40 On the Formation of the Bark of Trees. 



nerated in the cellular substance on the surface of the albur- 

 num of the sycamore and the apple-tree, traversed that sub- 

 stauce in almost ever)* direction; and the same thing appears 

 to occur beneath the old bark, when united lo the alburnum. 

 For, having attentively examined, through every part of the 

 spring and summer, the formation of ihc internal bark, and 

 alburnous layer bcnealh it, round the bases of regenerated 

 buds, which I had made to spring from sniooth spaces on 

 the roots and stems of trees, I found every appearance per- 

 fectly consistent with the preceding observations. A single 

 shoot only was suiTered to spring from each root and stem, 

 and from the base f this iii every iPiStance the cortical ves- 

 sels dispersed tiicnselves in diiilM\T.' directions. Some de- 

 scended perpendicularly do inwards, whilst others diverged 

 on each side, round the alburnunj, with more or less incli- 

 nation downwards, and met on the opposite side of it. The 

 same pulpous and cellular substapce appeared to cover the 

 surfaces of the bark and alburnum, when in contact with 

 each other, as when detached ; and through this substance 

 the ramifications of the vessels of ihe new bark extended 

 themselves, appearing to receive their direction from the 

 fluid sap which descended from the bark of the young shoots, 

 and not to be, in any degree, influenced in their course by 

 the direction taken by the conical and alburnous vessels of 

 the preceding vear. 



Whenever the vessels of the bark, which proceeded from 

 different points, met each other, an interwoven texture was 

 produced, and the alburnum bfenealh acquired a similar orga- 

 nisation : and the same ching occurs, and is productive of very 

 important effects, in the ordinary course of the growth of 

 trees. The bark of the principal stem, and of every lateral 

 branch, contains very numerous vessels, which are charged 

 with the descending true sap; and at the juncture of the 

 lateral branch with the stem, these vessels meet each oilier. 

 A kind of pedestal of alburnum, the texture of which is 

 much interwoven, is in consecjuence formed round the base 

 of the lateral branch ; which thus becomes firmly united to 

 the tree. This pedestal, though apparently a part of the 

 branch, derives a large portion of the matter, annually added 



to 



