288 STUDIES IN FOSSIL BOTANY 



sporangia of Senftenbergia find their nearest parallel 

 in the Schizaeaceae, to which family Corda, the dis- 

 coverer of the genus, referred it. The pluriseriate 

 structure of the annulus has been brought forward as 

 an argument against this view, but in Lygodium, among 

 recent Schizaeaceae, the annulus, as Zeiller has pointed 

 out, is often more than one cell in breadth. 



Upon the data available, it remains impossible to 

 determine the position of the genus. The analogy 

 with Angiopteris, on which Stur, who maintained the 

 Marattiaceous affinities of Senftenbergia, laid stress, 

 appears remote. There is, however, some evidence 

 that in the fossil genus the sporangial wall was several 

 cells in thickness, a character which points in the 

 direction of Marattiaceae. 



Sporangial characters, like any other characters, are, 

 in fact, insufficient by themselves to determine the 

 position of a genus in a doubtful case. 



The evidence for the Marattiaceous affinities of such 

 genera as Ptychocarpus, Asterotheca, Scolecopteris, and 

 Danaeites, in which the fructification is in the form of 

 synangia borne on the ordinary foliage, is still generally 

 accepted, and is much strengthened by the presence, at 

 "■similar horizons, of stems (Psaronius) with a Marat- 

 tiaceous anatomy (see below). Any doubt there may 

 be arises from two considerations : (i) Practically all the 

 fructifications in question were borne on Pecopteris fronds, 

 and one species referred to Pecopteris (P. Pluckeneti) 

 is now known to have been a seed-bearing plant (see 

 Chapter XL) ; (2) a species of Crossotheca, formerly 

 regarded as a Marattiaceous genus, has been shown by 

 Mr. Kidston to be the male fructification of the Pteri- 



