332 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1950 



Spitsbergen and the northwest coasts of Europe so much above it, 

 the contribution from the New World would presumably at least equal 

 that of the Old. 



There is, by the way, at least one plant in Iceland which is of New 

 World origin. The sea-rockets, Cakile, are shore-dwelling crucifers 

 with lilac flowers. Two Icelandic botanists. Dr. and Mrs. Love, have 

 recently shown that the sea-rocket of Iceland does not, as had been 

 generally assumed, belong to the species found in Scandinavia and 

 with us in Britain, Cah'de marltima, but reveals itself, both by its 

 slightly different form and its doubled chromosome number — 36 in- 

 stead of 18 — as the North American species, G. edentula. This holds 

 also for the sea-rockets of the Azores : the Loves' conclusion is that 

 the Gulf Stream has been responsible for the appearance of the Ameri- 

 can sea-rocket in these otherwise Old World islands, by transporting 

 the seeds in its slow, warm drift. 



At various times in the geological past, there was a land connection 

 between the Old and the New Worlds across what is now the Bering 

 Straits, and probably also, though not so often or so long, across the 

 North Atlantic, along the line still indicated by the submarine ridges 

 between Greenland, Iceland, Faeroe, and Shetland. The climate in 

 the regions connected by these land bridges was then less rigorous, and 

 there was more uniformity of animals and plants in the Holarctic 

 region than now. But isolation and time saw to it that the inevitable 

 differences were accentuated, and meanwhile the New World fauna 

 received large additions from the Central and South American region, 

 which were very different from the immigrants that the northern 

 Old World received from Africa and southwestern Asia. Thus even- 

 tually two quite distinct faunas and floras, the Palearctic and the 

 Nearctic, were differentiated — distinct, but with a number of elements 

 obviously of common origin, and still with a considerable number of 

 species shared by both and therefore classed as if Holarctic. 



The greater isolation of the two regions today may possibly be 

 due not only to the breaking of the land bridges between North 

 America and the Old World, but to an actual increase of the distance 

 across the Atlantic, caused by the slow drifting away of America 

 from Europe. 



This was postulated by Wegener in his theory of Continental 

 Drift. Iceland is well situated to test the theory. The position of 

 certain points should be determined with great accuracy, so that 

 after a lapse of years even a few yards' shift could be detected. Ger- 

 man scientists had begun on this project before World War II, and 

 had set up a number of triangulation points in Iceland. However, 

 the Icelanders were so suspicious that these might be camouflage for 

 some military project, that they destroyed them all — another of the 

 innumerable minor tragedies of modern war ! 



