390 VEGETABLES OF THREE EPOCHS. 



As the drifted seeds that occur in Sheppey seem to have 

 been collected by the action of. marine currents, the history 

 of European vegetation during the Tertiary period, must be 

 sought for in those other remains of plants, whose state and 

 circumstances show that they have grown at no great dis- 

 tance from the spot in which they are now found.* 



Conclusion. 



The following is a summary of what is yet known, re- 

 specting the varying conditions of the Flora of the three 

 great periods of Geological history we have been consider- 

 ing. 



The most characteristic distinctions between the vegeta- 

 ble remains of these 'periods are as follows. In the first 

 period, the predominance of vascular Cryptogamic, and 

 comparative rarity of Dicotyledonous plants. In the second, 

 the approximation to equality of vascular Cryptogamic, and 

 Dicotyledonous plants.f In the third, the predominance 

 of Dicotyledonous, and rarity of vascular Cryptogamic 

 plants. Among existing vegetables almost two-thirds are 

 Dicotyledonous. 



The Remains of Monocotyledonous plants occur, though 

 sparingly, in each period of Geological formations. 



The number of fossil plants as yet described is about five 

 hundred ; nearly three hundred of these are from strata of 

 the Transition series; and almost entirely from the Coal for- 

 mation. About one hundred are from strata of the Secondary 

 series, and more than a hundred from formations of the 



• The beautiful Amber, whicli is found on the eastern sliores of England, 

 and on the Coasts of Prussia and Sicily, and which is supposed to be fossil 

 resin, is derived from beds of Lignite in 'i'ertiary strata. Fragments of fossil 

 gum were found near London in digging tlie tunnel through tlie London 

 clay at Highgate. 



+ The dicotyledonous plants of tlie Transition and Secondary formations 

 present only that peculiar tribe of this class, whicli is made up of Cycadex 

 and Coniferie, viz. Gymnospermoiis Phanerogamic. 



