Читать книгу Wayside and Woodland Trees: A pocket guide to the British sylva - Step Edward - Страница 4

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There are two points of view from which to regard trees—the mercantile and the æsthetic. The former is well exemplified in Dumbiedyke's advice to Jock: "Jock, when ye hae naething else to do, ye may be aye sticking in a tree; it will be growing, Jock, when ye're sleeping." The canny Scot was thinking of the "unearned increment" another generation might gather in, due to the almost unceasing activity of the vegetable cells in the manufacture of timber. The other view was expressed by "the Autocrat of the Breakfast-table" in a letter to a friend: "Whenever we plant a tree we are doing what we can to make our planet a more wholesome and happier dwelling-place for those who come after us, if not for ourselves." But, after all, it is the trees that have been planted by Nature that give the greatest pleasure apart from commercial considerations—the lonely Pine, that grows in rugged grandeur on the edge of the escarpment where its seed was planted in the crevice by the wind; the Oak that grows outside the forest, where a squirrel or a jay dropped the acorn, and where the young tree had room all its life to throw out its arms as it would; the little cluster of Birches that springs from the ferns and moss of the hillside. All trees so grown develop an individuality that is not apparent in their fellows of the timber forest; and however we may delight in the peace and quiet of the forest, with its softened light and cool fragrant air, we can there only regard the trees in a mass. We might, indeed, reverse the old saying, and declare that we cannot see the trees on account of the wood.

Nature and the timber-producer have different aims and pursue different methods in the making of forests, though the latter is not above taking a hint from the former occasionally. Nature mixes her seeds and sows them broadcast over the land she intends to turn into forest, that the more vigorous kinds may act as nurses, sheltering and protecting the less robust. Then comes the struggle for existence, with its final ending in the survival of the fittest. In the mean time the mixed forest has given shelter to an enormous population of smaller fry—plants, mammals, birds, and insects—and has been a delightful recreation ground for man. The timber-producer aims at so controlling the struggle for existence that the survival of the fit is maintained from start to finish. He plants his young trees in regular order, putting in nurses at intervals and along the borders, intending to cut them down when his purpose has been served. The timber trees are allowed no elbow-room, the putting forth of lateral branches is discouraged, but steady upward growth and the production of "canopy" is abetted. His aim is to get these timber-sticks as near alike as possible, free from individuality, and with the minimum of difference in girth at top and bottom of each pole. This means a thicker and longer balk of clean timber when the tree is felled and squared. The continuous canopy induces growth in the upward direction only, and discourages the weeds and undergrowth that add to the charm of the forest, but which unprofitably use up the wood-producing elements in the soil. This plan contrasts strongly with the views on planting formerly prevalent in this country, John Evelyn, for example, making a special point of giving the Oak room to stretch out its arms, "free from all incumbrances." But, then, unlike the timber-producers, Evelyn had an eye for landscape beauty, and giving an opportunity for the display of such beauty. He says: "And if thus his Majesty's forests and chases were stored, viz. with this spreading tree at handsome intervals, by which grazing might be improved for the feeding of deer and cattle under them (for such was the old Saltus), being only visited with the gleams of the sun, and adorned with the distant landscapes appearing through the glades and frequent valleys, nothing could be more ravishing."

The greater the success of the forester, the more profound is the solemn stillness of the forest—and the more monotonous. In place of the natural forest, with its varied and teeming life, we have what Wordsworth called a timber factory. In the natural forest, with its mixture of many kinds of trees, the undergrowth of shrubs, and carpet of grass and weeds, the stronger trees spread out their arms in all directions, and fritter away (as the scientific forester would say) their wood-producing powers in making much firewood and little valuable timber. But the result is very beautiful, and the nature-lover can wander among it without tiring, and can study without exhausting its treasures. Emerson says: "In the woods is perpetual youth. Within these plantations of God a decorum and sanctity reign, a perennial festival is dressed, and the guest sees not how he should tire of them in a thousand years." To the scientific forester this is all waste land, and he pleads for the "higher culture" being applied to it. With every desire that the natural resources of our country should be properly developed, we do hope that he will not be entirely successful in his efforts, and that a few of the woods and wastes of Nature's own planting may be left for the recreation of the simple folk who have not yet taken to appraising the value of everything by the price it will fetch in the market.

The trees described in this volume are the really wild growths that have lived a natural life; and though many of the photographs are from planted trees, they are such as have been allowed to grow as they would, and show the characteristic branching of the species.

A few words on the life of a tree may be welcomed here by those readers who have not made a study of botany. Although the nurseryman makes use of suckers and cuttings for the quicker multiplication of certain species, every tree in its natural habitat produces seeds and is reproduced by them. The flowering of our forest trees is a phenomenon that does not as a rule attract attention, but their fruiting or seed-bearing becomes patent to all who visit the woods in autumn. A tree has lived many years before it is capable of producing seed. The seed-bearing age is different in each species; thus the Oak begins to bear when it is between sixty and seventy years old, the Ash between forty and fifty, the Birch and Sweet Chestnut at twenty-five years. Some produce seed every year after that period is reached, others every second, third, or fifth year; others, again, bear fitfully except at intervals of from six to nine years, when they produce an enormous crop. Most tree-seeds germinate in the spring following their maturity, but they are not all distributed when ripe. The Birch, the Elm, and the Aspen, for examples, retain their seeds until spring, and these germinate soon after they have been dispersed.

The seeds contain sufficient nutriment to feed the seedling whilst it is developing it roots and first real leaves. We can, of course, go further back in starting our observations of the life progress of the monarch of the forest. We can dissect the insignificant greenish flower of the Oak when the future seed (acorn) is but a single cell, a tiny bag filled with protoplasm. From that early stage to the period when the tree is first ripe for conversion into timber we span a century and a half, equal to two good human lives, and the Oak is but at the point where a man attains his majority. The Oak is built up after the fashion by which man attains to his full stature. It is a process of multiplication of weak, minute cells, which become specialized for distinct offices in the economy of the vegetable community we call a tree. Some go to renew and enlarge the roots, others to the perfecting of that system of vessels through which the crude fluids from the roots are carried up to the topmost leaf, whence, after undergoing chemical transformation in the leaf laboratory, it is circulated to all parts of the organism to make possible the production of more cells. Each of these has a special task, and it becomes invested with cork or wood to enable it to become part of the bark or the timber; or it remains soft and develops the green colouring matter, which enables it, when exposed to sunlight, to manufacture starch from carbon and water.

This is very similar to what takes place in the human organism, where the nutriment taken in is used up in the production of new cells, which are differentiated into muscle-cells, bone-cells, epidermal-cells, and so forth, building up or renewing muscles or nerves, bones or arteries; but the mechanism of distribution is different, the heart-pump doing the work of capillary attraction and gravitation. The ancients believed in the Dryads, spirits that were imprisoned in trees, and whose life was coterminous with that of the tree; and it will be seen that they had stronger physical justification for their belief than they knew. Shakespeare relates how Sycorax, the witch-mother of Caliban, imprisoned Ariel in a tree; and Huxley finely tells us that "The plant is an animal confined in a wooden case; and Nature, like Sycorax, holds thousands of 'delicate Ariels' imprisoned in every oak. She is jealous of letting us know this; and among the higher and more conspicuous forms of plants reveals it only by such obscure manifestations as the shrinking of the Sensitive Plant, the sudden clasp of the Dionæa, or, still more slightly, by the phenomena of the cyclosis."

The tree, as we have indicated, gets its food from the air and the soil. The rootlets have the power of dissolving the mineral salts in the soil in which they ramify; some authorities believing that they are materially helped in this respect—so far as organic matter is concerned—by a fungus that invests them with a mantle of delicate threads. However that may be, the fluid that is taken up by the roots is not merely water, but water plus dissolved mineral matter and nitrogen. At the same time as the roots are thus absorbing liquid nutriment, the leaves, pierced with thousands of little stomata, or mouths, take in atmospheric air, which is compounded chiefly of the gases oxygen and carbon. The leaf-cells containing the green colouring matter (chlorophyll) seize hold of the carbon and release the oxygen. The carbon is then combined with the fluid from the roots by the vital chemistry of the leaves, and is circulated all over the system for the sustenance of all the organs and tissues.

The flowering of the trees varies so greatly that it can only be dealt with satisfactorily as each species is described. It may be stated, however, that all the true forest trees are wind-fertilized, and therefore have inconspicuous greenish blossoms. By true forest trees we mean those that alone or slightly mixed are capable of forming high forest. The smaller trees, such as Crab, Rowan, Cherry, Blackthorn, Hawthorn, Buckthorn, etc., belong more to the open woodland, to the common and the hedgerow. These, from their habitat, can be seen singly, and therefore can make use of the conspicuous flowers that are fertilized by insects.