Succulent perennial herbs or shrubs; stems columnar, cylindric or flattened, often jointed and spiny. Lvs usually 0 or very reduced and caducous. Branches often furnished with areoles (± circular, cushion- like patches). Fls solitary, ☿, usually actinomorphic. Calyx often petaloid and grading into petals. Petals numerous, in several series, the innermost largest, sometimes coherent at base. Stamens numerous, free or adnate to base of petals. Ovary inferior, 1-locular, with 3 or more parietal placentas. Ovules numerous; style 1; stigmas 2-many. Fr. a berry, often spiny or bristly. Seeds usually numerous, immersed in pulp.