394 



APPENDIX. 



saturated aqueous solution of copper acetate for &bout a week, then 

 on a slide with a drop of 2 per cent, solution of iron sulphate for a 

 few minutes ; wash in water and in alcohol, and mount in glycerine. 

 (2) To demonstrate glucose in cells, lay the sections in alcoholic 

 solution of copper acetate, mixed with equal volume of alcoholic 

 solution of caustic soda and a little acetic acid, and bring to boiling 

 on a water-bath. Glucose being insoluble in alcohol, the copper 

 oxide indicating the presence of glucose is deposited in the cells 

 containing this sugar. (3) To detect presence of resin, lay sections 

 for a week in strong aqueous solution of copper acetate ; the resin 

 will be coloured bright green. 



Copper Sulphate is used in the preparation of cuprammonia 

 and of Fehling's solution and the Biuret test. For the blue solution 

 required in experiments with double-walled bell-jars, add ammonia 

 to 10 per cent, solution of copper sulphate, until the precipitate 

 first formed is redissolved. 



Corallin, dissolved in a saturated aqueous solution of sodium 

 carbonate to form "corallin soda," is useful in staining the callus 

 of sieve-tubes. It also gives a pink colour to starch grains and to 

 lignified walls. 



Cuprammonia is best freshly prepared when required, in one of 

 the following ways : (a) Put copper filings into a bottle with a 

 ground-glass stopper, pour in enough strong ammonia to cover the 

 filings, and shake gently. When the solution will dissolve cotton- 

 wool, it is ready for use. (2) To a solution of copper sulphate in 

 water add dilute caustic potash, collect the precipitate on a filter, 

 and dissolve it in a little ammonia. 



Dahlia. (1) This stain may be used in very dilute aqueous 

 solution about 0'002 per cent. to stain living nuclei, e.g. if 

 epidermis or hairs are placed in the solution for some hours. (2) To 

 demonstrate the structure of pyrenoids, fix the material in equal 

 parts of 10 per cent, solution of potassium ferricyanide and 50 per 

 cent, acetic acid, then stain with aqueous Dahlia solution, and treat 

 with dilute potash to make the pyrenoids swell. 



Diastase may be bought ready prepared, either as powder or as 

 extract of malt ; it is also present in '"liquor pancreaticus " and in 

 "holadin." To prepare diastase, germinate Barley between pieces 

 of wet blotting-paper until the shoot is 2 or 3 mm. long ; then dry 

 the Barley on a water-bath, powder it, and pour over 10 grams of 

 the powder a litre of water containing 2 c.c. of chloroform, let stand 

 for a day, filter, add a little chloroform, and keep the extract in a 

 dark place in a stoppered bottle. 



Dipheiiylamiiie is used to test for nitrates in plant tissues or in 

 soils. Dissolve O'Oo gram of diphenylamine in 10 c.c. of strong 

 sulphuric acid. The presence of nitrates is shown by a blue 

 colour. 



