MORPHOGENY REACTIONS 



121 



molds, Hyphomycetes, Pyrenomycetes, and Basidiomycetes can 

 develop in the absence of light. Long and Harsch (1918), for 

 example, found that sporophores of Polyporus cinnabar inns, P. 

 farloivii, and Trametes serialis develop in culture in absolute dark- 

 ness. 



Zonation. A variety of morphogenic effects may be expressed 

 by those species that respond to light. Perhaps the most striking 



Fig. 14. Culture of Aspergillus clavatus grown in blue light. 



is zonation, resulting from alternation of day and night, for it has 

 been encountered by all who have cultivated fungi. Moreau 

 (1912) observed the zone of conidia, produced daily, in Penicil- 

 lium glaucum, Hedgcock (1906) in Cephalothecinm roseum, and 

 Bisby (1925) in Fusarium discolor sulphur eum. Bisby reported 

 that exposure of the cultures to bright daylight for a period of 

 % to y 2 second was sufficient to produce a ring of conidia. As a 

 more accurate measure, he noted that exposure to a 2 5 -candle- 

 power tungsten light for 2 to 2% minutes was sufficient. 



In order to relate zonation to radiation of certain wavelengths, 

 Hedgcock (1906) subjected Cephalothecinm roseum and Reide- 



