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 interstinctus Vahl, Enum. 2: 251. 1806. Scirpus cquisetoides Ell. Bot. S. C. & Ga. 1: 79. 1816. Eleocharis interstincta R. & S. Syst. 2: 148. 1817. Eleocharis equisetoides Torr. Am. Lye. 3: 296. 1836.
Perennial by stout rootstocks, sometimes tuber-ifcrotis; culms terete, hollow, nodose, papillose, 1 1/2°-3° tall, the sterile ones sharp-pointed. Sheaths oblique, membranous, brown or green, the lower sometimes bearing short blades; spikelet terete, cylindric, many-flowered, subacute, i'-i 1/2" long, 2" in diameter, not thicker than the culm; scales ovate, orbicular or obo-vate, obtuse or the upper acute, narrowly scarious-margined, faintly many-nerved, persistent; bristles about 6, rigid, retrorsely barbed, as long as the body of the achene or shorter; stamens 3; style 3-cleft, exserted; achene obovoid, brown, shining, with minute transverse ridges, obtusely trigonous, 2 or 3 times as long as the conic acute black tubercle.
Perennial by stout rootstocks, sometimes tuberif-erous; culms sharply 3-4-angled, stout, not nodose, papillose, 2°-4° tall. Sheaths purplish-brown or green, membranous, sometimes bearing short blade::; cpikelet terete, acute, cylindric, l'-2' long, 2" in diameter, many-flowered, about as thick as the culm; scales coriaceous, broadly ovate or obovate, obtuse or the upper subacute, scarious-margined and sometimes with a narrow brown band within the margins, faintly many-nerved, persistent; bristles about 6, rigid, retrorsely barbed, about as long as the achene; stamens 3; style 3-cleft; achene obovoid, biconvex or slightly angled on the back, minutely cancellate, about twice as long as the conic acute tubercle.
Eleocharis Robbinsii Oakes, Hovey's Mag. 7: 178. 1841.
Perennial by slender rootstocks, culms slender, 3-angled, continuous, 6'-2° long, sometimes producing numerous filiform flaccid sterile branches from the base. Sheaths ap-pressed, obliquely truncate; spikelet subulate, few-flowered, not thicker than the culm, 6"-10" long, 1" in diameter; scales lanceolate or oblong-lanceolate, obtuse or subacute, strongly concave, faintly several-nerved, persistently clasping the rachis, narrowly scarious-margined; style 3-cleft; bristles 6, equalling the achene and tubercle, retrorsely barbed; achene obovoid, light brown, biconvex or very obtusely angled on the back, somewhat longer than the conic-subulate flattened tubercle, which has a raised ring around its base.
In shallow water, Nova Scotia to Michigan, south to Florida. Aug.-Sept.