Acta Bot. Neerl. 15: 477, figs. 1, 2. 1966.
Leaves not connate at base, ± linear, tapering from base, 12 × 0.3–0.5 mm, 1-veined. Stem and leaf scales absent. Inflorescences: bracts absent. Pedicels 0.5–1 mm in fruit. Flowers solitary or 1+ per axil; styles recurved, ± reflexed; pollen colorless. Schizocarps 1.1–1.8 × 1.5–2.5 mm, shorter than wide; mericarps black, not swollen, winged throughout, wings straight, 0.1–0.3 mm wide.
Phenology: Flowering Apr–May(–Jul).
Habitat: Vernal and permanent pools, running water.
Elevation: 0–1600 m.
Calif., Nebr., Oreg.
Callitriche fassettii is widespread in California and adjacent Oregon. The record from Nebraska is based on a single specimen, which could be due to introduction, or could involve an identification or recording error and requires confirmation.