Floral diagram

Floral diagram of Anagallis arvensis. The dot represents the main axis, green structure below is the subtending bract. Calyx (green arcs) consists of five free sepals; corolla (red arcs) consists of five fused petals. Antepetalous stamens are joined to petals by hairy filaments. Ovary is superior, placentation is free central and the ovules are atropous.

Floral diagram is a graphic representation of flower structure. It shows the number of floral organs, their arrangement and fusion. Different parts of the flower are represented by their respective symbols. Floral diagrams are useful for flower identification or can help in understanding angiosperm evolution. They were introduced in the late 19th century and are generally attributed to A. W. Eichler.

In the 19th century, two contrasting methods of describing the flower were introduced: the textual floral formulae and pictorial floral diagrams. Floral diagrams are credited to A. W. Eichler, his extensive work Blüthendiagramme (1875, 1878) remains a valuable source of information on floral morphology. Eichler inspired later generation of scientists, including John Henry Schaffner. Diagrams were included e.g. in Types of Floral Mechanism by Church (1908). They were used in different textbooks, e.g. Organogenesis of Flowers by Sattler (1973), Botanische Bestimmungsübungen by Stützel (2006) or Plant Systematics by Simpson (2010). Floral Diagrams (2010) by Ronse De Craene followed Eichler’s approach using the contemporaryAPG II system.

Floral diagram is a schematic cross-section through a young flower. It may be also defined as “projection of the flower perpendicular to its axis”. It usually shows the number of floral parts, their sizes, relative positions and fusion. Different organs are represented by distinguishable symbols, which may be uniform for one organ type, or may reflect concrete morphology. The diagram may also include symbols that don’t represent physical structures, but carry additional information (e.g. symmetry plane orientation).

There is no agreement on how floral diagrams should be drawn, it depends on the author whether it is just a rough representation, or whether structural details of the flower are included.

Diagrams can describe the ontogeny of flowers, or can show evolutionary relationships. They can be generalized to show the typical floral structure of a taxon. It is also possible to represent (partial) inflorescences by diagrams.

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Wikipedia