CHAPTER VII 
THE GLYCERIN METHOD 
It used to be an almost universal custom to mount unicellular 
and filamentous forms in glycerin or in glycerin jelly. The method 
is simple and easily mastered, but mounts must be sealed, and even 
when well sealed they do not long survive the ordinary use and abuse 
of the laboratory. However, some things are still mounted in glycerin 
or glycerin jelly. The greens and browns of moss protonema still 
keep much of their natural color in preparations which have been in 
use for many years. 
We have abandoned, completely, any mounting in glycerin; 
but the glycerin method, except the final mounting, precedes mounting 
in glycerin jelly, and it also constitutes the first part of the Venetian 
turpentine method. Consequently, it is very necessary to learn the 
capabilities and limitations of glycerin. 
The method, from fixing to mounting, as used in connection with 
staining and without staining, will now be described. 
Stained Preparations.—The familiar Spirogyra is a good form to 
begin with. Fix in the chromo-acetic-osmic solution described under 
(d) p. 26, or in this solution without the osmic acid, for 24 to 48 
hours. Wash in running water over night or 24 hours. If running 
water is not available, wash for 24 hours, changing the water 
frequently. 
The most satisfactory stain is Haidenhain’s iron-alum haematoxylin. 
Treat for 2 to 4 hours in a 2 per cent iron-alum; wash 10 to 20 
minutes in water, and then stain 4 hours, or over night, in J per cent 
haematoxylin. Wash in water 10 to 20 minutes and transfer to iron- 
alum again. This time the material must be watched under the 
microscope until the stain is just right. If the stain becomes weak 
in 2 or 3 minutes, the time in the stain was too short; if it re¬ 
quires an hour or more to reduce the stain to the proper tint, the 
time was too long. Different species of Spirogyra and even different 
collections, fixed in the same reagent, will differ in their reaction to 
stains; and different unicellular and filamentous forms, in different 
96 
