CHAP: II.] 
COURSE OF THE SAP. 
81 
transmission from one layer of wood to the 
other, independent of the longitudinal channels 
of the pith ? And that the upward sap is sup¬ 
plied 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 
central 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 outside of each annual growth of wood is a 
pith, which we have called concentrical piths, 
to distinguish them from the central pith ; and 
it may be argued that it is possible that the 
central pith of a budded bud, or of the scion in 
crown-grafting, may communicate with a con- 
centrical pith, and that the central pith of a 
shoot of a pollard, or of a coppice-wood stool, 
may originate in a concentrical pith. If the 
yearling shoots of pollards 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 
Do the central 
piths of budded 
buds, grafts, 
and of the 
shoots of cop¬ 
pice-wood, 
communicate 
with Dutro- 
chet’s concentri¬ 
cal piths ? 
