Page:Popular Science Monthly Volume 63.djvu/344

340 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 discovery of the root nodule bacteria were begun about 1863 by Hellriegel 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 useful 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 important points for consideration and upon which the research work indicated 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 extensive research work, in particular by German investigators, this question 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 importance is

2. Can rhizobia of leguminous plants be so modified by special culture 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 conclusive, yet the indications are that they will finally prove successful. German investigators have shown that one variety of leguminous rhizobium 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, however, generally admitted by investigators that the rhizobia of the majority of leguminous plants are morphologically very variable, and undergo 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,