312 



ESSENTIALS OF BIOLOGY 



Peridinians and Bacteria. The group is a dominant persistent 

 and versatile one with few episodes in its history. 



a. The Bryophytes : Hi. The Pteridophytes . The types are 



Brz/opJiijtob 



TJzallophijtcu \ P^T^id,- Speririjcdophi/tcb 

 ^. "^ ^ ,' ^^EH^^ , A ^ 



Tertiary 



Tertixxrif 



Cretojceous 



tlurcLsslc 



TvijObssijz 



PerTTilcLn 



CarboTu/erous 



DevoTxiojh 



Silarixxjv 



OrcLovlc'hajv 



CoumJbrlcxjL 



Fig. 41. — ^Approximate Periods of the Main Types of Plants. 



persistent ones, but the interest of their history Hes in the extra- 

 ordinary episodes of the later Paleozoic times when the Arbor- 

 escent Ferns, Lycopods and Horsetails became so very abundant. 



