Stains and Staining 49 



The solution A must ripen for two months. When wanted for 

 use, add about 10 drops of A to 10 c.c. of B. Stain 10 to 20 minutes. 

 Wash in water and proceed as usual. 



Cellulose walls take a deep violet. The closing membrane 

 (torus) of the bordered pits of conifers will usually stain deeply in 

 about 15 minutes. Lignified, suberized, and cutinized structures 

 stain slightly or not at all. When they do stain, the color is not 

 violet, but a light yellow or brown. 



THE CARMINES 



This group of stains, immensely popular several years ago, has 

 rapidly lost favor among botanists as newer stains and combinations 

 have appeared. Botanists have not given the carmines a fair trial 

 in recent years. It is possible that it would be worth while to try 

 again, especially after fixing agents containing mercury. When it is 

 desirable to stain in bulk, nothing has been found which will serve 

 better than the carmines. Only three of these stains will be con- 

 sidered : 



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 alcohol 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 to 3 days, 

 then treat with acid alcohol (50 c.c. of 70 per cent alcohol +2 drops 

 of hydrochloric 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 to 24 hours 

 each), cleared, imbedded, and cut. After the sections are fastened 



