8a. Blades to 1 5 mm. or more wide 



156. Erianthus contortus — Bent-awn Plumegrass 



Leaves rolled in bud-shoot; sheath distinctly flattened, smooth, split 

 with overlapping margins hyaline ; auricles absent ; collar medium broad, 

 divided, hairy; ligule membranous, 1.5 to 2 mm. long, rounded, ciliate; 

 blade 10 to 15 mm. wide, smooth above and below, keeled below, margins 

 rough and hyaline. Inflorescence— a narrow, dense, silky, brownish pan- 

 icle. Coastal Plain, Delaware south. Moist sandy ground. 



8b. Blades not more than 1 2 mm. wide 9 



9a. Usually growing in large tufts 



157. Andropogon gerardi — Big Bluestem 



Leaves rolled in bud-shoot ; sheath distinctly flattened, smooth or hairy, 

 split with overlapping hyaline margins; auricles absent; collar narrow to 

 broad, sometimes divided, may be hairy on margins; ligule membranous, 

 1 to 2.5 or 3 mm. long, truncate to rounded, mostly ciliate; blade 7 to 12 

 mm. wide, usually with at least a few hairs near base above, smooth and 

 keeled below, margins smooth to rough. Inflorescence— 2 or 3 terminal 

 spike-like branches. Throughout. Dry soil and old fields. 



9b. Not usually growing in large tufts 



10 



10a. Blade V-shaped to folded, at least at base 



158. Paspalum laeve — Field Paspalum 



Leaves rolled in bud-shoot; sheath distinctly flattened, smooth but 

 may be hairy at top, split with overlapping hyaline margins (occasionally 

 hairy) ; auricles absent; collar narrow, may be hairy on margins; ligule 

 membranous, mostly 1 to 2.5 mm. long, truncate; blade 8 to 12 mm. wide, 

 smooth above and mostly long hairy near base, smooth and keeled below, 

 margins rough and hyaline. Inflorescence— 3 to 4 spreading, one-sided, 

 spike-like branches with flat, round to oval seed. New Jersey south. Mead- 

 ows, old fields and waste ground. 



10b. Blade flat 



159. Digitaria ischaemum— Smooth Crabgrass 



Leaves rolled in bud-shoot ; sheath distinctly flattened, smooth or occa- 

 sionally sparsely hairy, split with overlapping hyaline margins; auricles 

 absent; collar narrow to broad, often divided, may be hairy on margins; 

 ligule membranous, 1.5 to 3 mm. long, truncate to rounded; blade 

 5 to 10 mm. wide, smooth above but mostly with a few hairs at least near 

 base, smooth and keeled below, margins smooth to rough and sometimes 

 sparsely long hairy. Inflorescence— 2 to 6 digitate spike-like branches. 

 Common throughout. Lawns, fields and waste places. 



• 47 



