REAGENTS 
25 
washtub with the bottom arranged as just described for the box. 
If one is using such a large box or tub and does not need all the 
streams of water, the tubes not in use may be closed by means of 
clamps. 
If running water is not available, put the material into a rather 
large bottle or dish; a 200 c.c. bottle is not too large for half a dozen 
J-inch cubes. Change frequently, especially at first. Nothing is 
safe with less than 24 hours of this sort of washing. Where running 
water is not available, Dudgeon’s method is particularly valuable, 
for the tubes can be lifted quickly from one dish into another. 
If the washing has not been thorough, the subsequent staining 
is likely to be unsatisfactory. 
Some of the chromic-acid formulas are as follows: 
a) Stock Chromo-Acetic Solution.— 
Chromic acid. 1 g. 
Glacial acetic acid. 1 c.c. 
Water. 100 c.c. 
This solution has been used quite extensively in embryological 
work upon the higher plants. It fixes thoroughly, but often causes 
plasmolysis in cells with large vacuoles. 
b) Weak Chromo-Acetic Solution (Shaffner’s formula).— 
Chromic acid. 0.3 g. 
Acetic acid. 0.7 g. 
Water. 99.0 c.c. 
This has also been used in embryological work. It causes little 
or no plasmolysis. Difficult material, like Aster heads and ripe 
Capsella pods, cuts more readily after this reagent than after the 
stronger solutions. 
c) Strong Chromo-Acetic Solution.— 
Chromic acid. 1 g- 
Glacial acetic acid. 3 c.c. 
Water. 100 c - c * 
For fern prothallia, most liverworts, moss capsules before they 
have begun to get reddish or brownish, and most filamentous algae 
and fungi, this is a good fixing agent. 
