PALEOBOTAXICAL EVIDENCE 515 



is further shown by the fact that certain types characteristic of th-3 

 northern province, such as Lepodendron, Lepidophlois, Sphenophyllum, 

 etcetera, had penetrated the southern province, and Gangamopteris and 

 Glossopteris had been able to reach the northern province in northern 

 Russia. 



White/^ writing of these conditions, says: 



'•The conditions which brought the new flora into being banished or exter- 

 minated the cosmopolitan or northern Permo-Carboniferous flora from the 

 Gangamopteris province. The early return of a few of the hardier lycopodia- 

 ceous forms in Argentina, Brazil, and South Africa has already been men- 

 tioned. Most of the former plant population of the province died in exile, and 

 only their posterity, especially among the Cladophleboid forms and the Arau- 

 carian, Ginkgodean, and Cycadalean gymnosperms were able to traverse the 

 lost territory and contest the Gangamopteris occupation." 



Triassic floras. — Eocks of Triassic age are known in many parts O: 

 the w^orld and indicate tw^o types of deposition, a fresh-water, marsh, or 

 lagoon phase and a marine phase, the latter being by far the most exten- 

 sive, which accounts for the meagerness of the flora. Owing to various 

 considerations, physical and otherwise, concerning which there is not 

 complete agreement, the lower portions of the Triassic afford but scanty 

 plant remains, and it is not until we come to the upper portion, ur 

 Ehsetic, tliat it can really be dignified as a flora. Our American Triassic 

 is thought to bel'ong largely to this portion. 



, The known plants of the Triassic are relatively few in number. In 

 Xorth America there are less than 150 species known, and the wholo 

 Triassic flora that has been recovered hardly exceeds 400 forms. The 

 principal Xorth American areas are in Xortli Carolina, Virginia, and 

 Pennsylvania, with relatively few in Maryland, Xew Jersey, Connecticut, 

 and Massachusetts. In the West we have a doubtful plant or tw^o from 

 Wyoming, a considerable number from 'New Mexico, and the extensive 

 fossil forests of Arizona. To the southw^ard we have small collections 

 from Sonora, from about the City of Mexico, and in the State of Oaxaca, 

 also in Honduras, Chile, and western Argentina. In other parts of the 

 world Triassic plants have been found in England, the east coast of 

 Greenland and various islands in the Arctic Ocean, Spitzbergen, north 

 Germany, southern Sweden, Italy, southwestern Spain, Persia, India, 

 China, Tonkin, Japan, N"ew South Wales, Xew Zealand, and Souti 

 Africa. Many identical or closely related species are widely distributed. 



The dominant plant types of the Paleozoic have largely disappeared. 



10 David White : Jour. Geology, yoI. 15, 1907, p. 628. 



