MINERAL NUTRITION OF FUNGI 5 



tinia, Sphaeropsis, and Vermicularia in Richards' solution with 

 Ca(N0 3 ) 2 substituted for KNO3 and maintained, although their 

 evidence is not conclusive, that best growth occurred in the solu- 

 tions containing calcium. They attribute this phenomenon to 

 the neutralization by calcium of the acids formed from sucrose. 

 In support of this theory they demonstrated that growth, when 

 inhibited by acids, can be renewed after neutralization of the 

 acids. They also grew F. oxysporum, A. niger, and R. nigricans 

 on similar solutions with the results shown in Table 1 . These data 

 show, for each fungus, greatest growth in the presence of calcium. 



TABLE 1 



Comparative Growth of Fungi in KNO3 and Ca(NOs)2 



Weight of Mycelial Mat {grams) 



Richards' solution Richards' solution 



Organism with KNO3 with Ca(NOs)2 



Fusarium oxysporum 0.2094 0.2428 



Aspergillus niger 0.5450 0.8270 



Rhizopus nigricans . 201 5 . 2787 



Concentration and proportion of minerals. Manifestly 

 chemical constitution is a factor of primary importance in the 

 preparation of suitable mineral substrata for the growth of fungi, 

 but account must also be taken of the proper balance of elements 

 and of their concentration. Several important papers have ap- 

 peared dealing with these factors. With Aspergillus niger 

 Haenseler (1921) used the same three-salt mineral nutrient and 

 quite the same procedure as has been utilized in physiological 

 studies with green plants. The salts consisted of Ca(NO :i )2 or 

 NaN0 3 , A4gS0 4 , and KH 2 P0 4 . Different concentrations of each 

 salt, making total concentrations of 0.5, 2.1, and 4.2 atm, were 

 employed, and to each culture flask were added equal amounts of 

 sugar and other nutrients. The dry weight of the mycelial mat 

 after 7 days served as Haenseler's basis for evaluating salt concen- 

 tration and balance. The data in Table 2 show the plan employed 

 by Haenseler in this type of study. 



Haenseler concluded that at concentrations equivalent to 4.2 

 atm. growth is best, so that total concentration must be regarded 

 as very important. Wide variation in the concentration of MgS0 4 

 and KH0PO4 did not greatly modify growth. Better growth was 



