Fl. Chil. 1: 286. 1846.
Herbs, emergent on wet substrates, 0.5–10 cm. Stems ascending or prostrate, branched. Leaves usually green, sometimes reddish green; stipules triangular, 0.5–0.6 mm, margins entire, apex acute; petiole 1–3 mm; blade obovate to broadly spatulate, 3–4(–8) × 0.5–2.5 mm, base cuneate to rounded, apex obtuse to slightly emarginate. Pedicels absent. Flowers: sepals 2–3, if 2, equal, if 3, 1 smaller, oblong, 0.5 × 0.3 mm; petals 3, pinkish white to reddish, elliptic to ovate, 1–1.5 × 0.5 mm; stamens 3; styles 3. Capsules depressed-ovoid, 3-locular, 1.5–2 mm diam. Seeds 23–33 per locule, ellipsoid, straight or curved to 20°, 0.4–0.5 × 0.1–0.2 mm; pits angular-hexagonal, length 3–5 times width, in 6 rows, 16–25(–35) per row.
Phenology: Flowering summer.
Habitat: Muddy shores (fresh or tidal), shallow vernal pools, ditches, rice fields.
Elevation: 0–2800 m.
Ariz., Calif., Nev., N.Mex., Oreg., Wash., South America.
The distribution of Elatine chilensis has an amphitropical disjunction between western North America and southern South America. The minute seeds of E. chilensis probably have been dispersed between the two regions by birds (S. Carlquist 1983).