Stains and Staining 55 



for a few minutes. Transfer to 10 per cent Venetian turpentine and 

 allow the turpentine to concentrate as described in chap. 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 

 combination with blue, green, or violet. 



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 this may prove to be a better method 

 of making the stain than either of the two well-known formulae. 



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 

 the alcohol : then transfer directly from water to 95 per cent alcohol, 

 allowing the alcohol to act for only 2 or 3 seconds, then allow the 



