14 BULLETIN 772, U. S. DEPARTMENT OF AGRICULTURE. 



Key to the genera of Agrostideae. 



la. Glumes wanting; a low annual 58. COLEANTHTTS. 



Ib. Glumes present (the first obsolete in ^fuJllcnJ)crgia scJircbcri and 



sometimes in Brachyelytrum and Phippsia) 2 



2a. Rachilla articulate below the glumes, these falling with the 



spikelet 3 



3a. Spikelets in pairs in a spikelike panicle, one perfect, the 



other staminate or neuter, the pair falling together- 63. LYCUBUS. 



3b. Spikelets all alike 4 



4a. Glumes long-awned_: 62. POLYPOGON. 



4b. Glumes awnless 5 



5a. Rachilla not prolonged behind the palea ; panicle 

 dense and spikelike ; glumes united toward the 



base, ciliate on the keel 61. ALOPECURUS. 



5b. Rachilla prolonged behind the palea ; panicle nar- 

 row or open, not dense; glumes not united, not 



ciliate on the keel , 6 



6a. Panicle narrow; lemma with a slender bent 



twisted awn from the bifid apex 60. LIMNODEA. 



6b. Panicle open and drooping ; lemma with a minute 



straight awn just below the entire apex 59. CINNA. 



2b. Rachilla articulate above the glumes 7 



7a. Fruit dorsally compressed, indurate, smooth and shining, 



awnless 74. MILIUM. 



7b. Fruit laterally compressed or terete, awned or awnless 8 



8a. Fruit indurate, terete, awned, the nerves obscure ; callus 



well developed, oblique, bearded 9 



9a. Awn trifid, the lateral divisions sometimes short, 

 rarely obsolete (when obsolete no line of demar- 

 cation between awn and lemma as in the 



next) 77. ABISTIDA. 



9b. Awn simple, a line of demarcation between the awn 



and the lemma 10 



lOa. Awn persistent, twisted and bent, several to 

 many times longer than the slender fruit ; callus 



sharp-pointed 76. STIPA. 



lOb. Awn deciduous, not twisted, sometimes bent, 

 rarely more than 3 or 4 times as long as the 

 plump fruit ; callus short, usually obtuse- 75. ORYZOPSIS. 

 8b. Fruit thin or firm, but scarcely indurate, if firm, the 

 nerves prominent or evident ; callus not well devel- 

 oped 11 



lla. Glumes longer than the lemma (lemma equaling 

 the glumes in Agrostis spica-venti, A. aequivalvis, 



and A. thurberiana) 12 



12a. Panicle feathery, capitate, nearly as broad as 



long; spikelets woolly 66. LAGURUS. 



12b. Panicle not feathery; spikelets not woolly 13 



13a. Glumes compressed-carinate, abruptly mu- 

 cronate, stiffly ciliate on the keels; 

 panicle dense, cylindric or ellipsoid- 64. PHLEUM. 

 13b. Glumes not compressed-carinate, not ciliate 14 



