54 METHODS IN PLANT HISTOLOGY 



and the stains have been kept in tightly stoppered bottles. If the solu- 

 tion becomes turbid, it should be filtered. 



Greenacher's borax carmine. — 



Carmine 3 g. 



Borax 4 g. 



Distilled water 100 c.c. 



Dissolve the borax in water and add the carmine, which is quickly 

 dissolved with the aid of gentle heat. Add 100 c.c. of 70 per cent alco- 

 hol and filter (Stirling). 



The following is a slightly different method for making this stain 

 from the ingredients mentioned above: Dissolve the borax in water, 

 add the carmine, and heat gently for 10 minutes; after the solution 

 cools, add the alcohol and filter; let the solution stand for 2 or 3 weeks, 

 then decant and filter again. 



Stain the material in bulk from 50 per cent alcohol 1-3 days, then 

 treat with acid alcohol (50 c.c. of 70 per cent alcohol-t-2 drops of hy- 

 drochloric acid) until the color becomes a clear red; this may require 

 only a few hours, but may take 2 or 3 days. The material may then be 

 passed through the rest of the alcohols (6-24 hours each), cleared, im- 

 bedded, and cut. After the sections are fastened to the slide, the paraf- 

 fin 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. 



Carmalum (alum lake).— Use 1 g. of the powdered stain to 100 c.c. 

 of very dilute ammonia water. Filter, if there is any precipitate. 



Mayer's carmalum. — 



Carminic acid 1 g. 



Alum 10 g. 



Distilled water 200 c.c. 



Dissolve with heat; decant or filter and add a crystal of thymol to 

 avoid mold. 



With material of Volvocales fixed in weak aqueous potassium iodide. 



