326 EXPERIMENT STATION RECORD. 



When grown separately in a nitrifying solution plus auximone the scum did 

 not appear. Tests of a number of soils, including loams, clays, and gravels, 

 showed that all yielded the scum, the best growth being obtained from a 

 virgin loam. It was found that the rate of growth and thickness of the 

 scum showed a progressive increase with the quantity of auximone present 

 fibove a certain minimum. Tests of fresh and well-rotted stable manure 

 showed that the quantity of auximone present increases with the progressive 

 decomposition of the organic matter of the manure. Further results brought 

 out by the experiments indicated that the organisms which form the scum 

 require no organic carbon for their growth and are similar to the nitrifying 

 organisms and sulphur and iron bacteria in that they can assimilate atmos- 

 pheric carbon dioxid by the process of chemosynthesis. They can not live on 

 nitrates, but must obtain their nitrogen from an ammonium salt, and they 

 are not destroye<l by heating. See also a previous note (E. S. R., 31. p. 826). 



Soil protozoa and soil bacteria, E. J. Russell (Proc. Roy. Soc. [London], 

 Ser. B, 89 (1915), No. B 610, pp. 76-52).— The author is of the opinion that the 

 conclusion drawn by Goodey (E. S. R., 33, p. 515) that ciliates, amoebae, and 

 flagellates can not function as a factor limiting the number of bacteria in 

 soils is not justified by the experimental data reported, and reviews investiga- 

 tions by himself and his associates (E. S. R., 29, p. 122; 32, p. 816; 33, p. 621) in 

 support of his theory. 



Soil fatigue and sterilization, D.' Zolla (Rev. G&n. Sci., 26 (1915), No. 4. 

 pp. 116-120). — The work of others is reviewed to show that soil fatigue is not 

 equivalent to soil exluiustioii, and ihat the cause of soil fatigue can usually 

 be removed by partial sterilization with heat or antiseptics. 



The control of soil washing, M. F. Milleb (Missouri Sta. Circ. 78 (1915), 

 pp. 12, figs. 9). — This circular briefly discusses soil wa.shing by gullying and 

 sheet washing and describes methods of prevention and control, consisting 

 mainly of the use of winter cover crops, deep plowing, contour farming, main- 

 taining the organic matter content in the soil, and the use of straw, bushes, 

 trees, dirt, brush, logs, stumps, dams, and debris for large gullies. 



The feeding of farm crops, W. ScHNEroEwiXD (Die Emahrung dcr Land- 

 wirtschaftlichc Kulturpflanzcn. Berlin: Paul Parcy. 1915, pp. yiII+487. figs. 

 16). — This is a practical treatise, in three parts, for the use of farmers and 

 contains only such experimental results as have a well-defined, practical as 

 well as a scientific value. 



The first part, presented as a scientific basis for the third part, deals with 

 the physiology of plant nutrition, both when germinating and during later 

 gro^^•th. The second part deals with the soil, describing the rock and mineral 

 constituents forming the earth crust, the physical, chemical, and biological 

 processes of soil formation, and the different soil types and their properties 

 and transformations through human agencies. The third part deals with fer- 

 tilization, first discussing the different fertilizers and fertilizing materials 

 and their uses, including stable and groon manures and artificial fertilizers 

 supplying nitrogen, potash, phosphoric acid, and lime, and, second, describing 

 the peculiarities of individual crops with reference to the kind. form, and 

 amount of fertilization required under different conditions. In this connection 

 plans for crop rotation and field experiments are given. The plans for the 

 fertilization of individual crops in the different rotations and on the different 

 soil tj'pes are intended to indicate to the farmer how and to what extent 

 the kind and amount of fertilization for each crop is dependent on the pre- 

 ceding crop and its fertilization. 



Plant food and soil bacteria, A. Koch (Mitt. Deut. Landic. OeselL, SO 

 (1915), No. 11, pp. 155-158). — The work of others Is briefly reviewed and ex- 



