FLORA OF THE PACIFIC 

 COAST 



BY HARVEY MONROE HALL 



Assistant Professor of Botany, 

 University of California 



THE flora of the Pacific Coast offers many at- 

 tractions to the botanical traveler. No matter 

 what phase of botany may interest him 

 most, whether it be the aesthetic, the systematic, 

 the genetic, or the ecologic, he will find ample ma- 

 terial for his studies and a never-ending succession 

 of problems to tax his skill as an investigator. The 

 flowers are more highly colored than are those 

 of most other regions, and the number of species 

 is larger, while fluctuating variations in vegetative 

 characters are exceedingly abundant and often give 

 rise to very dissimilar forms within the species. 



The diverse and variable character of the west- 

 ern flora is undoubtedly due in large measure to a 

 wide variety of climatic, soil, and other environ- 

 mental factors. At the lower altitudes are desert 

 areas where the vegetation is strongly xerophytic 

 and the flora evidently related to that of Mexico, the 

 high mountain summits are likewise arid but the 

 vegetation here is Alpine in character and the flora 

 undoubtedly of boreal origin. Between these ex- 

 tremes are areas of highly diversified topography. 

 Rugged mountains alternate with fertile valleys; 

 deep caiions furnish walls of varying slope and all 

 exposures; there are lakes, swamps, alkaline depres- 

 sions, and in addition such variety of soils that 

 nearly every class of plants somewhere finds condi- 

 tions suitable to its needs. The Sonoran, or Mexican, 

 element of the flora occupies most of southern Cali- 

 fornia and extends north through the interior val- 

 leys even into Washington. The boreal element is 

 naturally best represented in Washington, Oregon, 

 and Idaho although the boreal zones extend down 

 the whole length of the Sierra Nevada and into 

 southern California. Where the two meet there 

 occurs a mingling of the northern and southern 

 elements and in many places one also encounters 

 a peculiar flora, especially of shrubby species, not 

 closely related to that of any other region and 

 believed by many to be endemic. 



In the following account we shall be able to 

 mention the flora of only a few of the more promi- 

 nent and accessible plant formations. The desert 



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