From this general account of the vegetable structures that may be expected to occur in the mineral kingdom, the student will in some measure be prepared for the investigation of fossil trees and plants; but for the guidance of those who are wholly unacquainted with the principles on which the Natural System of Botany adopted in this work, is founded, I am induced to present the following concise view of the principal divisions of the vegetable kingdom, though it involves some repetition. [Sidenote: BOTANICAL PRINCIPLES.] The following summary is given nearly in Dr. Lindley's own language:-- Botanical Principles.--One of the first things that strikes an inquirer into the structure of plants, is the fact, that while all species are capable of propagating their race, the mode in which this function is effected is essentially different in different cases. In most tribes of plants, flowers are produced, and these are succeeded by fruit, containing seed, which is shed, or scattered abroad, and grows into new individuals. But in certain families (the _Cryptogamia_), as Ferns, Mosses, Mushrooms, and the like, neither flowers, nor seeds properly so called, have been detected; but propagation is effected by the dispersion of grains or spores, which are usually generated in the substance of the plant, and seem to have but little analogy with true seeds. Hence the vegetable kingdom is separated into two distinct groups, namely, the _flowering_ (_Phanerogamia_), and the _flowerless_ (_Cryptogamia_ or _Agamia_). As the former usually possess a highly developed system of spiral and other vessels, while the latter are either altogether destitute of them, or have them only in a few of the highest orders, and those in a peculiar state, the flowering plants are termed Vasculares, and the flowerless _Cellulares_. And as all the flowering, or vascular plants, when they form stems, increase by an extension of their ends, and a distension or enlargement of their circumference, but the flowerless or cellular plants form their stems simply by the addition of new matter to their points, the latter are called _Acrogens_, signifying increase from the summit. Flowering plants are also for the most part furnished with respiratory or breathing organs (_stomata_), of which the flowerless vegetables are to a great extent destitute. The flowering or vascular plants are also divisible into two well marked groups, namely, the _Exogens_, or _Dicotyledons_, and the _Endogens_, or _Monocotyledons_. The Exogens (growing from without), increase by the addition of new woody matter to the outside of the stems beneath the bark; and they are further characterized by the embryo having two or more cotyledons, or seed-lobes, hence they are also called _Dicotyledons_; such as the Elm, Beech, &c.