Leaves entire, alternate or occasionally opposite, semiterete from the more or less closely revolute margins, linear.
Much-branched erect, annual or perennial herbs.
Bracts persistent on the inflorescence axis.
Flowers in elongate, bracteate, spike-like thyrses formed of more or less distant, bibracteolate partial inflorescences consisting of a single fertile flower subtended by two modified sterile flowers to which a further fertile flower with a solitary sterile flower, and sometimes a further triad, may be added; sterile flowers consisting of a strap-shaped dentate process furnished on the abaxial surface with long, fine, smooth, unicellular hairs, these processes accrescent to become spinous-margined and indurate in fruit, fused with the indurate base of the partial inflorescence so that the latter falls as a unit complete with bracteoles.
Stamens 5; filaments filiform, delicate, fused at the base only, without intermediate pseudostaminodes; anthers narrow, bilocular, each theca with an awn-like tail at each end.
Perianth segments narrow, 3-nerved, long- or short-aristate.
Ovary uniovulate, somewhat compressed, delicate below; style very short, stigma with a tuft of penicillate hairs.