92 Hypothetical Continents. 



common to Japan include 26 not recent in Europe, and several 

 of these are eminently characteristic tertiary types. Taking 

 the orders of the Swiss miocene plants, 73 are common to the 

 Southern United States, and 71 to Japan; but while 6 of the 

 largest Japanese orders are represented in the Swiss miocene, 

 there are only 4 of the largest American. The inference 

 therefore appears natural and legitimate that the larger the 

 group which is taken as the basis of the comparison, the smaller 

 is the preponderance of American types ; and considering the 

 nature of many so-called species of fossil plants this fact has a 

 remarkable significance. Professor Oliver also uses as a basis 

 of comparison the proportion of ligneous species in each flora, 

 and he finds that while about 40 per cent, of the Japanese 

 flowering plants are ligneous, only about 22 per cent, of the 

 American come into that category. The proportion of ligneous 

 species in the Swiss miocene flora is even larger than in the 

 Japanese, amounting to 60 per cent., and the former therefore 

 corresponds more closely in this respect with the latter than 

 with the flora of the Southern United States. 



The foregoing facts seem to render reasonable the expecta- 

 tion that the true explanation of the affinity of the Swiss 

 miocene plants to those of the Southern United States should, 

 at the same time, account for its correspondence with that of 

 Japan, and for the occurrence of allies of other species in 

 different parts of the world. The Atlantis hypothesis does not 

 answer this expectation ; but a modification of the theory of an 

 Asiatic route does. On natural history grounds, therefore, we 

 should prefer the latter. 



Another consideration to which I must direct attention, is 

 the direction in which the migration took place. Hitherto it has 

 been taken for granted, that the migration was from America 

 to Europe during the miocene period, that is to say, the 

 American flora being stationary, it spread during the miocene 

 period as far as Europe. The Ex-President of the Geological 

 Society, Mr. "W. J. Hamilton, is, I believe, the only geologist 

 who has ventured to dispute this assumption, and he has 

 characterized the idea of a recent flora migrating to an ancient 

 as a physical impossibility.* 



I have just stated the assumption rather differently, and, 

 put in that way, it does not seem impossible ; still, I venture 

 to support Mr. Hamilton's view, that the Swiss miocene plants 

 emigrated towards America, and. that during the emigration, 

 many became dispersed to other regions ; but, at the same 

 time, I believe, on paleeontological grounds, that they came 

 from that continent at an earlier period. 



In any area undergoing great physical changes, such as 

 J* Quarterly Journal of the Geological Society, vol. xxi. p. 94. 



