FLOWERS AND THEIR USES 



275 



the lower part of each sac. Figs of both kinds are visited 

 by the females of a certain kind of wasp. 



Suppose that a wasp enters a fig which contains staminate 

 flowers and short-styled pistillate flowers. She inserts her 

 egg-depositing organ into a style and lays an egg in the 

 ovary. After this egg hatches, the young insect grows 

 rather rapidly and the tissues of the ovary wall surrounding 

 it also grow, forming a gall. 

 The young insect feeds on the 

 cells of this gaU. When it is 

 fully grown, it breaks out of 

 the gall. The female insects 

 (but not the males) finally 

 make their way out of the 

 cavity of the fig. But in 

 doing so an insect brushes 

 against the anthers of the 

 male flowers which are near 

 the opening of the cavity and 

 collects pollen on all parts of 

 her body. The wasps which 

 escape in this way visit other 

 figs in order to find a place 

 to lay their eggs. Some visit 

 figs containing staminate and 

 short-styled pistillate flowers 

 and repeat the history that we have just followed. Others 

 visit flgs of the other sort, which contain only long-styled 

 pistillate flowers. 



Coming in contact with these flowers, a wasp deposits on 

 the stigmas some of the pollen with which her body is cov- 

 ered, and so pollination is brought about. But when she 

 attempts to lay an egg in the ovary of one of these flowers, 

 her egg-depositing organ is not long enough to reach to the 

 base of the style. So the egg is laid, not in the ovary, but in 



Fig. 163. — A, a fig, showing how 

 the flowers are borne inside the hol- 

 low end of the peduncle. B 

 staminate flower of the fig. 

 long-styled pistillate flower, 

 short-styled pistillate flower. 

 Kemer. 



a 



C, a 



D, a 



After 



