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XIV. On the inverted Action of the alhurnous Vessels of Trees . 
By Thomas Andrew Knight, Esq. F. R. S. In a Letter to 
the Right Hon . Sir Joseph Banks, K. B . P. P. 
Read May 15, 1806, 
MY DEAR SIR, 
X 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 herbaceous plants whose organization is 
similar to that of trees,) are generated, has previously circu- 
lated through their leaves -f either in the same, or preceding 
season, and subsequently descended through their bark ; and 
after having repeated every experiment that occurred to me, 
from which I suspected an unfavourable result, I am not in 
possession of a single fact which is not perfectly consistent 
with the theory I have advanced. 
There is, however, one circumstance stated by Hales and 
• In the Phil. Trans, for 1801, 1803, 1804, and 1805. 
f During the circulation of the sap through the leaves, a transparent fluid is 
emitted, in the night, from pores situated on their edges ; and on evaporating this 
liquid obtained from very luxuriant plants of the vine I found a very large residuum 
to remain, which was similar in external appearance to carbonate of lime. It must, 
however, have been evidently a very different substance from the very large portion, 
which the water held in solution. I do not know that this substance has been ana- 
lyzed, or noticed by any naturalist 
