Moss-like plant. Roots to 30 mm long, to 2 mm wide. Stems 25–90 mm long, c. 1 mm wide including enveloping leaf bases. Leaves thick-textured, ± cuneate, strongly keeled, sessile, decurrent, ± stem-clasping at base and obscuring the stems, c. 0.5–2 mm long; apex of mature leaves 3-or 4-toothed; teeth mostly minute on fertile plants, but on sterile plants central tooth elongated, filiform, to 25 mm long. Spathella c. 2 mm long, globular-ellipsoidal, rupturing irregularly. Tepals narrowly lanceolate, 0.5–0.8 mm long. Staminal filament thick, c. 2 mm long; anther broad, c. 0.8 mm long, dorsifixed. Ovary ± globular to ellipsoidal, 1.5–2.1 mm long; stigmas oblong-lanceolate. Fruit broadly ellipsoidal, 10-ribbed, c. 1.8–2.5 mm long; fruiting pedicel 0.5–42 mm long.
Grows in streams, attached to basalt rocks (one record on gneiss) in fast-flowing or turbulent fresh water, often in rapids and waterfalls, submerged in depths to 50 cm or in continuous waterspray. Withstands desiccation when waters recede and flowers at the waterline when exposed.
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