9. Elatine heterandra H. Mason, Madroño. 13: 240. 1956.
Mosquito waterwort Mosquito waterwort
Herbs, emersed on wet substrates, 0.5–3 cm. Stems ascending or prostrate, branched. Leaves usually green, sometimes reddish green; stipules ovate-lanceolate, 1 mm, margins irregularly toothed, apex acute; petiole 0.5–2 mm; blade obovate to broadly elliptic-oblong, 2–4 × 0.5–1.5 mm, base usually cuneate, sometimes rounded, apex acute to obtuse, notched. Pedicels absent. Flowers: sepals 2(–3), if 2, equal, if 3, 1 smaller, oblong, 1.1–1.3 × 0.3 mm; petals 3, pinkish, elliptic to ovate, 1–1.5 × 0.5 mm; stamens 1–6 (number variable within plant); styles 3. Capsules globose, 3-locular, 1.1–1.7 mm diam. Seeds 8–12 per locule, broadly ellipsoid to oblong, straight or curved 15–30°, 0.3–0.5 × 0.1–0.2 mm; pits rounded-hexagonal, length 1–2 times width, in 9–10 rows, 12–18 per row.
Flowering summer. Wet mud of montane ponds; (400–)1000–1500 m; Calif., N.Mex., Tex.
In California, Elatine heterandra is known from the North Coast Ranges and the Sierra Nevada; additionally, two disjunct localities are known for the species in McKinley County, New Mexico, and Kenedy County, Texas.