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Floral diagram

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Title: Floral diagram  
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Subject: Floral formula, Botany, Glossary of botanical terms, Receptacle (botany), Classes Plantarum
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Floral diagram

Anagallis arvensis
floral diagram of Anagallis arvensis
Floral diagram of Anagallis arvensis.[1]:307 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. 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 A. W. Eichler.[1]


In the 19th century, two contrasting methods of describing the flower were introduced: the textual [6] by Sattler (1973), Botanische Bestimmungsübungen[7] by Stützel (2006) or Plant Systematics[8] by Simpson (2010). Floral Diagrams[1] (2010) by Ronse De Craene followed Eichler’s approach using the contemporary[Note 1] APG II system.

Basic characteristics and significance

Floral diagram is a schematic cross-section through a young flower.[1] It may be also defined as “projection of the flower perpendicular to its axis”.[3] It usually shows the number of floral parts,[Note 2] 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.[1]:37 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.[1]:xiii

Relation of a plant material (Campanula medium) to the floral diagram. Black dashed line shows the cross-section. 1 – position of the main axis; 2 – cross-section through the lateral flower; 3 – bracteole; 4 – subtending bract.

Floral diagram 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 position of the main stem relative to a lateral flower.[9]:12 When a terminal flower is depicted, the axis is not present and therefore cannot be shown. Bracteoles, if they are present, are usually drawn on the sides of the diagram.

Symbols used in diagrams

Not only the information contained within diagrams, but also their appearance commonly varies between authors. Just some publications incorporate an overview of used symbols.

Bracts and bracteoles, axes

Bracts and bracteoles are commonly shown as arcs. In Floral Diagrams by Ronse De Craene they consistently have a black fill and a little triangle on the outer side to distinguish them from the perianth. In Eichler’s Blüthendiagramme their representation alters between diagrams.

Ronse De Craene Eichler

The axis relative to the flower is shown as black circle in Floral Diagrams. When inflorescence is depicted, the position of its main stem is illustrated by a crossed circle. Eichler’s depiction of axes alternates between diagrams.

Ronse De Craene Eichler
axis relative to the flower inconsistent
main stem of an inflorescence


Perianth parts are also shown as arcs. They may be colored according to their type. In Blüthendiagramme the Estivation can be accurately shown in the diagram.

Ronse De Craene Eichler
for sepals or sepaloid tepals

for petals or petaloid tepals/sepals

for tepals

for sepals for petals


Stamens are represented by a cross-section through anthers. In case there are many stamens in the flower, they can be simplified and drawn as circles. Staminodes have a small black circle inside or are painted black in Floral Diagrams, Eichler also fills them black.

Ronse De Craene Eichler
stamen or
staminode or


The pistil is shown as a sectional view of the ovary. Ovary position is highlighted by small triangles in Floral Diagrams. Ronse De Craene also incorporates ovule morphology or shows the position of stigmatic lobes by white shapes.

Ronse De Craene Eichler
superior ovary
inferior ovary
half-inferior ovary


In Floral Diagrams, nectaries are filled by grey color, Eichler fills them by hatching.


Fusion can be shown in diagrams by full connecting lines between organs. Lost organs can be represented by a star (✶), lost perianth parts or bracts/bracteoles can be shown with dashed stroke. It is possible to show the direction of monosymmetry by a large arrow. Resupination may be illustrated by a curved arrow. Floral parts can be accompanied by numbers to show their sequence of inicialization.

Floral diagrams and floral formulae

Each of these two concepts is better in expressing some information. Floral diagrams can show the size and relative position of the organs. On the other hand, floral formulae are capable of broader generalization. Prenner et al. view them as complementary methods and state they make an “identikit” flower when utilized together.[2]:248 Ronse De Craene also approves of their combined use.[1]:xiii


Partial inflorescence of Theobroma cacao
Floral diagram of Pyrus communis
Partial inflorescence of Theobroma cacao (after Ronse De Craene).
Floral formula: ✶ K5 C5 A(5°+5²) G(5)
Floral diagram of Pyrus communis (after Eichler).
Floral formula: ✶ K(5) C5 A10+5+5 Ğ(4)

See also


  1. ^ APG II was contemporary at the time of book’s writing, now it has been succeeded by APG III.
  2. ^ It also shows organs that are not part of the flower, but may be closely associated with it, such as bracts and bracteoles.


  1. ^ a b c d e f g Ronse De Craene, Louis P. (2010-02-04). Floral Diagrams: An Aid to Understanding Flower Morphology and Evolution. Cambridge: Cambridge University Press.  
  2. ^ a b Prenner, Gerhard; Richard M. Bateman; Paula J. Rudall (February 2010). "Floral formulae updated for routine inclusion in formal taxonomic descriptions". Taxon 59 (1): 241–250.  
  3. ^ a b Eichler, August Wilhelm (1875). Blüthendiagramme, erster Theil: Enthaltend Einleitung, Gymnospermen, Monocotylen und sympetale Dicotylen. Leipzig: Wilhelm Engelmann. 
  4. ^ Eichler, August Wilhelm (1878). Blüthendiagramme, zweiter Theil: Enthaltend die apetalen und choripetalen Dicotylen. Leipzig: Wilhelm Engelmann. 
  5. ^ Church, Arthur Harry (1908). Types of floral mechanism; a selection of diagrams and descriptions of common flowers arranged as an introduction to the systematic study of angiosperms. Oxford: Clarendon Press. 
  6. ^ Sattler, Rolf (1973). Organogenesis of flowers; a photographic text-atlas. Toronto, Buffalo: University of Toronto Press.  
  7. ^ Stützel, Thomas (2006). Botanische Bestimmungsübungen: Praktische Einführung in die Pflanzenbestimmung (2nd ed.). Stuttgart (Hohenheim): UTB, Stuttgart.  
  8. ^ Simpson, Michael George (2010). Plant Systematics. Oxford (Great Britain): Academic Press.  
  9. ^ Weberling, Focko (1992). Morphology of Flowers and Inflorescences. Cambridge: Cambridge University Press.  
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