72 



COUESE OF THE SAP. 



PT. ri. 



any other part, and the pith-channel of the horse- 

 chestnut and ash is of the same size between any two 

 shoots as the pith-channel of the top of the lower 

 shoot. In these two trees, the pith of every shoot and 

 twig is snrmounted with cheesey pith ; so that every 

 bud is placed on cheesey pith, and is as much divided 

 from a spongy pith by a ' woody partition,' as the pith 

 is interrupted at each node or annual shoot by a 

 ' woody partition.' 



If De CandoUe's fact is true, that in the chestnut, 

 the ash, and the vine, ' the pith is interrupted at each 

 node or annual shoot by a kind of woody partition,' 

 if this fact of De Candolle's is true, what becomes of 

 his theory^ that the pith is the cotyledon of the bud ? 



I do not think it would be an improper description 

 of the piths of these trees to say that their spongy piths 

 begin with, or are seated on, cheesey pith, and end in 

 cheesey pith, on which the bud is seated. 

 Office of The only opinion which I should venture to ex- 



the pith • p 1 • 1 • 1 



not known, prcss, lu reierencc to the pith, is the negative one, that 

 no one has as yet discovered its offices. If this is so, 

 it is not saying much for our knowledge of vegetable 

 physiology. 



As the sap- Wcrc the upward sap supplied to each branch by 



dicinncls 



are general, longitudinal channels from the root, peculiar to that 



not pecu- 



inj'ir"°' pruning or cutting out of branches would 



th?suppiy benefit the leader and the remaining branches, 

 leaded, &c. The gTowtli of thcsc is, liowcvcr, increased by judicious 

 and gradual pruning, because the channels for the up- 



