Fungous Flora of the Soil 431 



without any further modifications. Of all the media used, this is superior 

 without question for the isolation of soil fungi and has been the standard 

 medium. While it shows superiority in isolation work, still it seems to 

 produce abnormal growth and for this reason the detailed study of species 

 has been made on other media, nutrient agar and wheat plugs. 



Soil extract agar III. — One and one half kilograms of sandy soil were 

 mixed with three liters of water and allowed to stand at room temperature 

 over night (approximately seventeen hours). It was extracted for two 

 hours in the autoclave at 20 pounds pressure. The filtrate obtained was 

 used in the following formula: 



Distilled water 800 cc. 



Soil extract 200 cc. 



Dextrose 10 gms. 



Dipotassium phosphate (K2HPO4) .5 gm. 



Magnesium sulfate .2 gm. 



Agar 15 gms. 



The medium was prepared as were I and II. 



Nutrient agar^ . — Prepared according to the following formula : 



Distilled water 1,000 cc. 



Glucose 5 gms. 



Sodium chlorid 5 gms. 



Witte's peptone 5 gms. 



Liebig's beef extract 3 gms. 



Agar 15 gms. 



Manure extract agar. — Prepared as follows: To 100 grams of well- 

 rotted horse manure was added 500 cc. of distilled water. This was 

 allowed to stand for twenty-four hours at room temperature and then 

 filtered. The filtrate was used as a stock solution. 



I. Distilled water 800 cc. 



Manure extract 200 cc. 



Agar 16 gms. 



II. Distilled water 666 cc. 



Manure extract 333 cc. 



Agar 16 gms. 



' This was made by first preparing the bouillon. The calculated amount of water was placed in 

 a double boiler, and beef extract, peptone, sodium chlorid, and glucose were added; this was then 

 cooked for one half hour and at the end the water lost by evaporation was restored. The agar was cut into 

 small pieces, tied loosely in clean cheesecloth, and washed in running tap water for twenty minutes. At 

 the end of this period, the agar was removed from the cloth, placed in a stewpan, and covered with 

 bouillon. It was then boiled over a free flame until all the agar was melted. The melted agar was 

 poured into the bouillon, the whole boiled for one half hour, and then cooled to 58° _C.; the well-beaterj 

 whites of two eggs were added, and the solution was thoroughly mixed. . Cooking in the double boiler 

 was continued for one hour. The water lost by evaporation was restored. Toward the end of the 

 cooking, the solution was titrated to 1.5 +. After cooking, it was filtered and sterilized In the autoclave 

 at 17 to 18 pounds pressure for one half hour. 



