LETTER XVI. 175 



and lengthening the whole season through, i. e* until 

 nipped by the frosts of autumn ; and why should not 

 the leaves formed the first in spring be larger and 

 longer than those formed many weeks later in the 

 summer? Dr Carpenter's theory will not explain 

 this ; and I will make bold to say, that quite inde- 

 pendently of all extrinsic causes periodically checking 

 the vegetative processes, there is a definite succession 

 observed by Nature in the formation of the Cambium 

 and of the buds of trees, and a definite character im- 

 parted to the structures evolved from them. It may 

 be that, in certain circumstances and in certain 

 climates peculiarly favouring the vegetative pro- 

 cesses, such a succession may occur twice in one year, 

 or even three times, — or five times in two years but 

 each is separate from every other, and one is com- 

 pleted before another is begun. And although the 

 lines of demarcation between the several layers of 

 wood, thus formed, may be fainter than in those of 

 trees in colder climates, or even be scarcely dis- 

 tinguishable, a sufficiently minute inspection of the 

 woody tissue will yet demonstrate, that it nowhere 

 presents an unbroken continuity of substance, — such 

 a contitnuity or homogeneousness, for example, as we 

 can easily discover in the woody matter of the annual 

 shoot or stem. 



* Carpenter, Ibid.^ p. 790. 



