486 
5. Trachypogon. Sessile spikelets staminate; pedicellate ones perfect. 
6. Heteropogon. Sessile spikelets perfect; pedice}late ones staminate or neutral. 
* * * Inflorescence paniculate, of many spikelike racemes: axis of the racemes 
articulate, usually bearded: sessile spikelets perfect, usually awned; pedicellate 
spikelets neutral, staminate or perfect, often awned. 
+ Panicle compound, 
++ Spikelets alike, all perfect; branches of the panicle spikelet-bearing to the base. 
7. Imperata. Spikelets awnless. 
8. Erianthus. Spikelets awned. 
+ ++Pedicellate spikelets staminate or neutral; branches of the panicle naked at 
the base. 
9, Chrysopogon. Outer glumes lance-ovate, coriaceous, lanceolate, 2-nerved, 
10. Sorghum. Outer glume broad, indurate and shining at maturity. 
++ Panicle simple or reduced to single secund spikes. 
11. Andropogon. Sessile spikelet perfect, awned; pedicellate one staminate or 
neutral, awnless. 
aa Floral glumes and palets membranaceous; empty glumes herbaceous or chart- 
aceous, the lower one usually larger, not embracing the second gliune and _ floret: 
spikelets falling singly or in groups from the continuous rachis. 
Tribe III. Spikelets in groups of 2 to 5, nearly sessile in solitary terminal spikes: 
floral glumes awnless.—ZOYSIEA. 
12. Hilaria. Empty glumes strongly nerved, awned. 
13. Nazia. Second empty gluine coriaceous, beset with hooked spines. 
aaaFloral glumes and palets cartilaginous, coriaceous or chartaceous; empty 
glumes thinner, the first usually smaller: spikelets falling singly from the ultimate 
branches of the panicle or continuous rachis of a spike. 
Tribe IV. Spikelets all alike, with one perfect floret and sometimes a second 
staminate or neutral in panicles or unilateral spikes: floral glumes awnless.—PAnI- 
CEE, 
‘ Spikelets not involucrate. 
+ Spikelets plano-convex in unilateral spikes: empty glimes2 (rarely 3), awnless. 
14. Paspalum. Spikelets sessile or nearly sessile, smooth or slightly pubescent. 
(See Panicum §§ 1 and 2.) 
15. Eriochloa. Spikelets with a ring-like callus at the base, silky pubescent. 
+ + Spikelets usually terete, spicate or paniculate: empty glunes 3, the first usually 
sminall (rarely wanting), or a staminate floret in place of the third glume, awn- 
less or awned. 
16. Panicum. Spikelets sessile or pediceled, glabrous, hispid or pubescent, awn- 
less except in P. Crus-qalli. 
17. Oplismenus. Eimpty glumes awned. 
* * Spikelets subtended by an involucre consisting of one to many bristles, some- 
times grown together and bur-like, 
18. Setaria. Bristles separate, persistent. 
19. Cenchrus. Bristles grown together, falling with the inclosed spikelets, 
** * Spikelets in short few-flowered spikes, in alternate notches in a thickened 
axis, awnless and not involucrate. 
