58 
METHODS IN PLANT HISTOLOGY 
water, with a 2 per cent aqueous solution of acetic acid for 5 to 10 
minutes, changing the acid several times; transfer to 10 per cent 
glycerin, leaving about 1 c.c. of the acid to keep the whole solution 
slightly acid. When the glycerin becomes thick, mount in glycerin 
jelly. If the Venetian turpentine method is to be used, wash the glyc¬ 
erin out in alcohol slightly acidulated with acetic acid (a couple of 
drops of acetic acid to 50 c.c. of alcohol), and do not drain off the last 
alcohol too completely before transferring to the 10 per cent Venetian 
turpentine. According to Lee, the glycerin should be slightly alka¬ 
line. The alkalinity can be brought about by adding half a gram of 
common salt to 100 c.c. of the 10 per cent glycerin. We have found 
that eosin keeps better when the media are slightly acid. 
For staining paraffin sections, the alcoholic solution is better 
and the time may not be more than a few minutes, especially if the 
eosin is being used as a contrast stain. 
We have found the Eosin Y, of Coleman and Bell, very satis¬ 
factory, especially for fungi to be mounted whole. With the rapid 
improvement in the manufacture of stains, it is very probable that 
other dealers will have equally good products. Investigators will 
save time and money by keeping track of the findings of the commis¬ 
sion on Standardization of Biological Stains. 
Haematoxylin and eosin and methyl blue and eosin are good 
combinations. The eosin should follow the other stain. 
Erythrosin.—This is really an eosin, but there is some difference 
in the method of manufacturing. It is more precise and a more 
transparent stain than eosin and is to be preferred for nearly all 
staining of paraffin sections. Make a 1 per cent solution in distilled 
water or in 70 per cent alcohol. It gives good results when made up 
according to the general formula. 
Erythrosin stains rapidly, 30 seconds to 3 minutes being sufficient. 
When used in combination with other stains, erythrosin should come 
last. 
Magdala Red. —At least two Magdala reds are sold by dealers, 
one the echt (genuine) Magdala red, and the other simply Magdala 
red. The latter is much cheaper and, in our experience, much 
superior to the echt stain. The directions apply to the cheaper stain. 
For staining algae which are to be mounted in Venetian turpentine, 
use a 1 per cent solution in 85 or 95 per cent alcohol. Stain for 6 
to 8, or even 24, hours. Rinse in 95 and 100 per cent alcohol for a 
