SOILS FERTILIZERS. 519 



The best temperature for tlie production of slime appears to be 22° C, althougli 

 an organism obtained from Robinia was exceptional in requiring a temperature 

 of 26° C. for most efficient action. The organisms produce the most slime on 

 media in which the nitrogenous and slime matter approximated that found in 

 soil water, or that which would for example be represented by 0.06 per cent of 

 asparagin and 0.1 to 0.2 per cent of alkaline phosphate. Mixed cultures of 

 slime-producing organisms are suggested for general use. 



On the biology of nitrogen-fixing micro-organisms, Severin and Helene 

 Krzemieniewski (Ans. Akad. Wiss. Krakati, 1906, pp. 560-577; abs. in Chcm. 

 Zenthh, 1907, I, No. 2.'f, pp. 1701, 1702).— A study of the bacterial flora and 

 activities in soil which has been used in fertilizer experiments for 11 years is 

 reported. 



Azotobacter was much more numerous in limed soil than in unlimed and the 

 fixation of free nitrogen was much more active in cultures inoculated with the 

 limed soil, regardless of whether the inoculating soil had been fertilized with 

 nitrogen or not. The cultures inoculated with limed soil showed a nitrogen 

 fixation in 10 days of 16.75 and 18.39 mg., and those inoculated with unlimed 

 soil of 6.S3 and 7.47 mg. The nitrogen content was in general always greater 

 in the limed soil than in the unlimed. 



In pure cultures of Azotobacter cliroococcuni the fixation of nitrogen by this 

 organism was quite small and there was no production of hydrogen or other 

 combustible gases. The amount of oxygen consumed in crude as well as pure 

 cultures agreed almost exactly with the carbon dioxid produced. 



The organisms which produce the root tubercles of leguminous plants, 

 G. de Rossi (Centbl. Bakt. [etc.], 2. Abt.. 18 (1907), Nos. 10-12, pp. 289SlJf: 

 16-18, pp. Ji81-489, pis. 2). — Investigations relating to the fixation of atmos- 

 pheric nitrogen by leguminous plants are reviewed and a bibliography of 165 

 references is given; the general nature of the micro-organisms heretofore 

 obtained from leguminous root tubercles, more especially Paeudomonas rudi- 

 cicola, and the artificial production of root tubercles are described ; the need of 

 further investigation is explained ; the author's experimental technique is 

 described; and studies of the tubercle contents and capacity of the tubercle 

 organisms of Vicia faba are reported. 



The author questions whether previous investigations have isolated a specific 

 organism producing root tubercles and shows that organisms which produce 

 tubercles and those which do not produce tubercles may be derived from tuber- 

 cles f)f leguminous plants. He describes and explains the method of isolation 

 and identification of a specific organism derived from root tubercles of V. faba 

 which produces root tubercles and which he claims is morphologically, biologic- 

 ally, and culturally widely different from Bacillus radicicola, Beijerinck. 



The author explains how the characteristic Y-form bacteroids of V. faba 

 undergo a kind of vacuolation in the process of their development, and shows 

 that this change has an important bearing on the activities of the organism 

 under different cultural conditions. 



The root bacteria of the Leguminosae, A. Rodella (CeiitbL Bakt. [etc.], 

 2. Abt., 18 (1907), No. 13-15, pp. .}.5o-^67; Jour. Inst. Bretoing, 13 (1907), No. //, 

 pp. 320-327 ; abs. in Jour. Soc. Chem. Indus., 26 (1907), No. 11, p. 627).— After 

 discussing the various views which have been held by investigators as to the 

 nature of the bacteroids of root tubercles of Leguminosse, the author reports 

 investigations from which he concludes that these ramified bodies, improperly 

 termed bacteroids, " are exclusively due to the acid generated in the tubercles 

 of the Leguminosse by the fermentation of the carbohydrates, and they can be 

 obtained in artificial cultures either by similar fermentation or by the addition 

 of organic acids, acetic, butyric, etc." 



