=Branched bast fibres= occur in only a few of the medicinal plants, notable examples being tonga root and sassafras root. Occasionally one is found in mezereum bark.
The bast fibre of tonga root (Plate 22, Fig. 2) often has seven branches, but four- and five-branched forms are more common. The walls are non-porous, non-striated, and nearly white.
The bast fibre of sassafras (Plate 22, Fig. 1) has thick, non-porous, and non-striated walls, and the branching occurs usually at one end only of the fibre. Most of the bast fibres of sassafras root are non-branched.
=Porous and striated= walled bast fibres occur in blackberry bark of root, wild-cherry bark, and in cinchona bark.
The fibres of blackberry root bark (Plate 23, Fig. 1) have distinctly porous and striated walls; the cavity, which is usually greater than the diameter of the wall, contains starch. These fibres usually occur as fragments.
In wild-cherry bark (Plate 23, Fig. 2) the fibre has short, thick, unequally thickened walls, which are porous and striated. Most of the fibres are unbroken.
1. Cocillana (_Guarea rusbyi_, [Britton] Rusby). 2. White oak (_Quercus alba_, L.) 3. Quebracho (_Aspidosperma quebracho-blanco_, Schlechtendal).]
1. Coca leaf (_Erythroxylon coca_, Lam.). 2. Eucalyptus leaf (_Eucalyptus globulus_, Labill). 3. Senna leaf (_Cassia angustifolia_, Vahl.).]
1. Sassafras root bark (_Sassafras variifolium_, [Salisb.] Kuntze). 2. Tonga root.]
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 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 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.