170 PANICACE^E. 



b. Spikelets not in pairs; empty glumes none. . . .(c) 



c. Pistillate spikelets all above the staminate in the 



panicles, linear, subterete, embryo as long as the 



grain ; 38 



c. Pistillate spikelets terminal and the staminate at the 



base of each branch of the panicle; grain subcom- 



pressed, ovate, embryo much shorter. , . 39 



c. Staminate and pistillate spikelets in sejDarate panicles, 



rarely in the same, when the staminate are 



terminal 37 



B. Spikelets in panicles, all perfect, much compressed. . . (e) 

 e. Empty glumes two; floral glumes of ten awned. ... 40 

 e. Empty glumes none or minute, floral glume awnless. . 41 



35. (39). Hydrochloa Beauv. Agrost. 135, t. 24, f. 4 (1812). 



Spikelets small, unisexual, monoecious, silicate, the staminate 

 terminal, the pistillate axillary. Glumes 2, slightly unequal, mem- 

 branous, concave, awnless, the lower one a little the larger; palea 

 0. Stamens 6. Styles short, distinct, sublateral; stigmas elongated, 

 sliortly plumose. Grain included by the glumes, but not adherent. 

 A slender, branching grass, floating or creeping, with flat and nar- 

 row leaf-blades. The peduncle terminal, slender, the staminate 

 spikelets few (3-5), towards the apex, subsessile. The pistillate 

 spikelets subsessile in the upper axils, few-flowered, slightly pro- 

 truding from the sheath of the upper leaf, the stigmas protruding 

 for some distance beyond the glumes. Seed flat, oval, with a thin 

 translucent ridge on one side, loose in the brittle pericarp. Only 

 one species, which is found in the soutli eastern part of the United 

 States. 



It dilTers from Zizania chiefly in the reduction of the 2- to fow- 

 flowered spikes, of which the terminal one is staminate and pedun- 

 culate, the lower one pistillate and sessile in the axils. 



1 H. Carolinensis Beauv. 1. c. 



An aquatic, 20-60 cm. high; leaf-blades 2-3 cm. long; very 

 seldom bearing good flowers. 



Infrequent. North Carolina to Florida, July and August. 



