94 



LEAF-ARCHITECTURE OF FERNS 



[CH. 



leading to more elaborate reticulation, and finally to small-meshed networks. 

 There is some evidence of ontogenetic progression from an open to a 



Fig. 91. 0!—/= juvenile leaves show^ing closed, or reticulate venation, a — d=Dipterts 

 conjugata ( x 6) ; e= Cheiroplenria ( x 3) ; f= Flatycerium Veitchii ( x 3). 



closed venation. The first leaves of Ceratopteris may be without fusions, 

 though these appear in the later leaves. The earliest juvenile leaves of 



