222 



CONIFERALES 



[CH. 



from the same source as the Dadoxylon wood. Though probably 

 Jurassic, a Tertiary source is by no means ruled out. 



Kraus^ transferred Witham's species to the genus Pityoxylon 

 and that name is used by Schroeter ^ and Schenk ^. The specimens 

 on which the following account is based are most of them in the 

 British Museum. Annual rings clearly defined, usually 1 — 1-5 mm. 



Fig. 72.5. Pityoxylon ttiggenst; c, resin-canal in a fusiform medullary ray. 

 (British Museum, 51427, 51641, 51727.) 



broad ; the reduction in diameter of the summer-tracheids extends 

 over several rows, the transition being much more gradual than 

 in some types of Coniferous wood. A characteristic feature is the 

 occurrence of more or less circular patches where the tracheids 

 have been destroyed with the exception of a single tracheid or a 



Kraus in Sclumpor (72) A. p. 378. 

 .Schimper and Schenlv (90) A. pp. 855, 874. 



Schroeter (80) p. 13. 



