Callitriche verna L.
Mostly perennial, forming a rosette, glabrous, up to 25 cm long; stem branched; leaves sessile, upper ones forming a rosette, broadly elliptic to ovate, entire, obtuse, attenuate at base, 4.5 - 15 x 1.2 - 4 mm; lower leaves linear, obtuse, with truncate base, 4 - 12 x 0.5 - 1.5 mm. Flowers: one to two per axil, sessile; male flower bracts 2, c. 1 x c.0.5 mm, oblong; stamen one, 1.5 - 2 mm long; female flower bracts 2, oblong, obtuse,,tnmcate, c. 0.8 mm x c. 0.4 mm; styles 2, filiform, 1 - 2 mm long. Fruit schizocarp, meric axps winged only at apex, obovate, 1 - 1.5 x 0.6 - 1 mm.
Type: Described for Europe.
Distribution: N.Europe, cold and temperate Asia and North America.