116 



EFFECTS OF TEMPERATURE OX FUNGI 



Temperature coefficients have been abundantly determined and 

 interpreted. Fawcett (1921) measured the growth-temperature 

 coefficients of Pythiacystis citrophthora and Fhytophthora terres- 

 tris within the range 8° to 36° C, of Fhovwpsis citri within the 

 rans;e 8° to 32° C, and of Diplodia natalensis within the range 8° 

 to 45° C. He found that for each 24-hour observation period, the 



320 



2 

 I 



E 160 



.as 



£ 



C3 







10 15 20 25 



Temperature ( degrees Centigrade ) 



30 



oo 



Fk.. 10. The extent of decav, measured in terms of diameter of lesions, 

 induced in turnips bv Rhizoctonia solani at various maintained temperatures. 



(After Lauritzen.) 



Qiu for mycelial growth is greatest for the lowest temperature 

 shown and becomes smallest for the highest temperatures. At 8° 

 to 18° C Fhytophthora terrestris showed a coefficient of 30, and 

 at 26° to 36° C a coefficient of 0.4". lor the 8° to 18° C range 

 the Oio of Fhowopsis citri was 4.0; for the 21° to 31° C range, 0.5. 

 Within the range investigated, the coefficient of Pythiacystis 

 citrophthora was 12.3 for the lowest temperature and 0.05 for the 

 highest; that of Diplodia natalensis was 16.7 for the lowest tem- 

 perature and 0.05 for the highest. 



ScherTer (1936) determined the rate of carbon dioxide produc- 

 tion bv Polystictus versicolor. He found that production was 



