already known to
Hunting, who described it in the year 1671.
Two centuries afterwards, in 1870, a new de-

Mult i plication of Ext rem cs 763

scription was given by Morren, and though
more than one varietal name is recorded in his
paper, it appears from the facts given that even
at that time only one variety existed. It was
commonly called Syringa vulgaris azurea
plena, and seems to have been very rare and
without real ornamental value.

Lemoine, however, conceived the desirability
of a combination of the doubling with the bright
colors and large flower-racemes of other lilacs,
and performed a series of crosses. The
'^ azurea plena '^ has no stamens, and therefore
must be used in all crosses as the pistil-parent ;
its ovary is narrowly inclosed in the tube of the
flower, and difficult to fertilize. On the other
hand, new crosses could be made every year,
and the total number of hvbrids with differ-
ent pollen-parents was rapidly increased.
After five years the hybrids began to flower and
could be used for new crosses, yielding a series
of compound hybrids, which however, were not
kept separate from the products of the first
crosses.

Gradually the number of the flowering speci-
mens increased, and the character of doubling
was observed to be variable to a high degree.
Sometimes only one supernumerary petal was
produced, sometimes a whole new typical corolla
was extruded from within the first. In the same

764 Fluctuations

way the color and the number of the flowers on
each raceme were seen to vary. Thousands of
hybrids were produced, and only those which
exhibited real advantages were selected for
trade. These were multiplied by grafting, and
each variety at present consists only of the buds
of one original individual and their products.
No constancy from seed is assumed, many
varieties are even quite sterile.

Of course, no description was given of the re-
jected forms. It is only stated that many of
them bore either single or poorly filled flow-
ers, or were objectionable in some other way.
The range of variability, from which the choices
were made, is obscure and only the fact of the
selection is prominent. What part is due to
the combination of the parental features and
what to the individual fluctuation of the hybrid
itself cannot be ascertained.

So it is in numerous other instances. The
dahlias have been derived from three or more
original species, and been subjected to cultiva-
tion and hybridization in an ever-increasing
scale for a century. The best varieties are only
propagated in the vegetative way, by the roots
and buds, or by grafting and cutting. Each of
them is, with regard to its hereditary qualities,
only one individual, and the individual charac-
ters were selected at the same time with the

Multiplication of Extremes 765

varietal and hybrid characters. Most of them
are very inconstant from seed and as a rule,
only mixtures are offered for sale in seed-lists.
Which of their ornamental features are due to
fluctuating deviation from an average is of
course unknown. Amaryllis and Gladiolus are
surrounded with the same scientific uncertain-
ties. Eight or ten, or even more, species have
heen combined into one large and multiform
strain, each bringing its peculiar qualities into
the mixed mass. Every hybrid variety is one
individual, being propagated by bulbs only.
Colors and color-patterns, shape of petals and
other marks, have been derived from the wild
ancestors, but the large size of many of the best
varieties is probably due to the selection of the
extremes of fluctuating variability. So it is
with the begonias of our gardens, which are
also composite hybrids, but are usually sown
on a very large scale. Flowers of 15 cm. diam-
eter are very showy, but there can be no doubt
about the manner in which they are produced,
as the wild species fall far short of this size.

Among vegetables the potatoes afford an-
other instance. Originally quite a number of
good species were in culture, most of them hav-
ing small tubers. Our present varieties are due
to hvbridization and selection, each of them
being propagated only in the vegetative way.

766 Fluctuations

Selection is founded upon different qualities, ac-
cording to the use to be made of the new sort.
Potatoes for the factory have even been selected
for their amount of starch, and in this case at
least, fluctuating variability has played a very
important part in the improvement of the race.

Vegetative propagation has the great advan-
tage of exempting the varieties from regression
to mediocrity, which always follows multiplica-
tion by seeds. It affords the possibility of keep-
ing the extremes constant, and this is not its
only advantage. Another, likewise highly in-
teresting, side of tlie question is the uniformity
of the whole strain. This is especially im-
portant in the case of fruits, though ordinarily
it is regarded as a matter of course, but there
are some exceptions which give proof of the
real importance of the usual condition. For ex-
ample, the walnut-tree. Thousands of acres of
walnut-orchards consist of seedling trees
grown from nuts of unknown parentage. The
result is a great diversity in the types of trees
and in the size and shape of the nuts, and this
diversity is an obvious disadvantage to the in-
dustry. The cause lies in the enormous diffi-
culties attached to grafting or budding of these
trees, which make this method very expensive
and to a high degree uncertain and unsatis-
factory.

Multiplication of Extremes 767

After this hasty survey of the more reliable
facts of the practice of an asexual multiplica-
tion of the extremes of fluctuating variability,
we may now return to the previously mentioned
theoretical considerations. These are con-
cerned with an estimation of the chances of the
occurrence of deviations, large enough to ex-
hibit commercial value. This chance may be
calculated on the basis of Quetelet's law,
whenever the agreement of the fluctuation of the
qualit}^ under consideration has been empiric-
ally determined. In the discussion of the meth-
ods of comparing two curves, we have pointed
to the quartiles as the decisive points, and to
the necessity of drawing the curves so that these
points are made to overlie one another, on
each side of the average. If now we calculate
the binomium of Newton for different values of
the exponent, the sum of the coefficients is
doubled for each higher unit of the exponent,
and at the same time the extreme limit of the
curve is extended one step farther. Hence it is
possible to calculate a relation between the
value of the extreme and the number of cases
required. It would take us too long to give this
calculation in detail, but it is easily seen that
for each succeeding step the number of individ-
uals must be doubled, though the length of the
steps, or the amount of increase of the quality

768 Fluctuations

remains the same. The result is that many-
thousands of seedlings are required to go be-
yond the ordinary range of variations, and that
every further improvement requires the doub-
ling of the whole culture. If ten thousand do
not give a profitable deviation, the next step re-
quires twenty thousand, the following forty
thousand, and so on. And all this work would
be necessary for the improvement of a single
quality, while practice requires the examination
and amelioration of nearly all the variable
characters of the strain.

Hence the rule that great results can only be
obtained by the use of large numbers, but it is
of no avail to state this conclusion from a scien-
tific point of view. Scientific experimenters
will rarely be able to sacrifice fifty thousand
plants to a single selection. The problem is to
introduce the principle into practice and to
prove its direct usefulness and reliability. It is
to Luther Burbank that we owe this great
achievement. His principles are in full har-
mony with the teachings of science. His meth-
ods are hybridization and selection in the
broadest sense and on the largest scale. One
very illustrative example of his methods must
suffice to convey an idea of the work necessary
to produce a new race of superlative excel-
lency. Forty thousand blackberry and rasp-

Multiplication of Extremes 769

berry hybrids were produced and grown
until the fruit matured. Then from the whole
lot a single variety was chosen as tlie best.
It is now known under the name of '' Paradox.'^
All others were uprooted with their crop of
ripening berries, heaped up into a pile twelve
feet wide, fourteen feet high and twenty-two
feet long, and burned. Nothing remained of
that expensive and lengthy experiment, except
the one parent-plant of the new variety. Sim-
ilar selections and similar amount of work have
produced the famous plums, the brambles and
the blackberries, the Shasta daisy, the peach-
almond, the improved blueberries, the hybrid
lilies, and the many other valuable fruits and
garden-flowers that have made the fame of Bur-
bank and the glory of horticultural California.

Lecture XXVII

INCONSTANCY OF IMPROVED RACES

The greater advantages of the asexual multi-
plication of extremes are of course restricted to
perennial and woody plants. Annual and bi-
ennial species cannot as a rule, be propagated
in this way, and even with some perennials hor-
ticulturists prefer the sale of seeds to that of
roots and bulbs. In all these cases it is clear
that the exclusion of the individual variability,
which was shown to be an important point in
the last lecture, must be sacrificed.

Seed-propagation is subject to individual as
well as to fluctuating variability. The first
could perhaps be designated by another term,
embryonic variability, since it indicates the
fluctuations occurring during the period of
development of the germ. This period begins
with the fusion of the male and female elements
and is largely dependent upon the vigor of these
cells at the moment, and on the varying qualities
they may have acquired. It comprises in the
main the time of the ripening of the seed, and

770

Inconstancy of Improved Races 771

might perhaps best be considered to end with
the beginning of the resting stage of the ripe
seed. Hence it is clear that the variability of
seed-propagated annual races has a wider range
than that of perennials, shrubs and trees. At
present it is difficult to discern exactly the part
each of these two main factors plays in the
process. Many indications are found however,
that make it probable that embryonic variability
is wider, and perhaps of far greater impor-
tance than the subsequent partial fluctuations.
The high degree of similarity between the single
specimens of a vegetative variety, and the large
amount of variability in seed-races strongly
supports this view. The propagation and multi-
plication of the extremes of fluctuating varia-
bility by means of seeds requires a close
consideration of the relation between seedling
and parent. The easiest way to get a clear con-
ception of this relation is to make use of the
ideas concerning the dependency of variability
upon nourishment. Assuming these to be cor-
rect in the main, and leaving aside all minor
questions, we may conclude that the chosen
extreme individual is one of the best nourished
and intrinsically most vigorous of the whole
culture. On account of these very qualities it
is capable of nourishing all of its organs bettor
and also its seeds. In other words, the seeds

772 Fluctuations

of the extreme individuals have exceptional
chances of becoming better nourished than the
average of the seeds of the race. Applying the
same rule to them, it is easily understood that
they will vary, by reason of this better nourish-
ment, in a direction corresponding to that of
their parent.

This discussion gives a very simple explana-
tion of the acknowledged fact that the seeds of
the extremes are in the main the best for the
propagation of the race. It does not include
however, all the causes for this preferment.
Some are of older date and due to previous in-
fluences.

A second point in our discussion is the appre-
ciation of the fact that a single individual
may be chosen to gather the seed from, and that
these seeds, and the young plants they yield, are
as a rule, numerous. Hence it follows that we
are to compare their average and their ex-
tremes with the qualities of the parents. Both
are of practical as well as of theoretical inter-
est. The average of the progeny is to be con-
sidered as the chief result of the selection in
the previous generation, while the extremes, at
least those which depart in the same direction,
are obviously the means of further improve-
ment of the race.

Thus our discussion should be divided into

Inconstancy of Improved Races ll'd

two heads. One of these comprises the rela-
tion of the average of the progeny to the excep-
tional qualities of the chosen parent, and the
other the relation of exceptional offspring to
the exceptional parents.

Let us consider the averages first. Are they
to be expected to be equal to the unique quality
of the parent, or perhaps to be the same as the
average of the whole unselected race? Neither
of these cases occur. Experience is clear and
definite on this important point. Vilmorin,
when making the first selections to improve the
amount of sugar in beets, was struck with the
fact that the average of the progeny lies be-
tween that of the original strain and the qual-
ity of the chosen parent. He expressed his ob-
servation by stating that the progeny are
grouped around and diverge in all directions
from some point, placed on the line which unites
their parent with the type from which it sprang.
All breeders agree on this point, and in scien-
tific experiments it has often been confirmed.
We shall take up some illustrative examples
presently, but in order to make them clear, it is
necessary to give a closer consideration to the
results of Vilmorin.

From his experience it follows that the aver-
age of the progeny is higher than that of the
race at large, but lower than the chosen parent.

:'7

774 Fluctuations

In other words, there is a progression and a re-
gression. A progression in relation to the whole
race, and a regression in comparison with the
parent. The significance of this becomes clear
at once, if we recall the constancy of the variety
which could be obtained from the selected ex-
treme in the case of vegetative multiplication.
The progression is what the breeder wants, the
regression what he detests. Regression is the
permanency of part of the mediocrity which
the selection was invoked to overcome. Mani-
festly it is of the highest interest that the pro-
gression should be as large, and the regression
as small as possible. In order to attain this
goal the first question is to know the exact meas-
ure of progression and regression as they are
exhibiting themselves in the given cases, and
the second is to inquire into the influences, on
which this proportion may be incumbent.

At present our notions concerning the first
point are still very limited and those concern-
ing the second extremely vague. Statistical in-
quiries have led to some definite ideas about the
importance of regression, and these furnish a
basis for experimental researches concerning
the causes of the phenomenon. Very ad-
vantageous material for the study of pro-
gression and regression in the realm of
fluctuating variability is afforded by the

Inconstancy of Improved Races lib

ears of corn or maize. The kernels are ar-
ranged in longitudinal rows, and these rows are
observed to occur in varying, but always even,
numbers. This latter circumstance is due to the
fact that each two neighboring rows contain
the lateral branches of a single row of spikelets,
the axes of which however, are included in the
fleshy body of the ear. The variation of the
number of the rows is easily seen to comply with
Quetelet's law, and often 30 or 40 ears suf-
fice to give a trustworthy curve. Fritz Miil-
ler made some experiments upon the inheritance
of the number of the rows, in Brazil. He chose
a race which averaged 12 rows, selected
ears with 14, 16 and 18 rows, etc., and sowed
their kernels separately. In each of these cul-
tures he counted the rows of the seeds on the
ears of all the plants when ripe, and calculated
their average. This average, of course, does
not necessarily correspond to a whole number,
and fractions should not be neglected.

According to Vilmorin's rule he always found
some progression of the average and some re-
gression. Both were the larger, the more the
parent-ear differed from the general average,
but the proportion between both remained the
same, and seems independent of the amount of
the deviation. Putting the deviation at 5,
the progression calculated from his figures is

776 Fluctuations

2 and the regression 3. In other words the av-
erage of the progeny has gained over the aver-
age of the original variety slightly more than
one-third, and slightly less than one-half of the
parental deviation. I have repeated this exper-
iment of Fritz Miiller's and obtained nearlv the
same regression of three-fifths, though working
with another variety, and under widely different
climatic conditions.

The figures of Fritz Miiller were, as given be-
low, in one experiment. In the last column I
put the improvement calculated for a propor-
tion of two-fifths above the initial average of 12.

Rows on
parent ears

Average of rows
of progeny

12 + ^ of

Difference

u

12.6

12.8

16

14.1

13.6

18

15.2

14.4

20

15.8

15.2

22

16.1

16.0

Gralton, in his work on natural inheritance,
describes an experiment with the seeds of the
sweet pea or Lathyrus odoratus. He deter-
mined the average size in a lot of purchased
seeds, and selected groups of seeds of differ-
ent, but for each group constant, sizes. These
were sown, and the average of the seeds was
determined anew in the subsequent harvest they
yielded. These figures agreed with the rule of
Vilmorin and were calculated in the manner

Inconstancy of Improved Races 111

given for the test of the corn. The progression
and regression were found to be proportionate
to the amount of the deviation. The progres-
sion of the average was one-third, and the re-
gression in consequence two-thirds of the total
deviation. The amelioration is thus seen to be
nearly, though not exactly, the same as in the
previous case.

From the evidence of the other correspond-
ing experiments, and from various statistical
inquiries it seems that the value of the pro-
gression is nearly the same in most cases, irre-
spective of the species used and the quality con-
sidered. It may be said to be from one-third to
one-half of the parental deviation, and in this
form the statement is obviously of wide and
easy applicability.

Our figures also demonstrate the great pre-
eminence of vegetative varieties above the im-
proved strains multiplied by seeds. They have
a definite relation. Asexually multiplied
strains may be said to be generally two times
or even three times superior to the com-
mon offspring. This is a difference of great
practical importance, and should never be lost
sight of in theoretical considerations of the pro-
ductive capacity of selection. Multiplication by
seed however, has one great advantage over
the asexual method ; it may be repeated. The

778 Fluctuations

selection is not limited to a single choice, but
may be applied in two or more succeeding gen-
erations. Obviously such a repetition affords
a better chance of increasing the progression of
the average and of ameliorating the race to a
greater degree than would be possible by a sin-
gle choice. This principle of repeated selection
is at present the prominent feature of race-
improvement. Next to variety-testing and
hybridizing it is the great source of the steady
progression of agricultural crops. From a
practical standpoint the method is clear and as
perfect as might be expected, but this is not the
side of the problem with which we are concerned
here. The theoretical analysis and explana-
tion of the results obtained, however, is sub-
ject to much doubt, and to a great divergence
of conceptions. So it is also with the applica-
tion of the practical processes to those occur-
ring in nature. Some assume that here repeated
selection is only of subordinate importance,
while others declare that the whole process of
evolution is due to this agency. This very im-
portant point however, will be reserved for the
next lecture, and only the facts available at pres-
ent will be considered here.

As a first example we may take the ray-florets
of the composites. On a former occasion we
have dealt with their fluctuation in number and

Inconstancy of Improved Races 11^

found that it is highly variable and complies in
the main with Qnetelet's law. Madia elegans,
a garden-species, has on the average 21 rays
on each head, fluctuating between 16 and 25 or
more. I saved the seeds of a plant with only

17 rays on the terminal head, and got from
them a culture which averaged 19 rays, which
is the mean between 21 and 17. In this second
generation I observed the extremes to be 22 and
12, and selected a plant with 13 rays as the
parent for a continuation of the ex})eriment.
The plants, which I got from its seeds, averaged

18 and showed 22 and 13 as extremes. The total
progression of the average was thus, in two gen-
erations, from 21 to 18, and the total regression
from 13 to 18, and the proportion is thus seen
to diminish by the repetition rather than to in-
crease.

This experiment, however, is of course too
imperfect upon which to found general conclu-
sions. It only proves the important fact that
the improved average of the second generation
is not the starting-point for the further un-
provement. But the second generation allows a
choice of an extreme, which diverges noticeably
more from the mean than any individual of the
first culture, and thereby gives a larger amount
of absolute progression, even if the proportion
between progression and regression remains

780 Fluctuations

the same. The repetition is only an easy meth-
od of getting more widely deviating extremes ;
whether it has, besides this, another effect, re-
mains doubtful. In order to be able to decide
this question, it is necessary to repeat the selec-
tion during a series of generations. In this
way the individual faults may be removed as
far as possible. I chose an experiment of Fritz
Miiller, relating to the number of rows of
grains on the ears exactly as in the case above
referred to, and which I have repeated in my
experimental garden at Amsterdam.

I started from a variety known to fructify
fairly regularly in our climate, and exhibiting
in the mean 12 - 14 rows, but varying between 8
and 20 as exceptional cases. I chose an ear
with 16 rows and sowed its seeds in 1887. A
number of plants were obtained, from each of
which, one ear was chosen in order to count its
rows. An average of 15 rows was found with
variations complying with Quetelet's law. One
ear reached 22 rows, but had not been fertilized,
some others had 20 rows, and the best of these
was chosen for the continuation of the experi-
ment. I repeated the sowing during 6 subse-
quent generations in the same way, choosing
each time the most beautiful ear from among
those with the greatest number of rows. Un-
fortunately with the increase of the number the

Inconstancy of Improved Races 781

size of the grains decreases, the total amount
of nourishment available for all of them
remaining about the same. Thus the
kernels and consequently the new plants be-
came smaller and weaker, and the chance
of fertilization was diminished in the ears
with the highest number of rows. Conse-
quently the choice was limited, and after having
twice chosen a spike with 20 and once one with
24 rows, I finally preferred those with the inter-
mediate number of 22.

This repeated choice has brought the aver-
age of my race up from 13 to 20, and thus to the
extreme limit of the original variety. Seven
years were required to attain this result, or on
an average the progression was one row in a
year. This augmentation was accompanied by
an accompanying movement of the whole group
in the same direction. The extreme on the side
of the small numbers came up from 8 to 12
rows, and cobs with 8 or 10 rows did not appear
in my race later than the third generation. On
the other side the extreme reached 28, a figure
never reached by the original variety as culti-
vated with us, and ears with 24 and 26 rows
have been seen during the four last generations
in increasing numbers.

This slow and gradual amelioration was part-
ly due to the mode of pollination of the corn.

782 Fluctuations

The pollen falls from the male spikes on the
ears of the same plant, but also is easily blown
on surrounding spikes. In order to get the
required amount of seed it is necessary in our
climate to encroach as little as possible upon
free pollination, aiding the self-pollination,
but taking no precautions against intercross-
ing. It is assumed that the choice of the best
ears indicates the plants which have had the
best pollen-parents as well as the best pistil-
parents, and that selection here, as in other
cases, corrects the faults of free intercrossing.
But it is granted that this correction is only a
slow one, and accounts in a great degree for the
slowness of the progression. Under better cli-
matic conditions and with a more entire isola-
tion of the individuals, it seems very probable
that the same result could have been reached
in fewer generations.

However this may be, the fact is that by re-
peated selection the strain can be ameliorated
to a greater extent than by a single choice. This
result completely agrees with the general expe-
rience of breeders and the example given
is only an instance of a universal rule. It has
the advantage of being capable of being re-
corded in a numerical way, and of allowing a
detailed and definite description of all the suc-
ceeding generations. The entire harvest of all

Inconstancy of Improved Races 783

of them has been counted and the figures com-
bined into curves, which at once show the whole
course of the pedigree-experiment. These
curves have in the main taken the same shape,
and have only gradually been moved in the
chosen direction.

Three points are now to be considered in
connection with this experiment. The first is
the size of the cultures required for the result-
ing amelioration. In other words, would it have
been possible to attain an average of 20 rows
in a single experiment? This is a matter of cal-
culation, and the calculation must be based upon
the ^experience related above, that the progres-
sion in the case of maize is equal to two-fifths of
the parental deviation. A cob with 20 rows
means a deviation of 7 from the average of 13,
the incipient value of my race. To reach such
an average at once, an ear would be required
with 7x^/2=17% rows above the average, or
an ear with 30-32 rows. These never occur,
but the rule given in a previous lecture gives a
method of calculating the probability of their
occurrence, or in other words, the number of
ears required to give a chance of finding such
an ear. It would take too long to give this cal-
culation here, but I find that approximately 12,-
000 ears would be required to give one witli 28
rows, which was the highest number attained in

784

Fluctuations

my experiment, while 100,000 ears would afford
a chance of one with 32 rows.* Had I been
able to secure and inspect this number of ears,
perhaps I would have needed only a year to get
an average of 20 rows. This however, not be-
ing the case, I have worked for seven years, but
on the other hand have cultivated all in all only
about one thousand individuals for the entire
experiment.

Obviously this reduction of the size of the ex-
periment is of importance. One hundred
thousand ears of corn could of course, be se-
cured directly from trade or from some indus-
trial culture, but corn is cultivated only to a
small extent in Holland, and in most cases the
requisite number of individuals would be larger
than that afforded by any single plantation.

Repeated selection is thereby seen to be the
means of reducing the size of the required cul-
tures to possible measures, not only in the ex-
perimental-garden, but also for industrial pur-
poses. A selection from among 60000 - 100000
individuals may be within reach of Burbank,
but of few others. As a rule they prefer a
longer time with a smaller lot of plants. This

* On about 200 ears the variability ranges from 8-22 rows,
and this leads approximately to one row more by each doubling
of the numbers of instances. One ear with 22 rows in
200 would thus lead to the expectation of one ear with 32
rows in 100,000 ears.

Inconstancy of Improved tiacea 785

is exactly what is gained by repeated selections.
To my mind this reduction of the size of the cul-
tures is probably the sole effect of the repeti-
tion. But experience is lacking on this point,
and exact comparisons should be made when-
ever possible, between the descendants of a
unique but extreme choice, and a repeated but
smaller selection. The effect of the repetition
on the nourishment of the chosen representa-
tives should be studied, for it is clear that a
plant with 22 rows, the parents and grandpar-
ents of which had the same number, indicates a
better condition of internal qualities than one
with the same number of rows, produced acci-
dentally from the common race. In this way it
may perhaps be possible to explain, why in my
experiment an ear with 22 rows gave an average
offspring with 20, while the calculation, found-
ed on the regression alone would require a
parental ear with 32 rows.

However, as already stated, this discussion
is only intended to convey some general idea
as to the reduction of the cultures by means of
repeated selections, as the material at hand is
wholly inadequate for any closer calculation.
This important point of the reduction may be
illustrated in still another manner.

The sowing of very large numbers is only re-
quired because it is impossible to tell from the

786 Fluctuations

inspection of the seeds which of them will yield
the desired individual. But what is impossible
in the inspection of the seeds may be feasible,
at least in important measure, in the inspection
of the plants which bear the seeds. Whenever
such an inspection demonstrates ditferences, in
manifest connection with the quality under con-
sideration, any one will readily grant that it
would be useless to sow the seeds of the worst
plants, and that even the whole average might
be thrown over, if it were only possible to point
out a number of the best. But it is clear that
by this inspection of the parent-plants the prin-
ciple of repeated selection is introduced for two
succeeding generations, and that its application
to a larger series of generations is only a ques-
tion of secondary importance.

Summing up our discussion of this first point
we may assert that repeated selection is only
selection on a small and practical scale, while a
single choice would require numbers of indi-
viduals higher than are ordinarily available.

A second discussion in connection with our
pedigree-culture of corn is the question whether
the amelioration obtained was of a dur-
able nature, or only temporary. In other
words, whether the progeny of the race would
remain constant, if cultivated after cessation
of the selection. In order to ascertain this, I

Inconstancy of Improved Races 787

continued the culture during several genera-
tions, choosing ears with less than the average
number of rows. The excellence of the
race at once disappeared, and the ordinary
average of the variety from which I had started
seven years before, returned within two or three
seasons. This shows that the attained improve-
ment is neither fixed nor assured and is depend-
ent on continued selection. This result only
confirms the universal experience of breeders,
which teaches the general dependency of im-
proved races on continued selection. Here a
striking contrast with elementary species or
true varieties is obvious. The strains which na-
ture affords are true to their type; their aver-
age condition remains the same during all the
succeeding generations, and even if it should
be slightly altered by changes in the external
conditions, it returns to the type, as soon as
these changes come to an end. It is a real aver-
age, being the sum of the contribution of all
the members of the strain. Improved races
have only an apparent average, which is in fact
biased by the exclusion of whole groups of in-
dividuals. If left to themselves, their appear-
ance changes, and the real average soon re-
turns. This is the common experience of breed-
ers.

A third point is to be discussed in con-

788 Fluctuations

nection with the detailed pedigree-cultures. It
is the question as to what might be expected
from a continuation of improvement selection.
Would it be possible to obtain any imaginable
deviation from the original type, and to reach
independency from further selection? This
point has not until now attracted any practical
interest, and from a practical point of view and
within the limits of ordinary cultures, it seems
impossible to obtain a positive answer. But
in the theoretical discussion of the problems of
descent it has become of the highest unportance,
and therefore requires a separate treatment,
which will be reserved for the next lecture.

Here we come upon another equally diffi-
cult problem. It relates to the proportion of
embryonic or individual fluctuation, to partial
variation as involved in the process of selec-
tion. Probably all qualities which may be sub-
jected to selection vary according to both prin-
ciples, the embryonic decision giving only a
more definite average, around which the parts
of the individual are still allowed to oscillate.
It is so with the corn, and whenever two
or more ears are ripening or even only flower-
ing on the same plant, differences of a partial
nature may be seen in the number of their rows.
These fluctuations are only small however, or-
dinarily not exceeding two and rarely four

Inconstancy of Improved Races 781)

rows. Choosing always the principal ear,
the figures may be taken to indicate the de-
gree of personal deviation from the average of
the race. But whenever we make a mistake, and
perchance sow from an ear, the deviation of
which was largely due to partial variation, the
regression should be expected to become con-
siderably larger. Hence it must be conceded
that exact calculations of the phenomena of in-
heritance are subject to much uncertainty,
resulting from our very imperfect knowledge
concerning the real proportion of the contribut-
ing factors, and the difficulty of ascertaining
their influence in any given case. Here also we
encounter more doubts than real facts, and much
remains to be done before exact calculations
may become of real scientific value.

Returning to the question of the effects of se-
lection in the long run, two essentially differ-
ent cases are to be considered. Extremes may
be selected from among the variants of ordinary
fluctuating variability, or from ever-sporting
varieties. These last we have shown to be
double races. Their peculiar and wide range of
variability is due to the substitution of two
characters, which exclude one another, or if
combined, are diminished in various degrees.
Striped flowers and stocks, "five-leaved" clover,
pistilloid opium-poppies and numerous other

790 Fluctuations

monstrosities have been dealt with as instances
of such ever-sporting varieties.

Now the question may be put, what would be
the effect of selection if in long series of years
one of the two characters of such a double race
were preferred continuously, to the complete
exclusion of the other. Would the race become
changed thereby? Could it be affected to such
a degree as to gradually lose the inactive qual-
ity, and cease to be a double race?

Here manifestly we have a means by which
to determine what selection is able to ac-
complish. Physiologic experiments may be
said to be too short to give any definite
evidence. But cases may be cited where
nature has selected during long centuries
and with absolute constancy in her choice.
Moreover unconscious selections by man have
often worked in an analogous manner, and
many cultivated plants may be put to the
test concerning the evidence they might give
on this point. Stating beforehand the result of
this inquiry, we may assert that long-continued
selection has absolutely no appreciable effect.
Of course I do not deny the splendid results of
selection during the first few years, nor the ne-
cessity of continued selection to keep the im-
proved races to the height of their ameliorated
qualities. I only wish to state that the work

Inconstancy of Improved Races 71)1

of selection here finds its limit and that cen-
turies and perhaps geologic periods of contin-
ued effort in the same direction are not capable
of adding anything more to the initial effect.
Some illustrative examples may suffice to
prove the validity of this assertion. Every bot-
anist who has studied the agricultural practice
of plant-breeding, or the causes of the geo-
graphic distribution of plants, will easily recall
to his mind numerous similar cases. Perhaps
the most striking instance is afforded by culti-
vated biennial plants. The most important of
them are forage-beets and sugar-beets. They
are, of course, cultivated only as biennials,
but some annual specimens may be seen each
year and in nearly every field. They arise
from the same seed as the normal individuals,
and their number is obviously dependent on
external conditions, and especially on the time
of sowing. Ordinary cultures often show as
much as 1^ of these useless plants, but the exi-
gencies of time and available labor often com-
pel the cultivator to have a large part of his
fields sown before spring. In central Eu-
rope, where the climate is unfavorable at this
season, the beets respond by the production of
far larger proportions of annual specimens,
their number coming often up to 20^ or more,
thus constituting noticeable losses in the prod-

792 Fluctuations

uct of the whole field. Rimpau, who has made
a thorough study of this evil and has shown its
dependency on various external conditions, has
also tried to find methods of selection with the
aim of overcoming it, or at least of reducing it
to uninjurious proportions. But in these ef-
forts he has reached no practical result. The
annuals are simply inexterminable.

Coming to the alternative side of the problem
it is clear that annuals have always been ex-
cluded in the selection. Their seeds cannot be
mixed with the good harvest, not even accident-
ally, since they have ripened in a previous year.
In order to bear seeds in the second year beets
must be taken from the field, and kept free
from frost through the winter. The following
spring they are planted out, and it is obvious
that even the most careless farmer is not liable
to mix them with annual specimens. Hence we
may conclude that a strict and unexcelled proc-
ess of selection has been applied to the destruc-
tion of this tendency, not only for sugar-beets,
since Vilmorin's time, when selection had be-
come a well understood process, but also for
forage-beets since the beginning of beet-
culture. Although unconscious, the selection of
biennials must have been uninterrupted and
strict throughout many centuries.

It has had no effect at all. Annuals are seen

Inconstancy of Improved Races 793

to return every year. They are ineradicable.
Every individual is in the possession of this
latent quality and liable to convert it into
activity as soon as the circumstances provoke
its appearance, as proved by the increase of an-
nuals in the early sowings. Hence the conclu-
sion that selection in the long run is not ade-
quate to deliver plants from injurious qualities.
Other proofs could be given by other biennials,
and among them the stray annual plants of
common carrots are perhaps the most noto-
rious. In my own cultures of evening-prim-
roses I have preferred the annuals and ex-
cluded the biennials, but without being able to
produce a pure annual race. As soon as cir-
cumstances are favorable, the biennials return
in large numbers. Cereals give analogous
proofs. . Summer and winter varieties have
been cultivated separately for centuries, but in
trials it is often easy to convert the one into
the other. No real and definite isolation has
resulted from the effect of the long continued
unconscious selection.

Striped flowers, striped fruits, and especially
striped radishes afford further examples. It
would be quite superfluous to dwell upon them.
Selection always tends to exclude the mono-
chromatic specimens, but does not proven t
their return in every generation. Numorous

794 Fluctuations

rare monstrosities are in the same category,
especially when they are of so rare occurrence
as not to give any noticeable contribution to
the seed-production, or even if they render their
bearers incapable of reproduction. In such
cases the selection of normal plants is very se-
vere or even absolute, but the anomalies are by
no means exterminated. Any favorable circum-
stances, or experimental selection in their be-
half shows them to be still capable of full devel-
opment. Numerous cases of such subordinate
hereditary characters constitute the greater
part of the science of vegetable teratology.

If it should be objected that all these cases
cover too short a time to be decisive, or at least
fail in giving evidence relative to former times,
alpine plants afford a proof which one can
hardly expect to be surpassed. During the
whole present geologic epoch they have been
subjected to the never failing selection of their
climate and other external conditions. They
exhibit a full and striking adaptation to these
conditions, but also possess the latent capacity
for assuming lowland characters as soon as
they are transported into such environment.
Obviously this capacity never becomes active
on the mountains, and is always counteracted
by selection. This agency is evidently without
any effect, for as we have seen when dealing

Inconstancy of Improved Races 7ii5

with the experiments of Nageli, Bonnier and
others, each single individual may change its
habits and its aspect in response to transplanta-
tion. The climate has an exceedingly great in-
fluence on each individual, but the continuance
of this influence is without permanent result.

So much concerning ever-sporting varie-
ties and double adaptations. We now come to
the effects of a continuous selection of simple
characters.

Here the sugar-beets stand preeminent.
Since Vilmorin's time they have been selected
according to the amount of sugar in their roots,
and the result has been the most striking that
has ever been attained, if considered from the
standpoint of practice. But if critically exam-
ined, with no other aim than a scientific appre-
ciation of the improvement in comparison with
other processes of selection, the support of the
evidence for the theory of accumulative influ-
ence proves to be very small.

The amount of sugar is expressed by percent-
age-figures. These however, are dependent on
various causes, besides the real quantity of su-
gar produced. One of these causes is the quan-
tity of watery fluid in the tissues, and this in its
turn is dependent on the culture in diyer or
moister soil, and on the amount of moisture in
the air, and the same variety of sugar-beets

796 Fluctuations

yields higher percentage-figures in a dry region
than in a wet one. This is seen when compar-
ing, for instance, the results of the analyses
from the sandy provinces of Holland with those
from the clay-meadows, and it is very well
known that Californian beets average as high
as 26^ or more, while the best European beets
remain at about 20^. As far as I have been
able to ascertain, these figures however, are not
indicative of any difference of race, but simply
direct responses to the conditions of climate
and of soil.

Apart from these considerations the improve-
ment reached in half a century or in about
twenty to thirty generations is not suggestive
of anything absolute. Everything is fluctuating
now, even as it was at the outset, and equally
dependent on continual care. Vilmorin has
given some figures for the beets of the first
generations from which he started his race. He
quotes 14^ as a recommendable amount, and 7
and 21 as the extreme instances of his analy-
ses. However incorrect these figures may be,
they coincide to a striking degree with the pres-
ent condition of the best European races. Of
course minor values are excluded each year by
the selection, and in consequence the average
value has increased. For the year 1874 we find
a standard of 10 - 14^ considered as normal,

Inconstancy of Improved Races 797

bad years giving 10;^, good years from Vl'j^ to
14;^ in the average. Extreme instances exceeded
17^. From that time the practice of the pohir-
ization of the juice for the estimate of the sugar
has rapidly spread throughout Europe, and a
definite increase of the average value soon re-
sulted. This however, often does not exceed
14^, and beets selected in the field for the pur-
pose of polarization come up to an average of
15 to 16^, varying downward to less than 10^
and upward to 20 and 21^. In the main the fig-
ures are the same as those of Vilmorin, the
range of variability has not been reduced, and
higher extremes are not reached. An average
increase of 1^ is of great practical importance,
and nothing can excel the industry and care dis-
played in the improvement of the beet-races.
Notwithstanding this a lasting influence has not
been exercised; the methods of selection have
been improved, and the number of polarized
beets has been brought up to some hundreds of
thousands in single factories, but the improve-
ment is still as dependent upon continuous selec-
tion as it was half a century ago.

The process is practically very successful, but
the support afforded by.it to the selection-
theory vanishes on critical examination.

Lecture XXVIII

ARTIFICIAL AND NATURAL SELECTION

The comparison of artificial and natural se-
lection has furnished material support for the
theory of descent, and in turn been the object
of constant criticism since the time of Darwin.
The criticisms, in greater part, have arisen
chiefly from an imperfect knowledge of both
processes. By the aid of distinctions recently
made possible, the contrast between elementary
species and improved races has become much
more vivid, and promises to yield better results
on which to base comparisons of artificial and
natural selection.

Elementary species, as we have seen in
earlier lectures, occur in wild and in culti-
vated plants. In older genera and systematic
species they are often present in small numbers
only, but many of the more recent wild types
and also many of the cultivated forms
are very rich in this respect. In agriculture
the choice of the most adequate elementary
forms for any special purpose is ac-

798

Artificial and Natural Selection 799

knowledged as the first step in the way
of selection, and is designated by the name
of variety-testing, applying the term variety to
all the subdivisions of systematic species indis-
criminately. In natural processes it bears tlie
title of survival of species. The fact that re-
cent types show large numbers, and in some in-
stances even hundreds of minor constant fonus,
while the older genera are considerably reduced
in this respect, is commonly explained by the
assumption of extinction of species on a corre-
spondingly large scale. This extinction is con-
sidered to affect the unfit in a higher measure
than the fit. Consequently the former vanish,
often without leaving any trace of their exist-
ence, and only those that prove to be sufficiently
adapted to the surrounding external conditions,
resist and survive.

This selection exhibits far-reaching analo-
gies between the artificial and the natural proc-
esses, and is in both cases of the very highest
importance. In nature the dying out of unfit
mutations is the result of the great struggle for
life. In a previous lecture we have compared
its agency with that of a sieve. All elements
which are too small or too weak fall through,
and only those are preserved which resist the
sifting process. Reduced in number they
thrive and multiply and are thus enabh^l to

800 Fluctuations

strike out new mutative changes. These are
again submitted to the sifting tests, and the fre-
quent repetition of this process is considered
to give a good explanation of the manifold,
highly complicated, and admirable structures
which strike the beginner as the only real adap-
tations in nature.

Exactly in the same way artificial selection
isolates and preserves some elementary species,
while it destroys others. Of course the time is
not sufficient to secure new mutations, or at
least these are only rare at present, and
their occurrence is doubtful in historic periods.
Apart from this unavoidable difference the
analog}^ between natural and artificial selection
appears to me to be very striking.

This form of selection may be termed selec-
tion between species. Opposed to it stands the
selection within the elementary species or va-
riety. It has of late, alone come to be known as
selection, though in reality it does not deserve
this distinction. I have already detailed the
historical evidence which gives preference to
selection between species. The process can best
be designated by the name of intra-specific se-
lection, if it is understood that the term intra-
specific is meant to apply to the conception of
small or elementary species.

I do not wish to propose new terms, but

Artificial and Natural Selection 801

I think that the principal differences might bet-
ter become understood by the introduction of
the word election into the discussion of (lues-
tions of heredity. Election meant formerly the
preferential choice of single individuals, wliilo
the derivation of the word selection points to a
segregation of assemblies into their hirger parts.
Or to state it in a shorter way, individual selec-
tion is exactly what is usually termed elec-
tion. Choosing one man from among thou-
sands is to elect him, but a select party is a
group of chosen persons. There would be no
great difficulty in the introduction of the word
election, as breeders are already in the
habit of calling their choice individuals ^' elite,"
at least in the case of beets and of cereals.

This intra-specific selection affords a second
point for the comparison between natural and
artificial processes. This case is readily grant-
ed to be more difficult than the first, but there
can be no doubt that the similaritv is due to
strictly comparable causes. In practice this
process is scarcely second in importance to the
selection between species, and in numerous
cases it rests upon it, and crowns it, bringing
the isolated forms up to their highest ])()ssiblo
degree of usefulness. In nature it does quite
the same, adapting strains of individuals to
the local conditions of their environment. Tm-

802 Fluctuations

proved races do not generally last very long
in practice; sooner or later tliey are surpassed
by new selections. Exactly so we may imagine
the agency of natural intra-specific selection.
It produces the local races, the marks of which
disappear as soon as the special external con-
ditions cease to act. It is responsible only for
the smallest lateral branches of the pedigree,
but has nothing in common with the evolution
on the main stems. It is of very subordinate
importance.

These assertions of course, are directly op-
posed to the current run of scientific belief, but
they are supported by facts. A considerable
part of the evidence has already been dealt
with and for our closing discussion only an ex-
act comparison remains to be made between the
two detailed types of intra-specific selection. In
coming to this I will first dwell upon some in-
termediate types and conclude with a critical
discussion of the features of artificial selection,
which to my mind prove the invalidity of the
conclusions drawn from it in behalf of an ex-
planation of the processes of nature.

Natural selection occurs not only in the wild
state, but is also active in cultivated fields.
Here it regulates the struggle of the selected
varieties and improved races with the older
types, and even with the wild species. In a pre-

Artificial and Natural Selection 803

vious lecture I have detailed the rapid increase
of the wild-oats in certain years, and described
the experiments of Risler and Rimpau in the
running out of select varieties. The agency is
always the same. The preferred forms, wliir-h
give a larger harvest, are generally more
sensitive to injurious influences, more dependent
on rich manure and on adequate treatment.
The native varieties have therefore the advan-
tage, when climatic or cultural conditions are
unfavorable for the fields at large. They suf-
fer in a minor degree, and are thereby enabled
to propagate themselves afterwards more rap-
idly and to defeat the finer types. This
struggle for life is a constant one, and can
easily be followed, whenever the composition
of a strain is noted in successive years. It is
well appreciated by breeders and farmers, be-
cause it is always liable to counteract their
endeavors and to claim their utmost efforts to
keep their races pure. There can be no doubt
that exactly the same struggle exempt from
man's intrusion is fought out in the wild stato.
Local races of wild plants have not been
the object for field-observations recently. Some
facts however, are known concerning them. On
the East Friesian Islands in the North Sea the
flowers are strikingly larger and brighter col-
ored than those of the same species on the

804 Fluctuations

neighboring continent. This local difference is
ascribed by Behrens to a more severe selection
by the pollinating insects in consequence of their
lesser frequency on these very windy isles.
Seeds of the pines from the Himalayas yield
cold-resisting young plants if gathered from
trees in a high altitude, while the seeds of the
same species from lower regions yield more
sensitive seedlings. Similar instances are af-
forded by Rhododendron and other mountain
species. According to Cieslar corresponding
differences are shown by seeds of firs and
larches from alpine and lowland provinces.

Such changes are directly dependent on ex-
ternal influences. This is especially manifest
in experiments extending the cultures in higher
or in more northern regions. The shorter
summer is a natural agent of selection; it ex-
cludes all individuals which cannot ripen their
seeds during so short a period. Only the short-
lived ones survive. Schiibeler made very strik-
ing experiments with corn and other different
cereals, and has succeeded in making their cul-
ture possible in regions of Norway where it for-
merly failed. In the district of Christiania, corn
had within some few years reduced its lifetime
from 123 to 90 days, yielding smaller stems and
fewer kernels, but still sufficient to make its
culture profitable under the existing conditions.

Artificial and Natural Selection 8(J5

This change was not permanent, but was ob-
served to diminish rapidly and to disappear
entirely, whenever the Norwegian strain was
cultivated in the southern part of Germany. It
was a typical improved race, dependent on con-
tinual selection by the short summers which liad
produced it. Similar results have been reached
by Von Wettstein in the comparison of kinds
of flax from different countries. The analogy
between such cultivated local races and the lo-
cal races of nature is quite striking. The prac-
tice of seed-exchange rests for a large part on
the experience that the characters, acquired un-
der the definite climatic and cultural conditions
of some select regions, hold good for one or two,
and sometimes even more generations, before
they decrease to practical uselessness. The
Probstei, the Hanna and other districts owe
their wealth to this temporary superiority of
their wheat and other cereals.

Leaving these intermediate forms of selec-
tion, we now come to our principal point. It
has already been discussed at some length in the
previous lecture, but needs further consider-
ation. It is the question whether intra-specifi<'
selection may be regarded as a cause of last-
ing and ever-increasing improvement. Tiiis
is assumed by biologists who consider fluc-
tuating variability as the main source of ]iro-

806 Fluctuations

gression in the organic world. But the ex-
perience of the breeders does not support this
view, since the results of practice prove that
selection according to a constant standard
soon reaches a limit which it is not capable
of transgressing. In order to attain further
improvements the method of selection itself
must be improved. A better and sharper
method assures the choice of more valuable
representatives of the race, even if these must
be sought for in far larger numbers of in-
dividuals, as is indicated by the law of Quetelet.

Continuous or even prolonged improvement
of a cultivated race is not the result of frequent-
ly repeated selection, but of the improvement of
the standard of appreciation. Nature, as far as
we know, changes her standard from time to
time only in consequence of the migrations of
the species, or of local changes of climate.
Afterwards the new standard remains un-
changed for centuries.

Selection, according to a constant standard,
reaches its results in few generations. The
experience of Van Mons and other breeders of
apples shows that the limit of size and luscious-
ness may be soon attained. Vilmorin's ex-
periments with wild carrots and those of Car-
riere with radishes lead to the same conclusion
as regards roots. Improvements of flowers in

Artificial and Natural Sdection 807

size and color are usually easy and rapid in the
beginning, but an impassable limit is soon
reached. Numerous other instances could be
given.

Contrasted with these simple cases is the
method of selecting sugar-beets. More than
once I have alluded to this splendid exam-
ple of the influence of man upon domestic races,
and tried to point out how little support it af-
fords to the current scientific opinion concern-
ing the power of natural selection. For this
reason it is interesting to see how a gradual
development of the methods of selection has
been, from the very outset, one of the chief aims
of the breeders. None of them doubts that an
improvement of the method alone is adequate to
obtain results. This result, in the main, is the
securing of a few per-cent more of sugar, a
change hardly comparable with that progress
in evolution, which our theories are destined to
explain.

Vilmorin's original method was a very sini])le
one. Polarization was still undiscovered in his
time. He determined the specific weight of his
beets, either by weighing them as a whole, or by
using a piece cut from the base of the roots and
deprived of its bark, in order to test only the
sugar-tissues. The pieces were floated in solu-
tions of salt, which were diluted until the pieces

808 Fluctuations

began to sink. Their specific weight at that mo-
ment was determined and considered to be a
measure of the corresponding value of the beet.
This principle was afterwards improved in two
ways. The first was a selection after the salt-
solution-method, but performed on a large scale.
After some few determinations, a solution was
made of such strength as to allow the greater
number of the beets to float, and only the best
to sink down. In large vessels thousands of
beets could be tested in this way, to select a
few of the very heaviest. The other improve-
ment was the determination of the specific
weight of the sap, pressed out from the tis-
sue. It was more tedious and more expensive,
but more direct, as the influence of the air-
cavities of the tissue was excluded. It pre-
pared the way for polarization.

This was introduced about the year 1874 in
Germany, and soon became generally accepted.
It allowed the amount of sugar to be measured
directly, and with but slight trouble. Thou-
sands of beets could be tested yearly by this
method, and the best selected for the production
of seed. In some factories a standard percent-
age is determined by previous inquiries, and the
mass of the beets is tested only by it. In others
the methods of taking samples and clearing the
sap have been improved so far as to allow the

Artificial and Natuial ISdcctiuu m\)

exact determination of three hundred Ihuuband
polarization-values of beets within a few weeks.
Such figures give the richest material for statis-
tical studies, and at once indicate the best roots,
while they enable the breeder to change his
standard in accordance with the results at an\-
time. Furthermore they allow the mass of
the beets to be divided into groups of dif-
ferent quality, and to produce, besides the
seeds for the continuation of the race, a iirst-
class and second-class product and so on. lu
the factory of Messrs. Kuhn & Co., at Xaarden,
Holland, the grinding machine has been mark-
edly improved, so as to tear all cell-walls asun-
der, open all cells, and secure the whole of the
sap within less than a minute, and without heat-
ing.

It would take too long to go into further de-
tails, or to describe the simultaneous changes
that have been applied to the culture of the
elite strains. The detailed features suffice
to show that the chief care of the breeder in this
case is a continuous amelioration of tlie method
of selecting. It is manifest that the ])rogres-
sion of the race is in the main due to great tech-
nical improvements, and not solely to the repe-
tition of the selection.

Similar facts may be seen on all the great
lines of industrial selection. An increasing ap-

810 Fluatuations

preciation of all the qualities of the selected
plants is the common feature. Morphological
characters, and the capacity of yielding the
desired products, are the first points that
strike the breeder. The relation to climate and
the dependence on manure soon follow, but the
physiological and chemical sides of the problem
are usually slow of recognition in the methods
of selection. When visiting Mr. de Vilmorin at
Paris some years ago, I inspected his laboratory
for the selection of potatoes. In the method in
use, the tubers were rubbed to pulp and the
starch was extracted and measured. A starch-
percentage figure was determined for each
plant, and the selection of the tubers for plant-
ing was founded upon this result. In the same*
way wheat has been selected by Dippe at
Quedlinburg, first by a determination of its
nitrogenous contents in general, and secondly
by the amount of the substances which deter-
mine its value for baking purposes.

The celebrated rye of Schlanstedt was pro-
duced by the late Mr. Himpau in a similar man-
ner and was put on the market between 1880 and
1890 and was received with great favor through-
out central Europe, especially in Germany and
in France. It is a tall variety, with vigorous
stems and very long heads, the kernels of
which are nearlv double the size of those of the

Artificial and Natural Selection bii

ordinary rye, and are seen protruding, wiiou
ripe, from between the scales of the spikelets.
It is unfit for poor soils, but is one of the very
best varieties for soils of medium fertility in
a temperate climate. It is equal in the produc-
tion of grain to the best French sorts, but
far surpassing them in its amount of straw.
It was perfected at the farm of SchlanstcMlt
very slowly, according to the current concep-
tions of the period. The experiment was
started in the year 1866, at which time Kini-
pau collected the most beautiful heads from
among his fields, and sowed their ker-
nels in his experiment-garden. From this first
culture the whole race was derived. Every year
the best ears of the strain were chosen for re-
peated culture, under experimental care, while
the remainder was multiplied in a field to fur-
nish the seeds for large and continually increas-
ing areas of his farms.

Two or three years were required to pro-
duce the quantity of seed of each kind reiiuired
for all the fields of Schlanstedt. The exi)ori-
ment-garden, which through the kindness of M r.
Rimpau I had the good fortune of visiting more
than once between 1875 and 1878, was situ-
ated in the middle of his fann, at some dis-
tance from the dwellings. Of course it was
treated with more care, and especially kept

812 Fluctuations

in better conditions of fertility than was
possible for the fields at large. A con-
tinued study of the qualities and exigencies of
the elite plants accompanied this selection,
and gave the means of gradually increasing the
standard. Eesistance against disease was ob-
served and other qualities were ameliorated in
the same manner. Mr. Eimpau repeatedly told
me that he was most anxious not to overlook any
single character, because he feared that if any
of them might become selected in the wrong
way, perchance unconsciously, the whole strain
might suffer to such a degree as to make all the
other ameliorations quite useless. With this
purpose the number of plants per acre was
kept nearly the same as those in the fields,
and the size of the culture was large enough
every year to include the best kernels of quite a
number of heads. These were never separated,
and exact individual pedigrees were not in-
cluded in the plan. This mixture seemed to
have the advantage of keeping up an average
value of the larger number of the characters,
which either from their nature or from their
apparent unimportance had necessarily to be
neglected.

After ten years of continuous labor, the rye
of Eimpau caught the attention of his neigh-
bors, being manifestly better than that of ordi-

Artificial and Natural Selection 813

nary sowings. Originally he bad made liis eul
tures for the improvement of his own fields only.
Gradually however, he began to sell his product
as seed to others, though he found the dilTereuce
still very slight. After ten years more, about
1886, he was able to sell all his rye as see<l
thereby making of course large profits. It is
now acknowledged as one of the best sorts,
though in his last letter Mr. Eimpau announced
to me that the profits began to decline as other
selected varieties of rye became known. The
limit of productiveness was reached, and to sur-
mount this, selection had to be begun again
from some new and better starting point.

This new starting point invokes quite another
principle of selection, a principle which threat-
ens to make the contrast between artificial and
natural selection still greater. In fact it is noth-
ing new, being in use formerly in the selection
of domestic animals, and having been api)liod
by Vilmorin to his sugar-beets more than half a
century ago. Why it should ever have bom
overlooked and neglected in the selection of
sugar-beets now is not clear.

The principle in itself is very simple. It
agrees that the visible characters of au animal
or a plant are only an imperfect measure foi' its
hereditary qualities, instead of being the real
criterion to be relied upon, as is the current be-

814 • Fluctuations

lief. It further reasons that a direct apprecia-
tion of the capacity of inheritance can only be
derived from the observation of the inheritance
itself. Hence it concludes that the average
value of the offspring is the only real standard
by which to judge the representatives of a race
and to found selection upon.

These statements are so directly opposed to
views prevalent among plant-breeders, that it
seems necessary to deal with them from the
theoretical and experimental, as well as from
the practical side.

The theoretical arguments rest on the divi-
sion of the fluctuating variability into the two
large classes of individual or embryonic, and of
partial deviations. We have dealt with this di-
vision at some length in the previous lecture.
It will be apparent at once, if we choose a defi-
nite example. Let us ask what is the real sig-
nificance of the percentage-figure of a single
plant in sugar-beets. This value depends in
the first place, on the strain or family from
which the beet has been derived, but this pri-
mary point may be neglected here, because it
is the same for all the beets of any lot, and de-
termines the average, around which all are fluc-
tuating.

The deviation of the percentage-figure of a
single beet depends on two main groups of ex-

Artificial and Natural Selection 815

ternal causes. First come those that have
influenced the young germs of the plant
during its most sensitive period, when still
an embryo within the ripening seed. They
give a new limitation to the average con-
dition, which once and forever becomes fixed
for this special individual. In the second
place the young seedling is affected dur-
ing the development of its crown of leaves,
and of its roots, by numerous factors,
which cannot change this average, but may in-
duce deviations from it, increasing or decreas-
ing the amount of sugar, which will eventually
be laid down in the root. The best young beet
may be injured in many ways during periods of
its lifetim^e, and produce less sugar than could
reasonably be expected from it. It may be sur-
passed by beets of inferior constitution, but
growing under more favorable circumstances.

Considered from this point of view the result
of the polarization-test is not a single value, but
consists of at least two different factors. It
may be equal to the algebraic sum of these, or
to their difference, according to whether the
external conditions on the field were locally and
individually favorable or unfavorable. A large
amount of sugar may be due to high individual
value, with slight subsequent deviation from it,

816 Fluctuations

or to a less prominent character combined with
an extreme subordinate deviation.

Hence it is manifest that even the results
of such a highly improved technical method do
not deserve the confidence usually put in them.
They are open to doubt, and the highest figures
do not really indicate the best representatives
of the race. In order to convey this conception
to you in a still stronger manner, let us consider
the partial variability as it usually shows itself.
The various leaves of a plant may noticeably
vary in size, the flowers in color, the fruits in
flavor. They fluctuate around an average, which
is assumed to represent the approximate value
of the whole plant. But if we were allowed to
measure only one leaf, or to estimate only one
flower or fruit, and be compelled to conclude
from it the worth of the whole plant, what mis-
takes we could make! "VVe might indeed hit
upon an average case, but we might as easily
get an extreme, either in the way of increase
or of decrease. In both cases our judgment
would be badly founded. Now who can
assure us that the single root of a given
beet is an average representative of the partial
variability? The fact that there is only one
main root does not prove anything. An annual
plant has only one stem, but a perennial species
has many. The average height of the last is a

Artificial and Natural Selection 817

reliable character, but the casual height of the
former is very uncertain.

So it is with the beets. A beet may be di-
vided by its buds and give quite a number of
roots, belonging to the same individual. These
secondary roots have been tested for the
amount of sugar, and found to exhibit a man-
ifest degree of variability. If the first root
corresponded to their average, it might be con-
sidered as reliable, but if not anyone will grant
that an average is more reliable than a single
determination. Deviations have as a fact been
observed, proving the validity of our assertion.

These considerations at once explain the dis-
appointment so often experienced by breeders.
Some facts may be quoted from the Belgian pro-
fessor of agriculture at Gembloux, the late Mr.
Laurent. He selected two beets, from a strain,
with the exceptional amount of 23^ sugar, but
kept their offspring separate and analyzed some
60 of each. In both groups the average was
only 11 - 12^, the extremes not surpassing
14-15^. Evidently the choice was a bad one,
notwithstanding the high polarization value of
the parent. Analogous cases are often observed,
and my countrymen, Messrs. Kuhn & Co., go so
far as to doubt all excessive variants, and to
prefer beets with high, but less extraordinary
percentages. Such are to be had in larger num-

818 Fluctuations

bers and their average has a good chance of ex-
emption from a considerable portion of the
doubts adhering to single excessive cases.

It is curious to note here what Louis de Vil-
morin taught concerning this point in the year
1850. I quote his own words: ^' I have ob-
served that in experiments on heredity it is
necessary to individualize as much as possible.
So I have taken to the habit of saving and sow-
ing separately the seeds of every individual
beet, and I have always found that among the
chosen parent-plants some had an offspring
with a better average yield than others. At the
end I have come to consider this character only,
as a standard for amelioration."

The words are clear and their author is the
originator of the whole method of plant -breed-
ing selection. Yet the principle has been aban-
doned, and nearly forgotten under the impres-
sion that polarization alone was the supreme
guide to be relied upon. However, if I under-
stand the signs rightly, the time is soon coming
when Vilmorin's experience will become once
more the foundation for progress in breeding.

Leaving the theoretical and historical as-
pects of the problem, we will now recall the ex-
perimental evidence, given in a former lecture,
dealing with the inheritance of monstrosi-
ties. I have shown that in many instances mon-

Artificial and Natural Selection 819

strositieS constitute double races, consisting of
monstrous and of normal individuals. At first
sight one might be induced to surmise that the
monstrous ones are the true representatives of
the race, and that their seeds should be ex-
clusively sown, in order to keep the strain up
to its normal standard. One might even sup-
pose that the normal individuals, or the so-called
atavists, had really reverted to the original
type of the species and that their progeny would
remain true to this.

My experiments, however, have shown that
quite the contrary is the case. No doubt, the
seeds of the monstrous specimens are trust-
worthy, but the seeds of the atavists are not
less so. Fasciated hawkweeds and twist-
ed teasels gave the same average constitu-
tion of the offspring from highly monstrous,
and from apparently wholly normal indi-
viduals. In other words the fullest devel-
opment of the visible characteristic was not
in the slightest degree an indication of better
hereditary tendencies. In unfavorable years a
whole generation of a fasciated race may exhibit
exclusively normal plants, without transmitting
a trace of this deficiency to the following genera-
tion. As soon as the suitable conditions return,
the monstrosity reassumes its full development.

The accordance of these facts with the ex-

820 Fluctuations

perience of breeders of domestic animals, and of
Louis de Vilmorin, and with the result of the
theoretical considerations concerning the fac-
tors of fluctuation has led me to suggest the
method of selecting, which I have made use of in
my experiments with tricotyls and syncotyls.

Seedling variations afford a means of count-
ing many hundreds of individuals in a single
germinating pan. If seed from one parent-
plant is sown only in each pan, a percentage-
figure for the amount of deviating seedlings
may be obtained. These figures we have called
the hereditary percentages. I have been able to
select the parent-plants after their death on
the sole ground of these values. And the re-
sult has been that from varieties which, on an
average, exhibited 50 - 55^ deviating seedlings,
after one or two years of selection this propor-
tion in the offs]3ring was brought up to about
90^ in most of the cases. Phacelia and mercury
with tricotylous seedlings, and the Eussian
sunflower with connate seed-leaves, may be
cited as instances.

Besides these tests, others were performed,
based only on the visible characters of the seed-
lings. The result was that this characteristic
was almost useless as a criterion. The atavists
gave, in the main, nearly the same hereditary
percentages as the tricotyls and syncotyls, and

Artificial and Natural Selection 821

their extremes were in each case far better con-
stituted than the average of the chosen type.
Hence, for selection purposes, the atavists must
be considered to be in no way inferior to the
typical specimens.

If it had been possible to apply this principle
to twisted and fasciated plants, and perhaps
even to other monstrosities, I think that it will
readily be granted that the chance of bringing
even these races up to a percentage of 90;^
would have been large enough. But the large
size of the cultures required for the counting of
numerous groups of offspring in the adult state
has deterred me from making such trials. Ee-
cently however, I have discovered a species,
Viscaria oculata which allows of counting
twisted specimens in the pans, and I may soon
be able to obtain proofs of this assertion. The
validity of the hereditary percentage as a stand-
ard of selection has, within the last few years,
been recognized and defended by two eminent
breeders, W. M. Hays in this country and Von
Lochow in Germanv. Both of them have start-
ed from the experience of breeders of domestic
animals. Von Lochow applied the principle
to rye. He first showed how fallacious the
visible characters often are. For instance
the size of the kernels is often dependent on
their number in the head, and if this number is

822 Fluctuations

reduced by the injurious varietal mark of la-
cunae (Liickigkeit), the whole harvest will rap-
idly deteriorate by the selection of the largest
kernels from varieties which are not quite free
from this hereditary deficiency.

In order to estimate the value of his rye-
plants, he gathers the seed of each one separate-
ly and sows them in rows. Each row corre-
sponds to a parent-plant and receives 200 or 150
seeds, according to the available quantity. In
this way from 700 to 800 parent-plants are
tested yearly. Each row is harvested sepa-
rately. The number of plants gives the aver-
age measure of resistance to frost, this
being the only important cause of loss. Then
the yield in grain and straw is determined
and calculated, and other qualities are taken
into consideration. Finally one or more groups
stand prominent above all others and are chosen
for the continuation of the race. All other
groups are wholly excluded from the ** elite,"
but among them the best groups and the very
best individuals from lesser groups are consid-
ered adequate for further cultivation, in order
to produce the commercial product of the race.
As a matter of fact the rye of Von Lochow is
now one of the best varieties, and even sur-
passes the celebrated variety of Schlanstedt. It
was only after obtaining proof of the validity

Artificial and Natural Selection 823

of his method that Von Lochow decided to give
it to the public.

W. M. Hays has made experiments with wheat
at the Minnesota Agricultural Experiment
Station. He chose a hundred grains as a
proper number for the appreciation of each
parent-plant, and hence has adopted the name
of ^^centgener power" for the hereditary per-
centage.

The average of the hundred offspring is the
standard to judge the parent by. Experience
shows at once that this average is not at all pro-
portional to the visible qualities of the parent.
Hence the conclusion that the yield of the
parent-plant is a very uncertain indication of its
value as a parent for the succeeding generation.
Only the parents with the largest power in the
centgener of offspring are chosen, while all
others are whollv discarded. Afterwards the
seeds of the chosen groups are propagated in
the field until the required quantities of seed are
obtained.

This centgener power, or breeding-ability, is
tested and compared for the various parent-
plants as to yield, grade, and percentage of ni-
trogenous content in the grain, and as to the
ability of the plant to stand erect, resist rust,
and other important qualities. It is evident that
by this test of a hundred specimens a far liotter

824 Fluctuations

and much more reliable determination can he
made than on the ground of the minutest exam-
ination of one single plant. From this point of
view the method of Hays commands attention.
But the chief advantage lies in the fact that it is
a direct proof of that which it is desired to
prove, while the visible marks give only very in-
direct information.

Thus the results of the men of practice are in
full accordance with those of theory and scien-
tific experiment, and there can be little doubt
that they open the way for a rapid and impor-
tant improvement. Once attained, progress
however, will be dependent on the selection-
principle, and the hereditary percentage, or
centgener power or breeding-ability, must be de-
termined in each generation anew. Without
this the race would soon regress to its former
condition.

To return to our starting point, the compari-
son of artificial and natural selection. Here we
are at once struck by the fact that it is hardly
imaginable, how nature can make use of this
principle. In some measure the members of the
best centgener will manifestly be at an advan-
tage, because they contain more fit specimens
than the other groups. But the struggle for
existence goes on between individuals, and not
between groups of brethren against groups of

Artificial and Natural Selection 825

cousins. In every group the best adapted in-
dividuals will survive, and soon the breeding-
differences between the parents must vanish
altogether. Manifestly they can, as a rule,
have no lasting result on the issue of the strug-
gle for existence.

If now we remember that in Darwin's time
this principle, breeding-ability, enjoyed a far
more general appreciation than at present,
and that Darwin must have given it full consid-
eration, it becomes at once clear that this old,
but recently revived principle, is not adequate
to support the current comparison between ar-
tificial and natural selection.

In conclusion, summing up all our arguments,
we may state that there is a broad analog>^ be-
tween breeding-selection in the widest sense of
the word, including variety-testing, race-im-
provement and the trial of the breeding-ability
on one side, and natural selection on the other.
This analogy however, points to the impor-
tance of the selection between elementary spe-
cies, and the very subordinate role of intra-
specific selection in nature. It strongly sup-
ports our view of the origin of species by
mutation instead of continuous selection. Or,
to put it in the terms chosen lately by Mr.
Arthur Harris in a friendly criticism of my
views: " Natural selection may explain the sur-

826

Fluctuations

vival of the fittest, but it cannot explain the ar-
rival of the fittest/'

f

■•

INDEX

Abies concolor fastigiata, 618
Acacia, 176, 196, 217, 458,
697

bastard, 343, 617, 618, 664,
665, 666
Acer compestre nanum, 613
Achillea millefolium, 131, 132,

441
Adaptation, 702

double, 430, 451, 452, 454,
455, 457, 458, 643
Aegilops ovata, 265

spelt aeformis, 265
Agave vivipara, 684
Ageratum coeruleum, 613
Agrostemma Coronaria hi-
color, 125

Githago, 282

nicaeensis, 163
Agrotis, 204

Alder, cut-leaved, 147, 596
Alfalfa, 264
Algae, 699
Allen, Grant, 237
Alliaria, 638

Alnus glutinosa laciniata, 615
Alpine plants, 437, 695, 794
Althaea, 490
Amaranth, 282, 453
Amaranthus caudatus, 282
Amaryllis, 272, 275, 762

brasiliensis, 275

leopoldi, 275

pardina, 275

psittacina, 275

vittata, 275
Amen-Hotep, 697
Ampelopsis, 239
Amygdalus persica laevis, 126

827

Anagallis arvensis, 162
Androsace, 634
Anemone, 266, 331

coronaria, 241, 491 var.

"Bride," 510
magellanica, 266
sylvestris, 266
Anemone, garden, 241
Annee, 760
Anomalies, taxonoraic, 658-

685
Anthemis, 236
nobilis, 130
Anthurium scherzerianum , 639
Antirrhinum ma jus, 315

luteum rubro-striatum , 315
Apetalous flowers, 622
Apples, 134, 240, 328, 454,
806
elementary species, 75
method of cultivating, 76
origin of cultivated varie-
ties, 73
use by the Romans, 74
" Wealthy," 78, 79
wild, 73, 74, 75, 76
Aquilegia chrysantha, 161
Arabis ciliata glabrata

hirsuta glaberrima, 126
Aralia crassifolia, 663
Arbres fruitiers ou Pomon-

omie beige, 76
Aralia papyrifera, 663
Arctic flora, 695
Arnica, 494

montana, 236
Aroids, 222, 631, 639
Artemisias, 131
Artificial selection, 18. 71. 77,
93, 95, 743, 744, 798-
826

828

Index

first employed, 72, 92
nature of, 19
Arum maculatuni immacula-

Aseidia,'310, 366, 367, 427,
428, 669, 670, 671, 672,
673, 674, 675
Ash, 135, 341

one-bladed, 666, 667
weeping. 196, 596
Ashe, 343
Aster, 132, 152, 242

seashore, 200, 282*
Aster Tripolium, 132, 200,

236, 282, 410
Astragalus alpinus, 696
Atavism, 154, 170, 172, 175,
176, 178, 182, 185, 187,
188, 198, 220, 222, 226,
235, 344, 354, 399, 405,
411, 660, 661
bud, 183, 226
definition of, 170, 631
false, 185, 187
negative, 344
positive, 344
seed, 176

systematic, 174, 222, 630-
657
Atavists, 156, 201
heredity of, 413
Atropa Belladonna lutea, 592
Aubretia, 241
Avena fatua, 100, 207
Azalea, 178, 323
Azolla caroliniana, 239

B

Babington, Manual of Brit-
ish Botany, 36
Bailey, 78, 306, 684
Balsams, 334
Bananas, 90, 134
Banyan. 244
Barberry, 133, 180

European, 270

purple, 596
Barharea vulgaris, 427
Barley, 98, 105, 133, 203, 678,
679

"Nepaul," 203, 676, 677,
679, 681, 683
Bastard-acacia, 133, 136, 140
Bateson, 250
Bauhin, Caspar, 72, 610
Baumann, 618

Beans, 90, 152, 327, 727, 735
Bedstraw, 648
Beech, 133, 135, 243

cut-leaved, 179, 196, 616

laciniated, 196

oak-leaved, 595

purple, 196, 593, 595
Beeches, 427

fern-leaved, 147
Beets, 68, 72, 92, 93, 792, 796,
801, 815, 817, 818

Californian, 796

European, 796

forage, 71, 72, 791

salad, 71
Beet-sugar, 67, 68, 69, 70, 71,
109, 165, 717, 791, 807,
813, 814
Begonia, 218, 366, 509, 765

ever-flowering, 148

tuberous, 272

clarkii, 273

davisii, 273

rosiftora, 273

sedeni, 273

semperflorens, 133, 148, 620

Begonia

bulbous, 372

veitchi, 273
Behrens, 804
Belladonna, 145
Bellis perennis, 236

perennis plena, 195
Bentham, 237
Bentham & Hooker

Handbook of British Flora,
36
Berhens, 133, 180, 455

ilicifolia, 270

vulgaris, 270
Bertin, 596

Berula atigustifoUa, 457
Bessey, 660
Beta maritima, 69

Index

829

patula, 69, 70
vulgaris, 69, 70
Betula, 133
Between-race, 358
Bewirkung, Theorie der di-

recten (Nageli),448
Biastrepsis, 402
Bidens, 131

atropurjmrea, 131
cernua, 131, 158
leucantha, 131
tripartita, 131
Bilberries, 577
Bindweed, 419, 424
Binomium, of Newton, 767
Birch, 133, 243

cut-leaved, 596, 616
fastigiate, 618
fern-leaved, 179
Biscutella, 283

laevigata glabra, 125
Bitter-sweet, 125
Blackberry, 268, 768

"Paradox," 769
Blue-bells, variation in, 54,

491, 577
Blueberries, 769
Blue-bottle, 499, 507, 509, 510
Blueflag, atavism of, 173
Boehmeria, 675

bilhoa, 685
Bonnier, 439, 441, 442, 444,

451, 795
Boreau, 663

Brambles, 126, 127, 147, 239,
244, 245, L68, 740, 769,
663
Brassica, 244
Braun, 738

Braun and Schimper, 494
Bread-fruits, 90
Briot, 618
Britton and Brown's Flora,

162
Brooks, 711
Broom, 140

prickly, 217
Broom-rape, 220
Broussonetia papyifera dis-

secta, 616

Brunella, 146, 268
vulgaris, 577
vulgaris alba, 201
Bryophyllum calycinum, 218
Buckwheat, 453
Bud-variation, 750
Buds, adventitious, 218
Burbank, Luther, 57, 79, 116,
134, 268, 758, 768, 769,
784
Buttercup, 331, 357, 410, 725,
740
Asiatic, 241

Cabbages, 428, 684

atavism in, 638

origin of varieties, 621
Cactuses, 444
Cactus-dahlia, 625
Calamintha Acinos, 437, 453
Calamus root, 222
Calendula officinalis, 503
CalUopsis tinctoria, 195
Calluna, 146

vulgaris, 437, 577
Caltha, 490

palustris, 331
Camelina, 684
Camellia, 178, 323

japonica, 368
Camellias, 331
Camomile, 130, 132, 156, 366,

494, 503, 509, 513
Campanula persioifolia, 161.

234

rotundifolia, 437
Campion, 283, 302, 304

evening, 281

red, 238
Canna, 751, 759, 761

indica, 760

" Madame Crozy," 760. 701

nepalensis, 760

icnrozeu'iczii, 760
Capsella Bursa-pastoris ape-
tala, 585

heegeri, 22, 582, 583, 084
Car ex, 53

830

Index

Carnation, 178, 241, 491

wheat-ear, 227
Carpinus Betulus hetero-

phylla, 180
Carriere, 491, 596, 612, 806
Carrots, 806
Catch-fly, 419

Carboniferous period, 699
Casuarina quadrivalvis, 649
Cauliflowers, origin of, 621
Caumzet, 614
Causation, theory of direct,

(Nageli), 448
Cedar, pyramidal, 618
Celandine, 147, 245, 280, 365

oak-leaved, 603, 610, 611
Celosia, 621

Celosia cristata, 327, 411
Centaurea, 242
Centgener power, 20, 823
Centranthus macrosiphon, 424
Cephalotaocus , 170, 226

pedunculata fastigiata, 169
Cereals, 105, 106, 107, 119,
801, 804

origin of cultivation, 104
Character-units, 633
Charlock, 424
Cheiranthus, 490

Cheiri, 370

Cheiri gynantherus, 371
Chelidonium laciniatum, 22,
609

ma jus, 147, 365, 600, 610,
611

ma jus foliis queznis, 610
Cherries, 79
Cherry, bird's, 617
Chestnuts, 427
Chromosomes, 306
Chrysanthemum, 178, 274

corn, 739
Chrysanthemum carinatum,
494

coronarium, 161, 202, 510

grandiflorum, 739

imbricatum, 494

indicum, 490

inodorum, 503

inodorum plenissimum, 366

new double, 501

segetum, 202, 493, 504, 729

segetum, var. grandifioruMi^
43, 495, 498, 504, 504
Chrysopogon montanus, 450
Cieslar, 804
Cineraria cruenta, 514
Cinquefoil, 53
Clarkia, 420

elegans, 198

pulchella, 282

pulchella carnea, 163
Clematis Vitalba, 663

Viticella nana, 613
Clover, 80, 102, 674

crimson (Italian), 353, 358,
359, 360

five-leaved, 340, 362, 374,
431, 509, 789

four-leaved, 340, 346, 353

red, 235, 281

white, 133, 366
Clusius, 610
Cochlearia anglica, 52

danica, 52

officinalis, 52
Coconut, 67, 82, 83, 87, 88,
89

dispersal of, 85, 89

geographic origin of, 88, 89
Coconut-palm, 84, 88
Coekerell, T. D. A., 139, 140,

591
Cocklebur, 139
Cockscomb, 165, 327, 356, 411,

621
Cocos nucifera stupposa, 83,
84

cupuliformis, 83

rutila, 83
Codiaeum appendicularum,

673
Colchium, 490
Coleus, 133
Columbine, 725

yellow, 161
Columbus, 89, 118
Columella, 106

Index

831

Composites, 130, 131, 336,

723, 778
Conifers, 168, 226, 239, 455

weeping, 617
Connation, of petals, 660, 601
" Conquests," 243
Contra-selection, 425
Cook, 84, 86, 88, 89
Corn, 81, 90, 118, 119, 135,
283, 287, 288, 775, 786,
788, 804

American, 205
Corn-cockle, 163
Corn-chrysanthemum, 739
Corn-flowers, 491, 493
Corn, "Forty-day," 118

"Harlequin," 327

sterile variety of, 623

sugar, 135, 158

"Tuscarora," 205
Corn-marigold, 493, 494
Cornel berry, yellow, 196
Cornaceae, 675
Cornu, 338
Cornus Mas, 196
Correlation, 143
Corylus, 133

Avellana, 181

tiibulosa, 181
Cotton, 725
Cotyledon, 674

variation in, 416
Crambe maritima, 621
Cranesbill, 599

European, 628

meadow, 323
Crataegus, 196

oxyacoMtha, 133
Crowfoot, 331

corn, 283
Crepis biennis, 410, 411
Cress, Indian, 193
Crosses

bisexual, 255, 276, 294, 298

reciprocal, 279

unisexual, 255, 261

varietal (see Hybrids).
Croton, 673, 674
Crozy, 760, 762
Crucifers, 222, 635

Cryptomeria, 109, 226

japonica, 239
Cucumbers, 118
Cucumis, 52
Cucurbita, 52
Cultivated plants, 65, 60

elementary species of, 63

improvement of, 92

mixed nature of, 90, 118

origin of, 91
Currants, 79

Californian, 270

flowering, 166

"Gordon's," 270

Missouri, 270

white, 158

white-flowered, 167
Cuttings, 721
Cyclamen, 323, 355, 627, 684

Butterfly, 627

vernum, 619
Cypripedium caudatum, 487
Cytisus adami, 271

candicans Attleyaniis, 307

Laburnum, 271

prostratus, 139

prostratus ciliata, 125

purpureus, 271

spinescens, 139

Dahlia, 131, 241, 272, 625

cactus, 625

" Jules Chretien," 628

purple-leaved, 626

" surprise," 230

tubular, 627

274, 490, 764

first double ones, 490

green, 227, 229, 230
Daisies, 131, 132, 494

double, 195

hen-and-chicken, 514

ox-eye, 202

Shasta, 769

yellow, 202
Dandelion, 411

parthenogenesis, 0 1

variations in, 00

832

Index

Daphne Mezereum, 146
Darwin, 1, 2, 3, 4, b, 6, 7,
18, 76, 85, 93, 109, 110,
180, 196, 205, 206, 242,
306, 324, 338, 448, 571,
604, 612, 689, 702, 710,
715, 743, 798, 825
Darwin, George, 711
Darwinian theory, 461

basis of, 5
Date, 134
Datura Stramonium, 139, 142

Stramonium, inermis, 300

Tatula, 139, 142, 300
Dead-nettle, 237
De Bary, 38, 47, 49
De Candolle, 76, 84, 85, 89,
228, 370, 403, 621

Alphonse, 74, 129, 226

A. P., 129

Casimir, 659, 676
De Graaff, 275
Delphinium Ajacis, 192
Deniaii, 617
Descent, theory of, 690, 694,

702, 707, 716, 798
De Serres, Olivier, 72
Desmodium gyrans, 655, 656,

663, 664, 65
Dewberry, California, 269
Dianthus barhatus, 322, 648

twisted variety, 408
Diatoms, 699
Dictoyledons

ancestors of monocot-
yledons, 15
Digitalis parvifiora, 161, 640

purpurea, 483

pelorism of, 483
Dimorphism, 445, 447, 454,

457, 458
Dippe, 810
Dipsacus fullonum, 402

sylvestris, 402, 403
Dominant character, 280
Double flowers

poppies 490

production of, 489

types of, 330
Double races (see also ever-

sporting varieties), 419,
427, 428
Dubois, Eugene, 712
Duchesne, 185, 188, 596
Duckweed, 222
Draba, 692, 693

verna, 47, 50, 51, 53, 125,
126, 518, 533, 546, 547,
561
Dracocephalum moldavicum,

419
Dragon-head, 419
Drosera anglica, 268
filiformis, 268
intermedia, 268
obovata, 267
rotundifolia, 268

E

Earth, age of, 710
Edelweiss, 438
Eichler, 660
Election, 801

Electric light, growth in, 442
Elementary species, 11, 13, 32,
67, 74, 76, 77, 78, 79, 91,
95, 116, 119, 124, 126,
128, 129, 207, 238, 252,
256, 307, 430, 435, 695,
696, 698, 702, 715, 787,
798, 800, 825
apples, 75
coconut, 82
corn, 81

cultivated plants, 63
definition of, 12, 35, 127
flax, 80

how produced, 16, 248
hybrids of, 253, 255
mutation of, 141
origin of, 459, 603
origin of, how studied, 463
selection of, 92
varieties vs., 14, 15, 141,
152, 224, 243, 247, 251,
495
Elm, 136, 219, 239, 427
Epilobium, 268
hirsutum, 683

Index

833

hirsutum cruciatum, 588
montanurriy 269
tetragonum, 269
Equisetum Telmateja, 642,

649
Erica TetralioOy 577, 661
Ericaceae, 146, 660
Erigeron aster oides, 450
canadensis, 132, 236, 453,
600, 695
Erodium, 146
Erodium cicutarium alhum,

161
Erucastrum, 630, 638, 639

pollichii, 222, 637
Eryngium campestre, 674

maritimum, 674
Erysimum cheiranthoides, 638
Erythraea pulchella, 453
Erythrina, 621

Crista-galli, 620
Eschcholtzias, 59
Esimpler, 337
Eucalyptus citriodora, 669

Globulus, 217
Euphorbia Ipecacuanha, 55
Evening-primrose, 62, 204,
256, 424, 686, 687, 688,
690, 691, 694, 695, 699,
702, 703, 705, 707, 708,
713 747 793
Evolution, 93, 685, 686, 689,
704, 707, 709, 710, 713,
718
degressive, 222, 223, 249
progression in, 630
progressive, 221, 222, 223,

248
regression in, 630
regressive, 221, 222, 223,

249
retrograde, 221, 631
Extremes, asexual multipli-
cation of, 742, 769

P

Fabre, 265
Fagus, 133

Fagus sylvatica pectinata, 179
Fan, genealogical, 700
Fasciated stems, 409, 413
Ferns, 63
cristate, 427
plumose, 427
Ficaria, 53
Ficus radicans, 436
religiosus, 244
repens, 436
stipulata, 436
ulmifolia, 436
Figs, 436
Filago, 53
Fir, 134, 804
Fittest, survival of, 826
Flax, 80, 805
springing, 80
threshing, 80
white-flowered, 158, 160
Fleabane, Canada, 132, 236,

600
Flowers, gamopetalous, 660
Fluctuability

embryonic, see individual
Fluctuation, 708, 715, 716,
718, 719, 724, 737, 741
curves of, 729, 734
defined, 191
individual, 718, 723, 732,

741, 745, 749, 788
mutation vs. 7, 16, 719
partial, 718, 723, 732, 741,

745, 748, 749, 771
inadequate for evolution,

18
in elementary species, 19
nature of, 18

specific and varietal char-
acters vs. 17
Forget-me-not, 308
Fothergill, John, 521
Foxglove, 163

peloric, 164, 356, 367
yellow, 161, 640
Fraxinus excelsior mono-
phylla, 667

exhcterophi/Ua, 667
simplicifolia, 607

834

Index

1

French flora (Grenier and

Godron), 433
Fries

on Hieracium, 60
Frostweed, 440
species of, 53
Fuchsia, 272, 355
Fuchsias, 491

G

Gaertner, 279

Galeopsis Ladanum canescens,

139
Galium, 648

Aparine, 409, 648

elatum, 52

erectum, 52

Mollugo, 52

verum, 648
Gallesio, 138
Gallon, 736, 776
Gamopetaly, 663
Garden-pansy, origin of, 38
Garlic, 638
Gaiichery, 453
Geikie, 711
Genera

artificial character of, 36

polymorphous, 693
Gentiana punctata concolor,

125
Gentians, 577
Georgics (Vergil), 106
Geranium pratense, 323, 628

album, 628

pyreniacum, 599
German flora (Koch), 433
Geum, 282
Gherkins, 118
Gideon, Peter M., 78
Glacial period, 696
Gladiolus, 241, 272, 274, 368,
765

cardinalis, 275

gandavensis, 275

psittacinus, 275

purpureo-auratus, 275
Glaucium, 241
Gleditschia sinensis, 614

triacanthos pendula, 617
Gloxinia, 282, 485

erect, 626
Gloxinia erecta, 485

peloric variety, 485
Gnaphalium Leontopodium,

438
Godetia amoena, 161
Godetias, 59, 232
Godron, 265, 433
Goeppert, 370
Gooseberry, 79, 140, 626

red, 133, 165, 241
Grapes, 90, 158, 328
Grape-hyacinth, plumosa, 134
Grasses, 102, 631, 681
Grenier, 433
Groundsel, 132
Growth, nutrition and, 714,

720, 722
Guelder-rose, 134, 239
Gum-tree, Australian, 217
Gypsophila paniculata

twisted variety, 409

H

Haeckel, 707

Half-races, 358, 372, 409, 419,

424, 427, 428
Hall, 444
Hallet, F. F., 109
Harebell, 232

peach-leaved, 234
Harris, Arthur, 825
Harshberger, John W., 591

on Euphorbia in New Jer-
sey, 55
Hawksbeard, 410, 411, 412
Hawkweed, 411 439, 443, 819
Hawkweeds.

seeding without fertiliza
tion, 61
Hawthorn, white, 133
Hays, W. M.

on individual selection, 20,
94, 95, 117, 821, 823, 824
Hazelnut, 133, 181, 243
Hazels, cut-leaved, 596, 616
Heath family, 146, 222, 660

Index

835

Heaths, origin of, 662
Heather, 577

Hedera Helix arhorea, 437
Hedgehog burweed, 140
Hedysarum, 664
Heeger, 582
Heer, Oswald, 74j 105
Heinricher, 172, 173, 174
Helianthemum, 53, 125, 126,
561

apenninum, 53

pilosum, 53

polifolium, 53

pulverulentum, 53

vulgare, 440
Helichrysum, 420
Heltoingia, 678, 678, 683

ruscifiora, 675
Hemp, 419
Henbane, 283
Bepatica, 322, 490
Heredity, 731, 734, 818

bearers of, 632

in teasels, 643
Hesperis, 241, 322

matronalis, 323, 411
Eeylandia latebrosa, 450
Hibiscus Moscheutos, 591
Hieracium, 59, 439

alpinum, 698
Hildebrand, 160, 240, 241
Hoffman, 160, 663
Hofmeister, 160, 370, 480
Holbein, 164, 596
Holly, 140, 196
PToltermann, 449, 451
Hollyhock, 427
Honeysuckle, 674

ground, 443
Hordeum distichum, 677

hexastichum, 677, 678

tetrastichum, 677

trifurcatum, 676, 678

vulgare trifurcatum, 203
Hornbeam, European, 180
Horse-chestnut, 219

thornless, 234
Horsetail, Canadian, 695

European, 649

Horsetail, family, 641
Horse- weed, 132
Canadian, 453
Hortensia, 134, 181
Horticulture, mutations in,

604
Houseleek, 370, 371
Hunneman, John. 521
Hyacinths. 178. 323

white, 160
Hybrids, 58, 201, 202, 206,
250, 575
between elementary species,

253
constant, 263, 264, 265, 266,

267, 268, 269
law of varietal, 716
Mendelian, 324
nature of, 20
species, 256, 260
splitting of, 210
varietal, 208, 209, 247 277,
278, 279, 281, 285, 293,
294
Hybridization, 706, 751, 752,

758, 759, 764
Hydrocotyle, 668
Hyoscyamus niger, 283

pallidus, 283
Hypericum perforatum, 725
Hyssopus officinalis, 161

Iberis umbellata rosea, 195
Improved races, inconstancy

of
Indian cress, 668

pelorism of, 485
Indian pipe, 661
Ipecac spurge, 55
Iris, 456

falcifolia, 173

kaempferi, 174

lortetii, 521

pallida, 173

pallida abavia, 681
Isolation, 108
Ivy, 436

836

Index

Jacob's ladder, 200, 202

Jacques, 614

Jacquin, 52, 633

Jaggi, 594, 595

Jaeger, 228, 663

Jalappa, 165

Janczewski, 266

Japanese plum, 58

Jasminum Samhac, 663

Joly, 712

Jordan, Alexis, 45, 47, 49, 50,

129
experiments with species,

37, 40
J uncus effusus spiralis, 684
Juniper, 684

K

Kapteyn, 716

Kelvin, Lord, 710, 711

Kerner von Marilaun, 266,

267
Keteleer, 618
Knight, 390, 719, 720
Koch, 433, 667
Koelreuter, 279
Korshinsky, 609, 612, 614,

617, 667
Krelage, 510, 619
Kuhn & Co., Messrs., 801,

809, 817

Labiates, 237

pelories of, 577
Labiatiflorae, pelorism of, 468
Labrador tea^ 661
Laburnum, 270, 284, 343

oak-leaved 147, 179

pelorism of, 485
Lactuca, 52

Soariola, 456
Lagasca, Mariano, 96, 97, 114
Lamarck, 1, 447, 461, 522, 523
Lamarckism

objections to, 449

Lamium album, 237

maculatum, 237

pelorism of, 486

purpureum, 237
Larch, 804
Larkspur, 124, 192, 311, 452

hybrid, 213

white, 160
Latency, 657

individual, 219

specific, 246

systematic, 219, 220, 235

varietal, 246
Latent characters, 216
Lathyrus odoratus, 776
Laurea pinnatifida, 450
Laurel, lady's, 146
Laurent, 802
Leaves, cleft, 685

variegated, 426, 431
LeBrun, Mme., 614
Le Couteur, 96, 97, 107, 108,

114, 115, 116, 743
Ledum, 222, 661
Lemna, 222
Lemoine, 762, 763
Lettuce, 684

crisped, 158

prickly, 456
Life, struggle for, 103, 119,

120
Lilacs, 59, 769

double, 762
Lilium candidum fiore pleno,
331

pardalium, 116
Lime-tree, 355, 366, 428, 669

fern-leaved, 147
Linaria, 467, 471, 480

dalmatica, 482

genistifolia, 267

italica, 267

vulgaris, 267, 471

vulgaris peloria, 464
Lindley, 63, 129, 506
Linnaeus, 32, 33, 129, 132,
256, 663

on the idea of species, 11,
13

Index

837

on origin of species, 2, 34

on primroses, 52
Linum angustifolium, 80

crepitans, 81

usitatissimum, 80, 161
Link, 466
Liver-leaf, 322
Lobelia syphilitica^ 161
Lonicera etrusca, 640

tartarica nana, 614
Lorenz, Chr., 482
Lothelier, 454
Lotus corniculatus, 443

corniculatus hirsutus^ 139
Loudon, 615, 616, 667
Lucerne, 264
Ludwig, 738
Lupines, 90
Lychnis, 283

chalcedonica, 161

diurna, 238, 578

preslii, 578

vespertina, 238, 281, 585
Lycium, 455
Ly coper sicum, 655

grandifolium, 654

latifolium (see L. grandi-
folium ) .

solanopsis, 654, 656

validum (see L. solanop-
sis).
Lyell, 1, 710
Lysimachia vulgaris, 684

M

MacDougal, D. T., 62, 575, 590
Macfarlane, 56, 255, 268
Madia elegans, 779
Magnolia, 355, 366, 428, 674,
675

ohovata, 355, 669
Magnus, 228
Mahonia aquifolia, 270
Maize, 134, 775

"Cuzco," 152

European, 206

" Gracillima," 152

" Horse-dent," 152

" Quarantino," 118

Mallow, 663, 684
Malva crispa, 684
Maples, laciniate, 615
Marchant, 592
Marigold, 131, 158

corn, 729

field, 503, 505, 508

garden, 503

Japanese, 490, 494, 495
Marsh-marigold, 331
Martinet, 80
Massart, 434
Masters, 228, 370, 372
Matricaria Chamomilla, 130

Chamomilla discoidea, 156
Matricaria discoidea, D. C,

157
May-thorn, red, 196
Medicago media, 264

falcata, 264
Melanimn, 39
Melons, 118
Mendel, 6, 210, 294, 296, 300,

308

Mendel's law, 276, 293, 204,
298, 299, 300, 301, 307,
611, 613, 616, 716
Mendelism, 307
Mentha, 52
Mercurialis annua, 420

annua laciniata, 592
Mercury, 420, 422, 425, 820
Methods of investigation, 21
Metzger, 205, 206
Milde, 38
Milfoil, 441
Millardet, 266
Miller, 611
Millet, 105
Mimulus, 151

quinquevulnertis, 725
Mimusops, 697
Miocene period, 698
Miquel, 83
Mirahilis, 241

Jalappa, 322
Mirbel, 615

Monardella macrnntha, 444
Monstrosities, 400, 401, 445,
446, 447

838

Index

Monkey-flower, 725
Monocotyledons

ancestry of, 15

regression in, 630
Monotropa, 222, 661
Morphologic units, 145, 153
Monstrosities, 818
Morgan

on mutation-theory, 9
Morren, 244, 763
Mountain-ash, 342
Muller, Fritz, 775, 776, 780
Multiplication, vegetative (see

Asexual propagation ) .
Munting, Abraham, 164, 165,

490, 762
Munting's drawings, 512
Murr, 158, 236
Muscari comosum, 134
Museum d'Histoire Naturelle,

Paris, 522
Mutability vs. fluctuating va-
riability, 568
Mutation, 659, 674, 677, 685,
686, 694, 713, 716, 825

absence of intermediate
steps in, 474, 480

conditions for observing,
601

decided within the seed, 28

definition of, 7

easily observed, 30

experimental, 688

few observations of, 8

fluctuation vs., 7, 16, 719

influence of on variability,
335

iterative nature of, 476,
703

laws of, 556, 558, 560, 562,
564, 566, 568, 570

limited in time, 29

observation of, 16

in Oenothera, 521, 525, 690

oldest known, 609

oldest recorded, 22

periodic, 690, 692, 694

perodicity of, 519

progressive, 307

repetition of, 476

in Saponaria caldhrica, 612

simultaneous, 614

in tomato, 655
Mutations, 141, 275, 280, 445,
449, 573, 608, 620, 626,
678, 685, 686, 701, 704,
712, 713, 716, 800

artificial, 402

chance for useful, 598

defined, 191

frequency of, 597

in garden-flowers, 488

in horticulture, 604, 706

latent, 703

mode of appearance, 517

numerical proportion of,
475

original production of, 703

peloric, 707

periodic, 686, 705

progressive, 704

retrograde, 704

stray, 704, 705, 706

synonyms of, 191
Mutation-period, 714
Myosotis azorica, 368
Myrtus communis, 684

N

Nageli, 60, 439, 443, 448, 795

Nagelian principle, 448, 450,
451

Natural selection, 18, 119,
120, 445, 456, 682, 694,
703, 743, 744, 798-826
basis, 604
nature of, 6, 19

Naudin, 118

Nectarines, 137, 138, 226, 627

Ngmec, 578

Neo-Lamarckians
principle of, 8

Neo-Lamarckism 447

'Nepenthes, 671, 672, 673, 674

Newton, 1, 732, 767

Nicandra, 152

Nigella, 134

Nightshade, 298
black, 282

Index

839

Nourishment

meaning of, 733

variability and 771
Nuphar, 268
Nutrition and growth, 720,

722
Nymphaea, 698

O

Oats, 98, 100, 101, 105, 112,
113, 115, 119, 133, 453

"Early Angus," 115

"Early Fellow," 115

"Fine Fellow," 115

"Hopetown," 112

"Longfellow," 115

" Make-him-rich," 113

wild, 207, 803
Oak, 136, 239

Oenothera, 260, 262, 279, 700,
706, 708, 709

European species, source of,
575

mutation in, 521, 525, 585,
690, 708

new species of, 516-546

albida, 537, 553, 555, 563,
565, 573

Uennis, 62, 205, 256, 257,
258, 259, 262, 263, 264,
521, 524, 527, 574, 575,
586, 587, 683, 690^ 708

biennis cruciata, 22, 587

brevistylis, 263, 280, 526,
529, 530, 547, 563, 564,

565, 573, 574, 702, 706
cruciata, 575, 585, 586, 589,

590, 683
elliptica, 540, 545, 555, 563
gigas, 533, 534, 535, 536,

537, 553, 554, 563, 565,

566, 567, 573, 574, 703
glauca, 424

hirtella, 263

laevifolia, 526, 528, 529,

547, 563, 564, 573, 574,

701, 706
lamarckiana, 17, 262, 263
522, 523, 527, 528, 529,

533, 574, 575, 586, 090,
699

pollination of, 524.
lata, 540, 541, 542, 549, 550,
551, 552, 555, 559, 563,
566, 573, 574, 703
leptocarpa, 540
muricata, 256, 257, 258,
259, 262, 263, 264, 513,
675, 690

pollination of, 524.
nanella, 526, 531, 549, 50,
551, 552, 555, 563, 564,
565, 566, 703
oblonga, 537, 538, 552, 555,

563, 565, 566, 573
rubrinervis, 533, 534, 536,
537, 550, 551. 552, 555,
563, 565, 568, 573, 574
scintillans, 540, 543. 553,
555, 563, 566, 573, 574
mutability of, 544
semilata, 540
suaveolens, 521
Oleander, 684
Onagra, 262, 708, 709
Onions, wild, 684
Ononis repens, 577
Orange, 90, 133, 134
Orchids, 631
Origin of species (Darwin)

109
Orobanche, 220
Othonna crassifolia, 443
Otin, 618
Oviedo, 89

Paeonia corallina leiocarpa,

126
Paillat, 618
Pangenes, 306
Pangenesis, 306, 689
Panicum, 105
Pansies, 640
Pansy, 118, 121
Papaver alpinum, 139

bracteatum, 661

bracteatum monopetalum,
661

840

Index

commutatum, 357

dubium glabrum, 126

hyhridum, 663

somniferum Danehrog, 163

somniferum monstruosum,
371

somniferum polycephalum,
371
Parris, 754
Paisley

crisped, 158, 181
Parsnip, water, 457
Pea-family, 344
Peach, 138, 226, 240
Peach-almond, 769
Pears, 79, 90, 134, 147, 152,

203, 283
Pearson, Karl, 716
Peas, sugar, 135, 158
Pedicularis, 410

palustris, 410
Pedigree-culture, 109

experimental, 547
Pelargonium, 272, 355
Peloria, definition of, 164
Peloric toad-flax

first record of, 466

origin of, 459, 464, 473

sterility of, 467
Pelorism

Antirrhinum majus (see
snapdragon).

Digitalis purpurea, 483

Gloxinia, 484, 485

labiates, 486

Laburnum, 485

Lamium, 486.

Linaria, see Toad-flax

Linaria dalmatica, 482

Linaria vulgaris, 464

orchids, 479, 486, 487

Salvia, 486
Scrophularia nodosa, 486

snapdragon, 481

toad-flax, 459-487

Tropaeolum majus, 485

Uropedium Lindenii, 487

wild sage, 486
Feltaria alUacea, 663

Pennywort, marsh, 668

Penzig, 638

Periodicity, law of, 365, 368,

721, 722
Periods, mutative, 706, 708
Periwinkles, 322
■Persicaria, water, 433, 434,

435, 643
Petalomany, 330
Petunia, 491, 626
Phacelia, 420, 422, 820
Phaseolus lunatus, 592

multiflorus, 202

nanus, 202
Phleum alpinum, 696
Phlox, 232

drummondi, 161
Phyllonoma ruscifolia, 676
Physiologic units, 144, 153,

249
Picris hieracioides, 411
Pimpernel, scarlet, 162
Pinacothec, Munich, 164
Pine, 368, 804
Pine-apples, 90, 134
Pinks, 178
Pinus sylvestris, 368
Pistillody in poppies, 369,

370, 372
Pitcher-plants, 671
Plankton, 711
Plantago, 53

lanceolata, 520, 671, 684
Plantain, 684
Plater, 610
Plum, 79, 134, 769

beach, 58

Japanese, 58

purple-leaved, 619
Plusia, 204

Poa alpina vivipara, 684
Podocarpus koraiana, 169
Polemonium coeruleum, 282

coeruleum album, 200

dissectum, 161, 202
Poly gala, 242
Polygonum amphibium, 433

var. natans Moench, 433,
434

5

^

Index

841

var, terrestris Moench, 433,
434

Convolvulus, 419, 424

viviparum, 684
Polymorphy, 188
Pomegranate, 90
Pond-lily, yellow, 268
Poplar, fastigiate, 623, 624

Italian, 623
Populus italica, 623

nigra, 624
Poppy, 146, 151, 152, 163, 165,
241, 356, 640, 723

"Danebrog," 283, 291

garden, 661

" Mephisto," 283, 291

opium, 89, 189, 195, 198,
282, 291, 369, 371, 373,
379, 383, 391, 405, 406,
420, 452, 720, 789

pistillody in, 369

pistilloid, 508

polycephalous, 405
Potatoes, 765, 810
Potentilla Tormentilla, 53
Pre-Linnean attitude, 2
Primrose, 268, 372, 410

evening ( see evening-prim-
rose ) .
Primula acaulis, 52, 633

elatior, 52, 633, 635

grandiflora, 268

imperialis, 697

japonica, 410

offioinalis, 52, 268, 633, 635

variabilis, 268

veris, 52, 633, 634
Prodromus (De Candolle)

370
Progression, 430, 705, 774,
775, 777, 779, 805

in evolution, 630
Propagation

asexual, 745, 751, 766, 767,
770, 774, 777

sexual, 745, 777

vegetative (see asexual).
Proskowetz, Em. von, 70
Prototype

definition of, 170

Prunus, 52

cerasifera, 619

Mahaleb, 617

nana, 613

maritima

Padus, 617

Pissardi, 619

variation in, 56
Pyrethrum roseum, 511
Pyrola, 222, 661

Q

Quartile, 736, 737, 767
Quercus pedunculata fastiga-

ta, 596

Quetelet's law, 463, 716, 717,

725, 730, 734, 738, 748,

753, 759, 767, 775, 779,

780, 806

R

Races, inconstancy of im-
proved, 770-797
Raciborsky, 682
Radishes, 325, 806
Ragwort, tansy, 157
Raisins, 134
Rameses, 697
Ranunculus, 331

acris, 331

arvensis, 283

arvensis inermis, 125

asiaticus, 241

bulbosus, 357, 410, 740
Ra-n-Woser, King, 104
Raphanus Raphanistrum, 202,
424, 520

caudatus, 202
Rasor, John, 588, 589
Raspberry, 268, 768

"Phenomenal," 268

" Primus," 269

Siberian, 269
Ratzeburg, 467
Raunkiaer

on variation in Taraxacum,
60
Recessive character, 280

842

Index

Regression, 95, 630, 705, 732,

774, 775, 777, 779, 789
Retrogression, 430
Reversion, 155, 167, 170

atavistic, 199

bud, 167, 168, 183, 284

definition of, 166

seed, 175

significance of, 215
Reversionists, 156
Rhingia, 173
Rhododendron, 804
Rhododendron ferrugineum,
267

hirsutum, 267

intermedium, 267

ponticum, 661
Rihes, 170, 226, 625

aureum, 270

sanguineum, 166, 270

scarlet, 166

Vva-crispa, 140
Rice, crown, 133
Ricinus, 139

Rimpau, 69, 70, 94, 98, 99,
207, 792, 803, 810, 811,
812, 813
Risler, 99, 207, 803
Rivett, 98, 99
Riviere, 134

Robinia Pseud-Acacia, 133,
343, 664

Pseud-Acacia monophylla,
196
Robinson, B. L., 590
Rose, 126, 127, 152, 178, 233
Rose, corn, 282

moss, 627
Rose, 610, 611
Rosen, 38, 47
Rothamstead, 102
Rubia tinctorum, 410
Rubus flexuosus, 663

fruticosus, 268

idaeus, 268

odoratus, 663
Rudberg, 466
Rumex scutatus, 139
Ru^cuSy 676

Rye, 105, 410, 453, 810, 813,
821, 822

S

Sagina apetala, 52

patula, 52
Sagittaria japonica, 671
Salix alba, 267
Ehrhartiana, 267
pentandra, 267
Salpiglossis sinuata, 622
Salter, Bell, 269
Salvia, 242

pelorism of, 486
sylvestris, 161
Sambucus niger laciniata,
616
racemosa laciniata, 616
Saponaria calabrica, 612

officinalis, 409, 663
Sarracenia, 672
Saxifraga crassifolia, 366

umbrosa, 684
Saxifrage, 366
Scabiosa, 514
Schimper, 663, 738
Schimper (Braun and), 494
Schindler, 70
Schlanstedt, 822
Schubeler, 805
Scirpus lacustris, 684
Scrophularia nodosa, pelorism

of, 486
Sea-burdock, 139
Secale Cereale, 410
Seden, 273
Sedum, 165
Seed-variation, 750
Sekera, 578

Selection, 108, 111, 114, 390,
399, 743, 751, 789, 790,
792, 793, 794, 797, 799,
800, 801, 804, 806, 807,
808, 813, 825
artificial (see Artificial se-
lection) .
between species, 744, 800,

801
continuous, 778, 784, 786,

I

Index

843

787, 788, 795, 797, 805,
806, 825
double meaning of, 109, 110

individual, 801
intra-specific, 741, 744, 749,
751, 800, 801, 802, 805,
825
natural (see Natural selec-
tion ) .
repeated ( see continuous ) .
species, 743, 744
within the species, 744, 800
Self-heal, 268

white, 201
Sempervivum tectorum^ 370
Senecio jacdbaea, 157

vulgaris, 132
"Sereh," 756
Series, The, of Braun and

Schimper, 494
Seringe, 523
Setaria, 105

Shepherd's purse, 582, 638,
639
Heeger's. 638, 684
Shirreff, Patrick, 107, 108,
109, 110, 111, 113, 114,
115, 116, 743
Silene annulata, 663
Armeria, 161, 232, 282
rosea, 163
conioa, 419
connoidea, 419
Silverchain, 133
Sinning, 668
Sisymhrium, 637
hirsutum, 637
officinalis, 637
supinum, 637
Sium latifolium, 457
Smith, 667
Snakeroot, 674
Snapdragon, 150, 152, 281,
315, 316, 321, 324, 326,
420, 452
" Black prince " variety,

782
"Brilliant," 151
"Delila," 151, 195, 782

"Firefly," 195
"Fleshy," 151
peloric, race of, 781
self-fertility of, 781
striped, 740
yellow, 194

Soapwort, 409

Solanuni, 655, 685
Dulcamara tomentosum , 125
nigrum chlorocarpum , 298

Solms-Laubach, 104, 107, 582,
583, 584

Soltwedel, 755

Sophora japonica pendula,
617
japonica, 136

Sorbus Aucuparia, 342

Species

artificial character of, 36
constancy of, 693, 697
crosses of with varieties,

247, 277, 278, 281
dimorphous, 447
elementary (see Elemen-
tary species),
experimental study of, 37
meaning of term, 10, 122
origin of, 307, 461, 550, 560,

825
origin of, easily observed,

26

polymorphous, 700
selection between, 744
selection within, 744
smaller (see Elementary

species),
spontaneous cross, 209
survival of, 799
systematic, see Systematic

species
two sorts, 12

Variety vs., 122, 154, 220
hybrid (see Hybrids).

Specific marks, origin of, 275

Spath, 619

Spergula media, 53
salina, 53

Spinage, 139, 158, 419

New Zealand, 162

Sport, 111, 310, 311, 316

844

Index

Sports, 191, 715, 689

bud, 427
Sprenger, 610^ 611
Stability, 155
Stahl, 611
Stellaria Holostea apetala,

585
Stocks, 146, 322, 328, 329, 332,

334, 336, 338, 432
Stock

" Brompton," 329

chamois-colored, 198

"Queen," 324

white, 160
Stork's-bill, white hemlock,

161
Strasburger, 196, 448
Strawberry, 158, 266, 343

" Gaillon," 135

"Giant of Zuidwijk," 614

one-leaved, 164, 596, 666

white, 158, 165
Striped flowers, 309, 374, 431,
606, 607

races, types of, 328
Struggle for life, 674, 571,
682, 702, 799, 803, 824,
825
St. Johnswort, 725
St. Sebastian, 164
Sub-species (see also Ele-
mentary species), 224,
225
Sugar-beets (see Beets, su-
gar).
Sugar-cane, 731, 752

"Black Manilla," 753

"Cheribon," 753, 755, 756

"Chunnic," 753

"Hawaii," 755, 756

seeds of, 754

" White Manilla," 753
Sundew, 268
Sunflower, 410, 425, 820
Sweet-flag, 222
SAveet-pea, 160, 776
Sweet William, 163, 282, 322,
648

twisted variety
Syncotyls, 417, 424

Syringa vulgaris azurea pie-

na, 763
Systematic species, 12, 64,
101, 128
nature of, 54, 63
Systematic units, 61, 91

Tagetes africana, 510

signata, 612
"Talavera de Bellevue," 97
Tanacetum vulgare, 131, 132,

236
Tansy, 131, 132, 236
Taraxacum, 125, 126

officinale, 59, 411
Tares, 105
Taj)us, 136

haccata, 169

haccata fastigiata, 170, 618

minor, 169
Teasels, 402, 642, 645, 674,
675

twisted, 405, 412, 446, 447,
643, 646, 647, 648, 819
Tetragonia expansa, 162
Theatre d'Agriculture, 72
Thibault, 618
Thomson, Sir William (see

Kelvin, Lord).
Thorn-apples, 139, 142, 143,
145, 238, 283, 300, 453

thornless, 234
Thorn-broom, 457
Thrincia hirta, 411
Thuret, 38, 47, 49
Thyme, white creeping, 201
Thymus Serphyllum album,
201

vulgaris, 577
Tili<i parvifolia, 355, 669
Toad-flax, 267, 282, 707

cross pollination of, 471

experiment with, described,

468
invisible dimorphous state

of, 470, 471, 478
latent tendency to mutation

in, 479

Index

845

peloric, see Peloric toad-
flax,

sterility of mutants, 477

unusual pelorism, 486
Tomato, 653

« Acme," 656, 657

" Mikado," 654

mutation of, 655

upright, 654

"Washington," 657
Tournefort

author of genera, 33
Tracy, W. W. 592
Trees, genealogic, 707, 708
Trieotyls, 416, 418, 419, 420
Trifolium incarnatum, 353
Triticum dicoccum, 105
Tropaeolum, 193, 668

majus, pelorism of, 485
"True Exercises with Plants"

(Hunting), 490
Tulips, 149, 178, 274, 323

black, 620
Turnip, 244, 621
Twisted stems, 402, 403, 405,

413
Twisted varieties

atavists of, 406

U

Ulex europaeus, 140, 217
Ulmus pedunculata, 615
pedunculata urticaefoUa,

615
Umbellifers, 457
Umhilicus, 669
Unger, 105
Unit-characters, 249, 261, 306,

307, 313, 658, 689, 715,

716
Urban, 265

Uropedium lindenii, 487
Utility, 685, 724
Utricularia, 672

Vaccinium Myrtillus, 577
Valerian, 402, 409 648

twisted, 403
Valeriana officinalis, 402
Vallisneria, 684
Van den Berg, 625
Van de Water, 614
Van Mons, 76, 77, 78, 806
Variability (see also Fluc-
tuation), 188, 190, 191

analogous, 244

apple, 75

asexual, 320

correlative, 142, 143, 148,
167

cultivated plants, 66

embryonic, 770, 771, 814

ever-recurring, 190

fluctuating (see also indi-
vidual), 62, 142, 190,
233, 375, 416, 454, 698,
759, 762, 765, 766, 767,
770, 771, 789, 805, 814

fluctuating vs. mutability
568

homologous, 244

individual (see also fluc-
tuating), 190, 716, 718,
746, 749, 770, 814

influence of mutation on,
335

kinds of, 715

nutrition and, 390, 391,
719, 771

parallel, 243

partial, 440, 444, 718, 746,
748, 753, 814, 816

repeated, 242

restricted, 598

sectional, 317

sexual, 320

sovirces of, 758
Variation

bud, 176, 178, 180, 284,
317, 318, 321, 338, 427,
750

definition of, 188

partial, 788, 789

seed, 750

spontaneous, 191

use of term, 189
Variegation, 426, 427

846

Index

Varietal marks, origin of,

275
Varieties, 84, 95, 126, 127,
128, 129, 132, 142

broom-like, 618, 624

constancy of, 532

constant, 135

crosses of species with, 247,
277, 278, 281 ^

elementary species vs. 459

ever-sporting, 178, 309,
310, 311, 312, 313, 321,
324, 328, 329, 332, 333,
334, 350, 358, 365, 368,
372, 399, 413, 420, 430,
431, 432, 434, 445, 606,
607, 628, 740, 789, 790,
795

fasciated (see Fasciated
stems) .

groups of, 606

horticultural, 607, 609

hybrid, 122, 190, 608

hybrids of, 210, 254, 255

inconstant, 135, 154, 155,
161

mutation of, 141

negative ( retrogressive ) ,
131, 132, 134, 224, 226,
238, 245, 277

positive, 131, 132, 134, 224,
238, 245

pure, 122, 190

retrograde, 14, 15, 16, 95,
121, 208, 430, 435, 606,
607

retrogressive ( see nega-
tive ) .

seed, 123

single, 191

spontaneous crosses, 209

sporting (see inconstant).

stability of, 207

sterile, 622

types of, 142

variable, 606

vegetative, 123

weeping, 617
Variety, 130

definition of, 11, 12

elementary species vs. 141,
152, 154, 224, 243, 247,
251
origin of, 141, 152, 224
use of term, 189, 435
Variety-testing, 95, 97, 116,

119, 743, 799, 825
Varro, 106
Veitch & Sons, 273
Venus' looking-glass, 367
Verlot, 186, 612
Vernon, 133
Vernonia cinerea, 450
Veronica longifolia, 282, 284
scutellata, 139
spicata nitens, 126
Viburnum Opulus, 134, 239
Vicinism, 185, 188, 203, 205,
206, 213, 214, 776
definition of, 188, 192, 606
Vicinist, 199, 201
Vicoa auriculata, 450
Victoria regia, 668
Villars

on Draha verna, 49
Vilmorin, 570, 607, 612, 622,
661, 662, 773, 775, 776,
792, 795, 796, 797, 806,
807, 810, 813, 818, 820
Vilmorin, Louis de, 72, 92,
93, 97, 108, 109, 110, 114,
185, 818
Vilmorin, Messrs., 322
Vinca, 242, 490

minor, 322
Vine, parsley-leaved, 179
Viola, 126, 546, 547, 693
agrestis, 45
alpestris, 40
altaioa, 39
anopetala, 44
arvensis, 39, 40, 41, 44
curtisepala, 45
striolata, 45
aurohadia, 44
calcarata, 39
cornuta, 39, 281
lutea, 38
lutescens, 44
nemausensis, 45

:

Index

847

ornatissima, 4l4:

palescens, 45

patens, 45

roseola, 44

segetatis, 45

stenochila, 41

tricolor, 38, 40, 41, 44, 46
ammotropha, 41
coniophila, 41
genuina, 42
versicolor, 42
Violets, 63, 232, 233, 490
Violet, dame's, 322, 323, 411

long-spurred, 281
Virgil, 105, 106, 108
Viscaria oculata, 4, 648, 821

twisted variety, 408
Vitis, 52
Volckamer, 228
Von Loehow, 821, 822, 823
Von Rliraker, 94
Von Wettstein, 448, 805
Vrolik, 164, 483

W

"Waare Oeffeninge der Plan-
ten'' (Munting), 490
Wallace, 5, 7, 8, 30, 205
Wall-flower, 370, 371
Walnut, 243, 766

cut-leaved, 616

one-bladed, 666
Water-lilies, 668
Weber, 228
Weeping-willow, 180

crisped, 181
Weigelias, 740
Wellingtonia, 618
Wheat, 96, 98, 105, 113, 119,
283, 810, 823

bearded, 98

"Blue-stem," 117

" Galland," 100, 207

"Hopetown," 112, 113

"Hunter's," HI, 113
"Minnesota No. 169," 117
" Mungoswell's," 110, 111

"Pedigree," 109

" Pringle's," 114

" Rivett's bearded," 207

" Sheriff's bearded red,"
114

" Sheriff's bearded white,"
114

"White Hunter's," 113
Wheat-ear carnation, 227
White, C. A., 656, 657
White varieties, 577
Whitlow-grasses, 63, 118, 119
Whorls, ternate, 684
Wild sage (see Salvia).
Willdenow, 468, 666, 667
Williamson, 491
Willows, 135, 267
Willow

weeping (see Weeping-wil-
low ) .
Willow-herb, 268, 269, 683
Wintercress, 427
Wintergreen, 661
Wittmack, 682
Wittrock, 38, 40, 41, 42, 43,

44, 45, 46
Wooton, E. 0., 140
Wormseed, 638

Xanthium canadense, 140
commune, 140, 152, 591
commune Wootoni, 22
Wootoni, 140, 152, 591

Yarrow, 131, 132
Yew, 136, 169
pyramidal, 618

Zea Mays cryptosperma, 641

tunicata, 641
Zinnia, 490
Zioberg, 466
Zocher & Co., 230

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