| Research Abstract |
1. Field and herbarium researches were undertaken in Indonesia, Thailand, Malaysia, India, and Papua New Guinea in order to investigate the evolution of epiphytes. Papers on the results of this study were read in meetings and symposia in Japan, Great Britain, Ireland, and Austria.
2. Three life forms, i.e. obligate epiphyte, secondary hemiepiphyte, and climber, were found within epiphyte sensu lato.
3. Molecular phylogenetic analyses were made, resulting that Davalliaceae and Polypodiaceae form an epiphytic monophyletic clade, which is sister to the hemiepiphytic Oleandra. From the results hypothesis was proposed that in Davalliaceae and related ferns, the terrestrial life form evolved to climber, then secondary hemiepiphyte and ultimately to obligate epiphyte.
3. Comparative morphological observations were made for scales of Davalliaceae and related, suggesting a close linkage between the epiphytic life form and the stalked scales. It was revealed that advanced species have elaborate pel
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tate, stalked scales with stalks sunken in concavities on the rhizome surface. Multilayered shields and sunken stalks of scales make space useful for external water storage, an adaptation to epiphytism.
4. A molecular phylogenetic analysis and comparative studies of seed morphology and germination were carried out for Lipari's, Orchidaceae. An epiphyte has larger seeds, which show a higher germination rate than a related terrestrial species.
5. Phylogenetic systematic, biogeographical, and evolutionary morphological researches were undertaken for Podostemaceae, an unusual aquatic, petrophytic angiosperm family, with the following results:
(1) The shoot was transformed into crustose by a flattened and dorsiventral shoot apical meristem.
(2) The shoot disappeared by reduction of the shoot apical meristem but retaining leaf formation.
(3) The main axis in body plan changed from vertical to horizontal by a loss of primary shoot and root apices and a gain of adventitious root in the hypocotyl during the evolution of Podostemaceae. Less
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