96 MBDULLOSEAE [CH^ 



they appear to be without secondary tracheids as in M. fusilla. 

 A zone of secondary cortex encloses the vascular system as in the 

 other British stems: it is pointed out by Miss de Fraine^ that 

 this tissue, usually described as a deep-seated periderm, must 

 have differed from cork in that there is no sign of drying up or 

 decay in the tissues external to it. The leaf -bases are of the usual 

 Myeloxylon type. In size this species is intermediate between 

 MeduUosa anglica and M. fusilla. 



'Fig. 417. MeduUosa eentrofiUs. Transverse section showing the deep-seated 

 'periderm' (broken line) surrounding four steles. (After de Fraine.) 



MeduUosa stellata Cotta. 



Cotta^ described MeduUosa steUata as a stem characterised 

 by the occurrence of several many-rayed stellate columns ('viel- 

 strahlige Sternsaule') in a pith enclosed by a double cylinder of 

 secondary xylem. The so-called pith is the central ground-tissue 

 of the stem and the double ' striated ring ' of Cotta is a cyHndrical 

 stele identical in structure with each of the steles of MeduUosa 

 anglica but having a tubular form instead of forming a relatively 

 broad and short band {of. fig. 416, D and A). Goeppert^ in his 

 Permian Flora gave a detailed account of the species, some of 

 his sections being cut from Cotta's material, and by the employ- 

 ment of varietal epithets emphasised the range of variation 

 within the limits of the type. Goeppert and Stenzel* and, several 



1 De Raine (14) p. 259. See also Kisoh (13). 



" Cotta (32) B. p. 66, PI. xm. The well-preserved specimen figured by Cotta 

 in his PI. xm. fig. 2 is in the Dresden Museum. 

 = Goeppert (65) A. p. 209, Pis. XL.— sun. 

 * Goeppert and Stenzel (81). 



