50 
ORGANOGRAPHY. 
BOOK I. 
lular state is distinctly visible upon a section (Plate I. fig. 2. a ) ; 
it even consists occasionally of several layers of vesicles, as 
in the Oleander and many Orchidaceae, and it varies in the 
density, form, and arrangement of its component cells in dif- 
ferent plants, according to the peculiar conditions to which 
they are exposed. 
External to the epidermis is a thin homogeneous membrane, 
formed of organic mucus (see page 1.) and overlying every 
part except the stomates and the stigmatic tissue. It was 
first observed by Adolphe Brongnlart in the Cabbage-leaf, af- 
terwards by Henslow in Digitalis, and by myself in Dionaea ; 
it has subsequently been the subject of more extended observ- 
ations, and appears to be a universal coating, which is even 
drawn over the hairs, as if to protect the tender cell form- 
ing their interior, and the plexus of capillary Cinenchyma, 
which is stationed on the outside of the walls of that cell. I 
have found this cuticular membrane on the delicate petals of 
Hydrotaenia Meleagris, from which it may be easily removed 
after maceration for a few days in spirit of wine ; and Ad. Brong- 
niart succeeded in separating it from the leaves of Potamo- 
goton lucens, after very long maceration in water. It is stated 
to be sometimes covered with a minute granular appearance, 
the nature of which is unknown, and which is not found at 
the lines indicating ^the place where the cuticle was pressed 
upon the united sides of cells. There are some good observ- 
ations upon this subject by M. Adolphe Brongniart {Ann. 
des Sc. 2 ser. I. 65.), who finds the cuticle by no means un- 
common ; and imagines that it overlies the stigma in Nym- 
• phaea and Mirabilis. It certainly does not cover the stomates, 
nor the glands found on the surface of the inside of the pitchers 
of Nepenthes. 
