Hugo de Vries

For more information on Hugo Marie de Vries, visit Britannica.com.

Dutch plant physiologist and geneticist (1848–1935)

Born the son of a politician at Haarlem in the Netherlands, de Vries studied botany at Leiden and Heidelberg. He became an expert on the Netherlands flora and later turned his attention from classification to physiology and evolution. He entered Julius von Sachs's laboratory at Würzburg University, where he conducted important experiments on the water of plant cells. He demonstrated that the pressure (turgor) of the cell fluid is responsible for about 10% of extension growth, and introduced the term plasmolysis to describe the condition in nonturgid cells in which the cell contents contract away from the cell wall. His work in this field led to Jacobus van't Hoff's theory of osmosis.

During the 1880s, de Vries became interested in heredity. In 1889 he published Intracellular Pangenesis, in which he critically reviewed previous research on inheritance and advanced the theory that elements in the nucleus, ‘pangenes’, determine hereditary traits. To investigate his theories, he began breeding plants in 1892 and by 1896 had obtained clear evidence for the segregation of characters in the offspring of crosses in 3:1 ratios. He delayed publishing these results, proposing to include them in a larger book, but in 1900 he came across the work of Gregor Mendel, published 34 years earlier, and announced his own findings. This stimulated both Karl Correns and Erich von Tschermak-Seysenegg to publish their essentially similar observations.

De Vries' work on the evening primrose, Oenothera lamarckiana, began in 1886 when he noticed distinctly differing types within a colony of the plants. He considered these to be mutants and formulated the idea of evolution proceeding by distinct changes such as those he observed, believing also that new species could arise through a single drastic mutation. He published his observations in The Mutation Theory (1901–03). It was later shown that his Oenothera ‘mutants’ were in fact triploids or tetraploids (i.e. they had extra sets of chromosomes) and thus gave a misleading impression of the apparent rate and magnitude of mutations. However, the theory is still important for demonstrating how variation, essential for evolution, can occur in a species.

De Vries was professor of botany at Amsterdam from 1878 to 1918 and was elected a fellow of the Royal Society in 1905.

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).

Hugo de Vries, ca. 1907

Hugo Marie de Vries (Feb 16, 1848, Haarlem - May 21, 1935, Lunteren) was a Dutch botanist and one of the first geneticists. He is known chiefly for suggesting the concept of genes, rediscovering the laws of heredity in the 1890s while unaware of Gregor Mendel's work, for introducing the term "mutation", and for developing a mutation theory of evolution.

Contents 1 Early life 2 Early career 3 Definition of the gene 4 Rediscovery of genetics 5 Mutation theory 6 Honors and retirement 7 Books 8 References 9 External links

Early life

De Vries was born in 1848, the oldest son of Gerrit de Vries (1818-1900), a lawyer and deacon in the Mennonite congregation in Haarlem and later Prime Minister of the Netherlands from 1872 until 1874^[1], and Maria Everardina Reuvens (1823-1914), daughter of a professor in archaeology at Leiden University. His father became a member of the Dutch Council of State in 1862 and moved his family over to The Hague. From an early age Hugo showed much interest in botany, winning several prizes for his herbariums while attending gymnasium in Haarlem and The Hague.

In 1866 he enrolled at the Leiden University to major in botany. He enthusiastically took part in W.F.R. Suringar's classes and excursions, but was mostly drawn to the experimental botany outlined in Julius Sachs' 'Lehrbuch der Botanik' from 1868. He was also deeply impressed by Charles Darwin's evolution theory, despite Suringar's skepticism. He wrote a dissertation on the effect of heat on plant roots, including several statements by Darwin to provoke his professor, and graduated in 1870.

Early career

After a short period of teaching, De Vries left in September 1870 to take classes in chemistry and physics at the Heidelberg University and work in the laboratory of Wilhelm Hofmeister. In the second semester of that school year he joined the lab of the esteemed Julius Sachs in Würzburg to study plant growth. From September 1871 until 1875 he taught botany, zoology, and geology at schools in Amsterdam. During each vacation he returned to the lab in Heidelberg to continue his research.

In 1875 the Prussian Ministry of Agriculture offered De Vries a position as professor at the still to be constructed Landwirtschaftliche Hochschule ("Royal Agricultural College") in Berlin. In anticipation, he moved back to Würzburg, where he studied agricultural crops and collaborated with Sachs. By 1877, Berlin's College was still only a plan, and he briefly took up a position teaching at the University of Halle-Wittenberg. The same year he was offered a position as lecturer in plant physiology at the newly founded University of Amsterdam. He was made adjunct professor in 1878 and full professor on his birthday in 1881, partly to keep him from moving to the Berlin College, which finally opened that year. De Vries was also professor and director of Amsterdam's Botanical Institute and Garden from 1885 to 1918.

Definition of the gene

In 1889, De Vries published his book Intracellular Pangenesis,^[2] in which, based on a modified version of Charles Darwin's theory of Pangenesis of 1868, he postulated that different characters have different hereditary carriers. He specifically postulated that inheritance of specific traits in organisms comes in particles. He called these units pangenes, a term 20 years later to be shortened to genes by Wilhelm Johannsen.

Rediscovery of genetics

Hugo de Vries in the 1890s

To support his theory of pangenes, which was not widely noticed at the time, De Vries conducted a series of experiments hybridising varieties of multiple plant species in the 1890s. Unaware of Mendel's work, De Vries used the laws of dominance and recessiveness, segregation, and independent assortment to explain the 3:1 ratio of phenotypes in the second generation^[3]. His observations also confirmed his hypothesis that inheritance of specific traits in organisms comes in particles.

He further speculated that genes could cross the species barrier, with the same gene being responsible for hairiness in two different species of flower. Although generally true in a sense (orthologous genes, inherited from a common ancestor of both species, tend to stay responsible for similar phenotypes), De Vries meant a physical cross between species. This actually also happens, though very rarely in higher organisms (see horizontal gene transfer).

In the late 1890s, De Vries became aware of Mendel's obscure paper of thirty years earlier and he altered some of his terminology to match. When he published the results of his experiments in the French journal Comtes Rendus de l'Académie des Sciences in 1900, he neglected to mention Mendel's work, but after criticism by Carl Correns he conceded Mendel's priority.

Correns and Erich von Tschermak now share credit for the rediscovery of Mendel’s laws. Correns was a student of Nägeli, a renowned botanist with whom Mendel corresponded about his work with peas but who failed to understand its significance, while, coincidentally, Tschermak's grandfather taught Mendel botany during his student days in Vienna.

Mutation theory

In his own time, De Vries was best known for his mutation theory. In 1886 he had discovered new forms among a display of the evening primrose (Oenothera lamarckiana) growing wild in a meadow. Taking seeds from these, he found that they produced many new varieties in his experimental gardens; he introduced the term mutations for these suddenly-appearing variations. In his two-volume publication The Mutation Theory (1900-1903) he postulated that evolution, especially the origin of species, might occur more frequently with such large-scale changes than via Darwinian gradualism, basically suggesting a form of saltationism. De Vries's theory was one of the chief contenders for the explanation of how evolution worked, leading, for example, Thomas Hunt Morgan to study mutations in the fruit fly, until the modern evolutionary synthesis became the dominant model in the 1930s. Somewhat ironically, the large-scale primrose variations turned out to be the result of chromosomal duplications (polyploidy), while the term mutation now generally is restricted to discrete changes in the DNA sequence.

Finally, in a published lecture of 1903 (Befruchtung und Bastardierung, Veit, Leipzig), De Vries was also the first to suggest the occurrence of recombinations between homologous chromosomes, now known as chromosomal crossovers, within a year after chromosomes were implicated in Mendelian inheritance by Walter Sutton^[4].

Honors and retirement

In May 1905, De Vries was elected Foreign Member of the Royal Society. In 1910, he was elected a member of the Royal Swedish Academy of Sciences. He was awarded the Darwin Medal in 1906 and the Linnean Medal in 1929.

He retired in 1918 from the University of Amsterdam and withdrew to his estate "De Boeckhorst" in Lunteren where he had large experimental gardens. He continued his studies with new forms until his death in 1935.

Books

His best known works are:

• Intracellular Pangenesis (1889)
• The Mutation Theory German edition Bd. 1-2 (1901-03), English edition Volume 2 (1909-10) Retrieved 2009-08-20
• Species and Varieties: Their Origin by Mutation (1905)
• Plant Breeding (1907), German translation (1908)

The standard author abbreviation de Vries is used to indicate this individual as the author when citing a botanical name.^[5]

References

1. ^ Nanne van der Zijpp, "De Vries." Mennonite Encyclopedia, Scottdale, PA: Herald Press, 1955-59: vol. IV, p. 862-863.
2. ^ http://www.esp.org/books/devries/pangenesis/facsimile/
3. ^ Stamhuis, Meijer, and Zevenhuizen. Hugo de Vries on heredity, 1889-1903. Statistics, Mendelian laws, pangenes, mutations., Isis. 1999 Jun;90(2):238-67.
4. ^ E.W. Crow and J.F. Crow, 100 Years Ago: Walter Sutton and the Chromosome Theory of Heredity, Genetics, Vol. 160, 1-4, January 2002
5. ^ "Author Query". International Plant Names Index. http://www.ipni.org/ipni/authorsearchpage.do. 

• Biography (in Dutch)
• Ridley, Matt, The Agile Gene, 2003, ISBN 0-06-000679-X, pp 231-2.
• History of Horticulture

External links

• Works by Hugo de Vries at Project Gutenberg
• Works by Hugo de Vries available online at the Biodiversity Heritage Library.
• Biographical sketch of Hugo de Vries with a picture
• Article relating the work of Gregor Mendel
• Concerning the Law of Segregation of Hybrids
• Pangenes

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)