In cramp bark the cork and phellogen cells are very large, while in cascara sagrada the phellogen and the cork cells are very small.
PLATE 104
Powdered White Pine Bark (Pinus strobus, L.)
1. Epidermis. 2. Parenchyma cells. 3. Parenchyma with starch. 4. Medullary rays. 5. Solitary crystals. 6. Solitary crystals and tannin. 7, 8 and 10. Resin masses. 9. Starch.
In canella alba bark the periderm is composed of stone cell cork or stone cells arranged in superimposed rows, which form the outer layers of the bark.
In white oak and most barks from woody trees the periderm consists of lifeless parenchyma, medullary rays, sieve cells, bast fibres, and in some cases stone cells and of phellogen cells.
In young wild cherry, cascara sagrada, and frangula are several layers of tangentially elongated collenchyma cells with chlorophyll. In the older barks of the above and in many other barks no collenchyma cells occur.
In cramp bark and in tulip tree bark the outer layers of the cortical parenchyma cells are beaded. In most barks there is no beaded walled parenchyma. The outer layers of most cortical parenchyma cells are tangentially elongated while the inner parenchyma cells are mostly circular in outline.
In white oak, cascara sagrada and prickly ash are groups of stone cells; in the cinnamon barks are bands of stone cells; in cinchona bark are isolated stone cells. In cramp bark, mezerum, elm, and white pine bark no stone cells occur.
In frangula, cascara sagrada, cocillina, cinnamon, cinchona, sassafras, and wild cherry barks the bast fibres occur in groups. In frangula, cascara sagrada, and cocillina the bast fibres are surrounded by crystal cells with crystals.