Prunus. Fig. 7.—Cross section of bark of Prunus Mahaleb, including outer, middle and outer portion of inner bark.

Fig. 7.—Cross-section of outer part of bark of Prunus Mahaleb, showing mode of cork formation.
a, outer layers of cork exfoliating at the surface and showing stratification lines. (The cork readily splits along these lines.)
b, cortex or middle bark;
c, cluster of primary bast fibres;
d, secondary cork forming interior to the clusters of primary bast fibres;
e, compressed sieve tissues.
Magnification about 75 diameters.

This image is from Structure of our Cherry Barks in the September issue of the American Journal of Pharmacy, 1895.