of the alburnous Vessels of Trees, 121 
eile the statements of these great naturalists (which I ac- 
knowledge 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 incisions 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, and in some degree to increase 
in size, though much more slowly than the parts above the 
incisions. They have also observed that a small elevated 
ridge (Lourvelet) is formed round the lower lip of the wound 
in the bark, which makes 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 inct- 
sions 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 to this supposition ; 
and the existence of a power in the alburnum to carry the 
sap in different directions, is proved in the growth of in- 
verted cuttings of different species of trees. But I have 
derived so many advantages, both as a gardener and farmer, 
(particularly in the management of fruit. and forest trees,) 
from the experiments which have been the subject of my 
former memoirs, that I am confident much public benefit 
might be derived from an intimate acquaintance with the 
use and office of the various organs of plants; and thence 
feel anxious to adduce facts to prove that the conclusions I 
have drawn are not inconsistent with the facts stated by my 
great predecessors, _ 
It has been acknowledged, I believe, by every naturalist 
who has written on the subject, (and the fact is, indeed, too 
obvious to be controverted,) that the matter which enters 
into the composition of the radicles of germinating seeds 
* Phil. Trans. for 1803. + Ibid. for 1804. 
existed 
