This is the hybride of Asplenium trichomanes subsp. quadrivalens and
Asplenium trichomanes subsp. trichomanes. With its own name it is actually called
Asplenium trichomanes nothosubsp. lusaticum (D.E.MEY.) LAWALREE.
A 'nothosubsp.' is a hybrid between subspecies.
LAWALREE it the abbbreviation for the Belgian botanist André Gilles Célestin Lawalrée (1921-2005),
who recombined the hybrid as hybrid between subspecies. The hybrid has first been found in Upper Lusatia,
according to that it got the name lusaticum. Later the hybrid has also been detected in Belgium,
and not until 2016 in the southern part of Nordrhein-Westphalia and the northern part of Rhineland-Palatina
in Germany, where also older enigmatic findings could be assigned to this hybrid.
At least at the German sites the hybrid can not only be indentified by tits leaf form,
but also by its bigger growth (heterosis). Final certainty on the status of the plant has been achieved
by microscopical inspection of the spores and by detemination of the degree of ploidy.
The article which is describing the German findings is JÄGER, W. & H. BÄPPLER,
Der Lausitzer Streifenfarn Asplenium trichomanes nothosubsp. lusaticum (Aspleniaceae) im Grenzgebiet
zwischen Nordrhein-Westfalen und Rheinland-Pfalz (2016), Veröff. Bochumer Bot. Ver. 8(10) 110-117.