CONIFERALES 



327 



feature of resemblance to cordaitean forms is the absence of a 

 torus in the membranes of the bordered pits of the tracheids lying 

 nearer to the primary wood. The situation in this respect is the 

 exact opposite of that found in the case of the araucarian conifers, 



FIG. 235. Highly magnified view of the tracheids of a species of pine, showing 

 the bars of Sanio (after Gerry). 



in which the torus is sometimes present in the region near the 

 primary xylem of the wood of the cone axis and is entirely absent 

 elsewhere. The organization of the wood alone in primitive 

 organs and regions justifies the conclusion of a filiation between 

 the Abietineae and the Cordaitales rather than between the 

 Araucariineae and the Cordaitales. 



