SECT. II. ASCENT OF THE SAP. J23 



cut off, the branch corresponding to it will be con- 

 3iderably affected by the loss. 



But a very little reflection will serve to show that Proved, 

 the above premises are by no means sufficient to 

 justify the conclusion that has been drawn from 

 them: for although the tracheae as they exist in 

 the living plant are not twisted one about another, 

 but only tangent or collateral, yet the longitudinal 

 film of which they are composed is itself perfo- 

 rated with pores, or interrupted with meshes, as 

 may be seen by inspecting those of the leaf-stalk 

 of the Artichoke ; so that it is very possible they 

 may be occasionally tangent, where the pores or 

 meshes shall meet. And the degeneration of the 

 root or branch in the cases above stated is just 

 what would have taken place, upon the supposition 

 that a lateral communication exists : for if by 

 default of nutriment in the direct line, any root 

 or branch is supposed to be nourished merely by 

 means of the sap that may be transmitted to it 

 through the lateral apertures, its growth will of 

 necessity be less luxuriant, because its supply is 

 now rendered both more scanty and more difficult 

 of access. So that we have in this argument a 

 refutation of the very doctrine it was meant to sup- 

 port ; for if the root or branch thus treated does 

 not absolutely die, it is a proof that lateral commu- 

 nication must exist. 



But the existence of a lateral communication 

 between the vessels conducting the sap has been 



