;part 2] 



REVIEW OF PLIOCENE FLORAS. 



149 



•of the comparison was merely to find out, if possible, how these 

 floras were related. If, in the end, the work led to results which 

 were not even thought of when the selection was made, 1 hope 

 that it may be considered that the balance has been kept true. 

 It can hardly be chance that these results have been reached. It 

 certainly is not design. I could not have arrived at them had I 

 tried to do so ; I should not have known how : the process would 

 have been too complicated. 



III. The Comparison of the Floras. 



The lists at the end of this paper give the selected species and 

 their allocation to the two categories of exotic species when they 

 belong to these ; the species of the Chinese-North American asso- 

 ■ ciation being marked with one asterisk *, other exotics with two **. 



It will appear in the course of the paper that the Chinese-North 

 American species mark an outgoing flora, the living West European 

 species and the other exotics, an incoming flora; and that these 

 two floras were derived from different sources, the one from a Polar, 

 the other from some other source. 



The first comparison of the Keuverian with the Pont-de-Grail 

 .and Teglian showed conclusively, that the lleuverian was much 

 nearer in age to the Pont-de-Gail flora than to the Teglian, and 

 that its position must be low down in the Lower Pliocene, not, as 

 we had suggested, at the top of the Middle Pliocene. 



This conclusion indicated that the change in the character of 

 the flora of Western Europe, north of the east-and-west mountain- 

 ranges, throughout the Pliocene Epoch, was much more gradual 

 than we had surmised ; and I was led to reconsider my first estimate 

 •of the probable age of the Castle-Eden flora, which it was suggested, 

 in a preliminary report, might be a little older than the Teglian. 



With the object of testing this new view, and of discovering 

 the way in which the West European flora changed throughout 



Table showing the Relationships of Five Pliocene Seed-Floras. 



I. 



II. 



III. 



IV. 



V. 



VI. 





Number 

 of species 



compared. 



Percentage 



Percentage 



Percentaae 



Age, or 



Name of 



of whole 



of exotic 



of Chinese- 



suggested age 



flora. 



flora 

 compared. 



and extinct 

 species. 



North -Ameri- 

 can species. 



of the 



strata. 



Croinerian 



135 



89 



5 



074 



Top of Plio- 

 cene. 



Teglian 



100 



75 



40 



16 



1 Upper Plio- 

 cene (Nor- 

 1 wichCrag). 



Castle Eden ... 



58 



oo 



64 



31 



Middle 

 ! Pliocene. 



1 Reuverian 



133 



46 



88 



54 



| Lower 

 Pliocene. 



Pont-de-Gail... 



17 



35 



94 



64 



Base of 













Pliocene. 



i 



