CYPEEACEAE. 43 



long as the achene: aclienes obovoid, fully 1 mm. long, S-augled, with a broad 

 face and narrower sides, dull. — N. Eather 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: s]iikelets 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. Eather rare, in swamps. — Schists. 

 — Sum. and fall. 



5. ELEOCHAHIS E. 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-augled, 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. ohtusa. 



Spikelets elongate : perianth-bristles as long as the 



achene or shorter : tubercle V4 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. SniaUii. 



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 ^2 as long as the 



achene, or wanting. 7. E. tenuis. 



Tubercle subulate : perianth-bristles longer than the 



achene. 8. E. 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 i 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 i its length. — W. Eather rare, in wet 

 soil. — Sandstones and shales. — Sum. 



