1256 MANURES AND MANURING 



Fanners should not use tanned leather, which is of no fertilising value, 

 nor roasted leather, the farm value of which is nmch below the commercial 

 value. These manures, even under the conditions of the experiment, which 

 were exceedingly favourable to nitrification, only gave the following quan- 

 ties of nitric acid per gr. of nitrogen contained : 



Ground tanned leather . 

 Ground roasted leather 



- On the other hand, leathers dissolved in sulphuric acid showed a con- 

 siderable nitrification, and they may be used to advantage by farmers ; 

 bitt even here, in order to obtain the maximum effect with these products, 

 the treatment with sulphuric acid must be very active, and must not leave 

 behind any non-disintegrated fragments of leather. 



962 - Catalytic Manures : Manganese as a Catalyser of the Biochemical Reactions 

 by means of which Plants Assimilate Atmospheric Nitrogen through Bacterial 



Agency. — De Gregokio Rocasolano Antonio, in Kcvista dc la Real Acadcmia dc CicnciAs 

 cxaclas, fisicas y mituralcs dc Madrid, Vol. XIV, No. 10, pp. 681-693, 3 diagrams. Madrid, 

 April iyi6. 



Experiments carried out starting from the hypothesis that any cause 

 capable of exciting the biochemical activit}^ of the nitrogen-fixing organisms 

 contained in, the soil will have the effect of increasing the quantit}^ of atmo- 

 spheric nitrogen fixed in the soil or in the plant, and consequently of increas- 

 ing the crop. There were used for these experiments pure cultures of Ba- 

 cillus radicicola isolated from the root nodules of red clover cultures of 

 Clostridium Pasteiirianum and Azotohader chroococcnm isolated from a cul- 

 tivated soil. 



Quantities of 100 cc. of culture bouillon (to which mannite had been 

 added and which contained a known percentage of nitrogen) were placed 

 in KrI/Enmeyer flasks, and inoculated with pure cultures of .B. radicicola. One 

 flask was used as control. To the 7 others increasing amounts of a graded 

 solution of manganese chloride were added. The flasks were incubated 

 for 25 days at a temperatitre of 22-23° C. and afterwards sterilised. Finally 

 the total quantity of nitrogen in the contents was determined b}' the KjEL- 

 DAHL method. The experiment was repeated in several series. The re- 

 sults show that B. radicicola fixes atmospheric nitrogen even in the absence 

 of manganese, but the manganese modifies the rapidity of reaction, that is 

 to say it is a catalyser of the biochemical reaction ; it accelerates the lattei 

 in increasing proportions up to the optimum quantity which is 0.006 gr. oJ 

 manganese ion per 100 cc. of bouillon. With this amount the quantity of 

 nitrogen fixed was about three times that of the control. With doses of 

 manganese in excess of the oiDtimum, the acceleration falls oft' suddenly, 

 then (at 0.020 gr. %) the action changes into one of retardation. The 

 experiments with Clostridium Pasteurianum were conducted in the same 

 way as those described above. The manganese is of great, importance to 

 this micro-organism, as it was fottnd that in the absence of this element it 



