CHAPTER XIII 



THE CURRENT-CONNECTIONS IN THE SOUTHERN HEMISPHERE 



In this chapter are discussed the current- connections between the 

 three great land-masses of the southern hemisphere, South America, 

 Africa, and Australia. The matter is scarcely germane to the subject 

 proper of this work; but, in the light of my own consideration of 

 the problems involved, I will briefly state the results obtained from 

 the bottle-drift data supplied by Schott's memoir and from other 

 sources. 



The Relationship between the Southern Floras. — It is 

 well known that there is a very interesting relationship between the 

 floras of these three widely separated regions, a subject which has 

 occupied the attention of Hooker, Grisebach, Engler, Drude, Schimper, 

 Hemsley, and many others. One of the most important of recent 

 contributions to the literature of the matter, though more concerned 

 with animals than with plants, is Mr. Hedley's paper on the palaeo- 

 geographical relations of Antarctica (Proc. Linn. Soc. Lond., June 

 6, 1912). 



A common source in the northern hemisphere would explain the 

 presence in these land-masses of the south of several of the genera, 

 such as Fagus, Podocarpus, Araucaria, etc. ; and here we are simply 

 assuming that the same principle which has been at work in recent 

 times within the lives of existing species of Sphagnum and Carex 

 (see Chapter XVI.) operated also in past ages. Birds would explain 

 the occurrence of the same species of Accena, Cotula, Nertera, Uncinia, 

 etc., in the extra- tropical portions of these areas ; and currents would 

 account for the existence of the same littoral plants, such as Sophora 

 tetraptera, Convolvulus soldanella, and perhaps Sicyos angulatus, 

 in regions separated by thousands of miles of ocean. It would, 

 however, be in the tropics that the currents would be most effective 

 in accounting for the occurrence of the same species of shore plants 

 on the opposite sides of the oceans. 



The Drift round the Globe in High Southern Latitudes. — 

 Before dealing with the current-connections of the southern hemi- 

 sphere I will refer to one of the most interesting phenomena concerned 

 with the currents of the globe, namely, the drifting round the earth 

 in high southern latitudes of bottles and wreckage. The subject 

 is one that could be treated in great detail. Here, however, it 

 will be only dealt with in an illustrative fashion, and the leading 

 considerations that arise will be presented in a general way, thus 

 introducing the discussion that follows. 



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