ANATOMY AND PHYSIOLOGY OF PLANTS. 229 



epidermis is, to prevent the action of the atmosphere 

 from destroying the plant, by an undue influence on the 

 vitality of the inner bark. 



If it so happen, that the inner bark should be injured to any great 

 extent, so that the air gets access to it, exfoliation and the death of 

 the part and sometimes of the whole plant follow, the cuticle form- 

 ing, as it were, a fine but essential barrier between life and de- 

 struction. 



ON THE CONSERVATIVE ORGANS. 

 1. We have hitherto given a general outline of 

 the simple textures which enter into the composition 

 of vegetables. We have now to consider the structure 

 and use of the* conservative organs, formed more or less, 

 by a combination of the elementary textures. 



2. The roots of plants, to the most common observer, 

 must appear of a very different structure ; but we will 

 first repeat, most roots are divided into the main body or 

 .caudex, and the radicula; or rootlets. 



The varieties in their figure have been noticed in the enumeration 

 of their names, and other peculiarities mentioned in the terminalogy 

 or Language of Botany. 



3. With respect to structure, the body of the root of 

 trees, may be regarded as a production and elongation 

 of the trunk beneath, and is constructed of the same 

 textures, disposed nearly in the same manner. 



Exteriorly is placed the cuticle, beneath which is the cellular 

 X 



