102 BOTANICAL GAZETTE [august 



respectively. Yet the average chresard for the aspect (8.8 per 

 cent.) shows a steady decrease from that of the vernal (10.7 per 

 cent.). 



Species of the estival floral aspect 



Facies. — Koeleria cristata,f Poa pratensis.*f 



Principal species. — Ratibida columnaris,t Amorpha canescens,f Erigeron 

 ramosus,f Symphoricarpus occidentalism Verbena stricta,t Festuca octoflora.f 



Secondary species. — Brauneria pallida, Delphinium carolinianum, Rosa 

 arkansana, Linum sulcatum, Panicum Scribnerianum, Meriolix serrulata,* 

 Euphorbia marginata, Potentilla hippiana, Plantago Purshii,* Hedeoma hispida,* 

 Polygala alba,* Hedeoma hispida.* 



Tertiary species. — Stipa spartea, Aristida purpurea, Allionia linearis, 

 Acerates viridiflora linearis, Osmodium molle,* Anemone cylindrica, Physalis 

 heterophylla, Gaura parviflora, Gaura coccinea.* 



Ruderal species. — Hordeum jubatum, Ixophorus viridis, Panicum capil- 

 lare, Melilotus alba,* Lappula Lappula,* Verbena bracteosa, Allionia nyctaginea, 

 Potentilla monspeliensis, Melilotus officinalis,* Lepidium virginicum.* 



* From earlier aspect. t Forming associations. 



Koeleria cristata is a perennial bunch-grass and a very important 

 sod-former, and may be considered one of the forerunners of the blue- 

 grass. It occurs generally distributed higher up the slopes, where not 

 infrequently it may reach facial rank. Above it seems to be encroach- 

 ing upon the grama and buffalo grasses and so is quite lacking at 

 the crests. Panicum Scribnerianum is likewise a perennial of the 

 bunch habit and is closely associated with Koeleria in distribution, 

 but never appears so abundantly as to become a facies. It is evi- 

 dently more of a mesophyte than the latter and follows it up the 

 slopes. In the formation studied it is mostly confined to the lower 

 part of the middle slopes. It blossoms slightly before Koeleria. 

 Stipa spartea is likewise a bunch-grass and the most xerophytic of 

 these three grasses. It is sparsely distributed upon the uppermost 

 slopes and crests and never forms a facies. It must be rated as an 

 unimportant element in sod-establishment in the formation. 



Almost coincident with the sod-formers listed above, blooms the 

 prairie rose, Rosa arkansana. It is the first woody perennial to bloom 

 and is distributed over upper slopes and crests where in the latter 

 habitat it commonly becomes copiogregarious. Its abundance, 

 large pink flowers, general anthesis, and height make it always one 



