IN USE AT THE ROYAL BOTANIC GARDEN. 239 
liable to be dried by the method just described, resort is had in 
applying the cement to a pipette surrounded by a_ hot-water 
jacket which keeps the gelatine within the pipette in a liquid 
condition. The specimen is not taken out of the spirit, but is 
held in position in a dish or trough of alcohol at the bottom of 
which lies the sheet of glass the specimen is to be fastened to. 
The pipette, with the surrounding jacket, is brought so that the 
nose of the pipette touches the mounting glass at the bottom of 
the trough. Some of the gelatine is pressed out on to the glass 
and before it coagulates in the alcohol the specimen is placed 
upon it and is held in position until the gelatine is set firm. 
B. CEMENTS USED WITH FORMALIN. 
1. For light objects. 
For light objects, and where the gelatine will be seen, a 
clear jelly is made from the best French gelatine. The 
glass plate is warmed and the warm liquid gelatine dropped 
on the specimen at those points at which it is desired to fix it. It 
hardens in formalin and remains practically transparent, but 
readily takes up colouring matters if these have not previously 
been extracted from the specimen. 
2. For heavy objects. 
Gelatine is used for heavy objects where the cement is hidden 
behind the object mounted. The gelatine solution employed is 
the same as is used for heavy specimens in alcohol. The specimen 
should be dried as completely as possible. Where, as with 
formalin, the aqueous medium is not inflammable, the glass plate 
at the points where the cement rests may be heated slightly from 
- below over a gas flame after the specimen has been laid in position 
Il—SUPPORTS FOR PREPARATIONS. 
Mica is used for round jars, but for rectangular vessels thin 
sheet glass possesses many advantages. It is cheap, perfectly 
transparent, can be obtained in any size, and, being rigid, will 
support specimens of any weight. Thé mica sheets are of limited 
size, hardly transparent at the best, and if thin not sufficiently 
rigid. Opal and blue glass have been used as backgrounds but 
