52 Origin of the British Flora. 



at the Roman town, and were certainly contemporaneous 

 with the Roman occupation. 



It is quite possible that more than one Interglacial 

 Period is represented in the deposits and plants that I 

 have examined ; but the classification has been kept pur- 

 posely as simple as possible. It so happens, also, that the 

 most prolific of the Interglacial deposits in the South and 

 East of England all seem to fall into a single period — 

 that immediately succeeding the greatest intensity of the 

 cold. Those that remain have at present yielded so poor 

 a flora, which consists so exclusively of species of wide 

 range, that from a botanical point of view they are of little 

 importance. The botanical characteristics of the different 

 periods may be summarised thus: — 



Preglacial (latest Pliocene). 



Found on the coasts of Norfolk and Suffolk. 



Plants are aquatic and wet-meadow species and forest 

 trees. 



All yet known are now natives of Britain except Trapa 

 natans, Najas minor, and Picea excelsa. 



Associated with many large mammals, the majority of 

 which are now extinct. 



Early Glacial. 

 Found at a few localities on the Norfolk coast. 

 Northern plants, including Salix polaris and Betula 

 nana; no forest trees except Birch and Alder. 



Interglacial. 



Southern and Eastern Counties (Hoxne beds D and E, 

 Hitchin, Grays, Selsey, Stone, West Wittering ; also 

 Deuben, Griinenthal, Klinge, Fahrenkrug, Lauenburg, 

 Honerdingen). 



