322 



SOME SPECIAL ADAPTATIONS 



Fig. 200. — Dog- 

 wood (Cornus). 



and the chances are fewer for a multiple pollination by 

 wind-blown pollen. Wind-pollinated flowers are usually 

 small and dull in color. 



587, On the contrary the insect (and bird) pollinated 

 flowers are usually bright colored (and it has been found 



that many insects are attracted long dis- 

 tances by bright colors) . They are usually 

 large enough to be easily visible, or if 

 small are bunched in large, conspicuous 

 masses (as in Elder). If not showy them- 

 selves they are often bordered by showy 

 leaves (as in Snow-on-the-Mountain Eu- 

 phorbia marginata) , or some of the flowers are con- 

 verted into showy structures at the sacrifice of their 

 sexual function (e.g. marginal flowers of some Dog- 

 woods). In addition to these it is usual for entomophi- 

 lous flowers to emit perfumes of various kinds, some 

 of which are perceived by insects at great distances. 

 Some of these are very unpleasant to man, but are 

 attractive to certain insects, e.g. Stapelia, whose car- 

 rion-like odor is attractive to carrion insects. 



588. Within the flowers are developed the secretory 

 glands which secrete a sugary liquid. Attracted by 

 color and odor the insects fly to the flowers and seek out 

 this nectar which they imbibe. In 

 so doing they come in contact with 

 the stamens, and become powdered 

 with pollen, and later touch the 

 pistil to which the pollen is trans- 

 ferred. In flowers with many 

 stamens and pistils the nectaries are usually several 

 in all the radii of the flower, and the insect in visiting 

 will manage to become thoroughly covered with pollen 

 and to put it on the summit of the stigma. In many 



_ Fio. 201. — Regular (ac- 

 tinomorphic) and irregular 

 (zygomorphic) flowers. 



