XXl] GLEICHENIACEAE 351 



fragments are correctly referred to the Schizaeaceae. The 

 sterile and fertile specimens figured by Heer^ from Tertiary beds 

 of Switzerland agree very closely with recent examples of 

 Lygodium. Similar though perhaps less convincing evidence 

 of the existence of this family in Europe is furnished by 

 Saporta^, who described two Eocene species from France. 



Gleicheniaceae. 

 The application by Goeppert^ and other earlier writers of 

 the generic name Gleichenites to examples of Palaeozoic ferns 

 was not justified by any satisfactory evidence. One of Goeppert's 

 species, Gleichenites neuropter aides, is identical with Neuropteris 

 heteropkylla*, a plant now included in the Pteridosperms. 



The resemblance of sporangia and sori, whether preserved 

 as carbonised impressions or as petrified material, from Car- 

 boniferous rocks, to those of recent species of Gleicheniaceae 

 is in many cases at least the result of misinterpretation of 

 deceptive appearances. Williamson^ drew attention to the 

 Gleichenia-like structure of some sections of sporangia from 

 the English Coal-Measures, but he did not realise the ease with 

 which sections of Marattiaceous sporangia in different planes 

 may be mistaken for those of annulate (leptosporangiate) 

 sporangia. In the regular dichotomous habit of Carboniferous 

 fronds described as species oi Diplothmema (Stur) and Mariopter is 

 (Zeiller)^ we have a close correspondence with the leaves of 

 Gleichenia, but the common occurrence of dichotomous branching 

 among ferns is sufficient reason for regarding this feature as 

 an untrustworthy criterion of relationship. It is, however, 

 interesting to find that in addition to the existence of some 

 Upper Carboniferous ferns with sori like those of recent Glei- 

 chenias, the type of stelar anatomy illustrated by Gleichenia 

 dicarpa (fig. 237, C, p. 310) and other species is characteristic 

 of the primary structure of the stem of the Pteridosperm 

 Heterangium. We find in Carboniferous types undoubted 

 indications of anatomical and other features which in succeeding 

 ages became the marks of Gleicheniaceae. 



1 Heer (55) A. PL xiii. " Saporta (72) A. PI. i. figs. 13, 1^. 



3 Goeppert (36^) A. Pis. iv. v. * Zeiller (88) A. p. 261. 



5 Williamson (77) PI. vii. ° See Ch. xxvii. 



