37^ Evolution by Jumps 



the appearance of variants that can transmit their new pe- 

 cuHarities. He thus connected up with Weismann's theory 

 of the germinal origin of hereditary traits, and he preceded 

 by a short time deVries' announcement of the mutation 

 theory. 



De Vries 



Hugo de Vries, the Dutch botanist, introduced a diver- 

 sion by announcing the results of many years of study on 

 discontinuous variations. He had attempted to establish 

 new strains of several different species, but he obtained hi; 

 most striking results with the evening primrose, CEnothera 

 lamarckiana. This plant had apparently been introduced 

 into Dutch gardens from North America, and had then 

 escaped from cultivation so that it was growing wild in open 

 fields at Hilversum, near Amsterdam. In the early eighties 

 de Vries observed many of these " weeds," showing the usual 

 variations as to size, vigor, toughness, color, and so on. A 

 few individuals among them, however, showed marked 

 deviations from the normal type. He took to the botanical 

 garden numbers of these deviates as well as of the normal 

 individuals. He grew them from seed and kept careful 

 records of the pedigrees. Year after year he found that 

 most of the seeds in a culture behaved themselves in a thor- 

 oughly normal and respectable manner. That is, they pro- 

 duced new individuals like their parents. Both the standard 

 forms and the radical departures from type were true to 

 seed. Yet in a few cases each generation exhibited a number 

 of sports (see Fig. 48) . 



The new kinds of individuals differed from their parents 

 not in single traits merely, but in all organs and tissues. 

 And they differed from their parents at every stage of de- 

 velopment. The evening primrose is a biennial plant. The 

 growth from the seed during the first year ends in a rosette 

 of leaves and a reserve of food in the root. During the 

 second year there is produced a rather tall, leafy stem bear- 



