MONOCOTYLEDONOUS OR ENDOGENOUS PLANTS. 611 



spike linear, about IJ'long; glumes by threes, collateral, 

 imbricated, lateral; abortive flowers awnless; awn of the 

 central sessile perfect flower as long as those of the invo- 

 lucre, twice the length (7") of the pales; glumes all awned, 

 the inner setaceous from the base. Northern Texas. 



GYMNOSTICHUM, Schreb. 



Spikelets 2-3 on each joint of the rachis, raised on a 

 short and thick stalk; glumes none, or a single awn-like 

 rudiment. Otherwise as in Elymus. 



G. Hystrix, Schreb. Spike erect, 3'-G' long, lax-flow- 

 ered; spikelets yellowish, 3-4-flowered, smooth or rough- 

 hairy, long-awned; leaves and sheaths smoothish. (Elymus 

 Hystrix, L.) July. Culms 2°-3° high ; rachis 2-edged. 



TRISETUM, Pers. 



Spikelets 2-several-flowered ; lower ^;rt/e^ compressed- 

 keeled, usually bearing a bent awn below the 2-cleft or 

 2-pointed apex ; spikelets in open or spiked panicles. 



T. PALUSTRE, Torr. Smooth; culms weak (1°-1^° 

 long) ; leaves flat, linear ; 2^ctiiicle long and narrow, loose ; 

 spikelets 2-3-flowered; the loicer floiver awnless, the iip>per 

 with a spreading awn and an awn-like rudiment at the 

 base, or rarely both flowers awnless. (Aira pallens, Muhl. ; 

 A. triflora. Ell. ?) Swamps. March and April. Panicle 

 pale, 4-8' long. 



ARRHEIS'ATHERUM, Beauv. 



Tall grasses, with/«^ leaves, and spreading panicles with 

 clustered or ivhorled branches; spikelets 2-flowered, with 

 the awn-like rudiment of a third flo"wer, the loiver one 

 staminate, the upper perfect; glumes membranaceous, con- 

 cave, the upper one as long as the flowers ; j!?rt?ecEJ herba- 

 ceous, the lower one of the perfect flowers slightly awned 



