[*][*] Spikelet cylindrical, many-flowered, 1–2´ long; scales in several ranks, firm-coriaceous with scarious margin, pale, nerveless or faintly striate; culms large and stout (2–4° high); basal sheaths often leaf-bearing.
2. E. equisetoìdes, Torr. Culm terete, knotted as if jointed by many cross-partitions; achene smooth (the minute reticulation transversely linear-rectangular), with a conical-beaked tubercle.—Shallow water, R. I. to Fla., west to Mich. and Tex.
3. E. quadrangulàta, R. Br. (Pl. 3, fig. 6–9.) Culm continuous and sharply 4-angled; achene finely reticulated, with a conical flattened distinct tubercle.—Shallow water, central N. Y. to Mich., and southward; rare.
§ 2. Spikelet terete and turgid-ovate, much thicker than the very slender culm; scales thin-coriaceous or firm-membranaceous, persistent, ovate; style 3-cleft; bristles stout, barbed downward (or sometimes upward), as long as the striate and pitted-reticulated triangular achene and its tubercle; culms tufted from fibrous roots, 1–2° high.
4. E. tuberculòsa, R. Br. (Pl. 3, fig. 10.) Culms flattish, striate; spikelet 3–6´´ long, many-flowered; tubercle flattish-cap-shaped, as large as the body of the achene.—Wet sandy soil, from Mass. along the coast to Fla.
5. E. tórtilis, Schult. Culms sharply triangular, capillary, twisting when dry; spikelet 2–3´´ long, few-flowered; conical-beaked tubercle much smaller than the achene. (E. simplex, Torr.)—Eastern shore of Md. to Fla.
§ 3. Spikelets terete, much thicker than the culm, many-flowered; scales imbricated in many or more than 3 ranks, thin-membranaceous or scarious, with a thicker midrib, usually brownish or purplish, sometimes deciduous.
[*] Style 2-cleft (often 3-cleft in n. 7 and 10) and the smooth achene lenticular; culms slender or thread-form, terete or compressed.
[+] Annuals; culms tufted, from fibrous roots.
6. E. capitàta, R. Br. Culms terete, ¼–8´ high or more; spikelets ovate to oblong (1–3´´ long), obtuse, 15–40-flowered; scales thickish, round-ovate, obtuse, brown or brownish with green keel and paler margins; stamens 2; achene obovate, black, about equalling the 6–8 bristles, tipped with a flattened or saucer-shaped tubercle. (E. dispar, E. J. Hill.)—In sand or gravel near sloughs, Md. (Canby) to Fla. and Tex.; N. Ind. (Hill). (S. Am., etc.)