208 PHARMACEUTICAL BOTANY 
nally and includes the cork cambium itself. ‘This term appears 
often in pharmacognic and materia medica texts. 
PHELLODERM.—Phelloderm or secondary cortex is all that 
tissue produced by the cork cambium on its inner face. Its 
cells frequently contain chloroplasts. 
Fic. 138.—Cascara Sagrada Bark. Transverse section. A, cork; kk, cork 
cambium; fh, phelloderm; st, group of stone cells; C, primary cortex; rer, rosette 
aggregate of calcium oxalate; P, phloem; df, bast fibers; crf, crystal fibers more or 
less surrounding a group of bast fibers; mr, medullary ray; mp, monoclinic prism 
of CaO. 
Histrotocy or A TypicaL Bark, CascaraA SacRaDa.—In 
transverse section passing from outer to inner surface, the following 
structural characteristics are evident: 
1. Cork, or outer bark, composed of several layers of rec- 
tangular cork cells. The most external layers are dead and 
appear black because they are filled with air. The inner layers 
of this region are living, and contain brownish, brownish red or 
purple contents. 
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