Species and Varieties, Their Origin by Mutation

H >> Hugo DeVries >> Species and Varieties, Their Origin by Mutation

Pages:
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44

Produced by Dave Gowan

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 and 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 object of inquiry.
DARWIN

The origin of species is an object of experimental investigation.
DeVRIES.

- - - - -

PREFACE BY THE AUTHOR

THE purpose of these lectures is to point out the means and methods by
which the origin of species and varieties may become an object for
experimental inquiry, in the interest of agricultural and horticultural
practice as well as in that of general biologic science. Comparative
studies have contributed all the evidence hitherto adduced for the
support of the Darwinian theory of descent and given us some general
ideas about the main lines of the pedigree of the vegetable kingdom, but
the way in which one species originates from another has not been
adequately explained. The current belief assumes that species 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 distant periods.

The principal features of the theory of mutation have been dealt with at
length in my book "Die Mutationstheorie" (Vol. I., 1901, Vol. II., 1903.
Leipsic, Veit & Co.), in which I have endeavored to present as
completely as possible the detailed evidence obtained from trustworthy
historical records, and from my own experimental 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 [vii] summer of 1904, and these
lectures are offered in this form to a public now thoroughly interested
in the progress of modern ideas on evolution. Some of my experiments and
pedigree-cultures are described here in a manner 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
experiments and observations have been added, and a wider choice of the
material afforded by the more recent current 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 lectures I have tried to devote
attention to the more important phases of the subject and have avoided
the details of lesser interest to the general reader.

Considerable care has been bestowed upon the indication of the lacunae
in our knowledge of the subject and the methods by which they may be
filled. Many interesting 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 perseverance, 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 Morgan 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 Botanical Garden for their painstaking work in
the preparation of the manuscript for the press. Dr. MacDougal, by
[viii] his publications, has introduced my results to his American
colleagues, and moreover by his cultures of the mutative species of the
great evening-primrose has contributed 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 accord 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 scientific research upon these
subjects, that after half a century many problems of major interest
remain to be taken up. The work now demanding our attention is
manifestly that of the experimental observation and control of the
origin of species. The principal object of these lectures is to secure a
more general appreciation of this kind of work.

HUGO DE VRIES.
Amsterdam, October, 1904.

[ix]

PREFACE BY THE EDITOR

PROFESSOR DE VRIES has rendered an additional service to all naturalists
by the preparation of the lectures on mutation published in the present
volume. A perusal of the lectures will show that the subject matter of
"Die Mutationstheorie" has been presented in a somewhat condensed form,
and that the time which has elapsed since the original was prepared has
given opportunity for the acquisition of additional facts, and a
re-examination of some of the more important conclusions with the result
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 investigation 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 facilitating 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]
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
possible. The editor wishes to acknowledge material assistance in this
work from Miss A.M. Vail, Librarian of the New York Botanical Garden.

D.T. MacDougal.
New York Botanical Garden, October, 1904.

PREFACE TO THE SECOND EDITION.

THE constantly increasing interest in all phases of evolution 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 smoothness. 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 investigations
in Amsterdam and New York.

The portrait which forms the frontispiece is a reproduction 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 selection. Evolution and
adaptation. Elementary species and varieties. Methods of scientific
pedigree-culture.

B. ELEMENTARY SPECIES.

II. Elementary species in nature. 32
_Viola tricolor_, _Draba verna_, _Primula acaulis_, and other
examples. _Euphorbia pecacuanha_. _Prunus maritima_. _Taraxacum_ and
_Hieracium_.

III. Elementary species of cultivated plants. 63
Beets, apples, pears, clover, flax and coconut.

IV. Selection of elementary species. 92
Cereals. Le Couteur. Running out of varieties. Rimpau and
Risler, _Avena fatua_. 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 composites.
[xiii] Progressive red varieties. Apparent losses. _Xanthium
canadense_. Correlative variability. Laciniate leaves and petals.
Compound characters.

VI. Stability and real atavism. 154
Constancy of retrograde varieties. Atavism in _Ribes sanguineum
Albidum_, in conifers, in _Iris pallida_. Seedlings of _Acacia_.
Reversion by buds.

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

VIII. Latent characters. 216
Leaves of seedlings, adventitious buds, systematic latency and
retrogressive evolution. Degressive evolution. Latency of specific
and varietal characters in wheat-ear carnation, in the green dahlias,
in white campanulas and others. Systematic latency of flower colors.

IX. Crossing of species and varieties. 247
Balanced and unbalanced, or species and variety crosses.
Constant hybrids of _Oenothera muricata_ and _O. biennis_. _Aegilops_,
_Medicago_, brambles and other instances.

X. Mendel's law of balanced crosses. 276
Pairs of antagonistic characters, one active and one latent.
_Papaver somniferum_. [xiv] _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.

XIII. Polycephalic poppies. 369
Permanency and high variability. Sensitive period of the
anomaly. Dependency on external conditions.

XIV. Monstrosities. 400
Inheritance of monstrosities. Half races and middle races.
Hereditary value of atavists. Twisted stems and fasciations. Middle
races of tricotyls 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.

[xv]
XVII. The production of double flowers. 488
Sudden appearance of double flowers in horticulture. Historical
evidence. Experimental 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 _O. laevifolia_, _O. brevistylis_, and
_O. nanella_. New elementary species, _O. gigas_, _O. rubrinervis_,
_albida_, and _oblonga_. _O. lata_, a pistillate form.
Inconstancy of _O. scintillans_.

XIX. Experimental pedigree-cultures. 547
Pedigree of the mutative products of _Oenothera lamarckiana_ in
the Botanical Garden at Amsterdam. Laws of mutability. Sudden and
repeated leaps from an unchanging main strain. Constancy 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 Moscheutos_. 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. [xvi] Purple
leaves. _Celosia_. Italian poplar. Cactus dahlia. Mutative origin of
_Dahlia fistulosa_, and _Geranium praetense_ in the experiment-garden.

XXII. Systematic atavism. 630
Reappearance of ancestral characters. _Primula acaulis umbellata_.
Bracts of crucifers. _Zea Mays cryptosperma_. Equisetum, _Dipsacus
sylvestris torsus_. Tomatoes.

XXIII. Taxonomic anomalies. 658
Specific characters occurring in other cases as casual
anomalies. _Papaver bracteatum monopetalum_. _Desmodium gyrans_ and
monophyllous varieties. Peltate 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 nutrition.
Periodicity curves.

XXVI. Asexual multiplication of extremes. 742
Selection between species and intra-specific selection.
Excluding individual [xvii] embryonic variability. Sugar-canes.
Flowering cannas. Double lilacs. Other instances. Burbank's method
of selection.

XXVII. Inconstancy of improved races 770
Larger variability in the case of propagation by seed,
progression and regression after a single selection, and after
repeated selections. Selection experiments 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 intraspecific selection may be
guided.

Index 827

[1]
A. INTRODUCTION

LECTURE I

DESCENT: THEORIES OF EVOLUTION
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 landmarks 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 common 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 evidence. To Darwin was reserved the task of [2] bringing the
theory of common descent to its present high rank in scientific and
social philosophy.

Two main features in his work have contributed to this early and
unexpected victory. One of them is the almost unlimited amount of
comparative 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 creation 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 external conditions. In his first
book Linnaeus adhered to this belief, but later changed his mind and
maintained the principle of the separate creation of species. The weight
of his authority soon brought this conception to universal 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 [3]
subspecies and varieties. If an origin by natural 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 features 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 generally 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 explanation
by the aid of this principle; without it, all similarity is only
apparent and accidental. Geographic and paleontologic facts, brought
together by Darwin and others on a previously unequalled scale, point
clearly in the same direction. The vast amount of evidence of all [4]
comparative sciences compels us to accept the idea. To deny it, is to
give up all opportunity 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
investigation 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 "Darwinian theory of descent."

Darwin's second contribution to this attainment was his proof of the
possibility of a physiological 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 outset, 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 [5] species in nature were unknown in the
time of Darwin. It was a happy idea to choose the experience of the
breeders in the production of new varieties, as a basis on which to
build an explanation of the processes of nature. In my opinion Darwin
was quite right, and he has succeeded in giving the desired proof. But
the basis was a frail one, and would not stand too close an examination.
Of this Darwin was always 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 conceptions.

The experience of the breeders was quite inadequate 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 imperfectly distinguished. The breeders'
conception was fairly sufficient for practical purposes, but science
needed a clear understanding of the [6] factors in the general process
of variation. Repeatedly Darwin tried to formulate these causes, but the
evidence available did not meet his requirements.

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 sudden 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 unsurmountable difficulties, Darwin
discovered the great principle which rules the evolution of organisms.
It is the principle of natural selection. 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 Darwin's adversaries, and unfortunately many of his followers
also, have so often asserted.

It is [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 sidepaths. 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 natural 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 individual steps are brought
about, is quite another side of the question.

On this point Darwin has recognized two possibilities. One means of
change lies in the sudden 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 indicated by
the common assertion that no two individuals of a given race are exactly
alike. The first changes are what we now call "mutations," the second
are designated as "individual variations," or as this term is often used
in another sense, as "fluctuations." Darwin recognized both lines of
evolution; Wallace disregarded the sudden changes and proposed
fluctuations [8] 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 recognized, and the battle rages
about the question, 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 divided into two camps. One group is called the
Neo-Lamarckians; they assume a direct modifying agency of the
environment, producing a corresponding and useful change in the
organization. The other group call themselves Darwinians 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.