EXPERIMENTAL EVOLUTION 



"S 



"That I really had hit upon a plant in:a mutable period 

 became evident from the discovery, which I made a year 

 later, of two perfectly definite forms which were immedi- 

 ately recognizable as two new elementary species. One of 

 them was a short-styled form : 0. brevisiylis, which at first 

 seemed to be exclusively male, but later proved to have 



Fig. 6o. — A plant of the evening-primrose (CEnotkera biennis) which, 

 by "bud sporting," has given rise (at the left) to a branch having the 

 characters of another species. 



the power, at least in the case of several individuals, of 

 developing small capsules with a few fertile seeds. The 

 other was a smooth-leaved form with much prettier foliage 

 than 0. Lamarckiana, and remarkable for the fact that 

 some of its petals are smaller than those of the parent type, 

 and lack the emarginate form which gives the petals of 



