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 



