America. The red oaks of Mexico are one of the groups of oaks that have most rapidly diversified into different species. Molecular evidence suggests that there are significant numbers of undescribed Quercus species in Mexico, so the number of known species in the section is likely to be an underestimate of the total diversity. Section Protobalanus Quercus sect. Protobalanus was first established as a subgenus by William Trelease in 1922 and then later treated as a section by Otto Karl Anton Schwarz in 1936 and Aimée Antoinette Camus in 1938. The staminate flowers have eight to ten stamens. The pollen ornamentation has only small wrinkles or folds (verrucae). The acorns mature after two years. The cup (cupule) at the base of the acorn has triangular scales that are fused at the base and have sharp angled tips. The scales are thick and compressed into rings, often forming small bumps, that may be obscured by glandular hairs. The leaf teeth end in spines. The section contains only five species, native to southwestern North America and northwestern Mexico. Section Ponticae Quercus sect. Ponticae was first established by Boris Stefanoff in 1930. It has also been treated as a subsection and a series, including under the name Q. ser. Sadlerianae Trelease. Species are shrubs or small trees, with rhizomes. The staminate catkins are up to 10 cm long. The cup (cupule) at the base of the acorn has scales with sharp angled ends. The leaves are either evergreen or deciduous, with simple or compound teeth. The leaf buds are large, enclosed in loosely attached scales. There are only two species, Quercus pontica and Quercus sadleriana. They have disjoint distributions. Quercus pontica is native to mountainous areas of north-eastern Turkey and western Georgia. Quercus sadleriana is native to northern-most California and southern-most Oregon in the United States. Section Virentes Quercus sect. Virentes was first established by John Claudius Loudon in 1838. It has also been treated as a series. Members of the section may be called live oaks. Species are trees or rhizomatous shrubs. They are evergreen or brevideciduous. The acorns mature in a year. The cup at the base of the acorn has narrowly triangular scales, with thin keels, at most small bumps (tubercules), and sharp angled ends. The leaves are evergreen or almost so. A distinctive feature of the section is that the germinating seed has fused seed leaves (cotyledons) and an