ANxlTOMY OF PLANTS. 



187 



in it. This is a short explanation of the artificial production 

 of trees, to which we shall again return, (306.) 



The bark cannot arise directly from any of the layers that 

 lie beneath it. It owes its origin entirely to the generative 

 sap, and may be reproduced when this flows outwards. 



As the bark forms the place of deposition for the peculiar 

 juices [of the plant, and as these are frequently of a thick, 

 hard, balsamic or oily nature, it becomes by these means a 

 sluggish conductor of heat, and protects the interior layers 

 from the cold as from other external causes of injury. It 

 maintains also the connection of all the interior layers with 

 each other, by means of the radiated cellular vessels, which 

 proceed from it to the pith. 



Great as these benefits are which the bark affords especial- 

 ly to the shrubby plants, its removal and the wounding of the 

 rind are not however attended with immediate danger to the 

 life of the tree. On the contrary, when the peeling of the 

 bark is effected cautiously, the young layers of inner bark 

 and of wood, which lie under it, arrive much earlier, though 

 rather violently, at the state of hard and perfect wood, from 

 the influence of the air. Even the fruitfulness of the tree 

 may be encreased by this peeling of the bark, because the in- 

 ner bark and the alburnum, laid open to the direct influence 

 of the atmosphere, are more powerfully excited, and the juices 

 become more concentrated. Nevertheless, a peeled tree of 

 this kind must necessarily die sooner, unless its superabun- 

 dant vital power affords an opportunity for the production of 

 new bark from the wood. 



295, 



The layer which lies under the bark, and which is called 

 the Inner Bark (liber), is readily distinguished by its whit- 

 ish colour, and by its distinctly fibrous and often mesh- 

 formed structure, as well as by its great flexibility, its tough- 

 ness, durability, and power of resisting the ordinary causes of 

 destruction, especially putrefaction. A closer examination 



