244 



FIELD CROP PRODUCTION 



Some farmers contend that there are not enough bumble- 

 bees during anj^ one season to bring about polHnation in 

 all of the flowers that produce seeds. Dr. Hopkins, in 

 reply to this argument, says that he has observed a bumble- 

 bee going through the motion of putting its bill into a 

 clover bloom and withdrawing it, thirty-four times per 

 minute, operating during this time upon seven heads. 

 It is possible, as is indicated in the experiment above 

 quoted, that insects other than bumble-bees may bring 

 about some pollination, and it is also probable that self- 

 pollination is effected in some cases. Scientists generally 

 agree that the bumble-bee is largely responsible for the 

 pollination of the clovers, and that their number in a 

 given season has some close correlation with the yield of 

 clover seed obtained. 



Recently there has been placed on the market a pollinat- 

 ing machine, which, it is asserted, when run over a clover 

 field in bloom, will so rub the clover heads as to cause 

 self-pollination. The North Dakota Station, in the ex- 

 periment reported above, found that the rubbing of the 

 heads did not produce pollination. Experience with 



