12 PKACTICAL BOTANY. 



be then mounted in Canada balsam, or it may be mounted in a 

 50 per cent, solution of potassium acetate in water. 



A useful preparation of methyl- violet is the following : Some 

 of that substance is dissolved in strong sulphuric acid, forming a 

 brownish-green solution : on the gradual addition of water the 

 violet colour reappears. This is especially useful for sieve-tubes. 

 If a section be treated with this fluid for a short time, and be 

 then washed with water, it, will be found that the cell- walls have 

 become swollen and transparent, that the protoplasm has become 

 deeply stained, aod that the sieve-plates are very well brought 

 out. Lignified tissues treated with this fluid assume a yellow 

 colour, as they do when treated with aniline sulphate. 



5. Hanstein's Aniline-violet. This is prepared by dissolving 

 equal parts of fuchsin and methyl- violet in alcohol. It stains 

 cellulose cell- walls of a faint violet colour, and lignified cell-walls 

 red. It is especially useful for bringing out the different parts 

 of the bast, since the bast-fibres stain red, whereas the sieve-tubes 

 and the parenchyma scarcely stain at all. The protoplasm is 

 stained pink ; amyloid substances, gums, and nuclei stain 

 different shades of red, resins blue, and tannin brick-red. 



6. Hoffmann's Blue. Used in solution in dilute alcohol 

 slightly acidified with acetic acid : it is a useful reagent, inas- 

 much as it stains the protoplasmic cell-contents and not the cell- 

 wall : it stains also the callus which closes the perforations of the 

 sieve-plates during the winter in perennial plants. (Water blue 

 is almost as good a reagent.) 



7. Methylene blue. Used in solution in water : stains the 

 cell- wall but not the protoplasm. 



To produce the differentiated staining mentioned in 6 and 7, 

 the preparations must be washed in water after staining, and also 

 before staining if the material has been previously kept in alcohol. 



8. Alizarine. Many of these aniline-dyes will not stain the 

 protoplasm of Fungi. Alizarine will do so at least in some cases. 



9. Eosin. Used in strong alcoholic solution for demonstrating 

 the structure of sieve-tubes, as it stains the protoplasm deeply : 

 a solution in water may also be used. 



10. Corallin (rosolic acid). A solution in 30 per cent, sodium 

 carbonate colours lignified tissue, the callus of sieve-tubes, and 

 starch grains pink. 



