456 



DR. E. A. NEWELL AKBEE ON 



[Oct. 1 9 13, 



Pig. 9. 



of D 



Tangential section 

 kayi, shovAng the 

 tracheides with the medul- 

 lary rays between them. 

 x46. 



are in some cases clearly seen (fig. 8, p. 455). They are bordered 

 pits, usually arranged in more than one row, two rows being fre- 

 quently observed ; while in some cases three alternating rows (fig. 8) 

 occur. The medullary rays (fig. 7, p. 455) vary greatly in height, 

 as is more clearly seen in tangential sections. 



In tangential sections of the wood, no pits are usually seen on 

 the walls. The abundance and great variation in the height of 

 the medullary rays (fig. 9) is seen to great advantage in these 

 sections. They vary from one to twenty-seven elements in height, 

 and measure in height between 0*06 and O66 mm. Occasionally, 

 a ray (fig. 9, below) becomes partly biseriate. 



Prom the above description it is clear that the structure of the 

 Witley wood agrees in its general 

 characters with that of the modern 

 Conifer Araucaria. The absence of a 

 discoid pith obviously removes it from 

 close proximity to Gordaites. -It has- 

 been long known that fossil woods of 

 this type occur widely, both in the 

 Palaeozoic and in the Mesozoic rocks, 

 as well as in more recent sediments. It 

 has been suggested, however, by Pelix,, 

 and later by Knowlton, 1 that it would 

 be well to group together such of these 

 woods as are of Palaeozoic age into 

 the genus Dadoxylon, and to reserve 

 the term Araucarioxylon for those 

 which are of Mesozoic or later age. 

 This convention has since been widely 

 adopted, one reason being that the- 

 evidence at present available for the 

 existence of the Araucariae in Palaeo- 

 zoic times is very unsatisfactory ; and 

 further, it may be that these Palaeozoic 

 woods represent a general type of 

 structure common to more than one 

 race of Conifers in the past. 



I therefore here refer the "Witley 

 specimens to the genus Dadoxylon ;. 

 and, since these woods in their specific 

 characters appear to me to differ from 

 those previously described, especially 

 as regards the abundance and height 



of the medullary rays, I have also referred them to a new species,- 



Dadoxylon Jcayi, in honour of their discoverer. 



The genus Dadoxylon is at present loosely defined, and purposely 

 so. It is merely a Palaeozoic wood resembling that of a modern 

 1 F. W. Knowlton, Proc. U.S. Eat. Mus. vol. xii (1889) p. 606. 



