S HITCHCOCK AND CHASE—GRASSES OF THE WEST INDIES. 265 
Spikelets on one side of the rachis; spikes usually more than 
1, digitate or racemose (see also Streptogyne with 
tendril-like stigmas) --_~- 10. CHLORIDEAE (p. 270). 
Spikelets pedicellate in open or contracted panicles, 
Spikelets 1-flowered; leaf blades never broad and net-veined. 
8. AGROSTIDEAE (p. 269). 
Spikelets 2 to many-flowered (often reduced to 1 floret and 
a prolonged rachilla joint, in Orthoclada, this with net- 
veined blades). 
Glumes as long as the lower floret, usually as long as the 
spikelet; lemmas awned on the back (except in 
Koeleria and Sphenopholis)__9. AVENEAE (p. 270). 
Glumes shorter than the first floret; lemmas awnless or 
awned from the tip (from a bifid apex in Bromus). 
11, FESTUCEAE (p. 271). 
KEY TO THE GENERA. 
1. TRIPSACEAE. 
Pistillate spikelets sunken in recesses in the thickened joints of the rachis; 
inflorescence of solitary or digitate spikes_______ 1. Tripsacum (p., 272). 
Pistillate spikelets inclosed in a bony beadlike involucre_____- 2. Coix (p. 272). 
2, ANDROPOGONEAE. 
Spikelets all perfect. 
Inflorescence of 2 to several digitate racemes______7. Ischaemum (p. 274). 
Inflorescence a densely flowered hairy panicle. 
Spikelets awned ___-------------------------~- 6. Erianthus (p. 274). 
Spikelets awnless. 
Rachis continuous_---------------------__- 3. Imperata (p. 272). 
Rachis disjointing__._._.____-___-_-_---------- 4. Saccharum (p. 273). 
Spikelets not all perfect, the sessile usually perfect, the pedicellate usually 
staminate or rudimentary (pistillate in Eriochrysis). 
Fertile spikelet with a hairy-pointed callus formed of the attached support- 
ing rachis joint or pedicel or of the upper part of the peduncle; awns 
usually long. 
Racemes reduced to a single joint, long-peduncled in a simple open 
panicle_______-__----_-_- eee 18. Rhaphis (p. 288). 
Racemes of few or many joints, not in an open panicle. 
Rachis continuous; perfect spikelets pedicellate, disarticulating at 
the base of the pedicel; awns plumose. 
10. Trachypogon (p. 276). 
Rachis disarticulating, the joints attached to perfect spikelets next 
above, forming a callus to them. 
Racemes solitary, not subtended by leaflike spathes; perfect 
spikelets several to many above; staminate spikelets sev- 
eral to many below_________ 17. Heteropogon (p. 287). 
Racemes several in a flabellate cluster, subtended by leaflike 
spathes; perfect spikelet 1 in each raceme. 
19. Themeda (p. 288). 
Fertile spikelet without a callus, the rachis disarticulating immediately 
below the spikelet. 
Inflorescence a dense golden brown silky panicle; spikelets awnless, the 
pedicellate one pistillate 5. Eriochrysis (p. 273). 
