Apr. 3. 1916 Climatic Conditions and Cercospora beticola 27 



One of the most striking characteristics of these temperatures at Rocky 

 F'ord was the wide range between the maximum and the minimum, and 

 this range may be observed throughout the entire records (fig. 2, 3). In 

 the case of the soil temperatures especially, the wide range appeared to 

 be due to a lack of moisture, the extreme variations being greater than if 

 more moisture had been present. A comparison of the records shows that 

 the variation in air temperature was much less and the mean daily 

 temperature constantly lower at Madison than at Rocky Ford, notwith- 

 standing the fact that the daily minimum temperature was usually lower 

 at Rocky Ford. A comparison of the soil temperatures at the two points, 

 however, shows that at Madison it probably remained more constant and 

 was never as low as at Rocky Ford. This was due apparently to the 

 greater amount of moisture in the soil at Madison and consequently its 

 continued frozen condition. After March 23, the date on which the 

 record was begun at Madison, the soil temperature at that place was 

 never below 29° F., notwithstanding the fact that the air temperature 

 was as low as 15° on April 8, while the minimum soil temperature at 

 Rocky Ford was 22° on December 21 and 25° on February 8. However, 

 as the air temperature on these dates was lower here than at Madison, 

 comparisons can not be drawn too closely. 



In view of the presence of snow on the ground, which, as is well known, 

 protects the soil from the extreme variations of air temperature, and the 

 prevailing low air temperatures, as shown by the records, it may be 

 assumed that the soil temperatures at Madison during January and 

 February and the early part of March varied but little from freezing. 

 This assumption is supported by Frodin's experiments (191 3), which 

 showed in general that when the air temperature was much lower than 

 that of the soil the soil temperature in ground covered with snow was 

 higher than in bare ground. He found that temperatures taken at a 

 depth of ID cm. in the former were the same as those taken at a depth 

 of 27.4 cm. in the latter. After the early part of April the minimum soil 

 temperatures at Rocky Ford and Madison agreed closely, although the 

 minimum air temperature at the former place remained generally the 

 lowest of the temperatures recorded. 



Temperatures obtained from the interior of a pile of hayed sugar-beet 

 leaves by means of a soil thermograph buried in the pile varied less than 

 temperatures taken outside the pile, as shown by the following records 

 made on May 8,1913, and as was probably the case during the entire winter 

 season : Temperature inside pile, maximum, 67° F. ; minimum, 58°; differ- 

 ence, 9°. Temperature outside pile, maximum, 84° F.; minimum, 45°; 

 difference, 39°. 



In view of the fact that the fungus lived twice as long inside the pile as 

 it did on the outside it would seem that a more uniform temperature 

 might be regarded as one of the controlling factors in the life of the fungus. 



