mercantile enterprise in the East and the discovery of America added greatly to botanical knowledge, hampered, however, by the different names given to the same plant by various discoverers, a difficulty which the brothers John and Casper Banhin endeavoured to overcome. Jung, the rector of the Gymnasium at Hamburg (died 1657), originated the Latin system of botanical nomenclature; and in 1700 Tournefort first classified plants into strictly defined genera founded on the form of the flower. It was, however, reserved to Carl von Linné, more generally known by his latinized name, Linnæus, in the eighteenth century, to place the science of botany on a firm foundation, and to propound the system which bears his name. The Linnæan system, although it possesses many advantages for the purpose of classification, is an artificial one, the Vegetable Kingdom being divided into 24 classes (23 comprising flowering plants, the 24th including the Cryptogamia, or flowerless plants), dependent on the number and arrangement of the stamens, and these, again, into orders with respect to the pistils or carpils. Linnæus also introduced the binomial system of classification, by means of which every plant is distinguished by two Latin names, the first denoting the genus, the second the species: for example, the common hemlock is described as Conium masculatum, L., the letter appended indicating the name of the botanist who first bestowed it. The Linnæan system has since been superseded by the natural system, originally promulgated by Jussieu (1748-1836) in his work "Genera Plantarum," the first complete exposition of the natural system, since modified by a combination of systems proposed by De Candolle, Endlicher, Meisner, Lindley, Sir W. and Dr. J. H. Hooker, Bentham, and other botanists. The natural system divides the Vegetable Kingdom into two great sections, Cryptogamia, or plants destitute of flowers, containing anthers, and Phanerogamia, or plants containing the organs above specified.
Lichens and Mosses.—These low classes of cryptogamous plants are widely distributed over the surface of the earth, the lichens being most abundant in the colder regions of the globe, and are of considerable importance in the economy of nature. They assist materially in the creation of the soil, and thrive in the coldest and most sterile situations, many of them growing on the barest rocks and receiving no other nourishment than that afforded by air and rain. They pass into a state of decay, and by their débris sustain other species, which in their turn supply nourishment to other plants. This continuous process of growth and decay assists by chemical and mechanical action in the disintegration of rock, and forms a soil sufficient to maintain larger plants, which also die and decay, and thus the soil is increased until it is sufficiently deep to sustain the beech or oak, or even the trees of a tropical forest. Some species of lichens are useful as articles of food to the inhabitants of the northern regions and their domesticated animals, as the "Iceland moss" (Cetraria islandica), which contains