328 ON THE CUTICLE OF PLANTS. 
sulphuric acid, and is not colourable by Iodine is perfectly 
even. Since the cuticle increases in thickness with age, and 
this increase can only take place by the change of the coat 
which dissolves in sulphuric acid into the cuticular mass; 
this change appears to consist not merely in a chemical 
metamorphosis of the cellular membrane; but also to be 
combined with a change of structure. The membranes | 
changed into cuticle, appear in consequence of this meta- 
morphosis as a peculiar organ, distinct both as to substance 
and structure from the epidermal cells. The portion of the 
cuticle arising from each epidermal cell is in so intimate 
a connexion with the adjacent portions arising from other 
epidermal cells, that not only in many cases the eye cannot 
trace the commissures ; but also the growth to which those 
raised lines over their origin is in common. Thus the 
cuticular membranes arising from different cells run together 
into a common compound organ, somewhat in the same way 
as the lateral walls of a long row of vascular cells after the 
disappearance of their dissepiments form one compound 
organ; viz. a vessel This circumstance justifies us com- 
pletely in distinguishing the cuticle by a particular name as à 
distinct coat from the epidermis, though I hope the above 
observations have proved that it is formed of the outer walls 
of the epidermal cells themselves. 
Tübingen, July 1, 1842. 
ExeLANATION Or PLATE. (Tas. XIII.) 
1. Epidermis of leaf of Elymus arenarius 
2. ditto Helleborus foetidus 
3. ditto Dianthus plumarius 
4. ditto Iris fimbriata 
5. ditto of stamen of Tulipa Gesneriana — 
6. ditto of leaf of Arbutus Unedo 
7. ditto Aloé obliqua 
8. ditto (treated with sulphuric acid) Hakea pachyphylla — 
9 
. ditto of leaf of Phormium tenax . 
10. ditto from the other side of the leaf. zr. 
