236 WESSONS WITH PLANTS 



271. It is evident that if self-fertilization is so 

 often excluded, the plant must frequently depend 

 upon extraneous agents for the transfer of pollen 

 and the perpetuation of its kind. 



272. If the pupil were to shake the staminate 

 catkins of the hazel, birch or walnut when they 

 are mature, he would be surprised at the showers of 

 pollen which are discharged ; and if he should 

 watch the destination of this pollen he would 

 probably see that some of it chances to drop upon 

 the pistillate flowers. He may make similar ob- 

 servations with Indian corn and staminate pine 

 cones. A common agent in distributing pollen is 

 the wind. Plants which bear protruding feathery 

 stigmas and protruding stamens (as the grasses) 

 are generally wind -pollinated. So are many or 

 most dioecious or monoecious plants.' 



273. "We have already referred to the fact (150) 

 that the showy petals sometimes attract insects. 

 The insects are also attracted by odors, as one may 

 infer by watching the visits of moths to the pe- 

 tunias at nightfall, at which time the flowers give 

 forth their odor. We would infer, therefore, that 

 those flowers which have neither showy colors nor 

 odors must be pollinated by the wind; and this 

 is true, as a general statement. 



273a. Plants habitually pollinated by the wind are said to be 

 anemophilous ("wind -loving"), and those pollinated by insects en- 

 tomophllous ("inseet-loving"). 



