10 BULLETIN 289, TJ. S. DEPAKTMENT OF AGEICULTUEE. 



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 in 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-pollinated 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 



