American waterwort, élatine américaine American waterwort, élatine américaine

Peplis americana Pursh, Fl. Amer. Sept. 1: 238. 1813; Elatine triandra Schkuhr subsp. americana (Pursh) Á. Löve & D. Löve; E. triandra var. americana (Pursh) Fassett

Herbs, submersed, 1.5–5 cm. Stems ascending or prostrate, branched. Leaves green; stipules lanceolate, 0.5–0.6 mm, margins dentate, apex acute; petiole 0.5–3 mm; blade obovate to broadly spatulate, 3–8 × 0.5–3.5 mm, base attenuate or cuneate, apex rounded to shallowly emarginate. Pedicels to 0.1 mm, erect. Flowers cleistogamous when submersed; sepals (2–)3, equal or 1 reduced, oblong-ovate or widely lanceolate, 0.5 × 0.3–0.5 mm; petals 3, greenish white or pinkish white to reddish, elliptic or ovate, 0.6–1.2 × 0.5 mm; stamens 3; styles 3. Capsules oblong-ovoid, 3-locular, 1.5 mm diam. Seeds 9–12 per locule, slenderly cylindric, ± straight, 0.4–0.6 × (0.1–)0.2 mm; pits angular-hexagonal, length 2–3 times width, in 6(–8) rows, (13–)16–25(–30) per row. 2n = 36.

Flowering summer–early fall. Muddy shorelines including estuaries, in water to 50 cm deep; 0–300(–900) m; Man., N.B., N.W.T., Ont., Que.; Calif., Conn., Del., Ill., Maine, Mass., Mich., Minn., Mo., Mont., N.H., N.J., N.Y., N.C., Okla., Pa., R.I., S.Dak., Va.