In Saigon cinnamon the bast fibres are not as numerous as they are in Ceylon cinnamon. The individual fibres are thicker than in Ceylon cinnamon, and the walls are yellowish and rough and the ends bluntly pointed. These fibres are rarely ever free from adhering fragments of parenchyma tissue. In sassafras root bark (Plate 26, Fig. 3) the fibre has one nearly straight side--the side in contact with the other bast fibres--and an outer side with a wavy outline, caused by the fibre’s pressing against parenchyma cells, the point of highest elevation being the point of the fibre’s growth into the intercellular space between two cells. The outer part of the wall tapers gradually at either end to a sharp point. The walls are white, thick, and non-porous. In soap bark (Plate 26, Fig. 1) the bast fibres have thick, white, wavy walls and a narrow cavity. One end of the cell is frequently somewhat blunt while the opposite end is slightly tapering. The branched stone cells of wild-cherry bark have three or more branches. The pores are small and usually non-branched, and the striations are very fine and difficult to see unless the iris diaphragm is nearly closed. The central cavity is very narrow and frequently contains brown tannin. The branched stone cells of hemlock bark are very large; the walls are white and distinctly porous bordering on the cell cavity, which contains bright reddish-brown masses of tannin. In cross-section bast fibres occur singly or isolated, as in Saigon cinnamon (Plate 34, Fig. 1); or in groups, as in menispermum (Plate 27, Figs. 1 and 2); or in the form of continuous bands, as in buchu stem (Plate 100, Fig. 5). Bast fibres are seen in longitudinal view in powdered drugs. The cell cavity shows throughout the length of the fibre. This cavity differs greatly in different fibres. In soap bark (Plate 26, Fig. 1) there is scarcely any cell cavity, while in mezereum bark (Plate 26, Fig. 4) the cell cavity is very large. [Illustration: PLATE 26 NON-POROUS AND NON-STRIATED BAST FIBRES 1. Soap bark (_Quillaja saponaria_, Molina). 2. Ceylon cinnamon bark (_Cinnamomum zeylanicum_, Nees). 3. Sassafras root bark (_Sassafras variifolium_, [Salisb.] Kuntze). 4. Mezereum bark (_Daphne mezereum_, L.).] [Illustration: PLATE 27 GROUPS OF BAST FIBRES 1. Menispermum rhizome (_Menispermum canadensis_, L.). 2. Althea root (_Althæa officinalis_, L.) showing two groups of bast fibres.] The pores, which are absent in many drugs, are, when present, either simple, as in echinacea root (Plate 24, Fig. 4), or they are branched, as in yellow cinchona (Plate 23, Fig. 3).