Blue and Violet Stainingsfor Vegetable Tissues. 185 



More water may now be poured on, and the solution, after filtration, 

 should present a clear, somewhat dark violet colour. If a dirty red 

 be obtained more alum must be incorporated and the mixture again 

 filtered. After standing several days add 75 per cent, alcohol in 

 the proportion of two drachms to one ounce of the fluid. Should a 

 scum form on the surface of the liquid at any time, a few drops of 

 alcohol and careful filtering will be all that is required. 



This fluid colours very rapidly, requiring but a few minutes, 

 whereas, if a slower tinting be desired, the fluid may be diluted with 

 a mixture of one part alcohol and three parts water.* 



Aniline blue, of which there are several shades, may be 

 dissolved in distilled water. A 1 per cent, solution, to which a 

 small quantity of alcohol and a trace of oxalic acid have been added, 

 answers admirably. For convenience I use '' Bower's Blue Ink," 

 slightly acidulated with oxalic acid. The tint is exactly that of 

 Eobert Dale and Co.'s Soluble Blue, No. 3. 



The hsematoxylin colour will not wash out, but the aniline 

 blue will do so unless precaution be taken. 



Having prepared suitable sections of parts having been kept in 

 alcohol, place them in a very weak dilution of Arnold's fluid, and 

 watching the result, transfer the morsel to dilute alcohol for wash- 

 ing, and afterwards to strong alcohol in anticipation of mounting. 



Or immerse the sections in the aniline fluid for five or ten 

 minutes, or longer; watch the result; wash in strong alcohol, and 

 drop them into absolute alcohol. 



The logwood stainings may be mounted at pleasure ; but the 

 aniline dyeings ought to be rendered transparent in oil colours 

 as soon as possible, and mounted speedily in a moderately thin 

 solution of old hard balsam. If it be intended to display the 

 general structure let the tint be decided ; but if it be wished to 

 give prominence to the vessels, for instance, a faint blue only 

 should suggest the other parts. 



A weight of a fourth or half-ounce ought to be placed on the 

 cover for a week. 



The treatment of thin leaves, or of fresh green sections, is 

 entirely diflerent. Colour must first be removed, or else staining 

 would be of little service. The bleaching is to be accomplished 

 through the agency of Labarraque's solution of chlorinated soda, in 

 which the objects ought to be macerated, and suftered to remain 

 until perfectly achromatic and transparent. Immediately thereafter 

 others must be transferred to distilled water for an hour or two, 

 and then to a 3 per cent, solution of oxalic acid in 50 per cent, 

 alcohol, which neutralizes the soda and disposes the tissue to accept 

 the aniline dye. 



* Soluble Blue, No. 3, Robert Dale and Co., Hulme, Manchester, Englaud. 

 Soluble Blue, Simpson and Maulc, Londoa. 



