Popular Science Monthly/Volume 12/April 1878/The Eucalyptus in the Future
|THE EUCALYPTUS IN THE FUTURE.|
By Professor SAMUEL LOCKWOOD.
A LITERARY venture of our boyhood comes upon us like the aroma of tropical fruit eaten for the first time. An uncle had given his eight-year-old favorite a silver sixpence. Never before had the youngling possessed so much money in his own right. Soon the young capitalist found himself confronting the shop-window of the nearest stationer, where his eyes became riveted to a little book "Life and Voyages of La Pérouse," price sixpence. The book was eagerly bought, and it proved an exciting morceau. This same Jean François de Galaup, Count de la Pérouse, when about thirty-seven years old, served in the American Revolution. In 1782 he led a small fleet into Hudson Bay, and destroyed the English trading-post. But Louis XVI. found that, while he had been helping to wrest the colonies from Great Britain, she was adding to herself new glory, and vast territories, by the discoveries of her great navigator, Captain Cook. So the French monarch dispatched La Pérouse, with two ships, on a mission of exploration in the Pacific. Neither the bold navigator nor any of his men saw home again. The last known of the expedition was from a letter written by La Pérouse at Botany Bay, February 7, 1788. Three years after, a French squadron was sent to search for the great voyageur, but in vain. With this expedition went as naturalist the famous botanist La Billardière. In Tasmania he found the most extraordinary arboreal flora he had ever seen. Especially wonderful for number and size was one tree, to which he gave the generic name Eucalyptus, meaning "well-covered," alluding to the singular form of the flower-bud, which has on it an operculum or cover not unlike the lid of a tiny sugar-bowl (see the object between the flower and the fruit at foot of Fig. 3). Thus the unexpanded flower-bud, being cup-like below and cone-like at top, was not dissimilar in form to the globular brass button formerly in vogue, and so the blue-gum received from this botanist the specific name globulus.
Fig. 1.—Eucalyptus Preissiana.
"One tree of the future one of hope," says Prof. Flückiger, "may be recognized in Eucalyptus globulus." And the prophecy is advancing to fulfillment, for already the eucalypt is becoming a cosmopolitan tree. It was discovered by La Billardière on the south of the island of Tasmania, near Entrecastenaux Channel, May 6, 1792, But, though soon after known to science, not until 1856 was it known to the arboriculturists of the Old World. In that year M. Ramel sent seeds from Melbourne to Paris. In 1857, and again in 1860, larger supplies arrived, which, being distributed, found their way over a great part of the civilized world. Of the many varieties of eucalypts, the blue-gum, or Eucalyptus globulus, was the first to be introduced into Europe; hence, perhaps, it may yet appear that the best variety for acclimatization has not received proper attention. The Eucalyptus globulus is only found in Tasmania and Victoria, but where found it is really the monopolist of the woods. The forest area of Victoria, the most southern colony of Australia, contains 73,000 square miles of forest, of which 71,500 is almost wholly of eucalypts. And so great is the diversity of these trees among themselves, that some one hundred and fifty varieties are recognized. This gave marked interest to the exhibits of the Australian colonies and Tasmania in the Philadelphia Exposition. But to the student of human progress a noteworthy fact was, that this Eucalyptus figured in the contributions of nations to whom the seed even was unknown twenty years ago. Eucalyptus woods, leaves, oils, essences, gums, etc., formed items in the exhibits from the south and the north of Africa, the Cape Colony and Algeria; the Orange Free State, Southern Europe, notably France and Italy, Brazil, the pampas of South America, Mexico, California, Jamaica, and even India, could have competed. Hence it would be no fiction' to pronounce to-day that the Eucalyptus is the cosmopolitan tree.
But our subject is interesting to three kinds of observers—the economist, or utilitarian, the botanist, and the geologist. Let us ask of each one a free-hand sketch.
The first, who is a matter-of-fact personage, adduces the economic uses of these gum-trees, as the Eucalypts are frequently called. When freshly cut the wood of these trees is soft, but so full is it of a resinous gum that it soon hardens, and becomes wellnigh imperishable. For ships, and docks, and jetties, it is invaluable. The terrible Teredo navalis, or ship-worm, lets it alone. It is proof also against that fearful scourge the termites, or white ant. Hence, in India, eucalyptus wood is used for the sleepers of the railroads, where it defies the insects and the climate. So great is the variety of the eucalypts, that they are provident for nearly every purpose which wood can subserve. The ship-builder, wheelwright, carpenter, coach-maker, and cabinetmakers, are all supplied. Usually the eucalypts are evergreens, and hold tenaciously to their leaves. But they readily shed their bark, as a rule, and in such immense pieces can this be detached that the natives make a rude tent of a single piece. Of many species the bark is serviceable for paper-making. For size no trees can equal these Australian gums in the magnitude of the timber afforded. A plank sent from Victoria, and intended for the London Exhibition, but which arrived too late, sold for ₤100. It was a clear plank, over 223 feet long, two feet six inches wide, and three inches thick. But, though excellent timber, some of the species are of little worth for fuel. In these the wood burns with such difficulty that it is regarded as specially suited for shingles.
These gum-trees are the Titans of the race. In the deep ravines of Dandenong, in Victoria, a Eucalyptus amygdalina measured 420 feet; while another, on the Black Spur, measured 480 feet, thus overtopping greatly the Pyramid of Cheops and every human achievement, and even beating by 155 feet the famous Sequoia gigantea (Torrey) ("Keystone State"), the biggest of the "big trees" of the Calaveras grove. Mr. G. W. Robinson found a eucalypt, which, at the height of four feet from the ground, had a girth of 81 feet, or 27 feet diameter. It is notable, too, that for amount of timber per acre these gum-trees are unmatchable. We read that, in one of the densest parts of the Mount Macedon state forest, an acre of Eucalyptus fissilis contained forty-two large standing trees and twelve saplings. Many of the largest of these trees were from six to seven feet in diameter four feet from the ground, and were from 200 to 220 feet high. Nor do such altitudes necessarily indicate a very high antiquity. The rapidity of growth is wonderful. Saplings fifty feet high, and but ten years old, are not remarkable. It is declared that seed sown in Jamaica at an elevation of 5,000 feet, in 1870, had in 1876 attained a growth of fifty feet. We have with our own eyes witnessed throughout an entire summer a growth of an inch a day. No one understood so well as Baron von Müller the nature and capacities of the Eucalyptus. He more than all others has made the world acquainted with it. With him was a scientific faith that this was the world's tree of promise. In this tree of Australia he saw the means with which to obliterate from the hydrographic map the rainless zones, to clothe with wood the desolate ranges of Tunis, Algeria, and Morocco, and render habitable parts of the Great Sahara, by indefinitely expanding the oases, to restore fertility to the Holy Land, to give rain to the Asiatic plateau, or the desert of Atacama, and furnish timber and fuel to Natal and La Plata.
None better than the baron, however, knew that, while able to stand great heat, these rapidly-growing eucalypti cannot resist great cold, and without these home conditions we must not expect of them their home achievements. Even at home the tribe does its best with its semi-tropical members. And there is a great range of variety until we meet even the Alpine species, of slow growth and very modest altitude. Skill and patience may do much; but in our country, except in a few favored spots, little can be hoped of the semi-tropical varieties north of latitude 30°, until acclimatization shall have been effected.
But it is claimed for the eucalypts that their presence is hygienic, or sanatory, especially in malarial regions. That the E. globulus has earned by fair experiment its name of fever-tree, as a preventive, seems now to be settled. Its rapid growth must make it a great drainer of wet soils, while its marked terebinthine odor may have its influence, and it is highly probable that the liberation of this essence into the air stands connected with its generation of ozone. But, whatever the sanatory activities of the eucalypt may be, the fact is squarely settled that spots in Italy, uninhabitable because of malarial fever, have been rendered tolerable by the planting of E. globulus, and it is believed that a more plentiful planting would nearly if not quite remove the difficulty. A military post is mentioned in Algeria, in which the garrison had to be changed every five days, such was the virulence of the malaria. A plantation of eucalypts cleared the miasma nearly away, and rendered unnecessary the frequent changes of the garrison. In this case 60,000 trees were planted.
But the eucalyptus has not a few medicinal virtues. Its oils and essences are antiseptic. Diffused in the sick-room, they purify the air and generate ozone. Already they have taken their places in the materia medica as very important internal medicines. The leaves contain the essence eucalyptol, and a resinous solid containing a bitter principle not yet understood, and which seems to afford the antifebrile virtue; hence an extract from the leaves, either aqueous or alcoholic, is used as a febrifuge. As a tonic, water may be aromatized by a slight infusion of the leaves. A liquor similar to that of mastic can be produced, and the pharmacy gives instructions for making a tonic eucalyptal wine. Some of the species are tapped for the sap, and gum-tree cider is obtained; the leaves of others yield manna. The famous East India kino of commerce, obtained from the Pterocarpus marsupium, a lofty legume growing on the mountains of India, now finds a rival in the Botany Bay kino, the concrete juice of the brown gum-tree (Eucalyptus resinifera), of which it is said that a single tree is capable of furnishing 500 pounds of kino in a year. In a word, in the modern pharmacopœia, eucalyptus, with its many preparations, occupies considerable space. A very interesting instance of what the therapeutist calls "masking" is an application of the oil of eucalypt for the deodorizing and aromatizing of cod-liver oil, thus rendering palatable and even additionally tonic this repulsive medicine.
At the Intercolonial Exhibition of 1866, in Australia, Baron von Müller caused to be exhibited, as from the Phyto-Chemical Laboratory of Victoria, tannic acid, gallic acid, pure wood-spirits, pure acetic acid, distilled wood-vinegar, and other products, obtained from several species of eucalyptus. Mr. Bosisto, a chemist of Victoria, sent to the Philadelphia Exhibition the following products of the one species (E. globulus): Essential oil—a tonic, stimulant, antiseptic, anthelmintic eucalyptol, for inhalation in bronchial or throat affections; eucalyptic acid; liquor of eucalyptus globulus—stimulant in ague or low fever; tincture of eucalyptus globulus—stimulant, tonic, antiperiodic; powder of eucalyptus globulus—antiseptic, cataplasma; cigarettes of eucalyptus globulus—disinfectant, employed in bronchial or asthmatic affections. But many mysteries are waiting solution in the laboratory of the pharmacist. New substances are to be discovered, and those already known will be better understood; all which revealings will be as new fruits on this tree of the future.
But let us hear the botanist's story. He says the thing has been a good deal of a bother to him; that he thought these gum-trees of Australia were pretty much like the animals there, specimens of Nature's jokes. Indeed, we find a recent authority saying, "Nine-tenths of the 8,000 species of plants in Australia are unknown elsewhere, and entirely unconnected with the forms of vegetation of any other division of the world." And then to think of the great variety of forms in this one genus, Eucalyptus. In one the leaves, six or seven inches long, are but a quarter of an inch wide, almost grass-like; while the leaves of the messmate, or E. amygdalina, are almond-shape, and nearly as wide as they are long. Those of E. Preissiana are bluntly rounded at the ends (Fig. 1), while the big-berry-gum-tree, E. macrocarpa (Fig. 2), has wide leaves with mucronate points. Compare these with the outline Fig. 3 of E. globulus, with its sickle-shaped leaves, ten inches long, in the specimen from which this was sketched. Alluding to the difficulty in defining the species, Woolls says, "Botanists, from Robert Brown to Baron Müller, have endeavored to reduce the varying forms to systematic arrangement," but without success. And a vast amount of acumen and ingenuity has been brought to the task; such as the consideration of the operculum or cap of the flower-bud, and the length of the pistil. Compare the long pistil in the seed-vessel of E. Preissiana, left side of Fig. 1, with the short one in the
Fig. 2.—Eucalyptus Macrocarpa.
flower of E. Globulus, in Fig. 3. The form of the anthers and the seed-vessels, and the texture of the bark, have all been taken as factors of the problem.
Owing to the bluish-green of its leaves, E. globulus is popularly known as the blue-gum tree. Abroad it is most known outside of its systematic name as the Tasmanian gum-tree, and Australian fever-tree. Among the settlers, gum-tree is the general name of the eucalypts. But, as might be expected of a genus so numerous in species, there are many trivial names, such as blue-gum, brown-gum, the red and the white mahogany, stringy-bark, and iron-bark, etc. The botanists reckon 150 varieties. These all belong to the great order Myrtaceæ, or myrtle-blooms. And a decidedly respectable relationship have these trees which shed "their medicinal gum," for they are close cousins to the well-known myrtle, the pomegranate, pimento, or allspice, cajeput, and clove. The flowers of this order are known in their structure as calycifloral. Perhaps this curious blending, or confusion, of the calyx and the corolla, is shown most interestingly in the flowers of these eucalypts. The calyx is really in two distinct parts, a woody cup below with an operculum or lid above. (See middle figure, bottom of cut 3.) When the flower is ready to open it pushes up, and thrusts off the calyx-cover, which falls to the earth, carrying with it the dubious corolla, which is intimately united to it on its inside. Thus, what is left is the lower part of the calyx, which is really a woody cup, with its pistillate organs in the centre. But, though a cup-like body, it has four rib-like markings on the outer side, which
Fig. 3.—Eucalyptus Globulus: Adult Leaves, Flower, Bud, and Fruit.
plainly indicate the sepaloid divisions. Look at the fruit, or seed-capsule, which is given about the natural size at the bottom and to the right of Fig. 3. Bristling from the inner rim or edge of the calyx, stand the thread-like stamens, each with its golden anthers atop, making a showy display for what would otherwise be, from its extreme simplicity, a very unhandsome flower.
The growth of the young eucalypt affords some points of strange interest. There is the rapidity of growth of the three species which have been best tried, and which certainly will figure largely as the world's future timber-trees: E. globulus, the blue-gum; E. gigantea, the stringy-bark; and E. amygdalina, the messmate, or peppermint-tree. The one best known in experiments at acclimatizing is the blue-gum. We have followed its growth from seeds planted by ourselves. Last October we saw in the back-yard of Dr. R. E. Kunzè, of this city, a eucalypt scarcely a year old, and over twelve feet in height. For four or five months it averaged an inch a day. Blue-gums but seven years from the seed have been known to reach a height of sixty-five feet, with a girth of stem near the ground of forty-five inches.
But, for all this rapidity of growth, the young eucalypt seems to be doggedly resolved that for some years at least it shall resemble its parent in no particular save one, namely, the aromatic odor of its leaves.
Suppose we compare Figs. 3 and 4, the one representing a young eucalypt, and the other an adult—that is, one old enough to bear flowers and seeds. Notice the stem of the young tree, Fig. 4, that it
Fig. 4.—Eucalyptus Globulus: a Young Tree.
is square, or four-sided, like those of the labiates, or Mint family of plants. On each side of this square stem is a depression, within which the leaf is attached, which, technically, may be said to be amplexicaul, or embracing, as it half surrounds the stem, and this at some disadvantage, since the attachment is not at the angle, but flush upon the side of the stem. The leaf is sessile, having no appreciable petiole or foot-stalk. And the leaves are opposite, so that each pair is set at right angles, or crosswise to the pair next below it or next above it. And the leaves are cordate, or heart-shaped, being deeply notched at the base, so that the lobes of one leaf lap over or lie upon the lobes of the other, thus appearing at first sight, by deception, like the perfoliate leaves on the upper part of a honeysuckle. Each leaf, too, has its upper and its lower plane, the upper one being exposed to the sunlight, and the under one being kept in the shade. The two sides of the leaf differ physiologically, as the stomata, or breathing organs, are on the under side of the leaf. The leaves, too, of the young eucalypt are bright, grassy green; they are also thin, and the tissue soft and somewhat succulent.
Now, not one of these particulars is carried into the maturity of the tree. Perhaps, in its enlarged arboreal wisdom, the big gum-tree eschews them all as the indiscretions of its youth. So the labiate character, or four-sidedness, gives place to a round stem. The leaves are now not amplexicaul, but stand well out from the branch-stems, and sometimes even hang suspended. They have now long petioles, or leaf-stems. In fact, as against the former sessile character of the leaf, the difference is almost forced to the point of exaggeration, since in E. globulus the long-lanceolate leaf seems really an extension and expansion of the petiole, or leaf-stalk. The leaves are no longer opposite, but alternate, nor are they heart-shaped, but long-lanceolate, and often even falcate, or scythe-shaped. Their color is now not grass green, but bluish-green, and the points are tipped with red. The tissue, too, is changed, for the leaves are thick, and leathery, and dry. Nor has the leaf now its sunny side and its shady side distinct—that is, the blade has no upper or lower plane, but an upper and a lower edge, the one edge being set toward the sky and the other toward the earth, thus exposing both planes equally to the sunlight. To accomplish this eccentric adjustment of the leaf, the petiole actually twists itself, as if it really knew what it was about—with, however, seemingly some of that discomfort which attends on strained etiquette. Often the twist or contortion is so evident as to arrest the attention at once; and the amount of torsion is wonderful when it is mentioned that the petiole seems to delight in holding the scythe-shaped leaf with its concave edge uppermost (Fig. 3). It is surely curious to find in the leaves of the adult tree the texture so different from that of the leaves of its youth. But the leaf is now the seat of a much greater physiological change. The two planes of the leaf are now virtually alike—the same in texture and in organs. The ribs and veins are the same, alike prominent on each side, much as if the roof of a house should have its beams and rafters inside and out. And two series of stomata, or breathing-organs, now appear—one series for each side of the leaf. Here, we think, lies much of the secret of the great draining capacity of the eucalypts. Both sides of the leaf work equally. It is as the double-cylinder engine against the single one. It is asserted of the gum-tree that it can eliminate from a swampy soil eight times its own weight of water in twenty-four hours.
What, then, is the logic of these facts? Let us give the geologist the last word; for it may be that, from his habit of dealing with the floras and the faunas of the long ago, his generalization may be more profound than that of the mere systematic botanist.
What about the eccentricities of the young eucalypt? Our mentor here denies the eccentricity in the sense of freakiness. He sees in it a law of the Creator. The young eucalypt, he thinks, in its marvelous vigor of growth, is tending to, or striving after, the forms and conditions of the higher and more recent groups; but that, with something of its growth-vigor abated in the adult state, it reverts back to its legitimate ancestral type. But we may not be too knowing; and surely a devout science can well afford to admit with reverence that "His ways are past finding out."
And this delver in the earth after organic relics assures us that these eucalypts are an extremely ancient race, and that they were formerly wide-spread. He even finds them in the Eocene times, composing in part the great forests of Europe. These, he tells us, were the arboreal ancestors of the gum-trees of Australia; and he bids us note that, of the existing floras of the world, that of Australia has the highest antiquity. With this instance, as almost paralleled, we may adduce the "big trees" of California. There can be no doubt that these gigantic and graceful trees once covered a large area, extending into an antiquity scarcely less ancient than that of the eucalypts. Even snow-clad Greenland in that ancient time had its flowery age, and was a home for the princely sequoias. 'Now, what reduced them to but two species, and what pushed them over the mountains, and bade them be content with that small domain centred by the Calaveras grove? And what a change must earth have undergone, that Australia should be isolated from its once-continental alliance, and these noble eucalypts, the tallest Titans that the world has known, should be thus put upon their limits! The sequoias promise little, and seem doomed ere long to pass away. Beyond their beauty and scientific interest, their virtues are few. Not so with the eucalypts. Give them a fair showing of place and climate, and they will thrive and enrich their environment. This tree has the hardiness of the ancient; it also has virtues which will enlarge the comforts and lengthen the days of men. As when some beneficent art, once enjoyed by a former people, has been lost, and, long known only in tradition, has been rediscovered and revived, and men are again enlivened with hope, so is the possession by the modern world of this ancient tree.