Nitrogen Fixation in Wild Legumes

Isolations of the rhizobia from nodules of field plants of Ulexeuropaeus and Medicago lupulina have been examined for effectivenessin fixation of nitrogen by inoculating them into host plantsgrowing in a medium free of combined nitrogen. The results indicatethat vigorous fixation may be presumed to occur in associationwith field plants of the Ulex species, but that fixation inMedicago is probably decreased by the presence of ineffectiverhizobia in some nodules. The general importance of fixationin wild legumes is discussed, and it is pointed out that dueattention must be paid to non-legume genera with root nodules.These genera are locally abundant, and in former periods werestill more prominent in some regions of the world.