3o6 



CYATHEACEAE 



[CH. 



most advanced states are seen in the C)'atheaceae, as indicated b)- their 

 occasional vein-fusions. 



The anatomy follows suit, the steps of progression being sometimes 

 illustrated in the individual development. The Gleicheniaceae are mostly 

 protostelic, even in the adult state, with highly condensed undivided leaf- 

 trace. But in G.pectinata, though the sporeling is protostelic at first, it passes 

 quickly to solenostely: nevertheless the leaf-trace remains undivided. Metaxya 



Fig. 567. Plant of HeiniUlia sctosa in Edinburgh Botanic Garden. Showing numerous 

 "aphlebioid" pinnae. (From a photograph prepared by direction of Sir Isaac Bayley 

 Balfour.) 



is also permanently solenostelic, and its leaf-trace is undivided. But LopJiO- 

 soria shows all stages from solenostely to an imperfect dictyostely in its 

 upward-growing axes, while the leaf-trace is divided in the petiole into three 

 straps. Similarly Alsophila aadeata has been shown by Stenzel to pass from 

 protostely, through solenostely, to dictyostely in the same upward-growing 

 shoot: while its leaf-trace becomes here, as in all the larger Cyatheaceae, 

 highly disintegrated. In addition there is a medullary system, and a cortical 



