292 BOTANICAL GAZETTE [october 



occurring in the open association, the Asters become quite noticeable 

 though they are all of a lower layer than S. rigida. The silky Aster, 

 A. sericeus, usually of low abundance and general occurrence, fre- 

 quently becomes copious on bunch-grass knolls, there forming very 

 distinct associations. Rising some 5o cm , with numerous spreading 

 branches terminating in prominent heads (2 to 3 cm in diameter) with 

 numerous violet rays, and bearing abundant leaves which are densely 

 covered above and below with a silvery-white silky pubescence, this 

 Aster is always a conspicuous element of the middle and late autumnal 

 aspect. Its achenes are equipped with a medium pappus. It is 

 a perennial from a thickened rootstock. 



The two other Asters are similar in frequency and abundance to 

 A. sericeus, but never attain its prominence. Of these A. oblongi- 

 folius always occurs with A. sericeus in the open association. With 

 us it always remains depauperate. Seldom more than ^o cm high, 

 it is ever inconspicuous, though its bluish rays make it noticeable at 

 short range, since it is usually overshadowed by A. sericeus. It is a 

 perennial and is wind-distributed; a copious pappus serves to bring 

 about a general invasion, which, as in the other Asters, seems to be 

 coupled with a high percentage of establishment, especially in the 

 open xerophytic associations of the formation. The dense-flowered 

 aster, A. multiflorus, occurs perhaps more frequently but less abun- 

 dantly than the former, and is similarly a xerophyte of the open asso- 

 ciation, in which situations it never reaches other than a reduced 

 stature. However, its bushy spreading branches, thickly beset with 

 numerous small white heads, invariably make it more prominent 

 than A. oblongifolius , particularly when it occurs in patches. It 

 seems to work down upon the lower slopes, here attaining a greater 

 stature and abundance as well as a greater prominence in anthesis. 



All the Asters are perennial from rootstocks and form small basal 

 rosettes, and are wind-disseminated. 



The hairy prairie clover, Kuhnistera villosa, is a perennial from a 

 deep tuberous root. Densely silky pubescent, abundantly branched, 

 and terminating in cylindrical clustered spikes (3 to 6 cm long) of 

 rose-purplish flowers, it is in itself quite conspicuous, but its restricted 

 frequency and rare abundance make it rarely a tonal component in the 

 formation. In the bunch-grass formation it becomes, with Amorpha 



