Perennial herb; stems creeping or floating, ascending towards apex, rooting at the lower nodes, branched, hollow, with a longitudinal hairy groove on 2 opposite sides. 

Leaves
Subsessile or with petiole to 5 mm long, with a ring of white hairs between the 2 opposite leaf bases.  Lamina 3-13 x 1-3.5 cm, elliptic to oblanceolate or obovate, glabrous or slightly hairy near the attenuate base; apex obtuse or acute.

Inflorescences
In upper axils, mostly 1-2 cm in diameter, capitate, white; pedicles to 9 cm long with 2 opposite longitudinal hairy grooves, occasionally heads shortly pedunculate and terminal.  Bracts 2.5-3.5 mm long, ovate-acuminate; bracteoles similar to bracts, somewhat smaller, persistent.  Tepals 5-7 mm long, oblong to ovate, acute or obtuse.  Fertile stamens 5; staminodes = stamens.  Style short, thick; stigma capitate.