PHARMACEUTICAL BOTANY 



panying the tracheae (ducts). The walls of these fibres show oblique 

 pores. Woody fibres are the supporting elements of the xylem. 



Hard Bast is composed of elongated, spindle-shaped, thick-walled 

 elements called bast fibres. The characteristic thickening of the walls. 



Fig. 4. — ^Laticiferous vessels from the cortex of root of Scorozonora hispanica. 

 A, as seen under low power, and B, a smaller portion under high power. {From 

 Steiens after Sachs.) 



of these fibres is due to deposits of lignin upon the inner surface of the 

 cellulose cell wall. Like the woody fibres the lumina of these contain 

 air and the fibre walls are provided with oblique pores. Bast is the 

 supporting tissue of the phloem. 



