315 THE ECOLOGY OF THE CENTRAL COASTAL AREA OF NEW SOUTH WALES. I. THE ENVIRONMENT AND GENERAL FEATURES OF THE VEGETATION. By Ilma M. Pidgeon, M.Sc, Linnean Macleay Fellow in Botany. (Plates xvi-xvii; six Text-figures.) [Read 24th November, 1937.] The area considered in this series of papers is the central coastal plateau region east of the main divide extending to the edge of the Hunter Valley in the north, to Cox's River in the west and to the Lower Shoalhaven Valley in the south. It includes the County of Cumberland, and the adjoining portions of the Counties of Northumberland, Hunter, Cook and Camden (Long. 150-151-5, Lat. 33-35 approx. ) . Two plant-formations occur in this area: Eucalyptus forest and sub-tropical rain-forest. The endemic Australian and Indo-Malayan floristic elements corres-pond respectively to these formations (Maiden, 1914). Eucalyptus forest is the dominant formation not only of the central coast but of the whole coastal area and adjacent highlands^ of New South Wales. It shows several important phases which are due to the variation in soils, climatic factors and physiographic habitats. Rain-forest is limited to the coastal belt where there is a high rainfall; there it occurs in scattered patches on good soil, usually in areas sheltered from winds and extreme insolation. In this series of papers a description is given of the structure and composition of these coastal Eucalyptus forests, especially those typical of the two charac-teristic geological formations of the area: Hawkesbury Sandstone and Wianamatta Shale. An attempt is made to classify the Eucalyptus forests on the basis of associations (Clements, 1916, 1936) within the formation. The successional phases of the sandstone vegetation are also discussed. The Mt. Wilson forests, which form part of the Eucalyptus forest formation occurring in this area, have been described in detail by Petrie (1925), and McLuckie and Petrie (1926); Davis (1936) has outlined the forest communities occurring on a portion of the Illawarra (South Coast). No other detailed forest ecology has been done in this area, but reference must be made to the general accounts by Robertson (1926) and Osborn (1932). A number of general floristic accounts of the sandstone flora, chiefly in the Sydney District, have also been published. Reference will be made to these in later publications. 1 On the western slopes of the Dividing Range, this formation gives place to a more open type of vegetation known as savannah woodland.