170 STERILE AND FERTILE REGIONS 



distinction is very perfectly bridged over. But I submit that the most 

 exact demonstration of similarity in detail of development, and the quotation 



FIG. 90. 



Osmnncia, L. A=O. Presliana, I. Small leaf. B and C = O. Regalis, L. 

 plant. C = leaf of a mature plant. (After Engler and Prantl.) 



of an infinity of middle-forms drawn from the most varied types of Ferns, 

 does not touch the question of phylogenetic priority. Such facts are the 



