BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 29, pp. 607-614 December 3o, i918 



PROCEEDINGS OF THE PALEONTOLOGICAL SOCIETY 



RELATIONS BETWEEN THE MESOZOIC FLORAS OF NORTH 

 AND SOUTH AMERICA 1 



BY F. H. KNOWLTON" 



{Bead before the Paleontological Society December 31, 1917) 



CONTENTS 



Page 



Introduction 607 



Triassic 607 



Jurassic 609 



Cretaceous 611 



^ Summary 612 



Inteoduction" 



The natural order of sequence in considering the relations between the 

 Mesozoic floras of North and South America must be the Triassic, the 

 Jurassic, and the Cretaceous. 



Teiassic 



Rocks of Triassic age are known in many and widely separated parts 

 of the world, and they are of great thickness, which implies a varied and 

 relatively long-continued period of geologic activity. It is also evident 

 from the thick deposits of coal known at several points, and in other ways, 

 that vegetation must have been fairly abundant and considerably varied 

 in character; yet the determinable forms of plant life that have thus far 

 been recovered from the Triassic are surprisingly few in number — in fact, 

 it is doubtful if the known flora far exceeds 300 species. This is, of 

 course, to be largely attributed to the fact that much of the deposits were 

 laid down under marine conditions, where one would hardly expect to 

 find the remains of land plants preserved except near shore and more or 

 less fortuitously ; and, further, if the evidence believed by some to indi- 



Manuscript received by the Secretary of the Society August 22, 1918. 



(607) 



