distribution between western Eurasia and western North America Section Virentes – American southern live oaks Section Quercus – white oaks from North America and Eurasia Subgenus Cerris – the Old World clade (or mid-latitude clade), exclusively native to Eurasia Section Cyclobalanopsis – cycle-cup oaks of East Asia Section Cerris – cerris oaks Section Ilex – ilex oaks The following cladogram summarizes the relationships among the sections: The subgenus division supports the evolutionary diversification of oaks among two distinct clades: the Old World clade (subgenus Cerris), including oaks that diversified in Eurasia; and the New World clade (subgenus Quercus), oaks that diversified mainly in the Americas. Subgenus Quercus Sect. Lobatae (synonym Erythrobalanus), the red oaks of North America, Central America and northern South America. Styles are long; the acorns mature in 18 months and taste very bitter. The inside of the acorn shell appears woolly. The actual nut is encased in a thin, clinging, papery skin. The leaves typically have sharp lobe tips, with spiny bristles at the lobe. Sect. Protobalanus, the canyon live oak and its relatives, in the southwestern United States and northwest Mexico. Styles are short; the acorns mature in 18 months and taste very bitter. The inside of the acorn shell appears woolly. The leaves typically have sharp lobe tips, with bristles at the lobe tip. Sect. Ponticae, a disjunct including just two species. Styles are short and the acorns mature in 12 months. The leaves have large stipules, high secondary venation, and are highly toothed. Sect. Virentes, the southern live oaks of the Americas. Styles are short and the acorns mature in 12 months. The leaves are evergreen or subevergreen. Sect. Quercus (synonyms Lepidobalanus and Leucobalanus), the white oaks of Europe, Asia and North America. Trees or shrubs that produce nuts, specifically acorns, as fruits. Acorns mature in one year for annual trees and two years for biannual trees. Acorn is encapsulated by a spiny cupule as characterized by the family Fagaceae. Flowers in the Quercus genera produce one flower per node, with three or six styles, as well as three or six ovaries, respectively. The leaves mostly lack a bristle on their lobe tips, which are usually rounded. The type species is Quercus robur. Subgenus Cerris Sect. Cyclobalanopsis, the ring-cupped oaks of eastern and southeastern Asia. These are evergreen trees growing tall. They are distinct from subgenus Quercus in that they have acorns with distinctive