EPIDERMIS. 59 
(see Cuticle), by which the cell-walls are rendered impervious 
to moisture, and thus adapted to protect the more tender cells 
beneath from an undue loss of moisture from the scorching heat 
Fie. 124, Pre. 125; 
Fig. 124. Vertical section through the leaf of a Banksia. a, a. Epidermis 
with two rows of cells. c. Spongiform parenchyma, 6. Hairs which are 
contained in little depressions on the under surface of the leaf, and at 
whose base peculiar stomata are found. After Schleiden.— Fig. 125, 
Vertical section through the leaf of Oleander, showing the epidermis, «, 
composed of three layers of thick-sided cells, and placed above a compact 
parenchyma of oblong cells, After Brongniart, 
of the sun. This thickening of the upper walls of the epidermal 
cells may be especially observed in Jeaves of a leathery or 
hardened texture, as in those of the Oleander (jig. 125, a), 
Aloes, Hoya (fig. 126, a), Box, and Holly, and in the succu- 
lent green stems of the Cactacez (jig. 127, a). 
Fie. 126. Hicai2%, 
Fig. 126. Vertical section of the epidermis of Hoya carnosa treated with 
caustic potash. a. The detached cuticle. 6. The thickened cuticularised 
layers of the outer walls of the epidermal cells. After Mohl. Fig. 
127. Vertical section through the epidermis of the stem of a Cactus, a. 
The thickened cuticularised upper walls of the epidermal cells, 
The epidermal cells are generally colourless, but in some 
cases they contain coloured fluids, and very rarely chloro- 
phyll; hence the green and other colours which leaves and 
other organs assume are due to colouring matters of various 
