190 A TEXT-BOOK OF GRASSES 



alliance with the second series, Poaeoidese. The spikelets 

 are l-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 saliva 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 Oryze^ 



A. Spikelets perfect, strongly compressed laterally. 



B. Glumes 2; lemma often awned ORYZA(Par.224) 



BB. Glumes wanting; lemma awnless Homalocen- 



AA. Spikelets unisexual, terete; plants monoecious. chrus. 



B. Plants slender, creeping in the mud or 

 floating in the water. 

 c. Inflorescence a few-flowered spike; plants 

 not stoloniferous. Southeastern United 



States Hydrochloa. 



cc. Inflorescence a panicle; plants stolonifer- 

 ous. Alabama Luziola. 



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 

 DD. Pistillate and staminate spikelets mixed (Par. 225). 



in the panicle, the former below and 

 the latter above on each branch. 

 Gulf States Zizaniopsis. 



224. Oryza L. — Rice. Characterized by the perfect 

 flowers, strongly compressed spikelets and the presence 



