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..
Scirpus capitatus L. Sp. PI. 48. 1753.
Eleocharis dispar E. J. Hill, Bot. Gaz. 7: 3. 1882.
Annual, roots fibrous, culms densely tufted, nearly terete, almost filiform, rather stiff, 2'-10' tall. Upper sheath 1-toothed; spikelet ovoid, obtuse, much thicker than the culm, 1 1/2"-2 1/2" long, 1"-1 1/2" thick, many-flowered; scales broadly ovate, obtuse, firm, pale or dark brown with a greenish midvein, narrowly scari-ous-margined, persistent; stamens mostly 2; style 2-cleft; bristles 5-8, slender, downwardly hispid, as long as the achene; achene obovate, jet black, smooth, shining, nearly 1/2" long; tubercle depressed, apiculate, constricted at the base, very much shorter than the achene.
In moist soil, Maryland to Florida, west to Indiana and Texas. Widely distributed in tropical regions. July-Sept.
Annual, roots fibrous, culms tufted, slender or filiform, rather deep green, nearly terete, mostly erect, 2'-16' tall. Upper sheath 1-toothed; spikelet ovoid or oblong, obtuse, many-flowered, 2"-5" long, 1"- 1 1/2" in diameter; scales thin, oblong-orbicular, very obtuse, brown with a green midvein and scarious margins; bristles 6-8, sometimes fewer or wanting, deciduous, usually longer than the achene; stamens 2 or 3; style 2-3-cleft; achene pale brown, shining, lenticular, obo-vate-oblong, smooth, 1/2" long or more; tubercle deltoid or depressed, acute, about one-forth as long as the achene and narrower.
In wet soil, New Brunswick to Ontario, Michigan and Connecticut. Also in Europe. July-Sept.
Eleocharis obtusa Schultes, Mant. 2: 89. 1824.
Annual, with fibrous roots; culms tufted, slender to filiform, 1-18' long. Upper sheath 1-toothed; spikelet ovoid to ovoid-oblong, 1"-6 1/2" long, 1"-2 1/2" thick, densely many-flowered; scales broadly obovate, obtuse, brown with pale margins; achene pale brown, obovate, smooth, lenticular, about 1/2" long; tubercle deltoid or depressed, nearly or quite as wide as the top of the achene; bristles mostly longer than the achene.
In wet soil. Cape Breton Island to Minnesota, British Columbia, Florida, Texas and Oregon. July-Sept.