2l8' 



THE DARWINIAN THEORY 



that insects visiting the flowers will carry pollen from 

 the long anthers of the short-styled form to the 

 stigma of the long-styled form, but would not reach 

 the stigma of the short-styled form. Darwin showed 

 that in this way more seeds were produced than by 

 any other of the four possible unions. Thus, 



Fig. 36. 



°y^ 



w 



1 



" A 



4 



Short-styled flower. Long-styled flower. 



Diagram of dimorphic flowers of Primula. 



a, Anthers. s, Stigma. 



although both forms are hermaphrodite, they bear 

 the same relation to each other as do the two sexes 

 of an ordinary animal. 



A few more botanical works must be mentioned, 

 published in 1875, each of which was the outcome 

 of many years of laborious observations and ex- 

 periments ; each breaking new ground and giving 

 results of great importance and interest. 



In " Climbing Plants," the spontaneous revolutions 

 of tendrils and of the stems of climbing plants were 



