WOODY STEMS 247 
parenchyma (7), which makes up a very small percentage of 
the xylem, is not readily found in the powder. The pith paren- 
chyma cells (8) have thick, porous side walls and perforated side 
walls. The wood fibres (9) usually occur in masses surrounding 
the conducting cells; when occurring singly, the oblique pores 
readily distinguish them from the bast fibres. 
The diagnostic elements of powdered buchu stems are: 
First, trichomes; secondly, reddish-brown and white-angled 
epidermal cells; thirdly, the long, white bast fibres. 
