10 
Nebraska Agricultural Exp. Station , Research Bui. 20 
1. 3, and 5 plants per hill yielded relatively 99.8, 100.0, and 
100.4 per cent. It does not appear advantageous to select seed 
from corn planted thicker than the standard planting rate; and 
as an average for the two varieties, a reduction in yield not 
greater than 2 per cent is suggested in case the seed is all con- 
tinuously selected from such a very thin stand as one plant per 
hill. 
11. Self-fertilization as it occurs ordinarily in the field 
seems not to exceed 1 per cent under our conditions. Our tests 
indicate that only 0.7 per cent of the kernels were actually 
selfed under natural field conditions. 
12. In an eight-year yield test, seed selected from detas- 
seled rows in a seed plat yielded 0.6 per cent more than did 
seed taken from normally field pollinated rows. This would in- 
dicate that no extensive self-fertilization had taken place, since 
selfing reduces the yield approximately one-third in the first 
generation. The immediate effect of detasseling upon the cur- 
rent crop was an increased grain yield of one per cent for the 
detasseled plants. 
13. Extensive observations have shown that in general the 
pollinating period of the tassel materially overlaps the silking 
period. Self-pollination might occur extensively were it not for 
the overwhelming preponderance of foreign pollen scattered 
promiscuously thru the air. 
14. The continuous natural segregation and recombination 
of elemental hybridizing characters together with the natural 
element of survival of the fittest accentuated by man’s repeated 
selection of well-developed ears for seed may account in a large 
measure for the inherently high productivity of field corn as 
now grown. 
15. More than one hundred distinct pure lines or elemental 
strains have been developed in these experiments by continuous 
self-fertilization for seven or more years. Such self-fertilization 
gradually so purifies the chromosome composition of the plant 
that both male and female gametes of all its progeny plants are 
alike and carry the same inheritance. All hybrid vigor has then 
been eliminated and the resultant pure lines have become stabi- 
lized in plant size and growth habit and no further heritable re- 
duction occurs. In a seven-year test, eight to twelve inbred 
strains of Hogue's Yellow Dent corn tested for yield in com- 
posite produced 32 per cent as much grain as the original 
Hogue’s Yellow Dent corn. In a five-year test of eight inbred 
strains of Nebraska White Prize corn planted in composite, the 
