Perennial, terrestrial, epiphytic or aquatic, herbs; sometimes the whole plant reduced to a minute flat or fleshy body (in the former Lemnaceae). Leaves alternate, 1-many, petiolate; petiole usually with a basal sheath; lamina simple or variously lobed. Inflorescence pedunculate, consisting of a fleshy ± cylindric spadix subtended by, or enclosed within, a sometimes showy spathe; or in the former Lemnaceae borne in a lateral cavity of the plant body or within lateral pouches. Spadix either uniform with bisexual flowers or monoecious with female flowers at base and male above; sterile flowers often present in various arrangements, sometimes forming a sterile apex. Bracts 0. Flowers minute, sessile; perianth cup-like or composed of 4-9 free or connate segments. Stamens opposite perianth segments, free or connate. Ovary usually superior, 1-many-locular, each loculus with 1-many ovules; stigma (sub)sessile. Fruit a 1-many-seeded berry, these often brightly coloured or a utricle in the former Lemnaceae.