62 



Evolution and Adaptation 



on the former are twice as long as those on the short-styled 

 form. The most important difference is found in the size of 

 the pollen grains. These are larger in the long-styled form, 

 being in the two cases in the proportion of ioo to 67. The 

 shape of the grains is also different. Furthermore, the long- 



FlG. 5. — A, long-styled, and B, short-styled, forms of Primula veris. C, D, E, 

 the three forms of the trimorphic flower of Ly thrum salicaria, with petals 

 and calyx removed on near side. (After Darwin.) 



styled form tends to flower before the other kind, but the 

 short-styled form produces more seeds. The ovules in the 

 long-styled form, even when unfertilized, are considerably 

 larger than those of the short-styled, and this, Darwin sug- 

 gests, may be connected with the fact that fewer seeds are 

 produced, since there is less room for them. The important 



