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..
Annual, roots fibrous, culms filiform, densely tufted, reclining or ascending, grooved, 4'-12' long. Upper sheath obliquely truncate, toothed on one side; spikelet ovoid-oblong, acute, 8-20-flowered, thicker than the culm; scales oblong-lanceolate, obtuse or the upper subacute, light purple-brown with a green midvein, tardily deciduous or the lower one persistent; bristles persistent, downwardly barbed, longer than the achene and tubercle, sometimes wanting; stamens 3; style 3-cleft; achene 3-angled, obovoid, light brown, finely reticulated; tubercle conic to conic-subulate, very acute, one-fourth to one-half as long as the achene.
Scirpus rostellatus Torr. Ann. Lye. N. Y. 3: 318. 1836. Eleocharis rostellata Torr. Fl. N. Y. 2: 347. 1843.
Perennial by a short caudex, culms slender, flattened, wiry, the fertile erect or ascending, the sterile reclining and rooting at the summit, grooved, 1°-5° long. Upper sheath truncate; spikelet oblong, narrowed at both ends, thicker than the culm, 10-20-flowered, 3"-6" long, about 1" in diameter; scales ovate, obtuse or the upper acute, green with a somewhat darker midvein, their margins slightly scarious; bristles 4-8, retrorsely barbed, longer than the achene and tubercle; stamens 3; style 3-clef t; achene oblong-obovoid, obtusely 3-angled, its surface finely reticulated; tubercle conic-subulate, about one-half as long as the achene or shorter, capping its summit, partly or entirely falling away at maturity.
In marshes and wet meadows, New Hampshire, Vermont and New York to British Columbia, Florida, Texas, Mexico and California. Also in Cuba. Aug.-Sept.