226 NATURE-STUDY 



in the way of the bee which, in attempting to go past it, 

 brushes off some pollen against the stigma. 



When a bee alights on a sweet-pea flower it rests upon the 

 wings and keel of the flower. The weight of the bee de- 

 presses these parts, which makes the stamens and style pro- 

 trude through the end of the keel. This dusts the bee with 



FIG. 76. Sphinx-moth. 



pollen, and in the next flower this pollen is rubbed off on the 

 stigma. 



The primrose illustrates another device for cross-pollina- 

 tion. Some of the plants have flowers with short stamen and 

 long style, and others just the reverse. Insects visiting these 

 flowers transfer the pollen of the short stamen to the short 

 style, and from the long stamen to the long style. 



The lady's-slipper is a remarkable case. The bee enters 

 by the incurving fold of the slipper. It cannot get out again 



