286 Sinnott and Bavtlett — Coniferous Woods. 



by one of the writers* in support of the contention that the 

 araucarian conifers had their origin from some ancient abie- 

 tineous stock by way of intermediate forms which were essen- 

 tially like the Podocarpineae. If this contention is well 

 founded, a large flora of podocarp-like forms in the Mesozoic, 

 some of them araucarian in their affinity, a flora the existence 

 of which the fossil record seems to indicate, is exactly what 

 one would expect to find. 



In this general argument as to the relationship between podo- 

 carps and araucarians, which brings in the whole vexed problem 

 of the ancestry of the Arancarineae, there is one factor which 

 has perhaps not been sufficiently emphasized, namely, the 

 importance of habitat in determining preservation. It seems 

 reasonable to infer that the Abietineae were as generally con- 

 fined to temperate climates in the past as in the present. Dur- 

 ing most of the Mesozoic, however, a temperate climate ap- 

 pears to have been limited almost entirely to upland regions, 

 and in these upland regions fossilization would rarely take 

 place. The Araucarineae, on the other hand, are to-day trop- 

 ical or subtropical in their distribution, and may always have 

 been so. They certainly throve in the hot lowlands of the 

 Mesozoic, where conditions were favorable for fossilization. 

 On this ground is it not possible to explain the comparative 

 infrequence of typical abietineous remains throughout the 

 Mesozoic and the great abundance of araucarians, a circum- 

 stance which has been one of the main supports of those who 

 believe that the latter are more ancient in type than the 

 former? May there not have been an abundant abietineous 

 flora on the Mesozoic uplands which largely escaped preserva- 

 tion, but from which were developed the lowland tropical 

 Araucarineae? It is significant in this connection that the 

 Podocarpineae to-day are both temperate and tropical in their 

 distribution and comprise both upland and lowland species, 

 precisely what we should expect of a group intermediate 

 between the temperate Abietineae and tropical Araucarineae. 



But whatever hypothesis as to phylogeny we may adopt, it 

 seems probable that the Podocarpoxylon type is characteristic 

 of at least the great majority of the Podocarpineae to-day ; and 

 that this type was relatively more frequent in past ages. We 

 have accordingly transferred Cupressinoxylon McGeei to Podo- 

 carpoxylon. If this wood is ultimately proved to belong to 

 Nageiopsis, as we believe it does, anatomical evidence will 

 have afforded striking confirmation of the affinity between 

 Nageiopsis and Nageia which Fontaine adduced from foliage 

 impressions alone. 



* Sinnott, E. W., " The Morphology of the Reproductive Structures in the 

 Podocarpineae; Ann. Bot., xxvii, 39-82, 1913. 



