Lichens are exceedingly diversified in their form, appearance, and texture. About five hundred different kinds have been found in Great Britain alone, while upward of three thousand species have been discovered in different parts of the world by the zealous researches of naturalists. In their very simplest rudimentary forms, they consist apparently of nothing more than a collection of powdery granules, so minute that the figure of each is scarcely distinguishable, and so dry and utterly destitute of organization that it is difficult to believe that any vitality exists in them. Some of these form ink-like stains on the smooth tops of posts and felled trees; others are sprinkled like flower of brimstone or whiting over shady rocks and withered tufts of moss; while a third species is familiar to every one, as covering with a bright green incrustation the trunks and boughs of trees in the squares and suburbs of smoky towns, where the air is so impure as to forbid the growth of all other vegetation. It also creeps over the grotesque figures and elaborate carving on the roofs and pillars of Roslin Chapel, near Edinburgh, and gives to the whole an exquisitely beautiful and romantic appearance. One species, the Lepraria Jolithus, is associated with many a superstitious legend. Linnæus, in his journal of a tour through Œland and East Gothland, thus alludes to it: “Everywhere near the road I saw stones covered with a blood-red pigment, which on being rubbed turned into a light yellow, and diffused a smell of violets, whence they have obtained the name of violet stones; though, indeed, the stone itself has no smell at all, but only the moss with which it is dyed.” At Holywell, in North Wales, the stones are covered with this curious lichen, which gives them the appearance of being stained with blood; and, of course, the peasantry allege that it is the ineffaceable blood which dropped from Ste. Winifred’s head, when she suffered martyrdom on that sacred spot. A higher order of lichens (Bæomyces) is furnished besides this powdery crust, with solid, fleshy, club-shaped fructification like a minute pink fungus; while a singularly beautiful genus (Calicium), usually of a very vivid yellow color, spreading in indefinite patches over oaks and firs, is provided with capsules somewhat like those of the mosses.