510 Mr Walter Gardiner, Methods for the Demonstration [Mar. 7, 



of experiments I also find that if the swelling is followed by 

 treatment with a dilute solution of sulphuric acid containing a 

 trace of Potassic permanganate the walls are- bleached, and at 

 the same time so altered in character that after mordanting they 

 no longer stain with the acid Violet, and thus the threads are 

 brought very clearly into view. The threads may be readily 

 demonstrated at the edges of the preparation by means of the 

 ordinary technique when due regard is paid to the special require- 

 ments already mentioned. The complete absence of threads from 

 the external walls is very striking, and still more striking is the 

 enormous number of the threads present. 



It now remains for me to make a few concluding observations 

 upon the rationale of the Iodine-Acid-Violet method. 



The great merit of Meyer's modification is, as I have already 

 remarked, that it places in the foreground the important role of 

 the Iodine and makes definite provision for mordanting the 

 protoplasm and threads before the application of the dye. This 

 was not done by earlier observers, although I quite agree with 

 Meyer in thinking that what success attended the somewhat 

 analogous methods of Russow 1 , Terletzki 2 , Kienitz-Gerloff 3 , and 

 (I may add) Poirault 4 , was not unconnected with the fact that 

 at the time of staining some traces of Iodine were present in the 

 tissue. 



The same is possibly true of the Iodine-Chlor-Zinc-Iod- 

 Aniline-Blue methods of Russow 5 and myself 6 . 



The mordanting properties of Iodine in combination with 

 Aniline dyes has of course been long known, having been used 

 in conjunction with Gentian violet by Gram 7 in 1884 and 

 Bizzozero 8 and Nissen 9 in 1886; and I see from my notes that 

 I have myself used it since 1895 in connection with my Kolossow- 

 Safranin method. These facts however in no way detract from 

 the excellence of Meyer's own researches. 



The mordanting properties of Iodine appear to result from 

 the remarkable and phenomenal manner with which it is taken 

 up by the protoplasmic structures of the cell. 



It is difficult to frame any adequate explanation of this 

 interesting fact, and the very expressions one uses in connection 

 with it must, I fear, be but vague and unsatisfactory. No 



1 Eussow. Sitzber. der Dorpat. Naturf. Gesell. 1883. 



2 Terletzki. Jahrb. f. Wiss. Bot. Bd. xv. 1884. 



3 Kienitz-Gerloff. Bot. Zeit. 1891. 



4 Poirault. Annales de Sci. Nat. Bot. 1893. 



5 Russow. Sitzber. der Dorpat. Naturf. Gesell. 1882. 



6 Gardiner. Phil. Trans. Roy. Soc. 1883. 



7 Gram. Fortschr. d. Medecin. n. No. 6. 18S4 



8 Bizzozero. Zeit. f. Wiss. Mik. in. 1. 1886. 



9 Nissen. Arch. f. mik. Anat. 1886. 





