Allium cepa. Onion.
Nat. Ord. — Liliaceae. Tribe— Scillese. Sex. Syst. — Hexandria Monogynia.
Description. — The onion is a biennial plant, the root bearing a tunicated bulb, compressed, or round, or oblong in figure, invested with a shining, thin, dry membrane. The scape, which appears the second year, is from two to four feet high, straight, naked, smooth, stout, fistulous, bearing at the top a large, round umbel of greenish- white flowers, and swelling toward its base. The leaves are fistulous, terete, distichous, glaucous, acute, shorter than the stem. Spathe reflexed, generally longer than the lower flowers. Umbels large, regular, compact, many-flowered, not bulbiferous. Pedicels about an inch long, thickened at the point. Stamens nearly twice as long as the perianth.
History. — The onion is supposed to be a native of Hungary, but is now found over the whole civilized world. The bulbs are of various shapes and sizes, are composed of concentric fleshy and succulent layers, and according to the variety are reddish, yellowish, or white. They have, in a high degree, the peculiar pungent odor of the plant, with a sweetish and acrid taste. It contains a white acrid volatile oil holding sulphur in solution, albumen, much uncrystallizable sugar and mucilage, phosphoric acid both free and combined with lime, acetic acid, citrate of lime, and lignin. The expressed juice is susceptible of the vinous fermentation.
Properties and Uses. — The onion is stimulant, diuretic, expectorant, and rubefacient ; used moderately it increases the appetite, and promotes digestion, but in large quantities it is apt to occasion flatulence, gastric uneasiness, and febrile excitement. The juice, mixed with sugar, forms a pleasant syrup, useful in coughs, catarrhs, and croup, to be given in the absence of much inflammatory action. Roasted and split, it is occasionally employed as an emollient cataplasm to boils and other suppurating tumors. In dropsy and gravel, a saturated tincture made with good gin, has been recommended. Boiling deprives the onion of its essential oil, and it then becomes a mild esculent, much used as food.