REAGENTS. 



809 



or mounts are of two kinds : they may serve a temporary pur- 

 pose only or they may be prepared so as to serve for future study, 

 the latter being known as permanent mounts. 



^cu 



Fig. 326. A cell from sassafras pith showing intercellular space (i); middle lamella 

 (m); layer of lignin (1); and layer of cellulose (c), which is subsequently modified to muci- 

 lage; simple pores (p) which are seen in the lower wall, the section being slightly oblique. 

 B, portion of wall showing the appearance of the pores when the view is transverse to the 

 wall and the focus is at the upper part of the pore (a) or at the lower part (b). 



In taking- up the study of a specimen it should first be mounted 

 in water and examined ; then the water may be replaced by a weak 

 aqueous solution of glycerin (5 to 10 per cent.) and the specimen 



