190 A TEXT-BOOK OF GRASSES 
alliance with the second series, Porwoidexe. The spikelets 
are 1-flowered, perfect or unisexual, and usually disposed 
in panicles. There are usually 6 stamens and the hilum 
is linear instead of punctiform, in which two respects 
the structure is somewhat anomalous. The palea is 
usually described as 1-nerved, but an examination of 
Oryza sativa shows a palea with the 2 nerves close to 
the margin, the region between convex instead of concave 
as is usual in the palea of other grasses. In several genera, 
glumes are rudimentary or wanting. The tribe includes 
about 16 genera, mostly inhabitants of tropical America, 
6 extending into the United States. 
KEY TO THE GENERA OF ORYZEX 
A. Spikelets perfect, strongly pee es 
B. Glumes 2; lemma often awned .... . .OryzA(Par.224) 
BB. Glumes wanting; lemma awnless...... . HOMALOCEN- 
AA. Spikelets unisexual, terete; plants moncecious. CHRUS. 
B. Plants slender, creeping in the mud or 
floating in the water. 
c. Inflorescence a few-flowered spike; plants 
not stoloniferous. Southeastern United 
BG ae ca On Soa ie Gs Oe a ee HyYDROCHLOA. 
cc. Inflorescence a panicle; plants stolonifer- 
ous. Alabama...... bak Era ctaca'als, eee LuziIoua. 
BB. Plants erect, stout; marsh plants or ter- 
restrial. 
c. Blades elliptical or oblanceolate, petiolate; 
fruit cylindrical, beset with hooked 
hairs; plants terrestrial. Florida....... PHARUS. 
cc. Blades elongated, linear, not petiolate; 
marsh plants. 
D. Pistillate spikelets in the usually narrow 
upper part of the panicle; staminate 
spikelets in the spreading lower part. .ZIZANIA 
pp. Pistillate and staminate spikelets mixed (Par. 225). 
in the panicle, the former below and 
the latter above on each branch. 
Cet FSGS inte aoe ie ZIZANIOPSIS. 
224. Oryza L—Rice. Characterized by the perfect 
flowers, strongly compressed spikelets and the presence 
