Chapter VIII 



— By- 



Distribution 



year, 20 per cent of all the colonics developing upon an ordinary agar 

 plate, when various soils were plated out in accordance with accepted 

 bacteriological procedures, consisted of actinomycetes. In the fall, the 

 number of actinomycetes increased to 30 per cent of the total microbial 

 population developing on the plate. This increase was believed to be 

 due to the greater amounts of fresh plant residues becoming available at 

 that time of year. In the winter, there was a drop in the relative num- 



Table 30 : Numbers of bacteria and actinomycetes in the soil developing on albumen agar (460) : — 

 Per 1 gm of soil 



ber of actinomycetes to 13 per cent, believed to be due to the effect of 

 frost. When the soil was treated with stable manure, there was a 

 marked increase in the total and relative numbers of these organisms. 

 Fisher (122) reported a much smaller number of actinomycetes 

 in various soils, seldom exceeding 15 per cent of the total number of 

 organisms developing on the plate. This may have been due to different 

 media used in the evaluation of the abundance 'of these organisms in 

 the soil. 



