pollen grains have vertical folds (rugulae). The stalk that joins the perianth to the ovary (the perianthopodium) has three to five distinct rings. The 'cup' (cupule) around the base of acorn also has distinct rings formed from thin membranes (lamellae), which also distinguishes the section from other oaks. The leaves are evergreen. The section contains about 90 species native to tropical and subtropical Asia including the southern Himalayas. Section Ilex Quercus sect. Ilex was first established by John Claudius Loudon in 1838. It has also been treated as a subgenus, under the name Quercus subg. Heterobalanus Oerst., and as subsection. Members may be called ilex oaks. Like all species of Quercus, those of section Ilex are trees or shrubs with acorn-like fruit. The staminate flowers have four to six stamens. The ornamentation of the mature pollen is distinctive, consisting of wrinkles or folds (rugulae). The acorns mature either annually or after two years. The cup of the acorn has triangular scales, usually thin and membranous. The toothed leaves are evergreen with spines or bristles at the ends of the teeth. The section contains about 40 species native to Eurasia and North Africa. Section Cerris Quercus section Cerris was first established by Barthélemy Charles Joseph Dumortier in 1829. It has been treated as a section under other names, including Quercus sect. Erythrobalanopsis Oerst., Quercus sect. Castaneifolia O.Schwarz, Quercus sect. Vallonea O.Schwarz, Quercus sect. Aegilops (Reichenb.) O.Schwarz and the illegitimate name Quercus sect. Eucerris Oerst. Members may be called cerris oaks. Like all species of Quercus, those of section Ilex are trees or shrubs with acorn-like fruit. The staminate flowers have four to six stamens. The ornamentation of the mature pollen is distinctive, consisting of scattered small bumps (verrucate). The cup of the acorn has narrowly triangular scales, thickened and with a keel and elongated recurved tips. The leaf is toothed, typically with bristle-like extensions to the teeth. There are about 13 species in Eurasia and North Africa, including the cork oak, Quercus suber, an important source of cork for wine stoppers, among other uses. Conservation The 2020 Red List of Oaks shows that within the species assessed across all eight sections of the genus Quercus, the sections Cyclobalanopsis and Ilex have the largest proportions of species put into the "critically endangered" category, representing the highest level of threat. A large number of section Cyclobalanopsis species occur in China: the Flora of