From this it can be observed that the principal element is the 

 Caribbean one, but that whilst generally much of the remaining 

 flora is warm temperate or sub-tropical, nevertheless there are 

 some cold temperate species. Further work in other parts of the 

 world should lead in the future to additional interesting results. 



The peculiar distribution of certain algae in the southern hemi- 

 sphere has prompted the author (1952) to comment upon it in rela- 

 tion to Wegener's theory of Continental Drift. The presence of 

 Macrocystis, Splachnidtum, Ecklonia and Ballia in South Africa, 

 widely distant from both Australia or South America, could con- 

 veniendy be explained if at one time all three countries were part, 

 with the Antarctic Continent, of a great southern continent which 

 later broke up. If the permanence of the present land masses and 

 oceans is accepted instead, then it must be assumed that fertile 

 fragments of these algae must have drifted to South Africa, pre- 

 sumably from South America via the Antarctic current. Portions of 

 algae can be found floating in the ocean, though whether fertile 

 fragments could survive such a long journey may be open to ques- 

 tion. At all events the distribution is one of very great interest. 



Another feature that is perhaps most conveniently considered 

 here is that of seasonal alternation of generations and of seasonal 

 dimorphism. Feldmann (1937) has studied this particularly in the 

 Mediterranean. In Ceramium corticatulum the tetrasporic plants 

 exist only at the end of autumn or in the winter whilst the sexual 

 plants are to be found at the end of summer. This is an example of 

 seasonal alternation of generations in which there are ephemeral 

 summer haploid plants with the diploid plants occurring during 

 the winter and persisting over a longer period. Seasonal dimorph- 

 ism is exhibited in the Mediterranean by Cutleria multifida and C. 

 monoica with their sporophytes Aglaozonia parvula and A . chilosa. 

 The two species are almost indistinguishable morphologically, but 

 the former occurs in spring in shallow waters off*-shore whilst the 

 latter occurs in summer at greater depths. Another example of 



