POACEAE. 19 



spike-like panicle or raceme. 

 Lemmas shorter than the glumes, usually 



with a bent awn rising from the back. Tribe 4. AVENEAE. 

 Lemmas longer than the glumes, awnless 



or with a straight apical awn. Tribe 5. FESTUCEAE. 



TRIBE 1. PANICEAE. 



Spiketets in clustered racemes or spikes. 30. ECHINOCHLOA, 20. 



Spikelets not in clusters. 



Inflorescence a dense spike-like panicle; pedicels 

 bristly. 31. CHAETOCHLOA, 20. 



Inflorescence a loose panicle; pedicels not bristly. 32. PANICUM, 21. 



TRIBE 2. PHALARIDEAE. 



First and second lemmas small, empty and not awned. 33. PHALARIS, 21. 



TRIBE 3. AGROSTIDEAE. 



Lemma with a long terminal awn and closely en- 

 veloping the grain. 



Fruiting lemma thin and membranaceous. 34. MUHLENBERGIA, 22. 



Fruiting lemma firm and indurated. 



Awns 3-branched. 35. ARISTIDA, 22. 



Awns simple, twisted. 36. STIPA, 22. 



Lemma awnless or short-awned and loosely en- 

 veloping the grain. 

 Inflorescence a dense spike-like raceme or 



panicle. 



Lemma awnless. 37. PHLEUM, 23. 



Lemma awned. 



Glumes awnless. 38. ALOPECURUS, 24. 



Glumes awned. 39. POLYPOGON, 24. 



Inflorescence a loose panicle. 



Palea 1 -nerved, stamen 1. 40. CINNA, 24. 



Palea 2-nerved; stamens 3. 



Lemma 1-nerved, rarely 3-nerved; fruit a 



utricle. 41. SPOROBOLUS, 25. 



Lemma 3-5-nerved; fruit a grain. 



Callus with a tuft of long hairs at the 



base. 42. CALAMAGROSTIS, 25. 



Callus naked. 43. AGROSTIS, 26. 



TRIBE 4. AVENEAE. 



Perfect flower only one, the other staminate. 

 Lower flower perfect, awnless; upper staminate, 



awned. 44. HOLCUS, 27. 



Lower flower staminate, long awned; upper 



perfect, awnless. 45. ARRHENATHERUM, 27. 



Perfect flowers two or more. 



Awn of lemma from between the 2 terminal 



teeth. 46. MERATHREPTA, 28. 



Awn of lemma dorsal or none. 



Spikelets large, more than 15 mm. long. 47. AVENA, 28. 

 Spikelets small, less than 15 mm. long. 



Lemma erose-truncate. 48. DESCHAMPSIA, 28. 



Lemma 2-toothed. 49. TRISETUM, 29. 



