126 BRITISH EOCENE ELORA. 



way for the newer and more vigorous types which are ushered in with the first dawn of 

 the Cretaceous period. Jurassic forests appear to have been composed mainly of genera 

 belonging to the Araucarieae and the Cupressineae, with an undergrowth of Cycads and of 

 various species of Brachyphyllum and Eerns. 



Of the five tribes into which existing Coniferae are grouped the Taxe,e, through Ginkgo, 

 are decidedly the most venerable for their antiquity. The pedigree of this tree is so 

 remarkable and is traceable through such ages, embracing as it does widely divergent 

 forms separated into many genera, that Saporta strongly urges that the extinct ancestral 

 and the living form should be elevated to the rank of a distinct tribe in classifying 

 Coniferae. 



It is somewhat remarkable that while some of the Jurassic species of Ginkgo are 

 almost indistinguishable from the living, they seem to have reverted during the Creta- 

 ceous and Wealden towards older forms, the leaves of at least one being laciniated or cut 

 up into narrow segments. The Carboniferous Ginlgophyllum died out with the Permian, 

 where it is associated with Trichopitys. The latter with Baieria persisted down to the 

 close of the Secondary period. No other genus is known in the Lias, but in the Jurassic 

 many species, some true Ginkgos, are met with ranging from Australia to within the Arctic 

 Circle. The tribe had greatly diminished in the Cretaceous period though Baieria and 

 Sclerophyllina were among the survivals. Its later history will be found at p. 46 of this 

 memoir. 



The rest of the Palaeozoic Coniferae cannot be placed with certainty in any one of the 

 existing tribes. Their characters seem to unite the Araucarieae, the Cupressineae, and the 

 Taxodieae, and there can be no doubt that the remote period in which they flourished was 

 antecedent to the differentiation of these tribes from each other. It has been proposed 

 by Saporta to unite them in a single tribe, that of the Walchie^e of Schimper, and the 

 advantages of this arrangement, at least as a provisional one, are obvious. The principal 

 genera would be Walchia, Ullmannia, and Brachyphyllum. The latter was an immense 

 genus, with very thick, closely inlaid, or imbricated leaves, and small cones, either 

 persistent or caducous, composed of persistent scales which were also closely imbricated, 

 and, not greatly differing, except that they were more lanceolate, from the foliar leaves. 

 None of the Walchieae so far as is yet known survived the Jurassic. Brachyphyllum is 

 the last of the Coniferae which cannot properly be classed in an existing tribe, 1 and in 

 leaving it we seem to quit the unknown. 



The Araucarieae are of an antiquity which is only surpassed among Conifers by 

 Ginkgo, though the Carboniferous woods, for a long time thought to be Araucarian, are 

 now placed in the widely removed progymnospermous genus Corda'ites. Undoubted 

 Araucarian forms first appear in the Trias, but with ambiguous characters, which render it 

 probable that they may be ancestors of all three existing genera. Mr. Carruthers was the 

 first to demonstrate beyond all doubt that true Araucaria existed in the Inferior Oolite of 



1 It is placed with the Taxodiese by Schimper. 



