Abstract
Epiphytes are plants that live on other plant bodies and account for 10% of vascular plants worldwide. We suggested that the obligate epiphyte life-form evolved from climber or secondary hemiepiphyte life-form in Davalliaceae and related ferns, based on molecular phylogeny and comparative morphology. Several morphological characters, long-creeping rhizomes and peltate scales seem likely to play significant roles in the hypothesized evolution. An anomalous morphology was observed in the secondary hemiepiphytic Oleandra pistillaris. The internodes are variously long and sometimes to 2 m long, resulting in an irregular phyllotaxy. Observation of the rhizomes showed that the species is characterized by the rhizome dimorphism; the rhizomes are erect and creeping. The erect rhizome produces leaves in apparent whorls separated by subequal internodes, but the creeping rhizome is dorsiventral with variously long internodes. Another secondary hemiepiphytic Nephrolepis also has similar dimorphic rhizomes. It is in contrast to the general monomorphic rhizome with regular phyllotaxy in other life forms of the related ferns.
