OTHER THEORIES OF SPECIES-FORMING. 343 



The same doubt exists as to the origin of the Capsella 

 Heegeri of Solms-Laubach, and of the oldest recorded muta- 

 tion, that of Chelidonium laciniatum in Heidelberg about 

 1600." 



Next, after introducing the necessity of experimental 

 proof and explaining how one must go to work to acquire 

 such proof he refers to his own well-known work with 

 Lamarck's evening primrose as follows (pp. 26-29) : 



"Complying with these conditions, the origin of species 

 may be seen as easily as any other phenomenon. It is only 

 necessary to have a plant in a mutable condi- 

 The work with tion. Not all species are in such a state at 

 ' present, and therefore I have begun by ascer- 

 taining which were stable and which were not. 

 These attempts, of course, had to be made in the experi- 

 mental garden, and large quantities of seed had to be pro- 

 cured and 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 the 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 fortune to find among them at least 

 one species in a state of mutability. It was not really a 

 native plant, but one probably introduced from America 

 or at least belonging to an American genus. It was the 

 great evening-primrose or the primrose of Lamarck. A 

 strain of this beautiful species is growing on an abandoned 

 field in the vicinity of Hilversum, at a short distance from 

 Amsterdam. Here it has escaped from a park, and multi- 

 plied. In doing so it has produced, and is still producing, 

 quite a number of new types, some of which may be con- 

 sidered as retrograde varieties, while others evidently are 

 of the nature of progressive elementary species. 



