Creeping or floating annual; lvs linear to obovate, 3-8 mm; fls mostly 3-merous; seeds axile, set at different levels in the fr, marked with transversely elongate, 6-sided areoles, the angular ends of the areoles dovetailed with those of adjacent rows, the longitudinal ridges appearing narrow or broken; 2n=ca 40. Three vars.: Var. triandra has linear to spatulate, often retuse lvs, and seeds with 16-26 areoles in each longitudinal row; Wis. and N.D. to Wash. and Calif., also in Eurasia, and intr. in Me. Var. americana (Pursh) Fassett has obovate, rarely retuse lvs, otherwise like var. triandra; muddy tidal shores, Que. and N.B. to Va., and also in Mo. Var. brachysperma (A. Gray) Fassett has obovate lvs, and seeds with 9-15 areoles in each longitudinal row; s. O. and c. Ill. to w. U.S.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Duration: Annual Nativity: Native Lifeform: Forb/Herb General: Prostrate and mat forming aquatic amphibian, the herbage glabrous. Leaves: Opposite, sub-sessile to short petiolate, 3-15 mm long, linear to narrowly oblanceolate to spatulate or oblong. Flowers: Sessile, 1-2 per node, with 3 sepals and 3 membranous petals. Fruits: Capsule of 4 carpels. Ecology: Found in still water and along lake margins from 5,000-8,000 ft (1524-2438 m), flowers from May-September. Distribution: Ranges north to Canada across the United States. Notes: There is still a little uncertainty about this species, the name for this species follows Tropicos. Ethnobotany: Unknown Etymology: Elatine is a Greek name for a low creeping plant, while triandra comes from Greek triandrus, meaning having three pollinia. Synonyms: Elatine americana, Elatine ambigua, Elatine chilensis, Elatine hydropiper var. triandra, Elatine senegalensis Editor: SBuckley, 2011