ANTARCTIC ZOOGEOGRAPHY 363 



ganisms have disappeared from intertropical regions through evolu- 

 tional transformation rather than extinction, but neither Theel nor 

 other recent workers discuss this point. Until it has been squarely 

 met, however, may not the data serve equally well to support the 

 converse theory of a universal cold sea in earlier geologic times, with 

 subsequent elimination of certain types from the intervening areas 

 as they became warm? 



In considering bipolarity in its historical aspect, care must be 

 taken to distinguish the original restricted meaning of the term 

 from various usages which have given it distinct though related sig- 

 nificance. Heintze^^, for instance, explains the "bipolarity" of many 

 species of plants through entozoic carriage of seeds by shore birds 

 (Limicolae) at the culmination of the last Ice Age. Similar methods 

 of approach might conceivably give a clue to some of the existing 

 problems in the sea. 



Terrestrial Biota 



The fauna and flora of the true Antarctic and adjacent regions 

 being mostly littoral or oceanic, with a minimum of terrestrial ele- 

 ments, it will be advisable to begin our discussion with the latter. 



PLANTS 



On one part of the continent only, and on islands near by, there 

 are two kinds of flowering plants, namely a grass and a Colobanthus, 

 both Fuegian species. North of the Arctic Circle, it should be re- 

 membered by way of comparison, some four hundred species of vas- 

 cular plants grow. On the very restricted exposed land surfaces of 

 the Antarctic Continent there are patches of cryptogamic vegetation 

 comprising mosses, lichens, and fungi. These, with a few fresh-water 

 algae and certain microphytes which flourish only In snow and ice, 

 make up the entire flora. Among the 63 south polar mosses, 27 species, 

 or 43 per cent, including one genus, are found nowhere else — a high 

 percentage of endemism. The present paucity of vegetation is doubt- 

 less postglacial. At any rate, a rich flora which resembled in many 

 respects that of modern New Zealand, Australia, and southern South 

 America once flourished. Fossil floras of both Jurassic and late Cre- 

 taceous or early Tertiary age, and including such trees as Sequoia, 

 Araucaria, and Fagus, are known from West Antarctica. It has been 

 suggested that from this region as a center many plants and animals 

 once extended their ranges into more northerly zones. 



Schenck-* emphasizes the fact that Antarctic plants can vegetate 



23 A. Heintze: Om bipolara vaxter och deras vandringar. Fauna och Flora, Vol. 13, 1918, pp. 145- 

 161. 



24 Heinrich Schenck: Vergleichende Darstellung der Pflanzengeographie der subantarktischen 

 Inseln (Wissenschaftliche Ergebnisse Deutsch. Tiefsee-Expedition, Vol. 2, Part I, pp. 1-178), Berlin, 

 1905; Flora der Antarktis, pp. 169-178. 



