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agriculturists that if a leguminose crop had been grown, and instead 

 of being taken away in the autumn, it had been ploughed into the soil 

 as a manure, the contents of nitrogen in the soil were increased by the 

 amount of it which the plants have absorbed in the air, even though it 

 was certain that they do not absorb it through the leaves. Berthelot, who 

 was investigating these aad related questions for years, came, as early as 

 in 1883, to the conclusion that lower microscopical plants must be instru- 

 mental in this assimilation ; but it was only through the researches of 

 of Wilfarth and Hellriegel that the enigma received its full solution. 

 They discovered that that roots of the leguminosae, grown in fertile 

 soils, become covered with nodules, originated from agglomerations of 

 bacteria (JB. radicicola), which enter into a sort of symbiotic association 

 with the plant. They borrow from the plant the necessary hydro- 

 carbons, and they supply it with nitrogen which they assimilate from 

 the air circulating in the soil. Minute as they are, they really feed the 

 the plant with nitrogen ; and if they have been destroyed by previously 

 calcinating the soil, the plant will never attain its full vigour. On the 

 other hand, the same calcined and sterilised soil soon becomes fertile, 

 and the plant soon regains its forces, if ever so minute quantities of the 

 precious germs are introduced into the soil. Wonderful as this dis- 

 covery seemed to be when it first became known, there is no longer any 

 doubt about its accuracy, the same experiments having been repeated by 

 Kossowitsch and Nobbe, as well as by Dr. Gilbert and Sir John Lawes 

 at Rothamsted. At a conversazione of the Royal Society one could 

 himself appreciate the effects of the microbe by comparing the portraits 

 of leguminose plants cultivated with its aid and without it. By this 

 time the bacteria of the nodules have already been carefully studied, 

 and it appears that each species of leguminosae has its own bacteria, es- 

 pecially appropriate for entering into a mutual benefit association. 



If the two just mentioned discoveries stood quite isolated they would 

 have been of an immense value. In science they have solved enigmas 

 of long standing, and to the practical agriculturist they promise a new 

 method for improving the value of the soil by watering it with liquids 

 containing the necessary microbes. Once inoculated into the soil, the 

 nitromonade (or Nitrosomonas) of Winogradsky and the Bacteria radi- 

 cicola of the leguminose nodules will continue their precious work. A 

 new chance is thus given to the agriculturist. However, the chief 

 value of the above discoveries is in their connection with subsequent dis- 

 coveries. The fact that the nitro-monade, although devoid of chloro- 

 phyll, is capable of making the synthesis of organic compounds out of 

 purely mineral matters, coupled with the fact that it thrives best in a 

 medium devoid of organic matter, is of an immense importance in the 

 economy of nature. Other bacteria accomplish a similar task. Some 

 of them, previously investigated by Winogradsky, oxidise sulphuretted 

 hydrogen and transform it into sulphur and sulphuric acid. And, 

 finally it has just been proved that if the Black Sea is totally devoid of 

 organic life at depths below the hundred fathoms level on account of 

 the considerable amounts of sulphuretted hydrogen dissolved in its 

 water, this is again due to the activity of similar organism. The Odessa 

 bacteriologists have now succeeded in isolating the bacterium which 

 renders the depths of an immense interior sea uninhabitable for higher 

 plants or animals. It decomposes the mineral deposits, chiefly gypsum, 



