XXVII] PECOPTERIS 579 



angle, as in Pecopteris polymorpha, Brongn.^ In Pecopteris 

 wnita, Brongn., already described as Ptychocarpus unita^, the 

 pinnules are joined together except in the apical region. Some 

 fronds included in Pecopteris possess pinnules in which Peco- 

 pteroid and Sphenopteroid features are combined ; P. Sterzeli, 

 Zeill.* and P. Pluckeneti, Schlot. are examples of fronds in 

 which the pinnules are lobed as in Sphenopteris, but the base 

 of the lamina is only slightly contracted and the venation is not 

 that of typical Sphenopteris species. 



The species to which Potoni6 has applied the generic name 

 Alloiopteris* also illustrates the impossibility of drawing a 

 sharp line between Pecopteris and Sphenopteris. The fronds 

 already described in chapter xxv. under the designation 

 Corynepteris bear pinnules with a contracted base ; in some 

 species the lamina is lobed, but in others (fig. 354, G) it is 

 entire with a midrib nearer one edge than the other. The 

 species which Potoni6 assigns to Alloiopteris, like many other 

 Sphenopteroid and Pecopteroid fronds, are characterised by 

 the occurrence of an abnormal pinnule (aphlebia) at the base 

 of each pinna (fig. 354, G, p. 535). Young fronds of Pecopteris 

 are occasionally met with showing very clearly the circinate 

 vernation of the pinnae as in the leaves of Cycas and Angiopteris 

 represented in fig. 220, p. 283. The genus Spiropteris was created 

 by Schimper° for coiled unexpanded fronds of fossil ferns ; it is 

 however superfluous to apply a distinctive term to specimens 

 of this kind. 



The designation Pecopteris is employed chiefly for leaves 

 of Palaeozoic age which are unknown in the fertile state, or do 

 not afford sufficient evidence as to the nature of the sporangia 

 to justify the substitution of a special generic name. Many 

 Mesozoic species have also been referred to Pecopteris, but most 

 of these are more appropriately included in Brongniart's later 

 genus Gladophlebis. The pinnules of Cladophlebis, as Brongniart 

 pointed out, are intermediate between Pecopteris and Neuro- 

 pteris; they are usually attached by the whole breadth of 



1 ZeUler (OO^) p. 88. ^ Page 397. 



» Renault and Zeiller (88) A. p. 178, Pis. v.— viii. Ante, p. 419. 



* Potoni^ (02). " Schimper (69) A. p. 688. 



