Page:The Zoologist, 1st series, vol 1 (1843).djvu/308

280 being the first part formed. Branches are formed indiscriminately on all parts of the axis, but most abundantly on the newest. Their mode of formation can be best observed in a longitudinal section. The results of numerous such sections are, that the first visible part formed is a white speck near the centre of the axis, separated from the pith by the interposition of several layers of the axis. This speck is at first very small, but it soon increases in size, and becomes triangular, having its base towards the pith, and apex towards the circumference of the axis. The apex, at first, is removed from the circumference of the trunk or branch by full two-thirds of its semi-diameter, but as it increases in size the intervening layers gradually disappear. At length the apex of the pith reaches the circumference, and the investing membrane, with the surface of the axis, becomes elevated into a small sharply -pointed eminence. This forms the first external appearance of a branch, and is observable only when the bark is taken off; having once become prominent, it increases and grows like the older branches. How the first nucleus is formed I have never been able to determine, but it seems most probable from a process going on in the axis itself; it certainly has no connexion with the presence of the grey enclosed matter mentioned above. This nucleus for the branches very closely resembles the pith, both in consistence and whiteness, while the other matter has a yellowish tinge. In a longitudinal section of seventeen specimens, the pith of all the branches bore the same relative situation to the pith of the trunk, and the triangular pith of such branches as had just reached the surface was exactly the same: it is not at all difficult to trace this pith from the branch to the mere speck. The rudimentary pith can therefore be readily distinguished from the other grey matter, first by its situation, then by its colour and shape, and, in addition to these, it may be noticed that the layers of the axis are always closely in contact with the young pith, while with the grey matter there is generally a vacancy between it and the surrounding axis. The axis thus seems to have an action going on within itself, entirely inconsistent with an inorganic character.

The specimens of this species which grow off our headlands, and in situations where they are liable to be disturbed with a variety of currents, become very bushy and irregular in their growth. Their branches, which are long and cross each other, frequently get denuded of a portion of their bark, and most probably by friction. When this occurs, the branches, at their points of crossing, become firmly united to each other, and, in some cases, for half an inch in extent. On