Citron, the fruit of a low, evergreen tree (citrus medica, Linn.), which belongs to the same genus as the lime, lemon, shaddock, and orange trees, attains in its wild state a height of about 8 ft., and is erect and prickly, with long reclining branches. Its leaves are alternate, oblong-acute, subserrate, and pale green; its petioles are naked, and its flowers 40-androus and externally purple; and its fruit is ovate, about 6 inches long, furrowed, with a protuberance at the tip, and with two rinds, the outer thin, greenish yellow, with numberless miliary glands, full of a most fragrant oil, and the inner thick, fungous, and white. The trees of this genus are among the most brilliant of fruit-bearing trees, are indigenous in the East, and are supposed to be alluded to in the golden apples which the Greeks attributed to the gardens of the Hespcridcs. There is, however, no evidence that any of them were cultivated either by the Greeks or earlier Romans. The citron tree, the most beautiful of them, and the first introduced into Europe, was obtained from Media and perhaps Assyria, and was first cultivated in Italy by Palladius in the 2d century.
In the East it is constantly in blossom, flowers and fruit always hanging upon the tree together; at Nice, Genoa, and Naples, and also in the West Indies, it endures the open air, but at Florence and Milan it requires protection in the winter, and in more northern climates it is cultivated in conservatories. In China there is a splendid variety, with large and solid fruit, divided at the end into five distinct lobes, whence it is called by the Chinese the fingered citron. It is kept for its agreeable fragrance on fine porcelain dishes in sitting rooms. The citron is a somewhat acid fruit, rarely eaten raw, and highly valued for its very fragrant rind, which by being preserved in sugar becomes a delicate sweetmeat. From the outside of the fruit and the leaves the oil of citron is prepared; the pulp furnishes citric acid; the seeds are very hitter and tonic; and the hark of the root is a febrifuge. There are 12 well known varieties of citron raised in Italy, and about 20 in French and 6 in English nurseries.
There are 17 varieties described and figured, and the methods of their culture minutely given, in Risso's Histoive naturelle des orangers (Paris, 1818).