ORCHIDE7E, or ORCITIDA'CER, often popularly called ORCIITDS, a natural order of endogenous plants, remarkable for the structure of their flowers, which are also of great beauty and exquisite fragrance. The perianth somatimes exhibits much variety of forms, even in the same species; but is always irregular, its segments differing much from each other. - There are unusually six segments, arranged in two rows (calyx and corolla); although some of the most extraordinary forms of orchideous flowers are produced by the combination of certain segments into one piece. Spurs and other appendages of some of the segments are alSo common. The inner segments are often beautifully colored. The inferior segment of the corolla is called the lip (labelluda), and is often lobed, spurred, or furnished with curious appendages of different kinds. The stamens are united with the style into a single central column, the distinctive character of the Linnxan class gynandria, of which the orchiden form the chief part. There is usually only one anther, with a tubercle on each side of it, the tubercles being abortive anthers; but sometimes the two lateral anthers are perfect, and the central one is abortive; and very rarely all the three anthers are perfect. The anthers are usuidly two-celled; the grains of pollen coher ing in two or more masses. The ovary is inferior, one-celled; the stigma usually a mere hollow in front of the column. The fruit is usually a capsule, opening with six valves, three of which have placentte; the seeds numerous and very small. In a few cases the fruit is fleshy. The orehidere are generally herbaceous perennials; but some of those found in warm climates are shrubs, and some of these, as vanilla, are climbers. The root is usually- composed of simple cylindrical fibers, which are often accompanied with one or two fleshy tubercles, a tubercle dying and a new one being produced annually. The leaves are always simple, alternate, often sheathing at the base, often leathery, sometimes arising, in tropical species, not directly from the stem, but from fleshy bulb like excrescences of it. The species of orchidem are very numerous, about 3,000 having
been described. They are found in all parts of the world, except the coldest and the most arid regions; but are most numerous in the humid forests of the torrid zone, and• particularly in America. Many of them are epiphytes, adorning the boughs of trees with splendid flowers. This is chiefly the c tse with tropical species, those of colder climates mostly growing on the ground. Only about thirty-eight species are reckoned in the British flora.—SALE? (q.v.), a delicate and nutritious article of food, is obtained from the root-tubereles of a number of species. The only other product of the order which is of any commercial importance is vanilla (q.v.). The fragrant falmi (q.v.) leaves are the leaves of an orchid. Several species ale known to possess tonic, stimulant, and antispasmodic properties, but none are of much importance in medicine.
Orchids have of late been much cultivated on account of their flowers, and many tropical species are amongst our most esteemed hot-house plants, houses being sometimes specially devoted to them. Many of the epiphytal kinds may be planted in pots filled with loose fibrous peat; the roots of others are placed in baskets, or are fastened to blocks of wood, with a little moss or some such thing around them, to keep them from becom ing too dry, and are thus placed on the shelves, or suspended from the roof of the house. Careful attention to temperature is necessary, and also to ventilation; and although much heat and moisture are requisite, the atmosphere must not be constantly very hot and humid, but seasons of rest must be given to the plants, which in their native climates have generally a wet and a dry season, the latter being to them in many respects what the winter is to plants of temperate regions.
Lindley has particularly signalized himself in the study of this interesting order of plants.