transversely rugose. Paspalidium geminatum (Forsk.) Stapf. 



Moist or wet ground or in shallow water, in Okla. (Jefferson Co.) and in e. 

 half of Tex., frequent nearest the coast, summer-fall; Fla., La., Tex., Okla. and 

 warmer regions of the world. 



10. Panicum paludivagum Hitchc. & Chase. Fig. 157. 



Perennial; vernal culms erect or decumbent often from somewhat knotty bases, 

 creeping, rooting, rather succulent, as much as 2 m. long, the lower part often 

 submerged, loosely branching; blades 15-40 cm. long, scabrous on the upper sur- 

 face; spikelets 2.5-3 mm. long, faintly 3-nerved; fertile lemma obscurely to ob- 

 soletely transversely rugose. Paspalidium paludivagum (Hitchc. & Chase) Parodi. 



Scattered in wet places, in shallow water of ponds, lakes and streams, in 

 s. Tex. (Cameron, Hidalgo, Brazoria and San Patricio cos.), summer-fall; Fla., 

 Tex., Mex.; Guat. 



This is not adequately separable from P. geminatum, being scarcely more than 

 a form of that species. 



11. Panicum gymnocarpon Ell. Fig. 158. 



Perennial, rooting at the lower nodes; culms basally prostrate, terminally ascend- 

 ing, 3-7 mm. thick; blades 14-25 mm. broad, basally with pronounced corners, 

 marginally finely serrate; ligule a thin scale 1 mm. long; inflorescence panicu- 

 loid, 12-40 cm. long, 7-25 cm. broad, of 14 to 35 loosely ascending remote or 

 remotely whorled branches ("racemes" of some descriptions) with each secundly 

 bearing a number of closely set appressed nearly sessile spikelets or (toward the 

 base) usually compound with short appressed secondary branchlets (each bearing 

 several appressed sessile spikelets); spikelets 5.5-7 mm. long, narrow; first glume 

 nearly as long as the sterile lemma, the second glume strongly 3- to 5-nerved 

 and surpassing the sterile lemma, both of them acuminate and glabrous; fertile 

 lemma 2 mm. long, smooth, shiny. 



Local in wet sand along streams or in shallow water, in mud about lakes and 

 ponds, in e. and s.e. Tex. (w. to Anderson and Colorado cos.), fall; Coastal 

 States, S.C. to Tex. and inland to Ark. 



12. Panicum hemitomon Schult. Maidencane. Fig. 159. 



Aquatic or subaquatic perennial from extensively creeping rhizomes, often 

 producing numerous sterile shoots with overlapping sometimes densely hirsute 

 sheaths; culms 5-15 dm. tall, usually hard; sheaths of fertile culms usually gla- 

 brous; blades 10-25 cm. long, 7-15 mm. broad, usually scabrous on the upper 

 surface and smooth beneath; panicles elongate, very narrow. 15-30 cm. long, the 

 branches erect, the lower branches distant, the upper ones approximate, 2-10 cm. 

 long; spikelets subsessile, 2.4-2.7 mm. long, lanceolate, acute, 3- to 5-nerved, 

 glabrous; first glume about half the length of the spikelet; fertile lemma less 

 indurate than usual in Panicum; apex of fertile palea scarcely enclosed by the 

 margin of the fertile lemma. 



Frequent (rarely flowering) on margin of lakes, ponds and streams, and in 

 shallow water of lakes and ponds, in e. and s.e. Tex., spring (usually May); 

 Coastal States, N.J. to Tex.; also Tenn.; Braz. 



13. Panicum obtusum H.B.K. Vine-mesquite. Fig. 160. 



Perennial forming large colonies from extensive stolons; culms in tufts from 

 a knotty base at intervals along the stolon, wiry, compressed, 2-8 dm. tall; ligules 

 about 1 mm. long; blades mostly elongate, 2-7 mm. broad, glabrous or nearly 

 so; panicles narrow, 3-12 cm. long, about 1 cm. broad, the few appressed 

 branches densely flowered, the short pedicels sccund; spikelets 3-3.8 mm. long, 

 obovoid, brownish, blunt, scabrous; first glume nearly as long as the spikelet; 



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