The Hymenophyllaceae (Pteridophyta) in Luxembourg. Past ...

Y. Krippel The Hymenophyllaceae (Pteridophyta) in Luxembourg. Past, present and future 

The Hymenophyllaceae (Pteridophyta) in 

Luxembourg. Past, present and future 

Ferrantia • 44 / 2005 

Yves KRIPPEL 

Research associate of the Luxembourg National Museum of Natural History 

18A, rue de Rollingen, L-7475 Schoos 

yves.krippel@mnhn.lu 

Keywords: Hymenophyllum tunbrigense, Trichomanes speciosum, Luxembourg, Petite Suisse 

Introduction 

Luxembourg, and in particular the 'Petite Suisse' 

sandstone region, is one of the few continental 

areas ever known for Hymenophyllum tunbrigense 

(L.) Smith, a species that generally occurs in a 

more Atlantic range (Jalas & Suominen 1972). The 

Tunbridge fi lmy-fern was fi rst discovered in this 

continental island in 1823, but the location of the 

major colonies remained uncertain until the early 

20 th 

century following its re-discovery in 1873. 

In 1993 the gametophytes of another fi lmy-fern, 

the Killarney fern (Trichomanes speciosum Willd.), 

were fi rst discovered for continental Europe in the 

same region. Investigations showed however, that 

unlike Hymenophyllum tunbrigense, the gametophytes 

of Trichomanes speciosum are quite common 

in the 'Petite Suisse' area, as well as on Devonian 

schist in the Luxembourg Ardennes region. 

Tunbridge Filmy-fern 

(Hymenophyllum tunbrigense) 

History of its discovery 

Hymenophyllum tunbrigense (Fig. 1) was fi rst 

discovered in Luxembourg - and so within continental 

Europe - by the Belgium Botanist B.C. Du 

Mortier on a botanical trip with his friend P. Michel 

in 1823 [1821 as o en mentioned in literature is 

not correct (Reichling 2005)]. At that time however 

nobody seemed very impressed by the discovery 

of that Atlantic species in this continental island. 

Half a century passed, and it was in 1873, that J.- 

P. J. Koltz rediscovered the plant near Berdorf in 

the valley of the Roitzbach (Koltz 1873). A er the 

fi rst discoveries in Luxembourg, numerous investigations 

were made in the region and several 

Fig. 1: Patch of Hymenophyllum tunbrigense (Tunbridge 

Filmy-fern) with leaves in good condition, near Berdorf 

(Luxembourg). Photo: Y. Krippel. 

sites were found in the 'Petite Suisse', but the 

long-awaited discovery in the German part of the 

Luxembourg sandstone sandstone area was only only made made in 

1963 (Nieschalk 1964). Within continental Europe 

the Tunbridge Tunbridge Filmy-fern Filmy-fern was was also also found found in in the 

Elbsandsteingebirge (sites unfortunately extinct) 

and in the French Vosges (Jalas & Suominen 1972). 

Nowadays the populations of Hymenophyllum 

tunbrigense have have seriously seriously suff suff ered and and many many sites 

sites 

are extinct extinct in in the the region, region, as as well well as as in in other other parts 

parts 

of Europe. 

Distribution and status 

The 'Petite Suisse' area in Luxembourg is one of 

the few continental areas ever known for Hymenophyllum 

tunbrigense. Due to environmental 

changes and external pressures (specimen collec- 

tions, tourism and outdoor activities, …) a certain 

amount of sites have disappeared in the last 

decades (Fig. 2). Recent surveys have now shown 

a certain population increase. 

209


210 

Fig. 2: Distribution map of Hymenophyllum tunbrigense (yellow squares: extinct sites, red squares: still existing 

sites). Grid: Gauss-Luxembourg, square kilometres. 

Ferrantia • 44 / 2005


An initial survey, realised in 1988, revealed the 

existence of 240 patches of fi lmy-fern which are 

sca ered amongst 27 sites. Their distribution 

shows a cluster of 5 major rock complexes which 

are situated circa one kilometre apart. A total of 

20849 leaves covering a surface area estimated 

at 11.88 m 2 were identifi ed. Of these, only 40% 

were considered to be in good conditions and the 

majority of the population comprised either dead 

or dying leaves, with only one of the colonies 

containing a few fertile leaves. (Schwenninger 

1988). 

A new survey carried out in 2000 has shown that 

the number of fi lmy-fern patches has increased to 

360 and the entire population now spreads over 

a surface area estimated at 12.38 m2 , consisting of 

some 74700 leaves of which 74% are considered 

to be in good condition. Fertile leaves totalled 212 

and were encountered in most sites. For the fi rst 

time, fi lmy-fern gametophytes and young sporophytes 

were identifi ed, thereby confi rming that it is 

capable of reproducing both by vegetative spread 

and spores in its continental refuge. (Schwenninger 

2001). Although the majority of sites generally 

refl ect this population increase, the remarkable 

recovery is due largely to the contribution of the 

two sites from which the public has been excluded 

since 1993. On a global level however, the number 

of sites is continuing to dwindle. Those sites 

where the fern was considered to be in danger of 

becoming extinct in 1988 have now disappeared 

and the total number of individual sites which 

are physically separated from each other appears 

to have gradually decreased throughout the 20th are physically separated from each other appears 

th 

century. 

Prospects and conservation 

The collection of botanical specimens, undesirable 

silvicultural interventions in the past, activities 

related to tourism as well as rock climbing, 

represent the major threats for the Hymenophyllum 

sites. Not surprising that the drastic measures 

to remove the massive human presence at some 

sites - by se ing up gates in 1993 - have well 

contributed to the expansion of some populations. 

It is however possible that overall climatic conditions 

may have been particularly benefi cial to the 

growth rates of the fi lmy-fern colonies in recent 

years, perhaps as a consequence of global warming 

or that we may be dealing with long-term fl uctuations 

in population cycles. 

Besides the mentioned gates, some other minor 

measures and a new set of local bylaws governing 

the legal conditions under which rock climbing 

is permi ed were carried out. But a empts to 

enhance the legal protection of fi lmy-fern sites 

and boost conservation initiatives in the area by 

offi cially designating the entire forest as a national 

nature reserve failed so far. 


Killarney Fern 

(Trichomanes speciosum) 

History of its discovery 

Although primarily a species of the UK, Ireland, 

Bri any and the Atlantic Islands (Canaries, 

Madeira and Azores), the fi lmy-fern Trichomanes 

speciosum (Killarney fern) is also found in Europe 

at sca ered locations in other parts of France, 

Spain, Portugal and Italy (Jalas & Suominen 1972). 

The gametophytic generation of Trichomanes 

speciosum can however be found independently 

of the sporophyte and seems to be widespread 

in Europe, in contrast to the sporophyte (Rumsey 

et al. 1999). It appears however to exist in a state 

of arrested development, unable to produce the 

mature form under present conditions. In Luxembourg 

the independent gametophyte of Trichomanes 

speciosum was fi rst discovered in 1993 (Jermy 

pers. comm., Rasbach, Rasbach & Jérôme 1993). 

And again this was the fi rst observation of this - 

even more Atlantic - species inside the continent! 

A er the fi rst discoveries in the "Petite Suisse" in 

Luxembourg, the gametophytes of T. speciosum 

were found in many places on the continent 

(France, Germany, Belgium, Czech Republic and 

more recently in Poland (Krukowski & Świerkosz 

2004)). In Luxembourg, systematic investigations 

revealed a great number of populations, not only 

in the Luxembourg Sandstone region, but also on 

Devonian Schist in the Ardennes region (Krippel 

2001). 

Fig. 3: Gametophytes of Trichomanes speciosum (Killarney 

fern) on Luxembourg sandstone. Photo: Y. Krippel. 

211


212 

Fig. 4: Distribution map of Trichomanes speciosum. Grid: Gauss-Luxembourg, square kilometres. 



Distribution and status 

Trichomanes speciosum is growing in Luxembourg 

as an 'independent gametophyte' with vegetative 

reproduction and dispersion by the way of 

gemmae (Fig. 3). Diff erent studies and systematic 

investigations over the last 5 years showed that 

the gametophytes of Trichomanes speciosum are 

relatively well distributed throughout the 'Petite 

Suisse' sandstone area with nevertheless 2 major 

distribution spots. The fi rst one is situated on 

both sides of the 'Ernz noire' between Echternach, 

Berdorf, Beaufort, Waldbillig, Christnach and 

Consdorf, the second one between the 'Ernz 

blanche' and the Valley of the Alze e. A third 

major distribution area is situated in the Ardennes 

region, especially in the valley of the Upper-Sûre. 

At present date, more than 120 sites are known in 

80 diff erent square kilometres (Fig. 4). Even if the 

species is quite widespread in Luxembourg, the 

populations occurring in the 'Petite Suisse' are the 

most luxuriant ones. The status of the independent 

Trichomanes speciosum gametophyte populations 

in Luxembourg is - as far as no major site alterations, 

resulting in drastic climatic changes, occur 

- considered as not threatened. 

Conclusion 

Luxembourg, and in particular the 'Petite Suisse' 

sandstone area, is one of the few regions in continental 

Europe where two species of the Hymenophyllaceae 

family occur. Hymenophyllum tunbrigense 

is - no doubt about that - the greatest treasure. 

Despite the recent increase in the overall Hymenophyllum 

population and the apparent success 

at securing the protection of the most 'valuable' 

sites, the further loss of small sites is regre able. 

The survival of the species isn't guaranteed, as the 

most important group of sites are all restricted 

to a single crevasse, currently holding 74% of 

the overall population. A global conservation 

management plan, integrating the recent microclimatic 

and genetic studies is therefore imperative in 

order to maintain the species. Concerning Trichomanes 

speciosum, only the gametophytic stage is to 

be found in Luxembourg. The gametophytes are 

quite widespread in Luxembourg and the species 

is considered as not threatened. However, pteridologists 

don't give up, and perhaps one day the 

sporophytic generation will also be found in the 

region. 


References 

Jalas J. & Suominen J. (eds.) 1972. - Atlas Florae 

Europae. Distribution of vascular plants in 

Europe. Vol.1: Pteridophyta (Psilotaceae to 

Azollaceae). - The Commitee for Mapping the 

Flora of Europe and Societas Biologica Fennica 

Venamo, Helsinki, 121 p. 

Koltz J.-P. J. 1873. - Hymenophyllum tunbridgense 

Sm. - Bull. Soc. roy. Bot. Belg. XII : 449-453. 

Krippel Y. 2001. - Aire de répartition et statut de 

Trichomanes speciosum Willd. (Hymenophyllaceae) 

au Grand-Duché de Luxembourg. - 

Bull. Soc. Nat. luxemb. 102: 3-13. 

Krukowski M. & Świerkosz K. 2004. - Discovery 

of the gametophytes of Trichomanes speciosum 

(Hymenophyllaceae: Pteridophyta) in Poland 

and its biogeographical importance. Fern Gaz. 

17(2): 79-84. 

Nieschalk A. et C., 1964. - Hymenophyllum 

tunbrigense (L.) Sm. (Englischer Hautfarn) im 

westlichen Deutschland. - Decheniana 117, 1/2: 

151-152. 2 pl h.t. 

Rasbach H., Rasbach K. & Jérôme C. 1993. - Über 

das Vorkommen des Hautfarns Trichomanes 

speciosum (Hymenophyllaceae) in den Vogesen 

(Frankreich) und dem benachbarten Deutschland. 

Carolinea 51: 51-52. 

Reichling L. (coll. Y. Krippel) 2005. - Die Farnpfl 

anzen (Pteridophyta) des Müllerthalgebietes. 

- In: Y. Krippel (ed.). - Die Kleine Luxemburger 

Schweiz. Geheimnisvolle Felsenlandscha im 

Wandel der Zeit, 251 p. 

Rumsey F.J., Vogel J.C., Russel S.J., Barret J.A. & 

Gibby M. 1999. - Population structure and 

conservation biology of the endangered fern 

Trichomanes speciosum Willd. (Hymenophyllaceae) 

at its northern distributional limit. 

- Biological Journal of the Linnean Society 66: 

333-344. 

Schwenninger J.-L. 1988. - Hymenophyllum 

tunbrigense (L.) Sm. - Rapport d”étude sur 

l”écologie et la conservation de l”espèce. - 

Ministère de l”Environnement. Administration 

des Eaux et Forêts,107 p. (unpublished). 

Schwenninger J.-L. 2001. Inventaire phytosanitaire 

et conservation des populations relictuelles 

de Hymenophyllum tunbrigense (L.) 

Smith (Hymenophyllaceae : Pteridophyta) au 

Grand-Duché de Luxembourg. - Ministère de 

l’Environnement, Administration des Eaux et 

Forêts,153 p. (unpublished). 

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Résumé de la présentation 

Les Hymenophyllaceae (Pteridophyta) au Luxembourg. Passé, présent et futur 

214 

Mots-clés: Hymenophyllum tunbrigense; Trichomanes speciosum; Luxembourg; Petite Suisse 

Le Grand-Duché de Luxembourg et en particulier la 

région gréseuse de la Petite-Suisse luxembourgeoise 

sont une des rares régions continentales renommées 

pour leurs populations rélictuelles d'Hyménophylle de 

Tunbridge (Hymenophyllum tunbrigense), espèce qui en 

général pousse dans des zones à caractère plus atlantique. 

Hymenophyllum tunbrigense fut découvert pour la 

première fois dans ce refuge continental en 1823, mais 

la localisation de la majeure partie des colonies restait 

incertaine jusqu'au début du 20 ième siècle, suite à la 

redécouverte de l'espèce en 1873. En 1993, les gamétophytes 

d'une autre fougère de la famille des Hyménophyllacées, 

à savoir Trichomanes speciosum Willd. ont été 

découverts pour la première fois en Europe continentale 

dans la même région. Des investigations ont cependant 

montré que contrairement à Hymenophyllum tunbrigense, 

les gamétophytes de Trichomanes speciosum sont 

assez communs dans la Petite Suisse luxembourgeoise, 

de même que sur les schistes dévoniens en Ardennes 

luxembourgeoises. 

En ce qui concerne le statut d'Hymenophyllum tunbrigense 

au Luxembourg, un certain nombre de sites ont malheu- 

reusement disparus au cours des dernières décennies, 

suite à des changement environnementaux ou des 

pressions externes (tourisme, escalade, …). D'un autre 

côté, des études récentes ont montré une ne e augmentation 

de la taille des populations, ceci particulièrement 

à cause de deux sites, dont l'accès du public a été interdit 

depuis 1993. La survie d'Hymenophyllum tunbrigense 

n'est toutefois pas garantie, car les plus belles stations 

- comprenant 74% de la totalité des populations - sont 

restreintes à une seule crevasse. Un plan de gestion et de 

conservation global, intégrant les récentes études microclimatiques 

et génétiques est donc impératif, en vue de 

maintenir l'espèce. 

En ce qui concerne Trichomanes speciosum, seul le stade 

gamétophytique est connu au Luxembourg. Actuellement 

plus de 120 sites sont connus dans 80 kilomètres carrés 

diff érents. Même si l'espèce est assez bien répandue au 

Luxembourg, les populations les plus luxuriantes sont 

cependant trouvées dans la région gréseuse de la Petite 

Suisse. Hormis des aménagements majeurs entraînant 

des changements climatiques drastiques, l'espèce peut 

être considérée comme non menacée au Luxembourg.

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