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 outHne (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. i) 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 ciimamon, 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. 



