This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Perennial by rootstocks; culms slender, triangular, 1 1/2°-4 1/2° tall, leafy. Leaves elongated, 2"-5" wide, rough-margined, the upper overtopping the culm, those of the involucre 3-5, dark-colored at the base, the longer of them exceeding the inflorescence; umbel 1-2-compound, large; spikelets cylindric, obtusish, 3"-5" long, in capitate clusters of 2-10 at the ends of the raylets or some of them distinctly peduncled; scales dark brown, keeled, mucronate, falling early; bristles 4-6, downwardly barbed from below the middle to the summit, longer than the achene; style 3-cleft; achene 3-angled, 1/4" long, oblong, narrowed at each end, slender-beaked.
S". divaricatus Ell. Bot. S. C. & Ga. 1: 88. pl. 2. f. 4. 1816.
Perennial. Roots fibrous, culms obtusely triangular, smooth, rather slender, 2 1/2°-4° tall. Leaves 2"-4" wide, rough-margined, the upper and those of the involucre not exceeding the inflorescence; umbel decompound, the primary rays very slender, sometimes 6' long, widely spreading or drooping; raylets filiform; involucels setaceous; spikelets mostly solitary at the ends of the raylets, sessile or peduncled, linear-oblong, obtuse, 3"-6" long, 1/2" thick; scales ovate, greenish-brown, subacute or obtuse, with a prominent midvein and scarious margins; bristles 6, flexuous, longer than the achene, somewhat pubescent, not barbed, shorter than the scales; stamens 3; style 3-cleft; achene sharply 3-angled, oblong, narrowed at both ends, apiculate, nearly white, not shining.
In swamps, Virginia to Kentucky, Missouri, Florida and Louisiana. The spikelets sometimes partially develop into tufts of leaves. June-Aug.
Scirpus lineatus Michx. Fl. Bor. Am. 1: 32. 1803.
Perennial by stout rootstocks; culms rather slender, triangular, erect, 1°-4 1/2° high, leafy, the upper leaves and those of the involucre not exceeding the inflorescence. Leaves 2"-4" wide, light green, flat, rough-margined; umbels terminal and commonly also axillary, decompound, the rays very slender, becoming pendulous; spikelets mostly solitary at the ends of the slender raylets, oblong, obtuse, 3"~5" long, about 1" in diameter; scales ovate or oblong, reddish-brown with a green midvein, their tips slightly spreading; bristles 6, weak, smooth, entangled, much longer than the achene, equalling the scales or slightly protruded beyond them at maturity; stamens 3; style 3-cleft; achene oblong or oblong-obovoid, pale brown, narrowed at both ends, 3-angled, short-beaked.