Fig. 111. Cross-section of bark of stem.

of Prunus Virginiana (P. serotina).
A. Cork.
B. Middle or green layer of bark.
C. Clusters of stone cells.
D. Compressed sieve tissue.
E. Medullary ray.
F. Fissure between medullary ray and bast.
G. Bast tissue.
H. Cambium zone.
I. Ducts in mature wood.

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