CHAPTEH T. 



OF THE BAHK. 



Under the Cellular Integument we find the Bark, con- 

 slstint^ of but one layer in plants or branehes 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 innermost be- 

 ing called the liher ; and it is in this layer only that the 

 essential vital functions are carried on for the time being, 

 after which it is pushed outwards with the Cellular In- 

 tegument, 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 dura- 

 tion, is very thick ; as in the Carrot, the red part of 

 which is all bark. In the Parsnep, though not distinctly 

 coloured, it is no less evident. In the Turnip it is 

 much thinner, though equally distinct from the wood or 

 body of the root. 



The Bark contains a great number of woody fibres, 

 running for the most part longitudinally, which give it 

 tenacity, and in which it differs very essentially from the 

 parts already described. These woody fibres when 

 separated by maceration exhibit in general a kind of 

 nel-work, and in many instances great regularity and 

 beauty of structure. In a family of plants to which 

 the Mezereon belongs, the fibres of the inner bark have 

 a beautiful white shining appearance like silk. In one of 

 this tribe, a native of Jamaica, and ciilled Lace Bark, 



