SPORULATION 333 



pathogenic on man do not produce the same reproductive stages in culture 

 that they do in their host (Conant et al., 1944). Much more intensive 

 study needs to be made of these pathogens. 



SUMMARY 



Reproduction in the fungi, particularly sexual reproduction, with all the 

 necessary preliminary metabolic activities, is a complex phenomenon. 

 Some fungi appear to be relatively indifferent to and independent of their 

 environment with respect to sporulation, while others appear to require 

 a special combination of environmental conditions. If we assume that 

 all fungi require similar internal conditions for sexual reproduction — 

 and we do not believe this to be an unreasonable assumption — we must 

 recognize the existence of numerous fundamental differences in the 

 metabolic activities of the many different fungi. Some are capable of 

 creating the necessary internal conditions in spite of external conditions 

 which may be limiting factors for other fungi. Other species may not 

 have the ability to create the necessary internal conditions without 

 specific action of certain external factors, such as light, proper nutrients, 

 vitamins, and others. As has been previously emphasized, these proc- 

 esses are often dependent upon the enzyme systems of the fungus, and 

 these systems and their activity vary widely among the different species. 



Many fungi reproduce sexually only as the vegetative growth is near or 

 past the maximum. At this time many of the cells of the mycelium are 

 dead or dying. Autolysis follows, and the cells that remain alive absorb 

 certain of these products of autolysis and are thus enabled to increase 

 their concentration of certain essential substances to such a degree that 

 reproduction is possible. If these speculations are valid, it might be 

 expected that nearly any type of injury which causes death of some of the 

 cells would have a favorable effect on reproduction of some fungi. Ultra- 

 violet radiation, which inhibits growth and often favors sporulation, may 

 act by killing some of the cells. Heat may also act by speeding up the 

 life processes of a fungus so that maturity is reached more quickly, which, 

 followed by death of cells and autolysis, would furnish the necessary 

 stimulus for reproduction. Treatment with hydrogen peroxide and 

 certain other chemicals may also result in death and autolysis of some 

 cells. No claim is advanced that these speculations are the true explana- 

 tion in all instances, but they do provide a hypothesis for interpreting 

 certain puzzling problems connected with sexual reproduction in the 

 fungi. 



Factors which may initiate or stimulate sporulation of fungi which 

 grow well but fruit only sparingly or not at all under the usual conditions 

 of artificial culture (assuming that genetic factors are favorable), are as 

 follows: (1) A change in the concentration of one or more of the nutrients. 



