GROUP 7 



la. Sheath distinctly flattened 2 



lb. Sheath not distinctly flattened 5 



2a. Sheath hairy 



84. Cenchrus tribuloides — Dune Sandbur 



Leaves rolled in bud-shoot ; sheath distinctly flattened, keeled, sparsely 

 long or short hairy, split with margins hairy; auricles absent; collar nar- 

 row, sometimes hairy; ligule a fringe of hairs, 1 to 2 mm. long; blade 4 

 to 7 mm. wide, smooth to rough above, smooth and keeled below, mar- 

 gins smooth to rough and hyaline. Inflorescence— a nearly round, hairy 

 bur with sharp spines. Staten Island, N. Y, south. Loose sands of coast. 



2b. Sheath not hairy 3 



3a. Sheath loose or inflated 



85. Cenchrus pauciflorus— Field Sandbur 



Leaves rolled in bud-shoot; sheath loose, distinctly flattened, keeled, 

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

 narrow; ligule a fringe of hairs, 1 to 1.6 mm. long; blade 5 to 10 mm. 

 wide, rough above, keeled and rough below at least near tip, margins 

 rough. Inflorescence— a nearly round, hairy bur with sharp spines. 

 Throughout. Sandy open ground. 



3b. Sheath not loose or inflated 



4a. Ligule more than 2 mm. long 



86. Setaria magna— Giant Millet 



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

 split with overlapping hairy margins; auricles absent; collar narrow; 

 ligule a fringe of hairs, 2.5 to 3.5 mm. long; blade 15 to 45 mm. wide, 

 rough above and below and on margins, keeled below. Inflorescence- 

 dense, bristly, cylindrical, nodding, spike-like, to 20 in. long. New Jersey 

 south. Marshes and wet places along coast. 



4b. Ligule less than 2 mm. long 



87. Setaria verticillata— Bristly Foxtail 



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

 split with overlapping hairy margins; auricles absent; collar narrow, 

 divided; ligule a fringe of hairs, 1 to 1.4 mm. long; blade to 8 mm. wide, 

 rough above, smooth near base and rough near tip below, margins rough 

 and hyaline. Inflorescence— dense, bristly, cylindrical, erect, spike-like, 

 with barbed bristles. Massachusetts south. Cultivated soil and waste 

 places. 



• 29 



