GENUS (Lat. a kind), in natural history, a group of species (q.v.), plosely connected by common characters or natural affinity. See GENERALIZATION. In all branches of zoology and botany, the name of the genus forms the first part of the scientific name of each species, and is followed by a second word—either an adjective or substantive— which distinguishes the particular species. Thus, in solanum tuberosum (the potato), solanum is the generic, and tuberosum the speelfic (sometimes styled the trivial) name. This method was introduced by Linumus, and has been of great advantage to the prog ress of science, simplifying the nomenclature, and making names serve, in some meas ure, for the indication of affinities. The affinities indicated by the generic name are often recognized even in popular nomenclature—thus, elm and u/mIts are perfectly synonymous; but there are many instances in which this is very lar from being the case, as that of the genus solanum. The arrangement of species in groups called genera has no real relation to any of the important questions concerning species.—Genera are arranged in larger groups, called orders, which are often variously subdivided into orders, families, tribes, etc.; and are themselves grouped together in classes, which are
referred to divisions of one or other of the kingdom's of nature. Some genera contain hundreds of species; others no more than one; and although future discoveries may add to the number in many of the smallest genera, yet it cannot be doubted that a very great difference exists in the number actually belonging to groups equally distinct and nat ural. Some of the larger genera are, by some authors, divided into sub-genera; and too many naturalists show an extreme anxiety to multiply generic divisions and names, perhaps forgetting that whilst certain affinities may be thus indicated, the indication of others is necessarily lost, whilst the memory of every student of science is more and more heavily burdened. There can be no doubt, however, that to a certain extent the fluctuations of nomenclature, so often felt to be annoying, mark the progress of science and the removal of errors.
In mineralogy, the generic name is not adopted as the primary part of the name of each species. Gem (q.v.) is an example of a mineralogical genus.