Rhizomatous perennial herbs or climbers. Stems erect, unbranched. Leaves alternate, often crowded at the end of stems, linear, lanceolate or ovate, rarely oblanceolate or obovate, usually resupinate. Inflorescence a terminal 2–many flowered corymbose cyme with leafy bracts, rarely a solitary flower. Flowers bisexual, actinomorphic or zygomorphic; perianth segments free, in 2 similar or differentiated whorls of 3, the inner 3 tepals often dissimilar. Stamens in 2 whorls of 3, free, anthers sagittate, 2-locular, dehiscing by longitudinal slits. Ovary inferior, 1-locular with parietal placentation, or 3-locular with axile placentation; ovules usually many; style terminal with 3 branches. Fruit a loculicidal capsule, rarely a berry; seeds ± globose, usually brown.
5 genera with about c. 170 species from South and Central America; 2 genera in Australia (1 naturalised).