OF BARK IXTO ALBUMEX. 14-7 



sive*. In the first of these, Duhamel shows that pieces of silver wire, 

 inserted in the bark of trees, were subsequently found in their alburnum ; 

 but Duhamel himself has shown, with his usual acuteness and candour, 

 that the evidence afforded by this experiment is extremely defective ; and 

 he declares himself to be uncertain that the pieces of wire did not, at their 

 first insertion, pass between the bark and the alburnum ; in which case 

 they would necessarily have been covered by every successive layer of 

 alburnum, without any transmutation of bark into that substance^. 



In the second experiment cited by Mirbel, Duhamel has shown that 

 when a bud of the peach-tree, with a piece of bark attached to it, is 

 inserted in a plum stock, a layer of wood perfectly similar to that of the 

 peach-tree will be found, in the succeeding winter, beneath the inserted 

 bark. The statement of Duhamel is perfectly correct ; but the experi- 

 ment does not by any means prove the conversion of bark into wood ; for 

 if it be difficult to conceive (as he remarks) that an inserted piece of bark 

 can deposit a layer of alburnum, it is at least as difficult to conceive how 

 the same piece of bark can be converted into a layer of alburnum of more 

 than twice its own thickness (and the thickness of the alburnum deposited 

 frequently exceeds that of the bark in this proportion), without any per- 

 ceptible diminution of its own proper substance. The probable operation 

 of the inserted bud, which is a well-organised plant, at the period when it 

 becomes capable of being transposed with success, appears also, in this 

 case, to have been overlooked ; for I found that when I destroyed the buds 

 in the succeeding winter, and left the bark which belonged to them unin- 

 jured, this bark no longer possessed any power to generate alburnum. It 

 nevertheless continued to live, though perfectly inactive, till it became 

 covered by the successive alburnous layers of the stock ; and it was found 

 many years afterwards inclosed in the wood. It was, however, still bark, 

 though dry and lifeless, and did not appear to have made any progress 

 towards conversion into wood. 



In the course of very numerous experiments which were made to 

 ascertain the manner in which vessels are formed in the reproduced 

 barkj, many circumstances came under my observation which I could 

 adduce in support of my opinion, that bark is never transmuted into 

 alburnum ; but I do not think it necessary to trouble you with an account 

 of them ; for though much deference is certainly due to the opinions of 

 those naturalists who have adopted the opposite theory, and to the doubts 

 of Duhamel, I am not acquainted with a single experiment which warrants 



* Chap. Hi. Article 5. f Physique des Arbres, Liv. IV. chap. iii. 



J See the last Paper. 



L 2 



