An associational study of Illinois sand prairie . , Tephrosia virginiana, Cycloloma atriplicifolia, Polanisiap:raviolens, Crotonopsis linearis, Monarda punctata, s,nd the westernspecies Cristatella jamesil. Euphorbia corollata Lespedezacapitata are two perennials sometimes seen on blow-sand. In theother sand regions of Illinois the floristic of theblow-sand association varies considerably. The large sandy v/astes are also referred by Gleason to theblowsand association. The origin of these large expanses of baresand is normally the confluence of a number of blowouts. Often,how
An associational study of Illinois sand prairie . , Tephrosia virginiana, Cycloloma atriplicifolia, Polanisiap:raviolens, Crotonopsis linearis, Monarda punctata, s,nd the westernspecies Cristatella jamesil. Euphorbia corollata Lespedezacapitata are two perennials sometimes seen on blow-sand. In theother sand regions of Illinois the floristic of theblow-sand association varies considerably. The large sandy v/astes are also referred by Gleason to theblowsand association. The origin of these large expanses of baresand is normally the confluence of a number of blowouts. Often,however, blowing has started in plowed fields, causing their aban-donment. The sand then drifts acroBS the level surface, Lmobstruct-ed by vegetable growth, and the only plants to be found are annuals,especially Cenchrus and Aristida. It seems that a distinctionbetween the blowsand of the large bare areas and the blowsand ofthe lee slope of the blowouts may be necessary. Floristic andphysiographic differences indicate that these may possibly repre-. Bent different associations. In one field a species of Apocyniamwas the most abundant plant. The large bare sand areas resiststabilization by plaiits and tend to maintain the physical conditions of wind control. In a sense, then, the blowsand might be coneid- ^Gprssen ^ s ered the climax stage of the blowout formation, for it the cul- A mination of the ecological conditions which characterize the form-ation, end also shows a tendency towards self-perpetuation. Onthe other hand, by climax stage we usually mean the highest stageof development of the vegetation of the association. The depositstage vrould then be the climax of the blowout formation, for it hasusually the moat luxuriant vegetation* The animals of the blowsand shov/ a peculiar relation between associations. In some of the lee slope areas in blowouts the growth ofannual plants is sufficient to support a considerable animal popu-lation. In the lar^e bare areas of sand, hov/eve
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