Popular Science Monthly/Volume 3/July 1873/The Longevity of Trees
|THE LONGEVITY OF TREES.|
IN the vegetable world, limits of growth and life are strangely diversified. Multitudes of forms mature and perish in a few days or hours; while others, whose beginning was in a remote antiquity, have survived the habitual period of their kind, and still enjoy the luxuriance of their prime. Some species of unicellular plants are so minute that millions occur in the bulk of a cubic inch, and a flowering plant is described by Humboldt, which, when fully developed, is not more than three-tenths of an inch in height. On the other hand, we have the great Sequoia, whose mass is expressed by hundreds of tons, and specimens of the Eucalyptus, growing in the gulches of Australia, surpass in height the dome of St. Peter's.
Some of the Fungi mature between the setting and rising of the sun, while the oak at our door, which awakens the memories of our childhood, has not perceptibly changed in bulk in half a century. Trees grow more slowly as they increase in age. Nevertheless, it is certain that growth continues while they continue to live. The development of foliage implies interstitial activity and organization of new material. In its vital processes there is little expenditure of force or waste of substance. Its functions are essentially constructive, and its growth and age are apparently without limits, excepting such as arise from surrounding conditions. Thus many trees represent centuries, and have a permanence that is astonishing and sublime. Travellers stand awe-struck before the monuments which for forty centuries have kept watch by the Nile, but the oldest of these may not antedate the famous dragon-tree of Teneriffe. It is not surprising that the ancients considered trees "immortal," or, as "old as Time."
But, if the life of the tree is continuous, its leaves—the organs of its growth—have their periods of decay, and are types of mortality. The life of man is likened to the "leaf that perishes." In an animal, the vital processes are carried on by a single set of organs, the impairment of which limits the period of its life. With the tree, decay of the organs is followed by constant renovation, and the foliage which covers it the present summer is as new and as young as that which adorned it a hundred or a thousand years ago. Trees which shed their leaves annually, or at longer intervals as do the evergreens,
grow by formation of new wood in layers upon their outer surface, and just beneath the bark. These constitute the class Exogens, or outside growers, as shown in Fig. 1. This plate, with others used to illustrate this article, are from Figuier's "Vegetable World," and have been placed at our disposal by the publishers of that interesting work.
A layer represents the growth of a year. Where these are accessible, there is no difficulty in ascertaining the age of a tree, or the rate of its growth; and the rate thus ascertained may be applied to other trees of its kind whose diameter is known, although its woody layers he inaccessible. In this way the age of many trees has been estimated. The relation between the age of a tree and its annual rings was first noticed and applied by Montaigne, in 1581.
In these a hard, inflexible shell forms around the inner portions, the tree increases little in diameter, and no woody layers are found. To this class belong the Palms, of which Fig. 3 is an illustration. The age of this class of trees is estimated by comparing specimens with others whose age is known, or from an ascertained rate of growth. The oldest palms may not exceed five centuries, and their average period is probably less than 200 years. The height of the tallest of the species is said to be 192 feet. Trees growing in dense forests are comparatively short-lived, and attain less bulk than those in open places, where side-branches develop in the unobstructed rays of the sun. In similar conditions the age and dimensions attained by trees of each species are tolerably constant. Thus the average period of oaks and pines may be 300 or 400 years; but the exceptions are so numerous and wonderful, that we shall present in this paper a few of the most interesting and best-authenticated instances.
Of the white-pines, once the glory of the New England forests, we are not aware that any have been found more than 430 years old. Nor have we any oaks of extraordinary age. The Charter-oak at Hartford may have been a small tree at the first settlement of New England. The Wadsworth oak, at Geneseo, New York, is said to be five centuries old, and 27 feet in circumference at the base. The massive, slow-growing live-oaks, of Florida, are worthy of notice, on account of the enormous length of their branches. Bartram says: "I have stepped 50 paces in a straight line from the trunk of one of these trees to the extremity of the limbs."
The oaks of Europe are among the grandest of trees. The Cowthorpe oak is 78 feet in circuit at the ground, and is at least 1,800 years old. Another, in Dorsetshire, is of equal age. In Westphalia is a hollow oak, which was used as a place of refuge in the troubled times of mediæval history.
The great oak at Saintes, in Southern France, is 90 feet in girth, and has been ascertained to be 2,000 years old. This monument, still or recently flourishing, commemorates a period which antedates the first campaign of Julius Caesar!
The oriental plane-tree is noted in Eastern countries for its size and longevity. Fig. 4 represents one near Constantinople, which is 100 feet high, and 150 feet in circuit. It has been suggested that this is really a group of trees originally planted near together for their shade. The figure, however, hardly confirms that opinion, and many trees of this species are mentioned by travellers not greatly inferior to this one in dimensions.
Most of the old plane-trees are hollow, their tops being sustained by wood of recent growth. In this respect an exogenous tree resembles a coral-reef, where the vitality and growth are at the surface only.Of chestnuts, we have the famous one at Tort worth, in
Gloucestershire, England, which was a large tree in the reign of King Stephen, and is over 1,000 years old. Fig. 5 represents the "Great Chestnut of Mount Etna," consisting, at present, of what appears to be several trees, fragments of the original one. By a writer in the North American Review, for July, 1844, these are supposed to be shoots from, rather than portions of, the old tree.
Jean Houel, who examined the trees, says "they are portions of one tree." By removing the soil, the outer rim of the tree has been found, and the circumference ascertained to be 175 feet. Other chestnuts near this are in girth 64, 70, and 72 feet respectively.
The lime or linden, in Europe, is an important tree. Those in the town of Morat are celebrated in the history of Switzerland. One was planted in 1476 to commemorate the defeat of the Burgundians, under Charles the Bold; the other was a noted tree at the time of the battle, and is now near nine centuries old. But, equally famous is the one at Wilrtemberg, called the "Great Linden," six centuries ago. It is, probably, 1,000 years old, and measures 35½ half feet in girth. Four and a half centuries ago its branches were supported by 67 columns of stone, now increased to 106, many of which are "covered with inscriptions."
The well-known olive-tree is associated with our most cherished recollections. There is an old one near Nice, 24 feet in girth, regarded by the inhabitants with great interest. Those on the Mount of Olives may be contemporary with the Christian era. They are known to have been in existence in 1217, when the Turks captured Jerusalem.
The evergreen cypress, long celebrated for its longevity, is abundant in the burial-grounds of Eastern nations, and, from it dark, dense foliage, forms an impressive feature of Oriental landscapes. In the Palace Gardens of Granada are cypresses said to be 800 years old; and there is one at Somma, in Lombardy, proved by authentic documents "to have been a considerable tree 40 years before the Christian era." Of this family of trees is our well-known white cedar, specimens of which, exhumed from the meadows on the coast of New Jersey, had from 700 to 1,000 rings of wood solid and fragrant as if of recent growth.The cedars of Lebanon are often referred to in the Sacred Writings. The present trees are, we believe, seven large ones, with many of smaller growth, situated in an elevated valley of the Lebanon Mountains, 6,172 feet above the Mediterranean. The valley is surrounded by peaks of the mountains, which rise 3,000 feet higher, and are covered with snow. Fig. 6 may give some idea of their massive grandeur. De Candolle supposes the oldest are 1,200 years old, but no sections of their wood have been examined to determine their age. The cedar is known to grow slowly, as does the North American or bald cypress, which we will next notice. This tree is common in our
Southern States, and its rate of growth lias been determined. On the Mexican table-lands its growth and antiquity are immense.
The "Cypress of Montezuma," near the city of Mexico, is 44 feet in girth, and its age is estimated at upward of twenty centuries. In the church-yard of Santa Maria del Tule, in the Mexican State of Oaxaca, is a cypress which "measures 112 feet in circuit, and is without sign of decay." At Palenque are cypresses growing among the ruins of the old city, whose streets they may have shaded in the days of its pride. By the usual methods, the writer in the North American Review calculates the age of the cypress at Santa Maria del Tule at 5,124 years, or, if it grew as rapidly during its whole life as similar trees grow when young, it would still be 4,024 years old.
The yew has long been used in Great Britain as an adornment of places of sepulture, and is often referred to in English literature:
Where heaves the turf in many a mouldering heap."
This tree, of almost imperishable wood, is indigenous to Great Britain. De Candolle ascertained its rate of growth, and concluded that individual specimens are of great antiquity. There is a yew at Ankerwyke House, older than Magna Charta. It was an old and celebrated tree when King John met the barons at Runnymede, in 1215, and its age is upward of eleven centuries; but the yews of Fountain's Abbey and the Darley yew' are from three to five centuries older than this. In Fortingal Church-yard, Perthshire, is a yew 18 feet in diameter, through decayed portions of which funeral processions pass on their way to the grave. The age of this tree is estimated at 1,800 years. But of greater antiquity is the one described by Evelyn, which stood in Braborne Church-yard, in Kent. It measured 59 feet in girth, and was believed to be 2,500 years old. This tree, which has long disappeared, was probably contemporary with the founding of Rome. The growth and decline of a great empire was spanned by the duration of a single life.More immense in bulk, but perhaps not older than these living monuments, are the pines of Oregon and the Sequoias of California. Mr. Douglas counted 1,100 annual layers in a Lambert pine, and 300 feet is not an unusual height for the Douglas spruce. Hutchings states that a Sequoia, which was blown down and measured by him, was 435 feet in length. It was 18 feet in diameter 300 feet from the around. Scientific observation has connected with these trees an interest equal to that awakened by their size and age. Our most distinguished botanist, Prof. Gray, has shown that the Sequoias, now growing on a limited area, had formerly a wide distribution, and are lineal descendants from ancestral types which flourished at least as far back in geologic time as the Cretaceous age. The descent has been with modifications furnishing an important link in the
chain of evidence which establishes the derivative origin of specific forms.
Prof. Gray thinks the age of the oldest living Sequoia may be about 2,000 years, and remarks: "It is probable that close to the heart of some of the living trees may be found the circle which records the year of our Saviour's nativity." Fig. 7 is a representation of the Sequoia.
The sacred banian, before noticed, is familiar to every reader. Its main trunk attains a diameter of from 20 to 30 feet, and its enormous roof of foliage may shelter the inhabitants of a considerable village. The pendent branches are really roots, which, on reaching the ground, penetrate it and form trunks. These correspond with the outer layers of wood in an oak or a pine, and sustain the top, although the original trunks decay and disappear.
The dragon-tree of Orotava, on the island of Teneriffe, is a well-known and historic tree. Our representation of it (Fig. 8) is from a drawing made in 1776. Twice during the present century it has been dismantled by storms. It is but 69 feet high, but is 79 feet in circumference. So slow is its growth that its diameter had scarcely changed in 400 years. Recently it bore flowers and luxuriant foliage, as it may have done before the "isles of the Western Ocean," on one of which it was growing, were a dream in the Grecian mythology.
The baobab, or monkey bread-fruit, is the last we can notice of the ancient trees. It was first described by a Venetian traveller in 1454. Fig. 9 is from a photograph of one on the west coast of Africa. These trees are found, however, in nearly all portions of that country south of the Desert, everywhere an imposing feature of the landscape, and objects of regard if not of reverence by the natives. In the rainy season they are in full luxuriance, and are covered with cup-shaped flowers six inches in diameter. The trunks grow from 20 to 60 feet high, but are sometimes 100 feet in circuit at the ground. The baobabs, like most other trees, grow rapidly when young, but slowly when old. Recent estimates attribute to some of the oldest a period of 3,000 years. This is scarcely more than one-half the age assigned to them by early writers.
In 1832 a baobab was transplanted into a garden at Caraccas, which grew as much in 40 years as would have required 100 years by early estimate. An account of this tree is published in Natur und Leben, No. 1, 1873.
By the native town of Shupanga, near the Zambesi, in Eastern Africa, is a venerable baobab, beneath which is the grave of Mrs. Livingstone.Such, briefly, are some of the great living monuments of the vegetable kingdom. In longevity they are in striking contrast with higher types of life. Fixed to a single spot, the tree is what it is because of the forces which act upon it. It is a monument of accumulated and
concentrated force. Transmuted sunlight is in all its fibres, and who shall estimate the dynamic work which has been expended in its structure?
Dr. Draper observes that "the beat of a pendulum occupies a second of time; divide that period into a million of equal parts, then divide each of these brief periods into a million of other equal parts, a wave of yellow light daring one of the last small intervals has vibrated 535 times. Yet that yellow light has been the chief instrument in building the tree." In the delicate texture of its leaves it has overcome molecular force; it has beaten asunder the elements of an invisible gas, and inaugurated a new arrangement of atoms. The old dragon-tree represents forty centuries of this dynamic work—a sublime monument reared without toil by the silent forces of Nature!
In the outer air it has awakened every note of sound, from the softest monotone to the rhythmic roar of the tempest; but in its inner chambers has been a murmur and music of life in the ceaseless movement of fluids and marshalling of atoms, as one by one they take their place in the molecular dance, which eludes the dull sense of hearing, and becomes obvious only in results. The veil which hides these ultimate processes of life has not yet been lifted, and Science pauses in waiting before it, but only waits.