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..
Pale green, rootstocks short, culms slender or almost filiform, glabrous, 6'-20' tall. Leaves bristlelike, 1/4"-1/2" wide, shorter than the culm, the lower very short; spikelets several or numerous, in 1-4 dense corymbose terminal and axillary clusters, narrowly oblong, acute at both ends, 2"-3' long; scales ovate or ovate-lanceolate, white, acute; bristles 9-15, downwardly barbed, slender, about as long as the achene and tubercle; style 2-cleft; achene obovate-oblong, smooth, pale brown, lenticular; tubercle triangular-subulate, flat, one-half as long as the achene.
In bogs, Newfoundland to Alaska, south to Florida, Kentucky, Minnesota, Idaho and California. Also in northern Europe and Asia. June-Aug.
Culms filiform, tufted, glabrous, 6'-20' tall. Leaves filiform, less than 1/4" wide, much shorter than the culm, the lower very short; spikelets few, in 1-3 terminal and axillary loose clusters, oblong, acute at both ends, 2"-3' long; scales ovate-oblong, chestnut-brown, keeled, mucronate; bristles 6, or sometimes 12, slender, downwardly barbed, or sometimes smooth, about equalling or becoming longer than the achene and tubercle; achene narrowly oblong, short-stalked, light brown, minutely wrinkled, lenticular; style 2-cleft; tubercle compressed, triangular-subulate, dark brown, about one-half as long as the achene.
In bogs, New Brunswick to Ontario, Minnesota, New Jersey, Pennsylvania, Indiana and Missouri. July-Aug.
R. Knieskernii Carey, Am. Journ. Sci. (II.) 4: 25. 1847.
Culms slender, tufted, smooth, 8'-18' tall. Leaves narrowly linear, flat, about 1/2" wide, much shorter than the culm; spikelets numerous, in several distant compact clusters, oblong, acute, about 1" long; scales chestnut-brown, ovate; bristles 6, downwardly barbed, equalling the achene; achene obovate, lenticular, brown, minutely wrinkled; style 2-cleft; tubercle triangular-subulate, pale, one-half as long as the achene or less and slightly decurrent on its edges.
Pine barrens, New Jersey to Virginia. July-Aug.
Schoenus glomeratus L. Sp. PI. 44. 1753. Rynchospora glomerata Vahl, Enum. 2: 234. 1806.
Rootstocks slender, culms smooth, triangular, slender or rather stout, 1/2°-4 1/2° high. Leaves flat, ¥'-2" wide, rough-margined, shorter than the culm; spikelets several or numerous, in 2-7 corymbose-capitate axillary rather loose clusters, oblong, narrowed at both ends, 1 1/2"-2" long; scales lanceolate, rich dark brown; bristles 6, downwardly barbed, rarely smooth, longer than or equalling the achene and tubercle; achene obovate, lenticular, smooth, dark brown; tubercle subulate, about as long as the achene.
In moist soil, New Brunswick to Ontario, Michigan, Arkansas, Florida and Texas. Consists of numerous races, differing in size, in width of leaves and in development of the inflorescence. July-Sept. False Bog-rush.