ON THE CUTICLE OF PLANTS. 325 
most is not coloured by iodine, while the more external 
layers become brown. Between these layers and the primary 
wall, we find a more or less thick, light coloured homoge- 
neous stratum. If we compare this structure with the epi- 
dermis of Taxus baccata, it cannot be doubted that this middle 
homogeneous layer consists of the outer secondary mem- 
branes of the epidermal cells, which have contracted so 
intimate a union with one another, that the limits between 
the different cells are no longer visible. 
B. If in the preceding case, together with a visible lami- 
nation of the wall of the cells, they are combined laterally to 
Such a degree as to lose all trace of their original division, 
in other cases, on the contrary, in combination with a dis- 
tinct preservation of the boundary lines between the different 
cells, we have a perfect amalgamation of the different yellow- 
coloured coats of the same cell, e. g. Phormium tenax, Aloé 
margantifera. 
C. Lastly it happens, that this intimate amalgamation, as 
well of the coats of each individual cell, as of the different cells 
one with another takes place to such a degree, that the cuticle 
forms one uniform mass. This intimate amalgamation takes 
place only in the outer layers of the cuticle, while, in the 
inner layers a distinction of individual cells and membranes 
is possible, as in Ephedra Distachya, Ilex Agnifolium ; 
sometimes it is found in the entire cuticle, as in Phormium 
tenax,* Lomatophyllum borbonicum, Ruscus aculeatus, Cycas 
revoluta. 
With this last form we have arrived at a modification of 
the euticle, which agrees in reality with the cuticle of soft 
herbaceous parts, with which we commenced. In either case 
the cuticle appears as an homogeneous membrane which 
mvests the epidermal cells on their outer side, with the single 
exception, that in the thick coriaceous leaves of a Cycas they 
* Though the leaf of this plant has no upper or under side; but both 
Surfaces of the leaves correspond with the under side in other plants, the 
epidermis of either side is not exactly of the same nature. This observation 
applies also to many species of Iris. | 
