MORE ABOUT POLLINATION 309 



Wind-pollinated flowers, as you have noted, are usually 

 much less conspicuous than are insect-pollinated ones. 

 This has the natural consequence that the latter are much 

 more familiar and include practically all the flowers that 

 are cultivated for their beauty. Wind-polHnated flowers 

 are not generally recognized as flowers at all. They lack 

 bright colors, odor, and nectar.^ The perianth is usually 

 inconspicuous or absent. 



So far as may be judged by the number of plants which 

 use this method, polhnation by wind appears to be Just 

 as successful as polhnation by insects. Of course wind- 

 pollination involves an enormous waste of pollen. On the 

 other hand, the chance of a favorable wind may be greater 

 than the chance of transfer by insects, especially if only a 

 particular kind of insect is able to make this transfer. 

 Oaks, pines, and grasses are very successful plants which 

 are wind-polhnated. The abundance of these plants may, 

 however, be due to other features than their polhnation. 

 Pollination is only one of many factors which determine the 

 success or non-success of plants. 



E. Insect-pollination. — The relations between flowers 

 and insects is one of the most wonderful things in nature. 

 Some insects are absolutely dependent upon certain flowers 

 for food and for the rearing of their young, and some 

 flowers are absolutely dependent upon certain insects for 

 pollination and the production of seed. The structures of 

 some flowers and of some insects so correspond to each 

 other that only these insects can get the pollen from these 

 flowers. Insects are the chief agents of polhnation for 



• Cottonwood and field sorrel are exceptions to this in that, though wind- 

 pollinated, their flowers are bright colored. 



