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, with short stolons, the base of the culm slightly thickened. Culms loosely tufted to solitary, very slender, smooth, striate, somewhat compressed, 1°-2° high; leaves rough-margined, involute, at least toward the tip, 1" wide or less, shorter than the culms; bracts of the involucre mostly shorter than the umbel, ciliate; umbel a little compound, its rays filiform; spikelets few to several, ovoid to ovoid-oblong, acutish, 5" long or less, many-flowered; scales yellow-brown, ovate, striate, mucronate or the lower ones awned, glabrous, dull; stamens 3; achene broadly obovate, blunt, cancellate in many rows, chestnut-brown, nearly \" long.
Colorado and Nebraska to Texas. Type collected by Geo. E. Osterhout at Sterling, Logan County, Colorado, Aug. 13, 1896.
Scirpus pubcrulus Michx. Fl. Bor. Am. 1: 31.
Perennial by stout rootstocks, culms slender, 3-angled, 8-2° tall, usually exceeding the leaves. Leaves involute, less than 1" wide when unrolled, often more or less pubescent, their sheaths green; leaves of the involucre 2-4, short; umbel simple or compound, the rays ¥-2' long; central spikelets sessi e; spikelets oblong, obtuse or subacute, 3"-5" long, 1"-1 1/2" in diameter; scales thin, brown with a lighter midvein, broadly oblong or nearly orbicular, dull, puberulent, obtuse or mucronate; stamens 2-3; style 2-cleft; achene obovate or oblong, biconvex, pale brown, longitudinally striate and reticulated.
F. Baldwiniana Torr. Ann. Lye. N. Y. 3: 344. 1836.
Annual, roots fibrous, culms slender, flattened, striate, densely tufted, erect or ascending, 2'-15' long, usually longer than the leaves. Leaves flat, about \" wide, glabrous or sparingly ciliate, pale green and appearing glaucous, those of the involucre 3-5, one of them often exceeding the umbel; umbel simple or slightly compound, the central spikelet sessile; spike-lets ovoid or ovoid-oblong, 3"-6" long, about 1" in diameter; scales ovate, thin, pale greenish-brown, subacute or mucronulate; stamen 1; style 2-cleft, pubescent; achene biconvex, obovoid, light brown, longitudinally ribbed, the ribs tubercled and connected by very fine cross-lines.