Olive (Lat. oliva), the name of plants of the genus olea, and of the fruit of 0. Europoea. The olive family consists of trees and shrubs without milky juice, distinguished from other monopetalous plants with a free ovary by having two stamens, or always fewer than the divisions of the corolla; it includes the lilac, the privet, and the ash, and several less known plants. The genus olea has evergreen leaves and minute white flowers in small racemes or clusters, which are axillary and terminal; the ovary is two-celled and two-ovuled, becoming in fruit a fleshy drupe with a hard two-celled stone, which is often only one-celled and one-seeded; the flesh of the drupe abounds in fixed oil. The common olive (O. Europaia) is one of the earliest trees mentioned in antiquity; probably it was a native of Palestine, and perhaps of Greece, and it was introduced to other countries at a very early day; it is largely cultivated in southern Europe, western Asia, and northern Africa; it was brought to South America and Mexico more than 200 years ago, and in various parts of California it was planted at the mission establishments, where some of the old groves still remain, notably that at San Diego, which is still in good bearing, and other plantations have recently been made there.
In the Atlantic states the olive was introduced before the revolution, and at several times since; it is perfectly hardy and fruitful in South Carolina; the chief obstacle to its cultivation seems to be the fact that its crop matures just at the time when all the labor is needed to secure the cotton. The olive tree rarely exceeds 20 ft. in height, has lanceolate or lance-oblong leaves, which are pale green above and whitish beneath, and axillary clusters of flowers; from the dull color of the leaves, an olive grove presents a sombre aspect. The French enumerate over 20 varieties, differing in the size and color of their leaves and fruits. The tree is propagated by various methods; seedlings are raised upon which to graft the choicer kinds, or these are multiplied by cuttings of the stems and roots, by suckers, by layers, and by protuberances; the trunks of old trees present numerous swellings or nodules containing undeveloped buds, which are removed and planted like bulbs. The tree is of slow growth, and does not come into bearing until about seven years old; but it continues indefinitely, and there are trees now standing which are supposed to have been in existence before the commencement of the present era.
In France the trees are regularly pruned to keep the heads low, in order to facilitate the gathering of the fruit. The wood of the olive is yellowish and very fine-grained, and, especially that of the root, often beautifully feathered and clouded; hence it is valued for small cabinet and inlaid work. - The products of the tree are the fruit and its oil. The fruit is too bitter to be eaten unless pickled, and in the olive-growing countries large quantities are prepared for home use and for export, and some kinds are cultivated especially for their superior fruit; the different varieties give fruits varying in size from an acorn to a large plum. The fruit is gathered when it has attained its full size, but while still green, and placed in a strong ley of wood ashes or a solution of potash; when the potash has penetrated to the stone, which is manifested by a change of color, the olives are placed in water, which is renewed several times a day for five days; a saturated brine is prepared of the purest salt, to which are added coriander, cloves, cinnamon, and such aromatics as are desired, and boiled a few minutes and strained; this when cold is mixed with an equal quantity of water and poured over the olives placed in jars or bottles, which are then sealed.
Thus prepared, olives are a condiment rather than an article of food, and are much eaten at lunches; they are thought to improve the flavor of wine as well as to excite an appetite for it; they are sometimes used in salads and to flavor made dishes. Olive oil is obtained from the ripe fruit, which when it has reached that state is of a dark purple color; the thoroughly ripe olives yield a larger quantity of oil, but not of so fine a quality as oil from those that have just begun to ripen; the pulp of the fully ripe fruit contains nearly 70 per cent, of oil. Those who make the finer kinds of oil gather the fruit by hand as soon as it begins to color, and spread it under sheds, where it is frequently turned and loses the greater part of its contained moisture; but for common oil the fruit is allowed to lie beneath the trees until it is convenient to gather it, which is sometimes all winter. The process of extracting the oil is essentially the same in different countries. The fruit is crushed to a pulp in a mill, and placed in coarse sacks, which are stacked one upon another and subjected to pressure; the oil flows into a cistern containing water, from the surface of which it is dipped; this first pressing is called virgin oil; a second quality is obtained by mixing the contents of the bags with boiling water, replacing them, and submitting them to greater pressure than before.
If the fruit is left in heaps until it ferments, it yields a greater quantity of oil, but of very poor quality. Oil of the finest quality has a slightly greenish color, a faint but agreeable odor, and a bland taste, leaving a slight sense of acridity in the throat. When it is cooled to nearly the freezing point of water, a solid fat is deposited. If allowed to congeal perfectly, and then subjected to pressure, about one third of fluid oil is separated, which is oleine and does not congeal at 25° or 20° F. The solid part consists of pal-mitine and similar principles. Olive oil is one of the oils not changed by the action of the air into a resinous substance, and is classed as a non-drying oil. It is sometimes adulterated by the admixture of cheaper oils, and unless the foreign oil be present in considerable amount it is very difficult to detect it; the greater specific gravity of the cheaper oils, as indicated by the elaiometer, is one of the tests; the chamber of commerce of Nice has recently offered a reward of 15,000 francs for a simple method of detecting adulterations.
The production of oil in Italy is estimated at 33,000,000 gallons annually, while that of France is only about 7,000,000. Not many years ago oil was imported almost exclusively in thin, round-bottomed flasks, covered with rush-work, stopped with cotton, and tied over with bladder; these packages are now rarely seen, but the finer kinds are imported in bottles of various styles; commoner kinds come in jars and casks. ' The imports into the United States during the year ending June 30, 1873, were 340,037 gallons, valued at $445,774. In countries where it is produced olive oil is largely used as food, replacing butter, not only with bread, but in cooking, especially for frying; like other fixed oils, it is very nutritious, but it is not readily digested by weak stomachs. In this country, where it is frequently called sweet oil, its use as food is limited almost entirely to the dressing of salads. In medicine it is sometimes used as a mild laxative in doses of one to two fluid ounces; in cases of poisoning by corrosive substances, it is given with a view to its mechanical effect in'shielding the stomach from their action; but its chief medical use is in the preparation of liniments, ointments, and plasters.
In the arts the oil is used as a lubricant, and the oleine separated by cold, as already described, makes the finest watch oil. The cheaper kinds were formerly somewhat used for burning, but have been superseded by the mineral oils. Much of the oil is consumed where it is produced in the manufacture of soap, it being the basis of the well known Castile, Marseilles, and Venetian soaps. (See Soap.) A resinous exudation is sometimes found upon the tree, which has been called olive gum and Lecca gum, and was formerly used in medicine as a stimulant; and the hark has been employed as a tonic. - The American olive (0. Americana), also called devilwood on account of the difficulty of cutting and splitting it, is a small tree found from Virginia to Florida; it has a whitish bark, and entire very smooth, evergreen leaves, 3 to 6 in. long; small, white, fragrant, polygamous flowers; and a spherical black fruit twice the size of a pea, with an oily flesh. According to Michaux, the inner bark on exposure to the air turns instantly to a bright red, and the wood becomes reddish by exposure. According to Decaisne and Naudin, the fruit of this is sometimes pickled.
Olea fragrans of the greenhouse, placed by some in the genus os-manthw, is an evergreen shrub from China and Japan; it has oblong or oval, finely serrate, dark green leaves, and numerous clusters of small white flowers, which have the most exquisite and delicate fragrance. The flowers are said to be used by the Chinese to scent the finer kinds of tea. It is a favorite greenhouse plant, as it blooms when only about 6 in. high; and in the southern states, where it is hardy, it makes a handsome bush 6 to 8 ft. high, and is a general favorite. Another related species is O. ilicifolia (or osmanthus), the holly-leaved olive, from Japan; it is a fine compact shrub, with dark green leaves like those of the holly; a variety with white-edged leaves is exceedingly beautiful. These are hardy in England, but in the United States their northern limit is yet undetermined.
Common Olive (Oloa Europaea).