i8 Plant-life of the Oxford District 



CarpinuS) Corylus^ Acer campestre^ Crataegtis, Pyrus Aria ; minor wood- 

 land-forms, as Cornus sanguinea^ Rubus fruticosus ; familiar herbaceous 

 types, as Ranunculus repens, Heracleum, Lapsana communis^ Solamim Dul- 

 camara ; aquatics, as CaWia, Hippuris> Hydrocotyle, Bidens tripartita, Men- 

 yanthes trffoliata^ Mentha aquatica, Lycopus^ Sparganium, Potamogeton, 

 Phragmites communis and Osmunda? 



The advancing waves of cold of the Pleistocene, commonly fore- 

 shortened to our perception as a ' Glacial Epoch ', culminated in an ice- 

 sheet over practically the entire country ; and the British Isles, together 

 with Northern and Central Europe, passed into a condition which has been 

 compared with that of Greenland and Spitzbergen at the present day. 

 A vast ice-sheet covered the mountains of Scandinavia ; the North Sea was 

 frozen, and glaciation extended as far south as the Thames Valley, entirely 

 blotting out the flora of the northern parts of Great Britain, except for 

 the possibility of the survival of a few residual Arctic types on isolated 

 hills, and attempts at a residual vegetation in the non-glaciated strip, south 

 of the Thames, over a short summer-season, much in the manner of the 

 flora of Spitzbergen at the present day. The subtropical vegetation of the 

 Tertiary Epoch wholly disappeared, and the mean temperature must have 

 been near the freezing-point most of the year. Arctic Willows have been 

 traced in Devonshire ; while the extension of winter ice-sheets is shown by the 

 erratic boulders floated as far as the Isle of Wight, and even across to France. 

 As the Oxford district is just beyond the southern limit of known glacia- 

 tion, it is evident that the whole of the modern flora must have been immi- 

 grant since the time of maximum cold, however mild and temperate may 

 have been any long-continued * Interglacial Periods '. 2 



The revival of the temperature similarly implies long-continued oscilla- 

 tion phases, just as does the advance of a modern spring on a smaller scale, 

 and the so-called Palaeolithic epoch commences with the first traces of man 

 and his stone-implements. The country was gradually re-afforested ; the 

 flora as we know it was introduced from the adjacent continent ; large 

 mammals as the Mammoth and Woolly Rhinoceros followed ; and with 

 them came primaeval hunters living on fish, wild fowl, and anything avail- 

 able. 3 



No trace is left in the Oxford district of such times ; the older strata 

 are worn down to the level of the Oxford Clay, and superjacent strata are 

 only left in patches, constituting the hills around the City. Much of these 

 may have been denuded before the deposition of the Upper Cretaceous. 

 The present modelling of the country is largely Post-Glacial, and has been 

 effected by water-erosion ; though to a certain extent the direction of the 



1 C. Reid (1899), loc. cit, for complete schedule, p. 171. The flora was at this time dominant; 

 and man, if actually existing in this land at that time, had no effect on the vegetation : ' He was 

 only one more carnivorous animal added to a fauna which already possessed several quite as dangerous, 

 and apparently occurring in greater numbers ', loc. cit., p. 38. 



2 C. Reid (1899), loc. cit., p. 171, for schedule of Interglacial plants. 



As vestiges of permanent glacial ice still remain at 3,600 ft. on the Cairngorm Mts., at a 

 distance of 400 miles from the Thames Valley, it might be supposed that the extension of the ice- 

 sheet this distance farther south was really only a minor climatic phenomenon in the history of 

 N. Europe. Much of the difficulty of the Glacial Epoch appears exaggerated when seen fore- 

 shortened, and changes in proportions of sea and land with diversion of oceanic currents, as the Gulf 

 Stream, might bring on a similar condition of things. Spitzbergen enjoyed a subtropical climate 

 with fauna and flora to correspond in the Miocene. 



Cf. Brooks (1921), Nature, Sept., p. 90. 



3 The heroic primal hunter chasing the Mammoth with a flint axe is probably a myth. The 

 first immigrants were undoubtedly a squalid race, the outcasts of the old world, with little knowledge 

 beyond that of fire, flint, and sticks. At any rate man in N. Europe was already indefinitely old, and 

 his tropical origin forgotten. Confusing decadent races, since apparently ' simple ', with the actual 

 stages of up-grade evolution, is sufficiently familiar in Botany, and is common to other biological 



