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ground, and under certain circumstances, in virtue of its physiological properties and of the action of the environment upon its structure. The germinated acorn gives rise to the seedling or young oak, and we shall proceed to regard this, again, as a subject for botanical study. It consists of certain definite parts or organs, each with its peculiar structure, tissues, etc., and each capable of behaving in a given manner under proper conditions. The study of the seedling leads naturally to that of the sapling and the tree, and the at first comparatively simple root-system, stem, and leaves, now become complex and large, and each demands careful attention in order that we may trace the steps by which the tree is evolved from the plantlet. A section will therefore be devoted to the root-system of the tree, its disposition, structure, functions, and accessories; another section will be occupied in describing the trunk, branches, buds, and leaves, and their co-relations and functions; the inflorescence and flowers will demand the space of another chapter, and then it will be necessary to treat of various matters of importance in separate chapters as follows: The timber must be considered with respect to its composition, structure, uses, and functions; then the cortex and bark have to be described and their origin and development explained. These subjects naturally lead to that of the growth in thickness of the tree—a matter of some complexity, and not to be understood without the foregoing knowledge of structure. Following what has been said concerning the normal