Page:Popular Science Monthly Volume 63.djvu/345

Rh, highly probable that these polymorphic rhizobia may be induced to change hosts, at least temporarily, which is really all that is required for the success of the experiments. That is, it is desired that i the rhizobia should live and multiply in or upon the roots of gramineous plants during one season or from the time of seed germination to i the ripening of the crop (in annuals). This question is intimately associated with the following:

3. Even should it be possible to induce the rhizobia to develop in; and upon roots of gramineous (and other non-leguminous) plants, would they still retain the power of assimilating free nitrogen? It is highly probable that this question can be answered in the affirmative, although Lafar makes the statement that the rhizobia in certain stages of existence, for instance those which exist in the infecting threads (Infectionsfäden) of nodules and predominate in young tubercles and in the apical areas of all tubercles, exist in a purely parasitic or harmful relationship with the host plant. It is, however, highly probable that this statement is not founded upon experimental proof. The assimilation of free nitrogen is an essential function of rhizobia, and it is certainly reasonable to assume that the function would continue, though perhaps in a modified degree, no matter how marked the morphological adaptive changes might be. This question can be settled very simply and easily as the experiments progress.

The following question should also be carefully considered:

4. Are there soil bacteria or other organisms, not found in leguminous root nodules, which assimilate free nitrogen and which may be especially adapted to gramineous plants? From what has already been stated, it would appear that the Bacillus Ellenbachiensis of Caron is such an organism. If it should become evident that this organism assimilates free nitrogen principally in association with gramineous plants, it would seem to give promise of great utility in the more effective cultivation of gramineous plants. This organism would be especially advantageous, because, in contradistinction to rhizobia, it forms spores. Spore-bearing cultures would be desirable, because they would keep better and longer. The microbic fertilizer could be put up in dried form and sent to farmers at great distances without danger of becoming worthless. It could be kept for months, or perhaps even a year or more, though this in itself would not be of prime advantage. Further extensive researches would be necessary to determine to what extent adaptive changes could be developed in this particular microbe.

Finally the question will arise,

5. In what morphological, biological and bio-chemical relationship would the modified organisms establish themselves with the prospective or new host plant? It is, of course, not to be anticipated that they would cause the development of root nodules or tubercles or cause