Genus: 2 species.
Region: one species is endemic to New Zealand, the other one is endemic to southern Patagonia and Tierra del Fuego.
Taxonomy: variously ascribed to
Lamiaceae by the
Cronquist classification and the Dahlgren classification, and
Scrophulariaceae.
Botany: reeping succulent, perennial, aquatic or semi-aquatic herbaceous herbs, bearing essential oils.hermaphrodites; stems prostrate rooting; leaves stem short, simple, opposite, with aromatic glands, no stipule, connate by flattened petioles, lamina is simple, minutely denticulate on the margin, leathery surface; flowers solitary, axillary or terminal,tetramerous, without free hypanthium; calyx distinct, of 4 fused sepals; corolla distinct, of 4 fused petals; androecium of 4 free, epipetalous, fertile stamens, alternate with the corolla lobes; anthers dorsifixed and introrse; pollen aperturate, colporate; gynoecium of 2 carpels, deeply lobed, seemingly 4 carpels, ostensibly isomerous with the perianth; ovary syncarpous, with 4 or 2 locules, each one housing 1 or 2 anatropous ovules; stigmas inconspicuous; placentation basal; fruit schizocarp, with 4, one-seeded, setulose nutlets; seeds extensively endospermic.