On account of the large quantity of starchy matter which they contain, they often considerably, and sometimes even entirely, form the diet of man and animals in those dreary inhospitable regions where the wintry rigor, or the scorching heat of the climate, forbids all other kinds of vegetation to grow. Every one is familiar with the fact that the reindeer-moss (Cladonia rangiferina) forms altogether the food of that animal during the prolonged northern winters. This lichen grows sparingly in little tufts among the heather in Scotland, and sometimes whitens the sides and plateaus of the Highland hills, covering bare and verdureless places where the snow first falls in winter and lingers longest in summer; but it is in the vast sandy plains, called by the Laplanders Flechten-tundra and Moos-tundra, as lichens or mosses predominate, which border the Arctic Ocean, that it flourishes in the greatest profusion and luxuriance. There it completely covers the ground with its snowy tufts, and occupies as conspicuous a place in the economy of nature as the grass in warmer regions. Linnæus says that no plant flourishes so luxuriantly as this in the pine-forests of Lapland, the surface of the soil being completely carpeted with it for many miles in extent; and that if by an accident the forests are burned to the ground, in a very short time the lichens reappear, and resume all their original vigor. When the ground is covered with hard and frozen snow, so that the reindeer can not obtain its usual food, it finds a substitute in a very curious lichen called rock-hair (Alectoria jubata), which covers with its beard-like tufts the trunk of almost every tree. In most severe weather the Laplanders cut down whole forests of the largest trees, that their herds may be enabled to browse at liberty upon the tufts which cover the higher branches. The vast, dreary pine-forests of Lapland possess a character which is peculiarly their own, and are perhaps more singular in the eyes of the traveler than any other feature in the landscapes of that remote and desolate region. This character they owe to the immense number of lichens with which they abound. The ground instead of grass is carpeted with dense tufts of the reindeer moss, white as a shower of new-fallen snow; while the trunks and branches of the trees are swollen far beyond their natural dimensions with huge, dusky, funereal bunches of the rock-hair hanging down in masses, exhaling a damp earthy smell, like an old cellar, or stretching from tree to tree in long festoons, waving with every breath of wind, and creating a perpetual melancholy twilight.