POACEAE. 



33 



Tribe 4. Agrostideae. 



Lemma with a long terminal awn and closely en- 

 veloping the grain. 

 Fruiting lemma thin and membranaceous. 55. 



Fruiting lemma firm and indurated. 56. 



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. 

 Rachilla not prolonged behind the 

 floret. 

 Lemma awned. 

 Glumes awned. 

 Glumes awnless. 



Glumes saccate at base; palea 



none. 

 Glumes not saccate at base; palea 

 present. 

 Inflorescence not spike-like. 

 Palea 1 -nerved; stamen 1. 

 Palea 2-nerved; stamens 3. 



Glumes none; plant very small. 

 Glumes 2; plant larger. 



Callus with a tuft of long hairs at the 



base. 

 Callus naked. 



muhlenbergia, 37. 

 Stipa, 38. 



Tribe 5. Aveneae. 



Perfect flower only one, the other staminate. 

 Lower flower perfect, awnless; upper stami- 

 nate, awned. 65. 

 Lower flower staminate, long awned; upper 

 perfect, awnless. 66. 

 Perfect flowers two or more. 



Rachilla not prolonged beyond the upper 



flower. 

 Rachilla prolonged beyond the upper flower. 

 Awn of lemma from between the two ter- 

 minal teeth. 

 Awn of lemma dorsal or none. 



Spikelets large, more than 15 mm. 



long. 

 Spikelets small, less than 15 mm. 

 long. 

 Lemma erose-truncate. 70. Deschampsia, 



Lemma 2-toothed. 71. Trisetum, 47. 



Holcus, 44. 

 Arrhenatherum, 45. 



67. Aira, 45. 



68. Danthonia, 45. 



69. Avena, 46. 



46. 



Tribe 6. Festuceae. 



Lemma 3-nerved, rarely l-nerved. 



Panicle loose; spikelets usually many-flowered. 

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

 Spikelets of two kinds in the same inflores- 

 cence, perfect and sterile. 

 Spikelets all alike in the same inflorescence. 



4 



72. Eragrostis, 48. 



73. 



74. 



Cynosurus, 48. 

 Koeleria, 48. 



