288 ASSOCIATIVE EFFECTS AMONG FUNGI 



centered around the complex problem of factors regulating 

 growth and reproduction in plants and animals. The terms auxins, 

 hormones, and vitamins, applied to stimulatory and regulatory 

 substances, are commonly used not only by the biologist but also 

 by the man in the street. 



Stimulation of vegetative activity. Wildiers (1901) first 

 established that Sacchacomyces cerevisiae will not grow in a syn- 

 thetic medium consisting of ammonium chloride and sugar unless 

 some substance essential for growth is added. This result revived 

 an old controversy that existed years before between Pasteur and 

 Liebig. Pasteur claimed that yeasts made abundant growth on a 

 nutrient medium containing sugar, ammonium salts, and the ashes 



DO 7 



of yeast. Liebig was unable to grow yeast successfully on this 

 formula, whereupon Pasteur offered to produce for him "all the 

 yeast he could require." Liebig declined the challenge, and in 

 consequence Pasteur was considered to have won the scientific 

 argument. Wildiers noted that, when he placed a single yeast 

 cell or a few cells only in this medium, little or no growth took 

 place. If, however, he introduced as many yeast cells as were 

 contained in two drops of beer wort from a vat in which yeast 

 was being grown, abundant growth resulted. He also induced 

 growth by the addition of a few cubic centimeters of boiled yeasts. 

 His results were so striking that he assumed some hypothetical sub- 

 stance that he called "bios" to be essential for growth. He ex- 

 tracted this bios from yeasts by boiling. It was dialyzable from a 

 watery extract; it was not present in yeast ashes. Of course, the 

 results of Wildiers attracted wide attention and were sharply 

 criticized. They were substantiated, however, and with the dis- 

 covery of vitamins and the flood of investigation that followed, it 

 became apparent that bios and vitamins are similar. In fact, bios 

 is now known to be a complex consisting of a number of compo- 

 nents identified as vitamin Bi (thiamin), biotin, /-inositol, and 

 additional factors [Eastcott (1928)]. 



Conflicting evidence exists regarding the necessity of the addi- 

 tion of growth factors to culture media used to grow other fungi. 

 Kogl and Fries (1937) have shown that Polystictas adustiis grown 

 on a synthetic medium requires the addition of thiamin, and 

 Nematospora gossypii requires biotin. Polystictus adustus is 

 capable of producing biotin, and N. gossypii thiamin, so that they 

 can supply their mutual needs when they are grown in association. 



