POLLINATION AND FERTILIZATION 



161 



melons, oaks, pecans, filberts, walnuts, and butternuts are 

 monoecious. When a plant bears either staminate or pistillate 





> JT 



FIG. 101. Multiplication of cells after fertilization. 



flowers, but not both kinds, it is said to be dioecious. 1 

 fras, hops, poplars, willows, date palms, and 

 most persimmons are dioecious. 



259. Relation of pollination and fertilization 

 to the se'tting of fruit. While the seed is 

 developing, its surrounding parts, which form 

 the edible portions of most orchard fruits, 

 are also evolving. The formation of the ing large 

 seed is necessary in order that the fruit may set and not 

 drop prematurely, except in the case of the navel orange, 

 and a few other fruits. 



A flower is said to be self-pollinated when its stigma has 

 received pollen from a flower of the same variety; it is 

 cross-pollinated when the pollen comes from a different 

 variety. Flowers which form fruits and seeds when fer- 

 tilized by pollen from the same variety are said to be self- 

 fertile and the process is known as self-fertilization. Flowers 



1 "Dioecious" means belonging to two households. 



