CRASSULACEAE, in botany, a family of dicotyledons, con taining 25 genera and 45o species; of cosmopolitan distribution, but most developed in South Africa. The plants are herbs or small shrubs, generally with thick fleshy stems and leaves, adapted for life in dry, especially rocky places. The fleshy leaves are often reduced to a more or less cylindrical structure, as in the stone crops (Sedum), or form closely crowded rosettes as in the house leek (Sempervivum). Correlated with their life in dry situations, the bulk of the tissue is succulent, forming a water-store, which is protected from loss by evaporation by a thickly cuticularized epi dermis covered with a waxy secretion which gives a glaucous ap pearance to the plant. The flowers are generally arranged in terminal or axillary clusters, and are markedly regular with the same number of parts in each series. This number is, however, very variable, and often not constant in one and the same species. The sepals and petals are free or more or less united, the sta mens as many or twice as many as the petals ; the carpels, usually free, are equal to the petals in number, and form in the fruit follicles with two or more seeds.
The means of vegetative propa gation are general. Many spe cies spread by means of a creep ing much-branched rootstock or, as in house-leek, by runners that perish after producing a terminal leaf-rosette. In other cases small portions of the stem or leaves give rise to new plants by bud ding, as in Bryophyllum, where buds develop at the edges of the leaf and form new plants.
The family is almost absent from Australia and Polynesia, and has but few representatives in South America; it is otherwise generally distributed. The largest genus, Sedum, contains about 15o species in the temperate and colder parts of the northern hemisphere ; nine occur wild in Britain, including S. Telephium (orpine) and S. acre (common stonecrop). The species are very easily cultivated and will thrive in almost any soil. Crassula has about 15o species, chiefly at the Cape. Cotyledon, a widely distributed genus with about Ioo species, is represented in the British Isles by C. umbilicus, pennywort, or navelwort, which takes its name from the succulent peltate leaves. It grows fusely on dry rocks and walls, especially on the western coasts, and bears a spike of drooping greenish cup-shaped flowers. The Echeveria of gardens is included in this genus. Sempervivum has about 5o species in the mountains of central and southern Europe, in the Himalayas, Abyssinia and the Canaries and Madeira ; S. tectorum, common house-leek, is seen often growing on tops of walls and house-roofs. The hardy species will grow well in dry sandy soil, and are suitable for rockeries, old walls or edgings.
In North America some 4o representatives of the family are found, most numerous from the Rocky Mountains westward, 20 occurring in California, mostly species of Sedum and Cotyledon.
The family is closely allied to Saxifragaceae, from which it is distinguished by its fleshy habit and the larger number of carpels.