10b. Blade smooth or very slightly rough above 



250. Erianthus coarctatus — Slender Plumcgrass 



Leaves rolled in bud-shoot; sheath somewhat flattened, smooth, long 

 hairy at top and hairy at nodes, split with overlapping margins; auricles 

 absent; collar broad, hairy; ligule membranous, to 1.6 mm. long, trun- 

 cate, ciliate; blade to 15 mm. wide, smooth above and below, midrib 

 whitish to reddish above and prominent below, margins rough and hya- 

 line. Inflorescence — a narrow, dense, silky, purplish-brown panicle. 

 Delaware south. Peaty, sandy, moist meadows and margins of swamps. 



1 1 a. Blade with midrib conspicuously white above 



251. Sorghum sudanense — Sudan Grass 



Leaves rolled in bud-shoot; sheath round, smooth, may be hairy at 

 base, split with overlapping hyaline margins; auricles absent; collar 

 broad, divided ; ligule membranous, 1 to 2 mm. long, truncate to rounded, 

 may be ciliate; blade to 25 mm. or more wide, smooth above and below 

 or sometimes sparsely hairy near base above, margins rough and hyaline. 

 Inflorescence — a large, loose, erect panicle. Cultivated for forage. 



1 1 b. Blade midrib not white above 



252. Arrhenatherum elatius — Tall Oatgrass 



Leaves rolled in bud-shoot ; sheath round, smooth, split with overlap- 

 ping hyaline margins; auricles absent; collar broad; ligule membranous, 

 1 to 2 mm. long, truncate; blade to 12 mm. wide, smooth to rough above, 

 keeled and smooth below at least near base, margins at least slightly 

 rough and hyaline. Inflorescence — a narrow, pale or purplish, shining 

 panicle. Throughout. Meadows, open ground and waste places. 



GROUP 21 



la. Blade wth midrib conspicuously white above 2 



lb. Blade midrib not white above 3 



2a. Plant with large creeping rhizomes 



253. Sorghum halepense — Johnson Grass 



Leaves rolled in bud-shoot; sheath round to somewhat flattened, 

 smooth, split with overlapping hyaline margins; auricles absent; collar 

 broad, may be divided, sometimes hairy; ligule membranous, 2 to 3 mm. 

 long, rounded, ciliate ; blade to 35 mm. wide, smooth above and below 

 at least near base, midrib white above and prominent below, margins 

 generally rough and hyaline. Inflorescence — a large, loose, erect panicle. 

 Massachusetts south. Open ground, fields and waste places. 



• 71 



