A perennial, succulent tree, shrub, or climber belonging to the family Cactaceae, most members of which bear spines. Spines, branches, and flowers arise from small protrusions arranged singly or along ridges. There are 131 genera with 1866 species, one species (Rhipsalis bassifera) occurring in Africa, Madagascar, and Sri Lanka, the remainder only in arid regions of America, although some have been naturalized elsewhere.