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The deficiency is much to be regretted, seeing that it is often of serious importance to the interests of society that means should be possessed for determining the exact period of a given life. The most important of all, the data whereby the age of one of our own species may be determined, are as yet altogether undiscovered. Though long habits of social intercourse may enable us to guess pretty nearly,—by the altered form of the features, wrinkles where once was smoothness, changes in the colour and luxuriance of the hair, also in the gait and general physical exterior,--still it is only a guess; we cannot be sure until we have consulted the register or the family Bible. With the lower animals it is a little easier ; the age of the horse, for instance, to about eight or nine years old, may be told by its teeth ; the horns of certain quadrupeds similarly announce their ages up to a given epoch ; in birds the age may sometimes be deduced from the wear and altered form of the bill ; in the whale it is known by the size and number of the laminæ of whale-bone,' which increase yearly, and seem to indicate a maximum of three or four hundred years to this creature; the age of fishes appears to be marked on their scales, as seen under a microscope; and that of molluscous animals, such as the oyster, in the strata of their shells ;-still, there is no certain and connected knowledge in reference to any but the first-named, and even this applies only to the youth of the animal. Of all the forms of nature, TREES alone disclose their ages candidly and freely. In the stems of all trees which have branches, the increase takes place by means of an annual deposit of wood, spread in an even layer upon the surface of the preceding one. The deposits commence the first summer of the trees existence, and continue as long as it survives ; hence, upon taking a horizontal section of the stem, a set of beautiful concentric circles becomes visible, each circle indicating an annual deposit, and thus marking a year in the biography of the general mass. So much for the felled tree; in the living and standing of course the circles are concealed from view; here, accordingly, some ingenuity is required; and the simplest and most certain method is to burrow into the trunk with an instrument like an immense cheese-taster, which intersects every layer, and draws out a morsel of each, sufficiently distinct for enumeration. Where this is not convenient, the age may be estimated by ascertaining, as nearly as possible, the annual rate of increase, then taking the diameter of the trunk at about a yard from the ground, and calculating by rule of three.' Thus, if in the space of an inch there be an average of five annual layers, a hundred inches will announce five hundred years of life. This method requires to be used, however, with extreme caution, because of the varying rate of growth, both in individual trees, and in their different species. In the earlier periods of life, trees increase much faster than when adult;--the oak, for instance, grows most rapidly between its 20th and 30th years ;—and when old, the annual deposits considerably diminish, so that the strata are thinner, and the rings proportionately closer. Unless allowance be made for this, and also for the irregular thickness of the layers, which vary both with seasons and with the position of the tree in regard to the sun, errors are inevitable. Some trees slacken in rate of growth at a very early period of life; the layers of the oak become thinner after forty, those of the elm after fifty, those of the yew after sixty. The concentric circles are not equally distinct in the different kinds of trees; the best examples occur perhaps, in the cone-bearers, as the fir, cedar, and pine. The opinion not infrequently held, that the trees of cold and temperate countries shew themselves better than those of the tropics, is, however, an ill-founded one; certainly there are equinoctial woods in which they are less decidedly marked than in particular European species, but in others again they are plainer. Indistinctness and emphasis in the rings are phenomena independent of climate, being characteristic, in fact, of particular species, genera,' and even families. There are trees which are altogether destitute of rings. These belong to the class called Endogens, of which the noblest and typical form is the Palm. Here the sign of age is furnished by the scars of the fallen leaves, which are of enormous size, few in number, and produced only upon the summit of the lofty, slender, branchless trunk. A certain number of new leaves expand every year, and about an equal number of the oldest decay, so that by taking the total of the scars, and dividing it by the average annual development of new leaves, a tolerably exact conclusion may be
Wood-sections, neatly cut and polished, so as to display the concentric circles, are highly ornamental objects, independently of their scientific instructiveness. A collection of specimens from the lopped boughs of the hedgerows and plantations, and from the timber-yard of the furniture-maker, where many rich exotics may be procured, rivals in beauty a cabinet of shells or fossils, and quite as abundantly rewards intelligent employment of the leisure hour.
The miscellaneous phenomena of vegetable life furnish an inexhaustible fund of curious interest. Thus, there are relations between the duration of life and the quality of the fruit wbich plants produce. Those which give tender and juicy fruit, or at all events such trees as do this, are in general shorter-lived than those which yield hard and dry, and these are shorter-lived than such as produce only little seeds. [Enl. Series.-No. 20, vol. ii.]
Thus, the apple and the pear live shorter lives than nut-trees, which are out-lived in turn by the birch and the elm. Such trees as the last named are useful to man for their timber, a service rarely rendered by the fruit-bearers. Trees again, that yield pleasant fruit, fit for human food, ordinarily live for shorter periods than those of which the produce is bitter and austere, and unserviceable to him as an edible. Most, if not all of the plants on which man in his civilized state depends for food, are exceedingly short-lived. The Cerealia or corn-producing plants, as wheat, rice, barley and oats, are annuals without exception; so are nearly all kinds of pulse. The large class of esculent vegetables represented by the turnip, carrot, and cabbage, are also either annual or biennial. How much man has benefited by this wise arrangement it is impossible to estimate. Did his daily bread grow on longeval trees, like acorns, asking no care and toil, the most efficient means to his development would have been wanting, as is still evidenced in the lands of the coco-nut, and banana ; but depending, as he has been so largely obliged to do, on annual plants, demanding incessant care, they may be gratefully regarded as the prime instrument of his rise in intelligence and morals.
The form or configuration of plants has most important relations with their lease of life. Those trees, for instance, usually live to the greatest age which attain the least vertical height in proportion to the diameter of their trunks, and the lateral spread of their branches. Size and substance have also to be taken note of. Small and attenuate plants almost always live for shorter periods than bulky ones, and tender and delicate species than the stout and hard-grained. The latter owe their longer lives, in a physiological point of view, to the abundance of firm, fibrous matter which enters into their composition, and without which it appears indeed impossible that any considerable age can be attained, though there are instances where hard and durable wood is found in trees of briefer life than some that are soft-wooded. The limetree has softer wood than the walnut, beech, and pear, yet lives longer than either of them; and the Baobab of Senegal, which undoubtedly lives to a great age, though some of the accounts of it are probably exaggerated, is said to be so soft that it may be sliced with a knife. That bulk should be accompanied by long duration it is easy to understand. The larger a plant or tree, the greater is the surface which it exposes to the atmosphere, and as it feeds by every leaf, the scope and opportunity for the exercise of the vital functions is proportionately extended. The more leaves a tree can put forth, and maintain in healthy action, the firmer is its hold upon the future. Viewed in regard to their annual rejuvenescence, trees may be regarded as little worlds in themselves, --solid masses from which a multitude of separate and perfect plants is vernally put forth, every new shoot and twig being exactly analogous to an annual that has risen from a seed. As the successive generations of plants fill the earth more and more with the seeds of life, and thus both maintain its actual splendour, and enlarge its potential, in reference to years to come; so the annual crops of twigs and leaves that clothe the tree, by their re-action tend to consolidate and strengthen it. The more exuberant its fertility, the more does it augment in energy of life,—picturing therein, one of the finest truths in our spiritual history; the soul energizes as it works. But extent of leafy surface will not of itself induce longevity. There are many annuals that develope an immense amount of leaf, as the gourd and the melon. In such plants it is counteracted by their exceedingly rapid growth, and consequent want of solidity. For while too great a degree of solidification of the tissues, whether in plants or animals, hinders their proper vital activity, especially those great processes on which life so eminently depends, namely, the free movements of the juices ;—the other extreme, or a too lax and succulent texture, is no less surely fatal to stability and endurance. Such texture is almost always found in the short-lived plants, coming, as in the gourd, of their rapid extension, while firm, dense, and compact texture is fully as characteristic of the longævals. Compare, for example, the wood of the
yew and the box-tree with that of the soft, sappy black poplar, and the willows that 'spring by the water-courses. Fungi, mushrooms, and toadstools, which are the most rapid in their development of any plants, often reaching their full size in the course of a night, are also the loosest in texture, and the soonest and speediest to dissolve.
The distinction of annual, biennial, and perennial, in regard to the duration of plants, is liable to be affected by certain accidents, but the changes are never so great or so deeply-seated as for the principle of a fixed lease of life to be abnegated by them. An inhospitable climate will shorten the life of perennials to a single season, as happens with mignionette, which in Barbary is shrub-like, and with the PalmaChristi, which in India is a stately tree, though in England neither survives a year in the open air ; on the other hand, unsuitable food, excess of wet, or any other circumstance by which the flowering of the plant is retarded, will induce unaccustomed longevity. This brings us to the consideration of one of the greatest truths in the philosophy of nature, namely, that all living things exist, and feed, and grow, and gather strength, in order that they may propagate their race. Doubtless, things universally have their social uses to subserve, and to perform which they were originally created, and are sustained in their respective places by the Almighty; but all these uses have reference, essentially, to the great ultimate use of preserving the race extant upon the earth, and multiplying it indefinitely, seeing that in the maintenance and multiplication without end of receptacles of His Life, consists the highest glory of God. This is the end and design not only of the physical, but even of the moral and intellectual uses performed by mankind towards one another, all of them tending, more or less directly, to promote and improve it. However unconscious we may be of their influence and private agency, and however little we may feel ourselves to be personally identified with the result, the perpetuation of the race is at once the beginning and the end of all the feelings incident to our nature. Whatever we may seem to ourselves to be working for, the secret aspiration of the heart is always Home and one's own fireside, bright and sweet with filial and conjugal affection ; every virtue, desire and passion that stirs the soul may finally be referred hither; in a word, whatever is friendly to humanity, in any of its needs, whatever gives life and solidity to existence, is a collateral means to reproduction, and was purposely instituted to aid it, and without such aid reproduction would languish and at last fail. Why reproduction is the great end of physical existence, is found in its needfulness as the counterpoise of Death. As the destiny of all things is to die, were there no means established for their replacement, the earth would soon become a desolate void; but through the magnificent law of procreation, nothing is ever extinguished, nor a gap ever caused that is not instantly filled 'up. Though Time slays and devours every individual in turn, whether animal or plant; by procreation the species is preserved perfect and immortal, the whole of nature unchanged and ever young ;—
States fall, arts fade, but Nature doth not die !
By the continual succession of beings, all exactly resembling each other, and their parents and ancestors, the existence of any one of them is virtually maintained in perpetuity; the balance and the relations of the different parts of nature are kept intact, and to philosophic view, Time itself, rather than the temporal, is the slain one. Thus looked at, or with the eyes of a large philosophic generalization, all the individuals of any given species that have ever existed, and all that have yet to come into existence, form but one great Whole ; the process of reproduction whereby they follow one another in the stream that unites the living representatives to the primæval Adam of the race, being only