LIST OF TREES AND SIIRUBS. 291 



David Douglas, on the banks of the Columbia, growing on 

 subalpine hills to the height of from 12 to 25 feet. 



Purshia tridentata inhabits the Rocky Mountain prairies 

 near the head waters of the Missouri and Columbia, and extends 

 northwards to the 49th parallel. Spircea opulifolia, nine bark, 

 ranges from Maine, Canada, and Wisconsin, westwards to the 

 valley of Oregon, in which it is found from the sources of the 

 Columbia downwards. It is common on the low islands of Lake 

 Superior, and has its polar limit in the colony of Red River. 

 S. chdmcedrifolia inhabits the north-w T est coast up to Sledge 

 Island in Beering's Straits, and Chamisso Island in Kotzebue 

 Sound. It does not cross the Rocky Mountains, nor does any 

 other Spircea go so far north on the east side of the continent. 

 S. betulifolia is another western species which inhabits the Blue 

 Mountains and Mount Hood, and crosses the Rocky Mountains 

 to their eastern valleys between latitudes 52° and 54°, but does 

 not descend to the lower eastern country. S. tomentosa, hard- 

 hack or steeple-bush, is common in the meadows and low grounds 

 of New England, and spreads through Nova Scotia, Canada, and 

 Rupert's Land to Lake Winipeg. S. douglasii is an Oregon 

 species resembling the preceding, which extends to the Straits 

 of Da Fuca. S. aricefolia forms part of the underwood in 

 forests on the Pacific coast, on the Ivooskoosky, Spokan, 

 Flathhead, Salmon, and M'Gillivray Rivers up to the 49th 

 parallel. S. salieifolia is very abundant on the banks of every 

 lake and river in the St. Lawrence and Saskatchewan basins, 

 and northwards to Slave River. It is often associated with the 

 Myrica gale, growing in the water. In its northern range it 

 approaches the S. chamcedrifolia of the west coast, but does not 

 attain so high a latitude, owing to the greater severity of the 

 climate on the east side of the mountains. 



Rubus occidentalism black raspberry or thimbleberry, ex- 

 tends from the Northern States to the Saskatchewan basin, and 

 also to the Pacific coast, R. strigosus, wild red raspberry, is 

 also found on both sides of the continent ; on the east side it 

 inhabits the United States, Newfoundland, and Canada, and 

 may be traced in the interior canoe route throughout the Sas- 



