Annual, biennial or perennial herbs. Leaves alternate; ochreae tubular. Inflorescences racemose or paniculate. Flowers unisexual (plants monoecious or dioecious) or hermaphrodite, on jointed pedicels, arranged in whorls subtended by ochreoles. Perianth segments 6, greenish; outer 3 usually spreading or reflexed in fruit; inner accrescent into valves and later enclosing achene. Stamens 6, in 2 whorls. Ovary trigonous, 1-ovuled; styles 3, with fringed stigmas. Valves membranous or leathery, dentate or entire, with or without swollen tubercle on midrib. Achene enclosed, trigonous. Embryo lateral. Certain species (not ours) feature gender chromosomal dimorphism.