134 



The Naturalist. 



eocene fern-flora, three sub-orders out of the eight are absent, Cyath- 

 eaceas, Hymenophyllaceae, and Ophioglossacese. In Polypodiacese there 

 are ten species, all apparently belonging to genera now known, Jdiantum, 

 Pteris, Woodivardia, Polypodium, and Acrodicliim. There seems every 

 reason to believe that the eocene AcrosticJmm is identical with Anros- 

 ticJium aureum, one of the the commonest tropical marsh-ferns of the 

 present day, both in the old and new world. Gleicheniacese is represented 

 in the British eocenes by a single unmistakeable species. At the 

 present day there are eighty species of this sub-order, widely spread in 

 the tropical and south temperate zones, and two of them extending 

 into temperate Asia. Of the sub-order Osmundaceae, there are two 

 species in the eocene beds, one of them apparently identical with 0. 

 regalis, and the other with O.javanica, a species confined at the present 

 time to tropical and temperate Asia. Of Schizseaceae there are two 

 species of two genera, and of Marattiaceae one species in the British 

 eocene beds. Not long ago I asked one of our most experienced 

 paleontologists to tell me, in general terms, what point of knowledge 

 had been reached in the investigation of these early tertiary beds, and 

 he estimated the number of their generic types, now known, at five 

 hundred, of which four hundred are still in existence ; and of species, 

 at two thousand, of which, perhaps, fifty are still in existence. I 

 suppose no competent authority would estimate the lapse of time 

 between the close of the miocene period and the present day at less 

 than five hundred thousand years. The most curious point about these 

 rich tertiary floras is that there seems, broadly speaking, to be no 

 geographical diff'ereij tiation in them. In Greenland or Austria, or in 

 our own island, at Bournemouth, or in the London basin, they appear 

 to contain substantially the same types. It is likely that in the next 

 twenty years we shall reap a rich harvest from paleontological work. 



Upon the general question of evolution, an important light is thrown 

 by studying the flora of Britain in comparison with that of Continental 

 Europe. The most important general character of the British flora is 

 its utter want of any distinctive individuality. Leaving out of count a 

 few doubtful Hieracia, WiUows, Rubi and Roses, I can give only two 

 good instances of British plants that do not occur in Continental 

 Europe. One of these, Potamogeton lanceolat'us, is known in Cam- 

 bridgeshire, Anglesea, and the north of Ireland ; the other, Eriocaulon 

 septan gulare, is found in Skye and Galway ; and, across the Atlantic, 

 it is widely spread in North America. It is now generally believed 

 that Britain was last separated from the Continent towards the close 

 of the glacial period. I do not think any competent authority would 



