108 LANDS OF THE ARID REGION OF THE UNITED STATES. 
turf is never seen. Where a sward is seen in moist places, about springs 
and in glades, the verdure consists in chief part of other plants, sedges and 
reeds. 
Of the bunch grasses the Poas are by far the most abundant. Of this 
genus nine species were obtained, but this gives an inadequate idea of the 
variety. Of one species alone Dr. Vasey has enumerated nine varieties, and 
advances the opinion that several will be eventually considered as species. 
They are found at all altitudes, mostly on the slopes. Perhaps the most 
important single species in that region is the Bouteloua oligostachya, the 
so called “Circle grass”. It has a peculiar habit of forming partial or 
complete circles on the ground, with areas of bare ground in the center. 
These turfy rings are comparatively narrow, often not more than three or 
four inches in width, while the circles are from two to four feet in diameter. 
The form is not always circular, but often assumes irregular shapes. 
The grass is sweet and nutritious, but its chief value consists in its power 
to resist inclement seasons, as it cures standing, like the “ Buffalo grass” of 
the Great Plains. 
Another very valuable grass is the Hriocoma cuspidata, which is 
known by the name of “Sand grass”. It grows at much lower altitudes, 
and is properly a valley grass. It has a solitary, scattering habit, or at 
least the bunches are small and turfless. Horses and cattle select it with 
care from among other species, and it seems especially nutritious. It has 
a large black grain, which is often collected by the Indians for food. 
A remarkable lowland grass is the Vilfa (Sporobolis atroides). It 
has something of the appearance of ‘‘ Hair grass”, with a widely spreading 
purple panicle and large perennial roots. The old culms persist at the base, 
and with the new ones form thick and almost woody tufts. These tufts are 
scattered about in the strongly akaline soils of the river bottoms, and 
are extensively pastured by large-herds of cattle. A marked characteristic 
of this grass, common, however, to several others, is its power to take up 
saline matter, which gives to the whole plant a salty taste. The effect of 
this upon the stock feeding upon it is doubtful, judging from the conflicting 
reports of the inhabitants; but it seems that when cattle are first pastured 
upon it they are injured by the excess of salt, but that after a time they 
