Herbs, perennial, suffrutescent, glabrous. Stems numerous from base, erect or prostrate, branched, ribbed, not jointed, not armed, not fleshy. Leaves opposite (rarely alternate), connate, clasping at base, sessile, succulent; blade linear or broadly ovate, margins entire, apex acute or apiculate. Inflorescences axillary, flowers solitary or in 2–3-flowered clusters, bibracteate. Flowers bisexual, with 1 or 2 bractlets ± equaling perianth length; perianth deeply 5[–7]-parted, segments strongly imbricate, chartaceous; stamens 5; stigmas 2. Fruiting structures: fruit a utricle; pericarp free from seed, membranous, indehiscent. Seeds vertical, lenticular; seed coat black, shiny; embryo annular, perisperm copious. x = 9.
w United States, Central America, South America.
Species ca. 5 (2 in the flora).