177 



liiiiil, to about the Skecna." Since the valley of the Skeena, 

 with its emi)()uchiire at Prince Rupert in latitude 54"^, does not 

 cross the entire breadth of the Pro\ince, but is replaced on the 

 eastern slope by the valley of the Peace and its tributaries, it 

 becomes somewhat difficult to fix an exact northern limit. But 

 in any case the territory covered by this manual cannot be less 

 than twice as large as the State of Washington, and extends far 

 enough to the east to take in the entire western slope of the 

 Rocky IMountain region, which lies far to the eastward of any 

 part of the State of Washington, so that the casual observer 

 would not unreasonably assume that of the two Floras, Henry's 

 would surpass Piper's in the total number of species. But over 

 against this hasty generalization must be set the fact, not only 

 of the steady increase of species from the poles toward the 

 equator, but the further consideration that the Upper Sonoran 

 Zone, which dominates the semi-arid portion of eastern Washing- 

 ton, and which is remarkably rich in number of species, is very 

 scantily represented in the Province, extending but a short 

 distance into the central plateau along the valley of the Okanogan. 

 More than this, Washington is characterized by an endemism 

 that is far less marked in the part of British Columbia under 

 consideration. The number of species that ha\"e been reported 

 from their t>'pe-locality only is surprisingly large; the Olympics, 

 the \A'enatchee Mountains, and Mount Rainier are all charac- 

 terized by a strongly local flora; and the general region of the 

 Columbia Gorge, including the greater part of the Columbia 

 Valley from the Great Falls at Celilo to the sharp northward 

 bend of the river at Pasco, contains a surprisingly large number of 

 species with a very restricted local range. Xo such marked 

 tendency to endemism seems to be displayed in any part of 

 British Columbia. W'hile the flora of \'ancouver Island is 

 perhaps the richest in species of local occurrence, and while 

 there is a well-defined succession of botanical areas as we ad- 

 \ance eastward from the region of coast forest into the dry in- 

 terior, and then through a second humid belt to the subalpine 

 and alpine Rocky Mountain zones, the fact remains that the 

 tendency to diversity is less marked in British O^lumbia than in 

 Washington. 



