332 
METHODS IN PLANT HISTOLOGY 
alum in a liter of distilled water. Allow the mixture to cool and 
settle; filter; add a crystal of thymol to preserve from mold (Lee). 
It is ready for use as soon as made up. Unless attacked by mold, 
it keeps indefinitely. 
Haidenhain’s Iron-Haematoxylin. —This stain was introduced 
by Haidenhain in 1892 and has gained a well-deserved popularity 
with those engaged in cytological work. Two solutions are used, 
and they are never mixed: 
A. to 4 per cent aqueous solution of ammonia sulphate of iron. Use 
the ferric (violet) crystals, not the ferrous (green) crystals. 
B. f per cent solution of haematoxylin in distilled water. 
The crystals of haematoxylin will dissolve in the distilled water 
in about 10 days; the stain reaches its greatest efficiency in about 
6 weeks. About 3 months from the time it is made up, it begins to 
deteriorate. A stain made by dissolving the crystals in strong alco¬ 
hol and then diluting with water so as to get a practically aqueous 
solution is not so good. 
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). 
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). 
Alum Cochineal.—• 
Powdered cochineal. 50 g. 
Alum. 5 g. 
Distilled water. 500 c.c. 
Dissolve the alum in water, add the cochineal, and boil; evaporate 
down to two-thirds of the original volume and filter. Add a few 
drops of carbolic acid to prevent mold (Stirling). 
