354 FIXATION OF FKEE NITROGEN BY BACTERIA. 



in the soil affords a new possible explanation of the activity of the 

 nodule bacteria of the Leguminosce, viz., that the actual absorption 

 of the free nitrogen goes on outside these root formations; sub- 

 stances unassimilable by higher plants being formed, and then 

 converted into an assimilable form by the nodule bacteria. This 

 provisional interpretation, which will not encroach on future re- 

 search, is not without its analogies ; one need only recall the 

 Mycorhiza, discovered by Frank on the rootlets of the majority 

 of forest trees (Cupuliferce, Coniferce), heaths (Ericaceae), &c., and 

 in regard to which the most important discoveries made up to 

 the year 1888 will be found briefly reviewed in a treatise by 

 F. BENECKE (II.). 



The great importance to General Physiology of the researches 

 reported above will be readily appreciated, since they have brought 

 to our knowledge organisms which dispense with combined nitro- 

 gen as a food stuff, and are consequently of the greatest importance 

 in the economy of Nature, by revealing the means for maintain- 

 ing the circulation of nitrogen. Large quantities of this element 

 are daily liberated by the activity of both de-nitrifying and nitrify- 

 ing bacteria, and restored to the atmosphere, the result being that 

 the stock of nitrogenous compounds, so essential to the nutrition 

 of all other plants and all animals, becomes reduced. To com- 

 pensate and reverse this loss is the task of the nitrogen-fixing 

 fungi, which, for this reason, must be regarded as the benefactors 

 and foster-mothers of all other living creatures. 



