170 FIELD CROPS FOR TH^ COTTON-BELT 



embryo.^' The endosperm of the grain develops as the 

 result of a fusion separate from the one already considered. 

 Mention has been made of the fact that the nucleus of 

 the pollen-grain divides into two nuclei, only one of which 

 fuses with the egg-cell. The second male nucleus from 

 the pollen-grain fuses with the nucleus of the embryo-sac, 

 this imion developing into the endosperm of the grain. 



Fia. 27. — Illustrating structure of corn kernel at pollination: 1, pollen- 

 grains; 2, silk;. 3, pollen tube; 4, kernel husk; 5, ovary wall; 6, testa; 

 7, tegmen; 8, nueellus; 9, embyro sac; 10, micropyle. 



The fertilization of both the nucleus of the egg-cell to 

 form the embryo and the nucleus of the embryo-sac to 

 form the endosperm is spoken of as double fertiUzation. 

 As a result of this process, the endosperm may acquire, 

 as well as the embryo, qualities of the pollen-producing 

 plant, such as color or chemical content. Examples of 

 this may be seen in the fact that when pollen from the 



1 " Text-book of Botany," by Coulter, Barnes & Cowles, Vol. 1, 

 pp. 267-269. 



