6 HISTOLOGY OF MEDICINAL PLANTS 
pinion, a glass stage, beneath which there is a groove for holding 
a metal plate with one black and one white surface. The 
nature of the object under observation determines whether a 
plate is used. When the plate is used and when the object is 
studied by reflected light it is sometimes desirable to use the 
black and sometimes the white surface. The mirror, which has 
a concave and a plain surface, is used to reflect the light on the 
glass stage when the object is studied by transmitted light. 
The dissecting microscope magnifies objects up to twenty 
diameters, or twenty times their real size. 
