to the expansion of the trunk by the bark, which 
has now become thick, hard, and unyielding. 
Mr. Knight found that old pear-trees, relieved 
of their outer bark, formed more wood in a 
couple of summers afterwards, than they had 
made in the 20 years that preceded the opera- 
tion.” “ However essential to a tree,” says Mr. 
Dovaston, “are all the skyey influences of air, 
which cannot be kept from it, light is the grand 
and indispensable agent of vegetation. A tree 
deprived of this will soon sicken, and sodie. I 
have very repeatedly seen, when a tree has been 
cut down near the edge of a thick wood, having 
the boughs all on the light side, the annual rings, 
instead of being concentric, have gone off round 
the place of the pith in vast parabolic curves, 
like the orbit of a comet on a planetary dia- 
gram, the layers being exactly equally numerous 
on both sides, but vastly wider on the side of the 
light. Two trees of equal organisation, were it 
possible, and in equal soils, the one incommoded 
and the other not, would in a very few years tell 
utterly distant in the scale of growth; though a 
tree may be too much exposed, and I have occa- 
sionally seen even a sycamore show a weather- 
side to the storm.” 
The maturity of trees, or the period at which 
they begin to lose their vigour, or have reached 
the extreme verge of maximum fitness for fell- 
ing, does not depend on mere age or bulk, but is 
largely determined by the aggregate of the cir- 
cumstances of growth, especially by those of soil, 
situation, and exposure. Very old living timber 
always perishes first in those parts which consti- 
tute the most interior ligneous layers; so that to 
suffer any timber-tree to stand till it begins to 
give slight exterior indications of decay is, in 
general, to allow it to lose some of the most 
valuable portions of its wood. Too young a tree 
has not all the excellence of timber which it 
would gain if it were permitted to grow to a 
higher maturity ; and too old an one commonly 
has the timber of its centre lighter and less valu- 
able than that of its circumference; and every 
tree is in its prime, as to both the quality and 
the homogeneity of its timber just at the mo- 
ment which immediately precedes the decay of 
its heart or innermest layer. And though the com- 
mencement of this decay is so entirely interior as 
to be profoundly beyond the reach of observation, 
yet it soon communicates its influence to the 
whole tree, and rapidly produces external symp- 
tomatic indications of its existence. A tree 
whose top forms one uniformly rounded mass— 
particularly if it naturally possess a somewhat 
straggling and freely-branching habit—is in a 
weak condition; one which comes prematurely 
into leaf in spring—particularly if it prematurely 
suffer discoloration and fall of foliage in au- 
tumn—is also in a weak condition; one which 
begins to shrink or die at the extremities of any 
of its principal shoots or branches has begun to 
decay in the innermost woody layers of its 
TREE. 
trunk; one whose bark is here and there cracked 
or fissured or fallen-off, has undergone a consi- 
derable degree of decay in the innermost parts 
of its trunk; one whose bark is marked with 
red or black spots, or infested with mosses, | 
lichens, and fungi, is In a suspicious condition, 
and may possibly be somewhat far-gone in heart- | 
decay; and one whose sap may be observed to 
ooze through crevices of the bark, is thoroughly 
diseased, and may already be half-dead. 
The upland regions of Britain, and most of all 
the mountain fastnesses of the Scottish High- 
lands, afford the best evidence as te the species 
of trees which are truly indigenous in our coun- 
try, and which may be grown in it with the 
highest degree of advantage. The original and 
natural vegetation of nearly all parts of the 
globe, excepting such as are covered by shifting 
soil or perennial snows, consists chiefly of trees 
and shrubs, differing according to the climate. 
If, after the revolutions and catastrophes which 
geology so clearly indicates, the surfaces con- 
sisted partly of bare rock, and partly of debris, 
gravel, sand, and clay, whatever may have been 
the first vegetation by which these surfaces were 
covered, it is at least apparent that trees were 
abundant upon them at a period antecedent to 
the formation of peat and other soils of vegetable 
origin; for the decayed stumps and roots of the 
oldest trees which we meet with may generally be 
traced to the subsoil, and in few cases occur in 
soil that is evidently of posterior origin. A con- 
siderable portion of Scotland can hardly be sup- 
posed to have been covered with trees for many 
ages back ; for in the soil and subsoil the opera- 
tions of the agriculturist disclose no roots, which, 
had they once existed, could scarcely have been 
so entirely decomposed as to leave no traces 
behind. But the sides of all the Highland moun- 
tains, the glens and ravines, the margins of the 
rivers and lakes, and very extensive tracts of the 
low grounds, have at some period been covered | 
by wood. Beyond the mere fact, however, that, 
at a former period, Scotland exhibited extensive 
ranges of uninhabited forest, where corn-fields 
and pastures now surround the habitations of a 
crowded population, little respecting the species 
is to be learned from the pages of our historians. 
They can only tell us at random of ‘noble 
forests of oak, ash, beech, and other hard tim- 
ber;’ and in order to discover the real species, 
we must have recourse to our peat bogs, and to 
the remnants of the ancient woods which still 
grace many parts of the country. Yet from the 
former of even these sources, little information 
is to be obtained. When trunks, branches, or 
roots are found in peat, they are generally so 
altered that the species to which they belong 
can in only few cases be discovered. The pine, 
the birch, the alder, and the oak, are all that 
can be made out with certainty, to which may 
be added the hazel, upon the occasional evidence 
of its nuts. In an insular situation like ours, 
