8 The Vegetation of the 



of the landscape will not abruptly change; species after species will disap- 

 pear and new ones will present themselves. 



Traveling from the Atlantic westward, we find at first deciduous- 

 leaved trees and conifera? ; on the Alleghenies, the same, with an additional 

 number of Ericaceae; then west of the Alleghenies, in the Ohio Valley, 

 deciduous-leaved woods; on the Upper Mississippi, the same, interspersed 

 with prairies, which prevail west of the Mississippi, only the banks of the 

 rivers being wooded, and farther westward the trees disappear entirely. 

 The similar changes take place going from the north to the south. 



An early publication on the geographical distribution of North Amer- 

 ican plants, is Barton's specimen of a geographical view of the trees and 

 shrubs of North America (1809), of the newer ones the most important 

 are: Richardson's Chapter on Woody Plants and Carices, in the second 

 volume of his Arctic Searching Expedition (1850;) then Cooper's Paper in 

 Smithsonian Reports (1858), on the Distribution of the Forests and Trees 

 of North America; A. Gray's Statistics of the Flora of United States 

 (1856); Grray and Hooker's: The Vegetation of the Rocky Mountains in 

 Geological and Geographical Survey of the Territories (1881), and finally 

 Sargent's Forest Trees of Norlh America, in Vol. IX of the United States 

 Census (1884.) 



For North America, I propose the following floral divisions: 



1. The Arctic Alpine. 



2. The Woodland. 



3. The Californian. 



4. The Prairie. 



5. As a part, or at least a transition to the West Indian Flora, 



that of South Florida. 



1. The Arctic Flora, which is nearly the same as in the eastern conti- 

 nent, covers all the country northeast of a line drawn from the mouth of 

 the Mackenzie to the Hudson's Bay, under 60° north latitude, and north 

 of aline from the mouth of the Mackenzie to the northwest coast under 66° 

 north latitude; then that part of Labrador that lies north of 59°, and the 

 highest points of the Rocky Mountains, Sierra Nevada and White Moun- 

 tains. Characteristic is the absence of any tree-growth. The whole 

 Arctic Flora does contain not quite four hundred and fifty species of 

 vascular plants, and many mosses and lichens. 



2. The North American Woodland, comprising the greater part of the 

 continent from the Atlantic to the northeast, from Labrador and North 

 Florida to East Texas, Missouri and the Lower Saskatchawan, could 

 be sub-divided in the following provinces : A sub-arctic province 

 from Alaska to the Hudson's Bay, an uninterrupted forest of coni- 

 ferse, mostly Pinus alba and a few p6plars, birch, alder and wil- 

 lows. A North Pacific Province: The coast from the peninsula Alaska, 

 to the Oregon and the wooded part of the Rocky Mountains, have 



