till it comes in contact with the lower lip, and 
then adhesion follows, and the wound is healed; 
or when a wound is inflicted in peculiar circum- 
stances, or upon peculiar kinds of trees, granula- 
tions form at the mouths of the exposed medul- 
lary processes, and gradually extend themselves 
over the excorticated surface till they become 
fused into one another, and constitute a cover- 
ing of bark ; or when a wound is so inflicted that 
communication between the upper and the lower 
lips is still partially or even slightly maintained, 
a lateral transfusion of the descending sap takes 
place, and all the current of it is gradually di- 
verted into the channel or remaining portion of 
communication till the wound is healed. When 
partial or total denudation of cortical matter 
takes place, as in the barking of the oak for tan- 
ners and the excortication of the cork-tree for 
commerce, or in the accidental or mischievous 
peeling of very large plates from any ordinary 
forest-tree, either the dead part alone of the bark 
-is removed, and no injury whatever is inflicted, 
or a sufficient though very thin portion of the 
| liber is left to enable the plant to recover its 
energies without any serious damage, or the 
whole of the liber is removed, and the plant, ac- 
cording to its own vigour, to the season of the 
year, to the presence or the absence of albur- 
num, or to other modifying circumstances, either 
speedily dies or maintains a severe and even- 
tually successful struggle for existence. The 
healing of any severe or doubtful wound is very 
greatly aided, in trees as in animals, by any ap- 
pliance which lessens electric action and excludes 
the atmospheric air. A practical gardener, writing 
in Loudon’s Magazine, gives the following recipe 
for “ making the bark grow over wounds and 
diseased places in forest or fruit trees, without 
fail and with speed :—When a branch is cut off a 
tree or otherwise wounded, make the place smooth 
with a sharp knife; and if the tree be cankered, 
either cut away the part affected, or scrape it out 
until you come to the sound wood. In all cases 
make the surface as smooth as possible; then put 
half a pound of tallow into two pounds of tar, and 
warm it over the fire, till the tallow is just melted 
in the tar; when one ounce of saltpetre should 
be added, and the whole stirred well together. 
The composition must then be laid on the parts 
that you want to heal; and I have found it, by 
long experience, to be an effectual cure, and su- 
perior by far to any thing yet practised.” 
Tannin, or the peculiar principle which changes 
hides into leather, abounds most in the white in- 
terior layers of oak bark, and has long occasioned 
that bark to be in great commercial demand for 
the supply of tan-yards ; yet it also exists in suf- 
ficient quantity in the barks of various other 
kinds of trees to be an important ingredient in 
their value. See the articles Oax, Tannine, and 
Barking. The proportion of tannin in the bark 
of any one species of tree differs according to 
various circumstances, particularly the season of 
the year at which the bark is removed, and the 
temperature of the period immediately preceding 
its removal; yet the quantity in each of some 
of the best known trees, as ascertained by Sir 
Humphrey Davy, may be regarded as, in nearly 
all instances, a close approximation, and, at all 
events, affords a fair comparative view of the 
tanniniferous value of the different trees. The 
average relative value of birch-bark in tannin, 
Sir Humphrey states to be 8; of horse chestnut, 
9; of beech, 10; of large common willow, 11; 
of sycamore, 11; of elm, 13; of hazel, 14; of 
black thorn, 16; of ash, 16; of Spanish chestnut, 
21; of oak cut in autumn, 21; of middle-sized 
oak cut in spring, 29; of coppice oak, 32 ; of large 
Leicester willow, 33; and of the white interior 
cortical layers of oak, 72. The tannin of the 
larch is usually a little less than one-half of the 
tannin of the oak ; the tannin of the interior 
cortical layers of any tree is always very much 
greater in proportion to the weight than that of 
the entire bulk of the bark; and the tannin of 
properly peeled and carefully harvested bark is 
always in far larger proportion than the tannin 
of bark which has been peeled under bad condi- 
tions, or which has been allowed to ferment in 
consequence of injudicious harvesting. Mr. Mon- 
teath of Stirling, by applying a chemical test to 
carefully prepared infusions and decoctions of the 
different kinds of barks, ascertained that tannin 
exists in greatest quantity in the oak, next in 
the ash and the hornbeam, next in the Spanish 
chestnut, next in the green willow, the bay- 
leaved willow, the common hoop willow, the gray 
willow, and the Huntingdon willow, next in the 
birch, the beech, and the larch, next in the spruce 
and the silver firs, next in the mountain ash and 
the common broom, next in the laburnum, and 
variously in the Scottish pine, the bramble, and 
the sawdust of oak timber; and he says that all 
these kinds will tan leather, and that the bram- 
ble, the dock, and the common broom might be 
good tanning substitutes for the ordinary tanning 
barks. Among other tanniniferous substances 
either now or formerly in use are heath, gall- 
nuts, myrtle leaves, wild laurel leaves, and wattle 
bark. The last of these is obtained from two 
species of mimosa which abound in New South 
Wales, Van Dieman’s Land, and New Zealand; 
and though only three-fifths of the tannin- 
strength of the best oak bark, is largely imported 
for the use of British tanners——The weight of 
bark afforded by any tree in proportion to its 
bulk of timber varies according to the kind of 
tree, its age, its healthiness, and the conditions 
under which it grew, whether upon good or bad 
soil, in a confined or an exposed situation, in free 
and open ground, or among choking underwood. 
Mr, Monteath, stating the results of his own ob- 
servation, that an oak of 40 years of age yields 
from 9 to 12 lbs. of bark per cubic foot of timber, 
an oak of from 80 to 100 years of age yields from 
10 to 16 lbs. of bark per cubic foot of timber, a 
