14 



HISTOLOGY OF MEDICINAL PLANTS 



furnished above the condenser; this iris becomes available the 

 instant an object is to be observed without the aid of the con- 

 denser, in which case the upper iris diaphragm allows proper 

 adjustment of the light. The mirror, one side plane, the other 

 concave, is mounted on a movable bar, along which it can 

 be slid — another convenience for the adjustment of the light. 

 The microscope stage of this stand is of the round, rotating 



Fig. 17. — Research Fig. 18. — Special 



Microscope Research Microscope 



and centring pattern, which permits a limited motion to the 

 object slide. The rotation of the microscope stage furnishes 

 another convenience in the examination of objects in polarized 

 light, allowing the preparation to be rotated in order to 

 distinguish the polarization properties of the objects under 

 observation. 



SPECIAL RESEARCH MICROSCOPE 



A special research microscope of the highest order (Fig. 18) 

 is supplied with an extra large body tube, which renders it of 



