Earliest floral evidence for the Ebenaceae in Australia
Flowers are seldom preserved in an identifiable condition. The limited knowledge of floral structure of ancient flowering plants makes comparisons with living plants difficult, as floral structure is the basis for classification of the angiosperms. When found, fossil flowers contribute considerably to our understanding of the evolution of flowering plants1–6. The flowers described here were recovered from Upper Eocene deposits near Anglesea, Australia. They are tetramerous, unisexual, male, with 16 stamens and tricolporate pollen. These flowers, and associated ebenaceous leaves, are the oldest known remains of the Ebenaceae from Australia.
Ecological biogeography of Australia.
Understanding the biogeography of Australia requires knowledge of both existing and former environments. The existing environment is discussed elsewhere in the volume but a few salient points should be reiterated. Three-quarters of Australia is either arid or semi-arid and even much of the better-watered fringes has long dry seasons. Vast stretches of ocean separate it from other land masses except in the north where New Guinea and Indonesia form 'stepping stones' to and from Asia. It is also a low continent with over 99% of its area below 1000 m; even the highest summits barely exceed 2000 m. Since most of the surface has undergone prolonged weath ering, poor soils are the rule. The impact of man on the landscape has been less than in more densely settled continents. Aboriginal man has inhabited the continent for 40,000 years or more but agriculture and stock rearing have operated for less than two centuries and the present rural population is sparse. Large parts of the dry interior are not occupied although they are affected to some extent by introduced feral animals."
Frequency distributions of the mixing height over an urban area from SODAR data
The height of the mixing-layer (MLH) is an important parameter in the assessment of the dilution of primarily emitted or secondarily formed air pollutants in the atmospheric boundary-layer. A continuous measurement of MLH is possible only by remote sensing. Here, 17 months of SODAR data have been analysed automatically to derive the MLH over the city of Hannover in Northern Germany. In contrast to earlier studies the MLH has been determined from vertical profiles of the acoustic backscatter intensity and from the variance of the vertical velocity component. The results are presented in form of monthly frequency distributions and mean daily courses of MLH. These statistical evaluations of MLH show a clear annual course and interannual variability. The study shows the possibility to derive meaningful climatological information from long-term SODAR measurements for air quality issues.