UPPER PAEEOZOIC FLORAS 333 
flora, has arisen in the wake of retreating ice, though it is not really 
a glacial flora. It probably originated in a great region, the “ Gond- 
wana land” of Suess, from which the Stephanian flora had been more 
or less completely expelled by the rigorous climate, and to which it 
had not yet been able to return, presumably on account of either 
temperature or isolation. 
The dominant characteristic types are Gangamopteris, Glossop- 
teris, and its rhizome Vertebraria, Neuropteridium, Noeggerathiopsis, 
Phyllotheca, Schizoneura, Ottokaria, and Derbyopsis. The distri- 
bution and the relations of this flora to the Northern or Cosmopolitan 
flora have already been discussed in this journal.t The geographical 
extension of this flora in Paleozoic time, as also the distribution of the 
northern or cosmopolitan Permian flora, are shown on the Permian 
map, Fig. 2. 
Distribution—The uniformity of the Gangamopteris flora is so 
nearly complete as emphatically to indicate freedom of migration 
between all the areas in which it dominated; but whether Australia 
communicated with South Africa by way of India and Arabia, or by 
connection through an Antarctic land mass is a matter of opinion. 
The former is perhaps more probable. South America was almost 
certainly made accessible either to Africa or Australia by route 
over Antarctic land. 
Gondwana climate-—The Gondwana climate following the glacia- 
tion was not too severe for the early return at distant points of a few 
of the presumably hardiest representatives of Psaronius, Sigillaria, 
Lepidophloios, and Lepidodendron, and at a higher stage, Voltzia 
Psygomophyllum, and Pterophyllum, both in Africa and South 
America. The early return of a climate not so widely different from 
that of the western Permian is further shown by the fact that though 
the early Gondwana woods found in beds more or less closely asso- 
ciated with the bowlder beds in Australia and South Africa show 
annual rings indicative of sharp seasonal changes, the woods from the — 
higher portion of the series in South America ‘show nearly continuous 
growth with but slight trace of seasonal differences. 
Ability of types to mingle in later Permian and early Mesozoic 
environments.—This amelioration of temperature harmonizes, firstly, 
t Jour. Geol., Vol. XV (1907), p. 615. 
