671 



arrived at would be very unsatisfactory; hul there are other circum- 

 stances which are worthy of noiice. The many Temperate-Euro- 

 pean or Atlantic species which occur can liardly be assumed to 

 have migrated across a land-bridge, because if such u land-bridge 

 were to be imagined Ihe climate prevailing on il would hardly snit 

 these piants; the sea lo the north of Ihc land connection would 

 unquestionably become frozen, turn ihto an ice-cellar«, al any 

 rate, Ihis would happen, were Ihc bridge to hc continued uninter- 

 ruptedly lo Greenland; and Ihe climate would beyond doubt be loo 

 raw, the land loo thickly enveloped in cold fogs, even if the Gull' 

 Stream were to wash ils south eoast. 



Ostenfeld (p. 118 above) follows, e. g. Drude, Blytt, A. de 

 Candolle, and others in helieving thai Ihe piants i m migrated 

 step by step and in collected bodies 1 .« 



But so far as I can see, there are no evidences in favour of 

 the above assumption, if we judge, as we ought to, from whal 

 we see every dav in nature, wherever piants immigrate into »new 

 earth.« Piants always immigrate one by one, according as they 

 are adapted for dissemination or travel 2 . 



Well-marked associations are developed little by little, and a 

 fairly constant vegetation, suited lo life in the different soil condi- 

 tions, arises in the course of time only. The plant-migration to 

 Krakatau verifies this. Sern ander also, who has made a long and 

 thorough study of the disseminating biology of piants, expresses 

 himself in favour of a gradual migration H , e. g. as regards the im- 

 migration to Spitzbergen (which according to sorae authors must 

 have taken place across a land connection between these islands 

 and Scandinavia), or to Gotland, Gotska Sandon, etc. 



The oldest piants of the Færoes, those which immigrated as 

 the ice retired, doubtless following hard at its heels, were unques- 

 tionably true arclic. As the climate gradually grew milder other 

 species entered, and the arclic were expelled from all the favour- 

 able habitats, so that at the present dav they occur on the highest 

 hills only, and many have probably hecome extincl. 



That an insular tlora like that of the Færoes, ultimately, after 



1 See Warming: Grønlands Vegetation, p. 201. 

 See Warming: Plantesamfund. Kjøbenh. 1895, p. .'JOS. Pflanzenvereine. 

 Deutsche Ausgabe von E. Knoblauch. Berlin 1896; 2><" Ausgabe, 1902. 



8 Sernander, Den skandinaviska Vegetationens Spridningsbiologi. Upsala 

 1901, p. 407, etc. 



