34 



LETTERS ON TREES. 



And on the summit of the terminal shoot of the tree 

 will be found a bud in immediate connection with the 

 pith of that shoot, and this pith (if the tree have re- 

 cently been felled) plump and succulent. 



6. The longitudinal woody layers then of the trunk, 

 though above ground, I have described as being 

 (equally with the continuations of them under ground) 

 the roots of the several plants that have grown sue* 

 cessively one above another. They are not, indeed, 

 commonly regarded as roots, but simply as the wood 

 and conjointly as forming the trunk of the tree, — the 

 term root being restricted to all that part of the tree 

 which lies buried in the soil. Believing them, how- 

 ever, to be really of the nature of roots, I call them 

 such, and their being so regarded forms an integral 

 part of my theory. 



7. The persistent stems and roots, then, of the seve- 

 ral fir-plants are successively set one above another, 

 and alongside of one another, — the stems of the plants 

 of one year resting on the stems of the plants of the 

 previous year, and their roots creeping down outside 

 both the stems and the roots of the latter, and even 

 extending beyond. Thus are the parts below a mecha- 

 nical support (a framework or scaffolding) to the parts 

 above ; while these in their turn become conservative, by 

 cutting off from the parts below atmospheric and other 

 influences, which would otherwise speedily entail their 

 decay. Thus, too, are successive additions made to 



