A hybrid may get a name if the author considers it necessary (in practice, authors tend to use this option for naturally occurring hybrids), but it is recommended to use parents' names as they are more informative (art. H.10B.1).
A hybrid may also be indicated by a formula listing the parents. Such a formula uses the multiplication sign『×』to link the parents.
"It is usually preferable to place the names or epithets in a formula in alphabetical order. The direction of a cross may be indicated by including the sexual symbols (♀: female; ♂: male) in the formula, or by placing the female parent first. If a non-alphabetical sequence is used, its basis should be clearly indicated." (H.2A.1)
A hybrid name is treated like other botanical names, for most purposes, but differs in that:[2]
A hybrid name does not necessarily refer to a morphologically distinctive group, but applies to all progeny of the parents, no matter how much they vary.
E.g., Magnolia × soulangeana applies to all progeny from the cross Magnolia denudata × Magnolia liliiflora, and from the crosses of all their progeny, as well as from crosses of any of the progeny back to the parents (backcrossing). This covers quite a range in flower colour.
Grex names (for orchids only) differ in that they do not cover crosses from plants within the grex (F2 hybrids) or back-crosses (crosses between a grex member and its parent).
Hybrids can be named with ranks, like other organisms covered by the ICNafp. They are nothotaxa, from notho- (hybrid) + taxon. If the parents (or postulated parents) differ in rank, then the rank of the nothotaxon is the lowest.[4] The names of nothospecies differ depending on whether they are derived from species within the same genus; if more than one parental genus is involved, then the nothospecies name includes a nothogenus name.
Names of hybrids between genera (called nothogenera) can be published by specifying the names of the parent genera, but without a scientific description, and do not have a type. Nothotaxon names with the rank of a subdivision of a genus (notho-subgenus, notho-section, notho-series, etc.) are also published by listing the parent taxa and without descriptions or types.[6]
amultiplication sign『×』placed before the name of an intergeneric hybrid or before the epithet of a species hybrid. An intervening space is optional. e.g.:
The multiplication sign and the prefix notho- are not part of the actual name and are disregarded for nomenclatural purposes such as synonymy, homonymy, etc. This means that a taxonomist could decide to use either form of this name: Drosera ×anglica to emphasize that it is a hybrid, or Drosera anglica to emphasize that it is a species.
The names of intergeneric hybrids generally have a special form called a condensed formula, e.g., × Agropogon for hybrids between Agrostis and Polypogon. Hybrids involving four or more genera are formed from the name of a person, with suffix -ara, e.g., × Belleara.[7] Names for hybrids between three genera can be either a condensed formula or formed from a person's name with suffix -ara.
The symbol used to indicate a hybrid is U+00D7×MULTIPLICATION SIGN. (Linnaeus originally used U+263F☿MERCURY, but abandoned it in favour of the multiplication sign.)[8]
^Stearn, William T. (May 1962). "The Origin of the Male and Female Symbols of Biology". Taxon. 11 (4): 111. doi:10.2307/1217734. JSTOR1217734. S2CID87030547. Later, in his Mantissa Plantarum (1767) and Mantissa Plantarum altera (1771), Linnaeus regularly used ♂, ♀ and ☿ for male, female and hermaphrodite flowers respectively. Their aptness made them easy to remember and their convenience led to their general acceptance in zoology as well as botany. Koelreuter found them especially convenient when recording his experiments in hybridization; as late as 1778 he used the sign to denote a hybrid plant. No evidence of the use of these signs for this purpose before Linnaeus's time has been found.
