Memoirs of the Torrey Botanical Club 5: 25. 1894.
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 × 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.
Phenology: Flowering late spring–summer (Jun–Sep).
Habitat: Acid waters of ponds, lakes, bogs, and streams
Elevation: 0–1100 m
Ont., Ala., Conn., Del., Fla., Ga., Md., Mass., Miss., N.J., N.Y., N.C., Pa., R.I., S.C., Va.