The Southern Blue Ridge Province of the Appalachian Mountains is defined by its geographic distribution, geology, soils, and vegetation. This province is bounded by the Piedmont Province to the east and the Valley and Ridge Province to the west and extends from northern Alabama and Georgia into southern Virginia. The underlying ancient rocks consist mostly of sandstones, shales, and related rocks that were metamorphosed and later overthrust onto rocks of the Valley and Ridge. Blue Ridge topography is but a remnant of a much more extensive mountain range. Present-day topography and climate are probably relicts of the Tertiary and Pleistocene. Because of the climate and bedrock, a dominant feature of the region is dynamic chemical weathering that has produced acidic soils and saprolite on dominantly steep slopes supporting acid-loving vegetation. The vegetation also has long history of development with many extant genera showing relationships to Pleistocene and earlier floras. The flora contains varied species including many genera that may be found in Tertiary fossils, such as Sassafras; tropically derived elements such as the filmy ferns, Trichomanes spp. and Hymenophyllum spp.; elements that are disjunct with other parts of the world, such as members of the magnolia family of southeast Asia; relicts of the glacial periods such as Trichophorum cespitosum; and narrow endemics such as Rhododendron vaseyi.