TOCHiNAi : STUDIES OX THE I'in'Sior.OGV OF Fusarium Uni. 33 



covers all over tlic surface of the medium with the aerial mycelium. 



The fact shows that a comi)arativ'ely higher concentration of citric acitl 

 docs not injure the fungus so severly as to casuc its deadi, at least of its 

 ch lamydospores . 



As the sj-ntlietic nutriti\e solution itself has somewhat weak acidit>- by 

 the potassium biphosphate (KILPOj, the addition of citric acid intensifies it 

 grcatl>-. 



In this experiment I have observed, that citric acid retards the growth 

 of the fungus in near!}' the same manner as tannic acid, especially in higher 

 concentrations. Comparing the tannic acid cultures with the citric acid cultures, 

 it does not seem that tannin is more to.xic than citric acid for the fungus in 

 this synthetic solution. 



Flax is a non-tannin-bearing plant, therefore Fusarium Uni may be 

 considered to have no adaptation to tannin in its natural condition. Then 

 it must be said that for such a fungus tannin is no more toxic than citric 

 acid. I do not think it reasonable to give an ecological meaning to the 

 tannin production of plants and to regard tannin especially as a toxic or 

 preventive substance for parasites generally. But tannin production is merely 

 a characteristic of a species or genus of plant, and tannin is no more than 

 a physiological product by assimilation or metabolism of a plant. 



Experiment 2. 



In the present experiment I have used potato decoction hard agar for 

 the standard cultural medium in order to investigate the effect of the change 

 of a cultural medium containing different percentages of citric acid upon the 

 growth of the fungus. 



The standard medium was prepared in the ordinally method. The 

 formula of the medium is as follows. 



Potato decoction lOOO cc. 



Cane sugar 100 grams 



Agar 20 ,, 



The medium was sterilized in a Koch's steam sterilizer for half an hour 

 twice with one day's interval. 



