310 



PHYSIOLOGY OF THE FUNGI 



into the formation of sporangia. Under conditions unfavorable to 

 conidium production, yet favorable to sporangium formation, both the 

 size and abundance of sporangia are increased. The effect of temperature 

 was also evident when pumpkin flowers artificially inoculated with C. 

 cucurbitarum were brought into the laboratory and placed at 30°C. 

 Under these conditions both conidia and sporangia were produced. 



Table 



54. The Effect of Temperature upon Asexual Reproduction op 



Choanephora cucurbitarum 

 (Barnett and Lilly, Phytopathology 40: 83, 1950.) 



Other critical temperature studies are needed, particularly those 

 designed to show the interrelated effects of temperature with other 

 environmental or nutritional factors and to determine the effects of tem- 

 perature upon the "internal environment" of the fungi. The tempera- 

 ture of incubation affects zygospore formation by Phycomyces blakes- 

 leeanus indirectly through the amount of acid formed in the medium 

 (Robbins and Schmitt, 1945). 



Light. Light has been a neglected and often ignored factor in many 

 studies of sporulation. Too often we place fungi in the laboratory or 

 refrigerator according to our own convenience, not to their needs, and 

 expect them to reproduce as they would in nature. Under natural con- 

 ditions many fungi fruit only when exposed to light, often to the direct 

 rays of the sun, for a part of the time. Numerous observations have been 

 reported regarding the need for light, but too few of these reports give 

 data as to the intensity, duration, or quality of the light required to 

 initiate sporulation. We should not conclude that intensity and duration 

 are without effect. 



A review of the early work on the influence of light on the growth and 

 fruiting of the fungi is presented by Coons (1916). Brefeld (1877) found 

 that some species of Coprinus failed to fruit in the dark. A culture of 

 Coprimis exposed to light for 2 or 3 hr. was then able to fruit in the normal 

 manner when removed from the light. He also found that higher tem- 

 peratures replaced, in part, the beneficial effect of light for some species. 



Sphaerographium fraxini produced a few pycnidia in the dark at 30°C., 

 whereas none were produced at room temperature in the dark (Leonian, 

 1924). Pycnidia were produced at room temperature in the light. 



