Hydrothrix Hook. f.
Species commonly cultivated
Hydrothrix gardneri Hook. f. (Brazil)
Annual. Delicate narrow branching stems, with adventitious roots produced at nodes. Leaves in whorls of 7-30, regularly spaced along entire stem, sessile; leaf blade elongate, linear, sheathed at base. Inflorescence axillary, subtended by a green spathe. Flowers paired (superficially appearing as a single flower); perianth tubular, of 6 tepals in 2 whorls of 3, lobes unequal, yellow. Flowers are self-fertilized if they are unopen (cleistogamous) under water, or they open above water and are fertilized by insects. Dispersal is by seed.
still or slow moving waters such as lakes, ponds, and large rivers