THE CUTICLE AND EPIDERMIS. 65 



surface is charged with earthy particles which it deposits, 

 where it is evaporated; and that, in consequence, the 

 memhrane where the evaporation takes place must be- 

 come denser. 



The cuticle is naturally transparent, and nearly white ; 

 all the colours of the leaves, branches, and flowers, are 

 due to the nature of the substances contained in the 

 parenchyma; the cuticle, however, slightly influences 

 the colouring, either by the degree of its transparency, 

 or by its adhesion being more or less strong with the 

 cellular tissue, or, perhaps, also, by the white or yellowish 

 tints it gives to some species. It influences, also, by its 

 peculiar nature, the smooth or rough appearance of the 

 organs. 



At the time when an organ begins to be exposed to 

 the air, the cuticle usually presents then all the stomata 

 and hairs which it is accustomed to bear ; they c.re, con- 

 sequently, very close to one another, and as the surface 

 increases, they become more distant ; wherefore old leaves 

 are, in proportion, less hairy than those which are young. 

 This effect is also due, in several cases, to the natural 

 fall of the hairs. 



When the cuticle is observed with a microscope, or 

 strong lens, we see a network of lines which form the 

 spaces, either parallelogram-shaped, as in the Narcissus 

 and the Oat, or angular, as in the Lily, or curiously 

 waving, as in Ranunculus repens, and Galium aparine. 

 These lines often resemble simple threads ; they also 

 frequently appear double ; whence we presume that they 

 are hollow, and form a system of cuticular vessels. Hed- 

 wig, Kieser, and Amici, maintained this opinion, contrary 

 to that of many other anatomists. It is believed that 

 these vessels serve for evaporating the water ; but they 

 exist in almost the same number on the surfaces which 

 evaporate very little, as on those which evaporate much. 



VOL. I. F 



