OAKS. t 321 



its object were accomplished. The ring of pellicle 

 next to it is the young wood, which may be ob- 

 served shooting as the season advances, the external 

 ring is the bark, and the pulpy matter between is 

 the substance furnished by the roots, and prepared 

 and also in part furnished by the leaves, out of 

 which the wood and bark are forming. All these 

 parts are exclusive of the epidermis, or mere 

 external covering, which merely serves to protect 

 the other parts from external interruption or in- 

 jury. [By the way, the possession of a protecting 

 epidermis is one of the best popular means of 

 distinction between organic and inorganic beings, 

 in those obscure species in which they resemble 

 each other the most.] 



At the close of the season, the whole of the 

 cambium, or changeable pulpy matter, is formed 

 into wood and bark, which adhere firmly to each 

 other at the line of separation ; and when that is 

 accomplished, the leaves are of no farther use, and 

 they change colour and fall off; for though there 

 are vessels apparently of a woody texture in the 

 leaves, they are not the product of the same action 

 as the wood of the tree. That action extends only 

 to the base of the petiole, or foot-stalk of the leaf, 

 and as a pellicle of epidermis gradually forms upon 

 that, as it becomes complete, the leaf separates 

 without a wound. Whenever indeed the action 

 of a tree ceases, whether naturally at the season 

 when it passes into repose, or in consequence of 

 an external check, such as transplanting it while 

 in leaf, the last action of the tree the effort of 

 nature by which , it preserves its vitality is the 

 formation of that epidermis between the twigs and 

 the petioles of the leaves. If the tree succeeds com- 



