of the world. Why should the solar year be so long, and no longer? Or, this being of such a length, why should the vegetable cycle be exactly of the same length? Can this be chance? And this occurs, be it observed, not in one, or in a few species of plants, but in thousands. Take a small portion only of known species, as the most obviously endowed with this adjustment, and say ten thousand. How should all these organized bodies be constructed for the same period of the year? How should all these machines be wound up so as to go for the same time? Even allowing that they could bear a year of a month longer or shorter, how do they all come within such limits? No chance could produce such a result; and, if not by chance, how otherwise could such a coincidence occur, than by an intentional adjustment of these two things to one another?-by a selection of such an organization in plants, as would fit them to the earth on which they were to grow; by an adaptation of construction to conditions; of the scale of the construction to the scale of conditions.'*

The concluding paragraph of the chapter from which we have just quoted, which carries the view of adjustment between organized existences and the annual cycle still farther, is also well worthy of being quoted: "The same kind of argument might be applied to the animal creation. The pairing, nesting, hatching, fledging, and flight of birds, for instance, occupy each its peculiar time of the year; and, together with a proper period of rest, fill up the twelve months. The transformations of most insects have a similar reference to the seasons, their progress and duration. "In every species except man," says a writerf on animals, "there is a particular period of the year in which the reproductive system exercises its energies. And the season of love, and the period of gestation are so arranged that the young ones are produced at the time wherein the conditions of temperature are most suited to the commencement of life." It is not our business

* Whewell's Bridgewater Treatise, pp. 28, 29.

+ Fleming's Zool. i. 400.

here to settle the details of such provisions, beautiful and striking as they are. But the prevalence of the great law of periodicity in the vital functions of organized beings, will be allowed to have a claim to be considered in its reference to astronomy, when it is seen that their periodical constitution derives its use from the periodical motions of the planets round the sun; and that the duration of such cycles in the existence of plants and animals, has a reference to the arbitrary elements of the solar system,-a reference which we maintain is inexplicable and unintelligible, except by admitting into our conceptions an Intelligent Author alike of the organic and inorganic universe.'

SIXTH WEEK-THURSDAY.

III. HYBERNATION OF PLANTS.-PHYSIOLOGICAL

PLANTS DURING WINTER.

CONDITION OF

THE beautiful variety of shades in our woods and groves, towards the close of autumn, which the most inattentive observer must have admired, arises from the preparation which nature is making for the winter state of our shrubs and trees. The functions of the productive seasons are ended; the forest trees have completed their annual growth; the fruit-bearing trees have yielded their stores; and the leaves, which performed such an important part in these processes, being no longer useful, are to be dropped, that they may, by mingling with their parent earth, supply the waste of the vegetable soil and repair its exhaustion from the efforts of the preceding year. The sap which had arisen profusely in the beginning of autumn, to aid nature in giving maturity to the fruits, and vigour to the young branches, and thus to crown the labours of the year, having performed this important office, has begun to flow downwards through the inner integuments of the bark, thus completing its periodical circulation. The leaf and flower-bud, destined to be developed in the ensuing spring,

have been already formed, and are carefully shut up in their winter cerements. The tree exposed naked to the wintry blast, is rendered, by a wonderful provision of the All-wise Creator, proof against the injurious effects of frost. It is in its state of hybernation, like many beasts and insects; for here, too, the analogy of nature is striking, it has fallen into its winter sleep.

The proofs of this state of torpidity are numerous and interesting. Among these, the most familiar is that of the capability of removal without material injury, to another place. There is no size or age of a tree which would prevent it from enduring transportation, at this season, with perfect safety, provided only it could be effected without greatly injuring the root; and it is only in winter that such an experiment can be performed with any chance of success. Why? Because the powers of nature are then suspended. The plant has ceased to draw nourishment from the earth, and its vital principle, though by no means extinguished, is in a state of temporary lethargy.

Now, the importance of this state of plants, in winter, will be obvious, if we consider the condition of the soil and climate of temperate regions, during that period. The genial warmth which caused the juices to flow is gone; the ground is frequently rendered, by frost, rigid and almost impenetrable; tempestuous weather would threaten the destruction even of firmly-rooted trees, did not the removal of the leaves admit a free passage to the wind through the branches; the cold would blast the delicate fibre of the growing shoot. All these dangers are either entirely provided against, or at least rendered by no means formidable, by the torpidity which invades the vegetable creation. The plant still lives, but its food is gone; its active operations would expose it to be the sport of the angry elements, and therefore it has retired within itself, like the coiled hedgehog, to sleep out the ungenial season, and to prepare, with new vigour, for the exercise of its renovated powers in the coming spring.

Much less is known of the physiology of plants, than the

interesting nature of the subject would lead us to desire; but there is one circumstance connected with their state in winter, which is too curious to be overlooked. The vital princi pie, whatever it may be, exerts a peculiar energy in defending them from the influence of frost. A very simple experiment, within the power of every person, will show this. Let a bud be cut off from the parent tree, and suspended, during a strong frost, either by a string, or even within a glass vessel, upon one of the branches, and it will be found that this severed bud will be completely frozen through, while all the buds still attached to the tree, are entirely unaffected by the coid. There is, then, a living power in plants, which, of itself, resists, to a considerable extent, the effects of cold. But the Author of Nature does not rest the security of vegetable productions on this principle-on the contrary, the safety of the bud, on which the future existence of the plant so materially depends, is provided for by its careful envelopment in plies of scales, or within a downy substance, besides being often united together by a coat of resinous matter, of which latter state the horse-chestnut furnishes a familiar example. The intention of this kind of protection is distinctly indicated by the fact, that it occurs only in northern countries, the buds of trees in milder regions being destitute of the scaly covering. The security from injury, which the resinous coat af fords, may be proved by a simple experiment. Let a bud of this kind be taken from the tree, and, sealing up the cut end, let it be plunged into water; and in this state it may be kept uninjured for several years. In tropical regions, the leaf or flower not requiring any such means of safety, starts into existence at once, without the intervention of buds,—another proof of the designing hand of Nature in this provision.

We have mentioned the power possessed by plants, in a living state, of resisting the effects of cold; and this fact has led some physiologists to conceive, that an internal heat is generated in plants, as it is in the animal frame. The experiments, however, which have been made to test this opinion, have been of sem mot doubtful result, though some cu

rious facts have been adduced in confirmation of it. It is well known, for example, that snow dissolves more quickly in a meadow than on bare ground; and this has, with apparent force, been attributed to the existence of a slight degree of heat in the vegetation. In certain states of some plants, it has been ascertained, that heat is evolved. M. Hubert relates a striking example of this kind, in the spadices of a Madagascar plant, the arum cordifolium. On applying a thermometer to five spadices, which had unfolded in the preceding night, he observed a rise of 25° from the temperature of the atmosphere. The temperature became gradually lower, till, in the evening of the second day, the difference between the heat of the spadices and of the surrounding atmosphere, was only 7°. The observation which we have recorded above, of the power of living buds to resist frost, Wildenow extends to the sap of trees, which, he says, will remain unfrozen in very intense cold. The case, however, is different, as he informs us, in plants of warm and hot regions. The sap of these plants congeals on a very slight cold, and the plants themselves decay; which shows a very remarkable difference between tropical plants and those of colder climates, and strikingly indicates intention. Another observation is, that, although the sap will not congeal in winter, yet, after the buds have been forced out by warm weather in spring, it will readily congeal on exposure to cold,—an effect which Dr. Smith ascribes to 'the increased susceptibility of the vital principle,' at that season. Dead or diseased branches, too, are said to be more liable to be frost-bitten than living and sound ones. These facts, though not conclusive, seem to give probability to the opinion, that the degree of heat necessary to the support of vege table life, in winter, is maintained by natural processes going on in the plant itself. But, whatever truth there may be in such an opinion, the facts themselves are sufficient to show the impress of an intelligent Cause, in this, as in every other department of organized matter. We may not be able satisfactorily to trace all the various steps of the process, but we are able confidently to say, Here, too, is the hand of God.