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LI1I. On facilitating the Emission of Roots from Layers. By 

 Thomas Andrew Knight, Esq. F. R.S. $c. President. 



Read February 4, 1812. 



It is my custom, annually, to repeat every experiment that 

 occurs to me, from which I have reason to expect informa- 

 tion either in opposition to, or in favour of, the opinions I 

 have advanced respecting the generation and motion of the 

 sap in trees; and one of these experiments appearing to 

 point out an improvement in the propagation of such trees by 

 laying, as do not readily emit roots by that process, I send 

 the following statement, under the hope that it may be ac- 

 ceptable to the Horticultural Society. 



I have cited, in a former communication,* a part of the 

 evidence upon which I have inferred that the sap of trees 

 descends from their leaves through the bark ; and I shall 

 here only observe, in support of that opinion, that if a piece 

 of bark be every where detached from the tree, except at its 

 upper end, it will deposit, under proper management, as 

 much, or nearly as much wood, upon its interior surface, as 

 it will if it retain its natural position ; and that the sap which 

 generates the wood, deposited in the preceding circum- 

 stances, must descend through the bark, as it cannot be 

 derived from any other source. 



vol. I. 



* Page 219- 

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