INTRODUCTION. 



3 



displaced by the American flora. If so, the floras without Proteacece may, in the absence 

 of other evidence, be looked upon as the more ancient ; and we should fix, in some 

 measure, the date of the arrival of that Australian element whose presence in Europe, 

 when discovered and described, caused so much surprise. 



The flora of the London Clay, unlike that of other stages, which are represented by 

 leaves principally, is known from seeds and fruits. I am indisposed at present to 

 speculate upon its affinities, since there is a possibility of obtaining leaves from the 

 Basement Bed. I will merely say that fruits belonging to the same genera, but specifically 

 different, are found in the Middle Bacjshot Beds, and that Heer believes the Sheppey 

 fruits and the Alum- Bay leaves belong to the same plants. 



The Alum-Bay flora, of Loioer Bayshot age, has been so well explored that it is 

 rare, even after long work, to discover any form in it that is new. It abounds with 

 what are generally accepted as Proteaceous leaves, and yet these are mingled with larger 

 leaves of Pigs, Laurels, Leguminous plants, and the lobed leaves of Aralias, Maples, &c., 

 representing a luxuriant flora which did not grow on sterile ground, or in a very dry 

 climate. It is a good example of the Australian type of an Eocene flora, and is most 

 distinct in England from those above and below it. 



The newer Botirnemouth flora, assigned in this work to the Middle Bagshot stage, 

 appears to be separated from the last by a great interval of time, for the flora seems 

 almost wholly American, and, singular to say, the small Pliocene flora of California, 

 described by Lesquereux, more resembles it generically, though the species are different, 

 than does any other knowai to me. In it the Proteacece are replaced by the American 

 Mpicacece, and it seems to contain a number of existing American genera not previously 

 recognised among fossils. 



If these tentative speculations, founded at present on somewhat superficial know- 

 ledge, have any basis of truth, they would show that it was between the Lower and 

 Middle Bagshot periods that North America and Europe were connected by land. The 

 floras of the Upper Eocene merge gradually, without further striking change, into those 

 of the Miocene, whose story has been so often and so ably traced by Ileer. 



Although all these floras are here spoken of as strikingly disconnected, it must not 

 be supposed they are absolutely so ; on the contrary, not a few forms are common to 

 many, and some may be found in all of them. 



As the British Eocene floras become better known through the progress of our work 

 these speculations may receive confirmation or be altogether set aside. I have, however, 

 ventured to put them forward, as they may invest the study with an interest beyond 

 that which the mere description and determination of the Plants alone would possess. 



The singularly little attention as yet bestowed upon this subject in England has been 

 doubtless primarily due to the difficulty in satisfactorily determining the fossils. These 

 floras, mainly composed of detached dicotyledonous leaves, present such exceptional 

 difficulties that even when very great thought and care have been bestowed upon the 



