POACEAE 67 



fourth scale twice bent, 2-3 cm. long, closely spiral to the second bend, thence loosely 

 twisted, the column very much exserted ; pedicel from f as long as the spikelet to nearly 

 equalling it. [Sorghum nutans Chapm.] 



In dry soil, South Carolina and Tennessee to Florida and Mississippi. Fall. 



3. Sorghastrum secundum (Ell.) Nash. Stems 8-14 dm. tall : leaf -sheaths smooth 

 and glabrous ; blades 6 dm. long or less, 7 mm. wide or less, smooth beneath, rough above, 

 often involute : panicle 2-4 dm. long, one-sided, its branches erect or nearly so, rarely 

 exceeding 4 cm. in length, usually shorter than the internodes of the axis, the ultimate 

 divisions much curved, making the spikelets reflexed : spikelet 6-8 mm. long, lanceolate, 

 the 2 outer scales golden brown and indurated at maturity, the first one pubescent with 

 long erect hairs, the awn of the fourth scale twice bent, 2.5-3 cm. long, closely spiral to the 

 second bend, thence loosely twisted, the column very much exserted ; pedicel from ^-f as 

 long as the spikelet. [Sorghum secundum (Ell.) Chapm.] 



In dry sandy soil, Georgia and Florida. Fall. WILD OATS. 



13. VETIVERIA Thouars. 



Tall grasses with simple stems, narrow leaf-blades and terminal panicles with the 

 branches usually much articulated and disposed in dense whorls. Spikelets in pairs, 

 narrow, acute, of 4 scales, the one sessile and perfect, the other pedicellate and staminate. 

 Sessile spikelets usually somewhat laterally compressed, the first scale coriaceous or char- 

 taceous, the margin inflexed or involute, the second awned or awnless, the third and fourth 

 scales hyaline, the latter entire or shortly 2-toothed, mucronate or awned from between the 

 teeth. Pedicellate spikelets usually awnless, rarely awned. Stames 3. Styles distinct. 

 Stigmas plumose. 



1. Vetiverla zizanioides (L. ) Nash. Stems 2 m. tall or more : sheaths smooth and 

 glabrous ; blades 9 dm. long or less, 4-10 mm. wide : panicle 2-3 dm. long, its slender as- 

 cending or nearly erect branches in dense whorls and readily disarticulating at the nodes : 

 sessile spikelet about 4 mm. long, about as long as the internode, the first scale minutely 

 tuberculate-roughened, 2-keeled, the keels muricate, the second scale 1 -keeled, the keel 

 muricate, the fourth scale awnless or short-awned, the awn not exserted beyond the 2 outer 

 scales ; pedicellate spikelet about as long as or a little shorter than the sessile, the 2 outer 

 scales sparingly muricate. 



Cultivated and escaping into fields in Louisiana. Fall. 



14. RH APHIS Lour. 



Perennial or rarely annual "grasses, with narrow leaf-blades and terminal panicles, 

 whose branches usually bear clusters of 3 spikelets, or very rarely more, at the end, one 

 spikelet sessile and perfect, the other 2 staminate or sterile and pedicellate. Sessile spike- 

 lets usually somewhat laterally compressed, of 4 scales, the first scale broadly involute, the 

 second somewhat distinctly keeled, and usually awned, the third and fourth scales hyaline, 

 the latter usually awned. Pedicellate spikelets dorsally compressed, awnless. or awned. 

 Stamens 3. Styles distinct. Stigmas plumose. 



1. Rhaphis pauciflorus (Chapm.) Nash. Annual. Stems 6-12 dm. tall, simple or 

 somewhat branched : leaf -blades 2 dm. long or less, 2-10 mm. wide, papillose-hirsute 

 above : panicle 2-3 dm. long, its branches erect or ascending, slender, the lower in whorls 

 of 2-5, rarely divided, the longer, exclusive of the spikelets and awn, 5-8 cm. long : ses- 

 sile spikelet about 15 mm. long, including the 6-7 mm. long and densely pubescent callus, 

 cylindric or slightly laterally compressed, the first and second scales dark brown, shining 

 and coriaceous at maturity, hispidulous at the apex, the fourth scale emitting a flexuous 

 more or less contorted usually geniculate awn 14-16 cm. long ; pedicellate spikelet 10-12 

 mm. long, on slender pedicels about reaching the apex of the sessile spikelet, empty or 

 containing a staminate flower. [Sorghum pauciflorum Chapm.] 



In dry sandy soil, eastern and peninsular Florida. Also in Cuba. Fall. 



15. HETEROPOGON Pers. 



Annual or perennial grasses, sometimes tall, with narrow leaf-blades and compressed 

 sheaths, and terminal solitary dense racemes. Spikelets 1-flowered, in pairs at the rachis- 

 nodes, one sessile and fertile, the other pedicellate, containing a staminate flower, or empty. 

 Scales of the sessile spikelets 4, the outermost empty, firm, convolute, awnless, the second 

 also empty, thinner, keeled, the third scale very thinly hyaline, likewise empty, the 



