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..
Culm obtusely triangular, stout or slender, smooth, 3°-7° tall. Leaves flat, broadly linear, 6'-18' long, 3"-8" wide, rough-margined; umbels terminal and axillary, sometimes 1° broad, usually compound; spikelets spindle-shaped, 4"-6" long in flower, capitate at the ends of the rays and raylets; primary rays slender, sometimes 6' long; scales lanceolate, thin, acute, light brown; bristles about 6, subulate or filiform, rigid, upwardly scabrous, shorter or longer than the achene; style subulate, entire or minutely 2-toothed at the apex, 2-4 times longer than the achene, upwardly scabrous, 1/2'-l' long, persistent and much exserted beyond the scales when mature; achene obovate, flat, 2" long, dark brown, smooth, its surface minutely cellular-reticulated.
R. pallida M. A. Curtis, Am. Journ. Sci. (II.) 7: 409. 1849.
Rootstocks slender, culms sharply triangular, 1 1/2 -2 1/2 tall. Leaves 1/2"-1" wide, flattish, nearly smooth, the lowest reduced to many-nerved lanceolate acuminate seal es; spikelets numerous, spindle-shaped, narrow, 2"-3" long, aggregated in a compound convex terminal head, or occasionally also in a filiform-stalked cluster from the upper axil; uppermost leaves subulate, little exceeding the spikelets; scales pale greenish-brown, lanceolate, acuminate; bristles minute and early deciduous, or wanting; style 2-cleft; achene lenticular, obo-vate-oblong, smooth, brown, somewhat shining, i" long, tipped by a short tubercle.
In bogs, New Jersey to North Carolina. Aug.-Sept.
R. oligantha A. Gray, Ann. Lye. N. Y. 3: 212. 1835.
Rootstocks short, culms tufted, almost thread-like, leafy only toward the base, 6-16' tall. Leaves filiform, resembling and shorter than the culm or sometimes equalling it; spikelets 1-4, terminal, narrowly oblong, acute, 3-4 long, sessile or peduncled, subtended by .1 or 2 filiform bracts; scales ovate, pale brown, acute, cuspidate; bristles usually 6, densely plumose below the middle, upwardly scabrous above, equalling or shorter than the achene; style 2-cleft; achene obovoid-oblong, obtuse, turgid-lenticular, pale brown, dull, transversely wrinkled; tubercle with a flat depressed border and a flattened conic acute central projection about one-fifth as long as achene.
In wet soil, New Jersey to Florida and Texas. June-Aug.