zontal direction of its boughs, spreading over a large surface, completes the idea of its sovereignty over all the trees of the forest. Even a decayed oak—

dry and dead,

Still clad with reliques of its trophies old,

Lifting to heaven its aged, hoary head,

Whose foot on earth hath got but feeble hold-"

-even such a tree as Spenser has thus described is strikingly beautiful: decay in this case looks pleasing. To such an oak Lucan compared Pompey in his declining state.

The CORK CAK (Quercus suber) is not so large a tree as the common oak. There are several varieties: a broad leaved and a narrow leaved, which are evergreens; besides other varieties which shed their leaves. The broad-leaved evergreen is, however, the most common, and it is the one from which the cork of commerce is chiefly obtained. It is mentioned by Theophrastus, Pliny, and some other ancient naturalists, as being well known in the days of the Greeks and Romans, the latter of whom used it for a variety of purposes, and among the rest for the stopping of bottles. They used it for floats to their nets and fishing tackle; for buoys to their anchors; and when Camillus was sent to the Capitol, through the Tiber, during the siege by the Gauls, he had a lifepreserver of cork under his dress.

The Cork Oak is indigenous, or at least abundant, in Portugal, Spain, part of the south of France, and Italy; on the opposite coast of the Mediterranean, and the Levant. Spain and Portugal supply the greater portion of the cork which is consumed in Europe. The cork is the bark which the tree pushes outwards, as is common to all trees: but here the outer bark is of larger quantity, and is more speedily renewed. When removed, there is a liber,

C

or inner bark, below it, and from this the cork is reproduced in the course of a few years,-while the tree is said to live longer, and grow more vigorously, than if the cork were not removed. The first time that the cork is taken off, is when the tree is about fifteen years old. That crop is thin, hard, full of fissures, and consequently of little value; and the second, which is removed about ten years after, is also of an inferior quality. After this, the operation is repeated once in eight or ten years, the produce being greater in quantity, and superior in quality, each successive time. According to Duhamel, a corktree thus barked will live a hundred and fifty years. The months of July and August are those which are chosen for removing the cork. The bark is cleft

longitudinally, at certain intervals, down to the crown of the root, with an axe, of which the handle terminates in a wedge; and a circular incision is then made from each extremity of the longitudinal. cuts. The bark is then beaten, to detach it from the liber; and it is lifted up by introducing the wedged. handle, taking care to leave sufficient of the inner laminæ upon the wood, without which precaution the tree would certainly die. The bark being thus removed, it is divided into convenient lengths; and it is then

flattened, and slightly charred, to contract the pores. This substance is the rough cork of commerce; and it is thus fit to be cut into floats, stoppers, shoesoles, and other articles of domestic use, by the manufacturer. The cork of the best quality is firm, elastic, and of a slightly red colour. Two thousand five hundred tons of cork were imported into the United Kingdom in 1827. Cork burned in vessels of a particular construction gives the substance called Spanish black.

The Oak from which the nut-galls of commerce are procured (Quercus infectoria) is minutely described by M. Olivier, in his Travels. The species is very common in Asia-Minor; but, till the time of this traveller, Europeans had very little information on the subject, although the galls were a considerable article of commerce. It is a shrub, seldom exceeding six feet in height; and it has not only been accurately described by M. Olivier, but was introduced by him into France, where it is cultivated as a garden shrub, and grows well in the open air.

The gall is a morbid excrescence produced by the puncture of a winged insect, to which Olivier has given the name of Diplolepis Galle Tinctoriæ. This excrescence is of a globular form, with an unequal and tuberculous surface. It is developed on the young shoots of the tree, and contains within it the eggs which the insect has deposited. The best galls are gathered before the transformation of the insect, because in that state they are heavier, and contain more of the tannin principle. When the insect has left them, they are pierced from the interior to the surface. The best galls come from Aleppo. The substance of which they are composed is peculiarly astringent; of which, according to Sir Humphry Davy, five hundred parts contain a hundred and eighty parts of soluble matter, principally formed of tannin and gallic acid. One

hundred and seventy-four tons of galls were imported into. the United Kingdom in 1827.

The instinct by which certain insects choose for the nests of their future offspring the substance of various vegetable bodies, is one of the most curious provisions in the economy of Nature. After having pierced those bodies, they deposit their eggs, which, being hatched, produce larvæ, that are more or less fatal to the vegetable substance to which they are attached. In the volume of this series, entitled "Insect Architecture," will be found a minute account of the mode in which this genus of insects (Cynips) conduct their remarkable operations. They are provided with a needle in a sheath, which has most surprising powers of extension, derived from the peculiar construction of the whole body of the insect, so much so that the needle can be extended to double the length of the animal itself; and with this instrument it forms a nest for its offspring, while the young, in the same manner, pierce their way out of the vegetable shell which has been their protection. In this way is the gall produced. The oak-apple is an excrescence of the same nature, though effected by a different species of insect. There are various insects possessing the instinct thus to deposit their eggs, that are furnished with an apparatus of the curious construction above described, necessary for puncturing the branch, as is done by the parent; and for piercing a way out of the gall, as is done by the insect produced, after it has passed its larva state. Each species of insect chooses not only the particular vegetable, but the part of that vegetable which is best adapted for the reception of its larvæ; and in this way the same plant, for instance the oak, sometimes receives the nests of twenty different species of insects. A gall sometimes contains a single larva, sometimes many, and it is thus either