DISTRIBUTION OF VEGETATION IN UNITED STATES. 41 



and the sweet illicium {Illicium floridanum) . In the extreme coastal 

 region and in peninsular Florida the saw palmetto {Serenoa serrulata) 

 is more conspicuous than the shrubs, although there is an increasing 

 number of species of the latter, including two dwarf oaks (Quercus 

 pumila and Quercus minima) . 



Northeastern Evergreen-Deciduous Transition Forest. — This type of 

 forest fringes the Northern Mesophytic Evergreen Forest from Minne- 

 sota to Maine and southward along the Alleghenies. It is sometimes 

 well marked as a nearly equal admixture of deciduous and evergreen 

 needle-leaved trees, but on its southern and northern edges it merges 

 into the larger types of forest, except where sudden changes of soil 

 break the influence of climate. The most important deciduous con- 

 stituents are sugar-maple {Acer saccharum), beech {Fagus atropunicea) , 

 birch {Betula spp.), and basswood {Tilia americana). The commonest 

 evergreen trees are hemlock {Tsuga canadensis), white pine {Pinus 

 strohus), balsam fir (Abies halsamea), and jack pine (Pinus divaricata). 



Northern Mesophytic Evergreen Forest. — This forest occupies portions 

 of the northern Pacific coast, all but the alpine portions of the Rocky 

 Mountains above an elevation of 6,000 to 7,000 feet, and the higher 

 summits of all the coastal and inland mountain ranges of the Western 

 States. It also occurs in northern Minnesota, Wisconsin, and Michi- 

 gan and extends from Maine over the higher elevations of the Appa- 

 lachian region through New York, Pennsylvania, and West Virginia 

 south to North Carolina. 



This widespread forest is essentially similar in its physiognomy 

 throughout. It is dominated in all portions by the needle-leaved ever- 

 green tree, although it is by no means free of an admixture of broad- 

 leaved deciduous trees, and the latter are particularly common along 

 the streams or as small trees beneath the canopy of evergreens. This 

 forest is usually between 50 and 100 feet in stature, and it is commonly 

 so dense that the entire ground is in shade, although this is notably 

 untrue of the forests at elevations approaching timber-line on high 

 mountains, and of those which approach the lower limit of timber on 

 the desert mountain ranges of the interior. The heaviest stands of 

 this forest are almost devoid of either shrubby or herbaceous under- 

 growth, but are carpeted by beds of moss. In the more open stands 

 there is usually considerable shrubbery, and when this exists it is made 

 up of deciduous plants. 



In spite of the essential similarity of the Northern IMesophytic 

 Evergreen Forest, throughout its extensive range of occurrence, it 

 is made up of a large number of tree species, and its composition varies 

 greatly from State to State, and especially when the eastern and 

 western portions of the forest are compared. Owing to differences in 

 habit of growth that exist between different coniferous trees there are 

 some very striking differences in the physiognomy of the forest that 



