FERNS— SUMMARY 347 



Botryopterideae as at present the best-known family, 

 has already been referred to, and the idea is likely to 

 be a fertile one. We are not, as yet, in a position to 

 fill in the features of this ancient race, for outside the 

 Botryopterideae themselves, or their immediate allies, 

 our knowledge of such Ferns is scanty. But, as Mr. 

 Arber points out, many of the Fern sporangia of the 

 petrifactions will doubtless find their place here, and so, 

 perhaps, will some of the fructifications, such as 

 Oligocarpia or Senftenbergia, which have been provision- 

 ally referred to definite recent families. Pteridotheca 

 Williamsonii (Fig. 112, p. 293) is a good example of a 

 Palaeozoic Fern with annulate sporangia borne on leaflets 

 of an ordinary vegetative type, and there are several 

 similar cases. Various families of Ferns are known to 

 have been well developed in the Mesozoic Period, and 

 their ancestors must have been present in Palaeozoic times. 

 For reasons already given, I can no longer regard the 

 Botryopterideae as lying on the direct line, but some of 

 the forms of " Primofilices " with non -specialised sporo- 

 phylls may well have been nearer the progenitors of 

 Ferns as we know them. 



The genus Corynepteris suggests a possible connection 

 between the Primofilices and the Marattiaceae, an 

 hypothesis which, indeed, is almost inevitable on general 

 grounds. The Ferns grouped under Primofilices, as 

 this name is intended to imply, are of great antiquity, 

 occurring commonly in the Lower Carboniferous (various 

 Botryopterideae) and extending back to the Devonian 

 {Asterochlaena), while the Marattiaceae are not known 

 to be older than the Upper Carboniferous (Lower 

 Coal-measures). 



