Floral Diagrams: An Aid to Understanding Flower Morphology and Evolution

Description

"There is no general agreement nor any rule about how a flower should be defined. Since the end of the nineteenth century two main contrasting hypotheses have been provided and the discussion is still ongoing (reviewed in Bateman, Hilton and Rudall, 2006). The pseudanthial hypothesis accepts that flowers evolved from a branched, multiaxial structure, i.e. a condensed compound inflorescence (e.g. Eichler, 1875; Eames, 1961). This means that a flower is an assemblage of separately functioning entities that became grouped together. The euanthium hypothesis stated that the flower evolved from a simple uniaxial (euanthial) structure, i.e. a condensed sporophyll-bearing axis with proximal microsporophylls and distal megasporophylls (e.g. Arber and Parkin, 1907). However, reconstructions of the early angiosperm flower (e.g. Sauquet et al., 2017) suffer from the absence of clear transitional forms between ancestral prototypes and angiosperms"--