80 GENERA OF TJNCEKTAIN POSITION [CH. 



Psygmopkyllum, show a considerable variation in the venation of 

 the leaves or leaflets : those represented in his Plate in. figs. 8 — 10^ 

 agree with P. flabellatum while others differ in the presence of a 

 midrib {e.g. Schmalhausen's PI. iv. fig. 3). There has been con- 

 siderable confusion in regard to the determination of these Russian 

 specimens: as Arber says, Kutorga's Cydopteris gigantea^ is 

 probably a true Psygmophyllum though other specimens subse- 

 quently referred to P. expansum should not be included in that 

 genus. Zalessky^ in 1912 proposed a new generic name Palamo- 

 phyllum for the Russian species but retained Psygmophyllum for 

 a Mongolian Permian specimen which he named P. mongolicum : 

 this fossil is clearly a portion of a compound frond with leaflets 

 like those of some forms of Palaeopteris. In a later paper* this 

 author assigns Psygmophyllum mongolicum. to Palamofhyllum, but 

 on his attention being called by Zeiller to Saporta's note of 1878, 

 Zalessky^ decided to abandon his proposed genus Palamophyllum 

 in favour of Psygmophyllum. 



Confusion has also been caused by lack of uniformity in the 

 use of the two generic names Psygmophyllum and Ginhgophyllum. 

 The type-species of these genera I believe to be generically identical ; 

 they agree in the general form of the leaves, the lamina being much 

 more deeply divided in the type-species of Ginkgophyllum, also in 

 the decurrence of the narrow basal portion of the lamina, and both 

 are probably shoots, though the morphological nature of these and 

 other types included in Psygmophyllum is by no means clear. 



Arber retains both names : as a matter of convenience he 

 restricts Psygmophyllum to leaves that are entire or only shghtly 

 lobed, e.g. P. flabellatum (fig. 665), and the more deeply dissected 

 leaves such as those of Psygmophyllum Grasserti (fig. 669) he refers 

 to Ginkgophyllum. This distinction is, however, purely arbitrary 

 and on the analogy of the leaves of Ginkgo hiloha it would seem 

 preferable to include both deeply divided and more or less entire 

 leaves in the same genus. Cambier^ and Renier prefer the name 

 Psygmophyllum to Ginkgophyllum on the ground that in the leaves 



1 Schmalhausen (87). = Kutorga (44) PI. n. fig. 7. 



3 Zalessky (12) p. 38, PI. vn. fig. 5. * Zalessky (12^) p. 27. 



* This decision was communicated in a letter (October, 1913). A. C. S. 

 " Cambier and Renier (10). 



