PROCESS OF NUTRITION. CHAP* III, 



Mr. Knight detached a ring of bark of half an 

 inch in breadth. The sap rose in them, and the 

 portion of the trunk above the ring augmented as 

 in other subjects that were not so treated, while the 

 portion below the ring scarcely augmented at all. 

 The upper lips of the wounds made considerable 

 advances downwards, while the lower lips made 

 scarcely any advances upwards ; but if a bud was 

 protruded under the ring, and the shoot arising 

 from it allowed to remain, then the portion of the 

 trunk below that bud began immediately to aug- 

 ment in size, while the portion between the bud and 

 incision remained nearly as before. When two 

 circular incisions were made in the trunk so as to 

 leave a ring of bark between them with a leaf 

 growing from it, the portion above the leaf died, 

 while the portion below the leaf lived ; and when 

 the upper part of a branch was stripped of its leaves 

 the bark withered as far as it was stript. Whence 

 it is evident that the sap which has been elaborated 

 in the leaves and converted into proper juice, de- 

 scends as air through the channel of the bark, or 

 rather between the bark and alburnum to the ex- 

 tremity of the root, effecting the developement of 

 new and additional parts. * 



But not only is the bark thus ascertained to be 



the channel of the descent of the proper juice, after 



Vessels entering the trunk ; the peculiar vessels through 



iii's it! ' which it immediately passes, have been ascertained 



* Phil. Trans. 1803. 



