Floral evolution in the Hamamelididae. I. General assessment of the probable phylogeny and taxonomic position of the group

After the publication of an emended version of the Anthocorm Theory and the introduction of the concept of the holomonandron and its meromonandrial derivatives, a number of major groups are re-interpreted as far as their floral morphology and phytogeny are concerned. The present paper is the first of a series dealing with the subclassis of the Hamamelididae. The “Amentiferae” appear to exhibit various trends of floral evolution, but the androecia sometimes remained primitive. Generally speaking, the structures conventionally called “flowers” represent modified gonoclads (or sometimes monogona) which function as reproductive units. These functional reproductive units (or anthoids) are usually coaxially arranged in so-called inflorescences (“catkins”) or “part-inflorescences” (“dichasia”, “cymes”, etc.), but as far as can be ascertained these names are utterly misleading. A characteristic trait of the group is that, in contrast to nearly all other major groups of dicots, the anthocorms hardly, if ever, evolved into a brachyblastic holanthocormous flower. The Juglandales, Hamamelidales and Urticales exhibit similar trends of anthocorm evolution, and apparently hang together. Neither euanthous forms, nor groups with primitive (macro- and leptoblastic) anthocormoids specialised (reduced, oligomerised) in a different way (such as Chloranthacecae, Piperales, some Laurales), can be derived from, or considered prototypic to, hamamelidid taxa. A common phylogenetic origin of the Hamamelididae with other major groups of Flowering Plants can only be visualised as a descent of both from a common group of progenitors with primitive (i.e., polymerous and macroblastic) anthocorms, and chances are that this ancestral group was still hemi- or pre- angiospermous. Within the hamamelidid assembly early 'specialisations caused a divergent evolution resulting in an early (presumably Mid-Cretaceous) separation of the casuarinalean, juglandalean, urticalean, betulalean/fagalean and hamamelidalean groups. These conclusions will serve as a basis for the discussions in other papers of these series.