XEROPHYTES AND HALOPHYTES. 



321 



ment of two or more layers of epidermal cells (fig. 370) j or 

 the excretion of wax or of varnish upon the surface of the epi- 



Fig. 359. — Transverse section of a leaf of a heath (Tylanthus ericoides), showing 

 revolute form. The stomata are on the under (concave) surface among the hairs, 

 which still further impede the transpiration. Magnified 130 diam. — After Kerner. 



dermis. The latter often becomes very thick, giving to the 

 leaves a shiny appearance. Wax is usually in the form of a 



Fig. 360. 



Fig. 362. 



Fig. 360. — Prickly pear {Opuntia vulgaris) with flattened jointed stem and no 



leaves. Ahout one fourth natural size. — After Frank. 

 Fig. 361. — Multicellular hairs of edelweiss. Magnified about 50 diam. — After Kerner. 

 Fig. 362. — Silky unicellular hairs of Convolvulus Cneorum. Magnified about 50 



diam. — After Kerner. 



