136 On the Inconvertibility of Bark into Alburnum. 

 with the spaces from which the surface had been scraped off, 

 and to have united agaiu immediately beneath them. 



Tu each of these experiments, anew cortical and alburn- 

 nous layer was evidently generated ; and apparently by the 

 same means that similar substances were generated beneath 

 a plaster composed of bees-wax and turpentine, in former 

 experiments*; and the only obvious difference in the result 

 appears to be, that the-transposed and newly generated hark 

 formed a vital union with each other: and it is sufficiently 

 evident, that if bark of any kind was convened into alburnum, 

 it must have been that newly generated. For it can scarcely 

 be supposed, that the bark of a crab tree was transmuted 

 into the alburnum of an apple tree, or that the sinuosities, 

 of the bark of the crab tree could have been obliterated, had 

 such transmutation taken place. There is not, however, any 

 thing in the preceding cases calculated to prove that the 

 newly generated bark was not converted into alburnum ; 

 and the elaborate experiments of Duhamel sufficiently evince 

 the difficulty of producing any decisive evidence in this case 5 

 nevertheless I trust that [ shall be able to adduce such facts 

 as, in the aggregate, will be found nearly conclusive. 



Examining almost every day, during the spring and sum- 

 mer, the progressive formation of alburnum in the young 

 shoots of an oak coppice, which had been felled two years 

 preceding, I was wholly unable to discover any thing like 

 the transmutation of bark into alburnum. The commence- 

 ment of the alburnous layers in the oak (quercus robur) is 

 distinguished by a circular row of very large tubes. These 

 tubes are of course generated in the spring; and during their 

 formation, I found the substance through which they passed 

 to be soft and apparently gelatinous, and much less tena- 

 cious and consistent than the substance of the bark itself; 

 and therefore, if the matter which gave existence to the 

 alburnum previously composed the bark, it must have been, 

 during its change of character, nearly in a state of solution; 

 but it is the transmutation of one organized substance into 

 the other, and not the identity only of the matter of both, 



* Philosophical Transactions for 1807, 



for 



