86 Dr. Wight on the Separation of the Pomegranate whether such is always the law of evolution, and taking place in every plant, is, I think, not sufficiently proved. In Tilia especially this law, however, can be seen operating, in the formation of the spiral fibres on the wall of the cells of the pleurenchyma. That the continuous spiral development is the base of all forms of annular reticulated and dotted vessels I think certain, and the various metamorphoses which arise from such base are to be sought for in the peculiar after-growth of the primary structureless membrane upon which the secondary fibrous layers were originally deposited. Very often, as may be seen in Tilia, this membrane becomes entirely absorbed, the coils of the secondary spire brought close together ; and this happening during the development of the fibres, the spiral continuity ceases to exist ; the mole-cules from which the fibres are formed hence pass into a series of more or less broad, flat, and continuous bands ; and vessels formed of such fibres, totally destitute of primary membrane, are to be found in the plant just referred to. In fact, much of the tissue of Tilia represents many stages and states of evolution of the secondary fibrous layers in con-nexion with peculiar after-growth of the primary structure upon which they have been deposited. I have observed com-pound spiral vessels in the petiole of Tilia pubescens. 4. — On the under surface of the leaf of Adelia nereifolia may be found a very beautiful and peculiar form of scale ; it consists of two circular layers of cellular membrane, the one layer of much smaller diameter than the other, puckered and plaited, and of a saucer-shaped form ; it is fixed by its centre, which apparently is connected with a gland having coloured contents. From this form of scale, through that met with on Eleagnus conferta, I think transitional states may be seen, to the stellate hairs of many of the Euphorbiacem and Malvacece ; in fact^ upon the peculiar adhesions taking place between the ceUs depends the appearance of the stellate hair or the scale of Adelia and Eleagnus. The occurrence both of stellate hairs and this form of scale in Euphorbiacece, shows the structural differences between the two not to be great in their origin. [To be continued.] X. — On the Separation of the Pomegranate as a distinct Natural Order from Myrtaceae. By Robert Wight, M.D., F.L.S., &c.* The most eminent botanists of the present day being divided in opinion as to the propriety or otherwise of separating the * From the Madras Journal of Literature and Science, No. xxix. p. 254.
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