12 



NUTRITION OF FUNGI 



this fact in connection with iron in Warburg's cytochrome, in 

 other heme-respiratorv pigments, in catalase, and in peroxidase. 

 Copper appears to act similarly in the oxidase molecule. Manga- 

 nese is well known to act powerfully as a coenzyme. 



Differences exist in methods of measurements of fungal growth 

 on semisolid substrata. Some workers measure dailv radial incre- 



R8 A 0.324 



Rl 



CI 



C2 



C3 



C4 C5 



KH 2 P0 4 



C6 



C7 



Fig. 2. Diagram illustrating triangle system of varying the concentrations 

 of three-salt nutrient solutions used in nutritional studies and showing the 



relative vields. (After Haenseler.) 



ments; others measure ring area. In a recent report Worley 

 (1939) indicates that several criteria should be considered in 

 growth measurements, namely: (1) growth in a radial direction, 

 (2) growth in a tangential direction, (3) number of units con- 

 tributing to the subsequent growth, (4) the relationship of new 

 increments of growth to the substrata being compared, and (5) 

 the relative importance of radial and tangential growth quantities. 

 The radial method of measurement ignores the effect of criteria 

 2, 4, and 5. The ring-area method omits criteria 3 and 4 and mag- 



