318 CONSERVATIVE ORGANS. [LECT. VII. 



which is the cuticle ; 2. a cellular layer which 

 adheres, although not very firmly, to the cuticle, 

 and is named the cellular integument ; 3. a vas- 

 cular layer ; and 4. a whitish layer, apparently 

 of a fibrous texture, which is the inner bark ; and 

 which, as we shall afterwards find, is of a more 

 complicated structure than the other layers. We 

 shall now view these parts separately under the 

 microscope. 



1. The Cuticle. Before demonstrating the 

 structure of this part, it is necessary to remark, 

 that I prefer the term cuticle to that of epider- 

 mis, in reference to the exterior covering of stems 

 and branches, in order to distinguish it from the 

 thin unorganized pellicle which has already been 

 described (page 93) under the name Epidermis, 

 as one of the general components of the vege- 

 table structure; and which is, in fact, the ex- 

 terior part of the cuticle. 



The cuticle may be raised from the cellular 

 integument by the point of a knife, and this is 

 the best method to obtain it for minute examina- 

 tion *. When thus separated and placed under 

 the microscope, it appears, to consist of two layers ; 



* Some authors recommend boiling the shoot or cutting, in 

 order to separate the cuticle ; but although it is thus readily 

 separated, yet, the boiling coagulates and thickens its sub- 

 stance, rendering it opaque and destroying its natural structure. 



