100 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



1. Pappophorum wrightii S. Wats., Amer. Acad. Arts and Sci. Proc. 



18: 178. 1883. 



Navajo County to Mohave County, south to Cochise, Santa Cruz, 

 and Pima Counties, 3,000 to 5,500 feet, rocky hills and plains, July to 

 October. Texas to Arizona and Oaxaca; Peru and Bolivia. 



Reported to have considerable forage value. 



2. Pappophorum mucronulatum Nees, Agrost. Bras. 412. 1829. 

 Cochise and Pima Counties, open groimd and low places on plains, 



July to September. Texas, Arizona, and northern Mexico; South 

 America. 



3. Pappophorum bicolor Fourn., Mex. PI. 2: 133. 1886. 



Santa Cruz River at La Noria, Santa Cruz County {Mearns 1175), 

 open valley land. Texas, southern Arizona, and Mexico. 



18. SCLEROPOGON. Burrograss 



Monoecious or dioecious, stoloniferous perennial, with short flexu- 

 ous leaf blades and narrow panicles; staminate spikelets several- 

 flowered; lemma similar to the glumes, mucronate; palea obtuse, 

 shorter than the lemma; pistillate spikelets several-flowered, the 

 florets falling together, the lowest one with a sharp-bearded callus, 

 the upper ones reduced to awns; nerves of the lemmas extending into 

 slender, spreading awns. 



1. Scleropogon brevifolius Phil., An. Univ. Chile 36: 206. 1870. 



Apache, Navajo, Mohave, Graham, Cochise, and Pima Counties, 

 at relatively low altitudes, mesas, open slopes, and valleys, May to 

 October. Texas, Colorado, and Arizona to central Mexico. 



Although grazed by livestock before reaching maturity, this grass 

 is inclined to increase on heavily grazed ranges at the expense of more 

 palatable species. The pointed awns penetrate clothing and wool. 



19. AGROPYRON. Wheatgrass 



Perennials, often with creeping rhizomes; culms erect or decumbent; 

 spikes usually erect; glumes equal, firm, acute or awned, usually 

 shorter than the first lemma; lemmas firm, rounded on the back, 

 acute or awned, the awn straight or divergent. 



Most of the species furnish forage, and some of them are among the 

 most valuable range grasses of the western United States. In the 

 valleys these grasses may grow in sufficient abundance to produce 

 . wild hay. Slender wheatgrass (A. trachycaulum) has been cultivated 

 in the Northwestern States. Western wheatgrass (A. smithii) 

 furnishes a good deal of forage in Arizona and in open depressions is a 

 source of hay. The species with strong creeping rhizomes are valu- 

 able soil binders. Quackgrass (A. repens) is a troublesome weed. 

 The rhizomes of this species, often adulterated with Bermuda grass, 

 are used in treating urinary disorders. 



Key to the species 



1. Plants with creeping rhizomes; leaf blades firm, strongly nerved (2). 



2. Glumes acuminate or gradually tapering into a short awn, more or less 

 asymmetric, the nerves usually obscure. _„ _ , 1. A. smithii. 



