This article is about "form" in botany. For the use in zoology, see Form (zoology).

In botanical nomenclature

Botanical nomenclature

Botanical nomenclature is the formal, scientific naming of plants. It is related to, but distinct from taxonomy. Plant taxonomy is concerned with grouping and classifying plants; botanical nomenclature then provides names for the results of this process. The starting point for modern botanical...

, a form (forma, plural formae) is one of the "secondary" taxonomic rank

Taxonomic rank

In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...

s, below that of variety

Variety (biology)

In botanical nomenclature, variety is a taxonomic rank below that of species: as such, it gets a three-part infraspecific name....

, which in turn is below that of species; it is an infraspecific taxon. If more than three ranks are listed in describing a taxon, the "classification" is being specified, but only three parts make up the "name" of the taxon: a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 name, a specific epithet, and an infraspecific epithet.

The abbreviation "f." or the full "forma" should be put before the infraspecific epithet to indicate the rank.

For example:

• Acanthocalycium
  Acanthocalycium
  Acanthocalycium is a genus of cactus consisting of three species from Argentina. The taxon name comes from Greek akantha and kalyx , which refers to the spines on the floral tubes....
  
   spiniflorum f. klimpelianum or
  • Acanthocalycium spiniflorum forma klimpelianum (Weidlich & Werderm.) Donald
• Crataegus aestivalis (Walter) Torr. & A.Gray var. cerasoides Sarg. f. luculenta Sarg. is a classification of a plant whose name is:
  • Crataegus aestivalis (Walter) Torr. & A.Gray f. luculenta Sarg.

A form usually designates a group with a noticeable but minor deviation. For instance, white-flowered forms of species that usually have coloured flowers can be named a "f. alba". Formae apomicticae are sometimes named among plants that reproduce asexually, by apomixis

Apomixis

In botany, apomixis was defined by Winkler as replacement of the normal sexual reproduction by asexual reproduction, without fertilization. This definition notably does not mention meiosis...

. Some botanists believe that there is no need to name forms, since there are theoretically countless numbers of forms based on minor genetic differences.

See also

• Trinomial nomenclature
  Trinomial nomenclature
  In biology, trinomial nomenclature refers to names for taxa below the rank of species. This is different for animals and plants:* for animals see trinomen. There is only one rank allowed below the rank of species: subspecies....
  
  
• Variety (botany)
• Subvariety
  Subvariety
  In botanical nomenclature, a subvariety is a taxonomic rank below that of variety but above that of form : it is an infraspecific taxon. Its name consists of three parts: a genus name, a specific epithet and an infraspecific epithet. To indicate the rank, the abbreviation "subvar." should be put...
  
  
• Variety (plant)
  Variety (plant)
  Plant variety is a legal term, following the International Union for the Protection of New Varieties of Plants Convention. Recognition of a cultivated plant as a "variety" in this particular sense provides its breeder with some legal protection, so-called plant breeders' rights, depending to some...
  
  
• Cultivar
  Cultivar
  A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...
  
  
• Hybrid (biology)
• Race (biology)
  Race (biology)
  In biology, races are distinct genetically divergent populations within the same species with relatively small morphological and genetic differences. The populations can be described as ecological races if they arise from adaptation to different local habitats or geographic races when they are...