270 Botanical Microtechnique 



inch camera. The massive, rigid Bausch & Lomb model L has the 

 above desirable features, as well as convertibility to Micro Tessar and 

 gross photography (Fig. 17.5) . In this apparatus, the microscope and 

 lamp are on a base that is slid as a unit from luider the camera for 

 visual study. This apparatus could be improved by providing a stable 

 base on which the microscope-lamp unit could be fastened for visual 

 study while someone else uses the camera, without mutual incon- 

 venience. 



The Leitz Lumipan goes one step further by incorporating the 

 illuminating system in the base of the microscope, and making the 

 microscope virtually an integral part of the camera and its base. 



Optical-Bench Cameras 



The optical-bench type of photomicrographic apparatus has long 

 been considered the ultimate in precision and rigidity. A standard 

 microscope may be used, fastened to an adjustable platform. The 

 three principal components, the camera, the microscope, and the 

 lamp, are mounted on a heavy metal track on which the units may 

 be slid back and forth in accurate alignment. If the microscope is 

 removed for visual study, the replacement and re-alignment are very 

 time-consuming. There is a temptation to keep an expensive micro- 

 scope, possibly a binocular, permanently on the apparatus where it 

 is not available for visual use, and may be used for photomicrography 

 only a fraction of the time (Fig. 17.6 A) . It is preferable to use a 

 special simplified photomicrographic microscope, which is built on as 

 a permanent part of the apparatus. Several workers can therefore use 

 the apparatus without mutual inconvenience, each worker bringing 

 the objectives and oculars from his personal microscope (Fig. 17.6 B) . 

 For low magnifications. Micro Tessars are used in conjunction with 

 special substage condensers. 



The sequence of operations for setting up and using these elab- 

 orate outfits is identical in principle with the procedures outlined for 

 simpler apparatus. When used in the horizontal position, no substage 

 mirror is used, and the horizontal beam of light is easily centered 

 with the axes of the microscope and camera. Focusing and centering 

 of the illuminant in the plane of the substage diaphragm are thus 

 easily accomplished, and the setting is practically permanent. A 

 lateral observation and focusing tube is available in some makes, or 

 a ground-glass screen may be used for focusing. A limitation of present 

 models is ihat they use large and expensive plates, 5- by 7-in. or 

 8- by 10-in. sizes. Reducing kits make possible the use of 314- by 



