1911 Encyclopædia Britannica/Houseleek

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HOUSELEEK, Sempervivum, a genus of ornamental evergreen plants belonging to the natural order Crassulaceae. About 30 species are known in gardens, some of which are hardy perennial herbs, and grow well in dry or rocky situations; the others are evergreen shrubs or undershrubs, fit only for cultivation in the greenhouse or conservatory. The genus Sempervivum is distinguished from the nearly allied Sedum by having more than five (about 12) petals, and by the glands at the base of the ovary being laciniated if present. The common houseleek, S. tectorum (Ger. Hauswurzel, Fr. joubarbe), is often met with in Britain on roofs of outhouses and wall-tops, but is not a native. Originally it was indigenous in the Alps, but it is now widely dispersed in Europe, and has been introduced into America. The leaves are thick, fleshy and succulent, and are arranged in the form of a rosette lying close to the soil. The plant propagates itself by offsets on all sides, so that it forms after a time a dense cushion or aggregation of rosettes. The flowering stem, which is of rather rare occurrence, is about 1 ft. high, reddish, cylindrical and succulent, and ends in a level-topped cyme, reflexed at the circumference, of reddish flowers, which bloom from June to September. The houseleek has been known variously as the houselick, homewort or great houseleek. Sedum acre (stone-crop) is styled the little houseleek. In Germany it is sometimes called Donnerkraut, from being supposed to protect the house on which it grows from thunder. The leaves are said to contain malic acid in considerable quantity, and have been eaten as salad, like Portulaca. S. glutinosum and S. balsamiferum, natives respectively of Madeira and the Canary Islands, contain a very viscous substance in large quantity, and are used for the preparation of bird-lime; fishermen in Madeira, after dipping their nets in an alkaline solution, rub them with this substance, rendering them as tough as leather. S. montanum, indigenous in Central Europe, according to Gmelin, causes violent purging; S. arboreum, τὸ μἐγα ἀείζωον of Dioscorides, is employed in Cyprus, the East, and northern Africa as an external remedy for malignant ulcers, inflammations and burns, and internally for mucous discharges.