70 PTERIDOSPERMEAE [CH. 



feature ; but in the presence of secondary conducting tissue they 

 agree with those of Phanerogams. 



Distribution of Lyginopteris. 



The frequency with which petrified fragments of Lyginopteris 

 stems occur in the calcare.ous nodules of the English coal seams 

 shows that the genus must have been plentifully represented in 

 the Upper Carboniferous vegetation, and the occurrence in both 

 North American 1 and European localities of fronds identical with 

 or closely resembling Sphenopteris Hoeninghausi affords evidence 

 of wide geographical range. Petrified specimens were recorded 

 by Felix 2 from Westphalia in 1886, and Zalessky 3 has recently 

 discovered Lyginopteris in the Donetz coal-basin of Russia. An 

 investigation by Kubart 4 of the calcareous nodules, to which 

 attention was first drawn by Stur, in the Ostrau Coal Measures 

 led to the discovery of several examples of Lyginopteris stems. 

 The descriptions and figures so far published are hardly sufficient 

 to enable us to estimate the degree of relationship to the English 

 type, but some of the stems appear to be new species and Kubart 

 considers them all to be specifically distinct from Lyginopteris 

 oldhamia. Lyginopteris heterangioides contains scattered tracheids 

 in the pith and thus affords an interesting transitional type between 

 Lyginopteris and Heterangium. In L. lacunosum the inner cortex 

 is lacunar and the primary xylem bundles pursue an independent 

 course in the stele in contrast to the anastomosing arrangement 

 in L. oldhamia and in another Hungarian species L. tristichum. 

 The species recorded by Kubart occur in the Millstone grit and 

 the Coal Measures. 



The geological range of Lyginopteris as represented by petrified 

 stems does not extend beyond the limits of the Carboniferous 

 system. 



HETERANGIUM. 



The generic name Heterangium was first used by Corda 5 for 

 a piece of stem from the Coal Measures of Radnitz, Bohemia, 

 represented by part of the vascular axis of a stem consisting 



i White (99) B. p. 40. 2 Felix (86) A. 



3 Zalessky (10). 4 Kubart (14); (11). 



Corda (45) A. PL xvi. 



