OF THE CUTICLE OR EPIDERMIS. 19 



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 accommodate itself only to the natural 

 growth of the plant, not to any monstrosities, 

 and those lumps cause it to burst; just as it 

 happens to ripe fruits in very wet seasons. 

 Their cuticle is constructed suitably to their 

 usual size or plumpness, but not to any im- 

 moderate increase from too great absorption 

 of wet. If the cuticle 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 veoe- 

 table body, But though so accommodating 

 in those parts where it is wanted, on the old 

 trunks of most trees it cracks in every direc- 

 tion, and in many is entirely obliterated, 

 the old dead layers of their bark performing 

 all the requisite offices of a cuticle. 



