SPECIAL METHODS. 153 



by alcohol. They are washed with the latter until no more 

 color is given off, and then transferred to Canada balsam in 

 the usual way. Especially if the washing with acid alcohol 

 is just right, only the lignified and suberized cell-walls are 

 stained in these preparations, in which the former show a 

 bluish, the latter a rather yellowish, color. 



If it is desired to stain the cellulose walls also, this maybe 

 -done by one of the following methods : 



a. Methyl Blue. 



The sections, stained with safranin and washed with alco- 

 hol, are placed in a concentrated aqueous solution of methyl 

 blue, in which they remain a quarter of an hour or longer. 

 They are then washed in alcohol and mounted in Canada 

 balsam. The cellulose walls are then stained blue, the su- 

 berized and lignified ones, red. 



ft. Aniline Blue 



This must be used in aqueous solution which must be 

 first washed off with water after the staining, since turbidity 

 readily results from the direct addition of alcohol. Other- 

 wise it is used like methyl blue. 



y. Haematoxylin. 



Bohmer's haematoxylin ( 315) may well be used for double 

 staining with safranin. This is allowed to act for a few min- 

 utes on sections stained with safranin and washed, is then 

 washed off with water, and the sections are mounted in 

 Canada balsam. Sections thus treated show the lignified 

 and suberized walls red, and the cellulose walls violet. 



b. Gentian Violet and Eosin. 



270. In the so-called Gram's staining process ( 321) with 

 gentian violet, only the lignified and suberized walls remain 

 stained after thorough washing with clove-oil ; but a fine 

 double staining may be obtained by proceeding according to 

 Gram's method and adding to the clove-oil used in washing 



