418 



STRUCTUKE OF CUTICLE AND LEAVES. 



in the generality of Tropical species, there exist two, three, or 

 even four layers of thick-sided Cells ; this last number being seen 



Fig. 221. 



Fig. 222. 



Cuticle of Leaf of Yucca. 



Cuticle of Leaf of Indian 

 Corn {Zen Mais). 



Fig. 223. 



Portion of the Cuticle of the inferior surface of the Leaf of the 

 Apple, with the layer of Parenchyma in immediate contact with 

 it : — a, a, elongated Cells of the Cuticle overlying the Veins of 

 the leaf ; b, b, ordinary Cuticle-cells, overlying the Parenchyma ; 

 c, c, Stomata ; d, d, green Cells of the Parenchyma, forming a 

 very open network near the lower surface of the leaf. 



