414 ON THE ELIGIBILITY OF DECORTICATING TREES. 
and closely connected therewith, and covered exteriorly with two layers 
of bark, the first cuticle being pushed outwards by the new layer 
within, which is now called the liber. In the third year, a third layer 
of wood is added on the outside of the two first, and a new liber is 
formed, at the same time, within the two first layers of bark; and thus 
the diameter of the stem is annually enlarged by a new layer of wood 
and a new liber, as long as the tree lives. 
Now, as the pith and inner layers of wood are first formed, it is 
observed, in the generality of trees, that they are also the first to decay, 
very old trees being usually hollow ; and the first layer of bark is also 
the first to lose its vitality, or be thrown off in various ways. In some 
trees, it is biennially or triennially discharged in irregular flakes, like 
that of the Arbutus andrachne ; in horizontal lamina, like the birch ; 
in longitudinal strips, like the grape-vine ; or is rent into vertical 
fissures, like that of the oak. From these facts an obvious deduction 
follows, viz. that both wood and bark are only of temporary use in the 
system, and both are, like the leaves and fruit, excrementitious pro¬ 
ductions. 
These are facts needing no proof; and therefore, respecting the bark, 
it is cpiite clear that every layer which has already done its duty, and 
ceased to be a living organ, is afterward only an incumbrance, which 
may be removed with impunity. It is also manifest that, as every 
year’s new growth is within the bark, the latter must necessarily be 
expanded, either by being periodically thrown off, or stretched horizon¬ 
tally, or rent longitudinally, as it is in the generality of trees. It is, 
therefore, a natural effort of the tree to be relieved from the constrict¬ 
ing action of the bark, and may often need assistance in this way. 
We know that there are many trees which, being placed in a rich soil 
and favourable situation, advance from the seed to their utmost stature, 
without appearing to sufler from constriction of the bark; but many, 
and particularly old fruit-trees in orchards, are subject to what is 
emphatically called hide-bound, and without any means being taken to 
relieve them ; and it is surprising that a practical man, who is aware 
that such a defect exists, should employ no means as a remedy. It is 
true, we sometimes see the stem scored from top to bottom with the 
point of a knife, for the purpose of relieving a hide-bound tree, and 
sometimes with the best eflfects; but an entire disbarking of the stem 
is seldom had recourse to, lest it should kill the tree outright. 
But, to have a right understanding how far the bark may be stripped 
off without injuring the tree, we have to consider what its special use 
is. In its youngest state it is green and soft, and consists chiefly of 
cellular membrane, but vascular on its inner side. The exterior being 
