Corn Investigations 
33 
Table 9. — Summary of the relationships between the shedding 
of pollen , silking . and fertilization of corn. 19H, 1915 , and 
19°20. 
1914 
1915 
1920 
Av. 
Days 
Days 
Days 
Days 
Av. number of days after tassel is visible until — 
a. Shedding of pollen begins 
5.2 
7.0 
6.9 
6.4 
b. Tassel is entirely out 
5.7 
5.8 
7.5 
6.3 
c. Silks first show 
7.8 
8.3 
8.9 
8.3 
d. Pollen is shed at maximum rate 
8.2 
10.8 
10.4 
9.8 
e. Silks attain maximum length 
9.9 
10.5 
11.8 
10.7 
f . Silks show fertilization 
11.6 
11.7 
12.7 
12.0 
g. Tassel ceases to shed pollen 
11.1 
13.2 
13.9 
12.7 
Av. number of days after pollen begins to shed 
until — 
a. Silks first appear 
2.6 
1.3 
2.0 
2.0 
b. Pollen is shed at maximum rate 
3.0 
3.8 
3.5 
3.4 
c. Silks show fertilization 
6.4 
4.7 
5.8 
5.6 
d. Pollen ceases to shed 
5.9 
6.2 
7.0 
6.4 
Av. maximum length attained by silks (inches) . . 
2.3 
2.4 
3.4 
2.7 
Av. length of pollination period for variety in 
which — 
4 per cent or more plants shed pollen (days) 
12.5 
13.8 
13.1 
12 per cent or more plants shed pollen (days) 
9.5 
10.4 
10.0 
Fourteen varieties were observed and averaged for the years 1914 and 
1915; and nine varieties were observed and averaged for 1920. 
In 1914, 1,498 normally developed plants were observed for pollination 
relationship and averaged; in 1915, 1,606 plants were so observed; and in 
1920, 67 such plants were observed. 
the pollen which fertilizes the corn falls upon the silks during a 
three-day period centering upon the maximum shedding of 
pollen by the same plant. Seasonal climatic conditions influence 
the time elapsing between the various flowering stages of the corn 
plant. Favorable conditions at the time of the flowering period, 
as existed in 1915, caused the silks to appear 1.3 days earlier in 
relation to the initial shedding of pollen than was the case in 
the somewhat drier year of 1914. Unfavorable conditions tend 
to delay the development of the ears more than that of the tas- 
sels. Under adverse conditions, the extension of the pollination 
period for a cornfield by the variability of its individual plants 
is an important factor in reducing the number of otherwise im- 
perfectly fertilized ears. 
