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1 



5 INCONVERTIBILITY OF BARK INTO ALBURNUM. 



ble of changing into a pulpous and cellular, and ultimately 

 a vascular substance ; the direction taken by the vessels be- 

 in^ apparently dependent on the course, which the descend- 

 ing fluid sap is made to take*. The object of the present 

 Always re- Memoir is to prove, that the bark thus formed always re- 

 nidin» ar . jjjains in the state of bark, and that no part of it is ever 

 transmuted into alburnum, as many very eminent naturalists 

 have believed. 

 Experiments Having procured, by grafting, several trees of a variety 

 and crab!'^ ^ **^ *^^ apple and crab tree, the woods of which were distin- 

 guishable from each other by their colour, I took off, early 

 Their bark mu- in the spring, portions of bark of equal length, from 

 tually moscu- branches of equal size, and I transposed these pieces of 

 bark, enclosing a part of the stem of the apple tree with a 

 covering of the bark of the crab tree, which extended quite 

 round it, and applying the bark of the apple tree to the 

 stem of the crab tree in the same manner. Bandages were 

 then applied to keep the transposed bark and the alburnum 

 in contact with each other; and the air wa.s excluded by a 

 plaster composed of bees wax and turpeniine, and with a 

 covering of tempered clay. 

 Interior sur- The interior surface of the bark of the crab tree pre- 

 faces different, gented numerous sinuosities, which corresponded with simi- 

 lar inequalities on the surface of the albarnum, occasioned 

 by the former existence of many lateral branches. The in- 

 terior surface of the bark of the apple tree, as well as the 

 . £xternal surface of the alburnum, was, on the contrary. 

 Union took . perfectly smooth and even. A vital union soon took place 

 ^ '^^'^' betwexu the transposed pieces of bark, and the alburnUm 



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

 A layer of aJ- the autumn it appeared evident, that a layer of alburnum 



Extravasated * I had observed this circumstance in many successive seasons ; but I 



anitnal fiuids ^fas not by aiiy means prepared to believe, that such an arrangement 

 u-e^^uine vascu- ^„,jf^| ,^kg place in the coa<^uliini afforded by an extravasated fluid; and 

 I am indebted to Mr. Carlisle f . r having pointed out to me many cir- 

 cumstancfs in the motion and powers of the blood of animals, which in- 

 duced rh'e to give credit to the accuracy of my observations ; and to that 

 gentleman and to Mr. Home I have also subsequently to acknowledge 

 ra^ny obligations, 



had 



