7 C. erythrorhizos Muhl. Culm 2 - 3f high, obtusely triquetrous, longer than the leaves; umbel compound; rays 5 - 9, 3 - 4 long, each with 3 - 1 sessile clusters; sheaths entire; spikelets very numerous, 6" long, crowded and spreading in the oblong subsessilo (heads) clusters, a little flattened, about 13-fiowered; outer glumes mucronate, closely imbricated, chestnut-brown, veinless and shining, the inner ones entirely free from the rachis; sta. 3; ach. smooth and shining, much shorter than the glume. - Wet grounds Penn. and Southern States.
8 C. Hydra Mx. Nut Grass. Culm 6 to 12' to 2f high, 3-angled; lvs. shorter than the culm; umbel simple, 3 or 4-rayed, rays nearly as long as the involucre; spikes linear, alternate and 2-rowed on the rachis, 14 to 24-flowered; glumes ovate, veinless, acute, separate at the tips, of a fine purple brown; stam. 3; sty. 3-cleft, much exserted; ach. 3-angled. - Sandy fields, Va. to Fla. and La. Very troublesome in cotton fields. Rhizomes creeping and branching extensively, bearing tubers. Spikes 6 to 12" long. Apr. - Jl.
9 C. pbymatodes Muhl. Culm 1 - 2f high, 3-angled, striate; lvs. subradical, as long as the stem; umbel 4 - 6-rayed; rays often branched, bearing 12 - 20 linear, obtuse spikelets somewhat in 2 rows; sheaths obliquely truncate, involu-cels 0; spikelets 12 - 20-flowered, 6 - 8" long, the lowest generally fasciculate; glumes veiny, yellowish. - Moist fields, N. Y. to Wis. and S. States. Rhizomes creeping, bearing small, round tubers at the ends. May - Aug.
10 C. dissitiflorus Torr. Culms slender, tumid at the base, 1 to 2f high; lvs. narrow, nearly radical; umbel 3 to 5-rayed, suberect, half as long as the involucre; spikes remotely alternate, subdistychous on the slender rays, teretish, slender, 5 to 7-iiowered, 6" to V long; glumes lance-oblong, acute; ach. brown, 3-angled - E. Tenn. ? to La. Plant slender, erect. Rays of the umbel 1 to 3' long. Spikes divaricate and reflexed. Aug.
11 C. Michauxianus Schultes. Culm acutely triangular; umbel compound, with short rays; spikelets 6 - 9-flowered, the lower ones compound; rachis very broad, easily separating at the joints; ova. ovoid-triangular, enfolded by the interior, adnate scales. - Brackish swamps, generally near the sea, Middle and Southern States. Stem 12 - 15' high, reddened at the base, longer than the leaves. Spikelets 9" long, 7 - 9-flowered.
12 C. tetragonus Ell. Culm 2 to 3f high; lvs. shorter, channeled, serrulate on the margins and keel; umbel many-rayed, invclucels none; clusters oblong-cylindric; spikes 3 to 5-flowered, with a broad rachis and distinctly 4-angled; glumes slightly mucronate; ach. oblong, 3-angled. - Marshes, S. Car. to Fla. (Elliott Baldwin.)
13 C. strigosus L. Culm triquetrous, leafy only at base; lvs. broad-linear, rough-margined, about as long as the stem; umbel some compound, with elongated rays and oblong, loose clusters, their sheaths 3-bristled; involucels 0 or setaceous; spikelets numerous, linear-subulate, spreading horizontally, 8 - 10-flowered, 7 - 9 ' long; invol. of about 6 leaves, the 2 outer ones very long. - Wet grounds, U. S., frequent. Stem 1 - 2f high, bulbous at base. Umbel yellowish. Sept.
β. specioscs. Umbel compound, the partial umbels with leaf-like involucels. (C. speciosus Vahl.)
14 C. stenolepis Torr. Culm 2 to 3f high, slender, 3-angled; umbel simple, of a or 4 elongated rays; invol. 3 or 4-leaved; ochreœ (sheaths) truncate, pointless; spikes crowded, spreading or reflexed, linear, flattened, 5 to 8-flowered, in ovoid clusters; glumes distant, lance-linear, veined; ach. linear-oblong. - N. Car. to Ga. and Tenn. Spikes 6 to 8" long, of a dusky yellow.
15 C. Schweinitzii Torr. Culm 8 - 12'high, triquetrous, rough on the angles; lvs. shorter than the stem, about a line wide; umbel simple, erect, 4 - 6-rayed, rays elongated, unequal; sheaths truncate, entire; invol. 3 - 5-leaved, longer than the leaves, scabrous on the margin; spikelets 6 - 7, alternate, approximate, in cylindric clusters, 6 - 8-flowered, with a small, setaceous bract at the base of each; scales membranaceous on the margin; sta. 3; sty. 3-cleft, scarcely longer than the smooth achenia, - Shore of L. Ontario (Sartwell) of Lake Erie (Sullivant) to Ark.
16 C. inflexus Muhl. Culm setaceous, leafy at base, 2 - 3' high; lvs. equaling the stem; umbel 2 - 3-rayed, or conglomerate and simple; invol of 3 long leaves; spikelets oblong, 8 - 12-flowered, 10 - 20 together, densely crowded into the ovoid heads; glumes yellowish, veined, squarrous-uncinate at tip; sta. 1. - Banks of streams. Free States and British Provinces. Aug., Sept.
17 C. acuminatus Torr. & Hook. Culm 3 to 12' high, slender, obtusely triquetrous; lvs. erect, radical, as long as the stem; umbel 1 - 6-rayed; invol. 3 - 4-leaved, very long; rays unequal, each with a globous head of 15 - 40 spikelets; spikelets 3 - 11 ', oblong-linear, obtuse, 15 - 25-flowered; fls. very regularly imbricated in 2 rows; glumes acute, with the point recurved; sta, 1; ach. dull-grayish. - I11. (Mead.) and westward.
18 C. virens Mx. Culm 2 to 4f high, stout, 3-angled; lvs. nearly as long, strongly keeled, rough-edged; umbel compound, with 5 to 7 very unequal rays; invol. of 4 or more leaves, very long, involucels leafy; spikes ovate, in dense, globular heads, flattened, 10 to 20-flowered; glumes acute, greenish; stam. 1; ach. 3-angled, acute at each end. - Swamps, S. States. Spikes 3 to 5" long. Nut dull yellow. (C. vegetus Ell. Torr.)
19 C. echinatus. Culm 10' to 2f high, 3-angled, bulbous at base; lvs. numerous, rather shorter; invol. 6 to 10-leaved, long; umbel simple, 6 to 10-rayed; spikes short, teretish, acute, 3 to 6-flowered, in dense, globular heads; glumes striate, tawny, appressed; stam. 3; ach. obovate. - Dry fields, S. States. Boot with numerous fibres. Plant very leafy. Spikes 2 to 5 ' long, with a broad rachis. (C. Baldwinii Torr. Mariscus, E1l)