SCIENCE-GOSSIP. 



3 



Thus, for example, Lloydia serotina is found on the 

 Alps and Himalayas besides the mountains of 

 North Wales ; and two questions arise : (a) Did 

 glaciation extend over the district between ihe 

 Himalayas and the Arctic regions ? (b) Did it 

 extend over that between the Alps and the Arctic 

 regions ? Probably no one will venture to answer 

 the first question in the affirmative, for the latitude 

 of the Himalayas is 30 , or that of North Africa ; 

 and the evidence that the Asiatic continent was 

 glaciated even north of 6o° has been questioned. 

 It setms a more reasonable supposition that the 

 common species were carried over the intervening 

 lower ground by birds or other agencies, than that 

 there was a Glacial period sufficiently intense to 

 permit Arctic plants to live on the plains in lat. 

 30 . Nor is there evidence that glaciation extended 

 over the area between the Arctic regions and the 

 Alps. If it had been so, a considerable portion 

 of northern France, of Austria, and of Russia 

 down to the shores of the Black Sea, must 

 have been glaciated, and for this there is no 

 evidence. 



What is here remarked of Lloydia serotina applies 

 equally to the greater number of the supposed 

 botanical relics of glacial conditions. Of course 

 the fact that the Glacial period will not account for 

 their existence on the Alps and Himalayas does not 

 prevent it being the cause of their presence in 

 Britain, yet it takes away from their value as 

 independent evidence of glaciation, and suggests 

 the possibility of another explanation. It is, 

 therefore, worth while to inquire whether the 

 occurrence of Arctic plants on our lofty mountains 

 may not be accounted for independently of the 

 Glacial period. A remarkable fact in botanical 

 distribution, not confined to our Arctic plants, is, 

 that similar or identical forms are wont to appear 

 under similar conditions in widely separated and 

 isolated areas. The possibilities of plant distribu- 

 tion are so great that it is not always necessary 

 to bring in the supposition of similar conditions 

 prevailing over the intervening tracts at seme 

 former period. Thus, certain marine plants occur 

 round the brine lakes of Cheshire, but it has not 

 been considered necessary to suppose Cheshire has 

 had communication with the sea in recent times. 

 Again, in the hot springs of the Azores, certain 

 tropical forms of plant life are found, yet we do 

 not assume an extension northwards of tropical 

 conditions to account for their presence. 



In connection with the plants we are considering, 

 the agency of currents may be left out of considera- 

 tion ; for, although they might bring marine and 

 lowland plants to our shores, they could hardly 

 bring Alpine plants to our mountain summits. 

 Bird migration is perhaps the only other means 

 by which it could be accomplished, for this is doubt- 

 less a potent agency in promoting plant distribution. 



B 



Every spring large numbers of birds leave tem- 

 perate regions to breed in Arctic lands. Thence 

 they return the succeeding autumn, and may 

 occasionally or frequently bring, in the soil 

 adhering to their feet, or in their feathers, 

 seeds of Arctic plants. This, then, is possibly 

 the origin of our Alpine flora. In a similar 

 way British plants might be carried to Arctic 

 lands. 



A land connection with the north being held by 

 many to be necessary to bring an Arctic flora to 

 Britain, one with the continent of Europe is con- 

 sidered equally essential to bring back a temperate 

 flora and fauna when the ice age had passed away, 

 on the supposition that these plants had been driven 

 out of the country or exterminated by the cold. 

 The apparent necessity for a land connection by 

 which temperate forms might return is one of the 

 strongest arguments for such a connection. The 

 possibility ought not to be lost sight of that a 

 portion- — perhaps a considerable portion — of our 

 pre-glacial flora was not driven out of the country 

 by glaciation. It must be remembered in what 

 close- proximity at the present day a temperate 

 flora is found to glaciers in Switzerland, the 

 Himalayas and North America ; while in New 

 Zealand glaciers even discharge their debris in the 

 midst of a sub-tropical vegetation. If we suppose 

 that the glaciers, or ice-sheet, extended so far south 

 as the latitude of London, there would still be left 

 an area sufficient to form an asylum for a remnant 

 of the pre-glacial flora. The belief that the ice did 

 extend so far is founded on the assumption that 

 the boulder clay was formed beneath it. The 

 balance of evidence, however, seems rather to 

 indicate that a great part of the boulder clay was 

 formed beyond the limits of the ice. Hence there 

 appears to be some justification for the belief that 

 some part, at least, of our pre-glacial vegetation 

 was not driven out of the country or exterminated. 

 The greater the number of possible survivals, the 

 less the need of a post-glacial land connection with 

 the Continent. 



That little colony of southern plants, isolated 

 from the rest of their kind, in the south-west corner 

 of Ireland also presents an interesting problem in 

 botanical distribution, and its solution is connected 

 with the subject of glaciation. The species in 

 question include Saxifraga umbrosa, Erica mediter- 

 ranea, Arbutus unedo, Pinguicula grandiflora, and 

 others, which are not found elsewhere in the 

 British Islands, and whose nearest habitat in 

 Europe is the North of Spain. When did these 

 plants migrate to their present quarters ? If they 

 did so in post-glacial times, then it would appear 

 that they did not cross England in the way in 

 which the flora and fauna of Ireland is generally 

 supposed to have reached that country ; for in 

 that case we should expect to find them still in the 



