172 THE GEOLOGICAL SUCCESSION 



plants appear to have been developed on an enlarged scale. 

 Coal owes its origin to the abundant vegetation of this 

 era; for it is now universally admitted that this substance 

 is of vegetable origin. This the microscope has fully de- 

 monstrated. In some kinds of coal, punctuated woody fibre 

 has been detected, in others dotted and scalariform tissue, 

 as well as cells of various kinds. The occurrence of dotted 

 and scalariform vessels indicates the presence of ferns and 

 their allied forms, such, as Sigillaria, Stigmaria and Lepi- 

 dodendra, whilst true punctuated wood implies the pre- 

 sence of Coniferae. 



Impressions of these plants are abundant amongst the 

 argillaceous and sandy beds of the carboniferous system. 

 About one hundred and fifty species of fossil ferns have 

 been distinguished by Botanists in the coal system of Eng- 

 land, and many of the fronds of these ferns have been 

 clearly ascertained to have fallen from the stems of tree- 

 ferns, which grew at the time that the coal was deposited. 

 The Lepidodendrons were gigantic Lycopodiums, or club 

 mosses, which rose to the height of sixty feet, although the 

 representatives of these plants are now mere herbs. 



In the Secondary formations we meet with a greater num- 

 ber of Coniferse and Cicadacese, whilst ferns and Lycopo- 

 diacese are not so abundant, and less gigantic in their 

 growth. 



The Tertiary period is characterized by an abundance of 

 Dicotyledonous and Monocotyledonous plants, especially 

 palms. 



Many of the fossil plants of these deposits, such as pines, 

 elms, beeches, and maples, may be referred to genera at 

 present existing, and merely present specific differences. 

 The general result of all researches in fossil botany tends 

 to prove that the early vegetation of the globe consisted of 



