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 hard oblong corms, culm smooth, slender or almost filiform, ascending or reclined, 6-18' long, usually longer than the rough-margined leaves. Leaves 1"-2" wide, keeled, those of the involucre, or some of them, much exceeding the inflorescence; spikelets densely clustered in 1-7 globose heads, linear, acute, 4-11-flowered, subterete or compressed, 1 1/2"-6" long, 1" wide or less; rachis wingless; scales ovate, acute or obtuse, pale green, strongly 7-11-nerved, appressed; stamens 3; style 3-cleft; achene oblong or obovoid, 3-angled, obtuse, apiculate, dull gray, two-thirds as long as the scale, about twice as long as thick.
Kyllingia cayennensis Lam. 111. 1: 149. I791-
Mariscus flavus Vahl, Enum. 2: 374. 1806.
C. flavus Boeckl. Linnaea 26: 384. 1869-70.
Perennial by short rootstocks; culms trigonous, smooth, 20 high or less. Leaves flat, 2"- 3 1/2" wide, the basal ones often as long as the culm, the largest one of the involucre sometimes half as long; spikelets 2.1/2" long or less, yellowish, turgid, spicate, the spikes oblong, mostly sessile in a terminal cluster, 5"-8" long, obtuse; scales ovate, striate, the lowest persistent; style 3-cleft; achene trigonous, oblong-obovoid, about half as long as the scale.
Waste grounds. Camden, N. J.. Philadelphia, Penna., and in the southern states. Adventive from tropical America.
Cyperus Grayi Torr. Ann. Lye. N. Y. 3: 268. 1836.
Perennial by thick hard oblong or ovoid corms, culms tufted, ascending or reclined, stiff, smooth, very slender, 6-20' long. Leaves shorter than the culm, bright green, 1" wide or less, those of the involucre 4-8, the longer somewhat exceeding the umbel; umbel 4-10-rayed, simple, the longer rays 3-4' long; sheaths of the rays truncate or nearly so; spikelets 2 1/2"-5" long, loosely capitate, compressed, linear, rigid, spreading; scales green, ovate, obtuse or subacute, strongly 13-15-nerved, rather widely spreading when old; joints of the rachis broadly winged; stamens 3; style 3-cleft: achene oblong or oblong-obovoid, obtuse, apiculate, about two-thirds as long as the scale.
In sands of the sea shore and in pine barrens, New Hampshire to Florida. July-Sept.