CONIFERAE 6n 



families is the most ancient, or to form any clear con- 

 ception of the course of their evolution. The direct 

 palseontological evidence, however, apart from theor- 

 etical considerations, is favourable to the opinion that the 

 Araucarieae have the longest fossil history, probably 

 overlapping that of the typically Palaeozoic Order 

 Cordaiteae. 



The discovery of fresh sources of evidence from 

 remains with structure preserved, as in the case of 

 the Cretaceous lignites of the eastern United States, 

 now under investigation by Professor Jeffrey and his 

 colleagues, is likely to throw much new light on the 

 geological record of the Coniferae. 



III. GlNKGOACEAE 



That isolated type, the genus Ginkgo, now regarded 

 as constituting an Order, or even Class, by itself, has 

 proved to be of great antiquity. Here we have to do 

 with a well-characterised, easily recognised group, and 

 the palseontological evidence is consequently of great 

 significance. 



The habit of the leaves of Ginkgo is so characteristic, 

 that the evidence from fossil leaves, agreeing in form 

 and venation with those of the recent genus, is in itself 

 of some value. Such leaves have been recorded in 

 abundance, from the Coal - measures onwards, and 

 though many are doubtful, and may probably have 

 belonged to Ferns, resembling in their foliage Actinop- 

 teris, or certain species of Schizaea, others are in all 

 probability rightly attributed to the Ginkgoaceae. The 

 genus Whittleseya, from the Lower Carboniferous, with 



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