The North American Forest 13 



redwood (Sequoia semperwrens\ that magnificent, 

 cypress-like giant which forms a belt, from ten to 

 twenty miles wide, along the California coast from 

 the Oregon boundary to a point in Monterey 

 Count}*, a little north of San Francisco. And even 

 the redwood is not equal in size to the famous big 

 tree (Sequoia gigaiUea)^ the pride of the Sierra. 

 This tree is known to tourists principally by the 

 comparatively few specimens growing in the pro- 

 tected groves of Calaveras and elsewhere, But it 

 reaches its grandest development farther south, in 

 the southern part of the Sierra, where it forms, not 

 small groves, but extensive forests. 



How did the forests and the species compos- 

 ing them come to be distributed over, the North 

 American continent in just the peculiar manner in 

 which we find them ? Before very much was 

 known about plant geography, people used to be 

 content with saying that each tree found itself in 

 that region the natural conditions of which were 

 most adapted to its nature. But such vague an- 

 swers no longer content us to-day. The science of 

 palaeobotany, or the knowledge of the plants which 

 existed on the globe in former geological periods, 

 has helped us on the track of this secret of nature. 

 To be sure even now we know these things frag- 

 mentarily only, and an almost limitless field is here 

 still open to investigation. But this we can now 

 affirm : The distribution of trees is due to two 

 sets of factors, one topographical and climatic, 

 based upon the differences of soil, elevation, 



