strikes upon the olDject tripping the flower or against 

 the standard has some influrnce in causing fertilization. 

 This effect may he hrought ahout either by "bringing the 

 pollen into contact v/ith the surface of the stigma or hy 

 irritating the surface cells of the stigma, or to hoth 

 of these causes. 



Alfalfa plants were ohserved at Pullman, Wash, and 

 at Chinook, Mont., in 1909 and 1910, to determine whether 

 pods and seed ever develop from flowers which have "been 

 automatically tripped. At Chinook, in 1909, two plants 

 were found on v/hich the flowers were becoming self -tripped 

 in large numbers. On one of these plants 57,88 percent 

 of the flowers and on the other plant 56.25 percent of 

 the flowers observed were automatically tripped. At 

 Pullman, Wash, in 1910, 7.7 percent of the flowers enclos- 

 ed under netting were self tripped. J|t Chinook, Montana 

 in 1910, nearly all of the flowers which opened during 

 a period of two weeks or more early in August became 

 tripped, when there were not enough insects in the fields 

 to trip more than a small proportion of the flowers; in 

 the few days succeeding this period, v^rhen climatic 

 conditions were fchanged, practically none of the flowers 

 were tripped. The results of these observations indicate 

 that usually a small percentage of the alfalfa flowers 



(57) 



