>I can't find a good discussion of nomen nud(a)? in the code.
>Recommendation 50B.1 (1988 code) describes how to cite a nomen nudum,
>but I don't see a comprehensive definition of nomen nudum, nor
>recommendations on how to deal with these epithets. Is this discussed
>elsewhere in the code? Is there another publication which gives a more
>thorough discussion of the term?
Of course, the code does in the first line define how to prevent nomina
nuda, so discussion of these is rather brief. Generally, if *one or few* of
the necessary criteria for valid names in the code (e.g. priority,
effective publication, Latin protologue, type indication, proper indication
of rank, acceptance of the name, proper basionym citation, &c.) is not
fulfilled (or in other words if some provision of the code is violated),
the name is a "nomen illegitimum" (special cases thereof being "nomen
invalidum" if e.g. the protologue is not Latin and published after 1935, or
"nomen superfluum" if a valid name was available at the time of publication
for the taxon at the same rank based on the same type), if *all or a
majority* are not fulfilled (description and type are the criteria for
Index Kewensis), it is a "nomen nudum".
Very tricky cases are "nomina ambigua" or "nomina confusa", and the
interpretation of these is rather difficult. Here, an otherwise valid name
has either been based on mixed type material (nomen ambiguum, e.g.
Nepenthes pectinata) or a name has consequently and persistently been
applied to a taxon not including the type (nomen confusum, e.g. Drosera
longifolia).
The first case can be proved by a study (and interpretation) of the type
material if this does exist (N.pectinata syntypes are composed of material
of _N.gymnamphora_ and _N.singalana_).
The second case is somewhat more elusive. Here, the literature which has
appeared since the protologue (and one or several botanists) have to
decide. Nearly all authors dealing with _Drosera_, e.g. DECANDOLLE,
PLANCHON, DIELS, SCHAEFTLEIN in HEGI, TUTIN/WEBB & al., HULTEN, SCHNELL and
many others have used the names _D.anglica_ for D.longifolia L. s.str. and
_D.intermedia_ for D.longifolia sensu auct. non L. and rejected the name
D.longifolia, with the notable exceptions of LINNAEUS (who did not
distinguish _D.intermedia_, however), HAMET, GREUTER, CULHAM, and some
others who repeatedly (and rather unsuccessfully) tried to reestablish
D.longifolia for formal reasons (indeed, the correct interpretation of the
hybrid D.longifolia * rotundifolia causes some trouble even in your text,
Alastair!).
Nowadays, conservation of otherwise illegitimate names (i.e. rejection of
formally legitimate ones) is even encouraged if it serves to prevent
unfavourable nomenclatural changes (so at the moment chances are rather
poor for the GREUTER & CULHAM version). I do regret if you do not like
this, Alastair and Guido (I admit usage of _D.anglica_ is a violation of
the strict rule of priority!), but here we have an obvious contradiction
between botanical practice and the strict rules, and it is not for
commercial reasons (if this is a consolation). If two opinions do exist
which exclude each other, any decision can be only a compromise, but a
compromise is still better than no decision at all.
Kind regards
Jan