We have frequently been asked, what is the best mode of preserving fruit, and whether there are not chemical means of keeping it, so that it may be preserved fresh and wholly unchanged for a long time; either by placing it in contact with some substance which shall counteract its tendency to spoil, or by plunging it in some gas or liquid which will prevent it from decomposing. There have been a great many attempts to do this, but they have all been attended with but very partial success. Fruit, for the most part,consists chiefly of sugar, gum, starch, cellular matter, water, and a small quantity of albumen and gluten; but besides all these, it also contains certain other substances, such as coloring matter, and a small quanity of some highly fragrant volatile oil, to which the taste and agreeable smell of the fruit is due. The most changeable component of fruit, therefore, is the azotised matter, which is generally that which first of all commences to decompose: usually, too, air is necessary to its change, ana consequently those fruits which have thick dense skins, dry and shrivel up, when they are kept, without being spoilt.

In drying, of course they lose some portion of the volatile flavorever, are not of this description; their skins are so porous and open, that they very soon allow the air to pass into the interior of the fruit, and consequently it is impossible to preserve them by drying.

The immediate consequence of air coming in contact with the pulpy matter of ripe fruit, is that the azotised matters begin to absorb oxygen, and decompose; then the sugar, starch, and gum are acted on; the flavor is rapidly destroyed, sometimes spirit is formed, the sugar simply undergoing the vinous fermentation: at other times, the change goes on more rapidly, and the fruit soon becomes putrid. Ail these effects may be easily observed, by watching the ripening of any of the common varieties of fruit. The drying up of ripe grapes, which are left to hang with their skins uninjured, and the immediate change which occurs if the skin is injured or punctured, is familiar to every one. The rapid change which takes place in ripe Gooseberries, when the skins burst, and which, in the first instance, is a mere case of common vinous fermentation,is also well known. The injury which all fruit sustains from bruises, though it often does not produce the same effect, is yet in chemical nature very similar to that which occurs in the gooseberry. The cause of the evil in all cases is the oxygen of the air; and the mode in which it acts consists in the skin or cuticle being destroyed or injured, so that the air finds an easy entrance through the damaged part.

In the case of delicate and thin skinned fruits, they are so porous that the air enters on all sides, as soon as they are fully ripe, and even though they are not in any way injured, and this constitutes the chief difficulty in preserving them.

The fresh juice of the grape readily ferments, as soon as it is exposed to the air, but the juice of a raisin or half dried grape no longer has the power of doing so, because it contains too much sugar to ferment. A weak solution of sugar, under favorable conditions, soon begins to ferment; whilst a strong one is unable to enter into the vinous fermentation. It is in part, on this fact, that the common mode of preserving fruits by means of sugar depends. In making preserves, too, the fruit is heated, and heat, by rendering the vegetable albumen solid, makes it less likely to decompose. The pre-servative influence of heat on all forms of organic matter is well known; the value of heat in preventing the decomposition of food generally, was minutely detailed by Apport in 1810, for which he was rewarded by the French Government with a sum of twelve thousand francs.

But both heat and sugar, though no doubt very useful agents in the preservation of fruit, are very far from being quite satisfactory; and though, by their use. the fruit may be prevented from undergoing actual fermentation, yet more fruit, without the use of any substance which could injure its flavor, either by the addition of a new flavor or the destruction of the natural one. After what has been done already in the storing and preservation of some sorts of fruit, and the improved modes of keeping it which have been devised, we do not altogether despair of a satisfactory mode of preserving the more delicate kinds being discovered, although most of the recorded experiments which have been made with that view are certainly not very encouraging. The experiments usually referred to on the preservation of fruit by chemical means, are some which were made by Dr. Henry in 1776, and described in the fourth volume of Dr. Priestley's '-'Essays on Air." The fruit in these experiments was suspended in carbonic acid, so that it was kept in an atmosphere containing no free oxygen. A bunch of grapes exposed to carbonic acid remained fresh and plump for six weeks, whilst a corresponding bunch placed near it in a similar vessel, containing common air, was quite mouldy in three weeks.

A second experiment was made with, some ripe and rather stale strawberries, which had been gathered the day before; the following day those which were exposed to the air had lost their taste, whilst the fruit kept in carbonic acid, " had become more dry, but was fragant and well tasted; their fragrancy was even thought to be improved." On the fourth day, those in air became quite musty and mouldy, whilst those in carbonic acid were some of them firm, and had still a moderate degree of flavor at the end of eight days.

In this experiment of Dr. Henry's there are two points which were decidedly against the preservation of the fruit, namely, that the fruit was already stale at the commencement of the trial, and that the carbonic acid employed was not pure, but contained common air. A number of similar experiments have since been made, the general result of which has been, that though the fruit kept well, it wholly lost its flavor; but we do not think that there is any reason to despair of ultimate success. It is plain, from all the trials which have been made, that it is easy to prevent the decay or fermentation of fruit; the difficulty is rather to preserve its fine flavor, and prevent it from becoming tasteless and insipid. "When an apple is bruised, the part thus injured soon turns brown, decay commences, it becomes mouldy, and the whole fruit soon rots; and this decay easily spreads from one apple' to another. If a little hole is cut through the skin of a sound apple, and a small piece of a rotton one is inserted under the skin, the sound fruit will soon be brought into a state of decay; but if this is done in a jar of carbonic acid, no such effect will take place - the sound apple will remain fresh, even though there is a portion of decaylikewise from the absorption of other volatile substances; for fruit of all descriptions has a very remarkable power of absorbing odorous matters of various kinds.

Amongst the many plans for preserving fruit which have been described, and which more or less depend in principle on the exclusion of air. such as packing it in close sealed vessels, wrapping in fine paper, covering the ends of the stalks with sealing-wax, or arranging it in boxes filled with thoroughly dry sand, bran, straw, fern, or other similar substance, the greatest care in all cases must be taken that the packing material has no odor; for if it has, the fruit, besides losing a portion of its own natural aroma, will acquire some of the odor of the packing material, and the delicate flavor of the fruit, and consequently its value, will be destroyed. On the other hand, when fruit is preserved by cold, and especially when for this purpose it is gathered before it is perfectly ripe, it is often found that on removing it from the ice-house or cold well in which it has been preserved, though at first it has but little flavor, yet that on gently warming it and keeping it a few days, the flavor improves and decidedly increases.

This and other similar facts may fairly lead to the consideration, whether the odor and flavor of fruit which has been preserved some time in carbonic acid, nitrogen, or hydrogen, and which has in consequence become deteriorated, is, in truth, really altogether destroyed; and whether it might not be possible to recover the whole, or at least a portion, of the lost flavor?

The absorption of manure, or rather manner in which plants fed with very strong manures acquire a peculiar and often very disagreeable flavor in consequence; and also the curious way in which the odor of flowers is sometimes modified by the absorption of particular suit-stances, are probably also examples of the facility with which vegetables absorb odorous substances. Concerning the formation of odors by plants, very little indeed is known. There are, however, a number of curious facts bearing upon the subject, and showing how volatile odors, closely resembling those secreted by plants, are sometimes formed in the most unexpected manner. Thus, for example, in the process of bleaching rags by chlorine for making paper, it frequently happens that the bleached pulp has precisely the odor of ripe apples; this is evidently due to the presence of some substance formed by the action of the chlorine. - Gard. Chronicle.- New Tree Paeonies.- We have lately received from Mr. Verschaffelt. of Ghent, flowers of two tree Paenies of admirable beauty.

They were intended for exhibition in London, but would not keep for that purpose.

some of the petals, though all of good substance, were much longer than the others, giving the general aspect of the flower a somewhat ragged appearance.

The other was French white, shading off into rose at the base of the petals, and rather smaller, but more double and regular, and consequently more compact, holding together well, even after it had been cut a very long time. Both kinds were exceedingly handsome, as all tree Paeonies are. A well grown specimen ornamented with such flowers in even tolerable profusion must produce a magnificent display.

We understand that these were produced by Mr. Charles Goethals, a gentleman residing at Ghent. The darker kind, called Gloria Bel-garum, is described in the "Journal d'Horticulture Pratique," as a seedling which, in 1844, had flowered for five successive years, and at that time was producing blossoms at least 10 inches in diameter; a single plant bearing seven of them. It would seem that they are now appearing in great abundance, Mr. Verschaffelt having been able to forward four of them. Certainly these Moutans are among the finest we have ever seen. - Gard. Chronicle.