96 HISTOLOGY OF MEDICINAL PLANTS 
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 frag- 
ments. 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. 
The simplest non-porous and non-striated walled bast fibres 
are found in mezereum bark (Plate 26, Fig. 4). The individual 
fibre is very long. If often measures over three millimeters in 
length, so that in the powder the fibre is usually broken. The 
wall is non-lignified, white, non-porous, and of uniform diameter. 
