PLATE 16 
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PERIDERM OF CASCARA SAGRADA (Rhamnus purshiana, D.C.) 
A. 1, 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. I, Cork cells; 2, Phellogen; 3, Form- 
ing parenchyma cells; 4, Cortical parenchyma cells. 
