the Olive-tree; a genus of the monocotyledonous order, belonging to the diandria class of plants.

There are two species, 1. The Europea, or common olive-tree, rises with upright solid stems, branching numerously on every side, 20 or 30 feet high; spear-shaped, stiff, opposite leaves, two or three inches long, and half an inch or more broad; and at the axils small clusters of white flowers, succeeded by oval fruit.

This species is the principal sort cultivated for its fruit; the varieties of which are numerous, varying in size, colour, and quality.

It is a native of the southern warm parts of Europe, and is cultivated in great quantities in the south of France, Italy, and Portugal, for the fruit to make the olive-oil, which is in so great repute, and is transported to all parts, to the great advantage of those countries where the trees grow in the open ground: the green fruit is also in much esteem for pickling, of which we may see plenty in the shops.

2. The capensis, or cape box-leaved olive, rises with shrubby stems, branching numerously from the bottom, six or seven feet high; small, oval, thick, stiff, shining leaves; and at the axils small clusters of whitish flowers; succeeded by small fruit of inferior value.

These plants in this country must be kept principally in pots for moving to shelter of a green-house in winter; for they are too tender to prosper well in the open ground here: though sometimes they are planted against a warm south wall, and sheltered occasionally from frost in winter, by mulching the roots, and matting their tops; whereby they may be preserved, and will sometimes produce fruit for pickling: a very severe winter, however, often kills or greatly injures their young branches; therefore let the principal part be potted in rich earth, and placed among the green-house shrubs, and managed as others of that kind.

These trees are often sent over from Italy to the Italian warehouses in London, along with orange-trees, &c. where pretty large plants may be purchased reasonably, which should be managed as directed for orange-trees that are imported from the same country. See CITRUS.

Their propagation here is commonly by layers.

The laying is performed on the young branches in spring. Give plenty of water all summer, and they will sometimes be rooted fit for potting-off by autumn; but sometimes they require two summers to be rooted effectually: when, however, they are properly rooted take them off early in autumn, and pot them separately, give water, and place them in the shade till they have taken fresh root; and in October remove them into the green-house, &c.

Those you intend to plant in the open ground, as before suggested, should be kept in pots; in order to have occasional shelter of a garden-frame two or three years, till they have acquired some size, and are hardened to the full air; then transplant them into a warm border against a wall; mulch their roots in winter, and mat their tops in frosty weather.

Olives have an acrid, bitter, extremely disagreeable taste: pickled (as we receive them from abroad) they prove less disagreeable. The Lucca olives, which are smaller than the others, have the weakest taste; the Spanish, or larger, the strongest; the Provence, which are of a middling size, are generally the most esteemed.

The oil obtained from this fruit has no particular taste or smell, and does not greatly differ in quality from oil of almonds. Authors make mention of two sorts of this oil, one expressed from the olives when fully ripe, which is our common oil olive; the other, before it has grown ripe; this is called oleum immaturum, and oleum immaturum. Nothing is met with in the shops under this name; and Lemery affirms, that there is no such oil, unripe olives yielding only a viscid juice to the press. From the ripe fruit, two or three sorts are obtained, differing in degree of purity: the purest runs by light pressure; the remaining magma, heated and pre- Oleaginous fed more strongly, yields an inferior sort, with some dregs at the bottom, called amurca. All these oils contain a considerable quantity of aqueous moisture, and a mucilaginous substance, which subject them to run into a putrid state: to prevent this, the preparers add some sea-salt, which, imbibing the aqueous and mucilaginous parts, sinks with them to the bottom; by this means the oil becomes more homogen, and consequently less susceptible of alteration. In its passage to us, some of the salt, thrown up from the bottom by the shaking of the vessel, is sometimes mixed with and detained in the oil, which, in our colder climate, becomes too thick to suffer it freely to subside; and hence the oil is sometimes met with of a manifestly saline taste. Oil-olive is used in the simple balsam of sulphur, Locatelli’s balsam, and several ointments. It is oftener employed in this last intention than the other expressed oils, but more rarely for internal medicinal purposes.