312 COMPOSITE ORGANS. CHAP. II. 



tach themselves to make way for a new layer, which 

 on its first exposure to the air is of a fine and deli- 

 cate green. If this layer is now stripped off, it will 

 be found to invest one or two more which are yet, 

 indeed, colourless and imbedded in pulp, heing only 

 in a state of preparation for future exposure, when 

 the layer that is now exterior shall have detached 

 itself in its turn. 



The above should, perhaps, be regarded as a suc- 

 cession of individual cuticles, consisting each of a 

 single layer, which their regular and consecutive 

 detachment seems to indicate, rather than as an 

 individual cuticle consisting of several layers ; 

 though there are cases in which several layers are 

 obviously incorporated so as to form in the aggre- 

 gate only an individual epidermis. Perhaps one of 

 the best examples of an epidermis consisting of 

 several layers, is that of the epidermis of the in- 

 terior and sheathing part of the leaf of Iris Pseuda- 

 corus or Yellow Iris, of which if you detach several 

 portions, some will be found to consist of more and 

 some of fewer layers 5 an d some apparently of only 

 one layer of net-work, either because the epidermis 

 is so constituted in different parts of the leaf accord- 

 ing to their distance from the base, or because 

 the layers have been forcibly separated in the act 

 of stripping them off. In the portion apparently 

 consisting of only one layer, the degree of trans- 

 parency is greater, and the hexagonal meshes of the 

 net-work are distinctly marked ; but in the portion 



