Herbs, perennial, to 70 cm; rhizomes absent; stolons present; corms present. Leaves emersed; petiole triangular, 10--40 cm; blade sagittate, 4.5--10 ´ 0.2--2 cm, basal lobes ± equal to remainder of blade. Inflorescences racemes, of 2--4 whorls, emersed, 5--14 X 2--4 cm; peduncles 20--38 cm; bracts distinct or if connate, then less than ¼ total length, lanceolate, 5--25 mm, not papillose; fruiting pedicels spreading, cylindric, 1.5--3.5 cm. Flowers to 30 mm diam.; sepals recurved to spreading, not enclosing flower or fruiting head; filaments linear, longer than to equal length of anther, glabrous; pistillate pedicellate, without ring of sterile stamens. Fruiting heads 1--1.8 cm diam.; achenes cuneate to obovoid, without abaxial keel, 2.4--4 ´ 1.5--3.8 mm, beaked; faces not tuberculate, wings 1--3, ± entire, glands 1--2; beak lateral, obliquely ascending, (0.7--)1--2.1 mm. 2n = 22. Flowering late spring--summer (Jun--Sep). Acid waters of ponds, lakes, bogs, and streams; 0--1100 m; Ont.; Ala., Conn., Del., Fla., Ga., Md., Mass., Miss., N.J., N.Y., N.C., Pa., R.I., S.C., Va.
Erect; lvs long-petioled, the blade sagittate (rarely merely lanceolate), its main portion mostly narrow, 4-10 נ0.2-2(-5) cm, (1-)2-many times as long as wide, with narrow, linear to lance-attenuate basal lobes; petioles rounded or with 2 blunt ridges on the abaxial side; scape 2-8 dm, with 2-4 whorls of fls, the upper staminate, the lower pistillate; pedicels 0.5-3.5 cm, ascending in fr; bracts herbaceous and relatively thick, 5-25 mm, mostly shorter than the pedicels; sep short, 4-7 mm, reflexed in fr; pet 8-12 mm; stamens 15-25, the slender, glabrous filaments as long as or longer than the anthers; mature receptacle markedly echinate; achenes 2.5-4 mm, with 1 or 2(3) wings on each face, these extending onto the obliquely ascending, 1-2 mm beak; achene- faces with resin-ducts; 2n=22. Acid waters of bogs, ponds, and streams near the coast from Mass. to Fla. and Miss., mainly on the coastal plain, but inland to w.c. N.Y. Aug., Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
