GBAMINEAE (GRASS FAMILY) 89 



29. Phleum. Lemma hyaline, awnless, glumes abruptly aristate ; panicle exserted, cylindrical. 

 '60. Alopecurus. Lemma hyaline, awned below the middle ; palea none ; glumes not aristate ; 

 panicle exserted, cylindrical. 



H- -H- Glumes not conspicuously compressed ; spikelets in open or narrow panicles. AGROST}NAE. 

 = Lemma 1 (rarely 3) -nerved, awnless ; pericarp readily separating from the grain. 



81. Sporobolus. Lemma as long as or longer than the glumes ; culms wiry or rigid. 



= = Lemma 3-5-nerved, awued or awnless ; pericarp adherent to the grain. 

 a. Floret not stipitate ; palea 2-nerved ; stamens 3. 

 b. Khachilla not prolonged behind the palea. 



82. Agrostis. Glumes longer than the floret, awnless ; panicle usually open. 

 33. Polypogon. Glumes longer than the floret, awned ; panicle spike-like. 

 84. Calamovilfa. Glumes shorter than the floret, awnless. 



b b. Rhachilla prolonged behind the palea, bristle-like. 



35. Calamagrostis. Perennial ; panicle loose or contracted ; prolonged rhachilla and callus with 



long hairs ; lemma short-awned below the middle. 



36. Ammophila. Perennial ; panicle dense and spike-like ; prolonged rhachilla and callus with 



short hairs ; lemma awnless. 



37. Apera. Annual ; panicle loose ; the prolonged rhachilla naked ; lemma long-awned below the 



bifid apex. 



a a. Floret stipitate ; palea 1-2-nerved ; stamen 1. 



88. Cinna. Spikelets in a loose panicle. 



Tribe VII. AVENEAE. Spikelets 2-several-flowered, panicled ; rhachilla prolonged behind the 

 palea of uppermost floret except in Aira; glumes usually longer than the first floret ; 1 or 

 more of the florets awned on the back or from the teeth of the bifid apex (or usually awnless in 

 SphenopJioUs and Koeleria) ; the callus and usually the rhachilla-joints hairy. 



* Rhachilla not prolonged behind the palea of uppermost floret ; spikelets 2-flowered, both perfect. 



89. Aira. Florets approximate ; glumes broad, boat-shaped. 



* * Rhachilla prolonged behind the palea of uppermost floret ; spikelets 2-several-flowered. 



*- Articulation below the glumes ; spikelets falling entire or the glumes and lowest floret together. 



H- Glumes much exceeding the two florets. 



40. HolCUS. Lower floret stipitate, awnless, upper with a hook -like awn. 



H- -M- Glumes exceeded by upper floret. 



41. SphenopholiS. Glumes dissimilar, the second obovate; florets usually awnless. 



-- -t- Articulation above the glumes. 

 H- Awns wanting or but a mucronate tip. 



42. Koeleria. Glumes unequal, exceeded by the upper floret. 



H- -H- Awns present. 

 = Awns dorsal, not flattened. 

 a. Spikelets 2-several-flowered ; florets all perfect or the uppermost imperfe 



b. Spikelets less than 1 cm. long ; grain free. 

 4-'?. Trisetum. Lemma keeled, bidentate, awn arising from above the middle. 



44. Deschampsia. Lemma convex, awn from the middle or below. 



b b. Spikelets more than 1 cm. long ; grain adherent to the palea. 



45. Avena. Florets approximate, exceeded by the striate glumes. 



a a. Spikelets 2-flowered ; lower floret staminate, upper perfect. 

 4fi. Arrhenatherum. Lower floret long-awneu, upper usually awnless. 



<= = Awns from between the teeth of the bidentate apex of the lemma, flattened, twisted. 

 47. Danthonia. Florets several, not closely approximate, glumes equaling or exceeding the 

 uppermost. 



