90 SWEET PEA. [CHAP. 



in Figs. 68 and 69 c ; thus a portion of the pollen and 

 also the tip of-the pistil are forced out at the point 

 of the keel, and against the breast of the bee, until 

 on the removal of the pressure the elasticity of the 

 flower causes the various organs to resume their 

 former position ; an obvious advantage, which pre- 

 vents the pollen from being wasted. The union of the 

 stamens at their base has probably reference to this, as 

 Sprengel has suggested. From the manner in which 



FIG. 72. Flower of Sweet Pea, in its FIG. 73. Ditto. The wings are de- 

 natural position. pressed, the stamens and pistil exposed. 



these flowers are evidently arranged with a view to 

 the visits of insects, we can hardly doubt but that 

 these visits are of importance to the plant, 



In the Sweet Pea (Figs. 72 and 73), on account of 

 its larger size the action is still more easily visible. 

 Fig. 72 represents a flower in the natural position. 

 Now if the two ends of the wings be taken between 

 the finger and thumb, and pressed down, so as to 

 imitate the effect produced by the pressure of an 

 insect, the keel is depressed with the wings, while 



