CYPEEACEAE. 43 



long as the achene: achenes obovoid, fully 1 mm. long, 3-angled, with a broad 

 face and narrower sides, dull. N. Bather rare, in swamps. Sandstones and 

 shales. Sum. and fall. 



9. S. cyperinus (L.) Kunth. Perennial. Stems smooth, stiff, 2 m. tall or less: 

 leaves elongate; blades stiff, 3-6 mm. wide, rough-margined: umbel terminal, 

 decompound, the rays at length somewhat drooping: spikelets ovoid-oblong, 3-5 

 mm. long, in capitate clusters of 3-15: perianth-bristles 6, entangled, much 

 longer than the achene, conspicuously exserted beyond the scales, and grayish- 

 brown at maturity : achenes 3-angled, barely 1 mm. long, nearly white. Com- 

 mon, in swamps. Sum. and fall. 



10. S. Eriophorum Michx. Similar to the next preceding species in habit. 

 Involucre more ferruginous at the base; umbel with laxer branches, the rays 

 elongate and drooping at the ends: spikelets ovoid or oblong-ovoid, 3.5-6 mm. 

 mostly 4.5 mm. long, more deeply colored, at least some of them distinctly 

 peduncled. Lower Susquehanna valley. Bather rare, in swamps. Schists. 

 Sum. and fall. 



5. ELEOCHARIS B. Br. Annual or perennial scapose herbs. Leaves 

 reduced to sheaths, or the lowest very rarely blade-bearing. Scapes simple, 

 terete, flattened, variously angled, or fluted. Spikelets solitary, terminal, erect, 

 several-many-flowered, without an involucre, or rarely with 2 small bracts. 

 Scales spirally imbricate. Perianth of 1-12 bristles, usually retrorsely barbed, 

 or wanting. Stamens 2 or 3. Stigmas 2 or 3. Achene lenticular or biconvex, or 

 3-angled, but sometimes with very obtuse angles and appearing turgid, each 

 tubercled by the persistent style-base. SPIKE-RUSH. 



Style-branches, or stigmas, 2 : achene lenticular or biconvex. 

 Annual plants with fibrous roots. 



Spikelets twice as long as thick or less : perianth-bristles much longer than 



the achene : tubercle % as long as the achene. 1. E. obtus-a. 



Spikelets elongate : perianth-bristles as long as the 



achene or shorter: tubercle % as long as the achene. 2. E. Engelmannii. 

 Perennial plants with horizontal rootstocks. 

 Tubercle of the achene flat-conic or ovate. 



Scape and spike stout : tubercle ovate. 3. E. palustris. 



Scape and spike slender : tubercle conic. 4. E. glaucescens. 



Tubercle of the achene swollen, bulb-like. 5. E. Smallii. 



Style-branches, or stigmas, 3 : achene 3-angled, or turgid. 



Achene cancellate, narrow. 6. E. acicularis. 



Achene papillose or nearly smooth, broad. 



Tubercle depressed : perianth-bristles y 2 as long as the 



achene, or wanting. 7. E. tenuis. 



Tubercle subulate: perianth-bristles longer than the 



achene. 8- & intermedia, 



1. E. obtusa Schult. Annual. Scapes tufted, relatively stout, rather deep-green, 

 nearly terete, 0.5-5 dm. tall: spikelet ovoid or oblong-ovoid, obtuse, many-flowered, 

 3-13 mm. long: scales obovate, oblong-obovate, or oblong-orbicular, rounded, 

 brown, each with a broad green midvein and scarious margins; perianth-bristles 

 6-8, deciduous, longer than the achene: achenes pale-brown, shining, lenticular, 

 obovoid-oblong, smooth, 1 mm. long or more; tubercle deltoid, acute, com- 

 pressed, scarcely constricted at the base, about | as long as the achene. Com- 

 mon, in wet soil. Sum. 



2. E. Engelmannii Steud. Annual, similar to the next preceding species, but 

 commonly taller, sometimes 5 dm. high. Spikelet cylindric, obtuse or rather 

 acute, 4-20 mm. long, many-flowered: scales ovate, pale-brown with a green 

 midvein and narrow scarious margins, obtuse: perianth-bristles about 6, not 

 longer than the achene, or very short or wanting: achenes obovoid or cune- 

 ate-obovoid, fully 1 mm. long, brown, smooth, lenticular; tubercle broad, low, 

 covering the top of the achene, less than J its length. W. Bather rare, in wet 

 soil. Sandstones and shales. Sum. 



