PLATE 1. 



Direct Colour Photomicrograph. 



Screen-plate process (Autochromej. 



CRYSTALS OF SALICIN UNDER POLARISED LIGHT x 18 



Objective Zeiss Planar 25 mm. F. 4.5. 



Ocular ... ... None. 



Condenser ... Watson's Universal Achromatic, top lens re- 

 moved. Polariser fitted under the con- 

 denser. A Selenite plate was also used. 



Illuminant ... Liliput 4 amp. arc. 



Aux. Condenser Double convex lens, projecting parallel light. 



Screen Lumiere's screen for arc light. 



Plate Lumiere's Autochrome. 



Exposure 4 sec. 



Developer ... Rodinal 1 in 10, (or 4 min. 



Photo. W. B. R. 



(Frontispiece. 



