146 AGE AND AREA FROM A [pt. ii 



mentary) examined by him. With regard to the age of the flora, 

 Dr Kryshtofovich, who has also worked much upon Japanese 

 fossil plants, believes that it should be assigned to the base of 

 the Pliocene (63). In that case it is contemporary with the flora 

 of Pont-de-Gail. 



Nathorst remarks of the Mogi flora that the outstanding fact 

 regarding it is its closeness to the living flora of the forest-belt 

 of the Japanese mountains; and we have only to consiflt his 

 lists to see how^ true the statement is. But though the living 

 flora be close to that of Mogi, it has changed. If we examine 

 Nathorst's list we shall see that about 44 species may be con- 

 sidered as belonging to what I have termed the Chinese-North- 

 American Association; and that of these. 39 are now represented 

 by different species or varieties. That is. about 89 per cent, have 

 changed. The figure approximates closely to the 90 per cent, of 

 changed species found, when we compared the Pont-de-Gail 

 species with living Chinese-North-American species. I do not 

 wish to press the similarity of the figures. Whether it be due to 

 chance, or really represents the degree of extinction of older 

 forms since the beginning of the Pliocene, I do not know. The 

 number of species in the Pont-de-Gail flora, belonging to the 

 Chinese-North- American plant association was small; also Prof. 

 Nathorst's references to living species suggest that the Japanese 

 Pliocene forms may be nearer to living forms than those of Pont- 

 de-Gail would ajipear to be. Anyhow, his work, like mine, bears 

 evidence that old forms have very largely given place to new. 

 We may say at once that the work gi\es no evidence as to how 

 the new forms arose, though the endemic Japanese species which 

 are related to these old Mogi species would seem to have arisen 

 in Japan ; but though Ave cannot trace the history of the new, we 

 can find out a little more about the extinction of the older forms. 



If a list be made from all the five European Pliocene floras 

 (those already named), of all the Chinese-North-x\merican species 

 which are still living — 26 in all — it will be seen that by far the 

 greater number are now found living in East Asia. Twenty 

 species, out of the 26, about 77 per cent., are there found; 

 5 species, or 19 per cent., in North America; whilst one species 

 {Brasenia), or 4 per cent., occurs in both continents. Again, 

 consider the living genera represented— 55 in all — 33 of these, 

 or 60 per cent., are found living on both continents; 17, or 31 per 

 cent., in East Asia only; 5, or 9 per cent., in America only. 

 Therefore, whether we consider genera or species, there would 



