I6() 



V(tssi<u however, can not grow upon such rapidly shifting sand 

 as Ceiiclinis can. and both are surpassed in this by Cycloluuia 

 afripUcifollmH. Cristafella Jamesii is absolutely confined to 

 blow-sand (PL XX., Fig. 1 ), and disappears when the blowing 

 is stopped. 



Numerous other species may occur, such as Cnifaii gl<indii- 

 losKfi, Euphorbia Get/eri, AiiiJjros/a ^jsilosfdc/ii/a, SporoJxiJioi rnjp- 

 fandrus, Mo/hn/o rerticiHata, and Acerates viridijiora. Others, 

 less abundant, are usually relics of the bunch-grass association, 

 the original occupant of the territory, which have persisted 

 because their sand-binding adaptations have prevented their 

 being undermined and blown away. 



Blowouts of any age may be tilled up and converted into 

 level stretches of blow-sand, covered with the blow-sand asso- 

 ciation already described, but with more ( 'iji-lolomii and less 

 Cdsfiid in the older ones. The vegetation is always sparse, and 

 the blowing of the sand during the fall and winter is sufhcient 

 to prevent the perennials of the bunch-grass association from 

 gaining a foothold. Over wide stretches of blow-sand there is 

 frequently absolutely no vegetation, while on others there is 

 nothing but CijcJohnini, Ai)ih)'Osi(i. ( V/.s-,s/r/, and ('ciichnin. 



Counts in a developing blowout and in a few typical areas 

 of blow-sand are here given. 



