The more than 2000 species of Cactaceae arealmost exclusively restricted to America (from Canada to Patagonia). They grow predominantly in dry regions and occur in the Andes up to a height of 4700 m a.s.l. Their representatives are mostly stem succulents, ramified or unramified, and of a cylindrical, disc-like, columnar, globular or flattened and leaf-like shape. The axis takes over photosynthesis, while the leaf blade becomes reduced and the leaf base transformed into a kind of cushion. Not infrequently, the leaves are modified into spines, bristles, or hairs. Reduced brachyblasts covered with spines, bristles or hairs, the areoles, are frequently found on stem and fruit. The flowers (usually solitary) are often large and attractive, being composed of a great number of petals. Certain species open their flowers only during the night (Queen of the night). The evolutionary tendency of this family is the reduction of the vegetative phase. In contrast to the Euphorbiaceae where the succulent types with a similar habit almost always develop laticifers, the Cactaceae rarely have latex, an attribute which very much facilitates distinction of the 2 families. Nitrogenous anthocyanins connect the Cactales with the Centrospermae. The Cactaceae are rich in polysaccharide or slime, found in slime cells and in lysigenous slime cavities. Dried shoots of the mexican cactus Lophophora williamsii supply the halucinogenic drug peyotl which contains the protoalkaloid mescaline. Extracts of Selenicereus grandiflorus have curative properties for the heart and are used in homoepathic drugs. Some species have fleshy and juicy fruits which are edible, many others are ornamental.

South American medicinal plants : botany, remedial properties, and general use / I. Roth, H. Lindorf. Berlin ; New York : Springer, c2002. -- p. 492.