Classificationof Plants

Classification of Plants is necessary owing to the enormous number of known forms or species and the impossibility of otherwise bearing their characters in mind, arranging collections, or treating of them in books. A classification may be artificial, based, that is, on some one character or set of characters, and will then serve mainly as a convenient and but slightly instructive index; or it may aim at being natural, taking into consideration, that is, all the characters of the plant, and endeavouring by grouping together those having the most general resemblance to reconstruct the genealogy, or to trace the blood-relationship, of the vegetable kingdom (q.v.). Of the first type of classifecation that known as the sexual system propounded by Carl von Linne (Linneeus) (q.v.) is the best, being based, primarily, on the stamens, their number, relative length, union, etc., and, secondarily, on the styles. The natural system, though foreshadowed by Caesalpinus, Ray, and Linne, was first thoroughly sketched out by the Jussieus and by Auguste de Candolle. It also is based mainly upon reproductive (i.e. floral) structures. It must always in its very nature be of a tentative character. One of the chief difficulties which it encounters is that of distinguishing between resemblances of structure which are merely apparent, functional, or analogous, and those that correspond to essential identity of origin or homoloyy.