THE FOSSIL OSMUNDACE^E. 217 



Brongniart proposes for the fern stem which was first described by Eichwald 

 under the name of Anomopteris Schlechtendali* and subsequently placed by him in 

 Sphallopteris, Corda, the new genus Thamnopteris,^ on the ground that Eichwald's 

 stem was not generically similar to the Anomopteris Mougeotii I which Corda had 

 made the type of his genus Sphalmopteris ( = Sphallopteris, Eichwald). 



Brongniart says in regard to his genus Thamnopteris : " I place under this name a 

 frutescent erect fern stem, but with persistent petioles arranged around a very slender 

 stem, which M. Eichwald designates under the name of Anomopteris Schlechtendali, 

 because it appeared to him to offer some analogy with the stem which I have referred 

 to Anomopteris Mougeotii ;§ but this latter differs notably in its very slender stem 

 surrounded by very numerous slender petioles, and which have evidently been persistent 

 as those of our herbaceous ferns with ascending stems." || 



We have not seen the specimen of Sphallopteris Schlechtendalii to which Brongniart 

 refers, but, judging from the specimen of Sphallopteris Schlechtendalii which Eichwald 

 gives on PI. III., fig. 2, of the Lethsea Rossica, one would scarcely be inclined to include 

 it in the same genus as Anomopteris Mougeotii, and in our future treatment of this 

 fossil we shall adopt the name of Thamnopteris Schlechtendali for this stem. 



There are other considerations which advocate this course, and one of these is that 

 a microscopical examination of the specimen of the Thamnopteris Schlechtendali figured 

 by Eichwald in the Lethsea Rossica reveals the fact that the true outer surface of the 

 stock is not preserved, but the stem was surrounded by a thick mantle of concrescent 

 leaf-bases, and an unknown thickness of these concrescent leaf- bases has been removed 

 from the stem. Probably the true appearance of the outer surface of the stock would be 

 a felted mass of rootlets in which the remains of the petioles were embedded. In fact, 

 this specimen and those we have examined of Zalesshya [Chelepteris, Eichwald non 

 Corda), Anomopteris, and Bathypteris are all more or less incomplete or even partially 

 decorticated as in Zalesshya, and none of them show the true outer surface of the stock, 

 and they might well be described as all representing a " Knorria" condition. There- 

 fore, if the figure given by Brongniart as Anomopteris Mougeotii shows its true outer 

 surface (which it may do), a comparison has been made between structures which hold 

 different positions in the stock. 



But a more weighty reason for the rejection of the genus Sphallopteris for 

 Eichwald's plant is found in the circumstance that the structure of the type of the 

 genus Sphallopteris (Anomopteris Mougeotii, Brongniart) is not known, and there is no 

 warrant for inferring that it was similar to that of Eichwald's specimen. All that is 

 known of the structure of Anomopteris Mougeotii is that the petioles seem to 

 possess semilunar vascular bundles " as in the petiole of Osmunda, regalis,'' but this 



* Eicswald, Urwelt Eusslands, Heft ii., p. 180, pi. iv., figs. 3-5. 



t Brongniart, Tableau d. genres d. ve'ge't.foss., p. 35, 1849. 



I Brongniart, Hist. d. ve'ge't.foss., vol. i., pi. lxxx. 



§ The Cottce Mougeottii of Schimper and Mougeot, Plantesfoss. du gres bigarre', p. 69, pi. xxxiii. 



|| Tableau d. genres d. ve'ge't.foss., p. 35. 



