LOSS OF WATER 
in many forms and disguises, and readily adjusting itself 
to wide variations in its surroundings. By virtue of this 
characteristic, it helps to enable the plant as a whole to 
become adapted to its surroundings. For the present 
purpose, we are primarily interested in leaves as foliage. 
33. Internal Anatomy of the Leaf-blade. If we take 
any convenient foliage-leaf, such as, for example, a leaf 
FIG. 23. Leaf of a live-for- 
ever (Sedum sp.), with a por- 
tion of the epidermis peeled 
back. Underneath the epi- 
dermis is the mesophyll. 
FIG. 24. Mullein (Verbascum Thap- 
sus). L, cross-section of leaf- blade, 
showing relative thickness of layer of 
epidermal hairs; H, a single hair from a 
leaf (greatly magnified). 
of the common lilac, we may readily demonstrate, with 
the aid of a scalpel or sharp knife, that the surfaces of 
the blade are covered with a thin skin or epidermis, 
which may be peeled off (Fig. 23), disclosing the mid-leaf 
substance (mesophyll'), lying between the upper and the 
lower epidermis. In many leaves (for example, those of 
