POLLINATION BY THE WIND 



39 



Flies, too, are agents in cross-pollination. Humming birds also 

 are active agents in some flowers. Snails are said in rare in- 

 stances to carry pollen. Undoubtedly, man and the domesticated 

 animals frequently pollinate flowers by brushing past them while 

 walking over the fields. 



Pollination by the Wind. — Not all flowers are dependent upon 

 insects or other animals for cross-pollination. Many of the earliest 

 spring flowers appear almost before the 

 insects do, and are dependent upon 

 the wind for carrying pollen from the 

 stamens of one flower to the pistil of 

 another. Most of our common trees, 

 oak, poplar, maple, and others, are 

 cross-pollinated by the wind. 



Flowers pollinated by the wind are 

 generally inconspicuous and often lack 

 a corolla. Their anthers are exposed 

 to the wind and provided with much 

 pollen, while the surface of their stigmas 

 may be long and feathery. Such flowers 

 may also lack odor, nectar, and bright 

 color. Can you tell why? 



Imperfect Flowers. — Some flowers, 

 especially those depending upon the 

 wind for pollination, are imperfect ; 

 that is, they lack either stamens or pis- 

 tils. The corn plant is an example. 

 Again, in some cases, imperfect flowers 

 having stamens only are found on one 

 plant, while those flowers having pistils 

 only are found on another plant of the 

 same kind. In such flowers, cross-pollination must of necessity 

 follow. Many of our common trees are examples. 



The Necessity of Fruit and Seed Dispersal to a Plant. — 

 We have seen that the chief reason for flowers, from the plant's 

 standpoint, is to produce fruits Avhich contain seeds. The scatter- 

 ing of fruits and seeds is absolutely necessary in order that colonies 

 of plants may reach new localities. It is evident that plants 



The corn plant has staminate 

 flowers at the top of the stalk 

 and pistillate flowers at the 

 side. (White circles were 

 painted on the photograph, to 

 show the location of the pistil- 

 late flowers.) 



