There are seven accepted families within the Apiales, though there is some slight variation and in particular, the Torriceliaceae may also be divided.[2]
The present understanding of the Apiales is fairly recent and is based upon comparison ofDNA sequences byphylogenetic methods.[3] Thecircumscriptions of some of the families have changed. In 2009, one of the subfamilies of Araliaceae was shown to bepolyphyletic.[4]
Under theCronquist system, only the Apiaceae and Araliaceae were included here, and the restricted order was placed among the rosids rather than the asterids. ThePittosporaceae were placed within theRosales, and many of the other forms within the familyCornaceae.Pennantia was in the familyIcacinaceae. In the classification system ofDahlgren the families Apiaceae and Araliaceae were placed in the order Ariales, in thesuperorder Araliiflorae (also called Aralianae).
The largest and obviously closely related families of Apiales areAraliaceae,Myodocarpaceae andApiaceae, which resemble each other in the structure of theirgynoecia. In this respect however, thePittosporaceae is notably distinct from them.[8]
Typical syncarpous gynoecia exhibit four vertical zones, determined by the extent of fusion of the carpels. In most plants, the synascidiate (i.e. "united bottle-shaped") and symplicate zones are fertile and bear the ovules.[9] Each of the first three families possess mainly bi- or multilocular ovaries in a gynoecium with a long synascidiate, but very short symplicate zone, where the ovules are inserted at their transition, the so-called cross-zone (or "Querzone").[8]
In gynoecia of the Pittosporaceae, the symplicate is much longer than the synascidiate zone, and the ovules are arranged along the first. Members of the latter family consequently haveunilocular ovaries with a single cavity between adjacent carpels.[8]
^Nicolas, A. N.; Plunkett, G. M. (2009). "The demise of subfamily Hydrocotyloideae (Apiaceae) and the re-alignment of its genera across the entire order Apiales".Molecular Phylogenetics and Evolution.53 (1):134–151.Bibcode:2009MolPE..53..134N.doi:10.1016/j.ympev.2009.06.010.PMID19549570.
^Winkworth, Richard C.; Lundberg, Johannes; Donoghue, Michael J. (2008). "Toward a resolution of Campanulid phylogeny, with special reference to the placement of Dipsacales".Taxon.57 (1):53–65.Bibcode:2008Taxon..57...53W.doi:10.2307/25065948.JSTOR25065948.
^Pankhurst, R. J. (1992).Morphology of flowers and inflorescences (1st pbk. ed.). Cambridge, England: Cambridge University Press. pp. 153–155.ISBN9780521438322.
