COURSE OF THE SAP. 59 



one h'^nd is added to the wood, and the liher, or inner 

 layer of the bark, is on the other annexed to the layers 



he concludes that the celUilar substance gives passage to the 

 sap. Though the conclusions of this paper can hardly be ad- 

 mitted in their full extent, it is nevertheless probable that the 

 cellular substance of the trunk may exert a vicarious office and 

 afford a temporary passage to the sap when its proper vessels 

 are interrupted. 



If a ring of bark only is removed, the sap may continue to as- 

 cend with freedom, but is obstructed in its descent. This ope- 

 ration may be performed with perfect safety to the tree, provid- 

 ed the ring taken out is sufficiently narrow, so that the space 

 may be filled up with new bark from above, during the same 

 season. In trees which form new bark readily upon the surface 

 ef the alburnum, as in the instance page 45, the whole trunk 

 may be stripped with impunity, and sometimes with advantage 

 to the future health and productiveness of the tree. It is how- 

 ever often necessary that the trunk should be artificially covered 

 during the reproduction of the bark Du Hamel mentions trees 

 in perfect health 15 or 18 years after having been thus depriv- 

 ed ot their barl-;. 



Some improvements in the cultivation of fruits have been 

 founded upon the intersection of the bark. Buffon removed a 

 girdle of bark. 3 inches in width, from the trunks of some fruit 

 trees, and found that they produced blossoms and fruit 3 weeks 

 sooner than the other trees in their neighbourhood. Mr Wil- 

 liams in the Transactions of the Horticultural Society, states that 

 grapes came to maturity much earlier, were larger, and better 

 fla>.oured, when a small circle of bark, one or two eighths of an 

 inch in width, was removed from around the alburnum of the 

 fruitful branches, while the fruit was in its young state. This 

 method is annually practised in the vicinity of Boston by differ- 

 ent individuals with the best success. The explanation depends 

 on the theory of Mr. Knigiit, the sap being interrupted in its de- 

 scent, and confined to the branches above the incision, so that ^ 

 greater quantity of it goes to nourish the fi-uit.] 



