GRAMINEAE (GRASS FAMILY) 89 



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



30. 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. — AGEOSiixAE. 

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



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



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

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

 b. Rhachilla not prolonged behind the palea. 



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



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



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



6 6. Ehachilla 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 ihe 



bifid apex. 



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



38. Cinna. Spikelets in a loose panicle. 



Tribe Vn. 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 

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



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



39. 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. 



++ Glumes much exceeding the two florets. 



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



++ +-»■ Glumes exceeded by upper floret. 



41. Sphenopholis. Glumes dissimilar, the second obovate; florets usuaUy awnless. 



4- ■*- Articulation above the glumes. 

 ++ Awns wanting or but a mucronate tip. 



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



++ -H- Awns present. 

 = Awns dorsal, not flattened. 

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

 6. Spikelets less than 1 cm. long ; grain fi-ee. 



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 staniiiiate. upper perfect. 



46. Arrhenatherum. Lower floret long-awneu. upper usually iwnless. 



= = A-.vns from between the tet-tli of tlie bidentiite ap»>x of Ihe lemma, flattened, twisted. 



47. Danthonia. Florets several, not closely approximate, glumes equaling or exct-edinjf the 



uppermost. 



