732 EXPERIMENT STATION EECOED. 



The results obtained by the methods of physical chemistry are held to indi- 

 cate the possibility of securing in this way more definite information on the 

 laws governing the exchange of substances between the interior and exterior 

 of the cell. A bibliography is given. 



A simplifi.ed apparatus for measuring: the conductivity of electrolytes, 

 R. P. HiHBAKD and C. W. Chapman {Michigan Sta. Tech. Bui. 2S {1915), pp. 41, 

 figs. IJf). — Attention is called to the value of the Wheatstone bridge for use in 

 biological studies, especially those on the determination of the concentration of 

 solutions and their conductivity. The authors have devised and described some 

 modifications of the apparatus by which it is claimed that greater accuracy 

 and simplicity of operation are secured. The method of operating the apparatus 

 is fully described, and the results are given of some experiments which show 

 the degree of precision obtained. 



[Report of the research, assistant in plant physiology], II. P. Hibbard 

 {Michigun Sia. lipi. 1H15. p. 216). — In connecticMi wiili the work reported, a 

 method of determining the mineral salt content of very dilute solutions was 

 worked out (see above). 



The agar shake for the detection of members of the coli-aerogenes group, 

 W. (jiLTNEH, O. W. BuowN, and J. C. Hurlfa" {Michigan Sta. Rpt. HH5, p. 209). — 

 Some of the advantages and disadvantages of the agar shake in flask and tube 

 detection of gas-producing bacteria are pointed out. 



Some factors influencing the longevity of soil micro-organisms subjected 

 to desiccation, with special reference to soil solution, W. (Jiltner and H. 

 Virginia Langworthy (l. S. Dcpt. Agr., Jour. Agr. Research, 5 {1916), No. 20, 

 pp. 927-9^2). — A report is given of exi>eriments conducted at the Michigan Ex- 

 periment Station to determine the possibility of a protective effect of the soil 

 solution on soil organisms subjected to desiccation. Suspensions of Psciido- 

 monas radicicola in various me<lia were usetl to determine the protective effect 

 of the solution when dried on sand and the longevity of this organism when 

 dried in quartz sand and in garden loam, and a study was ma«le of the changes 

 in the numbers and kinds t>f organisms when the solution was drieil in dif- 

 ferent types of soils. 



The autliors found that the survival of nonspore-bearing bacteria in air-dry 

 soil is due in part to the retention of moisture in hygroscopic fttrni. Bacteria, 

 so far as the species investigated are concerned, resist desiccation longer in a 

 rich clay loam than in sand under the conditions of the experiment. If they 

 are suspended in a solution extractetl from a rich clay loam before being sub- 

 jected to desiccation, they live longer than if subjected to desiccation after 

 suspension in physiological salt solutions. 



Attention is called to the fact that not one of the organisms isolated during 

 the last two months of the experiment correspondetl to any of the four organ- 

 isms which predominated in the original soil solution used to inoculate the 

 soils. Tlie extinction of these species, it is thought, may be due to the unfav- 

 orable influence of association with other organisms during the period of 

 active multiplication, or to their lack of endurance when supplied with less 

 than the optinuim amount of moisture. 



The vitality of seeds buried in the soil, W. J. Deal {Michigan Sta. Rpt. 

 1915, pp. 21s, 219). — In continuation of an experiment previously noted (E. S. 

 11., 6, p. C39), an account is given of the vitality of seeds burieil in the soil 

 for 3G years. Of 22 different species of weed seed, only Brassica nigra, Cap- 

 sella hursa-pasloris, Lcpidum rirginicum, Rumcr crispus. and Verhascum 

 tliiipsus gave any gorniination. 



Breeding experiments with CEnotheras, W. Batkson, F. Kkkiu.e. and U. P. 

 Gregory {Abs. in Rpt. Brit. Assoc. Adr. Sci., S'J (/.')/.}). p. 2.J7). — Tins is a roiK»rt 



