On the Inconvertibility of Bark into Alburnum, 135 



The interior surface of the bark of the crab tree presented 

 numerous sinuosities, which corresponded with similar ine- 

 qualiiies on the surface of the alburnum, occasioned by the 

 former existence of many lateral branches. The interior 

 surface of the bark of ihe apple tree, as well as the external 

 surface of the alburnum, was, on the contrary, perfectly 

 smooth and even. A vital union soon took place between 

 the transposed pieces of bark, and the alburnum and bark 

 of the trees to which they were applied; and in the autumn 

 it appeared evident, that a layer of alburnum had been, in 

 every instance, formed beneath the transposed pieces of 

 bark, which were then taken off. 



Examining the organization of the alburnum, which had 

 been generated beneath the transposed pieces of bark of the' 

 crab tree, and which had formed a perfect union with the 

 alburnum of the apple tree, I could not discover any traces 

 of the sinuosities 1 had noticed ; nor was the uneven surface" 

 of the alburnum of the crab tree more changed by the 

 smooth transposed bark of the apple tree. The newly gene- 

 rated alburnum, beneath the transposed bark, appeared per- 

 fectly similar to that of other parts of the stock, and the di'-' 

 rection of the fibres and vessels did not in any degree corre- 

 spond with those of the transposed bark *. 



Repeating this experiment, I scraped off the external sur- 

 face of the alburnum in several spaces, about three lines in 

 diameter, and in these spaces no union took place between 

 the transposed bark and the alburnum of the stock, nor was 

 there any alburnum deposited in the abraded spaces; but the 

 newly generated cortical and alburnous layers took a circu- 

 lar, and rather elliptical, course round those spaces, and 

 appeared to have been generated by a deseeding fluid, which 

 had divided into two currents when it came into contact 



* Duhamel having taken off, and immediately replaced, similar pieces of 

 the hark of young elms, subsequently found that the alburnum, which was 

 generated beneath such pieces of bark, had not formed any union with the 

 alburnum of the tree, beneath it. But this great naturalist did not employ 

 ligatures of sufficient power to bring the bark and alburnum into- close con- 

 tact, or the result would have been different. 



1 4 with 



