C 169 3 
VIII. On the Origin and Formation of Roots. In a Letter from 
T. A. Knight, Esq. F. R. S. to the Right Hon. Sir Joseph 
Banks, K. B. P. R. S. 
Read February 23, 1809. 
My dear Sir, 
In a former communication I have given an account of some 
experiments, which induced me to conclude that the buds of 
trees invariably spring from their alburnum, to which they 
are always connected by central vessels of greater or less 
length ; and in the course of much subsequent experience, I 
have not found any reason to change the opinion that I have 
there given.* The object of the present communication is to 
shew, that the roots of trees are always generated by the 
vessels which pass from the cotyledons of the seed, and from 
the leaves, through the leaf-stalks and the bark, and that they 
never, under any circumstances, spring immediately from the 
alburnum. 
The organ, which naturalists have called the radicle in the 
seed, is generally supposed to be analogous to the root of the 
plant, and to become a perfect root during germination ; and 
I do not know that this opinion has ever been controverted, 
though I believe that, when closely investigated, it will prove 
to be founded in error. 
A root, in all cases with which I am acquainted, elongates 
only by new parts which are successively added to its apex or 
* Phil. Tran$. 1805. 
z 
MDCCCIX. 
