THE CUTICLE AND EPIDERMIS. 63 



not so. A gfeat number of leaves have the cuticle 

 marked with spaces, the borders of which are irregularly 

 wavy, and of forms which do not correspond with the cel- 

 lules of the same plant, (PI. 3. Fig. 1.) Those, also, which 

 present hexagonal forms, differ in size, or other circmn- 

 stances, from the cellules of the plant. Amici has given 

 several examples which confirm this mode of reasoning ; 

 and I have myself seen this fact in different plants, and, 

 in particular, in Tritoma Uvaria, (PI. 3, Fig. 4.) 



3d. The cuticle of ahnost all leaves presents here and 

 there pores, which are called Stomata ; their form is very 

 remarkable, and they do not exist on the membranous 

 pellicles which are formed on the parenchyma when the 

 cuticle has been removed: but, if this were only the 

 external wall of the cellules dried by the air, we do not 

 see, on the one hand, how the stomata could be formed 

 in the primitive cuticle, or, on the other hand, why they 

 could not be formed a second time, as the fu'st. 



4th. Keith, who has studied this subject, remarks, 

 that the cuticle exists in organs protected from the 

 action of the air, — as the internal parts of buds, where 

 one cannot conceive its existence by the theory of 

 Mirbel. 



5th. The same author also remarks, that the cuticle 

 of leaves is never reproduced ^vhen it is taken off; which 

 would happen if it were formed by the action of the air 

 upon the cellular tissue. 



It results from all these facts, equally true, that the 

 cuticle of leaves appears to be formed of a layer of cel- 

 lules, usually differing in form, and various other cir- 

 cumstances, from those of the common parenchyma ; 

 and that it may on this account be considered as a kind 

 of peculiar membrane, independent of the subjacent 

 cellular tissue ; — that when it is removed by tearing it, 

 the external wall of the cuticular cellules is only 



