POACEAE. 33 



Tribe 4. AGROSTIDEAE. 



Lemma with a long terminal awn and closely en- 

 veloping the grain. 



Fruiting lemma thin and membranaceous. 55. MUHLENBERGIA, 37. 



Fruiting lemma firm and indurated. 56. STIPA, 38. 



Lemma awnless or short-awned and loosely en- 

 veloping the grain. 

 Inflorescence a dense spike-like raceme or 



panicle. 

 Lemma awnless. 



Rachilla prolonged behind the floret. 59. GASTRIDIUM, 39. 

 Rachilla not prolonged behind the 



floret. 57. PHLEUM, 38. 



Lemma awned. 



Glumes awned. 58. POLYPOGON, 39. 



Glumes awnless. 



Glumes saccate at base; palea 



none. 59. GASTRIDIUM, 39. 



Glumes not saccate at base; palea 



present. 60. ALOPECURUS, 39. 



Inflorescence not spike-like. 



Palea 1 -nerved; stamen 1. 61. CINNA, 40. 



Palea 2-nerved; stamens 3. 



Glumes none; plant very small. 62. COLEANTHUS, 40. 



Glumes 2; plant larger. 



Callus with a tuft of long hairs at the 



base. 63. CALAMAGROSTIS, 41. 



Callus naked. 64. AGROSTIS, 42. 



Tribe 5. AVENEAE. 



Perfect flower only one, the other staminate. 

 Lower flower perfect, awnless; upper stami- 

 nate, awned. 65. HOLCUS, 44. 

 Lower flower staminate, long awned; upper 



perfect, awnless. 66. ARRHENATHERUM, 45. 



Perfect flowers two or more. 



Rachilla not prolonged beyond the upper 



flower. 67. AIRA, 45. 



Rachilla prolonged beyond the upper flower. 

 Awn of lemma from between the two ter- 

 minal teeth. 68. DANTHONIA, 45. 

 Awn of lemma dorsal or none. 



Spikelets large, more than 15 mm. 



long. 69. AVENA, 46. 



Spikelets small, less than 15 mm. 



long. 



Lemma erose-truncate. 70. DESCHAMPSIA, 46. 



Lemma 2-toothed. 71. TRISETUM, 47. 



Tribe 6. FESTUCEAE. 



Lemma 3-nerved, rarely l-nerved. 



Panicle loose; spikelets usually many-flowered. 72. ERAGROSTIS, 48. 

 Panicle dense, spike-like; spikelets 2-4-flowered. 

 Spikelets of two kinds in the same inflores- 

 cence, perfect and sterile. 73. CYNOSURUS, 48. 

 Spikelets all alike in the same inflorescence. 74. KOELERIA, 48. 



4 



