202 TJic hish Naturalist. Dccciiibcr. 



the temperature in these latitudes had sunk far below its 

 present level, and then had attain risen. 



Edward Forbes, in 1846, seized this clue, and explained 

 througli it, as relics of the Glacial Period, the arctic plants 

 stranded on (nn mountain-tops; they were i)lants left 

 behind when the climate became too warm for them any 

 longer to survi\-e on the plains. The subsequent discovery 

 of fossil remains of these plants scattered over the plains 

 and often associated with relics of arctic animals now extinct 

 in Britain, seemed a brilliant ])rr)of of Forbes' view, which 

 has been generally adopted. 



In some curious way, howexer, botanists and zoologists 

 both seem to have overlooked the difficulty that, granting 

 Forbes' hypothesis to be sufficient to account for our alpine 

 flora, it rendered more difficult instead of easier the ex- 

 planation of our southern flora, which occurs in a similar 

 way stranded in some of the warmest low-l3dng parts of 

 Britain. 



We meet to-day to discuss this question, in the hojje that 

 botanists, zoologists, and geologists may realise each other's 

 difiiculties, and may be able in combination to give a clear 

 teaching on this important problem of geographical distri- 

 bution. 



The discussion I have been asked to open is limited to the 

 relation of the present Plant Population of the British Isles 

 to the Glacial Period. Our problem is a special one ; it is 

 not the same as that which confronts the botanist on the 

 Continent of Europe or America ; and it is not the problem 

 of the origin of the flora of an oceanic island. Also, the 

 wider question of the origin of the species composing the 

 British flora is outside the discussion, for it would lead us 

 into too many untrodden bypaths, and could not satis- 

 factorily be gone into in the present imperfect state of our 

 knowledge. 



Perhaps it will be well to explain at once why the inquiry 

 is thus limited to comparatively recent periods, and how it 

 is that we need not explore the unknown earlier periods and 

 deal with larger questions. 



Our first inquiry in this case must be : Has there been any 

 continuous occupation of Britain by a temperate flora and 

 fauna from pre-Glacial times to the present day ? Or, to 

 ])ut it in other words : Are any of our plants survivors that 



