224 TAGG—NOTES ON MUSEUM-METHODS 
In the stronger solutions the fading of the colours is more 
rapid than in the weaker ; but, as already stated, the disadvantage 
of the weaker solutions is that they permit the growth of moulds. 
If formalin is added to sea-water and the specimens are protected 
from the light the colours of marine alge are fairly well pre- 
served. These results are in agreement with most of the observa- 
tions recorded. 
White flowers may remain uncoloured, becoming nevertheless, 
as the fluid penetrates, more or less translucent, as may happen 
also with coloured flowers and other specimens, or they turn a 
dull brown colour. 
The specimens which show this discolouration are, as a rule, 
such as would darken if preserved in alcohol ; at the same time, 
according to Linsbauer,' Lathrea squamaria, L.,in formalin does 
not darken so badly as when it is preserved in alcohol, while, on 
the other hand, I find that specimens of some orchids which 
in alcohol brown only slightly become in formalin almost 
black. Formalin is used for many fungi, particularly the more 
succulent forms, and changes but little the colours of the darker 
and duller sorts. 
Formalin for Preservationof Plant-form. 
Formalin fails to preserve the form of many specimens chiefly 
because it does not harden. Reference has already been made 
to this defect and to the soft and flaccid character of specimens 
of Class I. preserved in it. In the weaker (2 per cent.) 
solutions there is a tendency on the part of the petals 
of fragile and of fully expanded flowers to drop off after being a 
short time in the preservative. For succulent plants it presents 
the advantage that when preserved in it they do not to any 
extent contract. 
For gelatinous or mucilaginous specimens it is valuable, 
causing little of the contraction and opacity which follow the 
' immersion of such specimens in alcohol. Gelatinous bodies are 
hardened, swelling or slightly contracting according to the 
amount of absorbed water originally present. It is advisable to 
avoid formalin if the specimen to be preserved be one coated in 
* Verhandl, der K,-K. Zoolog.—Bot. Gesellschaft in Wien, xliv. (1894), 
Sitz., p. 23. 
