HITCHCOCK AND CHASE GRASSES OF THE WEST INDIES. 267 



5. PANICEAE. • 



Spikelets unisexual ; plants monoecious. 



Inflorescence of 2 digitate spikelike racemes, one pistillate, the other 



staminate 55. Mniochloa (p. 360). 



Inflorescence paniculate, the panicle often much reduced. 



Panicles large, terminal on the culms or leafy branches, the pistillate 

 spikelets above, the staminate below in the same panicle. 



52. Olyra (p. 357). 

 Panicles all axillary or axillary and terminal, the terminal when pres- 

 ent wholly staminate. 

 Fruit laterally compressed, conspicuously gibbous on the upper 



dorsum 53. Lithachne (p. 858). 



% Fruit dorsally compressed, lanceolate 54. Raddia (p. 358). 



Spikelets perfect. 



Axis thickened and corky, the spikelets sunken in cavities in its joints, these 



disarticulating at maturity 51. Stenotaphrum (p. 356). 



Axis not thickened, the spikelets not sunken in it. 



Spikelets subtended or surrounded by 1 to many bristles or spines (sterile 

 branchlets), these distinct or more or less connate at base, forming a 

 false involucre. 



Bristles persistent; spikelets deciduous 47. Chaetochloa (p. 346). 



Bristles falling with the spikelets at maturity. 



Bristles solitary, much exceeding the appressed spikelet. 



48. Paratheria (p. 353). 

 Bristles numerous below each spikelet or cluster of spikelets. 

 Bristles not united at base, usually slender, often plumose. 



49. Pennisetum (p. 353). 

 Bristles more or less united at the base, forming a bur. 



50. Cenchrus (p. 354). 

 Spikelets not subtended nor surrounded by bristles (axis of branchlet ex- 

 tending beyond the base of the uppermost spikelet in Panicum, sub- 

 genus Paukochaetitjm ) . 

 Fruit cartilaginous-indurate, not rigid, papillose, usually dark-colored, 

 the lemma with white hyaline margins, these not inrolled. 

 Fruit open at the hyaline summit ; inflorescence a narrow grayish- 

 silky panicle 26. Leptoqpryphium (p. 291). 



Fruit not open at the summit ; inflorescence of digitate or flabellately 

 panicled slender racemes. 

 Spikelets conspicuously long-silky; fruit lanceolate-acuminate; 



racemes in a flabellate panicle 27. Valota (p. 291). 



Spikelets with short pubescence or glabrous ; fruit elliptic ; racemes 



digitate or subdigitate 28. Syntherisma (p. 292). 



Fruit indurate, rigid (or if thin not hyaline-margined). 



Sterile lemma splitting down the middle, the halves inrolled, appear- 

 ing like two glumes side by side; raceme solitary, the rachis 



broad-winged 29. Thrasya (p. 296). 



Sterile lemma not splitting. 



Spikelets solitary, subsessile, placed with the back of the fruit 

 turned away from the rachis. 

 Inflorescence a solitary erect spikelike raceme, the spikelets 

 swollen on the side toward the rachis and fitting into alter- 

 nate hollows 30. Mesosetum (p. 297.) 



Inflorescence of 2 to many racemes or paniculate. 



