<2QQ motion of the sap, 



Experiments In the fucceeding tyring, the buds vegetated flrongly, both 



and observations at tne proper anc j at the inverted ends of the layers, as the 

 on the motion or . r r . f „ , , , • r 



the fap in trees, experiments ot Hales and du Hamel had given me realon to 



expeft; and, in one inftance, the bud at the inverted end of 

 the layer grew with greater vigour than that at. its proper end : 

 but the growth of thefe buds was not the object which I had 

 in view. 



I have already ftated, that nearly an inch of wood was left at 

 each end of every layer, beyond the bud ; and, to this wood, at 

 the inverted ends of the layers, my attention was chiefly direct- 

 ed : for, if the veflels of the bark poflefled the powers I attributed 

 to them, I concluded that the fap would be impelled to the in- 

 verted ends of the layers, and be there employed in the pro- 

 duction of new wood, and roots ; and, in this, my expectations 

 were not difappointed. At the proper end of the layers, the 

 wood immediately beyond the buds became dry and lifelefs, 

 " early in the fucceeding fummer ; the ftems alfo, between the 

 buds and the mould in the pots, increafed in fize as ufual ; and 

 nothing peculiar occurred. But, at the inverted end, appear- 

 ances were extremely different : new wood here accumulated 

 rapidly beyond the buds, and numerous roots, of confiderable 

 length, were emitted, whilft no fenfible growth took place be- 

 tween the bafe of the young flioots and the mould in the pots. 

 It having been proved by Du Hamel, that inverted parts of 

 trees readily emit roots, I expected to derive further information 

 from cuttings of this kind : I therefore planted, in (he autumn 

 of 1802, forty cuttings of the goofeberry-tree, and an equal 

 number of the common currant-tree; one half of each being 

 inverted. Of the former, not one of the inverted cuttings fuc- 

 ceeded ; whereas few of the latter failed ; and in thefe I had an 

 opportunity of obferving the fame accumulation of wood above 

 the bales of the annual fiioots, and the fame mode of growth, 

 in every refpect, as in the inverted vines; except that no roots 

 were emitted at their upper ends. The fame thing occurred, 

 without any variation, in inverted grafts of the apple-tree. 



If it be admitted, according to the theory I have on a former 

 occafion laid before you, that the fap defcends from the leaves 

 through the veflels of the bark, and that fuch veflels are, in 

 their organization, better calculated to carry their contents to- 

 wards the original roots than in theoppofite direction, it will be 

 extremely eafy to explain the caufe of the accumulation of 



wood. 



