10 BULLETIN 289, U. S. DEPARTMENT OF AGRICULTURE. 
is probable that the only function of the stigmas in the germination 
of the pollen is that of supplying the requisite amount of moisture 
to the pollen. If such is the function of the stigmas, a wet soil or 
humid atmosphere, both of which tend to increase the water content 
of the stigmas, may allow the pollen to absorb too much water and 
thus prevent fertilization. Martin (25) found pollen lying dormant 
on stigmas 18 hours after pollination during cool, moist weather. 
This dormancy might have been due to the effect of low temperature 
upon the pollen alone, but could have been due to an interference 
with the moisture adjustment. 
FERTILIZATION OF RED-CLOVER FLOWERS. 
TIME REQUIRED BETWEEN POLLINATION AND FERTILIZATION. 
The time between the pollination and the fertilization of red-clover 
flowers varies. Flowers pollinated in July, when the temperature 
was high and killed 18 hours after pollination, showed that m most 
cases fertilization had taken place. In October, when the tempera- 
ture was much lower, the time between pollination and fertilization 
ranged from 35 to 50 hours. 
NECESSITY OF FERTILIZATION OF RED-CLOVER FLOWERS. 
It has been reported that red clover is able to develop seed without 
fertilization; but field experiments, as well as laboratory tests, have 
disproved this statement. One of the most noticeable features of 
this work was the fact that all the flowers of heads which were 
covered with tarlatan before they came into bloom and left in this 
condition until they withered remained in full bloom from 9 to 10 
days. Flowers of red clover wither shortly after fertilization takes 
place. This is why red clover heads usually contain flowers in bud, 
in bloom, and withered at the same time. 
In order to further test the necessity of fertilization, a large number 
of heads were covered with tarlatan before any flowers came into 
bloom. An examination of more than 500 flowers at various times 
after they began to wilt showed no embryos. The ovules were 
disintegrating. 
POTENCY OF POLLEN IN SELF-POLLINATION. 
In order to determine the potency of pollen in self-pollinated 
flowers of red clover, a number of heads were covered with tarlatan 
two or three days previous to the opening of the flowers. Some of 
these covered flowers were self-pollinated by springing the carinas, 
while the rest were cross-pollnated by springing the carinas and 
applying pollen from flowers on other plants to their stigmas. By 
mounting the pistils of these flowers in a 30 per cent sucrose solution 
