OF THE CUTICLE OR EPIDERMIS. 33 



mal, a fine but essential barrier between life and de- 

 struction. 



Some have imagined that the cuticle gave form to the 

 vegetable body, because it sometimes being over tight 

 causes contractions on the stem of a tree, as in the 

 plum or cherry, and because it is found to be cracked 

 wherever an unnatural excrescence is produced on the 

 bark. No doubt the cuticle is formed so as to accom- 

 modate itself only to the natural growth of the plant, 

 not to any monstrosities, and those lumps cause it to 

 burvSt ; just as it happens to ripe fruits in very wet sea- 

 sons. Their cuticle is constructed suitably to their 

 usual size or plumpness, but not to any immoderate 

 increase from too great absorption of wet. If the cuti- 

 cle be removed from any part, no swelling follows, as 

 it would if this membrane only kept the tree in shape. 



The extension of the cuticle is astonishing, if we 

 consider that it is formed, as Grew well observes, on 

 the tenderest embryo, and only extended during the 

 growth of the plant, and that it appears not to have any 

 connexion with the vascular or living part of the vege- 

 table body. But though so accommodating in those 

 parts where it is wanted, on the old trunks of most trees 

 it cracks in every direction, and in many is entirely 

 obliterated, the old dead layers of their bark performing 

 all the requisite offices of a cuticle. 



M. Mirbel indeed, though he admits the importance 

 of this part in the several ways above mentioned, con- 

 tends that it is not a distinct organ like the cuticle of 

 animals, but merely formed of the cellular parts of the 

 plant dilated and muhiplied, and changed by their new 



