58 EPIDERMAL TISSUE.—EPIDERMIS. 
is generally described as consisting of two parts; namely, of an 
inner portion called the Epidermis, and of an outer thin pellicle 
to which the name Cuticle has been given. 
a. Epidermis.—This consists of one (figs. 95, e, and 123, a), 
two (fig. 124, a, a), three (fig. 125, a), or more layers of cells, 
firmly united together by their sides, and forming a continuous 
structure, except at the points where it is perforated by the 
stomata, presently to be described (jigs. 131, s, and 132, s). 
These cells are generally of a flattened tabular character (figs. 
Fic. 120. Fic. 121. Fie. 122. 
Fig. 120. Epidermal tissue from the leaf of the Iris (Iris germanica). p, p. 
Cuticle. s, s,s. Oval stomata, e, e. Epidermal cells. After Jussieu. 
Fig. 121. Epidermis of the Maize. a, a. Oval stomata. 06, 6. Zigzag reti- 
culations formed by the sides of the cells, Fig. 122. Sinuous epidermis 
with stomata, from the garden Balsam. 
123-127), the sides of which vary much in their outline ; thus, 
in the epidermis of the Iris, and many other plants, they are 
elongated hexagons (fig. 120, e, e); in that of the Maize they are 
zigzag (fig. 121, b, b) ; while in the garden Balsam, Madder, and 
Fie. 1: the common Polypody, they are 
1G. 123. . . 
very irregular or sinuous (fig. 
g g 122); and in the epidermis of 
other plants we find them 
square, rhomboid, &c. 
Ordinarily in European plants 
and in those generally of cold 
and temperate climates, the epi- 
Fig. i geonlon of thie leaf of dermis is formed of but one row 
tie Maize showing theepitermis¢-4 of cells ; but in tropical plants 
jecting hairs, g, g. we frequently find two, three, or 
more rows of cells, by which 
provision such plants are admirably adapted, as will be after- 
wards explained, for growth in hot dry climates. 
The upper walls of the epidermal cells are generally much 
thickened and chemically altered, or cuticularised as it is termed 
