490 Introduction to the Study of Science 



cone-bearing trees the stigma is replaced by a peculiar arrange- 

 ment of smooth, scale-like bodies that guide the captured pollen 

 to the ovules. Trees put forth blossoms before leaves, or have 

 their blossoms conveniently located for the wind-borne pollen. 



Exercise. Examine the blossoms of some of the wind-pollinated 

 plants in your vicinity. What do you find the characteristic features 

 as to size, form, color, odor, and position of blossoms, staminate and 

 pistillate ? Are color and odor of value to wind-pollinated plants ? 

 Do such plants blossom earlier in the spring than those depending 

 upon some other agency for cross-pollination? Are the pistillate 

 blossoms produced by one plant and the staminate by another? 

 Are these blossoms so located that the wind carrying pollen from the 

 staminate flower is likely to deposit it upon the pistillate blossoms ? 



Waste through wind-pollination. The great uncertainty 

 and waste involved in pollination by wind are obvious. Only 

 where plants grow in groups, as is the case with corn and cer- 

 tain trees and shrubs, is there any certainty of pollination. 

 The isolated corn plant has a very slight chance of producing 

 seed. The pumpkin and squash would probably fail, if they 

 were dependent upon the wind for transfer of pollen from one 

 flower to another. These and many other plants depend upon 

 another agency than the wind for pollination. 



236. Insect-pollination. The plant uses a great deal of 

 energy in producing pollen, much of which is wasted . when 

 pollination depends upon the wind. Many plants have a 

 more economical method of securing the transfer of the- pollen. 

 By their color and perfume they attract insects, such as the 

 bee, moth, and certain flies, to visit them. In the search for 

 nectar the insect brushes against the anthers and transfers the 

 pollen from them to the stigma, or to the next flower it visits. 

 Some flowers have peculiar devices to prevent close- or. wind- 

 pollination. 



The wonderful adaptive structures of flowers to secure cross- 

 pollination by insects can best be studied in nature. The 

 important points may be suggested briefly; but they should 

 be verified in concrete illustrations of typical flowers and their 



