MINERAL NUTRITION OF FUNGI 7 



secured with Ca(N0 3 ) 2 than with NaN0 3 , the differences being 

 more pronounced at the higher concentrations. 



Young and Bennett (1922) also employed the triangle system in 

 determining the optimum concentration of Ca(N0 3 ) 2 , KH 2 P0 4 , 

 and MgS0 4 in solutions of these three salts. The solutions were 

 made up by molarity so that their osmotic concentrations were 

 equal. Sufficient carbon to make 3.43% was supplied from su- 

 crose. Fiisarhim oxysporum, Macrosporhim sarcinaeforme, and 

 Phoma apiicola were the test organisms. After 15 days' growth 

 on the solutions the mycelial mats were removed, carefully dried, 

 and weighed. The results indicate that a proper balance of inor- 

 ganic constituents is essential but that each organism appears to 

 require a different medium that can be determined only bv trial 

 and by techniques of the kind which Young and Bennett used. In 

 addition, calcium and zinc should be incorporated in synthetic 

 solutions, and it may be necessary to test several sugars before 

 the most desirable one can be known. 



Mann (1932) also employed the triangle method, with Pfeffer's 

 solution, to determine the influence of varying concentrations of 

 the three salts, ammonium nitrate, monopotassium phosphate, and 

 magnesium sulphate. She concluded that magnesium is absolutely 

 essential, although good growth of Aspergillus niger and Penicil- 

 lium sp. was secured at all concentrations greater than 0.0001 gram 

 molecule per liter of culture solution. Spectroscopic analysis 

 showed that calcium was present as a contaminant in proportions 

 less than 1 part per 25 million. Calcium chloride added to the 

 three salt solution caused no pronounced increase in the growth 

 of A. niger. 



More recently Talley and Blank (1941) performed a carefully 

 planned series of factorial experiments on the response of Phyma- 

 totrichum ormiivorum to the three salts K 2 HP0 4 , MgS0 4 , and 

 KC1 and on the effects of changes in the concentration of each 

 salt on responses to the others. Certain of their data which demon- 

 strate these interactions are assembled in Table 3. 



Optimum growth of P. omnivorum was secured when glucose 

 and nitrogen were not limiting. Solutions containing 0.008 M 

 dibasic potassium phosphate, 0.003 M magnesium sulphate, and 

 0.002 M potassium chloride were not improved, as indicated by 

 the growth of P. omnivorum, by increasing or by decreasing the 

 concentration of any one of the salts or of their ions. 



