Floral diagrams can describe flowers with a high degree of detail. Although it is difficult to represent specific three-dimensional depth, the amount of information provided is considerable and may include developmental and anatomical evidence (see p. 37).

Floral diagrams support recognition of plant species, as major groups can be identified by their floral diagram, but are also a reflection of the evolution of flowers in angiosperms. Major changes in the floral Bauplan can be stressed by representing floral diagrams in the context of the phylogenetic tree of angiosperms. Floral diagrams make a comparison between divergent characters possible by stressing the positional relationships of floral structures.

Floral diagrams are not rigidly fixed in time, but are an expression of the developmental plasticity in flowers. Important morphological changes are often the result of subtle shifts in the primordial body during development, and this is also reflected at the genetic level. One aspect of morphological observations is that changes are often gradual, without clear-cut boundaries in characters between different clades. Several plant groups are characterized by ‘tendential features’ or ‘apomorphic tendencies’ (see Endress and Matthews, 2006a), namely characters that may not be generalized in a clade, but occur on a much more frequent basis than in any related clades. I call these characters ‘cryptic apomorphies’. These characters can either be synapomorphic (present in a clade but not in all members), non-synapomorphic (a predisposition to evolve a character in a clade) or represent several independently derived features (autapomorphies) in a clade (Endress and Matthews, 2006a).