is immense; and if there were returning vessels, or a regular flow of sap or cambium from top to bottom, then surely the sucker buds at the upper part of the roots would receive the saine nourishment as the buds of the graft. That this is not the case, a moment's reflection will teach us.

It may be suggested that the suckers from trees not inoculated all produce fruit like the main stock; this is true only with particular trees-but it is one of the strongest proofs of the limited action of the tubular vessels; for we have observed, throughout, that the tubes furnish the proper juices only to those buds in their immediate section. If no buds grow under ground, then the elaborating vessels only absorb such portions of the crude sap as is requisite to sustain the tubular and porous organs of the section to which the absorbent vessels are attached.

The decay of trees has been the subject of much curious speculation, and it has settled down into an opinion that a tree, which has grown from a scion or graft taken from another tree, is merely the extension of the parent tree. It is inferred that, in consequence of the identity, the young tree must partake of the destiny, as well as the character, of the original. How physiologists could have fallen into this error, is inconceivable; for, according to this doctrine, if the parent tree died of age, then a tree grafted from it the year before must die at the same time.

Each slip or terminal shoot is as much a distinct and independent individual, when the roots are formed, as one of the Siamese twins would be if the membrane which united them could be severed. No one supposes for an instant that, if these young men were separated, one must necessarily die when the other did. We do not allude to death in consequence of cutting asunder the strong ligature which unites them, but to death from old age: one might live to the age of a hundred, and the other die of exhaustion at seventy-five. If the duration of the life of an apple tree was a century, a slip taken from this tree in its ninetieth year has the same chance of living out the term as the parent tree had. When the pores and tubes are divided at the junction of the articulation, which is effected by snapping asunder the slip and the section attached to it, there is an end of all connection between the parent and the slip. The organs of the new plant, being of the same formn and capacity as those of the tree whence the graft was taken, go on to enlarge the different parts-build up and repair-until the term allotted to its race has expired. As long as an animal or tree is permitted to grow as long as extension is possible-so long is there an enlargement, both in height and diameter, of each pore and organ. When the gravitating principle will not admit of fur

ther increase of size, the whole energies of the plant are in requisition to repair the waste and injuries to which it is subject, and to keep off the approach of death as long as possible. This is the instinctive property of organized matter-it belongs to the constitution of a plant as well as to that of an animal, to prevent decay when it can no longer increase in size.

The vital principle, therefore, is not the exclusive property of the whole tree, as one body, like that possessed by an animal, but belongs to every articulated section. The abstraction of life from one part does not affect the health of the rest. Vegetable life is a principle that can exist, or rather animate, a thousand parts at once, and yet connect itself with the whole. When the terminal shoot is cut off, vital energy still remains in it; and if the slip be so planted as that the embryo organs can protrude, and thus obtain nourishment for the upper part, life remains and animates the plant. If the slip is not planted, then the vital principle slowly leaves it and the slip dies. Even life can be stimulated to remain some time longer in a plant divided from the roots, by placing the stem-when the leaves, flowers, and bark, are in a state of collapse-in boiling water, showing of how much power gaseous action is in the economy of the vital principle. With a knowledge of this one important fact, why may not the trial be made of the introduction of certain gaseous fluids through the vascular tubes of an animal exhausted by hunger or disease? Oxygen gas, when inhaled, and thus forced by the lungs through the porous interstices, shows how speedily the system may be stimulated. It appears, therefore, that if the alimentary principles which nourish the body were forced either through the pores or tubular vessels by means of gases, the system might be sustained until the stomach and other digestive organs should recover their tone. We hope the trial may be made.

Trees, whether large or small, are not in the least indebted to high winds, or even to the ordinary winds of summer, for this enlargement or health. Many at the present day imagine that winds promote a healthy circulation, and that nature has endowed them with this invigorating power. But how could any one accustomed to the care and observation of plants fall into such an error? To be sure, we see the body and limbs of a tree bend to the blast, and toss to and fro when agitated by fitful gusts of wind, and we perceive that they apparently recover from these shocks, and give signs of health and fruitfulness; it is therefore concluded that this excitement is as necessary to the prolongation of their vigour and life as exercise is to an animal. The truth forced upon us by long experience is, that so far from being necessary, the action of winds is positively injurious.

It might as well be urged that gales of wind are of service to

a ship at sea, because she weathers the storm and comes sailing quietly into the harbour, looking as beautiful and as sound as when she left the port. But experienced seamen know that she has received many a strain, that her timbers have been wrung, her masts weakened, her sails rent, and that the foundation of decay sprung from those very gales.

A breeze just strong enough to give a gentle motion to the leaves, is, in reality, all the motion required from external causes. The experiment can be made at any time, by planting two trees of the same kind, of equal size and health, in different positions. If one be trained closely to the wall of a house, and confined by ligatures at every joint, continuing this restraint from year to year, and if the other be planted in an open field as a standard, the tree which is unable to move a single joint will grow rapidly under all the disadvantages of confinement. When all the twigs and limbs that were cut away from the tree which was trained, are taken into consideration, as well as the height and breadth of it as it stands, it will be perceived that it has grown to more than twice the size of the standard tree.

Winds undoubtedly retard the growth of a tree, and to one that is tall, the injury is very great; the bark and delicate vessels are not all that suffer, the petioles of the leaves also are tortured and twisted, until life is almost driven out. Every one must have witnessed this deplorable state of exhaustion which a tree is in after it has been thus violently blown about. The leaves droop, the tender limbs hang listlessly for several days, and many of a delicate nature wither and die.

Although trees are deprived of the power of locomotion, yet they are endowed with a capacity to resist or counteract many of the evils incident to their confined fixed position. One remarkable instance of this is the equilibrium to which they have the power of returning when accident or continued pressures have destroyed it. No sooner is a plant injured, than ramifications of equal extent to the wounds or amputations shoot out immediately and supply the waste. Another mode which a tree has of preserving a balance, when suffering under the harsh influence of regularly recurring northwest winds, is to strengthen the under or curved side of the limb or trunk that is bent out of its upright position. This is done by detaining a greater quantity of the proper juices, or assimilatory matter, in this curved spot.

If a transverse cut be made in the curved branch of a tree, it will be seen that the curved or concave part is thicker from the centre to the circumference than that of the upper or convex part. The concentric layers are equal in number, but the porous interstices are larger, and more of the elementary particles are deposited there. This same phenomenon occurs when trees are

placed in a cold northern exposure, even when they are not bent out of the perpendicular by strong winds. When cut cross, the layers on the south side will be found thicker and fuller than on the north side. This proceeds from some obstruction to the lateral pressure or direction of the secretions by the tubular and other vessels, for if external cold prevents the exit from within of rejected secretions, if the bark has not sufficient energy to slough off the fungus which is constantly deposited on unresisting substances, then the circulation on the north side must be weaker than that on the south.

It may not be irrelative to observe in this place, that it is to the presence of fungus or moss on the north side of trees, that travellers and Indians direct their course through unfrequented forests. In forests of pine, to which no moss adheres, travellers are guided by the enlargement of limbs and the fuller luxuriance which the south side exhibits. The particular qualities of the sap of resinous trees is not the sole cause that prevents the adhesion of atmospheric depositions, for in consequence of the enlargement of the porous and membranous organs, gaseous fluids are more abundantly present. Consequently the rejected secretions are forced off to the surface, and this lubrication of the bark or cuticle prevents the dust and other atmospheric particles from clogging up the pores. We perceive that the quickest growing limbs have the smoothest bark-neither canker, rust, nor fungi rest upon it.

But of all the mysteries connected with the rise of sap, and, in fact, connected with the circulation of the blood, there is none so extraordinary and inexplicable as the vital principle itself. Many physiologists have adopted the notion that this principle is transmitted to the different parts of a plant and animal through the medium of the sap and blood. We do not believe in the exclusive vivification of the sap and blood; the principle called life does not adhere to or traverse through any particular section or organ. It is an impulse which is diffused throughout the whole organic system of both plants and animals. It is a primary essence existing independently throughout space, traversing unrestrained, and attaching itself to all organized matter. As long as the organized body is sustained by the two great powers-centripetal and centrifugal pressures-as long as the one power can prevent the undue pressure of the other-or, in other words, as long as an equilibrium is kept up, the action of the vital principle is unimpaired. But if the centrifugal power, or levity, forces up alimentary particles in too great a quantity, so as to overcome that portion of centripetal, or gravitating power which is opposed to it-which two powers operate on organic as well as inorganic matter-then the action of

the vital principle is accelerated-the body is said to live too fast.

Life, therefore, is dependent on a prevention of excess. Both in animal and vegetable life, care is to be taken not to overcharge the system with alimentary stimulus, for if the vessels are too much excited, life, or the vital principle, cannot traverse the system with ease. A certain portion of this vital essence is necessary to the healthy operations of an organized being, but if the circulation is quickened, then it follows that, as life traverses every particle, and these particles are propelled more rapidly, the vivifying principle must accumulate to a greater degree than the economy of the system can bear; there is not only a superabundance of mere life, but of alimentary stimulus likewise, and in the end this stimulus must clog up the fine vessels of the brain; when this is the case, congestion and apoplexy, by putting a stop to the circulation, drive life from the system altogether. Too much stimulus at the roots of plants operates in the same manner on their system as on ours, and the greatest care should be taken to apply nutriment judiciously.

Life leaves the system also when the circulation is too slow, for then aliment is too sparingly diffused-there are fewer particles around which this vital principle can traverse, and as they continue to decrease, so will there be less animation. In vegetable life the centripetal and centrifugal power both operate from without at the extremities, but in animal locomotive life, the latter power emanates from the centre, the heart, and the centripetal, or gravitating principle, presses on every part of the body externally, so that the equilibrium is kept up when there is no preternatural or morbid action to intervene.

Life therefore, does not attach itself, solely to the elaborated particles in the tubular vessels, but also to every portion of the germ or organic structure of a plant and animal; but only as long as these organs or parts are capable of being acted upon by the joint and equal efforts of the two repelling powersgravity and levity. Life, or the vital principle, can exist in a paralysed limb when the contractile ligature on which the mind operated to produce motion, is either relaxed or broken asunder. Life-therefore does not of itself produce sensation or motion

-it is when all things accord, when there is a fitness and adaptation throughout, that life pervades every atom of an organized being.

When the contractile or elastic organs of an arm that is paralysed are only relaxed, the arm may be restored to motion; but if they are snapt asunder, and when complete paralysis occurs suddenly this snapping is both felt and heard by the sufferer, then the art of man can never restore the motion or use of the arm.