Callitriche muelleri Sond.

Monoecious, prostrate, branching, terrestrial herb. Lvs 2.5-7.5 × 1.5-4.8 mm; lamina thin, typically rhomboid, broader than long, with a single small tooth on either side and with a free vein running to it, otherwise 3-5-nerved; earlier-formed lvs simpler in outline. Fls usually 1 ♂ and 1 ♀ together in an axil, ebracteolate. Filaments c. 0.2-0.3 mm long. Styles c. 0.05 mm long, lengthening to 0.15 mm in young fr. but falling before maturity. Fr. 1.1-(1.2) × (1.2)-1.3-(1.4) mm, broadly obcordate or oblong, ferrugineous; wing broad and conspicuous, membranous, crispate, pale brown or whitish; faces shallowly grooved; commissural groove deep.