20 THE SOY BEAN ; HISTORY, VARIETIES, AND FIELD STUDIES. 



The limited amount of data concerning three other varieties indicate 

 that ButterbaU has likewise become later at Arlington or earlier at 

 the Minnesota Agricultural Experiment Station, while no change has 

 taken place in Buckshot and Manhattan. 



Table IV. — Variation in life periods of Jour soy-bean varieties, apparently due to place 



effect. 



POLLINATION AND HYBRIDIZATION. 



The soy-bean flower is completely self-fertile, bagged plants setting 

 pods as perfectly as those in the open. This was tested at the Arling- 

 ton Experimental Farm in 1909 by bagging .30 plants representing 

 10 varieties. In no case did the bagged individuals fail to produce 

 as well as neighboring unbagged plants. Ten plants were also 

 inclosed in box screens with similar results. 



The flowers are much visited by bees, mainly for the pollen, as but 

 a very small quantity of nectar is secreted. Cross-pollination would 

 be of frequent occurrence were it not that the abundant pollen of 

 eacli flower covers the stigma almost as soon as the flower opens. 



197 



