Previous to the settlement of the Gulf plains by Europeans and the clearing of much of the land for plantations it was clothed with such a dense growth of trees and vines as to be almost impenetrable. The southern pine there reaches its greatest perfection and is the basis of a great lumber industry, and oaks of several species, the wide-spreading white-trunked sycamore, the still more stately tulip-tree with its cup-like blossoms of yellow, the fragrant magnolia, the seemingly always aged cypress, the gum-tree, and many other species of arboreal vegetation also find most congenial conditions for their growth. The dwarf palmetto, which forms such a characteristic growth in Florida, extends northward in the Mississippi basin to the southern border of the Ozark uplift. Much of the luxuriant moss and lichen draped forest of the Gulf plains with all its primitive network of shrubs and vines still remains. _The Prairie Plains._--A prairie in the current use of the term is a generally level region, either a plain or a plateau, without forests but clothed with a carpet of luxuriant grasses and flowering annuals. A rolling prairie is an undulating or hilly, grass-covered region. The Great plains of the west-central portion of the Continental basin meet these requirements, and are typical prairies. On their eastern and northern border the Prairie plains merge with the adjacent forested plains, and on the west from Mexico northward to the subarctic forest pass by still less tangible gradations into the more elevated and drier Great plateaus or high plains, where bunch-grass, with bare intervals between the scattered tufts, takes the place of the continuous sod of the true prairies. The reasons for the change from forest to prairie and beyond to the land of the bunch-grass as one travels from east to west across the interior basin, lie in differences in the humidity of the climate.