PALEOBOTANY BEERY. 383 



phyton became extinct. The primitive Archaeocalamites were grad- 

 ually replaced by the true Calamites. Protolepidodendron and other 

 Bothrodendraceae originated the distinct families of Sigillariaceae 

 and Lepidodenclraceae, and the seed ferns and true ferns showed a 

 succession of forms that enables the paleobotanist to determine in just 

 what part of the coal measures a particular florule belongs. 



Throughout the Northern Hemisphere, and particularly in the 

 Appalachian province as compared with Europe, relative uniformity 

 of conditions lasted throughout the whole Carboniferous and into 

 the Permian, and while there was a steady march of vegetation and 

 a succession of varying forms, the general facies changed but little 

 as compared with the contemporaneous history of the Southern 

 Hemisphere (see Glossopteris flora). Already in the Carboniferous 

 of both Europe and America, Cycadophyte fronds appear in the 

 record, foreshadowing the great Mesozoic display of these plants. 

 A few Ginkgo-like types were present and Walchia and Yoltzia 

 among the Coniferophytes give promise of the impending change 

 from a sporophytic to a spermophytic vegetational regime. 



THE GLOSSOPTERIS-GANGAMOPTERIS FLORA. 



At a horizon believed to be Lower Permian in age and associated 

 with well-marked glacial deposits in Australia, Tasmania, India, 

 South Africa, and South America, and with less definitive evidence 

 of glaciation in several other areas, are found traces of a peculiar 

 and regional flora in which the cosmopolitan types of the late Car- 

 boniferous and Permian, such as characterize the floras of these 

 times in the Northern Hemisphere, are largely absent. This southern 

 flora is termed the Glossopteris or the Gangamopteris flora from its 

 two most characteristic elements. These were simple fern-like 

 fronds, shaped like those of the common hart's-tongue (Scolopen- 

 drium), and were borne on creeping stems or rhizomes, long known 

 by the name of Vertebraria. The fronds of both genera are much 

 alike, of a similar lanceolate to obovate form and with an anastomos- 

 ing venation. They are distinguished from one another by the pres- 

 ence of a thick midrib in Glossopteris, and by the practical absence 

 of a midrib in Gangamopteris. In the former genus the sporangia 

 are known and were borne upon very much reduced oval fronds. It 

 is not certain whether they were true ferns or represent the seed ferns 

 so common in the Paleozoic. Fronds of these two genera are shown, 

 much reduced, in the accompanying figures (fig. 29). 



Associated with these Glossopteris and Gangamopteris fronds 

 were the remains of Phyllotheca and Schizoneura, relatives of the 

 northern Calamites, fronds of Cycadophytes (Pterophyllum, Glosso- 

 zamites) and Neurophteridium, various fragments of ferns (Clado- 

 phlebis, Pecopteris, Sphenopteris, Taeniopteris), conifers (Yoltzia), 



