37 



Apr. 3. 1916 Climatic Conditions and Cercospora beticola 



changed from 30.8° to 40.5° only a very slight increase in growth was 

 apparent during the first three days at the higher temperature, and after 

 that it ceased entirely (Table III, series B). 



Table III. — Comparative diameter of colony growth (in millimeters) of Cercospora 

 beticola at different constant temperatures, o^ at decreasing and increasing constant tem- 

 peratures, and at daily varied temperatures 



SERIES A, CONSTANT TEMPERATURES 



Maximum 



Minimum 



Average 



Period of growth 



3 days 



6 days 



9 days 



II days 



14 days 



18 days 



23 days 



Diameter of colony growth at temperature (°C.) of — 



a. I 

 03 



7-9 

 4.0 



8.9 



14.4 

 II. S 



19. I 

 16.3 



20. 2 

 18.6 



21.0 

 19-5 



33- o 

 29. 7 



30.8 



36. 2 

 33-8 



37-4 

 34- S 



41. O 

 40.0 



40.6 



o. 65 



1-5 

 2.8 

 4.2 



o. 67 

 2-3 



4.6 

 6.4 



3-6 

 6.4 



7 



" The temperatures of each thermostat for all tests were averaged from two daily readings continued 

 throughout the time of the experiment. 

 ^ No growth occurred in these plates when held at 28° C. for 10 days. 



SERIES B, DECREASING AND INCREASING CONSTANT TEMPERATURES. 



Diameter of colony growth at tempera- 

 ture CO.) of— 



°34.7 "35-5 "40-S *30.8 "30.8 



Period of growth 



3 days 



6 days 



8 days 



'^8.3 



3-6 

 '9-3 



3-6 

 6 



6.4 



" Temperature changed to 30.8* C. after three days. 



f> Temperature changed to 34.7° C. after three days. 



« Temperature changed to 40.5° C. after three days. 



<* Only 19.2 per cent of the normal number of colonies developed. 



* Only 12.8 per cent of the normal number of colonies developed. 



SERIES C, DAILY VARIED TEMPERATURES 



16 hours at. 

 8 hours at . 



Diameter of colony growth at temperature (°C.) of — 



14.5 

 19. 2 



14- S 



21. 6 



30.8 



35-8 



40. 6 



Period of growth: 



3 days 



sdays 



7 days , 



9 days 



0.4 



• 7 

 2.7 



0.5 

 1.9 

 3-6 



0.7 

 3-4 

 5-3 



1-7 



6 



8.8 



0.6 

 3.6 

 4.8 



o. 6 

 3a 

 S-4 



Series C (daily varied temperatures). — In these tests the tempera- 

 tures were made to correspond closely with summer outdoor temperatures 

 of night and day by holding the cultures for 1 6 hours at the lower and for 

 8 hours at the higher. After seven days' exposure the growth of colonies 



