GENERA OF GRASSES OF THE UNITED STATES. maa 
Key to the genera of Andropogoneae. 
la. Spikelets all perfect, surrounded by a copious tuft of soft hairs______ 2 
2a. Rachis continuous, the spikelets falling; spikelets of the pair un- 
Ccrenbliya we Ce NM ease Se ee ee 3 
8a. Racemes in a narrow spikelike panicle, spikelets awn- 
TES Serer Aisa eR hs A Re oe ACE Re 128. IMPERATA. 
3b. Racemes in a broad fan-shaped panicle; spikelets awned. 
129. MIScANTHUS. 
2b. Rachis breaking up into joints at maturity with the spikelets at- 
tached ; one spikelet sessile, the other pedicellate_____________ 4 
EFA SPU EL CES fA WIR 130. SACCHARUM. 
ADE SPLECIEES) - ayy Oda LS Ns es Ee ee SEL 131, ERIANTHUS. 
1b. Spikelets unlike, the sessile perfect, the pedicellate sterile (sessile 
spikelet staminate, pedicellate spikelet perfect in Trachypogon ) ____ 5 
5a. Pedicel thickened, appressed to the thickened rachis joint (at 
least parallel to it) or adnate to it; spikelets awnless, ap- 
DLESSCC MO) (EME OLE S 20 oS RK BE Sey Le A le 6 
6a. Rachis joint and pedicel adnate, forming a short flat joint, 
this sunken in the open side of the globose first glume of 
the sessile spikelet; sterile spikelet conspicuous:_ 140. Ryvirrx. 
6b. Rachis joint and pedicel distinct, the sessile spikelet ap- 
pressed to them, its first glume lanceolate_______________ 
7a. Racemes subcylindric; rachis joints and pedicels glabrous, 
much thicker at the summit, the spikelets sunken in the 
hollow below; sterile spikelet rudimentary_____ 139. MANISURIS. 
7b. Racemes flat ; rachis joints and pedicels woolly, not much 
thicker at the summit; sterile spikelet staminate or neu- 
11,2) chiara eer eo Nie ie Re ee DTS ee a 138. HLyonurus. 
5b. Pedicel not thickened (if slightly so the spikelets awned), neither 
appressed nor adnate to the rachis joint, this usually slender ; 
-1 
aMIKcletsnspally, awned = = 2 =: “Secu es as 8 
8a. Fertile spikelet with a hairy-pointed callus, formed of the 
attached supporting rachis joint or pedicel; awns strong__ 9 
9a. Racemes reduced to a single joint, long-peduncled in a 
STi ey On phan ea ee 135. RHAPHIS. 
9b. Racemes of several to many joints, single_____________ 10 
10a. Primary spikelet subsessile, sterile, persistent on 
the continuous axis after the fall of the fertile pedi- 
cellate spikelet, the pedicel forming the callus. 
137. TRACHYPOGON. 
10b. Primary spikelet sessile, fertile; pedicellate spike- 
let sterile; lower few to several pairs of spikelets all 
StLAMINATE) OF, NEUE Tas eee alee eR 136. HreTrropoaon. 
8b. Fertile spikelet without a callus, the rachis disarticulating 
immediately below the spikelet; awns slender __________ dal 
11a. Racemes of several to many joints, solitary, digitate, 
OY SALSSTCLATC 2] = =) eee eee He 132. ANDROPOGON. 
11b. Racemes reduced to one or few joints, these mostly 
peduncled in a subsimple or compound panicle_____— 12 
12a. Pedicellate spikelets staminate____________ 133. Hocus. 
12b. Pedicellate spikelets wanting, the pedicel only 
DIESE ee ee ewe Ee eek 2 Shy 134. SoraHAsTRUM. 
