THE GREAT AMERICAN DESERT 



225 



sod, but with no standing water. The well-developed sod is a condition 

 that causes the vegetation of the valleys to be quite distinct in appear- 

 ance from that of the uplands, with the tufted appearance of the bunch- 

 grass association. Such dry valleys are very common throughout the 

 southern portion of the Sand Hills. They yield an abundant crop of 



Fig. 11. A Deep Blow-out; Redfieldia on the slopes. 



fine hay during moist seasons and always afford very fine forage because 

 of the presence of buffalo grass {Bulbilis dactyloides) , and grama grass 

 (Bouteloua oligostacliya) in considerable quantity. The soil of these 

 valleys is not so sandy as the uplands. This with the water table nearer 

 the surface makes possible the culture of certain agricultural crops, if 

 the proper care is taken to prevent the soil from blowing. When the 

 sod is broken in a dry valley where a considerable area of nearly flat soil 



VOL. LXXX. — 16. 



