49. 

 comes out, points downwards and towards the left, and 

 Francis Darwin inas shown that the tenth stamen, which is 

 free, bears an appendage which prevents a bee from taking 

 the honey, except from the left side. On the college grounds 

 the early flowers are invariably sterile. But those produced 

 in August are fertile. 



In the closely related Strophostyles angulosa Ell. the keel 

 is bent strongly to the right and occurs in such a way that its 

 tip stands over its base. Robertson says: "The base is 

 large and sac-like and is produced above into a ridge which 

 opposes tlie passage to the nectary. The left wing is turned 

 to the right so that the bee is required -to alight upon the 

 right side, and siie enters the flower between the tip and the 

 basal process of the keel. Seizing this process with her 

 front feet, the bee pulls the keel downward and backward, 

 whereupon the stigma and the pollen-laden brush of the 

 style sweep out over her thorax. In this way the stigma re- 

 ceives pollen already deposited by another flower, and the 

 style-brush leaves a new load." 



Tiiis plant, along with several other Leguminosae, es- 

 pecially the Cowpea of the South, Vigna Sinensis^ Hassk. has 

 conspicuous extra floral nectaries, on which Vespa maculata 

 and Formica are common. Robertson reports having found 

 several Hymp.iwptera (Andrinidae, Vespidae, Formididae,) 

 Diptera and Hemiptera, on Strophostyles angulosa. Ell. 



Apios tuberosa. Another near relative of Phaseolus is 

 Apios tuberosa, Moench. which has a large standard with a 

 rather flrm texture, at the tip of the standard is a small boss, 

 as seen from the back, or a shallow sack as seen from the 

 front. The sickle shaped keel is arched and fixed into the 

 notch at the upper end of the standard and it remains in this 

 position unless touched by an insect. When an insect touch- 



