Perennial, rarely annual, herbs. Hairs eglandular. Lvs opposite or rarely apparently alternate or whorled, linear to elliptic; stipules conspicuous, scarious, splitting lengthwise with age. Infl. a terminal or axillary cluster; bracts scarious, usually silvery, often concealing fls; epicalyx 0. Fls slightly perigynous; sepals 5, free, equal or unequal, often hooded and awned; petals 5, entire, minute or 0. Stamens 5, rarely more. Styles 2-(3). Fr. 1-seeded, indehiscent or with membranous pericarp rupturing at base. Seeds smooth, subglobose, not winged.