The part of the bark immediately below the epiphlœum is well developed, and is of a spongy consistence. When examined microscopically it is seen to be composed of cells of various shapes--some elongated fusiform, others rhomboidal, others with pointed appendages. The variety of forms is very great, but it is possible that this may be partly owing to the effects of frost on the cells. On the spontaneous separation of the bark, the portion below the epiphlœum was seen to consist of distinct plates of a more or less quadrilateral form, with some of the edges concave and others convex, a part in the centre indicating the connection with the leaf, along with which it is detached. In Fig. 6 a leaf is shown with one of these plates attached. [Illustration: Fig. 6.] [Sidenote: Fig. 6. Leaf of Araucaria with a portion of bark.] The appearances presented by the outer and middle bark of Araucaria imbricata bear a marked resemblance to those exhibited by certain fossils included in the genera Sigillaria and Lepidodendron. The sculpturesque markings on the stems of these fossil plants indicate their alliance to the ferns and lycopods of the present epoch. But it is evident, from these markings, that much caution is required in making this determination. Other points of structure must be examined before a proper decision can be formed. When, for instance, the presence of scalariform tissue, or of punctated woody tissue, has been satisfactorily shown under the microscope, we are entitled to hazard an opinion as to the affinities of the fossils. In many instances, however, external appearances are the only data on which to rely for the determination of fossil genera and species; and rash conclusions have often been drawn by geologists who have not been conversant with the structure of plants. The Araucaria markings point out the need of care in drawing conclusions, and their variations at different parts of the bark indicate the danger of a rash decision as to species. There can be no doubt that in vegetable Palæontology the number of species has been needlessly multiplied--any slight variation in form having been reckoned sufficient for specific distinction. We can conceive that the Araucaria bark markings in a fossil state might easily supply several species of Lepidodendron. A naturalist, with little knowledge of the present flora of the globe, ventures sometimes to decide on an isolated fragment. Hence the crude descriptions of fossil vegetable forms, and the confusion in which Palæophytology is involved. Every geologist who examines fossil plants ought to be well acquainted with the minute structure of living plants, the forms of their roots, stems, leaves, fronds, and fructification; the markings on the outer and inner surfaces of their barks, on their stems, and on their rhizomes; the localities in which they grow, and the climates which genera and species affect in various parts of the world. (Professor Balfour in the Proceedings of