258 BOTANICAL MICROTECHNIQUE. 



by mixing 10 ccm. of a 20$ aqueous tannin solution, 5 ccm. 

 of a cold saturated solution of ferrous sulphate, and I ccm. 

 of an aqueous solution of fuchsin. According to the char- 

 acter of the Bacteria, a few drops of sulphuric acid or of 

 caustic soda* must be added to this mixture. The cover- 

 glass holding it is now warmed over the flame until steam is 

 formed and, after half a minute to a minute, the mordant is 

 rinsed off with distilled water, and the cover-glass is dried 

 as usual. Then the staining fluid is dropped on until the 

 cover-glass is wholly covered by it, the whole is again 

 warmed for a minute until steam forms, and is finally rinsed 

 in a stream of water, dried, and mounted in balsam in the 

 usual way. Loeffler recommends as a staining-fluid, a solu- 

 tion of fuchsin in aniline-water, or a mixture of 100 ccm. of 

 aniline-water, I ccm. of a \% soda solution, and solid fuchsin 

 in excess. 



* For staining the cilia of typhus Bacilli, 22 drops of a i% aqueous solu- 

 tion of sodium hydrate should be added to 16 ccm. of the above mordant ; 

 for Bacillus subtilis, 28 to 30 drops. On the other hand, the cholera Bacilli 

 require the addition of -^ to I drop of a sulphuric acid that will just neutral- 

 ize the same volume of \% caustic soda ; Bacillus pyocyaneus, the addition of 

 5 to 6 drops of the above acid ; Spirillum rubrum, 9 drops of the same. 

 But the above mordant has just the right reaction for Spirillum concentri- 

 tum. According to the writer's experiments, it is also well suited to Spiril 

 lum Undula without further addition. 



