250 PRACTICAL BOTANY 



the material, before cutting sections, in a mixture of equal parts 

 of alcohol and glycerine. 



Alkanna (the root of Anchusa tinctoria) is used as a test for 

 resin, caoutchouc and oils. The alcoholic solution of alkannin, 

 as supplied by the dealers, may be used for this purpose ; but it 

 is found better to use sections of the dry alkanna root. 



Ammonia. The solution in water is often used for clearing 

 preparations instead of potash, as its action is less intense. It 

 is used with nitric acid as a test for proteids, and with copper 

 sulphate as a solvent for some forms of cellulose (see below, 

 Copper Sulphate). 



Ammonium Moiybdate, used, dissolved in a strong solution 

 of ammonium chloride, as a reagent for the detection of tannin 

 with which it gives a voluminous yellow precipitate. 



Aniline Sulphate and Chloride are used as reagents for 

 lignified cell- walls, which they stain yellow, while no other parts 

 of the tissue are coloured by them. A saturated solution of 

 either of these substances is made in distilled water, filtered, 

 and a few drops respectively of sulphuric or hydrochloric acid 

 are added, so that the solution shall give a distinctly acid 

 reaction : or a solution may be made in alcohol, and then be 

 diluted with water. 



Asphalte is used for sealing up slides in which glycerine has 

 been used as a mounting medium : it is liable to become very 

 brittle after a time, and, to prevent the cement breaking away, 

 it may with advantage be covered with a layer of gold-size. It 

 may be obtained ready for use from the dealers. 



Benzol, used as a solvent for various substances, e.g. the 

 coagulum of latex, eerie acid, &c. 



Brunswick Black may be bought ready prepared from dealers 

 in microscopic requisites : it is used for sealing up slides. 



Callus-reagent of Russow is prepared by mixing equal 

 volumes of chlor-zinc-iodine, and of the solution of iodine in 

 potassium iodide : it stains the callus of sieve-tubes a deep 

 brown. 



Canada Balsam is to be used dissolved in benzol and in such 

 quantity that it shall have the consistency of syrup. It is used as 

 a mounting medium for sections previously treated with alcohol, 



