i8z EQUISETACEAE, MARSILEOIDEAE, 



A. Br.). The leaves of the plant are still unknown in the fossil state. 

 Some remains also from the older formations have been placed by authors 

 with Hydropteridae, the genus Sagenopteris, Presl, for example, the leaves 

 of which were noticed above on page 138. Zigno l has observed some small 

 round bodies in company with these leaves, and Nathorst 2 , who found 

 similar objects in Schonen, thinks that they are sporocarps, but has given 

 no reason for his opinion. He then proceeds to argue in a manner which 

 is little convincing that these sporocarps belonged to Sagenopteris, and 

 that Sagenopteris therefore was one of the Marsileaceae. Schimper 3 too 

 has since given his assent to this view. 



It is extremely doubtful whether the fossil leaf described by Schenk 4 

 as Marsilidium speciosum from the Wealden formation of Osterwald in 

 Hanover, which was placed in the group which we are considering solely on 

 account of the habit of the single original specimen, really belongs to it. 

 The lamina is formed of six broadly wedge-shaped pinnae inserted on the 

 end of a long petiole ; the nervation is that of Cyclopteris and the anterior 

 margin is finely toothed. 



Remains of leaves have been described from the Keuper of N. Caro- 

 lina as Sphenoglossum quadrifolium 5 ; they consist of four broadly wedge- 

 shaped entire leaves or pinnae, which lie in one plane and are inserted at 

 the same point. 



The family of Salviniaceae, represented by several well-preserved and 

 indubitable species of Salvinia, has been found in the form of impressions 

 of leaves in the Miocene strata of Schrotzburg in Switzerland , and in the 

 same formation at Schossnitz in Silesia 7 , and at Priesen near Bilm in Bohe- 

 mia 8 . No similar forms have been found in older deposits, nor have any 

 remains of Azolla, as far as I know, been described hitherto. This of 

 course does not prove that these very peculiar plants had not made their 

 appearance in the earlier periods of the world's history. Their tender 

 vegetative organs perished perhaps by an early decay, and have not come 

 down to us. We may incline to this supposition in presence of certain 

 diminutive remains of fructification which are occasionally found in the 

 calcareous nodules of the English Coal-measures, and which have been 

 described in great numbers by Williamson 9 and by Carruthers io under 

 the names Sporocarpon, Will., Traquairia, Carr., and Zygosporites, Will. 

 I have made acquaintance with a large number of specimens of these 

 objects in Williamson's collection, and I have some myself for which I am 

 indebted to his kindness and to that of Mr. W. Cash of Halifax. Their 

 origin has been the subject of various conjectures ; they have been thought 



1 de Zigno (1), vol. i, t. 20, ff. 2, 3. 3 Nathorst (6). 3 Zittel (1), p. 154. ' Schenk (1), 

 t. 26. f. 3. * Emmons (1), t. i, f. 2. Heer (3), vol. iii, t. 145. 7 Goppert (18), t. i, 



ff. 21-23. * von Ettingshausen (4^. * Williamson '1\ IX, X. lg Williamson (1), x. 



