Plate 1.

Fig. 1. Cross-section of Canaigra root (Rumex hymenosepalus). X 5 ½. (Photomicrograph).
Fig. 2. Cross-section of Chinese Rhubarb. X 5 ½ (Photomicrograph).
Fig. 3. Cross-section of Rheum rhaponticum. X 5 ½ (Photomicrograph).

This image is from Rheum in Sayre's Manual of Organic Materia Medica and Pharmacognosy, 1917.