78 Journal of Agricultural Research voi. xin, no. 2 



It will be seen that the percentages were much lower in 19 16 than in 

 191 5, and in this connection it is interesting to note that the prevailing 

 temperature for the season of 1916 was much lower than for 191 5. The 

 temperature during the summer of 191 5 was extremely high, while that 

 of the season of 191 6 was unusually low. It will be observed that, as in 

 1 91 5, the percentage of infection was lower in the plots planted on 

 irrigated, previously cultivated land than in the plots planted on virgin 

 desert land. 



ISOLATION OF FUNGI FROM THE SOIL 



During the 191 6 season 109 cultures were made from the soil, either 

 in the field directly from the soil itself or in the laboratory from soil 

 samples collected in the field. In making the soil cultures, whether in 

 the field or in the laboratory, only sterile instruments, containers, and 

 media were employed, and every possible precaution was taken to guard 

 against air and other contaminations. It is believed that all such dangers 

 were reduced to a minimum. In all, 58 soil cultures were made in the 

 laboratory from five soil samples, and 51 in the field directly from the 

 soil. Hereinafter the designation "soil sample" will be used in referring 

 to the several sources of the cultures made in the laboratory from soil 

 samples, and the words "soil group" in referring to the cultures made in 

 the field directly from the soil. The soils employed are described as 

 follows : 



Soil sample i . — -From a rather hea\'y clay loam on the grounds of the Jerome Experi- 

 ment Station, at Jerome, Idaho. The land v.as reclaimed in 1910, planted to barley, 

 and seeded with alfalfa, remaining in alfalfa until the spring of 1916, when it was 

 plowed and put in condition for planting potatoes. The sample was taken on June 7, 

 prior to the planting of the potatoes. 



Soil sample 2. — From the same source as soil sample i, and taken a few feet distant. 

 Sample taken on June 7. 



Soil sample 3. — From a desert soil from which the desert plants have just been 

 removed and the soil put in condition for potato planting. Located just south of the 

 city of Jerome, Idaho. The soil was a sandy-clay loam, reclaimed in May, 1916. 

 The sample was taken on June 20 from a portion of the field which had not been 

 planted. Plot 9, of the 1916 experimental plot, planted with disease-free seed po- 

 tatoes, was planted in this field. 



Soil sample 4. — From a desert soil, supporting a typical growth of sagebrush and 

 desert grasses, located about 25 miles northwest of Aberdeen, Idaho. The land had 

 never been in cultivation and was situated nearly 20 miles from the nearest agricul- 

 tural lands. Sample taken on August 18. 



Soil sample 5. — From the same type of soil as soil sample 4, located about 2 miles 

 from the place where soil sample 4 was taken. Sample taken on August 18. 



Soil group A. — From a very sandy soil in the Snake River Canyon, 15 miles south- 

 east of Jerome, Idaho, and about 250 feet above the level of the river. This was a 

 desert soil supporting only a very scant growth of desert grasses and dwarfed sagebrush 

 plants. Cultures made on June 21. 



Soil group B. — From a desert soil located about 11 miles southeast of Jerome, 

 Idaho. The soil was principally of clay with a slight admixture of sand and was sup- 

 porting a heavy growth of sagebrush and desert grasses. Cultures made on June 21. 



