Bull. Torrey Bot. Club 18: 236. 1891.
Leaves connate at base, spatulate, 2.8–5 × 1.8–3.3 mm, 1+-veined. Stem and leaf scales present. Inflorescences: bracts caducous. Pedicels 0–25 mm in fruit. Flowers usually 1 staminate and 1 pistillate in 1 axil opposed by 1(+) pistillate; styles erect and spreading to recurved; pollen yellow. Schizocarps 0.9–1.4 × 0.8–1.2 mm, as long as or longer than wide; mericarps black, not swollen, evenly winged throughout, wings straight, 0.03–0.1 mm wide.
Phenology: Flowering Mar–May.
Habitat: Vernal pools.
Elevation: 0–700 m.
Callitriche longipedunculata is known from most of California, including the Inner North Coast Ranges, Cascade Range Foothills, Great Central Valley, San Francisco Bay Area, and western Pensisular Ranges (R. V. Lansdown and R. E. Preston, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=16691).