TEMPORARY MOUNTS AND MICROCHEMICAL TESTS 81 
With iodine and sulphuric acid cellulose turns blue. Treat 
first with the undiluted iodine-potassium-iodide solution described 
in the test for starch, then add a mixture of two parts of concentrated 
sulphuric acid and one part of water. 
With chloroiodide of zinc cellulose turns violet. Dissolve com¬ 
mercial chloroiodide of zinc in about its own weight of water and add 
enough metallic iodine to give the solution a deep-brown color. 
The cell walls of fungi consist of fungus cellulose. When young, 
they give a typical cellulose reaction; when older, they become 
insoluble in cuprammonia and, with iodine and sulphuric acid, show 
only a yellow or brown, instead of the typical blue. With chloroiodide 
of zinc, the wall stains yellow or brown, instead of violet. 
Reserve cellulose, which is common in thick-walled endosperm of 
seeds, shows the same microchemical reactions as ordinary cellulose. 
Callose.—The thickening on the sieve plate differs from cellulose 
in its staining reactions, and in its solubility. It is insoluble in 
cuprammonia, but will dissolve in a 1 per cent solution of caustic soda. 
Stain in a 4 per cent aqueous solution of soda (Na x CCh) for 
10 minutes, and transfer to glycerin. The callus should take a bright 
red. If stained very deeply and then transferred to a 4 per cent soda 
(without the corallin), the stain is extracted from the cellulose but 
remains in the callus. Unfortunately, the preparations are not 
permanent. 
If stained for about an hour in a dilute aqueous solution of anilin 
blue, the stain may be extracted with glycerin until it remains only 
in the callus. After the blue is satisfactory, a few minutes in aqueous 
eosin will afford a good contrast. The preparation may be mounted 
in balsam and is fairly permanent. 
Lignin.—Lignified walls are insoluble in cuprammonia. The 
iodine and sulphuric acid or the chloroiodide of zinc, used as in testing 
for cellulose, give the lignified walls a yellow or brown color. After 
a treatment with Schultze’s maceration fluid, lignified membranes 
react like cellulose. 
Phloroglucin in a 5 per cent aqueous or alcoholic solution applied 
simultaneously with hydrochloric acid gives lignified walls a reddish- 
violet color. The preparations do not keep. 
Cutinized and Suberized Walls.—These are insoluble in cupram¬ 
monia or concentrated sulphuric acid. They are colored yellow or 
brown by chloroiodide of zinc, or by iodine and sulphuric acid, when 
