

INTRODUCTION. 



The region covered by this flora is that lying between the summit of the 

 Cascade Mountains and the Pacific Ocean from the 49th parallel of latitude 

 across the southern portion of Vancouver Island, south to the headwaters 

 of the Willamette River or, more specifically, to the southern boundary of 

 Lane County, Oregon, marked in part by the Calapooia Mountains. In the 

 Umpqua Valley just south of these mountains, many California plants reach 

 their northern limits; while in the Rogue River Valley, the next southward, 

 the flora is predominantly Californian. 



The northern boundary chosen is, from a botanical standpoint, purely 

 artificial. Naturally, as marked by the northern limit of the characteristic 

 lowland trees, it would extend to about latitude 54, that is, nearly to the 

 southernmost extremity of Alaska. 



In general the flora below 5,000 feet altitude is characterized by dense 

 coniferous forests, the commonest tree being the Douglas spruce. Along the 

 narrow river valleys, however, the tree flora is in large part made up of de- 

 ciduous trees, such as alder, cottonwood, and maple. The only break in this 

 continuous forest cover consisted originally of a series of prairies extending 

 from the upper Willamette Valley northward to Vancouver Island. North 

 of the head of Puget Sound, however, these prairies are small and are limited 

 in the main to the extremities of points and to a portion of the islands in the 

 Sound. In Washington these prairies are all gravelly and are mainly the 

 deposit of glacial streams. In the Willamette Valley they appear at least 

 in part to have been due to the periodic burning of the dry grass by the Indians. 



The flora of the region may be classified into four life zones: 



The Humid Transition zone includes the great forests of Douglas spruce, 

 as well as the included prairie regions. Other characteristic trees are giant 

 cedar, red alder, broadleaf maple and Scouler willow. Along the seacoast 

 the Sitka spruce is abundant, accompanied by other northern plants. This 

 coastal strip may be looked upon as a southward extension of the Canadian 

 zone rather than as typical Humid Transition. 



The Canadian zone is not sharply limited. Such trees as western white 

 pine, amabilis fir, and Engelmann spruce mark it best. Western hemlock 

 is particularly abundant in this zone but also descends to sea level. 



The Hudsonian zone is indicated by subalpine fir, Alaska cedar, black 

 hemlock, and white-bark pine. At their extreme altituclinal limits all of these 

 become prostrate mats of branches. 



The Arctic zone consists of the alpine flora above the limits of trees. 



From a botanical standpoint the region is of unusual interest on account 

 of its magnificent coniferous forests, its wonderful mountain meadows, and 

 the large percentage of species that are peculiar to its flora. The extensive 



