18 



METHODS 

 The salts used in these experiments were "Baker's 

 analyzed chemicals" procured in the original packages. 

 Stock solutions of the different salts, from which the ex- 

 perimental solutions were afterwards prepared were made up 

 in 0.2 m, 0.5 m, or molecular concentration. In preparing 

 the stock solutions the salts were weighed in glass-stop- 

 pered weighing bottles directly from freshly openeJ pack- 

 ages and were dissolved in volumetric flasks. These solut- 

 ions were then made up to the required voliome at a temper- 

 ature of 15°C. They were stored in Jena glass bottles which 

 had been carefully washed with a saturated solution of pot- 

 assiiim dichromate in sulphuric acid, steamed for half a day, 

 again washed with distilled water and then allowed to soak 

 in distilled water for a month or more to remove any soluble 

 matter which might be present. Distilled water from a still 

 with tin lined boiler and condenser was used in making the 

 stock solutions as well as in diluting them for the cultural 

 work. Preliminary tests showed that the spores germinated as 

 well in this still as in the more nearly pure water distill- 

 ed from potassium permanganate using a hard flask and block 



tin condenser. 



The stock salt solutions were diluted to the concen- 

 trations required in making up the solutions for the experi- 

 ments, by pipetting out a certain amount into a hard glass 

 beaker and then adding the necessary distilled water from a 

 burrette. The concentrations of these solutions were so cal~ 



