I 



PICRO-ANILINE BLUE — PICRO-NIGROSIN 325 



picric acid and subsequent staining with cosin. The sections 

 are to remain in the alcoholic fixative for several hours. They 

 are then to be washed out in alcohol and stained for a few min- 

 utes in a solution of eosin in absolute alcohol. Then the sec- 

 tions are successively washed in absolute alcohol, transferred to 

 oil of cloves, and mounted in Canada balsam. The ground 

 substance is dark red, the crystalloid yellow, while the globoid 

 remains colorless. The pyrenoids and chloroplasts of algae may 

 be simultaneously fixed and stained by placing the algae for an 

 hour or longer in a concentrated solution of picric acid in 50 per 

 cent, alcohol, to which has been added about 5 drops of a solu- 

 tion of 20 gm. of acid fuchsin in 100 c.c. of aniline water. The 

 aniline water is prepared by shaking up 3.5 gm. of aniline in 

 96.5 gm. of water. The algae are then washed in alcohol, trans- 

 ferred to xylol, then to a thin solution of balsam in xylol, and are 

 finally mounted in the thicker solution of Canada balsam in xylol. 



Alcohol is a better solvent of picric acid than water, and accord- 

 ingly it gives quicker results in washing out the acid from the 

 fixed material than water does, but running water may be used 

 to wash out the fixative whether the latter has been dissolved in 

 alcohol or in water. 



Picro-aniline Blue. — A double stain, which is very rapid in 

 its action, is prepared by adding aniline blue to a saturated solu- 

 tion of picric acid in 50 per cent, alcohol until the solution has a 

 blue-green color. By this treatment the unmodified cell-walls 

 and the cell-contents are stained blue, while the lignified walls 

 are stained by the picric acid. 



Picro-nigrosin. — A solution of nigrosin in a concentrated 

 solution of picric acid in water or 50 per cent, or 95 per cent, 

 alcohol is a good fixative and stain for algae and leucoplasts, and 

 for double-staining modified and unmodified cell-walls. The 

 solution may, in some cases, need to act for twenty- four hours. 

 The strong alcoholic solution is particularly recommended for 

 material containing chlorophyll, since this will 1)C extracted by 

 the strong alcohol. Nuclei and leucoplasts are stained a steel 

 blue by the nigrosin. 



