GRAMINEAE (GRASS FAMILY) 89 



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

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

 panicle exserted, cylindrical. 



++ ++ Glumes not conspicuously compressed ; spikelets in open or narrow panicles. — AcBOsiiNAE. 



= 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 8-5-nerved, awued or awnless ; pericarp adherent to the grain. 



a. Floret not stipltate ; palea 2-nerved ; stamens 8. 



&. KhachlUa not prolonged behind the palea. 



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

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

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



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



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



long hairs ; lemma short-awned below the middle. 



86. Aininophila. Perennial; panicle dense and spike-like ; prolonged rhachilla and callus with 



short hairs ; lemma awnless. 

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

 bifld apex, 



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



88. Cinna. Spikelets in a loose panicle. 



Tribe VII. AV^NEAE. 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 

 SphenophoUa and Koeleria) ; the caDus and usually the rhachilla-joints hairy. 



* Ehachilla 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 2-8everal-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. 



++ +-f Glumes exceeded by upper floret. 



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



+- -I- Articulation above the glumes. 

 ++ Awns wanting or but a mucronate tip. 



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



++ ++ Awns present. 

 = Awns dorsal, not flattened. 

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

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



43. Trisetum. Lemma keeled, bidentate, awn arising from above the middle. 



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



h 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. 



46. Arrhenatheram. Lower floret long-awneu, upper usually awnless, 



^ — Awns from between the toeth of the bidentate apex of the lemma, flattened, twisted. 



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



uppermost. 



