Trichomanes speciosum Willd.
Family: Hymenophyllaceae

Although primarily a species of the UK, Ireland, Brittany and the Atlantic Islands (Canaries, Madeira and the Azores), the filmy ferm Trichomanes speciosum Willd. (Killarney fern) [Photo 1] is also found in Europe at scattered locations in other parts of France, Spain, Portugal and Italy. The gametophytic generation of Trichomanes speciosum Willd. [Photo 2] can be found independently of the sporophyte and seems to be widespread in Europe - in contrast to the sporophyte. It appears however to exist in a state of arrested development, unable to produce the mature form under present conditions. Trichomanes speciosum Willd. is listed on Annexes II and IV of the Habitats Directive and Appendix I of the Bern Convention. It is listed as rare on the IUCN global RDL. In Luxembourg the independent gametophyte of Trichomanes speciosum was first discovered in 1993 [Jermy, Rasbach, Rasbach & Viane (unpubl.)]. In 1994 some new locations were found [Colling, G. & L. Reichling, 1996. - Notes floristiques 1994-1995. - Bull. Soc. Nat. luxemb., 97: 25-38]. So, in late 1999 a project was launched, to investigate the sandstone region, commonly called 'Petite Suisse', in Luxembourg in order to fix the distribution area of the gametophyte. 

Many new locations of the gametophyte were found and at present date, more than 115 sites in 78 square kilometres are known. Most of the sites occur in the 'Petite Suisse' area, but the independent gametophyte of Trichomanes speciosum is largely present in the whole sandstone area as far as the valley of the river Alzette. The recent discoveries of the gametophyte on Devonian schist indicate that the species is quite widespread in the Luxembourg's Ardennes too.
DNA and allozyme analyses should clarify the question if Trichomanes speciosum like Hymenophyllum tunbrigense has to be considered a Tertiary relict.

The results of the investigation, with a description of the gametophyte, the history of its discovery, the present distribution and status in Luxembourg can be found in: Krippel, Y., 2001. - Aire de répartition et statut de Trichomanes speciosum Willd. (Hymenophyllaceae) au Luxembourg. - Bull. Soc. Nat. luxemb. 102: 3-13