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. 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. It 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. [Illustration: PLATE 23 POROUS AND STRIATED BAST FIBRES 1. Blackberry root (_Rubus cuneifolius_, Pursh.). 2. Wild cherry (_Prunus serotina_, Ehrh.). 3. Yellow cinchona (_Cinchona species_).] [Illustration: PLATE 24 POROUS AND NON-STRIATED BAST FIBRES 1. Sarsaparilla root (Hypoderm), (_Smilax officinalis_, Kunth). 2. Unicorn root (Endoderm). 3. Marshmallow root (_Althæa officinalis_, L.). 4. Echinacea root (_Echinacea angustifolia_, D. C.).] [Illustration: PLATE 25 NON-POROUS AND STRIATED BAST FIBRES 1. Elm bark (_Ulmus fulva_, Michaux). 2. Stillingia root (_Stillingia sylvatica_, L.). 3. Cundurango root bark (_Marsdenia cundurango_, [Triana] Nichols).] In Ceylon cinnamon (Plate 26, Fig. 2) the bast fibres measure up to .900 mm. in length, so that in powdering the bark the fibre is rarely broken. These bast fibres, unlike the bast fibres of mezereum, have thick, white walls and a narrow cell cavity. Both ends of the fibre taper gradually to a long, narrow point.