390 Chief of a Laboratory of Plant Pathology 



was the monk Gregor Mendel's celebrated study of " Plant hy- 

 brids," a paper submitted without ostentation and printed in 

 1865, without any recognition of its substantive worth, in the 

 proceedings of the Society of Natural History of Briinn (Brno) , 

 Austria (now of Moravia,, Czechoslovakia) . 



De Vries, himself at the time perfecting his celebrated mutation 

 theory based on years of experimental study of Oenothera la- 

 mar ckiana, the evening primrose, was enabled thus in 1900 to bring 

 Mendel's famous paper into widespread scientific notice by announ- 

 cing its discovery together with his first elaboration of his own 

 similarly famous hypothesis. His mutation theory and the theory 

 of genetic inheritance implicit in Mendel's hybridization results 

 provided science with not merely an extension of Charles Darwin's 

 theory of natural selection but really a new theory as to the origin of 

 some species. Experimental research workers were, therefore, soon 

 at work investigating the genetic truth of each theory. At about 

 the same time that De Vries became aware of the extraordinary 

 value of Mendel's paper, two other European botanists of world 

 renown, C. Correns and E. von Tschermak, properly evaluated its 

 significance. De Vries because of his mutation theory, however, 

 became the dominant figure of the scientific world. His work had 

 strengthened the Darwinian theory of evolution by adding a pro- 

 found, new, and fundamental truth: at least, an hypothesis to be 

 investigated by scientists for many years to come. In 1904, invited 

 by the Carnegie Institution of Washington to give the dedicatory 

 address of the Station for Experimental Evolution at Cold Spring 

 Harbor, Long Island, he visited America, lectured at several uni- 

 versities and institutions of science, and was a principal speaker 

 and attraction at the Congress of Arts and Science of the Universal 

 Exposition held at St. Louis. 



At the Missouri Botanical Garden then, Frank N. Meyer, once 

 a gardener at the botanic garden of Amsterdam and a plant 

 explorer for the Department of Agriculture, was working under a 

 part-time employment secured perhaps through a recommendation 

 from Smith to Trelease. He kept Smith advised as to De Vries's 

 movements in this country, and it is probable that at St. Louis, 

 Washington, or some other point, De Vries and Smith became 

 acquainted. On November 20, 1905, De Vries sent " a photograph 

 of Wakker in his earlier days " and added: 



