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Y.—Blue and Violet Stainings for Vegetable Tissues. 

 By Christopher Johnston, M.D., Baltimore, U.S.A. 



Without questioning the advantage of viewing vegetable tissues, 

 isolated or in section, in glycerjne or water when fret^hly obtained, I 

 proceed at once to point out methods by which very useful and 

 beautiful tinted objects of this class may be prepared and mounted 

 in balsam. 



As in the Bessemer process, iron must be thoroughly decarbonized 

 and afterwards regularly dosed with carbon for the making of steel, 

 so all colour must be destroyed in or withdrawn from vegetable 

 structures before a good staining material can be successfully em- 

 ployed. Alcohol decolorizes, but its prolonged action crisps the 

 tender material ; and although the latter might take the dye, it 

 would not always be possible to display the vegetable web, or, in 

 many instances, to render it distinctly transparent. But alcohol is 

 extremely important, indeed, I should rather say indispensable, in 

 the preparation of the class of objects under consideration. For 

 whatever may have been the early steps of several processes, alcoholic 

 saturation must precede balsamic embalming. 



With our present intention recent plant structures may be studied 

 in two conditions, first, in that requiring the section-cutter, and, 

 secondly, in their natural form. And this, without taking into 

 account the ultimate dissection accomplished by the knife, by needles, 

 by acids, or by alkalies. As a preliminary to the first it is only 

 necessary to keep fresh specimens of plants or parts of plants in 

 strong alcohol, in which, after the lapse of a month or two, colour 

 will oftentimes entirely disappear. Whereupon the desired sections 

 may be made, tinted if they be sufficiently blanched, and mounted 

 at once. 



For tinting such sections I have used the lilac fluid of Thiersch 

 as given in Frey, a double strength lilac fluid, a dilution of the 

 hematoxylin staining fluid of Dr. J. W, S. Arnold of New York, 

 as published in the ' Lens ' of July 1872, and aqueous solution of 

 aniline blue which I obtained ready made and labelled Blue ink of 

 F. G. Bower and Co., New York. I much prefer the two latter' 

 because distinct carmine stainings fatigue the eye when studied at 

 night, while the lilac of logwood, but especially the delicate blue 

 purple of the aniline, are most agreeable and not fatiguing at all. 



Arnold's fluid is prepared as follows : — " The ordinary logwood 

 extract is finely pulverized in a mortar, and about three times its 

 bulk of alum (in powder) added ; the two ingredients are well rubbed 

 up together, and mixed with a small quantity of distilled water. 

 The complete admixture of the alum and haematoxylin is necessary, 

 and this will require fifteen or twenty minutes' vigorous trituration. 



