S5 



CHAPTER V. 



OF THE BARK. 



UxDER the Cellular Integument we find the 

 Bark, consisting of but one layer in plants or 

 branches only one year old, and often not 

 distinguishable from the wood. In the older 

 branches and trunks of trees, it consists of as 

 many layers as they are years old, the in- 

 nermost being called the liber ; and it is in 

 this layer only that the essential vital func- 

 tions are carried on for the time being, 

 after which it is pushed outwards with the 

 Cellular Integument, and becomes like that 

 a lifeless crust. These older layers, however, 

 are for some time reservoirs of the peculiar 

 secreted juices of the plant, which perhaps 

 they may help to perfect. 



In some roots the bark, though only of 

 annual duration, is very thick; as in the 



