HISTORY OF SOIL MICROBIOLOGY 841 



of large amounts of ammonium salts will soon result in a reaction (the 

 degree depending on the buffer content of the soil) injurious to nitri- 

 fication, while the addition of a large quantity of organic nitrogenous 

 material may result in the formation of such large amounts of ammonia 

 that the nitrifying bacteria will be injured, were usually left out of 

 consideration. These investigators, often referred to as the physiological 

 group, consisted of practical men, often insufficiently interested in 

 microbiology, but primarily interested in the phenomena resulting 

 from soil processes rather than in the organisms active in the soil 

 itself. The first representatives of this group are Remy and Lohnis, 

 later followed also by various workers in Germany, J. G. Lipman, 

 Brown, Greaves, C. B. Lipman, and others in America, with Perotti 

 in Italy, Christensen in Denmark, and others contributing more to 

 one or another phase of the subject. 



The other group of investigators, often referred to as the botanical 

 group, were more interested in knowing how many bacteria there are 

 in the soil, what these bacteria are, and if physiological groups were 

 studied, they wanted to know the numerical relation of one group to 

 another. Hiltner and Stormer (1902) were the strongest advocates of 

 this method of attack, followed by H. Fischer in Germany, Chester, 

 H. J. Conn and others in this country, etc. In addition to these two 

 groups of investigators interested in soil biological processes chiefly 

 from the standpoint of the soil, a number of botanists, zoologists, general 

 microbiologists, and chemists continued to make definite contributions 

 to the science of soil microbiology, either by the study of one more 

 group of soil organisms, including the soil bacteria (A. Meyer and 

 associates, Ford et al.), fungi (Hagem, Lendner, Dale, Waksman, etc.), 

 algae (Chodat, Bristol, Esmarch, etc.), actinomyces (Krainsky, Conn, 

 Waksman, Drechsler), protozoa (Wolff, Goodey, Cutler et al.) and 

 invertebrate animals (Cobb, Micoletzky), or by the study of one 

 chemical process in the soil and the organisms concerned, such as 

 cellulose decomposition (Kellerman and associates, Barthel, Pring- 

 sheim, etc.), nitrogen fixation (Omeliansky, Bredemann, J. G. Lipman, 

 Christensen, Gainey, Winogradsky, etc.), evolution of C0 2 (J. Russell, 

 Stoklasa, van Suchtelen, Neller, etc.). 



The more outstanding recent contributions to the science of soil 

 microbiology deal with microorganisms non-bacterial in nature. It is 

 sufficient to mention the work of Russell and his associates on the 

 occurrence of protozoa in the soil and on the phenomenon of partial 

 sterilization; the occurrence and activities of algae, fungi, actinomyces 

 and nematodes in the soil. It is also important to call attention to 



