PERMANENT MOUNTING 53 



Dammar. It is better to varnish the edges of the cover- 

 slip of Dammar preparations, but this is not necessary 

 for those in Canada Balsam. 



The stain produced by aniline colours is apt to fade, 

 so that they are not to be recommended for preparations 

 which are to be kept for a long time. The staining of 

 haematoxylin also fades, but more slowly. In order 

 to prevent fading, the preparations should be kept in 

 the dark. 



Preparations of green parts of plants in glycerine 

 lose their colour. These may be best put up in a drop 

 of a strong solution of potassium acetate, or of alumi- 

 nium acetate. The cover-slip must be fastened down 

 as above described. 



