Reproductive biology of three Cheilanthoid ferns in Taiwan

Reproductive biology of Cheilanthes chusana Hook., Cheilanthes hirsute ( Poir.) Mett., and Cheilanthes tenuifolia (Burm.) Sw. native to Taiwan, were observed. Results showed that C. chusana and C. tenuifolia were diploid (2n = 60) and produced 32 spore-sporangia, whereas C. hirsute was tetraploid (2n = 120) and produces 16 spores per sporangium. The spores of C. hirsute were larger than the other two species. Spore germination was of Vittaria-type, and gametophyte development was of Adiantum-type in these three species. The gametophytes of C. chusana and C. tenuifolia produced young sporophytes sexually, whereas C. hirsute produced young sporophytes apogamously. Neutral gametophytes may be regarded as an immature individual and smaller size than other sexual gametophytes within C. chusana and C. tenuifolia. However, neutral gametophytes not only had the potential to produce sporophyte but also had the same developmental size with female and hermaphroditic gametophytes in C. hirsute. In addition, the life span may be associated with reproductive system, apogamous species had shorter gametophyte life span, e.g. 6 weeks in apogamous C. hirsute, 10 weeks in sexual C. chusana, and 12 weeks in sexual C. tenuifolia.