VITAMINS 



173 



E 



O 



10 



12 



14 



2 4 6 8 



Days of incubation 



Fig. 29. Growth curves of Chaetomiurn globosum, a self-sufficient fungus, in 25 ml. of 

 liquid glucose-casein hydrolysate medium in the absence of vitamins and when 

 thiamine, biotin, inositol, and pyridoxine were added. 



Fig. 30. Mutualistic symbiosis with regard to vitamins. Phycomyces blakesleeanus, 

 thiamine-deficient, inoculated on the right and Sordaria fimicola, biotin-deficient, 

 inoculated on the left. Both fungi made only slight growth until the two colonies met. 

 Note the perithecia of Sordaria on the right and the sporangiophores of Phycomyces on 

 the left. Each fungus excreted into the medium the vitamin which the other could not 

 synthesize. 



