XXIl] 



ANATOMY 



i6i 



1 U \ ' I \ I X ' ' i; 





V^l^rN 



P 



Fig. 445. Half of a meristele from the petiole of Anemia Phyllitidis, seen in transverse section. 

 Compare that of Davallia speluncae. Vol. i, Fig. 159. ed, endodermis : s, parenchymatous 

 sheath: ^/, ground parenchyma: p.ph, protophloem : si, sieve-tubes: /", fibres: st, spiral 

 tracheides: tt, scalariform tracheides: gg, ground tissue. ( x 80.) (After Prantl.) 



its dichotomous origin less obvious than in Schizaea. The other two genera 

 have as a rule open dichotomous venation with varying degrees of dichopodial 

 development. But both run into a low degree of reticulation in certain 

 species with especially wide pinnules. The strongly dichopodial development 

 of the unlimited leaf of Lygodiitm leads to the lateral position of the alter- 

 nating pinnae and pinnules, and it is only in the final branchings that equal 

 dichotomy asserts itself (Fig. 438, p. 155). In three species of Lygodium, 



