British North American Plants. 46 7 



on most high summits in middle and even southern tem- 

 perate countries, seem to me, likewise, an evidence of the 

 power of the winds in carrying spores to enormous 

 distances. 



Many of the special causes which have operated in Canada 

 to influence distribution have been of a physical character — 

 as, ocean currents, the enormous coast line with its peculiar 

 configuration and its effects on climate, the lie of the moun- 

 tain ranges, the vast stretches of .prairie country quite 

 divested of trees, and over a considerable extent of which 

 the annual rain-fall is limited, the breadth and the cooliDg 

 effects of the immense bodies of fresh water embraced in 

 the inland lakes, and the general prevalence of fogs on the 

 eastern coasts. All of these causes and others will be 

 referred to in detail in their special places. 



Divisions of the Flora. 



Taking a general view of the whole flora of the Dominion, 

 we can readily distinguish the following groups : — 



Canadian Group. — Embracing numerous species very 

 generally distributed over the whole country from the 

 Atlantic to the Pacific, and northward more or less to the 

 limit of growth of trees. They also occur in the Northern 

 United States, but probably the great mass of the individ- 

 uals of each species is rather in Canada than the United 

 States. 



Forest Group. — Comprising numerous species which 

 range more or less from Nova Scotia and New Brunswick 

 to the Eocky Mountains or towards there, but which appear 

 to affect the forest country and to avoid the prairie, unless 

 in those sections where there are extensive bluffs of trees, 

 or in the river valleys. The species of this group do not 

 cross the Eocky Mountains. 



Maritime Group. — Species confined to the immediate sea 

 shore, though several of them are also found along the 

 Great Lakes and in the neighbourhood of saline ground 

 farther inland. 



Eastern Coast Group. — Comprising plants confined in 



