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 very slender rootstocks, culms very slender, or filiform, erect, pale green, 3-angled, 2'-10' tall. Upper sheath with a white, hyaline, scarious limb; spikelet oblong or ovoid, subacute, 2.-5 times as thick as the culm, about 2" long, 1 1/4" in diameter, several-flowered; scales pale green, oblong-lanceolate, obtuse or the upper acute, thin, hyaline with a faint midvein; style 2-cleft; bristles about 6, slender, re-trorsely barbed, as long as or somewhat longer than the achene, or wanting; achene 1/4" long, lenticular, obo-vate, smooth, brown, 2-4 times as long as the conic acute tubercle, which is often constricted at the base.
In wet soil, New Jersey and Delaware to Florida and Mississippi. Also in tropical America. Aug.-Sept.
Eleocharis olivacea Torr. Ann. Lye. N. Y. 3: 300. 1836.
Perennial by running rootstocks, often tufted and matted, culms very slender, bright green, erect or reclining, flattened, 1'-4' long. Upper sheath with a white hyaline limb; spikelet ovoid, acute or obtuse, much thicker than the culm, several-many-flowered, about 2" long, 1" in diameter; scales ovate, thin, acute, reddish-brown, with a green midvein and narrow, scarious margins; stamens 3; style 2-cleft; bristles 6-8, slender, retrorsely barbed, longer than the achene and tubercle; achene obovoid, similar to that of the preceding species but twice as large, 3-4 times the length of the conic acute tubercle.
In wet soil, Maine to southern Ontario, Michigan, Pennsylvania, South Carolina and Kansas. Aug.-Sept.
Scirpus atropurpureus Retz, Obs. 5: 14. 1789. Eleocharis atropurpurea Kunth, Enum. 2: 151. 1837.
Annual, roots fibrous, culms tufted, very slender, I' -3 1/2' high. Upper sheath 1-toothed; spikelet ovoid, many-flowered, subacute, l 1/2"-2" long, 1" in diameter or less; scales minute, ovate-oblong, obtuse or the upper acute, persistent, purple-brown with green midvein and very narrow scarious margins; stamens 2 or 3; style 2-3-cleft; bristles 2-4, fragile, white, minutely downwardly hispid, about as long as the achene; achene jet black, shining, J" long, smooth, lenticular; tubercle conic, minute, depressed but rather acute, constricted at the base.
In moist soil, Nebraska and eastern Colorado to Central America, east to Iowa and Florida; widely distributed in tropical America, Europe and Asia. July-Sept.