Perennial herbs with a stout rootstock and slender, erect stems.
Leaves opposite, subopposite or some alternate, entire.
Stamens 5, filaments free, delicate, flattened; pseudostaminodes shortly and narrowly oblong with an incised apex, or more commonly small and tooth-like,to obscure or absent; anthers bilocular.
Ovary uniovulate, densely lanate in at least the upper two-thirds; style elongate (often exserted), stigma solitary and small.
Capsule delicate, irregularly splitting with the ripening of the seed.
Seeds yellow or reddish, somewhat compressed, feebly reticulate.
Flowers bibracteolate, hermaphrodite; inflorescences dense, capitate with one flower in the axil of each bract; bracts persistent after fruit fall, bracteoles deciduous with the fruiting perianth.