ON PRESERVATION OF PLANTS FOR EXHIBITION. 693 
PRESERVATIVE MEDIA. 
Spirit—I have used this medium for a number of years, usually 
diluted with 30 to 50 per cent. of water. I still employ it, but to a 
much less amount, and seldom as the only medium. It serves excellently 
after treatment with cupric acetate in suitable cases. Specimens treated 
in this way seldom discolour spirit sufficiently to require it to be changed. 
I have employed the acid spirit to decolourise specimens that would 
otherwise become dark in spirit ; but I seldom now attempt or wish to 
obtain bleached preparations. The retention of the more or less natural 
colours renders specimens both more pleasing and more instructive. 
Formic Aldehyde (Formol).—I have used this for over two years 
with varying results, employing solutions of from 0-5 to. 5 per cent. 
in water. Even the weakest solutions have in some cases proved 
sufficient when the object is small relatively to the amount of the fluid ; 
but in many cases there appeared a fungus after a few weeks in the weak 
solutions. I now employ habitually a 2 per cent. solution, except for 
fleshy specimens or where there is relatively little space for the fluid in 
the jar owing to the size of the specimen. Under these precautions I 
have not found the fungi appear. The colour of the specimens is not 
always well preserved, but they are usually superior to specimens treated 
with spirit alone in my experience. The 2 per cent. solution has in my 
experience retained the colours best. 
Cupric Acetate and Acetic Acid.—I have experimented with the object 
of retaining the green colour in preparations in fluids by forming the 
compounds of chlorophyll and copper. The results have been very satis- 
factory in some cases, notably so in Lycopodiwm and Selaginella, and 
good, though with a bluish tinge in the green, in most plants that are 
free from tannin. Where tannin is present it combines with the copper 
and discolours the specimen ; hence this method does not succeed where it 
occurs. The method is as follows : Acetic acid has cupric acetate dis- 
solved in it to saturation, and 1 part of the solution is added to 4 of 
water, which should have been distilled if not naturally soft. Or 1 part 
of acetic acid may be added to 4 of water, and this solution may be 
saturated with cupric acetate. In some cases it is sufficient to employ 
1 part of acid in 10 or even more of water. Sometimes one, sometimes 
another of these solutions has given the best results, according to the 
material to be treated. In each case the treatment is the same. The 
specimen, after having been washed clean, is submerged in the solution, 
and remains in it for at least a month ; it suffers no harm even if left a 
good deal longer. When it is to be transferred to the permanent pre- 
servative fluid it is washed in water, to remove any particles of acetate 
from the surface, and is then at once put into its jar in spirit or in what- 
ever other fluid is used. Specimens successfully treated in this way may 
be exposed to sunlight with impunity. Specimens are apt to become soft 
under this treatment. 
The cupric acetate solution may be used again and again, but acetate 
should be added occasionally to keep a sufficiently strong solution. 
Brine, Alum Solution, Wickersheimer’s Solution, Glycerine (10 to 50 
per cent. in water), Barff’s Boroglyceride (1 in from 20 to 50 of water), 
and Boracie Acid (1 per cent. in water) have all given good results in 
some cases. The solutions of the salts are apt to become turbid and to 
allow the growth of fungi, especially if any part of the specimens is 
uncovered. It is better to wash both the specimens and the vessel, 
