372 REPRODUCTION 



carbohydrate optimal for fruiting (59, 132, 133, 134, 135, 140). The 

 simplest explanation of this phenomenon is based on the fact that 

 thiamine accelerates glucose utilization (136); this is in accord with 

 our previous conclusion that exhaustion of the carbon source is re- 

 quired for the initiation of reproduction. 



There is no conclusive evidence that any fungus requires a known 

 vitamin specifically for the reproductive process and independently of 

 growth effects. The available data can more or less satisfactorily be 

 explained on the basis of the two generalizations just stated: that 

 fruiting may require more of a vitamin than measurable growth, and 

 that vitamins may accelerate sugar utilization and so hasten the onset 

 of reproduction. However, at least the possibility of a more direct 

 relation is raised by the work of Barnett and Lilly (17) on Ceratosto- 

 mella fimbriata; a thiamine-starved mycelium begins to fruit if trans- 

 ferred to a thiamine solution containing no other nutrients. 



Unidentified materials in crude plant and microbial extracts often 

 increase fruiting. Examples include both sexual reproduction (164, 

 186, 226, 259, 322) and asexual reproduction (121, 144, 169). 



It is often found, usually as a result of accidental contamination of 

 cultures, that other fungi and bacteria encourage fungal reproduction. 

 Many such cases are reviewed by Asthana and Hawker (6) and by 

 Raper (236); other instances may also be cited here (24, 143, 243, 

 258). However, there is no assurance that these are vitamin effects — 

 pH, for example, or nutrient concentration could be the decisive factor. 

 Stimulation of conjugation of Zygosaccharomyces spp. by Aspergillus 

 niger has been described; the effect of the fungus is replaced by a 

 mixture of riboflavin and an organic acid (216, 217). The association 

 in nature of Gonatorrhodiella highlei with Nectria coccinea may be 

 explained by some chemical influence of the latter on the reproduction 

 of G. highlei (7). 



Another series of investigations, reviewed by Buston and Khan (60), 

 suggests that the effect of contaminating organisms on perithecium 

 formation in Melanospora destruens and Chaetomium globosum is to 

 be attributed to organic phosphorus compounds, particularly 3-phos- 

 phoglyceric acid, liberated by the inducing fungus. Whether this is a 

 direct effect is, however, not yet clear. In C. globosum, perithecial 

 production is associated with a high level of organic phosphate esters 

 (61). 



Several apparently unrelated synthetic organic compounds are re- 

 ported to increase sporulation without a corresponding increase in 

 growth; possibly the effect is an antagonism of inhibitors present in 

 the growth medium (158, 295). 



