14 BULLETIN 772, U. S. DEPARTMENT OF AGRICULTURE. 
Key to the genera of Agrostideae. 
la. Glumes wanting; a low annual_________________________ 58. CoLEANTHUS, 
1b. Glumes present (the first obsolete in Muhlenbergia schreberi and 
sometimes in Brachyelytrum and Phippsia)_____________________ 
2a. Rachilla articulate below the glumes, these falling with the 
Spikelets ss. he eee RENAN CE SEE EERE ee 3 
3a. Spikelets in pairs in a spikelike panicle, one perfect, the 
other staminate or neuter, the pair falling together_ 63. Lycurus. 
to 
ob. ‘Spikelets#all alike 2" Ve ee ty eee es ee 4 
4a. Glumes long-awned_______________ 62. PoLyPocon. 
4b. Glumesawnless! 22 seus Jee Sl 2 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 22 owe es 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______________=___________ wf 
7a. Fruit dorsally compressed, indurate, smooth and shining, 
Frisia Cohn f Seen RE RE BY ee Cena Oe SRE ae MA Ns ges Ty Ca 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_____ ee 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 
b YE). GO) Vesa eel sic I ST 77. ARISTIDA. 
9b. Awn simple, a line of demarcation between the awn 
and ‘they lemma fire 0 aes elise ee 10 
10a. Awn persistent, twisted and bent, several to 
many times longer than the slender fruit; callus 
Sharp-pointed es 2S see ee 76. STIPA. 
10b.. 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- 
OPC eS i ce ge 11 
lla. Glumes longer than the lemma (lemma equaling ~ 
the glumes in Agrostis spica-venti, A. aequivalvis, 
and “A. thurnbeniand) === ee 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.,PHiEUM. 
13b. Glumes not compressed-carinate, not ciliate 14 
