Portrait of Hugo de Vries (1848-1935), Dutch plant physiologist and geneticist. De Vries was the son of a Dutch prime minister, and studied medicine in Holland and Germany. He was also an accomplished botanist. At Wurzburg he worked on plant turgor (stiffening of the cell walls due to osmotic water uptake), using the term plasmolysis to describe loss of turgidity. He then turned to plant heredity. His breeding experiments with evening primrose led him to a general theory of mutations, a rapid alternative to Darwinian theory. This was later shown to be wrong, due to the complex genetics of the evening primrose, but did much to stimulate experiment and debate in genetics.