de Vries, Hugo [key], 1848–1935, Dutch botanist. He opened a new approach to the study of evolution by using the experimental method to investigate the processes of evolution. His study of discontinuous variations, especially in the evening primrose, led to his rediscovery (reported in 1900) of Mendel's laws of heredity and to the development of the theory of mutation, which he expounded in The Mutation Theory (1901–3, tr. 1909–10) and in Plant-Breeding (1907). He maintained that mutations—sudden, unpredictable, inheritable changes in an individual organism—are the chief method by which new species develop in the course of evolution and that each quality subject to change is represented by a single physical unit (which he called a pangen). De Vries's work on osmosis is also important; he coined the term isotonic. He was professor (1878–1918) at the Univ. of Amsterdam, and he established an experimental garden at Hilversum.
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