Scyphostegia borneensis

Introduction

Scyphostegia borneensis is an enigmatic species endemic to the northern part of Borneo. Its unusual combination of dioecy, basal placentation, 3-merous flowers, and telescoping inflorescence bracts have puzzled botanists, and the species has been placed by different authors in several different and distantly-related families, including Monimiaceae, Moraceae, Tamaricaceae, and Flacourtiaceae. Most workers after the early 1900s placed it in its own monotypic family, the Scyphostegiaceae. Analyses of plastid DNA sequences have clearly demonstrated that Scyphostegia borneensis belongs in Malpighiales and is a close relative of Salicaceae. Like many Malpighiales, its leaves are toothed and stipulate and its seeds are arillate. Like Salicaceae, the anther dehiscence is extrorse, and some authors (e.g., Chase et al., 2002) place it in a broader Salicaceae. Because it differs from other Salicaceae in its telescoping bracts, connate and tubular perianth, connate stamens, basal placentation, and arillate seeds, it is probably best to continue to place Scyphostegia borneensis in its own family, the Scyphostegiaceae.

Characteristics

Shrubs or small trees. Leaves simple, alternate, toothed, stipulate. Dioecious. Inflorescences terminal, consisting of racemosely-arranged spikes or racemes, each spike or raceme a series of flowers within telescoped tubular bracts, the lower bracts subtending a single flower, the terminal bract subtending two. Perianth connate, tubular, with 6 lobes, 3 in an outer whorl (calyx) and 3 in an inner whorl (corolla), the whorls more or less equal in female flowers but the inner whorl conspicuously shorter in male flowers. Male flowers with 3 extrastaminal disk glands and with 3 connate stamens, opposite the petals, anther dehiscence longitudinal and extrorse. Female flowers lacking disk glands, with a gynoecium consisting of a superior, unilocular, urceolate ovary (appearing somewhat fig-like) with basal placentation and numerous erect, anatropous ovules; style and stigma not evident, perhaps depressed into the center. Fruits fleshy capsules deshicent from the apex, reminiscent of Monimiaceae. Seeds numerous, arillate; embryos straight, cotyledons foliaceous.

Other Names for Scyphostegia borneensis

• Scyphostegiaceae

References

Chase, M. W., S. Zmarzty, M. D. Lledó, K. J. Wurdack, S. M. Swensen, and M. F. Fay. 2002. When in doubt, put it in Flacourtiaceae: a molecular phylogenetic analysis based on plastid rbcL DNA sequences. Kew Bulletin 57: 141-181.

Swamy, B. G. L. 1953. On the floral structure of Scyphostegia. Proceedings of the National Institute of Science of India. Part B: Biological Science 19: 127-142.

van Heel, W. A. 1967. Anatomical and ontogenetic investigations on the morphology of the flowers and the fruit of Scyphostegia borneensis Stapf (Scyphostegiaceae). Blumea 15: 107-125.

van Steenis, C. G. G. J. 1957. Scyphostegiaceae. Pp. 297-299 in Vol. 5, Flora Malesiana, Series 1.