IO 



PHARMACEUTICAL BOTANY 



designated by numbers or by figures, as 3^2, M> ?> etc -> or in milli- 

 meters, as 2 mm., 4 mm., 16 mm., which represent focal lengths. 



The smaller the number or fraction representing the focal length 

 of an objective, the greater is its magnifying power. 



NoSEPlECE 



Oextcnves -I.j^ 



GRADUATED SHORT SLIDE 

 REVOLVING 



STAGE 



ADJUSTABLE 



SPRING FINGER 



CONDENSER; MOUNTING OK 

 DROP -SWING ARM*-~ "" , 

 LOWER IRIS DIAPHRAGM-'' 

 TOR OBUQUE 



STAGE CENTERING 



MIRROR 



MIRROJR 



MIRROR. BAR 

 RACK & PINION 



CONCENTRIC Awuyr- 



KG BUTTONS 



GRADUATED LONG 



FIG. 3. Illustrating the parts of a compound microscope. 



Objectives are either dry lenses or immersion lenses. If an air 

 space be present between the objective and the object, the lens is 

 called a dry one; if a liquid is present between the objective and the 

 object, the lens is called an immersion lens. If this liquid be oil, 



