238 THE SUPPOSED TERTIARY ANTARCTIC CONTINENT. 



Embothrium and three other genera in South America ; but though they reach in the 

 Old World as far north as Abyssinia, no representative crosses the northern tropic. 

 Mutisiacece, a remarkable tribe of Composite, reach Japan and California but are 

 characteristically southern, with headquarters in South America; Oldenburgia 

 represents them in South Africa and Trichocline in Australia. Restiacece, closely 

 related to the ubiquitous sedges, are equally localized in South Africa and Aus 



tralia with a single South American representative, a Leptocarpus , in Chile 



Perhaps the most striking case of all is Ravenala with only two species, one in 



Madagascar, the other in Brazil. 



In the face of these and other facts it is not to be wondered at that many 

 botanists have, like Darwin, thought "that there must have existed a Tertiary 

 Antarctic Continent from which various forms radiated to the southern extremi- 

 ties of our present continents" (Life and Letters, III, 231). 



But if such a continent ever existed it may be equally contended that it did 

 so at a much earlier age, for the gradual investigation of the Glossopteris flora 

 reveals the same facts as regards its distribution as are shown by flowering plants 

 in the Southern Hemisphere at the present time ; it has been detected in fact in 

 Brazil, in South Africa, in Southern Australia and in the Indian Peninsula. 

 Gadow therefore postulates the existence of a "great Permo-carboniferous 

 Gondwana land in its fullest imaginary extent, an enormous equatorial and 

 south temperate belt from South America to Africa, South India and Australia, 

 which seems to have provided the foundation of the present southern continents, 

 two of which temporarily joined Antarctica' ' (Darwin and Modern Science, 



p. 334). 



Wallace has stated forcibly the arguments against the vast changes in the 

 surface of the earth which the elevation and submergence of such an area involves. 

 For the distribution of land and water is antipodal in the two hemispheres, and 

 it may be concluded that elevation in the one would be compensated by sub- 

 mergence in the other, and of this there appears to be no evidence. On the other 

 hand the researches of the Challenger Expedition have shown that the oceanic 

 depths are covered by oozes which bear no resemblance to any rocks composing 

 existent land masses. And Geikie concludes "that the present land of the globe, 

 though consisting in great measure of marine formations, has never lain under 

 the deep sea." Each successive line of argument adds additional force to Dana s 

 original position and leaves the botanist still in search of a solution of his problem. 

 It is to be noted that Hooker gradually abandoned his belief in continental 

 extensions which he described in 1879 as " the forlorn hope of the botanical geog- 

 rapher . ' ' 



A problem of exactly the same kind presents itself to the zoologist. Mar- 

 supials exist in America as well as Australia and tapirs are found in Malaya an 

 tropical America. But fossil remains prove that these dissevered habitats are 

 but the isolated survivals of a former wide extension in the northern hemisphere. 

 If then the explanation is to be found in a common source of origin in the case 



