Gambar halaman
PDF
ePub

Plant.

“For the sap in all vegetables does probably recede against the windows of my hot-house, some within the plast in some measure from the tops of the branches, as the house and others without it. Through holes made for sun leaves them; because its rarefying power then this purpose in the panes of glass, I passed a branch of ceasing, the greatly rarefied sap, and air mixed with it, each of the shrubs, so that those in the inside bad a will condense, and take up less room than they did, and branch without, and those on the outside one within; the dew and rain will then be strongly imbibed by the after this, I took care that the holes should be exactly leaves; whereby the body and branches of the vegetable closed and luted. This inverse experiment, I thought, which bave been much exhausted by the great evapora if followed closely, could not fail affording sufficient tion of the day, may at night imbibe sap and dew points of comparison, to trace out the differences, by the from the leaves; for by several experiments, plants were observation of the effects. found to increase considerably in weight, in dewy and “ The 20th of January, a week after this disposition, moist nights. And by other experiments on the vine, all the branches that were in the hot-house began to disit was found that the trunk and branches of vines were close their buds. In the beginning of February there apalways in an imbibing state, caused by the great perspi- peared leaves; and towards the end of it, shoots of a ration of the leaves, except in the bleeding season ; but considerable length, which presented the young flowers. when at night that perspiring power ceases, then the con A dwarf apple-tree, and several rose trees, being submittrary imbibing power will prevail, and draw the sap and ted to the same experiment, showed the same appearance dew from the leaves, as well as moisture from the roots. then as they commonly put on in May; in short, all the

" And we have a farther proof of this by fixing mer branches which were within the hot-house, and consecurial gages to the stems of several trees which do not quently kept in the warm air, were green at the end of bleed, whereby it is found that they are always in a February, and had their shoots in great forwardness. strongly imbibing state, by drawing up the mercury se Very different were those parts of the same tree which veral inches : whence it is easy to conceive, how some were without and exposed to the cold. None of these of the particles of the gilded bud in the inoculated jes- gave the least sign of vegetation; and the frost, which samine may be absorbed by it, and thereby communicate was intense at that time, broke a rose-pot placed on the their gilding miasma to the sap of other branches; espe- outside, and killed some of the branches of that very tree cially when, some months after the inoculation, the which, on the inside, was every day putting forth more stock of the inoculated jessamine is cut off a little and more shoots, leaves, and buds, so that it was in full above the bud; whereby the stock, which was the vegetation on one side, whilst frozen on the other. counteracting part to the stem, being taken away, the “ The continuance of the frost occasioned no change stem attracts more vigorously from the bud.

in any of the internal branches. Tbey all continued in “Another argument for the circulation of the sap is, a very brisk and verdant state, as if they did not belong that some sorts of the graffs will infect and canker the to the tree which, on the outside, appeared in the state stocks they are grafted on: but by mercurial gages of the greatest suffering. On the 15th of March, notfixed to fresh cut stems of trees, it is evident that those withstanding the severity of the season, all was in full stems were in a strongly imbibing state ; and conse bloom. The apple-tree had its root, its stem, and part quently the cankered stocks might very likely draw sap of its liranches, in the bot-house. These branches were from the graff, as well as the graff'alternately from covered with leaves and flowers; but the branches of the stock; just in the same manner as leaves and the same tree, which were carried on the outside, and branches do from each other, in the vicissitudes of day exposed to the cold air, did not in the least partake of and night. And this imbibing power of the stock is the activity of the rest, but were absolutely in tbe same so great, where only some of the branches of a tree state which all trees are ix during winter. A rose-tree, are grafted, that the remaining branches of the stock in the same position, showed long shoots with leaves and will, by their strong attraction, starve those graffs; for buds; it had even shot a vigorous branch upon its which reason it is usual to cut off the greatest part of stalk; whilst a branch which passed through to the the branches of the stock, leaving only a few small ones outside had not begun to produce any thing, but was to draw up the sap.

in the same state with other rose-trees left in the “The instance of the ilex grafted upon the English ground. This branch is four lines in diameter, and oak, seems to afford a very considerable argument 18 inches high. against a circulation. For, if there were a free uni “ The rose-tree on the outside was in the same state; form circulation of the sap through the oak and ilex, but one of its branches drawn through to the inside of why should the leaves of the oak fall in winter, and not the hot-house was covered with leaves and rose-buds. those of the ilex ?

It was not without astonishment that I saw this branch " Anotber argument against an uniform circulation shoot as briskly as the rose-tree which was in the hotof the sap in trees, as in animals, may be drawn from an house, whose roots and stalk, exposed as they were to experiment, where it was found by the three mercurial the warm air, ought, it should seem, to have made it gages fixed to the same vine, that while some of its get forwarder than a branch belonging to a tree, whose branches changed their state of protruding sap into a roots, trunk, and all its other branches, were at the very state of imbibing, others continued protruding sap; one time frost-nipped. Notwithstanding this, the branch nine, and the other thirteen days longer."

did not seem affected by the state of its trunk ; but the To this reasoning of Dr Hales we shall sabjoin an ex action of the heat upon it produced the same effect as periment made by Mr Mustel of the Academy of Scien. if the whole tree had been in the bot house." ces at Rouen, which seems decisive against the doctrine Of the Perpendicularity of Plants. This is a curiof circulation. His account of it is as follows." On ous phenomenon in natural bistory, which was first ob-Seiten the 3 2th of January I placed several shrubs in pots served by M. Dodart, and published in an essay on the 4

affectation

de

[ocr errors]
[ocr errors]

Plant. affectation of perpendicularity observed in the stems or equally tend to straighten the part most exposed by the Plani.

stalks of all plants, in the roots of many, and even in shortening they successively occasion in it; for moisture their branches

, as much as possible. Though almost all shortens by swelling and heat by dissipating. What that plants rise a little crooked, yet the stems shoot up per structure is which gives the fibres such different qualities, pendicularly, and the roots sink down perpendicularly: or whereon it depends, is a mystery as yet beyond our even those, which by the declivity of the soil come out depth. inclined, or those which are diverted out of the perpen M. de la Hire accounts for the perpendicularity of the dicnlar by any violent means, again redress and straight- stems or stalks of plants in tbis manner: be supposes that en themselves and recover their perpendicularity, by the root of plants draws a coarser and heavier juice, and making a second and contrary bend or elbow without the stem and branches a finer and more 'volatile one. rectifying the first. We commonly look upon this af Most naturalists indeed conceive the root to be the stofectation without any surprise ; but the naturalist who mach of the plant, where the juices of the earth are subknows what a plant is, and how it is formed, finds it a tilized so as to become able to rise through the stem to subject of astonishment.

the extremity of the branches. This difference of juices Each seed we know contains in it a little plant, al- supposes larger pores in the roots than the stalk, &c.ready formed, and needing nothing but to be unfolded ; and, in a word, a different contexture. This difference the little plant has its root; and the pulp which is usu must be found even in the little invisible plant inclosed ally separated into two lobes, is the foundation of the in the seed : in it, therefore, we may conceive a point first food it draws by its root when it begins to germi• of separation ; such as, that all on one side, for example nate. If a seed in the earth, therefore, be disposed so as the root, shall be unfolded by the grosser juices, and all that the root of the little plant be turned downwards, on the other side by the more subtle ones. Suppose the and the stem upwards, and even perpendicularly up- plantule, when its parts begin to unfold, to be entirely wards, it is easy to conceive that the little plant coming inverted, the root at the top, and the stalk below; the to unfold itself, its stalk and root need only follow the juices entering the root will be coarsest, and when they direction they have to grow perpendicularly. But we have opened and enlarged the pores so as to admit juices know that the seeds of plants, whether sown of theni of a determinate weight, those juices pressing the root selves or by man, fall in the ground at random; and more and more will drive it downwards ; and this will among the great variety of situations with regard to the increase as the root is more extended or enlarged : for stalk of their plant, the perpendicular one upwards is the point of separation being conceived as the fixed point but one. In all the rest, therefore, it is necessary that of a lever, they will act by the longer arm. The volathe stalk rectify itself, so as to get out of the ground : tile juices at the same time having penetrated the stalk, but what force effects this change, which is unquestion- will give it a direction from below upwards; and, by ably a violent action ? Does the stalk find a less load of reason of the lever, will give it more and more every earth above it, and therefore go naturally that way day. The little plant is thus turned on its fixed point of where it finds the least obstacle? Were this so, the lit- separation till it become perfectly erect. tle root, when it happens to be uppermost, must also fol When the plant is thus erected, the stalk should still Jow that direction, and mount up.

rise perpendicularly, in order to give it the more firm To account for two such different actions, M. Dodart biding, and enable it to withstand the effort of wind and supposes that the fibres of the stalks are of such a nature weather. M. Parent thus accounts for this effect: If as to be contracted and shortened by the heat of the sun, the nutritious juice which arrived at the extremity of a and lengthened out by the moisture of the earth ; and, rising stalk evaporate, the weight of the air which enon the contrary, that the fibres of the roots are contract. compasses it on all sides will make it ascend vertically: ed by the moisture of the earth, and lengthened by the but if, instead of evaporating, it congeal, and remain heat of the sup. When the plantule therefore is invert- fixed to that extremity whence it was ready to go off, ed, and the root at the top, the fibres which compose the weight of the air will give it the same direction ; so one of the branches of the root are not alike exposed to that the stalk will have acquired a small new part vertithe moisture of the earth, the lower part being more ex cally laid over it, just as the flame in a candie held in posed than the upper. The lower must of course con any way obliquely to the horizon still continues verti. tract the most; and this contraction is again promoted cal by the pressure of the atmosphere. The new drops by the lengthening of the upper, whereon the sun acts of juice that succeed will follow the same direction; and with the greatest force. This branch of the root must as all together form the stalk, that must of course be therefore recoil towards the earth, and, in-inuating vertical, unless some particular circunstance intervene. through the pores thereof, must get underneath the bulb, The branches, which are at first supposed to proceed &c. By inverting this reasoning we discover how the laterally out of the stalk in the first embryo of the plant, stalk comes to get uppermost.

though they should even come out in an horizontal di. We suppose then that the earth attracts the root to it. rection, must also raise themselves upwards by the con. self, and that the sun contributes to its descent; and, on stant direction of the nutritious juice, which at first the other hand, that the sun attracts the stem, and the scarcely meets any resistance in a tender supple branch; earth contributes to send it towards the same. With re- and afterwards, even though the branch grow more spect to the straightening of the stalks in the open air, firm, it will act with the more advantage ; since the our author imagines that it arises from the impression of branch, being become longer, furnishes it with a longer external causes, particularly the sun and rain. For the arm or lever. The slender action of even a little drop upper part of a stalk tbat is bent is more exposed to the becomes very considerable by its continuity, and by the rain, dew, and even the san, &c. than the under; and assistance of such circumstances. Hence we may acthese causes, in a certain structure of the fibres, both count for that regular situation and direction of the

brancbes,

Plant branches, since they all make nearly the same constant of living vegetables, the case is reversed. The purest plus

angle of 45° with the stem, and with one another. air is the common e fluvium which passes off from vege

M. Astruc accounts for the perpendicularity of the tables; and this, however favourable to animal life, is stems, and their redressing themselves, thus : 1. He by no means so to vegetable; whence ve bave an addithinks the nutritious juice arises from the circumference tional proof of the doctrine concerning the food of plants of the plant, and terminates in the pith: And, 2. That deliveied under the article AGRICULTURE. fluids, contained in tubes either parallel or oblique to With regard to the effects of other kinds of air on the horizon, gravitate on the lower part of the tubes, vegetation, a difference of some consequence took place and not at all on the upper. Hence it follows, that, in a between Dr Priestley and Dr Percival. The former, in plant placed either obliquely or parallel to the horizon, the first volume of his Experiments and Observations on the nutritious juice will act more on the lower part of Air, had asserted that fixed air is fatal to vegetable as the canals than on the upper; and by this means they well as to animal life. This opinion, however, was opwill insinuate more into the canals communicating there- posed by Dr Percival, and the contrary one adopted by with, and be collected more copiously therein : thus Dr Hunter of York in the Georgical Essays, vol. v. the parts on the lower side will receive more accretion The experiments related by these two gentlemen would and be more nourished than those on the upper, the ex indeed bave been decisive, had they been made with suftremity of the plant will therefore be obliged to bend ficient accuracy. That this was the case, however, Dr upwards.

Priestley denies; and in the 3d volume of his Treatise This principle brings the seed into its due situation 'on Air bas fully detected the mistakes in Dr Percival's at first. In a bean planted upside down, the plume and Experiments ; which proceeded in fact from his baving radicle

may be seen with the naked eye shooting at first used, not fixed air, but common air mixed with a small directly for about an inch ; after which they begin to quantity of fixed air. "His experiments, when repeated bend, the one downward, and the other upward. The with the purest fixed air, and in the most careful nan same is the case in a heap of barley to be made into ner, were always attended with the same effect, namely, malt, or in a quantity of acorns laid to sprout in a moist the killing of the plant. place, &c. Each grain of harley and each acorn has a It had also been asserted by Drs Percival and Handifferent situation; and yet every sprout tends directly ter, that water impregnated with fixed air was more faopward, and every root downward, and the curvity or vourable to vegetation than simple water. This opinion bend they make is greater or less as their situation ap was likewise examined by Dr Priestley; however, bis proaches more or less to the direction wherein no curva experiments were indecisive; but seem rather uufature at all would be necessary. But two such opposite vourable to the use of fixed air than otherwise. motions cannot possibly arise without supposing some Another very remarkable fact with regard to the food difference between the two parts: the only one we know of plants has been discovered by Dr Priestley ; namely, of is, that the plume is fed by a juice imported to it by that some of them, such as the willow, comfrey, and tubes parallel to its sides, whereas the radicle imbibes duckweed, are nourished by inflammable air. The first, its nourishment at every pore in its surface. When the he says, flourishes in this species of air so remarkably, plume therefore is either parallel or inclined to the hori. that, “ it may be said to feed upon it with great avidity. Priest.cy zon, the nutritious juice, feeding the lower parts more This process terminates in the change of what remains on dir,

vol. v. .: than the upper, will determine its extremes to turn up of the inflamnable air into phlogisticated air, and someward, for the reasons before given. On the contrary, times into a species of air as good as common air, or when the radicle is in the like situation, the nutritious even better; so that it must he the inflammable princijuice penetrating through the upper part more copious-ple in the air that the plant takes, converting it, to ly than through the ouder, there will be a greater accre doubt, into its proper nourishment.” tion of the former than of the latter; and the radicle What the followers of Stabl call phlogisticated air will therefore be bent downwards, and this mutual cur and inflammable air, are so closely allied to each other, vity of the plume and radicle must continue till such that it is no wonder they should serve promiscuously for time as their sides are nourished alike, which cannot be the food of plants. The reason why both are not agreetill they are perpendicular.

able to all kinds of plants, most probably is the different of the Food of Plants. This hath been so fully quantity of phlogistic matter contained in them, and the discussed under the article AGRICULTURE, that little different action of the latent fire they contain ; for all remains to be said upon the subject in this place. The plants do not require an equal quantity of nourishment: method of making dephlogisticated or vital air de novo, and such as require but little, will be destroyed by havis now so much improved, that numberless experiments ing too much. The action of heat also is essentially ne. may be made with it both on animals and vegetables. cessary to vegetation; and it is probable that very much It appears, indeed, that these two parts of the creation of this principle is absorbed from the air by vegetables

. are a kind of counterbalance to one another; and the But if the air by which plants are partly nourished conpoxious parts or excrements of the one prove salutary tains too much of that principle, it is very probable that food to the other. Thus, from the animal body conti- they may be destroyed from this cause as well as the nually pass off certain effluvia, which vitiate or phlogis- other; and thus inflammable air, which contains a vast ticate the air. Nothing can be more prejudicial to ani- quantity of that active principle, may destroy such mal life than an accumulation of these effuvia : on the plants as grow in a dry soil

, though it preserves those other hand, nothing is more favourable to vegetables which grow in a wet one. See VEGETATION. than those excrementitious effluvia of animals; and ac Dissemination of Plants.—So great are the prolific cordingly they greedily absorb them from the earth, or powers of the vegetable kingdom, that a single plant alfrom the air. With respect to the excrementitious parts inost of any kind, if left to itself, would, in a short time,

overTON

Plant

overrun the whole world. Indeed, supposing the plant reflecting that their seeds are so minute that they are Plant.
to bave been only a single annual, with two seeds, it almost invisible to the naked eye. They float in the
would, in 20 years, produce more than a million of its air like atoms, and are dropped everywhere, but grow
own species ; what numbers then must have been pro- only in those places where there was no vegetation be-
duced by a plant whose seeds are so numerous as many fore; and hence we find the same mosses in North
of those with which we are acquainted ? In that part America and in Europe.
of our work we have given particular examples of the 7. Seeds are also dispersed by the ocean, and by rivers,
very prolific nature of plants, which we need not repeat In Lapland (says Linnæus), we see the most evident Amoen.
bere ; and we have made some observation on the means proofs how far rivers contribute to deposit the seeds of Acad.
by which they are carried to distant places. This is a plants. I bave seen Alpine plants growing upon their
very curious matter of fact, and as such we shall now shores frequently 36 miles distant from the Alps ; for
give a fuller account of it.

their seed, falling into the rivers, and being carried If nature had appointed no means for the scattering along and left by the stream, take root there. We may of these numerous seeds, but allowed them to fall down gather likewise from many circumstances how much the in the place where they grew, the young vegetables sea furthers this business.- In Roslagia, the island of must of necessity have choked one another as they grew Græsæa, Oeland, Gothland, and the shores of Scania, up, and not a single plant could have arrived at perfec- there are many foreign and German plants not yet nation. But so many ways are there appointed for the turalized in Sweden. The centaury is a German plant, dissemination of plants, that we see they not only do whose seeds being carried by the wind into the sea, the not hinder each others growth, but a single plant will wares landed ibis foreigner upon the coasts of Sweden. in a short time spread through different countries. The I was astonished to see the veronica maritima, a German most evident means for this purpose are,

plant, growing at Tornea, which hitherto had been found 1. The force of the air. That the efficacy of this only in Græsæa : the sea was the vehicle by which this may be the greater, nature has raised the seeds of

vege plant was transported thither from Germany; or possibly tables upon stalks, so that the wiod has thus an oppor it was brought from Germany to Græsca, and from tunity of acting upon them with the greater advantage. thence to Tornea. Many bave imagined, but erroneousThe seed-capsules also open at the apex, lest the ripe ly, that seed corrupts in water, and loses its principle of seeds should drop out without being widely dispersed by vegetation. Water at the bottom of the sea is seldom the wind. Others are furnished with wings, and a pap warm enough to destroy seeds; we have seen water cover pous down, by which after they come to maturity, they the surface of a field for a whole winter, while the seed are carried up into the air, and have been known to fly wbich it contained remained unhurt, unless at the bethe distance of so miles: 138 genera are found to have ginning of spring the waters were let down so low hy winged seeds.

drains, that the warmth of the sun-beams reached to the 2. In some plants the seed-vessels open with violence bottom. Then the seeds germinate, but presently bethen the seeds are ripe, and thus throw them to a con come putrescent; so that for the rest of the year the siderable distance; and we have an enumeration of 50 earth remains naked and barren. Rain and showers genera whose seeds are thus dispersed.

carry seeds into the cracks of the earth, streams, and 3. Other seeds are furnished with hooks, by which, rivers ; which last, conveying them to a distance from when ripe, they adhere to the coats of animals, and are their native places, plant them in a foreign soil.” carried by them to their lodging places. Linnæus rec 8. Lastly, some seeds assist their projection to a dikons 50 genera armed in this manner.

stance in a very surprising manner. The crupina, a spe4. Alany seeds are dispersed by means of birds and cies of centaury, has its seeds covered over with erect other animals; who pick up the berries, and afterwards bristles, by whose assistance it creeps and moves about in eject the seeds uninjured. Thus the fox disseminates such a manner, that it is by no means to be kept in the the privet, and man many species of fruit. The plants hand. If you confine one of them between the stockfound growing upon walls and houses, on the tops of ing and the foot, it creeps out either at the sleeve or high rocks, &c. are mostly brougẢt there by birds ; and neck-band, travelling over the whole body. If the it is universally known, that by manuring a field with bearded oat, after barvest, be left with other grain in new dung, innumerable weeds will spring up which did the barn, it extricates itself from the glume; nor does it not exist there before : 193 species are reckoned up stop in its progress till it gets to the walls of the buildwhich may be disseminated in this manner.

ing. Hence, says Linnæus, the Dalecarlian, after be has s. The growth of other seeds is promoted by animals cut and carried it into the barn, in a few days finds all in a different way. While some are eaten, others are the glumes empty, and the oats separate from them; for scattered and trodden into the ground by them. The every oat has a spiral arista or beard annexed to it, which squirrel gnaws the cones of the pine, and many of the is contracted in wet, and extended in dry weather. seeds fall out. When the loxia eats off their bark, al. Wben the spiral is contracted, it drags the oat along most his only food, many of their seeds are committed with. it: the arista being bearded with minute hairs to the earth, or mixed in the morass with moss, where pointing downward, the grain necessarily follows it; but he had retired. The glandularia, when she hides up when it expands again, the oat does not go back to its her nuts, often forgets them, and they strike root. The former place, the roughness of the beard the contrary same is observable of the walnut; mice collect and bury way preventing its return. If you take the seeds of equi. great quantities of them, and being afterwards killed by setum, or fern, these being laid upon paper, and viewed different animals, the nuts germinate.

in a microscope, will be seen to leap over any obstacle 6. We are astonished to find mosses, fungi, byssus, as if they had feet; by which they are separated and and mucor, growing everywhere; but it is for want of dispersed one from another; so that a person ignorant of

this

l'ant.

this property would pronounce these seeds to be so many “ Instincts analogous to these (says our author), ope. Ilant. mites or small insects.

rate with equal energy on the vegetable tribe. A seed We cannot finish this article without remarking, that contains a germ, or plant in miniature, and a radicle, many ingenious men believe that plants have a power of or little root, intended by nature to supply it with nouperception. Of this opinion we shall now give an ac rishment. If the seed be sown in an inverted positioni, count from the second volume of the Manchester Trans. still each part pursues its proper direction. The plumula actions, where we find some speculations on the percep turns upward, and the radicle strikes downward into tive power of vegetables by Dr. Percival, who attempts the ground. A hop-plant, turning round a pole, follows to show, by the several analogies of organization, life, the course of the sun, from south to west, and soon dies, instinct, spontaneity, and self motion, that plants, like when forced into an opposite line of motion : but reanimals, are endued with the powers both of perception move the obstacle, and the plant will quickly return to and enjoyment. The attempt is ingenious, and is in- its ordinary position. The branches of a honeysuckle geniously supported, but in our opinion fails to con shoot out longitudinally, till they become unable to bear vince. That there is an analogy between animals and their own weight; and then strengthen themselves, by vegetables is certain ; but we cannot from thence con changing their form into a spiral : when they meet with clude that they either perceive or enjoy. Botanists have, other living branches, of the same kind, they coalesce, it is truc, derived from anatomy and physiology, almost for mutual support, and one spiral turns to the right and all the terms employed in the description of plants. But 'the other to the left; thus seeking, by an instinctive imwe cannot from thence conclude, that their organization, pulse, some body on which to climb, and increasing the though it bears an analogy to that of animals, is the sign probability of finding one by the diversity of their course : of a living principle, if to this principle we annex the idea for if the auxiliary branch be dead, the other uniformly of perception ; yet so fully is our author convinced of the winds itself round from the right to the left. truth of it, that be does not think it extravagant to “ These examples of the instinctive economy of vegesuppose, that, in some future period, perceptivity may tables have been purposely taken from subjects familiar be discovered to extend even beyond the limits now as. to our daily observation. But the plants of warmer clisigned to vegetable life. Corallines, madrepores, mille mates, were we sufficiently acquainted with them, would pores, and sponges, were formerly considered as fossil probably furnish better illustrations of this acknowledged bodies: but the experiments of Count Marsigli evinced, power of animality : and I shall briefly recite the history that they are endued with life, and led him to class them of a very curious exotic, which has been delivered to us with the maritime plants. And the observations of El. from good authority; and confirmed by the obserralis, Jussieu, and Peysonel, have since raised them to the tions of several European botanists." rank of animals. The detection of error in long esta The doctor then goes on to give a description of the blished opinions concerning one branch of natural know- dionæa muscipula (B), for which see vol. vi. p. 32.; and ledge, justifies the suspicion of its existence in others, concludes, that if he has furnished any presumptive which are nearly allied to it. And it will appear from proof of the instinctive power of vegetables, it will nethe prosecution of our inquiry into the instincts, spon- cessarily follow that they are endued with some degree taneity, and self-moving power of vegetables, that the of spontaneity. More fully to evince this, however, the suspicion is not without foundation.

doctor points out a few of those phenomena in the vegeHe then goes on to draw a comparison between the table kingdom which seem to indicate spontaneity.instincts of animals and those of vegetables; the calf, as “ Several years ago (says he), whilst engagedin a course soon as it comes into the world, applies to the teats of of experiments to ascertain the influence of fixed air on the cow; and the duckling, though hatched under a vegetation, the following fact repeatedly occurred to me. ben, runs to the water.

A sprig of mint, suspended by the root, with the head

downwards,

(B) Dr Watson, the bishop of Landaff, who has espoused the same side of the question with Dr Percival (see the sth vol. of his Chemical Essays), reasons thus on the motions of vegetables. “ Whatever can produce any effect (says he) upon an animal organ, as the impact of external bodies, heat and cold, the vapour of burning sulphur, of volatile alkali, want of air, &c. are found to act also upon the plants called sensitive. But not to insist upon any more instances, the muscular motions of the dionæa muscipula, lately brought into Europe from America, seem far superior in quickness to those of a variety of animals. Now to refer the muscular motions of shell-fish and zoophytes to an internal principle of volition, to make them indicative of the perceptivity of the being, and to attribute the more notable ones of vegetables to certain mechanical dilatations and contractions of parts occasioned by external impulse, is to err against that rule of philosophizing which assigns the same causes for effects of the same kind. The motions in both cases are equally accommodated to the preservation of the being to which they belong, are equally distinct and uniform, and should be equally derived from mechanism, or equally admitted as criterions of perception.

“ I am sensible that these and other similar motions of vegetables may by some be considered as analogous to the automatic or involuntary motions of animals ; but as it is not yet determined amongst the physiologists, thether the motion of the heart, the peristaltic motion of the bowels, the contractions observable upon external impulse in the muscles of animals deprived of their beads and hearts, be attributable to an irritability, unaccompanied with perceptivity, or to an uneasy sensation, there seems to be no reason for entering into so obscure a disquisition; especially since irritability, if admitted as the cause of the motions of vegetables, must à fortiori be admitted as the cause of the less exquisite and discernible motions of being universally referred to the animal kingdom."

« SebelumnyaLanjutkan »