XXVIl] PECOPTERIS 577 



species, in many cases stands for the compound fronds of 

 true ferns, but the possibility of the inclusion of those of 

 Pteridosperms in the same category is by no means excluded. 

 The designation Pecopteris may conveniently be retained for 

 sterile bipinnate, tripinnate, or quadripinnate fronds bearing 

 pinnules having the following characteristics : 



Lamina short, attached to the rachis by the whole of the base and at a 

 wide angle, with the edges parallel or slightly converging towards the 

 usually blunt apex ; adjacent pinnules may be continuous basally by a 

 narrow lamina. A well-marked midrib extends to the apex and gives off 

 simple or forked lateral veins almost at right angles (fig. 352, D, p. 529). 



Hydathodes like those on the leaflets of Polypodium vulgare and other 

 recent ferns' are occasionally seen at the ends of the lateral veins of 

 Pecopteris pinnules. 



In addition to the examples of Palaeozoic fronds with 

 the Pecopteris form of pinnule referred to in chapter xxii., the 

 species Pecopteris arborescens may be briefly described. 



Pecopteris arborescens (Schlotheim)^- Figs. 352, D : 376. 



The species named by Schlotheim Filicites arborescens in 

 1804 is characteristic of the Upper Coal-Measures and is 

 recorded also from Permian strata ^ 



Fronds large ; the rachis, which may reach a breadth of 3 cm.*, gives off 

 long ovoid-lanceolate pinnae in two alternate rows (fig. 376) ; pinnules 

 small, 1-5— 4 mm. long and 1 — 2 mm. broad, contiguous, with rounded 

 apex, attached approximately at right angles ; the upper surface of the 

 lamina is shghtly convex and may be hairy^ The fertile pinnules, 

 identical in shape with the sterile, bear groups of ovoid exannulate 

 sporangia (synangia). The midrib extends to the apex of the pinnule and 

 gives off simple veins at a wide angle (fig. 352, D). 



Our knowledge of the reproductive organs is very meagre. 

 Grand'Eury described the synangia as consisting of 3 — 5 

 sporangia borne on a central receptacle ; sporangia have been 

 described also by Stur», Renault and Zeille^^ and Potonie', 



1 Potonie (922) . (93) p. 54. 2 For synonymy, see Kidston (88) p. 366. 



3 Zeaier (90) p. 46 ; Potoni6 (93) A. p. 57. 



* Germar (44) Pis. xxxv. xxxvi. '' Kidston (88) p. 366. 



6 Stur (83). ' Renault and Zeiller (88) A. p. 196. 



8 Potoni6 (93) A. p. 48. 



