METHODS. 1 5 



specially prepared, and which it is desirable to pre- 

 serve, should be mounted in glycerine, or in glycerine- 

 jelly, or in Canada balsam or Dammar. Glycerine and 

 glycerine-jelly may be used for sections which have been 

 prepared by any of the methods described above. 

 Dilute glycerine should be used for this purpose, con- 

 sisting of a mixture of pure glycerine with an equal 

 bulk of water. The cases in which these media are 

 especially suitable have been mentioned. Only those 

 sections which have been treated with absolute alcohol, 

 and either oil of cloves or the mixture of turpentine and 

 creosote can be mounted in Canada balsam or Dammar. 



When preparations are mounted in glycerine-jelly, 

 a trace of carbolic acid should be added in order to pre- 

 vent the growth of Fungi. The sections should be 

 previously soaked in glycerine so as to remove water or 

 alcohol from them. 



In order to make the preparations mounted in 

 glycerine quite permanent, the cover-slip should be 

 fixed to the slide by applying a coating of gold-size or 

 Brunswick black round its edge with a brush. Care 

 should be taken that no glycerine is on the slide outside 

 the v cover-slip; if any is there it should be removed by 

 means of blotting-paper before applying the varnish. 



It is better to varnish Dammar preparations in this 

 way also ; but it is not necessary for those in Canada 

 balsam. 



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 alu- 

 minium acetate. The cover-slip must be fastened 

 down as above described. 



