512 W. Gardiner, Methods for the Demonstration, etc. [Mar. 7, 189b. 



(2) Sections of swollen tissue treated as in B. (1) give a 

 result practically the same as B. (1). 



It is not the alteration in the cellulose produced by the acid 

 which determines the reaction, since experiment shows that a 

 swollen wall can be subsequently stained by an aqueous solution 

 of the dye; neither is it necessarily all acid solutions which produce 

 the result since when the dye is dissolved in acetic acid a sensible 

 staining of the wall occurs. 



As regards the relations between the dye and its solvent, the 

 following points deserve notice. 



A freshly made solution of Pyoktanin or Gentian violet con- 

 taining "5 % °f the dye dissolved in a 5 °/ aqueous solution of 

 sulphuric acid is at first of a vivid green colour with a yellowish 

 tinge. The colour however soon commences to fade, and after 

 some time entirely disappears. For a short period this liquid 

 would appear to contain a solution of the dye as such, but 

 decomposition soon commences and ends (I presume) with the 

 formation of a colourless sulphate of the base. Whether the 

 sulphuric acid may at any time be regarded as containing un- 

 altered Pyoktanin or Gentian violet, or whether at the moment 

 of admixture a chemical change occurs must for the present be 

 left an open question, but one salient fact becomes obvious, viz. 

 that the staining powers are greatly diminished and bear little 

 comparison to those exhibited by the dye when in aqueous 

 solution. Further, such staining as does take place is fairly 

 limited to the protoplasm. 



The selective characteristics of the Acid violet are naturally 

 accentuated by the use of Iodine, since the Iodine itself has 

 analogous affinities for the cytoplasm and threads, and has in 

 addition an intense affinity for the dye. 



That the mordanting action of the Iodine is mainly limited to 

 the protoplasm may also be proved by the following experiment : 



A section is swollen with acid and washed, and is then treated 

 with Iodine and stained with an aqueous solution of one of the 

 Violets, when it will be found that both the protoplasm and the 

 cell walls are deeply stained. If now placed in a 5 °/ solution of 

 sulphuric acid the dye is dissolved from the walls but not from 

 the protoplasm, so that both the protoplasm and the threads come 

 into view. 



As this paper is concerned with methods only, I do not 

 propose to give an account of my more recent results, but my 

 work in this direction is proceeding and will be published in due 

 course. I also intend to deal with other modifications of the 

 two methods I have now described. 



