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Good Words 1860
Sketches in Natural History

Ferns and Tree Ferns

The earliest traces of vegetable life yet discovered in the most ancient fossiliferous rocks, consist of fragments of sea-weed, accompanying graptolites, or sea-pens, in the anthracite beds of the Silurian system, which in all probability owed their origin to the decomposition of plants of this description, once forming submarine meadows, where zoophytes nestled and trilobites swam. So far as geological investigation has yet gone, it does not appear that a terrestrial flora flourished on the shores of the primeval sea till the age of the old red sandstone, when fishes of singular conformation,such as the pterichthys, with its wing-like arms, disported in the waters. The first indications of land plants are found in the lower beds of that series of rocks, and consist of the remains of lycopodiums or club - mosses, of tree-ferns, and the wood of coniferous trees, resembling the modern araucaria, or Norfolk Island pine. The deposits of this era, both in Ireland and Scotland, have yielded fragments of the fronds or leaves of a tree-fern named Cyclopteris Hibernica, which disappeared before the dawn of the carboniferous period, when, as we have seen, ferns and their allies prevailed over a great portion of the surface of the earth, laying up, for the use of distant ages, beds of coal, deriving their carbon from the carbonic acid gas floating in the then existing atmosphere, and their hydrogen from the decomposition of water, which, descending in rain, mottled, with its drops, the yielding sand; while, upon the same shores, the ripple of the rising and receding tide was tracing the curving and anastomosing lines now so frequently observable on slabs of building and paving stones. We thus learn, from the traces of life-history in the ancient rocks, that, however varied the forms of animals and plants existing in successive geological epochs, the conditions of life have been uniform in all ages. Geology teaches us, to use the words of Professor Owen, that "the globe allotted to man has revolved in its orbit through a period of time so vast, that the mind, in the endeavour to realise it, is strained by an effort like that by which it strives to conceive the space dividing the solar system from the most distant nebulae." The pages of the rocky science bear evidence not less equivocal to the conditions in which organised beings existed upon the earth's surface during all the different eras which it is the province of the geologist to investigate and define. The light and heat of the sun reached the earth through an atmosphere not different from that by which the surface of the globe at present receives the same vivifying influences. The eye of the trilobite was constructed upon the same optical principles, and adapted to the same conditions of light and vision, as the eye of the existing crustacean and insect. Vaporised moisture ascended from earth and sea, and became condensed in the atmosphere, whence it was precipitated in fertilising showers of rain. These showers have not only left, in the strata of successive systems, the casts of rain-marks, indicating by their slope or shape the direction from which they were blown by the wind; but the little rills formed by the gathering drops, as they rolled along the surface of the sand or mud, have also had their traces preserved—a phenomenon which has been detected in Lower Canada in rocks so early as those of the old red sandstone, contemporaneous with the first vestiges of terrestrial vegetation, and recording the most ancient showers of rain of which we have any geological memorial. The study of fossil botany shews, in like manner, that the extinct vegetables of the palćozoic flora must have existed in conditions of the air and earth, such as are still essential to the growth and development of the plant. But while we thus derive from the rocks incontestable proofs of the uniformity of the laws of nature throughout prolonged and successive epochs, we are called to contemplate an astonishing variety in the productions existing at different times in the organised world. Entire races of animals and plants were again and again extinguished, and replaced by new tribes, which have no specific representatives in our present flora and fauna. Yet amidst boundless diversity of form and function in the animal and vegetable kingdoms, viewed along the entire course of creation, we are able to discover an undeviating adherence to typical unity in the glorious plan of the Almighty's handiwork. In evolving this great central principle of the organic creation, science occupies its true position as the handmaid of religion. From the realms of living nature, and the records of past creations, it brings, as a tribute to the altar of the Christian faith, a confirmation of the personal unity of the adorable " I AM," revealed in the pages of eternal truth ; and in demonstrating the unity of the Creator, by tracing through creation the archetypical idea which must have dwelt for ever in the Divine Mind, it has also enriched natural theology with fresh and vivid illustrations of the wisdom and goodness of God, in adapting the typical forms of animals and plants to an endless diversity of benevolent purposes. The science of geology is a history of successive miracles of creation. The subtle sceptic who demanded the testimony of experience to convince him of the possibility of a miracle, lived before geology had borne evidence on the subject such as no rational man will be hardy enough to gainsay. It was a shrewd remark of Hugh Miller's —"Hume is at length answered by the severe truths of the stony science. He was not, according to Job, in league with the stones of the field,' and they have risen in irresistible warfare against him in the Creator's behalf."

Ferns, and tree-ferns, have descended to our time from the remotest period of vegetable life, although they nowhere exist in such abundance as they appear to have done during the carboniferous era, when, although the vegetation was scanty in the variety, it was profuse in the number, of species. Of 500 plants discovered in the coal measures, 346 were ferns and their allies, nearly 300 being true ferns. Many of these are preserved in the shales of the coal mines, with their fossilised fronds and minute venation as distinctly defined as if the plants had been laid up in a botanist's herbarium. In the mines of Bohemia, Dr Buck-land found the ferns and other vegetable remains of the coal exceeding in beauty the most elaborate imitations of living" foliage upon the painted ceilings of Italian palaces. The roofs of the mines were covered as with a canopy of gorgeous tapestry, enriched with festoons of most graceful foliage, flung in wild, irregular profusion over every portion of the surface, the effect being heightened by the contrast between the shining black colour of the coal plants and the light hues of the rocks to which they were attached. The ferns of the English coal-fields number about 140. The existing British species of ferns, including varieties raised to the rank of species, are under 50. In tropical countries, especially those having an insular climate, such as St Helena and the Society Islands, ferns preponderate over flowering plants. The extra-tropical island of New Zealand is preeminently the region of ferns, many of them arborescent, and of their allies the club-mosses, which give a luxuriant aspect to the vegetation, where flowering plants are comparatively rare. Within an area of a few acres, Dr Joseph Hooker observed thirty-six kinds of ferns, while the same space produced scarcely twelve flowering plants and trees. Hence, New Zealand is supposed to possess a climate somewhat resembling that of the carboniferous period, which is believed to have been humid, mild, and equable.

The lowly ferns of this country, whose graceful fronds adorn our hillsides and valleys, and fringe the shady banks of burn and rivulet with their luxuriant verdure, are characterised by having a creeping stem, or rhizome, running along or under the surface of the ground. The stem of the tree-fern of other lands rises into the air, in the form of a slender but stately trunk, surmounted by a crown of elegant drooping fronds, and resembles a palm in its appearance and habit of growth. When fully formed, the trunk is hollow, and is marked on the outside with the scars or cicatrices left by the falling fronds, which, along with the peculiar appearance of the cellular tissue and vascular bundles of the interior, enable the botanist to identify their fossilised remains in the rocks. The stem is formed by the union of the bases of the leaves, which carry up with them the growing point; and as the fern-stem, whether horizontal or vertical, increases only by additions to the summit, this family of plants is called acrogens, or summit-growers. In the young state, the fronds are rolled up in a crosier-like manner, familiar to all who have observed the development of ferns in spring and early summer; and the fronds of tree-ferns, in their native haunts and in our conservatories, exhibit the same curious arrangement. The so-called circinate or spiral mode in which the frond is coiled up, affords an instructive example of provident care in preserving the tender parts of the young plant from the danger they would incur by sudden exposure to the atmosphere. Each leaflet is rolled up towards the rib supporting it,—the rib again toward the midrib,—and the midrib toward the footstalk. In many species, the crosier-like coil is closely invested with brownish scales, serving still further to protect the delicate frond from the chills of early spring, as well as to bar the access of moisture and the invasion of insects. The whole arrangement presents a beautiful instance of the "packing" of plants, during the stage of venation, or when the tender leaf is in the bud; and may readily be studied by any one who will pick up a fern frond, while it is leisurely unfolding its green leaflets to the genial airs of spring.

In the tropical zone of vegetation, tree-ferns grow at an elevation of two or three thousand feet above the level of the sea, and in favourable circumstances their trunks attain a height of forty or fifty feet. They can only be imported into this country in their young state, and then not without difficulty; but even in their most developed form, they exhibit, on a diminished scale, in the conservatory, the majesty and grace of their structure and habits in the warm and humid climate of tropical regions, and even the more temperate parts of the southern hemisphere, where they give a marked character to the physiognomy of vegetation. Humboldt describes the arborescent ferns growing in the shaded clefts on the slopes of the Cordilleras, as standing out in bold relief against the azure of the sky, with their thick cylindrical trunks, and delicate lace-like foliage, and where they are associated with the cinchona tree, yielding the Peruvian bark. The Cyathea arborea, known in our collections, is a native of the West Indies, where it grows to a height of twenty-five feet. St Helena produces the Dicksonia arborescens, which has been observed nowhere else in the world. One of the most magnificent is Alsophylla excelsa, a native of Norfolk Island, where it attains to a height of fifty to eighty feet, with a trunk scarcely a foot in diameter, and a coronet of long pensile fronds. Speaking of tree-ferns in Australia, twenty feet high, Captain Mundy remarks:—"When I left England, some of my friends were fern-mad, and were nursing microscopic varieties with vast anxiety. Would that I could place them for a minute beneath the patulous umbrella of this magnificent species of cryptogamia." One familiar arborescent species (Aspidium baromez), the barometz, or baranetz, called also the Scythian lamb, possesses a woolly rhizome; and when the fronds are cut off, leaving a small portion of the stalk, and the specimen is turned upside down, credulous people have been persuaded, by its appearance, that in the deserts of Scythia there existed creatures half-animal, half-plant. Sir Hans Sloane, who founded the British Museum, described and figured it, in the Philosophical Transactions, under the name of the Tartarian Lamb. Darwin introduces this fantastic fiction into the "Loves of the Plants:"—

"Cradled in snow, and fann'd by arctic air,
Shines, gentle Barometz! thy golden hair;
Rooted in earth, each cloven hoof descends,
And round and round her flexile neck she bends;
Crops the gray coral moss and hoary thyme,
Or laps with rosy tongue the melting rime;
Eyes with mute tenderness her distant dam,
Or seems to bleat, a Vegetable Lamb."

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