THE FERTILIZATION OF FLOWERS 201 



that the variety is self-sterile, and requires for the develop- 

 ment of fruit the transfer of pollen from some other sort of 

 plum. 



Other investigators have also made further studies of the 

 subject, the more important of these having been made by 

 Bailey, Fletcher, Kerr, and Waugh, with results which are 

 of great importance to every fruit grower. 



It has been pretty conclusively shown that in the case of 

 a large proportion of orchard fruits, a much more abundant 

 crop is produced where cross-pollination with another va- 

 riety takes place. It has also been shown that in many 

 cases there is a decided increase in the size of such fruits. 

 This increase is so marked that it is well worth while 

 for any fruit grower to take it into consideration in plan- 

 ning his orchard. The increase in size is believed by 

 Fletcher to be due to the fact that " the foreign pollen gen- 

 erally stimulates the fruit to a better growth, because it is 

 more acceptable to the pistils, not because it carries over 

 the size-character of the variety from which it came." 



In selecting varieties of fruit trees with reference to 

 cross-fertilization it is important to choose those which 

 blossom at the same time. 



AGENCIES THAT CARRY POLLEN 



There are three principal agencies concerned in bring- 

 ing about the cross-pollination of plants. These are : 



i. The wind which carries the pollen for a large propor- 

 tion of the forest trees that blossom early in spring, but 

 which apparently has comparatively little to do with the 

 cross-pollination of the flowers of most fruit trees and cul- 

 tivated plants. Such plants are said to be ancmophilcns or 

 wind-loving plants. 



