Mat 22, 1914] 



SCIENCE 



763 



on Mylodon femurs from Ranclio La Brea. 

 The femur of Megalonyx, as figured by Leidy, 

 appears, also, to be without this notch. Pos- 

 sibly Marsh's type should be referred to 

 Megalonyx. 



Chester Stock 

 Paleontologic Labokatoey, 

 University of California, 

 December 9, 1913 



TEE SOCIETY OF AMERICAN BACTERIOL- 

 OGISTS^ 



WEDNESDAY, DECEMBER 31, 1913, TEN O'CLOCK; 



Soil Bacteriology 

 Bacterial Activities and Crop Production: P. E. 



Brown. 



The importance of correlating the results of 

 tacteriological tests with known facts regarding 

 Boil fertility is emphasized. The improvements in 

 methods for the bacterial examination of soils has 

 made possible the study of the relation between 

 bacterial activities and crops produced. Thus the 

 determination of the ammonifying power, the 

 nitrifying power or the azofying power of soils 

 may be an indication of their fertility or crop- 

 producing power, or at least of the relative fer- 

 tility of several soils. 



Soils under varying rotations and under differ- 

 ent treatment have been studied during the past 

 three years, and the results secured show in prac- 

 tically every case a similar, definite relation be- 

 tween the crops produced on the various plots and 

 the ammonifying power and the nitrifying power 

 of the soils determined by the fresh soil-casein 

 method for the one and the fresh soil-ammonium 

 sulfate method for the other. 



It is evident that the bacterial activities in soils 

 determine very largely the crop-producing power 

 of the soils. If the bacterial mechanism which 

 brings about the solution of insoluble plant food 

 is inadequate, crops will suffer for lack of food. 

 In soils where improper rotations and poor treat- 

 ment is practised the conditions very quickly be- 

 come unsatisfactory for optimum bacterial growth 

 and crops immediately feel the effect of this di- 

 minished growth in a reduced supply of food. 

 The work, as a whole, therefore, points toward the 

 value of bacterial tests as a measure of the crop- 

 producing power of soils. 



The Environment of Soil Organisms: F. H. Hes- 

 selink van Suchtelen. 



1 Abstract of papers presented. 



Growing out of the importance of the action of 

 media on organisms a study of soil as a cultural 

 medium was undertaken. So far as our present 

 knowledge concerning soils extends, the only 

 means at our disposal for judging the cultural 

 medium of soil organisms is drainage water. It 

 may be expected, however, that the soil solution 

 as it exists in the soil differs quantitatively from 

 the drainage water. 



A method was devised for obtaining this soil so- 

 lution based on its displacement by inactive sub- 

 stances (parafliiie oil, vaseline, etc.). Work by 

 means of the determination of osmotic pressure 

 and electrical conductivity was imdertaken, which, 

 demonstrated the value of such a displacement. 



The absolute amount of soil solution obtained 

 by the above-mentioned method varied from 100— 

 435 e.e. solution. As an example of the successful 

 extraction the following data may be quoted. 

 From 7.949 kilograms of sandy loam with a total 

 water capacity of 24.6 per cent, containing 14.3 

 per cent, water (all figured on the basis of dry 

 soil), there was obtained 330 c.c. of soil solution. 

 The concentration of the soil solution bears a re- 

 semblance to the very first portion of drainage 

 water obtained by careful percolation through a 

 large quantity of soil. 



Besides an extensive study of the soils employed 

 in our experiments, there were made physico-chem- 

 ical and chemical examinations of the liquid ob- 

 tained by the foregoing displacement process, to- 

 gether with a determination of the number of 

 microorganisms found by the plate method. It 

 was ascertained that difi:erent soils, soils closely 

 adjacent and the soils of different layers, con- 

 tained soil solutions of different compositions. 

 Detailed results will appear in a future publica- 

 tion. 



A New Medium for the Quantitative Determina- 

 nation of Bacteria in Soil: H. Joel Conn. 

 Three special media for soil work have been 

 proposed during the last few years: by Hugo 

 Pischer,2 by J. G. Lipmans and by P. E. Brown.* 

 Eecently an asparaginate agar containing wholly 

 chemicals of known composition has been prepared 

 at the New York Experiment Station. A fifth 

 medium, a soil-extract gelatin, has been compared 

 with them, because it has been found to give a 

 very high and regular count. The composition of 

 these media are as follows: 



2 Centhl. f. BaTct., II., Ab. 25, p. 457. 



3 Id., 25, p. 447. 

 ild., 38, p. 497. 



