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



and any tissue which can be stained with it, admits of very wide 

 treatment on account of the numerous and important substitu- 

 tions and combinations which can be subsequently effected. 



Tn connection with the Safranin method it is important to 

 note that it is the protoplasm and connecting threads which 

 appear to be mordanted by the Uranium, and that it is in these 

 structures that the precipitate of Uranium and Safranin which 

 cannot be dissolved by the Orange G. is formed. 



B. The Iodine- Acid-Violet Method. 



As the Kolossow-Safranin method depends upon the fact that 

 the Uranium salt in combination with certain elements of the 

 dead cytoplasm acts as a mordant to the Safranin, so in the 

 Iodine-Acid-Violet method, the Iodine is the mordant and an 

 Aniline violet the dye. 



We owe to Meyer 1 the latest exposition of the relations between 

 Iodine and certain of the Aniline violets, as well as the explicit 

 account of an excellent method, for the demonstration of "con- 

 necting threads." 



Meyer brings clearly into prominence the part played by 

 Iodine as a mordant, and to him belongs the credit of stating 

 with precision the great importance of this fact and dwelling 

 upon the significance of it in connection with his method. 



His method is as follows : 



Sections of fresh tissue are treated with a solution made b}^ 

 adding - 5 grms. Iodine and "5 grms. Potassic Iodide to 100 c.c. of 

 water. They are transferred to a slide together with a small 

 quantity (a half drop) of the Iodine solution. One or two drops 

 of a 30 % solution of sulphuric acid saturated with Iodine are 

 added and the cover-slip is put on. 



Then a half drop of a 3 °/ solution of Pyoktanin is run 

 under the edge of" the cover-slip. The Pyoktanin is at once 

 dissolved by the sulphuric acid, forming a brownish yellow or 

 greenish yellow solution which, together with the Iodine present, 

 stains the protoplasm and the " connecting threads " black. The 

 various details of staining may be observed under the microscope. 

 After some three minutes have elapsed the slide and its contents 

 are placed in a vessel containing about 400 c.c. of water. In 

 successful preparations the cell wall is stained light blue and 

 the protoplasm and "connecting threads" blue black. The fine 

 precipitate formed by the union of the Iodine and Pyoktanin, 

 which is frequently deposited upon the section, may be removed 

 by brushing. 



The author made a series of observations upon the aniline 



1 Meyer. Besichte der Deiitsch. Bot. Gesell. Bel. xv. Heft. 3. 1897. 



