STAIN TECHNIQUE 31 



On plant tissues the scarlet is similar to that of Biebrich Scar- 

 let. Leave the material in Ponceau 3R for 12 hours and counter- 

 stain with one of the following : ( 1 ) five minutes in Victoria Blue 

 B, C. I. No. 729, (2) five minutes in Brilliant Cresyl Blue, C. I. 

 No. 877, for reddish brown and violet, or (3) one minute in Methyl 

 Violet, C. I. No. 680, for fuchsia and violet. 



88. Bordeaux, Azo Bordeaux, Acid Bordeaux is an acid dye, 

 light 3 ; \ gram in 100 ml. of distilled water and 1 ml. of 1 per cent 

 sulfuric acid. The fuchsia on plant materials blends with blue 

 dyes to give colors of little contrast; a fair differentiation is 

 obtained with Victoria Blue B, C. I. No. 729. Bordeaux is also 

 used for coloring foods. 



101. Pontachrome Brown MW (Du Pont) is a mordant dye, 

 light 4. A clear brown of moderate fastness is obtained on blue- 

 green algae with the alkaline solution of the dye. Neutral solu- 

 tions in alcohol give a reddish brown on paraffin sections. 



120. Coccinine is an acid dye, light 3 to 4. Materials in 

 paraffin sections are stained a pale pink which is not the equal of 

 Biebrich Scarlet or of the Crocein Scarlets. 



133. Janus Green B is a basic dye, light 4. This dye, now 

 obsolete, was formerly used on fabrics. With staining properties 

 decidedly different from most basic dyes, it can be applied on cotton 

 in an acid bath. In whole mounts of algae the stain is poly- 

 chromatic; in a stem section all of the cells are either blue or 

 blue-green. If it were more fast Janus Green B would be a good 

 stain to use on freehand sections. 



138. Metanil Yellow is an acid dye, light 4 to 5. Cells of 

 parenchyma are stained a fugitive yellow. Upon the addition of 

 potassium dichromate the pigment becomes light brown. 



142. Methyl Orange, Helianthine, Orange III is an acid dye, 

 light 4. Because Methyl Orange is not affected by carbonates or 

 weak organic acids it is used principally as an indicator. On 

 paraffin sections it is similar to Orange G in both color and fast- 

 ness. 



143. Orange IV, Tropaeolin OO is an acid dye, light 4 to 5. 

 Cells of parenchyma are yellow in acid solutions of the dye but 



