The first vegetable forms to make their appearance at the limits of the snow-line, whether in high latitudes or on mountain-summits, are lichens; which flourish on rocks, or stones, or trees, or wherever they can obtain sufficient moisture to support existence. Upwards of two thousand four hundred species are known. The same kinds prevail throughout the Arctic Regions, and the species common to both the Eastern and Western Hemispheres are very numerous. They lend the beauty of colour to many an Arctic scene which would otherwise be inexpressibly dreary; the most rugged rock acquiring a certain air of picturesqueness through their luxuriant display. Their forms are wonderfully varied; so that they present to the student of Nature an almost inexhaustible field of inquiry. In their most rudimentary aspects they seem to consist of nothing more than a collection of powdery granules, so minute that the figure of each is scarcely distinguishable, and so dry and so deficient in organization that we cannot but wonder how they live and maintain life. Now they are seen like ink-spots on the trunks of fallen trees; now they are freely sprinkled in white dust over rocks and withered tufts of moss, others appear in gray filmy patches; others again like knots or rosettes of various tints; and some are pulpy and gelatinous, like aërial sea-weeds which the receding tide leaves bare and naked on inland rocks. A greater complexity of structure, however, is visible in the higher order of lichens,--and we find them either tufted and shrubby, like miniature trees; or in clustering cups, which, Hebe-like, present their “dewy offerings to the sun.” In the Polar World, and its regions of eternal winter, where snow and ice, and dark drear waters, huge glacier and colossal berg, combine to form an awful and impressive picture, the traveller is thankful for the abundance of these humble and primitive forms, which communicate the freshness and variety of life to the otherwise painful and death-like uniformity of the frost-bound Nature. It is true that here, “Above, around, below, On mountain or in glen, Nor tree, nor shrub, nor plant, nor flower,” may be found in the lands beyond the line of perpetual snow; it is true that “All is rocks at random thrown, Black waves, bare crags, and banks of stone; As if were here denied The summer’s sun, the spring’s sweet dew, That clothe with many a varied hue The bleakest mountain-side;” but vegetation is not absolutely wanting, and the lichens are so largely developed and so widely distributed as to impart quite a peculiar and distinctive character to the scenery.