153 



produce more. Of course, the timber of 

 such must not only be exceedingly knotty, 

 but small in quantity ; the sap being ra- 

 ther expended upon the branches than 

 the stem ; and hence, we see clearly the 

 necessity of iising means, in order to im- 

 prove the quality, and increase the quan- 

 tity, of TIMBER. 



A slight inspection of PI. Ill, A. A. A, 

 will shew the manner in which the sap is 

 intercepted by the branches, in its ascent. 

 It is to be noted that the curved lines were, 

 all in turn, at different periods, the situa- 

 tion of the principal sap-vessels. Ko. 1 

 gives a very clear idea of the manner in 

 which either a branch or a tree is en- 

 larged, by one coat of wood being annu- 

 ally laid upon another, likewise, we see, 

 by the top of this figure, the manner in 

 which the branches cause a contraction 

 in the sap-vessels, as noted at p. 36. 



Here it is well worthy of remark, that 



L 



