Page:Transactions NZ Institute Volume 17.djvu/385

Rh period as five or six years, even when the timber has been apparently sound and good at the first. How far this may be due to its being cut during the period of active growth, or to its having been used while in a green condition, both practices being the rule rather than the exception, it is impossible for me to say. Another possible cause of its early decay in certain cases may be its having grown upon wet ground. It must be admitted at least that its durability cannot have been fairly tested in the majority of cases. But making all possible allowances on these points I am compelled to place its good properties considerably below those of the tooth-leaved beech.

In the Oxford Forest it is sparingly mixed with white pine, miro, and matai, the last decidedly rare. A few fine trees run up to from 60 to 75 feet in height, but the bulk do not exceed 40 feet in the clear trunk. The manager of one of the largest sawmills informed me that "trunks capable of giving 4–14 feet lengths were extremely rare." I learned that the tree was termed "red birch," "brown birch," "white birch," "black birch," and "yellow birch," at different stages of its growth, but the application of these terms varied greatly: perhaps "black birch" was most generally applied to the mature condition before decay commenced, and "white birch" to the young state; but there were too many exceptions to allow of the names being other than misleading.

Unripe trees of this kind never afford durable timber, however large their dimensions; unless the tree is allowed to stand for a few years after attaining its full growth decay speedily commences. The time required for ripening, at present undetermined, cannot be very long, and when once the process is completed decay sets in very quickly, and progresses with greater or less rapidity. Sometimes it commences at the heart before full growth has been attained; the trunk appears perfectly sound, but on being squared or sawn its defective condition is exhibited at the expense of the woodman. All our beeches are more or less subject to this peculiarity, but I am inclined to believe that the period between the ripening of the wood and the commencement of decay is unusually short in the entire-leaved beech, and as the timber is of but little value at any other period, we have here one cause of its frequent early decay after conversion.

In this species the medullary rays of fully ripened timber are more durable than the wood formed by the fibro-vascular bundles of the annual cylinder. Logs decaying in the forest often present a curious appearance from this cause: after the sapwood has perished the outer surface of the heart-wood appears to be divided into numerous short laminae running longitudinally. These laminæ project more or less beyond the general mass owing to the early decay of the wood of the cylinder. If the log has been kept from the ground, the appearance is still more remarkable, the medullary