302 THE MIGRATION OF BRITISH BIRDS 



flora of South Africa has been derived by southern 

 emigration from range bases on the highlands and 

 mountains of the equatorial regions, just as Europe has 

 been so invaded by a noi'thern emigration. But the 

 southern movement has to a very great extent been 

 arrested, because South Africa now contains scarcely any 

 area which can fairly be classed as belonging to a Tem- 

 perate zone ; and this fact explains why the floral links 

 with Europe are only of a generic character. On the 

 other hand, nothing arrested the southern extension into 

 Temperate climates in Australia, New Zealand, and 

 South America from common equatorial bases, where the 

 Temperate zone extends almost to the same (if more 

 contracted) limits as it does in the Northern Hemisphere ; 

 and as a natural consequence many of the floral links be- 

 tween Australia and Europe, and even between America 

 and Australia, are of a speeific character. Dr. Wallace 

 asserts that this phenomenon is clearly due to a nortJieni 

 emigration from an Antarctic centre of dispersal, which 

 is obviously erroneous. Were South Africa prolonged 

 at the present time as far south as say S. lat. 50^ so that 

 it could present for occupation an equally extensive 

 South Temperate zone as South America or New Zealand, 

 there can be little doubt that no such differences would 

 exist. The comparatively few (and presumably very 

 ancient) resemblances between the floras of South Africa, 

 Australia, New Zealand, and temperate South America 

 cannot be remnants, as Dr. Wallace suggests, of an 

 ancient vegetation once spread over the Northern 

 Hemisphere, and driven sontJnvards by pressure of more 

 specialized types into these isolated areas, but are relics 

 unquestionably of a dominant flora which started from 



