20. C. Engelmánni, Steud. Resembles n. 19; but the spikelets more slender and terete, somewhat remotely 5–15-flowered, the zigzag joints of the axis slender and narrowly winged, and the oblong or oval broadly scarious scales proportionally shorter, so as to expose a part of the axis of each joint, the successive scales not reaching the base of the one above on the same side; achene oblong-linear, very small.—Low grounds, Mass. to Wisc. and southward.
§ 5. MARÍSCUS. Spikelets 1–4-flowered, subterete, usually in dense heads; scales oppressed, several-nerved, the lower empty and often persistent after the fall of the rest of the spikelet; joints of the rhachis winged, enclosing the triangular achene. Perennial.
[*] Spikelets slender and acuminate, more or less refracted in usually close umbelled spikes.—Connecting with § 4.
21. C. Lancastriénsis, Porter. Culm (1–2° high) triangular; leaves rather broadly linear; umbel of 6–9 mostly elongated rays; spikelets very numerous in short-oblong close heads, soon reflexed, of 3–6 narrow scales, the upper and lower empty, twice the length of the linear-oblong achene, which is nearly 1´´ long.—Rich soil, Penn. and N. J. to Ala.
22. C. retrofráctus, Torr. Culm and leaves usually minutely downy and rough on the obtusish angles (1–3° high); umbel many-rayed; spikelets slender-awl-shaped, very numerous in obovate or oblong heads terminating the elongated rays, soon strongly reflexed, 1–2-flowered in the middle (3–5´´ long); scales usually 4 or 5, the two lowest ovate and empty, the fertile lanceolate and pointed, the uppermost involute-awl-shaped; achene linear, 1¼´´ long.—Sandy fields, N. J. to Fla. and Tex.
23. C. refráctus, Engelm. Culm 1–2° high; rays usually more or less elongated; spikelets very slender, in rather loose heads, divaricate or more or less reflexed, 2–4-flowered; achene linear, 1¼´´ long.—N. J. to N. C. and Mo.
[*][*] Spikelets very short, blunt, in densely compacted globose or cylindrical heads.
24. C. ovulàris, Torr. Culm sharply triangular (6´–2° high); umbel 1–6-rayed; spikelets (50–100) in a globular head, 3-flowered, oblong, blunt (1½–2´´ long); scales ovate, obtuse, a little longer than the ovate-oblong achene.—Sandy dry soil, southern N. Y. to Fla., west to Ill., Ark., and Tex.—Var. robústus, Boeckl., is a form with large heads (4–8´´ long), the spikelets 3–4-flowered. (C. Wolfii, Wood.)—Ill. to Ark., and southward.
25. C. Torrèyi, Britton. Like the last, but the heads cylindrical or oblong, spikelets usually 2-flowered, and achene linear-oblong.—L. Island to Fla., west to Tex.
2. KYLLÍNGA, Rottboell. ([Pl. 1.])