i42 POPULAR SCIENCE MONTHLY. 



and nitrates. The last is the form in which the nitrogen is usually- 

 taken up by the plants. On the other hand, the nitrates are them- 

 selves subject to the opposite forces of deoxidation. There are species 

 of bacteria in the soil which reduce nitrates to nitrites, to ammonia 

 or even to gaseous nitrogen. To recapitulate, then, there take place 

 in the soil processes of nitrification, denitrification and also the fixation 

 of free nitrogen. It was necessary to consider the former two, in order 

 to understand the third. It would be out of place here to speculate 

 upon the manner in which the soil nitrogen is oxidized ; it might not be 

 out of place here to consider the possible ways in which nitrogen is set 

 free from its compounds, on the one hand, or is e fixed,' on the other 

 hand. Quite recently hypotheses have been advanced which would re- 

 gard the processes of ' fixation ' and of ' denitrification ' as being very 

 much related phases of the same physiological activities. The investi- 

 gators who have labored in this field of research, and to whom we owe 

 most of our knowledge on the subject, are Berthelot, Winogradsky, 

 Beyerink and Stoklasa. Berthelot was among the first to observe that 

 soils free from vegetation can increase their store of nitrogen. Wino- 

 gradsky, after much painstaking search, isolated from the soil an or- 

 ganism, 'which, in company with two others, can grow in nitrogen-free 

 media and fix considerable quantities of nitrogen in a short time. Bey- 

 rink, also, has isolated within the last few months several organisms that 

 possess a similar power, and Stoklasa has done a great deal of care- 

 ful work to determine just how the fixation of nitrogen is accomplished. 

 Moreover the subject has assumed more than a mere scientific interest 

 within the last three or four years. The firm of Friedrich Bayer and 

 Co., of Elberfeld, Germany, has placed on the market a bacterial culture 

 bearing the fancy name of ' Alinit.' This alinit they claim can under 

 favorable conditions increase the yield of non-leguminous crops 40 per 

 cent. On examination, the alinit proved to be a pure culture of B. 

 ellenbachii, mixed with a starchy material resembling dried and pulver- 

 ized potatoes. The organism was isolated by a German gentleman- 

 farmer, Caron by name, and named B. ellenbachii after his estate, 

 Ellenbach. This bacillus differs but little from the organism isolated 

 by Du Bary some years earlier, and called by him B. megaterium. This 

 organism, Stoklasa claims, is not only similar to, but identical with B. 

 ellenbachii. The accumulated evidence of several investigators on this 

 point inclines me to the belief that the two are not identical, though 

 very much allied. At any rate, Stoklasa has shown that B. megateri- 

 um is capable of fixing atmospheric nitrogen in media containing but 

 traces of fixed nitrogen; it develops and adds to the nitrogen content 

 of the medium by drawing upon the nitrogen of the air. This organ- 

 ism has, as it were, a double nature. In the first place, as just noted, it 

 is capable of fixing atmospheric nitrogen ; in the second place, it exerts 



