936 
charged into the bark below it : but I 
have proved with amputated branches 
of different species of trees, that the 
water which their leaves absorb, 
when iramersed in that fluid, wil! be 
carried downwards by the alburnum, 
and conveyed into a portion of bark 
below the decorticated space; and 
that the insulated bark will be pre- 
served alive and moist during several 
days ; and, if the moisture absorbed 
by a leaf can be thus transferred, 
it appears extremely probable that 
the true sap will pass through the 
same channel. This power in the 
alburnum to carry fluids in different 
directions probably answers very 
important purposes in hot climates, 
where the dews are abundagt and the 
soil very dry; for the moisture the 
dews afford may thus be conveyed 
to the extremities of the roots; and 
Hales bas proved that the leaves 
absorb most when placed in humid 
air; and that the sap descends, 
either through the bark or alburnum, 
during the night. 
If the inverted action of the alburn- 
ous vessels in the decurticated space be 
admitted, itis not difficult to explain 
the cause why some degree of growth 
takes place below such decorticated 
spaces on the stems of trees; and 
why a small portion of bark and 
wood is generated on the lower lip of 
the wound. A considerable portion 
of the descending true sap certainly 
stagnates above the wound, and of 
that which escapes into the bark 
below it, the greater part is probably 
carried towards, and into, the roots ; 
where it preserves life,and occasions 
some degree of growth to take place. 
But a small portion of that fluid 
will be carried upwards by capillary 
attraction, between the bark and the 
alburnum, exclusive of the imme- 
diate action of the latter substance, 
ANNUAL REGISTER, 1806. 
and the whole of this will stagnate 
on the lower lip of the wound, 
where I conceive it generates the 
small portion of wood and bark, 
which Hales and Du Hamel have 
described, 
[ should scarcely have thought an 
account of the preceding experi- 
ments worth sending to you, but 
that many of the conclusions I have 
drawn in former memoirs appear, at 
first view, almost incompatible with 
the facts stated by Hales and Du 
Hamel, and that I had one fact to 
communicate relative to the effects, 
produced by the stagnation of the 
descending sap of resinous trees, 
which appeared to lead to important 
consequences. I have in my posses- 
sion a piece of a fir-tree, from which 
a portion of bark, extending round 
its whole stem, had been taken off 
several years before the tree was 
felled ; and of this portion of wood 
One part grew above, and the other 
below the decorticated space, Cons 
ceiving that, according to the theory 
I am endeavouring to support, the 
wood above the decorticated space 
ought to be much heavier than that 
below it, owing to the stagnation of 
the descending sap, I ascertained the 
specific gravity of both kinds, taking 
a wedge of each as nearly of the 
same form, as I could obtain, and I 
found the difference greatly more 
than I had anticipated ; the specific 
gravity of the wood above the decor- 
ticated space being 0,590, and of 
that below cnly 0,491; and having 
steeped pieces of each, which weighed 
100 grains, during twelve hours in 
water, I found the latter had ab- 
sorbed 69 yrains, and the former 
only 51. 
The increased solidity of the wood 
above the decorticated space, in this 
instance, must, I conceive, have 
arisen 
