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 Hallii A. Gray, Man. Ed. 2, Add. 1863.
S. supinus var. Hallii A. Gray, Man. Ed. 5, 563. 1867.
Annual, culms very slender, smooth, tufted, obtusely triangular, erect, striate, 5'-12' tall. Lower sheaths oblique, and acuminate or mucronate on one side, the upper one commonly bearing a filiform blade, 4'-2 1/2' long; spikelets capitate in clusters of 1-7, oblong-cylindric, obtuse, many-flowered, 3"-6" long, about 1" thick, appearing lateral by the extension of the solitary involucral leaf which is 1'-4' long; scales ovate-lanceolate, light greenish brown, acuminate, keeled, cuspidate by the excurrent tip of the midvein; bristles wanting; stamens mostly 2; achene obovate-orbicular or slightly broader than high, black, planoconvex, mucronulate, strongly wrinkled transversely, about 1/2" in diameter.
In wet soil, Massachusetts to Florida, west to Illinois, Colorado, Texas and Mexico. Also in eastern Asia. The lowest sheaths occasionally subtend a flower with very long styles. July-Sept.
Scirpus debilis Pursh, Fl. Am. Sept. 55. 1814. Scirpus Smithii A. Gray, Man. Ed. 5, 503. 1867.
Annual, smooth, culms slender, obtusely triangular or nearly terete, tufted, erect or ascending, 6'-2° high. Sheaths obliquely truncate, the upper one rarely bearing a short subulate blade; spikelets capitate in clusters of 1-12, ovoid-oblong, subacute, many-flowered, appearing lateral, the solitary involucral leaf narrowly linear, 1 1/2-4' long, erect or divergent; scales light yellowish-brown with a green midvein, broadly ovate, obtuse or acute; bristles 4-6, downwardly barbed, somewhat unequal and about as long as the achene or short or wanting; stamens 2-3; style 2-cleft or rarely 3-cleft; achene plano-convex, broadly obovate or orbicular, smooth or slightly roughened, dark brown, shining, obtuse, mucronulate.
In wet soil. Maine to Ontario, Minnesota, Georgia, Alabama and Nebraska. July-Sept.
Acad. Sci. 11: 78. 1892. S. Olneyi contortus Eames, Rhodora 2: 220. 1907.
Perennial by long rootstocks, culms sharply triangular with concave sides or one of the sides nearly flat, erect, stiff, 1°-4° tall. Leaves 1-3, narrowly linear, keeled, shorter than the culm; spikelets oblong-ovoid, acute, 4"-12" long, capitate in clusters of 1-7, appearing as if lateral; involucral leaf solitary, slender, 1 1/2-4' long; scales broadly ovate, brown, often emarginate or sharply 2-cleft at the apex, the midvein extended into a subulate awn sometimes 1" long, the margins scarious, ciliolate or glabrous; bristles 2-6, downwardly barbed, shorter than or equalling the achene; stamens 3; style usually 2-cleft; achene obovate, plano-convex, smooth, dark brown, mucronate.