344 STUDIES IN FOSSIL BOTANY 



circumstances forbid us to assume that this simplicity 

 is primitive. The Zygopteris type of stele is far more 

 complex, and an interesting point is that its structure 

 lent itself to secondary growth, so that in Botrychioxylon 

 we find the primary wood replaced by secondary, 

 just as is the case in Botrychium as compared with 

 Ophioglossum. Of course nothing more than an 

 analogy is suggested here, for the internal xylem of 

 the Zygopteris group is unrepresented in the recent 

 family. Still it is quite possible that some real affinity 

 may exist. 



The Botryopterideae may fairly be called a synthetic 

 group, in so far as they show analogies with a number of 

 families of later origin. Attention has already been 

 called to points of resemblance between them and the 

 Hymenophyllaceae, Osmundaceae, and Ophioglossaceae. 

 They have also been compared with Schizaeaceae on 

 account of the biseriate annulus sometimes observed in 

 that family, though differing in position from that in 

 our fossils ; anatomically a basis of comparison may be 

 found in the internal tracheides occurring in the stele of 

 Schizaea malaccana and other species. 1 If Corynepteris 

 is rightly associated with Botryopterideae, the synangia 

 suggest a relation to Marattiaceae ; the fructification of 

 Diplolabis points in the same direction, and Sturiella 

 (Fig. 109, D) may also be regarded as combining 

 Marattiaceous with Botryopteridean characters. 



In the first edition of this book I expressed the 

 opinion that the Botryopterideae not improbably 



1 Tansley and Chick, " Structure of Schizaea malaccana," Ann. of Bot. 

 vol. xvii. 1903 ; Boodle, "Comp.Anat. of Hymenophyllaceae, Schizaeaceae, 

 and Gleicheniaceae. IV. Further Obs. on Schizaea" ibid. 



