A developmental series of flowers and fruits of Quercus acutissima Carruth. (subgenus Quercus section Cerris) in 2000 and Q. palmeri Engelm. (subgenus Quercus section Protobalanus) in 1995 was collected over a growing season, fixed, and sectioned using glycol methacrylate embedding and glass knife sectioning techniques for an intersectional, comparative anatomical study. For both species, pistillate flowers of the current growing season, each consisting of a pistil with three long, slightly recurved styles, six tepals, and an inconspicuous ovary subtended by a few cycles of cupule scales, emerged in early May, were pollinated by mid-May, and then were quiescent for the remainder of the growing season. Flowers from the previous growing season resumed growth in May, each forming three locules delimited by septa in the ovary, with two bitegmic, epitropous ovules developing in each locule. For Q. acutissima, flowers from the previous growing year resumed growth in mid-May, and mature embryo sacs were present by mid-July of the second growing season, although embryos were not observed until early August. Fruit maturation was complete by late September. For Q. palmeri, flowers from the previous growing year resumed growth in early May, and mature embryo sacs were present by mid-June of the second growing year, with embryos observed thereafter. Fruit maturation was complete by early August. Features that have not been described previously for section Cerris (Q. acutissima) include early-lignifying endocarp trichomes, persistent septa, and leaf primordia buttresses on the embryo. New features for section Protobalanus (Q. palmeri) that may have phylogenetic implications include: stigmatic surfaces restricted to capitate apex of styles, a perianth flange, presence of staminodia, thick-walled style/perianth epidermis cells, and persistent septal remnants at maturity. A comparison of flower and fruit developmental features in Q. acutissima and Q. palmeri with previous subgenus Quercus studies in sections Cerris, Lobatae, Protobalanus, and Quercus sensu stricto reveal a mosaic of shared features among the four sections of Quercus subgenus Quercus, as well as newly described features that had been never attributed to this group of taxa previously.