324 



THE ANATOMY OF WOODY PLANTS 



the opposite sense from that in the Ginkgoales; for, as has been 

 shown in the preceding chapter, the anatomical facts there justify 

 the assumption of the original presence of cordaitean structure, 

 characterized by alternation of pitting and absence of bars of 

 Sanio. In the case of the Araucariineae, on the contrary, we 

 must assume on the basis of the structure of primitive regions 

 that bars of Sanio and opposite pitting were an older feature of 



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FIG. 233. Longitudinal section of the wood of the cone axis in Araucaria Bid- 

 willii in the region of the pith. 



organization of the wood and that they are as a consequence not 

 nearly related to the Cordai tales. 



It becomes clear, when we consider the arguments derived 

 from comparative anatomical data and those furnished by the 

 study of extinct forms, that the organization of the mature wood 

 in the living Araucariineae cannot be accepted as sufficient evidence 

 of their relationship with the Cordaitales. The persistent foliar 

 traces of the two living araucarian genera have been regarded 

 in some quarters as an important indication of their primitive 

 character. Here again the comparative anatomical situation 



