Perennial, rhizomatous, glabrous herbs; aerial shoots unbranched, with green leaves. Leaves distichously to spirally arranged along the stem, composed of an open sheath and an entire lamina with closely set, pinnately arranged, parallel, secondary veins, lower side often glaucous or lanuginose; lamina supervolute in bud. Inflorescence terminal, bracteate, sympodially branched or simple, with 1- or 2-flowered cincinni. Flowers asymmetric, perfect, epigynous, pentacyclic, 3-merous; sepals composed of 3, free, slightly unequal, imbricate sepals; corolla composed of 3, unequal, imbricate petals, basally connate into a tube; androecium essentially composed of two 3-merous whorls, the inner whorl composed of 1 petaloid stamen, the staminode previously called ‘labellum’, and often a second inner staminode, the outer whorl composed of 0–2 staminodes; staminodes petaloid, varying in number; stamen with a solitary monothecal, 2-sporangiate, marginal anther; style petaloid, stigmatic areas terminal and marginal; floral tube formed by the connate parts of petals, staminodes, stamen, and style; ovary inferior, 3-locular, with numerous, anatropous ovules arranged on axile placentae in 2 alternating rows per locule, septal nectaries 3, opening by holes into the base of the floral tube. Fruit a capsule, crowned by the persistent sepals, loculicidally dehiscent or seeds released by the breakdown of the capsule wall, wall tuberculate. Seeds numerous, exarillate, with imbibition lid, copious perisperm, and straight embryo.