C 183 3 
VIII. Experiments and Observations on the Motion of the Sap in 
Trees. In a Letter from Thomas Andrew Knight, Esq. to the 
Right Hon. Sir Joseph Banks, Bart. K. B. P. R. S. 
Read February 16, 1804. 
MY DEAR SIR, 
In the Observations on the Descent of the Sap in Trees, which 
I last year took the liberty to request you to lay before the 
Royal Society, I offered a conjecture, that the vessels of the bark, 
which pass from the leaves to the extremities of the roots, were, 
in their organization, better calculated to carry the fluids they 
contain towards the roots than in the opposite direction. I had 
not, however, at that time, any experiment directly to support 
this supposition ; but I thought the forms generally assumed by 
trees in their growth, evinced the compound and contending 
actions of gravitation, and of an intrinsic power in the vessels 
of the bark, to give motion to the fluid passing through them. 
In the account of the experiments which I have now the honour 
to address to you, I trust I shall be able to adduce some interest- 
ing facts, in support of that inference. 
Having selected, in the spring of ,1802, four strong shoots of 
the vine, growing along the horizontal trellis of my vinery, I 
depressed a part of each shoot, whilst it was soft and succulent, 
about three inches deep, into the mould of a pot placed beneath 
it for that purpose ; but without making any wound, or incision, 
in the young shoots thus employed as layers. 
