88 
METHODS IN PLANT HISTOLOGY 
of 95 per cent alcohol and glycerin. The material may be left in 
this mixture indefinitely. 
After sections have been cut, wash them in tap water, then in 
distilled water, and stain half an hour or more in weak Delafield’s 
haematoxylin—about 5 parts of the solution, as given in the formula, 
to 100 parts of water—and then wash in distilled water. Stain in 
weak safranin—about 2 parts of the stock solution to 100 parts of 
water—over night or even for several days. Wash in tap water, 
then wash in 95 per cent alcohol for 30 seconds or longer, according 
to the appearance of the stain. Dehydrate in absolute alcohol, 
clear in clove oil, transfer to xylol, and mount in balsam. This 
method is very good for gymnosperm woods. 
Since it usually happens that processes are commenced, but 
cannot be completed at a single laboratory period, it is necessary 
to know where sections may be left for several hours or until the 
next day without suffering injury. At 1, 2, or the pure water of 8 in 
the schedule given above, sections may be left until the next day. If 
it is not desirable to mount all of the sections which have been pre¬ 
pared, they may be kept indefinitely in clove oil or xylol. If the 
sections are to remain for a year or more in the clearing agent, xylol 
is to be preferred. Shells with good corks are best for keeping such 
material. 
For the study of vascular anatomy, this is the most permanent 
stain which has come into general use. 
More recently, safranin combined with anilin blue or with light 
green has been coming into favor. Both these methods will be 
described. 
Safranin and Anilin Blue.—Use the alcoholic safranin already 
described, and a 1 per cent solution of anilin blue in 90 per cent 
alcohol. 
With this combination we should recommend a long stain in saf¬ 
ranin, not less than 24 hours. Wash in 50 per cent alcohol, but do not 
extract all the safranin from the cellulose walls. Stain 2 to 10 minutes 
in anilin blue. Rinse a few seconds in 95 per cent alcohol, 
then treat for about 5 seconds with 95 per cent alcohol slightly 
acidulated with hydrochloric acid. The weak blue should at once 
change to a bright blue and, at the same time, the acid will remove 
some of the safranin. It is for this reason that we proceed while 
the sections are still somewhat overstained in safranin. Wash for 
