IV. Botanical arrangement of Fossil Vegetables.--Mr. Artis, in the Introduction of his work, offers some judicious observations as to the proper method in which the study of Fossil Botany should be pursued. He remarks, "that from the imperfect state in which fossil vegetables are generally found, the ordinary characters by which recent plants are referred to their congeners, can scarcely ever be detected in them. The sexual organs on which the systems of Linnæus and Jussieu are founded, and even the integuments of those organs while in the state of flowering, have uniformly perished. The external parts of the seed or fruit exist, indeed, in a fossil state, but they are almost always insulated from the other organs. If leaves are found, it is almost certain that scarcely any portion of the stem will be attached to them; if the external parts of a trunk, then very rarely any vestiges of the branches and foliage. And when traces of the internal structure can be discovered, it is seldom that the external character of the stem remains. "In consequence of this deficiency of the essential characters on which the determinations of the botanist are founded, there exists a necessity for examining more minutely and accurately than has yet been done, the internal structure of recent plants; their habits of growth, the cicatrices or scars left on the stem by the leaves that are spontaneously shed, the different appearances which their fruits exhibit in their various stages of development--all these points must be minutely studied before we can obtain any certainty as to the identity of fossil and living species of plants. "It is not by publishing detached and unconnected delineations and descriptions of fossil plants, as they occasionally occur, that the knowledge of them can be considerably promoted. A systematic arrangement must be formed; and the first step to this is the accurate determination of the species. _Hoc opus, hic labor est._"