(x 183.)
A, Fragments of reticulate water tubes.
B, Spiral water tube.
C, Aggregate crystals of calcium oxalate.
D, Starch.
E, Parenchyma.
F, Phloëm.

This image is from Drug Powders (also see Rheum) in Sayre's Manual of Organic Materia Medica and Pharmacognosy, 1917.