116 



calcareous schist, friable, and in process of disintegration. Its wliole 

 mass is invaded by the nitric ferment. 



"When we consider the feeble intensity of these phenomena we are 

 tempted to underestimate their importance, but being so general and 

 continuous they really deserve to be classed among the geologic causes 

 to which the crust of the earth owes its actual physiognomy, and which 

 especially have contributed to the deposits of fine material which con- 

 stitute arable soil." 



In the view thus presented by ]\liintz, nitro bacteria, the existence of 

 which was first indicated by Schhising and himself in 1877, and which 

 were first isolated and definitely studied by Winogradsky a little over 

 a year ago, are of the highest interest to the geologist as one of the 

 dynamic agencies which decide the topography of the earth's surface; 

 and to the farmer as the means by which the nitrogen compouiuls of 

 the soil are changed into the nitrates upon which his crops feed, and 

 even the soil itself is formed. — [W. O. A.] 



Microbes and root tubercles in relation to the fixation of free 

 nitrogen by peas, Schlbsing, jr., and Laurent ( Comyj/.rc^K/., Ill (ISSMI), 

 p. 750). — Ex[)erimenls by the authors are repurted, which confirm the 

 fixation of free nitrogen by peas and the connection of microbes and root 

 tubeniles with the process. While previous experiments had been nuule 

 by what they designate the "indirect method "of comparing the nitrogen 

 in the seed and soil at the beginning of the experiment with the amount 

 found in the i)lant and soil at the end of the experiment, and taking 

 the dill'ereiic«? as the measure of the (juantity of nitrogt'u actpiired from 

 the air, these experimenters employed the "direct method," growing 

 l>lants in sand inside an apparatus containing a definite volume of air, 

 the nitrogen in which was estimated at the beginning and at the end of 

 the experiment, and taking the loss as the nu'asnre of the amount fixed 

 by the plant. The apparatus was also utilized in experiments where 

 the nitrogen gained was estimated by the " indirect method," explained 

 above. In two exi)eriments the api)aratus and sand were sterilized, peas 

 planted, and their inoculation provided lor by the addition of crnsht'd 

 root tubercles. The peas grew during 3 months. The plants were 

 small, apparently healthy, and produced fiowers, but no Irnit. At the 

 end of the experiment the roots had abundant tubercles, liy the 

 direct method it was estimated that the jjlants in the first experiment 

 acquired 30. 5 and those in the second experiment 32.5 mg. of nitrogen. 

 By the indirect method the quantities of nitrogen fixed were esti- 

 mated at 40.0 and 34.1 mg. resi)ectively. The dilVerence in results l)y the 

 two methods is attributed to unavoidable errors in analysis. Still 

 another ex|)eriment was made, but without determination of gaseous 

 nitrogen and without inoculation. The plants had no root tubereles 

 and showed by the indirect method no considerable gain of nitrogen. 

 The inference is that the peas which were inoculated by the bacteria 

 and had root tubercles, fixed gaseous nitrogen. — [W. O. A.] 



