CHAPTER TWENTY-ONE 



THE FERNS AND THEIR ALLIES 



The ferns and their allies are a large assem- 

 blage of plants. Like the simple plants that we 

 have studied, they reproduce by spores instead 

 of seeds ; but, like the seed plants, they possess 

 water-conducting and food-conducting tissues. 

 They appeared on the earth earlier than the 

 seed plants, and were more abundant during the 

 carboniferous or coal-making period of the 

 earth's history than they are now. Indeed, 

 judging by the fossils in coal, ferns and fernlike 

 plants dominated the vegetation of that time, 

 and the seed plants were much less prominent 

 than now. Ever since that period the seed 

 plants have been gaining in importance; and 

 now the ferns have been to a large extent 

 displaced, especially in the temperate and 

 colder parts of the earth. Three groups of 

 these plants that are sufficiently distinct to be '*''' 



J.I . , ^, , . Fig. i66. The walk- 



readily recogmzed occur rather commonly m ingfem. New plants 



North America. They are the ferns, equisetums, are developed from 



and club mosses. ^Llf^ ''''' "' 



283 



