ISOLATION', IDI.N'l'IIK A'lMON, ClI/riN' A'lloX , AND I'H IISIIUNATION 



21 



VERTICILLATE BRANCHING 



SPORULATION 



SCHEME OF BRANCHING OF THE AERIAL HYPHAE 



Figure 14. A typical verticil forming culture of a streptomyces, S. verticillatus (Reproduced from: 

 Kriss, A. E., Mikrobiologiya 7: 107, 1938.) 



or rose bengal. Conn found a much greater 

 number of organisms in the soil by this 

 method than could be measured by the or- 

 dinary plate methods. By the use of direct 

 staining, actinomycete mycelium \vas found 

 in abundance in soils, especially those rich 

 ill organic matter and not too acid in reac- 

 tion. This mycelium was not uniformly dis- 

 tributed throughout the soil mass, hence the 

 chief limitation of the method consists in not 

 permitting an accurate quantitative evalua- 

 tion of its abundance. The fact that the 

 method does not permit the recognition of 

 individual species or even genera is another 

 limitation. The direct examination of undis- 

 tiu'bed material offers a distinct advantage, 

 however, which consists in presenting a clear 



picture of the relati\'e mass of growth of 

 actinomycetes under the particular condi- 

 tions and in particular substrates. 



Kubiena and Renn used a vertically illu- 

 minated microscope to examine the soil in 

 an undisturbed state. Actinomycetes were 

 found growing in the soil spaces; aerial tufts 

 of hyphae, in the form of compact colonies 

 with long twisted strands, bridged the soil 

 crumbs. When the soil was enriched with 

 organic materials, the growth of actinomy- 

 cetes was found to be greatly stimulated. 



Contact slide method. This method lends 

 itself ciuite readily to the study of the ac- 

 tinomycete population of soils and composts. 

 It was first introduced by Rossi and Cho- 

 lodnv. A slit is made with a sharp knife in 



