HITCHCOCK—MEXICAN GRASSES. 
Spikelets 2 to many-flowered. 
Lemma of lower floret usually shorter than 
the glumes, usually with a bent awn 
on the back (Koeleria and Spheno- 
pholis awnless); rachilla produced. 
(AVENEAE.) 
Articulation below the glumes. ......-.. 
Articulation above the glumes. 
Lemmas awnless, acuminate......... 
Lemmas awned. 
Awns flattened, from between the 
lobes of the lemma. 
Spikelets in clusters of 3, 2-flow- 
ered, the upper floret fertile, 
the lower staminate.....- “eee 
Spikelets solitary, 3 to many- 
flowered, all the florets fertile, 
or the uppermost sterile... -. 
Awns not flattened, dorsal. 
Spikelets more than 1 cm. long; 
plants annual..........-..-. 
Spikelets less than 1 cm. long. 
Lemmas keeled; awn from 
above the middle.......... 
Lemmas convex; awn from be- 
low the middle.........--. 
Lemma of lower floret usually longer than 
the glumes; awn when present usually 
straicht and terminal. (FEsSTUCEAE.) 
Lemma 3 to many-cleft. 
Plants dicecious........ 
Plants hermaphrodite. 
Spikelets in 
short spike-like 
YACEMES........-------------- 
Spikelets in panicles. 
Divisions of lemma awn-like; pan- 
icle contracted.........---- 
Divisions of lemma membrana- 
ceous, awned; panicle open. . 
Lemma entire or 2-cleft. 
Rachilla or lemma, (at least of the fer- 
tile floret) bearing long hairs, as 
long as the lemma; tall, reed-like 
grasses. 
Plants dicecious....-.....-........ 
Plants hermaphrodite. 
Rachilla naked; lemmas hairy... - 
Rachilla hairy; lemmas naked... 
Rachilla and lemmas naked or hairy, 
but the hairs shorter than the 
lemmas. 
Spikelets concealed in the leaves. 
Plants dicecious; a creeping per- 
ennial..............-..-000-5 
77. 
78. 
80. 
81. 
79. 
76. 
- 101. 
. 104, 
99. 
100. 
105. 
106. 
107. 
102. 
SPHENOPHOLIS (p. 326). 
KoeE.ERIA (p. 326). 
TRISTACHYA (p. 327). 
DANTHONIA (p. 328). 
AvENA (p. 327). 
TRISETUM (p. 323). 
. DEscHAMPSIA (p. 322). 
ScLEROPOGON (p. 354). 
Orcurtia (p. 355). 
PapPpoPpHORuM (p. 353). 
CorTTEa (p. 354). 
GYNERIvUM (p. 355). 
ARUNDO (p. 355). 
PHRAGMITES (p. 356). 
MoNANTHOCHLOE (p. 354). 
193 
