The oak has long been known by the title of "monarch of the woods," and, we may add, justly.

The ancient Druids had a profound veneration for oak trees. Pliny says that "the Druids, as the Gauls call their magicians or wise men, held nothing so sacred as the mistletoe, and the tree on which it grows, provided it be an oak. They make choice of oak groves in preference to all others, and perform no rites without oak leaves; so that they seem to have the name of Druids from thence, if we derive their name from the Greek."

This useful tree grows to such surprising magnitude, that were there not many well-authenticated instances in our own country, it would certainly appear difficult to believe that it could attain such size. In the eighteenth volume of the Gentleman's Magazine we have the dimensions of a leaf twelve inches in length and seven in breadth; and all the leaves of the same tree were equally large. On the estate of Woodhall, purchased in 1775 by Sir Thomas Rumbold, an oak was felled which sold for L43, and measured twenty-four feet in circumference. We are also told of one in Millwood Forest, near Chaddeley, which was in full verdure in winter, getting its leaves again, after the autumnal ones fell off. In Evelyn's Sylva, we have an account of a very remarkable oak at Greendale, which Gough, in his edition of Campden, thus minutely describes: "The Greendale oak, with a road cut through it, still bears one green branch. Such branches as have been cut or broken off are guarded from wet by lead. The diameter of this tree at the top, whence the branches issue, is fourteen feet two inches; at the surface of the ground eleven feet and a half; circumference there thirty-five feet; height of the trunk fifty-three; height of the arch ten, width six. Mr Evelyn mentions several more oaks of extraordinary size in Worksop Park."

M. Hamel du Monceau, a member of the Royal Academy of Sciences at Paris, gave an account, in the year 1749, of an oak which he had kept in water eight years, and which yielded fine leaves every spring. The tree, he says, had four or five branches; the largest nineteen or twenty lines round, and more than eighteen inches in length. It threw more in the first two years than it would have done in the best earth; but it afterwards lost its vigour, and rather decayed, which he attributed more to a defect in the roots than to a want of aliment.

Buffon made some experiments upon oak trees, the result of which is recorded in the Gentleman's Magazine, 1754. He had compared barked with unbarked trees, and concluded, from a variety of trials, that timber barked and dried standing, is always heavier and considerably stronger than timber kept in its bark.

The use of oak bark in tanning, and in hot-beds, is generally known. For the latter of these purposes, however, oak leaves are now found to answer equally well, or rather better. In the notes to Dr Hunter's edition of Evelyn's Treatise on Forest Trees, we find certain directions for their use, by Mr Speechly. The leaves are to be raked up as soon as possible after they fall from the trees. When raked into heaps, they should immediately be carried into some place near the hot-houses, where they may lie to couch. It is the custom of some to fence them round with charcoal hurdles, or any thing to keep them from being blown about the garden in windy weather. They are then trodden well, and watered in case they happen to have been brought in dry. The heap is made six or seven feet thick, and covered over with old mats, or anything else, to prevent the upper leaves from being blown away. In a few days the heap will attain a strong heat. For the first year or two in which he used these leaves, Mr Speechly did not continue them in the heap longer than ten days or a fortnight; but by this method of management they settle so much when brought to the hot-house, that a supply was very soon required; and he afterwards found, that it was proper to let them remain five or six weeks in the heaps before they were brought to the hot-house. In getting them into the pine pots, if they appear dry, they are to be watered, and again trodden down exceedingly well, in layers, till the pits are quite full. The whole is then covered with tan bark, to the thickness of two inches, and well trodden down, till the surface becomes smooth and even. The pine pots are then to be placed in the manner in which they are to stand, beginning with the middle row first, and filling up the spaces between the pots with tan. In this manner we are to proceed to the next row, till the whole be finished; and the operation is performed in the same manner as when tan only is used. The leaves require no further trouble through the whole season, as they will retain a constant and reg- lar heat during twelve months without stirring or turning; and Mr Speechly informs us, that if he might judge from their appearances when taken out, being always entire and perfect, it was probable they would continue their heat through a second year; but, as an annual supply of leaves is easily obtained, the experiment is hardly worth making.

After this, the pines will have no occasion to be moved except at stated times of their management, as at the shifting them in their pots, when at each time a little fresh manure should be added to make up the deficiency arising from the settling of the beds; but this will be inconsiderable, as the leaves do not settle much after their long couching. During the first two years of our author's practice he did not use any tan, but plunged the pine pots into the leaves, and merely covered the surface of the beds, when finished, with a little saw-dust, to give it a neatness. This method, however, was attended with one inconvenience; for, by the caking of the leaves, they shrunk from the sides of the pots, by which they became exposed to the air, and at the same time the heat of the beds was permitted to escape.

See PLANTING.

OAK-Leaf Galls. These are of several kinds. The remarkable species called the mushroom gall is never found on any other vegetable substance than these leaves; and, besides this, there is a great number of other kinds.

The double gall of these leaves is very singular, because the generality of productions of this kind affect only one side of a leaf or branch, and grow all one way; whereas this kind of gall extends itself both ways, and is seen upon each side of the leaf, in the form of two protuberances, the one opposite to the other. These are of differently irregular shapes; but their natural figure seems that of two cones, with broad bases and very obtuse points, though they are sometimes round, or very nearly so.

These make their first appearance on the leaf in April, and remain on it till June, or even longer. They are at first green, but afterwards yellowish, and are softer to the touch than many other of the productions of this kind. They are usually about the size of a large pea, but sometimes they grow to the size of a nut. When opened, they are found to be of that kind which is inhabited each by one insect only, and contains but one cavity. The cavity in this, however, is larger than in any other gall of the size, or even in many others of three times its size; the sides of it being very little thicker than the substance of the leaf.