218 THE ELEMENTS OP VEGETABLE HISTOLOGY 



This silvered surface shows a small perforation in 

 line with the optic axis of the microscope lenses, 



Fig. 72. — Camera Lucida, Adjustable Mirror Type. 



(Bausch & Lomb.) 



thus permitting passage of light rays through the 

 silvered surface to the eye. The other reflecting 

 element is an adjustable mirror supported on a bar 



Fig. 73. — Camera Lucida, Fixed Mirror Type. 



(Bausch & Lomb.) 



extending at right angles to the optic axis of the micro- 

 scope. This mirror reflects the image of the drawing 

 paper to the silvered surface of the glass prism, which 



