18 EXPERIMENT STATION RECORD. 



teniper;itiires of from to 10°. Dextrose was found to be the most suitable 

 source of carbon. Fermentation processes were not observed in case of any of 

 the or^anisujs. Tlie amount of nitroj;en fixed per gram of dextrose assimilated 

 was greater in all cases than with C lost rid iuni pastcurianum, being on the 

 average as follows: M. commune S.92 mg., .-1. tcnids 5.02 mg., C. Iicrlxiniiii 4..38 

 mg., and H. dados porioidcs 2.50 mg. 



Incidentally the conclusions of other investigators that Aspergillus nigcr and 

 PenicilJium f/iaucum are capable of fixing free nitrogen were confirmed. It was 

 Jllso shown in the culture e.xperiments reported that llormofU ndron clado- 

 sporioidcs and VJadosporium hrrharum are two entirely distinct forms and not, 

 as has been often claimed, identical organisms. 



On the adaptability of different sources of energy to assimilation of atmos- 

 pheric nitrogen and the distribution of nitrogen-fixing bacteria in the soil, 

 H. Prinosheim {Centhl. Bakt. [ctc.^, 2. Abt., 20 {1908), No. 8-!K pp. ^'/8-^.56).— 

 In the investigations reported in this article the power of various Clostridia, 

 but especially Clostridium amcricfiuuni, to assimilate the carbon of cane sugai*, 

 starch, milk sugar, and ammonite under different conditions of concentration, 

 etc., was studied. It was found that these carbohydrates were about as effi- 

 cient as grape sugar as sources of energy in the fixation of nitrogen by 

 C. amcricanum. With concentrations varying from 0.5 to 4 per cent it was 

 found that the utilization of the energy-producing materials was best with the 

 lower concentration. C. americanuDi utilized the different sources of energy 

 more completely than C. pasteurianum. The addition of iron salts to the cul- 

 ture solutions did not increase the nitrogen-fixing capacity of the first-named 

 organism. 



The fixation of nitrogen by Rhizobium leguminosarum, R. Greig-Smith 

 (Proc. Linn. 8oe. y. .S. Wales. 31 {190G), pt. //, pp. G0S-615).—A study of the 

 production of slime in continuation of earlier work (E. S. R., 19, p. 51S) and 

 the fixation of nitrogen by Rhizobium from Robinia or lupine alone or in 

 association with Baeillus levanifornians. B. radiohacter, and Azotobacter on 

 culture media containing no asparagin or other nitrogenous substance, showed 

 that different I'aces of the Rhizobium can fix atmospheric nitrogen under such 

 conditions and that the fixation is coincident with and proportional to the 

 formation of slime. "Under conditions thai preclude the formation of slime, 

 there is no fixation. Conditions, such as the presence of another bacterium, 

 which assist the formation of slime, also assist fixation. It is a matter of in- 

 difference whether the medium is acid or alkaline." 



The author's studies on the structure of Rhizobium indicate that it is a com- 

 ])ound micro-organism of coccus type (leuconostoc or streptococcus-like) and 

 his observations on the fixation of nitrogen by the organism confirm and amplify 

 the' results obtained by Maze. The author believes that the slime produced by 

 this organism contains gum and a soluble albuminous constituent which is 

 assimilable by plants and thus makes the plant independent of the supply of 

 soil nitrogen under certain conditions, as for example, in nitrogen-free soils. 



"We are now certain of the kind of help which the bacterium gives the 

 plant. There exists a symbiosis; the plant supplies saline and saccharine mat- 

 ter, the latter of which the bacterium converts into gum and at the same time 

 elaborates atmospheric nitrogen into constituents which are partly contained 

 within the bacterial cell and partly diffused in the gum, which by virtue of 

 their presence appears as a slime. Both the nitrogenous and the carbohydrate 

 constituents of the slime are then elaborated by the plant cells into tissue 

 elements." 



The fixation of nitrogen by Azotobacter chroococcum, R. Greig-Smith 

 {Proc. Linn. Soc. X. S. Wales, 31 {1906), pt. .',. pp. 6 16-(j 18). —The slime pro- 



