40 Nebraska Agricultural Exp . Station , Research Bui. 20 
have uniformly ten in each egg or sperm cell. Upon hybridiza- 
tion these factors mingle and remain together in all the vegeta- 
tive cells until shortly before the formation of eggs and sperms 
when they are segregated as units or groups, forming new com- 
binations, part of which were derived from each of the parent 
plants. 
In commercial varieties, these units of heredity undergo 
chance rearrangement at each fertilization and practically no 
l 
2 
4 
Fig. 6. — Effect of inbreeding and hybridizing Hogue’s Yellow Dent corn. 
No. 1, typical Hogue’s Yellow Dent plant. Nos. 2 and 4. typical 
elemental strains or pure line plants produced from Hogue’s Yellow 
Dent (No. 1) by six years’ continuous self-fertilization. No. 3, first 
generation hybrid plant grown from seed produced on No. 2 ferti- 
lized with pollen from No. 4. 
plants occur in the simplicity of an elemental strain. However, 
thru controlled and repeated self-fertilization this simplicity of 
gametic constitution may be achieved, in which the Mendelian 
factors derived from the male and female parent are alike and 
