XLIV] MESEMBRIOXYLON 203 



states that there are no true spiral bands in Geoppert's supposed 

 Taxoxylon. The Permian species Taxoxylon ginkgo ides Ren. 1 and 

 Grand'Eury's Upper Carboniferous species T. stephanense 2 are 

 probably founded on wood of the Araucarian type in which the 

 tracheids show spiral striation. 



An Aptian species Taxoxylon anglicum Stopes 3 is referred to 

 that genus because of the occurrence of a spiral marking on the 

 tracheids which the author of the species believes to indicate the 

 presence of true spiral bands in the wood of recent Taxaceae, and 

 because of the groups of 3 4 bordered pits in the fields of the 

 medullary rays. 



There are no resin-canals in the wood ; the tracheids have a single 

 row of circular pits on the radial walls and occasional rims of Sanio 

 are preserved. There are 1 6 pits in the field and the presence of 

 a border is regarded by Dr Stopes as an argument in favour of the 

 tracheal nature of some of the medullary-ray elements, though the 

 appearance of the cells does not afford any substantial ground for 

 interpreting them as other than parenchymatous elements. 



An examination of the type-specimens convinced me that the 

 spiral markings on the tracheids are not true bands like those of 

 recent Taxineous wood and the pitting of the medullary-ray cells 

 is in itself by no means a trustworthy criterion. There are, I 

 venture to think, no good reasons for referring this wood to the 

 genus Taxoxylon. 



IV. MESEMBRIOXYLON. Gen. nov. 



This generic name 4 is proposed for fossil wood exhibiting 

 certain features associated with several recent genera which have 

 a southern distribution. It is intended to replace Gothan's two 

 genera Podocarpoxylon and Phyllocladoxylon, types differing from 

 one another in features which, as Dr Stopes 5 points out, are too 

 inconstant to justify the retention of both designations. Moreover 

 the use of Gothan's names implies affinities to recent genera which 

 there are no adequate reasons for assuming. In this instance, as 

 in many others, the anatomical characters do not enable us to 



1 Renault (85) p. 163. 



2 Grand'Eury (90) A. p. 317; Gothan (05) p. 68. 



3 Stopes (15) p. 204, PI. xix. text-fig. 59. 



4 fj.eari/ji.ppiv 6j, southern. 5 Stopes (15) p. 210. 



