HITCHCOCK—MEXICAN GRASSES, 185 
Plants stoloniferous...........- 19. Hizarta (p. 213). 
Plants producing rhizomes but 
not stoloniferous.......... 20. PLEURAPHIS (p. 214). 
Lemma and palea indurated, coriaceous or 
chartaceous, firmer than the glumes, 
(PANICEAE.) 
Spikelets unisexual; fruit bony-indurated. 
Panicles terminal on culms or leafy 
branches, the pistillate spikelets 
above, the staminate below in the 
same panicle. ..........-.-.-------- 51. Ouyra (p. 271). 
Panicles all axillary or axillary and ter- 
minal, the terminal when present 
wholly staminate. 
Fruit laterally compressed, conspic- 
uously gibbous on upper dorsum.... 52. LiTHACHNE (p. 272). 
Fruit dorsally compressed, lanceolate... 53. Rappta (p. 272). 
Spikelets perfect (one of a pair sometimes 
abortive). 
Axis broad and corky, the spikelets sunken 
in its cavities, the terminal portion 
disarticulating at maturity........... 50. STENOTAPHRUM (p. 271). 
Axis not broad and corky, the spikelets not 
sunken in cavities. 
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 falling with the spikelet at 
maturity. 
Bristles more or less united at base 
into a bur-like involucre ...... 49, CENCHRUS (p. 268). 
Bristles not united at base, usually 
slender, often plumose........ 48. PENNISETUM (p. 265). 
Bristles of involucre persistent, the 
spikelets deciduous. 
Sterile palea at maturity becoming 
cartilaginous and winged, much 
exceeding the spikelet in width; 
spikelets secund along the 
branches of a simple panicle, 
each subtended by a single 
viscid bristle..........-------- 47, IxopHorus (p. 265). 
Sterile palea not enlarged at ma- 
turity. 
Second glume and sterile lemma 
very broad, many-nerved, 
the glume saccate, auriculate, 
the lemma lyre-shaped, indu- 
rated on the margins; spike- 
let subtended by a single 
flexuous bristle.........-...- 45. SrTaRropsis (p. 259). 
