OBSERVATIONS ON THE FLORAL MORPHOLOGY OF SASSAFRAS RANDAIENSE (LAURACEAE)

摘要

The floral morphology of Sassafras randaiense (Hayata) Rehder (Lauraceae), a rare species endemic to Taiwan, has never been well documented. Consequently, much confusion exists in taxonomic literature regarding its flower structure and reproductive biology. To clarify these matters, we observed 20 flowering individuals of S. randaiense in their native habitats in the spring of 2007. The inflorescences of S. randaiense are highly reduced panicles to botryoid cymes, with up to 10 such inflorescences clustered subterminally to form an umbel of panicles and/or cymes. Its flowers are bisexual, and its third-whorl anthers are extrorse, structured as a typical hermaphroditic flower of Lauraceae. Our observations also revealed that its flowers are protogynous and flowers in a reproductive shoot alternate their sexual phase synchronously, suggesting the sexual system of synchronous dichogamy. The temporal dioecy imposed by this sexual system may explain why S. randaiense has been variously described as a dioecious, androdioecious, or polygamous species in the past.