1 (i:! 



plays a prominent part in deterniiniiitr the physiography, caus- 

 ing migrating dunes and blowouts, where the sand shifts so 

 readily tliat it remains entirely without vegetation (PI. XII.. 

 Fig. ] ), or is colonized only Ity those few species able to adapt 

 themselves to the peculiar ecological conditions (PL XIII. I. 

 Some resistance to the wind action is usually offered by the 

 vegetation, so that the area occupied by the blow-sand is lim- 



TABLK III. PASTURED BUNCH-GRASS. 

 (,In pasture up to time of count.) 



Paspalum setaceum 

 Panicum cogaatuin 

 BouteloLia hirsuta 

 ( •pLintia huinifiisa 

 Ambrosia psilostachya 

 Leptiloii caiiailense 

 Mouarda punctata 

 C'assia chanufcrista 

 (Enotliera rliombipetala 

 Euphorbia Geyeri 

 Grotou glandulosus 

 Froeiichia cainpestris 

 Go in me 1 ill a virginica 

 CMirysopsis cam pom in 

 (Jyperus Scliweuiitzii 

 Genclirus tribuloides 

 Lespedeza capitata 



a*aacaacccb 

 o a c a a 1) () a o b 

 o a o o b b o o o 

 b a c b I) b b o o a 

 g f f e e f e Ij f f 

 g f f a f d c o o o 

 a a c a I) b a a 1) b 

 a o a d b a a a a a 

 a o a a a a o o a a 

 o () a a o a b c c a 

 ooaaaaaaao 

 ooaaooaooa 

 o a a o o o o a o o 

 II o a a o o o o o o 

 () o a o o o o o o o 

 o o o o o o o o o a 

 o o o o o o () a o o 



ited. in the present case the covering of bunch-grasses, with 

 their hln'ous roots, and of such other sand-binding plants as 

 the matlike OjiKufin. or the dense clumps of Aiiinr/i/Ki cdni'sci'iis 

 or Chn/sopsis (■<ii)iji(innii. is very effectual. Blowing still takes 

 place, as is shown by the slight excavations between the bunches 

 on the hilltops (PI. XIV.. Fig. 2), but it results merely in a gen- 

 eral redistribution of the sand, the quantity removed being vir- 



* See p. 1511. 



