32 



POACEAE. 



Spikelets with one perfect flower. 



Spikelets with a staminate or neutral flower in 

 addition to the perfect one. 

 Rachilla jointed below the glumes which fall 



with the seed. 

 Rachilla jointed above the glumes which do 

 not fall with the seed. 

 Imperfect flower below the perfect. 



Arrhenatherum in 

 Imperfect flower above the perfect. 



Holcus in 

 Spikelets with only one flower. 



Rachilla jointed below the glumes which fall 

 with the seed. 

 Spikelets compressed dorsally or terete; 



glumes 2. 

 Spikelets compressed laterally; glumes 

 none. 

 Rachilla jointed above the glumes which do 

 not fall with the seed. 

 First two lemmas empty, variously modi- 

 fied, the third with a flower. 

 First lemma flower-bearing. 



Spikelets crowded in two rows in one- 

 sided spikes. 

 Spikelets not in one-sided spikes. 

 Spikelets in two opposite rows. 



Hordeum in 

 Spikelets not in two opposite rows. 



Tribe 1. 

 Tribe 2. 



Tribe 3. 

 Tribe 7. 



Tribe 8. 

 Tribe 4. 



Paniceae. 

 Oryzeae. 



Phalarideae. 

 Chlorideae. 



HORDEAE. 



Agrostideae. 



Tribe 1. Paniceae. 



Spikelets in clustered racemes or spikes. 

 Spikelets not in clusters. 



Inflorescence a dense spike-like panicle; pedicels 



bristly. 

 Inflorescence a loose panicle; pedicels not bristly. 

 Lemma one; spikelets in two rows on a flat- 

 tened rachis. 

 Lemmas two; spikelets not in two rows on a 

 flattened rachis. 



47. Echinochloa, 34. 



48. Chaetochloa, 35. 



49. Paspalum, 35. 



50. Panicum, 35. 



Tribe 2. Oryzeae. 

 Spikelets perfect; glumes none; lemmas awnless. -51. Homalocenchrus, 36. 



Tribe 3. Phalarideae. 



First and second lemmas narrow, bristle-like; 



glumes strongly compressed. 

 First and second lemmas broadly ovate or oblong; 

 glumes not strongly compressed. 

 Glumes very unequal; first and second lemmas 



much shorter than the glumes, awned. 

 Glumes nearly equal, scarcely exceeding the 

 first and second lemmas which are awnless 

 or short-awned. 



52. Phalaris, 36. 



53. Anthoxanthum, 37. 



54. Hierochloe, 37. 



