66 APPENDIX TO PART I. 



before being sealed, the gum hardens at the edge 

 of the cover, and so aids in fastening it. This 

 medium does not render sections so transparent 

 as pure glycerine. 



GLYCERINE AND ACETIC ACID in equal parts 

 make a convenient preservative for many fungi 

 and other preparations. The fluid should be boiled 

 and filtered to remove mold spores and other 

 impurities. 



Like other fluid media, this requires the employ- 

 ment of cells of some sort, the usual ring of 

 asphalt or the wax cell, if firmly fixed, answering 

 very well. In covering such a cell it is best to 

 lower the cover gradually from one side, so that 

 any superfluous fluid which is forced out shall 

 penetrate between the cell and cover-glass only 

 at one side, where it must be carefully wiped off 

 with blotting-paper before the cell is sealed. 



A neat and useful cell may be made by placing 

 three small balls of white wax on the slide, at 

 equal distances apart, just within the line where 

 the edge of the cover is to come, and flattening 

 them to the requisite thickness by pressing the 

 slide against any flat body covered by a piece of 

 muslin or paper. A drop of the mounting fluid 

 is put in the centre, and the object arranged in it 

 as it is to remain, after which the cover-glass is 

 slightly warmed, placed in position, and gently 

 pressed against the wax supports by the handle of a 

 dissecting needle or other convenient object. Any 



