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Pictures to the left

© 1991 P. Prusinkiewicz

Inflorescences are arrangements of more than one flower, like bostryx, head, cyme etc. They are modified parts of the shoot with leaves typically reduced to leaflike bracts.

Only rarely does the main shoot or a side shoot end with a single, terminally placed flower. More common are flowers that are grouped together to units that are more or less clearly set off from the rest of the plant's body. These units are called inflorescences. An inflorescence is a flowering and thus modified part of the shoot with leaves that are usually reduced to leaflike bracts.

The types of branching occurring in flowering plants can be studied especially well with inflorescences. As has been said when reviewing the different types of branching of the shoot, it is distinguished between monopodial and sympodial inflorescences.

Some technical terms to start off: both determinate and indeterminate inflorescences occur. The first type of inflorescence ends with a flower at the top of the axis while this is missing with the latter. Indeterminate inflorescences can therefore theoretically continue to elongate and produce new flowers, while determinate inflorescences cannot. Indeterminate types of inflorescences are racemes, corymbs, heads, cones and umbels. They are also called simple inflorescences since their main axis is not branched. Complex types are branched. Among the complex inflorescences are double racemes (where a single flower is replaced by a raceme), double umbels, etc. as well as panicles and thyrsi.

Panicles are typically closed with lateral inflorescences that decrease continuously in branching towards the top of the inflorescence (partial inflorescence). With thyrsi, the single inflorescences are organized sympodially. Since in dicots only the first two leaf organs of a lateral axis can have the function of bractlets, a sympodially organized axis has a maximum of two lateral shoots. This generates a dichasium with an often fork-like appearance. If only one axial product of a bractlet is produced, it is spoken of a monochasium. Depending on whether the branching takes place in an alternating way (left and right) or only at one side, the resulting inflorescence is called a cincinnus (scorpioid cyme) or a bostryx (heliocoid cyme). The corresponding monocotyledon units where usually only one bractlet per lateral axis is developed are called rhipidium (fan-shaped cyme) and drepanium (helicoid cyme).

© Peter v. Sengbusch - b-online@botanik.uni-hamburg.de