General: Aquatic or semi-aquatic perennial rooting in mud; stems matted, very slender, 5-10 cm long, leaf-bases joined by a tiny, winged ridge.
Leaves: All opposite; submerged leaves linear, single-nerved, very slightly notched terminally; emergent leaves wider, incompletely 3-nerved.
Flowers: Inflorescence of tiny, inconspicuous flowers borne without bracts or with tiny, brown, linear bracts; female flowers with distinct stalks, much longer than the fruits; styles sharply reflexed.
Fruits: Achene-like, 4, each 1-seeded, conspicuously wing-margined, oval, irregularly pitted in a fine network.
There are five Callitriche species in southern B.C. that may be confused with C. marginata: C. anceps, C. hermatophroditica, C. heterophylla ssp. bolanderi, C. stagnalis, and C. verna. The five species are very similar morphologically, but only C. marginata produces female flowers with distinct stalks that are longer than the fruit; styles are also sharply reflexed (Douglas et al. 1998b; M. Miller, pers. comm. 2008).
