200 FARM FRIENDS AND FARM FOES 



own anthers, it is said to be self-pollenized and the ovules 

 are said to be self-fertilized. 



As a matter of fact, the great majority of flowering 

 plants are cross-fertilized. Many of them have special 

 devices for preventing self-pollination. These devices 

 include the separation of the stamens and pistils in differ- 

 ent flowers, as in the case of the squashes and cucumbers, 

 the maturing of the stamens and pistils at different times, 

 or a difference in length of stamens, and pistils which pre- 

 vents the pollen from getting upon the stigmas. One of 

 the commonest methods that nature employs in preventing 

 self-fertilization is in rendering the pollen incapable of 

 fertilizing the ovules of the flower in which it developed. 

 Such flowers are said to be self-sterile, and' very commonly 

 none of the pollen upon a plant is able to fertilize the 

 ovules of any of the flowers upon that plant. Not only 

 this, but in many cases the pollen of a certain variety of 

 apple, pear, or plum is incapable of fertilizing any other 

 flowers of the same variety, even upon different trees. 

 In such cases the whole variety is said to be self-sterile 

 and must be pollenized by flowers of some other variety. 



The discovery that a large proportion of the varieties of 

 tree fruits are self-sterile is one of the most important re- 

 cent developments in our knowledge of fruit growing. It 

 has been observed for a longtime that the variety of plums 

 called the Wild Goose, when planted alone, will not set fruit, 

 even though there be many trees near together. It had 

 also been noticed that when other varieties of plums were 

 planted near the Wild Goose trees, the latter commonly 

 produced abundant crops. An investigation of the cause 

 of this, undertaken by M. B. Waite, of the United States 

 Department of Agriculture, showed that this lack on the 

 part of the Wild Goose trees was due chiefly to the fact 



