Root nodules in non-leguminous plants in New Zealand

[First paragraph(s)..]
Until recently there has been little interest in this subject of non-leguminous root nodules although they been recognised as characteristic plant organs since 1829 (Allen and Allen, 1958).
Plants from eight dicotyledonous genera out-side the Leguminosae have been shown to bear nodules. These have been stated by Bond et al, (1956) to belong to widely separated families, but they based this observation on the classification proposed by Engler and Diels (1936). If these families are placed in Orders according to Hutchinson's classification (1926) they appear to be more closely related than Bond et al have recognised (Table I).