44 HISTOLOGY OF MEDICINAL PLANTS 
The small size is si ea three-fourths and the large 
size seven-eighths. 
Cover glasses are circular (Fig. 41), square (Fig. 42), or 
rectangular (Fig. 43) pieces of transparent glass used in covering 
the specimens mounted on glass slides. A few years ago much 
difficulty was experienced in obtaining uniformly thick and 
Fic. 41.—Round Fic. 42.—Square Fic. 43.—Rectangular Cover 
Cover Glass Cover Glass Glass 
transparent cover glasses, but no such difficulty is experienced 
to-day. The type of cover glass used depends largely upon the 
character of the specimen to be mounted.. The square and 
rectangular glasses are selected when a series of specimens are 
to be mounted, but in mounting powdered drugs and histological 
specimens the round cover glasses are preferable because they 
are more sightly and more readily cleaned and rinsed. 
GLASS SLIDES 
Glass slides (Fig. 44) are rectangular pieces of transparent. 
glass used as a mounting surface for microscopic objects. The 
Fic. 44.—Glass Slide 
slides are usually three inches long by one inch wide, and they 
should be composed of white glass, and they should have ground 
