20 POACEAE. 



TRIBE 5. FESTUCEAE. 



Lemma 3-nerved, rarely 1-nerved. 



Glumes obtuse, very unlike. SO. SPHENOPHOLIS, 30. 



Glumes acute, subequal. 



Panicle close; spikelets 2^-flowered. 51. KOELERIA, 30. 



Panicle looser; spikelets usually many- 

 flowered. 52. ERAGROSTIS, 30. 

 Lemma 5-nerved or more. 



Spikelets with the upper florets sterile and 



folded about each other. 53. MELICA, 31. 



Spikelets with the upper florets perfect, or 



narrow and abortive. 



Stigmas arising below the apex of the ovary. 54. BROMUS, 32. 

 Stigmas arising at the apex of the ovary. 

 Lemmas compressed and keeled. 



Lemma awn-pointed. 55. DACTYLIS, 33. 



Lemmas pointless. 56. POA, 33. 



Lemmas convex or rounded on the back. 



Lemmas acute or awned. 57. FESTUCA, 36. 



Lemmas obtuse and scarious at apex. 58. PANICULARIA, 37.' 



TRIBE 6. CHLORIDEAE. 



Spikelets much flattened; glumes unequal, keeled. 59. SPARTINA, 38. 

 Spikelets subterete; glumes equal, convex. 60. BECKMANNIA, 38. 



TRIBE 7. HORDEAE. 



Spikelets solitary at the notches of the rachis; glumes 



usually acute, or awned. 61. AGROPYRON, 39. 



Spikelets 2-6 at each notch of the rachis; glumes mostly 



long-awned. 

 Rachis not readily breaking into joints; spikelets 



1-7-flowered, 2-4 at each joint. 62. ELYMUS, 40. 



Rachis readily breaking into joints. 



Spikelets 1-flowered, 3 at each joint, only the 



central one perfect. 63. HORDEUM, 41. 



Spikelets 1-5-flowered, 2-4 at each joint, all 

 perfect. 64. SITAMON, 42. 



30. ECHINOCHLOA. 



Coarse annuals with long leaves; spikelets 1-flowered, with 

 sometimes a staminate flower below, nearly sessile in 1 -sided 

 spikes or racemes; glumes unequal, hispid, mucronate; sterile 

 lemma similar and usually awned from the apex. 



Echinochloa crus-galli (L.) Beauv. Barnyard^ Grass. Glabrous; stems 

 stout, branching at the base, 30-120 cm. tall; panicle dense, 10-20 cm. long, 

 composed of many ascending or spreading racemes; spikelets green or purple, 

 3 mm. long, densely crowded in 3 or 4 rows; sterile lemma awned or in some 

 forms awnless. Introduced from Europe, a weed in moist ground. 



31. CHAETOCHLOA. 



Annual grasses with erect stems and flat leaves ; spikelets with 

 one perfect flower and rarely also a staminate one, in spike-like 



