THE AGRICULTUEAL GRASSES OF THE UNITED STATES. 57 

 ALOrECURUS ALPINUS. 



A species reseiiibliiig" the Alopecuriis pratensls grows in alpiue mead- 

 ows iu the Eoeky ]Mouiitains. 



♦ Aristida. 



This is a oeuus of grasses of which many species are found in the 

 United States, Mexico, and South America. They are principally an- 

 nual grasses aiid are of little value, unworthy of cultivation, but in 

 some regions, particularly the arid Western plains, they furnish a por- 

 tion of the wild forage. 



Aristida purpurascens. (Beard grass, Three-awn ed grass.) 



This species grows iu many of the States east of the Mississix)pi Elver, 

 usually- in poor, sandy, or clay soil, in thin woods or barren fields. It 

 grows usually about 2 feet high, with a slender, smooth culm, narrow 

 leaves, which are inclined to be involute when dry, and with a narrow, 

 loose, spike-like panicle a foot or more long, which usuallj' gracefully 

 droops or bends. The branches are short, appressed, mostly single at 

 the joints of the axis, and each having seldom more than two or three 

 spikelets. The spikelets are single-flowered, the outer glumes are nar- 

 rowly linear, four or five lines long, the lower one slightly the longer, 

 both usually sharply pointed. These glumes inclose the flower, which 

 consists of a slender, almost cylindrical flowering glume about three lines 

 long, having a short-pointed, hany base, and along, three-bearded apex. 

 This glume enrolls the narrow, thin palet and the floral organs. The 

 awns or beards are widely spreading, the middle one about an inch long, 

 the two lateral ones somewhat shorter. (Plate 35.) 



Aristida purpurea. (Western Beard grass. Purple Three-awned 



grass.) 



This species prevails extensively west of the Mississippi River, from 

 British America to Mexico, and is abundant on the plains of Kansas, 

 Xew 3Iexico, and Texas. It grows usually 1 to Ih feet high, with 

 slender culms, branching at the base, and with short, involute leaves. 

 It is an exceedingly variable species, or there are several distinct va- 

 rieties. The panicle is 6 to 8 inches long, rather narrow, erect, or flex- 

 uous. The spikelets are much like those of the preceding species, but 

 usually larger and with longer awns or beards. In some varieties these 

 awns are 2 or :> inches long, widely diverging, and purplish colored, the 

 whole panicle having a graceful and feathery appearance. 



Like the other species, this is an inferior grass, but furnishes a con- 

 siderable amount of wild forage. (Plate 30.) 



Aristida bromoides. 



A small, apparently annual, grass, growing in Xew Mexico, Arizona, 

 and Southern California. It grows in tufts, the culms from 6 to 12 

 inches high, slender, erect, and generally unbrauched. The spikelets 

 are seven to eight lines long, including the awn. (Plate 37.) 



