422 



THE ANATOMY OF WOODY PLANTS 



higher latitude of annual rings and their absence in the lower one. 

 On the other hand, in the beginning of the Mesozoic (the Triassic) 

 even at a distance of 10 degrees south of the latitude of Prince 

 Edward Island annual rings were quite clearly developed. 



Without considering the Jurassic we may pass at once to 

 the end of the Mesozoic period, namely, the Upper Cretaceous. 

 Fig. 291 reproduces the organization of the wood of a Cretaceous 



araucarian conifer 

 closely allied to, if 

 not identical with, 

 the living kauri 

 (A gat his). A per- 

 sistent leaf trace 

 appears running 

 through the figure 

 transversely. The 

 wood is considerably 

 over half a century 

 (as recorded in 

 annual rings) from 

 the center of the 

 stem, and the foliar 

 strand still persists 

 in the manner 

 characteristic of re- 

 lated living arau- 

 carian genera. The yearly increments of growth are distinctly 

 indicated, although not very strongly marked. For comparison 

 with the above illustration a photograph of the wood of Agathis 

 australis from New Zealand is shown in Fig. 292. Here annual 

 rings are clearly apparent, although the latitude in the Southern 

 Hemisphere is nearly the same as the place of origin of the 

 Cretaceous araucarian wood above, namely, 40 degrees. It is 

 thus apparent that the Cretaceous of Staten Island was marked 

 by a much less distinct annual variation of temperature than 

 is the South Island of New Zealand of today, although the two 

 localities are of almost identical latitude. Without pursuing the 



FIG. 291. Transverse section of an Araucarioxylon 

 from the Cretaceous of Staten Island. 



