372 



A TEXT-BOOK OF BOTANY. 



N 



FIG. 218. Digitalis leaves: A, transverse section near one of the veins showing the 

 separated or extra-epidermal layer occurring on the lower surface (S) with two non-glandular 

 hairs (N) and glandular hair (G), epidermal layer (E), lower epidermis (LE), chlorophyll 

 layer (M), upper epidermis (UE), and tracheae (T). B, transverse section of portion of 

 leaf showing the separated or additional epidermal layer; c, collenchyma. 



or dorsiventral leaves the palisade cells are distributed only below 

 the upper epidermal layer (Figs. 211, 215). 2. In unifacial or 



