402 GRAMINE^E. (GRASS FAMILY.) 



***** Flowering glumes 3 to 5 or many-nerved, more or less involute, the upper two or 

 more empty or imperfect. 



39. Melica. Spikelets 2 to many-flowered, usually convolute around each other, the upper 



1 to 3 smaller and imperfect. Outer glumes awnless, the lower 3 to 5-nerved, the 

 upper sometimes 7 to 9-nerved, the lateral nerves vanishing within the scarious mar- 

 gin: flowering glumes thicker, rounded or flattish on the back, 5 to 9-nerved, the 

 lateral nerves vanishing below the apex, the central one sometimes ending in a point 

 or awn : palets ciliate on keels and apex. 



****** Flowering glumes 5 to many-nerved, the upper one empty, style short, stigmas 

 plumose : leaves generally narrow, without transverse veins. 



40. Distielilis. Spikelets dioecious, many-flowered, compressed, crowded in a dense spi- 



cate or capitate or rather open panicle. Outer glumes herbaceous, narrow, keeled : 

 flowering glumes rigidly membranaceous or subcoriaceous, keeled : keels of the palet 

 narrowly winged. 



41. Poa. Spikelets somewhat compressed, usually 2 to 5-flowered, in a narrow or loose 



and spreading panicle, the rhachis between the flowers glabrous or hairy, the flowers 

 generally perfect, occasionally dioecious. Outer glumes keeled, 1 to 3-nerved, not 

 awned : flowering glumes 5 to 7-nerved, the intermediate nerves frequently obscure, 

 often with a few loose or webby hairs at the base. 



42. Grapliephorum. Spikelets 2 to 5-flowered, rather terete, in a narrow or loose pani- 



cle. Outer glumes nearly equalling the rather remote flowers, keeled, 3 to 5-nerved: 

 flowering glumes rounded on the back or obscurely keeled, faintly or strongly nerved ; 

 a tuft of villous hairs at the base of each flower. 



43. Glyceria. Spikelets several to many-flowered, terete or flattish, in a narrow or diffuse 



panicle, the rhachis smooth and readily disarticulating between the flowers. Outer 

 glumes unequal, 1 to 3-nerved : flowering glumes obtuse, more or less denticulate at 

 the apex, rounded (never keeled) on the back, 5 to 9-nerved, the nerves separate and 

 all vanishing before reaching the apex. 



44. Festuca. Spikelets 3 to many-flowered, variously panicled, pedicellate, rhachis not 



hairy. Outer glumes unequal, the lower 1-nerved, and the upper 3-nerved, narrow 

 and keeled : flowering glumes narrow, rounded on the back, more or less distinctly 

 3 to 5-nerved, acute or tapering into a straight awn. 



45. Bromus. Spikelets 5 to many-flowered, in a dense or lax or diffuse panicle, subterete 



or compressed, the rhachis between the flowers glabrous. Outer glumes more or less 

 unequal, acute, awnless or short mucronate, 1 to 9-nerved : flowering glumes rounded 

 on the back or compressed and keeled, 5 to 9-nerved, acute, or awned from below the 

 mostly 2-cleft apex. 



Tribe IX. Spikelets one to many-flowered, sessile on the teeth or excavations of the rha- 

 chis of the simple stout spike. HORDEACE.E. 

 * Spikelets solitary at the nodes, 3 to many-flowered, rarely 2-flowered. 



46. Agropyrum. Spikelets compressed, alternately sessile on the continuous or slightly 



notched rhachis. Outer glumes nearly equal and opposite, 1 to 3-nerved, scarcely 

 keeled, tapering to a point or awned : flowering glumes similar, rounded on the back, 

 3 to 7-nerved, pointed or awned from the apex : the two prominent nerves of the 

 upper palet almost marginal and scabrous ciliate. 



* * Spikelets two to many at each joint of the rhachis. 



47. Hordeum. Spikelets 1 -flowered, with an awl-shaped rudiment of a second flower, 



in a dense spike, in clusters of 2 or 3 ; central spikelet of each cluster perfect and 

 sessile, the lateral ones short-stalked and imperfect or abortive. Outer glumes side 

 by side, two to each spikelet or 6 at each joint, slender and awn-pointed or bristle- 

 form : flowering glume herbaceous, shorter, oblong or lanceolate, rounded on the back, 

 not keeled, 5-nerved, acute or long-awned. 



48. Elymus. Spikelets 2 to 4 at each joint, sessile, 1 to 6-flowered. Outer glumes two for 



each spikelet, nearly side by side in its front, forming a kind of involucre for the clus- 

 ter, narrow, rigid, 1 to 3-nerved, acuminate or awned : flowering glumes herbaceous, 

 oblong or lanceolate, rounded on the back, not keeled, acute or awned. 



