IX] 



THE PHYLLOPODIUM 



171 



Other climbing or straggling Ferns show consolidation of the vascular 

 trace similar to that in Gleichenia, though differing in the details. In Odon- 

 tosoria {Davallia) finiiarioides (Sw.), J. Sm., which is also a plant of the 

 savannahs, being grouped with O. aculeata (L.), J. Sm., as "bramble ferns," 

 the meristele of the leaf below the lowest pinnae has a form as in Fig. 165, e,f. 

 The two sides of the curve are massive and close together, while the adaxial 

 hooks of xylem are short and stout in strong leaves, but in weak ones they 

 are much reduced, and higher up they are obsolete. In Lygodium scandens, 

 which is a successful climber, the outline of the meristele is oval, and there 

 are no adaxial hooks, while the xylem of the two sides of the curve is 

 completely fused (Fig. 165,^). From comparison of different specimens all 



Fig. 165. Transverse sections of meristeles in the petioles of various Ferns, to show 

 their modifications of outline. a=^ Botryopteris ; j-^. stem, /'. leaf: b = Schizaea: 

 c = Anemia : d= Pellaea : e, f— Davalliafumarioides : g= Lygodium. Compare 

 text. The adaxial face is in all cases directed upwards. 



stages between the open C-shaped trace and the condensed state oi Lygodiiiui 

 may be found. As regards the orders of living Ferns it seems probable that 

 their petiolar traces are all variants of the Osmundaceous type, having the 

 form of an adaxially curved C. The traces of Gleicheniaceae, Cyatheaceae, 

 Dicksoniaceae, and their derivatives conform fairly readily to this type. 

 Bertrand and Cornaille have analysed those of the Hymenophyllaceae and 

 Marattiaceae with a like result. In the Schizaeaceae, Anemia has a very 

 typical C-shaped trace, but difficulty had hitherto been found with Lygodium. 

 Gwynne-Vaughan's posthumous memoir shows that a comparison with the 

 less specialised climber, Odontosoria, gives for it also an interpretation in 

 terms of the Osmundaceous meristele (m). The final conclusion is that 

 the meristele of the leaf of the living orders of Ferns is open to biological 



