cb:. ir. 



COURSE OF THE SAP. 



69 



which sheathed the sides of the ringed branch, have 

 been kept moist with sap, except by lateral transmission 

 from one layer of wood to the other, independent of 

 the longitudinal channels of the pith ? And that the 

 upward sap is supplied even to the bud by the wood, 

 and not by the pith, I think we may argue from the 

 success of budding. In this beautiful process, the pith 

 of the bud is totally disconnected from any other centi^al 

 pith. It is placed on the side-wood, and can only 

 receive the upward sap by lateral transmission from 

 that side-wood. The same may be said of the scion in 

 crown-grafting ; its pith is quite separated from any 

 central pith. 



Dutrochet has, however, started the idea, that the Do the cen- 



'''"^ piths 



outside of each annual growth of wood is a pith, of budded 



^ ^ _ ' buds, 



which we have called concentricai piths, to distinguish grafts, and 

 them from the central pith ; and it may be argued that coppice^-^ 

 it is possible that the central pith of a budded bud, or municate 



with 



of the scion in crown-graftmg, may communicate with Dutrochet's 

 a concentricai pith, and that the central pith of a shoot p^^^' 

 of a pollard, or of a coppice-wood stool, may originate 

 in a concentricai pith. If the yearling shoots of pol- 

 lards or coppice-stools are knocked off so as to have a 

 part of the old wood on which they grew still attached 

 to them, and if the lower ends of these shoots are split 

 down the piths into the old wood, the piths will be 

 seen each to originate in a point surrounded by the old 

 wood, and in conjunction with no other central pith. 

 But I should rather say that the central pith of each 



concentricac 



s? 



