42 CYPEEACEAE. 



1. S. planifolius Muhl. Perennial. Scapes tufted, slender, 3-angled, 1.5-4 dm. 

 tall: leaves various, the lower sheaths with short blades, the upper terminating 

 in a flat narrowly linear blade as tall as the scape : spikelet solitary, ovoid or 

 oblong, 5-7 mm. long, several-flowered, the involucral bract usually overtopping 

 it : scales yellowish-brown, except the green midvein, ovate-lanceolate : perianth- 

 bristles 4-6, upwardly barbed, usually about as long as the achene: stigmas 3: 

 achene broadly oblong, 3-angled, 1.5-2 mm. long, smooth, light-brown. — M. 

 Occasional, in woods. — Quartzite. — Spr. 



2. S. debilis Pursh. Annual. Scapes slender, tufted, terete or nearly so, 1.5 

 -5 dm. high: sheaths obliquely truncate, the upper ones rarely bearing short subu- 

 late blades: spikelets solitary or in clusters of 2-12, ovoid-oblong, many-flowered, 

 appearing lateral : scales light yellowish-brown with a green midvein, broadly 

 ovate, obtuse or acute: perianth-bristles 4-6, downwardly barbed, fully as long 

 as the achene: stigmas 3 or rarely 3: achenes plano-convex, broadly obovoid or 

 orbicular, 1.5-2 mm. long, smooth or slightly roughened, dark-brown, shining, 

 mucronulate. — - M. S. Bare, in swamps, on river shores and low islands. — 

 Limestones, schists. — Sum. and fall. 



3. S. americanus Pers. Perennial. Scapes stout, sharply triangular, stiff, 

 3-11 dm. tall: sheaths bearing 1-3 linear, keeled blades, shorter than the scape: 

 spikelets oblong-ovoid, 8-12 mm. long, in clusters of 2-7, appearing lateral: 

 scales broadly ovate, brown, often emarginate or 2-cleft, the midvein extended 

 into a subulate awn: perianth-bristles 2-6, downwardly barbed, shorter than the 

 achene: achenes obovoid, plano-convex, about 2.5 mm. long, smooth, dark-brown. 



— M. S. Bather rare, in swamps or low grounds. — Limestones, schists. ■ — Sum. 



4. S. validus Vahl. Perennial. Scapes stout, light-green, terete, 1-3 m. tall: 

 sheaths bladeless or nearly so: involucral bract shorter than the umbel: umbel 

 compound, appearing lateral, its primary rays 3-10 cm. long: spikelets becoming 

 oblong-cylindric, in mostly capitate clusters of 2-5, 5-16 mm. long: scales sub- 

 orbicular, ciliate, mucronate: perianth-bristles 4-6, downwardly barbed, equal- 

 ling or longer than the achene: stigmas 2: achenes plano-convex, obovoid, mostly 

 2 mm. long or less, black or nearly so, mucronate. — Common, in swamps. — Sum. 



5. S. fluviatilis (Torr.) A. Gray. Perennial, 1-2 m. tall. Leaves elongate; blades 

 8—20 mm. wide, long-attenuate: umbel terminal, compound, the rays mostly re- 

 curved-spreading: spikelets oblong, ovoid, or oblong-cylindric, 15-25 mm. long, 

 solitary or clustered : scales terminating in a curved tip : i^erianth-bristles 6, rigid, 

 as long as the achene or somewhat shorter: stigmas 3: achenes 3-angled, obovoid, 

 dull. — Lower Susquehanna valley. Eather rare, on river shores and islands. 



— Schists. — Sum. — Eiver-bulrush. 



6. S. sylvaticus L. Perennial, 1-2 m. tall. Leaves elongate; blades 1-1.6 cm. 

 wide, rough-margined: umbel terminal, sometimes 3 dm. broad, about 3 times 

 compound, the rays ascending or recurved: spikelets ovoid or ovoid-oblong, 3-5 

 mm. long, in clusters at the ends of the raylets: scales obtuse, brown with a 

 green center: perianth-bristles 6, downwardly barbed, slightly exceeding the 

 achene: achenes broadly oblong or obovoid, fully 1 mm. long, 3-angled, nearly 

 white. — E. S. Eare, in swamps. — Schists, quartzite. — Sum. 



7. S. atrovirens Muhl. Perennial, leafy, 5-12 dm. high. Leaf -blades elongate, 

 bright-green, 6-15 mm. wide, rough-margined: spikelets ovoid-oblong, 3.5-9 mm. 

 long, densely capitate at the ends of the rays or raylets: scales greenish-brown, 

 1.5-2 mm. long, the midvein excurrent: perianth-bristles usually 6, downwardly 

 barbed above, about as long as the achene : achenes oblong-obovoid, 1 mm. long, 

 3-angled, pale-brown, dull. — Common, in swamps. — Sum. and fall. 



8. S. pol5T)hyllus Vahl. Perennial, very leafy, 3-11 dm. tall. Leaf -blades pale- 

 green, 4-6 mm. wide, rough-margined: spikelets ovoid, 2.5-3.5 mm. long, capitate 

 at the ends of the raylets : scales 1-1.5 mm. long, bright-brown, mostly obtuse and 

 mucronulate : perianth-bristles 6, downwardly barbed above the middle, twice as 



