The gametophytes of the Victorian Hymenophyllaceae

Abstract

The unique types of gametophytes previously recorded for Hymenophyllaceae have been shown to occur in the Victorian species. Prothalli of the Hymenophyllum group (Mecodium australe, M. flabellatum, M. ravum, and Hymenophyllum cupressiforme) are branching and ribbon-like, while those of the Trichomanes group (Polyphlebium venosum and Macroglena caudata) are filamentous. An account is given of germination stages, development of the prothallus and reproductive organs, vegetative propagation, and young sporophytes of the four species of the Hymenophyllum group which were grown in culture for up to 8 years. Different methods of branching are described. In the gametophyte of M. australe, branching is often nearer a true dichotomy than in other species. The discontinuous marginal cushions are usually initiated close to the apical meristems (even in cells adjoining an apical initial cell) although they may develop far from the apices on the margins between old cushions. On dehiscence of antheridia of M. australe, the opercular cell lifts and the sperms retain their vesicles until outside an open archegonium. In Polyphlebium, as in ferns of other families, the vesicle is usually shed outside the antheridium. In antheridia of Polyphlebium the stalk cell develops from the prothallial mother cell after the antheridial initial cell has been delimited, as in Anemia (Schizaeaceae). Gemmae, which were produced in cultures of all species except H. cupressiforme and Macroglena caudata, were grown to mature prothalli; and development, although slow, was quicker than from spores. Uniseriate gemrnae produced by species in the Trichomanes group are compared with the biseriate Hymenophyllum type. The suggestion that species of the Trichomanes group reported with blade-like expansions on filamentous prothalli are hybrids is supported by polyploidy and apogamy in these species.