IN USE AT THE ROYAL BOTANIC GARDEN. 219 
loss of turgescence gradual, and the hardening of the specimen 
quick, little change of position of the organs results. Whereas 
when a specimen is placed in an aqueous medium it is from the 
first evident that the buoyancy of the parts tends greatly to 
distort its form. 
Method of Procedure.—The specimen when gathered is 
immersed in the preservative before the least flagging or 
withering occurs. In many cases it is found necessary to carry 
the jar with the alcohol into the garden or plant-house, and to 
drop at once the specimen, as it is gathered, into the preserva- 
tive. In the alcohol the specimen commonly as already stated 
slowly sinks, but if large quantities of air are present in the 
tissues it may at first float or only partially sink. It is undesir- 
able that any part of the specimen should be left uncovered, and 
when the specimen does not of itself sink readily, either a small 
weight is attached to it by a silk thread to sink it, or it is 
fastened in some way to the glass support on which it is finally 
to be mounted and is thus held immersed. 
The time taken to effect the hardening varies with the size 
and character of the specimen. With small specimens a few 
minutes will suffice; with others several hours will be required; 
but in all cases when once immersed the specimen should not be 
removed until it is completely hardened. 
As the alcohol enters, the air present in the tissues is driven 
out, and any colouring substances present are at same time 
discharged and diffuse in the surrounding fluid. Chlorophyll if 
present is thus extracted as well as the colours of most flowers, 
the blue colour of some alone, being to a certain extent retained. 
That the bleaching may prove satisfactory the jar containing 
the specimen is left in a position exposed to strong sunlight, 
which is most effective, aiding the discharge of the colouring 
substances and preventing the formation of discolouring decom- 
position-products, when the specimen is subjected to its action 
immediately after being immersed in the alcohol. 
In the majority of cases chlorophyll is the colour-substance 
principally discharged. The chlorophyll-solution thus produced, 
if left exposed to sunlight, decomposes, and the spirit becomes 
almost clear, but it proves advantage, if well-bleached specimens 
are desired, to pour off this chlorophyll-solution as soon as the 
