part 1] 



ARCTIC FLORA OF THE CAM VALLEY. 



11 



(b) The Group of Plants of Wider Distribution, 



In addition to the markedly Arctic or Alpine plants of the 

 preceding group, other fossils were identified with species which 

 have a wider geographical distribution, although their range is 

 more limited towards the north. In the Temperate Zone, these 

 plants are common in lowland situations, but the}^ also flourish on 

 higher ground. The plants identified include species which now 

 characterize such varied habitats as water, marsh, meadow, and 

 heath. They are as follows : — 



E,anunculus Flammula L. 

 Ranunctilus repens L. 

 Ranunculus hulbosus L. 

 Viola 'pcilustris L. 

 Potentilla A7iserina L. 

 Potentilla Tormentilla Neck. 

 MyriopliTjlUim spicatum L. 

 Hippuris vulgaris L. 

 Gentiana cruciata L. 

 Menyanthes trifoliata L. 

 Salix repens L. 



Sparganium simplex Hudson. 



Sparganiuin minimum Fries. 



Potamogetoii heteroplnjllus Sclireber. 



Potamogetoii Zizii Roth. 



Eleocharis palustris E. & S. 



Eleocharis uniglu'inis Link. 



Scirpus lacustris L. (?). 



Cavex arenaria L. (?). 



Carex Goodenovii Gay. 



Carex flava L. 



Carex rostrata Stokes. 



(c) The Soutlieni Element. 



A small number of the Barnwell plants were forms which have 

 an even more restricted northern range at the present time, and 

 these were designated the 'southern element' in the fiora. The 

 majority of them are now found as far north as about 63° lat. 

 N., but in one or two cases they extend only to Denmark or to 

 the extreme south of Scandinavia. This southern element is as 

 follows : — 



Ranunculus Lingua L. 

 Aj^lga reptans L. 

 Carpinus Betulus L. 

 Potamogeton ohtusifolius M. & K. 

 Potamogeton densus L. 



Zannichellia pedunculata Eeicliberg'. 

 Naias marina, var. intermedia 



A. Braun. 

 Carex vulpina L. (?). 

 Carex divisa Hudson. 



It is difiicult to account for the presence of such plants as 

 {Jarpinus JBetulus and Potamogeton densus in association with the 

 Arctic species previously enumerated. But the majority of the 

 ]-lants forming this southern element had seeds too delicate in 

 character to have survived from an earlier deposit ; and, since their 

 preservation was of exactly the same type as that of the Arctic 

 plants from Barnwell, they were probably contemporary with the 

 Arctic species. Perhaps the difference in altitude between the 

 low-lying tract of the plain around Barnwell, and the more elevated 

 ground in the higher reaches of the river, was sufficient to differ- 

 entiate between the conditions in the two areas to such an extent 

 that, while on the Chalk hills the most Arctic species could grow, 

 in the lowlands the southern element could find an habitation. 



