CHAPTER VII 

 THE GLYCERIN METHOD 



Ten years ago it was almost a universal custom to mount fila- 

 mentous algae and fungi in glycerin or in glycerin jelly. The method 

 is simple and easily mastered, but preparations must be sealed, and 

 even when well sealed they do not long survive the ordinary use 

 and abuse of the laboratory. The Venetian turpentine method is 

 now used for almost everything which went into glycerin ten years 

 ago. However, some things are still mounted in glycerin or glycerin 

 jelly. Glycerin preserves, to a considerable extent, the green of 

 chlorophyll, a great advantage in mounts of moss protonema and simi- 

 lar objects. Filamentous forms may be arranged with needles with- 

 out much danger, since material does not become brittle in glycerin. 



The method, from fixing to mounting, as used in connection with 

 staining and without staining, will now be described. 



Stained Preparations.- -The familiar Spirogyra is a good form to 

 begin with. Fix in chromo-acetic acid for 24 to 48 hours. The 

 strength of the fixing agent must be determined for every collection 

 of material. If there is in the laboratory a stock solution of 1 per 

 cent chromo-acetic acid (1 g. chromic acid and 1 c.c. glacial acetic 

 acid to 100 c.c. of water), take one part of this stock solution and 

 add an equal amount of water; then add 1 c.c. of glacial acetic acid 

 to each 100 c.c. of the weakened solution. Place a few filaments 

 in the solution and, if plasmolysis occurs, weaken the solution by 

 adding water, and then try again. When a solution is found which 

 causes no shrinkage, fix the material for 24 to 48 hours. Wash in 

 running water over night, or for 24 hours. If running water is not- 

 available, wash for at least 24 hours, changing the water frequently. 



The most satisfactory stain is Haidenhairi's iron-alum haema- 

 toxylin. 



Treat for 2 hours with a 2 per cent aqueous solution of ammonia 

 sulphate of iron. Wash in water for 20 minutes and then stain for 



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