3a. Sheath hairy 11 



3b. Sheath not hairy 4 



4a. Sheath distinctly flattened 9 



4b. Sheath not distinctly flattened 5 



5a. Collar hairy on margins 



104. Spartina pectinata — Prairie Cordgrass 



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

 lapping hyaline margins; auricles absent; collar broad, hairy on margins; 

 ligule a fringe of hairs, 1.5 to 2 mm. long; blade 6 to 10 mm. wide, - 

 smooth near base and rough near tip above and below, midrib prominent \ 

 below, margins rough and hyaline. Inflorescence — a series of comb-like 

 spikes forming an appressed panicle. Throughout. Fresh-water marshes. \ 



5b. Collar not hairy on margins X ;,.- • • 6 



6a. Plants with large creeping rhizomes 7 



6b. Plants without creeping rhizomes 



105. Setaria faberii — Giant Foxtail 



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

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

 broad; ligule a fringe of hairs, about 2 mm. long; blade to 25 mm. wide, 

 rough above, smooth and keeled below, margins rough and hyaline. In- 

 florescence — dense, bristly, cylindrical, nodding spike-like. New York 

 south. Common. Waste and cultivated ground. 



7a. Blade smooth above and below 8 



7b. Blade rough above and below at least near tip 



106. Tripsacum dactyloides — Eastern Gamagrass 



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

 lapping margins; auricles absent; collar narrow to medium broad, di- 

 vided; ligule a fringe of hairs, 1 to 1.5 mm. long, may be fused at base; 

 blade 15 to 30 mm. wide, rough above and below at least near tip, mar- 

 gins rough to very rough and hyaline. Inflorescence — 1 to 3 terminal, 

 unisexual spikes. Massachusetts south. Moist places and banks near 

 water. 



8a. Widest blades less than 20 mm. wide 



107. Spartina alterniflora — Smooth Cordgrass 



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

 lapping hyaline margins; auricles absent; collar broad, indistinct; ligule 

 a fringe of hairs, to 2 mm. long, may be fused at base and appear mem- 

 branous; blade 10 to 18 mm. wide, smooth above and below, margins 

 smooth to slightly rough and hyaline. Inflorescence — a series of comb- 

 like spikes forming an appressed panicle. Maine south along coast. Salt 

 marshes, often in water. 



34 



