DISTRIBUTION OF VEGETATION IN UNITED STATES. 39 



few new ones are met, as birch {Betula lutea) and popular {Populus 

 balsamifera) . On passing southward, the commonest forms of the 

 Alleghenian region are found to be confined to the mountainous dis 

 tricts, while their place is taken on the Piedmont and in the Mississippi 

 Valley by a still larger group of species, many of which are found not 

 only on the upland, but in the half-swampy areas of the level regions. 

 Prominent among these trees are Spanish oak {Quercus digitata), 

 water oak {Quercus nigra), willow oak {Quercus phellos), black gum 

 {Nyssa sylvatica), red gum {Liquidamhar styraciflua), and blue-jack oak 

 {Quercus hrevifolia) . 



The most southwesterly portion of the Deciduous Forest in central 

 Texas is made up almost solely of post oak {Quercus minor) and black- 

 jack oak {Quercus marilandica), while the most northwesterlj'- islands 

 of deciduous forest in the Dakotas are made up chiefly of bur oak 

 {Quercus macrocarpa). 



Southeastern Evergreen-Deciduous Transition Forest. — This transi- 

 tion lies between the coastal Evergreen Forest and the interior Deciduous 

 Forest, occupying hilly and broken land, except at the extreme western 

 end. Throughout this area there are small bodies of pure evergreen 

 needle-leaved forest and other bodies of pure deciduous forest, but the 

 vegetation consists in the main of an admixture of the two types of 

 trees in such percentages that neither dominates strongly over the 

 other. As in all other transition regions, the local conditions of soil 

 and topography often determine the precise composition of the forest. 



East of the Mississippi the Evergreen-Deciduous Transition is 

 formed chiefly of the loblolly pine and the species of deciduous oaks 

 that will be mentioned in connection with the inner portion of the 

 Southeastern Evergreen Forest. West of the Mississippi the loblolly 

 pine occurs near the Gulf coast and is chiefly replaced by the shortleaf 

 pine {Pinus echinata) above the Neches River, while the same species 

 of deciduous oaks accompany each of the pines. 



Southeastern Mesophytic Evergreen Forest. — This region stretches 

 from Long Island to Louisiana along the Coastal Plain, with an exten- 

 sion into peninsular Florida, and with outlying areas in central Ala- 

 bama and in Arkansas, Louisiana, and Texas. This area is dominated 

 by evergreens, and a secondary role in the vegetation is played by 

 deciduous broad-leaved trees and by evergreen broad-leaved trees. 

 The forest stands of this region are nowhere dense in the same sense 

 as are some of the evergreen stands of Montana or Maine; indeed, 

 many of the pine stands in all parts of the area, and particularly in 

 Florida, are rather open. Some of the heaviest stands are found in 

 Louisiana and Texas and the lightest are those of Florida and New 

 Jersey. As a rule the pinelands which lie nearest the coast, particu- 

 larly in the Gulf States, are the purest, while those of Maryland and 

 the Carolinas, as well as the interior areas of Alabama and Arkansas, 



