Centema

Erect perennial herbs or subshrubs; stems sometimes tuberculate. Leaves opposite, entire. Inflorescences pedunculate or sessile spike-like bracteate thyrses, each bract with a partial inflorescence of 1 or 2 bisexual flowers and 2 or 3 modified sterile flowers consisting of single very rapidly developing spines, partial inflorescence falling as a 2- or 3-spined burr. Tepals 5, inner becoming narrower, outer several-nerved, hardened at base, woolly on back. Stamens 5, unequal; filaments filiform, flattened, connate at extreme base; pseudostaminodes 0; anthers narrow, 2-thecous. Ovary +/- compressed, glabrous; ovule solitary, basal; style slender, with 2 short or elongated stigma branches. Capsule scarcely compressed, delicate except for a small firm area about base of style, irregularly ruptured by developing seed, thin-walled, indehiscent. Seed +/- horseshoe-shaped; perisperm/endosperm copious.