114 



LETTERS ON TREES. 



smallest husli^ solely by their herbaceous layer of the liber, 

 annually produced at the inner surface of their bark. The 

 concentric layers of preceding libers constitute the mass of the 

 wood, a lifeless skeleton^ serving solely to support the new- 

 formed parts, and to conduct to them the juices by which they 

 are fed ; nor is it even necessary for these functions that this 

 should be in an entire state. Willows and chesnuts, when 

 quite hollow at the heart, still continue to grow with vigour ; 

 but in their soundest state strip them of their bark, and they 

 quickly perish. 



Thus reflection teaches us that the long life of the greater 

 part of trees, and the immortality which at first sight appears 

 to have been imparted to others, .... form in reality no 

 exception to the general law which destines every organised 

 individual to perish in determined course ; since we see .... 

 that the concentric layers which constitute the wood or heart 

 of the trunks of trees, are no other than the accumulated re- 

 mains of hy-gone generations^ in which vegetation and life are 

 entirely extinct. 



" This appears to us the true view of the natm-e of the life 

 and death of such beings as are constantly regenerated by the 

 successive evolution of continuous parts. 



And we may observe, that the liber which is formed on 

 the stem of a tree centuries old, if the treee have met with no 

 accidental injury to afi'ect its health, enjoys the vegetative 

 power in as full force as the liber which is formed on that of 

 the sapling ; and that a sound, well-grown scion from the aged 

 but healthy tree, affords as good a cutting for propagation as 

 that taken from the young one, so that the race might be 

 perpetuated by cuttings alone^ without the assistance of seeds. 

 From this we are entitled to conclude, that according to the 

 course of nature, the progress of regeneration by continuous 

 evolution would never be arrested.^ if the over-grown size of 

 the branches and stem, the hardening of the wood, and the 



