Temporary Mounts and Microchemical Tests 77 



monia can be prepared by pouring 15 per cent ammonia water upon 

 copper turnings or filings. Let the solution stand in an open bottle. 

 It does not keep well, but its efficiency is readily tested. Cotton 

 dissolves almost immediately as long as the solution is fit for use. 



With iodine and sulphuric acid cellulose turns blue. Treat 

 first with the undiluted iodine-potassium-iodide solution described 

 in the test for starch, then add a mixture of two parts of concentrated 

 sulphuric acid and one part of water. 



With chloroiodide of zinc cellulose turns violet. Dissolve 

 commercial chloroiodide of zinc in about its own weight of water and 

 add enough metallic iodine to give the solution a deep-brown color. 



The cell walls of fungi consist of fungus cellulose. When young, 

 they give a typical cellulose reaction; when older, they become 

 insoluble in cuprammonia and, with iodine and sulphuric acid, show 

 only a yellow or brown, instead of the typical blue. With chloroiodide 

 of zinc, the wall stains vellow or brown, instead of violet. 



> 



Reserve cellulose, which is common in thick-walled endosperm of 

 seeds, shows the same microchemical reactions as ordinary cellulose. 



Callose. The thickening on the sieve plate differs from cellulose 

 in its staining reactions, and in its solubility. It is insoluble in 

 cuprammonia, but will dissolve in a 1 per cent solution of caustic 

 soda. 



Stain in a 4 per cent aqueous solution of soda (NaiCO 2 ) for 10 

 minutes, and transfer to glycerin. The callus should take a bright 

 red. If stained very deeply and then transferred to a 4 per cent soda 

 (without the corallin), the stain is extracted from the cellulose but 

 remains in the callus. Unfortunately, the preparations are not 

 permanent. 



If stained for about an hour in a dilute aqueous solution of anilin 

 blue, the stain may be extracted with glycerin until it remains only 

 in the callus. After the blue is satisfactory, a few minutes in aqueous 

 eosin will afford a good contrast. The preparation may be mounted 

 in balsam and is fairly permanent. 



Lignin. Lignified walls are insoluble in cuprammonia. The 

 iodine and sulphuric acid or the chloroiodide of zinc, used as in testing 

 for cellulose, give the lignified walls a yellow or brown color. After 



