Based on the most current phylogenetic data, you should use the following:
Actinidia - Actinidiaceae
Schisandra - Schisandraceae
Hydrangea - Hydrangeaceae
These answers are gleaned from
the Angiosperm Phylogeny Website. They are confirmed by the Royal Horticultural Society Plant Finder 2002-2003 (which is the standard reference that we use at UBC Botanical Garden for genus-family relationships). Two out of three are also in agreement with the International Association of Plant Taxonomy listings (I believe the research team behind that initiative collaborate with the Angiosperm Phylogeny Website).
The question that then arises is why is the
International Plant Names Index "incorrect" on two of three accounts?
The International Plant Names Index is a compilation of the Index Kewensis, the Gray Card Index and the Australian Plant Name Index. Of these, the one that typically addresses family-genus relationships is the Index Kewensis.
Index Kewensis is not a list of valid plant names, but rather a list of published plant names with bibliographic references. In other words, the names listed in Index Kewensis do not necessarily reflect modern taxonomic evidence of our understanding of plant relationships. Instead, the names merely represent an incidence of publication of that name.
To use an example,
Schisandra is listed in the Index Kewensis as being (for the most part) in Magnoliaceae. However, that's because at the time of publication, that's where it was placed. Our current understanding of the genus deems that it belongs in its own family, Schisandraceae. However, the Index Kewensis is not updated to reflect that.
* I believe I've once read that the International Plant Names Index should actually be called the International Publication of Plant Names Index.
** I was unable to find where
Actinidia was placed in the Vitaceae in IPNI.
Hope this answers your question,
Daniel
