FUNCTION OF ACTINOMYCETES IN SOIL 207 



SUMMARY 



1. In general more colonies of Actinomycetes develop on plates 

 made from sod soil than on those from cultivated soil. The 

 average ratio between their numbers in neighboring sod and 

 cultivated spots in the same soil type is sHghtly over 2:1. The 

 maximum ratio is about 6:1. 



2. Actinomycetes average about 38 per cent of the total flora 

 of sod soil, as determined by means of gelatin plates, but only 

 about 20 per cent of the total flora of cultivated soil. 



3. In a study of three neighboring spots in a single soil type 

 it has been found that Actinomyces colonies not only appear in 

 greater numbers from sod than from cultivated soil, but also 

 in greater numbers from old sod than from sod only two or three 

 years old. 



4. This relation has been found to hold with very few exceptions 

 In the isolated cases where more Actinomyces colonies have 

 developed from a sample of cultivated soil than from the corre- 

 sponding sample of sod soil, the ratio has never been greater 

 than 1.8: 1. 



5. Although the reason for this difference in numbers has not 

 been learned, a probable explanation seems to be that Actinomy- 

 cetes are active in the decomposition of grass roots. 



BIBLIOGRAPHY 



Beijerinck, M. W. 1900. Uebei* Chinonbildung durch Streptothrix chromo- 

 gena und Lebensweise dieses Mikroben. Centbl. f. Bakt. Abt. 2, 6, 

 2-12. 



Gasperini, G. 1894. Versuche iiber das Genus "Actinomyces." Paper pre- 

 sented at the Eleventh International Medical Congress at Rome. 

 Abstract, Centbl. f. Bakt. Abt. 1, 15, 684. 



HiLTNER, L. AND Stormer, K. 1903. Studicn fiber die Bakterienflora des Ac- 

 kerbodens, mit besonderer Beriicksichtigung ihres Verhaltens nach 

 einer Behandlung mit Schwefelkohlenstoff und nach Brache. Kaiser- 

 liches Gesundheitsamt, Biol. Abt. Land- u. Forstw. 3, 445-545. 



Krainsky, a. 1914. Die Aktinomyceten und ihre Bedeutung in der Natur. 

 Centbl. f. Bakt., Abt. 2, 4I, 649-688. 



LuTMAN, B. F. AND CUNNINGHAM, G. C. 1914. Potato Scab. Vermont Agric. 

 Exper. Sta., Bui. 184. 



