746 



THE WONDERS OF GEOLOGY. Lect. VII. 



yet the characters of the floras of certain formations differ 

 in so striking a manner from those of others, that it is very 

 improbable the essential features will be destroyed. 



The flora of the ancient world constitutes three eras. The 

 first period comprehends the earliest strata in which traces 

 of vegetation appear, and includes the carboniferous. The 

 plants of this epoch consist of fuci,* and other cellulosae, 

 ferns of various kinds in great abundance, coniferous 

 trees related to species of warm climates, of palms and 

 other monocotyledonous tribes; gigantic lycopodia, and 

 trees (Sigillariae) in great abundance, whose precise relations 

 to known forms is not satisfactorily determined. In this 

 flora the tree-ferns predominate, constituting nearly two 

 thirds of the whole known species, and the general type of 

 the vegetation is analogous to that of islands and archi- 

 pelagos of intertropical climates. 



The second epoch extends from the Triassic or New 

 Red to the Chalk inclusive, and is characterized by the 

 appearance of many species of the Cycadeae or Zamiae, 

 and of coniferae, while the proportion of ferns is much less 

 than in the preceding period, and the lycopodiaceous tribes, 

 calamites, &c. of the carboniferous strata, are absent. A 

 flora of this nature corresponds with that of the coasts and 

 maritime districts of New Holland and the Cape of Good 

 Hope. 



The third epoch is that of the tertiary, in which the dicoty- 

 ledonous tribes appear in great abundance ; the cycadeas are 

 very rare, the ferns in diminished numbers, and the coni- 

 ferae are more numerous. Palms, and other intertropical 

 forms, are found associated with the existing European 

 forest-trees, as the elm, ash, willow, poplar, &c, presenting, 

 in short, the general features of our continental floras. 



* Fossil fuci abound in the Silurian rocks of the Alleghany 

 Mountains ; sometimes forming entire layers, one hundred of which 

 occur in a thickness of twenty feet.- /)/•. Harlan's Medical and 

 Physical Researches^ p.. 390. 



