IN USE AT THE ROYAL BOTANIC GARDEN, 221 
and the two are then firmly tied together with thin twine. The 
pieces of glass with the specimen thus secured between them are 
placed in the preservative and are allowed to remain there undis- 
turbed until the specimen is completely hardened. 
Alcohol being extremely volatile, it must always be kept in 
well sealed jars if its strength as a preservative is to be main- 
tained. Regarding the one disadvantage attaching to its use— 
viz., the destruction of the natural colours—a compensating 
feature exists in the readiness with which it bleaches white the 
majority of specimens. Such bleaching, if the form of the speci- 
men is well preserved, is perhaps more to be desired than the 
temporary or imperfect retention of colour to be secured in some 
cases by the use of formaline. 
‘6b A lcohol—8o per cent., 70 per cent., 60 per cent. 
The lower percentages of alcohol are prepared by mixing with 
water the requisite amount of 90 per cent. alcohol after distilla- 
tion. 
The objection urged against aqueous media that they do not 
harden delicate specimens applies also to weak alcohol. 
Experiments made with alcohols of varying degrees of strength 
go to show that while the weaker percentages may be employed 
with some success in preserving certain plants they possess even 
for these, with the exception of succulent specimens coming 
under Class III., no advantages over the 90 per cent. alcohol. 
For the great majority of specimens the weaker alcohol proves 
unsatisfactory, and the results of experiments with it show that 
where it is desirable to fix in the best manner possible the 
natural lie of the parts of a specimen it is not safe to employ 
alcohol of less strength than 90 per cent. 
70 per cent. and 80 per cent. alcohols are useful, however, for 
the firmer and more woody specimens of Class II., while 50 per 
cent. alcohol or even 30 per cent. is valuable as a commencing 
medium for the more succulent specimens. 
e. Alcohol and Glycerine—go per cent. Alcohol 50 cc, and 
Glycerine 50 C6. 
This has proved useful for the temporary preservation of 
material before dissection when the 90 per cent. alcohol alone 
would have made the material too brittle. 
