INSECT POLLINATION 79 



dry seeds of a plant can undoubtedly resist greater extremes 

 and longer duration of heat, cold and drouth than buds and 

 can be carried to much greater distances by natural means and 

 by man. Many believe that sexual reproduction gives the 

 plants much more vigor than non-sexual reproduction. This 

 belief seems to be supported by tlie fact that when some varieties 

 of plants are grown continuously from cuttings, tubers or bulbs, 

 they tend to lose their original varietal characters and vital- 

 ity. Sexual reproduction, owing to the fact that the two 

 parents are never exactly the same, tends to cause variations in 

 plants, and results in new varieties. This tendency to pro- 

 duce variations is greatly increased by cross breeding different 

 varieties and has given rise to some of our most valuable fruits, 

 vegetables and oraajnentals. (Page 148.) The transfer of the 

 pollen from the stamens to the stigma is knoAvn as pollination 

 and should not be confused with fertilization. (Page 76.). 



Pollen may be carried by the wind, and some of our most 

 valuable plants depend entirely upon the wind for pollination. 

 The corn and other grains and grasses belong to this class. The 

 tassel of the corn is a mass of small staminate flowers, while 

 each thread of the silk represents a pistil with a single grain 

 of corn for its ovary. During the blooming season there is a 

 rain of pollen grains, some of which fall upon the silk. Of 

 course, this is in a sense very wasteful for the number of 

 pollen grains which are lost is infinitely greater than the number 

 which fall upon the silk {i. e., pistils). 



Insect Pollination. — The great majority of our flowering 

 plants are pollinated through the agency of insects, which visit 

 the flower primarily to collect the nectar and pollen. Many 

 insects use the nectar immediately for food, but the bees take 

 it into their bodies where it undergoes chemical changes by 

 which it is transformed into honey and then stored up for 

 future use. Many insects are doubtless attracted by the odors 

 of flowers and some few may be attracted by the color, although 



