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PATTERSON *. M'CAUSLAND). 75
hundred years ago it was called the great chesnut; and though it
is supposed to be more than a thousand years old, its trunk was
still perfectly sound, and its branches were annually laden with
fruit, (p)
All forest trees have a range of climate within which they flourish
best, and far beyond which they will not grow, or cannot be propa-
gated; and even within the range of their appropriate climate, they
are all more or less affected by the soil and situation in which they
happen to be rooted. As the great Parent, nature, rolls round the
seasons of the changeful year, all of them assume different external
appearances in succession. That they do not put forth their foliage
or bloom in winter is obvious; but how they are, in other respects
and internally, affected by the revolutions of the seasons, seems to
be a mystery. Yet an opinion has become very prevalent, that the
structure of their wood, visible on dissection, affords evidence of
the periodical progress of nature in effecting their enlargement.
'Wood in vegetable anatomy, is that more or less hard and com-
pact substance, which makes up the bulk of the trunk and branches
of a tree or shrub, and is concealed from view by the bark. When
cut transversely, the wood is found to consist of numerous concen-
tric layers, very distinct in the fir, and in trees of cold or temperate
countries in general; less so in those appropriated to a tropical
climate. The external part of each circular layer being much the
most hard and compact, often with somewhat of a horny appear-
ance, distinguishes the limits of each. Scarcely any two layers of
the same tree are precisely alike, in the proportion which this com-
pact part bears to the rest; nor does any one layer exhibit a pre-
cise uniformity of diameter in its whole circle.' (q) And it is also
said, that 'the bark of trees annually changes into lifeless wood;
whence the concentric rings, which are seen in the trunk of trees,
when they are felled, are annually produced; and are said generally
to be thicker on that side of the trunk, which grows towards the
south, than on the northern side; and thicker in the summers most
favourable to vegetation than the contrary. These rings, as they
lose their vegetable life, and at the same time a part of their mois-
ture by evaporation or absorption, gradually become harder and of
a darker colour; insomuch, that by counting their number, it is said
that not only the age of the tree, but that the mildness or moisture
(p) 2 Mich. Am. Sylva, 142.—(q) Rees' Cyclo, v. Wood in Vegetable Anatomy.
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