40 ANCIENT PLANTS 



succeeding the Carboniferous, we have a Httle more 

 knowledge. Yet for all these periods, even the Tertiary 

 immediately preceding the present day, our knowledge 

 is far less exact and far less detailed than it is for that 

 unique period, the Carboniferous itself 



The characteristic plants of the Carboniferous period 

 are all very different from those of the present, and 

 every plant of that date is now extinct. In the succeed- 

 ing periods the main types of vegetation changed, and 

 with each succeeding change advanced a step towards 

 the stage now reached. 



The Permian, geologically speaking, was a period 

 of transition. Toward the close of the Carboniferous 

 there were many important earth movements which 

 raised the level of the land and tended to enclose the 

 area of water in what is now Eastern Europe, and to 

 make a continental area with inland seas. Many of the 

 Carboniferous genera are found to extend through the 

 Permian and then die out, while at the same time others 

 became quite extinct as the physical conditions changed. 

 The seed -bearing plants became relatively more im- 

 portant, and though the genus Cordaites died out at the 

 end of the period it was succeeded by an increasing 

 number of others of more advanced type. 



When we come to the older Mesozoic rocks, we 

 have in England at any rate an area which was slowly 

 submerging again. The more important of the plants 

 which are preserved, and they are unfortunately all too 

 few, are of a type which has not yet appeared in the 

 earlier rocks, and are in some ways like the living 

 Cycas, though they have many characters fundamentally 

 different from any living type. In the vegetation of 

 this time, plants of Cycad-like appearance seem to have 

 largely predominated, and may certainly be taken as 

 the characteristic feature of the period. The great 

 Lycopod and Equisetum-like trees of the Carboniferous 

 are represented now only by smaller individuals of the 

 same groups, and .practically all the genera which were 



