40 T. G. HALLE, LOWER DEVONIAN PLANTS FROM RÖRAGEN IN NORWAY. 



as suggested by Prof. Lignier. The sporangia would then be pre-existent in respect to 

 the laminae of the pinnules. As possibly representing an intermediate form between 

 Dawsonites arcuatus on one hand and fertile fronds of Archaeopteris or other Upper De- 

 vonian and Carboniferous Primofilices on the other may be mentioned Sphenopteris 

 Condrusorum (Créptn) Gilkinet from the Upper Devonian of Belgium. 



The antiquity of the sporogonium. 



Sporogonites exuberans as deseribed above must be regarded as a structure closely 

 agreeing with the sporogonium of the Bryophyta, although it cannot be included within 

 any of the existing groups of that phylum but should be held to be a generalized type. 

 The occurrence of this form among the very oldest remains of land-plants known at pre- 

 sent is very surprising considering the opinions commonly held regarding the geological 

 distribution and development of the Bryophyta. Undoubted sporogonia are not known 

 from any horizon older than the Tertiary, and as regards the occurrence of the Bryophyta 

 in older formations there is the negative evidence, in this case unusually strong, of the 

 Carboniferous coal-balls. The only evidence founded on structural material of the exist- 

 ence of Carboniferous Bryophyta has been brought to light by Lignier. This author 

 has recently deseribed (1914, p. 128, text-fig. 1) from the Carboniferous a petrified stem- 

 like specimen which is regarded as a möss, partly because of the structure of the rhiz- 

 oids, but it is difficult to know what weight should be attributed to this in the face of 

 the overwhelming negative evidence. 



The Röragen fossil is remarkably large if compared with recent bryophytic sporo- 

 gonia, being comparable in size to the largest forms existing. The spores, too, are at 

 least as large as the largest among existing mosses (cfr. K. Muller in Engler & 

 Prantl). The sporogonium has not been found attached to the gametophyte; and the 

 possibility must be faced that it may represent only the upper part of a more highly 

 developed sporophyte, perhaps on the line of descent of the pteridophytes. At present 

 there is no evidence on this point. 



Attention may be called in this connection to a problematic fossil shown in pl. 3, 

 fig. 36. It represents the impression of a curious thallus-like fragment which shows a 

 peculiar ruggedness of the surface, looking as if it were caused by a sort of tomentum. 

 From the thallus-like structure spring in a peculiarly abrupt manner narrow stalks which 

 have a great general resemblance to the setae of Sporogonites. This resemblance may be 

 quite accidental, however. 



At any råte it is evident that the sporogonium as a type of structure existed among 

 the oldest land-flora at present known. 



