HITCHCOCK—GRASSES OF CUBA. 187 
Spikelets unisexual; plants moncecious; blades abruptly contracted into 
petiole-like bases. 
Inflorescence consisting of 2 slender racemes, one staminate the other 
pistillate, digitate at the summit of a naked culm; leafy stems dis- 
tinct from the base; plants low ............- ..44. Mniochloa (p. 233). 
Inflorescence borne on leafy culms; fruit bony-indurated. 
Fruit dorsally compressed; panicles terminal on culms or leafy 
branches, pistillate spikelets above, staminate spikelets below in 
same panicle ..............252-0200 0000-0 eee eee 42, Olyra (p. 233). 
Fruit laterally compressed, conspicuously gibbous on upper dorsum; 
panicles all axillary or axillary and terminal, the terminal when 
present wholly staminate ...........-.-.-- 43. Lithachne (p. 233). 
Spikelets all perfect. 
Spikelets 2 to 4 together sunken in the alternate notches of a broad, 
thickened rachis; creeping grasses ........ 41. Stenotaphrum (p. 232). 
Spikelets not sunken in notches of a thickened rachis. 
Spikelets solitary or in small clusters subtended by an involucre 
consisting of 1 to many bristles (sterile branches), these some- 
times grown together. 
Involucre persistent on the axis, spikelets deciduous. 
36. Chaetochloa (p. 230). 
Involucre deciduous with and attached to the spikelets. 
Involucre a spiny bur inclosing 1 to 5 spikelets. 
37. Cenchrus (p. 231). 
Involucre of distinct bristles. 
Involucre of a single sterile branch produced beyond 
each spikelet -.............-. 40. Paratheria (p. 232). 
Involucre of numerous often plumose bristles. 
38. Pennisetum (p. 232). 
Spikelets not involucrate. 
Fruits not rigid, margins of lemma not inrolled. 
Inflorescence of slender racemes, divergently digitate at 
‘the summit of the culm, both glumes wanting. 
18. Reimarochloa (p. 198). 
Inflorescence paniculate. 
Blades cordate-clasping, fruit open at'summit; aquatic 
or semiaquatic grasses.....-... 29. Hymenachne (p. 212). 
Blades not cordate-clasping. 
Spikelets awned, first glume with a pedicel-like 
callus....................39. Chaetium (p. 282). 
Spikelets awnless; fruits cartilaginous-indurated, 
papillose, usually dark-colored, lemmas with 
thin, usually white margins. 
Fruit open at the white-margined summit; 
spikelets tuberculate-hispid between the 
nerves......-- 21. Leptocoryphium (p. 207). 
Fruit not open nor white-margined at summit. 
Sterile lemma like the fertile lemma in 
texture .......26. Alloteropsis (p. 210). 
Sterile lemma like the glumes in texture. 
Spikelets clothed with long silky 
hairs........-.. 25. Valota (p. 210). 
Spikelets glabrous or pubescent only. 
24. Syntherisma (p. 208). 
