320 CONSERVATIVE ORGANS. JJLECT. VII. 



Laburnum, it is composed of the epidermis simply 

 covering a layer of an irregularly cellular or 

 spongy character ; in the Laurustine, Viburnum 

 Tinus, of one layer of cells covered by the epider- 

 mis ; and the same is the case in the Vine, except 

 that the cells are extremely minute, and oblong in 

 the length of the stem, having the appearance of 

 vessels in the transverse section. These and similar 

 varieties in the structure of the cuticle account 

 for the want of coincidence in the descriptions of 

 authors. 



The true epidermis or exterior layer of the 

 cuticle is necessarily cribriform, whether it act as 

 an exhaling or an absorbing surface ; and the man- 

 ner in which the pores are arranged, does not 

 differ less, in different plants, than the structure 

 of the interior layer. It is frequently studded 

 with hairs, glands, and prickles ; but, as these 

 are not peculiar to stems, their particular struc- 

 ture shall be demonstrated, when we treat of the 

 general vegetable appendages. In young and 

 succulent shoots, the cuticle is generally almost 

 colourless, and semi-transparent, transmitting 

 the green colour of the exterior part of the cel- 

 lular integument over which it lies; but it becomes 

 opaque and coloured by age, or rather on losing 

 its vitality ; for, as it is annually reproduced, on 

 the ligneous stems under consideration, the old 

 layer, if it does not fall off, cracks and is pushed 



