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PLAGIOGYRIACEAE 



[CH. 



a modification of the former. The facts for Plagiogyria are distinctly sug- 

 gestive in relation to the branching of Ferns (see Vol. I, Chap. iv). The 

 leaves are simply pinnate, forming a dense rosette: the broader sterile leaves 

 are distinct from the narrow fertile leaves, which are often longer (Fig. 542). 

 The venation is always open and forked (Bower, "Studies, I," Aim. of Bot. 



Fig. 542. Plagiogyria Kze. A-F=P. semicordata (Presl) Christ. .-7=habit: B, C = sporangia in 

 face, and lateral view: Z)=base of the leaf: >£■ = portion of a sterile leaf M'ith venation: /'=part 

 of a fertile leaf with venation and sori. (After Mettenius, from Engler and Prantl.) 



1 909, p. 428). The leaf-stalks are enlarged at the base as in the Osmundaceae : 

 they bear on the abaxial face two rows of pneumatophores (Fig. 543). Similar 

 organs are also found on the upper leaf, and are specially prominent alter- 

 nating with the pinnae in the young circinate state in P. pycnophylla. The 

 young leaves are densely covered with mucilaginous hairs, as in the Osmun- 



