430 Bulletin 315 



Preparation and sterilization of media 

 The media used were soil extract agar, nutrient agar, manure extract 

 agar, potato decoction agar, moist bread, gelatin, Uschinsky's solution, 

 Raulin's culture fluid, Cohn's nutrient solution, lactic acid solution, 

 lactose solution, potato plugs, and wheat stem plugs. The preparation 

 and formula of each follows: 



Soil extract agar I. — Prepared according to the following formula 



Distilled water 800 cc 



Soil extract* 200 cc 



Dextrose 10 gms 



Dipotassium phosphate (K2HPO4) .5 gm 



Magnesium sulfate (MgS04) .2 gm 



Agar 15 gms 



After washing, the agar was always melted over a free flame and stirred 

 constantly in order to prevent burning. It was next added to the above 

 solution and cooked in a double boiler for one hour, then titrated, filtered, 

 and sterilized in the autoclave. 



Soil extract agar II. — Prepared according to the formula given under 

 soil extract agar I. The extract was prepared as follows: The soil that 

 served as a basis for this extract was a gravelly sandy loam. It was 

 taken from land seeded to grass and contained many small roots. The 

 moistiire content was first determined and was found to be approximately 

 15.6 per cent. To obtain approximately 3,000 grams of dry soil, 3,555 

 grams of the wet soil was used. To this soil was added 625 cc. of hydro- 

 chloric acid (125 cc. HCl sp. gr. 1.1328, and 500 cc. distilled water). 

 Digestion was allowed to proceed at room temperature for twenty-four 

 hours. The soil was next placed over a warm radiator and allowed to dry 

 for two days. To the soil was then added 1,000 cc. of ammonia water 

 solution (400 cc. ammonia sp. gr. .96, and 600 cc. of distilled water). The 

 soil was allowed to stand at room temperature for twenty-four hours, 

 and then kept over a warm radiator for five days with repeated stirring. 

 No ammoniacal odor could be detected at the end of the period, and the 

 soil felt dry to the touch . Water sufficient to make four liters of filtrate was 

 added. The filtrate constituted the soil extract used during the winter 

 of 1910-1911 and the spring and summer of 1911. 



As already stated, this agar was made up identically as was soil extract agar 

 I . It was always titrated and found invariably to be acid. It has been used 



* The writer is indebted to Dr. H. J. Conn, a graduate student in the Department of Soil Technology, 

 College of Agriculture, Cornell University, at the time this investigation was begun, for the soil extract 

 used as a basis of the agar for isolations A, B. and C, and for suggestions as to making this extract as 

 well as the medium. His work on soil bacteria had led him to conclude that this medium might well be 

 adapted for fungus isolation. While the details of obtaining this extract cannot be given, it does not 

 differ particularly from that described under soil extract agar IL 



