324 ON THE CUTICLE OF PLANTS. 
it is necessary to search for examples which are less ambi- 
guous. Such are afforded by the following observations. In 
the epidermis of the stem of Kleinia neriifolia, as in Hoya 
carnosa, the inner uncoloured coat, which is so easily taken 
for the whole epidermal cellis wanting ; and the incrassated 
outer membrane, which is turned brown by iodine, is very 
clearly seen to be composed of many coats lying one over the 
other, which are deposited on the outer wall of the cell 
within its cavity, and by which the continuation of the lateral 
walls to the outer surface, as one membrane is clearly proved. 
The same appearance is exhibited in the epidermis of the 
leaf of Hakea pachyphylla (in which the inner coat is really 
present, though like the true cuticle, it assumes a yellow tinge 
with iodine, and is proved by its dots to be a secondary 
membrane), if the epidermis is treated with sulphuric acid, 
(fig. 8), for the mass deposited in the cavity of the cells is 
then seen evidently to consist of coats. In the epidermis of 
Hakea gibbosa the laminated structure is not only clear with- 
out the application of sulphuric acid in the greatest part of 
this deposited mass, but there are found also in it a great 
number of radiating narrow dot-canals which leave no doubt 
as to its real nature. In many cases, as in Taxus baccata, 
the different colouring also which the inner and outer por- 
tions of the cuticle assume from the action of iodine indicate 
a similar lamination. 
If these cases shew with the most complete evidence, that 
the cuticle is formed of the outer thickened walls of the epi- 
dermal cells, in many other plants possessing a thick cuticle 
it is not easy to ascertain the fact, since the different parts | 
which compose the cuticle are more or less perfectly com- 
bined into an homogeneous mass. 
We must distinguish here some modifications. 
A. In many plants, e. g. Sanseviera zeylanica, Nerium 
Oleander, Agave lurida, the primary membrane is recog- 
nisable as a distinct stratum, as also many layers of Se^ we 
condary membrane on the outer wall, and the outer half 
the lateral walls of the epidermal cells, of which the inner- 
