330 



PHYSIOLOGY OF THE FUNGI 



ment. Sterile thiamine-starved mycelium may be obtained by growing 

 C. fimhriata on a synthetic medium containing 25 g. glucose and less than 

 2 ng of thiamine per liter. When a small portion of this sterile mycelium 

 is transferred to the surface of distilled water, no perithecia are formed. 

 How^ever, under the same treatment, but with the addition of thiamine 

 to the water, fertile perithecia are formed within a few days. We may 

 assume that, when thiamine is added, the fungus uses this vitamin as a 

 coenzyme in transforming the protoplasmic reserves into perithecia and 



Table 57. The Effect of Various Concentrations of Thiamine upon Growth 

 AND Estimated Abundance of Perithecia Formed by Ceratostomella fimhriata 



in the Presence of Various Concentrations of Nutrients 

 Growth in milligrams. Abundance of perithecia indicated by: = none; + = 



less than 20; ++ = 20 to 200; + + + = 200 to 1,000; + + + + = more than 1,000. 



(Barnett and Lilly, Mycologia 39, 1947.) 



ascospores. This experiment has been successfully conducted using other 

 fungi deficient for thiamine, and similar results also were obtained with 

 biotin and biotin-deficient fungi. The amount of biotin added to the 

 medium affected not only the number of perithecia formed by Sordaria 

 fimicola, but also the time required for this fungus to form mature peri- 

 thecia (Lilly and Barnett, 1947). This period ranged from 13 to 41 days, 

 depending on the concentration of biotin used. 



There is a pronounced effect of biotin deficiency upon the formation 

 and development of the ascospores of S. fimicola (Barnett and Lilly, 

 1947). This fungus is well suited for such a study, for normally nearly 

 all the ascospores mature at the same time. Figure 68 shows the effects 

 of biotin starvation upon the formation of ascospores. Severe effects 

 are evident by the failure of the protoplasm of the asci to be delimited 

 into ascospores or by the failure of many of the ascospores to mature. 

 Other conditions being equal, the amount of biotin required for the pro- 



