INTRODUCTION. 



This volume is the first of four which are to deal with all the 

 native forest trees of North America north of the Mexican boundary. 

 It contains an account of the tree species known to inhabit the Pacific 

 region, 150 in all. Part II will be devoted to the Rocky Mountain 

 trees, Part III to the trees of the southern States, and Part IV to the 

 trees of the northern States. 



The region covered by Part I includes Alaska, British Columbia, 

 Washington, Oregon, and California (see maps, frontispiece). Many 

 trees described occur wholly within this region, but none are repre- 

 sented throughout it. A few are found on it^ southern border and 

 range into Mexico, while three or four trees stretch from within the 

 Pacific region to the Atlantic. 



DEFINITION OF A TREE. 



The definition of a tree followed by the author includes woody 

 plants having one well-defined stem and a more or less definitely 

 formed crown (but not excluding unbranched cactuses, yuccas, and 

 palms), and attaining somewhere in their natural or planted range 

 a height of at least 8 feet and a diameter of not less than 2 inches. 

 It has been difficult to apply this definition in all cases, for there is 

 no sharp line between some shrub-like trees and some tree-like 

 shrubs. However, though wholly arbitrary, it has been serviceable. 

 A considerable number of species included are, over much of their 

 range, little more than chaparral shrubs, becoming tree-like only 

 in exceptionally favorable places. Recent discoveries in this region 

 have made it necessary to class as trees several species previously 

 regarded as shrubs. Some species are shrubs within this territory. 

 but are trees outside of it. There still remain for further careful 

 consideration several species of Arctostaphylos, Ceanothus, and 

 Styrax, which may prove to be trees. 



DESCRIPTIONS VXD ILLUSTRATIONS OF SPECIKS: 



Since this work was prepared solely for the layman, the use of 

 technical terms has been avoided. In describing species the writer 

 has endeavored to define essential and simple characters in plain 



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