220 ENTOMOLOGY 



to be supposed, however, that insects realize that they confer any benefit 

 upon the plant in the flowers of which they find food. At any rate, 

 most flowers are so constructed that certain insects cannot get the 

 nectar or pollen without carrying some pollen away, and cannot enter 

 the next flower of the same kind without leaving some of this pollen 

 upon the stigma of that flower. Take the iris, for example, which is 

 admirably adapted for pollination by a few bees and flies. 



Iris. In the common blue-flag (Iris versicolor, Fig. 256) each of the 



FIG. 256. Bumblebee (Bombus) entering flower of blue-flag (Iris versicolor}. ^Slightly 



reduced. 



three drooping sepals forms the floor of an arched passageway leading 

 to- the nectar. Over the entrance and pointing outward is a movable 

 lip (Fig. 257, /), the outer surface of which is Stigmatic. An entering 

 bee hits and bends down the free edge of this lip, which scrapes pollen 

 from the back of the insect and then springs back into place. Within 

 the passage, the hairy back of the bee rubs against an overhanging 

 anther (an) and becomes powdered with grains of pollen as the insect 

 pushes down towards the nectar. As the bee backs out of the r passage 



