§ 2. CYPERUS proper. Achene triangular; spikelets usually many-flowered, more or less flattened, with carinate scales, the rhachis marginless or nearly so (winged in n. 12).
[*] Stamen 1; spikelets short and small (1½–5´´ long) in globular heads, ovate or linear-oblong, many-flowered; achene oblong-obovate to linear.
[+] Low annuals; involucre 2–3-leaved; heads few; scales pointed.
6. C. aristàtus, Rottb. Dwarf (1–5´ high); spikelets chestnut-brown, oblong becoming linear, 7–13-flowered, in 1–5 ovate heads (sessile and clustered, or short-peduncled); scales nerved, tapering to a long recurved point; achene oblong-obovate, obtuse. (C. inflexus, Muhl.)—Sandy wet shores; common. Sweet-scented in drying.
7. C. acuminàtus, Torr. Slender (3–12´ high); spikelets ovate, becoming oblong, 16–30-flowered, pale; scales obscurely 3-nerved, short-tipped; achene oblong, pointed at both ends.—Low ground, Ill. and southwestward.
[+][+] Tall perennial (1–4° high); heads many, greenish; scales pointless.
8. C. calcaràtus, Nees. Culm obtusely triangular; leaves and involucre very long, keeled; umbel compound, many-rayed; spikelets ovate (1½´´ long), in numerous small heads; achenes pale, linear, on a slender stipe; scales narrow, acutish, obscurely 3-nerved. (C. virens, Gray, in part; not Michx. C. Luzulæ, var. umbellatus, Britt.)—Wet places, Del. to Fla. and Tex.
[*][*] Stamens 3 (2 in C. fuscus); spikelets clustered on the rays of a simple umbel (or in a single sessile head); scales mostly green or greenish and many-nerved, abruptly sharp-pointed; achene obovate, sharply triangular.
[+] Low annuals.
9. C. Compréssus, L. Culms 3–9´ high, with a simple sessile or a few umbellate clusters of oblong to linear spikelets (15–30-flowered and 3–8´´ long) with crowded strongly keeled and very acute pale scales.—Sterile fields along the coast, Md. to Fla. and Tex.; also adventive near Philadelphia.