50 Methods in Plant Histology 



to the slide, the paraffin should be dissolved off with xylol. The 

 balsam and cover may be added immediately, or the xylol may be 

 rinsed off with alcohol and a contrast stain may be added. 



Alum Carmine. A 4 per cent aqueous solution of ammonia alum 

 is boiled 20 minutes with 1 per cent of powdered carmine. Filter 

 after it cools (Lee). 



Stain from 12 to 24 hours and wash in water. No acid alcohol 

 is needed, since the solution does not overstain. 



Alum Cochineal.- 



Powdered cochineal 50 g. 



Alum 5 g. 



Distilled water 500 c.c. 



Dissolve the alum in water, add the cochineal, and boil; evapo- 

 rate down to two-thirds of the original volume, and filter. Add a 

 few drops of carbolic acid to prevent mold (Stirling). 



Stain as with alum carmine. It used to be a common practice 

 to stain in bulk in alum cochineal and counter-stain on the slide 

 with Bismarck brown. 



THE ANILINS 



Many of the most brilliant and beautiful stains yet discovered 

 belong to this group. These stains are so numerous that we shall 

 not attempt to mention even their names, but shall consider only 

 those which are in most common use by botanists. The following 

 general formula has proved to be fairly satisfactory for most anilins, 

 but the formulae mentioned in describing the different stains are 

 usually to be preferred. Solutions containing anilin oil do not keep 

 as well as aqueous or alcoholic solutions. 



General Formula. Make a 10 per cent solution of anilin oil in 

 95 per cent alcohol; when the anilin oil is dissolved, add enough water 

 to make the whole mixture about 20 per cent alcohol; add 1 g. of 

 cyanin, erythrosin, safranin, gentian-violet, etc., to each 100 c.c. of 

 this solution. 



The anilins keep well in balsam but not in glycerin. Xylol 

 is a good clearing agent for all of them, but clove oil should be used 

 with gentian-violet. Unfortunately they are not very permanent. 



