> that D_spathulata isn't a valid name!
This is correct.
> I realized that D_spathulata (Labillardiere) is a synonym
This is not entirely correct. The name that was created by
Labillardiere (=Labill.) reads _D.spatulata_ (without "h"). It is a
valid name and not a synonym.
> , but of what? I found the following text:
> N: [Drosera spathulata {Hort.}]
> S: =[Drosera aliciae {R.Hamet}] /[Drosera spatulata
> {Labill.}]
> Does it mean that D_spathulata (Labill.)...
*spatulata* without "h". Read your previous sentence carefully!
> ...is a synonym of D_spathulata (Hort)?
No. The "S:" field is to be read in the other direction (i.e.
following is the correct name/names). In our case: the plants that
are labelled "D.spathulata" in horticultural collections ("Hort.")
are sometimes plants of _D.aliciae_ and sometimes (this is the
meaning of the slash "/") _D.spatulata_ (without "h", i.e. the thing
described by Labill., and obviously the name you were looking for).
> If so, which is the correct nomenclature of both?
Drosera spathulata is an orthographic error *and* a partially
misapplied name. The valid names are indicated in the "S:" field.
DANGER, PLEASE NOTE: "spatulata" and "spathulata" are both
valid, Latin (originally Greek) expressions, and they can be used
alternatively (!) in an original description (protologue). But once
written, it is the *original* spelling (in the line that continues
"... nov.") of this particular word that has to be retained (!).
Therefore, the name _Nepenthes spathulata_ is as valid and correct as
_Drosera spatulata_. Any alteration in these cases (e.g. "Nepenthes
spatulata, Drosera spathulata") is to be treated like an orthographic
error and to be corrected automatically (any nomenclaturally relevant
text containing the wrong spelling has to be treated as if it was
spelled correctly).
Kind regards
Jan