ZOOLOGY AND BOTANY, MICROSCOPY, ETO. G89 



dant gives up anilin stains to acids very slowly, subjected some fission fungi 

 to a corresponding treatment. Dry preparations of rotting meat infusion 

 treated with a strong tannin solution, and then stained for twenty-four hours 

 with anilin or methyl violet, were found to be thoroughly stained after acid, 

 while the preparations not treated with tannin were either only faintly 

 stained or not at all. The difference became more apparent if a saturated 

 solution of tannin were used, and this peculiarity was found to affect all 

 kinds of Bacteria alike. A similar effect, but less marked, was obtained 

 with various albuminates and fats. By preparing a decomposing fluid con- 

 taining tannin, the author found the same resistance to acids in living 

 Bacteria. 



Demonstration of Phloroglucin.* — Herr 0. Lindt has discovered that 

 vanillin in very dilute solution (1 : 1000) gives a colour reaction with 

 phloroglucin and orcin, but not with resorcin. Both these bodies are, 

 however, sharply distinguished from each other by the different colour 

 given to these solutions. The j)hloroglucin is a bright red, assuming a 

 violet-red tone later on. The orcin solution is a bright blue with a trace 

 of red. Tiie reaction is so sensitive that 0*000001 grm. of the dry sub- 

 stance can be easily recognized on the addition of a drop of the vanillin 

 solution made according to the following formula: — Dissolve vanillin 

 0*005 grm. in spirit 0*5 grm., to this add water 0*5 grm., strong hydro- 

 chloric acid 3*0 grm. The reaction takes place so quickly that the 

 disturbing influence of secondary appearances does not interfere with the 

 histo-chemical investigation. 



It is, however, necessary that the microscopical sections should bo 

 previously dried on the slide, because water impedes the reaction and 

 lessens its intensity. It is further recommended that a control examina- 

 tion should be simultaneously carried on. By means of this solution the 

 author has been able to determine the presence of phloroglucin in tissues 

 which have been hitherto supposed to be devoid of it. On the other hand, 

 phloroglucin was found to exist in considerable quantity in the tissues of 

 certain leaves which later on became crimson, although the leaves of 

 most plants which remain green in autumn contain little or none. 



Dr. Lindt suspects that the red colour of certain leaves and plant stems 

 is not less dependent on the presence of phloroglucin than on the ex- 

 istence of a certain quantity of tannin, for it is quite possible that the 

 relations which exist between the latter and the red colouring matter may 

 depend on a similar reaction of certain transformation-products due to the 

 action of tannic acid on phloroglucin — a reaction comparable to the effect 

 of vanillin on phloroglucin. 



It may be mentioned that the presence of a mineral acid does not seem 

 to be indispensable to the appearance of the reaction, for if vanillin, 

 phloroglucin, and oxalic acid be dissolved in water and the solution 

 evaporated to dryness, the residue is bright red. 



Staining Preparations for Photography .f — Dr. P. Francotte gives the 

 results of experiments in j)hotographing preparations stained with various 

 colours. 



For picro-carmine preparations two baths are necessary — (1) The plate 

 is steeped for two minutes in distilled water 200 cc. ; ammonia 2 cc. 

 (2) Then for two minutes in distilled water 200 cc. ; ammonia 2 cc. ; 

 alcohol 10 cc. ; solution of cyanin 1 : 500 in absolute alcohol 5 cc. 



* Zeitschr. f. Wiss. Mikr., ii. (1885) pp. 495-9. 

 t Bull. Soc. Belgo Micr., xiii. (1887) i>p. 151-8. 



