Phyllode Structure, Taxonomy and Distribution in Some Australian Acacias

The phyllode anatomy of 144 species of Acacia belonging to sections Juliflorae, Plurinerves, Lycopodiifoliae and Phyllodineae was examined in respect of variation in structure of the outer mesophyll. Using the ratio of central mesophyll thickness to outer rnesophyll thickness as an index of xeromorphy, a relationship was established between higher xerornorphy and an arid environment and lower xeromorphy and a more humid environment. Both features are related to infrageneric groupings, the Juliflorae and the Plurinerves being more xeromorphic in structure than the Phyllodineae.