Plant: perennial, aquatic or amphibious herb, of brackish and fresh water, generally glabrous; AERIAL STEMS mostly 20-60 (-100) cm tall Leaves: mostly 5-35 mm long, 1-3 mm wide; whorled in sets of (4-)6-12(-16), simple, estipulate; margins entire; submersed leaves slender, thin and flaccid, often soon degenerating; aerial leaves thicker and firmer, numerous and rather crowded, linear-attenuate Flowers: solitary in upper leaf axils, inconspicuous, sessile or the lower on short pedicels; perfect or rarely imperfect, occasionally polygamous; calyx reduced to an inconspicuous, 2-4-lobed or subentire rim around the top of the ovary; petals none; stamen 1, with a short, slender filament and a large 2-celled sagittate anther; pistil simple, the ovary inferior, unicarpellate; style terminal, elongate, slender, generally lying in the groove between the two anther sacs, with anthers 1 mm long, 0.5-1 mm wide, the filament about as long; style 1-2 mm long Fruit: FRUITS ellipsoid-obovoid, 1.7-2.5 mm long, 1 mm wide Misc: Rooted in mud of shallow, standing or slow-moving water, and in wet meadows; 2300-2850 m (7600-9400 ft); Jun-Jul (fr. Jul-Aug) REFERENCES: Ricketson, Jon. 1995 Hippuridaceae. J. Ariz. - Nev. Acad. Sci. 29(l): 25.
Perennial aquatic herb 20 cm - 1 m tall Stem: emersed, soft but erect, usually unbranched, hollow. Leaves: whorled, stalkless, thin and often soon degrading when submersed, thick and firm when emersed, the many crowded emersed leaves 1 - 3 cm long and 1 - 3 mm wide. Flowers: borne solitary in the leaf axils, stalkless, tiny, with sepals reduced to a small tube around the ovary, zero petals, a single stamen, and a single pistil. Fruit: an achene 1.7 - 2.5 mm long.
Similar species: No information at this time.
Habitat and ecology: Rare in streams and ponds.
Occurence in the Chicago region: native
Etymology: Hippuris is the Greek name meaning horse-tailed. Vulgaris means common.
Stems soft but stiffly erect, unbranched, mostly 2-6(-10) dm, the internodes of the submersed part often longer than the lax, thin lvs, which may soon degenerate; emersed lvs thicker and firmer, numerous and rather crowded, usually widely spreading, linear, 1-3 cm נ1-3 mm; fls sessile; frs 1.7-2.5 mm; 2n=32. In shallow, quiet water, or seldom on mud; circumboreal, in Amer. s. to Me., n. N.Y., n. Ind., Io., and N.M.; Australia and s. S. Amer. A salt-marsh form with elliptic obtuse lvs in 4's has been called f. maritima Hellenius. (H. tetraphylla)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.