306 PLANTS, SEEDS, AND CURRENTS 



Plants. — Seed- drift travels west in tropical latitudes and east in 

 temperate latitudes, from which it follows that whilst in the temperate 

 latitudes of the southern hemisphere we look to the west for the 

 source of the littoral and estuarine plants that are dispersed by- 

 currents, in the tropics we look to the east. On account of the 

 usual slant of the trans-oceanic traverses of the drifting bottles 

 there is, however, generally a marked shifting of the latitude either 

 to the north or to the south. But, apart from this, the general 

 effect would be that in the tropics we should look for West African 

 affinities on the eastern shores of South America, for South American 

 affinities on the coasts of Malaya and Australia, and for Malayan 

 and Australian affinities in East Africa. So also in temperate 

 latitudes we should look for South American relations in South 

 Africa, Australia, and New Zealand; for South African affinities 

 in Australia ; and for Australian and New Zealand relations in South 

 America. 



Although the general principle, just enunciated, still applies, 

 some important modifications are necessitated on account of the 

 usual northward and southward slant of the currents, as evidenced 

 by bottle- drift. Except within the narrow limits of the equatorial 

 Atlantic the shifting in the latitude generally amounts to several 

 degrees. We have seen that Fuegian drift when it reaches Australia 

 has diminished its latitude by about twenty degrees. On the other 

 hand, New Zealand drift when crossing the Pacific to South America 

 is deflected only four or five degrees to the north. Bottles from off 

 the equatorial coasts of South America would strike the shores of 

 North-east Australia a dozen degrees farther south. This southerly 

 slant of drift in the South Equatorial Current is continued right 

 cross the Pacific, and may be even greater than is just indicated. A 

 bottle thrown into the sea on the 10th parallel of south latitude in 

 the meridian of the Galapagos Islands would be stranded on the 

 east coast of Australia on about the 30th parallel of latitude. The 

 effect of this slant, as already shown, is the throwing back of East 

 Australian drift on the shores of that island continent, so that 

 Australia is in this manner unable to contribute drift to South 

 America. The only drift that could reach South America from these 

 longitudes would be from higher latitudes, namely, from the southern 

 end of New Zealand and the Antarctic islands to the southward. 



In the southern tropics of the Indian Ocean drift carried along 

 in the South-east Trade or South Equatorial Current is inclined 

 to the north, so that bottles dropped into the sea about the 

 16th parallel of south latitude between Java and North-west Australia 

 would be beached on the East African coast under the equator. 

 It is remarkable, as shown by the tracks of bottles laid down in 

 Schott's Chart 5, that drift from the southern extreme of Africa, 

 which is carried by the Agulhas Current into the West Wind Current, 

 is transported across the Indian Ocean without much change of 

 latitude, being ultimately thrown up on the south coasts of Australia. 



In applying, therefore, to the southern hemisphere the principle 

 that in the case of littoral and other plants dispersed by currents we 

 should in temperate latitudes look to the west for their source and 



