3 



BRITISH EOCENE FLORA. 



Beginning witli the Woohoich and Heading Beds, we have a flora, very limited in 

 extent, and consisting of a few, but apparently persistent types, which have a temperate 

 facies. It would be interesting if this could be proved to be a fragment of a flora 

 descended from the oldest indigenous dicotyledonous flora of the European or Eastern- 

 Atlantic area, before the Eocene temperature had been raised by causes about which I 

 have elsewhere hazarded some speculations.^ 



The next British Eocene flora, second in age and supposed to belong to the 

 Oldhaven Beds, has quite another character, as far as we can judge from the present 

 materials. A small collection only has l)een made ; but, by systematic work, results may 

 be looked for not surpassed by those obtained at Bournemouth. These materials seem 

 to indicate a relation to the Eocene floras of Sezanne. The same types, and the same 

 luxuriant preponderance of serrate dicotyledonous leaves, are characteristic of both. It 

 would almost seem that we have here another really indigenous, but somewhat more 

 sub-tropical, European flora, without the Australian or American types, which later on 

 so very considerably modified it. 



In America we have, though possibly belonging to a far removed age, just such another 

 purely indigenous flora in the so-called Cretaceous BaJcota Beds. These floras, which 

 are perfectly distinct from each other, seem to belong to a period antecedent to the 

 connection of Europe and America, although the rise of . the afterwards connecting 

 land was probably, I think, even then gradually raising the temperature by shutting 

 off more and more completely the Arctic currents from the Atlantic, As at Sezanne, 

 there appears to be an absence of those Australian forms, especially the Proteacea, 

 which became so abundant at a later Eocene time. Saporta shows that in the so-called 

 Cretaceous and Eocene European floras, wherever European types are present, the 

 Australian element, or, at least, the Proteacea, are almost excluded, and that the 

 reverse is equally the case." But the presence or absence of Australian forms is known 

 in so many localities where they occur, in an apparently arbitrary manner, which cannot 

 be accounted for either by diff'erence of soil or climate, that the thought arises whether 

 it may not be possible that the relative ages of the isolated floras on the Continent have 

 been wrongly inferred. Instead of appearing and disappearing frequently, did not the 

 members of the Australian flora, like those of the American at a later date, come in, in 

 the way newly introduced species are now seen to do when climatic conditions are 

 favorable ? The Australian type of plants had a great and sudden extension until 

 1 'Nature,' December 12tli, 1878, p. 124. 



- With regard to Sezanne, however, it may be urged that there are reasons wliy leaves of Proteaceae 

 should not be found. The flora is evidently that of a shady, moist, and luxuriantly woody valley. The 

 leaves are found in a tufaceous matrix, and must have fallen from overhanging trees and adhered to the 

 sides of a ravine, wet, probably, with ihe spray of an adjacent waterfall charged with carbonate of lime. 

 Under such conditions travertine rocks are formed rapidly and enclose masses of leaves, as we see at Tivoli, 

 for instance, at the present day. It is, perhaps, unlikely, therefore, that Proteacece, which generally have 

 a dry habitat, even if abounding contemporaneously, would be preserved under such circumstances. 



