INTRODUCTION. 



7 



country is concerned, comparatively a blank. It is true that for long ages we have but the 

 scantiest remains to tell us how vegetation progressed in this area, and the subject, until 

 Tertiary times are reached, from its very meagreness, has offered few attractions to its 

 research. Such materials as have been brought to light have been investigated by 

 Carruthers, who has published in a series of papers as much as there is known respecting 

 British Cretaceous floras. The vast fresh-water deposits of the Wealden, in which, from 

 analogy, we should have expected to find series of plant-remains important in the history 

 of evolution, have yielded little else but Ferns, Cycads, and Conifers. The Neocomian 

 flora appears to have been similar. The marine beds of our Cretaceous rocks have from 

 top to bottom yielded only a few isolated remains of Conifers, which had probably been 

 drifted out to sea. No remains whatever of Dicotyledons have been found in them ; and 

 a few rolled pellets of wood, with a palm-like structure, are the only traces of 

 Monocotyledons which they anywhere present. 



I have elsewhere^ spoken of the immense gap in the geological record which exists in 

 England between our Uppermost Chalk and our Lowest Eocene, completely severing the 

 plant-life of the latter period from all that preceded it. If we turn to other countries 

 we see that this gap is but partially filled up, for it is still doubtful whether any of the 

 foreign Cretaceous beds containing Dicotyledons were contemporaneous even with our 

 Chalk, oar highest member of the scries. 



Erom nearly the commencement of our Eocenes, on the contrary, almost every 

 section has been found to contain more or less extensive series of plant-remains, forming 

 a striking contrast, from their abundance and variety, to the remains found in beds 

 preceding them. Although this has long been familiar to English Botanists and 

 Geologists, the only attempts to describe English Eocene plants, so far as I know, have, 

 with few exceptions, been on a very limited scale. These are hereafter noticed in 

 detail in their stratigraphical and chronological order. 



The nearly unbroken sequence seen in the Eocene floras extends into the Miocene. 

 There is no great break in passing from one to the other when we compare them over 

 many latitudes, and but little change beyond that brought about by altered temperature 

 or migration. But if Tertiary floras of different ages are met with in one area, great 

 changes on the contrary are seen, and these are mainly due to progressive modifications 

 in climate, and to altered distribution of land. Erom Middle Eocene to Miocene the 

 heat imperceptibly diminished. Imperceptibly, too, the tropical members of the flora 

 disappeared ; that is to say, they migrated, for most of their types, I think, actually 

 survive at the present day, many but very slightly altered. Then the sub-tropica^ 

 members decreased, and the temperate forms, never quite absent even in the Middle 

 Eocenes, preponderated. As decreasing temperature drove the tropical forms south, 

 the more northern must have pressed closely upon them. The Northern Eocene, or the 

 temperate floras of that period, must have pushed, from their home in the far north, 



1 ' The Popular Science Eeview,' January, 1879, p. 55. 



