Theories of Evolution 27 



sown. Cultivated plants of course, had only 

 a small chance to exhibit new qualities, as they 

 have been so strictly controlled during so many 

 years. Moreover their purity of origin is in 

 many cases doubtful. Among wild plants only 

 those could be expected to reward the investi- 

 gator which were of easy cultivation. For this 

 reason I have limited myself to the trial of wild 

 plants of Holland, and have had the good for- 

 tune to find among them at least one species in a 

 state of mutability. It was not really a native 

 plant, but one that had been introduced from 

 America and belongs to an American genus. I 

 refer to the great evening-primrose or the even- 

 ing-primrose of Lamarck. A strain of this 

 beautiful species is growing in an abandoned 

 field in the vicinity of Hilversum, at a short dis- 

 tance from Amsterdam. Here it has escaped 

 from a park and multiplied. In doing so it has 

 produced and is still producing quite a number 

 of new types, some of which may be considered 

 as retrograde varieties, while others evidently 

 are of the nature of progressive elementary 

 species. 



This interesting plant has afforded me the 

 means of observing directly how new species 

 originate, and of studying the laws of these 

 changes. My researches have followed a double 

 line of inquiry. On one side, I have limited 



