HITCHCOCK—-MEXICAN GRASSES. 191 
Spikelets 1-flowered, sometimes with sterile 
lemmas below or with a rudiment of a 
second floret above. 
Spikelets moncecious. 
Spikelets in pairs at the nodes of the pan- 
icle-branches, one large, pistillate, 
sessile, the other small, staminate, 
long-pediceled; lemma cylindrical- 
oblong .......---------+---------- 54. PHarus (p. 272). 
Spikelets not in pairs, ovate; glumes 
NONC....-. eee eee eee eee 55. Luzioua (p. 272). 
Spikelets perfect. 
Sterile lemmas below fertile floret 2. 
Sterile lemmas reduced to small scales; 
panicle ovate or oblong, spike-like 57. PHALARIS (p. 273). 
Sterile lemmas mostly as large as the 
fertile; panicle somewhat open, 
bronze-colored.........-.------ 58. SAVASTANA (p. 274). 
Steril2 lemmas none. 
Spikelets strongly laterally com- 
pressed; glumes none.........--- 56. HoMALOCENCHRUS (p. 272). 
Spikelets often laterally compressed 
but not strongly flattened; glumes 
usually present. (AGROSTIDEAE. ) 
Lemma firmer than the glumes, in- 
durated, awned and provided 
with a strong callus. 
Lemma 3-awned (the lateral awns 
short or wanting in some spe- 
cies, but in these the central 
awn not geniculate or twisted) 59. ARIsTIDA (p. 274). 
Lemma l-awned. 
Awn dorsal...............---- 64, TRINIOCHLOA (p. 303). 
Awn terminal. 
Lemma narrow, oblong or lin- 
ear; awn stout, genicu- 
late, twisted, persistent.. 60. Strpa (p. 281). 
Lemma short and broad; awn 
slender, more or less de- 
ciduous, straight, or 
curved, scarcely genicu- 
late and twisted. 
Lemma not gibbous at the 
summit..........---- 61. Oryzoprsts (p. 285). 
Lemma obovate, gibbous at 
the summit, the awn 
eccentric..........--- 62. PrerocHAETIUM (p. 286). 
Lemma more delicate than the 
glumes or of about the same 
texture. 
Spikelets articulated below the 
glumes. 
81544°—13——2 
