88 ANNALS NEW YORK ACADEMY OF SCIENCES 



South America can easily be explained by place erosion of the highland 

 pre-Permian floor, by the erosion of the Serra do Mar and its southern 

 spur, Serra Geral, on the east side of the Permian inland basin, and by 

 similar changes of the Serras de Cordova, San Luis and de la Ventana 

 on the west. All these mountains have a general north and south trend, 

 and there is no evidence of an east-west trend in any of this region. The 

 Gondwana formations of Brazil, Africa and India dip as a whole toward 

 the south and west. This has a ready explanation from the location of 

 the Archean and pre-Permian rock, but there appears to be no explana- 

 tion showing how these formations could have been a part of a greater 

 continuous homogeneous Gondwana Land. Its flora being only known 

 from this special type of environment, how did it traverse these obvious 

 Gondwana barriers ? 



Permian and Carboniferous deposits of coal are laid down along the 

 sides of the Andes-Eocky Mountain system which extends into Eurasia 

 and also on the sides of the Appalachian system, and extending through 

 Guiana down the divide along the eastern coast of Brazil. I am not 

 aware of any similar formations extending through the Antarctic islands 

 toward either Australia or Africa. The Antarctic islands appear to bear 

 the same relation to southern South America as do the West Indies to 

 northern South America. They are well separated from both Australia 

 and Africa by great depths of the ocean as well as by many miles of dis- 

 tance. Hence it appears more probable that the Gondwana flora or its 

 ancestral forms would have migrated along lines where the conditions of 

 the environments of Gondwana Land were at least partially duplicated, 

 i. e., where coal was deposited, rather than over about 2,000 or more 

 miles where such conditions probably did not exist. 



The fact that the northern Permian plants had many identical species 

 in the southern hemisphere, that there is considerable difference between 

 the Permian reptiles found in Texas and those of South Africa, as well 

 as the fact that the Gangamopteris flora is found in the late Permian of 

 Russia, is good evidence that both the cosmopolitan and the Ganga- 

 mopteris flora were resistent forms which (or their ancestral stock) could 

 migrate into remote regions with comparative ease. The presence of 

 Cardiocarpon, SpTienopteris, Psaronius, Sigillaria and Lepidodendron in 

 both North America and South America, as well as the presence of the 

 Mississippian flora at Cacheuta, Argentina, indicates an exchange of 

 plants between North and South America. Some of these plants (Lepi- 

 dodendron) are not yet positively known in South Africa. The cosmo- 

 politan flora is also known from Europe and other parts of the eastern 

 hemisphere, and it is remarkable that this flora could not only become so 



