British North American Plants. 461 



upon it, is evidenced by the rings of black vegetable loam 

 which appear in excavations made at Winnipeg for tanks 

 and wells. It does not, however, appear to me necessary 

 to assume that these were milder inter-periods. A north- 

 ern temperate vegetation was already in Canada, I cannot 

 avoid concluding. There is also some evidence of more than 

 one depression during or after the glacial epoch in the 

 Lower St. Lawrence valley, or of the renewed action of 

 glaciers on the rising of the land there. 



The hypothesis of a universal ice cap throughout Canada 

 almost dispels the notion of any phsenogamous flora in 

 northern temperate America, or, at least, of any vegetation 

 short of an extremely Arctic type. It assumes the gradual 

 extermination of all northern and middle temperate plants 

 in their native habitats, and the crowding of the species 

 into a very circumscribed area to the southward, presently 

 occupied by the south-temperate vegetation of the continent, 

 of which crowding we have no evidence left, and which is 

 hardly in accordance with existing possibilities. It also 

 assumes the migration of the Arctic flora southward to at 

 least northern temperate countries. Does not, however, 

 the comparatively limited flora of the summits of the 

 White Mountains and other considerable heights in New 

 England and New York, comprising chiefly four or five 

 really arctic and a few sub-arctic and boreal plants, nearly 

 all also found on the coast of the Lower St. Lawrence, of 

 the Gulf of St. Lawrence or of Labrador, show that the true 

 Arctic flora had hardly reached as far south as these points ? 

 If, however, as I believe, there were only individual gla- 

 ciers everywhere over the Laurentian and immediately 

 surrounding country, on the high peaks and mountain 

 ranges of that period, perhaps all of which are at much 

 lower elevations now, it by no means follows that vegeta- 

 tion was entirely driven southward at this time. There 

 could be a cold sufficient to produce glaciers on the moun- 

 tain sides, and their resultant icebergs where, farther north, 

 these glaciers met the sea, and these icebergs might be 

 found even as far south as the New England States, for the 

 cold Labrador current now existing would, without doubt, 



