r50 Origin of the British Flora. 



POPULUS CANESCENS, Sm. 

 Interglacial : — 



Grays, Essex ; some leaves collected by Prestvvich 

 suggest this species, though they may belong to P. tremula, 

 The specimens have suffered from long keeping. 



POPULUS TREMULA, L. 

 Neolithic : — 



Caerwys, Flintshire, in calcareous tufa. 



Recorded from Klinge bei Cottbus, in Prussia (Carl 

 Weber); from Honerdingen, in Hanover (Carl Weber); 

 also from the Birch, Pine, Oak, and Spruce Zones in 

 Sweden (Gunnar Andersson). 



Empetrum nigrum, L. 

 Neolithic : — 



Close y Garey, Isle of Man (beds B and C). 

 Late Glacial : — 



Hailes, near Edinburgh (lower bed) ; Dronachy, Fife ; 

 Corstorphine, near Edinburgh (lower bed); Crianlarich 

 Perthshire ; Ballaugh, Isle of Man. 



Interglacial : — 



Airdrie, Lanark. 



Also recorded from Honerdingen, in Hanover, asso- 

 ciated with Platanus, Jugtans, Najas, &c. (Carl Weber). 



Ceratophyllum demersum, L. 

 Neolithic (?) :— 



Casewick, Lincolnshire. 



Late Glacial : — 



Hoxne, Suffolk (bed C). 



