:J4 On the Origin and Fwmai'ion of Roots. 



calculated to carry the "sap it contains, from the root up- 

 wards, than in any other direction ; and I concluded that the 

 sap when arrived at the top of the cutting through the al- 

 burnum would be there employed, as I had observed in many 

 similar cases, in generating buds, and that these buds would 

 he protru<led where the bark was young and thin, and con- 

 sequently afforded little resistance*. I had also proved the 

 bark to be better calculated to carry the sap towards the roots 

 than in the opposite direction, and I thence inferred that as 

 soon as any buds, emitted by the cuttings, afforded leaves, 

 the sap would be conveyed from these to the lower extremity 

 of the cuttings by the cortical vessels, and be there employed 

 in the formation of roots*. 



Both the alburnum and bark of trees evidently contain 

 their true sap; but whether the fluid, which ascends in such 

 cases as the preceding through the alburnum to generate 

 buds, be essentially different from that which descends down 

 the bark to generate roots, it is perhaps impossible to decide. 

 As nature, however, appears in the vegetable world to ope- 

 rate by the simplest means ; and as the vegetable sap, like 

 the animal blood, is probably filled with particles which are 

 endued with life, were I to offer a conjecture, I am much 

 more disposed to believe that the same fluid, even by merely 

 acquiring different motions, may generate different organs, 

 than that two distinct fluids arc employed to form the root, 

 and the bud and leaf. 



When alburnum is formed in the root, that organ pos- 

 sesses, in conmion with the stem and branches, the power 

 of producing buds, and of emitting fibrous roots; and when 

 it is detached from the tree, the buds always spring near its 

 upper end, and the roots ncv'ir the opposite extremity, as in 

 the cuttings above mentioned. The alburnum of the root 

 is also similar to that of otiitr parts o? the tree, except that 

 it is more porous, probably owing to the presence of abun- 

 dant moisture durmg the period in which it is deposited f. 

 And possibly the same cause may retain the wood of the root 

 permanently in the state of alburnum; for I have shown, in 



' Philosophical Tranoactions for 1805. f Ibid, for 1801. 



a former 



