246 THE USE OF THE MICROSCOPE 



pink or colorless. Cell walls are uiisiainecl. The staining 

 effect is sharpened by the use of green Wratten filters, 

 especially No. 57A (on the monocular) ; or the blue-green 

 filter, No. 64; or a combination of No. 56 and No. 64. 



If haematoxylin is dissolved in 70 per cent alcohol (0.5 

 gram to 100 cubic centimeters), the same procedure can be 

 used as for brazilin. A longer differentiation is always 

 needed, however, and the cytoplasm is usually not so clear. 

 The writer prefers brazilin, especially for the study of 

 chromomeres. Iron-brazilin does not seem to give such 

 good results with some animal tissues, though smears of 

 the blood corpuscles of a salamander have been well 

 stained w4th it. 



Other Methods. — Other special methods of fixing and 

 staining to show nuclear details are given in the papers 

 written by cytologists, both for plant and animal tissues. 

 The two described here are those which have sufficed for 

 the writer in chromosome work. 



