GROUPS OF PLANTS. 



69 



phtyes. It is also called the Coal Age from the fact that the coal 

 measures were chiefly laid down during this period. By some it 

 is thought that the deposits of coal of this age were probably 



Fig. 45. Some Pteridophytes. A, Creeping Selaginella {Selaginella apus); B, field 

 horsetail (Equisetum arvense) showing cone-bearing branch and foliage branch; C, Ophio- 

 glossum palmatum; D, adder's-tongue {Ophioglossum vulgatum). 



principally formed from the remains of certain marsh plants 

 including two extinct groups of huge, tree-like club mosses (Lepi- 

 dendron and Sigillaria) and the Calamites, representatives of the 

 scouring rushes. 



