Action of Aniline Dyes on Vegetable Tissues. 191 



sized bottle being filled with alcohol, pieces of the root 

 from one to two iuches in length are cut, and immediately 

 placed in it. Coagulation of the latex is quickly effected. 

 After lying thus for a week or longer, sections are cut 

 with the hand, or by aid of a microtome. The second point 

 is most important, and on its success the beauty of the 

 object will depend. The sections are placed in alcoholic 

 solution of saffrauine, obtained by dissolving 1 part of this 

 dye in 800 parts spirit. After eighteen to twenty-four 

 hours they are removed from the stain and decolorised by 

 washing repeatedly in spirit. It will be found that the 

 stain leaves the cellular tissue rapidly, while it is retained 

 by the latex in the vessels. We will notice lastly the 

 best method for mounting these. While such media as 

 balsam or dammar would cause unnatural contraction, fluids, 

 on the other hand — especially acetic acid solution — are apt 

 to act slightly on the dye. I have found nothing to equal 

 glycerine jelly, as it preserves the tint and is easily worked. 



II. Double Staining of Stems, &c. — The dyes usually 

 recommended for this purpose are rosaniline and iodine 

 green ; but saffranine and emei'aldine are preferable, as the 

 former is, for vegetable tissues, a most permanent dye, while 

 the latter imparts a brighter colour than iodine green. 



III. Staining of Cell Contents. — While some aniline 

 dyes act specially on the thickened walls of cells, others 

 are extremely useful for demonstrating the structure of 

 protoplasm. Heliocin and naphthaline in this respect are 

 valuable ; and eosin, though not an aniline dye, is equally 

 so. For epidermis cells and ordinary parenchyma the 

 latter is preferable. It is best prepared by dissolving 

 1 part, in 1200, of alcohol. The specimens are allowed to 

 lie for five minutes in the stain, and are then washed in 

 water and mounted in a cell with acetic acid, or Goadby's 

 solution. The cells of Spirogyra, however, have their 

 minute structure beautifully revealed by treatment with 

 heliocin. The following is the best method to adopt : — 

 Decolorise the filaments by placing them in a 1 per cent, 

 solution of cliroinic acid for two days ; add then to the 

 solution 1 part, in 2000, of the dye and shake slightly, so 

 that it may dissolve equally. In an hour the filaments 

 will be ready for examination or permanent preparation. 



