Diplazium megaphyllum (Bak.) Christ, a Rare Fern in Taiwan, Reproduces by Apogamy

The reproductive behavior and morphology of the spores, gametophytes, and juvenile sporophytes of Diplazium megaphyllum, a rare fern in Taiwan, were studied, and the following results were obtained. This species is triploid (2n=123) and produces 32-spore sporangia. Spore germination and gametophyte development are the Vittaria-type and Adiantum-type, respectively. Adult gametophytes are heart-shaped and naked. Male and female gametophytes appeared in culture, but no hermaphrodites were observed. Antheridia released active sperm, but archegonia did not develop properly and lost their function. Young sporophytes were produced apogamously. They arose directly from cells of the cushion on the ventral surface of gametophytes, behind the notch. The 1st frond of a young sporophyte has a midrib and is pinnate. The methods of propagation used in this study can also be used as reference data for the ex situ conservation of this rare fern.