"But it is in the tendency to the production of compound fabrics, each containing a number of individuals, which have the power of existing independently, but which are to a certain degree connected with one another, that we recognise the greatest affinity in structure between this group and the vegetable kingdom. Every tree is made up of a large number of buds composed of leaves arranged round a common axis; each bud has the power of preserving its own life and reproducing the original structure when removed from the parent stem, if placed in circumstances favourable to its growth, and yet all are connected in the growing tree by a system of vessels which form a communication between them. This is precisely the nature of those structures which are formed by the animals of the class that may be regarded as the most characteristic of the group. Every mass of coral is the skeleton of a compound animal, consisting of a number of polypes, connected together by a soft flesh in which vessels are channelled out; the polypes are capable of existing separately, since each one, when removed from the rest, can in time produce a massive compound fabric like that of its parent, but they all contribute to the maintenance of the composite structure so long as they are in connection with it. In some instances the skeleton is stony, and is formed by the deposition of calcareous matter either in the centre of each fleshy column, so as to form a solid stem, or on its exterior so as to form a tube. In other cases it is horny, and then it may be a flexible axis in a delicate tube. Both the stony and horny corals often possess the form of plants or trees, and as their skeletons are often found with no obvious traces of the animals to which they belong, they have been accounted vegetable growths." DESCRIPTION OF A VEGETABLE AND ITS PARTS. As has been said before, it is extremely difficult to make any distinction between the lower tribes of the vegetable and animal kingdoms, and physiologists are not yet agreed, with respect to some members, as to which kingdom they belong. Their whole substance is made up of cellular tissue, and there are but few distinctions of parts, forming generally a broad foliaceous expansion called the "thallus," as in lichens and sea-weeds, or a sort of root composed of fibres and called the "mycelium," as in the fungi. But, a very few steps higher, the distinctive characters become so evident that they are impossible to be mistaken, the following description will therefore apply to vegetables of the more elevated character, such as trees or flowering plants.