346 PHYTOLOGY. 



in the Hazel, which shows that the surface of the barked part keeps 

 alive. 



The effect that the removal of the bark has upon trees is twofold : 

 one producing death in that part, as deep as the centre or pith ; the 

 other death only a little way beneath the surface, like an exposed sur- 

 face of a bone : and I believe that, in some, life is retained on the very 

 surface, as is often seen in the Pear-tree. 



If the barking be only partial, little or no effect upon the tree in 

 general is produced, whatever be the influence on the part barked ; for 

 if the barked part dies to the centre, the remaining bark on the same 

 plane is sufficient to carry on the communication between the two parts 

 of the tree, viz. the root with the part barked, and the tree beyond the 

 part barked. But if the tree be barked all round, two very different 

 and material effects take place in the two degrees of influence ; for the 

 tree that dies from the surface to the centre, now dies all round to the 

 centre, and we find that every part of the tree beyond the barked part 

 dies, although not immediately ; but, in the other case, the wood only 

 dies a small depth from the surface all round, and the parts beyond 

 the barked part do not die, but produce a number of new parts. 



I have said that in the tree which dies to the centre when barked all 

 round, the parts beyond do not lose their life immediately ; but this 

 happens sooner or later, according to circumstances, at least so far as 

 my experiments have yet gone. If the bark be taken off in the autumn, 

 the parts beyond appear to die sooner than when the bark is taken off 

 in the spring experiment. 



In the month of September 1779 I took off a circular piece of bark 

 from two branches of a Laburnum, with the view to see if the parts 

 beyond lived the first year. April 1780 they began to shoot forth, but 

 they both died. From the circumstance of their beginning to throw out 

 leaves, &c, we must allow that they had lived through the winter, 

 and probably this was because they had at this time little or no action 

 to perform. 



Experiment second, April 1780 : on the same Laburnum I took off a 

 circular piece of bark from a branch, and it shot forth its leaves, 

 flowers, &c. as strongly as in any of the other branches. In March 

 17S1 it began to shoot forth its leaves and flowers a second time, but 

 they were both very small ; and in the autumn it visibly died. 



Experiment third. — The same experiment was made upon another 

 Laburnum, in March 1781 and was attended with nearly the same cir- 

 cumstances ; the only difference being that this was rather more lively 

 in all its actions. 



Experiment fourth. — At the same time, viz. March, the same expe- 



