'2 INIEODUCTIOSr. 



Although an account of Triassic vegetation based on data 

 furnished by extra-British strata -would be out of place in the 

 present volume, it is important that brief reference should be 

 made to the nature of the floras immediately preceding those of 

 Ehaetic and Jurassic age. The object of a detailed description of 

 the Jurassic plants of Britain is not merely to supply information 

 as to the composition of local floras, but to furnish facts -which 

 may be of service in the consideration of questions of -wider 

 application. 



The general character of the vegetation during the Coal period 

 appears to have persisted into the Permian epoch -without any 

 s-weeping change. Over a considerable portion of the northern 

 hemisphere the Upper Palseozoic vegetation -was characterised by 

 a striking uniformity ; an assemblage of plants of similar facies 

 occupied a wide area in China, and traces of the same northern 

 flora have been found as far south as the Zambesi district of 

 Africa.^ On the other hand, the Permo-Carboniferous forests, 

 of -which scattered remnants are preserved in India, South 

 America, South Africa, and Australia, must have presented a 

 very different appearance, due for the most part to the almost 

 complete absence of Calamites, Zepidodendron, Sigillaria, and 

 other common types of the great northern flora. The southern or 

 Glossopteris flora is of interest from the point of vie-w of the later 

 northern floras. The occurrence in Lower Triassic rooks of the 

 Vosges of Neuropteridium and SoM%oneura — two characteristic 

 members of the Permo-Carboniferous vegetation in southern 

 regions — affords a connecting link between the Triassic flora in the 

 north and the Ghssopteria flora of Gond-wana Land.^ It seems 

 clear that a few of the Triassic types migrated to the north at 

 the close of the Palaeozoic era, and established themselves in 

 Europe as members of the oldest Triassic vegetation. On the 

 other hand, the Permian floras of Europe contain some genera, 

 such as Squisetites and a few Cycadean plants, -which may be 

 regarded as pioneer forms foreshadowing the transition from the 

 Palseozoic to the Mesozoic vegetation. Making due allo-wance for 



1 ZeiUer (83). 



2 See Seward (97 and 02). See also Zeiller (97) for an excellent account of 

 Permo-Carboniferous floras. 



