LETTER Xir. 



125 



add this other consideration, that the layer in question 

 is strictly an annual formation, of the same year's 

 growth with the plants proceeding from the buds, and 

 equally short-lived. And with reference to this point, 

 it is not a little singular that, however they may differ 

 in their views as to the nature of this layer, both M. 

 Du Petit-Thouars and M. Mirbel (as we have already 

 seen in Letter XL) agree in regarding every tree as 

 being in its nature composite, and, as such, without 

 natural limit to its duration and growth. They both 

 arrive at the same conclusion as to this, which is the 

 main point of my theory, although they reach it in 

 different ways. 



7. That the woody layer is both structurally and 

 physiologically the roots of the young plants, that 

 issue from the buds, I maintain. Nor will it, I think, 

 be difficult to demonstrate that they are. That in the 

 manner of its formation and growth there is a pecu- 

 harity, I readily allow. That is to say, I allow that 

 with the exception of a small portion, the fibres com- 

 posing it do not actually creep and grow dowmvards 

 from the base of the buds and young plants above to 

 the soil below. The portion which I except is that 

 part of the root beginning at the tip of the last year's 

 root, and thence extending a short way beyond it into 

 the soil. This portion does in fact grow and creep 

 downwards, just as does the root of the seedling. 

 Excepting this part, however, I admit that there is 



