Corn Investigations 
69 
vantage in their early growth because of the reduced kernel 
size upon which the seedling plant draws for its early nourish- 
ment. To overcome this, the substitution of double crossed seed 
has been suggested in which two unrelated F 1 hybrids are 
crossed. The hereditary constitution of the resultant kernel is 
as complex as for the F 1 hybrid and yet the kernels are normal 
in size. The data in Table 24 record the rate of growth and 
general early development in 1921 of standard Hogue’s Yellow 
Dent corn having kernels of normal size, with the average re- 
sults from a number of pure lines which had been inbred for 
ten years, and with eight vigorous F n hybrids between these 
pure lines. The results suggest that the size of the F n hybrid 
kernel may, in some cases at least, be sufficient to supply ample 
nourishment for the young plant under normal soil and climatic 
conditions at time of planting. 
DEGREES OF INBREEDING 
There are various degrees of kinship between the ovules of 
the ear and the pollen grains which fertilize them. The past 
discussion has indicated that a large number of distinct ele- 
mental strains with independently inherited Mendelian charac- 
ters are the basis for an ordinary corn variety, and that broad 
fertilization to avoid the pairing of identical Mendelian factors 
is desirable. Investigation has been made to determine the effect 
of intermediate degrees of close breeding. Two separate experi- 
ments have been conducted, one beginning in 1909 with Hogue’s 
Yellow Dent corn and one in 1912 with Nebraska White Prize. 
Beginning with ear-to-row strains, the following degrees of re- 
lationship between source of ovule and pollen have been studied : 
1. Self-fertilization , in which the seed has been continued 
each year with a single ear of corn, fertilized by pollen from 
the same plant. 
2. Close breeding within an ear-to-row strain, in which the 
seed has been continued each year with a single ear of corn, fer- 
tilized with pollen from a single sister plant of the same strain. 
3 a . Narrow breeding within an ear-to-row strain, in which 
the seed has been continued each year with a single ear of corn, 
fertilized with composite pollen from 15 sister plants of the 
same strain. 
3 b . Narrow breeding within an ear-to-row strain, in which 
the seed has been continued each year with ears in composite 
from 15 sister plants, all fertilized with pollen from a single 
sister plant of the same strain. Class 3 a and 3 b represent the 
