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. CHLOMDEAE (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. ANDROPOGQNEAE. 



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 joiiyt, long-peduncled in a simple open 



panicle 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). 



