Pool: THE VEGETATION OF THE SANDHILLS OF NEBRASKA 231 



the region. A variety, C. ovatus puhescens, is more common in the 

 sandhills than the glabrous form. This low brush with pubescent 

 leaves and petioles occurs in characteristic tangles of fine woody 

 stems about two feet in height. The individual plants become much 

 branched and very bushy so that during midsummer when they arc 

 in full leaf they present a conspicuous appearance. The typical 

 growth habits of the plant result in the development of such low 

 bushy patches which vary from 3 to 30 feet in diameter with an 

 approximately circular outline. The smaller-sized patches are more 

 plentiful and typical. Such patches frequently occur as a conspicu- 

 ous modification of the bunch-grass association over large areas. 

 Sometimes very regular colonies with a uniform diameter of about 

 one and one-half yards and nearly equal intervals greatly change the 

 typical appearance of the association. Many of the highest hills 

 south of the Dismal River in Thomas and Logan counties are domi- 

 nated by this species. The density of the plants, especially in the 

 larger colonies, often becomes so great that few species invade such 

 areas. Consequently when the leaves have fallen from the plants 

 in a local area controlled by Ceanothus a peculiar barrenness 

 becomes prominent. 



Rosa arkansana assumes a position of importance in this asso- 

 ciation in various parts of the region. Over the less exposed slopes 

 the wild rose becomes aggregated into dense brush. The low tangle 

 of flexible, thorny stems is often controHing in patches several acres 

 in extent over the uplands. Societies of this nature are especially 

 noteworthy constituents of the early aestival period when thousands 

 of large showy blossoms charge the atmosphere with delicate per- 

 fume. These patches occur in such dense stand as to resist invasion 

 by bunch-grasses and bunch-grass interstitials to a high degree. 

 The species can not endure serious movements of the surface soil 

 and is slow to recover after being buried by the sand so that it is not 

 often found in abundance in exposed situations. Even in protected 

 situations, as on the lee slopes of hills with active blow-outs, the 

 rose soon gives way before the encroaching sand and quite early 

 yields up its habitat to species better fitted to endure and finally to 

 conquer these conditions. 



Toward the southwestern limits of the sandhill region Arte- 

 misia iilifolia becomes very abundant as a member of this associa- 

 tion. This sagebrush covers many acres of land, somewhat harder 

 than typical bunch-grass land, with its characteristic gray bushlike 



