436 COENOPTEEIDEAE [CH. 



a metre in length and to bear compound fronds a metre long. 

 The orientation of the leaf-trace with its concavity turned 

 outwards is in striking contrast to the relation between leaf- 

 trace and stem in recent ferns. 



TuhicauUs Sutcliffii, Stopes^. 



In this species the vascular axis, 2 mm. in diameter, is 

 almost cylindrical and of the protostelic type with the proto- 

 xylem " near to or at the edge " : the tracheae are scalariform 

 or reticulate. The leaf-traces, when first separated from the 

 edge of the stele, are oval and gradually assume the curved 

 form seen in T. solenites (fig. 304) with the convex side towards 

 the axis of the stem. The transition from the scalariform to 

 the reticulate type of pitting on the tracheal walls referred to 

 by Miss Stopes has also been noticed in some recent fems 

 (e.g. Helminthostachys) and in Sigillaria (fig. 200, C, p. 212). 

 The fact that the scalariform type of pitting is practically 

 universal in the xylem of recent ferns, would seem to show 

 that this character has been acquired in the course of evolution 

 and retained in preference to the reticulate form characteristic 

 of several Palaeozoic species. The distinction between the two 

 methods of pitting is one of little phylogenetic importance. 



Botryopteris. 



This genus, founded by Renault on a specimen from Autun, 

 is represented in the Lower Coal-Measures of England by 

 Botryopteris hirsuta {= Rachiopteris hirsuta Will.), B. ramosa 

 (= M. ramosa Will.'') (fig. 306) and B. cylindrica (fig. 305), also 

 by B. antiqua (fig. 307) from the Culm of Pettycur, Scotland. 



An important characteristic of the genus is the solid stele 

 of the stem which agrees with that of TuhicauUs and Gram- 

 matopteris, except in the central or peripheral position of the 

 smallest tracheae. 



1 Stopes (06). 



" Williamson (89) A. p. 162. The term Rachiopteris was adopted by 

 Williamson for petrified petioles from the Coal-Measures which he believed 

 to be filicinean. 



