Changing floral concepts: anthocorms, flowers, and anthoids

As a logical consequence of the Anthocorm Theory, two alternative pathways of evolution within the reproductive region of the Flowering Plants appear to be possible, viz., the transformation of either a whole anthocorm or a subordinate part of an anthocorm (a gonoclad or occasionally a monogonon) into a functional reproductive unit, i.e., into a morphologically, ontogenetically, and anthecologically more or less self-contained and discrete entity. A number of criteria deduced from the architecture and the likely specialisations of the postulated, archaeic type of anthocorm, although each by itself not always unequivocal or sharply discriminating, seem adequate, if applied in conjunction, to discern the different types of functional floral units. Apart from having some considerable bearing upon comparative and phylogenetic floral morphology and ontogeny, the recognition of diverse categories of blossoms casts light on the somewhat paradoxical and incongruous incidence of morphologically altogether different, functional floral units in two anatomically, embryologically, palynologically, karyogenetically, phytochemically and/or serologically closely related taxa (sometimes even within the same family), the incongruity simply becoming explicable by divergent trends of evolution within the reproductive region. The new concepts of the holanthocormous versus the anthoidal (gonocladial or monogonial) reproductive entities also obviate the conventional necessity of having to explain “simple” (i.e., haplo- or achlamydeous, oligomerous and often unisexual) reproductive entities as much “reduced” (depauperated) derivatives of a phaneranthous, diplochlamydeous and bisexual, archetypic kind of flower. This undoubtedly will have repercussions in the assessment of the relative degree of phylogenetic advancement of reputedly “derived” groups such as Piperales, Amentiferae, and Cyperales. The distribution of the holanthocormous and the anthoidal functional reproductive units among the Angiosperms is more wide-spread than previously anticipated, some major taxa such as Hamamelididae and many orders of the Monocotyledons entirely exhibiting an anthoidal reproductive morphology, and other ones, such as Magnoliidae, Ranunculidae and Caryophyllidae, being partly euanthous and partly anthoidal.