Herbs or low shrubs with alternate sessile leaves, usually spiny or spinulose at apex. Flowers hermaphrodite or polygamous, solitary or in 3-flowered glomerules. Perianth-segments 5, free nearly to base, hyaline, the anterior segment usually developing a long prickle in fruit. Stamens usually 5; anthers not appendaged. Stigmas 2. Utricle included in perianth, ovoid, laterally compressed, free from perianth. Seed vertical with a spiral embryo.