Critical Dates in Botanical Nomenclature

Some rules on valid publication are limited by date. They apply on or after a particular date but not before. The main ones that affect the validity of algal names are listed below. Perhaps the one that causes most confusion is that specifying later starting-point dates for several algal groups.

Names before all of these dates are invalid and have no standing until validated after the prescribed starting point. The are also known as "devalidated names". No validly published name can exist before the starting-point of a particular group.

The list below is modified from "The Code Decoded" by N. Turland, which provides a more extensive account.

1 May 1753

Starting point for the nomenclature of most algae (Linnaeus, Species plantarum, ed. 1, 1753) except for:
1 January 1892 Nostocaceae Homocysteae (Gomont, "Monographie des Oscillariées", in Ann. Sci. Nat., Bot., ser. 7, 15: 263-368; 16: 91-264). The two parts of Gomont's "Monographie", which appeared in 1892 and 1893, respectively, are treated as having been published simultaneously on 1 January 1892.
1 January 1886 Nostocaceae Heterocystaceae (Bornet & Flahault, Révision des Nostocacées hétérocystées, in Ann. Sci. Nat., Bot., ser. 7, 3: 323-381; 4: 103-373; 5: 51-129; 7: 177-262). The four parts of the "Révision", which appeared in 1886, 1886, 1887, and 1888, respectively, are treated as having been published simultaneously on 1 January 1886.
1 January 1848 Desmidiaceae (in the broad sense), (Ralfs, British Desmidieae).
1 January 1900 Oedogoniaceae [Hirn, "Monographie und Iconographie der Oedogoniaceen", in Acta Soc. Sci. Fenn. 27(1)].

1 January 1908

For the name of a new taxon at generic or lower rank, an illustration with analysis is no longer acceptable in place of a validating description or diagnosis (Art. 38.7 and 38.8; for the definition of "analysis" see Art. 38.9 and 38.10).

1 January 1912

The name of a new genus may no longer coincide with a Latin technical term in use in morphology at the time of publication (Art. 20.2). Such a name may be validly published before 1912 provided that it was accompanied by a binomial species name.

For example, "Lobata" a genus name introduced by V.J.Chapman (1952), is not valid as it coincides with a Latin technical term.

1 January 1935 through 31 December 2011

For a new combination, name at new rank, or replacement name, the reference to the basionym or replaced synonym must be full and direct. For such names published before 1953 there must be a reference, but it may be indirect (e.g., via another name) or even cryptic (e.g., merely an author citation) (Art. 41.3 and 41.5). For the name of a new taxon, a reference to a previously and effectively published description or diagnosis (when a description or diagnosis is not included in the protologue) must be full and direct. For the name of a new taxon published before 1953 such a reference may be indirect or even cryptic (Art. 38.13). There must be a clear indication of the rank of the taxon concerned (Art . 37.1). The termination (ending) of a suprageneric name is acceptable as an indication of the rank (e.g., -aceae indicates the rank of family) (Art. 37.2). Prior to 1953, a name may be validly published without a clear indication of rank.

1 January 1958

For the name of a new taxon at generic or lower rank , the type must be indicated (Art. 40.1). Prior to 1958, a name may be validly published without indicating a type.

1 January 1958-31 December 2011

For the name of a new taxon of algae (fossil algae excepted), the validating description or diagnosis must be in Latin (Art. 44.1). For a name published prior to 1958, the validating description or diagnosis may be in any language.

1 January 1973

For a name to be validly published without simultaneous fulfilment of all the relevant requirements of the Code for valid publication , a full and direct reference must be given to the places where these requirements were previously fulfilled (Art. 33.1). Prior to 1973, such a name is validly published when the last of these requirements is fulfilled.

1 January 1990

For the name of a new taxon at generic or lower rank , the type must be indicated using the word "holotypus" or "typus", or its abbreviation ("typ."), or its equivalent in a modern language (Art. 40.6). For the name of a new taxon at specific or lower rank , the single herbarium or collection or institution in which the type is conserved must be specified if the type is a specimen or unpublished illustration (Art. 40.7).

1 January 2007

For the name of a new taxon at specific or lower rank, the type may no longer be an illustration (Art. 40.4) and must be a specimen except for non-fossil microscopic algae for which an illustration or illustrations are permitted "...if there are technical difficulties of preservation or if it is impossible to preserve a specimen that would show the features attributed to the taxon by the author of the name." (Art. 40.5). For a new combination, name at new rank, or replacement name, the basionym or replaced synonym must be cited (Art. 41.5). It is no longer permitted to indicate the basionym or replaced synonym without actually citing it. (To indicate does not necessarily mean to cite.)

1 January 2012

For the name of a new taxon in all groups, the validating description or diagnosis must be in either Latin or English (Art. 39.2). Other languages are not acceptable after this date.