RED-CLOVER SEED PRODUCTION. 11 



and flattening them with a little pressure on the cover glass, the 

 pollen tubes could be traced through the stylar canals, as pollen tubes 

 have a denser and more granular content than the cells of the style. 



An examination of 30 flowers which had been self -pollinated for 55 

 hours showed good germination on the stigmas but no fertilization. 

 The number of pollen grains germinating on the stigmas ranged 

 from 3 to 25 in each of the 30 flowers. The tubes had made a slow 

 growth and none exceeded 4 millimeters in length. An examination 

 of 20 flowers which had been self-pollinated for 90 hours showed that 

 one pollen tube had attained a length of 7.5 millimeters, while the 

 others were 5 millimeters or less in length. At this rate of growth 

 the longest tube would have required about 48 hours more to reach 

 me ovules, or about six days to traverse the entire distance from 

 stigma to ovule. Flowers examined four days after springing the 

 carinas showed the eggs in a disintegrated condition. It is therefore 

 probable that in case of self-pollination the pollen tubes do not reach 

 the ovules in time to effect fertilization. 



An examination of the 30 flowers which had been cross-pollinated 

 for 55 hours showed that fertilization had taken place in all of them. 



CROSS-POLLINATION AND SELF-POLLINATION OF RED CLOVER. 



The results published by previous investigators on the cross- 

 pollination and the self-pollination of red clover do not agree. These 

 investigators appear to be about equally divided as to whether red- 

 clover flowers are self-fertile or not. The experiments of Frandsen, 

 according to Lindhard (23), Fruwirth (12, p. 163-166), and others 

 show that red-clover heads which were covered during their blooming 

 period and not pollinated failed to set seed Frandsen and Fruwirth 

 also show that pollen must come from an entirely separate plant 

 in order to fertilize the ovules of red-clover flowers. On the other 

 hand, Garton, according to McAlpine (24) states that self-pollination 

 is as common with red clover as it is with the bean. 



The relative efficiency of the bumblebee and honeybee as cross- 

 pollinators of red clover has also been discussed by scientific investi- 

 gators, as well as by agricultural papers and bee keepers. Bee men 

 generally agree that the Italian race of honeybees can extract nectar 

 from red-clover flowers. Little has been said, however, about the 

 ability of the honeybee to collect pollen from red clover. 



In view of the above diverse opinions in regard to the self-pollination 

 and the cross-pollination of red clover, a number of experiments were 

 outlined in order to determine (1) whether red-clover flowers were 

 self -fertile; (2) if self -fertile, whether any effective method of self- 

 pollination could be found which would be applicable for use on a field 

 scale; and (3) the relative efficiency of the bumblebee and honeybee 

 as cross-pollinators of red clover. 



