APPENDIX A 507 



previously treated with potash, and the alkali thoroughly washed 

 out. 



Under this reagent cellulose walls turn blue, or violet (p. 37), 

 lignified walls yellow, or various shades to a sherry brown (pp. 39, 

 95), corky walls yellow or brown (p. 39), protoplasm brown, 

 while starch-grains swell and turn blue (p. 45). 



Chromic Acid, A strong aqueous solution of this acid, 10 per 

 cent, dissolves lignified and cellulose cell- walls : cuticularized 

 cell-walls resist its action ; but they become very transparent, 

 and may be easily overlooked. A dilute solution brings out the 

 stratification of cell-walls very clearly. A 1 per cent, solution 

 may be used in the preparation of Seaweeds. 



Clove-oil is used as a clearing agent before mounting specimens 

 which have been treated with alcohol in Canada balsam (p. 52). 



Copper Sulphate is used in the preparation of Fehling's fluid 

 (see below), and the preparation of ammoniacal solution of cupric 

 hydrate (see below). 



Corallin (Rosolic Acid). A solution of corallin in a 30 per 

 cent, solution of sodium carbonate colours lignified tissue, the 

 callus of sieve-tubes (p. 115), and starch-grains pink. 



Creosote is used together with turpentine as a clearing agent 

 before m' .tinting in Canada balsam (p. 52) : 1 part of creosote 

 and 4 parts of turpentine are to be shaken well together, 

 and set aside till the cloudiness formed on their first mixing 

 disappears. 



Cupric Hydrate. The ammoniacal solution of cupric hydrate 

 is used as a solvent for pure cellulose (p. 37). To a solution of 

 copper sulphate in water add dilute potash : collect the precipitate 

 on a filter, wash with water, and then dissolve it in a little strong 

 ammonia : this solution, which is of a dark blue colour, must be 

 prepared fresh each time it is required for use. 



Dammar, dissolved in warm turpentine, and evaporated to 

 the consistency of syrup, is sometimes used as a mounting medium 

 instead of Canada balsam : it does not set so firmly as balsam, and 

 it is well to seal up slides in which it has been used (p. 52). 



Ether is used as a solvent for wax, oils (p. 223), &c. When 

 very small objects have been embedded in paraffin or cocoa-butter, 

 it may be convenient to dissolve off the fragments of embedding 



