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The Bermuda oceanic islands are comprised mainly of lithified dunes (i.e. calcareous eolianites) which formed during Quaternary sea-level regressions. This short communication considers the vegetation history of Bermuda in relation to these dune-building episodes. At 32?N, Bermuda is the northernmost limit of most frost-intolerant stibtropical vascular plant species in the northern hemisphere. The global cooling that caused the Quaternary glacial periods and also the lowering of sea level, may have led to the local extinction of Bermuda's subtropical interglacial floras. Located >900 km from the nearest continental source area, the filling of the vacated niches on Bermuda by long-distance dispersal may have involved low frequency events requiring more than 6000 years. The result would have been a very sparse vegetative cover during the dune-building episodes which would explain why the Bermuda eolianites reach elevations greater than 60 m above the present-day sea level. This hypothesis is supported by: (1) the absence of reliable fossil evidence for vegetation interfering with, or interbedded within, the eolian deposits; and (2) preliminary palynological analyses of.the clay-rich fossil soils intercalated between the eolianite formations which have revealed pollen that does not appear to correspond to the existing native flora of Bermuda.

Aboveground adventitious roots emerging from the stems and branches of the montane tropical rain forest canopy tree species, Ceratopetalum virchowii, do not require epiphyte mats to stimulate their growth. The adventitious roots grow in dense clumps on fully exposed aboveground woody surfaces of this species on Mount Bellenden Ker in northeast Queensland, Australia, where mean annual rainfall exceeds 6000 mm. While the soil at the study site is nutrient-poor, the nutrient content of the rainwater draining from the stems of C. virchowii is unusually high compared to the stemflow of other neighboring canopy tree species. Ceratopetalum virchowii is particularly prone to the leaching of Ca2+, Mg2+, K+, and Na+. The aboveground adventitious roots of C. virchowii, therefore, may serve the adaptive function of nutrient recovery before its nutrient-rich stemflow reaches the ground and becomes available to other plants. I hypothesize that the growth of the aboveground adventitious roots of C. virchowii is influenced by the high nutrient content of its stemflow and branchflow drainage, and by the moist condition of its woody surfaces which remain wetted for relatively long periods after rainfalls.

The objective of our study was to determine whether Z. dumosum exhibits a significant difference between the upslope and downslope distribution of its roots on these hillslopes