Perennial, the fibrous roots often prominently tuberculate; scape at first erect, but soon prostrate and even rooting, often producing small lvs and bulbils at the nodes of the infl; lvs erect, broadly ovate, obtuse, ±cordate at base, 5-20 נ3-15 cm; pellucid lines of the lvs mostly 1 mm or more apart and rarely over 1 mm long; fls in whorls of 5-15 on long, lax, often ±recurved pedicels; bracts lance-linear, long-acuminate, 1-2.5 cm; sep ovate to orbicular, obtuse, 5-7 mm, ±reflexed in fr, the veins evidently raised-roughened on the back; pet white, obovate, 6-12 mm; stamens ca 21; anthers 1-1.5 mm, versatile; achenes 40+, brown, 1.8-2.5 mm, with an ascending beak only 0.2-0.5 mm, the fruiting head ca 1 cm thick, nearly smooth in profile; each side of the achene with 3-4 abruptly curved and sometimes joining ribs of which the 1 or 2 toward the dorsal edge are wing-like distally; summit of the keel often crested; glands of the achene rounded at both ends and not closely approaching the beak; 2n=22. Swamps; D.C. to Fla., along the coastal plain, w. to Tex., and n. in the interior to s. Ind., Ill., Mo., and Kans., s. to tropical Amer. July-Oct. (E. radicans) Ours is nomenclaturally typical.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.