1. Family: Hymenophyllaceae Mart.
    1. Genus: Hymenophyllum Sm.
      1. Hymenophyllum tunbrigense (L.) Sm.

        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.

    [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.

    [FTEA]

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

    Type
    Type: ‘habitat in Anglia, Italia’ (type not designated)
    Habit
    Epiphyte, less often on wet rocks.
    Rhizomes
    Rhizome creeping, thin, glabrous or with a few hair-like scales to 0.5 mm long
    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
    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

    Images

    Distribution

    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, 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

    Common Names

    English
    Tunbridge filmy fern

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

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

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

    Accepted by

    • 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.

    Literature

    Kew Species Profiles
    • JSTOR (2013). Global Plants – Hymenophyllum tunbrigense.
    • 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.
    • 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.
    • Cheffings, C. M. & Farrell, L. (eds) (2005). The Vascular Plant Red Data List for Great Britain. Joint Nature Conservation Committee, Peterborough.
    • Richards, P. W. & Evans, G. B. (1972). Hymenophyllum tunbrigense. Journal of Ecology 60: 245–268.
    • 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.
    Flora of Tropical East Africa
    • J.P.Roux, Conspect. southern Afr. Pteridoph.: 41 (2001).
    • Burrows, S. Afr. Ferns: 97, fig., map (1990)
    • Schelpe, F.Z. Pterid.: 80, t. 22E (1970)
    • Sowerby, English Bot.: 3, t. 162 (1794)

    Sources

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

    Herbarium Catalogue Specimens
    'The Herbarium Catalogue, Royal Botanic Gardens, Kew. Published on the Internet http://www.kew.org/herbcat [accessed on Day Month Year]'. Please enter the date on which you consulted the system.
    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 2018. 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 2018. 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