132 SEAT OF VEGETABLE LIFE. 



of these protuberances, is evidently similar to those 

 callosities formed at the base of cuttings, and therefore 

 it may be said to be an effort of the vital envelope to 

 produce new roots, instead of those from which the 

 communication is partially cut off by the ligature. 

 But admitting this, we are still in the dark respect- 

 ing which component it is that is thus obstructed in 

 its course. We might, indeed, bring forward a very 

 plausible idea of a modern writer to account for this 

 processional movement down the stems of trees, 

 which he attributes to the descending electrising 

 principle of the sun's rays ;" but we fear to quote, 

 lest we should err in referring to what we do not 

 clearly understand. 



The seat of vegetable life. Every developed mem- 

 ber of a tree is imbued with the vital principle in its 

 early existence, and retains it while in the act of ex- 

 pansion, but no longer. The bark is an exterior, and 

 the wood an interior increment ; both have been in- 

 flated into form, and forced into position by the life ; 

 but as soon as the form is complete, and the position 

 imposed, they are deserted by it, and when they cease 

 to partake of its influence entirely they succumb to 

 decay. Nothing shows the truth of this more de- 

 cidedly than the circumstance that if a tree were 

 divested of all its coats of bark but one, viz. the liber, 

 it would continue to live and even prosper ; and were 

 it possible to take out from a trunk the pith and al} 

 the concentric layers of wood save one, viz. the albur- 

 num, the tree would nevertheless continue to live 



