The International Code of Nomenclature for algae, fungi, and plants (ICN) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all those "traditionally treated as algae, fungi, or plants".:Preamble, para. 8 It was formerly called the International Code of Botanical Nomenclature (ICBN); the name was changed at the International Botanical Congress in Melbourne in July 2011 as part of the Melbourne Code which replaces the Vienna Code of 2005. As with previous codes, it took effect as soon as it was ratified by the congress (on Saturday 23 July 2011), but the documentation of the code in its final form was not finished until some time after the congressional meeting. Preliminary wording of some of the articles with the most significant changes has been published in September 2011.
The name of the Code is partly capitalized and partly not. The lower-case for "algae, fungi, and plants" indicates that these terms are not formal names of clades, but indicate groups of organisms that were historically known by these names and traditionally studied by phycologists, mycologists, and botanists. This includes blue-green algae (Cyanobacteria); fungi, including chytrids, oomycetes, and slime moulds; photosynthetic protists and taxonomically related non-photosynthetic groups. There are special provisions in the ICN for some of these groups, as there are for fossils.
The ICN can only be changed by an International Botanical Congress (IBC), with the International Association for Plant Taxonomy providing the supporting infrastructure. Each new edition supersedes the earlier editions and is retroactive back to 1753, except where different starting dates are specified.:Principle VI
For the naming of cultivated plants there is a separate code, the International Code of Nomenclature for Cultivated Plants, which gives rules and recommendations that supplement the ICN.
The rules governing botanical nomenclature have a long and tumultuous history, dating back to dissatisfaction with rules that were established in 1843 to govern zoological nomenclature. The first set of international rules was the Lois de la nomenclature botanique ("Laws of botanical nomenclature") that was adopted as the "best guide to follow for botanical nomenclature" at an "International Botanical Congress" convened in Paris in 1867. Unlike modern codes, it was not enforced. It was organized as six sections with 68 articles in total.
Multiple attempts to bring more "expedient" or more equitable practice to botanical nomenclature resulted in several competing codes, which finally reached a compromise with the 1930 congress. In the meantime, the second edition of the international rules followed the Vienna congress in 1905. These rules were published as the Règles internationales de la Nomenclature botanique adoptées par le Congrès International de Botanique de Vienne 1905 (or in English, International rules of Botanical Nomenclature adopted by the International Botanical Conference of Vienna 1905). Informally they are referred to as the Vienna Rules (not to be confused with the Vienna Code of 2006).
Some but not all subsequent meetings of the International Botanical Congress have produced revised versions of these Rules, later called the International Code of Botanical Nomenclature. Some important versions are listed below.
|Year of adoption||Informal name|
|1999||St Louis Code, The Black Code|
|2011||Melbourne Code (current, supersedes all previous codes)|
The Nomenclature Section held just before the 18th International Botanical Congress in Melbourne, Australia in July 2011 saw sweeping changes to the way scientists name new plants, algae, and fungi.
Specific to botany