476 Palaeotologie. 



the Cycadofilices. is represented by a species which can hardly 

 be distinguished from that which flourished in South Ame- 

 rica, South Africa, and India in the Permo-Carboniferous 

 period. This genus and another southern type, Scliizoneiira, 

 both oi which are met with in the Triassic rocks of the Vosges, 

 would seem to point to a northern migration of certain mem- 

 bers of the Glossopteris flora, which took place at the close 

 of the Palaeozoic era. In the lower Triassic flora Conifers are 

 relatively more abundant than in the earlier periods. Lep'ido- 

 dendra have apparently ceased to exist; Siglllaria may be said 

 to survive in one somewhat doubtful form, Siglllaria oculina. 

 The genus Pleuromeia, which makes its appearance in Triassic 

 rocks, is perhaps more akin to Isoetes than to any other exis- 

 ting plant. The Calamites are now replaced by large Equiseta- 

 ceous plants, which are best described as Horsetails with much 

 thicker stems than those of their modern descendants. 



Passing to the peninsula of India, we find the genus 

 Glossopteris abundantly represented in strata which there is 

 good reason for regarding as homotaxial with the European 

 Trias, and the occurrence in the same beds of some other 

 genera of Permo-Carboniferous age shows that the change in 

 the character of the southern Vegetation at the close of the 

 Palaeozoic era was much more gradual than in the north. 



The comparative abundance of plant remains in the northern 

 hemisphere in rocks belonging to the Rhaetic formation, is in 

 welcome contrast to the paucity of the records from the 

 underlying Triassic strata. The geographical distribution of 

 plants of approximately Rhaetic age demonstrates an almost 

 worldwide ränge of a Vegetation of uniform character. The 

 character of the plant-world is entirely different from that which 

 we have described in speaking of the Palaeozoic floras. Gymno- 

 sperms have ousted Vascular Cryptogams from their position 

 01 superiority; ferns, indeed, are still very abundant, but they 

 have undergone many and striking changes, notably in the 

 much smaller representation of the Marattiaceae. The Palaeo- 

 zoic Lycopods and Calamites have gone, and in their place 

 we have a wealth of Cycadean and Coniferous types. As we 

 ascend to the Jurassic plantbeds the change in the Vegetation 

 is comparatively slight, and the same persistence of a well-marked 

 lype of Vegetation extends into the Wealden period. 



Mesozoic Floras. 



It may be of interest to glance at some of the leading 

 types of Mesozoic floras with a view to comparing them with 

 their modern representatives. 



a. Conifers. Conifers were abundant, but the majority 

 were not members of that group to which the best known and 

 most widely distributed modern forms belong. A comparison 

 of fossil and recent Conifers is rendered difficult by the lack of 

 satisfactory evidence as to the systematic position of many of 



