While examining lately some examples of bad grafting, we met with the following remarkable case, which will be regarded with no small interest by those who are desirous of learning how wood is really formed. A small scion of an apple had been whip-grafted upon one side of the cut of a much larger stock, as is shown in the annexed figure, 1. It had apparently formed as strong a union as is usually found in such cases, but upon applying a little lateral pressure the scion came away, as at 2, bringing with it a considerable quantity of young wood, 2 a. Upon a more minute examination it was found that this wood had been insinuated between the bark and wood of the stock as at 3, the wood of the scion having remained quite independent* of that upon which it was moulded; it had moreover divided into very fine descending fibres, the broken points of which are shown at 2 a. In other words, the scion had formed a woody sheath of its own, which covered over the wood of the stock and was independent of it.

How is this to be explained? Those who believe with Gaudichaud, Dupetit Thouars, and others of their school, will accept the specimen as a new proof of the accuracy of their views, that wood really descends from above in the form of fully organized tissue. On the other hand, those who adopt the more common opinion that wood is organized where it is found by organizable matter passing downwards, will see here a confirmation of their theory; while the physiologists who maintain that wood is a mere secretion from the surface of old bark or old wood will, it is to be hoped, admit that such a specimen as this is inexplicable upon their interpretation. It is obvious, indeed, that the new wood 2 a is really derived in either a solid or liquid form from the two branches at 2.

This is much the same as the case of a Willow which formed a sheath of wood several feet long over dead wood, and beneath dead bark, where any superficial deposit was obviously impossible. Or it may perhaps be better compared to the celebrated example of a Rose Acacia mentioned by the late Prof. Achille Richard. The Rose Acacia had been grafted on the common Pseudacacia. The stock had died; but the scion had continued to grow, and had emitted from its base a kind of. plaster composed of very distinct fibres, which surrounded the extremity of the stock to some distance, forming a sheath, and thus showed incontestably that wood descends from the base of a scion to overlay the stock.

That being demonstrated, it becomes the more difficult to understand how it is that although the wood of a stock is derived from the scion, yet the branches which sprout from that wood are not like those of the scion but of the stock. In other words a (the scion) under its new condition of life does not produce a, but b (the stock).

The true explanation of this puzzling phenomenon is, doubtless, that in 'our common trees there are two distinct systems of organization, simultaneous in their appearance, coexistent and coeval, but independent; the one longitudinal, which is what passes downwards, and the other horizontal; that the first is incapable of producing new roots, and is to be regarded as a mere provision for conveying sap, and for giving strength to a tree; that the latter alone has the power of furnishing new shoots. This latter, called the medullary system, is perpetually growing outwards and fitting on its myriads of extremities to the surface of the wood beneath the bark; so that when a branch is produced it necessarily comes from the horizontal system, derived in the beginning from the stock and not interfered with by the scion.

This is the view that was many years since taken by the writer of the present notice, and we are not aware of any attempt having been made to show its inaccuracy. Dr. Harvey, in his "Trees and. their Nature (noticed at p. 132 of the present volume) does not advert to it; or if he does we have failed to find the place, for which we trust to be excused, seeing that life is not long enough to permit the use of books without an index.

It is not for the sake of puzzling physiological heretics, or for the sake of the orthodox that this question has been thus revived. The case before us has been fixed to our pages for the sake of the ignorant, or the ill-informed, who have not yet discovered that to remove the branches of a tree is to paralyze its wood-producing powers; and who sally forth in mid-winter, or indeed in mid-spring, or whenever they happen to think about it, armed with saw and axe, and good brown bills, for the purpose of making a raid upon the plantations under their care. Incredible as it may seem, there are plenty of woodmen who firmly believe that few branches will furnish. as much new timber as many. Let us hope that they will reflect upon our apple-tree, repent of their foolish courses, and resolve in future to follow a wiser and better practice. - From the Gardeners' Chronicle.