SPORULATION 305 



pointed out that the responses of a fungus in nature cannot always be 

 duplicated in the laboratory. 



Snyder and Hansen (1947) have given a brief and clear statement 

 regarding the advantages of culturing fungi on natural media and under 

 natural environmental conditions. These conditions are important, if 

 one desires to obtain reproduction of a fungvis which does not sporulate 

 readily in culture. However, if one desires to study critically the indi- 

 vidual nutritional and environmental requirements and their effects upon 

 reproduction of a fungus which sporulates abundantly on the usual 

 cultural media, it is often necessary to subject the fungus to unfavorable 

 conditions. Thus, only by preventing sporulation, by varying but one 

 factor at a time, may we discover the need for that factor. 



Riker and Riker (193G) have listed 11 methods which have been suc- 

 cessfully employed to induce sporulation of different fungi in culture. 

 Since the writing of their manual much has been learned about this phase 

 of fungus physiology. A revised list of the conditions known to influence 

 sporulation of fungi is presented in the summary of this chapter. 



Kauffman (1929) called attention to the views of Klebs, who held that 

 living cells are influenced during their lifetime in three ways: (1) by the 

 specific structure; (2) by the internal conditions; and (3) by the external 

 conditions. Kauffman equated the first of these to heredity and the last 

 two to environment. The external environment comprises the various 

 physical and chemical factors, such as temperature, light, composition 

 of the medium, and the like. Kauffman used the term internal environ- 

 ment to designate the complicated influences and reactions between cells 

 wdthin the organism. The physical and chemical effects of the external 

 environment may be transmitted through the cells and become evident at 

 some distance from the point of the stimulus. 



The meaning of these statements may be clearer if we consider the 

 effect of various external environmental factors upon fruiting. It is well 

 known that various external stimuli may initiate the reactions which lead 

 to reproduction. These stimuli must act through the internal environ- 

 ment. Most of the discussion that follows will be concerned with the 

 external environment and the resulting development of the fvmgus. 

 Some external factors may so modify the internal milieu as to favor 

 sporulation, w^hile others may inhibit or prevent sporulation. 



Not all fungi respond in the same way to the external factors such as 

 light, temperature, or nutrition. Each species produces spores when the 

 internal environment is suitable, but the external factors do not operate 

 upon the internal environment of all fungi alike. Thus, there is no univer- 

 sal set of external conditions which lead to fructification in all fungi. The 

 external conditions favorable for sporulation must be studied for each 

 species. This does not imply, however, that no two fungi react alike or 



