STUDIES ON THE I'llVSIOl.OfiV OF Fusarium Uni. 23 



7. Potato decoction hard agar 



Boil 500 grams of peeled potatoes in lOOO cc. of distilled water for an 

 hour in a water bath, and strain through filter paper. Add 100 grams of 

 cane sugar and 20 grams of agar to 1 000 cc. of this filtrate, melt the agar 

 with boiling and strain through cotton. Distribute this medium in test tubes, 

 about 10 cc. each, and sterilize in Koch's steam sterili/.er for two hours twice 

 \vith one day's interval. 



Inoculate with a bit of mycelium or conidia, and incubate at 25^C. 

 Colour of the medium is white and semitransparent. 



White cottony aerial mj-cclium grows thickl>% covering all over the 

 surface of the medium. Afterward the mycelium present a light pink colour, 

 especially when the culture is exposed to light. 



Conidia are produced abundantly, and microconidia are more numerous 

 than macroconidia. Chlamydospores are produced poorly. 



Colour of the medium remains unchanged. 



This medium is suitable for the growth of the mycelium and also for 

 the conidial formation of this fungus. 



8. Soil decoction 



Steep I kilogram of soil in 2000 cc. of distilled water for 24 hours, 

 then boil it for an hour and filter. Thus may be obtained 300 cc. of trans- 

 parent soil decoction. Take 50 cc. of this decoction in each Erlenmeyer's 

 flask having 200 cc. capacity. Sterilize them in Koch's steam sterilizer for 

 two hours twice with one day's interval. The colour of the fluid is light 

 yellow. Inoculate with a bit of mycelium or conidia, and incubate at 25''C. 

 Mycelium develops poorly, and produces no aerial mycelium. 

 Formation of conidia is also poor, but chlamydospores are produced 

 abundantly. The colour of the medium remains unchanged. 



The medium of the following formula is generally suitable for the cul- 

 ture of the soil organism. 



Soil decoction lOOO cc. 



Cane sugar 20 grams. 



Potassium biphosphate 0.5 grams. 



