Trichomanes speciosum Killarney Fern

Trichomanes speciosum (Vandenboschia speciosa), Killarney Fern, is a very rare fern with an extremely oceanic distribution. It occurs as scattered populations in western Britain and Ireland where it grows in dark, humid and shelterd ravines. Like all ferns its life cycle conisits of two independent generations, a macroscopic, fern-like sporophyte generation and a smaller, gametophyte generation which in Killarney Fern is composed of microscopic filaments. The sporophyte generation has a fern-like structure that is quite distinctive but it is very rare and has suffered in the past from over-collection, almost to the point of extinction. It has disappeared from many of its historic sites in Britain and Europe (e.g. Portugal). In Britain, the sporophyte still occurs in a few places in Ireland, south-western Scotland, north-west Wales, northern England and Cornwall but these populations, apparently, have poor spore procuction. However, the sporophyte has not been recorded in south Wales in recent history. In contrast the gametophyte generation is more widespread but requires diligent searching to find it. It grows as a very small green mound or weft over rock in humid ravines and valleys and can be overlooked for a filamentous alga (like Cladophora). It can also be confused with the gametophtes of our 2 Filmy Ferns (Hymenophyllum tunbrigense and H. wilsonii). Nevertheless, new colonies are discovered fairly frequently and a small colony was found in the Melincwrt Valley several years ago. The gametophyte generation is able to sustain local populations by asexual production of gemmae. 

Native