462 COENOPTERIDEAE [CH. 



climbing habit of A. scandens and possibly A. Grayi. The 

 radial extension of the xylem and the consequent alternation of 

 the yielding parenchymatous cortex and the more rigid tracheal 

 arms would probably render the water-conducting elements less 

 liable to injury in a twisting axis^. In Anachoropteris De- 

 caisnii", described by Renault, and more especially in Astero- 

 chlaena laxa^ Stenzel, a Lower Permian type from Saxony 

 (fig. 324), the xylem of the stele is much more deeply lobed 

 than in Ankyropteris Grayi or A. scandens. 



Fig. 318. Etapteris Scotti, P. Bert. (From Tansley, after Eenault.) 



Etapteris Scotti. Figs. 308, B; 309, E; 318. 



P. Bertrand has proposed this name for a species of petiole 

 from the Lower Coal-Measures of England referred by Binney* 

 to Zygopteris Lacattii Ren., and included by Williamson^ in 

 his comprehensive genus Rachiopteris. Bertrand^ regards the 

 English species, which is recorded also from Germany', as 

 distinct from Renault's type^ and therefore proposes a new 

 name. The petiole stele has the H-form, but its structure 

 is simpler than that of the Ankyropteris petiole. 



The horizontal band of xylem has at each end two oval 

 groups of tracheae connected with it by a single row of xylem 



1 Compare figures of the vascular cylinders of climbing Dicotyledons given 

 by Schenck (93). 



2 For a figure of the stele see Tansley (08) p. 25, fig. 20. 

 =* Stenzel (89) Pis. in. and iv. 



■> Binney (72). e Williamson (74) A. « Bertrand, P. (09) 



■> Felix (86) A. s Renault (69). 



