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a double influence is exerted in gradually decomposing its texture: one arises from the union of its carbon with oxygen, as in the ordinary process of decomposition; and the other from the humidity by which it is penetrated, dissolving some parts of the tissue, and in reducing it generally to a soft and disorganized state. These results will of course be very different according to the nature of the wood attacked, and to the length of time that the wound requires to be healed over. As soon, however, as the wood is secured from further exposure to the atmosphere, the damage ceases to increase, though the blemish which has been introduced admits of no remedy. The new wood and bark which form over the wound, are derived from the growth of the alburnum and liber, which gradually extend themselves from its upper edge, and from along each side, till they meet in the middle and then unite and blend together as in the case of grafting. By judiciously splitting a block vertically at the zone which corresponds to that year's growth in which the surface of a pruned brauch was covered over by the fresh wood, every mark of the pruning knife will be found on the discoloured surface of the old wound, as fresh as when it was first impressed upon it, and the new wood will have received a reverse impression of this surface as accurately as a counter receives the stamp of a die. Vertical wounds on the surface of the trunk are those which heal the most readily, because their direction tallies with the course of the cambium, which soon forms a tumour at the upper extremity of the wound and down each side, in the manner just described ; and this is more readily extended over the wound in proportion as its surface is smoother. Various composts are useful for protecting the exposed surface from the atmosphere, whilst the healing process is in progress: but nothing of an oily or poisonous description should be employed. Whenever, therefore, pruning is absolutely necessary, it is advisable to prune close, in order to reduce the exposed surface to the condition of a vertical wound; unless, indeed, the limb be very large, when it may be more advisable to prune at some little distance from the trunk, lest the blemish which would be introduced into the timber should be so considerable as more than to counterbalance any advantage that would be obtained. There is no direct means by which a transverse section through the wood may be healed over, and if a branch be lopped at a distance from its point of union with a main branch, or with the trunk itself, the exposed surface never heals over, but causes the decay and death of the branch for some distance back, until this is stopped at some spot where the returning sap is in sufficient quantity to produce fresh wood and bark. The system of " fore-shortening” rests upon the gradual decay of the pruned

branch, until it be ultimately killed by the increasing shade of the superior branches, when its fall will take place in the natural way; as in all branches which

grow
low
upon

the stem, and are early stifled by the shade of the upper branches, and which slough off, without producing any very marked blemish in the heart of the tree. Here, however, we must observe, that there is no process for “ sloughing off” the decayed parts of vegetables which at all resembles that which takes place in animals; but when the branch has become so completely rotten, as to fall off upon the application of the slightest force, it will be found that the new bark and alburnum which are formed round the base of its stump, always envelops more or less of the rotten wood, which forms a rough and jagged surface to the wound. It is erroneous to suppose that those branches which fall off by a sort of natural pruning, resulting from their being killed by an obstruction of the light, leave comparatively little or no trace of their decay in the heart of the tree; but since it happens that those branches which perish early are always proportionably small, when compared with the bulk to which the trunk attains, the blemishes which they leave may easily be underrated, and this we believe to have been the origin of the error which supposes that the blemish introduced upon the natural decay and fall of a branch is, ceteris paribus, of less consequence than that which results upon closely pruning it. The danger which attends all pruning may be diminished by paying attention to a few rules, such as cutting the surface quite smooth, cutting it obliquely so as to prevent the wet from lodging upon it, and especially by cutting close to the main branch or stem. The main object is to procure a rapid development of the new wood, in order that the exposed surface may be secured as speedily as possible from the action of air and moisture; and this, we believe, is best obtained by reducing the cut as nearly as possible to the condition of a vertical wound on the stem. All pruning, then, should be avoided as much as possible : but where it is absolutely necessary, should be performed as soon and as completely as the young plant or branch may bear it with safety.

We have yet to detail the effects produced by poisons on the vegetable structure, and to refer to some of the important practical results which follow from their consideration. The action of poisons on vegetables is analogous to that which they produce on animals. One class is corrosive, and destroys the tissue on which it acts; whilst another class is narcotic, and destroys vitality without producing any decided alteration on the tissue itself. It has been ascertained that nearly all substances which are poisonous to animals, are likewise so to vegetables, though

the intensities of their several actions are different in the two kingdoms; but, besides these, there are many substances innoxious to animals which are destructive to vegetable life. In fact, it should seem that almost every thing that vegetables can imbibe is injurious to them, excepting water, the insipid earthy salts, carbonic acid, and other gases, gums, and mucilaginous substances, and finally, certain animal inatters when introduced in very weak solution. It has been supposed that the presence of a nervous system might be assumed to exist in vegetables, from the mode in which they are destroyed by narcotic poisons; but there is this remarkable difference in the mode in which these substances act on animals and on vegetables: on the former they act by “sympathy” upon certain parts with which they have no immediate contact, whilst in the latter they produce their effect only on those parts of the tissue into which they are introduced. In vegetables, also, all poisons exert their action upon the cellular tissue, whilst in the more complicated structure of the animal frame different poisons will attack only particular tissues ; which again seems to prove the existence of no more than one single faculty in vegetable life, as we concluded to be the case, from other considerations, in the beginning of this article. It is a curious fact in the action of vegetable poisons, that a plant may be killed by the poison which it has itself secreted, as a viper may be stung to death by its own venom.

Hence it has been very generally noticed, that the soil in which any particular plant has grown, and into which it has consequently discharged the escretions of its roots, is rendered noxious to the growth of plants of the same or of allied species, though it be quite adapted to the support of other species. This fact is of the greatest importance in an economical point of view, as the whole theory of the rotation of crops may be considered to depend upon it. The discovery of this important step in agriculture was probably made by the Belgians; at least they have the merit of having developed the theory of it. Formerly it used to be said, that the whole secret of good husbandry consisted in ploughing well, and in manuring well; but to these must now be added the equally important art of so arranging the cultivation of different crops that they may mutually assist each other, and thus enable the farmer to obtain the greatest possible annual return from the same land. The whole theory depends upon the fact, that all plants succeed badly upon lands which have lately borne crops of the same species with themselves, or even of the same genus, or of the same family. This effect is not owing to any exhaustion of the soil that must have taken place during the growth of the previous crop, but arises from a corruption of the soil, by the

Some

intermixture of vegetable excretions given out at the root, which excretions are always more deleterious to plants of the same kind than to others. It is even ascertained that the excretions of some plants are beneficial to the growth of others of a different family; the Leguminosa, for example, improving the soil for the Graminece. Agriculturists have proposed various theories to account for the beneficial results obtained by a rotation of crops. have supposed that one species, by its denser foliage, chokes the weeds which otherwise would spring up, and assists the crop

in exhausting the soil; others have attributed the improvement that has taken place to the remains of the previous crop, which they suppose may have served as manure; a third have said, that the roots of different crops extend themselves to different depths, and so extract their nourishment from portions of the soil which do not interfere with each other; and lastly, it has been urged, that plants of different families may possibly derive their nourishment from different materials. It may be true that some of these causes have a certain degree of influence in determining which may be the most proper plants for a rotation, but they can only be considered as of very secondary importance when compared with that which relates to the deterioration of the soil, by its intermixture with the radical excretions of a previous crop. After enumerating some of the collateral circumstances which should direct the judgment of cultivators in selecting such plants as may be best adapted to a rotation of crops in any particular district, De Candolle proposes the following fundamental and physiological principles, which ought to be attended to where complete success is to be expected. First, a new crop ought never to succeed another of the same kind, unless under some very peculiar circumstances, as where the soil is annually renewed, or where it is naturally so fertile as to be capable of resisting the inconveniences which ordinarily result from such a system. Secondly, a new crop ought not to succeed another which has been raised from plants of the same family. A remarkable exception to this rule occurs in the practice adopted in the valley of the Garonne, where the soil admits of a biennial alternation between wheat and maize. Thirdly, all plants with acrid and milky juices injure the quality of the soil, and their remains should never be buried after the removal of a crop. Fourthly, plants with sweet and mucilaginous juices improve the soil for others of a different family. The chief of these are the Leguminosa, which are commonly adopted in practice for this purpose.

The great importance of this subject may well excuse our author for having entered somewhat more into its details than a work devoted to vegetable physiology might otherwise have war

ranted. But botany and agriculture are like two provinces of the same empire, which are separated by a broad river, with theory on the one side, and practice on the other; numerous bridges ought therefore to be constructed across this river, and our author has succeeded in erecting some, and in rebuilding others, on better principles than those which have hitherto been adopted. It now becomes the duty of the agriculturist to take advantage of them, and to study botany more zealously than he has hitherto done, and perhaps than it was possible for him to do, whilst the descriptive department of the science was still restricted within the limits of an artificial system, and its physiology was entirely based upon vague bypotheses.

An Appendix is added to the work, for the purpose of pointing out to those who may be desirous of rendering their assistance towards the further elucidation of the subject, how they may best accomplish this object. There are many points of first-rate importance in the establishment of a correct theory, which are as yet undetermined ; so that any one who chooses to enter on this field may soon expect to find ample opportunity for making fresh discoveries. Not only the descriptive botanist, but the chemist, the natural philosopher, the agriculturist, the distant traveller, and the physiologist, are all called upon to lend their aid in determining certain questions within the sphere of their respective observation, and we cannot possibly do better than close this long article by seconding the wishes of our author, that they may be persuaded to listen to his advice.

Art. IV.-Yurii Miloslavsky, ili Russkie v' 1612 godu. (Yurii

Miloslavsky, or the Russians in the Year 1612.) By M. J.

Zagoskin. Second Edition, Moscow, 1830. 3 vols. Svo. Ir was our intention to have noticed this production at some length, in a former article on Russian novels;* but we then contented ourselves with briefly adverting to it, from a belief that an English translation of it, which had been long-promised, would appear simultaneously with that number of our Review. As all idea of publishing that seems now entirely abandoned, our readers will probably not be sorry to be furnished with the means of judging whether the non-appearance of the projected translation need be matter of regret. Perhaps the very circumstance of this literary miscarriage here, may excite more curiosity to learn

See Foreign Quarterly Review, vol. viii. pp. 117 and 139. + To such as are unacquainted with the language of the original and we are afraid that the number is very large compared with those that have that advantage - the information that translations of this romance have been published both in French and German, may be an acceptable piece of intelligence.

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