STAINING AGENTS. 



Only a few of the more important staining agents will be men- 

 tioned, and directions given for their general use. 



Ammonium Carmine. 



This stain is best prepared, as suggested by Hartig. Dissolve 

 a little carmine in water until the mixture has the consistency of 

 paste. Add to this a little strong ammonia and evaporate the whole 

 to dryness over a water bath. The resulting powder dissolved in 

 water is used for staining. 



Alum Carmine. 



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Make a concentrated solution of alum and add to it enough 

 powdered carmine to give it a deep color, (1 gram to 100 c.c. of 

 alum solution). Boil for 10 minutes and, when cold, filter. This 

 agent is much used and is often valuable as a selective stain. It 

 colors pure cellulose cell walls a bright red, but does not effect 

 those that are lignified or suberized. 



Picro-Carmine (Gage). 



Twenty grams of picric acid are dissolved in 200 parts of 

 water, and mixed with 5 grams of carmine in 250 c.c. of strong 

 ammonia. Stir the whole thoroughly and evaporate to dryness. 

 Dissolve the residue in 700 c.c. of water. All of the carmine stains 

 are very useful, easily handled, and quite selective. Picro-carmiue 

 turns protoplasm a yellowish red. 



