Every one of those sword-like leaves is, of course, the record of a period of time. A tree of this size makes a "screw," or imperfect spire, of leaves in about three years; and there are about sixteen pairs of leaves in each screw, which will give us nearly eleven leaves for the development of each season. Now, on the trunk, there are numerous waved lines quite covering its surface, which are the traces of old leaves that have in succession been produced and decayed away;--the trunk is, in fact, composed of these leaf-bases. By counting these, we may obtain then an approximate notion of the age of this plant;--an _approximate_ notion only, because in its young stages the development of leaves probably took place more rapidly than it does now. There are then on this trunk about one hundred and fifty horizontal rows of scars, and each row numbers four leaf-bases, so that the trunk is inscribed with an autographic record of six hundred leaves. If then we reckon eleven leaves as the produce of a single season, and add the four screws which are still flourishing, we shall obtain a result of about fifty-five years as the age of this _Pandanus_. This, for the reason just assigned, would probably be considerably too much; perhaps, forty years would be nearer the truth. There are, however, other marks of age here, though they are less definite. The great hardness of the surface-wood, which we perceive on trying to indent it, is an indication of age, as it is produced by the successive bundles of woody fibre, which, year after year, have passed down from each leaf, curving, in their descent, towards the circumference of the stem, and, therefore, constantly augmenting the density of the outer portions. Another very curious proof of age is seen in the number of aerial roots which descend from various points of the trunk towards the soil. You would at first be inclined to think them posts, which a carpenter had set to "shore up" the tree, as props to prevent its being blown down. And truly this is their purpose; but they are natural adjuncts, not artificial. These thick rods, some of which have not yet reached the ground, have been shot forth in turn from the stem, in order to afford it additional support in the loose sandy soil. And mark, by the way, a beautiful contrivance here. Because the growing tender extremity of the root has to pass through the sun-parched air in its progress towards the earth, there is a curious exfoliation of its extremity, forming a sort of cup, which, collecting the scanty dews, retains sufficient moisture for the refreshment of the spongy rootlet. Now, I say, these supporting roots, since they must have originated from the trunk, after the latter had attained a considerable height, are so many evidences--and cumulative evidences--of age, though their testimony cannot be so well made to bear on a known period as that of the leaf-bases.