Yellow cinchona bark (Plate 23, Fig. 3) has very thick, prominently striated porous-walled fibres, with either blunt or pointed ends. The cavity is narrow, and the pores are simple or branched.
POROUS AND NON-STRIATED BAST FIBRES
Porous and non-striated bast fibres occur in marshmallow root and echinacea root.
The fibres of marshmallow (Plate 24, Fig. 3) usually occur in fragments. The walls have simple pores, and the diameter of the cell cavity is very wide; the pores on the upper or lower wall are circular or oval in outline (end view).
The bast fibres of echinacea root (Plate 24, Fig. 4) are seldom broken; the walls are yellow, the pores are simple and numerous. The edges and surface of the fibres are frequently covered with a black intercellular substance.
NON-POROUS AND STRIATED BAST FIBRES
Non-porous and striated bast fibres occur in elm bark, stillingia root, and cundurango bark. The bast fibres of elm bark (Plate 25, Fig. 1) occur in broken, curved, or twisted fragments. The central cavity is very small, and the walls are longitudinally striated.
In powdered stillingia root (Plate 25, Fig. 2) the bast fibres are broken, and the wall is very thick and longitudinally striated. The central cavity is small and usually not visible. Bast fibres of cundurango (Plate 25, Fig. 3) are broken in the powder. The cavity is very narrow, and the striations are arranged spirally, less frequently transversely.
NON-POROUS AND NON-STRIATED BAST FIBRES
Non-porous and non-striated walled bast fibres occur in mezereum bark, in Ceylon cinnamon, in sassafras root bark, and in soap bark.