340 POPULAR SCIENCE MONTHLY. 



■ In spite of the wonderful opportunities for the dissemination of 

 learning, the exchange of scientific thought and plans of research and 

 the efficient modern laboratory equipment, scientific progress is slow. 

 To illustrate, the observations and experiments which led to the dis- 

 covery of the root nodule bacteria were begun about 1863 by Hell- 

 riegel in Germany and Lawes and Gilbert in England. The nodule 

 microbe was not discovered or recognized until 1886. At the present 

 time we are just beginning to become scientifically familiar with the 

 microbe and are undertaking experiments with a view to practical use- 

 ful application of this microbe. In consideration of these facts it 

 need not appear surprising that conclusive results should not, at the 

 time, have been obtained in the line of research indicated. It is of 

 course understood that any scientific research deserving of the name 

 must be founded upon reasonable and sound principles. The entire 

 experimental plan must be in harmony with the highest and best 

 results already obtained. The following are the essential and impor- 

 tant points for consideration and upon which the research work indi- 

 cated is to be based : 



1. Do rhizobia (nodule bacteria of leguminous plants) assimilate 

 free nitrogen in artificial culture media or when not symbiotically 

 associated with leguminous plants? Based upon the results of exten- 

 sive research work, in particular by German investigators, this ques- 

 tion is to be answered in the affirmative. A negative result would 

 mean that it would in all probability be wholly impossible to obtain 

 the anticipated outcome of the experiments. Since this question is, 

 however, to be answered in the affirmative, the next question in impor- 

 tance is 



2. Can rhizobia of leguminous plants be so modified by special cul- 

 ture methods as to induce them to develop in and upon the roots of 

 other plants, as corn, wheat, rye, barley, etc.? Although, as already 

 indicated, the experimental results thus far obtained are not conclu- 

 sive, yet the indications are that they will finally prove successful. 

 German investigators have shown that one variety of leguminous rhizo- 

 bium may, by culture methods, be converted into another variety. 

 That is, for example, the rhizobium of the bean nodules may be induced 

 to develop nodules on the roots of the pea, and perhaps other species of 

 closely related genera. This is, in part, denied by Nobbe and Hiltner 

 in the specifications of patent claim, as above recorded. It is, how- 

 ever, generally admitted by investigators that the rhizobia of the major- 

 ity of leguminous plants are morphologically very variable, and un- 

 dergo very marked structural changes in different culture media and 

 within the host root nodules at different periods of the season and of 

 growth. Such pronounced polymorphism coincides with marked 

 adaptive changes to new or changed environment, and it is, there- 



