tree-fern trunks, commonly perceived to adorn tree-ferns from top to bottom. In Tasmania, Hymenophyllum australe was found to exhibit a significant preference to grow on the trunks of the more prevalent Dicksonia antarctica than the trunks of the rarer Cyathea cunninghamii tree-ferns. Reproduction Sexual reproduction Like all ferns, Hymenophyllum australe has a life cycle with two distinct phases: a minor haploid gametophyte stage, which grows from spores and produces the gametes, and a sporophyte stage which is diploid and yields spores from the sporangia. The gametophytic generation begins with the formation of spores from the sporangia on the leaf of a sporophyte, under favourable conditions (adequate moisture, temperature, pH range and light intensity) these spores will germinate and subsequently develop into a filamentous prothallus (or gametophyte). The prothallus in Hymenophyllum australe (including all Hymenophyllum species) is long and narrow and often referred to as ribbon-like. This is atypical of the archetypal heart-shaped prothallus seen in other ferns. The prothallus harbours sporadic marginal archegonial cushions and this is where the archegonia are borne, while the antheridia are borne on slender branches on the basal margins of the prothallus. In the presence of water, spores germinate following a typical fern progression, with the antheridia trapped under the prothallus bursting to release the sperm cells. A chemical signal (sperm chemotaxis) is released from the archegonia which attracts the motile sperm cells towards it. Once the sperm cells reach the archegonium, they open and enable the male gamete to travel down to the ovum, with which it unites to induce fertilisation and form a zygote. This fertilised zygote is diploid and develops into an embryo and sporophyte, or ‘true fern’ that is most readily recognised, while remaining embedded in the prothallus. The sporophyte is dependent on the prothallus for nutrition (parasitic) until the embryo forms its first roots and leaves, whereupon the sporophyte becomes independent and the prothallus subsequently dies. The cycle is complete when spores are produced on the sporophyte. Notably, as in all ferns, water is required for successful sexual reproduction, with the fusion of the gametes entirely dependent on the availability of free water. Asexual reproduction Both gametophytes and sporophytes are capable of vegetative reproduction. In the gametophyte stage this is typically through regeneration of fresh prothalli from older ones, but it can also occur through gemmae which are more organised means of vegetative propagation. It has been recognised that adverse