C 289 J 
XVIII. On the action of detached leaves of plants. By 
T. A. Knight, Esq. F. R. S. In a letter addressed to ih 
Right Hon. Sir Joseph Banks , Bart. G. C. B. P. R.S. 
Read June 13, 1816. 
Dear Sir, 
Since I had last the honour to address a communication to 
you, with a request that you would lay it before the Royal 
Society, I have repeated great nart of the experiments which 
formed the subjects of my former Letters, with such addi- 
tions and variations, as might probably lead to the detection 
of any erroneous conclusions which I might have drawn : 
but I have not been able to detect any errors, nor to add any 
thing very important to my former observations. I have, 
however, been able to ascertain a few new facts, which I 
think too interesting to be lost. 
I endeavoured, in my former communications, to adduce 
evidence, that the matter, which becomes vitally united to 
trees, previously passes through their leaves ; and I shall 
now proceed to state some facts, which, 1 trust, will prove, 
that a fluid possessing the power which I have attributed to 
the true sap, actually descends through the leaf stalks. 
A slender knife was passed through some leaf stalks of the 
vine, about two thirds of an inch distant from their junction 
to the branch; and, down to that point, the leaf stalks were 
divided longitudinally, and a transverse section, about half an 
