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..
N. Y. Acad. Sci. 11: 89. 1892.
Culms stout, 3-angled, 2°-4° tall. Leaves flat, keeled, i"-i 1/2" wide; spikelets spindle-shaped, 2 1/2"-3" long, exceedingly numerous, in several short-peduncled axillary and terminal very dense globose heads 4"-12" in diameter; scales dark brown, ovate-oblong, acute; bristles usually 6, longer than or equalling the achene and tubercle, downwardly or rarely upwardly barbed; achene obovate, brown, smooth, lenticular; tubercle subulate, about as long as the achene, somewhat de-current on its edges.
Schoenus fuscus L. Sp. PI. Ed. 2, 1664. 1763.
R. fusca Ait. Hort. Kew, Ed. 2, 1: 127. 1810.
Rootstocks short, culms slender, 3-angled, smooth, tufted, 6'-18' tall. Leaves setaceous, channeled, scarcely 1/2" wide, much shorter than the culm; spikelets spindle-shaped, acute, about 2 1/2" long, several, or rather numerous, in 1-4 loose clusters; scales oblong-lanceolate, brown, shining, concave; bristles 6, upwardly barbed, often unequal, the longer ones usually exceeding the achene and tubercle; achene narrowly obovate, turgid-lenticular, smooth, shining; tubercle triangular-subulate, nearly as long as the achene, its margins serrulate or nearly smooth.
In bogs, Newfoundland to Delaware and Florida, west along the St. Lawrence and Great Lakes to Michigan. Also in Europe. July-Aug.
Rynchospora filifolia Torr., with long filiform leaves and much smaller achenes. of the Southeastern States and Cuba, has recently been found to range northward into southern New Jersey.
R. gracilenta A. Gray, Ann. Lye. N. Y. 3: 216. 1835.
Culms very slender or filiform, smooth, obtusely triangular, 1°-2° tall. Leaves flat or becoming involute in drying, rather less than 1" wide, elongated but shorter than the culm; spikelets narrowly ovoid, acute, 2" long, few, in 1-4 loose clusters, the lower clusters borne on filiform stalks; scales ovate, brown, mu-cronate; bristles 6, upwardly barbed, equalling the achene and tubercle; achene broadly oval or nearly orbicular, dark brown, lenticular, dull, smooth; tubercle narrowly subulate, flat, widened at the base, pale, about as long as the achene.
In pine barren swamps, southern New York to Florida and Texas, near the coast. June-Aug.