PLATE 16 



1 QgsgBsg 



Periderm of Cascara Sagrada (Rhamnus purshiana, D.C.) 



^4. i, Outline of cork cells; 2, Line of contact of adjoining cork cells. 



B. Radial longitudinal section of cascara sagrada. 1, Cork cells; 2,Phel- 

 logen; 3, Forming parenchyma cells; 4, Cortical parenchyma cells. 



C. Cross-section of cascara sagrada. 1, Cork cells; 2, Phellogen; 3, Form- 

 ing parenchyma cells; 4, Cortical parenchyma cells. 



