320 



THE ANATOMY OF WOODY PLANTS 



structure of a Cretaceous araucarian wood of the type designated 

 Araucarioxylon. The annual rings are much less clearly developed 



than in the wood of 

 Agathis. The rays 

 are uniseriate, as in 

 the living type, but 

 a marked contrast is 

 presented by the 

 presence of wood 

 parenchyma in the 

 fossil. The longitu- 

 dinal section por- 

 trayed in Fig. 228 

 shows both alter- 

 nating pitting and 

 the presence of 

 parenchyma. C e r - 

 tain of the tracheids 



FIG. 227. Transverse section of Araucarioxylon from 

 the Cretaceous of the eastern United States. 



rived as an exuda- 

 tion from the rays. 

 This is a condition 

 often present in both 

 living and extinct 

 woods of araucarian 

 affinities. We may 

 now turn our atten- 

 tion to another 

 araucarian type 

 commonly present 

 in the Mesozoic- 

 the genus Brachy- 

 oxylon. In this type 

 the wood in trans- 

 verse section shows 

 annual rings and the 



are also filled with 

 dark contents de- 



FIG. 228. Longitudinal section of the same 

 Araucarioxylon. 



