Each segment used for histological study included skin and cortex to a 

 depth of 3 or 4 mm. 



A highly magnified segment of skin and cortex, drawn to illustrate 

 the various cells and structures studied in apples, is shown in figure 2. 



break in cuticle . 



incipient break 

 spongy cuticle 



channel 



SKIN 



EPIDERMIS 



waxy layer 



cuticle 

 epidermal cell 



HYPODERMIS 



supplementry 

 cutin deposits 



hypodermal 

 cells 



CORTEX 



Figure 2. — A composite drawing illustrating apple skin and a shallow portion of 



cortex. 



The Skin 



Epidermis and waterproofing layers. — The epidermis or outermost 

 zone is a single cell layer in thickness. As seen in sections, the 

 epidermal cells of all apple varieties studied appeared to be of uniform 

 size and shape, but the epidermis varied in other ways, as shown in 

 table 2 and in plates 1, 2, and 3. 



Cutin occurring in the outer walls of the epidermal cells forms the 

 waterproofing layer called cuticle (11) (fig. 2). Further waterproofing 

 is provided by a waxy layer external to the cutin (26, 27) . 



16 



