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Delicate, sensitive and engagingly beautiful, this tiny fern is found in moist woodlands, temperate rainforests and mountain cloud forests, where it occurs on the vertical surfaces of acidic rocks and sandstone, or sometimes as an epiphyte on mossy branches.

Hymenophyllum tunbrigense (Tunbridge filmy fern)

[KSP]

Kew Species Profiles

General Description

Delicate, sensitive and engagingly beautiful, this tiny fern is found in moist woodlands, temperate rainforests and mountain cloud forests, where it occurs on the vertical surfaces of acidic rocks and sandstone, or sometimes as an epiphyte on mossy branches.

The scientific name Hymenophyllum (literally, 'membranous leaf') refers to the many delicate fronds, the beauty of which is most apparent under a magnifying glass or hand lens. The specific epithet tunbrigense was presumably chosen to refer to the town of Tunbridge Wells, where some of the earliest British specimens were found.

Species Profile
Geography and distribution

Tunbridge filmy fern has a cosmopolitan, but discontinuous, distribution. It occurs along the Atlantic fringe of Europe, with small populations in Germany and the Mediterranean. Within Africa it is found in Kenya, South Africa, Madagascar and Mauritius. It is also found in New Zealand, Central and South America, Jamaica and in a single locality (in South Carolina) in North America.

It usually occurs on steep rock faces, more rarely on tree trunks, in moist woodlands, temperate rainforests and mountain cloud forests, where humidity is consistently high.

In the UK, Tunbridge filmy fern is confined mainly to western areas, with an outlier population in West Sussex. It occurs at up to 500 m above sea level in the UK.

Description

Overview: Often described as resembling the ruffled plumage of a bird, this small fern has many membranous, translucent fronds that are only 2-10 cm long.

Fronds: Each frond is almost as wide as it is long, is blue-green in colour and glistens with moisture under ideal conditions. Thin petioles (leaf stalks) or 'stipes' hold each frond above dark, thread-like, wiry rhizomes that creep across the surface, forming dense masses over time. Fronds live for several years, and can shrivel up in dry spells, only to be revived in the next rains. Frond growth usually occurs during the wettest months in winter.

Life-cycle: In common with all ferns, filmy ferns have life-cycles with two phases. The more visible and recognisable membranous fronds produce spores, from which the much smaller, threadlike gametophyte or prothallus develops, which produces male and female reproductive cells, and after fertilisation produces the next generation of ferns.

Spores: The minute spores are enclosed in a purse-like covering (indusium) with a toothed edge; this feature can be used to identify Tunbridge filmy fern, as the spore cases of the other species of Hymenophyllum occurring in the UK, Wilson's filmy fern ( Hymenophyllum wilsonii ), are smooth.

Threats and conservation

Tunbridge filmy fern is listed as Least Concern (LC) globally according to IUCN Red List criteria.

However, in southeastern England up to 20% of its sites have been lost since 1950, mainly through woodland loss, plant collection and shading by Rhododendron ponticum . By 1995 a 72% decline was reported in the number of surviving colonies in southeastern England. Since that date, several organisations, including Kew, have been involved independently in protecting habitat sites or propagating plants in order to re-establish colonies.

In 2011, The National Trust Nymans Estate in West Sussex lost a large community of Tunbridge filmy ferns hundreds of years old to an unscrupulous plant collector who virtually destroyed the site in their desire to possess the plant. A five-year project at the estate, to improve and protect the fern's habitat, had just reached completion when the theft occurred.

This species at Kew

Tunbridge filmy fern can be seen growing in its natural habitat within the Francis Rose Reserve at Wakehurst, one of only 12 locations in the High Weald where it survives.

Micropropagation of Tunbridge filmy fern at Kew

Hymenophyllum tunbrigense is cultivated using plant tissue culture and micropropagation techniques at Kew.

Tiny sections of plant material were grown on in petri dishes of alginate and subsequently weaned onto small chips of sandstone with the ultimate aim of attaching those rock pieces to the surfaces of sandstone outcrops in-situ at new habitat sites in the wild, and in particular, at Kew's Francis Rose Reserve.

Distribution
Australia, Belgium, Chile, Costa Rica, France, Germany, Ireland, Italy, Jamaica, Kenya, Madagascar, Mauritius, Mexico, New Zealand, Portugal, South Africa, Spain, United Kingdom, USA, Venezuela
Ecology
Often grows in large groups on steep, acidic rock faces, more rarely on tree trunks, in moist woodlands, temperate rainforests and mountain cloud forests.
Conservation
Least Concern (LC) according to IUCN Red List criteria, but under threat from habitat loss in southeastern England.
Hazards

None known.

[CPLC]

Bernal, R., Gradstein, S.R. & Celis, M. (eds.). 2015. Catálogo de plantas y líquenes de Colombia. Instituto de Ciencias Naturales, Universidad Nacional de Colombia, Bogotá. http://catalogoplantasdecolombia.unal.edu.co

Distribution
Colombia

[FTEA]

Hymenophyllaceae, Henk Beentje. Flora of Tropical East Africa. 2008

Type
Type: ‘habitat in Anglia, Italia’ (type not designated)
Morphology General Habit
Epiphyte, less often on wet rocks.
Vegetative Multiplication Rhizomes
Rhizome creeping, thin, glabrous or with a few hair-like scales to 0.5 mm long
Morphology Leaves
Fronds spaced 1–7 cm apart, erect, pale to dark green; stipe 0.5–4 cm long, glabrous or with a few minute brown hairs, not winged or winged in upper part; lamina ovate to lanceolate in outline, 3–14 × 1.2–3.5 cm, 2(–3)pinnatifid, rachis winged; pinnae in 6–14 pairs; ultimate segments 3–7 per pinna, linear, to 0.9 mm wide, obtuse to truncate, margin serrate near apex; glabrous
Morphology Reproductive morphology Sori
Sori 2(–3) per pinna, on the inner acroscopic lobes, 1.1–2 mm long, 1.1–1.5 mm wide; valves serrate
Figures
Fig, 2,1-2. 10, p7
Ecology
Moist forest, ridge-top mist forests; low to medium epiphyte or on damp rocks in deep shade, occasionally on overhanging earth banks; (1000–)1900–2700 m (to 2850 m fide Greenway)
Conservation
Widespread; least concern.
Distribution
Range: Gabon, Malawi, Mozambique, Zimbabwe, South Africa; Madagascar and Indian Ocean islands, western and southern Europe Flora districts: K4 T2 T3 T6

[KSP]
Use
None known.

Native to:

Alabama, Argentina South, Azores, Belgium, Bolivia, Canary Is., Cape Provinces, Chile Central, Chile South, Colombia, Costa Rica, Ecuador, France, Free State, Gabon, Germany, Great Britain, Guatemala, Haiti, Honduras, Ireland, Italy, Jamaica, Kenya, KwaZulu-Natal, Madagascar, Madeira, Malawi, Mexico Central, Mexico Gulf, Mexico Northeast, Mexico Southeast, Mexico Southwest, Mozambique, Northern Provinces, South Carolina, Spain, Swaziland, Tanzania, Tristan da Cunha, Turkey, Venezuela, Zimbabwe

Introduced into:

Yugoslavia

English
Tunbridge filmy fern

Hymenophyllum tunbrigense (L.) Sm. appears in other Kew resources:

Date Reference Identified As Barcode Type Status
Jan 1, 2007 Pocs, T. [6285/T], Tanzania K000889242
Jan 1, 2007 Beesley, J.S.S. [235], Tanzania K000889236
Jan 1, 2007 Pocs, T. [6285/T], Tanzania K000889240
Jan 1, 2007 Faden, R.B. [74/389], Tanzania K000889241
Jan 1, 2007 Braithwaite, A.F. [421], Tanzania K000889226
Jan 1, 2007 Faden, R.B. [70/637], Tanzania K000889237
Jan 1, 1982 Balslev, H. [265], Tanzania K000889234
Jan 1, 1967 Chase, N.C. [6678], Zimbabwe K000932617
Jan 1, 1967 Fries, T.C.E. [3684], Zimbabwe K000932616
Jan 1, 1967 Fries, T.C.E. [3684], Zimbabwe K000932618
Jan 1, 1959 Mitchell, D.S. [287], Zimbabwe K000932619
Thomasset, J.F.H. [s.n.], Malawi K000435601 Unknown type material
Beccari, O. [440], Indonesia K000420237
Elmer, A.D.E. [11690], Philippines K000420466
Loher, A. [4179], Philippines K000420468
Gardner [5951], Brazil K000589634
Gardner [212], Brazil K000589635
Faden, R.B. [72/182], Kenya K000889224
Grimshaw, J.M. [93998], Tanzania K000889231
Lovett, J. [885], Tanzania K000889233
Drummond, R.B. [1770], Tanzania K000889235
Teysmann, J.E. [nn3], Indonesia K000420238
Greenway, P.J. [3028], Tanzania K000889239
Hemp, A. [934], Tanzania K000421058
Grimshaw, J.M. [93825], Tanzania K000889230
s.coll. [6408], Rio de Janeiro K000589633
Faden, R.B. [69/692], Kenya K000889228
Faden, R.B. [74/1338], Kenya K000889225
Steere, J.B. [s.n.], Philippines K000420467
Faden, R.B. [69/516], Kenya K000889222
Greenway, P.J. [3858], Tanzania K000889227
Elmer, A.D.E. [9747a], Philippines K000420465
Greenway, P.J. [3028], Tanzania K000889238
Drummond, R.B. [1291], Tanzania K000889229
Faden, R.B. [70/84], Kenya K000889223
Lovett, J. [885], Tanzania K000889232

First published in Engl. Bot. 3: t. 162 (1794)

Accepted by

  • Güner, A. (ed.) (2018). Resimli Türkiye Florasi (Illustrated Flora of Turkey) 2: 1-1054. ANG Vakfi/Nezahat Gökyigit Botanik Bahçesi, Istambul.
  • Merryweather, J. (2020). Britain's Ferns. A field guide to the clubmosses, quillworts, horsetails and ferns of Great Britain and Ireland: 1-280. Princeton University Press.
  • Roskov Y. & al. (eds.) (2018). World Ferns: Checklist of Ferns and Lycophytes of the World Species 2000 & ITIS Catalogue of Life Naturalis, Leiden, the Netherlands.
  • Stace, C. (2019). New Flora of the British Isles ed. 4: 1-1266. C & M Floristics.

Literature

Catálogo de Plantas y Líquenes de Colombia

  • ColPlantA (2021). "ColPlantA. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; http://www.colplanta.org/"

Kew Species Profiles

  • Cheffings, C. M. & Farrell, L. (eds) (2005). The Vascular Plant Red Data List for Great Britain. Joint Nature Conservation Committee, Peterborough.
  • Christenhusz, M. J. M., Zhang, X.-C. & Schneider, H. (2011). A linear sequence of extant families and genera of lycophytes and ferns. Phytotaxa 19: 7–54.
  • Evans, G. B. & Jermy, A. C. (1962). Notes on the history of British fern species: I. Confusion in the filmy ferns. British Fern Gazette 9: 81–84.
  • Fern ID (2012). The Ferns Identifier for the British Isles – Hymenophyllum tunbrigense.
  • Hassler, M. & Schmitt, B. (2012). Checklist of Ferns and Lycophytes of the World.
  • JSTOR (2013). Global Plants – Hymenophyllum tunbrigense.
  • Richards, P. W. & Evans, G. B. (1972). Hymenophyllum tunbrigense. Journal of Ecology 60: 245–268.

Kew Backbone Distributions

  • Merryweather, J. (2020). Britain's Ferns. A field guide to the clubmosses, quillworts, horsetails and ferns of Great Britain and Ireland: 1-280. Princeton University Press.

Flora of Tropical East Africa

  • Burrows, S. Afr. Ferns: 97, fig., map (1990)
  • J.P.Roux, Conspect. southern Afr. Pteridoph.: 41 (2001).
  • Schelpe, F.Z. Pterid.: 80, t. 22E (1970)
  • Sowerby, English Bot.: 3, t. 162 (1794)

Catálogo de Plantas y Líquenes de Colombia
http://creativecommons.org/licenses/by-nc-sa/3.0

Flora of Tropical East Africa
Flora of Tropical East Africa
http://creativecommons.org/licenses/by-nc-sa/3.0

Herbarium Catalogue Specimens
Digital Image © Board of Trustees, RBG Kew http://creativecommons.org/licenses/by/3.0/

Kew Backbone Distributions
The International Plant Names Index and World Checklist of Selected Plant Families 2021. Published on the Internet at http://www.ipni.org and http://apps.kew.org/wcsp/
© Copyright 2017 World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0

Kew Names and Taxonomic Backbone
The International Plant Names Index and World Checklist of Selected Plant Families 2021. Published on the Internet at http://www.ipni.org and http://apps.kew.org/wcsp/
© Copyright 2017 International Plant Names Index and World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0

Kew Species Profiles
Kew Species Profiles
http://creativecommons.org/licenses/by-nc-sa/3.0