March 21st, ig22.'] Proceedings. xxi. 



the geological past be made so as to explain one set of pheno- 

 mena, many others fall naturally into line. Taking as a test 

 case the two sides of the North Atlantic, supposed by Wegener 

 to have lain in close proximity until a late geological date, Mr. 

 Wright examined critically their geological history, and 

 demonstrated the very close analogy in lithological aspect, fossil 

 content, and tectonic movement that has obtained between these 

 two regions from the earliest periods until their supposed 

 separation in the Tertiary. 



Professor F. E. Weiss said that it is a generally accepted fact 

 that in Tertiary times the floras of North America and Europe 

 were very similar and of a subtropical nature. Magnolias, 

 Tulip-trees, Aralias, Swamp-cypresses, Sequoias now limited to 

 America, were growing in Greenland and over the European 

 Continent, so that Heer and Engler assumed that a northern 

 circumpolar continent connected the Old and the New Worlds. 

 But such a northern connection would not adequately account 

 for the many American plants found in Southern Europe and 

 also in Africa. To explain the occurrence of closely related 

 species of many genera of flowering plants which occur in South 

 Africa and America, it is necessary to assume a connection of 

 these continents at all events in early Tertiary times. Wege- 

 ner's theory, therefore, greatly facilitates the explanation of the 

 presence of many American plants in the Old World in Miocene 

 times. The close correspondence between the floras of the Cape 

 and of Western Australia and the occurrence of certain allied 

 genera and species in Australia and South America respectively 

 is also easily explained by the union of these countries into an^ 

 Antarctis up to Tertiary times. 



The shifting of the poles, too, which seems to follow from the 

 shifting of land masses, is a great help to the understanding of 

 the changes in climate, which the nature of the fossil plants 

 seems to demand. The absence of annual rings in the wood of 

 the trees forming the coal measure forests indicates a climate 

 similar to that of existing tropical forests, while the Cycads and 

 their allies found in the Yorkshire Oolites and as far north as 

 Spitzbergen, prove that at that period a semi-tropical climate 

 must have reigned in those regions. A different position of the 

 North Pole during the Great Ice Age would also explain why 

 Siberia was not glaciated at that time, as it cannot have been, 

 for it was from Northern Asia that the new vegetation spread 

 into Northern and Central Europe after the last glacial period. 

 There is no doubt, therefore, that we can more readily explain 

 the facts of the present and past distribution of plants by 



