336 DAVID WHITE 
changes in the western American areas, which are more pronounced 
than in the Appalachian trough, may be due either to changed physical 
conditions consequent to nearer and greater orogenic movements, or 
possibly to position nearer to the region of Gondwana glaciation. In 
our trans-Mississippi region the contrast between the Permian and 
Stephanian floras does not seem so sharp as that between the Ural 
flora and those, for example, of the fresh-water basins of France or 
England. 
Greater contrasts in eastern Europe.—In France and in the Appa- 
lachian trough the early Permian floras are to a large extent identical, 
thus indicating continued freedom of intercourse. Also the woods 
present obscure rings or none atall. But in Kansas and Texas annual 
rings while still but slight are increasing in distinctness though many 
of the associated plants have a European distribution. 
The plant fragments from the Permian of Nova Zembla are quite 
too insufficient to support the hypothesis of a far-northern route of 
intercontinental migration, or even to show that the climate of 
western Europe extended so far north. 
Ural Mountains on western edge oj a great climatic zone.—Indeed, 
on the contrary, the great scarcity of true Neuropterid and Pecop- 
terid elements, the great development of Psygmophyllum, and the 
remarkable phases of Callipteris observed even in the Artinsk of the 
Ural region indicate, in my judgment, either temporary isolation or 
an appreciable difference in climatic conditions. At the same time 
the somewhat unique forms of Odontopteris are not without repre- 
sentation both on the central plateau of France and in the Wichita 
of Texas. ‘This testimony of migration is supported by the supposed 
land relations, which, if Lapparent is correct, should have been 
particularly favorable for such a migration during portions of Per- 
mian time. 
Extension oj Gondwana flora into northern Asia.—Eastward of the 
Ural Mountains the floras of the Altai and headwaters of the Yenesei 
and in northern Mongolia, though provisionally referred to the Per- 
mian on account of the presence of Rhipidopsis, mingled with other 
types, including some of Gondwana facies, are possibly wholly lack- 
ing in specific types characteristic of the Cosmopolitan Western 
Permian. ‘Though the stage of these plant beds is not yet fixed on 
