INCONVERTIBILITY OF BARK INTO ALRURNUM. tf 



bad been, in e\e!y instance, formed beneath the transposed bumum form- 

 pieces oi bark, which were then taken olf. ^'^^ beneath. 

 Exanaining the organization of the alburnum, which had Alburnum did 



been generated beneath the trarssposed pieces of bark of the ""* ^^^P^ ''^ 



, ,,.,,,,. , ,. ^ . • 1 , surface to that 



crab tree, and which had rormed a periect union with the of the foreign 



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

 of the sinuosities 1 had noticed ; nor was the uneven -sur- 

 face of the alburnum of the crab tree more changed by the 

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

 nerated alburnum, beneath the transposed bark, appeared 

 perfectly similar to that of other parts of the stock, and the 

 direction of the fibres and vessels did not in any degree cor- 

 respond with those of the transposed bark *. 



Repeating this experiment, I scraped off the external Surface of the 



surface of the alburnum in several spaces, about three lines ^'""''"""^ 



' . scraped, 



in diameter, and in these spaces no union took place be- 

 tween 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 circular, and rather elliptical, course roun(J 

 those spaces, and appeared to have been generated by a de- 

 scending fluid, which had divided into two currents when it 

 came into contact with the spaces from which the surface 

 had been scraped off, and to have united again immediately 

 beneath them. 



In each of these experiments, a new cortical and albur- New- cortical & 

 nous layer was evidently generated ; and apparently by the r ^"^"''^°'^'^ ^"'•'^ 

 same means that similar substances were generated beneath 

 a plaster composed of bees wax and turpentine, in former 

 experiments t; and the only obvious difference in the result 

 appears to be, that the transposed and newly generated bark 

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



• Dvjhamel having taken off, and immediately replaced, similar pieces Duhamel's ex- 

 of the 1» r« of young elms, subsequently found, that the alburnum, periment de- 

 which was generated beneath such pieces of bark, had not formed any fectiTe. 

 union with the alburnum of the tree beneath it. But this great natu- 

 ralist did not employ ligatures of sufficient power, to bring the bark 

 and alburnum into close contact, or the result would have been dif- 

 ferent. 



•f Phil, Trans, for 1807; or Journal, toI. XIX, p, 243. 



evident, 



