DESCRIPTIONS OF TRIBES AND GENERA. 95 



TRIBE VIII. AGBOSTIDEJS. 



Spikelets usually all $ , one-flowered, rachilla some- 

 times prolonged beyond the palea. Empty glumes often 

 somewhat unequal, usually as long as or longer than the 

 flowering glume, very rarely none ; palea usually two- 

 nerved ; grain not sulcate ; embryo usually small ; 

 starch-grains compound. 



A. Flowering glume indurated at maturity (at least firmer 

 in texture than the empty glumes} and very closely en- 

 veloping the fruit. (Sub-tribe Stipece.) 

 a. Spikelets all $ , fertile. 



a. Eachilla not prolonged beyond the palea. 



I. Flowering glume deeply three-cleft, each 

 segment awned ; palea two-awned. 



100. Amphipogon. 



II. Flowering glume entire, awned ; awn trifid 

 or three-branched (lateral divisions often 



very short) 1O1. Aristida. 



III. Flowering glume entire [two-toothed or 

 bifid] ; awn simple. 



1. Lodicules usually three, flowering 

 glume and palea finally very hard. 

 * Flowering glume narrow. Awn 



twisted, stout, persistent. 



102. Stipa. 



** Flowering glume broad, awn 

 slender, falling off after flowering, 

 t Flowering glume elliptical or 

 ovate, not gibbous at top ; awn 

 terminal or but slightly ec- 

 centric ; embryo small. 



103. Oryzopsis. 



ft Flowering glume obliquely 

 obovate, gibbous at top ; awn 

 decidedly eccentric ; embryo 

 small. 



O Palea membranaceous, 

 without nerves or keel. 



104. Nassella. 



