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Remarks on the Geograph. Distrib. of British Plants - 1835 by H. C. Watson & Letters on var. of Agraria Plants

In Appendix II in which all British Plants are tabulated (omitting the doubtful one, those in Italic supposed to have been naturalised, & whole genus Salix) there are 499 British Plants found in America, of these 110 do not extend into his Arctic Region (ie not north of Behring's St, the Arctic circle in America, Hudson's St. S. extremity of Greenland, Iceland, Lapland, & shore of White sea; & 60 do not extend at same time in America & Europe into his Arctic circle; most of these extend further N. in Europe than in

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America, which I attribute to Gulf stream so that I think it may be said that 150 do not extend into his Arctic Circle, as far as passage is concerned. But between 50° & 60° by the Aleutian isld, I can see no reason why the plants may not have passed, for I believe Climate more mild there.

I think that probable fluctuation of climate in extreme north destroying organism over tracts of country & these always there to be colonised wd favour migration oscillation of climate like those in Alps & which in N. America has produced bands of dead trees.