xlii 



INTRODUCTION. 



that they did not play such a part in the true Mesozoic floras. The 

 Mesozoic facies of vegetation is first found fully developed in 

 Rhaetic times, and persisted in the Jurassic and "Wealden. It is 

 especially characterised by a general absence of the older Palaeozoic 

 types ; such as existed being numerically inferior and quite over- 

 shadowed by the development of new types of plant life. It is 

 true that in Tonquin, China, Europe, and elsewhere a few 

 survivals, such as Schizoneura, Glossopteris, etc., have been found 

 associated with the Rhcetic flora, but these, as recent research has 

 shown, are all of secondary importance as compared with the other 

 elements of the flora. Similarly, Phyllotheea survived as late as 

 the Jurassic period in Italy, whereas almost all the other elements 

 of the Jurassic flora are essentially of a Mesozoic type. 



It has been assumed by many palaeobotanists in the past that 

 the Mesozoic facies of the Glossopteris flora is beyond dispute, since 

 several of its most characteristic members are found in the Trias, 

 and even extend to the Rhsetic. I have endeavoured to show that 

 this conclusion is incorrect. Further evidence may be found in 

 the general absence of Mesozoic types from the rocks of Gondwana- 

 land, with the exception of a few Ferns, Cycads, Ginkgoales, and 

 Coniferae, which both in the Northern and the Southern Hemi- 

 spheres arc among the earliest arrivals of a Mesozoic facies. 

 "We find practically no representatives of such typical Mesozoic 

 genera as JEquisetites, Clathropteris, Laccopteris, Dictyophyllum, 

 Sagenopteris, WiUiamsonia, Otozamites, Podoza mites, Nilssonia, 

 Ginkgo, and Baiera, among many others which might be mentioned 

 as having a worldwide distribution. 



In the past, the evidence of the Mesozoic facies of this flora has 

 been based parti}' on inaccurate generic determinations. I have 

 already noticed (p. xxx) some of these in relation to the Cycads, 

 a group which in reality is very scantily represented in the 

 Glossopteris flora. Similarly, the name Glossopteris lias been 

 applied by some of the older authorities on paleobotany to 

 Mesozoic plants which do not belong to that genus. 1 The 

 converse has also occurred in the case of Sagenopteris, a typical 

 frond of a Mesozoic facies, which has been recorded from 



1 Schimper (69), vol. i. pp. 641-2. 



