386 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



in the Northern Triassic, and Phyllotheca, which is not a typical 

 member of the true Glossopteris flora, since it is found in the Car- 

 boniferous of Europe and Asia Minor (Heraclea), persisted into the 

 Jurassic of Italy. 



Some students interpret these facts of distribution as indicating 

 that the Paleozoic cosmopolitan floras became extinct at or shortly 

 after the close of that age and that Gondwana Land was the place of 

 origin and the center of radiation of the Mesozoic floras, which, as 

 regards those of the Northern Hemisphere, were hence of southern 

 origin. There is but slight ground for this opinion, which will be 

 referred to subsequently in the account of the Triassic flora. The 

 only additional statement necessary in concluding this brief sketch 

 of the Glossopteris flora is that during the Upper Triassic (Ehaetian) 

 and the Jurassic, at which times the paleobotanical record again 

 becomes reasonably complete, there is not the slightest trace of a 

 northern and a southern floral province such as characterized the 

 Permian, but from Greenland and Spitzbergen on the north to Graham 

 Land on the south, and including Australia, India, Africa, and South 

 America, the whole earth is once again clothed with a cosmopolitan 

 flora as it had been in the Carboniferous, but one which, on the whole, 

 was very different from the latter. 



THE TRIASSIC FLORA. 



The change in the terrestrial floras in passing from the Paleozoic 

 to the Mesozoic is not as great as tradition holds; nevertheless, it 

 is sufficiently marked. Older paleobotanists thought that the Lepi- 

 doclendrons, Sigillarias, Cordaites, Calamites, and the characteristic 

 ferns and seed ferns of the coal measures all became extinct by the 

 end of Permian time. However, few if. any of these types that 

 gave the facies to the late Paleozoic floras, did not have some sur- 

 viving relatives in the Triassic, and, moreover, many of the Paleo- 

 zoic types were obviously on the wane during the Upper Permian, 

 while new types, such as Baiera, Ginkgo, and some of the Cyca- 

 dophytes (Plagiozamites, Pterophyllum, Sphenozamites), praenun- 

 cial of the Mesozoic, had already made their appearance. 



One reason for the sharp contrast between the known Triassic 

 floras and those of the later Paleozoic was the long interval, corre- 

 sponding to the Bunter and Muschelkalk of European Triassic 

 chronology, during which the character of the deposits was pre- 

 vailingly inimical for the preservation of vegetation (coarse aeolian 

 or current bedded sands and saliferous salt pan sediments). It 

 was not until the Upper Triassic (Newark formation of eastern 

 North America, Lettenkohle and Rhaetian of Europe and the other 

 continents) that fossil plants became abundant, and by that time 



