192 PO.UE.E. 



i. Floral glume and palea char- 



taci'ous, panicle spikelike. . . G9 

 i. Floral glume and palea cluirtace- 



ous panicle open 70 



g. Callus naked or with a very few 



short hairs (i) 



i. Spikelets in a long narrow pani- 

 cle V)l 



i. Spikelets in a pyramidal or oval 

 panicle, or short and spikelike. . (n) 

 n. Empty glumes shorter than 

 the floral glume. Spikelets 



large 04 



n. Empty glumes longer than the 

 floral glumes, with no exten- 

 sion of the rachilhi above the 



palea 66 



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

 Fam. 2:31 (1TG3). Chwtaria, Ciirtopoyoii, Arthratherum Beauv. 

 Agrost. 30, 32 (1812). Streptachne II. B. K. Nov. Gen. et. Sp. 

 1:124(1815). Moulinsia Rafin. Ser. Bull. Bot. 1:221 (1830). 

 Stipagrostis Nees, Linn. Soc. 7:290(1833). Sc/n'sfacli no Figaw 

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

 Xees, Seem. liot. ller. 225 (1857). 



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

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

 The 2 empty glumes persistent, keeled, awnless: the floral glumo 

 usually with a blunt hairy callus at the base, narrow rigM 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 off with the stipes and awn. 



Tufted grasses, with the narrow blades often involute, usually 

 flowering late in the season. In the dry regions of tlie Soutlnvest, 

 including ^lexico, many of the species contribute largely toward 

 the upland pasturage. 



