International Code of Botanical Nomenclature

(Tokyo Code), Electronic version



Article 21

21.1. The name of a subdivision of a genus is a combination of a generic name and a subdivisional epithet connected by a term (subgenus, sectio, series, etc.) denoting its rank.

21.2. The epithet is either of the same form as a generic name, or a plural adjective agreeing in gender with the generic name and written with a capital initial letter (see Art. 32.6 and 60.2).

21.3. The epithet in the name of a subdivision of a genus is not to be formed from the name of the genus to which it belongs by adding the prefix Eu-.

Ex. 1. Costus subg. Metacostus; Ricinocarpos sect. Anomodiscus; Valeriana sect. Valerianopsis; Euphorbia sect. Tithymalus; Euphorbia subsect. Tenellae; Sapium subsect. Patentinervia; Arenaria ser. Anomalae; but not Carex sect. Eucarex.

Note 1. The use within the same genus of the same epithet in names of subdivisions of the genus, even in different ranks, based on different types is illegitimate under Art. 53.

Note 2. The names of hybrids with the rank of a subdivision of a genus are formed according to the provisions of Art. H.7.

Recommendation 21A

21A.1. When it is desired to indicate the name of a subdivision of the genus to which a particular species belongs in connection with the generic name and specific epithet, the subdivisional epithet should be placed in parentheses between the two; when desirable, the subdivisional rank may also be indicated.

Ex. 1. Astragalus (Cycloglottis) contortuplicatus; A. (Phaca) umbellatus; Loranthus (sect. Ischnanthus) gabonensis.

Recommendation 21B

21B.1. The epithet in the name of a subgenus or section is preferably a substantive, that of a subsection or lower subdivision of a genus preferably a plural adjective.

21B.2. Authors, when proposing new epithets for names of subdivisions of genera, should avoid those in the form of a substantive when other co-ordinate subdivisions of the same genus have them in the form of a plural adjective, and vice-versa. They should also avoid, when proposing an epithet for a name of a subdivision of a genus, one already used for a subdivision of a closely related genus, or one which is identical with the name of such a genus.

21B.3. When a section or a subgenus is raised to the rank of genus, or the inverse change occurs, the original name or epithet should be retained unless the resulting name would be contrary to this Code.

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