pN THE ALBURNUM OF TREES, %J 



v, 



On the Origin and Office of the Alburnum of Trees. In 

 a Letter from T. A. Knight, Esq. F.R.S. to $ir Joseph 

 Banks, Bart. K. B. P. R. S*. 



Mr. Dear Sir, , 



N my last communication I endeavoured to prove, that The bark not 

 the bark of trees is not subsequently transmuted into albur- changed into 

 num ; and if the statements that I have there given be cor- 

 rect, they are, I conceive, decisive on the point for which I 

 .contended : and jf the bark be not converted into alburnum, 

 the experiments of Duhamel, and subsequent naturalists, but deposits 

 and those of which I have given an account in former me- l he alburnous 

 moirs, afford sufficient evidence, that the bark deposits the 

 alburnous matter. If the succulent shoot of a horse chesr 

 nut, or other tree, be examined, at successive periods in the 

 spring, it will be seen, that the alburnum is deposited, and 

 its tubes arranged, in ridges beneath the cortical vessels; 

 and the number of these ridges, at the base of each leaf, 

 will be found to correspond accurately with the number of 

 apertures through which the vessels pass from the leaf-stalks 

 into the interior bark, the alburnpus matter being apparently 

 deposited (as I have endeavoured to prove in former me- 

 moirs) by a fluid which descends from the leaves, and subse- 

 quently secretes through the barkf . I shall therefore ven- 

 ture to conclude, that it is thus deposited, and shall pro- 

 ceed to enquire into the origin and office of the alburnous 

 tubes. 



The position and direction of these tubes have induced al- Origin and of- 



most all naturalists to consider them as the passages through fice of ttie f'- 

 , , in r • i burnous tub**, 



which the sap ascends; and at their nrst formation, when 



the substance which surrounds them is still soft and succu- 

 lent, they are always filled with the fluid, which has appa- 

 rently secreted from the bark. They appear to be formed 

 in the soft cellular mass ? which becomes the future albur- 



f Philos. Trans, for 1808, Part II, p. 313. 

 f f nil. Trans. J807, p. 33^. 



num, 



