24 Journal of Agricultural Research voi. vi, no. i 



temperature and moisture conditions in boxes of soil exposed above- 

 ground to winter conditions are much more varied than in soil at different 

 depths in the field where normal overwintering usually occurs. 



In the overwintering experiments here described the host material was 

 kept in an environment comparable to ordinary field conditions. The 

 experiments at Rocky Ford, Colo., were started about the middle of Octo- 

 ber, 1 91 2, and continued for 1 1 months. In these experiments some of the 

 infected material was mixed with soil, placed in boxes, and exposed above- 

 ground during the winter (PL III, i); a second portion was buried from 

 I to 8 inches in the ground (PI. Ill, 2), wire netting being used above and 

 below the infected material to insure ready location when examinations 

 were made for cultural tests (Pool and McKay, 191 5); a third portion of 

 the infected tops was placed in a pile on top of the ground (PI. Ill, 3). 

 During the experiment records were kept of soil and air temperatures, the 

 former being taken at a depth of 5 inches and the latter being obtained 

 from the Weather Bureau station at Rocky Ford.^ 



The experiments carried on near Madison, Wis., were started the last of 

 November, 191 3, and continued through the winter. Infected sugar-beet 

 tops were buried in the soil at depths of 5 and 8 inches, while seed-beet 

 stalks were left under ordinary conditions in the field. In this experi- 

 ment also records were kept of soil and air temperatures, the former being 

 taken from March until June at a depth of 5 inches and the latter obtained 

 from the Weather Bureau station at Madison. 



The effect of desiccation on material kept under herbarium conditions 

 was to kill probably all life of the fungus within 12 months, as already 

 shown, but material kept under an environment having more or less 

 moisture accompanied by the disintegrating action of various organisms 

 was affected in an entirely different manner, as will be shown. All cul- 

 tures from the infected material used in the two experiments above out- 

 lined were made from definite leaf-spots. Although the diseased tissue 

 was the last to be completely disorganized and consequently could be 

 found as long as any portion of the leaf remained, it became more and 

 more difficult to obtain such tissue as time went on. 



The fungus was unable to survive six months' outdoor exposure in boxes 

 of soil (Table II, experiment 2), and this was also true of the fungus on 

 leaves which had been freely exposed to outdoor conditions — for instance, 

 on the outside of a hayed pile of sugar-beet tops (experiment 3), and 

 on leaves buried 6, 7, and 8 inches in the ground (experiments 19 to 23). 

 In cultures from infected mother-beet stalks and leaves that had been 

 left in the field for a time and then plowed under or stored there was no 

 growth, or only an indefinite growth, of the fungus after 7 months (ex- 

 periments 8 to 10), while in infected material that had been protected 

 in the interior of a pile of hayed beet tops (experiment 4) and in material 



' All the records included in this paper from the Weather Bureau station at Rocky Ford, Colo., were 

 kindly furnished by Mr. P. K. Blinn, the local observer. 



