The final position of aborted ovules in the mature fruit of Quercus has historically been an important character in delimiting major subgeneric and sectional groups. Previous anatomical studies of the aborted ovules have been restricted to the red oak (section Lobatae) and white oak (section Quercus) groups of subgenus Quercus. We present here a detailed analysis of carpel and ovule development from early stages to maturity in Quercus acutissima (section Cerris), and Q. palmeri (section Protobalanus). In Q. acutissima, the abortive ovules remain basal in the seed, while in Q. palmeri they are variable in position. A comparison of abortive ovules and of several additional fruit and seed developmental features among the major subgroups of Quercus will be presented.

Key words: abortive ovules, acorn, carpel, Fagaceae, fruit, Quercus