THE EPIDERMIS AXD PERIDERM 



63 



of raspberry, on the fruit of bayberry, etc. Resinous deposits 

 occur on the leaves and stems of grindelia species, and on yerba 

 santa. 



In certain leaves there are two or three layers of cells beneath 

 the epidermis that are similar in structure to the epidermal cells. 

 These are called hypodermal cells, and they function in the 

 same way as the epidermal cells. 



Hypodermal cells are very likely to occur on the margin of 

 the leaf. Uva-ursi leaf has a structure typical of leaves with 

 hypodermal marginal cells. Uva-ursi. like other leaves with 

 hypodermal cells has a greater number of hypodermal cells 

 at the leaf margin than at any other part of the leaf 

 surface. 



The cutinized walls of epidermal cells are stained red with 

 saffranin. 



TESTA EPIDERMIS 



Testa epidermal cells form the epidermal layers of such 

 seeds as lobelia, henbane, capsicum, paprika, larkspur, bella- 

 donna, scopola. etc. 



In surface view the end walls are thick and wavy in outline; 

 frequently the line of union — middle lamella — of two cells is in- 

 dicated by a dark or light line, while in others the waU between 

 two cells appears as a single wall. The walls are porous or 

 non-porous, and the color of the wall varies from yellow to 

 brown, to colorless. These cells always occur in masses, com- 

 posed partially of entire and partially of broken fragments. 



In lobelia seed (Plate 4. Fig. 2) the line of union of adjacent 

 ceU walls appears as a dark line. The walls are wavy in out- 

 line, of a yellowish-red color and not porous. 



In henbane seed I Plate 4. Fig. 3) the line of union between 

 the cells is scarcely visible; the walls are decidedly wavy, more 

 so than in lobelia, and no pits are visible. 



In capsicum seed 1 Plate 4. Fig. 1) the cells are very wavy 

 and decidedly porous, the line of union between the cell walls 

 being marked with irregular spaces and lines. 



In belladonna seed ('Plate 5. Fig. 1) the walls between two 

 adjacent cells are non-striated and non-porous, and extremely 

 irregular in outline. 



