"Blossom Hosts and Insect Guests 



Darwin states it as his belief that none of the 

 higher forms of plant life (flowering plants) can 

 fertilize itself for a number of successive generations. 

 It must be crossed with another individual occa- 

 sionally, preferably one on a different plant, and the 

 more frequently this crossing of races occurs the 

 better it is for the plant. 



