52 
METHODS IN PLANT HISTOLOGY 
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 
Botanists have never given the carmines a fair trial, doubtless 
because the stains were not considered worth it; but the splendid 
preparations by Professor Powers of various merfibers of the Volvo- 
caceae prove that we should pay more attention to this group. Only 
a few of the multitudinous formulas will be considered. 
The carmine solutions keep for several years, some of them even 
improving with age, if distilled water has been used in the formulas 
and the stains have been kept in tightly stoppered bottles. If the 
solution 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 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 
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. 
