84 PLANT GEOGRAPHY 



extensive basalt-flows of early Tertiary (Eocene or 

 Oligocene) date. This bridge seems to have been covered 

 with forest, leaves of many trees, including Sequoia, 

 Taxodium, Platanus, Sassafras, Nyssa, and Magnolia 

 being preserved in associated beds of lignite and tuff. 



AFRO-SOUTH-AMERICAN BRIDGE. Whilst the great 

 Permo-Carboniferous land-girdle known as Gondwana- 

 land extended from Eastern Brazil southwards to the 

 Falkland Islands, and apparently eastward to Guinea 

 and northern Cape Colony, and so to the Deccan and 

 Australia, it is supposed "to have been interrupted in 

 Jurassic times by subsidence in the Indian Ocean region, 

 and also to have been narrowed by the encroachment of 

 the South Atlantic in the Cretaceous period. A bridge, 

 for which the name " Arch-Helenis " has been proposed, 

 extending eastward from between the mouths of the 

 Amazon and the La Plata, is believed to have lasted into 

 Eocene times. Such a continuous tract of land or chain 

 of large islands in Tertiary times, especially in con- 

 junction with a similar connection between Natal and 

 Madagascar and by way of the Seychelles with India, 

 would elucidate much of the distribution of the tropical 

 flora. 



ANTARCTIC AND AUSTRALASIAN CONNECTIONS. In- 

 teresting problems of distribution are connected with 

 the probable greater extension in previous times of the 

 Antarctic Continent and the existence of land-connec- 

 tions between it and the other southern continental 

 areas. The Antarctic land appears to be continuous, 

 and is about twice the area of Europe, but is at present 

 so completely ice-bound as to be all but destitute of 

 vegetable life and of little apparent interest to the 

 biologist. The ocean surrounding it is in general deep, 

 but appears to present slight shallowings in the direction 

 of the three main southern continental land-masses. 

 While the plants of South Africa are only ordinally 

 related to those of Australia, -as by the Pvoteacece, the 

 connection between America and Australasia is more 

 intimate. The order Proteacece, which is, perhaps, a 

 very early group of Angiosperms geologically speaking, 

 is represented in Chile and Fuegia, is abundant in South 

 Africa, is found in New Zealand and New Caledonia, 

 and has numerous species in Australia restricted either 

 to the eastern or western half of the continent. Such 



