432 Prof. Oliver on the Distribution of Northern Plants. [March 7, 



tiary, as Glyptostrobus, numerous Fici, coriaceous-leaved oaks and 

 Lauracece, Juglandece, Liquidambar, &c. 



The genera, common to the Swiss tertiary and the United States, 

 which are not found also in the old world, are Sabal, Taxodium, 

 Bumelia, Liriodendron, Ceanothus^ Ptelea, and Carya. But in 

 respect to these 7 it was observed that at least 5 were very doubtful 

 determinations. The 9 largest orders of the ' Flora Tertiaria Hel- 

 vetiae' are Leguminosce, Ameritacece^ Cyperacece, Proteacece, Lau- 

 racecB, Graminece^ ConifercB, Compositce, and Aceracece. Of these 

 Orders 3 are included in the 9 largest of Europe, 4 in the 9 largest of 

 the United States, and 6 in the 9 largest of Japan, while the remaining 

 3 of the tertiary, not included in the 9 largest orders of Japan, are 

 much more largely developed in Japan than in the United States. 

 They are LauracecB, Aceracece, and Proteacece. 



The proportion of ligneous to herbaceous species in the above 

 floras was alluded to. Heer estimates ligneous plants to have formed 

 about 66 per cent, of the phanerogamic vegetation of the tertiary 

 in Switzerland. The speaker considered this estimate as too high, 

 believing that sufficient allowance had not been made for the ad- 

 vantages that ligneous plants, which are often tall-stemmed, possess 

 over herbaceous species in securing access of their leaves and debris to 

 the waters in which they had been floated, and ultimately preserved. 

 He admitted, however, that ligneous species were relatively very 

 numerous in the vegetation of the tertiary period. The proportion of 

 ligneous plants he estimates in the existing flora of Japan at near 40 

 per cent., in the Southern States 22, Northern States 18, Europe 9 

 to 12. 



The intimate relationship traceable between the tertiary and 

 Japanese floras in the numerous characteristic types common to both ; 

 the issue of the ordinal and generic comparisons given above ; the 

 larger proportion of ligneous species in the Japanese than in the 

 Eastern American flora ; and the number of types peculiar, at the 

 present day, to Eastern America and Eastern Asia, compared with the 

 few restricted to Europe and America, the speaker contends, favour 

 the view advanced by Professor Asa Gray in reference to plants and by 

 Mr. Darwin as to animals, viz. — that the migration of forms to which 

 is due the community of types in the Eastern States of North America 

 and the miocene of Europe, took place to the north of the Pacific ; an 

 overland communication it may be supposed, having existed during 

 the tertiary time somewhere about Behring's Straits or the line of the 

 Aleutian Islands. This view is confirmed by the occurrence of 

 miocene vegetable remains in North-west America (including genera 

 yet growing in Japan but lost to America), which prove, further, the 

 temperature of these latitudes to have been at that time sufficiently 

 high to have permitted their existence so far north. 



The evidence in favour of the ' Atlantis ' hypothesis might, more- 

 over, be expected to have been more marked in the existing vegetation 

 of the Atlantic Islands than is the case. Professor Heer points out the 



