Diplazium megaphyllum (Bak.) Christ, A Rare Fern in Taiwan, Survives Through Apogamous Reproduction

The gametophyte morphology and reproductive behavior of Diplazium megaphyllum, a rare fern in Taiwan, were studied. It was triploid (2n = 123) and produced 32-spored sporangia. Spore germination and gametophyte development were of “Vittaria-type” and “Adiantum-type”, respectively. Adult gametophytes were heart-shaped and naked. Both male and female gametophytes appeared in the cultures, but no hermaphroditic ones were found. Antheridia released active sperms, but archegonia did not develop well and lost function. Young sporophytes were produced apogamously, directly from the cells of cushion of ventral surface of gametophytes behind the notch. The first frond of young sporophyte was of midribed type and pinnate.