FERNS— FRUCTIFICATIONS 291 



others to the Marattiaceae, but is now regarded by 

 Mr. Kidston as most probably a member of the 

 Pteridospermeae. 



The evidence for the existence of Palaeozoic 

 Osmundaceae is now under investigation ; 1 it is not at 

 all uncommon to find isolated sporangia in the petrified 

 material, which might well be of that nature. The 

 presence of a lateral group of enlarged cells, resembling 

 the annulus or areola of Osmundaceae, is a frequent 

 feature. Professor Bower some years ago drew attention 

 to the Osmundaceous character of certain Carboniferous 

 sporangia ; 2 some of the sporangia of this type no 

 doubt belonged to the Botryopterideae described in the 

 next chapter. 



In the calcareous specimens showing structure, from 

 the British Carboniferous strata, sporangia like those 

 of Ferns are frequent enough, but unfortunately they 

 are usually isolated, so that it is impossible to tell 

 what was their arrangement, or to determine the nature 

 of the leaf on which they were borne. The specimens, 

 however, prove the frequency, in Palaeozoic times, of 

 free sporangia not grouped into synangia. They also 

 prove that the presence of an annulus of some kind 

 was almost as common then as now, though the form 

 of the annulus was, no doubt, different from that usual 

 among recent Ferns. The generic name Pteridotheca 

 may conveniently be used provisionally for such 



1 See the work of Kidston and Gwynne-Vaughan referred to below 



(PP- 345. 350- 



2 " Is the Eusporangiate or the Leptosporangiate the more Primitive 

 Type in the Ferns?" Annals of Botany, vol. v. 1891. The Sarcopteris 

 Bertrandi of Renault also has Osmundaceous characters (see Cours de tot. 

 foss., vol. iii. p. 129 Plate xxi, Figs. 12-15). 



