INTRODUCTION 



The aim of the i)resent work is to furnish an authentic reference book that will 

 be of o-reatest service not only to the trained botanist .but to everyone interested in 

 the native plant life of the Pacific States. It is patterned after the classical work of 

 Britton and Brown,— "Illustrated Flora of the Northern United States and 

 Canada." — and is the second comprehensive illustrated flora published in this coun- 

 try. Every species of fern, flower, tree, and shrub known to grow wild in the 

 Pacific States is illustrated and described. 



The Physical Features of the Pacifiic States. 



The three Pacific States— Washington, Oregon, and California— form the 

 western boundary of the United States extending along the shore of the Pacific 

 from 49° to 2>Z° 35' north latitude, a distance of 1,300 miles. They have an average 

 width of about 250 miles, and an area of 324,123 square miles. 



The outstanding physical features are the two great mountain systems, the 

 Cascade-Sierra Nevada and the Coast Ranges, which in general parallel the coast. 

 Of these the former is much the more prominent, and exerts the greater influence 

 on climatic conditions, forming a remarkably distinct divide between the Pacific 

 slope on the west and the interior or Great Basin region on the east. The Pacific 

 slope has an oceanic climate with mild, rainy winters and cool (especially near the 

 coast), dry summers, while east of the divide the climate is continental, with cold 

 winters and hot summers. 



Rainfall is greatest in the Northwest, diminishing southward and toward the 

 interior. From northwestern California to the Puget Sound region the average 

 annual rainfall is 75 to 100 inches ; in the San Francisco I'ay region 20 to 25 

 inches, and at San Diego 10 inches. East of the Cascade-Sierra Nevada Divide it is 

 much reduced, producing semi-arid conditions in eastern Washington and Oregon, 

 and typical desert conditions in southeastern California, where the annual rainfall 

 is only 2 to 5 inches. 



Floral Features of the Pacific States. 



The great coniferous forests of the Northwest and the mountains of California 

 are the most prominent floral feature. Nowhere are there more extensive forests, 

 more majestic trees, or greater variety of cone-bearing species. In the foothills and 

 coastal valleys of California chaparral and oaks replace the conifers, the open park- 

 like groves of the latter contributing much to the charm of the region. Finally, 

 fonning a striking contrast to the forests, are the bunch-grass plains of eastern 

 Washington and' Oregon, the sage-brush tracts of southeastern Oregon and 

 adjacent California, and the weird cacti and yuccas of the southern California 

 deserts. 



Life Zones. 



The usual manual method of noting geographical distribution by states is 

 inadequate in the Pacific region, where, owing to the diversity of topography and 

 climate, plant distribution is unusually complex. As an aid therefore in designating 

 distribution. Merrianvs system of Life Zones has been used. These zones as repre- 

 sented in the Pacific States are as follows : 



'Arctic-Alpine Zone 

 Boreal Region {Hudsonian Zone 



Canadian Zone 



Austral Region - 



Transition Zone 

 Upper Sonoran Zone 

 Loiver Sonoran Zone 



