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Principles and Rules of Botanical Nomenclature

  • Botany

In this principles and rules of botanical nomenclature post we have briefly explained about history, principles and rules of ICBN (botanical nomenclature).

The process of naming plants based on international rules  proposed by botanists to ensure stable and universal system is called botanical nomenclature. It is an essential process to overcome the problems of common names. 

The botanists agreed to lay down certain rules and conditions known as rules of ICBN. The main suggestion was that language should be in Latin as it is not a national language of any country and moreover it is dead language. Much of the previous literature was written in Latin. The International Code of Botanical Nomenclature (ICBN) is a global agreement among botanists to use the Binomial system of naming.


Prior to the middle of the 18th century, plant names were polynomials made up of several words. Linnaeus proposed basic rules of ICBN in his book ‘Philosophia botanica’ in 1751. 

In Theorie elementaire de la botanique, A.P. de Candolle proposed details of plant nomenclature rules of ICBN in 1813. Alphonse de Candolle, son of A.P. de Candolle, called a meeting of all botanists in 1867 to present these rules. The first Botanical Congress was held in Paris, and the laws enacted there were known as the Paris code.

In 1930, the fifth International Botanical Congress (IBC) was held in England to frame rules and regulations for naming plants. In July 1975, twelfth meeting was held at Leningrad, USSR. Based on the resolutions of these meetings, the existing system of International Code of Botanical Nomenclature (ICBN) was adapted from 1978. 

The IBC meets every 5 to 6 years to decide any additions or changes in the naming and numbering of plants. The 18th IBC congress was held at Melbourne in 2011 and the latest 19th IBC was held in Shenzen, China in July 2017.

Principles and Rules of ICBN

Principle: 1

“Botanical nomenclature is independent of zoological nomenclature.” The rules of ICBN do not apply to animals and bacteria. Therefore botanists do not have to be concerned with the names or rules of ICBN associated with animals and bacteria.

Principle: 2

The application of names of taxonomic groups is determined by means of nomenclatural types.” Each plant has a physical (type) specimen associated with it. A plant taxonomist doing research has to study type specimens in order to ensure that names associated with plants are correct.

Principle: 3

The nomenclature of a taxonomic group is based upon the priority of publication.” The rule of priority means that the earliest applicable, properly published name is the correct one. Priority extends back to 1 May 1753 for most plants, the publication date for Linaeus’ Species Plantarum.

Principle: 4

Each taxonomic group with a particular circumscription, position, and rank can bear only one correct name, the earliest that is in accordance with the rules of ICBN, except in specified cases.” The names that can be considered as the correct names are those that are published effectively and validly.

Principle: 5

Scientific names of taxonomic groups are treated as Latin regardless of their derivation.” The ICBN provides instructions on the use of proper Latin grammar for taxonomic names.

Principle: 6

The rules of ICBN nomenclature are retroactive unless expressly limited.” This means that the rules of ICBN apply to work done before the acceptance of these rules of ICBN.

Rules of ICBN

Rule 1: Rank of taxa

The The International Code of Botanical Nomenclature (ICBN) provides the series of rank with names which are the hierarchialcatagories. The ranks, in descending sequence, provided by the Code are shown in the following table.

The International Code of Botanical Nomenclature

Rules of ICBN

Rule 2 : The Type Method

Names are established by reference to a nomenclatural type. Taxonomists use the type method as a legal device to provide the correct name for a taxon. The nomenclatural type of a species, a type specimen, is a single specimen or the plants on a single herbarium sheet. Type specimen (herbarium sheet) is of different type:

Holotype: The single specimen designated as the type of a species by the original author at the time the species name and description was published. Lectotype: In case of holotype is lost, second herbarium sheet prepared from the original plant is called lectotype. Neotype: In case holotype and original plant is lost then herbarium sheet prepared from some other plant of same species is called neotype. Syntype: In case holotype and original, plant is lost then many herbarium sheet prepared from many plants of same species is called syntype. Isotype: Duplicate of holotype – In presence of holotype a second herbarium sheet prepared from the original plant is called isotype. Paratype: Additional herbarium sheet used in the first description of plant is called para type. It is prepared from some other plant of same species having some variations.

Rule 3: Priorities of Names

Priority is concerned with the precedence of the date of valid publication and determines acceptance of one of two or more names that are otherwise acceptable. A name is said to be legitimate if it is accordance with the rules of ICBN and illegitimate if it is contrary.

Rule 4: Effective and Valid Publications of Names

The names of taxa must meet the requirement of the Code when it is published. It is effective under this code only when the distribution of printed is performed properly. It should be effectively published i.e. in a journal commonly available to botanists and not in a local newspaper or in any other printed form. It should be published in a correct form i.e.Latinized with rank indicated and with Latin description (may be in brief). More detailed description is given in vernacular language. For the taxa of the rank of genus and below, nomenclature type must be indicated and location of the type also indicated. If the Names are published effectively and validly using the rules of ICBN then the names are legitimate otherwise they are illegitimate. The name of the newly described taxon is usually indicated bywords sp.nov (species nova); gen.nov. (genusnovum).

Rule 5: Citation of Author’s Name

The botanical name is incomplete without author’s name. According to article 46 it is necessary to cite the name of the author who first validly published the name. Single author citation: When single author is involved in naming the plant. If the author’s name is too long it should be abbreviated e.g. Solanum nigrum, L.L for Carolus Linnaeus. Double author citation: When more than one author is involved. If those authors is in different manner in different conditions.

Rule 6: Conserved name (NominaConservanda)

Some of the names of taxa are not followed the rule of ICBN but they are using since a long time, hence The International Code of Botanical Nomenclature (ICBN) has decided to retain the popular in addition to valid name.

Rule 7 : Priority of Publication

Preference will be given who will publish earlier and only a single name is accepted for a taxon.

1. According to binomial system name of any species consists of two names i.e. generic and species name.

In plant nomenclature (The International Code of Botanical Nomenclature (ICBN)), tautonyms are not valid i.e. generic name and specific name should not be same in plants e.g. Mangifera mangifera But tautonyms are valid for animal nomenclature (ICZN-International Code of Zoological Nomenclature) & Naja naja (Indian cobra), Raitus rattus (Rat).

Length of generic mime or specific name should not be less than 3 letters and not more than 12 letters e.g Mangifera indica Exception: Ricciapaihankotensis More than 12 letters According to The International Code of Botanical Nomenclature (ICBN) this name is not valid but this name was proposed before 1961, so it is valid.

First letter of generic name should be in capital letter and first letter of specific name should be in small letter. e.g Mangifera indica. But if specific name is based on the name of some person, its first letter should be in capital letter e.g. lsoetespantii.

When written with free hand or typed, then generic name and specific name should be separately underlined. But during printing, name should be Italized.

Name of scientist (who proposed nomenclature) should be written in short after the specific name e.g. Mangifera indica Lin.

Name of scientist should be neither underlined nor written in italics, but written in roman, letters (simple alphabets).

If any scientist has proposed wrong name then his name should be written in bracket and the scientist who corrected the name should be written after the bracket. e.gTsuga canadensis (Lin.) Salisbury.

Scientific names should be derived from Latin or Greek languages because they are dead languages.

Type specimen (Herbarium Sheet) of newly discovered plant should be placed in herbarium (dry garden).Standard size of herbarium sheet is 11.5 × 16.5 inches.

Further Readings