FUNCTION OF ACTINOMYCETES IN SOIL 



205 



4, 1915, made after keeping the samples in the laboratory twelve 

 Weeks. On the date of collection the ratio obtained in the case 

 of one pair of samples was in favor of the cultivated soil, while 

 in two of the others case it was nearly unity. At the time of 

 the later analysis the ratios in these three cases were still all 

 near unity, although none of them were actually in favor of 

 cultivated soil. 



The results of the other series of tests, comparing three neigh- 

 boring spots in a single soil type, are given in Table III. The 



TABLE III 

 Number of Aclinomycetes in three neighboring spots of a single soil type. A com- 

 parison of old sod, neio sod, and cultivated soil. Numbers determined by means 

 of gelatin plates 



* The first two samples of cultivated soil were taken from a different spot 

 from the rest, although similar in kind of soil and in state of cultivation. 



numbers obtained in this test were so constant that the few 

 analyses mean as much as longer series of irregular results. 

 The average number of Aclinomycetes in the old sod was 9,800,000 

 per gram, in the new sod 6,600,000 and in the cultivated soil, 

 2,900,000; or in percentages, they averaged 41.7, 23.6 and 

 14.1 per cent, respectively, of the total flora in these three spots. 

 The lowest count (of Actinomycetes) in old sod was higher than 

 the highest in new sod, and the lowest in new sod higher than 

 the highest in cultivated soil. These figures indicate that the 

 number of Actinomycetes in sod soil increases as the age of the 

 sod grows greater. 



