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. They are typically used with the floral formula of that flower to study its morphology. History 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 contemporary APG II system. Basic characteristics and significance A 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. Substantial amount of information may be included in a good diagram. It can be useful for flower identification or comparison between angiosperm taxa. Paleontologists can take advantage of diagrams for reconstruction of fossil flowers. Floral diagrams are also of didactic value. Orientation Diagrams are usually depicted with the subtending bract below and the axis above the flower itself, both in the median line. The axis corresponds to the