A century has passed since the days when the law of homologous series in variation
was first manifested. This event happened in 1920 in Saratov, in the third post-revolution
year, in the frameworks of the III All-Russian Conference on Plant Breeding, then
mobilized in view of current needs of agricultural practice, science and education.
The report of a 33-year-old professor Nikolai Vavilov, who was accompanied by his
students from the Saratov University, caused a sensation. Vavilov’s generalization
on the phenomenon of the homologous series in variation of cultivated plants was reported
on June, 4, 1920 and enthusiastically appreciated by the qualified breeders as a great
scientific achievement comparable with the Mendeleev’s periodic Law of the chemical
elements. On June 21, 1920, a message of the provincial Saratov branch of the Russian
Telegraph Agency shared internationally the information on “the greatest discovery
of world significance” which was addressed to the State government by the decision
of the meeting. Very soon after the initial Russian publication (Vavilov 1920), the
paper entitled “The Law of Homologous Series in Variation” was published in the Journal
of Genetics, edited by W. Bateson and R.C. Punnett, the elder statesmen of genetics
(Vavilov 1922). In 1925, William Bateson, Director of the John Innes Horticultural
Institute, with colleagues, visited experimental fields and laboratories of Nikolai
Vavilov, Director of the Bureau of Applied Botany and Plant Breeding (future N.I.
Vavilov Institute of Plant Breeding) in a Petrograd – Leningrad (now Saint Petersburg)
suburb (Fig. 1). The paper took 42 pages of Volume XII (1) (April, 1922, p. 47–89).
The substance of this work by Vavilov was recalled in the chapters of N. Timofeeff-Ressovsky
(1940) and N. Vavilov (1940) in the monograph “The New Systematics” (Huxley 1940),
a synoptic book, preceding the publication on the new synthesis of theory of evolution
(Huxley 1942). Since then and till now, genetic nature of homologous variation, the
matter of the Vavilov’s law, has been in the focus of various disciplines, from agriculture
to paleontology, being rejuvenated with the progress of molecular biology. Nowadays,
molecular homology can be established universally at various levels, from unique genes
to gene orders in chromosomes through genetic, cytogenetic and molecular analyses
(Zakharov 1987) up to gene networks studied by bioinformatics (Suslov et al. 2008).
It seems rational to meet the 100th anniversary of this significant event of young
hereditary science with a digital copy saving the author’s idea for future readers
and investigators. The text is here reproduced in the Archives format from printed
pages of the Introduction (p. 48–53) and the concluding section (p. 86–89) of the
original English version (Vavilov 1922). The title page copied on Fig. 2 presents
the whole contents of this work. Details of punctuation and citation are generally
N. I. Vavilov (left below) and Russian geneticists V.A. Dogel, Yu.A. Filipchenko with
the visiting European delegation: H. Federley, O. Fogt and W. Bateson (left to right
in the second row). 1925, Leningrad (Vavilov 2012).
The title page of the Vavilov’s paper in the Journal of Genetics, 12(1), 1922.
Introduction [p. 48–53]
Evolution of the study of systematics of plants
The characteristic feature of the history of plant investigation, from Tournefort
up to the present, has been the varied conception of systematic units. Further investigation
did away with the former conception of species, as introduced by Linné. The history
of systematics of plants gives a vivid illustration of attempts to arrange in a convenient
and harmonious system all newly discovered morphological and physiological characteristics,
the number of which grows rapidly with improved methods of discerning hereditary forms,
and with the study of new specimens of the same plants, gathered in different regions.
The Linnean species had to be divided into subspecies and varieties (in sensu bot.);
varieties into races. Genetical studies of the last decades have proved even the divisibility
of the minutest morphological and physiological units in systematics (races, Elementararten
of de Vries), and established that, although outwardly similar, they can be different
genotypically. The same is applicable to the animal world.
Lotsy, in his book Evolution by Means of Hybridization (1916), proposes to introduce
a new terminology to distinguish fundamental units in the classification of hereditary
forms. He proposes to call the old Linnean species, which, as was shown in the nineteenth
century, are of collective nature – “Linneons”; races, varieties, which make up the
elementary species of Jordan and de Vries he proposes to define as “Jordanons”. The
term “species”, Lotsy would retain (as it seems to us not very successfully) for the
modern conception of genetics – the genotype, as a fundamental unit covering similar
hereditary groups of individuals.
Statistics of the diversity of the plant world
Up to the present, statistics of the plant and animal world are available only for
“Linneons”. According to Hooker and Engler there are known altogether about 130,000–140,000
Linnean species of higher seed plants, including
. Families most abounding in Linneons are, according to Engler
, those of
Although these numbers of Linneons are quite large, they give a very superficial representation
of the real diversity of the plant world. Only a closer study of Jordanons and genotypes
would give a true idea of this diversity.
The systematic study of numerous varieties among Linnean species, which was initiated
by Lindley (Monograph on Roses), de Candolle (
), Kraus, Metzger, and Alefeld on cultivated plants, and by Séringe
, Jordan and Naegeli on wild plants, and is continued nowadays by plant breeders and
by botanists (Swedish school of systematists: Wittrock, Dalstedt, Almquist and others),
has revealed a total absence of monotypical Linneons. Linnean species, which, in the
nineteenth century were regarded as uniform, in the twentieth century were separated
by plant breeders and systematists into large numbers of Jordanons, easily distinguishable
both morphologically and physiologically; e.g. many species of
, Linnea borealis, etc. Up to the present, not many Linneons of wild and cultivated
plants have been studied thoroughly, but still the data available shows an immense
diversity of Jordanons among Linneons.
Thus, after investigations of local Russian and Asiatic wheats at our experimental
station, the existence was proved of about 3000 Jordanons of
Vill., perfectly recognizable morphologically and physiologically
. This number does not include many hundreds of varieties of hybrids created artificially
by plant breeders of Western Europe during the last thirty or forty years, but only
the natural local varieties of wheat.
For barley we know at least 600 to 700 Jordanons, for oats more than 600. In Rye,
, many hundreds of forms, differing in hereditary morphological and physiological
characters, were collected by Mrs V. P. Antropova, from different parts of Persia,
Bokhara, Asiatic and European Russia. Hundreds of easily distinguished forms are found
in sorghum by American investigators. Investigations in Japan and India discovered
thousands of varieties in rice. Thousands of varieties might be established in Indian
. Hundreds of varieties were found in peas,
; lentils, Ervum Lens; beans,
. Hundreds of varieties are found among
. Jordan and Rosen found about 200 constant varieties in wild
. Miss Sinskaja, at our experimental station, found more than 300 well recognizable
, a weed occurring in field of flax in Turkestan and Bokhara. Thousands of forms,
perfectly distinguishable, exist among species of
. Hundreds of forms are found among wild Linnea borealis (Wittrock),
Wild and cultivated plants
The majority of cultivated and wild Linneons propagated by seeds, are represented
by hundreds of well-defined Jordanons. There is no essential difference in this respect
between wild and cultivated plants. Wild Linneons, like clover (
, yellow alfalfa (
, studied in detail at Russian Experimental Stations by plant breeders (Roudzinski,
Lorch, Jegalov, Bogdan), proved to be no less variable than cultivated wheats, barleys,
oats, and peas. The monotypic nature of many wild Linnean species is kept only so
long as they are studied by a few specimens in the herbarium. The individual study
in culture of many samples of the same Linneon inevitably discovers its polymorphic
Still greater diversity is observable in plants multiplying vegetatively or apogamically,
like roses, potatoes, apples,
We do not exactly know if there are really monotypic Linnean species in nature, fairly
well specific and separated from other Linnean species and represented by one variety,
one Jordanon only. The whole impression is that the more we study our plants and animals,
the more variable thay are, the more varieties we find among Linnean species. Several
Linnean species of plants and animals, like roses, wheats, Indian corn, rice, squashes,
, seem to be extremely variable, but these have attracted more attention than others.
We easily notice sharp differences in colour, size, and shape of several organs and
are rather inattentive to others.
The differences of Jordanons within the limits of the same Linneon, in the shape and
colour of their flowers, form and size of leaves, fruits and other organs, are very
often no less marked than the differences between Linneons themselves. For instance,
some varieties of
Pepo are characterized by fruit the size of hen’s eggs; other varieties, growing under
the same conditions, bear fruit three and four feet in diameter. Some varieties of
have opposite leaves and fruits, others have alternate. Some varieties of wheat and
rye have simple leaves, without differentiation into vaginae and plates, having no
“ligula”, or “auriculae”; others have the usual complicated leaves, with “ligula”,
Plants self-fertilized, as wheat, barley, peas, soya, etc., and cross-fertilized,
as rye, maize, beet, ale alike polymorphous. The seeming uniformity of several cross-fertilized
wild and cultivated plants is only apparent when they are not studied carefully. The
difference consists only in the homozygotic nature of many characters in cross-fertilized
plants, and in the homozygotic nature of self-fertilized plants. Some recessive characters
may be hidden in cross-fertilized plants by the dominance of other characters, but
by artificial self-fertilization of these plants, and by inbreeding, it is possible
to re-establish them. From what we know at present from the study of Indian corn (Emerson,
Collins, and others), of rye, beetroot,
, man himself, cross-fertilized organisms are not less variable than self-fertilized.
The above mentioned numbers of Jordanons are in reality still greater, because, up
to the present time, African and Asiatic varieties of even the most important cultivated
plants, like wheat, oats, barley, peas, lentils,
, are almost unknown.
Problems of the future
There is a real need for the study and systematizing of these Jordanons, especially
in cultivated plants and domesticated animals, for the benefit of geneticists, as
well as systematists and agriculturists. Only the closest study of Jordanons and genotypes
will give a real re-presentation of what a Linneon is. To construct the general genetic
schemes, it is necessary to know the composition of Linnean species. Before creating
new varieties by crossing we ought to know what exists in nature. Even for cereals,
, and other most important plants, we have no adequate knowledge of even easily recognizable
botanical varieties. Regions of ancient culture in Asia, Africa, and America still
preserve numbers of varieties unknown to systematists and plant breeders.
In 1880, Alphonse de Candolle wrote in his remarkable book La Phytographie: “Un jour
la science traitera les elements de l’espece comme les elements des genres, comme
ceux de la famille et tous ces groupes seront coordonnes, les uns au-dessus des autres
d’une maniere parfaitement uniforme” (p. 80). This day has arrived, but the task is
not very simple. The closest study of some Linneons of cereals,
, persuades one of the immensity of this work. The diversity of plants and animals
is too great to admit of giving a complete list of existing forms. There comes the
necessity to establish some principles and schemes of classification.
The near future promises to differentiate the Linneons still more, and to multiply
the number of Jordanons and species in Lotsy’s sense. Artificial hybridization threatens
considerably to enlarge the external diversity of forms.
It may be expedient to define even at the present time the multi-formity in Linneons,
not by the number of described and possible compositions, but by the number and list
of varietal characters through which Jordanons differ from each other, not forgetting
that separate characters can be dependent on several hereditary factors or genes,
involving complicated genotypical formulae. The complete genotypical compositions
of Linneons is a problem for the future.
The multitudinous chaos of innumerable forms obliges investigators to look for some
way of simplification. The process of differentiation will go on inevitably, adding
to the records of existing forms, and giving a true conception of Linneons. But parallel
to differentiation it is natural to search for ways of integration of our knowledge
of Jordanons and Linneons themselves. If some 130,000 Linneons are difficult to manage
for investigation, the work with tens and hundreds of millions of Jordanons will be
still more complicated.
As formerly, in the study of dead organic and inorganic worlds, so at the present,
the problem before the investigator of the animal and plant world is to explore the
regularities in polymorphism, and to establish its classes.
The object of this work
Below is an attempt to integrate the phenomena of polymorphism which we define as
“The Law of Homologous Series of Variation”. These regularities were noted by the
author during the study of innumerable varieties of cultivated and wild plants.
The ideas expounded below in some parts are not foreign to biological literature.
Separate facts of regular variation were known long ago. Naudin noticed them in his
classical study of
, who was in general rather the adherer of fortuitous variations in all directions
in his Origin and Variation, paid attention to regular variation, which, as he states,
“occasionally” happens in plants and animals.
M.J. Duval-Jouve collected a great many data on the variation of wild Linnean species
in his paper on “Variations paralleles des types congeneres” published in 1865 in
Bull. De la Ste. Botanique de France, Vol. XII. His conclusions in some part come
near to the statements of our study. De Vries notices in his
the existence of series of variation
. Eimer in his study of Orthogenesis approached the same subject from a different
point of view. Several palaeontologists (Cope, Oscborn) noticed regular variation
in animals. More recently Saccardo
gave extremely instructive instances of regular variation in fungi and
The detailed study of variation among many different groups, and the great number
of new facts permits us to take this subject anew and bring all known facts into the
form of a general law to which all organisms are submitted.
X. General conclusions [p. 86–89]
Parallelism in varietal polymorphism, and the existence of regularity in differentiation
of greater groups as Linneons, genera, and families, is a great help in the study
of varieties in self- and cross-fertilized plants and animals. Instead of searching
for unknown forms, the investigator can definitely look for, and foresee, forms lacking
in a system, by noticing the similarities with the nearest known Linneons and genera.
In this respect a biologist places himself in the position of a chemist, who classifies
substances according to their place in a system, and creates them through synthesis.
The investigation of polymorphism and the description of new forms become full of
scientific meaning and interest. New forms have to fill vacancies in a system. The
collections of immense numbers of butterflies and beetles in our museums and herbariums
will play a more worthy role in the immediate future than ever before. For a systematist
is not a man who knows all the curiosities of nature, but one who grasps the order
and sense of it all.
The existing systems of Linneons and varieties ought to be fundamentally changed,
and constructed according to a general plan. Instead of occasional characters, which
usually determine species and varieties, it would be more rational to follow a general
system. The greatest problem of systematists is to build up a general well sustained
monotypical system, where similarity and homological series of variation would be
considered as the fundamental basis, instead of an indefinite tangle of names impossible
to remember. This may seem rather revolutionary for systematists, and it must be done
very carefully, in consideration of existing orders. It would be easier to arrange
in general systems of minutest systematical units, varieties and races which are as
yet almost untouched by systematists. We have tried this for cultivated plants, and
have found it expedient. Instead of remembering endless forms, usually named after
occasional places of origin or in honour of persons, we have the possibility of studying
a system and introducing into it individual additions, where it may be necessary to
do so, for single Linneons and genera. We realize well the size and difficulty of
the whole problem. Without a differential work, and without studying in detail, the
integral work will be groundless. To integrate it is necessary to differentiate. We
know that perhaps a century will pass before botanists and zoologists will create,
through collective work, an organized world system; but this way is historically necessary
Analogy with chemistry
The above-mentioned analogy of the present day position of the biologist and chemist
is deeper than it might seem at first. We have spoken conventionally about characters,
colours, hairiness, beardedness, etc. Chemistry says little about the exterior of
its substances; it considers the chemical nature of its compounds and their formulas.
Numerous chemical substances are required to a harmonious system of combinations of
a few elements. The biologist is still far behind. During the last decades, however,
genetics has advanced greatly and is rapidly overtaking chemistry – at least the old
chemistry of complicated organic compounds. Genetics is creating a laconic language
of signs for hereditary factors, determining external characters. The biologist has
learned to analyze organisms, and to get a hold on methods for the synthesis of new
The regularities in polymorphism of plants, established by a minute examination of
variation in different genera and families which we have examined, can be compared
to homologous series of organic chemistry, e.g. carbohydrogen (CH4, C2H4, C2H2, …).
Its series of compounds differing from each other, are still characterized by many
common properties in reactions, by definite cycles of compounds, by definite reactions
of exchange and adhesion. Every single hydrocarbon gives a series of compounds similar
to that of other hydrocarbon.
In general, genera (G1, G2, G3, …) and Linneons (L1, L2, L3, …) of plants and animals
display, in just the same manner, their homologous series of varieties, corresponding
to different homologous series of hydrocarbons.
G1L1 (a+b+c…) _ _ _ _ G2L1 (a+b+c…)
G1L2 (a+b+c…) _ _ _ _ G2L2 (a+b+c…)
G1L3 (a+b+c…) _ _ _ _ G2L3 (a+b+c…)
L1a1, L1a2, L1a3, …
L2a1, L2a2, L2a3, …
L3a1, L3a2, L3a3, …
Where a1, a2, a3, … are different characters which distinguish different varieties.
The series of forms are strikingly analogous to homologous series of organic chemistry.
Besides their chemical structure, different forms of organized nature are characterized
by physical structure, and perhaps it would be better to trace also the analogy of
homologous series of plants and animals, with systems and classes of crystallography
with definite chemical structure (Crystallo-Chemistry of Fedoroff).
We leave the question, in detail, of these analogies, which is already discussed in
literature (Johannsen, Lohmann, Tischler). Further investigations will establish more
precisely the law of homologous variation in plants and animals, and it may be posiible
to bring the same series into mathematical expression. The variation in form might
be reduced to some geometrical scheme.
The problem of the origin of species cannot be separated from the problem of variation.
A great many forms are undoubtedly only different combinations of the same genes,
some primary types. The study of variation will give us the possibility of establishing
these primary types, the fundamental series of variation of organisms.
The idea of the homologous series in variation in its essence is only a development
of the general idea of Goethe’s “Metamorphosis of plants”, the idea of the unity in
variety of C. Dresser
In conclusion, we take the liberty of expressing our strong conviction that the most
rational and expedient method of studying the diversity of plants and animals open
to breeders of both, even for practical purposes, is through the establishment of
parallelism and homologous series of variation.