Annual herbs, pubescent or hairs long-villous, rarely glabrous. Stem erect, short, much branched. Leaves fleshy, alternate, linear, terete, tip mucronate, mucro dehiscent. Flowers solitary axillary, sessile, subtended by adpressed bracts. Perianth segments 5, ± oblong, free, membranous when young, hardening in fruit and flask-shaped below, enveloping the fruit with erect connivent upper parts, without wing-like appendages or with short wing-like protuberances. Stamens (4-) 5; anthers linear; connective appendages prominent, vesicular, generally yellow, subsessile. Style bifid. Seeds vertical; embryo spiral; endosperm absent.