328 



PHYSIOLOGY OF THE FUNGI 



ence of growth factors in the yeast extract. The addition of pyridoxine 

 to the basal medium caused little change in mycelial growth, but a great 

 increase in abundance of macroconidia resulted. On the other hand, the 

 addition of thiamine or of a mixture of thiamine and pyridoxine caused 

 no increase in growth or production of macroconidia. 



An interesting observation of the constant natural association between 

 Nectria coccinea and Gonatorrhodiella highlei is reported by Ayres (1941). 

 Because of this constant association it was believed that G. highlei was 

 either parasitic upon A^. coccinea or dependent upon it for some nutri- 

 tional substance. On potato-glucose, malt extract, and other common 



Fig. 67. The stimulating effect of Aspergillus rugulosus (small colony at the bottom) 

 on the production of perithecia by Sordaria fimicola grown on glucose-asparagine 

 medium low in biotin. The zone of black perithecia of Sordaria around the colony of 

 Aspergillus is attributed to the biotin excreted by the latter fungus. 



media G. highlei made only slight growth and formed no conidiophores or 

 conidia. However, the fungus grew well and produced numerous conidio- 

 phores and conidia on the same media in the presence of A^. coccinea, N. 

 galligena, or N. cucurhitula. Neither N. cinnabarina nor N . coryli caused 

 stimulation. G. highlei was cultivated successfully with production of 

 abundant conidia on oatmeal mush, without the presence of other fungi. 

 These results strongly suggest a nutritional relation between G. highlei 

 and N . coccinea, other than that of parasitism. 



The beneficial effect of one fungus upon reproduction of another can 

 easily be demonstrated by placing Aspergillus rugulosus and Sordaria 

 fimicola on a plate of agar containing little or no biotin (Fig. 67). S. 

 fimicola, being a more rapid grower, produces a sparse mycelium, which 

 surrounds the slow-growing colony of Aspergillus. The Sordaria myce- 



