Callitriche japonica Engelm. ex Hegelm.

Plants terrestrial on wet soil, riverine mud, or graveled tracks. Petiole 1-1.5 mm; leaf blade expanded, 1.5-4.5 × 1-2.5 mm, shiny and very neat in appearance; venation simple, generally limited to 1 primary and a pair of secondary veins with occasional short veins arising within and outside secondary veins. Flowers solitary, most frequently a pair of axils with a carpellate flower opposed by a staminate flower; bracts lacking; styles 0.28-0.33 mm, ± straight; filament 0.2-0.4 mm, ± straight; anthers 0.1-0.2 × 0.1-0.3 mm; pollen ca. 13 × 15.4 µm. Fruit 0.7-1 × 0.7-1 mm, brown to blackish when mature, tapering toward base; wing 0.05-0.13 mm at apex, 0.03-0.08 mm at side. Fr. Mar-Aug.

Fujian, Jiangxi, Taiwan [India, Indonesia, Japan, Thailand].

Riverbanks, disturbed ground, roads; near sea level to 2100 m.

Callitriche nana B. C. Ho & G. T. P. Vo.