vegetable life effectually keeping down and banishing plants of a simpler structure, and of a more sluggish and feeble nature. On the loftiest mountains of the globe they constitute the last remnants of vegetation, the last efforts of expiring nature which fringe around the limits of eternal snow; and long after the botanist has left behind him the last stunted Alpine flower, blooming like a lone star on a midnight sky, amid the loose crumbling stones of the moraine; long after the last moss has ceased to deck the brown and lifeless ground with a scarce perceptible film of green, his eye, wearied by the universal desolation, rests with peculiar interest and pleasure on the hardy lichens, which clothe every rugged rock that lifts up its head through the avalanche, and which luxuriate amid “the rack of the higher clouds and the howling of glacier winds." On the Alps of Switzerland the last lichens are to be found on the highest summits, attached to projecting rocks, exposed to the scorching heats of summer and the fierce blasts of winter; and from forty to forty-five kinds have been found in spots, surrounded by extensive masses of snow, between 10,000 and 14,780 feet above the level of the sea. It is interesting to know, that the only plant found by Agassiz near the top of Mont Blanc, was the Lecidea geographica (Fig. 9), a very beautiful lichen, which covers the exposed rocks on the sides and summits of all our British hills, with its bright-green map-like patches. This species was also gathered by Dr. Hooker at an elevation of 19,000 feet on the Himalayas, and occupied the last outpost of vegetation which gladdened the eyes of the illustrious Humboldt, when standing within a few hun

dred feet of the summit of Chimborazo, the highest peak of the Andes. Strange it must have seemed to this enterprising traveller to stand on that elevated spot, and to see around and beneath him an epitome, as it were, of what takes place on a grander scale over the whole globe-a condensed picture of all the climates of the earth from the tropics to the poles, with all their different zones or belts of vegetation. Above towered the inaccessible summit in its everlasting shroud of stainless snow, boldly relieved against the deep cloudless blue of the tropical sky; around him the bare and rugged

trachytic rocks, adorned with the green crust of this beautiful lichen, a few pale tufts of moss, or a solitary flower drooping here and there its frail head from a crevice; immediately beneath him the green grass-clad slopes, variegated with rainbow-coloured flowers and stunted willow-like shrubs; and far down in the valleys at the base, a glowing gorgeous world of tropical luxuriance-palms and bananas and bamboos, dimly revealed through the seething, sweltering vapours which perpetually surrounded them.

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The Lecidea geographica affords, I may mention, the most remarkable example of the almost universal diffusion of lichens, being the most Arctic, Antarctic, and Alpine lichen in the world-facing the savage cliffs of Melville Island in the extreme north, clinging to the volcanic rocks of Deception Island in the extreme south, and scaling the towering peak of Kinchin-junga, the most elevated spot on the surface of the earth. A catholic beauty, it is to be found in every zone of altitude and latitude" a pilgrim bold in Nature's care."

On the British mountains we find lichens in great abundance and luxuriance, in spots which favour their growth by the humidity continually precipitated from the atmosphere. Most of the species found sparingly scattered at the highest elevations, are identical with those found in the greatest profusion covering immense areas on the plains of Lapland, and on the level of the sea-shore in the Arctic regions; the isotherms or lines of equal temperature passing through these points. Similar species are also found all over the world below the level of perpetual snow, which on the Alps is 7000 feet, and on the Andes and Himalayas about 15,000 feet. It is somewhat remarkable that Alpine lichens generally are more or less of a brown or black colour. This peculiarity seems to be owing to the presence of usnine or usnic acid, which in a pure state is of a green colour, as in the lichens which grow in shady forests, but which becomes oxidized, and changes to every shade of brown and black, when exposed to the powerful agencies of light and heat, on the bleak barren rocks on the mountain side and

The

summits. These gloomy lichens, associated as they almost always are with the dusky tufts of that singular genus of mosses the Andreas, give a very marked and peculiar character to many of the Highland moun tains, especially to the summit of Ben Nevis, where they creep, in the utmost profusion, over the fragments of abraded rocks which strew the ground on every side, otherwise bare and leafless, as was the world on the first morning of creation, and reminding one of the ruins of some stupendous castle, or the battle-field of the Titans. Some of the Alpine lichens, however, are remarkable for the vividness and brilliancy of their colours. mountain cup-moss, with its light-green stalk clothed and fillagreed with scales, and emerald cup studded round with rich scarlet knobs, presents no unapt resemblance to a double red daisy. It grows in large clusters on the bare storm-scalped ridges, and forms a kind of miniature flower-garden in the Alpine wilderness. The loveliest, however, of all the mountain lichens is the Solorina crocea, which spreads over the loose mould in the clefts of rocks, and on the fragments of comminuted schist on the summits of the highest Highland mountains, forming patches of the most beautiful and vivid green, varied, when the under-side of the lobes is curled up, by reticulations of a very rich orange-saffron colour. This species is not found at a lower elevation than 4000 feet; hence it is unknown in England, Ireland, and Wales, whose highest mountains fall considerably short of this altitude. I have gathered it on Cairngorm, Ben Macdhui and Ben Lawers. In this last locality, which is well known to botanists as exhibiting a perfect garden of rare and

beautiful Alpine plants, it grows in greater abundance, I believe, than in any other spot in the Highlands. It occupies the whole ridge of rugged and splintered rocks, marked by the tear and wear of elemental wars during countless ages, which runs along the summit of the hill. The surface of these rocks is covered with masses of sharp abraded stones, interspersed with meagre tufts of grass and moss; and among these the saffron Solorina luxuriates in large patches. With what delight have I seen this beautiful lichen, beaming out on me from its dreary and desolate home, in the blustering days of early April, when the snow was falling thick around, and the howling wind sweeping by with unobstructed keenness ! With fingers almost benumbed with the cold, I have picked it up to admire its beauty—a beauty, such is the arrogant idea which man entertains of his own importance in the world--which seems utterly thrown away in a spot where human foot and human eye rarely if ever rest. How often among those wildly desolate and pathless solitudes, where one may wander for whole days without catching a glimpse of a single living thing, save perhaps some raven on its way to its nest, leaving behind it the blue sky without speck or cloud, or a ptarmigan scarcely distinguishable from the grey rocks around, winging its slow wheeling flight to the neighbouring hills, and uttering its soft clucking cry; or when standing on some lofty storm-riven summit, cut off from the rest of creation, by the howling mists that come writhing up from the dark abysses on every side, and as lone as a shipwrecked mariner on some desolate island in the sea, thousands of miles from any shore; how