60 EPIBLEMA.—CUTICLE. 
kinds which are contained in the cavities of the subjacent 
parenchymatous cells, and which show through the transparent 
epidermal cells. In the walls, however, of the epidermal cells 
of many plants, waxy matter is contained ; in those of Chara 
and Nitella; carbonate of lime; and in those of the species of 
Equisetum, and of the Grasses generally, silica is met with in 
such abundance that, if the organic matter be removed by the 
agency of heat or acids, a perfect skeleton of the structure will 
be obtained. 
The epidermis covers all the young parts of plants which 
are directly exposed to the air, except the stigma in Flowering 
Plants, and it is in all cases absent from those 
Fie, 128, which live under water. No true epidermis 
is to be found in Thallophytes. The epider- 
mis which at first covers the young stem and 
branches of trees is replaced at a subsequent 
period by the corky layer of the bark. 
The roots of plants are invested by a 
modified epidermal tissue to which the term 
Epiblema has been given by Schleiden ; this 
name is, however, now but rarely used. It 
consists of cells with thin walls, without 
stomata, but possessing cellular hair-like pro- 
longations termed fibrils or root-hairs (fig. 128). 
b. Cuticie.—This consists generally of a 
thin transparent pellicle, which covers the 
entire surface of the epidermal cells (figs. 120, 
p, p, and 126, a) with the exception of the 
openings called stomata (fig. 129); and it 
Fig. 128. Fibrils or also forms a sheath over the hairs (fig. 129). 
root-hairs on the Not unfrequently the cuticle becomes of 
surface of a young : : : : = 
root, considerable thickness, as in the epidermis 
of the upper surface of the leaf of Cycas (fig. 
130, a). The cuticle is formed on the outer walls of those cells 
which are exposed to the chemical influences of air and light. 
Fie. 129. Fre. 130, 
Fig. 129, Cuticle of the Cabbage, showing that it is perforated by the 
stomata, and forms sheaths over the hairs.——Fig. 130. Vertical section 
through the epidermis, b, of Cycas revoluta, showing that itis covered bya 
thickened cuticle, a. After Schleiden. 
The cell-wall in such a position becomes greatly thickened and 
altered in its texture ; so much so that the outer part is clearly 
