480 



ISLAND LIFE. 



[part II. 



identical with European species. These islands are more than 

 800 miles from Europe, and, as we have already seen in Chapter 

 XII., there is no reason for supposing that they have ever been 

 more nearly connected with it than they are now, since an exten- 

 sion of the European coast to the 1,000-fathom line would very 

 little reduce the distance. Now it is a most interesting and 

 suggestive fact that more than half the European genera which 

 occur in the Australian flora occur also in the Azores, and in 

 several cases even the species are identical in both.^ The im- 

 portance of such a case as this cannot be exaggerated, because 

 it affords a demonstration of the power of the very plants in 

 question to pass over wide areas of sea, some no doubt wholly 

 through the air, carried by storms in the same way as the 

 European birds and insects which annually reach the Azores, 

 others by floating on the waters, or by a combination of the two 

 methods ; while some may have been carried by aquatic birds, to 

 whose feathers many seeds have the power of attaching them- 

 selves. We have in such facts as these a complete disproof of 

 the necessity for those great changes of sea and land which are 

 continually appealed to by those who think land-connection the 

 only efficient means of accounting for the migration of animals 

 or plants ; but at the same time we do not neglect to make the 

 fullest use of such moderate changes as all the evidence at our 

 command leads us to believe have actually occurred, and 

 especially of the former existence of intermediate islands, so 

 often indicated by shoals in the midst of the deepest oceans. 



Means hy which Plants have migrated from North to South. — 

 But if plants can thus pass in considerable numbers and variety 

 over wide seas and oceans, it must be yet more easy for them to 

 traverse continuous areas of land, wherever mountain-chains 

 offer suitable stations at moderate intervals on which they might 

 temporarily establish themselves. The facilities afforded for 

 the transmission of plants by mountains has hardly received 

 sufficient attention. The numerous land-slips, the fresh sur- 

 faces of broken rock and precipice, the dihris of torrents, and 

 the moraines deposited by glaciers, afford numerous unoccupied 



1 Hooker, On the Flora of Australia, p. 95. — H. C. Watson, in Godman's 

 Azores, pp. 278-286. 



