Page:The Zoologist, 1st series, vol 1 (1843).djvu/307

Rh enclosed by the subsequent growth of the same animal." This does not appear to be the true explanation. In the case of the globular protuberances mentioned before, it is formed by, or beneath, the inTesting membrane of the axis, while the fleshy bark remains entire; and the repetition of these spots in the bend of the branches precludes the idea of such a fortuitous enclosure. The opinion of Ellis appears, therefore, to be erroneous, but is rather an error of deduction than of observation. Near the root the axis is frequently studded with small cavities, some of which are empty, while others are more or less filled with this greyish matter; the most inferior are generally empty, while in the more recent it is more or less abundant. From the gradation of quantity observed in these cavities, it seems reasonable to suppose that each had formerly been occupied by this grey matter, which, in some way or other, had been since removed. There appear to be only two methods in which such a removal could occur; either from degeneration or absorption. It is exceedingly rare to observe any marks of degeneration, either in the form of powder or a disorganized appearance of the substance itself, and therefore it seems most probable that its removal depends upon absorption.

The pith is white, and runs through the centre of the trunk and branches, and is smaller in the lower and older than in the upper and newer portions. In a transverse section of recently formed parts, it is found to be composed of irregular-sized cells, quincuncially arranged; in a longitudinal section, to be formed of cells similar in shape to those observed in the fleshy bark, but smaller in size. In the older portions of the pith this cellular structure cannot be observed. From the pith being smaller in the older than in the younger parts, the cells are most probably obliterated by pressure, either becoming ruptured, or so closely compacted that their ultimate structure cannot be detected, even by maceration. This pith differs in several important particulars from the pith of vegetables. In vegetables it is continuous from the trunk through all the branches; in the Gorgonia verrucosa it is divided into numerous small compartments by transverse horny septa, and the pith of the branches is separated from the pith of the trunk by several layers of the fibres of the axis, in such a manner as to have no immediate communication with each other. This has been noticed and figured by Ellis and others. The pith of vegetables is also surrounded by ducts and tracheae, which 1 have never detected in the Gorgonia; hence there are several important discrepancies between them.

The pith acts an important part in the formation of new branches,