Stems: slender, glabrous. Leaves: linear or lanceolate, acute, sessile, in crowded verticles of six to twelve, more or less sphacelate at the apex. Flowers: small, axillary; calyx-limb minute, entire; petals none; stamen one, with a short thick filament and comparatively large two-celled anther dehiscent by lateral slits. Fruit: a small, one-celled, one-seeded drupe.

This is also an aquatic herb, with slender erect stems, bearing circles of from six to twelve narrow leaves in the axils, and curious tiny flowers which have no petals and only one stamen inserted on the margin of the calyx. The plant grows from eight to twenty inches high.

Hippuris montana, or Mountain Mare's Tail, is a tiny species growing only two to four inches high, and has narrow pointed leaves in whorls and an oval fruit.