334 POPULAR SCIENCE MONTHLY. 



It has been provecV experimentally that not only do the bacteria 

 (rhizobia) of leguminous root tubercles have the power of assimila- 

 ting or chemically binding the free nitrogen of the air, but also other 

 soil bacteria and various simple algae and hyphal fungi. Undoubt- 

 edly the true ecological significance of these free nitrogen-assimilating 

 functions of these organisms is to neutralize, balance or equalize the 

 work of nitrifying and denitrifying (nitrogen-liberating) bacteria, 

 which are very plentiful and widely distributed. More si^ecifically 

 considered, the organisms referred to chemically bind the free nitrogen 

 of the air, forming nitrogenous compounds which may be taken up and 

 assimilated by various plants. In the case of leguminous plants these 

 nitrogen-assimilating bacteria (rhizobia) live within the roots (root 

 tubercles) and supply the host directly with the enriching nitrogenous 

 food compounds formed; in other instances the nitrogen-assimilating 

 organisms live in the soil and the various higher plants as corn, wheat, 

 etc., take up the compounds formed and deposited in the soil without 

 being in actual biologic (symbiotic) association with them. These 

 discoveries have suggested to the scientists interested in agriculture 

 various possible improvements for increasing the yield of crops. Ex- 

 tensive and interesting experiments have already Ipeen made, and some 

 noteworthy results have been obtained and, in other instances, investi- 

 gations are under way which give promise of final useful results. Sev- 

 eral processes for inoculating the soil or seeds with b^eficial bacteria 

 have been patented and, remarkable as it may seem, the slow, plodding 

 German investigator is the first in the field with patent claims and 

 'practical' plans for utilizing bacteria in the interests of the farmer 

 or the tiller of the soil. 



The history of the discovery of the free-nitrogen-assimilating bac- 

 teria found in the root tubercles of leguminous plants is familiar to all 

 botanists, but the general reader of science requires some detailed 

 explanations and some specific statements regarding the subject in order 

 that he may have reasonably clear ideas concerning the practical pos- 

 sibilities and probabilities of bacteria in modern agriculture. These 

 necessary explanations will be given as we proceed. 



The first to suggest a plan for practically utilizing root bacteria 

 (rhizobia) and to secure letters patent for the process in Germany and 

 in the United States were Nobbe and Hiltner, of Tharand, Gerinauy. 

 Since the wording of tlic specifications for a patent are required to be 

 simj)l(' and intelligible to persons of ordinary tcclmical learning, the 

 scheme can best l)e presented l)y siin])ly quoting the specifications. 

 The following is the specification which forms part of letters patent 

 No. 570,873 granted Nol)b(' and Uiltncr in ihe Uuiied States, Novem- 

 ber 3, 1890: 



