APPENDIX. 



BEAGENTS EEQUIRED FOE MICEOCHEMICAL 

 AND PHYSIOLOGICAL EXPEEIMENTS. 



Acetic Acid. A dilute (1 to 5 per cent.) aqueous solution of 

 acetic acid (1) dissolves calcium carbonate with evolution of bubbles 

 of carbon dioxide ; (2) dissolves the globoids in protein grains, but 

 does not affect crystals of calcium oxalate ; (3) dissolves most 

 ethereal oils, while most fatty oils are insoluble in it ; (4) brings 

 out clearly the nuclei of cells, and is for that purpose often used 

 along with methyl green ; (5) corrects the too great transparency 

 often produced by the clearing action of potash. Stronger solutions, 

 or the glacial acid, serve for (6) maceration of herbaceous organs, 

 isolating the cells ; (7) the clearing of dense growing-points, etc. 

 (8) the preparation of various fixatives. 



Alcohol. (1) For dehydration of specimens to be mounted in 

 Canada balsam, absolute alcohol is necessary. For most other pur- 

 poses, ordinary methylated spirit will answer. This is used for 

 (2) the solution of chlorophyll and other pigments, wax, ethereal 

 oils, some fatty oils, resins, etc. ; (3) the precipitation of sugars, 

 inulin, proteins, asparagin, etc. ; (4) the fixation and hardening of 

 tissues. 



If material becomes brown and discoloured in alcohol, it may be 

 decolorised by placing it for a few days in 100 c.c. of alcohol to 

 which is added about 1 c.c. of strong sulphuric acid and one or two 

 crystals of potassium chlorate, and then transferring it to alcohol or 

 to equal parts of alcohol, glycerine, and water. 



Commercial alcohol (methylated spirit) is about 95 per cent, 

 alcohol. In making from this alcohols of different strengths, 

 proceed as if it were absolute (100 per cent.) alcohol. If, however, 

 it is desired to dehydrate the methylated spirit, so that it may be 

 used as absolute alcohol, heat some copper sulphate in an iron pot 

 (to drive off the water by crystallisation), place the powdered 

 salt in a bottle, pour the 95 per cent, (methylated) alcohol in, and 

 keep the bottle tightly stoppered. 



Alkannin. Use either the alcoholic solution, made from the 

 roots of Alkanna tinctoria, or sections of the dry root itself, in 

 making tests for (1) oils and resins, which are stained pink; (2) 

 suberised and cutinised walls, also stained pink but often requiring 

 the action to continue for some hours. 



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