LETTER XIV. 



" Setting aside mere hypothesis, it seems incontestable that wood, 

 in whatever manner it is deposited, is created out of organisable 

 matter prepared in the leaves, or their equivalents, and therefore 

 derived from them. This being so, it matters nothing whether the 

 matter descending from leaves, and acquiring the condition of wood, 

 be theoretically called roots, or by some other name: it is certainly 

 descending matter. ''^ — Dr Lindley. 



April 30, 1855. 



My Dear Sons, 



1. The object of my last letter was to show you 

 that the woody tissue of the Cambium is of the nature 

 of roots — in other words, that the concentric woody 

 cylinders formed annually in the trunk of the Exogen 

 are none other than the roots of the plants annually 

 evolved from the buds, and growing at the upper part 

 of the tree. And I would fain hope that the evidence 

 there laid before you in support of that view was such 

 as to satisfy you that it is a correct view. 



2. The evidence, indeed, is singularly diverse. It 

 is also wonderfully cumulative. When I finished that 

 letter, I fancied I had said all that there was any need 

 to say in that behalf. I find, however, that I had 



K 



