1917] SOILS FEKTILIZEES. 517 



ueeds for a soil flora study is the development of methods by which the dif- 

 ferent species in this group may be identified. 



" Tlie numbers of the nouspore-forming bacteria in soil show greater fluctua- 

 tions than do those of spore- forming bacteria or of Actinomycetes (the two 

 other large groups of soil bacteria). High numbers of nouspore formers have 

 been especially noticed in freshly aerated and in freshly manured soil. This 

 indicates that they are among the most active soil microorganisms." 



Soil flora studies. — V, Actinomycetes in soil, H. J. Conn (New York State 

 Stn. Tech. Bui. 60 (1911), pp. 3-25).— This bulletin completes the series of five 

 soil flora studies and deals with Actinomycetes or the higher bacteria. 



It was found that " ordinarily from 12 to 50 per cent of the colonies on plate 

 cultures made from soil are those of Actinomycetes. Description of species of 

 Actinomycetes is at present very difficult. The literature abounds with de- 

 scriptions that have liecome invalidated as better methods of study have been 

 developed. About 70 difl'erent types have been found in the soils studied. Three 

 of them are of fairly conuuon occurrence. One of these three, A. pheochromo- 

 ffenus n. sp., is considered distinct enough to be given a specific name. One 

 of the other two types agrees in cultural characteristics with the potato-scab 

 organism, but its pathogenicity has not yet been tested. The other common 

 type probably is not a distinct species. . . . The significance of these organ- 

 isms in soil needs further investigation. There are good indications that they 

 are active as well as numerically important." 



Are all the soil bacteria and streptothrices that develop on dextrose agar 

 azofiers? P. Emerson (Soil Sci., 3 (1911), No. 5, pp. 4^7-^2i).— Experiments 

 conducted at the Iowa State College are reported in which it was found that 

 97 per cent of the soil organisms developing on dextrose agar plates were 

 azofying bacteria. " No Azotobacter were present, showing clearly that there 

 are a large number of organisms in the soil other than Azotobacter and Kadi- 

 cicola which have the power of fixing atmospheric nitrogen." 



Some effects of organic growth-promoting substances (auxiniones) on the 

 soil organisms concerned in the nitrogen cycle, F. A. Mockeridge (Proc. Roy. 

 Soc. [Loudon], Ser. B, 89 (1911), No. B 621, pp. 50S-533; abs. in Jour. Soc. 

 Cliem. Indus., 36 (1911), No. IS, p. 129). — Experiments on the influence of so- 

 called organic growth-promoting substances (auximones) exti'acted with water 

 from bacterized peat on the nitrogen-fixing, nitrifying, denitrifying, and am- 

 monifying bacteria of soil are reported. 



It was found " that soluble humus, and especially that produced by bacteria! 

 decomposition, is a very important factor from the point of view of the activities 

 of soil bacteria. Its effect upon the organisms appears to be largely independent 

 of any inorganic matter which it may contain or any physical action brought 

 about by its colloidal nature, and is shown to be due to the presence in the 

 humus of growth-promoting substances or auximones. The influence of these 

 auximones upon the organisms concerned in the nitrogen cycle may be briefly 

 summed up in the general statement that they increase the rate of nitrogen 

 fixation and nitrification, depress the rate of denitrification, and do not appre- 

 ciably affect the rate of ammonification." 



The organic matter of the soil. — V, A study of the nitrogen distribution 

 in different soil types, C. A. Morrow and R. A. Gortner (Soil Sci., 3 (1911), 

 No. Jt, pp. 297-33i).— Continuing previous work (E. S. R., 37, p. 121), studies 

 conducted at the Minnesota Experiment Station are reported on the nitrogen 

 distribution in fibrin, hydrolyzed in the presence of an ignited mineral subsoil ; 

 calcareous black peat ; an acid sphagnum covered peat, hydrolyzed alone, in the 

 presence of a mineral subsoil, and in the presence of stannous chlorid ; an acid 

 muck soil ; samples of mineral surface soil representative of Fargo clay loam, 



