26 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.YI. 



On the eastern plains they are the characteristic feature. When we get 

 beyond the eastern prairie border, the grasses of xvhich are prevailingly 

 eastern in character, we come upon plains which are generally covered 

 with the very low and tufted grasses peculiar to the drier plains, which 

 form, if not a sward, yet something which serves as a substitute for itr 

 not green, except in early spring, but of a dull grayish hue, and the 

 characteristic species usually rising only a hand-breadth above the sur- 

 face. These are the Buffalo Grasses or Bunch Grasses, which have 

 nourished hordes of bison and flocks of antelopes down to a few years 

 ago, and which are now the capital of the herdsmen or ranchmen, and 

 the nutritious food of increasing numbers of domestic cattle. 



The Buffalo Grass, 2mr excellence, and by its abundance, is Buchloe 

 dactyloides of Engelmann. This is a dioecious Chlorideous grass, the 

 male and the comparatively scarce female plants of which were very 

 naturally thought to be of quite different genera until their relation- 

 ship was suspected and determined by Dr. Engelmann, and this apt 

 name was applied to it. 



Munroa squarrosa of Torrey {Crypsls squarrosa, Nutt.), another much 

 depressed and peculiar Chlorideous grass, is nest in importance. Both 

 are wholly peculiar to this region. 



Bouteloua, a Chlorideous genus of a more ordinary type, of several 

 species, chiefly endemic to this region and to corresponding districts in 

 Mexico, is the third in rank. These are the " Grama^^ Grasses — a name 

 which probably came from the Spanish. They are taller, of sparser 

 growth, and make good forage. 



FleurapMs Jamesi, Torr., is a Buffalo Grass peculiar to the southern 

 part of the region, with some westward extension. 



Vaseya' comata, Gray, represents another peculiar genus ; but the spe- 

 cies extends to the Californian region. 



Eriocoma cuspidata is the Bunch Grass of the very driest soils, and 

 naturally extends across the Great Basin. 



Sporobolus airoides, Torr., abounds over the whole length of the region 

 and beyond it, in the more low and subsaline soils. It is accompanied 

 by BecJcmannia (also a IsTorth Asiatic grass), by BisticJilis mariUma, by 

 one or two wide-spread species of Atropis, &c. The drier ground in 

 many places bears species of Stipa and Aristida. Hordeum jubatuni and 

 the peculiar Elymus Sitanion are characteristic grasses. 



Of other dominant and more or less peculiar forms of vegetation — liav- 

 ing chiefly in view the central tract — we should mention a great white- 

 flowered Argemone {A. Iiispida, Gray) ; Stanleya, and the greater part of 

 the known species of Vesicaria: Gleome integrifolia ; the whole genus 

 Callirrhoe; a> Krameria ; a GlyeyrrJiiza ; the herbaceous Sophora sericea; 

 the principal development of the peculiar genus Fetalostemon, and south- 

 ward numerous species of Balea (which go on increasing into Mexico); 

 also of Psoralea; most of the species of Gaura, several of (Enothera, and 

 the peculiar genus iStenosipJion, allied to Gaura; a good number of Oac- 



