POLLINATION BY INSECTS 



63 



or are scented, or secrete honey, have the office of pollination 

 performed for them by insects which visit them for the pollen 

 or honey; the pollen as well as the honey being used by insects 

 as food. The colors and scents of flowers are evidently related 

 to the senses of sight and smell of insects and serve to attract 

 the insects to them. 



141. Insects on visiting the flowers necessarily come in 

 contact with the anthers and some of the pollen clings to the 



B 



Fig. 31. — The dichogamous flowers of Polygala. The flower A shows the 

 anthers protruding from the hood. In B the stigma has advanced and is ready 

 for polHnation. 



insect's body; for the character of the pollen grains in such 

 plants differs from the powdery pollen of anemophilous plants 

 in that it is sticky by virtue of a viscid or oily coating, or 

 because of the prickles, grooves, ridges or other structural 

 peculiarities of the wall of the pollen grain which cause it to 

 cling more readily to the hairs of the insect's body. Now as 

 the insect moves on to another flower it will in all probability 



