The significance of the use of floral diagrams is discussed in this chapter, including different types as well as its advantages and limitations. Floral diagrams can catch the diversity of flowers, including accessory structures and floral heteromorphism. The importance of floral development, the drive of pollination and evolutionary developmental genetics is shown in the shaping of floral structures and as a reflection of floral evolution.

Floral diagrams are presented for fourteen families out of six orders of the basal groups of angiosperms. The floral diagrams of the basal angiosperms illustrate the early progression of flower diversification. Starting with the most basal angiosperms, different trends in flower evolution are shown through diagrams, illustrating the transition of spiral to whorled trimerous flowers, incipient transformations of floral organs and accessory structures, and the progressive fusion of organs. The major orders are presented with representatives of the most important families and their trends, including Laurales, Magnoliales and Piperales.

Floral diagrams are presented for twenty-eight families out of ten orders of monocots, covering the diversity and evolutionary trends within this largely homogeneous group. The monocots are basically defined by their trimerous Bauplan, regulating the structure of the flower as well as its evolution. The basalmost orders demonstrate greater variation with higher or lower stamen numbers, while higher groups have evolved within the constraint of a pentacyclic arrangement that has changed very little. Variations in flower morphology as adaptations to different pollination systems are regulated by hypanthial growth, reductions of organs or stamen increases, and monosymmetry.

The Pentapetalae have diversified very rapidly, leading to two major successful clades, the superrosidae and superasteridae. Although it is still uncertain how the Pentapetalae diverged from ancestral flowers, their regular floral pentacyclic and pentamerous Bauplan is almost unversal and firmly established in all evolutionary lines. The possibility is presented that intermediates such as Berberidopsis regulate the transition from a spiral to a pentamerous pentacyclic flower. The diversity and unique evolutionary trends of early diverging orders with unclear affinity, Dilleniales and Santalales, are presented.

Floral diagrams are presented for thirty-six families out of nine orders of SupperAsteridae. Asterids represent the pinacle in Pentapetalae floral evolution, expressing a strong synorganization between whorls and the stabilization of a tetracyclic Bauplan with five sepals, five petals, a single whorl of stamens (haplostemony) and two carpels. The lower Asterids share characters of basal Pentapetalae and rosids and present all characteristics of a transition to euasterids. Diferent trends are higlighted in lamiids and campanulids. The development of a stamen-petal tube emerges in the basal Asterids and is prominent in the lamiids in association with median monosymmetry. An important evolutionary trend representing the sterilisation of stamens in Lamiales is shown through floral diagrams. In Campanulids there is a shift towards the reduction of the stamen-petal tube as well as the reduction of the calyx linked with an inferior ovary and a lower number of ovules.

This chapter represents a summary of the major taxonomic groups and their floral evolution. The value of floral diagrams is highlighted as a means to stress similarities and differences between the major angiosperm groups.

Floral diagrams are presented for twenty-one families of the highly diverse orders caryophyllales and polygonales. The caryophyllids represent a small but important clade close to the asterids. The flowers show important evolutionary trends linked with a progressive loss of petals, and their reinvention of petal-like structures in derived groups, such as coloured sepals or staminodes. Stamen evolution also shows unique trends linked with spatial constraints and secondary multiplications. The ovary shows a general tendency to the development of central placentas and the reduction in the number of ovules. Floral diagrams are used to illustrate the major evolutionary trends within caryophyllales and specifically within the diverse family Polygonaceae, in addition to specific diagrams representative of families.