192 POACE^. 



i. Floral glume and palea cliar- 



taceous, panicle spikelike. . . 69 

 i. Floral glume and palea chartace- 



ous jDanicle open 70 



g. Callus naked or witli a very few 



short hairs (i) 



i. SjDikelets in a long narrow pani- 

 cle 61 



i. Spikelets in a pyramidal or oval 

 panicle, or short and spikelike. . (n) 

 n. Empty glumes shorter than 

 the floral glume. Spikelets 



large 64 



n. Empty glumes longer than the 

 floral glumes, with no exten- 

 sion of the rachilla above the 



palea 66 



45. (108). Aristida L. Sp. PI. 82 (1753). Kielboul Adans. 

 Fam. 2:31 (1763). Chmtaria, Curtopogon, Arthratherwn BesLuy . 

 Agrost. 30, 32 (1812). Streptachm H. B. K. Nov. Gen. et. Sp. 

 1:124(1815). MouUnsia Eafin. Ser. Bull. Bot. 1:221 (1830). 

 Stipagrosfis Nees, Linn. Soc. 7:290(1833). ScJi isfacJnie Yigsir. 

 & De Not. Mem. Acad. Torin. (II.) 12:252 (1852). Ortachne 

 Xees, Seem. Bot. Her. 225 (1857). 



Spikelets 1-flowered, narrow on slender pedicels or nearly sessile 

 in a terminal panicle, rachilla articulate above the empty glumes. 

 The 2 empty glumes persistent, keeled, awnless; the floral glume 

 usually with a blunt hairy callus at the base, narrow rig'd entire, 

 with a terminal trifid awn, or the lateral awns erect or obsolete. 

 Palea small or obsolete, 2-nerved. Stamens 3. Styles distinct. 

 Grain narrow, enclosed in the hard floral glume, but free from it, 

 the whole falling oS with the stipes and awn. 



Tufted grasses, with the narrow blades often involute, usually 

 flowering late in the season. In the dry regions of the Southwest, 

 including Mexico, many of the species contribute largely toward 

 the upland pasturage. 



