36 Nebraska Agricultural Exp. Station , Research Bui . £0 
was only 6.0 days, the spread of time between the initial and 
final shedding of pollen by different plants within the variety 
equaled 13.1 days. This is due to a number of causes, including 
strain differences, delayed development, and soil inequalities. 
The average spread of time for the various varieties in which 
12 per cent or more of the plants were shedding pollen equaled 
9.9 days. 
As a grand average for the three years, 1914, 1915, and 
1920, the entire pollination period for a plant was 6.3 days. The 
silk first appeared two days after the dropping of the pollen 
began. Pollen was shed at the maximum rate 3.4 days after it 
began, which is practically midway in the pollinating period of 
t lie plant. The silks showed fertilization 5.6 days after the 
pollen began dropping, which is practically a day before it 
ceased. This suggests that the average plant in the average 
year is shedding pollen at approximately the maximum rate at 
the time when its ear is pollinated, thus providing ample oppor- 
tunity for self-fertilization. The average length of time in 
these three years during which cornfields shed their pollen was 
13.1 days, and 12 per cent or more of the plants in these fields 
shed pollen for a period of ten days. 
amount;of self-fertilization occurring normally in a cornfield 
In the year 1915, 40 plants of Nebraska White Prize corn 
were grown, distributed systematically 60 hills apart in a field 
of pure Hogue’s Yellow Dent corn. Both varieties had identical 
flowering periods. The per cent of self-fertilization occurring 
in the Nebraska White Prize corn could be determined after 
maturity by the per cent of kernels on the Nebraska White Prize 
ears which were pure white. As a result of xenia the kernels 
fertilized by other plants were yellow. Upon maturity all of 
the kernels produced by the Nebraska White Prize plants were 
separated into four groups: (1) Those distinctly showing a 
yellow cast, which were unquestionably cross-fertilized; (2) 
those which were pure white and without a doubt self-fertil- 
ized; (3) those which showed only a very faint yellowish tinge 
and were doubtful as to purity; and (4) those kernels which 
had very light yellow caps and whose verification was desired. 
In the following year, 1916, the last three groups were 
planted in the field and their pure or hybrid nature established 
by inbreeding 50 plants of each. (Table 11.) By this test the 
1.05 per cent apparently pure white kernels were reduced to 0.7 
per cent pure white. All of the kernels in the somewhat doubt- 
