STAINS AND STAINING 
57 
If safranin is to be used alone, pass through 50, 70, 85, 95, and 
100 per cent alcohol, through the xylol-alcohol, then through xylol 
to balsam. If clove oil is used, omit the xylol-alcohol, but follow 
the clove oil with xylol to hasten the hardening of the preparation. 
If a second stain is to be added, transfer from the 50 per cent 
alcohol to any alcoholic stain. If the second stain is an aqueous 
stain, rinse the slide or sections for a minute in water before applying 
the stain. 
Safranin is the most generally useful of all the red stains, and, 
fortunately, it is quite durable. Lignified, suberized, cutinized, and 
chitinized structures stain red, as do also the chromosomes, nucleoli, 
and centrosomes. 
Acid Fuchsin.—Use a 1 per cent solution in water or in 70 per cent 
alcohol. The solution in alcohol is preferable if sections are to be 
mounted in balsam. This stain often acts with great rapidity, 
2 or 3 minutes being sufficient. The method for using acid fuchsin 
with woody tissues is given in the chapter on “Freehand Sections’’ 
(chap. vi). In staining embryo sacs, pollen grains, and such struc¬ 
tures, longer periods are better. Stain 1 or 2 hours, and then differ¬ 
entiate in a saturated solution of picric acid in 70 per cent alcohol. 
This may require 30 seconds, or even several minutes. Rinse in 
70 per cent alcohol until a bright red replaces the yellowish color 
due to the acid, and then proceed as usual. 
Congo Red.—This is an acid stain resembling acid fuchsin. 
For cytological work use a \ per cent aqueous solution; for anatomical 
work use a saturated solution. It is a good stain to use after mala¬ 
chite green or anilin blue. Transfer to the Congo red from water, 
stain 15 minutes, wash in water, transfer—for wood sections—to 
85 per cent alcohol, and wash until the green or blue color of the 
previous stain begins to show through the red. Then treat quickly 
with absolute alcohol, clear xylol, and mount in balsam. 
Eosin.—This has long been a favorite stain, but for most pur¬ 
poses it has been replaced by similar stains giving better differentia¬ 
tion. The dry stain is made in two forms, one for aqueous and the 
other for alcoholic solution. Each should be used with its intended 
solvent. Make a 1 per cent solution in alcohol or water. 
For material to be mounted whole in glycerin, glycerin jelly, or 
Venetian turpentine, stain several hours, or over night; pour off the 
stain, which may be used repeatedly; treat, without washing in 
