CONIFERALES 325 



as well as the conditions found in allied fossil conifers do not 

 justify the conclusion reached. The seedlings of both Araucaria 

 and Agathis show the earlier leaf traces as evanescent structures 

 which cease to be formed by the cambium after the leaves to which 

 they belonged have disappeared. It is only in the older trunk 

 that the formation of foliar strands is perpetuated for many 

 years, amounting even to centuries, after their corresponding 

 leaves have disappeared. The persistent leaf traces which con- 

 stitute so remarkable a feature of the organization of the mature 

 trunk of the existing Araucariineae cannot therefore be regarded 

 as anything but a bizarre and freakish feature which has no evo- 

 lutionary importance. If any remaining doubt can be considered 

 to exist on the subject, it is set aside by the organization of the 

 Mesozoic araucarian woods, which (with the exception of the 

 type known as Araucarioxylon) , are distinguished by the absence of 

 persistent foliar traces. Comparative anatomy lends very little 

 support to the inference of cordaitean affinities for the araucarian 

 conifers, and the evidence against this widely cherished view 

 becomes quite overwhelming when the anatomical situation in 

 the other subtribes of the Coniferales is considered. The further 

 estimation of the claims of the Araucariineae to the pre-eminence 

 of being the oldest conifers may appropriately be delayed until 

 the anatomical features of other important subtribes have been 

 examined. 



The Abietineae have in recent years made progress as claimants 

 to the primitive position among Coniferales and to that of nearest 

 proximity to the Cordaitales. At first sight the extremely com- 

 plicated organization of both vegetative and reproductive struc- 

 tures in the abietineous conifers appears to stand in the way of 

 any such conclusion; but the results of the comparative investiga- 

 tion of the living and fossil representatives of groups which have 

 passed the zenith of their development has taught us not to consider 

 complexity of organization as necessarily a criterion of modernity. 

 It will be shown in subsequent paragraphs that the Abietineae 

 are in a very strong position as regards primitiveness, both because 

 they are apparently related, on good anatomical evidence, to such 

 ancient groups as the Cordaitales and Ginkgoales and because 



