100 HISTOLOGY OF MEDICINAL PLANTS 



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. 



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. i) 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. i); or in groups, as in meni- 

 spermum (Plate 27, Figs, i 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. i) there is scarcely any cell cavity, while in mezereum 

 bark (Plate 26, Fig. 4) the cell cavity is very large. 



