STKUOTUEE OF THE FOEMATION 65 



of showy, cream-colored flowers, too heavy to be sustained 

 by the plant, are strewn over eastern, western, and southern 

 slopes, sometimes extending almost to the crests of ridges. 

 It is normally a low prairie species, as is shown by its distri- 

 bution. As to duration, it is perennial, and its average is 

 about one individual for three or four quadrats. The strong 

 papilionaceous corolla admirably protects the pollen from 

 rain and admits of fertilization by means of bumble bees only. 

 As the bee's head is thrust far into the flower to reach the 

 nectar, the keel and wings of the corolla are forced down, thus 

 uncovering the incurved stamens and styles, and bringing the 

 anthers and hairy stigma into direct contact with the abdo- 

 men of the bee. Since the bee has no means of determining 

 whether nectar is present, except by trying, the flowers are 

 visited many times during the day and thus allogamy is se- 

 cured. Upon examination, I found the abdomens of several 

 bees colored yellow with the abundant pollen masses. Astrag- 

 alus crassicarpus is found at only one station in the prairie, 

 viz., on the western slopes of Great ridge near the south side. 

 It is a low prairie species tending toward xerophilous condi- 

 tions. The purplish blue racemes of the ground plum appear 

 at a time when there is little else in the floral covering, hence 

 the important part they play. The low, reclining stems 

 spread from the perennial, woody root in all directions, a 

 single individual frequently occupying considerable space. 

 Vicia americana is a rootstalk plant and flnds its favorite 

 haunts in meadows near streams and woodlands. This plant 

 grows at a few locations in the meadow formation near the 

 creek, where it occupies rather deflnite patches. Its climbing 

 habit renders all the more conspicuous the numerous showy 

 racemes of purplish and light blue flowers, so that a patch 

 may be recognized at a distance of twenty to forty meters. 

 During the month of May, Yioia dominates the floral aspect 

 within its limited range. Patches of Vicia are the favorite 

 resorts of bumble bees, fertilization being accomplished as 



