136 MEDULLOSEAE [CH. 



in fig. 432, A. Renault describes some phloem in sections which 

 he examined. 



The mesophyll next the upper surface is in most cases repre- 

 sented by spaces between the veins which give a crenulated 

 outline to the parenchyma (fig. 430, C, D) ; in some places the 

 spaces contain remains of very loose and crowded cells suggesting 

 the original presence of very lacunar tissue or possibly of thin- 

 walled storage-cells. The confinement of stomata to what is 

 assumed to be the upper surface may,, as Renault and others 

 have suggested, indicate leaves which floated on water, an 

 inference opposed to the view that the gaps in the mesophyll 

 mark the position of water-tissue. 



No specimens have been described which enable us to correlate 

 with certainty mature leaves or foliage-shoots with the petrified 

 bud. It is, however, not improbable that the impression from 

 Mount Pele near Epinac named by Renault Dolerophyllum 

 Berthieri 1 may be correctly referred to the same genus. The 

 type-specimen consists of an axis, whether a rachis of a compound 

 leaf or a shoot with simple leaves cannot be determined, bearing 

 partially overlapping more or less orbicular leaves 18 20 cm. in 

 diameter, with a Cyclopteris venation. Among other leaves of 

 unknown affinity referred to the same genus attention is drawn 

 to Dolerophyllum pseudopeltatum (Grand'Eury) 2 with an orbicular 

 lamina reaching in some specimens 22 x 19 cm. Specimens 

 of Dolerophyllum pseudopeltatum are figured by Renault from the 

 Commentry coal-field 3 , some of which reach a diameter of 12 cm. 

 The only British specimen of a leaflet of this type which I have 

 seen is one in Dr Kidston's collection from the Stephanian series, 

 Glamorganshire. It is probable that some at least of the 

 impressions assigned to Dolerophyllum or Doleropteris would be 

 more appropriately included in Cyclopteris or Car diopter is and 

 may have been borne on the axis of large Pteridosperm fronds. 

 Grand'Eury 4 has also called attention to the difficulty of distin- 

 guishing the larger Cyclopteris leaflets from Dolerophyllum. Some 



1 Renault (96) A. p. 262, PL xxn. fig. 1. 



2 Grand'Eury (77) A. p. 196, PL xvi ; (90) A. PL vra. fig. 1 ; Zeiller (06) B. p. 192. 



3 Renault and Zeiller (90) A. p. 556, PL LVII. 



4 Grand'Eury (04). 



