PHYLETIC RELATIONS 



653 



FIG. 354. 



Scheme to illustrate approximately the relations of the several families of Ferns, as 

 concluded from the discussions in the text. It will be noted that the distinctions as 

 Simplices, Gradatae, and Mixtae traverse several of the probable evolutionary- lines: 

 the grouping is so disposed that Ferns with marginal sori lie to the left, with superficial 

 sori to the right. No attempt is made to connect the lines into a phyletic tree. 



