well as upon feveral others; and the conclufions deducible from it appear to me decifive.

On the 12th of January I placed feveral thrubs in pots against the windows of my hot-houfe, fome within the house, and others without it. Through holes made for this purpose in the panes of glass, I paffed a branch of each of the fhrubs, fo that those on the infide had a branch without, and thofe on the outfide one within; after this, I took care that the holes fhould be exactly closed and fluted. This inverfe experiment, I thought, if followed closely, could not fail affording fufficient points of comparison, to trace out the differences, by the obfervation of the effects.

The 20th of January, a week after this difpofition, all the branches that were in the hot-house began to disclose their buds. In the begin. ning of February there appeared leaves, and towards the end of it, fhoots of a confiderable length, which prefented the young flowers. A dwarf apple - tree, and feveral rofe-trees, being fubmitted to the fame experiment, thewed the fame appearance then as they commonly put on in May; in fhort, all the branches which were within the hot-house, and confequently kept in the warm air, were green at the end of February, and had their fhoots in great forwardnefs. Very different were thofe parts of the fame tree, which were without and expofed to the cold. None of thefe gave the leaft fign of vegetation; and the froft, which was intenfe at that time, broke a rofe-pot placed on the outfide, and killed fome of the branches of that very tree, which, on the infide, was every day putting forth more and more fhoots,

leaves, and buds, fo that it was in full vegetation on one fide, whilft frozen on the other.

The continuance of the froft occafioned no change in any of the internal branches. They all continued in a very brisk and verdant ftate, as if they did not belong to the tree, which, on the outside, appeared in the state of the greatest fuffering. On the 15th of March, notwithstanding the feverity of the feafon, all was in full bloom. The apple-tree had its root, its ftem, and part of its branches, in the hothoufe. Thefe branches were covered with leaves and flowers; but the branches of the fame tree, which were carried to the outfide, and expofed to the cold air, did not in the leaft partake of the activity of the reft, but were abfolutely in the fame ftate which all trees are in during winter. A rofe-tree, in the fame pofition, fhewed long thoots with leaves and buds; it had even fhot a vigorous branch upon its ftalk, whilft a branch which paffed through, to the outfide, had not begun to produce any thing, but was in the fame ftate with other rofe-trees left in the ground. This branch is four lines in diameter, and eighteen inches high.

The rofe-tree on the outfide was in the fame ftate; but one of its branches drawn through to the infide of the hot-house, was covered with leaves and rofe-buds. It was not without astonishment that I faw this branch fhoot as brifkly as the rofe - tree which was in the hothoufe, whofe roots and stalk, expofed as they were to the warm air, ought, it fhould feem, to have made it get forwarder than a branch belonging to a tree, whofe roots, trunk, and all its other branches,

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were at the very time froft-nipt. Notwithstanding this, the branch did not feem affected by the ftate of its trunk; but the action of the heat upon it produced the fame effect as if the whole tree had been in the hot-house.

It would be useless to give an ac. count of the diary I kept throughout the courfe of this interefting experiment. It may be fufficient to obferve, that the walk of nature was uniformly the fame. The interior branches continued their productions in a regular manner, and the external ones began theirs at the fame time, and in the fame man ner, as they would have done, had they been left in the ground. The fruits of the interior branches of the apple-tree were, in the beginning of May, of the fize of nutmegs; whit the bloffoms but just began to fhew themfelves on the branches without. I fhewed Mr. Da-Tillet, of the Academy of Sciences at Paris, on his paffage through this town, the effects of my experiments, and likewife com municated to him another obfervation, which chance occafioned, and ought not to be omitted.

I obferved that three of the flower buds of the apple-tree had been gnawed off by a fail in fuch a manner, that all the petals and ita mens had disappeared, being eat up close to the calyx. This not having been entered by the fnail, the bafis of the piftillum, and the embryo, were preferved.

I took it for granted that these flowers would bear nothing; but I was foon convinced of my mistake. Almost all of them bore fruit; the apples were perfectly formed, and fix or seven pretty large ones too were feen upon each bunch. On

the other hand, the fnail had spared fome other bunches, (doubtleis becaufe more difficult to be got at ;) but out of ten or twelve flowers in each bunch, not above one or two fhewed any figns of fruit. This fuggeted to me the idea, that, when the flowers of trees are full blown, the prevention of the natural fall of the petals and ftamens gives a greater affurance of the fructification; and on feveral times repeating the following experiment, I convinced myself that it did fo. In imitation of the fnail, I cut with my fciffars the petals of apple, pear, plum, and cherry bloffoms, clofe to the calyx. Almost every one of thofe, which were thus cut, fucceeded, whilst feveral of the neighbouring flowers mifcarried.

Thus did a fail teach me how to render a tree fruitful; nor is it the first time that animals have been the inftructors of mankind. I confefs, however, that this procefs is not very practicable in a large or chard: but it might be adopted in an efpalier; in which one would chufe to procure a great deal of fruit from trees of the best fort. It may indeed be queftioned, whether the fuppreffion of the ftamens would not render the fruit barren; and in fact I found, that, though the flowers of the dwarf apple- tree, whofe petals and ftamens were eat up by the fnail, gave me apples equally large and beautiful, and that, when I came to open them, I found the capfules formed as ufual at the center of them; yet they were entirely empty, without the leaft appearance of a pip. Abfolute fructification confequently did not take place; fince botaniits, with reafon, call nothing fruit but the feed, which contains the germen,

which is to perpetuate the fpecies. All the other parts being only in tended to co-operate in the formation and prefervation of the feeds, perish of courfe, when once the feeds are come to maturity and perfection, and the work of nature fulfilled.

Another remarkable thing in thefe apples is, that in the upper part there was found a much deeper cavity than ufual. It was eight or nine lines deep. The orifice of this cavity was bordered by five tubercles, indented, and fomewhat elevated; but there was no veftige of the calyx, which, it is well known, remains always to the upper part of apples and pears, and is commonly called the eye.

I now return to my first experiment; the confequences of which, as I have defcribed them, feem to prove,

I. First, that the circulation of the fap does not take place in plants, as the circulation of the blood in animals. This may be deduced from the following obfer

vations:

The tree in the hot-house went through all its changes during the winter, and the branch exposed to the open air underwent none; confequently the fap, which was in action in the root, ftock, and head, of the tree, did not circulate through the branch without: which had no fhare in the vegetation of the roots and trunk. It might, indeed, be argued, that the cold air, to which this branch was expofed, ftopped the circulation, and there fore that the first experiment would not be decifive; but the inverfe of it feems fully fo.

The tree placed on the outfide of the hot houfe continued, during

the whole winter, in the ftate of numbnefs, natural to all trees, which are expofed at that season; but one of its branches, which was in the hot-house, put forth fucceffively its buds, leaves, blossoms, and fruits. Whilst therefore the root of the tree, to which this branch belonged, was in the ground fo frozen, that the pot itself, in which it flood, was broken by it, whilft the ftock and top of the tree were fo covered over with ice, that many of the branches were killed; this branch alone did not in the leaft partake of the common state of numbnefs and fuffering, but was, on the contrary, in full vegetation. The fap in it must have been extremely rarefied, and in very quick motion, whilft that of the tree was greatly condensed, and in total inaction. How is it poffible to conceive a cireulation of the fap from fuch a frozen root and stock, to a branch full of vigour, and, loaded with leaves and flowers? Surely this experiment must appear conclufive against the fyftem of circulation; fince in this cafe it could at best only be admitted to have taken place in the vegetating branch; and that would very improperly be termed circulation, which fhould be confined to one limb.

II. This experiment proves, that each part of a tree is furnished with a fufficient quantity of sap to effec&t the first production of buds, flowers, and fruits. There is little proba-> bility that the branch, drawn into the hot-house, should have derived its fap from the roots of the tree: as they, at that time, lay in a very fmall quantity of earth, rendered extremely hard and dry by the frost, they could have but little liquor to

Spare;

fpare; and even this, confidering the congealed ftate of the lymphatick veffels of the stock, could have found no paffage to the branch. This branch mutt of course have been enabled to continue its vegetation by the quantity of fap with which it was provided, the confumption of which must have been fupplied at the firft breaking of the froft.This truth, now demonftrable by experience, had been pointed out before by a multiplicity of other facts. Every body may have observed, that a tree which has been blown down in autumn, though separated from its trunk, begins the fame vegetation that it would have done if it had rémained standing. Its buds open, it bears leaves, and even fhoots, which fometimes are very long, and must be the effects of the fap it contained. It is true, indeed, that this appearance does not continue long, because the provifion of fap once exhaufted, without be. ing renewed, every thing mult of neceffity perish.

An effect of the like kind often deceives us in trees that have been newly planted, and in fcions which produce flowers, and even fruits, without ever having taken root. But in this cafe the symptoms, which would feem to promife life, are on the contrary the forerunners of death; because the leaves, being from their nature the most powerful organs of transpiration and dif fipation, the graft is the more readily exhausted, when there is no root to furnish it with a fresh fupply of nutritive juices.

III. This experiment proves that it is heat which unfolds the leaves, and produces the other parts of fructification in the branch expofed to its action.

Autumn is the time, in which nature employs itself as it were clandeftinely, under the cover of the leaves, in forming the buds which contain the rudiments of the leaves, bloffoms, and fruits, that are to be produced in the course of the fucceeding fummer. Thefe buds prepare and work themselves out, during the winter, under the rough coats, that are deftined to preferve them from the injuries of the weather. As foon as the warm weather in the fpring begins to be felt, the buds open, and their coats, which then become useless, drop off, and give place to the produc tions which they contained and preferved. Immediately after this, the bloffoms, flowers, and fruits, make their appearance. This is the ufual operation; but, in the cafe before us, nature was as it were furprized by art: what the fhould not have done tili fpring, fhe did in the winter, because the heat of the hot-houfe produced that expanfion, which, according to the natural course, ought to have been effected by the rays of the fun darting lefs obliquely than before upon the horizon. There is no doubt but it is to heat, either natural or artificial, that this expanfion is owing; and the experiment proves, that it is only in that part of the tree, which is expofed to the effect of heat, that the fap, which in every other part remains torpid and inactive, is put into motion, and produces vegetation. From this it appears, that the vegetable economy is different from the animal, and that thofe who endeavoured to establish the circulation in both, carried their analogy too far.

This fact, now established, farnihes a good reason why, in the

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