50 Nebraska Agricultural Exp. Station, Research Bui. 20 
appeared to be uniform in all characteristics. Further proof of 
this pure (homozygous) condition was had in 1916. Several 
ears of each strain were fertilized with pollen from sister plants 
of the same strain in 1915. These were planted in 1916 in com- 
parison with the self-fertilized seed. The sister bred corn was 
no more vigorous than the inbred and could not be distinguished 
from it. This lack of increased vigor following sister breeding 
is evidence of purity as to Mendelian factors. All plants of 
each strain appeared to have identical germ plasm and all 
plants were similar except as affected by slight environmental 
differences. 
Strain Orig. 1 2 4 5 8 9 10 12 
No. 
Fig. 12. — Typical plant of Hogue’s Yellow Dent corn at left. At right, 
typical plants of eight distinct pure lines of the same variety after 
six years of self-fertilization. When used in hybridization, each 
strain transmits some unique characters to its hybrid offspring. The 
comparative growth and grain yields for these strains in 1916 are 
given in Table 14. Corn photographed in 1915. 
HYBRIDS 
Where many elemental strains are being grown in close 
proximity, hybridization between them must be effected by 
