932 
grown ina dry soil, on the margin of 
a lake or river, has been found to 
point to the water; whilst those of 
another species of tree, which thrive 
best: in a dry soil, have been ascer- 
tained to take an opposite direction ; 
but the result of some experiments 
I have made, is not favourable. to 
this bypothesis, and I am rather in- 
clined: to believe that the roots dis- 
perse themselves in every direction, 
and only become most numerous 
where they find most employment, 
anda soil best adapted to the spe- 
ciesof plant. My experiments have 
not, however, been sufficiently va- 
ried or numerous to decide this 
question, which I prepose to make 
the subject of future investigation. 
Iam, &c. 
T. A. Knight. 
Elton, Nov. 22, 1805. 
On the inverted Action of the Albur- 
nous Vessels of Trees. By Thos. 
Andrew Knight, Esq. F. R. 8. In 
a Letter to the Right Hon. Sir 
Joseph Banks, K. B. P. B.S. 
ie (13B1D. ) 
Read May 15th, 1806. 
My dear sir, 
I have endeavoured to prove, in 
several Memoirs which you have 
done me the honour to lay before 
the royal society, that the fluid by 
which the various parts (that are 
annually added to trees and herba- 
ceous plants, whose organiZation is 
similar to that of trees) are gene- 
rated, has previously circulated 
through their leaves, either in the 
same, or preceding season, and sub- 
sequently: descended through their 
bark; and after having repeated 
every experiment that occurred to 
me, from which I suspected an un- 
ANNUAL REGISTER, 1806. 
favourable result, I am not in pos~ 
session of a single fact which is not, 
perfectly consistent with the theory 
I have advanced. 
There is, however, one circum- | 
stance stated by Hales and, Du Ha- © 
mel, which appears. strongly to 
militate against my hypothesis; and 
as that circumstance probably in- 
duced Hales to deny altogether the 
existence of circulation in plants, 
and Du Hamel to. speak less deci- 
sively in favour of it, than he possi- 
bly might have done, I am anxious 
to reconcile the statements of these 
great naturalists (which I acknow- 
ledge to be perfectly correct) with 
the statements and opinions I have 
on former occasions communicated 
to you. 
Both Hales and Du Hamel have 
proved, that when two circular in- 
cisions through the bark, round the 
stem of a tree, are made at a small 
distance from each other, and when 
the bark between these incisions is 
wholly taken away, that portion of 
the stem which is below the incisions © 
through the bark, continues to live, 
aud in some degree to increase in ~ 
size, though much more slowly ob- 
served than the parts above the 
incisions. They have also observed 
that a small elevated ridge (bour- 
velet) is formed rownd the lower lip 
of the wound in the bark, with 
some slight advances to meet the 
bark and wood projected, in much 
larger quantity, from the opposite, 
or upper lip of the wound. 
I have endeavoured, in a former 
Memoir, to explain the cause why 
some portion of growth takes place 
below incisions through the bark, by 
supposing that a small part of the 
true sap, descending from the leaves, 
escapes downwards through the 
porous substance of the alburnum, 
Several facts stated by Hales, seem 
favourable 
