FLOWERS AND INSECTS 



249 



adapted to the large moths, with long proboscides which 

 can reach the bottom of the tube. As the moth thrusts 

 its proboscis into the tube, its head is pressed against 

 the sticky button on each side, so that when it flies away 

 these buttons stick to its head and the pollen masses are 

 torn out. When the next flower is visited these pollen 

 masses are thrust against the stigmatic surface. 



(2) Consecutive maturity. In these cases pollen and stig- 

 ma of the same flower are not mature at the same time. 

 This is a common method of preventing self-pollination, 

 and it is evident that it is effective. When the pollen is 

 being shed, the stigma is not ready to receive; or when the 

 stigma is ready to receive, the pollen is not ready to be 

 shed. 



When the flowers of the ordinary figwort first open, the 

 style bearing the stigma at its tip is found protruding 



B C 



FIG. 244. Protogynous flower of figwort: .4, first stage, with stigma receptive; 

 B, section of A, showing stamens within the corolla; C, second stage, with 

 stigma past and anthers in position for shedding. After GRAY. 



from the urn-like flower, while the four stamens are curved 

 down into the tube, and are not ready to shed their pollen 

 (Fig. 244, A and B}. At some later time, the style bearing 

 the stigma wilts, and the stamens straighten up and pro- 

 trude from the tube (Fig. 244, C). In this way, first the 



