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CRASSULACEAE

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Originally appearing in Volume V07, Page 380 of the 1911 Encyclopedia Britannica.
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CRASSULACEAE , in See also:

botany, a natural See also:order of See also:dicotyledons, containing 13 genera and nearly 500 See also:species; of See also:cosmopolitan See also:distribution, but most strongly See also:developed in See also:South See also:Africa. The See also:plants are herbs or small shrubs, generally with thick fleshy stems and leaves, adapted for See also:life in dry, especially rocky places. The fleshy leaves are often reduced to a more or less cylindrical structure, as in the stonecrops (See also:Sedum), or See also:form closely crowded rosettes as in the See also:house-See also:leek (Sempervivum). Correlated with their life in dry situations, the bulk of the See also:tissue is succulent, forming a See also:water-See also:store, which is protected from loss by evaporation by a thickly cuticularized epidermis covered with a waxy secretion which gives a See also:glaucous See also:appearance to the plant. The See also:flowers are generally arranged in terminal or axillary clusters, and are markedly See also:regular with the same number of parts in each See also:series. This number is, however, very variable, and often not Stonecrop (Sedum See also:acre) slightly reduced. 1, See also:Horizontal See also:plan of arrangement of See also:flower of stonecrop; 2, flower of Sedum See also:rubens. See also:constant in one and the same species. The sepals and petals are See also:free or more or less See also:united, the stamens as many or twice as many as the petals; the carpels, usually free, are equal to the petals in number, and form in the See also:fruit follicles with two or more seeds. Opposite each carpel is a small See also:scale which functions as a nectary. Means of vegetative See also:propagation are See also:general. Many species spread by means of a creeping much-branched rootstock, or as in house-leek, by runners which perish after producing a terminal See also:leaf-rosette.

In other cases small portions of the See also:

stem or leaves give rise to new plants by budding, as in Bryophyllum, where buds develop at the edges of the leaf and form new plants. The order is almost absent from See also:Australia and See also:Polynesia, and has but few representatives in South See also:America; it is otherwise very generally distributed. The largest genus, Sedum, contains about 140 species in the temperate and colder parts of the See also:northern hemisphere; eight occur See also:wild in See also:Britain, including S. Telephium (orpine) and S. acre (See also:common stonecrop) (see fig.). The species are easily cultivated and will thrive in almost any See also:soil. They are readily propagated by seeds, cuttings or divisions. Crassula has about See also:loo species, chiefly at the Cape. Cotyledon, a widely distributed genus with about 90 species, is represented in the See also:British Isles by C. Umbilicus, pennywort, or navelwort, which takes its name from the succulent peltate leaves. It grows profusely on dry rocks and walls, especially on the western coasts, and bears a spike of drooping greenish See also:cup-shaped flowers. The Echeveria of gardens is now included in this genus. Sempervivum has about 50 species in the mountains of central and See also:southern See also:Europe, in the Himalayas, See also:Abyssinia, and the Canaries and See also:Madeira; S. tectorum, common house-leek, is seen often growing on tops of walls and house-See also:roofs.

The See also:

hardy species will grow well in dry sandy soil, and are suitable for rockeries,old walls or edgings. They are readily propagated by offsets or by See also:seed. The order is closely allied to See also:Saxifragaceae, from which it is distinguished by its fleshy See also:habit and the larger number of carpels.

End of Article: CRASSULACEAE

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CRASSUS (literally " dense," " thick," " fat ")

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