CURRENT-CONNECTIONS IN S. HEMISPHERE 309 



Tropical littoral plants, both strand and estuarine, divide the 

 warm latitudes of the globe into two great regions, the New World 

 region including both sides of America and also West Africa, and 

 the Old World region excluding West Africa and including Poly- 

 nesia. Whilst several beach plants range through both regions, 

 more are restricted to only one. Amongst the mangroves and 

 their associates, the genera Rhizophora, Avicennia and Carapa 

 occur in both regions, but represented by different species; whilst 

 Brugiera and Lumnitzera are confined to that of the Old World 

 and Laguncularia to that of the New World. The contrast between 

 the two regions is best shown in the mangrove flora, and nowhere 

 is this better displayed than on the opposite sides of tropical Africa, 

 all the plants concerned being known to be dispersed by currents. 



Looking at the current- connections between Australia and New 

 Zealand on the one side and South America on the other, we may 

 infer that whereas New Zealand in its relation with South America 

 appears both as a giver and a recipient, Australia would receive 

 South American plants but could make no return. In New Zealand 

 there is a singular reciprocal relation, the northern island receiving 

 littoral plants from Fuegia and the southern island returning shore 

 plants to South America, some nine or ten degrees north of the 

 Straits of Magellan. It is remarkable that concerning the general 

 relations of the faunas and floras of these ocean-parted regions of 

 the southern hemisphere Mr. Hedley arrives at a very similar con- 

 clusion in his discussion of " the community of austral life " given in his 

 paper on the palaeographic relations of Antarctica (Proc. Linn. Soc. 

 Lond., June 1912, p. 88), the chief point of difference being that he 

 considers the transference to have taken place by way of the Ant- 

 arctic continent. " Whereas New Zealand " (thus he writes) " in its 

 relation with South America, via Antarctica, appears both as a giver 

 and a receiver, Australia, on the contrary, seems to have made no 

 return to South America, but to have received all and given nothing." 

 It is not without significance that if the questions of the relations 

 between the faunas and floras of these ocean-parted regions had 

 been entirely one of currents, Mr. Hedley could not have employed 

 different language. 



One may conclude this chapter with the remark that as far as 

 the currents are concerned many of the same principles would 

 apply, with limitations, to the northern hemisphere. Thus we 

 have in the north the same rule, with the same implications, that 

 drift travels east in temperate and west in tropical latitudes. This 

 is abundantly illustrated for the North Atlantic in Chapters III 

 and IV, and it would also be true of the North Pacific Ocean. 



Summary 



1. The matter of the current- connections of the southern hemi- 

 sphere is dealt with here only in so far as it can throw light on the 

 dispersal of seeds in the Southern Ocean, and the operations of 

 the currents are discussed only in so far as they are reflected in the 

 track of the drifting bottle, itself " the resultant effect of all the 



