MINUTE STRUCTURE OF LEAVES to? 
to soak through it with ease. Merely examining sections 
of the various kinds of epidermis will not give nearly 
as good an idea of their properties as can be obtained 
My, 
r~}) 
by studying the behavior during severe droughts of 
those which have not. Fig. 121, however, may convey 
some notion of the difference between the two kinds of 
cases, as in the india- TT LE 
rubber tree, the ex- | 
(and often two or LX A CS) 
three layers of cells j= Nir S 
filled with water, and oe ( 
thus serve as reser- —<—- Pay oe rac. Sade Van 
plants which have strongly cutinized surfaces and of 
structure. In most c 
Wi 
ternal epidermal cells 
beneath these) are 
voirs from which the Fiq. 121. — Unequal Development of Cuticle 
outer parts of the leaf by Epidermis-Cells. 
A, epidermis of Butcher’s Broom (Ruscus); B, 
and the stem are at epidermis of sunflower; c, cuticle; e, epi- 
times supplied. dermis-cells. 
In many cases, noticeably in the cabbage, the epidermis 
is covered with a waxy coating, which doubtless increases 
the power of the leaf to retain needed moisture, and 
which certainly prevents rain or dew from covering the 
leaf-surfaces, especially the lower surfaces, so as to hinder 
the operation of the stomata. Many common plants, like 
the meadow rue and the nasturtium, possess this power 
to shed water to such a degree that the under surface of 
the leaf is hardly wet at all when immersed in water. 
The air-bubbles on such leaves give them a silvery 
appearance when held under water. 
