Callitriche petriei R.Mason

Monoecious or dioecious herb of wet ground with creeping unbranched stems ascending 3-7 cm, less often aquatic with submerged stems to 20 cm or more long, without definite rosettes. Terrestrial lvs (1)-2.2-(8) mm long, thin, spathulate or obovoid to suborbicular, entire, 3-5-nerved; submerged lvs slightly longer and linear or linear-spathulate, 1-nerved. Fls usually solitary in 1 lf axil of each pair, ebracteolate. Filaments 2-4 mm long; Style 1.7-2.2 mm long, ± persistent. Fr. 0.6-0.9 × 0.7-1.1 mm, suborbicular and broader than long; wing 0; faces strongly convex; commissural groove shallow and narrow.