344 



SPHENOPH YLLEAE. 



its being the same in all species for reasons to be discussed presently. How 

 far the degree of division and incision of the lamina can be employed 

 in determining species requires further consideration, for Coemans and 

 Kickx 1 state that the stems of several species have deeply incised leaves 

 below, and almost entire leaves above, in the manner of our living Batrachiae. 

 If they mean to infer that Sphenophylleae were aquatic plants, their view is 

 opposed by both Schimper 2 and Schenk 3 , who appeal to the anatomy of the 

 stem. I prefer not to give a decided opinion on this point for the present. 

 As regards the heterophylly, which Weiss 4 also regards as an established 

 fact, the only instances of it which I can find are the branched specimens 

 figured in Germar 5 and Schenk 6 ; and in these it is only the main axis 

 which bears incised leaves, those of the lateral branches are alike and have 

 entire margins, so that the comparison with Batrachiae is not exact. 



As soon as the wedge-like form of the leaves is disguised by the copious 

 and deep incision of the anterior margin, it necessarily becomes difficult 

 and sometimes quite impossible to distinguish the remains of Sphenophylleae 

 with any certainty from Asterophyllitae and Annulariae. To be convinced 

 of this, we have only to examine the figures of Sphenophyllum angusti- 

 folium, Germ, in Schenk 7 . Gerrnar's 8 figure of the same species is not to 

 be distinguished from an Asterophyllites ; it may even be doubted whether 

 it belongs to Sphenophylleae. It is necessary to insist upon this point 

 because of its importance as showing, in opposition to Williamson's results 

 which will be considered further on, that in impressions where the anatomy 

 cannot be examined no certain line of distinction can be drawn between the 

 two genera, if Asterophyllites may be called a genus. We must not lose 

 sight of this in judging of Slur's Asterophyllites mentioned above on p. 314, 

 from which a branch of Sphenophyllum is growing. It is possible that 

 some of the remains which we should now call Asterophyllitae will ulti- 

 mately prove to be Sphenophylleae. We have a case already in Spheno- 

 phyllum tenerrimum. Ett. which gives room for much doubt. This slender 

 diminutive plant has been figured and described by Stur 9 with his usual 

 care. Its furrowed stems bear whorls of dissimilar once or twice divided 

 leaves, in which the incisions follow the nervation in such a manner, that 

 each point is traversed only by a median nerve. Where the whorls lie. 

 spread out in the plane of stratification, the number of leaves has been 

 found to vary ; I find the numbers nine, ten, eleven, and twelve given in 

 Stur, which does not quite agree with the regularity observed in genuine 

 Sphenophyllae, though I do not consider the point to be very important. 

 But this specimen might quite as well be compared with Archaeocalamites, 



1 Coemans et Kickx (2), p. 139. 2 Zittel (1), p. 178. 3 Schenk (2), p. 220. 4 Weiss 



(1), P- 33- 5 Germar (1), t. 6, f. 3. Schenk (2), t. 44, f. i. 7 Schenk (2), t. 38, 



ff- 2 . 3, 5- " Germar (1), t. 7, f. 8. Stur (f>), p. 214, t. 7. 



