Establishment and Maintenance of Aseptic Culture of Trichomanes speciosum Gametophytes from Gemmae

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A technique is described for surface sterilization of gemmae of Trichomanes specio- sum. The subsequent aseptic growth of gametophytes in artificial media under different temper- ature and light regimes is described. The utility of the technique as an alternative to surface sterilization of spores for the inception of gametophyte cultures of gemmiferous ferns and bryo- phytes is demonstrated. Aseptic culture of fern gametophytes is routinely initiated from surface-ster- ilized spores (e.g., Dyer, 1979). There are many reasons for generating such cultures, but most concern the elucidation of substrate requirements or doc- umentation of growth and reproductive behavior in defined conditions. Ga- metophytes of the filmy ferns (Hymenophyllacaeae) have been cultured from spores by several workers, largely with the aim of observing their subsequent ontogeny (e.g., Stokey, 1940; Stone, 1958; Yoroi, 1972). These workers reported successful culture, but admitted to significant losses through contamination and slow germination and growth. The Killarney fern, Trichomanes speciosum Willd., is one of the rarest ferns in Europe, and a licence is required for the collection of any material (Perring and Farrell, 1983). Sporophytes produce chlorophyllous spores (Stokey, 1940) very infrequently in Britain (e.g., Sheffield, 1994). The spores germinate and grow extremely slowly (Yoroi, 1972). Collection and surface-sterilization of spores of this species are therefore fraught with problems.