perfect. This kind of character is, however, admirable for the illustration of any difficult natural order. Mr. Gawler's elucidations of the Ensatæ, Sword-leaved plants, Annals of Botany, v. 1, 219, and Curt. Mag. afford excellent specimens of it, serving as a store of facts and observations for following systematical writers.
Specific characters should be constructed on similar principles to the generic ones, as far as regards certainty, clearness and conciseness. The genus being first well defined, we are to seek for characters, not mentioned among the generic marks, for distinguishing the species. A specific difference for a solitary species of any genus, is therefore an absurdity. Linnæus at first intended his specific definitions should be used as names; but the invention of trivial names happily set aside this inconvenient scheme. On this account however he limited each to twelve words, a rule to which all philosophical naturalists have adhered, except in cases of great necessity. Nor is the admission of one or two words beyond the allotted number reprehensible, provided the whole sentence be
