Germination of Acacia auriculiformis A. Cunn. ex Benth. seeds was related to seed development. Full physiological development of seeds, indicated by maximum seed dry weight, was reached 82 days after anthesis; however, maximum percent germination was not reached before day 89. Later, germination declined gradually as dormancy and mortality increased. Most seeds were capable of germination without pretreatment at the time of collection, indicating that seed coats were not impermeable to water. Germination of seeds with moisture content from 14 to 29% can be achieved. Anatomical studies revealed that seeds reached maturity after compressing the parenchyma cells against the inside of the seed coat. The physical properties of the seed coat, therefore, did not control its permeability to water. After the developmental period, seed dormancy increased by further drying of seeds during storage.