VRIES, HUGO DE

(b. Haarlem, Netherlands, 16 February 1848; d. Lunteren, Netherlands, 21 May 1935), Plant physiology, genetics, evolution.

The ancestors of Hugo de Vries¹ had been Baptists since the Reformation. As dissenters they were not eligible for public office, but they found an outlet for their talents and energy in trade; during the seventeenth and eighteenth centuries they were prosperous merchants. When the drastic political changes at the end of the eighteenth century brought more liberal views, the activities of the family also changed; they became professors, lawyers, and statesmen.

Hugo de Vries’s paternal grandfather, Abraham de Vries, was a Baptist minister and librarian for the city of Haarlem; he was a noted expert on the history of printing. His maternal grandfather, Caspar Jacob Christiaan Reuvens, was the first professor of archaeology at the University of Leiden and founder of its archaeological museum. An uncle, Matthias de Vries, was professor of Dutch literature at Leiden and a pioneer in Dutch philology. The dictionary he started with Lambert A. te Winkel (1863), completed in 1888, was the authoritative source for Dutch spelling for half a century.

Hugo de Vries’s father, Gerrit de Vries, studied law and literature at the University of Leiden. He served as a representative in the Provincial States of North Holland for many years and became the leading expert on legislation concerning water management. In 1862 he was appointed to the Council of State, a position he held until his death. Ten years later he was asked by William III to form a cabinet, and he took the post of minister of justice. De Vries’s mother, Maria Everardina Reuvens, came from a family of scholars and statemen.

De Vries was educated in Haarlem at a private Baptist grammar school and subsequently at the municipal Gymnasium. The area around Haarlem was a botanist’s paradise, and it awakened in him a deep love for plants at an early age. During his vacations he roamed the entire country on foot, in search of plants for his herbarium. When he entered the university, he felt that his collection of dried phanerogams of the Netherlands was complete.

In 1862 the family moved to The Hague, where de Vries attended the Gymnasium for four years. Since there was no Baptist community in The Hague, he was sent to Leiden on weekends to receive religious instruction. Here he was soon invited by Willem Suringar, a professor of botany, to help classify the plants in the herbarium of the Netherlands Botanical Society.

Consequently, when de Vries matriculated at the University of Leiden in 1866, he was already an expert on the flora of the Netherlands. He therefore turned to other fields of interest. These he found after reading Sachs’s Lehrbuch der Botanik (1868), to which he owed his interest in plant physiology, and Charles Darwin’s Origin of Species, which aroused his interest in evolution. The University of Leiden was ill-equipped for the pursuit of either of these studies; plant physiology was not taught there, and there was no laboratory for experimental work. The experimental work for his doctoral dissertation on plant physiology was done in his attic. Suringar was hostile to the theory of evolution; and this hostility, combined with de Vries’s youthful enthusiasm, caused a permanent estrangement between them.

De Vries was not happy with the education he had received at Leiden, and he decided to continue his studies in Germany. In the autumn of 1870 he went to Heidelberg, where he studied with Hofmeister. In the spring and summer of 1871 he was at Sachs’s laboratory in Würzburg, where he finally found what he had been seeking. Sachs took a keen interest in his progress and considered him his best pupil.

Although he intended to work in Würzburg for several years, in September 1871 de Vries accepted an appointment as teacher of natural history at the First High School in Amsterdam.² He was still able to spend most of the long summer vacations in Sachs’s laboratory at Würzburg; the reports of his experimental work there are found in Arbeiten des botanischen Instituts in Würzburg, Sach’s journal.

De Vries’s teaching duties became more and more demanding, and began to interfere with his studies. Sachs then recommended him for a position at the Prussian Ministry of Agriculture. In January 1875 de Vries was given the task of writing monographs on agricultural plants that were published in the Landwirtschaftliche Jahrbücher. The necessary experimental work was done at Würzburg, in space provided by Sachs in his laboratory. Here de Vries wrote monographs on red clover, the potato, and the sugar beet. In addition, he carried out extensive studies on osmosis in plant cells during this period. He frequently traveled to other university towns to meet with the leading professors of botany.

Sachs showed his continued interest in de Vries’s future by recommending him for the post of Privatdozent in the physiology of cultivated plants at the University of Halle. To be eligible for the appointment, de Vries had to pass a doctoral examination. He defended a dissertation based on his work on the stretching of cells and received the appointment on 12 February 1877.

The lectures at Halle were not a success. Attendance was poor, and there was no real interest in the subject. Thus de Vries was much relieved when he was appointed lecturer in plant physiology at the newly constituted University of Amsterdam. The Amsterdam Athenaeum was founded in 1632 but did not have the authority to grant degrees; it was necessary for students to pass examinations at an accredited university, usually Leiden or Utrecht. In 1877 the Athenaeum was given university status, and many new teachers were needed. De Vries was the first instructor in plant physiology in the Netherlands. In the summer of 1877, he traveled to England to meet the botanists of that country. The highlight of the trip was a visit with Darwin.

In the autumn of 1878 de Vries was appointed extraordinary professor and, on his birthday in 1881, ordinary professor. Until about 1890 he conducted research on osmosis in plant cells—the famous experiments on plasmolysis. In addition to his teaching and research, he sponsored the research of his pupil J. H. Wakker on the diseases of bulb plants; he investigated the causes of the contamination of the water mains of Rotterdam; and he served on the committee to study the future water supply of the city of Amsterdam. During this period Wakker, J. M. Janse, F. A. Went, H. P. Wijsman, and H. W. Heinsius earned their doctorates under de Vries’s guidance.

In addition to his experimental work in plant physiology, de Vries made extensive studies of the theories and literature on heredity and variation in plants. About 1890 he abruptly abandoned the study of plant physiology and devoted himself exclusively to heredity and variation. This period in his career began with his Intracellular Pangenesis (1889), in which he reviewed critically the work of Spencer, Darwin, Nägeli, and Weismann, and proposed his own theory that “pangenes” were the carriers of hereditary traits. One of the most important books in the history of genetics, it attracted little attention at the time.

De Vries’s experimental work in the 1890’s led to the rediscovery of Mendel’s laws and the discovery of the phenomenon of mutation. The rediscovery of Mendel’s laws was announced almost simultaneously by de Vries, Correns, and Tschermak-Seysenegg—in that order. De Vries certainly knew the segregation laws in 1896, and he deduced these laws from his own experimental work and not from reading Mendel’s paper or any reference to Mendel’s work in the literature.

The results of his more than ten years of experimentation and study were laid down in de Vries’s Die Mutationstheorie …(1901-1903), in which he described in detail his work on the segregation laws, on phenomena of variation, and on plant mutations. The book made him famous, and he was recognized as one of the foremost botanists of his time.

During the 1890’s no doctorates were earned under de Vries’s guidance. These were years of hard personal work, but apparently they were not happy ones. In 1896 he succeeded C. A. J. A. Oudemans as senior professor of botany at Amsterdam. He was charged with teaching systematic botany and genetics; instruction in plant physiology and pharmacology was turned over to Eduard Verschaffelt.

De Vries’s physiological work was well known on the continent of Europe, less so in England, and hardly at all in the United States. His rediscovery of Mendel’s laws and the formulation of the mutation theory, however, became widely known, especially in the United States. During the summers of 1904 and 1906, de Vries was invited to lecture at the University of California at Berkeley; in 1912 he was invited to participate at the opening of the Rice Institute in Houston, Texas. He wrote books about each of his American journeys.

After 1900 a number of students earned their doctorates under de Vries: C. J. J. van Hall, T. Weevers, P. J. S. Cramer, J. A. Lodewijks, A. R. Schouten, J. M. Geerts, J. A. Honing, T. J. Stomps, and H. H. Zeylstra. In that period de Vries received many honors. Eleven honorary doctorates were conferred upon him; he was awarded seven gold medals, and was made a regular or honorary member of most of the major academies and societies.

In 1918 de Vries reached mandatory retirement age. He had already bought a house at Lunteren, a remote village, where the soil was suitable for an experimental garden. He also built a laboratory, and he remained professionally active until his death. He also produced a large number of scientific papers during this time. His rather lonely life in Lunteren was relieved by visits from former pupils, friends, and admirers from all over the world, and several students from the the universities of Amsterdam and Utrecht came to Lunteren to do the experimental work for their dissertations.

Scientific Work. In his doctoral dissertation de Vries reviewed the literature concerned with the influence of temperature on the vital processes of plants. Based on an essay that received a gold medal, the dissertation was supported by original experimental data that affirmed or refuted the statements of various authors.

At Würzburg, Sachs studied plant physiology from a mechanical point of view. Initially he assigned de Vries subjects for study, but later he gave him a free hand in the choice of subjects. In 1871 de Vries discovered that stalks and isolated ribs of leaves usually have a greater growth capability on the upper side than on the underside. He called this phenomenon “epinasty” and the reverse phenomenon, which is sometimes found in young organs, “hyponasty,” He claimed that these two phenomena, together with the already recognized phenomena of geotropism and heliotropism, are sufficient to explain all growth patterns of plants. In 1872 he studied the mechanism of tendril curving and found it to be almost exclusively the result of increased growth in the outer region of the tendril. In the same year he studied the mechanism of the movements of climbing plants and established that the nutating shoots of such plants are not irritable and that the nutation is caused by the shoots’ having a zone of increased growth parallel to the axis, with the zone slowly rotating around the axis of the organ. Darwin greatly admired this work and praised it in his Climbing Plants,³ which started the correspondence between Darwin and deVries. The next year de Vries investigated the rate of cell growth at various points on the growing shoot and found that the zone of fastest growth is not located at the tip but farther back on the organ.

As a student in Lieden and in Hofmeister’s laboratory, de Vries had shown that the contraction of the protoplast of a plant cell, caused by its introduction into a salt solution of appropriate concentration, did not kill the cell, as was generally believed. In addition, he established that the protoplast is permeable only by water. At Würzburg, while writing his monographs on agricultural plants, de Vries continued this research. He wanted to decide how much of the increase of the cell wall of a growing plant organ was the result of the growth of the cell and how much was the result of the stretching of the cell wall caused by the pressure of the cell fluid—turgor. Annulling the turgor by submerging the plant organ in a suitable salt solution, de Vries found that in young, growing cells the expansion caused by turgor amounts to some 10 percent of the total length. In mature cells there was no turgor expansion. He described this work in the Habilitationsschrift submitted at Halle.

As a professor at Amsterdam, de Vries continued his research on the function of the cell contents. He theorized that calcium is a waste product in plants, absorbed for the sake of the needed elements with which it is combined and stored in cells as an organic salt (often calcium oxalate). He formulated a growth theory, stating that growth in plants is caused primarily by extension of the cell walls by turgor, with the extension fixed later. He conjectured that organic acids are the chemical compounds that contribute most to the turgor, a conjecture that he qualified later when he had analyzed the cell fluid of some plants. He applied his growth theory to explain many forms of plant movement, including the movement of tendrils, the erection of lodged grain, and the contraction of roots of biennial plants in autumn.

These and other investigations posed questions. How great is the pressure caused by the turgor in the cell? How much does each of the components of the cell fluid contribute to this pressure? What is the cause of an increase of this pressure in cells? In order to answer these questions, de Vries returned to his observations of the effect of salt solutions on plant cells. In previous experiments he had found that if a plant cell is immersed in successively stronger salt solutions, the cell initially contracts; subsequently the protoplast starts contracting and frees itself from the cell wall until it becomes a globular body within the cell. De Vries called this process “plasmolysis.” In the new research he used the plant cell as an indicator, immersing the cell in solutions of increasing strength until he found the concentration at which the protoplast just starts to free itself from the cell wall. At this concentration the osmotic pressures of the solution and of the cell contents are equal or — in de Vries’s terminology— “isotonic.” He determined the isotonic concentration for the solution to be tested and for a reference solution; three times the concentration of the reference solution, divided by the concentration of the solution to be tested, was called the “isotonic coefficient.” Saltpeter (KNO₃) was always used as a reference solution.

After determining the isotonic coefficients of a great many chemicals, de Vries found that isotonic coefficients always have a near integer value—ranging from 2 to 5. Generalizing this, he stated the following rules; for neutral organic compounds and organic acids, the isotonic coefficient is 2; for salts with one alkali atom, 3; with two alkali atoms, 4; with three alkali atoms, 5; with one alkaline earth atom, 2; and with two alkaline earth atoms, 4. This is known as the law of isotonic coefficients. Using this law, de Vries was able to determine the proportional contribution to the total osmotic pressure in the cell for each component of the cell fluid. It appears that for different species, different chemicals in the cell fluid account for the largest part of the osmotic pressure: in Rheum it is oxalic acid, in Rosa it is glucose, and in Gunnera it is calcium chloride.

De Vries’s work on the isotonic coefficients of solutions led van’t Hoff to his formula for the osmotic pressure of solutions, one of the first results in physical chemistry. Van’t Hoff’s law in turn enabled de Vries to determine the total osmotic pressure in plant cells. At about the same time, Arrhenius discovered the dissociation of molecules in solution. This explained why de Vries had to use a factor of 3 in his computation of the isotonic coefficient. Even under laboratory conditions the reference solution was only about 50 percent ionized, and different salt solutions dissociate to different degrees. The phenomenon of ionization indicates that de Vries’s law of isotonic coefficients cannot be exactly true.

The law of isotonic coefficients enabled de Vries to determine the molecular weight of raffinose during a discussion of that weight at a meeting of the Royal Netherlands Academy of Sciences and, in a few minutes, to settle this long-standing question.

During the late 1880’s de Vries studied protoplasm. He found that the inner lining of the cell wall, the protoplast, consists of three layers, not two, as was currently believed. He discovered the innermost of these, the tonoplast. He also established that the vacuoles in the cell have a lining of their own, investigated the aggregation of the protoplasm of insectivorous plants, and studied the ribbon-shaped parietal chloroplasts of Spirogyra.

In addition to his physiological research on plants, de Vries conducted an extensive study of the literature on variability and heredity. Based on this research, he wrote nineteen articles for a Dutch agricultural journal. This series, “Thoughts on the Improvement of the Races of Our Cultivated Plants” (1885-1887), resembles Darwin’s Origin of Species and Variation of Animals and Plants Under Domestication in its organization and approach. The study probably was of no great use to the farmers for whom it was written, but it was of great importance to de Vries as a means of formulating a program for future research.

In his first work in this new field of interest, Intracellulare Pangenesis (1889), de Vries presented his own theory. He considered the hereditary characteristics of living organisms as units that manifest themselves independently of each other and that can, therefore, be studied separately. Each independent characteristic is associated with a material bearer, which de Vries called a “pangene.” The pangene is a morphological structure, made up of numerous molecules, that can take nourishment, grow, and divide to yield two new pangenes. After cell division, each daughter cell receives one set of pangenes from the mother cell. A pangene can be either active or latent. Some characteristics may be represented by more than one pangene. Where conflicting characteristics are possible-for example, red or white flowers—the characteristic represented by the largest number of pangenes is dominant. In each reproductive cell at least one of the representative pangenes, either active or latent, is present.

Using these concepts, de Vries explained all the vital phenomena of an organism: how a cell develops into an organ, how metamorphosis is brought about, and how an offspring becomes and remains uniform with the parents. The characteristics of the genus are caused by large aggregates of pangenes, which remain unchanged in the offspring. It is possible that one (or more than one) pangene starts to multiply in an extraordinary way or is changed during cell division. In such a case the different pangene that is created results in a new characteristic of the organism. This is, according to de Vries, the principal mechanism of evolution.

De Vries’s pangene theory is remarkably close to the theory formulated later by geneticists, including T. H. Morgan. The concept that a characteristic is represented by two pangenes, each of which may be active or latent, and the concept that the pangenes are linked in groups (later called chromosomes) were not part of de Vries’s theory.

De Vries called his material units pangenes to honor Charles Darwin, whose gemmule theory he rejected, however. The name “gene,” given to the hereditary unit by Johannsen, was derived from de Vries’s pangene.⁴

The research undertaken by de Vries to follow up his theoretical considerations covered several fields. He studied the causes and hereditary properties of many kinds of monstrosities, including forced tensions (Zwangsdrehungen—on which he wrote a monograph), fasciations, symphysis, and virescence. Jules MacLeod, professor at the University of Ghent, may have introduced him to the statistical methods of Quetelet and Galton. They had shown that in the animal kingdom the magnitude of variations (for example, the body length of soldiers) was distributed according to a probability curve (Gauss curve; de Vries used the term Galton curve). De Vries demonstrated that this is often true for the plant kingdom as well. This distribution manifested what he called the normal fluctuation of the considered characteristics. There were many cases where a symmetrical curve was not obtained. In some cases only a half Galton curve was obtained; deVries expressed the opinion that such a curve shows the emergence of a discontinuous variation. In other cases the distribution curve showed two peaks; de Vries conjectured that such a curve indicates that a mixture of two races is present, and he succeeded in isolating these races by selection.

Because of his pangenesis theory and his work on variability, de Vries decided that experimental work in heredity should be performed with closely allied races or varieties, differing in only one characteristic or, at most, a few characteristics. In 1896 he demonstrated to his advanced students the segregation laws, now known as Mendel’s laws, in Papaver somniferum var. Mephisto and var. Danebrog. He examined many species belonging to several families, and found the segregation laws confirmed in each case. He did not publish these results, however, reserving them, with his work on mutations, for a single large book. When he accidentally came across a reprint of Mendel’s paper early in 1900, de Vries felt obliged to publish in order to protect his priority. This publication triggered the publications of Correns and TschermakSeysenegg. The work of de Vries did not quite parallel the work of Mendel, who had studied only two species, Pisum and Hieracium, and whose work with the latter had been unsuccessful. De Vries demonstrated the segregation laws in some twenty species. On the other hand, Mendel examined not only monohybrids but also dihybrids and trihybrids, and followed the offspring through a great many generations. In his rediscovery papers, de Vries reported on only two dihybrid experiments, and he followed the offspring of a cross through two generations at most. L. C. Dunn correctly states; “It is clear that de Vries was not a ‘rediscoverer’ but a creator of broad general principles.”⁵

After the rediscovery of Mendel’s laws, many investigators took up the subject. De Vries was not among them, however. He believed that hybridization only causes redistribution of existing characters and for that reason cannot explain the appearance of new species. Therefore, he concentrated on the phenomenon of mutation, which he believed explained the origin of new species and therefore gave necessary support to the theory of evolution.

One difficulty in studying the origin of new species was that the concept of “species” was ill-defined. Plants recognized as belonging to the same species often showed marked differences. The French botanist Alexis Jordan had found that, among plants recognized as belonging to the same species, there are subgroups of which the members are exactly alike and breed true under self-fertilization. These subgroups were later called “jordanons,” while the traditional species, “which a good naturalist intuitively recognizes,”⁶ were later called “linneons.” De Vries claimed that the jordanon is the true species. Among specimens of the same jordanon, individual differences, including size of leaves and weight of seeds, are still possible; these “individual variations” follow Galton’s law.

In 1886, near Hilversum, de Vries noticed on a plot of formerly cultivated land, overgrown with Oenothera lamarckiana (evening primrose), a number of specimens that differed markedly from the others. He took seeds of the normal form and of two differing ones for planting in his experimental garden. He went through considerable trouble to discover the origin of these Oenotheras (which had escaped from a nearby garden) and to ascertain the history of the introduction of the species into Europe. Although it was said that the plant had originally been introduced from Texas and was known to Lamarck in 1796 under the name O. grandiflora, the plant was unknown in the United States. De Vries was convinced that O. lamarckiana was a pure species.

New forms that appeared suddenly and unexpectedly were called “single variations” by de Vries; he later called them “mutations.” The Oenotheras that he had collected near Hilversum soon started to produce new forms, which he judged to differ sufficiently from the parent species for him to consider them a new species, and hence to give them a binomial name. He obtained a giant form, which he named O. gigas; a form with pale-green; delicate, narrow leaves, which he named O. albida; one with red veins in the leaves, O. rubinervis; one with narrow leaves on long stalks, O. oblonga; and a dwarf form, O. nanella. These mutants appeared to be constant or almost constant under self-fertilization. Another mutant showed only female flowers and still another yielded, after self-fertilization, the original lamarckiana plus some mutants. The two mutants found in Hilversum also produced lamarckianas as well as mutants, including some new ones.

In order to explain why only the Oenothera lamarckiana produced so rich a harvest of mutants, while only a very few other species were known to product mutants (and then only a few mutants at a time), de Vries postulated that in its evolutionary life a species produces mutants over discrete, comparatively short periods of time only—their mutation periods. In addition, he conjectured that these periods are preceded by permutation periods, during which the latent characters are formed.

On the basis of his Oenothera research, de Vries distinguished mutations that supply a useful characteristic, which he called “progressive,” and those that supply a useless or even harmful characteristic, which he called “retrogressive.” Only the progressive characteristics contribute to the evolution of the species.

De Vries carried out extensive crossings between his Oenothera mutants. On the basis of this work and additional work on variability, he distinguished two kinds of crosses; bisexual and unisexual. In bisexual crosses the parents differ in at least one characteristic. These characteristics are all active in one parent and latent in the other. In unisexual crosses only one parent possesses a certain characteristic. De Vries associated these concepts with earlier terminology as follows; variety crossings are bisexual, exhibit a Mendel split, and produce fertile offspring; species crossings are unisexual, do not exhibit a Mendel split, and produce less fertile or even infertile offspring. It must be remembered that these concepts date from before the discovery that a characteristic is represented in the somatic cell by two genes, each of which can be either dominant or recessive.

De Vries’s work on variability and mutation, necessarily only briefly sketched above, was reported in Die Mutationstheorie…(1901-1903), a heroic effort to correlate and explain the existing knowledge in this field and his own discoveries. De Vries’s 1904 lectures at Berkeley were published as Species and Varieties (1905), a book that is much easier to read than The Mutation Theory. In his 1906 lectures in Berkeley, his topic was the application of his doctrines to agricultural and horticultural practice. These lectures were published in Plant Breeding (1907).

In 1906 de Vries considered his mutation research finished, and he prepared to study, as his next research project, the adaptation of plants to an adverse environment, such as a desert. That year, however, his Oenothera cultures showed “twin hybrids” for the first time; to gather information to explain this phenomenon, he decided to continue his Oenothera research for a few years. Circumstances forced him to continue the Oenothera study for the rest of his life.

Although the mutation theory was generally enthusiastically received, there were critics. The first of these was William Bateson, who suggested as early as 1902 that the O. lamarckiana might well be a hybrid. This idea was vigorously advocated by B. M. Davis, who questioned de Vries’s arguments for the provenance and the purity of the lamarckiana. Davis tried, without notable success, to synthesize a lamarckiana by crossing O. biennis with O. grandiflora and O. franciscana. Zeylstra, a student of de Vries’s, declared that O. nanella was nothing but a diseased lamarckiana; another of his students, J. A. Honing, gave a critique that anticipated the later work of O. Renner.

From about 1908 Morgan, Sturtevant, Hermann J. Muller, and Calvin B. Bridges had been studying the genetics of the fruit fly Drosophila. This work, which was first summarized in The Mechanism of Mendelian Heredity (1915), provided the essentials of the chromosome theory of heredity as it is known today. In this theory de Vries’s pangenes, which he had described as single material units existing in a free state in the cell nucleus, became the genes, grouped on the chromosomes in the cell nucleus.

The first mutant to be explained was O. gigas. In 1907 Anne M. Lutz found that this mutant is a tetraploid; it has twenty-eight chromosomes in the somatic cells instead of fourteen, as is common with the Oenotheras. In 1912 Lutz discovered that O. lata is a triploid and that it has fifteen chromosomes.

In the course of time, new anomalies in Oenothera were added to those described by de Vries in his Mutation Theory. He himself discovered the “twin hybrids” : two true-breeding parents yield two different types in the first-generation offspring. Another phenomenon, the significance of which was not realized until 1914, was the fact that often a large percentage of the seeds ontained in Oenothera cultures were infertile. These and other phenomena were studied by Renner, who discovered that O. lamarckiana is a permanent heterozygote (hence a hybrid) containing two chromosome complexes, which are transmitted as a whole and which he called “gaudens” and “velans.” They are balanced lethals. Hence, of the four combinations formed in equal numbers during the first generation of the offspring of self-fertilized lamarckianas—that is, gv, vg, vv, gg—the latter two (half the total number of seeds) were not viable, the others having the same phenotype as the parent and hence creating the illusion that the plant breeds true. When a lamarckina was crossed with another Oenothera species-for example, O. muricata— half of the offspring contained the mg combination and the other half the mv combination, hence the twin hybrids.

Studies by Renner and others showed that the genetic makeup of Oenothera is very unusual and complicated; few genera show such phenomena, and those to a much lesser extent. Because of the work of a large number of investigators, the genetic properties of Oenothera are now quite well known. Among these investigators were de Vries himself and his students T. J. Stomps, D. J. Broekens, K. Boedijn, H. Dulfer, and J. A. Leliveld. Much of the Oenothera work was done at the Station for Experimental Evolution at Cold Spring Harbor, New York. De Vries gave the keynote speech at the opening of the station in 1904. A. F. Blakeslee and R. E. Cleland, who showed that the chromosome complexes are ring formations, were leaders in this work. The Oenothera problem was solved finally by Sturtevant and Sterling Emerson.

The fact that de Vries’s mutants were superseded does not mean that his work on the phenomenon of mutation was valueless. Many true mutations have been discovered in the animal and plant kingdoms and mutation is still the cornerstone of the theory of evolution. Next to the Drosophila experiments, the work with Oenothera has contributed most to the chromosome theory of heredity.

NOTES

1. Sometimes—for example, in Isis Cumulative Bibliography. II, 603—the name is given as Hugo Marie de Vries. The addition of Marie is not justified, for no member of the de Vries family ever had more than one Christian name.

2. A secondary school that emphasized modern languages and science.

3. Charles R. Darwin, The Movements and Habits of Climbing Plants (London, 1876), see 9, 22, 160, 165, 181.

4. Wilhelm L. Johannsen, Elemente der exakten Erblichkeitslehre (Jena, 1909; 2nd ed., 1913). In the 1st ed. (124) Johannsen ignored the use of “pangene” by de Vries: in the 2nd ed. (p. 143) he corrected this omission. Johannsen made the change from pangene to gene to express his opinion that the hereditary unit to be named, formerly designated by the German Anlage, is nonmaterial. When the materiality of the hereditary unit was confirmed, the name gene was retained.

5. L. C. Dunn, A Short History of Genetics (New York, 1965), 43.

6. In determining whether a form should be ranked as a species or a variety, the opinion of naturalists having sound judgment and wide experience seems the only guide to follow. Darwin, The Origin of Species (London, 1859), 47.

BIBLIOGRAPHY

I. Original Works. A complete bibliography of de Vries’s works contains more than 700 entries. About half of these were contributions to popular literature. The most important scientific papers, selected by de Vries himself, are collected in Opera e periodicis collata, 7vols. (Utrecht, 1918-1927).

His most important scientific books and papers are Deinvoled der temperatuur op de levensverschijnselen der planten (The Hague, 1870); “Sur la perméabilité du protoplasme des betteraves rouges,” in Archives néerlandaisesdes sciences exactes et naturelles, 6 (1871), 117–126; “Sur la mort des cellules végétales apr l’effet s’une tempéracute élevée,” ibid., 245–295; “Ueber einige Ursachen der Richtung bilateral symmetrischer Pflanzentheile,” in Arbeiten des botbischen Institutes in Würzburg, 1 (1872), 233–277; “Längenwachsthum der Obe- und Unterseite sich krümmender Ranken,” ibid., 1 (1873), 302–316; “Zur Mechanik der Bewegung von Schlingpflanzen,” ibid., 317–342; “Ueber die Dehnbarkeit wachesender Sporsse,” ibid., 1 (1874), 519–545; “Ueber Wundholz,” in Flora, oder allgemeine botanische Zeitung, 59 (1876), 2–6, 17–25, 38–42, 49–55, 81–88, 97–108, 113–121, 129–139; “Ueber longitudinal Epinastie,” in Flora, oder allgemeine botanische Zeitung, 60 , (1877), 385–391; and Untersuchungen über die mechanischen Ursachen der Zellstreckung, ausgehend von der Wirkung von Slazösungen auf den Turgor wachsender Pflanzenzellen (Leipzidg, 1877): “Ueber die Ausdehnung wachsender Pflanzenzellen druch ihren Turgor,” in Botanische Zeitung, 35 (1877), 20–10; “Beiträge Zur speziellen Physiologie landwirtschaftlicher Kulturpflanzen, 1 . Rother Klee,” in Landwirtschaftliche Jahrbücher, 6 (1877), 465–514, 893–956; “II. Kartoffeln,” ibid.,7 (1878), 19–39, 217–249, 591–682; “III. Zuckerrüben,” ibid.,8 (1879), 13–35, 417–498.

Other works include De ademhaling der planten (Haarlem, 1878); “Ueber die Verkürtzung pflanzlicher Zellen durch Aufnahme von Wasser,” in Botanische Zeitung, 37 (1879), 649–654; “Ueber die inneren Vorgänge bei den Wachsthumskrümmungen mehrzelliger Organe,” ibid., 830–838; “Ueber die Bedeutung der Pflanzensäuren für den Turgor de Zellon,” ibid., 847–853; “Over de bewegung der ranken van Sicyos,” in verslagen en mededeelingen der Koninklijke Akademie van Wetenschappen, Afdeeling Natuurkunde, 2nd., ser., 15 (1880), 51–174; “Ueber den Antheil der Pflanzensäuren an der Turgorkraft wachsender Organe,” in Botanische Zeitung, 41 (1883), 849–854; “Ueber die periodische Säurebildung der Fettpflanzen,” ibid.,42 (1884), 337–343, 353–358; “Eine Methode zur Analyse der Turgorkraft,” in Jahrbüchern für wissenschaftliche Botanik14 (1884), 427–601; “Beschouwingen over het verbeteren van de rassen onzer cultuurplanten,” in Maandblad van de Hollandsche Maatschappij van Landbouw, 19 articles (May 1885– July 1887).

Also see “Ueber die Bedeutung der Circulation und der Rotation des Protoplasma für den Stofftransport in den Pflanzen,” in Botanische Zeitung, 43 (1885), 1–6, 17–24; “Plasmolytische Studien über die Wand der Vacuolen,” in Jahrbücher für wissenschaftliche Botanik, 16 (1885); 464–598; “Ueber die Periodicität im Säuregehalt der Fettpflanzen,” in Verslagen en mededeelingen der Koninklijke Academie van Wetenschappen, Afdeeling Natuurkunde, 3rd ser., I (1885), 58–123; “Ueber die Aggregation im Protoplasma von Drosera rotundifolia,” in Botanische Zeitung,44 (1886), 1–11, 17–26, 33–43, 57–64; “Uber den isotonischen Coefficient des Glycerin,” ibid.,46 (1888), 229–235, 245–253; “Osmotische Versuche mit lebenden Membrane,” in Zeitschrift für physikalische Chemie, 2 (1888), 415–432; “Détermination du poids moléculaire de la raffinose par la méthode plasmolytique,” in Comptes rendus … de l’Académie des sciences, 106 (1888), 751–753; “Isotonische Koeffizienten einiger Salze,” in Zeitschrift für phusikalische Chemie, 3 (1889), 103–109; and Irtracellulare Pangenesis (Jena, 1889), English trans. as Intracelluar Pangenesis (Chicago, 1910), Dutch trans. as Intracellulaire pangenesis (Amsterdam, 1918).

Further works are Die Pflanzen und Thiere in den dunklen Räumen der Rotterdamer Wasserleitung (Jena, 1890); Monographie der Zwangsdrehungen (Berlin, 1891), also in Jahrbücher für wissenschaftliche Botanik,23 (1892), 13–206; “Ueber halbe Galtonkurcven als Zeichen diskontinuierlicher Variation,” in Berichte der Deutschen botanischen Gesellschaft,12 (1894), 197–207; “Sur l’introduction de I’ Oenothera lamarckiana dans les Pays Bas,” in Nederlandsch kruidkundig archief, 2nd ser., 6 (1895), 579–583; “Eine Zweigipflche Variationskurve,” in Archiv für Entwicklungsmechanik der Organismen, 2 (1895), 52–64; “Eenheid in veranderlijkheid,” in Album der Natuur, 47 (1898), 65–80; “Over het omkeeren van halve Galtonkruven,” in Botanisch Jaarboek,10 (1898), 27–61; “Alimentation et sélection,” in Volume jubilaire de la Société de biologie de Paris (1899), 17–38; “Ueber Curvenselektion bei Chrysanthemum segetum,” in Berichte der Deutschen botanischen Gesellschaft,17 (1899), 84–98; and “On Biastrepsis in Its Relation to Cultivation,” in Annals of Botany,13 (1899), 395–420.

Subseqent writings include “Sur la loi de disjonction des hybrides,” in comptes rendus … de l’Académie des sciences, 130 (1900), 845–847; “Das Spaltungsgesetz der Bastarde,” in Berichte der deutschen botanischen Gesellschaft, 18 (1900), 83–90; “Sur les unités des charactères spécifiques et leur application à l’étude des hybrides,” in Revue générale de botanique, 12 (1900), 257–271; “Sur l’origine expémentale d’une nouvelle espèce végétale,” in Comptes rendus … de l’Académie des sciences, 131 (1900), 124–126; “Ueber erbungleiche Kreutzungen (vorläufige Mitthelilung),” in Berichte der Deutschen botanischen Gesellschaft, 18 (1900), 435–443; “Hybridizing of Monstrosities,” in Journal of the Royal Horicultural Society, 24 (1900), 69–75; “Over het ontstaan van nieuwe soorten in planten,” in Verslagen van de zittingen der wis- en natuurkundige afdeeling van de Koninklijke Academie van wetenschappen, 9 (1900), 246–248; Die Mutationstheorie, Versuche und Beobactungen über die Entstehung von Arten im Pflanzenreich, 2 vols. (Leipzig, 1901-1903), English trans. as The Mutation Theory, Experiments and Observations on the Origin of Species in the Vegetable Kingdom, 2 vols. (Chicago, 1909-1910), from which translation all discussions of Mendel’s segregation law have been omitted, and Die Mutationen und die Mutationsperioden bei der Entstehung der Arten (Leipzig, 1901).

Also see “Ueber tricotyle Rassen,” in Berichte derDeutschen botanischen Gesellschaft, 20 (1902), 45–54; “La loi de Mendel et les charactéres constants des hybrides,” in Comptes rendus…de l’Académie des sciences, 136 (1903), 321–323; “On Atavistic Variation in Oenothera cruciata,” in Bulletin of the Torrey Botanical Club, 30 (1903), 75–82; “Anwendung der Mutationslehre auf die Bastardierungsgesetze,” in Berichte der Deutschen botanischen Gesellschaft, 21 (1903), 45–82; “Sur la relation entre les charactères des hybrides et leurs parents,” in Revue générale de botanique, 15 (1903), 241–252; “Bastaardeering en bevrunchting,” in De Gids, 4th ser., 21 (1903), 403–450; “Experimenteele evolutie,” in Onze Eeuw, 4 (1904), 282–309, 362–393; “The Evidence of Evolution,” in University Record of the University of Chicago, 9 (1904), 202–209; Naar Californië, Reisherinneringen (Haarlem, 1905; 2nd ed., 1906); Het Yellowstone Park; Experimenteele evolutie (Amsterdam, 1905); Species and Varieties (Chicago, 1905); “Aeltere und neuere Selektionsmethoden,” in Botanisches Zentralblatt, 26 (1906), 385–395; “Die Neuzuchitigungen Luther Burbanks,” ibid., 609–621; and “Burbank’s Production of Horticultural Bovelties,” in Open Court, 20 (1906), 641–653.

Additional works are “Evolution and Mutation,” in Monist, 17 (1907), 6–22; “New Principles in Agricultural Plantbreeding,” ibid., 209–219; Naar CaliforniëII (Haarlem, 1907); Plant Breeding, Comments on the Experiments of Nilson and Burbank (Chicago, 1907; 2nd ed., 1919), Dutch trans, as Het veredelen van kultuurplanten (Haarlem, 1908); “On Twin Hybirds,” in Botanical Gazette, 44 (1907), 401–407; “Bastarde von Oenothera gigas,” in Berichte der Deutschen botanischen Gesellschaft, 26a (1908), 754–762; “On Triple Hybirds,” in Botanical Gazette, 47 (1909), 1–8; “Ueber doppelt reziproke Bastarde von Oenothera biennis L. und Oenothera muricata L.,” in Botanisches Zentralblatt, 31 (1911), 97–104; “The Evening Primroses of Dixie Landing,’ in Science, n.s. 35 (1912), 599–601, written with H.H. Bartlett; Die Mutationen in der Erblichkeitslehre (Belin, 1912); “Oenothera Nanella, Healthy and Diseases,” in Science, n.s. 35 (1912), 753–754; Van Texas naar Florida (Haarlem, 1913); Gruppenweise Artbildung (Berling, 1913); “L’ Oenothera grandiflora de l’herbrier de Lamarck,” in Revue générale de botanique, 25b (1914), 151–166; and “The Probable Origin of Oenothera lamarckiana,” in Botanical Gazette, 57 (1914), 345–361.

Further, see “Ueber Künstliche Beschleunigung der Wasseraufnahme in Samen durch Druck,” in Botanisches Zentralblatt, 35 (1915), 161–176; “The Coefficient of Mutation in Oenothera biennis L.,” in Botanical Gazette, 59 (1915), 169–196; “Oenothera nanella, a Mendelian Mutant,” ibid.,60 (1915), 337–345; “Die Grundlagen der Mutationstheorie,” in Naturwissenschaften, 4 (1916), 593–598; “Ueber die Abhängigkeit der Mutations Koeffizienten von äusseren Einflüseen,” in Berichte der Deutschen botanischen Gesellschaft, 34 (1916), 1–7; “New Dimorphic Mutants of the Oenotheras,” in Botanical Gazette, 62 (1916), 249–280; “Die endemischen Pflanzen von Ceylon und die mutierenden Oenotheren,” in Botanisches Zentralblatt, 36 (1916), 1–11; “Gute, harte und leere Samen von Oenothera,” in Zeitschrift für induktive Abstammungs-und Vererbungslehre, 16 (1916), 239–292; “The Origin of the Mutation Theory,” in Monist, 27 (1917), 403–410; “Oenothera lamarckiana mut. velutina,” in Botanical Gazette, 63 (1917), 1–25; “Halbmutanten und Zwillingsbastarde,” in Berichte der Deutschen botanischen Gesellschaft, 35 (1917), 128–135; and “Ueber monohybride Mutationen,” in Botanisches Zentralbalt, 37 (1917) 139–148.

Additional works by de Vries are “Kreutzungen von Oenothera lamarckiana mut, velutina” in Zeitschrift für induktive Abstammungs-und Vererbungslehre, 19 (1918). 1–13; “Mass Mutations and Twin Hybirds of Oenothera hookeri, T. and G.,” in Genetics, 3 (1918), 397–421; “Mutations of Oenothera suaveolens, Desf.,” ibid., 1–26; “Mass Mutations in Zea mais,” in Science, 47 (1918), 465–467; Van anroebe tot mensch (Utrecht, 1918); “Oenothera lamarckiana mut. simplex.” in Berichte der Deutschen botanischen Gesellschaft, 37 (1919), 65–73; “Oenothera Rubinervis, a Half Mutant,” in Botanical Gazette, 67 (1919), 1–26; “Oenothera lamarckiana erythrina, eine neue Halmutante,” in Zeitschrift für Indyktive Abstammungs- und Vererbungslehre, 21 (1919), 91–118; “Ueber die Mutabilität von Oenothera lamarckiana mut. simplex,” ibid.,31 (1923), 313–357; “Ueber sesquiplex Mutanten von Oenothera lamarckiana,” in Zeitschrift für Botanik, 15 (1923), 369–408; “Oenothera lamarckiana mut. perennis,” in Flora, oder allgemeine bptanische Zeitung, 116 (1923), 336–345; “Ueber die Entstehung von Oenothera lamarckiana mut. velutina,” in Botanisches Zentralblatt, 43 (1923), 213–224; and “On the Distribution of Mutant Characters Among the Chromosomes of Oenothera lamarckiana,” in Genetics, 8 (1923), 233–238, written with K. Boedijn.

Also see “Die Gruppierung der Mutanten von oenothera lamarckiana,” in Berichte der Deutschen botanischen geselleschaft, 42 (1924), 174–178, written with K. Boedijn; “Doubled Chromosomes of Oenothera semigigas,” in Botanical Gazette, 78 (1924), 249–270, written with K. Boedijn; “Die Mutabilität von Oenothera lamarckiana gigas,” in Zeitschrift für induktive Abstammungs-und Verebungslhre, 35 (1924), 197–237; “Sekundäre Mutationen von Oenothera lamarckiana,” in Zeitschrift für Botanik, 17 (1925), 193–211; “Mutant Races, Dervied From Oenothera lamarckiana,” in Genetices, 10 (1925), 211–222; “Brittle Races of Oenothera lamarckiana,” in Botanical Gazette, 80 (1925), 262–275; “Die latente Mutabilität von Oenothera biennis,” in Zeischrift für induktive Abstammungs-und Vererbungslehre, 38 (1927), 141–197; “A Survey of the Cultures of Oenothera lamarckiana at Lunteren,” ibid.,47 (1928), 275–286, written with R. R. Gates; “Ueber das Auftreten von Mutanten aus Oenothera lamarckiana,” ibid.,52 (1929), 121–190; and “Udber semirezessive Anlagen in Oenothera lamarckiana,” ibid., 70 (1935), 222–256.

II. Secondary Literature. Discussions of de Vries adn his work include G. E. Allen, “Hugo de Vries adn the Reception of the ‘Mutation Theory,’” in Journal of the History of Biology, 2 (1969), 55–87; F. M. Andrews, “Hugo de Vries,” in Plant Physiology, 5 (1930), 175–180; Annelén [pseud.]. “Professor Hugo de Vries en de Amsterdamsche Universiteit,” in Algemeen Handelsblad (15 Oct. 1927); A. F. Blakeslee, “The Work of Porfessor Hugo de Vries,” in Scientific Monthly, 36 (1933), 378–380; and “Hugo de Vries, 1848-1935,” in Science81 (1935), 581–582; J. H. van Burkom, “In Memoriam Prof. Hugo de Vries,” in Natura34 (1935), 161; F. Chodat, “Hugo de Vries. 1848-1935,” in Comptes rendus des séances de la Société de physique et d’historie naturelle de Genéve. 54 (1937), 7–10; R. Cleland, “Hugo de Varies, 1848–l1935,” in Journal of Herdity, 26 (1935), 289–297; and “Hugo de Vries,” in Procedings of the American philosophical Society76 (1936), 248–250; J. C. Costerus, “Professor Hugo de Vries,” in Eigen Haard, 21 (1895), 261–264; C. F. Cox, “Hugo de Vries on the Origin of Species and Varieties by Mutation,” in Journal of the New York Botanical Garden, 6 (1905), 66–70; E. O. Dodson, “Mendel and the Rediscovery of His Work,” in Scientific Monthly, 58 (1955), 187–195; and P. Fröschel, “Einige Briefe von Hugo de Varie,” in Acta botanica neerlandica, 10 (1961), 202–208.

Also see S. S. Gager, “De Vries and His Critics,” in Science, n.s. 24 (1906), 81–89; R. R. Gtes, “Prof. Hugo de Vris, For. Mem. R. S.,” in Nature, 136 (1935), 133–134; G. C. Gerrits , Grote Nederlkanders bij de opbouw der natuurwetenschappen (Leiden, 1947); A. D. Hall, “Hugo de Vries,” in Obituary Notices of Fellows of the Royal Society of London, 4 (1935), 371–373; J. Heimans, “Hugo de Vries,” in Hugo de Vries, Voordrachten ter herdenking van zijn honderdste ge boortedag op 16 Februari 1948 (Amsterdam, 1948), 1–9: Zeventilg jaar pangenenleef (Amsterdam, 1959); “Deherontdekking,” in Honderd jaar Mendel (Wageningen, 1965), 62–80; and “Gregor Mendel and Hugo de Vries on the Species Concept,” in Acta botanica neerlandica, 18 (1969), 95–98; H. W. Heinsius, “Hugo de Vries, 16 Februari 1848-1918,” in De Amsterdammer (16 Feb. 1918); J. Van der Hoeven, “In Memoriam Hugo de Vries,” in Verslagen en mededeelingen der Koninklijke Akademie van Wetenschappen, Afdeeling Naturkunde, 44 (1935), 59–62; A. A. W. Hubrecht, “Hugo de Vries’ mutatietheorie,” in De Gids, 4th ser., 19 (1901), 492–519; H. T. A. Hus, “The Work of Hugo de Vries,” in Sunset Magazine13 (1904), 39–42; and “Hugo de Vries,” in Open Court, 20 (1906), 713–725: and W. van Itallie-van Embden. “Sprekende portretten.” in Haagsche post (19 Dec. 1925), an interview with Hugo de Vries.

Other works on de Vries are Ilse Jahn, “Zur Geschichte der Wiederentdeckung der Mendelschen Gesetze,” in Wissenschaftlilche Zeitschrift der Friedrich Schiller-Universität Jena. 7 (1957-1958), 215–227; E. Lehmann, Die Theorien der Oenotheraforschung (Jena, 1922); and “Die Entwicklung der Oenotheraforschung,” in Hugo de Vries, sechs Vorträge zur Feier seines 80 Geburtstages, gehalten im botanischen Institut, Tübingen (Stuttgart, 1929), 36–42; (D. Manassen), “Prof. Hugo de Vries,” in Algemeen handelsblad (18 Nov. 1910); M. Moebius, “Hugo de Vries und sein Lebenswerk,” in Revista sudamericana de botánica, 2 (1935), 162–168; in J. W. Moll, “Hugo de Vries 16 Februari 1848-1918,” in De neiuwe Amsterdammer (16 Feb. 1918); and D. Müller, “Dreis Brief über rein Linien, von Galton, de Vries und Yule and Wilhelm Johnnsen in 1903 geschrieben,” in Centaurus, 16 (1972), 316–319.

Further works are H. R. Oppenheimer, “Hugo de Vries als Pflanzenphysiologe,” in Palestine Journal of Botany and Horticultural Science, 1 (1935-1936), 51-69; P. van Oye, “Julius MacLeod en Edward Verschaffelt, “in Mededelingen van de Koninklijke Vlaamsche adademie voor wetenschappen, letteren en schoone kunsten van België23 (1961), 3-20; P. W. van der Pas, “Hugo de Vries als taxonoom,” in Scientiarum historia. 11 (1969), 148–166: “The Correspondence of Hugo de Vries and Charles Darwin,” in Janus, 57 (1970), 173–213; “Hugo de Vries visits San Diego, “in Journal of san Diego History, 17 (1971), 12-23; and “Hugo de Vries in the Imperial Valley,” ibid.; O. Renner, “Hugo de Vries,” in Erbarzt, 3 (1935), 177-184; and “Hugo de Vries, 1848-1935,” in Naturwissenschafteb, 24 (1936), 321-324: H. F. Roberts. Plant Hybridization Before Mendel (New Haven, 1929); and Elisabeth Schiemann, “Hugo de varies,” in Züchter, 7 (1935), 15-161; and “Hugo de Varies zum hundertsen Geburtstage,” in Berichte der Deutschen botanischen Gesellschaft, 62 (1948), 1-15.

In addition, see A. Schierbeek, “De pangenesis the orie van Hugo de Vries,” in Bijdragen tot de geschiedenis der geneeskunde, 24 (1943), 64–67; G. H. Schull, “Hugo de Vries at Eighty-five,” in Journal of Heredity, 24 (1933), 1–6; Sinotō Yositō “Tabi ni ahishi hitobito,” in Kagaku zassan, 3 (8), (1933), 295–297, a pilgrimage to famous men; T. J. Stomps, “Aus dem Leben und Wirken von hugo de Vries,” in Hugo de Vries, Sechs Vorriäage zur Feier seines 80 Geburstages, gehalten imbotanischen Institut, Tübingen (Stuttgart, 1929), 7–16; Vijf en twintig jaren Mutatietheorie (The Hague, 1936); “Hugo de Vries,” in Berichte der Deustchen botanischen Gesellschaft, 53 (1936), 85–96; “Hugo de Vries et la cytologie,” in Revue de cytologie et de cytophysiologie végétales, 2 (3) (1937), 281–285; and “On the Rediscovery of Mendel’s Work by Hugo de Vries,” in Journal of Heredity, 45 (6) (1954), 293–294; E. Von Tschermak-Seysenegg, “Hugo de Vries, der Bergünder der Mutationstheorie.” in Reichspost (2 Feb. 1936); and “Historischer Rückblick auf die Wiederentdeckung der Gregor Mendelschen Arbeit,” in Verhandlungen der Zoologisch-botanischen Gesellschaft in Wien, 92 (1951), 25–35.

Also see F. J. van Uildriks, “Professor Hugo de Vris zeventing jaar,” in Aarde en haar volken, 54 (1918), 45–46: T. W. Vaughan, “The Work of Hugo de Vries and Its Importantce in the Study of Promblems of Evolution,” in Science, n.s. 23 (1906), 681–691: J. H. Verduyn de Boer, “Hugo de Vries, de groote Nederlandsche geleerde drie en tachtig jaar,” in Huisgennot (6 Feb. 1931; J. H. de Vries De Amsterdamsche doopsgezinde familie de Vries (Zutphen, 1911); T. Weevers, “Hugo de Vries als plantenphysioloog,” in Hugoo de Vries, Voordrachten ter herdenking van zijn honerdste geboortedag op 16 Februari 1948 (Amsterdam, 1948), 11–15; and F. A. F. C. Wnet, “Hugo de Vries,” in Mannen en vrouwen van beteekenis in onze dagen, 31 (7) (1900), 263–320: “Hugo de Vries en de mutatietheorie,” in Elsevier’s maandschrift, 39 (1905), 35–42; and “Herinneringen aan Hugo de Vries,” in Natura, 27 (1928), 19–21.

Peter W. van der Pas

VRIES, HUGO DE

(b. Haarlem, Netherlands, 16 February 1848;

d. Lunteren, Netherlands, 21 May 1935), plant physiology, genetics, mutation theory. For the original article on de Vries see DSB, vol. 14.

After the appearance of the entry on Hugo de Vries in the DSB, scholars mainly focused on de Vries’s work and ideas on heredity. His role in the rediscovery of the Mendelian laws in 1900 was the topic of various publications. Newly discovered letters showed that de Vries considered these laws unimportant. Because of the difference between the Mendelian laws and de Vries’s ideas and experimental work in the 1890s, various scholars argued that, notwithstanding de Vries’s assertion, it is improbable that he rediscovered the Mendelian laws independently. However, from a research note by de Vries from 1896 one could conclude that de Vries had already formulated those statistical laws in that year, although in the framework of his own theory of heredity. In other publications his motivations for his different research topics have been discussed and related to opinions on the significance of his mutation theory for evolution and his broader ideas on the role of science for society. A scholarly biography is still lacking.

Research Topics and Relevance for Society. Looking at de Vries’s topics of research, his change from plant physiology to heredity and evolution in the 1880s is striking. Can a thread be discerned in his scientific development? An answer is that this ambitious young man, who from his early youth showed a focused interest in botany, was from the very beginning of his career not only interested in plant physiology, but also in heredity and evolution. He chose to work in physiology because a research program in plant physiology was more easily attainable for him. He was, however, also steeped in Charles Darwin’s publications on evolution and heredity. When it became clearer to him how to approach the problems of heredity and when the circumstances became favorable, he did not hesitate and started to work in that field. The reason that de Vries probably wanted to leave the field of plant physiology was his collaboration with his colleague at the University of Amsterdam, the physical chemist Jacobus Hendricus van't Hoff. Aided by de Vries’s work on osmosis, van't Hoff was able to formulate his theory of dilute solutions for which he and the Swede Svante Arrhenius would later receive a Nobel Prize. De Vries subsequently felt that he had to redefine the demarcation between their spheres of activity. De Vries then chose to focus on hereditary questions, because of his early interest in this field and its relevance for evolution. At first de Vries’s work in heredity was mainly theoretical, but later he started a sizable experimental program, first in variability and heredity but later—through his work on mutations—also in evolution. De Vries always argued that his ideas were in accordance with the essence of Darwin’s evolutionary theory.

Another explanation for the choice of his research topics is to point to their possible relevance. At that time Dutch scientists thought that science could have a civilizing influence. It could help to solve problems of society, both social and economic. According to de Vries, botany could very well serve that goal. Moreover, de Vries's

ultimate aim, to be able to control mutations, was in accordance with Dutch scientists’ more general idea of the “improvability” of society with the help of science.

Ideas about Heredity. In 1889 Hugo de Vries published Intracellulare Pangenesis, in which he formulated his ideas on heredity. From Darwin he had adopted the idea of independent hereditary particles, termed gemmules, which represented individual characters instead of the whole organism, and he agreed with the argument by the German zoologist August Weismann, based on his sharp distinction between germplasm and somatoplasm, that acquired characters were not hereditary.

According to de Vries’s theory the visible characters of organisms depended on the properties of small invisible particles in all cells, which he called “pangenes.” They were either inactive or active, and they were able to grow and multiply in both states. Their activity depended on the type of cells in which they were located. De Vries claimed that pangenes were usually inactive or latent in the germ lines, and developed their greatest activity in the somatic lines. Differentiation of organs was because individual pangenes, or groups of pangenes, developed more strongly than others. In the nuclei of all cells all types of pangenes of the individual were present; in each organ only those pangenes that had to carry out their function would go to the cytoplasm and become active. Pangenes multiplied in the nucleus, partly in preparation for the division of the cell nucleus, and partly in order to be transported to the cytoplasm later on. Pangenes represented specific individual characters. De Vries stressed the independence of hereditary properties. Fluctuating variability resulted from varying numbers of pangenes of one kind. During successive divisions, pangenes might change their nature slightly, or even considerably. These changes were the starting points of the emergence of new varieties and species.

De Vries’s high expectations of the impression these ideas would make were not fulfilled. From the reactions of his Dutch colleagues and the discussion with Weismann it was clear that the assertion that each cell contains all hereditary material was controversial, and even more the claim that characters are inherited independently of each other. De Vries felt that he had to convince his colleagues of the validity of his theory by providing experimental evidence. He felt compelled to set up an extensive research program, which resulted in the rediscovery of the Mendelian laws and the publication of the Mutationstheorie (1901). According to William Bateson, in the third edition of Mendel’s Principles of Heredity of 1913, the Mendelian laws rescued de Vries’s ideas on heredity. Bateson commented upon Intracellulare Pangenesis that “this essay is remarkable as a clear foreshadowing of that conception of unit-characters which is destined to play so large a part in the development of genetics” and so de Vries became regarded as a scientist with ideas ahead of his time.

The Rediscovery and Statistics. De Vries’s work in the 1890s can be characterized as an attempt to defend his pangene theory, especially the fundamental and controversial idea that different characters have different material hereditary carriers. He started a research program that included the study of variability and hybridizations. In both cases a statistical approach began to play an important role.

In the second half of the 1880s de Vries had probably become accustomed to a statistical interpretation of the results of botanical experiments. From 1894 he regularly applied statistical methods in his publications. He argued that the Belgian statistician Adolphe Quételet and the English scientist Francis Galton had demonstrated that, when a specific trait of a group of individuals was studied, its values are distributed symmetrically around a center and that the distribution can be described by Newton’s binomial or Galtonian curve. De Vries showed that this result was not only valid for human and animal traits, but also for plants. In that way such a study of fluctuating variability demonstrated that the value of a character can vary, independently of the value of other characters. The study of variability therefore supports the idea of the independence of characters. The statistical approach also proved applicable to the study of specific variability. During his investigations de Vries had observed variability which had the form of the symmetric half of a Galtonian curve. According to de Vries this phenomenon was the result of a novel “specific variability.” The distribution of a character distributed according to such a curve, which he called a “half Galtonian curve,” might gradually adopt the form of a symmetrical Galtonian curve and ultimately begin to display the normal fluctuating variability. His conclusion was that such a curve indicated the initial stage of the occurrence of a new character.

In 1894 de Vries started to publish about hybridization experiments. Because by hybridization a property can be transferred from one variety to another, these kinds of experiments could support the view that characters are independent and mixable. From research notes it can be concluded that already in 1896, while unaware of Gregor Mendel’s work, de Vries used the laws of dominance and recessiveness of hereditary factors, their segregation in the germ cells, and their independent assortment, to explain the 75 percent–25 percent ratio in the second generation. He had discovered them by applying the “1:2:1 law,” as he called it, which law he knew through Quételet. This was the already longer known law of the probabilities to draw two white balls (¹/4), two black balls (¹/4), or one white and one black ball (¹/2) from an urn containing equal numbers of black and white balls.

It is obvious from the correspondence between de Vries and his colleague and friend Jan Willem Moll that during the period of the “rediscovery” he did not pay much attention to Mendel, because he was engaged in the composition of Die Mutationstheorie. Only eight months after the “rediscovery” did de Vries refer to Mendel for the first time. By then the Mendelian laws were generally recognized as important. In the early part of 1900, de Vries felt that the Mendelian laws were a rather unimportant sideline of his work. He never seemed impressed by Mendel’s theory at all.

In Die Mutationstheorie, in his attempts to describe Mendelian crossings in terms of pangenes and mutations, de Vries became entangled in a number of contradictions. He tried to identify a pair of Mendelian factors, one recessive and one dominant, with a pair of identical pangenes, one in the latent and one in the active state (see the picture of the lecture plate). Because the pair of concepts

dominant-recessive denotes a relation while the pair active-latent does not, the two pairs of properties of hereditary characters can not, however, be identified with each other. De Vries did not, however, admit that. Some of his remarks convey the impression that he was aware that the Mendelian laws on the one hand and his theories of pangenes and mutations on the other hand could not be brought in line.

SUPPLEMENTARY BIBLIOGRAPHY

WORKS BY DE VRIES

Intracellulare Pangenesis. Jena, Germany: G. Fischer, 1889. Translated by C. Stuart Gager as Intracellular Pangenesis: Including a Paper on Fertilization and Hybridization. Chicago: Open Court, 1910.

Die Mutationstheorie: Versuche und Beobachtungen über die Entstehung von Arten im Pflanzenreich. Leipzig, Germany: Veit, 1901. Translated by J. B. Farmer and A. D. Darbishire as The Mutation Theory: Experiments and Observations on the Origin of Species in the Vegetable Kingdom. 2 vols. Chicago: Open Court, 1909–1910.

OTHER SOURCES

Bateson, William. Mendel’s Principles of Heredity. Cambridge, U.K.: Cambridge University Press, 1913.

Bowler, Peter J. “Hugo de Vries and Thomas Hunt Morgan: The Mutation Theory and the Spirit of Darwinism.” Annals of Science 35 (1978): 55–73.

Campbell, Margaret. “Did de Vries Discover the Law of Segregation Independently?” Annals of Science 37 (1980): 639–655.

Darden, Lindley. “Reasoning in Scientific Change: Charles Darwin, Hugo de Vries, and the Discovery of Segregation.” Studies in the History and Philosophy of Science 7 (1976): 127–169.

———. “Hugo de Vries’s Lecture Plates and the Discovery of Segregation.” Annals of Science 42 (1985): 233–242.

“Hugo de Vries 1848–1998.” Special Issue, Acta Botanica Neerlandica 47 (1998): 405–507. In English.

Kottler, Malcolm J. “Hugo de Vries and the Rediscovery of Mendel’s Laws.” Annals of Science 36 (1979): 517–538.

Meijer, Onno G. “Hugo de Vries No Mendelian?” Annals of Science 42 (1985): 189–232.

Pas, Peter W. van der. “Hugo de Vries and Gregor Mendel.” Folia Mendeliana 11 (1976): 3–16.

Stamhuis, Ida H. “The ‘Rediscovery’ of Mendel’s Laws Was Not Important to Hugo de Vries (1849–1935): Evidence from His Letters to Jan Willem Moll (1851–1933).” Folia Mendeliana 30 (1997): 13–30.

———. “The Reactions on Hugo de Vries’s Intracellular Pangenesis; The Discussion with August Weismann.” Journal of the History of Biology 36 (2003): 119–152.

———. “Hugo de Vries’s Transitions in Research Interest and Method.” In A Cultural History of Heredity III: 19th and Early 20th Centuries. Preprint 294 of the Max Planck Institute for the History of Science, 2005. Available from http://www.mpiwg-berlin.mpg.de/en/research/preprints.html

Stamhuis, Ida H., Onno G. Meijer, and Erik J. A. Zevenhuizen. “Hugo de Vries on Heredity, 1889–1903: Statistics, Mendelian Laws, Pangenes, Mutations.” Isis 90 (1999): 238–267.

Theunissen, Bert. “Closing the Door on Hugo de Vries’ Mendelism.” Annals of Science 51 (1994): 225–248.

———. “Knowledge Is Power: Hugo de Vries on Science, Heredity and Social Progress.” British Journal for the History of Science 27 (1994): 291–311.

Visser, Rob P. W. “Hugo de Vries (1848–1935): Het begin van de experimentele botanie in Nederland.” In Een brandpunt van geleerdheid in de hoofdstad: De Universiteit van Amsterdam rond 1900 in vijftien portretten, edited by J. C. H. Blom. Amsterdam: Amsterdam University Press, 1992.

Zevenhuizen, Erik J. A. De Wereld van Hugo de Vries. Amsterdam: University of Amsterdam, 1996. The inventory of the archive of Hugo de Vries. In Dutch with English summary.

———. “Keeping and Scrapping: The Story of a Mendelian Lecture Plate of Hugo de Vries.” Annals of Science 57 (2000): 329–352.

Ida H. Stamhuis

Hugo de Vries

Hugo de Vries (1848-1935), Dutch botanist and geneticist, is the author of the mutation theory of evolution. His work led to the rediscovery and establishment of Mendel's laws.

Hugo de Vries was born on Feb. 16, 1848, in Haarlem. His father had been prime minister of the Netherlands. After studying at the universities of Leiden, Heidelberg, and Würzburg, De Vries was appointed a lecturer in botany at the University of Amsterdam in 1871. In 1878 he became professor of botany, a position he retained until his retirement in 1918. He was at the same time director of the Botanic Gardens at the University of Amsterdam.

De Vries made his first notable contributions to science in the 1880s in the field of plant physiology. While investigating the movement of fluids in plants, he confirmed Jacobus Hendricus Van't Hoff's theory of osmosis and Svante Arrhenius's theory of ionic diffusion. During the 1870s De Vries had carried out a series of studies for the Prussian Ministry of Agriculture involving the problems of plant breeding and hybridization. The results of this research were published in monographs on clover, the sugarbeet, and the potato. After his appointment as professor, he turned his attention more and more to questions concerned with the theory of evolution and the ways in which new species might evolve.

Evolutionary Theory in the Late 19th Century

To understand the significance of De Vries's research, it is important to place his investigation in the context of the scientific debates of the period. Charles Darwin's theory of evolution by natural selection was published in 1859. He held that species evolved or changed in form from generation to generation because some members of the species lived for a longer time than others and were able to produce more offspring than their less fit fellows. In the long run, this would result in a species becoming more like the favored variation and less like the unfavored variations. In his Origin of Species Darwin did not establish how variations occurred or how they were inherited. Subsequently, the area of heredity and variation became a recognized field of research for biologists interested in evolutionary theory.

Darwin had put forward the idea that variations between different individuals in a species were usually of a continuous nature. He believed that because of natural selection certain ranges of this continuous variation would be more favored in the struggle for survival and the species would become changed toward those ranges. However, by the late 1880s and the 1890s some biologists were becoming convinced that evolution depended on the effect of natural selection on discontinuous variations, not on continuous variations. In the period of De Vries's greatest contributions to science, 1880-1910, he participated vigorously in the debate about the respective roles of continuous and discontinuous variations in the evolutionary process.

Biologists were at the same time involved in much debate and research about the nature of heredity. Darwin realized that one of the gaps in his theory of evolution was an adequate explanation of the mechanism of heredity. To fill this gap, he proposed his theory of pangenesis: Each character in a mature organism was determined by a minute particle, or pangene, passed on from the parental organisms via the sex cells. The pangenes passed from all parts of the parental body through the bloodstream to the sex cells and then determined the character of the appropriate parts of the offspring by similar diffusion as the offspring grew.

One aspect of Darwin's theory of pangenesis caused much debate among biologists. How, they asked, could the pangenes, which were discrete particles, give rise to continuous variations? For this to occur, there would probably have to be some blending of the pangenes from different parents into one pangene. Some biologists preferred to believe that if heredity did depend on the passing of discrete units from parents to offspring, these units would remain discrete in the offspring and give rise to discontinuous variations in the mature offspring. De Vries played an important role in the debate about the process of heredity.

Another area of research was of great importance in the overall picture of evolution. This was the question of the structure of the cell and its nucleus and the analysis of the behavior of cell and nucleus during division. During the last quarter of the 19th century cytologists established a fairly detailed picture of what happened to the nuclear material during cell division. The material was chemically identified, and biologists began to speculate on the connection between the nucleic acids of the chromosomes and the mechanism of inheritance. Again De Vries played an important role in pointing out the connection between the nuclear material and the particles which controlled the inheritance of characteristics from generation to generation.

De Vries's Pangenesis Theory

De Vries published his theory of pangenesis in Intracellular Pangenesis (1889; trans. 1910). He took the name "pangenesis" from Darwin and, like Darwin, he held that characters were passed from parent to offspring through the medium of small particles or elementary units. These units he called "pangenes." De Vries held that the pangenes were located in the nucleus of each cell and that every nucleus contained a complete set of the pangenes for that particular individual. The complete set of pangenes represented all the potential characters of the mature organism. He further maintained that at the time of cell division the whole set of pangenes also divided so that every daughter cell contained a complete set of pangenes. By placing his pangenes in the nucleus and suggesting that they were present in the chromosomes, he was able to tie his theory of pangenesis much more closely to cytological observations than Darwin was.

Although De Vries was not able to outline in any detail how the pangenes determined the character of an organism, he suggested that a pangene left the nucleus of the cell, entered the surrounding cytoplasm, and thus controlled the activity of the cell. In Intracellular Pangenesis he stated that each pangene represented "a special hereditary character … The pangenes are not chemical molecules, but morphological structures each built of numerous molecules … they assimilate and take nourishment and thereby grow, and then multiply by division; two new pangenes, like the original one, usually originate at each cleavage. Deviations from this rule form a starting point for the origin of variations and species."

De Vries's theory of pangenesis put forward a hereditary mechanism which did not allow for any possibility of environmental or Lamarckian influence on heredity. His theory was also capable of fitting in with the findings of the contemporary cytologists on the nature of cell division and the role of the nucleus. The most important area for further work seemed to him to be the whole question of the source and nature of biological variation.

De Vries's Work on Variation

Darwin's theory of evolution maintained that new species were formed by the action of natural selection on variations which always occurred among the members of a species. In the mid-1880s De Vries did a great deal of work on the inheritance of the different characteristics of marigolds. He was impressed by the constancy of the species over several generations and became convinced that the ordinary or continuous variations were not the source of the new forms needed for new species.

In 1886 De Vries came across some evening primroses (Oenothera lamarckiana) growing in a field near Amsterdam and noticed that they showed great variations in height, form of leaves, and pattern of branching. By 1889 he had examined over 53,000 of these primrose plants from eight generations. In that time he found eight completely new types, which he felt were different enough from the original plants to be called new species. These new types bred true, that is, they had offspring similar to themselves, when they were cross-pollinated. He felt that he had at last uncovered the secret of the origin of new species, which he put forward in The Mutation Theory (1901-1903; trans. 1909).

De Vries's Mutation Theory

In his theory of mutation De Vries combined his theory of pangenesis, which explained heredity, with his theory that new species could arise only from a very large and completely spontaneous variation, which he called a "mutation." This mutation was the result of a new pangene or several new pangenes. In The Mutation Theory he said that the adoption of this new theory "influences our attitude toward the theory of descent [or evolution] by suggesting to us that species have arisen from one another by a discontinuous, as opposed to a continuous, process. Each new unit, forming a fresh step in the process, sharply and completely separates the new form as an independent species from that from which it sprang. The new species appears all at once; it originates from the parent species without any visible preparation and without any obvious series of transitional forms."

De Vries contrasted his mutation theory with the Darwinian theory of selection, emphasizing that he saw the origin of species through mutation whereas Darwin had seen it through the selection of ordinary or fluctuating variation. The mutation theory was widely accepted in the years immediately after it was published. In 1904 he made a lecture tour of the United States, where he expounded his theory. It soon came under attack, particularly by some of the geneticists who had adopted Mendelian principles.

Rediscovery of Mendel's Work

During the 1890s De Vries carried out many experiments in breeding plants. He crossed plants with different characteristics (for example, hairy and smooth stems) and counted the numbers of plants in succeeding generations which had the different parental characteristics. By the end of the 1890s he had gathered much evidence to show that there were definite rations which kept recurring among the offspring (for instance, hairy and smooth stems would occur in the ratio 3 to 1). By late 1899 he had obtained similar results in more than 30 different species and varieties. De Vries reasoned that the obtaining of fixed ratios supported his theories of pangenesis and mutation. The pangenes, which determined the characters of the plants, were seen as units which must separate and recombine according to regular patterns during breeding; these regular patterns would give rise to the fixed ratios he had discovered. Mutations would arise from the loss or great change of some of the pangenes.

Sometime in 1900, before De Vries published his new findings about the fixed ratios of characters among the offspring in cross-breeding experiments, he discovered a paper by Gregor Mendel which included an account of the same laws about the regular patterns of inheritance. Mendel's paper had been published in 1866 and had been ignored by the scientific world. The laws which Mendel had originally discovered and which De Vries had independently rediscovered became the basis of the modern study of genetics. Simultaneously, two other European biologists, Karl Correns and Eric Tschermak, rediscovered Mendel's work.

There has been some controversy about De Vries's role in the rediscovery of Mendel's work, including the suggestion that he did not want to acknowledge Mendel's priority in the discovery of the basic laws of genetics. However, it would seem that De Vries never felt that the Mendelian laws were as significant as his own mutation theory, so that his apparent lack of recognition for Mendel could stem from a feeling that biologists were placing too much emphasis on Mendel's laws and not paying enough attention to De Vries's mutation theory.

From 1900 until he retired in 1918 De Vries spent most of his energy trying to find further evidence for his mutation theory. It drew less support as geneticists found more evidence to support Darwin's original theory that the source of evolutionary change was the normal variations that occurred among all numbers of a species. By the time of De Vries's death in Amsterdam on May 21, 1935, the action of natural selection on ordinary variations had again become the accepted version of evolutionary theory and the term "mutation" was used to apply to any new character of a plant or animal—not only very large and striking variations.

Further Reading

There is no standard biography of De Vries in English. For a general account of his work the best books are L. C. Dunn, A Short History of Genetics (1965), and A. H. Sturtevant, A History of Genetics (1965). For De Vries's part in the rediscovery of Mendel see Robert C. Olby, Origins of Mendelism (1966). □

Hugo de Vries

The botanist Hugo de Vries (1848-1935) worked in the fields of heredity and its relation to the origin of species, developing a mutation theory. He also brought the earlier work of Gregor Mendel to the attention of the scientific world.

In the latter half of the 19th century, the field of botany was dominated by problems of heredity, variation, and evolution. Stemming both from Darwin's highly influential On the Origin of Species by Natural Selection (1859) and from intense interest in improving agricultural productivity, much investigation aimed at discovering the nature and extent of variation, its mode of inheritance, and the problem of how new varieties and species actually originate.

De Vries was a major figure in the study of heredity and its relation to the origin of species: in 1889 his book on Intracellular Pangenesis provided a theoretical outline for a particulate theory of inheritance; in 1900 he was one of the three rediscoverers of Gregor Mendel's laws of segregation and random assortment; and in 1901-1903 he published his massive, two-volume study, The Mututation Theory (Die Mutationstheorie), proposing a new mechanism which he called "mutations" or "sports" for the origin of species. By the early 1900s de Vries had become recognized as one of the leading botanists in the world and was elected to many scientific societies and was the recipient of a number of honorary degrees. While his theories of pangenesis and mutation gradually slipped into oblivion, in his own day de Vries was highly influential in focusing biologists' attention on heredity as a discrete process that could be studied experimentally and quantitatively.

De Vries was born in Haarlem, the Netherlands, on February 16, 1848, the son of Gerrit de Vries and Maria Everardina Reuvens. His father's family had been Baptist ministers and businessmen, and his mother's family scholars and statesmen. Educated first at a private Baptist school in Haarlem, young de Vries attended gymnasium (equivalent to high school) in the Hague, matriculating in the University of Leiden in 1866. Here, he read two works that greatly stimulated his interest in botany: Darwin's Origin of Species (1859) and Julius Sachs' Textbook of Botany (1868). Darwin's book raised de Vries' curiosity about variation and its relationship to the process of evolution, particularly the diversification of species. Sachs' textbook aroused de Vries' enthusiasm of quantitative, experimental work, as opposed to the old-style taxonomy that made up so much of the field of botany at the time. One of the weakest parts of Darwin's argument for evolution by natural selection had been his lack of coherent understanding of heredity and of how one ancestral population actually gave rise to two or more species. De Vries was eventually to make this issue central to his scientific investigations.

Experimental Work with Sachs

Pursuing physiological studies at Leiden, de Vries earned his doctorate in plant physiology in 1870, but felt stifled by the university, where conditions for experimental work were crude and where there was open hostility to Darwinism. He therefore decided to continue his education in Germany, first at Heidelberg (1870) and then at Würzburg (1871) with Sachs. Sachs took a great interest in de Vries' career, helping him refine his experimental techniques and nominating him for several important posts over the next few years. Sachs was a strong proponent of experimentation. Under his guidance de Vries began a series of detailed studies of osmosis, plasmolysis, and the effects of salt solutions on plant cells. He carried out these experiments at Würzburg, then at Amsterdam while teaching in a gymnasium (1871-1877), and finally at the University of Amsterdam where he was appointed lecturer in plant physiology in 1877 and professor in 1881; he remained at Amsterdam until compulsory retirement in 1918, when he moved to the small village of Lunteren.

In the late 1880s de Vries shifted from experimental work in plant physiology to the study of heredity. His first major publication on this subject was Intracellular Pangenesis in 1889, a critical review of the hereditary theories of Darwin, Herbert Spencer, August Weismann, and Carl von Nägeli. All of these writers had proposed some form of particulate theory of heredity. De Vries added to the list one of his own, the theory of "pangenes" (a term he borrowed from Darwin), unitary particles representing individual traits of an organism and manifesting themselves independently in the adult. De Vries considered the pangene a material unit that could combine and recombine in successive generations much like atoms in the formation of molecules. Although de Vries' hypothesis cannot be considered a forerunner of the Mendelian-chromosome theory that emerged in the 20th century, it was an elegant example of the sorts of theories of heredity and evolution that dominated much of later 19th-century biological thought.

As a result of his physiological training, de Vries was interested in studying heredity and evolution from a quantitative and experimental, rather than a purely theoretical, point of view. In the early to mid 1890s, he learned of the statistical work on variation being developed by Francis Galton in England. A strict Darwinian, Galton measured traits in animal populations and showed that they generally graphed as a smooth or "normal curve" of distribution. De Vries' studies showed that such curves also existed for many traits in plants. But he also found that many traits showed a bimodal or discontinuous distribution, suggesting that populations are often mixtures of varieties, or races, that can be separated from one another by selection. Crossing several closely related races of poppy, xenia, and other species that differed from one another by only one or a few traits, de Vries arrived independently (by 1896) at what is now known as Mendel's law of segregation. In 1900 he accidently came across and read Mendel's original paper of 1866 and incorporated a discussion of Mendel's results in his own work on the poppy, published in 1900. This publication appears to have triggered both Carl Correns and Erich von Tschermak-Seysengg to read Mendel's work and recognize its importance. The result was to bring to the attention of the scientific world the work of Gregor Mendel which was soon to lay the foundation for modern genetics.

Working Out the Mutation Theory

It was for his work on the mutation theory, however, that de Vries ultimately became most well-known. In 1886 near Hilversum, outside of Amsterdam, de Vries noted what appeared to be several species of the evening primrose, Oenothera lamarckiana, growing side-by-side. Taking seeds from these plants and growing them in his experimental garden, de Vries found they produced many variant forms which he classified as new and distinct species. These suddenly-appearing variations de Vries called mutations, and in his The Mutation Theory (1901-1903) he suggested that evolution might occur more frequently by these large-scale jumps than Darwin's natural selection acting on slight individual variations. There were, de Vries noted, several types of mutations that occurred in plants: progressive (introducing a wholly new character, and usually making the plant a new species); retrogressive (loss of a trait); and degressive (activation of a trait long-latent in the species). While de Vries saw retrogressive and degressive mutations as following Mendel's laws (progressive mutations did not), he made little of the point. His major interest lay less in the problem of heredity and more in that of the origin of species.

De Vries' mutation theory was enthusiastically received by many investigators at the time as meeting many of the difficulties they saw in the Darwinian theory: lack of sufficient geological time for the slow and haphazard process of natural selection to produce new species; the problem of new traits being swamped or blended out by backcrossing with the parents; and the reliance of Darwinians on the heritability of slight, individual (as opposed to largescale) variations as the raw material on which selection could act. De Vries travelled widely lecturing on the mutation theory, going to the United States in 1904, 1906, and again in 1916, where he stimulated many investigators to seek in other organisms, including animals, large-scale mutations of the sort he had found in Oenothera. While no such mutations were forthcoming, de Vries' work did stimulate much interest in the experimental study of evolution, as investigators sought ways to produce mutations artificially and to detect their presence through experimental breeding. One result of de Vries' influence was that in 1908 Thomas Hunt Morgan at Columbia University began to search for mutations in the fruit fly Drosophila melanogaster, an organism whose favorable breeding characteristics were to become a major focus for experimental genetics in the 20th century.

Among his many honors, de Vries was the recipient of 11 honorary degrees and became a corresponding member of many foreign academies of science. His world-wide esteem was reflected in invitations to give the major lectures at the opening of the Station for Experimental Study of Evolution at Cold Spring Harbor, Long Island (1904), and at the dedication of Rice Institute in Houston, Texas (1916).

As influential as it was in his own day, de Vries' mutation theory did not pass the test of time. Between 1907 and 1915 various cytogeneticists showed that heredity in Oenothera involved a number of unusual chromosomal phenomena (polyploidy, or increased numbers of chromosomes; two groups of chromosomes attached end-to-end, each transmitted as a whole from parent to offspring) that gave only the illusion of new species. In reality the mutants of Oenothera were explicable not by de Vries' pet mutation theory but by the very Mendelian theory de Vries had helped to recover. Eventually, by the early 1920s, the mutation theory was abandoned as an explanation for origin of species. (The modern term "mutation" refers only to small, discrete variations in particular traits, and thus has a much different meaning from de Vries' usage.)

Further Reading

A biographical sketch of Hugo de Vries written by Peter van der Pas for the Dictionary of Scientific Biography includes a lengthy bibliography. For the reception of de Vries' work, see Garland E. Allen, "Hugo de Vries and the reception of the 'mutation theory'," Journal of the History of Biology (1969). For the relationship between de Vries and evolutionary problems, see: Lindley Darden, "Reasoning in scientific change: Charles Darwin, Hugo de Vries, and the discovery of segregation," in Studies in History and Philosophy of Science (1976) and Peter van der Pas, "Correspondence of Hugo de Vries and Charles Darwin," Janus (1970). De Vries' role in modern genetics is discussed in J. Heimans, "Hugo de Vries and the gene concept," in Human Implications of Scientific Advance: Proceedings of the XV^e International Congress of History of Science, E. G. Forbes, editor (Edinburgh, 1978); in Malcolm Kottler, "Hugo de Vries and the rediscovery of Mendel's laws," Annals of Science (1979); and in Peter van der Pas, "Hugo de Vries and Gregor Mendel," Folia Mendeliana (1976). □

DE VRIES, HUGO

DE VRIES, HUGO (1848–1935), Dutch botanist.

Hugo Marie de Vries was one of the leading scientists of the Netherlands around 1900, the year in which he and three other plant biologists independently rediscovered Gregor Mendel's whole-number ratios in the distribution of inherited characteristics.

Born in Haarlem on 16 February 1848, de Vries trained in medicine at Heidelberg and Leiden and became a full professor of plant physiology, a new branch of botany, at the new University of Amsterdam in 1881. He belonged to the generation of European scientists most affected by the late-nineteenth-century fascination with statistics, aware of the basic mathematics pioneered in Ludwig Boltzmann's thermodynamics and Francis Galton's studies of human variation. Some, like Galton himself, went on to research in human breeding ("eugenics"), but de Vries was among the majority who confined its application to breeding plants and animals.

galton curve and osmosis

De Vries published, as contemporary Dutch scientists had to, in at least four languages. His first major paper on the biological use of the "Galton curve" (the name he gave to the so-called normal, bell, or Gaussian curve used in statistics to sort out data) appeared in German in 1894. To de Vries, a "half-Galton curve" result indicated discontinuous variation and a double-peaked curve showed the presence of two characteristics or races, which further selective breeding could isolate from each other.

At the time this paper was published, de Vries's major scientific contributions had been to the understanding of the fluid pressure and fluid exchange in plant tissues—plasmolysis and osmosis. His early papers on these subjects appeared in German and French in 1888.

Four years before however, in 1884, de Vries had told his Dutch colleague Jacobus Hendricus van't Hoff (1852–1911) about experiments by the German botanist Wilhelm Pfeffer showing that osmotic pressure across semipermeable (ferrocyanide) membranes was proportional to the concentration of solutes. Van't Hoff suggested an explanation that followed the entropy law of thermodynamics based on the assumption of molecules, and his research in this vein led to a Nobel prize in chemistry in 1901.

plant breeding and genetics

For de Vries, this line of research petered out around 1890, and he returned to botany. In the year that Mendel died, 1884, de Vries began publishing on the subject of plant breeding, starting with the first of a three-year series called "Thoughts on the Improvement of the Races of Our Cultivated Plants." In 1885 he began breeding Dipsacus sylvestris, the common teasel or thistle, and later Oenothera lamarckiana, or evening primrose. His goal became the elucidation of the true submicroscopic mechanism of heredity, something that Charles Darwin had attempted in 1868 with his ultimately unsatisfactory "gemmule" theory. In 1889 de Vries published Intracellular Pangenesis, in which he maintained that hereditary qualities were independent units. These "pangenes," as he called them, were multiple, one for each trait, and they divided in their own cells and propagated to daughter cells. Some entered the cell's cytoplasm and thus had an effect, whereas others stayed in the cell's nucleus and did nothing. By changing occasionally, they might spontaneously cause mutations and new species. The idea excited great interest but seemed essentially unproven, either by observational or by statistical methods.

discontinuous inheritance, mendel, and the gene

Continuing his long-term breeding experiments in 1896, de Vries crossed two varieties of the opium poppy, Papaver somniferum, "Mephisto" and "Danebrog," which yielded 1,095 with a black petal base and 358 with a white petal base in the third generation after the first cross, or "F3." De Vries presented these results to his advanced students as a demonstration of a law of "segregation of characteristics," segregation that could be teased from the raw data using statistics and Galton (normal) curves. De Vries had in fact arrived at the Mendelian genetic law but refrained from publishing it until 1900.

By then it was almost too late. Four plant biologists were zeroing in on the same law of segregation or discreteness of heritable characteristics—the "gene" or atomic idea of heredity—in the spring of 1900. On 17 January, in Vienna, the Austrian botanist Erich Tschermak von Seysenegg defended his doctoral thesis ("On Crossbreeding in Peas"), which was published later in the year in Austria; it mentioned Mendel but underplayed the idea. De Vries's own paper came second, but the word law was in its title ("The Law of Segregation of Hybrids"); it was received on 14 March by the leading German-language journal, Berichte der deutschen botanischen Gesellschaft (Reports of the German Botanical Association). Twelve days later de Vries was presenting it in French at the Paris Acadèmie des sciences. In May it was the turn of William Bateson, whom de Vries had met in England in 1899; Bateson's lecture called "Problems of Heredity as a Subject for Horticultural Investigation" appeared in the Journal of the Royal Horticultural Society. In retrospect, however, it was the paper by the German botanist Carl Correns, received by the Berichte in April, whose title ("Mendel's Law concerning the Behavior of Progeny of Varietal Hybrids") best revealed the event. The "law" was in fact not de Vries's; it was the discovery of a substitute high school physics teacher named Gregor Mendel, whose two-year experiment in crossbreeding peas had been published by his local scientific society in 1866 and ignored for thirty-four years, until the times became more receptive to discontinuitarian explanations. De Vries's paper, like the other two, acknowledged Mendel's priority. In a letter to H. F. Roberts in 1924, de Vries wrote that he had found the 1866 result in the bibliography of a pamphlet appended by the American horticulturist Liberty Hyde Bailey to later editions of his 1895 book (Plant-Breeding), though Theo J. Stomps argued in 1954 that de Vries had gotten the news in a letter from his colleague Martinus Willem Beijerinck in Delft in 1900. De Vries had nevertheless secured his research and reputation, if not his priority, and in 1909 a colleague, Wilhelm Johannsen, discussing de Vries's work in a book, coined the word gene by dropping the "pan" from de Vries's term pangene, from 1889.

After 1900 de Vries returned to his 1886 discovery of a new form of evening primrose in a field in Hilversum, and he became identified with the evolutionary mechanism he called "mutation," by which new species might arise with saltatory (dis-continuous) suddenness amid the continuous, almost imperceptible change implied by Darwin's natural selection. He published a book on this topic, Die Mutationstheorie (1901–1903; The mutation theory), and more than thirty papers. In 1904 he went to the United States, opening the Cold Spring Harbor Laboratory's Station for Experimental Evolution on Long Island, lecturing at the University of California, Berkeley, and giving a paper at the scientific congress of the St. Louis World's Fair. He returned to the United States in 1906 and 1912, remaining on the lookout for any new mutations in his research plant, the evening primrose, though in the end the mutations all turned out to be hybrids.

De Vries's work was fundamental and timely but not quite original enough to win him one of the first Nobel prizes, like those won by his Dutch colleagues, van't Hoff in chemistry in 1901 and Hendrik Antoon Lorentz (1853–1928) in physics in 1902. De Vries died near Amsterdam on 21 May 1935, a scientific statesman.

See alsoDarwin, Charles; Evolution; Galton, Francis; Science and Technology.

bibliography

Allen, Garland E. "Hugo De Vries and the Reception of the 'Mutation Theory."' Journal of the History of Biology 2 (1969): 55–87.

Darden, Lindley. "Reasoning in Scientific Change: Charles Darwin, Hugo de Vries, and the Discovery of Segregation." Studies in History of Philosophy and Science 7 (1976): 127–169.

Mayr, Ernst. The Growth of Biological Thought: Diversity, Evolution, and Inheritance. Cambridge, Mass., 1982.

Olby, Robert C. Origins of Mendelism. 2nd ed. Chicago, 1985.

Stomps, Theo J. "On the Rediscovery of Mendel's Work by Hugo De Vries." Journal of Heredity 45, no. 6 (1954): 293–294.

William Everdell