REAGENTS AND MOUNTING MEDIA. 489 



s. 



Safranin in alcohol (absolute). Saturated solution. Stains nucleus well in 

 material hardened in alcohol, chromic acid, or picric acid. In the 

 latter two cases the sections must first be washed in water, and then 

 placed in a little of the safranin solution diluted with an equal 

 quantity of distilled water. Leave in this from twelve to twenty- 

 four hours. They can be examined from time to time in a drop of 

 the same fluid to see how the staining is proceeding. Then wash in 

 absolute alcohol till they cease to give off colour ; place in oil of 

 cloves or of marjoram, and then mount in dammar or Canada balsam. 

 in ivatt^r. Saturated solution, one of the best single stains for differ- 

 entiating tissues, and permanent See pp. 111-2. Its action is 

 illustrated on the stem of Lycopodium, 177. 



A very highly recommended safranin stain is prepared by 

 mixing equal quantities of a saturated solution in alcohol and 

 another saturated solution in water. 



Saltpetre. See Potassium nitrate. 



Schultze's macerating mixture. See Macerating mixture. 



Schweizer's Reagent. See Copper Amman-oxide. 



Shellac. The clearest possible, dissolved in absolute alcohol to the thickness 

 of syrup, and filtered. Sometimes used as a mounting medium. 



Sodium chloride (table salt). Used in 5 or 10 per cent, solution as a 

 plasmolysing agent 



Starch paste (from Potato starch). Used in 1 per cent, solution as a nutrient 

 material in pollen -cultures, 392. 



Sugar (Cane). For solutions. 2-5 per cent, can be used to observe 

 living cells in (pp. 38, 434) ; 15-20 per cent, solution (or stronger) 

 to induce plasmolysis ; 2-4 per cent, to induce conjugation in 

 Spirogyra (p. 292) ; and solutions of various strengths, with 1*5 per 

 cent, gelatine added, serve as culture fluids for pollen -tubes (p. 391 

 et seq.). 



Sulphuric acid, concentrated. 



dilute. Equal volumes of sulphuric acid and water. Also 2 

 acid : 1 water. 



12 per cent. Used as a test for Bacteria, 270. 



T. 



Tannin solution (in water). Used for colouring crystalloids. See p. 36. 



Also a.s a mordant, 111. 



Tartar emetic (antiinonio-potassio tartrate). Also used as a mordant, 111. 

 Turpentine. 



V. 



Vaseline. 

 Vesuvin. Water solution. Used for staining bacteria, 230. 



