52 PRACTICAL BOTANY 



A mixture of two parts of glycerine, and one part of 

 glacial acetic acid, boiled together, is useful in some 

 cases ; e.g. for mounting the tissues of seaweeds, which 

 are liable to swelling. 



In order to make the preparations mounted in gly- 

 cerine permanent, the cover-slip should be fixed to the 

 slide by applying a coating of gold size, Brunswick 

 black, or Canada balsam dissolved in benzol, round its 

 edge with a brush. If a circular cover-slip be used, a 

 turn-table will be found to save much time in this 

 process. Care should be taken that no glycerine is on 

 the slide outside the cover-slip ; if any is there it should 

 be removed by means of blotting-paper before applying 

 the varnish. 



Glycerine Jelly. Objects which may be mounted 

 in glycerine may equally well be mounted in glycerine 

 jelly, in which case since the jelly sets firmly, it is un- 

 necessary to use any cement or varnish. The sections 

 should be previously soaked for a considerable time (e.g. 

 one or two days) in glycerine so as to remove water or 

 alcohol from them. A trace of carbolic acid should be 

 added to the glycerine jelly in order to prevent the 

 growth of Fungi. 



Canada Balsam and Dammar. These are both 

 highly refractive media, and are thus well adapted for 

 lending transparency to objects. These media are 

 specially suited to sections stained with hsematoxylin. 

 Water must be completely extracted from the objects 

 before mounting, by treatment with absolute alcohol, or 

 strong methylated spirit ; they are then to be transferred 

 to oil of cloves, or a mixture of turpentine and creosote, 

 or cedar-wood oil, and finally mounted in Balsam or 



