While preparing some of the earlier parts of this series I was inclined to the view that Metrosideros Banks ex Gaertn., as it had come to be understood, should be divided into several genera. I now feel that a wider concept is advisable at this time, although further information, particularly from other lines of evidence, may eventually lead to subdivision. The present concept includes Mearnsia Merrill, but excludes Nani Adanson and Kania Schlecht. The first two were reviewed in Parts 3 and 4 of this series (Dawson, 1970b, 1972a) and the last will be the topic of a later part.