CHAPTER XLVIIl. 



ABIETIXEAE. 



The relative antiquity of the different families of the Conif erales 

 is a question which every student of the geological history of the 

 group desires to answer. Reference has already been made to the 

 different views that are held with regard to the phylogenetic 

 relations of the Araucarineae and the Abietineae: conclusions on 

 this subject are based partly on the morphological characters ex- 

 hibited by recent types and in part on palaeobotanical data. The 

 evidence afforded by petrified wood is briefly dealt with in Ch. xliv: 

 this shows that the features associated with modern Abietineae do 

 not stretch as far back into the past as is the case with the type 

 represented by the wood of the Araucarineae. The evidence derived 

 from a study of impressions of foliage-shoots and cones as well as 

 the meagre data supplied by petrified cones is less easy to interpret 

 because of the greater imperfection of the records. The southern 

 distribution of the Araucarineae predisposes the student in favour 

 of a southern origin, while the essentially northern range of the 

 Abietineae suggests that this family had its birth north of the 

 equator. But conclusions based on such considerations require 

 confirmation from other kinds of evidence. In the Jurassic- Wealden 

 period the Araucarineae were well represented in the northern 

 hemisphere and the impression gained from a survey of Jurassic 

 records is that the Araucarineae shared with other types an almost 

 world-wide distribution. It is much easier for a palaeobotanist to 

 form an opinion as to the period of maximum development and 

 vigour of a given set of plants than to discover a substantial 

 foundation on which to rest a view as to the first appearance or 

 the original home of the earliest representatives of the family-type. 

 It is, perhaps, significant that the Araucarineae are represented in 

 the Jurassic floras of Graham Land on the edge of Antarctica, 

 Austraha, and India. The Abietineae, on the other hand, do not 



