XLIV] CLASSIFICATION OF CONIFEROUS WOOD 175 



IX. WOODWORTHIA. 



Araucarian tracheal pitting; annual rings feebly marked. 

 Short shoots and a subtending leaf are present in the secondary 

 wood. Resin-canals absent. 



Medullary rays uniseriate ; pits confined to the radial walls. 



Triassic. 



X. ARAUCARIOPITYS. 



Similar to Woodworthia in the possessfbn of short shoots and 

 in the pitting of the tracheids though separate and circular pits 

 also occur. Vertical resin-canals abundant in wounded regions. 



Medullary rays uniseriate; all the walls pitted. 

 Cretaceous. 



XI. PROTOCEDROXYLON. (Including Metacedroxylon.) 

 Bordered pits on the radial walls of the tracheids in 1^3 rows, 



usually of the Araucarian type but separate pits also occur. No 

 rims of Sanio and no resin-canals. 



Xylem-parenchyma usually absent. Medullary rays generally 

 uniseriate ; all the walls pitted ; 1 — 3 circular, simple, pits in the 

 field. 



Jurassic. 



XII. XENOXYLON. 



Tracheal pits large, generally flattened above and below though 

 not always, often transversely elongated. Eesin-canals absent. 



Medullary rays uniseriate ; pitting confined to the radial walls ; 

 usually one large simple pit in the field. 



Jurassic (Triassic?). 



XIII. ANOMALOXYLON. 



When uniseriate the pits on the tracheids are usually contiguous 

 and flattened ; if biseriate the pits are opposite ; separate pits also 

 occur. 



True resin-canals absent, but canal-like spaces lined with small 

 cells occur in some large medullary rays and constitute a charac- 

 teristic feature. 



Medullary rays uniseriate; pits confined to the radial walls; 

 2 — 3 circular simple pits in the field. 



Jurassic. 



