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LETTERS ON TREES. 



as I have stated, there can be no doubt. But on Dr 

 Carpenter's assumption, no such results should follow 

 any such mutilation of the branches, because nothing 

 need hinder the Cambium-layer in either of them from 

 drawing the requisite supplies of elaborated sap from 

 the neiglibouring branches, or even from remote 

 parts of the fabric." 



8. This single consideration seems to me to have 

 all the value of an experimentum crucis, and to possess 

 besides a double value. It is clearly adverse to 

 Dr Carpenter's assumption ; but in the measure and 

 degree in which it is so, it is favourable to mine. And 

 I would beg particularly to observe, that, while (as 

 before remarked) I have nowhere taken so narrow a 

 view of the growths that issue from the buds as to 

 have regard merely to the leaves, I think the facts 

 furnished by the mutilated branches shew decisively 

 that, in relation to the Cambium, the leaves are some- 

 what more than organs for the elaboration of sap for 

 the growth of this layer — have another office to serve 

 besides this in relation to it ; — and, conversely, that 

 the layer in question is beholden to the leaves for 

 somewhat more than a supply of sap, and is itself 

 somewhat besides a mere continuous product of the 

 general cellular basis. 



9. It is true that, in a tree (a fir-tree for example) 

 growing in the middle of a crowded plantation and 

 growing only at the top— the lateral branches having 



