100 HISTOLOGY OF MEDICINAL PLANTS 
In Ceylon cinnamon (Plate 26, Fig. 2) the bast fibres measure 
up to .goo mm. in length, so that in powdering the bark the 
fibre is rarely broken. These bast fibres, unlike the bast fibrés 
of mezereum, have thick, white walls and a narrow cell cavity. 
Both ends of the fibre taper gradually to a long, narrow point. 
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 inter- 
cellular 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 meni- 
spermum (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 arugs. 
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. 
