I/O 



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 



Fi<;. 90. 



Osiiiundu, \,. A = O. Prcsliana, I. Small leaf. />' and C = O. Kcgitlis, L. 

 plant. C=leaf of a mature plant. (After Easier and I'rantl.) 



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 



