Annuals or low subshrubs, usually profusely hairy with mostly whorled branches. Leaves alternate, sessile, filiform, linear or ovate-triangular, usually terminating in divergent articulated bristles. Flowers perfect, axillary, with a pair of lateral bracteoles; perianth (4-) 5-merous, with a tuft of long hairs at base, the free segments unchanged in fruit; stamens with long filaments and oblong appendiculate anthers; style with 2 filiform stigmas. Fruit included, ovoid or orbicular, vertical, compressed, membranous, rugulose; seed exalbuminous with spiral embryo.