NUMBERS OF MICROORGANISMS 



41 



Similar results were obtained by other investigators. 95 It is not known 

 whether this is due to the greater resistance of these organisms to the 

 lack of oxygen, to the washing down of the conidia, or to some other 

 cause. Since these organisms are very sensitive to acidity and to an 

 excess of moisture, acid soils and water-logged soils contain a minimum 

 number of actinomyces; since they play an active part in the decom- 

 position of soil organic matter, heavy soils and soils rich in undecom- 

 posed organic matter, especially when well limed or buffered, contain 



Noun- Occ.i Dec.19 Jan.7 Oanze, Feb.H Fetu? Mar2l Aprs Aprzz 



Fig. 3. Variation of numbers of bacteria and actinomyces at different seasons 

 of the year and different depths of soil (from Lochhead). 



high numbers of actinomyces, in comparison with the bacteria of the 

 same soil. 



The addition of manure 96,97 as well as of different other forms of unde- 

 composed organic matter greatly stimulates the development of actino- 

 myces and may even result in an increase in their relative abundance, in 



96 Lochhead, 1924 (p. 34). 



96 Hiltner, L. Uber neuere Ergebnisse und Probleme auf dem Gebiete der 

 landwirtschaftlichen Bakteriologie. [ Jahrb. Ver. angew. Bot. for 1907, 5: 200-222. 

 1908. 



97 Bright, J. W., and Conn, H. J. Ammonification of manure in soil. N. Y. 

 Agr. Exp. Sta. Tech. Bui. 67. 1919. 



