STAIN TECHNIQUE 43 



brate tissues the unevenly distributed dull black is undesirable. 

 Specialized uses of Erie Black do not compare favorably with 

 Niagara Sky Blue, C. I. No. 520, or Haematoxylin, C. I. No. 1246. 



593. Direct Green B, Diazine Green B is a direct dye, light 3 

 to 4. There are few green acid dyes suitable for animal tissues. 

 On invertebrates or paraffin sections, try Crocein Scarlet 7B, C. I. 

 No. 286, for five minutes and counterstain with Direct Green B 

 two minutes. 



The spores of blue-green algae are blue-green or black; the 

 vegetative cells, clear blue. In an acid solution of the dye, green 

 or red algae are given a polychromatic stain that varies through 

 red to purple or blue. Parenchyma of vascular plants is dull blue. 



594. Direct Green G, Alkali Green D is a direct dye, light 4 to 

 3 ; i gram in 95 ml. of distilled water, 5 ml. of 5 per cent sodium 

 sulfate, and 1 ml. of 4 per cent sodium hydroxide. This formula 

 constitutes the stain for blue-green algae and whole mounts giving 

 the best direct green ; it is moderately fast in glycerin. On paraffin 

 sections of animal tissues and vascular plants the dark green is too 

 indefinite. 



Class VI. Tetrakisazo Colouring Matters 



This class includes yellow, brown, and black direct dyes that are 

 not used as biological stains. 



