94 LETTER XXXIV. 



leaf is not a thin homogeneous mass of firm pulp, nor 

 a confused mixture of pulp and fibre ; but a most 

 elaborate, and yet simple apparatus, in which every 

 part is adjusted with the utmost nicety ; that, more- 

 over, thin as the leaf appears, it is actually composed of 

 at least nineteen or twenty layers of cells, besides a large 

 line of vessels in its middle. That you may under- 

 stand this the better, let me refer you to the accompa- 

 nying sketch of such a slice as I have been talking 

 of {Plate XXW.fig. 1.). Let A be the upper sur- 

 face, and B the lower surface. The upper surface is 

 protected by a very thin, transparent, rather tough, 

 homogeneous membrane (a.), which overlies all the 

 cuticle, except perhaps the stomates, and does not 

 appear to be in any degree cellular. It is not impro- 

 bable that a similar membrane is found on the upper 

 side of all leaves ; it has been seen in the Cabbage, 

 the Foxglove, &c. but has not hitherto been much 

 investigated. On the lower surface of Dionsea-leaf, 

 this membrane is absent. Immediately beneath the 

 membrane, comes the skin or cuticle (Z>.), which, al- 

 thouo'h it may be stripped off, nevertheless consists of 

 long, flat, thick-sided cells, adhering very firmly 

 to each other. This you will see more distinctly, 

 if you strip ofl^ a piece of the skin fi'om another por- 

 tion of the leaf, and place it in water, in the same 

 manner (fys. 2 & 3.). 



From the cuticle of the upper surface there spring, 

 at very short intervals, little red glands (Jig. l.dd d.), 

 which grow from minute, green, oval spaces, composed 

 of two, parallel, green cells, and resembling stomates. 



