casualties to which they are the more subject in consequence of being deprived of the powers of speech and locomotion. The reproductive capacity, which plants possess in so remarkable a degree, eminently proves that they have this superabundant quantity of the vital principle.

Each articulation or joint of a plant has the special power assigned to it, not only to receive from the roots its own share of the crude sap as it rises, but of retaining and apportioning this sap to its own use, so as to sustain the particular twig that emanates from this articulation. Of course, when the terminal shoot is separated from the joint there is a reservoir of this cambium or elaborated juice at the base, which is sufficient to sustain the slip until it can strike out roots and support itself.

There is an important fact corroborative of this, which is this-the extremities of the tallest trees exhibit the first appearance of life when excited by the sun's rays in the spring; they show as much animation and vigour after being exposed to the cold of a Siberian winter, as if the general circulation had never been checked. Whereas tortoises, and other animals which lie torpid during the winter, are obliged to draw their limbs within the shell, or curl up their bodies in such a manner as to bring the extremities as closely as possible to vital heat. Plants, therefore, have a power connected with that of divisibility, by which heat is generated at the articulated sections, and this heat is excited even before the frost is out of the ground in the spring.

Although the organic structure of plants varies so much in different species, yet the same phenomena of vitality, instinct, and irritability, exist in all. The circulation of sap is so rapid in the grape vine, owing to the peculiarity of the interstitial medium, that, when wounded, the exhaustion from the copious discharge often endangers the life of the plant. The same effect is produced in seasons of great drought: the grape vine suffers for the want of a constant supply of fluid nutriment; if it be withheld the plant slowly loses its energy, the leaves hang loosely and without motion, and the unripe flaccid berries wither on the vines. Here an analogy can be traced between the animal and plant; but our object is chiefly to speak of vegetation, and not to draw comparisons.

The electric fluid will sometimes prostrate the energies of the grape vine. We have seen the leaves of a whole vineyard hang lifeless after a warm, gentle, July shower, during the hottest period of the day. Many of the vines never recovered from this syncope, if so it may be called. A warm shower in mid-day will sometimes produce the like effect on the sensitive plant, but it always revives after the shower is over.

Every thing that has life is more or less affected by the elec

tric fluid; that the sensitive plant shows its presence so instantaneously, is owing to the peculiarity of the ligament which connects the articulations and the cellular tissues. But the same revulsion or collapse takes place in all plants, only in a greater or less degree according to the activity of the vital principle. If we wound the bark of a tree, no external motion is visible; this arises from the rigidity of its parts, yet we feel assured that some commotion takes place internally at the very instant that the injury occurs. The work of repair goes on immediately; for, no sooner is the bark bruised than there is a rush of secretive matter to the spot, which covers the wound from the air, and in a short time the broken bark is renewed, having acquired additional strength by the healing process.

The external motion of some plants, and the motion that we feel assured is going on within others, may as well be called irritability as nervimotion. No one refers to mental action for the production of that convulsive movement of the spider's leg, nor of the hen when the head has been chopped off. These movements are the remains of the same principle which is common to plants and animals-vitality. This power, life, gradually disappears from the parts when they are separated from the head, but neither sensation nor consciousness have any share in producing these irregular movements; they are altogether involuntary. It is a fact worthy of observation, that these convulsive movements will be more violent in a hen that has been chased about for some time before her head was cut off, than if she had been taken quietly from the roost.

We perceive, therefore, that on any emergency the vital principle can be accumulated, and that it will remain in the system for some time after the controlling power, the will, has been separated from it. The body of the hen flounders and writhes about without any effort of will or design, just as a paper kite is dashed about by the winds when the string has been cut from the hand which controlled its motions.

If matter, undergoing fermentation, be placed under ground within the reach of the spongelets of an exhausted tree, its vigour will be restored. It is the gaseous particles which infuse new life, and why may we not expect a similar result from an introduction of gases into the veins when the system is in a state of collapse or exhaustion? Why not hope that it may renew life in a body that is debilitated by typhus, or sinking with a protracted disease. It is reasonable to suppose that when a fever is subdued, or has worn itself out, the introduction of certain vivifying gases, through a fluid medium, would at once give a new tone to the system, and prevent it from sinking.

Thoughts like the above present themselves to the mind while

studying the beautiful science of vegetable physiology. It is in vain for the closet philosopher to insist that no conclusion can be drawn from analogies such as these, or that no analogies exist. Our knowledge will eventually amount to this-that gases have been selected, by the wisdom of the Almighty, as the propelling power which is to circulate all elementary matter. When bodies are to be formed, or when injuries are to be repaired, the process is effected through the medium of a fluid. All equable and slow depositions of matter have been transferred to their resting place by the instrumentality of gases aided by a fluid menstruum. But when a rupture or a dismemberment, or any convulsion of nature, is to take place, gases are the sole agents; they then want no fluid medium-they are sufficient of themselves to produce all the pains incident to the human body, and all the violent phenomena which occur on earth. They are as necessary to the existence of a plant as to an animal; and it is only when there is an excess, or too small a portion of them, that organized systems perish.

Nerves seem only necessary to a system where sensation is to be conveyed, and sensation, or a consciousness of it, appears only to belong to animal life. Pliancy and contractibility are all that the organs of a plant possess, and all that vegetation requires, if we except the power of absorption; and yet that power, on reflection, is a mere contractile force. But, in which ever way we view the subject, we still find that gases are the propelling power.

The vitality of plants and of the inferior order of animals, particularly those which have the power of reproducing a limb, or an outer case or skin, continues long after sensation has ceased-for we must insist on calling that violent action which the headless body of a chicken exhibits, the effect of the vital principle. It is of precisely the same nature as it was when it pervaded the whole system, during the time when the animal was completely imbued with it, and when the will could control the movements of each organ.

It may be urged that galvanism can produce similar movements; but, in the case of the headless chicken, the agency of that fluid is not perceptible, although we grant that the time is fast approaching when the propelling power of the galvanic and electric fluids will be identified with that which animates or renders active the principle of life itself. Of this we are certain, that electricity has a powerful effect on vegetationnot only blasting and shattering the largest trees, but rupturing the sap vessels-thus producing congestion and death. But still, even in this, the propelling power, that which transports the electric fluid, is gas.

Although it is needless to enquire into the nature of that

principle called life, yet we should certainly endeavour to comprehend what it is that sustains it and gives it facilities when it is present in organized life. Both in plants and animals, life is sustained by a due attention to the changes of the atmosphere, and to the judicious application of nutriment. We should recollect, however, that although large masses of food are taken into the stomachs of animals, and are applied likewise to the roots of plants, yet, while in its crude state, the solid parts are not forced into the absorbent vessels as the proper food for organized bodies. The stomach to animals is what the stercoraceous or compost heap is to plants-a place where food is elaborated. We apply this fermented mass to the roots or spongelets of a plant; but, separated as the particles are, only such portions of it as can be combined with or elevated by gases can ever find their way through the minute pores of the spongelets.

Yet whatever be the quality of the gaseous compound, when presented to the pores for absorption, it is to water that they are indebted for the equal and healthy admixture of the nutritive particles. In like manner, the whole system of an animal is indebted to a fluid menstruum for the equable diffusion of the proper juices which are to sustain life. In this respect the analogy is perfect.

We learn, therefore, that by the agency of gases in a fluid medium, nutriment is conveyed from without to the pores of the spongelets of a plant, and from within to the ducts of an animal. This is for the purpose of enlarging the size, repairing the waste and continuing the life of both, for it is by these disunited nutritive particles, that the interstices of the germ of every organized body are enlarged. Here nature operates alike and to the same end; the only difference of the economy is, that in an animal, the labour of preparing the food for the above purpose is performed in the centre of the system, whereas, in a plant, the food is prepared for it from without, at a distance, there being no such viscus in vegetable life as a stomach, strictly so called. Yet an elaboration of the ascending particles is effected by some means within the plant, for that which is admitted in the first instance becomes very different in its nature and character after it is deposited around the annular swellings that lie at the base of each limb or twig. Let us understand how this elaboration is effected.

In a healthy plant each articulated section appropriates to itself a sufficient quantity of this nutritive matter, for the purpose of enlarging and sustaining its own individual parts, having no other connection with the rest of the plant than by a slight ligament which unites it at the base. It may be said that it is united also by the bark; but this is error, for the bark vessels are likewise connected by this slight ligament, the loss

of which ligament is of no disadvantage or injury to either the twig, the tree, or the tubular action, for the action is confined to short limits.

On a close inspection, it will be seen that at those places of deposit, the annular swellings, there is a concentration of this vegetable chyle, or elaborated sap, and it is there held in reserve during the winter, so that these parts are not dependent on the parent stem for their support. The ascending sap in the spring excites the vessels to make use of this conserve, and to distribute it to the leaf and flower buds which exist on its own section. This rise of sap takes place as soon as the air is sufficiently heated by the sun's rays in the spring to excite the extremities of each individual terminal shoot to action.

With respect to the long agitated question of the circulation of sap, taking into consideration the physical organisation of both plants and animals-the one rigid and immovable, the other flexible and capable of voluntary motion--we think the rise of sap in one continued stream is equivalent to the circulation in animals. Nor need we wonder at this, and object to the term circulation, because it is not like that in animals, for, even with them, the process varies as much, and is as diversified, as the different orders themselves. In our apprehension, there is not only a circulation in plants, but one of a more peculiar and simple character than would be inferred from an inspection of their organs. It does not alter the fact of positive circulation, because it is different in plants.

The leaves of plants, delicate and transient as they are, perform the office of lungs, or, rather, are the outlets and inlets of gaseous matter, and yet no one doubts that they are the respiratory organs, although so different from those of animals. They not only supply the system with new matter, but they submit, likewise, a portion of that which ascends to their surface to the action of atmospheric gases, and other portions of it they reject.

The upper surfaces of leaves, as well as the bark of the tree, imbibe through their pores a great deal of the humidity of the atmosphere, and allow of the evaporation of ascending sap. Knowing this, and that the edges of all leaves throw off the fluid and gaseous secretions which have been rejected by the circulation, we may with safety infer that some portions of the cuticle, even of the spongelets, minute as they are, have likewise the power of discarding the residuum of elaborated sap. The spongelets-the name given to these absorbents by Dr. Dutrochet, and a very appropriate one-have the same office assigned them as the leaves. In fact, they should be considered as subterraneous leaves or lungs, and notwithstanding that pores have never yet been detected in the bark of a tree, yet if fluids can VOL. XXI. No. 41.

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