28 Agrostideae 



Flowering glumes awned or mucronate pointed. 



Awn of flowering glume terminal or from between the teeth of the- 



bifld apex, sometimes wanting in Epicampes. 

 Awns 3-branched. 9. ABISTIDA. 



Awns simple. 



Awns articulate with the glumes. 



Awns usually long, geniculate and twisted below, persistent. 



10. STIPA. 



Awns short, caducous, or wanting. 15. EPICAMPES. 



Awns not articulate with the glume. 11. MUHLENBERGIA.. 



Awn dorsal. 



Spikelets articulated with the pedicel below the empty glumes. 



16. POLYPOGON. 



Spikelets not articulated below the empty glumes. 



Empty glumes saccate at the base, several times larger than the 



flowering glumes; inflorescence spike-like. 18. GASTRIDIUM. 

 Empty glumes not saccate, never exceeding the flowering glumes- 

 more than a third. 

 Empty glumes smooth or minutely scabrous along the keel. 



17. AGBOSTIS. 

 Empty glumes more or less hairy; inflorescence spike-like. 



13. A LOPECURUS. 



Flowering glumes awnless. 



Pericarp free from the grain. 14. SPOROBOLUS. 



Pericarp closely adherent to the grain. 



Empty glumes abruptly awn-pointed. 12. PLEUM. 



Empty glumes not abruptly awn-pointed. 17. AGROSTIS. 



9. ABISTIDA L. TRIPLE-AWNED GRASS. 



Plants various in habit and inflorescence, with very 

 narrow, often involute setaceous leaves. Spikelets nar- 

 row, 1-flowered. Glumes 3, narrow, the 2 empty ones 

 carinate ; the third rigid and convolute, bearing 3 

 awns, sometimes rudimentary or rarely wanting. Palea 

 2-nerved. Stamens 3. Styles distinct. Grain free, 

 tightly enclosed in the glumes. 



1. A. Americana bromoides (H. B. K.) Scribn. & Merrill. 

 Culms slender, branching below and tufted, 8-35 cm. high; 

 sheaths shorter than the internodes; ligule reduced to a short 

 fringe ; sterile shoots few, the leaves 2-8 cm. long, involute, 

 setaceous, scabrid above; panicle exserted, spike-like, secund^ 

 purplish, 2-5 cm. long; spikelets on short pedicels; empty 

 glumes narrow, linear, abruptly pointed, scabrous on the back,, 

 the first 3-5 mm. long, second 5-9 mm. long; flowering glume 



