MIDLAND NATURALIST. 73 
as perfectly green as when alive, and will retain its green color 
indefinitely. The method may be extended to all small green forms 
like the smaller liverworts, fern prothallia, and moss protonemata. 
o get the material into glycerin, add first a considerable 
quantity of 5 or ro per cent. glycerin in water, and put the dish 
near but not on a radiator. In a few days the evaporation will leave 
the fluid thick. Once the preparation is in thick glycerin the color 
will not change, if the formalin has been completely removed. 
he potassium-copper-acetate solution will not keep the natural 
color of diatoms, It has the property of removing the diatomin or 
yellow coloring matter from the diatoms and leaving the plants per- 
fectly green. The solution can thus be used in demonstrating the 
presence of chlorophyll in these plants. The diatomin is removed 
or absorbed in a few minutes after application. 
As I have found some difficulty in keeping the microscopic 
mounts made in the potassium-copper-acetate solution because of 
drying, I have evolved a modification of the glycerin method in 
combination with it. The mounts made by this method are per- 
fectly durable, and when carefully prepared are superior to ordinary 
glycerin mounts, as all the green algae treated with it keep their 
natural colors indefinitely. Glycerin jelly can also be used at the 
end to make the mount even more durable than the ordinary 
glycerin mount would be. The procedure is as follows. 
The algae to be used are fixed in the potassium-copper-acetate 
2 per cent. solution. After they have been killed and fixed in this 
fluid (the time varying according to the specimen treated), add to 
the above solution an equal part of ro per cent. glycerin solution 
and allow to concentrate by evaporation in a warm dry place pro- 
tected from dust. The algae must be thoroughly separated from 
dirt and soil or the concentrated solution will precipitate a reddish- 
brown cloud of reduced copper. In nearly all cases the preparation” 
when thickened will be covered with a film of acetates, which can 
be removed from the top of the fluid without injury to the material. 
The concentrated solution should be perfectly clear, of a light green 
color, and the chromatophores of the algae perfectly green as in life. 
I have often been asked by students, and in fact by those well 
acquainted with algae, whether the plants thus given them for ex- 
amination were not really alive. The advantage of having plant 
material, especially for elementary students, in a condition as near 
as possible to the live state, obviates explanations about stains. I 
