STAINS AND STAINING 
59 
few minutes. Transfer to 10 per cent Venetian turpentine and allow 
the turpentine to concentrate as described in chapter viii. 
In staining sections to be mounted in balsam, the same stain may 
be used, but it is better to dilute it one-half with water. Stain for 
6 to 24 hours, dehydrate in 95 per cent and absolute alcohol, clear 
in clove oil, and mount in balsam. 
Magdala red stains lignified, suberized, and cutinized structures, 
and also chromosomes, centrosomes, nucleoli, and pyrenoids. It is 
likely to overstain, but the differentiation is easily secured by placing 
the finished mounts upon a white background in the direct sunlight. 
When the desired differentiation has been reached, it is better to 
avoid direct sunlight, although the mounts do not seem to fade in 
the ordinary light of a room. 
Except for special purposes, it is better to use this stain in com¬ 
bination with blue, green, or violet. 
Magdala red (not echt) has always been erratic in its behavior, 
and recent analyses of samples show that it is variable in composi¬ 
tion. A stain called phloxine, made by the National Anilin and 
Chemical Co., behaves like the best Magdala red and seems to give 
uniform results. 
Gentian-Violet.—This is one of the most important stains in the 
botanical laboratory. It may be made according to the general 
formula for anilin stains, but that solution does not keep well. A 
1 per cent solution in distilled water keeps indefinitely and seems to 
be as good as, if not better than, the anilin solution. Gentian- 
violet dissolves readily in clove oil and some prefer to use it this way, 
rather than in water or alcohol. 
With the aqueous or anilin-oil solutions, the following directions 
will enable the student to become acquainted with the behavior of 
the stain. Transfer to the stain from water and allow the stain to 
act for 1 to 30 minutes. The time depends upon the fixing and upon 
the structures to be stained. The brilliancy of the stain in achromatic 
structures may often be increased by leaving the slide from 2 to 5 
minutes in a 1 per cent aqueous solution of permanganate of potas¬ 
sium before applying the stain. The greatest objection to the 
aqueous and anilin-oil solutions of gentian-violet is that the stain 
washes out so rapidly in alcohols that it is impossible to run the 
slide up through the series. The usual practice is to dip the slide 
in water to remove most of the stain and thus avoid carrying it into 
